JP2005206422A - High density lithium cobaltate and its producing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide lithium cobaltate as a positive electrode active material for a lithium secondary battery, which can be filled in a high density and is excellent in charge and discharge characteristic. <P>SOLUTION: The method for producing lithium cobaltate comprises mixing a cobalt compound characterized in that 10% volume particle diameter obtained by wet particle size distribution measurement is 3-8 μm, 50% volume particle diameter is 5-15 μm, 90% volume particle diameter is 15-25 μm, 100% volume particle diameter is 20-60 μm, the bulk density is 1.00-2.00 g/cm<SP>3</SP>, the TAP density is 1.50-3.00 g/cm<SP>3</SP>, and the ratio of the bulk density to the TAP density is 0.50-0.80, and a lithium compound characterized in that 10% volume particle diameter obtained by wet particle size distribution measurement is 0.5-7 μm, 50% volume particle diameter is 5-21 μm, 90% volume particle diameter is 20-50 μm, and 100% volume particle diameter is 30-80 μm, in a ratio of Li to Co of 0.97-1.015, and firing only once the resulting mixture in an atmosphere containing oxygen in an amount of 12-20 vol.% while injecting dried air. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a high-density lithium cobalt oxide that can be filled at a high density and has excellent charge / discharge characteristics, and a method for producing the same at low cost.

  Lithium cobalt oxide has already been put into practical use as a positive electrode material for lithium ion secondary batteries. In recent years, lithium ion secondary batteries have been widely used in various fields such as automobiles, personal computers, mobile phones, and the like, and an increase in battery capacity has become an urgent issue to cope with an increase in power consumption. .

  The theoretical capacity of lithium cobalt oxide is large (274 mAh / g), but in actual batteries, only about 60% of the theoretical capacity is used. This is because the actual capacity of the battery varies somewhat depending on the selection of raw materials, composition, firing method, and the like, but usually does not change dramatically within the voltage range used. Therefore, in order to increase the capacity of the lithium ion secondary battery, it can be said that the most efficient means is to increase the filling amount of the active material per unit volume in the battery.

  Conventionally, as a method of filling more active materials per unit volume, for example, primary particles of lithium cobaltate, which is an active material, are greatly grown to improve the filling performance of the powder itself, thereby improving the electrode density. (Refer to Patent Document 1) Also, focusing on charge / discharge performance, preparing an electrode using lithium cobaltate that does not grow the primary particle size, and pressing the electrode with a very large pressure Is adopted.

  As a method for growing primary particles of lithium cobalt oxide, in a solid phase method in which a raw material mixture obtained by mixing a lithium compound and a cobalt compound is directly subjected to solid reaction, the Li / Co molar ratio is increased, A method of firing the raw material mixture at a high temperature is common. From the viewpoint of emphasizing the charge / discharge performance of the obtained battery, a trace amount of alkali metal, alkaline earth metal, transition metal or the like is added to the raw material mixture (see Patent Document 2), or in an atmosphere in which the oxygen content is increased. Also known is a method of firing the raw material mixture (see Patent Document 3). In addition, methods for improving the powder density by controlling the particle shape mechanically or controlling the particle size distribution by airflow classification or the like have been studied.

  However, if the growth of the primary particle size is facilitated easily, the handling property at the time of electrode preparation will be lower than the effect obtained thereby, and in the obtained battery, the charge / discharge cycle characteristics will be deteriorated and the high efficiency discharge will be reduced. Various adverse effects on the charge / discharge characteristics such as deterioration occur.

  Further, if a trace amount of alkali metal, alkaline earth metal, transition metal or the like is added to the positive electrode active material, the cycle characteristics of the resulting battery are improved, but there is a disadvantage that the charge / discharge capacity is reduced. Further, since it is hardly possible to improve the filling property by this method, it is necessary to press the electrode with a very large pressure, and as a result, various adverse effects such as breakage of the electrode and handling are caused.

  In addition, firing in an atmosphere with an increased oxygen content, mechanically controlling the particle shape during the manufacturing process, and airflow classification not only increase the manufacturing process, but also loss of raw materials due to the increased process. This is also a major factor in increasing manufacturing costs.

Thus, depending on the conventional method, it is difficult to produce lithium cobalt oxide that can be filled at a high density and has excellent charge / discharge characteristics, and it is also difficult to realize a reduction in production cost. I have to say that.
Japanese Patent Laid-Open No. 10-259027 Japanese Patent Laid-Open No. 10-1316 Japanese Patent Laid-Open No. 10-324522

  As a result of earnest research to obtain lithium cobaltate that can be filled with high density and has excellent charge / discharge characteristics as a positive electrode active material for a lithium ion secondary battery, the present inventors have obtained cobalt as a raw material. The physical properties of each of the compound and the lithium compound are strictly controlled, and the manufacturing conditions are strictly controlled, and the mixture of the raw materials is baked to have predetermined physical characteristics. As a positive electrode active material for a secondary battery, the present inventors have found that lithium cobaltate that can be filled at a high density and has excellent charge / discharge characteristics can be obtained at low cost.

According to the present invention, 10% volume particle size by wet particle size distribution measurement is 3-8 μm, 50% volume particle size is 8-13 μm, 90% volume particle size is 12-25 μm, 100% volume particle size is 20-80 μm. The specific surface area according to the BET method is 0.25 to 0.65 m ² / g, the bulk density is 1.20 to 2.20 g / cm ³ , and the TAP density is 2.30 to 3.00 g / cm ³ . In addition, lithium cobaltate having a bulk density / TAP density ratio in the range of 0.45 to 0.75 is provided.

Furthermore, according to the present invention, the 10% volume particle size is 3 to 8 μm, the 50% volume particle size is 5 to 15 μm, the 90% volume particle size is 15 to 25 μm, and the 100% volume particle size is 20 by wet particle size distribution measurement. -60 μm, bulk density of 1.00 to 2.00 g / cm ³ , TAP density of 1.50 to 3.00 g / cm ³ , and bulk density / TAP density ratio of 0.50 to 0.80. And at least one cobalt compound selected from cobalt carbonate, cobalt oxyhydroxide, cobalt hydroxide and cobalt oxide, and 10% volume particle size by wet particle size distribution measurement is 0.5-7 μm, 50% volume particle Li / Co ratio of at least one lithium compound selected from lithium carbonate and lithium hydroxide having a diameter of 5 to 21 μm, a 90% volume particle size of 20 to 50 μm, and a 100% volume particle size of 30 to 80 μm The lithium cobalt oxide is mixed in the range of .97 to 1.015, and the mixture is fired only once in an atmosphere having an oxygen content of 12 to 20% by volume while blowing dry air. A manufacturing method is provided.

  According to the method of the present invention, the manufacturing process can be simplified by controlling the physical properties of the cobalt compound and the lithium compound used as raw materials. In particular, by performing the firing only once, lithium When used as a positive electrode material for an ion secondary battery, lithium cobalt oxide having high charge density and excellent charge / discharge characteristics can be obtained at low cost. Therefore, by using the lithium cobalt oxide according to the present invention as the positive electrode material for a lithium ion secondary battery, the weight that can be filled per unit volume can be greatly increased, and thus the capacity of the lithium ion secondary battery is remarkably increased. Can be increased.

  First, the manufacturing method of the high-density lithium cobalt oxide according to the present invention will be described. According to the method of the present invention, a cobalt compound and a lithium compound, each having a controlled physical property, are mixed at a predetermined molar ratio to prepare a raw material mixture, and this raw material mixture is subjected to a single operation under predetermined conditions. Only by firing, lithium cobaltate having the desired physical properties can be obtained.

Here, according to the present invention, as the cobalt compound, 10% volume particle size by wet particle size distribution measurement is 3-8 μm, 50% volume particle size is 5-15 μm, 90% volume particle size is 15-25 μm, 100%. The volume particle size is 20 to 60 μm, the bulk density is 1.00 to 2.00 g / cm ³ , the TAP density is 1.50 to 3.00 g / cm ³ , and the bulk density / TAP density ratio is 0.00. At least one selected from cobalt carbonate, cobalt oxyhydroxide, cobalt hydroxide and cobalt oxide in the range of 50 to 0.80 is used.

  According to the present invention, lithium cobaltate is obtained by a solid phase method in which a cobalt compound and a lithium compound are mixed and fired. In the case of such a solid phase method, a uniform lithium cobalt oxide can be obtained by uniformly diffusing lithium ions in the cobalt compound particles during firing of the mixture.

  The 10% volume particle size is a value when the cumulative frequency of the particle size of the powder becomes 10%. This value tends to depend on the primary particles of the powder. According to the present invention, when the 10% volume particle size of the cobalt compound to be used is smaller than 3 μm, not only is the handling property inferior, but the bulk density and TAP density of the resulting lithium cobaltate are lowered, and as a result, the electrode Increase in density is unlikely. On the other hand, when the 10% volume particle diameter of the cobalt compound used exceeds 8 μm, it is difficult to prepare a uniform raw material mixture with the lithium compound, and as a result, lithium cobaltate having a uniform particle shape is obtained. It becomes difficult. Moreover, such a raw material mixture also requires a long time for firing.

  Similarly, the 90% volume particle size is a value when the cumulative frequency of the particle size of the powder reaches 90%, and this value tends to depend on the secondary particle size of the powder. According to the present invention, when the 90% volume particle size of the cobalt compound to be used is smaller than 15 μm, the bulk density and the TAP density of the obtained lithium cobaltate are lowered, and as a result, it is difficult to expect an improvement in the electrode density. On the other hand, when the 90% volume particle diameter of the cobalt compound used exceeds 25 μm, it is difficult to prepare a uniform raw material mixture with the lithium compound, and as a result, lithium cobaltate having a uniform particle shape is obtained. It becomes difficult. Moreover, such a raw material mixture also requires a long time for firing. Regarding the 100% volume particle size of the cobalt compound to be used, the same inconvenience as in the case of the 90% volume particle size occurs outside the above range.

  The 50% volume particle size is a value when the cumulative frequency of the particle size of the powder becomes 50%, and this value tends to depend on both the primary particle size and the secondary particle size of the powder. There is. The measured value tends to depend on the relative balance of the abundance ratio between the primary particle size and the secondary particle size, and is therefore the most important value among the volume particle sizes. According to the present invention, when the 50% volume particle size of the cobalt compound to be used is not in the range of 5 to 15 μm, either or both of 10% and 90% volume particle size will be outside the above specified range. .

  The bulk density is a value obtained by dividing the weight of powder that can be filled in a predetermined container by the volume of the container. In the case of powder, the bulk density includes the space that exists between individual particles. TAP density refers to filling a powder into a predetermined container and then shaking the container up and down under predetermined conditions to eliminate the space between individual particles in the container. In this case, it is a value obtained by dividing the weight of the powder at this time by the volume of the powder.

  Such bulk density and TAP density are closely related to the volume particle size and aggregation state of the powder, and the value of 50% volume particle size and the powder density tend to be proportional. In general, lithium cobaltate having a high powder density tends to have a good filling property in a lithium ion secondary battery. However, as a means of improving the powder density, the primary particles can be easily enlarged. Also, when the powder density is improved by making all the particle shapes spherical or elliptical, the packing density is expected to improve to some extent, but the high capacity of current lithium ion secondary batteries is expected. On the contrary, various adverse effects on charge / discharge characteristics such as deterioration of charge / discharge cycle characteristics, deterioration of high-efficiency discharge in addition to deterioration of handling characteristics during electrode preparation are still insufficient. give. However, according to the present invention, by setting the bulk density and TAP density value of the cobalt compound to be used and the bulk density / TAP density ratio within a certain range, the obtained lithium cobalt oxide has excellent filling properties. It can be shown.

  When lithium cobaltate is produced by a solid phase method as in the method of the present invention, uniform lithium cobaltate can be obtained by diffusing lithium ions into the cobalt compound particles during firing. Therefore, according to the present invention, the cobalt compound to be used preferably has a primary particle diameter of 0.1 to 5 μm and a secondary particle diameter of 5 to 80 μm in SEM (scanning electron micrograph) observation. .

  Next, according to the present invention, as the lithium compound, 10% volume particle size by wet particle size distribution measurement is 0.5-7 μm, 50% volume particle size is 5-21 μm, 90% volume particle size is 20-50 μm, At least one lithium compound selected from lithium carbonate and lithium hydroxide having a 100% volume particle size of 30 to 80 μm is used.

  As described above, in order to obtain lithium cobaltate having a uniform particle shape and excellent charge / discharge characteristics by the solid phase method, lithium ions should be uniformly dissolved in the cobalt compound particles. is important.

  Lithium compounds with a 10% volume particle size smaller than 0.5 μm are very fine, so it seems easy to prepare a uniform raw material mixture with a cobalt compound. Such a lithium compound has a strong cohesive force and a low dispersibility. Therefore, a special apparatus is required to prepare a uniform raw material mixture with the cobalt compound, and the manufacturing cost is increased. In addition, since it is difficult to obtain a uniform raw material mixture with a cobalt compound, the obtained lithium cobaltate has a large variation in the primary particle size, and accordingly, in the obtained battery, charge and discharge are also performed. There is a risk of deterioration of characteristics.

  Similarly, when the 50% volume particle size, 90% volume particle size, and 100% volume particle size of the lithium compound to be used are out of the above specified range, uniform mixing with the cobalt compound becomes difficult and obtained. As a result, it takes a long time to fire the mixture. Thus, the obtained lithium cobaltate is concerned about variations in the primary particle diameter and associated charge / discharge characteristics.

Furthermore, according to the present invention, the lithium compound used has a bulk density of 0.2 to 0.8 g / cm ³ , a TAP density of 0.31 to 1.5 g / cm ³ and a bulk density / TAP density ratio. Is preferably in the range of 0.20 to 0.80. When these characteristics deviate from the above specified values, it is difficult to uniformly mix with the cobalt compound as in the case of the volume particle size, and there is a risk that it may take a long time to fire the obtained mixture. Because there is.

  Further, the lithium compound to be used preferably has a primary particle diameter in the range of 0.1 to 30 μm and a secondary particle diameter in the range of 5 to 80 μm in SEM observation. When the primary particle diameter of the lithium compound by SEM observation exceeds 30 μm, it is difficult to obtain a uniform mixture with the cobalt compound, and it takes a long time to fire such a mixture. Lithium is concerned about variations in the primary particle size and associated reduction in charge / discharge characteristics.

  According to the present invention, a cobalt compound and a lithium compound as described above are mixed in a Li / Co molar ratio in the range of 0.97 to 1.015, the raw material mixture is positioned, and the dew point is 0 ° C to- While blowing dry air adjusted to a range of 80 ° C., this raw material mixture was calcined at a temperature in the range of 900 to 1200 ° C. for 3 to 15 hours in an atmosphere having an oxygen content of 12 to 20% by volume, and thus obtained. The fired product can be crushed and sieved to obtain the target lithium cobalt oxide. Here, according to this invention, a raw material mixture can be baked only once on the said conditions, and lithium cobaltate which has an expected characteristic can be obtained.

  When the Li / Co molar ratio in the raw material mixture of the cobalt compound and the lithium compound used as the raw material is smaller than 0.97, cobalt oxide is mixed in the product obtained by firing the raw material mixture. It becomes difficult to obtain a single phase. On the other hand, when the Li / Co molar ratio in the raw material mixture of cobalt compound and lithium compound used as a raw material is larger than 1,015, the sintering of lithium cobaltate proceeds more than necessary during firing, and the specific surface area decreases. In connection with this, even in a battery using this as a positive electrode active material, the charge / discharge characteristics deteriorate. Moreover, the alkali content of the particle | grain surface of the lithium cobalt oxide obtained rises, and the problem that handling property falls will also arise.

  When the mixture of the cobalt compound and the lithium compound is baked, if the dew point of the dry air to be blown is insufficiently adjusted, the progress of the reaction may be hindered and the crystallinity of the resulting lithium cobaltate may be reduced. . When the oxygen content of the atmosphere when firing the raw material mixture of the cobalt compound and the lithium compound is lower than 12% by volume, oxygen necessary for the reaction is not sufficiently supplied. There is a risk that the discharge characteristics may deteriorate. On the other hand, when the oxygen content in the atmosphere when the mixture of the cobalt compound and the lithium compound is calcined is more than 20% by volume, there is no particular problem in the progress of the reaction. It is necessary to use a gas mixture, which increases manufacturing costs.

  In the method of the present invention, the means and method for mixing the cobalt compound and the lithium compound are not limited at all, and for example, a nauter mixer, a speed mixer, a drum mixer and the like are appropriately used. Moreover, there is no limitation also about the time for mixing a cobalt compound and a lithium compound. Moreover, crushing of the obtained baked product is not limited at all as long as primary particles are not crushed. For example, a hammer mill, a jet mill, or the like is appropriately used. The sieve after pulverization is preferably passed through a sieve of 150 mesh or less.

As described above, according to the method of the present invention, 10% volume particle size by wet particle size distribution measurement is 3-8 μm, 50% volume particle size is 8-13 μm, 90% volume particle size is 12-25 μm, 100 % Volume particle size is 20 to 80 μm, specific surface area by BET method is 0.25 to 0.65 m ² / g, bulk density is 1.20 to 2.20 g / cm ³ , and TAP density is 2.30. Lithium cobalt oxide having a bulk density / TAP density ratio in the range of 0.45 to 0.75 can be obtained while being ˜3.00 g / cm ³ .

  According to the present invention, the lithium cobalt oxide thus obtained can be filled with high density as a positive electrode active material for a lithium ion secondary battery, and has excellent charge / discharge characteristics. Moreover, such lithium cobalt oxide can be obtained by firing the raw material mixture only once. According to the present invention, as described above, for the cobalt compound and the lithium compound used as raw materials, the physical properties of each of the cobalt compound and lithium compound are controlled within a predetermined range, and by firing this under predetermined conditions, Such lithium cobalt oxide can be obtained at low cost.

  However, when the cobalt compound and lithium compound used as raw materials are those whose physical properties are not within the predetermined ranges, lithium cobaltate having the properties according to the present invention cannot be obtained. In addition, as described above, the lithium cobaltate having no characteristics according to the present invention has a low filling property and a relatively good filling property even when it is used as a positive electrode active material in a lithium ion secondary battery. Even if there is, excellent charge / discharge characteristics cannot be obtained.

  Further, the lithium cobalt oxide obtained according to the present invention has a primary particle diameter in the range of 0.1 to 10 μm and a secondary particle diameter in the range of 5 to 80 μm in SEM observation, and both primary particles and secondary particles exist. Such a dispersed state is shown, and the secondary particles have a spherical or elliptical spherical shape formed by aggregation of primary particles.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In the following examples and comparative examples, the physical properties and other measurements of the cobalt compound, the lithium compound, and the obtained lithium cobaltate were performed as follows.

Bulk density Measured using a powder density measuring device KYT-3000 manufactured by Seishin Enterprise Co., Ltd. Used sieve 500 μm, cylinder volume 20 cm ³ , used brush hair length 20 mm, hair width 15 mm. The powder passed through the sieve using the above brush with a filling drop of 19 cm was filled into the cylinder by free fall, and then the excess powder on the top of the cylinder was scraped off using a spatula. The weight of the powder filled in the cylinder was weighed with a measuring instrument, and the bulk density was calculated from the following equation.

Bulk density = (filling weight (g)) / 20 (cm ³ )

TAP density The TAP density was measured using a powder density measuring device KYT-3000 manufactured by Seishin Enterprises. Used sieve 500 μm, cylinder volume 20 cm ³ , used sieve 500 μm, cylinder volume 20 cm ³ , used brush hair length 20 mm, hair width 15 mm. The powder passed through the sieve using the above brush with a filling drop of 19 cm was filled into the cylinder by free fall, and then the excess powder on the top of the cylinder was scraped off using a spatula. The cylinder was covered and tapped 300 times at a speed of 2 times / second with a tap distance of 5 cm. Thereafter, the weight of the powder filled in the cylinder was weighed with a measuring instrument, and the TAP density was calculated from the following equation.

TAP density = (filling weight (g)) / (volume of powder after tapping (cm ³ ))

Scanning electron microscope observation JSM-5510 manufactured by JEOL Ltd. was used.
Powder X-ray diffraction analysis RINT2000 manufactured by Rigaku Corporation was used.

Wet particle size distribution measurement 0.1 g of sample and 50 mL of deionized water were placed in a beaker, and 1 drop of a 2% aqueous solution of sodium hexametaphosphate was added thereto. This mixture was put into an ultrasonic homogenizer US-150T manufactured by Nippon Seiki Seisakusho Co., Ltd. and dispersed for 3 minutes with a dispersion capacity of 150W. The sample dispersion thus obtained was put into a wet particle size distribution measuring apparatus HRA manufactured by Reed & Northrop, and the particle size distribution was measured.

Charging / discharging measurement BTS-2004 manufactured by Nagano Co., Ltd. was used.

Specific surface area measurement Flow soap 2300 manufactured by Shimadzu Corporation was used.
Measurement of Li / Co molar ratio in raw material mixture A sample of 1 g of the raw material mixture was precisely weighed and dissolved in hydrochloric acid to make 200 mL, and then 5 mL was taken from this and diluted to 1000 mL. With respect to this aqueous solution, spectral lines of lithium and cobalt were measured at wavelengths of 670.784 nm and 238.3346 nm, respectively, and using the obtained measured values, the following formula (measured value (mg / L) × 0.2 (L) × 1000 / 5) / (sample weight (g) × 1000) × 100
Each content (% by weight) is obtained from the following formula: Li / Co molar ratio = (lithium content (% by weight) /6.941) / (cobalt content (% by weight) /58.93)
From this, the Li / Co molar ratio was determined.

Example 1
(Manufacture of lithium cobaltate)
10% volume particle size by wet particle size distribution measurement is 4.8 μm, 50% volume particle size is 11.8 μm, 90% volume particle size is 21.6 μm, 100% volume particle size is 30-60 μm, and bulk density is 1.15 g / cm ^3, with TAP density is 1.76 g / cm ^3, a cobalt oxyhydroxide bulk density / TAP density ratio is 0.65, 10% volume particle size by wet particle size distribution measurement 2 0.7 μm, 50% volume particle size is 9.6 μm, 90% volume particle size is 28.9 μm, 100% volume particle size is 20-80 μm, bulk density is 0.28 g / cm ³ , and TAP density is 0.00. Lithium carbonate having a bulk density / TAP density ratio of 0.33 and 84 g / cm ³ was mixed at a Li / Co molar ratio of 0.98 to prepare a raw material mixture.

  While blowing dry air having a dew point of −30 ° C., the raw material mixture was baked at 950 ° C. for 5 hours in an atmosphere having an oxygen content of 16% by volume, and then pulverized and sieved. As a result of measurement with a powder X-ray diffractometer (RINT2000 manufactured by Rigaku Corporation), it was confirmed that the powder thus obtained was composed of a single-phase lithium cobalt oxide.

This lithium cobalt oxide has a 10% volume particle size of 4.2 μm, a 50% volume particle size of 9.4 μm, a 90% volume particle size of 17.8 μm, and a 100% volume particle size of 20 to 80 μm as measured by wet particle size distribution. The BET method has a specific surface area of 0.54 m ² / g, a bulk density of 1.51 g / cm ³ , a TAP density of 2.48 g / cm ³ , and a bulk density / TAP density ratio of 0. 61. According to SEM observation, this lithium cobaltate shows a dispersed state in which both primary particles and secondary particles exist, and the secondary particles have a spherical or elliptical spherical shape formed by aggregation of the primary particles. It was.

(Production of lithium ion secondary battery)
The lithium cobaltate, acetylene black, and N-methyl-2-pyrrolidone solution of 12% by weight polyvinylidene fluoride were mixed at a weight ratio of 100 / 2.2 / 27.8 to obtain a paste having a thickness of 15 μm. It apply | coated to aluminum foil, and it heated and dried at 130 degreeC, and prepared the positive electrode plate. When this positive electrode plate was cut into a disk shape having a diameter of 16 mm and pressed at a pressure of 1.3 T / cm ² , the bulk density of the positive electrode plate (density of the positive electrode plate excluding aluminum foil, the same applies hereinafter) was 3.42 g. / Cm ³ .

A polypropylene porous membrane with a thickness of 25 μm is used as a separator, a metal lithium foil with a thickness of 200 μm is used as a negative electrode active material, and LiPF ₆ is mixed at a concentration of 1M in a mixed solvent of ethylene carbonate / dimethyl carbonate (weight ratio 1/1) as an electrolyte. Using the dissolved solution, a stainless steel sealed simple lithium ion secondary battery was assembled in an argon glove box.

  With respect to this battery, the positive electrode active material (lithium cobaltate) 1 mg at 25 ° C., the first cycle 0.05 mA, the second cycle 0.35 mA, and the load current of 0.15 mA up to the 40th cycle 3.0 to 4 A charge / discharge test was conducted in a voltage range of 3V. As a result, the discharge capacity was 154.5 mAh / g in the first cycle and 124.7 mAh / g in the fourth cycle, and the capacity retention rate after 40 charge / discharge cycles was 84.0%.

Example 2
Cobalt oxyhydroxide and lithium carbonate were mixed at a Li / Co molar ratio of 1.00 to prepare a raw material mixture. A scanning electron micrograph (2000 times) of the cobalt oxyhydroxide used here is shown in FIG. 1, and a scanning electron micrograph (2000 times) of lithium carbonate is shown in FIG.

  Thus, lithium cobaltate which consists of a single phase was obtained like Example 1 except having prepared the raw material mixture. The lithium cobalt oxide thus obtained shows a dispersed state in which both primary particles and secondary particles are present as shown in FIG. 3 in a scanning electron micrograph (2000 magnifications). The particles had a spherical or elliptical shape formed by agglomerating primary particles.

This lithium cobalt oxide has a 10% volume particle size of 4.5 μm, a 50% volume particle size of 9.7 μm, a 90% volume particle size of 19.6 μm, and a 100% volume particle size of 20 to 80 μm as measured by wet particle size distribution. Met. The specific surface area by the BET method was 0.44 m ² / g, the bulk density was 1.47 g / cm ³ , the TAP density was 2.47 g / cm ³ , and the bulk density / TAP density ratio was 0.60. It was.

Using this lithium cobaltate as the positive electrode material, a positive electrode plate was prepared in the same manner as in Example 1, and this was cut into a disk shape having a diameter of 16 mm and pressed at a pressure of 1.3 T / cm ² . The bulk density was 3.45 g / cm ³ . Further, when a stainless steel sealed simple battery assembled in the same manner as in Example 1 was subjected to a charge / discharge test under the same conditions as in Example 1, the discharge capacity was 159.5 mAh / g in the first cycle and 123 in the second cycle. The capacity retention rate after 40 charge / discharge cycles was 83.5%.

Example 3
10% volume particle size by wet particle size distribution measurement is 6.0 μm, 50% volume particle size is 9.9 μm, 90% volume particle size is 16.6 μm, 100% volume particle size is in the range of 30-60 μm, Cobalt oxyhydroxide having a density of 1.64 g / cm ³ , a TAP density of 2.35 g / cm ³ , and a bulk density / TAP density ratio of 0.70 and the same lithium carbonate as in Example 1 were mixed with Li / Co. A raw material mixture was prepared by mixing at a molar ratio of 0.98. While blowing dry air having a dew point of −30 ° C., this raw material mixture was calcined at 1000 ° C. for 10 hours in an atmosphere having an oxygen content of 16% by volume, pulverized, and sieved to obtain lithium cobalt oxide consisting of a single phase. It was.

The lithium cobalt oxide thus obtained showed a dispersed state in which both primary particles and secondary particles existed, and the secondary particles had a spherical or elliptical spherical shape formed by aggregation of the primary particles. . The lithium cobaltate has a 10% volume particle size of 5.0 μm, a 50% volume particle size of 9.2 μm, a 90% volume particle size of 18.4 μm, and a 100% volume particle size of 20 by wet particle size distribution measurement. a ～80Myuemu, a specific surface area of 0.44 m ² / g by BET method, the bulk density is 1.73 g / cm ^3, TAP density is 2.71 g / cm ^3, bulk density / TAP density ratio 0. 64.

Using this lithium cobaltate, a positive electrode plate was prepared in the same manner as in Example 1, and this was cut into a disk shape having a diameter of 16 mm and pressed at a pressure of 1.3 T / cm ² . The bulk density was 3.53 g / cm ³ . Further, when a stainless steel sealed simple battery assembled in the same manner as in Example 1 was subjected to a charge / discharge test under the same conditions as in Example 1, the discharge capacity was 153.3 mAh / g in the first cycle and 113 in the second cycle. The capacity maintenance rate after 30 charge / discharge cycles was 85.1%.

Example 4
In Example 3, single-phase lithium cobaltate was obtained in the same manner as Example 3 except that cobalt oxyhydroxide and lithium carbonate were mixed at a Li / Co molar ratio of 1.00. The lithium cobalt oxide thus obtained showed a dispersed state in which both primary particles and secondary particles existed, and the secondary particles had a spherical or elliptical spherical shape formed by aggregation of the primary particles. . The lithium cobaltate has a 10% volume particle size of 4.9 μm, a 50% volume particle size of 9.0 μm, a 90% volume particle size of 16.8 μm, and a 100% volume particle size of 20 by wet particle size distribution measurement. The specific surface area by the BET method is 0.47 m ² / g, the bulk density is 1.74 g / cm ³ , the TAP density is 2.72 g / cm ³ , and the bulk density / TAP density ratio is 0.8. 64.

Using this lithium cobaltate as the positive electrode material, a positive electrode plate was prepared in the same manner as in Example 1, and this was cut into a disk shape having a diameter of 16 mm and pressed at a pressure of 1.3 T / cm ² . The bulk density was 3.71 g / cm ³ . Further, when a stainless steel sealed simple battery assembled in the same manner as in Example 1 was subjected to a charge / discharge test under the same conditions as in Example 1, the discharge capacity was 152.9 mAh / g in the first cycle and 122 in the second cycle. The capacity maintenance rate after 30 charge / discharge cycles was 84.9%.

Example 5
10% volume particle size by wet particle size distribution measurement is 5.9 μm, 50% volume particle size is 10.9 μm, 90% volume particle size is 20.2 μm, 100% volume particle size is 60 μm or less, and bulk density is 1 .48 g / cm ³ , the TAP density is 2.00 g / cm ³ and the bulk density / TAP density ratio is 0.74, and the 10% volume particle size by wet particle size distribution measurement is 4. 6 μm, 50% volume particle size is 19.7 μm, 90% volume particle size is 37.2 μm, 100% volume particle size is in the range of 20-80 μm, bulk density is 0.46 g / cm ³ , TAP density is 0 with a .85g / cm ^3, bulk density / TAP density ratio of lithium carbonate 0.54, were mixed with Li / Co molar ratio 1.00 was prepared a raw material mixture. While blowing dry air having a dew point of −30 ° C., this raw material mixture was calcined at 1000 ° C. for 5 hours in an atmosphere having an oxygen content of 16% by volume, pulverized, and sieved to obtain lithium cobalt oxide composed of a single phase. It was.

The lithium cobalt oxide thus obtained showed a dispersed state in which both primary particles and secondary particles existed, and the secondary particles had a spherical or elliptical spherical shape formed by aggregation of the primary particles. . Further, this lithium cobaltate has a 10% volume particle size of 6.3 μm, a 50% volume particle size of 10.2 μm, a 90% volume particle size of 17.1 μm, and a 100% volume particle size of 20 by wet particle size distribution measurement. a ～80Myuemu, specific surface area by BET method was 0.31 m ² / g, with a bulk density of 1.82g / cm ^3, TAP density is 2.75 g / cm ^3, bulk density / TAP density ratio It was 0.66.

Using this lithium cobaltate as the positive electrode material, a positive electrode plate was prepared in the same manner as in Example 1, and this was cut into a disk shape having a diameter of 16 mm and pressed at a pressure of 1.3 T / cm ² . The bulk density was 3.47 g / cm ³ . A stainless steel sealed simple battery assembled in the same manner as in Example 1 was subjected to a charge / discharge test under the same conditions as in Example 1. As a result, the discharge capacity was 155.7 mAh / g in the first cycle and 123 in the second cycle. 0.1 mAh / g, and the capacity retention rate after 40 charge / discharge cycles was 84.5%.

Example 6
10% volume particle size by wet particle size distribution measurement is in the range of 6.8 μm, 50% volume particle size is 9.7 μm, 90% volume particle size is 16.7 μm, and 100% volume particle size is in the range of 30-60 μm. Cobalt hydroxide having a density of 1.15 g / cm ³ , a TAP density of 1.55 g / cm ³ and a bulk density / TAP density ratio of 0.74 and the lithium carbonate used in Example 5 were Li / A raw material mixture was prepared by mixing at a Co molar ratio of 1.00. While blowing dry air having a dew point of −30 ° C., this raw material mixture was calcined at 950 ° C. for 5 hours in an atmosphere having an oxygen content of 16% by volume, pulverized, and sieved to obtain lithium cobalt oxide consisting of a single phase. It was.

The lithium cobalt oxide thus obtained showed a dispersed state in which both primary particles and secondary particles existed, and the secondary particles had a spherical or elliptical spherical shape formed by aggregation of the primary particles. . This lithium cobaltate has a 10% volume particle size of 6.1 μm, a 50% volume particle size of 8.4 μm, a 90% volume particle size of 13.4 g / cm ³ and a 100% volume particle by wet particle size distribution measurement. The diameter is in the range of 20 to 80 μm, the specific surface area by the BET method is 0.51 m ² / g, the bulk density is 1.44 g / cm ³ , the TAP density is 2.46 g / cm ³ , and the bulk density The / TAP ratio was 0.59.

Using this lithium cobaltate as the positive electrode material, a positive electrode plate was prepared in the same manner as in Example 1, and this was cut into a disk shape having a diameter of 16 mm and pressed at a pressure of 1.3 T / cm ² . The bulk density was 3.45 g / cm ³ . Further, when a stainless steel sealed simple battery assembled in the same manner as in Example 1 was subjected to a charge / discharge test under the same conditions as in Example 1, the discharge capacity was 157.5 mAh / g in the first cycle, and 134 in the second cycle. The capacity maintenance rate after 40 charge / discharge cycles was 84.9%.

Example 7
10% volume particle size by wet particle size distribution measurement is 4.6 μm, 50% volume particle size is 10.4 μm, 90% volume particle size is 19.0 μm, 100% volume particle size is in the range of 30-60 μm, bulk density 1.12 g / cm ^3, with TAP density is 2.12 g / cm ^3, the lithium carbonate was used bulk density / TAP density ratio in example 5 cobalt oxide is 0.53 Li / Co A raw material mixture was prepared by mixing at a molar ratio of 1.00. While blowing dry air having a dew point of −30 ° C., this raw material mixture was calcined at 950 ° C. for 5 hours in an atmosphere having an oxygen content of 16% by volume, pulverized, and sieved to obtain lithium cobalt oxide consisting of a single phase. It was.

The lithium cobalt oxide thus obtained showed a dispersed state in which both primary particles and secondary particles existed, and the secondary particles had a spherical or elliptical spherical shape formed by aggregation of the primary particles. . This lithium cobaltate has a 10% volume particle size of 4.4 μm, a 50% volume particle size of 10.6 μm, a 90% volume particle size of 20.4 g / cm ³ and a 100% volume particle by wet particle size distribution measurement. The diameter is in the range of 20 to 80 μm, the specific surface area by the BET method is 0.41 m ² / g, the bulk density is 1.26 g / cm ³ , the TAP density is 2.63 g / cm ³ , and the bulk density The / TAP ratio was 0.48.

Using this lithium cobaltate as the positive electrode material, a positive electrode plate was prepared in the same manner as in Example 1, and this was cut into a disk shape having a diameter of 16 mm and pressed at a pressure of 1.3 T / cm ² . The bulk density was 3.64 g / cm ³ . Further, when a stainless steel sealed simple battery assembled in the same manner as in Example 1 was subjected to a charge / discharge test under the same conditions as in Example 1, the discharge capacity was 158.9 mAh / g in the first cycle, and 131 in the second cycle. The capacity maintenance rate after 30 charge / discharge cycles was 86.1%.

Comparative Example 1
In Example 1, as a cobalt compound, 10% volume particle size by wet particle size distribution measurement is 1.8 μm, 50% volume particle size is 4.9 μm, 90% volume particle size is 11.2 μm, and 100% volume particle size is 100%. in the range of 30 to 60 m, except that the bulk density of 0.51 g / cm ^3, with TAP density is 1.25 g / cm ^3, bulk density / TAP density ratio was used cobalt oxide is 0.41, In the same manner as in Example 1, lithium cobaltate having a single phase was obtained.

The lithium cobalt oxide thus obtained shows a dispersed state in which both primary particles and secondary particles are present as shown in FIG. 4 in a scanning electron micrograph (2000 magnification). The particles were aggregated. The lithium cobaltate has a 10% volume particle size of 3.3 μm, a 50% volume particle size of 9.2 μm, a 90% volume particle size of 18.9 μm, and a 100% volume particle size of 20 by wet particle size distribution measurement. In the range of ˜80 μm, the specific surface area by BET method is 0.59 m ² / g, the bulk density is 0.91 g / cm ³ , the TAP density is 2.01 g / cm ³ , and the bulk density / TAP ratio Was 0.45. Using this lithium cobaltate as the positive electrode material, a positive electrode plate was prepared in the same manner as in Example 1, and this was cut into a disk shape having a diameter of 16 mm and pressed at a pressure of 1.3 T / cm ² . The bulk density was 2.71 g / cm ³ . Further, when a stainless steel sealed simple battery assembled in the same manner as in Example 1 was subjected to a charge / discharge test under the same conditions as in Example 1, the discharge capacity was 155.7 mAh / g in the first cycle and 114 in the second cycle. The capacity maintenance rate after 40 charge / discharge cycles was 85.4%.

Comparative Example 2
In Comparative Example 1, as the cobalt compound, 10% volume particle size by wet particle size distribution measurement is 1.8 μm, 50% volume particle size is 4.3 μm, 90% volume particle size is 8.4 μm, and 100% volume particle size is 100%. in the range of 30 to 60 m, a bulk density together with 1.04g / cm ^3, TAP density of 1.65 g / cm ^3, bulk density / TAP density ratio in example 5 cobalt oxide of 0.63 Lithium cobaltate consisting of a single phase was obtained in the same manner as in Comparative Example 1 except that the same lithium carbonate as used was mixed at a Li / Co molar ratio of 1.00 to prepare a raw material mixture. .

The lithium cobalt oxide thus obtained showed a dispersed state in which both primary particles and secondary particles were present, and the secondary particles were formed by aggregation of the primary particles. This lithium cobaltate has a 10% volume particle size of 3.3 μm, a 50% volume particle size of 6.2 μm, a 90% volume particle size of 12.2 μm, and a 100% volume particle size of 20 by wet particle size distribution measurement. In the range of ˜80 μm, the specific surface area by BET method is 0.57 m ² / g, the bulk density is 0.91 g / cm ³ , the TAP density is 2.04 g / cm ³ , and the bulk density / TAP ratio Was 0.45. Using this lithium cobaltate as the positive electrode material, a positive electrode plate was prepared in the same manner as in Example 1, and this was cut into a disk shape having a diameter of 16 mm and pressed at a pressure of 1.3 T / cm ² . The bulk density was 2.85 g / cm ³ . Further, when a stainless steel sealed simple battery assembled in the same manner as in Example 1 was subjected to a charge / discharge test under the same conditions as in Example 1, the discharge capacity was 155.2 mAh / g in the first cycle and 112 in the second cycle. The capacity maintenance rate after 40 charge / discharge cycles was 81.6%.

Comparative Example 3
A lithium cobaltate composed of a single phase was obtained in the same manner as in Comparative Example 2 except that the raw material mixture was fired at 1000 ° C. The lithium cobalt oxide thus obtained consists essentially of primary particles. The 10% volume particle size is 3.2 μm, the 50% volume particle size is 6.1 μm, and the 90% volume particle size is 10 by wet particle size distribution measurement. 0.9 μm, 100% volume particle size is in the range of 20-80 μm, specific surface area by BET method is 0.49 m ² / g, bulk density is 1.20 g / cm ³ , TAP density is 2.30 g / cm ³ and the bulk density / TAP ratio was 0.52.

Using this lithium cobaltate as the positive electrode material, a positive electrode plate was prepared in the same manner as in Example 1, and this was cut into a disk shape having a diameter of 16 mm and pressed at a pressure of 1.3 T / cm ² . The bulk density was 2.84 g / cm ³ . Further, when a stainless steel sealed simple battery assembled in the same manner as in Example 1 was subjected to a charge / discharge test under the same conditions as in Example 1, the discharge capacity was 156.7 mAh / g in the first cycle and 118 in the second cycle. The capacity maintenance rate after 40 charge / discharge cycles was 86.5%.

Comparative Example 4
10% volume particle size by wet particle size distribution measurement is 11.6 μm, 50% volume particle size is 16.0 μm, 90% volume particle size is 23.4 μm, 100% volume particle size is in the range of 30-60 μm, with density of 1.56g / cm ^3, TAP density of 2.10 g / cm ^3, bulk density / TAP density ratio the same lithium carbonate as used in example 5 cobalt oxide is 0.74 A raw material mixture was prepared by mixing at a Li / Co molar ratio of 1.00. The resulting mixture was baked at 900 ° C. for 10 hours in an atmosphere having an oxygen content of 16% by volume while blowing dry air having a dew point of −30 ° C., then pulverized and sieved, and lithium cobalt oxide consisting of a single phase Got.

The lithium cobalt oxide obtained in this manner consists essentially of secondary particles, and the 10% volume particle size by wet particle size distribution measurement is 11.0 μm, the 50% volume particle size is 14.1 μm, and the 90% volume particle size is 19.2 μm, 100% volume particle size is 20-80 μm, specific surface area by BET method is 0.24 m ² / g, bulk density is 2.25 g / cm ³ , TAP density is 2.49 g / cm ^3. And the bulk density / TAP density ratio was 0.77.

Using this lithium cobaltate as the positive electrode material, a positive electrode plate was prepared in the same manner as in Example 1, and this was cut into a disk shape having a diameter of 16 mm and pressed at a pressure of 1.3 T / cm ² . The bulk density was 3.32 g / cm ³ . Further, when a stainless steel sealed simple battery assembled in the same manner as in Example 1 was subjected to a charge / discharge test under the same conditions as in Example 1, the discharge capacity was 155.5 mAh / g in the first cycle and 109 in the second cycle. The capacity maintenance rate after 40 charge / discharge cycles was 81.3%.

Comparative Example 5
The raw material mixture was prepared by mixing the cobalt hydroxide used in Example 6 and the lithium carbonate used in Example 1 at a Li / Co molar ratio of 1.03. While blowing dry air having a dew point of −30 ° C., this raw material mixture was calcined at 1000 ° C. for 10 hours in an atmosphere having an oxygen content of 16%, pulverized, and sieved to obtain lithium cobalt oxide composed of a single phase. .

The lithium cobalt oxide obtained in this way consists essentially of secondary particles. The 10% volume particle size by wet particle size distribution measurement is 7.2 μm, the 50% volume particle size is 10.5 μm, and the 90% volume particle size is 90%. 16.0 μm, 100% volume particle size is 20-80 μm, specific surface area by BET method is 0.23 m ² / g, bulk density is 1.59 g / cm ³ , TAP density is 2.59 g / cm ³ The bulk density / TAP density ratio was 0.61.

Using this lithium cobaltate as the positive electrode material, a positive electrode plate was prepared in the same manner as in Example 1, and this was cut into a disk shape having a diameter of 16 mm and pressed at a pressure of 1.3 T / cm ² . The bulk density was 3.23 g / cm ³ . When a stainless steel sealed simple battery assembled in the same manner as in Example 1 was subjected to a charge / discharge test under the same conditions as in Example 1, the discharge capacity was 158.2 mAh / g in the first cycle and 114 in the second cycle. The capacity retention rate after 40 charge / discharge cycles was 80.8%.

Comparative Example 6
In Example 1, the 10% volume particle size is 8.2 μm, the 50% volume particle size is 10.6 μm, the 90% volume particle size is 14.9 μm, and the 100% volume particle size is 30 to 60 μm by wet particle size distribution measurement. In Example 5, cobalt hydroxide with a bulk density of 1.34 g / cm ³ , a TAP density of 1.58 g / cm ³ and a bulk density / TAP density ratio of 0.85 was used. Lithium cobaltate consisting of a single phase was obtained in the same manner as in Example 1 except that the same lithium carbonate as in was mixed at a Li / Co molar ratio of 1.00 to prepare a raw material mixture.

The lithium cobalt oxide obtained in this way consists essentially of secondary particles, and the 10% volume particle size measured by wet particle size distribution is 6.7 μm, the 50% volume particle size is 9.2 μm, and the 90% volume particle size is 90%. 14.0 μm, 100% volume particle size is 20-80 μm, specific surface area by BET method is 0.56 m ² / g, bulk density is 1.90 g / cm ³ , TAP density is 2.51 g / cm ³ In addition, the bulk density / TAP density ratio was 0.76.

Using this lithium cobaltate as the positive electrode material, a positive electrode plate was prepared in the same manner as in Example 1, and this was cut into a disk shape having a diameter of 16 mm and pressed at a pressure of 1.3 T / cm ² . The bulk density was 3.25 g / cm ³ . Further, when a stainless steel sealed simple battery assembled in the same manner as in Example 1 was subjected to a charge / discharge test under the same conditions as in Example 1, the discharge capacity was 159.1 mAh / g in the first cycle and 120 in the second cycle. The capacity maintenance rate after 40 charge / discharge cycles was 86.1%.

Comparative Example 7
10% volume particle size by wet particle size distribution measurement is 5.3 μm, 50% volume particle size is 8.2 μm, 90% volume particle size is 13.0 μm, 100% volume particle size is in the range of 30-60 μm, bulk with density of 0.75g / cm ^3, TAP density of 1.20 g / cm ^3, the same lithium carbonate as the bulk density / TAP density ratio was used in example 5 and cobalt hydroxide of 0.63 Were mixed at a Li / Co molar ratio of 1.00 to prepare a raw material mixture. The resulting mixture was baked at 950 ° C. for 10 hours in an atmosphere having an oxygen content of 16% by volume while blowing dry air having a dew point of −30 ° C., and then pulverized and sieved to form lithium cobaltate consisting of a single phase. Got.

The lithium cobalt oxide obtained in this manner consists essentially of secondary particles, and the 10% volume particle size is 5.0 μm, the 50% volume particle size is 7.6 μm, and the 90% volume particle size is 90% by wet particle size distribution measurement. 12.2 μm, 100% volume particle size is 20-80 μm, specific surface area by BET method is 0.58 m ² / g, bulk density is 1.04 g / cm ³ , TAP density is 2.07 g / cm ³ The bulk density / TAP density ratio was 0.50.

Using this lithium cobaltate as the positive electrode material, a positive electrode plate was prepared in the same manner as in Example 1, and this was cut into a disk shape having a diameter of 16 mm and pressed at a pressure of 1.3 T / cm ² . The bulk density was 2.79 g / cm ³ . Further, when a stainless steel sealed simple battery assembled in the same manner as in Example 1 was subjected to a charge / discharge test under the same conditions as in Example 1, the discharge capacity was 157.9 mAh / g in the first cycle and 121 in the second cycle. The capacity retention rate after 40 charge / discharge cycles was 84.9%.

Comparative Example 8
10% volume particle size by wet particle size distribution measurement is 7.1 μm, 50% volume particle size is 9.8 μm, 90% volume particle size is 15.0 μm, 100% volume particle size is in the range of 30-60 μm, bulk with density of 1.89 g / cm ^3, TAP density of 2.34 g / cm ^3, and cobalt oxide is bulk density / TAP density ratio 0.81, 10% volume particle size by wet particle size distribution measurement 6 0.8 μm, 50% volume particle size 22.2 μm, 90% volume particle size 57.5 μm, 100% volume particle size 20 to 80 μm, bulk density 0.51 g / cm ³ , TAP density Lithium carbonate having a bulk density / TAP density ratio of 0.57 and 0.88 g / cm ³ was mixed at a Li / Co molar ratio of 0.99 to prepare a raw material mixture. The resulting mixture was baked at 900 ° C. for 5 hours in an atmosphere having an oxygen content of 16% by volume while blowing dry air having a dew point of −30 ° C., then pulverized and sieved, and lithium cobalt oxide consisting of a single phase Got.

The lithium cobalt oxide obtained in this way consists essentially of secondary particles, and the 10% volume particle size by wet particle size distribution measurement is 7.0 μm, the 50% volume particle size is 10.1 μm, and the 90% volume particle size. 16.2 μm, 100% volume particle size was 20-80 μm. Specific surface area by BET method was 0.26 m ² / g, bulk density with 1.88g / cm ^3, TAP density is 2.48 g / cm ^3, bulk density / TAP density ratio 0.76 met It was.

Using this lithium cobaltate as the positive electrode material, a positive electrode plate was prepared in the same manner as in Example 1, and this was cut into a disk shape having a diameter of 16 mm and pressed at a pressure of 1.3 T / cm ² . The bulk density was 3.24 g / cm ³ . Further, when a stainless steel sealed simple battery assembled in the same manner as in Example 1 was subjected to a charge / discharge test under the same conditions as in Example 1, the discharge capacity was 155.8 mAh / g in the first cycle and 116 in the second cycle. The capacity maintenance rate after 40 charge / discharge cycles was 79.1%.

Comparative Example 9
The raw material mixture was prepared by mixing the cobalt oxide used in Example 6 and the lithium carbonate used in Comparative Example 8 at a Li / Co molar ratio of 0.97. The resulting mixture was baked at 900 ° C. for 5 hours in an atmosphere having an oxygen content of 16% by volume while blowing dry air having a dew point of −30 ° C., then pulverized and sieved, and lithium cobalt oxide consisting of a single phase Got.

A scanning electron micrograph of the lithium cobaltate thus obtained is shown in FIG. This lithium cobaltate is substantially composed only of secondary particles. The 10% volume particle size is 7.2 μm, the 50% volume particle size is 9.9 μm, the 90% volume particle size is 14.8 μm, 100 by wet particle size distribution measurement. % Volume particle size is 20-80 μm, specific surface area by BET method is 0.21 m ² / g, bulk density is 1.68 g / cm ³ , TAP density is 2.63 g / cm ³ , The density / TAP density ratio was 0.64.

Using this lithium cobaltate as the positive electrode material, a positive electrode plate was prepared in the same manner as in Example 1, and this was cut into a disk shape having a diameter of 16 mm and pressed at a pressure of 1.3 T / cm ² . The bulk density was 3.25 g / cm ³ . In addition, when a stainless steel sealed simple battery assembled in the same manner as in Example 1 was subjected to a charge / discharge test under the same conditions as in Example 1, the discharge capacity was 151.8 mAh / g in the first cycle and 106 in the second cycle. The capacity maintenance rate after 40 charge / discharge cycles was 78.5%.

Comparative Example 10
Except that the raw material mixture was prepared by mixing the cobalt oxide used in Example 6 and the lithium carbonate used in Comparative Example 8 at a Li / Co molar ratio of 1.00, A lithium cobaltate consisting of a single phase was obtained.

The lithium cobalt oxide obtained in this manner consists essentially of secondary particles, and the 10% volume particle size by wet particle size distribution measurement is 7.3 μm, the 50% volume particle size is 9.9 μm, and the 90% volume particle size is 90%. The particle size was 14.8 μm and the 100% volume particle size was 20 to 80 μm. Specific surface area by BET method was 0.19 m ² / g, bulk density with 1.63g / cm ^3, TAP density is 2.65 g / cm ^3, bulk density / TAP density ratio 0.62 met It was.

Using this lithium cobaltate as the positive electrode material, a positive electrode plate was prepared in the same manner as in Example 1, and this was cut into a disk shape having a diameter of 16 mm and pressed at a pressure of 1.3 T / cm ² . The bulk density was 3.30 g / cm ³ . Moreover, when a stainless steel sealed simple battery assembled in the same manner as in Example 1 was subjected to a charge / discharge test under the same conditions as in Example 1, the discharge capacity was 152.3 mAh / g in the first cycle, and 104 in the second cycle. The capacity maintenance rate after 40 charge / discharge cycles was 77.1%.

  10% (D10%), 50% (D50%) and 90% (D90%) volume particles by wet particle size distribution measurement of cobalt compounds and lithium compounds used in Examples 1-7 and Comparative Examples 1-10. Diameter, bulk density, TAP density, bulk density / TAP density ratio, reaction conditions of raw material mixture of cobalt compound and lithium compound, 10% (D10%), 50% (D50%) and 90% of the obtained lithium cobaltate (D90%) Volume particle size, bulk density, TAP density, bulk density / TAP density ratio, bulk density of the positive electrode plate using the obtained lithium cobaltate as the positive electrode active material, and the obtained lithium cobaltate as the positive electrode active material Tables 1 and 2 show the discharge capacity and capacity retention rate of the lithium ion secondary battery.

In Example 2, it is a scanning electron micrograph photograph (2000 times) of the cobalt oxyhydroxide used for manufacture of lithium cobaltate. In Example 2, it is a scanning electron micrograph photograph (2000 times) of the lithium carbonate used for manufacture of lithium cobaltate. 2 is a scanning electron micrograph (2000 × magnification) of lithium cobalt oxide according to Example 2. FIG. 2 is a scanning electron micrograph (2000 times) of lithium cobalt oxide according to Comparative Example 1. FIG. 6 is a scanning electron micrograph (2000 × magnification) of lithium cobalt oxide according to Comparative Example 9.

Claims (3)

10% volume particle size by wet particle size distribution measurement is 3-8 μm, 50% volume particle size is 8-13 μm, 90% volume particle size is 12-25 μm, 100% volume particle size is 20-80 μm, and according to BET method The specific surface area is 0.25 to 0.65 m ² / g, the bulk density is 1.20 to 2.20 g / cm ³ , the TAP density is 2.30 to 3.00 g / cm ³ , and the bulk Lithium cobaltate having a density / TAP density ratio in the range of 0.45 to 0.75. 10% volume particle size by wet particle size distribution measurement is 3-8 μm, 50% volume particle size is 5-15 μm, 90% volume particle size is 15-25 μm, 100% volume particle size is 20-60 μm, and bulk density is Cobalt carbonate with 1.00 to 2.00 g / cm ³ , TAP density of 1.50 to 3.00 g / cm ³ and bulk density / TAP density ratio in the range of 0.50 to 0.80 , At least one cobalt compound selected from cobalt oxyhydroxide, cobalt hydroxide and cobalt oxide, 10% volume particle size by wet particle size distribution measurement is 0.5-7 μm, 50% volume particle size is 5-21 μm, Li / Co molar ratio of 0.97 to 1 with at least one lithium compound selected from lithium carbonate and lithium hydroxide having a 90% volume particle size of 20 to 50 μm and a 100% volume particle size of 30 to 80 μm In the range of 015, a raw material mixture is prepared, and while blowing dry air, the raw material mixture is placed in an atmosphere having an oxygen content of 12 to 20% by volume at a temperature in the range of 900 to 1200 ° C. for 3 to 15%. The method for producing lithium cobaltate according to claim 1, wherein the firing is performed only once for a time. The method for producing lithium cobalt oxide according to claim 2, wherein the raw material mixture is fired while blowing dry air having a dew point in the range of 0 ° C to -80 ° C.