JP2001199728A - Lithium cobaltate and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain lithium cobaltate suitable as an anode material for a lithium ion secondary battery having a high capacity and excellent in cycle characteristics. SOLUTION: This lithium cobaltate is characterized by the first point of inflection obtained by suspending 1.0 g lithium cobaltate in 100 ml ion-exchanged water, and titrating the resultant suspension with 0.1 N diluted nitric acid solution while stirring the suspension, and present at <=1.0 ml titrating amount of the diluted nitric acid solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a lithium cobalt oxide and a method for producing the same, and more particularly to a lithium active material having a particularly high discharge capacity as a positive electrode active material for a non-aqueous electrolyte secondary battery.
The present invention relates to a lithium cobalt oxide useful for improving the cycle characteristics of a secondary battery and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, portable and cordless electronic devices such as AV devices and personal computers have been rapidly advanced, and there has been a demand for small, lightweight and high energy density secondary batteries as power sources for driving these devices. Is getting higher. Under such circumstances, lithium-ion secondary batteries have attracted attention because of their high charge / discharge voltage and large charge / discharge capacity.

Conventionally, as a positive electrode material useful for a high-energy type lithium ion secondary battery having a voltage of 4 V class, LiMn ₂ O ₄ having a spinel structure, LiMnO ₂ , LiCoO having a rock salt structure have been used.
₂ , LiCo1-X NiXO ₂ , LiNiO _{2 and the} like are generally known. Among them, LiCoO ₂ is advantageous in that it has high voltage and high capacity.

However, generally, the synthesis of LiCoO ₂ is
When mixing powders of Li ₂ CO ₃ and Co ₃ O ₄ by dry method, uniform mixing is difficult due to the difference in specific gravity of each powder, so that the composition after firing is not constant, cobalt oxide or lithium carbonate This may cause problems such as the presence of residual impurities and the incorporation of impurities due to abrasion of the material of the dry mixing apparatus, which may lead to variations in quality and a reduction in capacity.

[0005] Conventionally, there are the following three means for developing a material for improving the variation in material performance and the reduction in capacity. Mixture of lithium ions and cobalt ions.
5966, JP-A-6-44970, WO98 / 29915 and the like.

Mixing of Metal Oxide Powder and Soluble Lithium by Suspension in Water
1799, JP-A-10-106562, JP-A-11-240721 and the like.

Mixing of a metal oxide powder and lithium carbonate in an aqueous medium.
299, JP-A-10-27613, JP-A-10-279315 and the like.

[0008] In the case of the above-mentioned type, in JP-A-5-325966 and JP-A-6-44970, lithium and the transition metal are mixed in an ionic state in an aqueous solution, so that the mixed state is uniform. And segregation at the same time, and the desired homogeneous mixed state may not be maintained. Also,
In WO98 / 29915, it is reported that a uniform mixed state can be obtained by mixing ions, adding a complexing agent and then spray drying, but there are technical limitations and industrial problems, and Not satisfactory. On the other hand, in the case of the above type, since only Li is in an ionic state,
When drying by spray drying or the like, Li may become a mist and evaporate, leading to a change in composition. Furthermore, in the case of the above-mentioned type, even if the dried cobalt oxide or hydrated cobalt oxide is once suspended in an aqueous solution, the aggregates formed during drying cannot be easily disintegrated, so that a variation in the composition occurs. It is necessary to use a very large crushing force to cause the dispersion to completely disperse the primary particles.Therefore, there is a possibility of causing contamination due to abrasion of the apparatus, etc. Insufficient for lithium production.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a lithium cobaltate which is excellent in composition homogeneity and purity and is useful as a positive electrode active material for a non-aqueous electrolyte secondary battery. It is to provide a manufacturing method.

[0010]

That is, the first object of the present invention to achieve the above object is to provide a lithium cobaltate of 1.0 g.
Is suspended in 100 ml of ion-exchanged water, and the initial inflection point obtained by titrating a 0.1 N diluted nitric acid solution with stirring is 1.0 ml or less as a titer of the diluted nitric acid solution. The present invention provides lithium cobalt oxide having the following properties (claim 1).

A second aspect of the present invention for producing the above-mentioned lithium cobalt oxide is that when a mixture of cobalt oxide and a lithium compound is calcined to produce lithium cobalt oxide, the cobalt oxide obtained by wet synthesis is washed with water. Then, without going through a drying step, by reslurrying and adding a lithium compound, after mixing in a liquid state, a mixture of cobalt oxide and the lithium compound is dehydrated and dehydrated.
It is intended to provide a method for producing lithium cobalt oxide, characterized by drying and firing.

In a preferred embodiment, the mother liquor used for reslurrying is a saturated aqueous solution of a lithium compound. The method for producing lithium cobaltate according to claim 2 (claim 3).

In a preferred embodiment, the method for producing lithium cobaltate according to claim 2 or 3, wherein the concentration of cobalt oxide during reslurrying is 50 to 500 g / liter. 4).

In a preferred embodiment, the Li / Co molar ratio of the mixture of cobalt oxide and the lithium compound is 0.97 to 1.05, wherein the lithium cobaltate according to any one of claims 2 to 4 is used. This is a manufacturing method (claim 5).

In a preferred embodiment, the method for producing lithium cobalt oxide according to any one of claims 2 to 5, wherein the mixture is formed after dehydrating a mixture of cobalt oxide and a lithium compound. 6).

In a preferred embodiment, the molded product of the mixture of cobalt oxide and lithium compound has a molded density after drying of 1.5 to 3.0 g / ml. It is a method (claim 7).

A preferred embodiment is the method for producing lithium cobaltate according to any one of claims 2 to 7, wherein the lithium compound is lithium carbonate (claim 8).

Conventionally, as the performance of lithium cobalt oxide,
By performing composition analysis and structure analysis of the lithium cobalt oxide powder, it is a minimum necessary condition that impurities such as cobalt oxide and lithium compound do not remain. The control technology was inadequate because it was difficult to analyze a trace amount of impurity composition that greatly affected the characteristics. The inventors of the present invention synthesized lithium cobalt oxide using parameters such as the Li / Co mixing ratio, the mixing method, and the sintering temperature, and analyzed and examined the results. It was found that the pH behavior was different when the dilute nitric acid solution was titrated in spite of the same.

As a result of examining the cause of this difference, it was found that the dilute nitric acid titer at which the first inflection point of the titration curve was obtained differs between those having a large amount of lithium and those having a small amount of lithium other than those contained in the lithium cobaltate crystal. It was found that lithium cobaltate, which exhibits the first inflection point with a small amount of dilute nitric acid added, is more excellent in the stability, capacity and cycle characteristics of the paint.

Therefore, in order to synthesize lithium cobalt oxide having excellent capacity and cycle characteristics, first, a homogeneous firing reaction is important. For that purpose, a more homogeneous mixed state can be obtained. We thought that it was important to establish a synthesis method that would enable precise control of the composition, and as a result of intensive studies, we arrived at the present invention.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
Lithium cobaltate of the present invention is lithium cobaltate 1.
0 g was suspended in 100 ml of ion-exchanged water.
The first inflection point (first inflection point) obtained by titrating a prescribed dilute nitric acid solution is not more than 1.0 ml as a titer of the dilute nitric acid solution. As lithium cobalt oxide having improved battery capacity and cycle characteristics, it is important that impurities such as cobalt oxide and lithium compounds other than lithium cobalt oxide are small, but the lithium cobalt oxide of the present invention satisfies these requirements. Things.

That is, the presence or absence of impurities in the lithium cobalt oxide powder can be confirmed by, for example, structural identification by powder X-ray diffraction or elemental analysis by ICP. It is difficult to specify cobalt or lithium of lithium cobaltate, cobalt of cobalt oxide, lithium of a lithium compound, and the like. For example, even if the mixture is substantially a mixture of lithium cobaltate, cobalt oxide, and a lithium compound, It can happen that each element of the cobalt and lithium compounds happens to be 1: 1 by chance. In powder X-ray diffraction,
In many cases cannot be detected with the content of. Therefore, it is difficult for these analytical methods to measure the purity of lithium cobaltate, and the technology for controlling the purity is also insufficient. However, according to the present invention, by showing the first inflection point of the titration curve with a specific amount of diluted nitric acid added,
Lithium cobaltate with reduced impurities is provided.

In order to obtain the above-mentioned lithium cobalt oxide, it is important to carry out a homogeneous firing reaction, and for that purpose, the mixed state of the cobalt oxide and the lithium compound must be uniform. To obtain a uniform mixing state,
Cobalt oxide must be in a monodispersed state, so after being made by an oxidative precipitation reaction in an aqueous solution,
It is important to use a re-slurried cobalt oxide as a precursor after being sufficiently washed with water to remove anionic species and the like.

At this time, the method of washing with water may be a method of repeating dilution or concentration, such as decantation, or a method of performing continuous washing, a method of washing with ion-exchanged water after filtration, and a method of washing before reslurry. If no drying treatment is performed, there is no particular limitation. Once dried after washing with water, it is difficult to obtain a monodispersed state, and when a lithium compound is added, a uniform mixed state of cobalt oxide and the lithium compound cannot be obtained.

The mixture of cobalt oxide and lithium compound preferably has a Li / Co ratio of 0.97 to 1.05. Li / Co ratio is
If the ratio is less than 0.97, the residual amount of cobalt oxide in the product after the firing reaction increases, which causes a decrease in the battery capacity and an increase in the Li / Co ratio.
If it exceeds 1.05, the residual amount of lithium carbonate in the product after the calcination reaction increases, which causes a decrease in battery capacity.
A more preferred range of the Li / Co ratio after drying of the mixture is 0.98
~ 1.02.

The concentration of cobalt oxide at the time of reslurrying is preferably 50 to 500 g / liter. When the re-slurried concentration of cobalt oxide is less than 50 g / l, productivity is deteriorated, which is not preferable. When the concentration exceeds 500 g / l, the viscosity at the time of mixing with the lithium compound becomes too high, resulting in a uniform mixing. Difficult to achieve state. More preferably, 100 to 350 g / liter, and still more preferably, 150 to 30 g / l.
0 g / liter.

The mother liquor for reslurrying the cobalt oxide after washing is preferably a saturated solution of a lithium compound used for mixing. As the lithium compound used for mixing, lithium carbonate, lithium oxide, lithium hydroxide,
Lithium hydroxide monohydrate and the like can be mentioned, and particularly in the case of mixing in an aqueous solution, it is preferable to use lithium carbonate from the viewpoint of solubility. From the viewpoint of cost, it is preferable to repeatedly use this solution.

The mixture of cobalt oxide and lithium compound obtained as described above is dehydrated, dried and fired. The mixture is preferably formed into pellets or the like after dehydration and then fired. The density of the mixture after drying is preferably 1.5 to 3.0 g / ml. If the amount is less than 1.5 g / ml, the molded product has low strength, so that powdering is likely to occur.
If it exceeds / ml, the hardness of the molded article after firing becomes high, and as a result, strong pulverization is required and the risk of contamination is increased. The mixture is calcined in the form of a dewatered cake or pellets, or in a state where these are pulverized. The calcination is performed in an atmosphere containing oxygen, preferably in air.
The firing temperature is usually from 700 to 1000C, and the firing time is usually from 2 to 20 hours. The fired product is
It is pulverized by a conventional method to obtain lithium cobaltate particles.

When the lithium cobaltate of the present invention is used as a positive electrode active material for a non-aqueous electrolyte secondary battery,
The negative electrode active material is not particularly limited, and for example, a lithium metal, a lithium alloy, or a substance capable of inserting and extracting lithium can be used. For example, lithium / aluminum alloy, lithium / tin alloy, graphite, graphite and the like can be mentioned.

The electrolyte is not particularly limited, either. For example, lithium perchlorate, quaternary carbonate or the like is used in at least one organic solvent such as carbonates such as propylene carbonate, diethyl carbonate and dimethyl carbonate, and ethers such as dimethoxyethane. A solution in which at least one lithium salt such as lithium fluoroborate and lithium hexafluorophosphate is dissolved can be used.

[0031]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. still,
The identification and crystal structure of the reaction product powder were determined by X-ray diffraction (RI
GAKU Cu-Kα 40kV 40mA). The morphology of the particles was observed with a transmission electron microscope (manufactured by Hitachi, Ltd.) and a scanning electron microscope (manufactured by JEOL). Furthermore,
The BET specific surface area was measured by a nitrogen adsorption method.

Example 1 As a precursor, first, 10 liters of a solution obtained by mixing 4.0 liters of a 1.5 mol / l cobalt sulfate solution, 2.448 liters of a 5.0 mol / l sodium hydroxide solution and 3.552 liters of ion-exchanged water were oxidized. Temperature to ℃
The cobalt oxide (BE
(T specific surface area = 31 m ² / g) was washed with water and filtered to form a cake. A portion of the cobalt oxide was dried and subjected to powder X-ray diffraction measurement. As a result, it was found that the obtained cobalt oxide was a single phase of Co ₃ O ₄ as shown in FIG. After the content of cobalt oxide in the remaining cake was determined, a cake corresponding to 250 g of cobalt oxide was reslurried using a saturated solution of lithium carbonate (30 ° C.) so that the total volume became 1 liter. 117.36 in 1 liter of this slurry
g (1.02 as Li / Co ratio) of lithium carbonate,
After stirring for 0 minutes, after performing dehydration treatment at 0.1 MPa,
It was formed into pellets by an extruder and dried at 60 ° C. for 12 hours. The scanning electron micrograph after drying is shown in FIG. The large particles observed in this photograph are lithium carbonate particles having a particle size of about 5 μm, and the cobalt oxide particles adsorbed around them. From this photograph, it can be seen that the mixture is in an extremely excellent state. The density of the molded dried product was 1.8 g / ml. The dried product is placed in the air at 850
After sintering at 10 ° C. for 10 hours and pulverization, lithium cobalt oxide particles having a single phase and an average particle diameter of 5 μm were obtained. 1.0 g of this lithium cobaltate is suspended in 100 ml of ion-exchanged water,
The result of titration of the 0.1 mol / l dilute nitric acid solution with stirring is shown in FIG. 3. The titration point of 0.7 ml of the dilute nitric acid solution showed the first inflection point.

(Configuration of Battery Cell) 8.7 g of lithium cobalt oxide thus obtained, 0.5 g of acetylene black as a conductive agent, and 0.8 g of polytetrafluoroethylene as a binder were mixed in a mortar. After mixing N-methyl-2-pyrrolidone as a solvent, coating and drying on Al foil, 15.8
A 5 mm disc was punched out to produce a positive electrode mixture. A lithium foil was used for the negative electrode, and a solution prepared by dissolving lithium hexafluorophosphate in a solvent in which propylene carbonate and dimethyl carbonate were mixed at a volume ratio of 1: 1 at a concentration of 1 M was used as the electrolytic solution.

(Evaluation) Using this battery cell, 0.5 mA / cm
^At a constant current of ² , charging and discharging were repeated at a battery voltage of 3.0 V to 4.2 V.

The initial discharge capacity is 145 mAH / g, the discharge capacity in the 20th cycle is 140 mAH / g, and the discharge capacity in the first cycle is 97 mAH / g.
% Had been maintained. In addition, about the charge / discharge evaluation of the following Example and the comparative example, it measured on the same conditions using the battery cell of all the same structures.

Example 2 Lithium cobaltate was produced in the same manner as in Example 1 except that the sintering temperature was 900 ° C. Table 1 shows manufacturing conditions and characteristics of lithium cobalt oxide.

Example 3 The weight of lithium carbonate to be added was 116.21 g (as a Li / Co ratio).
1.01), and a lithium cobalt oxide was produced in the same manner as in Example 1 except that the firing temperature was 900 ° C. Table 1 shows manufacturing conditions and characteristics of lithium cobalt oxide. The obtained lithium cobaltate had an average particle diameter of 10 μm, as is clear from the scanning electron micrograph shown in FIG.

Example 4 The weight of lithium carbonate to be added was 115.06 g (as a Li / Co ratio).
1.00), and a lithium cobaltate was produced in the same manner as in Example 1 except that the firing temperature was 900 ° C. Table 1 shows manufacturing conditions and characteristics of lithium cobalt oxide. As shown in FIG. 5, the obtained lithium cobaltate was a single phase of lithium cobaltate as in the other examples.

Example 5 A dehydration treatment was performed at a pressure of 0.3 MPa, and a firing temperature was 900 ° C.
A lithium cobalt oxide was produced in the same manner as in Example 1 except that the above conditions were satisfied. Table 1 shows manufacturing conditions and characteristics of lithium cobalt oxide.

Example 6 Lithium cobaltate was produced in the same manner as in Example 4 except that the dehydration treatment was performed at a pressure of 0.2 MPa. Table 1 shows manufacturing conditions and characteristics of lithium cobalt oxide.

Example 7 Lithium cobaltate was produced in the same manner as in Example 6, except that the sintering temperature was 800 ° C. Table 1 shows manufacturing conditions and characteristics of lithium cobalt oxide.

Comparative Example 1 After washing the cobalt oxide obtained in Example 1 with water, 250 g of the dried cobalt oxide was reslurried using a saturated solution of lithium carbonate (30 ° C.). To 1 liter of this slurry, 116.21 g (1.01 as Li / Co ratio) of lithium carbonate was added, stirred for 30 minutes, dehydrated at 0.2 MPa, formed into pellets, and then heated at 60 ° C.
Dried for 12 hours. The density of the obtained molded dried product is 2.2 g / ml
Met. The dried product is fired at 900 ° C for 10 hours in air.
As a result of X-ray diffraction, diffraction lines of cobalt oxide (Co ₃ O ₄ ) as well as lithium cobalt oxide were observed.
Table 1 shows manufacturing conditions and characteristics of lithium cobalt oxide.

Comparative Example 2 The amount of lithium carbonate to be added was 120.81 g (Li / Co ratio was 1.
Baking was performed in the same manner as in Comparative Example 1 except that the above was changed to 05). As a result of powder X-ray diffraction of the obtained sample, it was found that the sample was a single-phase lithium cobalt oxide. Table 1 shows manufacturing conditions and characteristics of lithium cobalt oxide.

COMPARATIVE EXAMPLE 3 The cobalt oxide obtained in Example 1 was washed with water, dried and treated with 50 g of cobalt oxide and 23.01 g (Li / Co ratio of 1.10 g).
00) lithium carbonate in an automatic raikai machine for 30 minutes,
Pellet molding was performed with a mold at a pressure of 100 MPa. The density of the obtained molded product was 2.5 g / ml. A sample obtained by firing this molded product in the same manner as in Example 1 was
From the X-ray diffraction results, it was found that cobalt oxide (Co ₃ O ₄ ) remained in addition to lithium cobalt oxide. Table 1 shows manufacturing conditions and characteristics of lithium cobalt oxide.

Comparative Example 4 A fired sample was obtained in the same manner as in Comparative Example 3 except that the amount of lithium carbonate was changed to 24.16 g (as a Li / Co ratio: 1.05). From the result of X-ray diffraction of the obtained sample, it was found that lithium carbonate (Li ₂ CO ₃ ) remained in addition to lithium cobaltate. Table 1 shows the production conditions and characteristics of lithium cobalt oxide.
Shown in

[0046]

[Table 1]

As is clear from Table 1, in Examples 1 to 7, all single-phase lithium cobalt oxides were obtained.
Further, the titration analysis shows that the titration of the dilute nitric acid solution showing the first inflection point is 1.0 ml or less, indicating that the discharge capacity is high and the cycle stability is excellent. In addition, no re-aggregation during coating was observed.

On the other hand, as shown in Comparative Examples 1 and 2, when the dried cobalt oxide particles were reslurried and mixed, the cobalt oxide remained when the Li / Co ratio was about 1.01 (Comparative Example 1). In order to completely react the cobalt oxide, the Li / Co ratio at the time of mixing must be set to a large value. Therefore, a slight diffraction line of Li ₂ CO ₃ is observed in the X-ray diffraction, and the first deviation by titration is observed. Since the inflection point is larger than 1.0 ml, it can be seen that lithium carbonate remains (Comparative Example 2). Therefore, although the cobalt oxide as the precursor is equivalent, as a result, it has been found that the initial discharge capacity is low because the coating once passed through the drying step, and that the characteristics are not sufficient in the cycle stability. In addition, as shown in Comparative Examples 3 and 4, cobalt oxide tends to remain in some cases by dry mixing, and when it was attempted to avoid this, the presence of lithium carbonate was recognized from the results of X-ray diffraction. It is also found that the amount of the diluted nitric acid solution corresponding to the first inflection point is larger than 1.0 ml, and that the residual alkali component is large.

From the above results, according to the present invention, the homogeneity of the mixture of the cobalt oxide and the lithium compound is increased, and as a result, the homogeneity of the two during the calcination reaction is increased, and the mixing of the cobalt oxide and lithium carbonate is improved. It is considered that the unreacted components could be reduced and the crystallinity of lithium cobaltate itself was also improved. The reason for this is that, since the process up to mixing is performed in an aqueous medium consistently, a mixed state in which the fine particles of cobalt oxide are in close contact with lithium carbonate is obtained, which improves the degree of completion of the firing reaction. It is considered to be.

[0050]

As described above, the lithium cobaltate of the present invention has a small amount of impurities and is excellent in capacity and cycle performance as a positive electrode active material of a lithium ion secondary battery, for example. Further, according to the production method of the present invention, a mixed state having excellent reactivity between cobalt oxide and a lithium compound can be obtained, and the Li / Co ratio can be precisely controlled. By calcining, lithium cobalt oxide with few impurities can be produced.

[Brief description of the drawings]

FIG. 1 shows a precursor (cobalt oxide Co ₃ O ₄ ) used in Example 1.
FIG. 2 is a view showing a powder X-ray diffraction pattern of the sample.

FIG. 2 is a scanning electron micrograph of a mixture of cobalt oxide and lithium carbonate produced in Example 1 after drying.

FIG. 3 is a diagram showing the results of potentiometric titration of lithium cobaltate produced in Example 1.

FIG. 4 is a scanning electron micrograph of lithium cobaltate produced in Example 3.

FIG. 5 is a view showing a powder X-ray diffraction pattern of lithium cobaltate produced in Example 4.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hiroyasu Watanabe 1-1-1 Shinoki, Onoda-shi, Yamaguchi Prefecture Inside the Onoda Plant of Toda Kogyo Co., Ltd. (72) Mitsuaki Hataya 1-1-1, Shinoki, Onoda-shi, Yamaguchi Prefecture No. 1 Toda Kogyo Co., Ltd. Onoda Plant (72) Inventor Hideaki Sadamura 1-1-1, Shinoki, Onoda City, Onoyama, Yamaguchi Prefecture F-term 4G048 AA04 AB01 AB02 AB05 AC06 AE05 5H029 AJ02 AJ14 AK03 AL06 AL12 AM03 AM05 AM07 CJ02 CJ08 CJ12 HJ02 HJ08 HJ10 5H050 AA02 AA19 BA17 CA08 CB07 FA17 GA02 GA10 GA12 HA02 HA08 HA10

Claims (8)

[Claims] 1. The first inflection point obtained by suspending 1.0 g of lithium cobaltate in 100 ml of ion-exchanged water and titrating a 0.1 N dilute nitric acid solution with stirring is determined by titration of the dilute nitric acid solution. Lithium cobaltate having a content of 1.0 ml or less. 2. A method for producing lithium cobalt oxide by calcining a mixture of cobalt oxide and a lithium compound, wherein the cobalt oxide obtained by wet synthesis is washed with water and reslurried without a drying step to convert the lithium compound. By adding, after mixing in a liquid phase state, the mixture of cobalt oxide and lithium compound is dehydrated and dried,
A method for producing lithium cobalt oxide, characterized by firing. 3. The method for producing lithium cobaltate according to claim 2, wherein the mother liquor used for reslurrying is a saturated aqueous solution of a lithium compound. 4. The method according to claim 2, wherein the concentration of cobalt oxide during reslurrying is 50 to 500 g / l.
Or the method for producing lithium cobaltate described in 3. 5. The method for producing lithium cobaltate according to claim 2, wherein the molar ratio of Li / Co of the mixture of cobalt oxide and the lithium compound is 0.97 to 1.05. 6. A molding after dehydrating a mixture of cobalt oxide and a lithium compound.
The method for producing lithium cobaltate according to any one of the above. 7. The method for producing lithium cobaltate according to claim 6, wherein the molded density of the molded product of the mixture of cobalt oxide and lithium compound after drying is 1.5 to 3.0 g / ml. 8. The method for producing lithium cobaltate according to claim 2, wherein the lithium compound is lithium carbonate.