JP2011181193A - Nickel-cobalt composite hydroxide for nonaqueous electrolyte secondary battery positive electrode active material, manufacturing method thereof, and method of manufacturing nonaqueous electrolyte secondary battery positive electrode active material using nickel-cobalt composite hydroxide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a nonaueous electrolyte secondary battery positive electrode active material with the charging density improved to attain further improved high energy density of the battery, and furthermore, to provide a high-density and substantially spherical nickel-cobalt composite hydroxide having a large particle size suitable for use as the nonaqueous electrolyte secondary battery positive electrode active material, and to provide an industrial manufacturing method thereof. <P>SOLUTION: The substantially spherical nickel-cobalt compound hydroxide having an average particle size of 15-50 μm is obtained by the manufacturing method including a reaction process of obtaining nickel-cobalt hydroxide primary reaction particles in a reaction tank, and a growth process of obtaining nickel-cobalt composite hydroxide particles by further reacting the primary reaction particles in a growth tank. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a lithium nickel-cobalt composite oxide suitably used as a positive electrode active material for a non-aqueous electrolyte secondary battery, and in particular, a nickel-cobalt composite used as a precursor of the lithium nickel-cobalt composite oxide. The present invention relates to a hydroxide and a method for producing the same, and a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery using the nickel-cobalt composite hydroxide.

  In recent years, with the advancement of electronic technology, electronic devices are rapidly becoming smaller and lighter. In particular, as portable electronic devices such as mobile phones and notebook PCs have become popular and highly functional, the development of small, lightweight batteries with high energy density has become strong as portable power sources used in these devices. It is desired.

  Non-aqueous electrolyte secondary batteries are already used as power sources for portable electronic devices because they are small and have high energy. In addition to such applications, research and development aimed at using lithium-ion secondary batteries as large-scale power sources such as hybrid vehicles and electric vehicles are being promoted.

Lithium cobalt composite oxide (LiCoO ₂ ), which is relatively easy to synthesize, is used as the positive electrode active material of the lithium ion secondary battery that is a non-aqueous electrolyte secondary battery. Is a rare and expensive cobalt compound, which increases the cost of the positive electrode active material. Lowering the cost of the positive electrode active material and realizing the manufacture of cheaper non-aqueous electrolyte secondary batteries can be achieved by reducing the cost of portable electronic devices that are currently popular and non-aqueous electrolyte secondary batteries for future large-scale power supplies Therefore, it can be said that it has significant industrial significance.

Other positive electrode materials applicable as a positive electrode active material for non-aqueous electrolyte secondary batteries include lithium manganese composite oxide (LiMn ₂ O ₄ ) using manganese, which is cheaper than cobalt, and lithium nickel composite oxide using nickel. Product (LiNiO ₂ ).

  Lithium-manganese composite oxides are inexpensive materials and have excellent thermal stability, especially safety in terms of ignition. Since it is only about half of the complex oxide, it has a drawback that it is difficult to meet the demand for higher capacity of non-aqueous electrolyte secondary batteries that are increasing year by year. Moreover, at 45 degreeC or more, it has the fault that self-discharge is intense and a charge / discharge lifetime also falls.

  On the other hand, the lithium-nickel composite oxide has an advantage that it has a higher capacity than the current mainstream lithium-cobalt composite oxide, and the nickel as a raw material is cheaper and more stable than cobalt. Therefore, it is expected as a next-generation positive electrode material, and research and development of lithium-nickel composite oxides are being continued actively.

However, the lithium nickel composite oxide does not replace nickel with other elements, and when a non-aqueous electrolyte secondary battery is manufactured using a lithium nickel composite oxide that is purely composed of nickel as a positive electrode active material, There exists a problem that cycling characteristics are inferior compared with lithium cobalt complex oxide. Lithium-nickel composite oxide changes its crystal structure from hexagonal to monoclinic and then again hexagonal as lithium is desorbed. This is thought to be due to the gradual loss of sites where lithium can be inserted and removed during repeated discharge reactions.

  As a method for solving this, it has been proposed to replace a part of nickel with cobalt (for example, Patent Documents 1 to 3). Substitution with cobalt suppresses the phase transition of the crystal structure that accompanies the elimination of lithium, and as the amount of cobalt substitution increases, the crystal phase becomes more stable and the cycle characteristics are improved.

  Thus, since the addition of cobalt has the purpose of stabilizing the crystal phase by substituting nickel in the crystal structure, cobalt and nickel must be uniformly mixed at the atomic level. A method using a hydroxide prepared by coprecipitation of a nickel source and a cobalt source is effective as a raw material of the positive electrode active material for realizing this. For example, in Patent Document 4, by controlling the particle shape, particle diameter, specific surface area, tap density, pore volume, pore occupancy of nickel cobalt coprecipitated hydroxide, cycle deterioration is prevented, It has been reported that a battery having good charge / discharge characteristics can be obtained, and in fact, certain characteristics can be obtained by such a method.

  However, in recent years, the performance required of batteries has been increasing as the added value of portable devices increases, and batteries with higher energy density are required by packing as much positive electrode active material as possible in a limited volume. It has come to be.

  Increasing the particle size of the positive electrode active material is one effective method for increasing the packing density when molded as a battery electrode. Although it is easy to increase the packing density when the particles (primary particles) can be enlarged by synthesizing at a high firing temperature, such as lithium cobalt composite oxide, the firing temperature of lithium nickel composite oxide is high. Since it is as low as 850 degrees C or less, a primary particle cannot be enlarged and it is hard to raise a packing density.

  Therefore, the packing density is maintained by using an active material in which a large number of fine primary particles gather to form substantially spherical secondary particles (for example, Patent Document 5). On the other hand, the powder characteristics of the lithium nickel composite oxide are largely influenced by the powder characteristics of the nickel compound used as a raw material. Therefore, controlling the powder characteristics of the raw material nickel compound is important for improving the packing density of the lithium nickel composite oxide.

  However, in the conventional methods of synthesizing hydroxide by coprecipitation of the nickel source and the cobalt source used for the purpose of improving the cycle characteristics, the average particle size should be increased to 15 μm or more. However, it was difficult to realize further high filling properties.

JP-A-63-114063 JP 63-2111565 A Japanese Patent Laid-Open No. 8-213015 JP-A-9-270258 JP 2000-30893 A

The present invention has been made paying attention to such problems, and can produce a positive electrode active material for a non-aqueous electrolyte secondary battery that can improve the packing density and further increase the energy density of the battery. It is intended to provide a method. Further, the nickel-cobalt composite hydroxide having a large particle size, a high density and a substantially spherical shape suitable as a precursor of the non-aqueous electrolyte secondary battery positive electrode active material, and its industrial production without sacrificing mass productivity It is intended to provide a method.

  In order to achieve the above object, the present inventor has conducted extensive research on nickel-cobalt composite hydroxide used as a precursor of a non-aqueous electrolyte secondary battery positive electrode active material. Are separated into a reaction step of obtaining nickel-cobalt hydroxide primary reaction particles and a growth step of growing the primary reaction particles to obtain nickel-cobalt composite hydroxide particles, and a reaction step and a growth step. It was found that by controlling the crystallization conditions in the above specific range, a nickel-cobalt composite hydroxide having a large particle size, a high density and a substantially spherical shape can be obtained industrially efficiently.

  Further, when the obtained nickel-cobalt composite hydroxide particles were used as raw materials, it was found that a positive active material for a non-aqueous electrolyte secondary battery that can be expected to have a high packing density and a very high capacity as a battery was obtained. Completed the invention.

That is, the non-aqueous electrolyte secondary battery cathode active material for the nickel of the invention - method for manufacturing cobalt composite hydroxide is represented by the general _{formula: Ni 1-x-y Co} x M y (OH) 2 (0.05 ≦ x ≦ 0.95, 0 ≦ y ≦ 0.15, x + y ≦ 0.95, M is one or more selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Nb, Mo, and W A mixed aqueous solution containing a nickel salt and a cobalt salt, an aqueous solution containing an ammonium ion supplier, and a caustic aqueous solution in a reaction vessel. A reaction step of supplying and reacting to obtain primary reaction particles of nickel-cobalt hydroxide; an aqueous solution containing the primary reaction particles in the growth tank; and the mixed aqueous solution, an aqueous solution containing an ammonium ion supplier, and a caustic alkali Water soluble And a growth step for obtaining nickel-cobalt composite hydroxide particles, and the reaction step and the growth step are controlled so as to satisfy the following conditions (A) and (B): And
(A) The pH of the reaction step is maintained in the range of 11.0 to 13.0, the pH of the growth step is in the range of 10.5 to 12.5, and the pH of the growth step is controlled below the reaction step.
(B) The temperature of the reaction step is 20 to 70 ° C., the temperature of the growth step is 30 to 70 ° C., and the ammonium ion concentration in the reaction step and the growth step is kept in the range of 5 to 20 g / L. Control the temperature and ammonium ion concentration more than the reaction step.
In the reaction step and the growth step, the mixed aqueous solution and the aqueous solution containing the ammonium ion supplier are quantitatively continuously supplied, and the pH and ammonium ion concentration are maintained by adjusting the addition amount of the caustic aqueous solution. It is preferable to continuously supply the nickel-cobalt hydroxide primary reaction particles to the growth tank of the growth step by overflowing the reaction vessel in the reaction step.

  Moreover, it is preferable to coat the surfaces of the nickel-cobalt composite hydroxide particles obtained in the growth step with M hydroxide.

Furthermore, the nickel salt and cobalt salt are preferably at least one of sulfate, nitrate, or chloride, and the ammonium ion supplier is preferably at least one of aqueous ammonia, ammonium sulfate, or ammonium chloride. .
Non-aqueous electrolyte secondary battery cathode active material for the nickel of the present invention - cobalt composite hydroxide, there is obtained by the above production method, the general _{formula: Ni 1-x-y Co} x M y (OH) ₂ (0.05 ≦ x ≦ 0.95, 0 ≦ y ≦ 0.15, x + y ≦ 0.95, M is Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Nb, Mo, W And one or more elements selected from the group consisting of: substantially spherical and having an average particle size of 15 to 50 μm.

  The present invention also provides a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the nickel-cobalt composite hydroxide for a non-aqueous electrolyte secondary battery and a lithium compound are mixed and fired. The lithium compound is preferably mixed in a ratio of 0.95 to 1.15 with respect to a metal element other than lithium in the nickel-cobalt composite hydroxide.

Furthermore, in the method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, the positive electrode active material for the obtained non-aqueous electrolyte secondary battery has a general formula: Li _t Ni _1-xy Co _x M _y O ₂ (0. 95 ≦ t ≦ 1.15, 0.05 ≦ x ≦ 0.95, 0 ≦ y ≦ 0.15, x + y ≦ 0.95, M is Mg, Al, Ca, Ti, V, Cr, Mn, Zr Lithium nickel having a spherical shape and an average particle diameter of 15 to 50 μm, comprising a hexagonal lithium-containing composite oxide having a layered structure represented by Nb, Mo, or W) It is preferable to consist of cobalt complex oxide.

  According to the present invention, the nickel-cobalt composite hydroxide for the positive electrode active material of the non-aqueous electrolyte secondary battery having a large particle size, high density, and substantially spherical shape is used, the packing density is high, and the battery is further increased in energy density. Thus, a positive electrode active material for a non-aqueous electrolyte secondary battery capable of achieving the above can be obtained. Moreover, the manufacturing method does not sacrifice mass productivity and has an extremely high industrial value.

2 is a scanning electron micrograph of a nickel-cobalt composite hydroxide for a non-aqueous electrolyte secondary battery positive electrode active material obtained in Example 1. FIG. 2 is a scanning electron micrograph of a nickel-cobalt composite hydroxide for a non-aqueous electrolyte secondary battery positive electrode active material obtained in Example 2. FIG.

[Nickel-cobalt composite hydroxide for positive electrode active material of non-aqueous electrolyte secondary battery]
The nickel-cobalt composite hydroxide for the non-aqueous electrolyte secondary battery positive electrode active material of the present invention (hereinafter sometimes simply referred to as nickel-cobalt composite hydroxide) is the above-mentioned nickel-cobalt composite hydroxide. be those obtained by the manufacturing method, the general _{formula: Ni 1-x-y Co} x M y (OH) 2 (0.05 ≦ x ≦ 0.95,0 ≦ y ≦ 0.15, x + y ≦ 0 .95, M is one or more elements selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Nb, Mo, and W) and is substantially spherical and has an average particle diameter of 15 to 50 μm. It is characterized by being.

  In the above general formula, x indicating the ratio of nickel and cobalt is 0.05 to 0.95, preferably 0.1 to 0.9, and more preferably 0.1 to 0.3. That is, when x exceeds 0.95, the raw material cost increases because the ratio of Co is large. On the other hand, when x is less than 0.05, the thermal stability and charge / discharge cycle characteristics of the positive electrode active material using the nickel-cobalt composite hydroxide of the present invention deteriorate.

  The nickel-cobalt composite hydroxide is selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Nb, Mo, and W in order to further improve the thermal stability and output characteristics. M which is an additional element of seeds or more can be added as 0.15 or less as y in the above general formula. When y exceeds 0.15, the amount of the M element substituted for nickel becomes excessive, and the battery capacity of the obtained positive electrode active material decreases.

The nickel-cobalt composite hydroxide of the present invention is substantially spherical and has an average particle size of 15-5.
0 μm. Since the nickel-cobalt composite hydroxide is maintained up to the positive electrode active material of the non-aqueous electrolyte secondary battery, the nickel-cobalt composite hydroxide of the present invention is formed by making it approximately spherical and having an average particle size of 15 to 50 μm. The packing density of the positive electrode active material of the nonaqueous electrolyte secondary battery obtained by using can be increased. Here, the term “substantially spherical” includes a true spherical shape having a fine unevenness on the surface, and an elliptical rotating body shape. However, in order to achieve a high packing density, it is preferable to approximate the spherical shape as much as possible.

[Method for producing nickel-cobalt composite hydroxide for positive electrode active material of non-aqueous electrolyte secondary battery]
The method for producing a nickel-cobalt composite hydroxide of the present invention is a method for producing a nickel-cobalt composite hydroxide represented by the above general formula, wherein a mixed aqueous solution containing a nickel salt and a cobalt salt, and an ammonium ion supply An aqueous solution containing a body and a caustic aqueous solution are supplied to the reaction vessel and reacted to obtain a nickel-cobalt hydroxide primary reaction particle, an aqueous solution containing the primary reaction particle in the growth vessel, and A growth step of obtaining nickel-cobalt composite hydroxide particles by supplying and reacting a mixed aqueous solution, an aqueous solution containing an ammonium ion supplier, and a caustic aqueous solution, and the reaction step and the growth step are performed under the following conditions: Control is performed so as to satisfy (A) and (B).
(A) The pH of the reaction step is maintained in the range of 11.0 to 13.0, the pH of the growth step is in the range of 10.5 to 12.5, and the pH of the growth step is controlled below the reaction step.
(B) The temperature of the reaction step is 20 to 70 ° C., the temperature of the growth step is 30 to 70 ° C., and the ammonium ion concentration in the reaction step and the growth step is kept in the range of 5 to 20 g / L. Control the temperature and ammonium ion concentration more than the reaction step.

  Here, separating the process of producing the nickel-cobalt composite hydroxide into a reaction process and a growth process, and controlling the crystallization conditions of the reaction process and the growth process within a specific range are particles having an average particle diameter of 15 μm or more. It has an important significance for constantly obtaining.

  In order to obtain large particles, the crystallization conditions in the reaction system are set so that new nucleation is unlikely to occur, the number of particles staying in the system is reduced, and the amount of monomer per consumed particle is increased. There is a need. As a method therefor, it is conceivable to reduce the supply rates of the nickel source and the cobalt source, but a decrease in the supply rate is unfavorable industrially because it causes a deterioration in productivity. As a method not sacrificing productivity, it is conceivable to increase the solubility of nickel and cobalt, and specifically, means such as a decrease in pH, an increase in ammonium ion concentration, and an increase in temperature are conceivable.

  In general, when an overflow tank is used, the generated particles are continuously discharged out of the system, so that the number of particles in the system can be made constant by suppressing nucleation in the reaction system. . However, when the number of particles in the system is below a certain value, the monomer consumption due to particle growth becomes too small relative to the monomer supply, and most of the monomer supplied is consumed for nucleation. As a result, a nuclear abnormality called a Cycling phenomenon occurs, the particle size of the particles in the tank almost grows, and particles with a large particle size cannot be obtained.

  The present inventor separated the process of producing a nickel-cobalt composite hydroxide into a reaction process and a growth process, so that nickel and cobalt in the reaction process, which is a particle generation stage, and in the growth process, which is a grain growth stage, can be obtained. It has been found that particles having a large particle size can be obtained with high productivity by individually controlling the solubility and growing the particles produced in the reaction step under conditions that suppress nucleation in the growth step.

That is, in the above production method, the reaction step and the growth step are separated, the reaction step has a pH of 11.0 to 13.0, preferably 11.5 to 12.5, and the growth step has a pH of 10.5. It is necessary to control the pH of the growth step to be equal to or lower than that of the reaction step while maintaining it at ˜12.5, preferably 10.5 to 11.5.

  When the pH of the reaction step is less than 11, the number of particles in the reaction step becomes too small, and the above-described abnormal nucleus occurs. When the pH of the reaction process exceeds 12, many nuclei are constantly generated and the number of particles in the system increases, so that the particle size does not grow greatly.

  On the other hand, when the pH of the growth step is less than 10.5, the nickel-cobalt hydroxide particles are easily gelled, and the cleaning properties for removing halogen, sulfuric acid traces and the like are deteriorated. When the pH of the growth process exceeds 12.5, new nucleation becomes remarkable in the growth process, so that the particles do not grow greatly.

  Furthermore, by controlling the pH of the growth step below the reaction step, the nickel solubility in the growth step can be made higher than in the reaction step, and the generation of fine particles in the growth tank can be suppressed.

  In addition, controlling the temperature and ammonium ion concentration in each of the above steps is also important in controlling the solubility of nickel and cobalt. That is, the temperature of the reaction step is 20 to 70 ° C., the temperature of the growth step is 30 to 70 ° C., and the ammonium ion concentration in the reaction step and the growth step is maintained in the range of 5 to 20 g / L. It is necessary to control the ammonium ion concentration more than the reaction step.

  The temperature of the reaction step is 20 to 70 ° C, preferably 40 to 70 ° C. When the temperature is less than 20 ° C., fine particles are likely to be generated because the solubility of nickel is low. In addition, it is necessary to introduce a chiller or the like in order to eliminate the influence of seasonal fluctuations, which increases the equipment cost. When the temperature exceeds 70 ° C., the volatilization of ammonia becomes intense and it becomes difficult to control the ammonium ion concentration in the system.

Further, the ammonium ion concentration in the reaction step is 5 to 20 g / L, preferably 10 to 15 g / L. When the ammonium ion concentration is less than 5 g / L, since the solubility of nickel is low, fine particles are easily generated, and the particle size becomes small. In addition, when the particles grow, the monomer is not supplied to the inside of the particles and a precipitation reaction occurs on the surface of the particles, so that only low-density hydroxide particles can be obtained. Thus, the energy density per volume decreases. If the ammonium ion concentration exceeds 20 g / L, the concentration of nickel remaining in the liquid increases, leading to an increase in cost due to compositional deviation and increased nickel loss.
On the other hand, the temperature of the growth step is 30 to 70 ° C, preferably 50 to 70 ° C. When the temperature is less than 30 ° C., the nickel solubility in the reaction solution becomes too low, and new nucleation becomes remarkable, so that the particles do not grow greatly. When the temperature exceeds 70 ° C., the volatilization of ammonia becomes intense as in the reaction step, and it becomes difficult to control the ammonium ion concentration.

  Further, the ammonium ion concentration in the growth step is maintained at 5 to 20 g / L, preferably 10 to 15 g / L. When the ammonium ion concentration is less than 5 g / L, since the solubility of nickel is low, fine particles are likely to be generated, and the particle size cannot be increased. When the ammonium ion concentration exceeds 20 g / L, the concentration of nickel remaining in the liquid increases, resulting in an increase in compositional deviation and nickel loss, resulting in an increase in cost.

  Furthermore, by controlling the temperature and ammonium ion concentration in the growth step to be higher than that in the reaction step, nickel solubility in the growth step can be made higher than that in the reaction step, and generation of fine particles in the growth step can be suppressed.

  In the reaction step and the growth step, the mixed aqueous solution and the aqueous solution containing the ammonium ion supplier are quantitatively continuously supplied, and the caustic aqueous solution is supplied by adjusting the addition amount. It is preferable to suppress fluctuations while maintaining the ion concentration at a predetermined value. By suppressing the fluctuation, particle generation and particle growth in the reaction step and the growth step can be accurately controlled to the above state. In addition, since the pH and ammonium ion concentration in each step must be controlled to relative numerical values in both steps, since the relative control is facilitated by suppressing the fluctuation, continuous supply is performed. It is preferable to do.

  In the production method of the present invention, the nickel-cobalt hydroxide primary reaction particles obtained in the reaction step (hereinafter sometimes simply referred to as primary reaction particles) are supplied to the growth step and grown. Is a feature of the present invention, and may be grown by switching from the reaction process to the growth process conditions in a single tank, and growing in a batch-type batch method using separate batch tanks in the reaction process and the growth process. You may let them.

However, in the reaction process, the primary reaction particles are continuously supplied from the reaction process to the growth process using the overflow tank in both the above processes and the composite hydroxide particles obtained from the growth process are continuously discharged. The number of particles newly generated in the system and the number of particles supplied from the reaction step can be continuously discharged in the growth step to maintain the number of particles in the system. That is, it is possible to increase the amount of monomer per particle consumed by controlling the number of particles staying in the system in each step to be constant in a small state. Therefore, it is preferable to continuously supply the primary reaction particles to the growth tank in the growth step by overflowing the reaction vessel in the reaction step. Moreover, since the continuous method by overflow has good productivity, it is advantageous in terms of cost. In addition, for example, the continuous method and the batch method may be combined such that the reaction step is a continuous method by overflow and the growth step is a batch method.
Hereinafter, the production method of the present invention will be described in detail.

  In the manufacturing method, the mixed aqueous solution containing nickel salt and cobalt salt is a supply source of nickel and cobalt. Moreover, the aqueous solution containing an ammonium ion supplier plays the role which controls the particle size and shape of the nickel-cobalt hydroxide particle to produce | generate as a complex formation agent. Moreover, since ammonium ions are not taken into the produced nickel-cobalt hydroxide particles, they are a preferable complexing agent for obtaining nickel-cobalt composite hydroxide particles free from impurities. Further, the caustic aqueous solution is a pH adjuster for the neutralization reaction.

  The concentration of nickel and cobalt in the mixed aqueous solution is not particularly limited, but is preferably 0.5 to 2.2 mol / L. If it is less than 0.5 mol / l, the amount of liquid in each step increases so that productivity is lowered, which is not preferable. If it exceeds 2.2 mol / l, the nickel salt or cobalt salt may be recrystallized in the mixed aqueous solution and the pipes and the like may be clogged when the temperature drops.

  On the other hand, the supply amount of nickel and cobalt to the reaction vessel and the growth vessel is not particularly limited, but the total amount of nickel and cobalt is 0.0005 to 0.01 mol with respect to the liquid amount in the two vessels. / L · min is preferable. If it is less than 0.0005 mol / l · min, productivity is lowered, which is not preferable. If it exceeds 0.015 mol / l · min, nucleation is likely to occur in each step, and the fine particles mixed in the resulting hydroxide may increase. The supply amount of nickel and cobalt is preferably continuously supplied in order to stabilize the generation and growth of particles.

The nickel salt and cobalt salt are preferably at least one of sulfates, nitrates or chlorides, more preferably sulfates free from contamination by halogen. For example, manganese sulfate and nickel sulfate are preferably used. Also, when preparing the mixed aqueous solution, the nickel salt and cobalt salt should match the atomic ratio of nickel and cobalt in the target composite hydroxide in the atomic ratio of metal ions present in the mixed aqueous solution. Adjusted to

  The aqueous solution containing the ammonium ion supplier is not particularly limited, but aqueous ammonia, ammonium sulfate or ammonium chloride is preferable, and aqueous ammonia or ammonium sulfate free from halogen contamination is more preferable. The concentration of the ammonium ion supplier is not particularly limited, and may be adjusted within a range in which the ammonium ion concentration in each step can be maintained.

  The aqueous caustic solution is not particularly limited, and an aqueous alkali metal hydroxide solution such as sodium hydroxide or potassium hydroxide can be used. In the case of an alkali metal hydroxide, it is preferable to add it as an aqueous solution to the reaction system in each step because of easy control of the pH value in each step.

  In the nickel-cobalt composite hydroxide of the present invention, one or more elements selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Nb, Mo, and W are added as the additional element M. can do. M element can be added to the mixed aqueous solution as a compound of M element. The M element compound is not particularly limited. For example, magnesium sulfate, calcium nitrate, barium nitrate, strontium nitrate, titanium sulfate, ammonium peroxotitanate, potassium titanium oxalate, vanadium sulfate, ammonium vanadate, Chromium sulfate, potassium chromate, zirconium sulfate, zirconium nitrate, niobium oxalate, ammonium molybdate, sodium tungstate, ammonium tungstate, and the like can be used.

  When the M element compound is added to the mixed aqueous solution, the concentration and supply amount of the mixed aqueous solution are maintained under the above conditions. The amount of M element added is adjusted so that the atomic ratio of metal ions in the mixed aqueous solution matches the atomic ratio of metals in the target composite hydroxide.

  On the other hand, it is not always necessary to add M element to the mixed aqueous solution and coprecipitate with nickel-cobalt composite hydroxide particles. For example, nickel and cobalt are coprecipitated to obtain nickel-cobalt composite hydroxide particles. Then, a compound such as a hydroxide of M element or an oxide may be deposited on the surface of the nickel-cobalt composite hydroxide particles by a wet neutralization method. Furthermore, when adding several types of M element, you may obtain the target nickel- cobalt composite hydroxide by combining the said addition method.

  The reaction vessel and the growth vessel used in the above production method are not particularly limited, but it is preferable to use a vessel equipped with a stirrer, an overflow port, and temperature control means.

  By the above production method, a large-diameter, high-density, substantially spherical nickel-cobalt composite water having a composition suitable as a precursor for a positive electrode active material for a non-aqueous electrolyte secondary battery, free from complexation agents and halogens. An oxide can be obtained.

[Method for producing positive electrode active material of non-aqueous electrolyte secondary battery]
The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention is characterized in that the nickel-cobalt composite hydroxide and a lithium compound are mixed and fired.

The nickel-cobalt composite hydroxide may be mixed with a lithium compound in the state of hydroxide, but the composite hydroxide is oxidized and roasted in a non-reducing atmosphere to form a nickel-cobalt composite oxide. After conversion, it may be mixed with a lithium compound. The conditions for the oxidative roasting are not particularly limited, and may be those normally used. For example, oxidation roasting may be performed so that the shape of the composite hydroxide particles is maintained in the range of 600 to 900 ° C. in an air atmosphere. Moreover, the apparatus used may also be a normally used apparatus, and an electric furnace, kiln, tubular furnace, pusher furnace, etc. are used.

  The mixing is preferably performed at a ratio of 0.95 to 1.15 with respect to the metal compound other than lithium in the lithium compound and the nickel-cobalt composite hydroxide.

  The lithium compound is not particularly limited, and at least one selected from the group consisting of lithium hydroxide, oxyhydroxide, oxide, carbonate, nitrate and halide is used. More preferred are lithium hydroxides, oxyhydroxides, oxides and carbonates free from contamination by impurities such as halogens.

  As a mixing method, a commonly used method may be used, and a method of mixing nickel-cobalt composite hydroxide or composite oxide and a lithium compound with various powder mixers in a solid state is used. Any method may be used, but it may be mixed sufficiently using a shaker or the like so that the composite hydroxide particles or composite oxide particles are not destroyed.

  By firing the mixture, a non-aqueous electrolyte secondary battery positive electrode active material is obtained. Firing is performed under conditions that are normally used. For example, as an atmosphere during firing, in order to sufficiently supply oxygen, the oxygen concentration is preferably 60% by volume or more, and oxygen is nitrogen or an inert gas. It is preferable to mix. If it is less than 60% by volume, the partial pressure of oxygen is insufficient, resulting in a state of insufficient oxygen as described above, and the formation of the lithium nickel composite oxide may be insufficient.

  Moreover, as a calcination temperature, it is preferable to set it as the range of 650-800 degreeC. If it is less than 650 degreeC, the crystal growth of the lithium nickel complex oxide obtained may not be enough, and may have a bad influence on battery performance. Further, when the temperature exceeds 800 ° C., the resulting lithium nickel composite oxide starts to decompose, and during the battery reaction when used as the positive electrode active material, crystals that prevent the movement of lithium ions begin to be mixed, resulting in a decrease in battery performance. You may be invited.

  As the furnace used for firing, various furnaces whose atmosphere can be controlled can be used, but it is preferable to use an electric furnace which does not generate exhaust gas. In industrial production, in particular, a pusher furnace or a roller hearth furnace. It is preferable to use a furnace that can be continuously fired.

By the manufacturing method of the nonaqueous electrolyte secondary battery positive electrode active material, the general _{formula: Li t Ni 1-x-} y Co x M y O 2 (0.95 ≦ t ≦ 1.15,0.05 ≦ x ≦ 0 .95, 0 ≦ y ≦ 0.15, x + y ≦ 0.95, M is one or more elements selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Nb, Mo, and W Non-aqueous electrolyte secondary battery positive electrode active material composed of a lithium nickel-cobalt composite oxide having a spherical shape and an average particle diameter of 15 to 50 μm. Is obtained. The obtained non-aqueous electrolyte secondary battery positive electrode active material has a high packing density and can further increase the energy density of the battery, and is suitable for a non-aqueous electrolyte secondary battery.

  The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited to these examples. In addition, the evaluation method of the nickel-cobalt hydroxide used by the Example and the comparative example is as follows.

Analysis of metal components: ICP emission analysis was performed.
Analysis of ammonium ion concentration: Measured by distillation method according to JIS standard.
Measurement of average particle diameter: Measurement was performed using a laser diffraction particle size distribution meter (manufactured by Nikkiso Co., Ltd., Microtrac HRA).
Observation of form: The shape and appearance were observed using a scanning electron microscope (JSM-6360LA, manufactured by JEOL Ltd.).

(Example 1)
Pure water so that nickel sulfate hexahydrate (industrial) and cobalt sulfate heptahydrate (industrial) have a molar ratio of nickel: cobalt of 84:16 and nickel and cobalt combined to 2 mol / l. A mixed aqueous solution was prepared by dissolving in the solution.

[Reaction process]
Pure water was put to the upper limit in an overflow reaction tank having a capacity of 34 l to the overflow port, and the inside of the tank was heated to 50 ° C. by a water bath. While stirring the reaction vessel, the mixed aqueous solution, 25 mass% aqueous ammonia (industrial), and 25 mass% aqueous sodium hydroxide (industrial) were continuously fed into the reaction vessel. Here, the supply flow rates were 60 ml / min of mixed aqueous solution (0.00352 mol / l · min) and 4.8 ml / min of aqueous ammonia. The pH of the slurry in the tank was adjusted to 12.2 by adjusting the flow rate of the aqueous sodium hydroxide solution using a pH controller installed in the reaction tank. During the reaction, nitrogen was introduced into the reaction vessel at a rate of 3.5 l / min, and the inside of the vessel was maintained in an inert atmosphere.

  After operating for 32 hours in this state, it was confirmed that the pH in the tank was stable at 12.2, the temperature was 50 ° C., and the ammonium ion concentration was 10 g / l. Then, the reactor was kept in the reaction tank from 32 hours to 60 hours later. The above aqueous solutions were supplied. The nickel-cobalt hydroxide primary reaction particles recovered from the slurry were substantially spherical, and the average particle size was 13.5 μm.

[Growth process]
Pure water was added to the upper limit of the growth tank which is the same overflow tank as in the reaction step, and nickel-cobalt hydroxide primary reaction particle slurry overflowed from the reaction tank was introduced into the growth tank. While stirring the inside of the growth tank heated to 60 ° C. with a water bath, the above mixed aqueous solution, ammonia water, and sodium hydroxide aqueous solution were continuously supplied into the growth tank.

  Here, the supply amount was 30 ml / min (0.00176 mol / l · min) of the mixed aqueous solution and 2.4 ml / min of aqueous ammonia. The pH of the slurry in the tank was adjusted to 11.8 by adjusting the flow rate of the aqueous sodium hydroxide solution using a pH controller installed in the reaction tank. During the reaction, nitrogen was introduced into the growth tank at 3.5 l / min, and the inside of the tank was maintained in an inert atmosphere. After operating for 32 hours in this state, it was confirmed that the pH in the tank was stable at 11.8, the temperature was 60 ° C., and the ammonium ion concentration was 10 g / l, and the reaction time in the reaction tank was 32 hours to 60 hours later. The nickel-cobalt composite hydroxide particles discharged from the growth tank were recovered as a slurry. The recovered slurry was subjected to solid-liquid separation and dried to obtain a nickel-cobalt composite hydroxide.

  When the obtained nickel-cobalt composite hydroxide was observed with a scanning electron microscope (hereinafter sometimes referred to as SEM), it was substantially spherical and the average particle size was 30.1 μm. The SEM image of the obtained nickel-cobalt composite hydroxide is shown in FIG.

(Example 2)
In the same manner as in Example 1, nickel-cobalt hydroxide primary reaction particles obtained in an overflow type reaction vessel were recovered and subjected to solid-liquid separation. 3 kg of the nickel-cobalt hydroxide primary reaction particles in a dry weight are put into a 50-liter baffled SUS growth tank (batch type), 5.7 l of pure water is added, and the inside of the tank is water bathed. To 60 ° C. After flowing nitrogen gas in the tank at a flow rate of 10 L / min for 30 minutes to make a nitrogen atmosphere, 25 mass% ammonia water (Wako Pure Chemicals first grade reagent) and 64 mass% sulfuric acid (Wako Pure Chemicals first grade reagent) are added. Then, the ammonium ion concentration was adjusted to 15 g / l, and the pH was adjusted to 11.3.

  Next, with stirring in the tank, a 0.95 mol / l mixed aqueous solution (the mixed aqueous solution of Example 1 was diluted with pure water), the aqueous ammonia, a 5% by mass sodium hydroxide aqueous solution (the above 25% by mass hydroxide). A sodium aqueous solution was diluted with pure water) was continuously fed into the reaction vessel. Here, the supply flow rate was 70 ml / min (0.00111 mol / l · min) of the mixed aqueous solution and 10.3 ml / min of aqueous ammonia. The pH of the slurry in the tank was adjusted to 11.3 by adjusting the flow rate of the 5 mass% sodium hydroxide aqueous solution using a pH controller installed in the reaction tank.

  While maintaining the pH and ammonium ion concentration at the above values, 16.8 l of the mixed aqueous solution was supplied, and then the stirring was stopped to settle the particles, and 35 l of the supernatant in the reaction vessel was discharged. After discharging, stirring was resumed, and further 16.8 l of the mixed aqueous solution was added while keeping the pH and ammonium ion concentration constant. After completion of the addition, it was separated into solid and liquid and dried to obtain a nickel-cobalt composite hydroxide.

  The obtained nickel-cobalt composite hydroxide was substantially spherical, and the average particle size was 21.5 μm. The SEM image of the obtained nickel-cobalt composite hydroxide is shown in FIG.

(Comparative Example 1)
A nickel-cobalt composite hydroxide was obtained in the same manner as in Example 1 except that the pH in the growth tank was 12.0, the temperature was 50 ° C., and the ammonium ion concentration was 5 g / l. The obtained nickel-cobalt composite hydroxide was substantially spherical, but the average particle size was 14.3 μm, and it grew almost as compared with the nickel-cobalt hydroxide primary reaction particles obtained in the reaction vessel. I did not.

(Comparative Example 2)
A nickel-cobalt composite hydroxide was obtained in the same manner as in Example 1 except that the pH in the growth tank was 9.5. The solution in the growth tank was gelled and solid-liquid separation was difficult. Further, the obtained nickel-cobalt composite hydroxide had an indefinite particle shape, and particles suitable as a raw material for a non-aqueous electrolyte secondary battery positive electrode active material could not be obtained.

Claims (10)

General _{formula: Ni 1-x-y Co} x M y (OH) 2 (0.05 ≦ x ≦ 0.95,0 ≦ y ≦ 0.15, x + y ≦ 0.95, M is, Mg, Al, Ca 1 or more elements selected from Ti, V, Cr, Mn, Zr, Nb, Mo, and W), which are nickel-cobalt composite hydroxides, A mixed aqueous solution containing, an aqueous solution containing an ammonium ion supplier, and a caustic aqueous solution are supplied to the reaction vessel and reacted to obtain primary reaction particles of nickel-cobalt hydroxide, the primary reaction in the growth vessel Including a growth step of obtaining nickel-cobalt composite hydroxide particles by supplying the aqueous solution containing particles to the mixed aqueous solution, an aqueous solution containing an ammonium ion supplier, and reacting with an aqueous caustic solution. Reaction step and the growth step the following conditions (A) and a non-aqueous electrolyte secondary battery cathode active material for nickel and controls to meet the (B) - method for producing cobalt composite hydroxide.
(A) The pH of the reaction step is maintained in the range of 11.0 to 13.0, the pH of the growth step is in the range of 10.5 to 12.5, and the pH of the growth step is controlled below the reaction step.
(B) The temperature of the reaction step is 20 to 70 ° C., the temperature of the growth step is 30 to 70 ° C., and the ammonium ion concentration in the reaction step and the growth step is kept in the range of 5 to 20 g / L. Control the temperature and ammonium ion concentration more than the reaction step. In the reaction step and the growth step, the mixed aqueous solution and the aqueous solution containing the ammonium ion supplier are quantitatively continuously supplied, and the addition amount of the caustic aqueous solution is adjusted to maintain the pH and ammonium ion concentration. 2. The method for producing a nickel-cobalt composite hydroxide for a positive electrode active material of a non-aqueous electrolyte secondary battery according to claim 1. The non-aqueous system according to claim 1 or 2, wherein the primary reaction particles of the nickel-cobalt hydroxide are continuously supplied to the growth tank of the growth step by overflowing the reaction vessel in the reaction step. The manufacturing method of the nickel-cobalt composite hydroxide for electrolyte secondary battery positive electrode active materials. 4. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the surface of the nickel-cobalt composite hydroxide particles obtained in the growth step is coated with M hydroxide. For producing a nickel-cobalt composite hydroxide for use. The nickel-cobalt for a positive electrode active material of a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the nickel salt and cobalt salt are at least one of sulfate, nitrate or chloride. A method for producing composite hydroxide particles. The nickel-cobalt composite water for a non-aqueous electrolyte secondary battery positive electrode active material according to any one of claims 1 to 5, wherein the ammonium ion supplier is at least one of ammonia, ammonium sulfate, and ammonium chloride. Production method of oxide. Be one obtained by the production method according to any of claims 1 to 6, the general _{formula: Ni 1-x-y Co} x M y (OH) 2 (0.05 ≦ x ≦ 0.95, 0 ≦ y ≦ 0.15, x + y ≦ 0.95, M is one or more elements selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Nb, Mo, and W) A nickel-cobalt composite hydroxide for a positive electrode active material for a non-aqueous electrolyte secondary battery, characterized in that it is substantially spherical and has an average particle size of 15 to 50 μm. A nickel-cobalt composite hydroxide for a non-aqueous electrolyte secondary battery according to claim 7 and a lithium compound are mixed and fired, and a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery. The non-aqueous electrolyte secondary according to claim 8, wherein the lithium compound is mixed in a ratio of 0.95 to 1.15 with respect to a metal element other than lithium in the nickel-cobalt composite hydroxide. Manufacturing method of battery positive electrode active material. Non-aqueous electrolyte secondary battery positive electrode active material obtained has the general _{formula: Li t Ni 1-x-} y Co x M y O 2 (0.95 ≦ t ≦ 1.15,0.05 ≦ x ≦ 0.95 0 ≦ y ≦ 0.15, x + y ≦ 0.95, M is one or more elements selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Nb, Mo, and W) 10. The lithium nickel-cobalt composite oxide, which is composed of a hexagonal lithium-containing composite oxide having a layered structure and is substantially spherical and has an average particle size of 15 to 50 μm. The manufacturing method of the non-aqueous electrolyte secondary battery positive electrode active material of description.