JPWO2011016334A1 - Method for producing positive electrode material for lithium ion secondary battery - Google Patents

Abstract

Provided is a production method in which a lithium composite oxide having excellent charge / discharge cycle durability, a low amount of free alkali, and high discharge capacity, fillability and volume capacity density can be obtained. General formula LiaNibCocMndMeO2 (M represents at least one element selected from the group consisting of transition metal elements other than Ni, Co and Mn, aluminum, tin, zinc and alkaline earth metals. 0.95 ≦ a ≦ 1.2 0 ≦ b ≦ 1, 0 ≦ c ≦ 1, 0 ≦ d ≦ 0.6, 0 ≦ e ≦ 0.2, a + b + c + d + e = 2), and the aluminum concentration is 10 to 250 ppm. A method for producing a positive electrode material for a lithium ion secondary battery, wherein the positive electrode material is obtained by contacting an aluminum aqueous solution, wherein the aluminum aqueous solution is separated from the lithium composite oxide.

Description

  The present invention relates to a method for producing a positive electrode material for a lithium ion secondary battery, a positive electrode using the positive electrode material obtained by the production method, and a lithium ion secondary battery.

In recent years, as devices become more portable and cordless, demands for non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries that are small, lightweight, and have high energy density are increasing. Common positive electrode materials for non-aqueous electrolyte secondary batteries include LiCoO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , A composite oxide of lithium and a transition metal element such as LiNiO ₂ , LiNi _0.8 Co _0.2 O ₂ , LiMn ₂ O ₄ , LiMnO ₂ (in the present invention, sometimes simply referred to as a lithium composite oxide) Are known.
Among them, lithium secondary batteries using LiCoO ₂ as a positive electrode material and lithium alloy or carbon such as graphite or carbon fiber as a negative electrode are widely used as batteries having a high energy density because a high voltage of 4V can be obtained. It is used.

Moreover, positive electrode materials such as LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , LiNiO ₂ , LiNi _0.8 Co _0.2 O ₂ are Since the content of expensive Co is small, it is expected as a low-cost material. Furthermore, it is known that in these positive electrode materials, the higher the Ni content, the greater the charge / discharge capacity per unit weight and the higher the energy density.

  However, in any positive electrode material, discharge capacity, fillability, volume capacity density related to discharge capacity per unit volume, charge / discharge cycle durability related to reduction of discharge capacity due to repeated charge / discharge, and left in a charged state for a long time. The amount of free alkali related to the storage characteristics related to the amount of gas generated at the time of coating and the coating properties related to the coating state on the current collector at the time of electrode preparation are insufficient, and all satisfactory ones have been obtained. Absent.

In order to solve these problems, various studies have been made conventionally. For example, a positive electrode material obtained by dispersing lithium nickel cobalt composite oxide in water and then filtering, or obtained by dispersing lithium nickel cobalt composite oxide in water and adding phosphoric acid, followed by filtration. A positive electrode material or a positive electrode material obtained by filtering lithium cobaltate after stirring in an acidic aqueous solution containing sulfuric acid, nitric acid or hydrochloric acid has been proposed (see Patent Document 1 and Patent Document 2).
Also, lithium composite oxide particles such as lithium manganese composite oxide having a spinel structure are dispersed in water or alcohol, then alkoxide of aluminum or zirconium is added, and water is further added to hydrolyze the alkoxide, followed by filtration. And the positive electrode material obtained by heating is proposed (refer patent document 3 and patent document 4).

A solution in which Al (OCH ₃ ) ₃ is dissolved in 2-ethoxyethanol is mixed with lithium nickel cobalt composite oxide, stored at room temperature for 24 hours, washed with 2-ethoxyethanol, and heated at 300 to 800 ° C. Thus, a positive electrode material obtained by covering the particle surface with a metal compound such as Al has been proposed (see Patent Document 5).
Lithium nickel cobalt manganese composite oxide is dispersed in a 2-propanol solution in which Al (OC ₃ H ₇ ) ₃ is dissolved or an aqueous solution in which Al (CH ₃ COCHCOCH ₃ ) ₃ is dissolved, stirred and filtered, A positive electrode material obtained by irradiating ultrasonic waves and then heat-treating at 500 ° C. has been proposed (see Patent Document 6).
In addition, a positive electrode material in which lanthanum and aluminum are included in the surface layer of lithium nickel cobalt manganese composite oxide particles has been proposed (see Patent Document 7).
A positive electrode material in which lithium nickel cobalt manganese composite oxide is coated with aluminum fluoride (AlF ₃ ) has been proposed. (See Patent Document 8).

JP 2000-090917 A JP 2003-123755 A JP 2001-313034 A Special Table 2003-500318 Japanese Patent Laid-Open No. 9-055210 JP 2005-310744 A JP 2008-226495 A US Patent Application Publication No. 2010/0086853

As described above, various studies have been made heretofore, but the lithium composite oxide satisfying all the characteristics such as discharge capacity, filling property, volume capacity density, charge / discharge cycle durability and free alkali amount, It has not been obtained yet.
For example, in the positive electrode materials described in Patent Document 1 and Patent Document 2, by washing the particle surface of the lithium composite oxide, the alkali compound on the particle surface can be removed, and a decrease in the amount of free alkali is observed. Since the surface is in contact with water or acid with high acidity, lithium, nickel, cobalt and manganese ions are eluted from the surface of the positive electrode material particles, resulting in unstable crystal structure and extreme charge / discharge cycle durability. Deterioration was seen and it was not able to withstand practical use.

  In the positive electrode materials described in Patent Documents 3 to 5, the solvent to be brought into contact with the lithium composite oxide is an organic solvent such as alcohol, and the organic solvent is relatively difficult to dissolve the alkali compound. Alkaline compounds present on the particle surface cannot be removed. Therefore, when the amount of free alkali is increased and used as a positive electrode material of a battery, when processing into an electrode, the slurry in which the positive electrode material is dispersed becomes a gel, or the positive electrode material is peeled off from the current collector, Deterioration of coatability is observed. 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.

  Furthermore, the positive electrode material obtained by dispersing lithium composite oxide in an organic solvent in which an aluminum alkoxide is dissolved and irradiating ultrasonic waves described in Patent Document 6 requires irradiation with ultrasonic waves. In addition, since the dispersed solvent is an organic solvent and the alkali compound present on the surface of the lithium composite oxide particles cannot be removed, the amount of free alkali is high, storage characteristics and coating properties are poor, and can be used practically It was not. In addition, the positive electrode material obtained by dispersing lithium composite oxide in an aqueous solution in which aluminum acetylacetonate is dissolved and irradiating with ultrasonic waves needs to be irradiated with ultrasonic waves, and the aluminum concentration in the aqueous solution Very low as 2.5 ppm, lithium, nickel, cobalt and manganese ions elute from the particle surface of the positive electrode material and the grain boundary of the particle, the crystal structure becomes unstable, the charge / discharge cycle durability is low, It could not withstand practical use. In addition, aluminum acetylacetonate has a problem of high cost.

  Although the positive electrode material described in Patent Document 7 also showed a reduction in the amount of free alkali and improved charge / discharge cycle durability, it was necessary to use an aluminum compound and a lanthanum compound to produce this positive electrode material. In particular, lanthanum is a rare rare earth element, and there are problems such as high raw material costs and difficulty in procuring raw materials, making mass production difficult.

In addition, as described in Patent Document 7, generally, a positive electrode material having a high amount of free alkali tends to be in a gel state when it is processed into an electrode from a slurry in which this is dispersed in a solvent. There was a problem that the positive electrode material peeled off from the electric body and the coating property was poor. In addition, if a positive electrode material with a high amount of free alkali is used as the positive electrode of a battery and it is stored for a long time in a charged state or is repeatedly charged and discharged over a long period of time, the decomposition reaction of the electrolytic solution proceeds, accompanied by heat generation. However, gas such as carbon dioxide and water are generated to cause a decomposition reaction of the positive electrode material, which leads to expansion and rupture of the battery, resulting in poor storage characteristics.
In the manufacturing method described in Patent Document 8, since aluminum fluoride is electrochemically inactive, there is a problem that the discharge capacity is reduced.
Accordingly, the present invention is a method for producing a positive electrode material having excellent charge / discharge cycle durability, low free alkali amount, high discharge capacity, filling property and volume capacity density, and a positive electrode comprising a positive electrode material obtained by the production method, An object of the present invention is to provide a lithium ion secondary battery containing the positive electrode material.

  As a result of intensive research, the inventors of the present invention obtained a positive electrode material obtained by contacting a lithium composite oxide with an aluminum aqueous solution in a predetermined concentration range and then separating the lithium composite oxide from the aluminum aqueous solution. It has been found that the above-mentioned problems can be achieved by using them.

This invention is based on said novel knowledge, and makes the following a summary.
(1) General formula Li _a Ni _b Co _c Mn _{d Me} O ₂ (where M is at least selected from the group consisting of transition metal elements other than Ni, Co and Mn, aluminum, tin, zinc and alkaline earth metals) Represents one element, 0.95 ≦ a ≦ 1.2, 0 ≦ b ≦ 1, 0 ≦ c ≦ 1, 0 ≦ d ≦ 0.6, 0 ≦ e ≦ 0.2, a + b + c + d + e = 2) Lithium ion secondary characterized in that after the lithium composite oxide represented is brought into contact with an aqueous aluminum solution having an aluminum concentration of 10 to 250 ppm, the aqueous aluminum solution is separated from the lithium composite oxide to obtain a positive electrode material A method for producing a positive electrode material for a battery.
(2) The manufacturing method as described in said (1) which heats the positive electrode material obtained by isolate | separating aluminum aqueous solution from lithium complex oxide at the temperature of 50-1000 degreeC.
(3) The manufacturing method as described in said (2) whose heating temperature is 60-830 degreeC.
(4) The aqueous aluminum solution dissolves at least one compound selected from the group consisting of aluminum sulfate, aluminate, alum, aluminum oligomer, aluminum hydroxy acid salt, and aluminum carboxylate having a carbonyl group. The manufacturing method in any one of said (1)-(3) which is aqueous solution.
(5) The production method according to any one of (1) to (4), wherein the aluminum aqueous solution is brought into contact with the lithium composite oxide in a mass ratio of 1 to 20 times.
(6) The manufacturing method in any one of said (1)-(5) whose quantity of aluminum contained in the positive electrode material obtained is 30-800 ppm.
(7) The manufacturing method in any one of said (1)-(6) whose amount of free alkalis contained in the positive electrode material obtained is 0.7 mol% or less.
(8) The lithium composite oxide is 0.97 ≦ a ≦ 1.1, 0.2 ≦ b ≦ 0.9, 0.1 ≦ c ≦ 0.4, 0.1 ≦ d ≦ 0.4, 0 The manufacturing method in any one of said (1)-(7) represented by <= e <= 0.1.
(9) The lithium composite oxide is 1.08 ≦ a ≦ 1.2, 0.12 ≦ b ≦ 0.25, 0.1 ≦ c ≦ 0.15, 0.45 ≦ d ≦ 0.6, 0 The manufacturing method in any one of said (1)-(7) represented by <= e <= 0.05.
(10) After mixing the positive electrode material obtained by the manufacturing method in any one of said (1)-(9), a electrically conductive agent, a binder, and a solvent, and apply | coating the obtained slurry to metal foil, it is a solvent by heating. A method for producing a positive electrode for a lithium ion secondary battery, which is obtained by removing
(11) A lithium ion secondary battery obtained by laminating a separator and a negative electrode on a positive electrode obtained by the production method of (10) above, storing the battery in a battery case, and then injecting an electrolytic solution. Manufacturing method.
(12) A positive electrode containing a positive electrode material, a conductive agent and a binder, wherein the positive electrode material is a positive electrode material obtained by the method according to any one of (1) to (9) above. Secondary battery positive electrode.
(13) A lithium ion secondary battery comprising a positive electrode, a negative electrode, and an electrolytic solution, wherein the positive electrode is the positive electrode described in (12) above.

  According to the present invention, a production that is useful as a positive electrode of a lithium ion secondary battery, is excellent in charge / discharge cycle durability, has a low free alkali amount, and has a high discharge capacity, fillability, and volume capacity density. A method is provided. Moreover, the positive electrode for lithium ion secondary batteries and a lithium ion secondary battery which have the outstanding battery performance are provided using the positive electrode material obtained by said manufacturing method.

In the present invention, the abundance of an alkali compound present on the particle surface of the positive electrode material or the grain boundary of the particle is evaluated by measuring the amount of free alkali. The positive electrode material obtained according to the present invention has a low free alkali amount, prevents gelation of the slurry of the positive electrode material, improves the coating property, and suppresses the generation of gas and water accompanying the decomposition reaction of the electrolytic solution, It prevents battery expansion and improves storage characteristics.
The reason why the positive electrode material obtained in the present invention has the above-mentioned excellent characteristics is not necessarily clear, but is estimated as follows.

  In general, the lithium composite oxide is obtained by mixing a lithium source and a transition metal source containing nickel, cobalt, manganese, and the like, and firing the obtained raw material mixture. In the lithium composite oxide, There are alkaline compounds such as lithium atoms that exist out of the lattice points of the crystal lattice and lithium compounds that remain insufficiently reacted. When charging and discharging are repeated in a battery using a positive electrode material made of such a lithium composite oxide, the alkali compound is eluted from the particle surface or particle boundary into the electrolytic solution, the composition of the positive electrode material changes, or the electrolytic solution This promotes the decomposition of the battery and causes deterioration of battery performance such as coating properties and storage characteristics.

  However, when the particle surface of the lithium composite oxide and the grain boundary of the particle are simply washed with water or an acidic aqueous solution in order to remove the alkali compound, lithium, nickel, cobalt, Components such as manganese are eluted as ions, the crystal structure becomes unstable, and charge / discharge cycle durability deteriorates.

  On the other hand, according to the present invention, the alkaline compound can be efficiently removed by bringing the lithium composite oxide particles into contact with an aqueous aluminum solution in a predetermined concentration range, and elution of lithium, nickel, cobalt, manganese, etc. is suppressed. In the case of elution, it is considered that the charge / discharge cycle durability is not deteriorated because aluminum is substituted at the site of the eluted atom. In addition, when the amount of the alkali compound in the lithium composite oxide is reduced, the gelation of the slurry using this is suppressed, so that the coating property is improved and the gas generated in the battery is reduced, so that the storage characteristics are improved. It is thought to improve.

Thus, in the present invention, by bringing an aluminum aqueous solution in a predetermined concentration range into contact with the lithium composite oxide, a good removal effect of the alkali compound in the lithium composite oxide and elution of the components in the lithium composite oxide are achieved. Combined with the suppression effect, it is considered that the charge / discharge cycle durability is greatly improved and the amount of free alkali is remarkably reduced.
Also, by contacting the aluminum compound with the lithium composite oxide in the form of an aqueous solution, it prevents the aluminum compound from adhering to the particle surface of the lithium composite oxide, and is derived from the aqueous aluminum solution contained in the particle surface of the positive electrode material. It is considered that the amount of aluminum can be controlled within an appropriate range, and the charge / discharge cycle durability can be improved without reducing the discharge capacity.

  In the present invention, as described above, the lithium composite oxide particles having a predetermined composition are brought into contact with an aluminum aqueous solution having a predetermined concentration to remove an alkali compound present on the surface of the particles. It consists of a step of separating the aqueous aluminum solution to obtain a positive electrode material for a lithium ion secondary battery.

The lithium composite oxide used in the present invention is represented by the general formula Li _a Ni _b Co _c Mn _{d Me} O ₂ . The definitions of a, b, c, d and e in the general formula are as described above. When d is d ≦ 0.4, 0.97 ≦ a ≦ 1.1, 0.2 ≦ b ≦ 0.9, 0.1 ≦ c ≦ 0.4, 0.1 ≦ d ≦ 0. 4, 0 ≦ e ≦ 0.1 is preferable, 0.97 ≦ a ≦ 1.1, 0.2 ≦ b ≦ 0.83, 0.1 ≦ c ≦ 0.4, 0.1 ≦ d ≦ 0. 4, 0 ≦ e ≦ 0.1 is more preferable, 0.99 ≦ a ≦ 1.05, 0.4 ≦ b ≦ 0.7, 0.15 ≦ c ≦ 0.3, 0.15 ≦ d ≦ 0 .3, 0 ≦ e ≦ 0.05 is particularly preferable. Further, 0.97 ≦ a ≦ 1.03, b = 0, 0.97 ≦ c ≦ 1, d = 0, and 0 ≦ e ≦ 0.03 are preferable. When d is d> 0.4, 1.05 ≦ a ≦ 1.2, 0.1 ≦ b ≦ 0.3, 0.05 ≦ c ≦ 0.2, 0.4 <d ≦ 0.8, 0 ≦ e ≦ 0.1 are preferable, 1.08 ≦ a ≦ 1.2, 0.12 ≦ b ≦ 0.25, 0.1 ≦ c ≦ 0.15, 0.45 ≦ d ≦ 0.7, 0 ≦ e ≦ 0.05 are more preferable, 1.08 ≦ a ≦ 1.2, 0.12 ≦ b ≦ 0.25, 0.1 ≦ c ≦ 0.15, 0.45 ≦ d ≦ 0.6 and 0 ≦ e ≦ 0.05 are particularly preferable.

  The method for producing the lithium composite oxide used in the present invention is not particularly limited, and a solid phase method, a coprecipitation method, or the like can be used as appropriate. Specific examples of the nickel source, cobalt source, manganese source, and M element source include hydroxides, oxides, and oxyhydroxides of the respective elements. 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.

In the present invention, the molar ratio a / (b + c + d + e), which is a value obtained by dividing the molar amount of lithium in the lithium composite oxide by the total molar amount of Ni element, Co element, Mn element, and M element, is 0.95. Is preferably ˜1.20, more preferably 0.97 to 1.10, and particularly preferably 0.99 to 1.05. In this case, the growth of lithium composite oxide particles is promoted, and higher density particles can be obtained.
In the method for producing a lithium composite oxide used in the present invention, in order to improve the safety of the obtained lithium ion secondary battery, 0.01 to 5 mol%, preferably 0.1 to 2% of oxygen atoms of the lithium composite oxide. You may substitute mol% with a fluorine atom.

  In the present invention, the M element 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 standpoint 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

  In the present invention, the aluminum aqueous solution means an aqueous solution in which an aluminum compound is dissolved. The aqueous aluminum solution used in the present invention does not include suspension and colloidal forms, and is dissolved to such an extent that at least the aluminum source cannot be visually recognized as a solid component. The aluminum concentration of the aqueous solution is preferably in the following range. Here, the aluminum concentration means the concentration of the aluminum element, and is determined by calculation from the raw material used or by measurement by ICP (inductively coupled plasma) emission spectrometry. In examples and comparative examples to be described later, they are obtained by calculation. The upper limit of the aluminum concentration is 250 ppm, preferably 200 ppm, and more preferably 150 ppm. Moreover, the minimum of aluminum concentration is 10 ppm, 20 ppm is preferable and 50 ppm is more preferable. When the aluminum concentration is within this range, the amount of free alkali contained in the obtained positive electrode material is low, and the tendency to improve the charge / discharge cycle durability is preferred. On the other hand, when the concentration of the aluminum aqueous solution is higher than 250 ppm, excessive aluminum adheres to the lithium composite oxide, and the amount of free alkali becomes high, which is not preferable. In addition, when the aluminum concentration is lower than 10 ppm, the elements forming the lithium composite oxide particles are eluted and the charge / discharge cycle durability is deteriorated.

  3-12 are preferable and, as for pH of aluminum aqueous solution, 5-11 are especially preferable. Moreover, 7-13 are preferable and, as for pH of the aluminum aqueous solution after isolate | separating from lithium complex oxide, 9-12 are especially preferable. When the pH of the aqueous aluminum solution is lower than the above range, the lithium composite oxide is exposed to an acidic environment, Li, Ni, Co, Mn and the like are eluted from the particles, and the charge / discharge cycle durability tends to deteriorate. is there. Moreover, when pH is higher than the above-mentioned range, there exists a tendency for the amount of free alkalis to increase, without fully removing the alkali compound which exists in the particle | grain surface and grain boundary of lithium composite oxide.

A water-soluble aluminum compound is used as the aluminum source for forming the aluminum aqueous solution, and in particular, it is obtained by reacting at least one acid selected from the group consisting of inorganic acids and organic acids with aluminum or an aluminum-containing compound. The aluminum salt is preferably an aluminum salt, more preferably at least one selected from the group consisting of aluminum sulfate, aluminate, alum, aluminum oligomer, aluminum hydroxy acid salt, and aluminum carboxylate. As alum, potassium aluminum sulfate hydrate, iron aluminum sulfate hydrate, magnesium aluminum sulfate hydrate, sodium aluminum sulfate hydrate, and aluminum sulfate hydrate are preferable. As the aluminum oligomer, polyaluminum chloride is preferred. This polyaluminum chloride is a polymer of basic aluminum chloride, represented by [Al ₂ (OH) _n Cl _6-n ] _m (n and m represent 1 ≦ n ≦ 5 and m ≦ 10, respectively). Is done. As the hydroxy acid salt of aluminum or the carboxylate of aluminum having a carbonyl group, a hydroxy acid salt having 2 to 8 carbon atoms or a carboxylate is preferable. The aluminum hydroxy acid salt is preferably basic aluminum lactate, aluminum lactate, aluminum glycolate, aluminum hydroxybutyrate, aluminum malate, or aluminum citrate, and basic aluminum lactate, aluminum lactate, aluminum malate, or citric acid. Aluminum is more preferred. The carboxylate of aluminum having a carbonyl group means an aluminum salt of a carboxylic acid having a carbonyl group, preferably aluminum glyoxylate, aluminum pyruvate, or aluminum levulinate, and particularly preferably aluminum glyoxylate.

  Among the aluminum sources described above, at least one compound selected from the group consisting of polyaluminum chloride, aluminum sulfate, basic aluminum lactate, aluminum lactate, aluminum glyoxylate, aluminum citrate, and sodium aluminate is more preferable, More preferred is at least one compound selected from the group consisting of polyaluminum chloride, aluminum sulfate, basic aluminum lactate and sodium aluminate. In particular, polyaluminum chloride is particularly preferable because it is easy to handle and inexpensive, and the performance of the obtained positive electrode material is excellent. By using an aluminum aqueous solution in which these aluminum sources are dissolved, an alkali compound is removed from the surface of the lithium composite oxide particles, and at the same time, elements such as lithium, nickel, cobalt, and manganese that form the lithium composite oxide from the particle surface. Elution can be suppressed and a reduction in the amount of free alkali can be realized.

  When an organic solvent in which an aluminum source is dissolved is used instead of an aluminum aqueous solution, the alkali compound present on the surface of the lithium composite oxide particles cannot be removed, and the battery is swollen by decomposing the electrolyte. , Preservation characteristics deteriorate. Further, when aluminum alkoxide is used as the aluminum source and water is used as the solvent, the aluminum alkoxide is hydrolyzed into a suspension or slurry, so that a large amount of aluminum is formed on the surface of the lithium composite oxide particles. The fine particles of the compound adhere, and the amount of free alkali cannot be reduced, and the discharge capacity is further reduced.

  The method of bringing the lithium composite oxide particles into contact with the aqueous aluminum solution is not particularly limited. For example, the lithium composite oxide is added to the aluminum aqueous solution in a beaker or a stainless steel bath, and a stirring means such as a stirring blade is used. And a method of mixing an aqueous solution of aluminum and a powder of lithium composite oxide by circulating an aqueous solution with a pump. Alternatively, a method of spraying an aluminum aqueous solution on the lithium composite oxide placed on the filter cloth and sucking it from under the filter cloth, or filtration with a filter press may be used. By contacting with the above method, the alkali compound present on the surface of the lithium composite oxide particles can be efficiently removed. Moreover, the conditions for bringing the aqueous lithium solution into contact with the lithium composite oxide are not particularly limited, but the time is preferably 10 seconds to 8 hours, more preferably 1 minute to 5 hours, and particularly preferably 5 minutes to 3 hours. . The temperature is preferably 5 to 80 ° C., particularly preferably 10 to 60 ° C., further 20 to 40 ° C., and the pressure is preferably 0.5 to 3 atm, particularly preferably atmospheric pressure.

  Moreover, the ratio of the aluminum aqueous solution brought into contact with the lithium composite oxide is preferably in a range of 1 to 20 times in terms of mass ratio with respect to the lithium composite oxide. In particular, the ratio of the aluminum aqueous solution brought into contact with the lithium composite oxide is more preferably 3 to 10 times, particularly preferably 4 to 6 times in terms of mass ratio. When the ratio of the aqueous aluminum solution is in the above range, the lithium composite oxide can be sufficiently brought into contact with the aqueous aluminum solution, and the alkali compound can be sufficiently removed. When the mixing ratio is higher than the above, the amount of the aqueous aluminum solution used tends to increase and the amount of waste water tends to increase.

  In the present invention, after the contact between the lithium composite oxide and the aqueous aluminum solution, the aqueous aluminum solution is separated from the lithium composite oxide. The separation of the aqueous aluminum solution is performed in order to separate the free alkali component eluted from the lithium composite oxide into the aluminum aqueous solution from the lithium composite oxide. Various methods can be adopted as a method for separating the aqueous aluminum solution from the lithium composite oxide. For example, a filter pressing method, a suction filtration method and the like can be mentioned.

  In the present invention, the positive electrode material can be obtained by separating the aqueous aluminum solution from the lithium composite oxide. However, the positive electrode material is preferably subjected to heat treatment next. The heating temperature is preferably 50 ° C. or higher, more preferably 60 ° C. or higher, further preferably 400 ° C. or higher, and particularly preferably 600 ° C. or higher. The heating temperature is preferably 1000 ° C. or lower, more preferably 900 ° C. or lower, and particularly preferably 830 ° C. or lower. When the lower limit of the heating temperature is lower than the above, water remaining in the positive electrode material after separating the aqueous aluminum solution cannot be completely removed, and the battery performance may be deteriorated. On the other hand, when the upper limit of the heating temperature is higher than the above, the particles of the positive electrode material may sinter to form coarse particles, which may reduce the discharge capacity and the rate characteristics. The heating method is not particularly limited, but it is preferably performed in a continuous furnace such as a roller hearth kiln or a rotary kiln, preferably in an oxygen-containing atmosphere. The heating time is not particularly limited, but is preferably 1 to 24 hours, more preferably 2 to 18 hours, and particularly preferably 3 to 12 hours.

  The positive electrode material obtained by the present invention has a low free alkali amount, and the free alkali amount is preferably 0.8 mol% or less, and 0.7 mol% or less with respect to the lithium-containing composite oxide contained in the positive electrode material. More preferred. In addition, since the contact time between the lithium composite oxide and the aqueous aluminum solution can be shortened and the positive electrode material of the present invention can be synthesized efficiently, the lower limit of the amount of free alkali is preferably 0.05 mol%. It does not affect. When the amount of free alkali is within the above range, the slurry of the positive electrode material tends not to gel when the electrode material slurry is applied to a current collector during electrode production, and can be applied easily and uniformly. Workability is improved. Further, when the battery is charged and held for a long period of time, or when the charge / discharge cycle is repeated, the generation of gas can be suppressed, the battery can be prevented from being swollen, and the storage characteristics are improved.

  The amount of free alkali in the present invention is a value related to the amount of alkali compound present on the particle surface of the positive electrode material and the grain boundary of the particle. The amount of the free alkali is a liquid obtained by mixing 50 g of water with 1 g of the positive electrode material powder, stirring for 30 minutes, and filtering the filtrate obtained by washing the filtrate with 10 g of water three times. It is measured by titrating the alkali in it with dilute hydrochloric acid.

  Although a small amount of aluminum remains in the positive electrode material obtained by the present invention, the amount of aluminum contained in the positive electrode material is preferably 30 to 800 ppm, more preferably 50 to 750 ppm, and particularly preferably 70 to 650 ppm. When the amount of aluminum contained in the positive electrode material is within the above range, a positive electrode material having excellent charge / discharge cycle durability and a small amount of free alkali can be obtained with good reproducibility. In the present invention, the amount of aluminum derived from the aqueous aluminum solution contained in the positive electrode material is sometimes referred to as the remaining amount of aluminum (the remaining amount of Al). This remaining amount of aluminum can be measured by ICP (inductively coupled plasma) emission spectrometry. In addition, when aluminum is previously contained in the lithium composite oxide before being brought into contact with the aluminum aqueous solution, the remaining amount of aluminum (the remaining amount of Al) is determined based on the amount of aluminum contained in the positive electrode material measured by ICP analysis. This is a value obtained by subtracting the amount of aluminum previously contained in advance.

The press density of the positive electrode material obtained by the present invention is preferably 2.7~3.6g / cm ^3, more preferably 2.8~3.4g / cm ^3. In the present invention, the press density refers to an apparent press density when 5 g of the positive electrode material powder is pressed at a pressure of 0.32 t / cm ² . Moreover, 8-25 micrometers is preferable and, as for the average particle diameter of the particle | grains of positive electrode material, 10-20 micrometers is more preferable. Further, the specific surface area of the positive electrode material, as 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. The measurement of the average particle diameter of the positive electrode material means a cumulative 50% value of the 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 size may be referred to as average particle size 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 material particles are secondary particles, the average particle diameter of the secondary particles is represented, and when the positive electrode material particles are primary particles, the average particle diameter of the primary particles is represented. The particle shape of the positive electrode material is affected by the shape of the lithium composite oxide used as the raw material.

  When producing a positive electrode for a lithium ion secondary battery from the positive electrode material obtained in the present invention, a carbon-based conductive material such as acetylene black, graphite, or ketjen black and a binder are mixed into the positive electrode material powder. It is formed by. For the binder, polyvinylidene fluoride, polytetrafluoroethylene, polyamide, carboxymethyl cellulose, acrylic resin, or the like is preferably used. The powder of the positive electrode material, the conductive material, and the binder obtained by the present invention are made into a slurry or a kneaded material 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 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 material obtained in the present invention, a vinylidene fluoride-hexafluoropropylene copolymer (for example, product name: Kyner manufactured by Atchem Co.) or vinylidene fluoride-perfluoropropyl vinyl ether is used. A gel polymer electrolyte containing a 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 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 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.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to these Examples. Examples 1 to 5 below, Examples 11 to 16 and Examples 20 to 29 are examples, and Examples 6 to 10 and Examples 17 to 19 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 = 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 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 5.6 m ² / g and an average particle diameter D50 of 11.8 μm.

Lithium hydroxide powder was mixed with the obtained composite hydroxide powder and fired at 500 ° C. for 10 hours in the air atmosphere. The obtained fired product was mixed again, fired at 900 ° C. for 24 hours, and 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 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. Moreover, it was 20 ppm when the amount of aluminum contained in the said powder was measured using ICP.

Subsequently, water was added to 2 g of polyaluminum chloride aqueous solution (PAC 250A manufactured by Taki Chemical Co., Ltd.) having an aluminum content of 5.39% by mass to obtain 1000 g, and an aluminum aqueous solution having an aluminum concentration of 108 ppm was prepared. A slurry liquid obtained by adding 200 g of the lithium composite oxide powder to 1000 g of the aluminum aqueous solution 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 stirring and separation operations were performed at room temperature. The pH of the aqueous aluminum solution was 4.4, and the pH of the aqueous aluminum solution after separation was 11.6. The granulate was heated at 120 ° C. for 5 hours and then at 400 ° C. for 5 hours. The obtained granular material was passed through a sieve to obtain a positive electrode material powder. Stirring, separation, and heating were all performed in an air atmosphere. The average particle diameter D50 of the positive electrode material was 15.7 μm, D10 was 8.0 μm, D90 was 31.0 μm, and the specific surface area was 0.78 m ² / g.
The slurry obtained by mixing 1 g of the positive electrode material powder and 50 g of water and stirring for 30 minutes was filtered, and the filtrate was titrated with a 0.02 mol / L aqueous hydrochloric acid solution until the pH reached 4.0. When the amount of free alkali of the positive electrode material was determined from the amount of hydrochloric acid used for titration, the amount of free alkali was 0.47 mol%.

The particles of the obtained positive electrode material had a press density of 2.77 g / cm ³ and the amount of aluminum contained in the particles was 160 ppm. That is, the amount of aluminum derived from the aqueous aluminum solution, that is, the remaining amount of aluminum (the remaining amount of Al) was 140 ppm.
The positive electrode material 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 this is an aluminum foil having a thickness of 20 μm. One side coating was performed 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 simple sealed cell type lithium battery is charged at a current of 170 mA per 1 g of the positive electrode active material at 25 ° C. with an upper limit voltage of 4.3 V and charged for 3 hours in the CCCV mode (constant current of 170 mA, and the battery voltage reaches the upper limit voltage. Then, 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 85 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 170.2 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 93.4%.

[Example 2]
A positive electrode material was synthesized in the same manner as in Example 1 except that an aluminum aqueous solution having an aluminum concentration of 162 ppm was used as the aluminum aqueous solution, and each characteristic was measured. The pH of the aqueous aluminum solution was 4.3, and the pH of the aqueous aluminum solution after separation was 11.4. As a result, the average particle diameter D50 of the obtained positive electrode material was 16.1 μm, D10 was 8.2 μm, D90 was 32.8 μm, the specific surface area was 0.81 m ² / g, and the press density was 2.76 g. / Cm ³ . Moreover, the amount of free alkalis of the obtained positive electrode material was 0.67 mol%, and the residual amount of aluminum was 590 ppm. The initial discharge capacity was 167.3 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 90.1%.

[Example 3]
A positive electrode material was synthesized in the same manner as in Example 1 except that an aluminum aqueous solution having an aluminum concentration of 54 ppm was used as the aluminum aqueous solution, and each characteristic was measured. The pH of the aqueous aluminum solution was 4.7, and the pH of the aqueous aluminum solution after separation was 11.7. As a result, the average particle diameter D50 of the obtained positive electrode material was 15.8 μm, D10 was 8.0 μm, D90 was 31.5 μm, the specific surface area was 0.68 m ² / g, and the press density was 2.82 g. / Cm ³ . The amount of free alkali of this positive electrode material was 0.49 mol%, and the remaining amount of aluminum was 65 ppm. The initial discharge capacity was 164.4 mAh / g, and the capacity retention rate was 90.3%.

[Example 4]
A positive electrode material was synthesized in the same manner as in Example 1 except that an aluminum aqueous solution having an aluminum concentration of 27 ppm was used as the aluminum aqueous solution, and each characteristic was measured. The pH of the aqueous aluminum solution was 5.0, and the pH of the aqueous aluminum solution after separation was 11.7. As a result, the obtained positive electrode material had an average particle diameter D50 of 15.0 μm, D10 of 7.8 μm, D90 of 31.1 μm, a specific surface area of 0.85 m ² / g, and a press density of 2.80 g. / Cm ³ . The amount of free alkali of this positive electrode material was 0.54 mol%, and the remaining amount of aluminum was 45 ppm. The initial discharge capacity was 168.0 mAh / g, and the capacity retention rate was 86.1%.

[Example 5]
A positive electrode material was synthesized and each characteristic was measured in the same manner as in Example 1 except that an aluminum aqueous solution having an aluminum concentration of 11 ppm was used as the aluminum aqueous solution. The pH of the aqueous aluminum solution was 5.5, and the pH of the aqueous aluminum solution after separation was 11.9. As a result, the average particle diameter D50 of the obtained positive electrode material was 11.0 μm, D10 was 6.9 μm, D90 was 19.7 μm, the specific surface area was 0.81 m ² / g, and the press density was 2.76 g. / Cm ³ . The amount of free alkali of this positive electrode material was 0.54 mol%, and the remaining amount of aluminum was 34 ppm. The initial discharge capacity was 168.8 mAh / g, and the capacity retention rate was 84.3%.

[Example 6]
A positive electrode material was synthesized in the same manner as in Example 1 except that an aluminum aqueous solution having an aluminum concentration of 1 ppm was used as the aluminum aqueous solution, and each characteristic was measured. The pH of the aqueous aluminum solution was 5.8, and the pH of the aqueous aluminum solution after separation was 11.9. As a result, the average particle diameter D50 of the obtained positive electrode material was 11.0 μm, D10 was 6.9 μm, D90 was 19.8 μm, the specific surface area was 0.81 m ² / g, and the press density was 2.77 g. / Cm ³ . The amount of free alkali of this positive electrode material was 0.57 mol%, the amount of aluminum contained in the particles was 20 ppm, and the amount of aluminum derived from the aqueous aluminum solution could not be confirmed. The remaining amount of aluminum was 10 ppm or less. The initial discharge capacity was 168.3 mAh / g, and the capacity retention rate was 78.4%.

[Example 7]
A positive electrode material was synthesized and each characteristic was measured in the same manner as in Example 1 except that an aluminum aqueous solution having an aluminum concentration of 270 ppm was used as the aluminum aqueous solution. The pH of the aqueous aluminum solution was 4.0, and the pH of the aqueous aluminum solution after separation was 11.3. As a result, the average particle diameter D50 of the obtained positive electrode material was 15.7 μm, D10 was 7.9 μm, D90 was 31.6 μm, the specific surface area was 0.87 m ² / g, and the press density was 2.77 g. / Cm ³ . The amount of free alkali of this positive electrode material was 0.82 mol%, and the remaining amount of aluminum was 1060 ppm. When the electrode was applied in the same manner as in Example 1, the coatability was poor, and peeling of the positive electrode material from the aluminum foil was confirmed in a part of the electrode after coating, drying and roller pressing. When a battery was produced using the electrode part that did not peel off, the initial discharge capacity was 165.0 mAh / g, and the capacity retention rate was 88.6%.

[Example 8]
A positive electrode material was synthesized and each characteristic was measured in the same manner as in Example 1 except that pure water was used instead of the aluminum aqueous solution. The pH of water was 6.7, and the pH of water after separation was 12.1. As a result, the average particle diameter D50 of the obtained positive electrode material was 15.9 μm, D10 was 8.2 μm, D90 was 28.2 μm, the specific surface area was 0.92 m ² / g, and the press density was 2.70 g. / Cm ³ . The amount of free alkali of this positive electrode material was 0.63 mol%. The initial discharge capacity was 164.4 mAh / g, and the capacity retention rate was 74.2%.

[Example 9]
A positive electrode material was synthesized in the same manner as in Example 1 except that it was not brought into contact with the aqueous aluminum solution in Example 1. That is, using the lithium composite oxide having a composition of Li _1.02 (Ni _0.6 Co _0.2 Mn _0.2 ) _0.98 O ₂ obtained in Example 1 as a positive electrode material as it is, It was measured. This positive electrode material had an average particle diameter D50 of 14.0 μm, D10 of 7.6 μm, D90 of 28.5 μm, a specific surface area of 0.29 m ² / g, and a press density of 2.79 g / cm ^3. It was. The amount of free alkali of this positive electrode material was 1.27 mol%. When the electrode was applied in the same manner as in Example 1, the coatability was poor, and peeling of the positive electrode material from the aluminum foil was confirmed in a part of the electrode after coating, drying and roller pressing. When a battery was produced using the electrode part that did not peel off, the initial discharge capacity was 167.7 mAh / g, and the capacity retention rate was 94.7%.

[Example 10]
Water was added to 2.4 g of an aqueous solution of basic aluminum lactate (manufactured by Taki Chemical Co., Ltd.) having an aluminum content of 4.4% by mass to obtain 30 g of an aqueous aluminum solution. The aluminum aqueous solution was added to a lithium composite oxide powder having a composition of Li _1.02 (Ni _0.6 Co _0.2 Mn _0.2 ) _0.98 O ₂ synthesized in the same manner as in Example 1, It mixed and it heated at 80 degreeC, stirring, without filtering, and was made to dry. The mixture was then heated at 350 ° C. for 5 hours to obtain a positive electrode material powder. The positive electrode material had an average particle diameter D50 of 15.0 μm, D10 of 7.8 μm, D90 of 30.2 μm, a specific surface area of 0.41 m ² / g, and a press density of 2.74 g / cm ^3. It was. The amount of free alkali of this positive electrode material was 1.12 mol%, and the remaining amount of aluminum was 540 ppm. When the electrode was applied in the same manner as in Example 1, the coatability was poor, and peeling of the positive electrode material from the aluminum foil was confirmed in a part of the electrode after coating, drying and roller pressing. When a battery was fabricated using the electrode part that did not peel off, the initial discharge capacity was 168.3 mAh / g, and the capacity retention rate was 94.3%.

[Example 11]
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, an average particle diameter D50 of 12.7 μm, and the amount of aluminum contained in the powder was 4100 ppm.

A predetermined amount of lithium carbonate was mixed with the composite hydroxide thus obtained, calcined at 1000 ° C. for 15 hours in the air atmosphere, and then pulverized to obtain Li _1.02 (Co _0.969 Al _0.015 Mg _{0 .015} Zr _0.001 ) _0.98 O ₂ lithium composite oxide powder 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 that this lithium composite oxide was used, it was contacted with an aqueous aluminum solution in the same manner as in Example 1, followed by filtration to separate the aqueous aluminum solution from the lithium composite oxide to obtain a positive electrode material powder. The pH of the aqueous aluminum solution was 4.4, and the pH of the aqueous aluminum solution after separation was 10.8.

The obtained positive electrode material has an average particle diameter D50 of 13.7 μm, D10 of 8.7 μm, D90 of 21.6 μm, a specific surface area of 0.36 m ² / g, and a press density of 2.91 / cm ^3. Met. The amount of free alkali of this positive electrode material was 0.10 mol%, and the amount of aluminum contained in the particles was 4240 ppm. That is, the amount of aluminum derived from the aqueous aluminum solution, that is, the remaining amount of aluminum (the remaining amount of Al) was 140 ppm. . The initial discharge capacity was 143.0 mAh / g, and the capacity retention rate was 98.4%.

[Example 12]
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 11.0 m ² / g, an average particle diameter D50 of 10.8 μm, and the amount of aluminum contained in the powder was 20 ppm.

A predetermined amount of lithium carbonate powder was mixed with the composite hydroxide powder thus obtained, and calcined in air at 1000 ° C. for 15 hours and then pulverized to obtain Li _1.02 (Ni _0.333 Co _{0 .333} Mn _0.333 ) _0.98 O ₂ lithium composite oxide powder 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 that this lithium composite oxide was used, it was brought into contact with an aqueous aluminum solution in the same manner as in Example 1, followed by filtration to separate the aqueous aluminum solution from the lithium composite oxide to obtain a positive electrode material powder. The pH of the aqueous aluminum solution was 4.4, and the pH of the aqueous aluminum solution after separation was 11.2.

The obtained positive electrode material had an average particle diameter D50 of 11.9 μm, D10 of 7.4 μm, D90 of 19.8 μm, a specific surface area of 0.56 m ² / g, and a press density of 2.83 / cm ^3. Met. The amount of free alkali of this positive electrode material was 0.26 mol%, and the remaining amount of aluminum was 120 ppm. The initial discharge capacity was 149 mAh / g, and the capacity retention rate was 93.9%.

[Example 13]
The powder of the positive electrode material was synthesized in the same manner as in Example 1 except that aluminum sulfate was used as the aluminum source and an aluminum aqueous solution having an aluminum concentration of 85 ppm was used. The average particle diameter D50 of the positive electrode material was 15.5 μm, D10 was 7.9 μm, D90 was 32.0 μm, the specific surface area was 0.82 m ² / g, and the press density was 2.81 / cm ³ . . The amount of free alkali of this material was 0.55 mol%, and the remaining amount of aluminum was 140 ppm. The initial discharge capacity was 173.2 mAh / g, and the capacity retention rate was 90.9%.

[Example 14]
A positive electrode material powder was synthesized in the same manner as in Example 1 except that sodium aluminate was used as the aluminum source and an aluminum aqueous solution having an aluminum concentration of 99 ppm was used. The pH of the aqueous aluminum solution was 10.9, and the pH of the aqueous aluminum solution after separation was 11.8. The average particle diameter D50 of the positive electrode material was 14.5 μm, D10 was 7.8 μm, D90 was 30.4 μm, the specific surface area was 0.75 m ² / g, and the press density was 2.71 / cm ³ . . The amount of free alkali of this positive electrode material was 0.55 mol%, and the remaining amount of aluminum was 56 ppm. The initial discharge capacity was 172.4 mAh / g, and the capacity retention rate was 91.4%.

[Example 15]
A powder of the positive electrode material was synthesized in the same manner as in Example 1 except that basic aluminum lactate (manufactured by Taki Chemical Co., Ltd.) was used as the aluminum source and an aluminum aqueous solution having an aluminum concentration of 100 ppm was used. The pH of the aqueous aluminum solution was 5.0, and the pH of the aqueous aluminum solution after separation was 11.7. The average particle diameter D50 of the positive electrode material was 15.3 μm, D10 was 7.9 μm, D90 was 29.8 μm, the specific surface area was 0.78 m ² / g, and the press density was 2.81 / cm ³ . . The amount of free alkali of this positive electrode material was 0.59 mol%, and the remaining amount of aluminum was 130 ppm. The initial discharge capacity was 171.7 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 91.3%.

[Example 16]
A powder of the positive electrode material was synthesized in the same manner as in Example 1 except that primary aluminum phosphate was used as the aluminum source and an aluminum aqueous solution having an aluminum concentration of 91 ppm was used. The pH of the aqueous aluminum solution was 2.6, and the pH of the aqueous aluminum solution after separation was 11.4. The average particle diameter D50 of the positive electrode material was 15.5 μm, D10 was 7.9 μm, D90 was 32.6 μm, the specific surface area was 0.71 m ² / g, and the press density was 2.72 / cm ³ . . The amount of free alkali of this positive electrode material was 0.84 mol%, and the remaining amount of aluminum was 210 ppm. The initial discharge capacity was 168.7 mAh / g, and the capacity retention rate was 86.1%.

[Example 17]
Instead of the aqueous aluminum solution, an isopropanol solution in which aluminum isopropoxide was dissolved so as to have a concentration of 0.003% by mass, that is, an isopropanol solution having an aluminum concentration of 4 ppm was used, and the heating temperature was 650 ° C., and the heating was performed for 1 hour. Otherwise, the same procedure as in Example 1 was performed to synthesize a positive electrode material powder. The average particle diameter D50 of the positive electrode material was 13.8 μm, D10 was 7.6 μm, D90 was 25.5 μm, the specific surface area was 0.30 m ² / g, and the press density was 2.75 / cm ³ . . The amount of free alkali of this positive electrode material was 1.37 mol%. When the electrode was applied in the same manner as in Example 1, the coatability was poor, and peeling of the positive electrode material from the aluminum foil was confirmed in a part of the electrode after coating, drying and roller pressing. When a battery was produced using the electrode part that did not peel off, the initial discharge capacity was 167.6 mAh / g, and the capacity retention rate was 93.0%.

[Example 18]
In the same manner as in Example 17 except that an isopropanol solution in which aluminum isopropoxide was dissolved so that the concentration was 0.03% by mass, that is, an isopropanol solution having an aluminum concentration of 40 ppm, was used instead of the aluminum aqueous solution. A powder was synthesized. The average particle diameter D50 of the positive electrode material was 13.7 μm, D10 was 7.6 μm, D90 was 27.2 μm, the specific surface area was 0.31 m ² / g, and the press density was 2.84 / cm ³ . . The amount of free alkali of this positive electrode material was 1.43 mol%. When the electrode was applied in the same manner as in Example 1, the coatability was poor, and peeling of the positive electrode material from the aluminum foil was confirmed in a part of the electrode after coating, drying and roller pressing. When a battery was fabricated using the electrode part that did not peel off, the initial discharge capacity was 167.6 mAh / g, and the capacity retention rate was 93.2%.

[Example 19]
In the same manner as in Example 17, except that an isopropanol solution in which aluminum isopropoxide was dissolved so as to have a concentration of 0.3% by mass, that is, an isopropanol solution having an aluminum concentration of 396 ppm, was used instead of the aqueous aluminum solution. A powder was synthesized. The average particle diameter D50 of the positive electrode material was 13.9 μm, D10 was 7.5 μm, D90 was 27.8 μm, the specific surface area was 1.92 m ² / g, and the press density was 2.83 / cm ³ . . The amount of free alkali of this positive electrode material was 3.2 mol%. When the electrode was applied in the same manner as in Example 1, the coatability was poor, and peeling of the positive electrode material from the aluminum foil was confirmed in a part of the electrode after coating, drying and roller pressing. When a battery was fabricated using the electrode part that did not peel off, the initial discharge capacity was 163.6 mAh / g, and the capacity retention rate was 88.1%.

[Example 20] to [Example 28]
In these examples, a positive electrode material was synthesized in the same manner as in Example 1 except that the heating temperature in the heating step after separating the lithium composite oxide from the aqueous aluminum solution was changed to the temperature shown in Table 1. Moreover, the result of having measured each characteristic similarly to Example 1 is combined with Table 1, and is shown.

[Example 29]
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 = 35: 20: 105, 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 5.2 m ² / g and an average particle diameter D50 of 10.8 μm.

Lithium hydroxide powder was mixed with the obtained composite hydroxide powder and fired at 500 ° C. for 10 hours in the air atmosphere. The obtained fired product is mixed again, fired at 900 ° C. for 24 hours, and pulverized to obtain a lithium composite having a composition of Li _1.20 Ni _0.175 Co _0.100 Mn _0.525 O _2. An oxide powder was obtained. When the particles of the powder were observed using SEM, they were secondary particles in which many primary particles were aggregated. Moreover, it was 20 ppm when the amount of aluminum contained in the said powder was measured using ICP.

Subsequently, water was added to 2 g of polyaluminum chloride aqueous solution (PAC 250A manufactured by Taki Chemical Co., Ltd.) having an aluminum content of 5.39% by mass to obtain 1000 g, and an aluminum aqueous solution having an aluminum concentration of 108 ppm was prepared. A slurry liquid obtained by adding 200 g of the lithium composite oxide powder to 1000 g of the aluminum aqueous solution 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 stirring and separation operations were performed at room temperature. The pH of the aqueous aluminum solution was 4.4, and the pH of the aqueous aluminum solution after separation was 11.6. The granulate was heated at 120 ° C. for 5 hours and then at 800 ° C. for 5 hours. The obtained granular material was passed through a sieve to obtain a positive electrode material powder. Stirring, separation, and heating were all performed in an air atmosphere. When the powder physical properties were evaluated in the same manner as in Example 1, the average particle diameter D50 of the positive electrode material was 11.2 μm, D10 was 6.2 μm, D90 was 20.2 μm, and the specific surface area was 0.35 m ² / g. The amount of free alkali was 0.40 mol%.

The amount of aluminum contained in the obtained positive electrode material particles was 170 ppm. That is, the amount of aluminum derived from the aqueous aluminum solution, that is, the remaining amount of aluminum (the remaining amount of Al) was 150 ppm.
A cell produced in the same manner as in Example 1 was charged at a current of 170 mA per 1 g of the positive electrode active material at 25 ° C. with an upper limit voltage of 4.6 V, and charged for 3 hours in CCCV mode (constant current of 170 mA. 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 37.5 mA per 1 g of the positive electrode active material. The initial discharge capacity was determined. At this time, the initial discharge capacity was 260 mAh / g.

According to the present invention, a lithium composite oxide 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, and has high discharge capacity, fillability, and volume capacity density is obtained. Provided manufacturing method. Moreover, the positive electrode for lithium ion secondary batteries and a lithium ion secondary battery which have the outstanding battery performance are provided using lithium complex oxide obtained by said manufacturing method.
The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2009-181939 filed on Aug. 4, 2009 are incorporated herein as the disclosure of the specification of the present invention. Is.

Claims (13)

General formula Li _a Ni _b Co _c Mn _{d Me} O ₂ (where M is at least one selected from the group consisting of transition metal elements other than Ni, Co and Mn, aluminum, tin, zinc and alkaline earth metals) 0.95 ≦ a ≦ 1.2, 0 ≦ b ≦ 1, 0 ≦ c ≦ 1, 0 ≦ d ≦ 0.6, 0 ≦ e ≦ 0.2, a + b + c + d + e = 2) A positive electrode for a lithium ion secondary battery, wherein a lithium composite oxide is brought into contact with an aqueous aluminum solution having an aluminum concentration of 10 to 250 ppm, and then the aqueous aluminum solution is separated from the lithium composite oxide to obtain a positive electrode material. Material manufacturing method.   The manufacturing method of Claim 1 which heats the positive electrode material obtained by isolate | separating aluminum aqueous solution from lithium complex oxide at the temperature of 50-1000 degreeC further.   The manufacturing method of Claim 2 whose heating temperature is 60-830 degreeC.   The aqueous aluminum solution is an aqueous solution in which at least one compound selected from the group consisting of aluminum sulfate, aluminate, alum, aluminum oligomer, aluminum hydroxy acid salt and aluminum carboxylate having a carbonyl group is dissolved. The manufacturing method in any one of Claims 1-3.   The manufacturing method according to any one of claims 1 to 4, wherein the aluminum aqueous solution is brought into contact with the lithium composite oxide in a mass ratio of 1 to 20 times.   The manufacturing method in any one of Claims 1-5 whose quantity of aluminum contained in the positive electrode material obtained is 30-800 ppm.   The manufacturing method in any one of Claims 1-6 whose amount of free alkalis contained in the positive electrode material obtained is 0.7 mol% or less.   The lithium composite oxide is 0.97 ≦ a ≦ 1.1, 0.2 ≦ b ≦ 0.9, 0.1 ≦ c ≦ 0.4, 0.1 ≦ d ≦ 0.4, 0 ≦ e ≦. The manufacturing method in any one of Claims 1-7 represented by 0.1.   Lithium composite oxide is 1.08 ≦ a ≦ 1.2, 0.12 ≦ b ≦ 0.25, 0.1 ≦ c ≦ 0.15, 0.45 ≦ d ≦ 0.6, 0 ≦ e ≦ The manufacturing method in any one of Claims 1-7 represented by 0.05.   The positive electrode material obtained by the production method according to claim 1, a conductive agent, a binder and a solvent are mixed, and the resulting slurry is applied to a metal foil, and then 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 10 and storing the laminate in a battery case; and then injecting an electrolytic solution.   A positive electrode for a lithium ion secondary battery, comprising a positive electrode material, a conductive agent, and a binder, wherein the positive electrode material is a positive electrode material obtained by the method according to claim 1.   A lithium ion secondary battery comprising a positive electrode, a negative electrode, and an electrolytic solution, wherein the positive electrode is the positive electrode according to claim 12.