JP2011187174A - Method for manufacturing positive electrode active material for lithium ion secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a positive electrode active material excelling in charge-discharge cycle durability, low in the amount of free alkali and having high discharge capacity, high filling property and high volume capacity density. <P>SOLUTION: The method for manufacturing the positive electrode active material includes carrying out water contact treatment of a lithium composite oxide expressed by general formula: Li<SB>a</SB>Ni<SB>b</SB>Co<SB>c</SB>Mn<SB>d</SB>M<SB>e</SB>O<SB>2</SB>(a element M is at least one kind of element selected from a group consisting of transition metal elements other than Ni, Co and Mn, and Al and group 2 elements, and a, b, c, d and e are 0.9≤a≤1.2, 0≤b≤1, 0≤c≤1, 0≤d<1, 0≤e≤0.3, a+b+c+d+e=2), then separating treatment water from the lithium composite oxide, bringing the lithium composite oxide separated from the treatment water, into contact with a solution of a compound of a group 3 element or a group 4 element to stick 0.02-0.9 mol% of the group 3 element or group 4 element to the lithium composite oxide, and then heating it at 600-1,000°C. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a positive electrode active material used for a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery.

In recent years, with the rapid development of information-related equipment and communication equipment such as personal computers and mobile phones, there is an increasing demand for non-aqueous electrolyte secondary batteries such as lithium secondary batteries that are small, lightweight, and have high energy density. . The positive electrode active materials for non-aqueous electrolyte secondary batteries include LiCoO ₂ , LiNi _0.8 Co _0.2 O ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.5 Co _{0. 2} Composite oxides of lithium and transition metals such as ₂ Mn _0.3 O ₂ (in the present invention, sometimes simply referred to as lithium composite oxide) are known.
Among them, a lithium secondary battery using lithium cobalt composite oxide (LiCoO ₂ ) as a positive electrode active material and using a lithium alloy or carbon such as graphite or carbon fiber as a negative electrode can obtain a high voltage of 4 V class. Therefore, it is particularly widely used as a battery having a high energy density.

Also, lithium composite oxidation such as LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , LiNiO ₂ , LiNi _0.8 Co _0.2 O ₂ Since the product has a low content of expensive Co, it is expected as a low-cost material. Furthermore, when these lithium composite oxides are used as a positive electrode active material, it is known that the higher the Ni content, the larger the discharge capacity per unit weight and the higher the energy density. ing.

  However, in any lithium composite oxide, the discharge capacity, the filling property, the volume capacity density related to the discharge capacity per unit volume, the charge / discharge cycle durability related to the decrease in the discharge capacity due to repeated charge / discharge, and the long state in the charged state. The storage characteristics related to the amount of gas generated when left for a long time and the amount of free alkali related to the coating properties related to the state of application to the current collector during electrode preparation are insufficient, and all satisfying requirements are obtained. It is not done.

In order to solve these problems, various studies have been made conventionally. For example, a positive electrode active material in which a lithium composite oxide is washed with water and a lithium compound present on the surface of the particles is removed has been proposed (see Patent Documents 1 to 4).
Moreover, the positive electrode active material which coat | covered the titanium compound or the zirconium compound on the particle | grain surface of lithium complex oxide is proposed (refer patent document 5-patent document 7).

JP-A-8-138669 JP 2003-017054 A JP 2007-273106 A JP 2008-277087 A JP 2002-151078 A JP 2005-310744 A JP 2006-156032 A

As described above, various studies have been made heretofore, but a positive electrode active material that satisfies all the characteristics such as discharge capacity, filling property, volume capacity density, charge / discharge cycle durability, and free alkali amount has not yet been developed. Not obtained.
For example, the positive electrode active material described in Patent Documents 1 to 4 can remove the alkali compound on the particle surface by washing the particle surface of the lithium composite oxide with water, and a decrease in the amount of free alkali is observed. Lithium, nickel, cobalt, or manganese ions were eluted from the surface of the active material particles, the crystal structure became unstable, and the charge / discharge cycle durability was extremely deteriorated.

  Moreover, although the positive electrode active material of patent document 5-patent document 7 can improve charge-discharge cycle durability, since the amount of free alkalis becomes high, when used as a positive electrode active material of a battery, it is processed into an electrode. In this case, the slurry in which the positive electrode active material is dispersed becomes a gel, the positive electrode active material is peeled off from the current collector, and the coating property is deteriorated. In addition, the storage characteristics were poor, and as charging / discharging was repeated, gas was generated inside the battery and the battery swelled and could not withstand practical use. The amount of free alkali in the coated positive electrode active material increases because the compound used in the coating treatment reacts with the lithium composite oxide of the base material, and lithium-containing alkali compounds are formed on the surface of the lithium composite oxide particles. It is thought that it is for generating.

  As described above, the positive electrode active material having a high amount of free alkali is likely to be gelled when the slurry is dispersed in a solvent to form an electrode, and the positive electrode active material is peeled off from the current collector. If the positive electrode active material having a high free alkali amount is used as the positive electrode of the battery and stored for a long time in a charged state or repeatedly charged and discharged for a long time, There was a problem that the decomposition reaction of the liquid progressed, and gas such as carbon dioxide and water were generated with heat generation, leading to expansion and rupture of the battery, and poor storage characteristics.

  The present invention uses a positive electrode active material that is excellent in charge / discharge cycle durability, has a low amount of free alkali, has a high discharge capacity, high fillability, and high volume capacity density, and a positive electrode active material obtained by the production method An object of the present invention is to provide a positive electrode and a method for manufacturing a lithium ion secondary battery.

  As a result of intensive research, the present inventors contacted the lithium composite oxide particles having a predetermined composition with water, and then separated the treated water from the lithium composite oxide. The oxide is brought into contact with a solution of a Group 3 element or a Group 4 element compound, and a predetermined amount of the Group 3 element or the Group 4 element is attached to the lithium composite oxide, and then at a temperature in a predetermined range. It discovered that the positive electrode active material obtained by heating can achieve the said subject.

That is, the present invention has the following gist.
(1) General formula Li _a Ni _b Co _c Mn _{d Me} O ₂ (M element is at least one element selected from the group consisting of transition metal elements other than Ni, Co and Mn, Al and Group 2 elements) A, b, c, d and e are 0.9 ≦ a ≦ 1.2, 0 ≦ b ≦ 1, 0 ≦ c ≦ 1, 0 ≦ d <1, 0 ≦ e ≦ 0.3, a + b + c + d + e, respectively. = 2) is contacted with water, the treated water is separated from the lithium composite oxide, and then the treated lithium is separated from the lithium composite oxide by 3 After contact with a solution of a group element or group 4 element compound to attach 0.02 to 0.9 mol% of a group 3 element or group 4 element to the lithium composite oxide, heating at 600 to 1000 ° C. Positive electrode active for lithium ion secondary battery Method of manufacturing quality.
(2) The manufacturing method as described in said (1) whose temperature to heat is 600-950 degreeC.
(3) The production method according to (1) or (2), wherein the Group 3 element or Group 4 element is at least one element selected from the group consisting of lanthanum, titanium, zirconium, and hafnium.
(4) The amount of the Group 3 element or the Group 4 element attached to the group 3 element or the Group 4 element compound in contact with the solution is 0.02 to 0.5 mol% with respect to the lithium composite oxide. The production method according to any one of (1) to (3) above.
(5) The lithium composite oxide from which the treated water is separated is dried at 60 to 200 ° C., and then contacted with a solution of a compound of a group 3 element or a group 4 element. The manufacturing method as described.
(6) The solution of the group 3 element or group 4 element compound is an aqueous solution of at least one compound selected from the group consisting of ammonium zirconium carbonate, lanthanum acetate, and titanium lactate. The manufacturing method in any one.
(7) The manufacturing method in any one of said (1)-(6) whose amount of free alkalis of a positive electrode active material is 0.7 mol% or less.
(8) In the lithium composite oxide represented by the general formula Li _a Ni _b Co _c Mn _{d Me} O ₂ , a, b, c, d, and e are 0.95 ≦ a ≦ 1.1, 0.3 ≦ b ≦ 0.9, 0 ≦ c ≦ 0.5, 0.1 ≦ d ≦ 0.5, 0 ≦ e ≦ 0.1, any of (1) to (7) above The manufacturing method as described.
(9) The production method according to any one of (1) to (8), wherein the positive electrode active material is in the form of particles and the average particle size is 3 to 25 μm.
(10) The production method according to any one of (1) to (9), wherein the positive electrode active material has a specific surface area of 0.1 to 1.5 m ² / g.
(11) The manufacturing method according to any one of (1) to (10), wherein the positive electrode active material has a press density of 2.7 to 3.8 g / cm ³ .
(12) After mixing the positive electrode active material obtained by the manufacturing method in any one of said (1)-(11), a electrically conductive agent, a binder, and a solvent and apply | coating the obtained slurry to metal foil, it is heated. The manufacturing method of the positive electrode for lithium ion secondary batteries characterized by removing a solvent.
(13) A lithium ion secondary characterized by laminating a separator and a negative electrode on a positive electrode obtained by the production method described in (12) above, storing the battery in a battery case, and then injecting an electrolytic solution. Battery manufacturing method.

ADVANTAGE OF THE INVENTION According to this invention, the positive electrode active material which is useful as a positive electrode of a lithium ion secondary battery, is excellent in charging / discharging cycle durability, has a low amount of free alkalis, and has high discharge capacity, filling property and volume capacity density is obtained. A manufacturing method is provided.
In the present invention, as will be described later, the amount of the alkali compound present on the particle surface of the positive electrode active material or the grain boundary of the particle is evaluated by measuring the amount of free alkali. The positive electrode obtained by the present invention The active material has a low amount of free alkali, prevents gelation of the positive electrode active material slurry, improves coating properties, suppresses the generation of gas accompanying the decomposition reaction of the electrolyte, and prevents the battery from expanding. , Storage characteristics can be improved.

The reason why the positive electrode active material obtained in the present invention has the above-mentioned excellent characteristics is not necessarily clear, but is estimated as follows.
In general, a lithium composite oxide is obtained by firing a raw material mixture obtained by mixing a lithium source and a transition metal source containing nickel, cobalt, manganese, and the like. In this case, there are lithium atoms that are deviated from the lattice points of the crystal lattice, and there are remaining lithium compounds that are not sufficiently reacted. The lithium atom and the remaining lithium compound react with moisture and carbon dioxide contained in the atmosphere to form an alkali compound. When a positive electrode active material made of such a lithium composite oxide is used, gelation of the slurry occurs at the time of electrode preparation, electrode coating cannot be performed, or when the battery is repeatedly charged and discharged, the alkali compound is It elutes from the particle surface and grain boundaries into the electrolyte, changing the composition of the positive electrode active material and accelerating the decomposition of the electrolyte, leading to deterioration in battery performance such as charge / discharge cycle durability and storage characteristics. Cause. On the other hand, when the surface of the lithium composite oxide particles and the grain boundaries of the lithium composite oxide are simply washed with water or an acidic aqueous solution in order to remove the alkali compound, other than alkali from the lithium composite oxide particle surface. In addition, components such as lithium, nickel, cobalt, and manganese are also eluted, the crystal structure becomes unstable, and the charge / discharge cycle durability deteriorates.

  However, in the present invention, the lithium composite oxide particles are contacted with water to remove the alkali compound, and then are contacted with a solution of a Group 3 element or a Group 4 element compound to obtain a Group 3 element. Alternatively, a group 4 element compound can be adhered to the particle surface of the lithium composite oxide, and as a result, a positive electrode active material having a low free alkali amount and excellent battery performance such as charge / discharge cycle durability can be obtained. I think that the.

  If the lithium composite oxide and water are merely contact-treated, the charge / discharge cycle durability is deteriorated, but after that, by attaching a compound of a group 3 element or a group 4 element to the particle surface, it is altered by washing. By allowing the reaction to proceed between the particle surface and the compound attached to the particle surface, the elution of components such as lithium can be suppressed, and the crystal structure can be further stabilized. It is estimated that a positive electrode active material having both excellent charge / discharge cycle durability can be obtained.

Lithium composite oxide used as a raw material in the present invention has a composition represented by the general formula _{Li a Ni b Co c Mn d} M e O 2. Here, the definitions of a, b, c, d, and e are as described above. Among them, 0.95 ≦ a ≦ 1.1, 0.3 ≦ b ≦ 0.9, 0 ≦ c ≦ A lithium composite oxide satisfying 0.5, 0.1 ≦ d ≦ 0.5, 0 ≦ e ≦ 0.1 is preferable, 0.95 ≦ a ≦ 1.08, 0.4 ≦ b ≦ 0.9, More preferably, the lithium composite oxide satisfying 0 ≦ c ≦ 0.4, 0.1 ≦ d ≦ 0.4, and 0 ≦ e ≦ 0.05, 0.95 ≦ a ≦ 1.05, 0.5 ≦ b A lithium composite oxide satisfying ≦ 0.9, 0 ≦ c ≦ 0.3, 0.2 ≦ d ≦ 0.4, and 0 ≦ e ≦ 0.03 is particularly preferable. In particular, in the lithium composite oxide having a large proportion of Ni, the value of the free alkali amount tends to be very large, and by applying the present invention, the amount of free alkali can be greatly reduced. There is an effect. When the lithium composite oxide used as a raw material is a lithium composite oxide mainly composed of a cobalt component, 1 ≦ a ≦ 1.05, 0 ≦ b ≦ 0.01, 0.95 ≦ c ≦ 1, A lithium composite oxide satisfying 0 ≦ d ≦ 0.01 and 0 ≦ e ≦ 0.05 is preferable, 1 ≦ a ≦ 1.04, b = 0, 0.96 ≦ c ≦ 1, d = 0, 0 ≦ A lithium composite oxide satisfying e ≦ 0.04 is more preferable.

  The M element in the general formula is at least one element selected from the group consisting of transition metal elements other than Ni, Co, and Mn, Al, Sn, Zn, and alkaline earth metals. The above transition metal element represents a transition metal of Group 4, Group 5, Group 6, Group 7, Group 8, Group 9, Group 10, or Group 11 of the Periodic Table. Among these, the M element is preferably at least one selected from the group consisting of Al, Ti, Zr, Hf, Nb, Ta, Mg, Sn, and Zn. In particular, from the viewpoint of discharge capacity, safety, charge / discharge cycle durability, etc., the M element is more preferably at least one selected from the group consisting of Al, Ti, Zr, Hf and Mg, and from Al, Zr and Mg. Particularly preferred is at least one selected from the group consisting of However, when importance is attached to the discharge capacity, the general formula does not include the M element, that is, e = 0 may be preferable.

  The method for producing the lithium composite oxide used in the present invention can appropriately use a solid phase method, a coprecipitation method or the like, and is not particularly limited, and a known lithium composite oxide can be used. For example, as the nickel source, cobalt source, manganese source, and M element source, sulfate, nitrate, carbonate, chloride, hydroxide, oxide, oxyhydroxide, and the like of each element can be used. Moreover, coprecipitated hydroxide, coprecipitated oxide, coprecipitated oxyhydroxide, coprecipitated carbonate, etc., in which each element of nickel, cobalt, manganese, and M element is coprecipitated in any combination can be used. . Further, the lithium source is not particularly limited, but at least one selected from the group consisting of lithium carbonate and lithium hydroxide is preferable, and lithium carbonate is more preferable. The average particle size of the lithium source is preferably 2 to 25 μm. In addition, water may be mixed as necessary to a mixture of raw materials including a lithium source. Lithium composite oxide can be obtained by baking the mixture which mixed each element source mentioned above, or using another well-known method.

In the present invention, the lithium composite oxide is preferably particulate, and the average particle size is preferably 3 to 25 μm, more preferably 5 to 20 μm. The specific surface area of the lithium composite oxide is measured by the BET method, preferably 0.1~1.5m ² / g, more preferably 0.15~1.2m ² / g, 0.2~1. 0 m ² / g is particularly preferred.

  In the present invention, the lithium composite oxide is contacted with water to elute the alkali compound from the lithium composite oxide. The method of contacting the lithium composite oxide with water is not particularly limited, and the method of washing the lithium composite oxide with running water, the method of contacting the lithium composite oxide by dispersing it in water and stirring it. But you can. Moreover, you may make it contact in multiple times. The amount of water used for contact is not particularly limited, but is preferably 10,000 g or less, more preferably 5000 g or less, even more preferably 1000 g or less, and particularly preferably 500 g or less of water with respect to 100 g of the lithium composite oxide. As for the lower limit, 10 g of water is preferable, and 50 g of water is more preferable. The contact time between the lithium composite oxide and water is not particularly limited, but is preferably 10 seconds to 24 hours, more preferably 30 seconds to 12 hours, and particularly preferably 1 minute to 3 hours. The amount of water used for contact and the contact time do not affect the battery characteristics, but if a large amount of water is used, there may be a problem with wastewater treatment, or productivity may be reduced if contacted for a long time. is there.

  The water used for contacting the lithium composite oxide is preferably ion exchange water or pure water. Further, in order to promote the elution of the alkali compound from the lithium composite oxide, a small amount of an organic acid or an inorganic acid may be added to the water used for the contact within a range in which the water after the contact does not become acidic. Examples of the organic acid to be added include acetic acid, succinic acid, and citric acid, and examples of the inorganic acid include hydrochloric acid and nitric acid.

  In the present invention, after the lithium composite oxide is contacted with water, the treated water adhering to or contained in the lithium composite oxide is separated or removed. By separating the treated water, the alkaline compound eluted from the lithium composite oxide is removed from the lithium composite oxide. The method for separating the treated water is not particularly limited, but it is preferable to separate or remove the treated water as much as possible. Specific methods include a filter pressing method, a decantation method, a centrifugal separation method, a pressure filtration method or a suction filtration method, and the like.

  Furthermore, the lithium composite oxide obtained by separating the treated water is preferably dried at 30 to 24 hours in the air or under reduced pressure, preferably at 60 to 200 ° C., more preferably at 80 to 150 ° C., for 30 minutes to 24 hours. It is preferable to remove moisture. By sufficiently removing the water, it can be made into a powder form, which is preferable because it is easy to handle when the lithium composite oxide is brought into contact with the solution of the group 3 element or group 4 element compound in the next step.

  Next, the lithium composite oxide obtained by separating the treated water is brought into contact with a solution of a group 3 element or group 4 element compound, and then heated at 600 to 1000 ° C., whereby the positive electrode active material of the present invention. Can be obtained. In the present invention, a solution of a group 3 element or group 4 element compound in the periodic table may be referred to as an adhesion solution. The Group 3 element and Group 4 element are preferably at least one element selected from the group consisting of scandium, yttrium, lanthanum, titanium, zirconium and hafnium, and at least one selected from the group consisting of lanthanum, titanium, zirconium and hafnium. More preferably, at least one element selected from the group consisting of lanthanum, titanium and zirconium is more preferable, and lanthanum or zirconium is particularly preferable.

  Although it does not specifically limit as a compound of a 3 group element or a 4 group element, A hydroxide, carbonate, a phosphate, nitrate, a sulfate, a C2-C8 carboxylate, a halide, and an ammonium salt are used. Can, among others, hydroxide, carbonate, sulfate, acetate, propionate, oxalate, malonate, succinate, lactate, malate, citrate, glyoxylate , At least one selected from the group consisting of glucose, pyruvate, tartrate, acetoacetate, halide and ammonium salt, carbonate, acetate, oxalate, lactate, citrate, Particularly preferred is at least one selected from the group consisting of glyoxylate, tartrate and ammonium salt. More specifically, at least one compound selected from the group consisting of ammonium zirconium carbonate, lanthanum acetate and titanium lactate is preferred.

  In the present invention, the amount of the Group 3 element or Group 4 element attached to the lithium composite oxide is 0.02 to 0.9 mol%, preferably 0.02 to 0.5 mol%, 0.05 to 0.5 mol% is more preferable, 0.05 to 0.3 mol% is further preferable, and 0.05 to 0.1 mol% is particularly preferable. In addition, when attaching both a group 3 element and a group 4 element, or when attaching two or more types of elements to a group 3 element or a group 4 element, the total amount of those elements is meant. When the adhesion amount of the group 3 element or the group 4 element is within the above range, a positive electrode active material having further excellent charge / discharge cycle durability, a particularly low free alkali amount, and a high discharge capacity can be obtained. Tend.

  In the present invention, the adhesion amount of the group 3 element or the group 4 element is small with respect to the amount of the lithium composite oxide, but the group 3 element or the group 4 element contained in the finally obtained positive electrode active material. The amount can be easily measured by inductively coupled plasma (ICP) emission spectrometry. In addition, in the case where the lithium composite oxide used as a raw material contains a Group 3 element or a Group 4 element, it is included in advance from the amount of the Group 3 element and the Group 4 element contained in the positive electrode active material before contacting the adhesion solution. The value obtained by subtracting the amount of the Group 3 element and Group 4 element.

The solution for attaching the Group 3 element or Group 4 element used in the present invention is not particularly limited, but an aqueous solution is preferable and an aqueous solution is more preferable from the viewpoint of safety, ease of handling, cost, and the like. The aqueous solution means a solution mainly composed of water, and includes an organic solvent such as alcohol, glycol, and ketone in addition to water.
In the present invention, the adhesion solution for the group 3 element or group 4 element compound is particularly preferably an aqueous solution of at least one compound selected from the group consisting of ammonium zirconium carbonate, lanthanum acetate and titanium lactate.

In the present invention, the content of the Group 3 element and Group 4 element contained in the adhesion solution is not particularly limited, but is preferably 0.01 to 30% by mass, more preferably 0.1 to 15% by mass, and 1-10 mass% is especially preferable. The amount of the adhesion solution brought into contact with the lithium composite oxide is not particularly limited, but is preferably 100 g or less, more preferably 50 g or less, still more preferably 30 g or less, and particularly preferably 20 g or less with respect to 100 g of the lithium composite oxide. . Further, the amount of the adhesion solution brought into contact with the lithium composite oxide is not particularly limited, but is preferably 0.5 g or more and more preferably 1 g or more with respect to 100 g of the lithium composite oxide. In the next heating step, heat treatment can be performed in a short time with less energy, so that the adhesion of the Group 3 element and the Group 4 element of the lithium composite oxide becomes insufficient, so long as the properties of the present invention obtained are not impaired. The amount of solution used is preferably small.
The temperature at which the lithium composite oxide is brought into contact with the adhesion solution is preferably 0 to 100 ° C, more preferably 0 to 50 ° C.

  The method of bringing the lithium composite oxide into contact with the adhesion solution is not particularly limited. For example, the lithium composite oxide is added to the adhesion solution in a beaker or a stainless steel layer, and a stirring means such as a stirring blade is used. Mix the adhering solution and lithium composite oxide while spraying the adhering solution using a Ladige mixer or solid air, and mixing the adhering solution and the lithium composite oxide. It can be contacted by spraying the adhesion solution onto the lithium composite oxide.

In this invention, after making the lithium containing complex oxide obtained by isolate | separating water contact with the solution for adhesion, the positive electrode active material of this invention is obtained by heating at 600-1000 degreeC. Especially, this heat processing temperature has preferable 600-950 degreeC, and 700-800 degreeC is more preferable. The heating atmosphere is not particularly limited, but it is preferably performed in an oxygen-containing atmosphere, and heating in the air is more preferable. Although heat processing time is not specifically limited, 10 minutes-24 hours are preferable, and 30 minutes-12 hours are more preferable. It is preferable for the heat treatment conditions to be in the above-mentioned range because the production efficiency is improved and the equipment cost is low.
The press density of the positive electrode active material obtained by the present invention is preferably 2.7~3.8g / cm ^3, more preferably 2.8~3.6g / cm ^3. In the present invention, the press density means an apparent press density when 5 g of the positive electrode material powder is pressed at a pressure of 1.91 t / cm ² .

The positive electrode active material obtained by the present invention is preferably in the form of particles. The average particle size of the positive electrode active material is preferably 3 to 25 μm, more preferably 5 to 20 μm. The specific surface area of the positive electrode active material is measured by the BET method, preferably 0.1~1.5m ² / g, more preferably 0.15~1.2m ² / g, 0.20~1.0m ² / g is particularly preferred. In the present invention, the average particle size means a cumulative 50% value of a volume particle size distribution obtained by a laser scattering particle size distribution measuring apparatus (for example, using Microtrack HRAX-100 manufactured by Nikkiso Co., Ltd.). In the present invention, this average particle diameter may be referred to as average particle diameter D50 or simply D50. Further, D10, which will be described later, means a cumulative 10% value, and D90 means a cumulative 90% value. In addition, when the positive electrode active material particles are secondary particles, it represents the average particle size of the secondary particles, and when the positive electrode active material particles are the primary particles, it represents the average particle size of the primary particles. Note that the particle shape of the positive electrode active material is affected by the shape of the lithium composite oxide used as a raw material.

  The amount of free alkali in the present invention is a value related to the amount of alkali compound present on the particle surface and grain boundaries of the positive electrode active material. The amount of the free alkali is a liquid obtained by mixing 5 g of the positive electrode material powder with 100 g of water and stirring for 30 minutes and filtering, and a washing solution obtained by washing the filtrate with 10 g of water three times. It is determined from the amount of hydrochloric acid used when the alkali in the solution is titrated to pH 4.0 with 0.02 mol / L hydrochloric acid. The amount of free alkali of the positive electrode active material obtained in the present invention is preferably 0.7 mol% or less, more preferably 0.6 mol% or less, and particularly preferably 0.5 mol% or less. The alkali compound present on the particle surface of the positive electrode active material and the grain boundary of the particle specifically means lithium carbonate, lithium hydroxide, and the like.

  When manufacturing a positive electrode for a lithium ion secondary battery from the positive electrode active material obtained in the present invention, first, a carbon-based conductive material such as acetylene black, graphite, ketjen black, and a binder are added to the positive electrode active material powder. Mix. For the binder, polyvinylidene fluoride, polytetrafluoroethylene, polyamide, carboxymethyl cellulose, acrylic resin, or the like is preferably used. The positive electrode active material powder, conductive material and binder obtained by the present invention are made into a slurry or a kneaded product using a solvent or a dispersion medium. This is supported on a positive electrode current collector such as an aluminum foil or a stainless steel foil by coating or the like to produce a positive electrode for a lithium ion secondary battery.

In the lithium ion secondary battery using the positive electrode active material obtained in the present invention, 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.

In the lithium ion secondary battery using the positive electrode active material obtained in the present invention, a vinylidene fluoride-hexafluoropropylene copolymer (for example, product name: Kyner manufactured by Atchem Co.) or vinylidene fluoride-perfluoropropyl is used. A gel polymer electrolyte containing a vinyl ether copolymer may be used as the electrolyte. Solutes added to the electrolyte solvent or polymer electrolyte include ClO ₄ ⁻ , CF ₃ SO ₃ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , CF ₃ CO ₂ ⁻ , (CF ₃ Any one or more of lithium salts having SO ₂ ) ₂ N ^— or the like as an anion is preferably used. The concentration of the lithium salt contained in the electrolyte solvent or polymer electrolyte is preferably 0.2 to 2.0 mol / l (liter), particularly preferably 0.5 to 1.5 mol / l. In this concentration range, the ionic conductivity is large, and the electrical conductivity of the electrolyte is increased.

In the lithium ion secondary battery using the positive electrode active material obtained in the present invention, 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 using the positive electrode active material obtained by this invention. 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.

  The present invention will be specifically described below, but the present invention is of course not limited to these examples. Examples 1 to 4, Example 10, Example 11, Example 13, Example 14, Example 16, Example 20, Example 24 and Example 26 are examples, and Examples 5 to 9, Example 12, Example 15, and Example 26 are examples. Examples 17 to 19 Examples 21 to 23, Example 25, and Examples 27 to 29 are comparative examples.

[Example 1]
In an aqueous solution in which nickel sulfate, cobalt sulfate, and manganese sulfate are dissolved so that the atomic ratio of nickel, cobalt, and manganese is Ni: Co: Mn = 5: 2: 3, the pH of the aqueous solution is 11.0, and the temperature is 50 ° C. Then, an aqueous solution of ammonium sulfate and an aqueous solution of sodium hydroxide were continuously supplied with stirring to precipitate a coprecipitate. The amount of liquid in the reaction system was adjusted by the overflow method, and the overflowed coprecipitation slurry was filtered, washed with water, and then dried at 80 ° C. to obtain a nickel cobalt manganese composite hydroxide powder. The composite hydroxide powder had a specific surface area of 6.5 m ² / g and an average particle diameter D50 of 11.5 μm.
Lithium carbonate powder was mixed with the obtained composite hydroxide powder, calcined in the atmosphere at 900 ° C. for 10 hours, and then pulverized to obtain Li _1.02 (Ni _0.5 Co _0. to obtain a powder of the lithium composite oxide having a composition of ₂ Mn _{0.3) 0.98} O _2. When the powder X-ray diffraction spectrum using CuKα ray was measured for the powder, it was found to have a rhombohedral (R-3m) similar structure. For measurement, RINT 2100 type manufactured by Rigaku Corporation was used. Further, when the particles were observed with respect to the powder using a scanning electron microscope (hereinafter referred to as SEM), they were secondary particles in which a large number of primary particles were aggregated.

Next, a slurry-like liquid obtained by adding 100 g of the lithium composite oxide powder to 500 g of ion-exchanged water was stirred for 10 minutes. Subsequently, the obtained liquid was subjected to suction filtration using No. 5C filter paper, and the liquid was separated to obtain a granular material. The granular material was dried at 120 ° C. for 5 hours with an air dryer to obtain a dry powder.
Next, an aqueous zirconium zirconium carbonate solution having a zirconium content of 14.1% by mass (Baitcoat 20 manufactured by Nippon Light Metal Co., Ltd.) (0.68 g) was added with ion-exchanged water to prepare a zirconium aqueous solution as 14 g. The chemical formula of the ammonium zirconium carbonate used is represented by (NH ₄ ) ₂ [Zr (CO ₃ ) ₂ (OH) ₂ ]. The zirconium concentration in the zirconium aqueous solution was 0.68% by mass. After spraying the zirconium aqueous solution 7g on the said dry powder at room temperature, it heat-processed at 800 degreeC for 5 hours, and passed the sieve, and obtained the positive electrode active material. Stirring, separation, spraying, and heating were all performed in an air atmosphere. The amount of zirconium deposited on the lithium composite oxide was 0.05 mol% with respect to the lithium composite oxide. The obtained positive electrode active material had an average particle diameter D50 of 11.9 μm and a specific surface area of 0.27 m ² / g. Further, when the amount of zirconium contained in the positive electrode active material was measured using ICP, it was 0.05 mol% with respect to the positive electrode active material.

After mixing 5 g of the positive electrode active material powder and 100 g of water, the slurry obtained by stirring for 30 minutes is filtered, and the filtrate is titrated with 0.02 mol / L hydrochloric acid until the pH reaches 4.0. did. When the amount of free alkali of the positive electrode active material was determined from the amount of hydrochloric acid used for titration, the amount of free alkali was 0.34 mol%.
The positive electrode active material powder, acetylene black, and polyvinylidene fluoride powder are mixed at a mass ratio of 90/5/5, and N-methylpyrrolidone is added to prepare a slurry, which is made of aluminum having a thickness of 20 μm. The foil was coated on one side using a doctor blade. The obtained aluminum sheet was dried and roll press rolled three times to produce a positive electrode sheet for a lithium battery.

Next, the positive electrode sheet is used 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. For the electrolyte, a 1M LiPF ₆ / EC + DEC (1: 1) solution (meaning a mixed solution of EC and DEC with a volume ratio (1: 1) of LiPF ₆ as a solute) is used. A sealed cell type lithium battery was assembled in an argon glove box.

  The above-mentioned simple sealed cell type lithium battery is charged at a current of 180 mA per 1 g of the positive electrode active material at 25 ° C. with an upper limit voltage of 4.3 V, and charged at a constant current of CCCV mode for 3 hours (180 mA, the battery voltage reaches the upper limit voltage After that, the battery was charged at a constant voltage of the upper limit voltage (the total charging time was 3 hours), and then discharged to 2.75 V at a current value of 75 mA per 1 g of the positive electrode active material to obtain an initial discharge capacity. Asked. Moreover, about this battery, charge and discharge were repeated on the same conditions, and the charge / discharge cycle test was done 30 times. As a result, the initial discharge capacity of the positive electrode active material placed at 25 ° C. and 2.75 to 4.3 V was 160.0 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 99.6%.

[Example 2]
14 g of an aqueous zirconium solution having a zirconium concentration of 1.35% by mass was prepared by adding ion-exchanged water to 1.34 g of ammonium zirconium carbonate, and 7 g of the zirconium aqueous solution was sprayed to determine the amount of zirconium adhered to the lithium composite oxide. The positive electrode active material was synthesized in the same manner as in Example 1 except that the amount was 0.10 mol% with respect to the lithium composite oxide, and each characteristic was measured. As a result, the average particle diameter D50 of the obtained positive electrode active material was 11.9 μm, the specific surface area was 0.35 m ² / g, and the amount of zirconium contained in the positive electrode active material was 0.10 mol relative to the positive electrode active material. %Met. Moreover, the amount of free alkalis was 0.34 mol%. The initial discharge capacity was 156.4 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 99.6%.

[Example 3]
Ion-exchanged water was added to 4.02 g of ammonium zirconium carbonate to prepare 14 g of an aqueous zirconium solution having a zirconium concentration of 4.05% by mass, 7 g of which was sprayed to determine the amount of zirconium deposited on the lithium composite oxide. The positive electrode active material was synthesized in the same manner as in Example 1 except that the amount was 0.30 mol% with respect to the lithium composite oxide, and each characteristic was measured. As a result, the average particle diameter D50 of the obtained positive electrode active material was 12.0 μm, the specific surface area was 0.26 m ² / g, and the amount of zirconium contained in the positive electrode active material was 0.30 mol relative to the positive electrode active material. %Met. Moreover, the amount of free alkalis was 0.52 mol%. The initial discharge capacity was 152.0 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 99.4%.

[Example 4]
Ion exchange water was added to 6.70 g of ammonium zirconium carbonate to prepare 14 g of a zirconium aqueous solution having a zirconium concentration of 6.75% by mass, 7 g of which was sprayed to determine the amount of zirconium adhered to the lithium composite oxide. The positive electrode active material was synthesized in the same manner as in Example 1 except that the amount was 0.50 mol% with respect to the lithium composite oxide, and each characteristic was measured. As a result, the average particle diameter D50 of the obtained positive electrode active material was 13.0 μm, the specific surface area was 0.26 m ² / g, and the amount of zirconium contained in the positive electrode active material was 0.50 mol with respect to the positive electrode active material. %Met. Moreover, the amount of free alkalis was 0.61 mol%. The initial discharge capacity was 151.6 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 99.4%.

[Example 5]
Ion exchange water was added to 0.14 g of ammonium zirconium carbonate to prepare 14 g of an aqueous zirconium solution having a zirconium concentration of 0.14% by mass, 7 g of which was sprayed to determine the amount of zirconium deposited on the lithium composite oxide. The positive electrode active material was synthesized in the same manner as in Example 1 except that the amount was 0.01 mol% with respect to the lithium composite oxide, and each characteristic was measured. As a result, the average particle diameter D50 of the obtained positive electrode active material was 12.2 μm, the specific surface area was 0.35 m ² / g, and the amount of zirconium contained in the positive electrode active material was 0.01 mol with respect to the positive electrode active material. %Met. Moreover, the amount of free alkalis was 0.34 mol%. The initial discharge capacity was 157.8 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 96.7%.

[Example 6]
Ion exchange water was added to 13.4 g of ammonium zirconium carbonate to prepare 14 g of an aqueous zirconium solution having a zirconium concentration of 13.50% by mass, 7 g of which was sprayed to determine the amount of zirconium adhered to the lithium composite oxide. The positive electrode active material was synthesized in the same manner as in Example 1 except that the amount was 1.0 mol% with respect to the lithium composite oxide, and each characteristic was measured. As a result, the average particle diameter D50 of the obtained positive electrode active material was 12.4 μm, the specific surface area was 0.29 m ² / g, and the amount of zirconium contained in the positive electrode active material was 1.0 mol with respect to the positive electrode active material. %Met. Moreover, the amount of free alkalis was 0.77 mol%. The initial discharge capacity was 148.0 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 98.8%.

[Example 7]
In Example 1, a positive electrode active material was synthesized in the same manner as in Example 1 except that the zirconium aqueous solution was not sprayed.
D50 of the obtained positive electrode active material was 13.1 μm, and the specific surface area was 0.34 m ² / g. Further, the amount of zirconium contained in the positive electrode active material was measured by ICP, but zirconium was not detected. Moreover, the amount of free alkalis was 0.30 mol%. The initial discharge capacity was 159.3 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 87.9%.

[Example 8]
In Example 2, a positive electrode active material was synthesized in the same manner as in Example 2 except that contact with ion exchange water, filtration, and drying treatment were not performed. That is, the lithium composite oxide obtained in Example 1 was prepared, sprayed, and heat-treated in the same manner as in Example 2 to obtain a positive electrode active material.
D50 of the obtained positive electrode active material was 12.1 μm, the specific surface area was 0.48 m ² / g, and the amount of zirconium contained in the positive electrode active material was 0.10 mol% with respect to the positive electrode active material. Moreover, the amount of free alkalis was 0.82 mol%. When an electrode sheet was prepared using the positive electrode active material in the same manner as in Example 1, the coatability was poor, and peeling was observed on part of the electrode after coating, drying and roller pressing. When a battery was produced using the electrode part that did not peel, the initial discharge capacity was 165.0 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 98.3%.

[Example 9]
A positive electrode active material was synthesized in the same manner as in Example 1 except that it was not contacted with ion-exchanged water and no zirconium aqueous solution was sprayed. That is, the lithium composite oxide having the composition of Li _1.02 (Ni _0.5 Co _0.2 Mn _0.3 ) _0.98 O ₂ obtained in Example 1 was used as a positive electrode active material as it was. Was measured. D50 of this positive electrode active material was 11.6 μm, and the specific surface area was 0.34 m ² / g. Moreover, the amount of free alkalis was 0.67 mol%. When an electrode sheet was prepared using the positive electrode active material in the same manner as in Example 1, the coatability was poor, and peeling was observed on part of the electrode after coating, drying and roller pressing. When a battery was produced using the electrode part that did not peel, the initial discharge capacity was 167.0 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 97.5%.

[Example 10]
In Example 1, a positive electrode active material was synthesized in the same manner as in Example 1 except that the heat treatment temperature was 700 ° C.
D50 of the obtained positive electrode active material was 12.6 μm, the specific surface area was 0.44 m ² / g, and the amount of zirconium contained in the positive electrode active material was 0.10 mol% with respect to the positive electrode active material. Moreover, the amount of free alkalis was 0.54 mol%. The initial discharge capacity was 159.1 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 98.0%.

[Example 11]
In Example 1, a positive electrode active material was synthesized in the same manner as in Example 1 except that the heat treatment temperature was 900 ° C.
D50 of the obtained positive electrode active material was 13.1 μm, the specific surface area was 0.25 m ² / g, and the amount of zirconium contained in the positive electrode active material was 0.10 mol% with respect to the positive electrode active material. Moreover, the amount of free alkalis was 0.30 mol%. The initial discharge capacity was 156.2 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 98.5%.

[Example 12]
In Example 1, a positive electrode active material was synthesized in the same manner as in Example 1 except that the heat treatment temperature was 500 ° C.
D50 of the obtained positive electrode active material was 12.4 μm, the specific surface area was 0.64 m ² / g, and the amount of zirconium contained in the positive electrode active material was 0.10 mol% with respect to the positive electrode active material. Moreover, the amount of free alkalis was 0.63 mol%. The initial discharge capacity was 163.3 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 97.7%.

[Example 13]
In Example 1, lanthanum having a lanthanum concentration of 0.52% by mass, prepared by dissolving 0.18 g of lanthanum acetate hemihydrate (manufactured by Wako Pure Chemical Industries, Ltd.) in ion-exchanged water instead of zirconium aqueous solution A positive electrode active material was obtained in the same manner as in Example 1 except that an aqueous solution was used. The prepared lanthanum aqueous solution was 14 g, and 7 g of lanthanum aqueous solution, which is half of the aqueous solution, was sprayed on 100 g of lithium composite oxide in the same manner as in Example 1.
D50 of the obtained positive electrode active material was 13.0 μm, the specific surface area was 0.30 m ² / g, and the amount of lanthanum contained in the positive electrode active material was 0.025 mol% with respect to the positive electrode active material. Moreover, the amount of free alkalis was 0.29 mol%. The initial discharge capacity was 159.1 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 98.3%.

[Example 14]
In Example 13, the amount of lanthanum acetate hemihydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was 0.36 g, and an aqueous lanthanum solution having a lanthanum concentration of 1.04% by mass was prepared and adhered to the lithium composite oxide. A positive electrode active material was obtained in the same manner as in Example 13 except that the amount of lanthanum was 0.05 mol% with respect to the lithium composite oxide.
D50 of the obtained positive electrode active material was 13.5 μm, the specific surface area was 0.28 m ² / g, and the amount of lanthanum contained in the positive electrode active material was 0.05 mol% with respect to the positive electrode active material. Moreover, the amount of free alkalis was 0.29 mol%. The initial discharge capacity was 156.8 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 98.5%.

[Example 15]
In Example 14, a positive electrode active material was synthesized in the same manner as in Example 14 except that contact with ion-exchanged water, filtration, and drying treatment were not performed.
D50 of the obtained positive electrode active material was 12.8 μm, the specific surface area was 0.43 m ² / g, and the amount of lanthanum contained in the positive electrode active material was 0.05 mol% with respect to the positive electrode active material. Moreover, the amount of free alkalis was 0.85 mol%. When an electrode sheet was prepared using the positive electrode active material in the same manner as in Example 1, the coatability was poor, and peeling was observed on part of the electrode after coating, drying and roller pressing. When a battery was produced using the electrode part that did not peel, the initial discharge capacity was 165.3 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 96.6%.

[Example 16]
In an aqueous solution in which nickel sulfate, cobalt sulfate, and manganese sulfate are dissolved so that the atomic ratio of nickel, cobalt, and manganese is Ni: Co: Mn = 6: 2: 2, the pH of the aqueous solution is 11.0 and the temperature is 50 ° C. Then, an aqueous solution of ammonium sulfate and an aqueous solution of sodium hydroxide were continuously supplied with stirring to precipitate a coprecipitate. The amount of liquid in the reaction system was adjusted by an overflow method, the overflowed coprecipitation slurry was filtered, washed with water, and then dried at 80 ° C. to obtain a nickel cobalt manganese composite hydroxide powder. The composite hydroxide powder had a specific surface area of 5.6 m ² / g and an average particle diameter D50 of 11.8 μm.

The composite hydroxide powder thus obtained was mixed with lithium hydroxide powder and calcined at 500 ° C. for 10 hours in an air atmosphere. The obtained fired product was mixed again, fired at 900 ° C. for 24 hours, and then pulverized to obtain Li _1.02 (Ni _0.6 Co _0.2 Mn _0.2 ) _0.98 O ₂ . A lithium composite oxide powder having a composition was obtained. When this lithium composite oxide particle was observed by SEM, it was a secondary particle in which a large number of primary particles were aggregated, and the shape of the secondary particle was almost spherical or elliptical. Except for using this lithium composite oxide, it was brought into contact with ion-exchanged water in the same manner as in Example 2, filtered, dried, sprayed with an aqueous zirconium solution, and heat-treated to obtain a positive electrode active material. The amount of zirconium deposited on the lithium composite oxide was 0.10 mol% with respect to the lithium composite oxide.
D50 of the obtained positive electrode active material was 14.0 μm, the specific surface area was 0.27 m ² / g, and the amount of zirconium contained in the positive electrode active material was 0.10 mol% with respect to the positive electrode active material. Moreover, the amount of free alkalis was 0.39 mol%. The initial discharge capacity was 165.0 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 93.3%.

[Example 17]
In Example 16, a positive electrode active material was obtained in the same manner as in Example 16 except that the zirconium aqueous solution was not sprayed.
D50 of the obtained positive electrode active material was 16.1 μm, and the specific surface area was 0.22 m ² / g. Further, the amount of zirconium contained in the positive electrode active material was measured by ICP, but zirconium was not detected. Moreover, the amount of free alkalis was 0.54 mol%. The initial discharge capacity was 164.4 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 79.3%.

[Example 18]
In Example 16, a positive electrode active material was synthesized in the same manner as in Example 16 except that contact with ion exchange water, filtration, and drying treatment were not performed.
D50 of the obtained positive electrode active material was 13.6 μm, the specific surface area was 0.54 m ² / g, and the amount of zirconium contained in the positive electrode active material was 0.10 mol% with respect to the positive electrode active material. Moreover, the amount of free alkalis was 1.01 mol%. When an electrode sheet was prepared using the positive electrode active material in the same manner as in Example 1, the coatability was poor, and peeling was observed on part of the electrode after coating, drying and roller pressing. When a battery was fabricated using the electrode part that did not peel, the initial discharge capacity was 167.5 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 93.8%.

[Example 19]
In Example 16, a positive electrode active material was synthesized in the same manner as in Example 16 except that it was not contacted with ion-exchanged water and the zirconium aqueous solution was not sprayed. That is, using the lithium composite oxide having the composition of Li _1.02 (Ni _0.6 Co _0.2 Mn _0.2 ) _0.98 O ₂ obtained in Example 16 as a positive electrode active material as it is, Was measured. D50 of this positive electrode active material was 14.2 μm, and the specific surface area was 0.31 m ² / g. Moreover, the amount of free alkalis was 1.21 mol%. When an electrode sheet was prepared using the positive electrode active material in the same manner as in Example 1, the coatability was poor, and peeling was observed on part of the electrode after coating, drying and roller pressing. When a battery was produced using the electrode part that did not peel, the initial discharge capacity was 167.0 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 93.0%.

[Example 20]
In an aqueous solution in which nickel sulfate, cobalt sulfate, and manganese sulfate are dissolved so that the atomic ratio of nickel, cobalt, and manganese is Ni: Co: Mn = 3: 3: 3, the pH of the aqueous solution is 11.0 and the temperature is 50 ° C. Then, an aqueous solution of ammonium sulfate and an aqueous solution of sodium hydroxide were continuously supplied with stirring to precipitate a coprecipitate. The amount of liquid in the reaction system was adjusted by an overflow method, the overflowed coprecipitation slurry was filtered, washed with water, and then dried at 80 ° C. to obtain a nickel cobalt manganese composite hydroxide powder. The composite hydroxide powder had a specific surface area of 6.9 m ² / g and an average particle diameter D50 of 10.8 μm.

The composite hydroxide powder thus obtained was mixed with lithium carbonate powder, calcined in air at 1000 ° C. for 10 hours, and then pulverized to obtain Li _1.05 (Ni _1/3 Co _{1 / 3} Mn _1/3 ) _0.95 O ₂ to obtain a lithium composite oxide powder. When this lithium composite oxide particle was observed by SEM, it was a secondary particle in which a large number of primary particles were aggregated, and the shape of the secondary particle was almost spherical or elliptical. Except for using this lithium composite oxide, it was brought into contact with ion-exchanged water in the same manner as in Example 2, filtered and dried, sprayed with an aqueous zirconium solution, and heat-treated to obtain a positive electrode active material. . The amount of zirconium deposited on the lithium composite oxide was 0.10 mol% with respect to the lithium composite oxide.
D50 of the obtained positive electrode active material was 11.5 μm, the specific surface area was 0.32 m ² / g, and the amount of zirconium contained in the positive electrode active material was 0.10 mol% with respect to the positive electrode active material. Moreover, the amount of free alkalis was 0.21 mol%. The initial discharge capacity was 152.9 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 98.9%.

[Example 21]
In Example 20, a positive electrode active material was obtained in the same manner as in Example 20 except that the zirconium aqueous solution was not sprayed.
D50 of the obtained positive electrode active material was 11.0 μm, and the specific surface area was 0.35 m ² / g. Further, the amount of zirconium contained in the positive electrode active material was measured by ICP, but zirconium was not detected. Moreover, the amount of free alkalis was 0.19 mol%. The initial discharge capacity was 153.2 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 94.8%.

[Example 22]
In Example 20, a positive electrode active material was synthesized in the same manner as in Example 20 except that contact with ion-exchanged water, filtration, and drying treatment were not performed.
D50 of the obtained positive electrode active material was 10.8 μm, the specific surface area was 0.40 m ² / g, and the amount of zirconium contained in the positive electrode active material was 0.10 mol% with respect to the positive electrode active material. Moreover, the amount of free alkalis was 1.01 mol%. When an electrode sheet was prepared using the positive electrode active material in the same manner as in Example 1, the coatability was poor, and peeling was observed on part of the electrode after coating, drying and roller pressing. When a battery was produced using the electrode part that did not peel, the initial discharge capacity was 152.8 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 99.0%.

[Example 23]
In Example 20, a positive electrode active material was synthesized in the same manner as in Example 20 except that it was not brought into contact with ion-exchanged water and the zirconium aqueous solution was not sprayed. That is, using the lithium composite oxide having the composition of Li _1.05 (Ni _1/3 Co _1/3 Mn _1/3 ) _0.95 O ₂ obtained in Example 20 as it is as the positive electrode active material, Was measured. D50 of this positive electrode active material was 11.2 μm, and the specific surface area was 0.35 m ² / g. Moreover, the amount of free alkalis was 0.35 mol%. The initial discharge capacity was 153.0 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 97.0%.

[Example 24]
In Example 1, in place of the zirconium aqueous solution, a titanium lactate solution having a titanium content of 8.2% by mass (manufactured by Matsumoto Kyosho Co., Ltd.) 0.6 g was dissolved in ion-exchanged water 14 g, and the titanium concentration was 0.35. A positive electrode active material was obtained in the same manner as in Example 1 except that a titanium aqueous solution having a mass% was used. The prepared titanium aqueous solution was 14 g, and 7 g of titanium aqueous solution, which is half of the titanium aqueous solution, was sprayed on 100 g of lithium composite oxide in the same manner as in Example 1.
D50 of the obtained positive electrode active material was 13.0 μm, the specific surface area was 0.27 m ² / g, and the amount of titanium contained in the positive electrode active material was 0.05 mol% with respect to the positive electrode active material. Moreover, the amount of free alkalis was 0.33 mol%. The initial discharge capacity was 158.0 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 98.0%.

[Example 25]
In Example 24, a positive electrode active material was synthesized in the same manner as in Example 24 except that contact with ion-exchanged water, filtration, and drying treatment were not performed. D50 of the obtained positive electrode active material was 11.8 μm, the specific surface area was 0.28 m ² / g, and the amount of titanium contained in the positive electrode active material was 0.05 mol% with respect to the positive electrode active material. Moreover, the amount of free alkalis was 0.79 mol%. When an electrode sheet was prepared using the positive electrode active material in the same manner as in Example 1, the coatability was poor, and peeling was observed on part of the electrode after coating, drying and roller pressing. When a battery was produced using the electrode part without peeling, the initial discharge capacity was 161.2 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 99.0%.

[Example 26]
Cobalt sulfate, aluminum sulfate, magnesium sulfate and zirconium sulfate are used so that the atomic ratio of cobalt, aluminum, magnesium and zirconium is Co: Al: Mg: Zr = 0.969: 0.015: 0.015: 0.001. To the dissolved aqueous solution, an aqueous ammonium sulfate solution and an aqueous sodium hydroxide solution were continuously supplied with stirring so that the pH was 11.0 and the temperature was 50 ° C. to precipitate a coprecipitate. The amount of liquid in the reaction system was adjusted by the overflow method, and the overflowed coprecipitation slurry was filtered, washed with water, and then dried at 80 ° C. to obtain cobalt aluminum magnesium zirconium composite hydroxide powder. The composite hydroxide powder had a specific surface area of 5.0 m ² / g and an average particle diameter D50 of 12.7 μm.
A predetermined amount of lithium carbonate was mixed with the composite hydroxide thus obtained, calcined at 1000 ° C. for 15 hours in the atmosphere, and then pulverized to obtain Li _1.02 (Co _0.969 Al _0.015 Mg A powder of lithium composite oxide having a composition of _0.015 Zr _0.001 ) _0.98 O ₂ was obtained. When this lithium composite oxide particle was observed by SEM, it was a substantially spherical or elliptical particle composed of primary particles.

Except for using this lithium composite oxide, it was brought into contact with ion-exchanged water in the same manner as in Example 2, filtered and dried, sprayed with an aqueous zirconium solution, and heat-treated to obtain a positive electrode active material. . The amount of zirconium contained in the positive electrode active material was 0.20 mol% from analysis by ICP. Since the amount of zirconium contained in the lithium composite oxide was 0.10 mol%, the amount of zirconium attached to the lithium composite oxide was 0.10 mol% with respect to the lithium composite oxide.
D50 of the obtained positive electrode active material was 13.0 μm, and the specific surface area was 0.20 m ² / g. Moreover, the amount of free alkalis was 0.19 mol%. The initial discharge capacity was 148.8 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 97.0%.

[Example 27]
In Example 26, a positive electrode active material was obtained in the same manner as in Example 26 except that the zirconium aqueous solution was not sprayed.
D50 of the obtained positive electrode active material was 12.6 micrometers, and the specific surface area was 0.19 m < ² > / g. Moreover, the amount of zirconium contained in the positive electrode active material was 0.10 mol% with respect to the positive electrode active material. Moreover, the amount of free alkalis was 0.17 mol%. The initial discharge capacity was 148.2 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 80.0%.

[Example 28]
In Example 26, a positive electrode active material was synthesized in the same manner as in Example 26 except that contact with ion exchange water, filtration, and drying treatment were not performed.
D50 of the obtained positive electrode active material was 13.5 μm, the specific surface area was 0.21 m ² / g, and the amount of zirconium contained in the positive electrode active material was 0.20 mol% with respect to the positive electrode active material. That is, the amount of attached zirconium was 0.10 mol%. Moreover, the amount of free alkalis was 0.25 mol%. The initial discharge capacity was 146.6 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 97.2%.

[Example 29]
In Example 26, a positive electrode active material was synthesized in the same manner as in Example 26 except that it was not contacted with ion-exchanged water and no zirconium aqueous solution was sprayed. That is, the lithium composite oxide having the composition of Li _1.02 (Co _0.969 Al _0.015 Mg _0.015 Zr _0.001 ) _0.98 O ₂ obtained in Example 26 was used as it is as the positive electrode active material. Each characteristic was measured. D50 of this positive electrode active material was 12.5 μm, and the specific surface area was 0.28 m ² / g. Moreover, the amount of free alkalis was 0.25 mol%. The initial discharge capacity was 148.9 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 68.1%.

  According to the present invention, a positive electrode active material that is useful as a positive electrode of a lithium ion secondary battery, has excellent charge / discharge cycle durability, has a low amount of free alkali, high discharge capacity, high fillability, and high volume capacity density. The resulting manufacturing method is provided. Moreover, the positive electrode containing the positive electrode active material obtained by this manufacturing method and a lithium secondary battery are provided. Furthermore, the manufacturing method of this positive electrode and this lithium secondary battery is provided.

Claims (13)

General formula Li _a Ni _b Co _c Mn _{d Me} O ₂ (M element is at least one element selected from the group consisting of transition metal elements other than Ni, Co and Mn, Al and Group 2 elements. A, b, c, d, and e are 0.9 ≦ a ≦ 1.2, 0 ≦ b ≦ 1, 0 ≦ c ≦ 1, 0 ≦ d <1, 0 ≦ e ≦ 0.3, and a + b + c + d + e = 2, respectively. The lithium composite oxide represented by the formula (1) is contacted with water, and then the treated water is separated from the lithium composite oxide. It is contacted with a solution of a group element compound to deposit 0.02 to 0.9 mol% of a group 3 element or a group 4 element with respect to the lithium composite oxide, and then heated at 600 to 1000 ° C. Manufacturing positive electrode active materials for lithium ion secondary batteries Method.   The manufacturing method of Claim 1 whose temperature to heat is 600-950 degreeC.   The production method according to claim 1 or 2, wherein the Group 3 element or Group 4 element is at least one element selected from the group consisting of lanthanum, titanium, zirconium, and hafnium.   The amount of the group 3 element or the group 4 element deposited by contacting with the solution of the group 3 element or the compound of the group 4 element is 0.02 to 0.5 mol% with respect to the lithium composite oxide. The manufacturing method in any one of 1-3.   The manufacturing method according to any one of claims 1 to 4, wherein the lithium composite oxide from which the treated water is separated is dried at 60 to 200 ° C and then contacted with a solution of a compound of a group 3 element or a group 4 element.   The production according to any one of claims 1 to 5, wherein the solution of the group 3 element or group 4 element compound is an aqueous solution of at least one compound selected from the group consisting of ammonium zirconium carbonate, lanthanum acetate, and titanium lactate. Method.   The manufacturing method in any one of Claims 1-6 whose amount of free alkalis of a positive electrode active material is 0.7 mol% or less. In the general formula _{Li a Ni b Co c Mn d} M lithium composite oxide represented by _{e O 2, a, b,} c, d and e are, respectively, 0.95 ≦ a ≦ 1.1,0.3 The manufacturing method according to claim 1, wherein ≦ b ≦ 0.9, 0 ≦ c ≦ 0.5, 0.1 ≦ d ≦ 0.5, and 0 ≦ e ≦ 0.1.   The manufacturing method in any one of Claims 1-8 whose positive electrode active material is a particulate form and whose average particle diameter is 3-25 micrometers. The manufacturing method in any one of Claims 1-9 whose specific surface area of a positive electrode active material is 0.1-1.5 m < ² > / g. The manufacturing method in any one of Claims 1-10 whose press density of a positive electrode active material is 2.7-3.8 g / cm < ³ >.   The positive electrode active material obtained by the production method according to claim 1, a conductive agent, a binder and a solvent are mixed, and after applying the resulting slurry to a metal foil, the solvent is removed by heating. A method for producing a positive electrode for a lithium ion secondary battery.   A method for producing a lithium ion secondary battery, comprising: laminating a separator and a negative electrode on a positive electrode obtained by the production method according to claim 12, housing the battery in a battery case, and then injecting an electrolytic solution. .