JPH06310145A - Manufacture of nickel acid lithium for lithium secondary battery - Google Patents

Abstract

PURPOSE:To improve the battery performance such as the discharge property by mixing a hydroxide compound or oxide compound including trivalent lithium ions, and then heat-treating it. CONSTITUTION:A tetrafluoroethylene resin and a graphite are mixed to a nickel acid lithium obtained as a positive electrode compound 6, and it is pressurized at a specific weight to make into pellets. And as an electrolyte solution, tetrafluorolithium borate is solved in a mixing solvent of the same amounts of propylene carbonate and 1,2-dimethoxyethane, and it is included in a separator 5 so as to be used. Furthermore, as a negative electrode material 4, a metallic lithium is used, and the charge and the discharge are repeated to make the amount of the metallic lithium in a sufficient amount to the positive electrode compound 6. In this case, the nickel acid lithium of the compound 6 is used by heat-treating, after mixing a lithium salt to a hydroxide or an oxide including trivalent nickel ions. As a result, it is not necessary to provide the oxygen in the heating time, and the mixing of rock salt type crystals in the X-ray diffraction map is reduced. Consequently, the battery performance such as the discharge property can be improved.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing lithium nickel oxide (LiNiO ₂ ) for a lithium secondary battery,
More specifically, it relates to a method for producing LiNiO ₂ used as a positive electrode active material for a lithium secondary battery, which uses lithium, a lithium alloy or carbon as a negative electrode active material.

[0002]

_2. Description of the Related Art As a positive electrode active material for a non-aqueous lithium secondary battery, materials represented by Li _y Ni _2-y O ₂ and LiCo _y Ni _1-y O ₂ have been proposed.

For Li _y Ni _2-y O ₂ , a method of mixing LiOH.H ₂ O and NiO, pre-baking at 600 ° C. in an air atmosphere, pulverizing again, and sintering at 600 to 800 ° C. ( JP-A-2-40861), or LiNO ₃
And NiCO ₃ and Ni (OH) ₂ are mixed and molded, then heated and baked at 650 ° C. in an oxygen stream, pulverized again, and molded, then 75
Method of heating and baking at 0 ° C. (T. Ohzuku, AU
eda, M .; Nagayama, Y. Iwasaki,
K. Sawai; Chem. express, vol.
7, No. 9, p689-692 (1992)) and the like have been proposed.

These characteristics are due to Li _y having a layered structure by pre-doping lithium in nickel oxide.
Ni _2-y O ₂ is used, and it is possible to smoothly dope and dedope lithium by charging and discharging.

However, in these conventional techniques, 2
Since a compound having a valent nickel ion is used as a starting material, a large amount of oxygen is required during firing, and when the oxygen concentration during heating is reduced, the obtained Li _y Ni _2-y O ₂
There is a problem in that rock salt type crystals are mixed in and the cycle characteristics (charge / discharge characteristics) of the lithium secondary battery are adversely affected.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing lithium nickel oxide for a lithium secondary battery, which can improve battery performance such as discharge characteristics.

[0007]

The above object of the present invention is achieved by using a hydroxide or oxide having trivalent nickel ions as a raw material.

That is, according to the present invention, a hydroxide and / or oxide containing trivalent nickel ions is mixed with a lithium salt and then heat-treated, which is a method for producing lithium nickelate for a lithium secondary battery. On the way.

In the present invention, a hydroxide or oxide having trivalent nickel ions is used as a raw material. As used herein, a hydroxide or oxide having trivalent nickel ions means nickel (III) hydroxide or nickel (III) oxide hydrate, that is, NiO (OH) or N.
i ₂ O ₃ · nH ₂ O.

To obtain such a hydroxide or oxide having trivalent nickel ions, a known method is adopted. For example, nickel (III) hydroxide (NiO (O
H): Nickel oxyhydroxide) is obtained by the following method.

First, divalent nickel hydroxide (Ni (OH) ₂ ) is dispersed in an aqueous sodium hydroxide solution having a pH of 11 or more and heated to 60 to 80 ° C. Next, a predetermined amount of an aqueous solution of sodium hypochlorite, an aqueous solution containing chlorine, an aqueous solution containing bromine, etc. is dropped into this dispersion liquid, and after reaction, filtration, washing and drying are performed to obtain a black powder of nickel oxyhydroxide. .

The hydroxide or oxide containing trivalent nickel ions thus obtained is mixed with a lithium salt such as lithium nitrate in a predetermined ratio, pressure-molded, dried and then 6
After heating in air at 00 to 800 ° C and crushing and molding again, 7
Heat-sinter in air at 00 to 900 ° C. The heating time is 6 to 24 hours, respectively. In this way, lithium nickelate is obtained.

[0013]

Since the starting material is a hydroxide or oxide having trivalent nickel ions, oxygen is not required during heating. Therefore, as compared with lithium nickel oxide obtained by heating a divalent nickel compound in the air, the rock salt type crystal is extremely less mixed in the X-ray diffraction pattern. Characteristic X-ray diffraction line of lithium nickelate (CuKα: 2θ = 18.7 degrees (00
The diffraction intensity ratio of (3) plane, 2θ = 44.3 degrees (104) plane) is I ₍₀₀₃₎ / I ₍₁₀₄₎ ≧ 1.34, and the lithium content is about 7.2 wt%.

When a compound containing divalent nickel ions is heated in air, the X-ray diffraction intensity ratio is 1.1 or less and the lithium content is 6.9% by weight or less. When the mixing ratio of lithium is increased from 1: 1 in advance, the stoichiometric content approaches 7.11% by weight, but lithium exists in the state of Li ₂ O and is not LiNiO ₂ .

[0015]

EXAMPLES The present invention will be specifically described below based on Examples and the like.

Example 1 A glass container having an internal volume of 3 liters was charged with 2 liters of sodium hydroxide solution having a pH of 11 or more, 100 g of nickel hydroxide (Ni (OH) ₂ ) powder was added, and the mixture was added to 60-80.
Warm to 0 C with stirring. Then, 150 ml of 5% sodium hypochlorite solution was added dropwise and stirred for 3 hours. The nickel oxyhydroxide produced here was measured and identified by the powder X-ray diffraction method.

Next, after mixing 70 g (1 mol) of lithium nitrate and 93 g (1 mol) of nickel oxyhydroxide, a diameter of 10 was obtained.
Press-molded into a cylindrical pellet of mmφ and height of 40 mm,
The reaction was carried out in the air at a reaction temperature of 650 ° C. for 12 hours. After that, it was pulverized and molded again, and reacted in the air at a reaction temperature of 750 ° C. for 24 hours to obtain lithium nickelate. The obtained powder of lithium nickelate was subjected to X-ray diffraction and I
The peak intensity ratio of ₍₀₀₃₎ / I ₍₁₀₄₎ was calculated. The results are shown in Table 1.
It was shown to.

Further, using this lithium nickel oxide as a positive electrode active material, a lithium secondary battery shown in FIG. 1 was constructed. The lithium secondary battery used was a discharge electrode having an inner diameter of 10.8 mmφ, and the construction work was performed in a dry box under an argon atmosphere.

In FIG. 1, 1 is a negative electrode terminal, 2 is an insulator (Teflon material), 3 is a negative electrode current collector plate, 4 is a negative electrode material, 5 is a separator, 6 is a positive electrode mixture, and 7 is a positive electrode terminal. .

As the positive electrode mixture 6, 90 mg of the obtained lithium nickel oxide was mixed with 6 mg of graphite and 4 mg of tetrafluoroethylene resin, and the mixture was pressure-molded with a load of 2 t to give pellets having a diameter of 10.6 mmφ. Was used.

As the electrolytic solution, a solution obtained by dissolving lithium tetrafluoroborate (LiBF ₄ ) in a 1: 1 mixed solvent of propylene carbonate and 1,2-dimethoxyethane was used by being contained in the separator 5.

As the negative electrode material 4, metallic lithium is used,
It was designed to be a sufficient amount (about twice equivalent) with respect to the positive electrode mixture 6.

Using the obtained lithium secondary battery,
Charge and discharge are repeated at a voltage in the range of 4.2 to 3.0 V with a current of 9 mA, the first cycle, the tenth cycle and 50
The secondary battery discharge capacity was measured for each cycle. The results are shown in Table 1.

Example 2 The addition amount of the sodium hypochlorite solution of Example 1 was set to 450.
Lithium nickelate was obtained by the same method as in Example 1 except that the amount was changed to ml. X-ray diffraction of the powder is performed I
The peak intensity ratio of ₍₀₀₃₎ / I ₍₁₀₄₎ was calculated, and the results are shown in Table 1.

Further, using this lithium nickel oxide as a positive electrode active material, a lithium secondary battery was constructed in the same manner as in Example 1, and the battery performance was evaluated. The results are shown in Table 1.

Example 3 The amount of the sodium hypochlorite solution of Example 1 added was 600.
Lithium nickelate was obtained by the same method as in Example 1 except that the amount was changed to ml. X-ray diffraction of the powder is performed I
The peak intensity ratio of ₍₀₀₃₎ / I ₍₁₀₄₎ was calculated, and the results are shown in Table 1.

Further, using this lithium nickel oxide as a positive electrode active material, a lithium secondary battery was constructed in the same manner as in Example 1, and the battery performance was evaluated. The results are shown in Table 1.

Example 4 The heating temperature of Example 2 was 650 ° C., 12 hours, 700 ° C.
Lithium nickelate was obtained in the same manner as in Example 2 except that the time was changed to 24 hours. X-ray diffraction of the powder is performed to calculate the peak intensity ratio of I ₍₀₀₃₎ / I ₍₁₀₄₎ ,
The results are shown in Table 1.

Further, a lithium secondary battery was constructed in the same manner as in Example 1 using this lithium nickel oxide as a positive electrode active material, and the battery performance was evaluated. The results are shown in Table 1.

Example 5 The heating temperature of Example 2 was 650 ° C., 12 hours, 800 ° C.
Lithium nickelate was obtained in the same manner as in Example 2 except that the time was changed to 24 hours. X-ray diffraction of the powder is performed to calculate the peak intensity ratio of I ₍₀₀₃₎ / I ₍₁₀₄₎ ,
The results are shown in Table 1.

Further, using this lithium nickel oxide as a positive electrode active material, a lithium secondary battery was constructed in the same manner as in Example 1, and the battery performance was evaluated. The results are shown in Table 1.

Example 6 The heating temperature of Example 2 was 650 ° C. for 12 hours at 900 ° C.
Lithium nickelate was obtained in the same manner as in Example 2 except that the time was changed to 24 hours. X-ray diffraction of the powder is performed to calculate the peak intensity ratio of I ₍₀₀₃₎ / I ₍₁₀₄₎ ,
The results are shown in Table 1.

Further, using this lithium nickel oxide as a positive electrode active material, a lithium secondary battery was constructed in the same manner as in Example 1, and the battery performance was evaluated. The results are shown in Table 1.

Comparative Example 1 Commercially available reagent Nickel hydroxide monohydrate 112 g (1 mol)
And 70 g (1 mol) of lithium nitrate were pressure-molded, heated at 650 ° C. in air for 12 hours, pulverized and molded again, and then heated at 750 ° C. in air for 24 hours to obtain lithium nickelate. Obtained. X-ray diffraction of the powder is performed I
The peak intensity ratio of ₍₀₀₃₎ / I ₍₁₀₄₎ was calculated, and the results are shown in Table 1.

Further, using this lithium nickel oxide as a positive electrode active material, a lithium secondary battery was constructed in the same manner as in Example 1, and the battery performance was evaluated. The results are shown in Table 1.

Comparative Example 2 The heating temperature of Comparative Example 1 was 650 ° C. for 12 hours at 900 ° C.
Lithium nickelate was obtained in the same manner as in Comparative Example 1 except that the time was changed to 24 hours. X-ray diffraction of the powder is performed to calculate the peak intensity ratio of I ₍₀₀₃₎ / I ₍₁₀₄₎ ,
The results are shown in Table 1.

Further, using this lithium nickel oxide as a positive electrode active material, a lithium secondary battery was constructed in the same manner as in Example 1, and the battery performance was evaluated. The results are shown in Table 1.

[0038]

[Table 1]

As is clear from Table 1, the lithium nickel oxides of Examples 1 to 6 have an I ₍₀₀₃₎ / I ₍₁₀₄₎ plane diffraction intensity ratio of 1.34 or more, while Comparative Example 1 Of lithium nickelate having an I ₍₀₀₃₎ / I ₍₁₀₄₎ plane diffraction intensity ratio of 1.1
It is the following. Further, it can be seen that the lithium secondary batteries of Examples 1 to 6 have a larger discharge capacity in each cycle than the lithium secondary batteries of Comparative Examples 1 and 2 and are excellent in battery performance.

[0040]

INDUSTRIAL APPLICABILITY The lithium nickelate obtained according to the present invention is of good quality, with almost no rock salt type crystals being recognized, as compared with LiNiO ₂ obtained by heating a compound containing divalent nickel ions in air.

Further, by using this lithium nickel oxide as a positive electrode active material of a lithium secondary battery, a lithium secondary battery having a large discharge capacity and excellent other battery characteristics such as charge / discharge characteristics can be obtained. It will be possible.

Therefore, the manufacturing method of the present invention is very useful as a manufacturing method of lithium nickel oxide for a lithium secondary battery.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an example of a lithium secondary battery according to the present invention.

[Explanation of symbols]

1: Negative electrode terminal, 2: Insulator, 3: Negative electrode current collector plate, 4: Negative electrode material, 5: Separator, 6: Anode mixture, 7: Anode terminal.

Claims (1)

[Claims] 1. A method for producing lithium nickel oxide for a lithium secondary battery, which comprises mixing a hydroxide or oxide containing trivalent nickel ions with a lithium salt and then heating the mixture.