JPH1087332A - Production of spherical lithium-nickel complex oxide and nonaqueous electrolyte cell using the same as positive electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the density of an electrode and the energy density of a cell by using a spherical lithium-nickel complex oxide. SOLUTION: A mixed slurry of lithium nitrate and a nickel compd. is spray- dried and the resultant powdery mixture of spherical particles is fired at 550-900 deg.C in a firing furnace under continuous or intermittent fluidization to produce the objective spherical lithium-nickel complex oxide. This complex oxide is used as a positive electrode to obtain the objective nonaq. electrolyte cell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a spherical lithium / nickel composite oxide and a non-aqueous electrolyte battery using the same as a positive electrode active material.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for portable devices such as portable telephones, laptop personal computers, camera-integrated VTRs, and the like. For these devices, small and lightweight secondary batteries are indispensable. At present, as a secondary battery, Ni-C
Although d batteries and Ni hydrogen batteries are used, these batteries have reached the limit of miniaturization and weight reduction.

On the other hand, development of non-aqueous electrolyte secondary batteries using metallic lithium or a substance capable of occluding / desorbing lithium for the negative electrode has been promoted. This battery is characterized by a higher voltage and a higher energy density than conventional small secondary batteries, and can be made smaller and lighter than conventional batteries.

The positive electrode of this battery is generally made of LiCoO
₂ is used, but Co is expensive and has a small amount of reserves. Therefore, a lithium-nickel composite oxide such as LiNiO ₂ is inexpensive and has a high charge / discharge capacity compared to LiCoO ₂ . Is attracting attention as a new electrode active material and is being studied.

As a method for synthesizing a lithium-nickel composite oxide, for example, Japanese Patent Application Laid-Open No. H5-251079 discloses a method.
Lithium nitrate and at least one of nickel hydroxide or nickel oxyhydroxide are mixed such that the atomic ratio of lithium to nickel is 1: 1 and calcined at 500 ° C. to 1000 ° C. to obtain a lithium-nickel composite oxide. A method is disclosed. Japanese Patent Application Laid-Open No. 7-230808 discloses a method of obtaining a spherical lithium-nickel composite oxide by mixing lithium hydroxide, spherical nickel hydroxide, and citric acid and firing the mixture.

[0006]

When a lithium-nickel composite oxide is used as a positive electrode of a battery, a lithium-nickel composite oxide having a spherical shape is used to increase the electrode density and the energy density of the battery. It is necessary. However, spherical lithium-nickel composite oxides can be obtained only when lithium hydroxide is used as the lithium source and spherical nickel hydroxide is used as the nickel source. In this case, the spherical lithium-nickel obtained in this case is used. The composite oxide has a problem that the density of the spherical particles themselves is low due to the presence of many pores despite being spherical, and the tap density does not increase, so that the electrode density does not increase. Furthermore, since the spherical lithium-nickel composite oxide has insufficient oxidizing power even when synthesized in an oxygen atmosphere,
There is a problem that the discharge capacity does not increase.

When a lithium-nickel composite oxide is synthesized using lithium nitrate having oxidizing power as a lithium source, a lithium-nickel composite oxide having a large discharge capacity can be obtained. Even when used, the fired product solidifies and hardens. In order to use a positive electrode as a positive electrode active material for a spiral-structured battery such as a cylindrical nonaqueous electrolyte battery, the positive electrode must be a sheet electrode having a thickness of several hundred microns. It must be ground to a micron or less, and spherical particles cannot be obtained when grinding is performed. Therefore,
There is a problem that the tap density does not increase and the electrode density does not increase.

[0008]

SUMMARY OF THE INVENTION The present invention provides a high-density spherical powder obtained by spray-drying a mixed slurry of lithium nitrate and a nickel compound at a specific temperature while moving it in a firing furnace. It has been found that a spherical lithium / nickel composite oxide can be obtained by the above method.

That is, according to the present invention, a mixed powder composed of spherical particles obtained by spray-drying a mixed slurry of lithium nitrate and a nickel compound is fired at 550 to 900 ° C. while continuously or intermittently moving in a firing furnace. The present invention relates to a method for producing a spherical lithium / nickel composite oxide, and a nonaqueous electrolyte battery using the same as a positive electrode.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
Here, the term “spherical” does not necessarily mean only a true sphere, but rather a particle with a slightly uneven surface, a sphere that is slightly distorted as a whole, a part that is partially dented, and some of the spherical particles that aggregate. It shall include those that have been done.

The nickel compound preferably contains a metal element other than nickel in an amount of 25 mol% or less in the metal element in the nickel compound. Preferably, the metal element other than nickel is cobalt, iron, manganese, or a mixture thereof. Further, the compound is preferably a hydroxide, an oxide or a mixture thereof.

When the nickel compound is insoluble, the average particle size is preferably smaller, and more preferably 5 μm or less. For example, to obtain fine powder of nickel hydroxide, commercially available nickel hydroxide may be pulverized by a ball mill, a vibration mill, a jet mill, or the like, or to obtain a nickel hydroxide slurry having a smaller particle size, sulfuric acid may be used. An aqueous solution of an alkali such as caustic soda may be mixed with an aqueous solution of nickel or nickel nitrate, and the dissolved nitrate may be removed by decantation to obtain a nickel hydroxide fine particle slurry. If the average particle diameter is large, it takes a long time to complete the reaction, and the composition of the lithium-nickel composite oxide after firing may vary, so that a large discharge capacity may not be obtained.

As a solvent for preparing a slurry of lithium nitrate and a nickel compound, it is preferable to use a solvent that does not contain a nonvolatile component, such as water, aqueous ammonia, or alcohol.
When an organic solvent containing carbon is used, impurities such as lithium carbonate are generated depending on firing conditions and the like, and the composition of the lithium-nickel composite oxide shifts, causing a reduction in discharge capacity due to the impurities. It is preferred that

It is preferable that the mixed slurry of lithium nitrate and nickel compound is well dispersed and stirred and mixed before spray drying. If dispersion and stirring and mixing are insufficient, the composition may vary, and a lithium / nickel composite oxide having a large discharge capacity may not be obtained.

In the spray drying of the mixed slurry, the uniformly mixed slurry is formed into droplets using a nozzle, an atomizer, or the like.
In addition to the general method of drying this in a very short time, spray freeze-drying in which the droplets are frozen in a short time and then drying under reduced pressure or the like, or spraying in which the general spray drying and baking are combined Thermal decomposition may be used.

The powder mixture to be granulated by spray drying must be spherical. The average particle size of the mixed powder granulated by spray drying is preferably 100 μm or less, more preferably 50 μm or less. The mixed powder is slightly shrunk by firing, and the average particle size after firing is smaller than before firing, but when firing the mixed powder having an average particle size of more than 100 microns, 50 μm or more, which is not preferable as an active material of a battery, It is not preferable because the ratio of particles increases. When a mixed powder having a large particle size is contained, it is preferable to perform calcination after removing large particles by classification such as sieving.

Since it is highly possible that the mixed powder immediately after spray drying has absorbed some moisture, it is preferable to dry the mixed powder at about 100 ° C. to remove water. Further, the spray-dried mixed powder is preferably stored in a low humidity state until firing. Since the mixed powder contains deliquescent lithium nitrate,
When stored in a state of high humidity, the spherical mixed powder may aggregate.

In the firing of the mixed powder, the firing must be performed while moving the mixed powder continuously or intermittently in a firing furnace. If firing is performed while the mixed powder is allowed to stand, the mixed powder is sintered and spherical lithium / nickel oxide cannot be obtained.
The method of moving the mixed powder is, for example, a method in which the mixed powder is put into a tubular rotary kiln and the tube is continuously or intermittently rotated and fired, a method of repeatedly dropping the mixed powder from the upper part of the vertical firing furnace, a method of mixing There is a method of continuously or intermittently vibrating the container containing the powder or the entire firing furnace. If the mixed powder is in contact for a long time, it is likely to agglomerate. Therefore, in the case of intermittent operation, it is preferable to shorten the standing time. In addition, when the collision between the mixed powders is strong, agglomeration is likely to be caused on the contrary. Therefore, it is preferable that, for example, the moving direction of the mixed powder is only a certain direction so as to reduce the collision force.

The firing temperature of the mixed powder must be 550-900 ° C. If the temperature is lower than 550 ° C., the reaction does not proceed, and lithium nitrate remains. If the temperature exceeds 900 ° C., sintering of the mixed powder proceeds, and a spherical lithium-nickel composite oxide cannot be obtained. To avoid these effects,
More preferably, the firing temperature is preferably from 600 to 730C.

Since the lithium content tends to slightly decrease during firing, the mixing molar ratio of Li / metal element in the mixed slurry of lithium nitrate and nickel compound is preferably equimolar or a small excess of lithium. / Metal element mixture molar ratio is 1.00 ≦ Li / metal element ≦ 1.
05 is more preferable.

The firing time of the mixed powder may be appropriately selected depending on the firing temperature, the firing method and the like. The firing of the mixed powder is preferably carried out in an oxygen-containing atmosphere such as air in order to promote oxidation, and the oxygen partial pressure is preferably higher. In addition, since water and carbon dioxide in the gas may cause generation of impurities and aggregation of spherical particles, it is preferable to remove as much as possible, and it is more preferable to remove the gas in pure oxygen. During the firing, the oxygen partial pressure is reduced by a decomposition gas or the like generated during the firing, and therefore it is preferable to perform the firing while flowing the gas in the furnace. It is preferable to appropriately adjust the gas flow rate so that the mixed powder during firing is not discharged out of the firing furnace system accompanying the flowing gas.

The lithium / nickel composite oxide after calcination may contain not only spherical powder but also agglomerates of several spherical particles. Not suitable for making batteries 5
It is preferable to remove particles having a size of 0 μm or more by classification or the like.

In general, powder composed of spherical particles has a large bulk density, but if the particle size distribution is narrow, the bulk density may be difficult to increase. If the bulk density of the spherical lithium-nickel composite oxide after firing is difficult to increase, synthesize spherical lithium-nickel composite oxides with different particle sizes as necessary and mix them in an appropriate ratio to obtain a bulk density. It is preferable that the mixture is mixed or mixed powders having different particle sizes are mixed as necessary, followed by baking.

The spherical lithium-nickel composite oxide obtained by the present invention has a large discharge capacity because it uses lithium nitrate as a starting material. In addition, since the obtained particles are spherical, the density of the electrode is increased due to the high bulk density, so that a battery having a high energy density can be manufactured.

[0025]

【Example】

Example 1 694.1 g (10.1 mol) of commercially available lithium nitrate was dissolved in pure water to prepare 10 L of a 1.01 mol / L aqueous solution of lithium nitrate. 946.6 g (10.0 mol) of commercially available nickel hydroxide pulverized to an average particle diameter of 3 μm or less with a vibration mill was added to the aqueous lithium nitrate solution, and the mixture was stirred and mixed for 20 hours. This mixed slurry was spray-dried with a spray drier to obtain a spherical mixed powder. It was confirmed by a scanning electron microscope that it was spherical. The spherical mixed powder was dried in a dryer at 100 ° C. for 15 hours, and then 1000 g was charged into a rotary kiln having a column placed horizontally. After covering the portion corresponding to the bottom of the cylinder except for the gas inlet / outlet, the rotary kiln was rotated at about 1 rpm while flowing oxygen gas, and the temperature was increased at 200 ° C./h to 70 ° C.
The calcination was carried out at 0 ° C. for 10 hours. The calcined powder taken out after cooling was passed through a 200-mesh sieve to obtain a positive electrode active material. The XRD diffraction peak of this positive electrode active material was obtained from the card No. of the powder diffraction data file of JCPDS. 9
-0063 (hereinafter described as JCPDS / 9-0063) almost coincides with the diffraction peak of LiNiO ₂ ,
No other diffraction peaks were observed. When the shape was observed with a scanning electron microscope, the shape was spherical.

The tap density was measured by the following method.
First, about 45 to 50 ml of the positive electrode active material was
and placed in a 1 graduated cylinder and weighed. Next, the measuring cylinder was lightly tapped on a rubber plate, and the volume was read every minute until the volume no longer changed. The value obtained by dividing the weight of the used positive electrode active material by the convergence value of the capacity was defined as the tap density.
As a result, the tap density was 2.50 g / cm ³ .
In order to examine the battery characteristics of the synthesized lithium-nickel composite oxide, the lithium-nickel composite oxide, acetylene black as a conductive material, and polyfluoroethylene as a binder were kneaded at a predetermined weight ratio and formed into pellets. To make a positive electrode. A button-type battery was assembled using metallic lithium as the negative electrode and a propylene carbonate / diethyl carbonate mixed solution in which lithium hexafluorophosphate was dissolved at 1 mol / l. To check the performance of this battery,
After charging to 4.3 V at a constant current of 0.5 mA / cm ^2, the battery was discharged to 3.0 V and the discharge capacity was measured. Table 1 shows the results.

Example 2 The commercially available nickel hydroxide of Example 1 was replaced with the commercially available nickel hydroxide.
Kel 757.3 g (8.0 mol) and commercially available hydroxide
The mixture was changed to a mixture of 189.2 g (2.0 mol).
Except for this, the procedure was the same as in Example 1. X of this positive electrode active material
RD diffraction peak is a powder diffraction data file of JCPDS
Card No. 9-0063 LiNiO₂Diffraction peak
Approximately matches the peak, and no other diffraction peaks were seen
Was. LiNiO₂And the same crystalline phase of LiNi_0.8Co
_0.2O₂Is considered to have been generated. Also, the shape
When observed with a scanning electron microscope, the shape was spherical.
Was. When the tap density was examined in the same manner as in Example 1, 2.
56g / cm³Met. Synthesized lithium nickel
The battery characteristics of the composite oxide were measured in the same manner as in Example 1.
Was. Table 1 shows the results.

Comparative Example 1 A spherical mixed powder obtained in the same manner as in Example 1 was dried in a drier.
After drying at 00 ° C for 15 hours, the mixture was charged into an alumina crucible,
It was left still in a box type firing furnace. Do not allow oxygen gas to flow
The temperature was raised to 700 ° C at 200 ° C / h and
The firing was performed while holding for 0 hour. Baking taken out after cooling
The whole thing was solidified in the alumina crucible. The fired product
After crushed roughly in a mortar, crushed in a ball mill for 1 hour and collected
The powder passed through a 200 mesh sieve was used as the positive electrode active material.
did. The XRD diffraction peak of this positive electrode active material is JCPDS
/ 9-0063 LiNiO ₂Almost coincides with the diffraction peak of
No other diffraction peaks were observed. Scan shape
When observed with a scanning electron microscope, the shape was rocky.
Was. When the tap density was examined in the same manner as in Example 1, 2.
00g / cm³Met. Synthesized lithium nickel
The battery characteristics of the composite oxide were measured in the same manner as in Example 1.
Was. Table 1 shows the results.

Comparative Example 2 The lithium nitrate of Example 1 was replaced with lithium hydroxide monohydrate 42.
Example except that it was changed to 2.3 g (10.1 mol)
This was performed in the same manner as in Example 1. XRD diffraction of this positive electrode active material
The peak is LiNiO of JCPDS / 9-0063. ₂Times
Almost coincides with the diffraction peak and no other diffraction peaks are seen.
won. The shape was observed with a scanning electron microscope.
After all, the shape was spherical. Tap density as in Example 1.
Was found to be 1.82 g / cm³Met. Synthesize
The battery characteristics of the lithium-nickel composite oxide obtained in Example 1
The measurement was performed in the same manner as described above. Table 1 shows the results.

Comparative Example 3 The same procedure as in Example 1 was carried out except that the sintering temperature in Example 1 was changed from 700 ° C. to 500 ° C. XRD of this positive electrode active material
The diffraction peak shows LiNi of JCPDS / 9-0063.
In addition to the diffraction peak of O _2, seen the peak of LiNO ₃ of JCPDS / 8-0046, reaction was not completely finished. Since it is obvious that the battery characteristics are poor due to the inclusion of impurities, the measurement of the battery characteristics and the measurement of the tap density were not performed.

[0031]

[Table 1]

[0032]

The spherical lithium / nickel composite oxide of the present invention for a lithium battery positive electrode has excellent physical properties such as a large discharge capacity, and has a high bulk density due to the spherical and high density of the sphere itself. And the density of the electrode increases,
It is a positive electrode material that is superior to conventional lithium-nickel composite oxides.

Claims (8)

[Claims] 1. A mixed slurry of lithium nitrate and a nickel compound is spray-dried, and the resulting mixed powder composed of spherical particles is continuously or intermittently moved in a firing furnace.
A method for producing a spherical lithium / nickel composite oxide, characterized by firing at 50 to 900 ° C. 2. The method for producing a spherical lithium-nickel composite oxide according to claim 1, wherein the metal element in the nickel compound contains 25 mol% or less of a metal element other than nickel. 3. The method for producing a spherical lithium-nickel composite oxide according to claim 1, wherein the metal element in the nickel compound is a hydroxide or an oxide containing 25 mol% or less of a metal element other than nickel. . 4. A mixed slurry of lithium / metal element in a mixed slurry of lithium nitrate and a nickel compound having a mixing molar ratio of 1.0 to 1.0.
4. The condition of 0 ≦ lithium / metal element ≦ 1.05.
Item 14. The method for producing a spherical lithium-nickel composite oxide according to any one of the items. 5. The method for producing a spherical lithium-nickel composite oxide according to claim 1, wherein the calcination is performed while flowing oxygen through a calcination furnace. 6. The spherical lithium powder according to claim 1, wherein the solvent of the mixed slurry is water.
A method for producing a nickel composite oxide. 7. The metal element other than nickel is cobalt,
7. Iron or manganese or a mixture thereof.
Item 14. The method for producing a spherical lithium-nickel composite oxide according to any one of the items. 8. A nonaqueous electrolyte battery using the spherical lithium / nickel composite oxide according to claim 1 as a positive electrode.