KR20070015637A - Process for producing positive-electrode active material for lithium secondary cell - Google Patents

Abstract

Using inexpensive cobalt hydroxide and lithium carbonate, there is provided a method for producing a lithium cobalt composite oxide for lithium secondary battery positive electrode having excellent volume capacity density, safety, charge and discharge cycle durability, press density and productivity.

The mixture obtained by mixing the cobalt hydroxide powder and the lithium carbonate powder in such a manner that the atomic ratio of lithium / cobalt is 0.98 to 1.01 was calcined in an oxygen-containing atmosphere at 250 to 700 ° C., and the calcined product was then heated in an oxygen-containing atmosphere at 850 to 1050 ° C. The temperature is raised to 4 ° C./min or lower at a temperature of 250 ° C. to 600 ° C., and the temperature is raised at 850 ° C. to 1050 ° C. in an oxygen-containing atmosphere.

Method for producing lithium cobalt composite oxide for lithium secondary battery positive electrode

Description

Manufacturing method of positive electrode active material for lithium secondary battery {PROCESS FOR PRODUCING POSITIVE-ELECTRODE ACTIVE MATERIAL FOR LITHIUM SECONDARY CELL}

The present invention is a lithium secondary battery positive electrode having a high bulk capacity density, high large current discharge characteristics, high safety, large charge and discharge cycle durability, high press density, and high productivity using cobalt hydroxide and lithium carbonate, which is an inexpensive raw material The present invention relates to a method for producing a lithium cobalt composite oxide, a cathode for a lithium secondary battery including the manufactured lithium cobalt composite oxide, and a lithium secondary battery.

In recent years, as portable devices and wireless devices have progressed, demands for nonaqueous electrolyte secondary batteries such as lithium secondary batteries having small size, light weight, and high energy density have increased. As a cathode active material of these nonaqueous electrolyte secondary battery _{is, LiCoO 2, LiNiO 2, LiNi} O .8 Co 0 .2 O 2, LiMn 2 O 4, LiMnO 2 has a composite oxide of lithium and transition metal, such as known.

Among them, lithium secondary batteries using lithium cobalt composite oxide (LiCoO ₂ ) as a cathode active material and carbons such as lithium alloy, graphite, carbon fiber, etc. as a negative electrode can obtain a high voltage of 4V class, and thus have high energy density. It is widely used as a battery having a.

As a method for producing a lithium cobalt composite oxide, it is common to use cobalt trioxide as a cobalt raw material and to use lithium carbonate as a lithium raw material.

In addition, a method of using oxy cobalt hydroxide and lithium carbonate has also been recently performed industrially. These cobalt trioxide and oxy cobalt hydroxide are produced by oxidation of cobalt hydroxide. Cobalt hydroxide is inexpensive because it is a raw material of cobalt trioxide or cobalt oxyhydroxide as a raw material of cobalt.

A method for producing lithium cobalt acid from cobalt hydroxide and lithium carbonate is known from Japanese Laid-Open Patent Publication No. 2002-321921. In Japanese Laid-Open Patent Publication No. 2002-321921, first, cobalt hydroxide powder and lithium carbonate powder are mixed so as to have a molar ratio of Li / Co of 1.02 to 1.06, granulated mixtures, and primary firing is performed at 600 to It is characterized by performing secondary baking at 750-1000 degreeC after grinding at 700 degreeC, after baking a sintered material. However, the method described in Japanese Unexamined Patent Publication No. 2002-321921 requires the granulation of the raw material mixed powder before firing, the pulverization step after the primary firing, and the like, which makes the manufacturing process complicated and the manufacturing cost expensive. There are problems such as a lack of discharge cycle durability. Therefore, it can be expected by those skilled in the art that a cobalt hydroxide which is an inexpensive raw material can be used to produce a lithium cobalt composite oxide having a desirable particle size distribution and a good anode as a positive electrode of a lithium secondary battery. It wasn't.

Disclosure of the Invention

The present invention uses lithium cobalt hydroxide and lithium carbonate which are inexpensive raw materials, respectively, as a cobalt source and a lithium source, and have a lithium secondary battery having high bulk capacity density, high safety, high charge / discharge cycle durability, high press density, and high productivity. A novel method for producing a lithium cobalt composite oxide for a positive electrode, a lithium secondary battery positive electrode comprising a manufactured lithium cobalt composite oxide, and a lithium secondary battery.

MEANS TO SOLVE THE PROBLEM The present inventor continued to research in order to achieve the said subject, and it uses the cheap cobalt hydroxide as a cobalt source, and also uses lithium carbonate which is inexpensive, and specifically controls the mixture which mixed these at the specific mixing ratio. It was found that by firing under the same conditions, a lithium cobalt composite oxide can be produced without performing granulation of raw materials, grinding in an intermediate step, or the like. In addition, it has been found that the obtained lithium cobalt composite oxide has excellent characteristics in all aspects of volume capacity density, safety, charge and discharge cycle durability, press density, and productivity as a positive electrode of a lithium secondary battery.

It is not clear why the above object is achieved by firing the above specific raw material mixture in the present invention under specific controlled conditions. However, compared to cobalt oxide, cobalt hydroxide is believed to be due to the slow reactivity with lithium carbonate and unreacted lithium carbonate when the temperature increase rate is too high, resulting in phase separation of cobalt and lithium, resulting in incomplete lithiation. .

In this way, this invention makes the following structure a summary.

(1) A mixture obtained by mixing cobalt hydroxide powder and lithium carbonate powder so as to have an atomic ratio of lithium / cobalt of 0.98 to 1.01 is calcined at 250 to 700 ° C. in an oxygen-containing atmosphere, and the calcined product is then oxygenated at 850 to 1050 ° C. A method for producing a lithium cobalt composite oxide for a positive electrode of a lithium secondary battery, which is fired in a containing atmosphere.

(2) The production method according to the above (1), wherein the fired product fired at 250 to 700 占 폚 is fired in an oxygen-containing atmosphere at 850 to 1050 占 폚 without pulverization.

(3) The mixture obtained by mixing the cobalt hydroxide powder and the lithium carbonate powder so that the atomic ratio of lithium / cobalt is 0.98 to 1.01 is raised to a temperature increase rate at 250 to 600 ° C to 4 ° C / min or less, and oxygen at 850 to 1050 ° C. A method for producing a lithium cobalt composite oxide for a positive electrode of a lithium secondary battery, which is fired in a containing atmosphere.

(4) X-ray diffraction spectrum using Cu-Kα ray of cobalt hydroxide, where the half width of diffraction peak of (001) plane of 2θ = 19 ± 1 ° is 0.18 to 0.35 °, and 2θ = 38 ± 1 ° The method according to any one of (1) to (3), wherein the half width of the diffraction peak of the N-side surface is 0.15 to 0.35 ° and the specific surface area is 5 to 50 m 2 / g.

(5) The production method according to any one of (1) to (4), wherein the cobalt hydroxide powder is a substantially spherical secondary particle having an average particle diameter D50 of 5 to 25 µm in which primary particles are aggregated.

(6) Any of the above (1) to (5), wherein the secondary particles of the cobalt hydroxide powder are 1/4 or less with respect to the average particle diameter D50 before being dispersed in the pure water after the average particle diameter D50 is dispersed in the pure water. The manufacturing method of one.

(7) The positive electrode for lithium secondary batteries containing the lithium cobalt composite oxide manufactured by the manufacturing method in any one of said (1)-(6).

(8) A lithium secondary battery using the positive electrode described in the above (7).

To practice the invention  Best form for

The lithium cobalt composite oxide LiCoO ₂ for the lithium secondary battery positive electrode produced by the present invention may further contain element M. The element M is a transition metal element or alkaline earth metal except Co. The transition metal element represents transition metals of Groups 4, 5, 6, 7, 8, 9, 10 and 11 of the periodic table. Among them, at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Mg, Ca, Sr, Ba, and Al is selected. Especially, Ti, Zr, Hf, Mg, or Al is preferable from a viewpoint of capacity expression property, safety, cycle durability, etc.

In addition, the lithium cobalt composite oxide may further contain a fluorine atom F. In the case where the lithium cobalt composite oxide produced by the present invention contains the M and / or F, both of M and F are preferably within 100 nm, particularly preferably within 30 nm on the surface or surface of the lithium cobalt particle. It is preferable to exist in the surface layer substantially. When present inside the particles, not only the effect of improving the battery characteristics is small but also the battery characteristics may be lowered, which is not preferable. By being present on the surface, it is possible to improve important battery characteristics such as safety and charge / discharge cycle characteristics without causing a decrease in battery performance by addition of a small amount. Whether or not present on the surface can be determined by spectroscopic analysis, for example, XPS analysis, with respect to the positive electrode particles.

Any cobalt hydroxide used in the production of the lithium cobalt composite oxide of the present invention can be used, but among them, the diffraction peak of the (001) plane of 2θ = 19 ± 1 ° measured by X-ray diffraction using CuKα as a source. It is preferable to use the one having a half value width of 0.18 to 0.35 ° and the half value width of the diffraction peak of the (101) plane with 2θ = 38 ± 1 °, and having a specific surface area of 5 to 50 m 2 / g. Do.

Half width of the diffraction peak of the (001) plane of 2θ = 19 ± 1 ° and half width of the diffraction peak of the (101) plane of 2θ = 38 ± 1 ° measured by X-ray diffraction using CuKα of cobalt hydroxide as a source If it is outside the range prescribed | regulated by the said this invention, the volume of powder becomes large, the press density of a positive electrode falls, or safety falls. In the above half-value width, the half-value width of the diffraction peak of the (001) plane of 2θ = 19 ± 1 ° is 0.22 to 0.30, and the half-value width of the diffraction peak of the (101) plane of 2θ = 38 ± 1 ° It is preferable that it is 0.18-0.30 degrees.

Moreover, when the specific surface area of cobalt hydroxide is smaller than 5 m <2> / g, the press density of a positive electrode will fall or safety will fall. On the contrary, when it exceeds 50m <2> / g, the volume of powder becomes large. In particular, the specific surface area is preferably 10 to 300 m 2 / g. In addition, the press density of cobalt hydroxide is not preferable because the press density of the positive electrode decreases when the volume of powder becomes large when it is smaller than 1.0 g / cm <3>, and when it exceeds 2.5 g / cm <3>.

In addition, the press density of cobalt hydroxide is preferably 1.0 to 2.5 g / cm 3, particularly 1.3 to 2.2 g / cm 3. In addition, the press density of cobalt hydroxide in this invention refers to the press density of the external appearance when the particle powder is pressed by the pressure of 0.3 t / cm <2> unless there is particular notice. In addition, the press density of a lithium cobalt complex oxide refers to the press density of the external appearance when press-pressing at the pressure of 0.96 t / cm <2>.

In addition, the cobalt hydroxide powder preferably has an average particle diameter D50 of which primary particles are aggregated is preferably 5 to 25 µm, particularly 8 to 20 µm. When the average particle diameter is not in the above range, the press density of the anode is lowered, or the large current discharge characteristic or the self discharge characteristic is lowered, which is not preferable. In addition, the average particle diameter D50 in the state where the secondary particles of the cobalt hydroxide powder are dispersed in water is preferably 1/4 or less, preferably 1/8 or less of the average particle diameter D50 before being dispersed in water. In this case, the measurement of the average particle diameter D50 in the state disperse | distributed in the water of cobalt hydroxide particle | grains is performed, irradiating an ultrasonic wave (42KHz, 40W) for 3 minutes.

And it is preferable that the shape of the said secondary particle of cobalt hydroxide is substantially spherical. The shape of the particle is substantially spherical, but includes spherical shape, rugby ball shape, polygonal shape, etc., but its long diameter / short diameter is preferably 2/1 to 1/1, in particular 1.5 / 1 to 1/1. It is preferable. Especially, it is preferable to have spherical shape as much as possible.

Cobalt hydroxide which has the said specific physical property used for manufacture of the lithium cobalt complex oxide of this invention is manufactured by various methods, The manufacturing method is not limited. For example, by continuously mixing the cobalt sulfate aqueous solution, the ammonium hydroxide aqueous solution, and the sodium hydroxide aqueous solution, a slurry containing cobalt hydroxide can be easily produced. And cobalt hydroxide which has the physical property of this invention is obtained by changing reaction conditions, such as pH and stirring at this time.

The present invention preferably uses cobalt hydroxide having the above specific physical properties as a cobalt source, and in some cases, the cobalt hydroxide may be replaced with other cobalt sources to further improve the balance of battery characteristics or positive electrode manufacturing productivity. As another cobalt source, oxy cobalt hydroxide, cobalt trioxide, etc. are illustrated.

When manufacturing a lithium cobalt composite oxide by this invention, lithium carbonate which is a cheap lithium source is used as a lithium source, and lithium cobalt composite oxide of the outstanding performance is obtained in this invention. Moreover, as a raw material of the element M used as needed, hydroxide, oxide, carbonate, and fluoride are selected preferably. As the fluorine source, metal fluoride, LiF, MgF ₂ and the like are selected.

In the present invention, a lithium cobalt composite oxide is produced by firing a mixture of cobalt hydroxide, lithium carbonate, and the M element source and fluorine source used as necessary in an oxygen-containing atmosphere. In this case, when obtaining a lithium cobalt composite oxide having excellent performance, the ratio of lithium and cobalt in the mixture to be fired is important, and lithium / cobalt needs to be 0.998 to 1.01 in an atomic ratio. If this ratio is smaller than 0.98, the by-product amount of cobalt oxide will increase, and when used for the positive electrode of a lithium battery, discharge capacity will fall. On the other hand, when the said ratio is larger than 1.01, charge / discharge cycle durability falls and it becomes easy to sinter, and it is unpreferable. Especially, the case where lithium / cobalt is 0.990-1.005 in atomic ratio is especially preferable.

In addition, the firing conditions of the mixture to be fired are also important, and in the present invention, the conditions are carried out by two-stage firing or one-stage firing described below. That is, in the case of two-stage firing, the mixture is fired at 250 to 700 ° C, preferably 300 to 550 ° C, and then the fired product is fired at 850 to 1050 ° C, preferably 900 to 1000 ° C. In the case of single stage firing, the mixture is heated at a temperature increase rate at 250 ° C to 600 ° C of 4 ° C / minute or less, preferably 3 ° C / minute or less, and 850 to 1050 ° C, preferably 9O0 to 1000. Calcining at &lt; RTI ID = 0.0 &gt; When baking which satisfy | fills any one of these conditions, the lithium cobalt complex oxide which has the characteristic of satisfying the objective of this invention is obtained, without performing granulation of a raw material, grinding | pulverization in an intermediate | middle stage, etc. are obtained. Thus, for example, when the mixture is calcined directly at 850 to 1050 ° C. without firing in two stages, or when the temperature increase rate at 250 to 600 ° C. is increased at a rate exceeding 4 ° C./min, the following comparison is made. As shown in the example, a lithium cobalt composite oxide having satisfactory performance cannot be obtained.

In the present invention, lithium cobalt composite oxide particles are produced by pulverizing and classifying the calcined product obtained by baking for 2 to 48 hours, preferably 5 to 20 hours, and then pulverizing and classifying.

The lithium cobalt composite oxide produced in this way preferably has an average particle diameter D50 of 5 to 15 µm, particularly preferably 8 to 12 µm, and a specific surface area of preferably 0.3 to 0.7 m 2 / g, particularly preferably 0.4 The (110) diffraction peak half-value width of 2θ = 66.5 ± 1 ° measured by X-ray diffraction using ˜0.6 m 2 / g and CuKα as a source is preferably 0.07 to 0.14 °, particularly preferably 0.08 to 0.12 °, The press density is preferably 3.15 to 3.8 g / cm 3, particularly preferably 3.0 to 3.55 g / cm 3. In addition, the amount of residual alkali contained in the lithium cobalt composite oxide of the present invention is preferably at most 0.3 mass%, particularly preferably at most 0.01 mass%.

When manufacturing the positive electrode for lithium secondary batteries from such a lithium cobalt composite oxide, it forms by mixing carbonaceous conductive materials, such as acetylene black, graphite, and ketjen black, and a binder with the powder of such a composite oxide. As the binder, polyvinylidene fluoride, polytetrafluoroethylene, polyamide, carboxymethyl cellulose, acrylic resin and the like are preferably used.

The powder, conductive material and binder of the lithium cobalt composite oxide of the present invention are used as a slurry or a kneaded product using a solvent or a dispersion medium, and supported on a positive electrode current collector such as aluminum foil or stainless steel foil by coating or the like for a lithium secondary battery. The positive electrode of is manufactured.

In the lithium secondary battery using the lithium cobalt composite oxide of the present invention as a positive electrode active material, a porous polyethylene, a film of porous polypropylene, or the like is used as the separator. Moreover, although various solvent can be used as a solvent of the electrolyte solution of a battery, carbonate ester is especially preferable. Carbonic acid ester can use either cyclic or chain form. As cyclic carbonate, propylene carbonate, ethylene carbonate (EC), etc. are illustrated. Examples of the chain carbonate include dimethyl carbonate, diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate, methyl isopropyl carbonate and the like.

In this invention, the said carbonate ester can be used individually or in mixture of 2 or more types. Moreover, you may mix and use with another solvent. In addition, depending on the material of the negative electrode active material, when the chain carbonate and the cyclic carbonate are used in combination, the discharge characteristics, cycle durability, and charge and discharge efficiency may be improved.

In addition, in a lithium secondary battery using the lithium cobalt composite oxide of the present invention as a positive electrode active material, vinylidene fluoride-hexafluoropropylene copolymer (for example, manufactured by Atchem Co., Ltd., trade name Kynar) or vinylidene fluoride- It is good also as a gel polymer electrolyte containing a perfluoro propyl vinyl ether copolymer. Examples of the solute added to the electrolyte solvent or the polymer electrolyte include ClO _4- , CF ₃ SO _3- , BF _4- , PF _6- , AsF _6- , SbF _6- , CF ₃ CO _2- , (CF ₃ SO ₂ ) At least one of lithium salts having ₂ N- and the like as an anion is preferably used. It is preferable to add to the electrolyte solvent or polymer electrolyte which consists of said lithium salt in the density | concentration of 0.2-2.0 mo1 / L. If it deviates from this range, ion conductivity will fall and the electrical conductivity of electrolyte will fall. Especially, 0.5-1.5 mo1 / L is especially preferable.

In a lithium battery using the lithium cobalt composite oxide of the present invention as a positive electrode active material, a material capable of occluding and releasing lithium ions is used as the negative electrode active material. Although the material which forms this negative electrode active material is not specifically limited, For example, an oxide, a carbon compound, a silicon carbide compound, and a silicon oxide compound mainly consisting of a lithium metal, a lithium alloy, a carbon material, a periodic table 14, or a metal of group 15 , Titanium sulfide, boron carbide compound and the like. As the carbon material, those obtained by thermal decomposition of organic matter under various thermal decomposition conditions, artificial graphite, natural graphite, soil graphite, expanded graphite, scaly graphite, and the like can be used. As the oxide, a compound mainly composed of tin oxide can be used. As the negative electrode current collector, copper foil, nickel foil and the like are used. Such a negative electrode is preferably manufactured by kneading the active material with an organic solvent to form a slurry, and applying the slurry to a metal foil current collector to obtain a slurry.

There is no particular limitation on the shape of a lithium battery using the lithium cobalt composite oxide of the present invention as a cathode active material. Sheet type, film type, folding type, winding type user cylindrical type, button type and the like are selected according to the use.

EXAMPLE

Although an Example demonstrates this invention concretely below, this invention is not limited by these Examples of course. In the following, Examples 1 to 6 are examples of the present invention, and Examples 7 to 10 are comparative examples.

<Example 1>

The mixed solution of the cobalt sulfate aqueous solution and ammonium hydroxide was continuously mixed with the sodium hydroxide aqueous solution, and the cobalt hydroxide slurry was continuously synthesized by a known method to obtain cobalt hydroxide powder through a flocculation, filtration, and drying process. The obtained cobalt hydroxide was powder X-ray diffraction using CuKα rays (manufactured by Rigaku Electric Co., Ltd., type RINT2100, 40 KV-40 mA, sampling interval 0.020, scanning rate 2 ° / min, same also in the following examples). The half-width of the diffraction peak at the (001) plane with 2θ = 19 ± 1 ° was 0.27 °, and the half-width of the diffraction peak at the (101) plane with 2θ = 38 ± 1 ° was 0.23 °. In addition, the scanning electron microscopic observation revealed that the amorphous fine particles aggregated and formed from substantially spherical secondary particles. As a result of the particle size distribution analysis on the volume basis determined from the image analysis of the scanning electron microscope observation, the average particle diameter D 50 was 17.5 μm, D0 was 7.1 μm, and D90 was 26.4 μm.

As a result of dispersing the cobalt hydroxide secondary particles in pure water, the secondary particles easily collapsed to form a suspension mainly composed of the primary particles, indicating that the cohesive force of these secondary particles was weak. In addition, the particle size distribution of the secondary particle powder was measured after irradiating water (42 kHz 40 W) with a dispersion medium for 3 minutes using a laser scattering particle size distribution measuring device. As a result, the average particle diameter D50 was 0.75 µm and Dl0 was 0.35 µm. And D90 was 1.6 µm. In addition, the slurry after the measurement of the average particle diameter was dried, and as a result of scanning electron microscopy, the secondary particle shape before the measurement was not observed. The specific surface area of the cobalt hydroxide particles composed of secondary particles was 17.lm 2 / g, a press density of 1.75 g / cm 3, and a substantially spherical cobalt hydroxide powder in which primary particles were weakly aggregated.

The cobalt hydroxide powder and the lithium carbonate powder were dry mixed with an atomic ratio (Li / Co) of lithium and cobalt of 1.000. This mixed powder was filled into a ceramic square open container, and was heated up at a rate of 1.2 ° C./min from room temperature to 600 ° C. in the firing furnace. Moreover, after heating up at 1.5 degree-C / min from 600 degreeC to 950 degreeC, it baked at 950 degreeC for 12 hours. The fired product was a homogeneous finish. LiCoO ₂ formed by agglomeration of primary particles obtained by pulverizing a fired product The particle size distribution of the powder was measured using a laser scattering particle size distribution analyzer as a dispersion medium. As a result, the average particle diameter D50 was 9.5 µm, D0 was 4.9 µm, and D90 was 22.9 µm. In addition, the specific surface area determined by the BET method was 0.47 m 2 / g. The by-product amount of cobalt oxide was 0.2% or less.

LiCoO _{2 above} 100 g of the powder was dispersed in 100 g of pure water, and after filtration, potentiometric titration was carried out with 0.1 N of 0.1 N, and the residual alkali amount was found to be 0.02% by weight. Moreover, X-ray diffraction spectrum was obtained by X-ray diffraction with respect to the said powder. In powder X-ray diffraction using CuKα rays, the half-width of the diffraction peak at the (110) plane at 2θ = 66.5 ± 1 ° was 0.095 °, and the press density was 3.4Og / cm 3.

The powder, acetylene black, and polyvinylidene fluoride powder are mixed at a mass ratio of 90/5/5, N-methylpyrrolidone is added to prepare a slurry, and a doctor blade is applied to an aluminum foil having a thickness of 20 µm. It was used to apply one side. It dried and rolled 4 times by roll press, and produced the positive electrode sheet for lithium batteries. It was 3.45 g / cm <3> when the density of the electrode layer was measured from the thickness of the positive electrode body after rolling, and the weight per unit volume of the electrode layer.

The punched sheet of the positive electrode was used as a positive electrode, a metal lithium foil having a thickness of 500 μm was used as the negative electrode, and a nickel foil 20 μm was used as the negative electrode current collector, and the separator was a porous polypropylene having a thickness of 25 μm. In addition, the electrolyte solution refers to a mixed solution of a LiPF6 / EC + DEC (1: 1) solution (1: 1) having a concentration of 1 M of EC and DEC having a solute of LiPF6 in the electrolyte solution. 2) were assembled in an argon glove box.

One battery using an EC + DEC (1: 1) solution as the electrolyte was charged at 25 ° C to 4.3 V with a load current of 75 mA for 1 g of positive electrode active material, and at a load current of 75 mA for 1 g of positive electrode active material. It discharged to 2.5V and calculated | required initial discharge capacity. In addition, the discharge capacity ratios at 1.5C and 0.25C were obtained. In addition, the volumetric capacity density was calculated from the density of the electrode layer and the capacity per weight. In addition, this battery was then subjected to 30 charge and discharge cycle tests.

As a result, the initial volume capacity density of the anode electrode layer at 25 ° C. and 2.5 to 4.3 V is 497 mAh / cm 3 electrode layer, the initial weight capacity density is 160 mAh / g-LiCo0 ₂ , and the capacity retention rate after 30 charge / discharge cycles is 97.2%. In addition, the ratio of the discharge capacity of 1.5C / discharge capacity of 0.25C was 0.91.

In addition, with respect to the remaining batteries using the EC + DEC (1: 1) solution as the electrolyte solution, each was charged at 4.3 V for 10 hours, disassembled in an argon glove box to remove the positive electrode sheet after charging, and the positive electrode sheet was removed. After washing, the resultant was punched out to a diameter of 3 mm, sealed in an aluminum capsule with EC, and heated at a rate of 5 ° C./minute with a scanning differential calorimeter to measure the heat generation start temperature. As a result, the heat generation start temperature of the 4.3V charged product was 161 ° C.

  <Example 2>

Using the same mixed powder as in Example 1, the temperature was first raised from room temperature to 480 ° C. at a rate of 7 ° C./min, and then calcined for 1 hour at 480 ° C. in air. Subsequently, the temperature was raised to 950 ° C. at a rate of 7 ° C./min without disintegration or pulverization, followed by firing for 2 hours at 950 ° C. in the air for 14 hours. LiCoO ₂ powder was synthesized in the same manner. The fired product was a homogeneous finish. LiCoO ₂ obtained had an average particle diameter D50 of 9.7 µm, a D0 of 4.0 µm and a D90 of 20.1 µm, and a specific surface area of 0.48 m 2 / g determined by the BET method.

An X-ray diffraction spectrum of the powder was obtained by X-ray diffraction. In powder X-ray diffraction using CuKα rays, the half width of the diffraction peaks on the (110) plane at 2θ = 66.5 ± 1 ° was 0.098 °. The press density of the powder was 3.45 g / cm 3 and the residual alkali amount was 0.02 wt%.

In the same manner as in Example 1, a positive electrode sheet using the powder was produced, and the characteristics as a positive electrode active material of a lithium secondary battery were determined. As a result, the initial weight capacity density at 25 ° C. and 2.5 to 4.3 V was 161 mAh / g. -LiCoO ₂ and the capacity retention rate after 30 charge and discharge cycles was 97.1%. In addition, the ratio of the discharge capacity of 1.5C / discharge capacity of 0.25C was 0.90, and the heat generation start temperature of the 4.3V charged product was 162 ° C.

 <Example 3>

In Example 2, the LiCo0 ₂ powder was synthesize | combined by the method similar to Example 2 except having set the baking temperature of the 1st stage | stage to 380 degreeC. The fired product was a homogeneous finish. LiCo0 ₂ obtained had an average particle diameter of D50 of 10.2 µm, D10 of 6.0 µm, and D90 of 24.6 µm, and a specific surface area of 0.52 m 2 / g determined by the BET method.

Regarding the LiCo0 ₂ powder, an X-ray diffraction spectrum was obtained using an X-ray diffractometer (RINT210O type manufactured by Rigaku Electric Co., Ltd.). In powder X-ray diffraction using CuKα rays, the half width of the diffraction peaks on the (110) plane at 2θ = 66.5 ± 1 ° was 0.099 °. The press density of the obtained LiCo0 ₂ powder at a press pressure of 0.96 t / cm 2 was 3.43 g / cm 3. The amount of alkali remaining of LiCo0 ₂ was 0.2 wt%.

A positive electrode sheet using the powder was produced in the same manner as in Example 1, and the properties as a positive electrode active material of a lithium secondary battery were determined. As a result, the initial weight capacity density at 25 ° C. and 2.5 to 4.3 V was 163 mAh / g−. The capacity retention rate after LiCo0 ₂ and 30 charge and discharge cycles was 98.0%. In addition, the heat generation start temperature of the 4.3V charged product was 160 ° C.

<Example 4>

In Example 1, it carried out similarly to Example 1 except having raised the temperature increase rate from room temperature to 600 degreeC at 0.7 degreeC / min, and after heating up at a temperature increase rate of 1.5 degreeC / min to 950 degreeC, for 12 hours Firing LiCoO ₂ Powders were synthesized. LiCo0 ₂ obtained had an average particle diameter D50 of 9.7 µm, a D10 of 3.7 µm, and a D90 of 21.5 µm, and a specific surface area of 0.47 m 2 / g determined by the BET method.

An X-ray diffraction spectrum was obtained by X-ray diffraction with respect to the LiCo0 ₂ powder. In powder X-ray diffraction using CuKα rays, the half width of the diffraction peaks on the (110) plane at 2θ = 66.5 ± 1 ° was 0.095 °. The press density of the obtained LiCo0 ₂ powder at a press pressure of 0.96 t / cm 2 was 3.47 g / cm 3. The residual alkali amount of LiCo0 ₂ was 0.02% by weight.

In the same manner as in Example 1, a positive electrode sheet using the powder was produced, and the characteristics as a positive electrode active material of a lithium secondary battery were determined. As a result, the initial weight capacity density at 25 ° C. and 2.5 to 4.3 V was 161 mAh /. g-LiCo0 ₂ and the capacity retention rate after 30 charge / discharge cycles was 97.4%. In addition, the heat generation start temperature of the 4.3V charged product was 161 ° C.

Example 5

In Example 2, the positive electrode active material was calcined under the same conditions as in Example 2, except that cobalt hydroxide used in Example 1 and cobalt hydroxide as primary cobalt particles were co-molded with cobalt atomic ratio to 15 mol of oxyhydroxide. Was synthesized. The firing state of the small powder in the baking container was homogeneous. LiCo0 ₂ obtained had an average particle diameter of D 5 O of 10.8 µm, DlO of 3.0 µm, and D90 of 18.5 µm, and a specific surface area of 0.47 m 2 / g obtained by the BET method.

An X-ray diffraction spectrum was obtained for the LiCo0 ₂ powder by using an X-ray diffraction apparatus (type RINT210O manufactured by Science and Electrical, Inc.). In powder X-ray diffraction using CuKα rays, the half width of the diffraction peaks on the (110) plane at 2θ = 66.5 ± 1 ° was 0.095 °. Obtained LiCo0 ₂ The press density at powder press pressure 0.96 t / cm 2 was 3.30 g / cm 3. The amount of alkali remaining of LiCo0 ₂ was 0.02% by weight.

In the same manner as in Example 1, a positive electrode sheet using the powder was produced, and the characteristics as a cathode active material of a lithium secondary battery were determined. As a result, the initial weight capacity density at 25 ° C. and 2.5 to 4.3 V was 161 mAh. / g-LiCo0 _2, and the capacity retention rate after 30 charge and discharge cycles was 97.4%. In addition, the exotherm onset temperature of the 4.3V charged product was 163 degreeC.

Example 6

In Example 2, a positive electrode was calcined under the same conditions as in Example 2, except that cobalt hydroxide used in Example 1 and cobalt hydroxide triturated with cobalt trioxide having a secondary particle size of 7 µ were formed in an equimolar ratio in a cobalt atomic ratio. An active material was synthesized. The baking form of the small powder in the baking container was homogeneous. LiCo0 ₂ obtained had an average particle diameter D50 of 7.7 µm, D10 of 3.0 µm and D90 of 19.1 µm, and a specific surface area of 0.47 m 2 / g determined by the BET method.

An X-ray diffraction spectrum was obtained by X-ray diffraction with respect to the LiCo0 ₂ powder. In powder X-ray diffraction using CuKα rays, the half width of the diffraction peaks on the (110) plane at 2θ = 66.5 ± 1 ° was 0.95 °. Obtained LiCo0 ₂ The press density of the powder at a press pressure of 0.96 t / cm 2 was 3.2Og / cm 3. The residual alkali amount of LiCo0 ₂ was 0.2 wt%.

In the same manner as in Example 1, a positive electrode sheet using the powder was prepared, and the characteristics as a positive electrode active material of a lithium secondary battery were determined. As a result, the initial weight capacity density at 25 ° C. and 2.5 to 4.3 V was 161 mAh /. g-LiCo0 ₂ and the capacity retention rate after 30 charge / discharge cycles was 97.4%. In addition, the heat generation start temperature of the 4.3 V filler was 160 ° C.

Example 7

In Example 1, LiCo0 ₂ was synthesized by baking at 950 ° C for 12 hours in the same manner as in Example 1 except that the temperature increase rate from room temperature to 950 ° C was 6 ° C / min. The firing state of the small powder in the baking container was heterogeneous. Although the small component powder of the lower layer part of the small powder powder in a container was sintered and the upper layer part was not sintered, the atomic ratio Li / Co of lithium and cobalt in the small powder was less than one. The initial weight capacity density was 154 mAh / g-LiCo0 _2, and the ratio of the discharge capacity of 1.5C / discharge capacity of 0.25C was 0.75.

<Example 8>

In Example 2, LiCo0 ₂ was synthesize | combined by the method similar to Example 2 except having set the baking temperature of the 1st stage | stage at 800 degreeC, and making the baking of the 2nd stage | stage at 950 degreeC 12 hours. The firing state of the small powder in the firing container was heterogeneous. Although the small component powder of the lower layer part of the small component powder in a container was sintered and the upper layer part was not sintered, the atomic ratio Li / Co of lithium and cobalt in the small component powder was less than one. The initial weight capacity density was 153 mAh / g-LiCo0 ₂ , and the ratio of the discharge capacity of 1.5 C / discharge capacity of 0.25 C was 0.78.

Example 9

In Example 2, LiCo0 ₂ was synthesize | combined by the method similar to Example 2 except having set the baking temperature of the 1st stage to 200 degreeC, and setting the baking temperature of the 2nd stage to 950 degreeC 12 hours. The firing state of the small powder in the firing container was heterogeneous. The small powder of the lower layer of the small powder in the container was sintered and the upper layer of the small powder was not sintered, but the atomic ratio Li / Co of lithium and cobalt in the small powder was less than one. The initial weight capacity density was 155 mAh / g-LiCo0 _2, and the ratio of the discharge capacity of 1.5C / discharge capacity of 0.25C was 0.82.

Example 10

In Example 2, the LiCo0 ₂ powder was synthesized and evaluated in the same manner as in Example 2, except that the mixed atomic ratio of lithium / cobalt as the raw material was 1.025. As a result, the capacity retention rate after 30 charge and discharge cycles was 89%.

According to the present invention, inexpensive cobalt hydroxide and lithium source also use lithium carbonate, which is inexpensive, and has a large volume capacity density, high large current discharge characteristics, high safety, large charge / discharge cycle durability, high press density, and high productivity. A novel method for producing a lithium cobalt composite oxide for a positive electrode of a lithium secondary battery is provided.

In addition, a positive electrode for a lithium secondary battery and a lithium secondary battery including the prepared lithium cobalt composite oxide are provided.

Claims (8)

The mixture obtained by mixing the cobalt hydroxide powder and the lithium carbonate powder so that the atomic ratio of lithium / cobalt is 0.98 to 1.01 is calcined at 300 to 550 ° C. in an oxygen-containing atmosphere, and the calcined product is then heated at 850 to 1050 ° C. in an oxygen-containing atmosphere. A method for producing a lithium cobalt composite oxide for a positive electrode of a lithium secondary battery, which is fired. The method according to claim 1, wherein the fired product fired at 300 to 550 占 폚 is fired in an oxygen-containing atmosphere at 850 to 1050 占 폚 without grinding. The production method according to claim 1 or 2, wherein the cobalt hydroxide powder is a substantially spherical secondary particle having an average particle diameter D50 of aggregated primary particles of 8 to 20 µm. The manufacturing method of Claim 1 or 2 whose average particle diameter D50 after disperse | distributing the said secondary particle of cobalt hydroxide in pure water is 1/4 or less with respect to the average particle diameter D50 of the primary particle. The positive electrode for lithium secondary batteries containing the lithium cobalt complex oxide manufactured by the manufacturing method of Claim 1 or 2. The lithium secondary battery using the positive electrode of Claim 5. The production method according to claim 1 or 2, wherein a mixture of the cobalt hydroxide powder and the lithium carbonate powder is mixed so that an atomic ratio of lithium / cobalt is 0.990 to 1.005. The manufacturing method of Claim 1 or 2 which bakes the baking material obtained by baking the mixture which mixed the said cobalt hydroxide powder and lithium carbonate powder further at 950-1050 degreeC.