JP2010116302A - Lithium cobaltate particulate powder and method for producing the same, and non-aqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium cobaltate particulate powder which has high density, a uniformly-grown crystal and is useful as a positive electrode active material for a non-aqueous electrolyte secondary battery. <P>SOLUTION: The lithium cobaltate particulate powder is characterized in that the average secondary particle diameter (D50) is 15.0-25.0 μm, the BET specific surface area (BET) is 0.10-0.30 m<SP>2</SP>/g, and the compression density (CD 2.5 t/cm<SP>2</SP>) is 3.65-4.00 g/cm<SP>3</SP>. The lithium cobaltate particulate powder is obtained by using a specified cobalt oxyhydroxide particulate powder as a precursor. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lithium cobalt oxide particle powder having a high density and having crystals uniformly grown. The lithium cobalt oxide particle powder according to the present invention is useful as a positive electrode active material (lithium cobalt oxide particle powder) used in a non-aqueous electrolyte secondary battery.

  In recent years, electronic devices such as AV devices and personal computers are rapidly becoming portable and cordless, and there is an increasing demand for secondary batteries having a small size, light weight, and high energy density as power sources for driving these devices. Under such circumstances, a lithium ion secondary battery having advantages such as a high charge / discharge voltage and a large charge / discharge capacity has attracted attention.

Conventionally, as positive electrode active substances useful for high energy-type lithium ion secondary batteries having 4V-grade voltage, LiMn ₂ O ₄ of spinel structure, LiMnO ₂ having a zigzag layer structure, LiCoO ₂ of layered rock-salt structure, LiCo _1-X Ni _X O ₂ , LiNiO _{2 and the} like are generally known, and among them, a lithium ion secondary battery using LiCoO ₂ is excellent in that it has a high charge / discharge voltage and charge / discharge capacity. There is a need for further improvement in characteristics.

That is, when LiCoO ₂ pulls out lithium, Co ³⁺ becomes Co ^{4+ and} yarn teller distortion occurs, and in the region where Li is pulled 0.45, from hexagonal to monoclinic, when further drawn, it changes from monoclinic to hexagonal. The crystal structure changes. Therefore, by repeating the charge / discharge reaction, the crystal structure becomes unstable, and oxygen release, reaction with the electrolytic solution, and the like occur.

Therefore, there is a need for LiCoO ₂ having excellent cycle characteristics that can stably maintain characteristics even after repeated charge / discharge reactions.

  In addition, regarding the packing density, it is also desired to increase the capacity of the positive electrode, and in order to improve the electrode density of the positive electrode, the packing properties such as the compression density of lithium cobaltate (under pressure assuming electrode rolling) are improved. It is required to make it.

  Further, regarding the specific surface area, it is required to make the specific surface area of lithium cobalt oxide as small as possible in order to prevent battery swelling and improve thermal stability.

  Furthermore, since the reaction with the electrolytic solution becomes active at high temperatures, the structure of the positive electrode active material is stable even at high temperatures and thermal stability needs to be improved to ensure safety as a secondary battery. Has been.

Lithium cobaltate is usually a cobalt raw material such as cobalt oxyhydroxide (CoOOH), cobalt hydroxide (Co (OH) ₂ ) or cobalt oxide (Co ₃ O ₄ ), and a lithium raw material such as lithium carbonate or lithium hydroxide. Obtained by mixing and firing.

  Conventionally, it is known to control the tap density, compression density, and the like of lithium cobalt oxide particle powder (Patent Documents 1 to 4).

Japanese Patent Laid-Open No. 2003-2661 JP 2004-182564 A JP 2004-196603 A JP 2005-206422 A

  A positive electrode active material and lithium cobalt oxide particle powder satisfying the above-mentioned properties are currently most demanded, but have not yet been obtained.

Patent Document 1 describes a lithium cobalt oxide particle powder having a weight average particle diameter of 5 to 15 μm and a specific surface area of 0.15 to 0.6 m ² / g, but the precursor has a high specific surface area. Therefore, when the precursor is fired, it is difficult to say that the primary particles are sintered and the cycle characteristics are excellent.

The Patent Document 2, a tap density of 1.8 g / cm ³ or more, 2 ton / cm ² by pressurized compressed density described lithium cobaltate particles is 3.5~4.0g / cm ³ However, it is a physical property that can be achieved by mixing two components, and it is difficult to say that rate characteristics and cycle characteristics are excellent.

  Patent Document 3 describes a lithium cobalt oxide particle powder having an average particle size of 10 to 15 μm. However, it is difficult to say that the primary particle size is small from the SEM photograph, so that it is excellent in thermal stability. Since the tap density of the precursor is low, it is difficult to say that the electrode density is high.

Patent Document 4 discloses a lithium cobalt oxide particle having a specific particle size distribution, a bulk density of 1.20 to 2.20 g / cm ³ , and a tap density of 2.30 to 3.00 g / cm ^3. Although powder is described, since the average particle size is small, the compression density is low, and when the electrode (positive electrode) is used, the density is low.

  Therefore, an object of the present invention is to obtain a lithium cobalt oxide particle powder having a high packing density, a low specific surface area, and uniform crystal growth.

  The technical problem can be achieved by the present invention as follows.

That is, in the present invention, the average particle diameter (D50) of the secondary particles is 15.0 to 25.0 μm, the BET specific surface area value (BET) is 0.10 to 0.30 m ² / g, and the compression density (CD2. 5t / cm < ² >) is 3.65 to 4.00 g / cm < ³ >, It is a lithium cobaltate particle powder characterized by the above-mentioned (Invention 1).

  Further, according to the present invention, in the X-ray diffraction pattern of the lithium cobalt oxide particle powder according to the present invention 1, the intensity ratio I (104) / I (003) of the (003) plane to the (104) plane is 0.70 to 1. 20 (invention 2).

Further, the present invention is a lithium cobalt oxide particle powder according to the present invention 1, wherein the total alkali amount is 0.10 wt% or less and the residual Co ₃ O ₄ amount is 1000 ppm or less (this book) Invention 3).

Further, the present invention provides a solution containing a cobalt salt in an aqueous solution and an alkaline solution by neutralization at the same time, and promptly oxidizes to obtain cobalt oxyhydroxide particles. The cobalt oxyhydroxide particles and the lithium compound And the mixture is heat-treated in a temperature range of 600 to 1100 ° C., wherein the cobalt oxyhydroxide particle powder has an average particle diameter (D50) of secondary particles. Is 15.0-25.0 μm, the BET specific surface area value (BET) is 0.1-20.0 m ² / g, and the tap density (TD) is 1.0-3.5 g / cm ³ . The crystallite size ratio (D110 / D003) between the (110) plane and the (003) plane in the X-ray diffraction pattern is 0.50 to 2.00, and the crystallite size on the (003) plane is 300 to 700 mm. It is a manufacturing method of a lithium cobaltate particles according to any one of claims 1 to 3, characterized in that (present invention 4).

  Moreover, this invention is a nonaqueous electrolyte secondary battery which consists of a positive electrode containing the lithium cobaltate particle powder in any one of this invention 1 thru | or 3 (this invention 5).

Since the lithium cobalt oxide particle powder according to the present invention has a small BET specific surface area value, when it is used as an electrode for a secondary battery, it is possible to suppress battery swelling derived from the positive electrode and to improve thermal stability.
Moreover, since the lithium cobalt oxide particle powder according to the present invention has a high compression density, an improvement in electrode density can be expected, and an increase in capacity can be expected.
Furthermore, since the lithium cobalt oxide particle powder according to the present invention controls the peak intensity ratio of a specific diffraction surface and can expect uniform crystal growth, when it is used as an electrode, the rate and cycle characteristics may be improved. Can expect

  Moreover, the manufacturing method of the lithium cobalt oxide particle powder which concerns on this invention uses the cobalt oxyhydroxide particle powder as a precursor, and can obtain the lithium cobalt oxide particle powder excellent in the characteristic.

  The configuration of the present invention will be described in more detail as follows.

First, lithium cobalt oxide particle powder (LiCoO ₂ ) according to the present invention will be described.

  The average particle diameter (D50) of the secondary particles of the lithium cobalt oxide particle powder according to the present invention is 15.0 to 25.0 μm. When the average particle diameter (D50) of the secondary particles is less than 15.0 μm, the compression density is low, and when the electrode (positive electrode) is used, the density is very low. When the average particle diameter (D50) of the secondary particles exceeds 25.0 μm, the electrode may be peeled off due to the bending or bending of the electrode due to the electrode thickness, and the particle may be exposed, which is not preferable. . The average particle diameter (D50) of the secondary particles is preferably 15.0 to 23.0 μm, more preferably 15.5 to 20.0 μm.

The BET specific surface area value (BET) of the lithium cobaltate particles according to the present invention is 0.10 to 0.30 m ² / g. When the BET specific surface area value is less than 0.10 m ² / g, it is practically difficult to obtain by synthesis, and when it exceeds 0.30 m ² / g, the electrode (positive electrode) and In this case, it is difficult to say that the cycle characteristics and the suppression of battery swelling are excellent. A more preferable BET specific surface area value is 0.10 to 0.25 m ² / g.

The compression density (CD: 2.5 t / cm ² ) of the lithium cobalt oxide particle powder according to the present invention is 3.65 to 4.00 g / cm ³ . When the compression density is less than 3.65 g / cm ³ , the target electrode density (positive electrode) cannot be obtained. Although the compression density may exceed 4.00 g / cm ³ , there may be insufficient penetration of the electrolyte when the electrode is used, and it is difficult to manufacture in practice. A more preferable compression density is 3.70 to 3.95 g / cm ³ .

  In the X-ray diffraction pattern of the lithium cobaltate particles according to the present invention, the intensity ratio I (104) / I (003) between the (003) plane and the (104) plane is preferably 0.70 to 1.20. . The intensity ratio may exceed 1.20, but it is practically difficult to manufacture. When the intensity ratio is less than 0.70, the crystal growth direction is the ab axis direction, Li insertion / extraction becomes difficult, and cycle characteristics deteriorate, which is not preferable. A more preferred intensity ratio I (104) / I (003) is 0.70 to 1.15, and even more preferably 0.75 to 1.10.

  The total alkali amount of the lithium cobalt oxide particle powder according to the present invention is preferably 0.10 wt% or less. If the total alkali amount of the lithium cobalt oxide particle powder exceeds 0.10 wt%, the battery may swell when the electrode (positive electrode) is used. More preferably, it is 0.001-0.08 wt%.

The amount of residual Co ₃ O _{4 in the} lithium cobalt oxide particle powder according to the present invention is preferably 1000 ppm or less. When the amount of residual Co ₃ O _{4 in} the lithium cobalt oxide particle powder exceeds 1000 ppm, an electrode (positive electrode) may cause an OCV defect in the battery, which is not preferable. More preferably, it is 10-800 ppm.

  Next, a method for producing lithium cobalt oxide particle powder according to the present invention will be described.

  The lithium cobalt oxide particle powder according to the present invention is obtained by mixing cobalt oxyhydroxide particle powder and a lithium compound so as to be 1.00 to 1.02 with respect to the number of moles of cobalt (including different metals), The mixture can be obtained by heat treatment in a temperature range of 600 to 1100 ° C.

  The mixing treatment of the cobalt oxyhydroxide particle powder and the lithium compound in the present invention may be either dry or wet as long as it can be uniformly mixed.

  The lithium compound may be either lithium hydroxide or lithium carbonate, but lithium carbonate is preferred.

  If necessary, a small amount of different metals such as Mg, Al, Ti, Zr, Ni, Mn, and Sn may be added.

When the heat treatment temperature of the mixture of the cobalt oxyhydroxide particle powder and the lithium compound is less than 600 ° C., LiCoO ₂ which is a low temperature phase having a pseudo spinel structure is generated, which is not preferable. When the heat treatment temperature exceeds 1100 ° C., LiCoO ₂ having a high temperature irregular phase in which the positions of lithium and cobalt are random is generated. The atmosphere during firing is preferably an oxidizing gas atmosphere. The reaction time is preferably 5 to 20 hours.

  The cobalt oxyhydroxide particle powder in the present invention will be described.

  The cobalt oxyhydroxide particle powder according to the present invention is obtained by dropping a solution containing a cobalt salt and an aqueous alkali solution into an aqueous solution, performing an instantaneous neutralization reaction, and then performing an oxidation reaction promptly. Cobalt particle powder can be used.

  As the alkaline aqueous solution, for example, an aqueous solution of sodium hydroxide, potassium hydroxide, sodium carbonate or the like can be used, but it is preferable to use sodium hydroxide, sodium carbonate or a mixed solution thereof. An ammonia solution is not preferable from the viewpoint of environmental load.

  The addition amount of the alkaline aqueous solution used for the neutralization reaction may be an equivalent ratio of 1.0 with respect to the neutralized content of the total metal salt contained, but it is preferable to add the alkali excess together for pH adjustment.

  The pH of the reaction solution is preferably controlled in the range of 11.0 to 13.0. When the pH of the reaction solution is less than 11.0, it is difficult to aggregate the primary particles and it becomes difficult to form secondary particles, or fine powder is generated and the number of particles increases, which is not preferable. . When the pH of the reaction solution exceeds 13.0, the primary particles grow in a plate shape, the secondary particles become sparse, and the packing density decreases, which is not preferable. The pH of the reaction solution is more preferably 12.0 to 13.0.

  As the cobalt salt, cobalt sulfate, cobalt nitrate, cobalt acetate, and cobalt carbonate can be used. In particular, cobalt sulfate is preferable.

  Moreover, it is preferable to control the dripping speed | rate (m value) of a cobalt solution to 0.005-0.300 mol / (l * h). In addition, this unit is a cobalt molar concentration dripped per reaction volume 1L and reaction time 1h. Furthermore, in order to stabilize the salt concentration, sodium sulfate may be previously contained in the reaction mother liquor. A more preferable dropping rate (m value) of the cobalt solution is 0.010 to 0.280 mol / (l · h).

  The oxidation reaction is performed by venting a gas containing an oxygen-containing gas or a nitrogen-containing gas. The oxygen gas is preferably vented from the inside of the draft tube and the lower part of the reactor.

  The reaction temperature is preferably 30 ° C or higher, more preferably 35 to 70 ° C.

  If necessary, a small amount of different metals such as Mg, Al, Ti, Zr, Ni, Mn, Sn may be added. A method of mixing with a cobalt salt in advance, a method of adding simultaneously with a cobalt salt, or a reaction in the middle of the reaction Any means of adding to the solution may be used.

  In the present invention, a concentrator is connected to the reactor, and a solution containing a cobalt salt and an alkaline solution are dropped and neutralized simultaneously in the aqueous solution of the reactor, and a rapid oxidation reaction is performed to obtain lithium cobalt oxide particles. It is preferable to circulate the reaction slurry produced in the reactor between the reactor and the concentrator as a reaction slurry containing. Therefore, it is preferable to circulate the reaction slurry between the reactor and the concentrator by using a device equipped with a baffle, a draft tube and an external concentrator in the reactor.

  The circulation flow rate between the reactor and the concentrator is preferably such that the stirring state of the reactor is not changed. Concentration is preferably performed at a rate at which the raw material solution to be dropped is filtered without delay. The filtration method may be either continuous or intermittent.

  The reaction time is not particularly limited because it depends on the target particle size. In addition, the upper limit of the reaction concentration is not particularly defined as long as the facility operates stably to such an extent that it does not adhere to the piping and does not block due to properties such as the viscosity of the reaction slurry. Practically, the upper limit is preferably about 20 mol / l.

The cobalt oxyhydroxide particle powder obtained under the above production conditions has an average particle diameter (D50) of secondary particles of 3.0 to 25.0 μm and a BET specific surface area value (BET) of 0.1 to 20.0 m ^2. / G, the tap density (TD) is 1.0 to 3.5 g / cm ³ , and the crystallite size ratio (D110 / D003) of the (110) plane to the (003) plane in the X-ray diffraction pattern is 0.50 to 2 The crystallite size on the .00 and (003) planes is preferably 300 to 700 mm.

  Moreover, in this invention, it is preferable that the average particle diameter (D50) and BET specific surface area value (BET) of the secondary particle of cobalt oxyhydroxide particle powder satisfy | fill the relational expression 1.

(Relational formula 1)
D50 <12, BET ≦ -12.536 × LN (D50) +32.65
D50 ≧ 12, BET ≦ 1.5

  In the present invention, when the average particle diameter (D50) and the specific surface area value (BET) of the secondary particles of the cobalt oxyhydroxide particle powder are outside the range of the relational expression 1, When the electrode (positive electrode) is used, it is difficult to say that the cycle characteristics and the suppression of battery swelling are excellent.

  In the present invention, it is preferable that the average particle diameter (D50) and tap density (TD) of the secondary particles of the cobalt oxyhydroxide particle powder satisfy the relational expression 2.

(Relational expression 2)
D50 <17, TD ≧ 1.627 × LN (D50) −1.65
D50 ≧ 17, TD ≧ 3.0

  In the present invention, when the average particle diameter (D50) and the tap density (TD) of the secondary particles of the cobalt oxyhydroxide particle powder are outside the range of the relational expression 2, It is difficult to obtain a high compression density and electrode density (positive electrode).

  In the present invention, it is preferable that the average particle diameter (D50) of the secondary particles of the cobalt oxyhydroxide particle powder and the crystallite size ratio (D110 / D003) satisfy the relational expression 3.

(Relational expression 3)
D50 <12, D110 / D003 ≦ −1.083 × LN (D50) +3.65
D50 ≧ 12, D110 / D003 ≦ 1.00

  In the present invention, when the average particle diameter (D50) of the secondary particles of the cobalt oxyhydroxide particle powder and the crystallite size ratio (D110 / D003) are outside the range of the relational expression 3, lithium cobalt oxide is used. In this case, it becomes difficult to obtain a target high compression density and electrode density (positive electrode).

As a cobalt oxyhydroxide particle powder more preferable as a precursor of lithium cobaltate particle powder, the average particle diameter (D50) of secondary particles is 15.0 to 25.0 μm, and the BET specific surface area value (BET) is 0. 0.1 to 20.0 m ² / g, tap density (TD) is 1.0 to 3.5 g / cm ³ , and crystallite size between (110) plane and (003) plane in X-ray diffraction pattern Cobalt oxyhydroxide particles having a ratio (D110 / D003) of 0.50 to 2.00, a crystallite size of (003) plane of 300 to 700 mm, and satisfying the relational expressions 1 to 3 is there.

  Next, the positive electrode using the positive electrode active material which consists of lithium cobaltate particle powder concerning this invention is described.

  When a positive electrode is produced using the positive electrode active material according to the present invention, a conductive agent and a binder are added and mixed according to a conventional method. As the conductive agent, acetylene black, carbon black, graphite and the like are preferable, and as the binder, polytetrafluoroethylene, polyvinylidene fluoride and the like are preferable.

  The secondary battery manufactured using the positive electrode active material according to the present invention includes the positive electrode, the negative electrode, and an electrolyte.

  As the negative electrode active material, lithium metal, lithium / aluminum alloy, lithium / tin alloy, graphite, graphite, or the like can be used.

  In addition to the combination of ethylene carbonate and diethyl carbonate, an organic solvent containing at least one of carbonates such as propylene carbonate and dimethyl carbonate and ethers such as dimethoxyethane can be used as the solvent for the electrolytic solution.

  Further, as the electrolyte, in addition to lithium hexafluorophosphate, at least one lithium salt such as lithium perchlorate and lithium tetrafluoroborate can be dissolved in the above solvent and used.

The electrode density of the positive electrode produced by using the lithium cobalt oxide particle powder according to the present invention in accordance with the method described later is preferably 3.5 to 4.0 g / cm ³ .

  About the secondary battery manufactured using the lithium cobaltate particle powder which concerns on this invention, 1.0% or less of the weight decreasing rate of the lithium cobaltate particle powder taken out after charge is preferable.

<Action>
In the present invention, the most important point is that a cobalt oxide having a small specific surface area and a high compression density is used as a precursor, so that the lithium cobaltate has a small specific surface area and a high compression density. Lithium powder can be obtained. Furthermore, when an electrode is used, a high-density, high-capacity electrode (positive electrode) can be obtained, and a battery having good thermal stability, less swelling, and excellent cycle characteristics can be obtained.
In particular, by controlling the crystal growth properties of LiCoO ₂ by the characteristics of the precursor and the firing conditions, LiCoO ₂ crystals are grown isotropically, Li diffusion from the ab axis is smoothed, and the cycle characteristics in the battery are improved. The inventor presumes that this has been improved.

  A typical embodiment of the present invention is as follows.

  The particle shape of the lithium cobalt oxide particle powder was observed using a scanning electron microscope SEM-EDX with an energy dispersive X-ray analyzer [manufactured by Hitachi High-Technologies Corporation].

  The average particle diameter (D50) of secondary particles of cobalt oxyhydroxide particle powder and lithium cobaltate particle powder and the frequency of volume-based median diameter were measured using a particle size distribution meter Microtrac HRA9320-X100 (manufactured by Nikkiso Co., Ltd.). did.

  The specific surface areas of the cobalt oxyhydroxide particle powder and the lithium cobaltate particle powder were measured by BET method using Macsorb HM model-1208 (manufactured by Mountech Co., Ltd.).

The compression density (CD) of the lithium cobalt oxide particle powder was calculated from the volume after pressurizing at 2.5 t / cm ² with a desktop press machine (RIKEN S1-150) by putting 10 g of a sample weighed into a cylindrical mold.

  The tap density (TD) of the cobalt oxyhydroxide particle powder is a powder density after filling a sample of 40 g into a 100 ml measuring cylinder and tapping 300 times using a tamp denser (KYT-3000, manufactured by Seishin Enterprise Co., Ltd.). Was measured.

  Powder X-ray diffraction (RIGAKU Cu-Kα 40 kV 40 mA) was used to identify the lithium cobalt oxide particle powder. Further, the strength ratio ((104) plane, (003) plane) was calculated by preparing a sample plate by the following method and measuring it under the following conditions.

  First, 30 g of a commercially available adhesive (such as cemedine) is dissolved in 70 g of an acetone solution to prepare a cemedine solvent having a concentration of about 30%. Next, 1.5 g of the cemedine solvent is added to 2.0 g of lithium cobaltate particles, and mixed in an agate mortar to form a slurry. Thereafter, the slurry is poured into a glass sample plate, and an excess amount is removed using a knife or the like before acetone volatilizes. At this time, be careful that the glass plate and flat surface come out. Finally, XRD measurement is started after the acetone is completely volatilized.

  For identification of the cobalt oxyhydroxide particle powder, powder X-ray diffraction (RIGAKU Cu-Kα 40 kV 40 mA) was also used. The crystallite size ((D110) plane, (D003) plane) was calculated from each diffraction peak of the powder X-ray diffraction.

  The measurement conditions of powder X-ray diffraction were adjusted to Rigaku's RINT use tube Cu, tube voltage 40 kV, and current 40 kV manufactured by Rigaku. The strength of the (003) plane was measured at a measurement angle of 18.2 ° to 19.5 °, and the strength of the (104) plane was measured at a measurement angle of 44.2 ° to 46.1 °. The measurement was performed at a step angle of 0.002 ° and a scan speed of 0.05 ° / min.

  As the remaining alkali, a numerical value converted into the amount of lithium carbonate using the Walder method was used.

  That is, 10.0 g of a sample was dispersed in 50 ml of water for 1 hour, then allowed to stand for 1 hour, and then the supernatant was titrated with hydrochloric acid. In this case, phenolphthalein and bromophenol blue were used as indicators, and lithium hydroxide and lithium carbonate were quantified, and all were converted to the amount of lithium carbonate.

The amount of residual Co ₃ O ₄ was obtained by dissolving 5.0 g of a sample by heating with concentrated hydrochloric acid (35%) in a state in which nitrogen gas was passed and suppressing oxidation, adding a small amount of ascorbic acid dropwise, and adjusting the pH to 5.0. After adjusting to ˜6.0, the precipitate is filtered off, the pH of the filtrate is adjusted to 3.0 to 4.0, and titrated with EDTA (indicator Cu-PAN) while heating until boiling. Cobalt was quantified and a numerical value converted to Co ₃ O ₄ amount was used.

  The TG evaluation is performed by disassembling a coin-type battery after charging 0.1C and 4.3V in argon, taking out the electrode (positive electrode), washing with dimethyl carbonate (DMC) and drying, and then peeling off the positive electrode active material. The temperature was raised to 400 ° C. at 10 ° C./min in an oxygen atmosphere using TG / DTA (TG / DTA 6300 manufactured by Seiko Instruments Inc.), and the change in weight was measured.

  The battery characteristics and thermal stability of the positive electrode active material were evaluated by preparing a positive electrode, a negative electrode, and an electrolytic solution by the following production method to produce a coin-type battery cell.

<Coin cell evaluation>
<Preparation of positive electrode>
The positive electrode active material and the conductive agent acetylene black, graphite, and the binder polyvinylidene fluoride were precisely weighed to a weight ratio of 93: 3: 4 and dispersed in N-methyl-2-pyrrolidone. Thorough mixing was performed to prepare a positive electrode mixture slurry. Next, this slurry was applied to an aluminum foil as a current collector with a doctor blade, dried at 120 ° C., and then punched into a disk shape of φ16 mm to obtain a positive electrode plate.

<Production of negative electrode>
A metal lithium foil was punched into a disk shape of φ16 mm to produce a negative electrode.

<Preparation of electrolyte>
An electrolyte solution was prepared by mixing 1 mol / liter of lithium hexafluorophosphate (LiPF6) as an electrolyte in a mixed solution of ethylene carbonate and diethyl carbonate in a volume ratio of 30:70.

<Assembly of coin-type battery cells>
A SUS316L case was used in a glove box in an argon atmosphere, and a coin battery having a diameter of 20 mm and a thickness of 3.2 mm was manufactured by injecting an electrolyte solution through a polypropylene separator between the positive electrode and the negative electrode.

<Evaluation of rate characteristics>
A charge / discharge test of a secondary battery was performed using the coin-type battery. Measurement conditions include a cut-off voltage of 3.0V to 4.3V, one cycle charge / discharge at 0.1C, then one cycle charge / discharge at 1C, and the discharge capacity ratio (1C / 0.1C). The rate characteristic was calculated.

<Thermal stability evaluation>
The coin-type battery was charged at 0.1 C to 4.3 V, and then the positive electrode active material was measured by TG / DTA according to the method described above. The weight loss rate at 250 ° C. was 0.7%.

<Lamination cell evaluation>
<Preparation of positive electrode>
The positive electrode active material and the conductive agent acetylene black, graphite, and the binder polyvinylidene fluoride were precisely weighed to a weight ratio of 93: 3: 4 and dispersed in N-methyl-2-pyrrolidone. Thorough mixing was performed to prepare a positive electrode mixture slurry. Next, this slurry was applied to an aluminum foil as a current collector with a doctor blade, dried at 120 ° C. and dried, and then pressed with a roll press to produce a positive electrode sheet.
Next, the positive electrode sheet was cut out to obtain a positive electrode having a length of 25 mm and a width of 25 mm. At one end of the positive electrode, a positive electrode active material layer having a length of 25 mm and a width of 5 mm was scraped from the positive electrode current collector to form a lead welded portion. Then, an aluminum lead was welded to the lead welded portion to form a positive electrode terminal.

<Production of negative electrode>
As a component of the negative electrode mixture, graphite as a negative electrode active material and polyvinylidene fluoride are precisely weighed to a weight ratio of 94: 6, dispersed in N-methyl-2-pyrrolidone, and thoroughly mixed with a high-speed kneader. A negative electrode mixture slurry was prepared. Next, this slurry was applied to the copper foil of the current collector with a doctor blade, dried at 120 ° C., and then pressed with a roll press to produce a negative electrode sheet.
Subsequently, the negative electrode sheet was cut out to obtain a positive electrode having a length of 25 mm and a width of 25 mm. At one end of the positive electrode, a negative electrode active material layer having a length of 25 mm and a width of 5 mm was scraped from the positive electrode current collector to form a lead welded portion. Then, a nickel lead was welded to the lead welded portion to form a negative electrode terminal.

<Preparation of electrolyte>
An electrolyte solution was prepared by mixing 1 mol / liter of lithium hexafluorophosphate (LiPF6) as an electrolyte in a mixed solution of ethylene carbonate and dimethyl carbonate in a volume ratio of 1: 2.

<Assembly of laminate cell>
Next, the positive electrode and the negative electrode obtained as described above were laminated via a separator to obtain an electrode body. And this electrode body was immersed in the non-aqueous electrolyte solution, and the positive electrode active material layer, the negative electrode active material layer, and the separator were impregnated with the non-aqueous electrolyte solution.
Next, the electrode body impregnated with the non-aqueous electrolyte was sandwiched between laminate films, and the outer peripheral edge of the laminate film was heat-sealed under reduced pressure and sealed, and the electrode body was sealed in the laminate film.

  A nonaqueous electrolyte battery was produced as described above. The positive electrode terminal and the negative electrode terminal are led out of the laminate film.

<Battery evaluation>
The cut-off voltage was 4.2-3.0 V. Charging was performed until the current value converged to C / 200 after energization to the cut-off with a constant current of 1 C. In discharging, a constant current of 1 C was applied to cut off, and this cycle was repeated 100 cycles. In addition, the measurement was performed in a 25 degreeC thermostat.

Example 1
<Manufacture of positive electrode active material>
In a 10 L reactor equipped with a draft tube, baffle, and blade-type stirrer, 8 L of ion-exchanged water is stretched, the temperature is adjusted to 50 ° C. while stirring sufficiently, and sufficient oxygen is contained from the bottom of the reactor. A gas was vented, and a 4 mol / l sodium hydroxide aqueous solution was added dropwise so that the pH was 12.5. A 1.5 mol / l aqueous solution of cobalt sulfate was continuously fed to the reactor at an average feed rate of 0.025 mol / (l · hr). At the same time, a 4 mol / l aqueous sodium hydroxide solution was continuously supplied so that the pH was 12.5. Cobalt oxyhydroxide particles generated by rapid oxidation overflow from the top of the reactor, concentrate in a 0.4 L concentrator connected to the overflow pipe, circulate to the reactor, and the cobalt oxyhydroxide in the reactor The reaction was continued until the particle concentration reached 15 mol / l.

After the reaction, the suspension taken out was washed with water using a filter press and then dried to obtain cobalt oxyhydroxide particles. The obtained cobalt oxyhydroxide particles were analyzed by XRD. As a result, the cobalt oxyhydroxide particles were a single phase of cobalt oxyhydroxide, the secondary particles had an average particle diameter (D50) of 17.6 μm, a frequency of 9.7%, and a specific surface area BET. The value (BET) is 1.26 m ² / g, the tap density (TD) is 3.08 g / cm ³ , the (003) plane crystallite size (D003) is 602 mm, and the (110) plane crystallite size (D110). Was 470 mm and the crystallite size ratio (D110 / D003) was 0.78 (precursor 1).

  The obtained cobalt oxyhydroxide particle powder (precursor 1) and the lithium compound are sufficiently mixed in a predetermined amount so that the lithium / cobalt molar ratio is 1.01, and the mixed powder is heated at 1030 ° C. in an oxidizing atmosphere. Was calcined for 10 hours to obtain lithium cobaltate particles.

As a result of X-ray diffraction of the obtained lithium cobaltate particle powder, it was a lithium cobaltate single phase and no impurity phase was present (FIG. 1). The average particle diameter (D50) of the secondary particles is 15.7 μm, the BET specific surface area value is 0.19 m ² / g, and the compression density CD (2.5 ton / cm ² ) is 3.73 g / cm. ³ , the XRD intensity ratio I (104) / I (003) was 0.80, the total alkali amount was 0.06%, and the residual Co ₃ O ₄ amount was 208 ppm.

  The SEM observation result of the lithium cobaltate particle powder obtained in FIG. 2 is shown. As shown in FIG. 2, it was an aggregate of primary particles, there were no sharp parts, and there was no fine powder.

The coin-type battery produced using the positive electrode active material had an electrode density of 3.7 g / cm ³ and a rate characteristic (1C / 0.1C) of 95%. Further, the weight loss rate at 250 ° C. in the TG measurement of the positive electrode active material peeled off from the electrode after charging was 0.7%, and the capacity retention rate at 100 cycles at 1C-1C in the laminate cell was 95%. Met.

Comparative Example 1
<Manufacture of positive electrode active material>
The cobalt-containing solution was adjusted to 0.5 mol / l, and 1.05 equivalent of an aqueous sodium hydroxide solution was added to the neutralized portion of cobalt to cause a neutralization reaction. Next, an oxidation reaction was performed at 90 ° C. for 20 hours while blowing air to obtain cobalt oxide particles. The obtained cobalt oxide particles are Co ₃ O ₄ single phase, the average particle diameter of the secondary particles is 0.1 μm, the BET specific surface area is 12.0 m ² / g, and the tap density TD is 1.30 g. / Cm ³ (Precursor 5).

  A predetermined amount of the obtained cobalt oxide particle powder (precursor 5) and the lithium compound are sufficiently mixed so that the lithium / cobalt molar ratio is 1.04, and the mixed powder is subjected to an oxidizing atmosphere at 1030 ° C. Calcination was performed for 10 hours to obtain lithium cobalt oxide particle powder.

As a result of X-ray diffraction of the obtained lithium cobaltate particle powder, it was a lithium cobaltate single phase and no impurity phase was present (FIG. 3). The average particle diameter (D50) of the secondary particles is 13.5 μm, the BET specific surface area value is 0.35 m ² / g, and the compression density CD (2.5 ton / cm ² ) is 3.58 g / cm. ³ , the XRD intensity ratio I (104) / I (003) was 0.60, the total alkali amount was 0.12%, and the residual Co ₃ O ₄ amount was 100 ppm.

  The SEM observation result of the lithium cobaltate particle powder obtained in FIG. 4 is shown. As shown in FIG. 4, the particles had an angular portion, and fine powder was observed on the particle surface.

The coin-type battery produced using the positive electrode active material had an electrode density of 3.4 g / cm ³ and a rate characteristic (1.0 C / 0.1 C) of 92%. Further, the weight loss rate at 250 ° C. in the TG measurement of the positive electrode active material peeled from the post-charge electrode was 0.3%, and the capacity retention rate at 100 cycles at 1C-1C in the laminate cell was 87%. Met.

Precursors 2-4, 6
A cobalt oxyhydroxide particle powder was obtained in the same manner as in the precursor 1 except that the supply rate of the aqueous cobalt sulfate solution, the reaction temperature, and the pH of the reaction solution were variously changed. The production conditions of the cobalt oxyhydroxide particle powder are shown in Table 1, and various characteristics of the obtained cobalt oxyhydroxide particle powder are shown in Table 2.

Examples 2 to 15 and Comparative Examples 2 to 8
A lithium cobalt oxide particle powder was obtained in the same manner as in Example 1 except that the type of precursor, the mixing ratio with Li, and the heating temperature were variously changed. Table 3 shows the production conditions of the lithium cobalt oxide particle powder, and Table 4 shows the characteristics of the obtained lithium cobalt oxide particle powder.

  As shown in the above examples, all the secondary batteries (Examples 1 to 15) using the lithium cobalt oxide particle powder according to the present invention have a rate characteristic of 94% or more, and in the laminate cell. Since the capacity retention rate was 93% or more, it was confirmed that the capacity maintenance rate was suitable as a secondary battery.

  By using the positive electrode active material having the lithium cobalt oxide particle powder as a precursor according to the present invention as a precursor, the specific surface area is small, the compression density is high, the electrode density as a secondary battery is also high, and the cycle characteristics and thermal stability are also good. A non-aqueous electrolyte secondary battery can be obtained.

2 is an X-ray diffraction pattern of lithium cobaltate particles obtained in Example 1. FIG. It is an electron micrograph (SEM) of the lithium cobaltate particle powder obtained in Example 1 (5000 times magnification). 3 is an X-ray diffraction pattern of lithium cobaltate particles obtained in Comparative Example 1. It is an electron micrograph (SEM) of the lithium cobalt oxide particle powder obtained in Comparative Example 1 (magnification 5000 times).

Claims (5)

The average particle diameter (D50) of the secondary particles is 15.0 to 25.0 μm, the BET specific surface area value (BET) is 0.10 to 0.30 m ² / g, and the compression density (CD 2.5 t / cm ² ) is. 3. Cobalt-acid lithium particle powder characterized by being 3.65 to 4.00 g / cm ³ . The cobalt acid whose intensity ratio I (104) / I (003) of (003) plane and (104) plane is 0.70-1.20 in the X-ray-diffraction pattern of the lithium cobalt oxide particle powder of Claim 1 Lithium particle powder. The lithium cobalt oxide particle powder according to claim 1, wherein the total alkali amount is 0.10 wt% or less and the residual Co ₃ O ₄ amount is 1000 ppm or less. A solution containing a cobalt salt in an aqueous solution and an alkali solution are simultaneously neutralized dropwise, and a rapid oxidation reaction is performed to obtain cobalt oxyhydroxide particles. The cobalt oxyhydroxide particles and a lithium compound are mixed, A method for producing lithium cobaltate particles, wherein the mixture is heat-treated at a temperature in the range of 600 to 1100 ° C., wherein the cobalt oxyhydroxide particles have an average secondary particle size (D50) of 15.0 to 25. 0.0 μm, a BET specific surface area value (BET) of 0.1 to 20.0 m ² / g, a tap density (TD) of 1.0 to 3.5 g / cm ³ , and an X-ray diffraction pattern The crystallite size ratio (D110 / D003) of the (110) plane to the (003) plane is 0.50 to 2.00, and the crystallite size of the (003) plane is 300 to 700 mm. Preparation of lithium cobaltate particles according to any one of claims 1 to 3, The nonaqueous electrolyte secondary battery which consists of a positive electrode containing the lithium cobaltate particle powder in any one of Claims 1 thru | or 3.