JP4927369B2 - Method for producing lithium-containing composite oxide for positive electrode of lithium secondary battery - Google Patents

Description

  The present invention provides a method for producing a lithium-containing composite oxide for a lithium secondary battery positive electrode having a large volumetric capacity density, high safety, excellent charge / discharge cycle durability and low temperature characteristics, and a lithium-containing composite oxide produced. The present invention relates to a positive electrode for a lithium secondary battery and a lithium secondary battery.

In recent years, as devices become more portable and cordless, demands for non-aqueous electrolyte secondary batteries such as lithium secondary batteries that are small, lightweight, and have high energy density are increasing. As a positive electrode active material for such a non-aqueous electrolyte secondary battery, lithium and transition metal composite oxides such as LiCoO ₂ , LiNiO ₂ , LiNi _0.8 Co _0.2 O ₂ , LiMn ₂ O ₄ , LiMnO ₂ (Lithium-containing composite oxide) is known.

Among lithium-containing composite oxides, a lithium secondary battery using LiCoO ₂ as a positive electrode active material and carbon such as lithium alloy, graphite, or carbon fiber as a negative electrode can obtain a high voltage of 4 V, and thus has high energy. It is widely used as a battery having a density.

However, in the case of a non-aqueous secondary battery using LiCoO ₂ as a positive electrode active material, further improvement in capacity density per unit volume and safety of the positive electrode layer is desired, and by repeatedly performing a charge / discharge cycle, There have been problems such as deterioration of cycle characteristics in which the battery discharge capacity gradually decreases, a problem of low weight capacity density, and a large decrease in discharge capacity at low temperatures.

In order to solve these problems, Patent Document 1 discloses that the average particle size of LiCoO ₂ as a positive electrode active material is 3 to 9 μm, and the volume occupied by a particle group having a particle size of 3 to 15 μm is 75% or more of the total volume. And by setting the ratio of diffraction peak intensities at 2θ = about 19 ° and 2θ = 45 ° measured by X-ray diffraction using CuKα as a radiation source to a specific value, the coating characteristics, self-discharge characteristics, and cycle characteristics are improved. It has been proposed to be an excellent active material. Further, Patent Document 1 proposes a preferred embodiment in which the particle size of LiCoO ₂ does not substantially have a particle size distribution of 1 μm or less or 25 μm or more. However, such a positive electrode active material has improved coating characteristics and cycle characteristics, but has not been sufficiently satisfactory in safety, volume capacity density, and weight capacity density.

Moreover, in order to solve the problem regarding battery characteristics, Patent Document 2 proposes to replace 5-35% of Co atoms with W, Mn, Ta, Ti, or Nb for improving cycle characteristics. . In Patent Document 3, hexagonal LiCoO ₂ having a c-axis length of a lattice constant of 14.051 mm or less and a crystallite diameter in the (110) direction of 45 to 100 nm is used as a positive electrode active material. It has been proposed to improve cycle characteristics.

Further, Patent Document 4 discloses the formula Li _x Ni _1-m N _m O ₂ (wherein N is at least one element selected from the group consisting of transition metal elements other than Ni, Al, and alkaline earth metal elements). , 0 <x <1.1, 0 ≦ m ≦ 1, and the primary particles are plate-like or columnar, and (volume-based cumulative 95% diameter−volume-based cumulative 5% diameter) / volume It is disclosed that a lithium composite oxide having a reference cumulative 5% diameter of 3 or less and an average particle diameter of 1 to 50 μm has high initial discharge capacity per weight and excellent charge / discharge cycle durability.

  In Patent Document 5, primary particles having an average particle diameter of 0.01 to 2 μm and agglomeration of primary particles of cobalt hydroxide, cobalt oxyhydroxide, and cobalt oxide are aggregated. It has been proposed to lithiate cobalt compound powders that have formed secondary particles. However, even in this case, a positive electrode material having a high volume capacity density cannot be obtained, and the cycle characteristics, safety, and large current discharge characteristics are still insufficient.

  Patent Documents 6 and 7 also propose a method of coating lithium cobaltate particles with a different metal element by a sol-gel method. However, the coated lithium cobaltate is unsatisfactory in battery performance, that is, discharge capacity, charge / discharge cycle durability and safety, and the alkoxide as a starting material is a material suitable in the laboratory, It is too expensive to employ industrially and cannot be employed. In addition, since alkoxide is very sensitive to moisture and easily hydrolyzed, it requires a reactor that does not affect the moisture in the air, resulting in high equipment costs and high cost. There's a problem.

In addition, Patent Document 8 also proposes that a colloidal coating solution obtained by adding water to (NH ₄ ) ₂ HPO ₄ and Al (NO ₃ ) · 3H ₂ O acts on lithium cobalt oxide particles. The obtained lithium cobalt oxide is unsatisfactory in its battery performance, that is, discharge capacity, charge / discharge cycle durability and safety.

  As described above, in the conventional technology, in a lithium secondary battery using a lithium composite oxide as a positive electrode active material, all of volume capacity density, safety, coating uniformity, cycle characteristics, and low temperature characteristics are all achieved. We have not yet obtained a satisfactory content.

JP-A-6-2443897 Japanese Patent Laid-Open No. 3-201368 JP 10-31805 A JP-A-10-72219 JP 2002-60225 A JP 2000-305884 A JP 2002-279991 A JP 2003-7299 A

  The present invention provides a method for producing a lithium-containing composite oxide for a positive electrode of a lithium secondary battery, which has a large volumetric capacity density, high safety, excellent charge / discharge cycle durability, and excellent low temperature characteristics. Another object is to provide a positive electrode for a lithium secondary battery and a lithium secondary battery including the lithium-containing composite oxide.

  In the present invention, the M element, which is a substitution element of the N element, is allowed to act in an aqueous solution, so that the N element such as cobalt in the lithium-containing composite oxide is replaced with the M element sufficiently and uniformly. Is achieved, and further, a lithium-containing composite oxide for a lithium secondary battery positive electrode having high safety, excellent charge / discharge cycle durability, and excellent low-temperature characteristics is obtained. This is in contrast to the case where the conventional method does not provide good results as shown in Comparative Example 1 described later.

Thus, the gist of the present invention is as follows.
(1) Lithium source, N element source, M element source, and a lithium-containing composite represented by the following formula 1 , wherein a mixture containing a fluorine source is fired in an oxygen-containing atmosphere when a is greater than 0 in the following formula 1. A method for producing an oxide, wherein the M element source is an aqueous solution of a carboxylate compound having an M element in the molecule, and an aqueous solution adjusted to pH 2 to 12 by adding an alkali to the aqueous solution is used. A method for producing a lithium-containing composite oxide.
_{Li p N x M m O z} F a ··· Formula 1
N is Co, Ni, Co and Ni, Mn and Ni, or Co and Ni and Mn, and M is at least one element selected from the group consisting of Ti, Zr, Hf, Mg, and Al. . 0.9 ≦ p ≦ 1.2, 0.97 ≦ x <1.00, 0 <m ≦ 0.03, 1.9 ≦ z ≦ 2.2, x + m = 1, 0 ≦ a ≦ 0.02. is there.
(2) The manufacturing method as described in said (1) whose carboxylate compound is a C1-C4 carboxylate compound.
(3) The production method according to (1) or (2) above, wherein the aqueous solution of the carboxylate compound is an aqueous solution containing formic acid or acetic acid and adjusted to pH 4 to 10 by adding ammonia.
(4) The production method according to any one of (1) to (3), wherein the N element source is a powder having an average particle diameter (D50) of 1 to 25 μm.
(5) The production according to any one of (1) to (4), wherein the N element source is at least one selected from the group consisting of cobalt hydroxide, cobalt oxyhydroxide, cobalt tetroxide, and cobalt carbonate. Method.
(6) N element source is nickel-cobalt coprecipitation hydroxide, nickel-cobalt coprecipitation oxyhydroxide, nickel-cobalt coprecipitation oxide, nickel-manganese coprecipitation hydroxide, nickel-manganese coprecipitation oxyhydration objects, nickel - manganese coprecipitated oxide, nickel - cobalt - manganese coprecipitated hydroxide, nickel - cobalt - manganese coprecipitated oxyhydroxide and nickel - cobalt - at least one selected from the group consisting of manganese coprecipitated oxide The manufacturing method in any one of said (1)-(4) which is.
(7) were mixed aqueous solution and N element source Powder carboxylate compound, after removal of the water from the resulting mixture, mixing the fluorine source powder lithium source powder, and in the formula 1 when a is greater than 0 Then, the production method according to any one of the above (1) to (6), which is produced by firing at 800 to 1050 ° C. in an oxygen-containing atmosphere.
(8) Mixing an aqueous solution of a carboxylate compound, an N element source powder, a lithium source powder, and a fluorine source powder when a is greater than 0 in Formula 1, removing moisture from the resulting mixture, and then containing oxygen The manufacturing method in any one of said (1)-(6) baked at 800-1050 degreeC in atmosphere.
(9) A lithium source powder, an N element source powder, and a lithium-containing composite oxide powder obtained by mixing and baking a fluorine source powder when a is greater than 0 in Formula 1 , and an aqueous solution of a carboxylate compound And after removing water from the resulting mixture, the production method according to any one of the above (1) to (6), wherein firing is performed at 300 to 1050 ° C. in an oxygen-containing atmosphere.
(10) A positive electrode for a lithium secondary battery comprising a lithium-containing composite oxide produced by the production method according to any one of (1) to (9) above.
(11) A lithium secondary battery using the positive electrode described in (10) above.

According to the present invention, a lithium-containing composite oxide having excellent characteristics for a lithium secondary battery positive electrode such as a large volumetric capacity density, high safety, excellent charge / discharge cycle durability, and excellent low temperature characteristics is obtained. And a method for producing a lithium-containing composite oxide having high productivity that is excellent in storage stability of the intermediate, and further, a positive electrode for a lithium secondary battery including the produced lithium-containing composite oxide, and A lithium secondary battery is provided.
The reason why such an excellent effect is achieved by the present invention is not necessarily clear, but is estimated as follows. That is, in the conventional addition of the M element source in the solid phase method, since the amount of the M element source added is very small, uniform addition to the N element source or the positive electrode material is difficult. It was difficult to obtain the additive effect. However, according to the method of the present invention, since the M element source is applied to the N element source or the positive electrode material in the form of an aqueous solution, the M element can be uniformly dispersed in the pores of the positive electrode active material. It is presumed that the effect of improving battery performance is manifested by the addition of. Further, since the M element source is allowed to act on the N element source in the form of an aqueous solution or on the positive electrode material, control of the composition and particle size of the positive electrode active material is easier than in the conventional coprecipitation method, and is industrial. There is an advantage.

The lithium-containing composite oxide for a lithium secondary battery positive electrode obtained by the production method of the present invention is :
_{Li p N x M m O z} F a ··· Formula 1
It is represented by In Equation 1 , p, x, m, z and a are defined above. Among these, p, x, m, z and a are preferably as follows. 0.9 ≦ p ≦ 1.1, particularly preferably 0.97 ≦ p ≦ 1.03, 0.975 ≦ x <0.998, 0.002 ≦ m ≦ 0.025, 1.9 ≦ z ≦ 2.1, particularly preferably 1.95 ≦ z ≦ 2.05, x + m = 1, 0.001 ≦ a ≦ 0.01. Here, when a is larger than 0, a composite oxide in which some of the oxygen atoms are substituted with fluorine atoms is obtained. In this case, the safety of the obtained positive electrode active material is improved. In the present invention, the total number of cations atoms is equal to the total number of anions atoms. That is, it is preferable that the sum of p, x, and m is equal to the sum of z and a.

N is, Co, Ni, Co and Ni, Ru Mn and Ni, or Co, Ni and Mn der. Further, M, capacity expression, safety, than the viewpoint such as the cycle durability is at least one element selected Ti, Zr, Hf, Mg, and from the group consisting of Al.

In the present invention, the balance of battery performance, that is, the balance between initial weight capacity density, initial volume capacity density, safety and charge / discharge cycle stability is excellent. The atomic ratio of Mg is preferably 1/5 to 5/1, more preferably 1/3 to 3/1, particularly preferably 2/3 to 3/2, and m is preferably 0.002 ≦ m ≦ 0.025, more preferably 0.005 ≦ m ≦ 0.025, and particularly preferably 0.01 ≦ m ≦ 0.02. When M is composed of Mg and M2 (M2 is at least one element selected from the group consisting of Ti, Zr, Ta, and Nb), the atomic ratio of M2 to Mg is preferably 1/40 to 2/1, particularly preferably 1/30 to 1/5, and m is preferably 0.002 ≦ m ≦ 0.030, more preferably 0.005 ≦ m ≦ 0.030, and particularly preferably 0. .010 ≦ m ≦ 0.020. Furthermore, M Ri is Do from Mg and Al, and if the Ti or Zr coexist, since the battery performance balance of the more excellent, particularly preferred. In this case, the coexistence of 1/2 to 1/20 mole of Ti or Zr of the total number of moles of Mg and Al is preferable.

In the present invention, when the M element and / or F is contained, both the M element and F are preferably present on the surface of the lithium-containing composite oxide particles. The presence of these elements on the surface can improve important battery characteristics such as safety and charge / discharge cycle characteristics without causing a decrease in battery performance when added in a small amount. That these elements are present on the surface, for the positive electrode particles, spectroscopic analysis, for example, it can be determined by carrying out XPS analysis.

  The present invention requires the use of an aqueous solution of a carboxylate compound having an M element in the molecule as the M element source. The carboxylic acid used here is preferably a monocarboxylic acid represented by the general formula R—COOH (where R is a hydrogen atom or a chain hydrocarbon group). As the monocarboxylic acid, those having 1 to 4 carbon atoms such as formic acid, acetic acid, propionic acid and butyric acid are preferable. These carboxylic acids are preferred because they can increase the solubility of the carboxylate compound having M element in the molecule in an aqueous solution. In particular, formic acid or acetic acid is preferable as the carboxylic acid.

Aqueous carboxylate, Ru aqueous der the pH was adjusted to 2 to 12 by adding an alkali. When a highly acidic carboxylic acid is used, if the pH of the aqueous solution is less than 2, the N element source is easily dissolved. Therefore, it is necessary to adjust the pH to 2 to 12 by adding a base such as ammonia. It is . A pH exceeding 12 is not preferable because the N element source is easily dissolved.
The aqueous carboxylate solution is particularly preferably an aqueous solution containing formic acid or acetic acid, and adjusted to pH 4 to 10 by adding ammonia as an alkali.

  The concentration of the aqueous carboxylate solution used in the present invention is preferably higher because it is necessary to remove moisture by drying in a later step. However, if the concentration is too high, the viscosity increases, the uniform mixing with other element source powders forming the positive electrode active material decreases, and the solution does not easily penetrate into the N element source powder. % By weight, particularly 4 to 20% by weight is preferred.

  As the N element source used in the present invention, when the N element is cobalt, cobalt carbonate, cobalt hydroxide, cobalt oxyhydroxide, cobalt oxide and the like are preferably used. In particular, cobalt hydroxide or cobalt oxyhydroxide is preferable because performance is easily exhibited. When the N element is nickel, nickel hydroxide, nickel oxyhydroxide, nickel oxide or the like is preferably used. Further, when the N element is manganese, manganese dioxide or manganese carbonate is preferably used.

When the N element is nickel and cobalt, nickel-cobalt coprecipitated hydroxide, nickel-cobalt coprecipitated oxyhydroxide, and nickel-cobalt coprecipitated oxide are nickel and manganese. -Manganese coprecipitated hydroxide, nickel-manganese coprecipitated oxyhydroxide, nickel-manganese coprecipitated oxide is nickel, cobalt and manganese, nickel-cobalt-manganese coprecipitated hydroxide, nickel-cobalt- Manganese coprecipitated oxyhydroxide or nickel-cobalt-manganese coprecipitated oxide is preferred as the N element source. More specifically, when the N element is nickel and cobalt, Ni _0.8 Co _0.2 OOH, Ni _0.8 Co _0.2 (OH) _2, etc. are nickel and manganese. When Ni _0.5 Mn _0.5 OOH or the like is nickel, cobalt and manganese, Ni _0.4 Co _0.2 Mn _0.4 OOH, Ni _1/3 , Co _1/3 Mn _1/3 OOH and the like are each preferably exemplified as the N element source.

  As the N element source, a powder having an average particle diameter (D50) of 1 to 25 μm is used. The average particle diameter (D50) refers to a particle diameter having a volume-based cumulative 50%. If the average particle size is less than 1 μm, the filling property of the positive electrode powder is lowered, which is not preferable. On the other hand, if the average particle diameter exceeds 25 μm, a uniform coated electrode surface cannot be obtained, and the large current discharge characteristics are deteriorated. A preferable average particle diameter is 4 to 20 μm. Here, the average particle diameter means the average particle diameter of secondary aggregate particles in the case of aggregate particles. In the present invention, an N element source compound in which primary particles aggregate to form secondary particles is preferably used.

As the lithium source used in the present invention, lithium carbonate or lithium hydroxide is preferably used. In particular, lithium carbonate is preferable because it is inexpensive. As the lithium source, a powder having an average particle diameter (D50) of 2 to 25 μm is preferably used. As the fluorine source, metal fluorides such as LiF and MgF ₂ are selected.

As a preferable aspect in the method for producing a lithium-containing composite oxide using an aqueous solution of a carboxylate compound having an M element in the molecule as an M element source, which is a feature of the present invention, the following (A) and (B) Or (C) is mentioned.
(A) An aqueous solution of a carboxylate compound, an N element source powder, and, if necessary, a fluorine source powder are mixed. After removing moisture from the resulting mixture, a lithium source powder and, if necessary, a fluorine source powder. It is mixed and then fired at 800-1050 ° C. in an oxygen-containing atmosphere.
(B) An aqueous solution of a carboxylate compound, an N element source powder, a lithium source powder, and, if necessary, a fluorine source powder are mixed, water is removed from the resulting mixture, and then at 800 to 1050 ° C. in an oxygen-containing atmosphere. Bake.
(C) A mixture obtained by mixing a lithium source powder, an N element source powder, and, if necessary, a fluorine source powder and mixing a lithium-containing composite oxide powder obtained by firing and an aqueous solution of a carboxylate compound. After removing moisture from the substrate, firing is performed at 300 to 1050 ° C. in an oxygen-containing atmosphere.

  In the present invention, when an aqueous solution of a carboxylate compound is allowed to act on the N element source powder, it is preferably performed while heating as necessary. The temperature is preferably 40 ° C to 80 ° C, particularly preferably 50 ° C to 70 ° C. By heating, the N element source and the M element source are easily dissolved, and the N element source and the M element source can be stably dissolved in a short time.

In the means such as (A), (B) and (C), an aqueous solution of a carboxylate compound having an M element in the molecule is used as an aqueous solution containing an M element salt of a carboxylic acid . Also, the amount of M element source is such that the ratio of each element desired and within the scope of a general formula of the positive electrode active material prepared in the present invention the _{Li p N x M m O z} F a Is done.

  As a method of impregnating the N element source powder with the aqueous solution of the carboxylate compound in the means (A), (B) and (C), spraying the N element source powder with the aqueous solution of the carboxylate compound It is also possible to impregnate. However, the powder is put into the aqueous solution in a tank and stirred to impregnate, or more preferably, a biaxial screw kneader, an axial mixer, a paddle mixer, a turbulizer, etc. are used to form a slurry. It is preferable to impregnate by mixing uniformly. As the solid content concentration in the slurry, a higher concentration is preferable as long as it is uniformly mixed. Usually, the solid / liquid ratio is preferably 30/70 to 90/10, particularly preferably 50/50 to 80/20. It is. Moreover, it is preferable to perform a reduced pressure treatment in the state of the slurry because the solution penetrates more into the N element source powder.

  A mixture of an aqueous solution of a carboxylate compound, an N element source powder, and optionally a fluorine source powder, an aqueous solution of a carboxylate compound, an N element source powder, a lithium source powder, and an optional fluorine source powder Removal of water contained in a mixture comprising: N element source powder, lithium source powder, and, if necessary, a mixture comprising a powder obtained by mixing and baking a fluorine source powder and an aqueous solution of a carboxylate compound Is preferably carried out by drying at 50 to 200 ° C., particularly preferably at 80 to 120 ° C., usually for 1 to 10 hours. Since the water in the mixture is removed in the subsequent firing process, it is not always necessary to completely remove it at this stage, but it is necessary to remove as much energy as possible in order to vaporize the water in the firing process. It is preferable to keep it. Examples of the water removal industrial method include spray dryers, flash dryer ears, belt dryers, paddle dryers, and biaxial screw dryers. Among these, biaxial screw dryers are preferable. Examples of the biaxial screw dryer include a thermoprocessor and a paddle dryer.

  Firing after removing moisture from the mixture is preferably performed at 800 to 1050 ° C. in an oxygen-containing atmosphere in the means (A) and (B). When the calcination temperature is lower than 800 ° C., the formation of lithium composite oxide becomes incomplete, and when it exceeds 1050 ° C., charge / discharge cycle durability and initial capacity are lowered. In particular, the firing temperature is preferably 900 to 1000 ° C. In the means of (C), 300 to 1050 ° C. is preferable. When the temperature is lower than 300 ° C., the organic matter is not sufficiently decomposed, and when it exceeds 1050 ° C., charge / discharge cycle durability and initial capacity are lowered. . In particular, the firing temperature is preferably 400 to 900 ° C.

The lithium-containing composite oxide thus produced has an average particle diameter D50 of preferably 5 to 30 μm, particularly preferably 8 to 25 μm, and a specific surface area of preferably 0.1 to 0.7 m.
² / g, particularly preferably 0.15 to 0.5 m ² / g, preferably a half width of (110) plane diffraction peak of 2θ = 66.5 ± 1 ° measured by X-ray diffraction using CuKα as a radiation source Is 0.08 to 0.14 °, particularly preferably 0.08 to 0.13 °, and the press density is preferably 3.65 to 4.10 g / cm ³ , particularly preferably 3. It is suitable that it is 70-4.00 g / cm < ³ >. The present invention has a feature that a high press density can be obtained as compared with the prior art. In the present invention, the press density means the apparent density of the powder when the lithium composite oxide powder is pressed at a pressure of 2 ton / cm ² . In addition, the lithium-containing composite oxide obtained by the production method of the present invention preferably has a residual alkali content of 0.03% by weight or less, particularly preferably 0.02% by weight or less.

  When producing a positive electrode for a lithium secondary battery from such a lithium-containing composite oxide, the composite oxide powder is mixed with a carbon-based conductive material such as acetylene black, graphite, and Ketchen black and a binder. It is formed by. For the binder, polyvinylidene fluoride, polytetrafluoroethylene, polyamide, carboxymethyl cellulose, acrylic resin, or the like is preferably used. The lithium-containing composite oxide powder, conductive material and binder obtained by the production method of the present invention are made into a slurry or a kneaded product using a solvent or a dispersion medium, and this is a positive electrode current collector such as an aluminum foil or a stainless steel foil. A positive electrode for a lithium secondary battery is manufactured by being supported by coating or the like.

  In the lithium secondary battery using the lithium-containing composite oxide obtained by the production method of the present invention as the positive electrode active material, a porous polyethylene film, a porous polypropylene film, or the like is used as the separator. Various solvents can be used as the solvent for the electrolyte solution of the battery, and among them, carbonate ester is preferable. The carbonate ester can be either cyclic or chain. Examples of the cyclic carbonate include propylene carbonate and ethylene carbonate (EC). 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. Moreover, depending on the material of the negative electrode active material, when a chain carbonate ester and a cyclic carbonate ester are used in combination, discharge characteristics, cycle durability, and charge / discharge efficiency may be improved.

Further, in the lithium secondary battery using a lithium-containing composite oxide obtained by the process of the present invention as the positive electrode active material, vinylidene fluoride - hexafluoropropylene copolymer (for example, Kynar (Atochem tradename) or A gel polymer electrolyte containing a vinylidene fluoride-perfluoropropyl vinyl ether copolymer may be used, and the solute added to the electrolyte solvent or polymer electrolyte may be ClO ₄ ⁻ , CF ₃ SO ₃ ⁻ , BF ₄ ⁻ , or PF. Any one or more of lithium salts having anions such as ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , CF ₃ CO ₂ ⁻ , (CF ₃ SO ₂ ) ₂ N ^{− and the} like are preferably used. Add to the electrolyte solvent or polymer electrolyte at a concentration of 0.2-2.0 mol / l (liter) Preferably that. If outside this range, ionic conductivity will decrease, and the electrical conductivity of the electrolyte is decreased. Among them, 0.5 to 1.5 mol / l is particularly preferred.

  In the lithium battery using the lithium-containing composite oxide obtained by the production method of the present invention as the positive electrode active material, a material capable of inserting and extracting lithium ions is used as the negative electrode active material. The material for forming the negative electrode active material is not particularly limited. For example, an oxide, a carbon compound, a silicon carbide compound, or a silicon oxide compound mainly composed of lithium metal, lithium alloy, carbon material, periodic table 14 or group 15 metal. , Titanium sulfide, boron carbide compounds and the like. As the carbon material, those obtained by pyrolyzing an organic substance under various pyrolysis conditions, artificial graphite, natural graphite, soil graphite, expanded graphite, flake 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, a copper foil, a nickel foil, or the like is used. Such a negative electrode is preferably produced by kneading the active material with an organic solvent to form a slurry, and applying the slurry to a metal foil current collector, drying, and pressing.

  There is no restriction | limiting in particular in the shape of the lithium battery which uses the lithium containing complex oxide obtained by the manufacturing method of this invention for a positive electrode active material. A sheet shape, a film shape, a folded shape, a wound-type bottomed cylindrical shape, a button shape, or the like is selected depending on the application.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
Example 1
A cobalt hydroxide slurry was prepared by continuously mixing an aqueous solution of cobalt sulfate and ammonium hydroxide and an aqueous solution of sodium hydroxide. The slurry was agglomerated, filtered and dried to obtain cobalt hydroxide powder. The obtained cobalt hydroxide has a diffraction peak half-width of (001) plane of 2θ = 19 ± 1 ° in powder X-ray diffraction using CuKα ray is 0.24 °, and 2θ = 38 ° ± 1. The diffraction peak half-value width of the (101) plane was 0.23 °, and as a result of observation with a scanning electron microscope, it was found that the fine particles were aggregated and formed from substantially spherical secondary particles. As a result of volume-based particle size distribution analysis obtained from image analysis under scanning electron microscope observation, the average particle size D50 was 15.4 μm, D10 was 12.2 μm, and D90 was 19.9 μm. The cobalt content of the cobalt hydroxide was 62.5%.

  On the other hand, 0.87 g of commercially available magnesium carbonate powder, 1.41 g of aluminum lactate and 2.73 g of titanium lactate were added, 1.68 g of acetic acid and 192.7 g of water were added, and 1.83 g of ammonia was added, whereby pH 7. Thus, an aqueous solution obtained by uniformly dissolving 1 magnesium, aluminum, and titanium acetate was obtained. The aqueous solution was added to 215.43 g of the cobalt hydroxide to form a slurry. The solid content concentration in the slurry was 60% by weight.

The slurry was dehydrated with a dryer at 120 ° C. for 2 hours, and then dry-mixed with 85.23 g of lithium carbonate having a specific surface area of 1.2 m ² / g. This mixture was baked in air at 950 ° C. for 12 hours to obtain LiCo _0.99 Al _0.004 Mg _0.004 Ti _0.002 O ₂ . As a result of measuring the particle size distribution of the lithium-containing composite oxide powder obtained by agglomerating primary particles obtained by crushing the fired product in a water solvent using a laser scattering type particle size distribution measuring device, the average particle size D50 Was 12.4 μm, D10 was 8.0 μm, D90 was 18.4 μm, and the specific surface area determined by the BET method was 0.39 m ² / g.

With respect to this lithium-containing composite oxide powder, an X-ray diffraction spectrum was obtained using an X-ray diffractometer (RINT 2100 type, manufactured by Rigaku Corporation). In powder X-ray diffraction using CuKα ray, the half value width of the diffraction peak of (110) plane at 2θ = 66.5 ± 1 ° was 0.127 °. The press density of this powder was 3.80 g / cm ³ . 10 g of this lithium cobalt composite oxide powder was dispersed in 100 g of pure water, filtered and subjected to potentiometric titration with 0.1N HCl to determine the residual alkali amount, which was 0.01% by weight.

  The lithium-containing composite oxide powder, acetylene black, and polyvinylidene fluoride powder are mixed at a weight ratio of 90/5/5, N-methylpyrrolidone is added to prepare a slurry, and aluminum having a thickness of 20 μm is prepared. The foil was coated on one side using a doctor blade. The positive electrode sheet for lithium batteries was produced by drying and performing roll press rolling 5 times.

The positive electrode sheet is punched out as a positive electrode, a metal lithium foil having a thickness of 500 μm is used as a negative electrode, a nickel foil of 20 μm is used as a negative electrode current collector, and a porous polypropylene having a thickness of 25 μm is used as a separator. Further, the electrolytic solution used is a LiPF ₆ / EC + DEC (1: 1) solution having a concentration of 1 M (meaning a mixed solution of EC and DEC in a weight ratio (1: 1) containing LiPF ₆ as a solute. Solvent described later) In accordance with this, two stainless steel simple sealed cell type lithium batteries were assembled in an argon glove box.

For the one battery, the initial discharge capacity was charged at 25 ° C. with a load current of 75 mA per gram of the positive electrode active material to 4.3 V and discharged with a load current of 75 mA per gram of the positive electrode active material to 2.5 V. Asked. Furthermore, the density of the electrode layer was determined. Moreover, about this battery, the charging / discharging cycle test was done 30 times continuously. As a result, the initial weight capacity density of the positive electrode layer at 25 ° C. and 2.5 to 4.3 V was 160 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 99.0%.

  The other battery was charged at 4.3 V for 10 hours, disassembled in an argon glove box, taken out of the positive electrode sheet after charging, washed the positive electrode sheet, punched into a diameter of 3 mm, and together with EC The container was sealed in an aluminum capsule and heated at a rate of 5 ° C./min with a scanning differential calorimeter to measure the heat generation start temperature. As a result, the first peak temperature (exothermic peak temperature) of the exothermic curve of the 4.3V charged product was 188 ° C.

Example 2
In Example 1, by adding 0.87 g of magnesium carbonate powder, 1.41 g of aluminum lactate and 2.73 g of titanium lactate, adding 2.77 g of formic acid and 192.2 g of water, and adding 2.33 g of ammonia, An aqueous solution obtained by uniformly dissolving magnesium, aluminum, and titanium formate having a pH of 7.0 was obtained. The aqueous solution was added to 215.43 g of cobalt hydroxide obtained in Example 1 to form a slurry. The solid content concentration in the slurry was 60% by weight.

The slurry was dehydrated with a dryer at 120 ° C. for 2 hours and then dry-mixed with 85.23 g of lithium carbonate having a specific surface area of 1.2 m ² / g. This mixture was baked in air at 950 ° C. for 12 hours to obtain LiCo _0.99 Al _0.004 Mg _0.004 Ti _0.002 O ₂ . As a result of measuring the particle size distribution of the lithium-containing composite oxide powder obtained by agglomerating primary particles obtained by crushing the fired product in a water solvent using a laser scattering type particle size distribution measuring device, the average particle size D50 Was 12.5 μm, D10 was 8.3 μm, D90 was 18.0 μm, and the specific surface area determined by the BET method was 0.41 m ² / g. In powder X-ray diffraction, the half value width of the diffraction peak of (110) plane at 2θ = 66.5 ± 1 ° was 0.126 °. The press density of this powder was 3.83 g / cm ³ . When the residual alkali amount of the lithium cobalt composite oxide powder was determined, it was 0.01% by weight.

As a result, the initial weight capacity density of the positive electrode layer at 25 ° C. and 2.5 to 4.3 V was 161 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 98.9%.
Moreover, the exothermic peak temperature of the 4.3V charged product was 189 ° C.

Comparative Example 1
In Example 1, instead of dry mixing the dehydrated slurry and lithium carbonate and firing, 0.73 g of aluminum hydroxide powder, 0.54 g of magnesium hydroxide powder, 0.37 g of titanium oxide powder, cobalt hydroxide LiCo _0.99 Al _0.004 Mg _0.004 Ti _0.002 O ₂ was synthesized in the same manner as in Example 1 except that 215.43 g and lithium carbonate 85.23 g were dry-mixed and fired. The fired product had an average particle diameter D50 of 11.9 μm, D10 of 6.5 μm, D90 of 17.9 μm, and a lump with a specific surface area of 0.45 m ² / g determined by the BET method. Moreover, about this powder, the X-ray-diffraction spectrum was obtained using the X-ray-diffraction apparatus (Rigaku Corporation RINT2100 type | mold). In powder X-ray diffraction using CuKα ray, the half value width of the diffraction peak of (110) plane in the vicinity of 2θ = 66.5 ± 1 ° was 0.140 °. The press density of this powder was 3.80 g / cm ³ . Moreover, it carried out similarly to Example 1, the positive electrode body was manufactured, the battery was assembled, and the characteristic was measured. The initial weight capacity density of the positive electrode layer was 158 mAh / g, the capacity retention after 30 cycles was 96.9%, and the exothermic peak temperature was 182 ° C.

Claims (11)

Lithium source, N element source, M element source, and a lithium-containing composite oxide represented by the following formula 1 , wherein a mixture containing a fluorine source is fired in an oxygen-containing atmosphere when a is greater than 0 A manufacturing method, wherein the M element source is an aqueous solution of a carboxylate compound having an M element in the molecule, and an aqueous solution adjusted to pH 2 to 12 by adding an alkali to the aqueous solution is used. A method for producing a lithium-containing composite oxide.
_{Li p N x M m O z} F a ··· Formula 1
N is Co, Ni, Co and Ni, Mn and Ni, or Co and Ni and Mn, and M is at least one element selected from the group consisting of Ti, Zr, Hf, Mg, and Al. . 0.9 ≦ p ≦ 1.2, 0.97 ≦ x <1.00, 0 <m ≦ 0.03, 1.9 ≦ z ≦ 2.2, x + m = 1, 0 ≦ a ≦ 0.02. is there.   The manufacturing method according to claim 1, wherein the carboxylate compound is a carboxylate compound having 1 to 4 carbon atoms.   The production method according to claim 1 or 2, wherein the aqueous solution of the carboxylate compound is an aqueous solution containing formic acid or acetic acid and adjusted to pH 4 to 10 by adding ammonia.   The production method according to claim 1, wherein the N element source is a powder having an average particle diameter (D50) of 1 to 25 μm.   5. The production method according to claim 1, wherein the N element source is at least one selected from the group consisting of cobalt hydroxide, cobalt oxyhydroxide, cobalt tetroxide, and cobalt carbonate. N element source is nickel-cobalt coprecipitated hydroxide, nickel-cobalt coprecipitated oxyhydroxide, nickel-cobalt coprecipitated oxide, nickel-manganese coprecipitated hydroxide, nickel-manganese coprecipitated oxyhydroxide, nickel - manganese coprecipitated oxide, nickel - cobalt - manganese coprecipitated hydroxide, nickel - cobalt - manganese coprecipitated oxyhydroxide and nickel - cobalt - is at least one selected from the group consisting of manganese coprecipitated oxide wherein Item 5. The production method according to any one of Items 1 to 4. Aqueous solution of the carboxylate compounds, and a mixture of N element source Powder, after removing the water from the resulting mixture, a fluorine source powder are mixed when a is greater than 0 in a lithium source powder, and the formula 1, Subsequently, the manufacturing method in any one of Claims 1-6 manufactured by baking at 800-1050 degreeC in oxygen containing atmosphere. An aqueous solution of a carboxylate compound, an N element source powder, a lithium source powder, and a fluorine source powder when a is greater than 0 in Formula 1 above , and after removing moisture from the resulting mixture, in an oxygen-containing atmosphere, 800 The manufacturing method in any one of Claims 1-6 baked at -1050 degreeC. A lithium source powder, an N element source powder, and a lithium source composite oxide powder obtained by mixing and baking a fluorine source powder when a is greater than 0 in Formula 1 above , and an aqueous solution of a carboxylate compound are mixed. And after removing a water | moisture content from the mixture obtained, the manufacturing method in any one of Claims 1-6 baked at 300-1050 degreeC in oxygen containing atmosphere.   The positive electrode for lithium secondary batteries containing the lithium containing complex oxide manufactured by the manufacturing method in any one of Claims 1-9.   A lithium secondary battery using the positive electrode according to claim 10.