JP7069749B2 - Nickel composite hydroxide and its manufacturing method, and manufacturing method of positive electrode active material - Google Patents

Description

The present invention relates to a nickel composite hydroxide and a method for producing the same, and a method for producing a positive electrode active material.

In recent years, with the widespread use of portable electronic devices such as mobile phones and notebook personal computers, there is a strong demand for the development of small and lightweight non-aqueous electrolyte secondary batteries having high energy density. As such a secondary battery, there is a lithium ion secondary battery. Lithium metal, lithium alloy, metal oxide, carbon or the like is used as the negative electrode material of the lithium ion secondary battery. These materials are materials capable of desorbing and inserting lithium.

Currently, research and development of such lithium-ion secondary batteries is being actively carried out. Among these, the lithium ion secondary battery using the lithium transition metal composite oxide, particularly the lithium cobalt composite oxide (LiCoO ₂ ), which is relatively easy to synthesize, as the positive electrode material is high because a high voltage of 4V class can be obtained. It is expected and put into practical use as a battery with energy density. In the lithium ion secondary battery using this lithium cobalt composite oxide (LiCoO ₂ ), many developments have been made to obtain excellent initial capacity characteristics and cycle characteristics, and various results have already been obtained. ing.

However, the lithium cobalt composite oxide (LiCoO ₂ ) uses a rare and expensive cobalt compound as a raw material, which causes an increase in battery cost. Therefore, it is desired to use a material other than the lithium cobalt composite oxide (LiCoO ₂ ) as the positive electrode active material.

Recently, there are increasing expectations for the application of lithium-ion secondary batteries not only as small secondary batteries for portable electronic devices but also as large secondary batteries for power storage and electric vehicles. .. Therefore, reducing the cost of the active material and making it possible to manufacture a cheaper lithium-ion secondary battery is expected to have a great ripple effect in a wide range of fields, and is expected to have a large ripple effect on the positive-sided active material for the lithium-ion secondary battery. Examples of the newly proposed materials include lithium manganese composite oxide (LiMn ₂ O ₄ ) using manganese, which is cheaper than cobalt, and lithium nickel composite oxide (LiNi O ₂ ) using nickel. can.

Lithium-manganese composite oxide (LiMn ₂ O ₄ ) is a promising alternative to lithium cobalt composite oxide (LiCoO ₂ ) because it is inexpensive as a raw material and has excellent thermal stability. Since the theoretical capacity is only about half that of the lithium cobalt composite oxide (LiCoO ₂ ), it has the disadvantage that it is difficult to meet the increasing demand for higher capacity lithium-ion secondary batteries. Further, at 45 ° C. or higher, there is a drawback that self-discharge is severe and the charge / discharge life is shortened.

On the other hand, the lithium nickel composite oxide (LiNiO ₂ ) has almost the same theoretical capacity as the lithium cobalt composite oxide (LiCoO ₂ ), and exhibits a slightly lower battery voltage than the lithium cobalt composite oxide. For this reason, decomposition due to oxidation of the electrolytic solution is less likely to be a problem, and higher capacity can be expected, so that development is being actively carried out. However, when it is used as an in-vehicle secondary battery, it is necessary to satisfy the high output as well as the high capacity.

In order to overcome such a drawback, for example, in Patent Document 1, a non-aqueous system having a high specific surface area is obtained by firing using a raw material powder obtained by finely pulverizing and spray-drying using a wet bead mill. Positive electrode active materials for electrolyte secondary batteries have been proposed.

Japanese Unexamined Patent Publication No. 2005-276597

However, although the lithium nickel composite oxide obtained by the production method as in Patent Document 1 has a high specific surface area, it has a small particle size and a low tap density, so that even if the discharge capacity per unit weight is high, There is a problem that the capacity as a battery cannot be increased due to the poor filling property of the electrode plate.

In order to achieve both high capacity and high output characteristics, a positive electrode active material having a high specific surface area while increasing the tap density is required. Therefore, an object of the present invention is to provide a nickel composite hydroxide that can easily obtain a positive electrode active material having a high tap density and a high specific surface area when used as a precursor of a positive electrode active material.

The present inventor has diligently studied the physical properties of the precursor of the non-aqueous electrolyte positive electrode active material, and nickel composite water in which the amount of impurities and the crystallinity contained in nickel hydroxide, which is the precursor of the positive electrode active material, is within a specific range. The present invention has been completed based on the finding that a non-aqueous electrolyte positive electrode active material having both a high tap density and a high specific surface area can be obtained by using an oxide.

That is, in the first aspect of the present invention, nickel, cobalt, and optionally the metal element M are contained, and the atomic number ratio of each metal element is Ni: Co: M = (1-ab). : A: b (where 0.05 ≦ a ≦ 0.35, 0 ≦ b ≦ 0.10, M is at least one element selected from Mn, V, Mg, Ti and Al) It is a composite hydroxide having a chlorine content of more than 0.1% by mass and 1.0% by mass or less, and the half value of the peak of the (101) plane in X-ray diffraction using CuKα ray as a radiation source. Nickel composite hydroxides having a width of 0.35 ° or more and 1.4 ° or less are provided.

Further, the nickel composite hydroxide preferably has a sulfuric acid root content of 0.01% by mass or more and 1.0% by mass or less.

In the second aspect of the present invention, nickel, cobalt, and optionally the metal element M are contained, and the atomic number ratio of each metal element is Ni: Co: M = (1-ab): a. : B (where 0.05 ≦ a ≦ 0.35, 0 ≦ b ≦ 0.10, M is at least one element selected from Mn, V, Mg, Ti and Al) Nickel composite water represented by A method for producing an oxide, which is a nickel composite hydroxide by crystallization in a reaction aqueous solution containing a salt containing nickel, a salt containing cobalt, and a salt containing optionally a metal element M, and a neutralizing agent. The present invention comprises obtaining a crystallization product and washing the cake obtained by filtering the slurry containing the crystallization product with an alkaline aqueous solution to obtain a nickel salt-nickel composite hydroxide. At least one of the cobalt-containing salts contains chloride, and the washed nickel composite hydroxide has a chlorine content of more than 0.1% by mass and 1.0% by mass or less, and CuKα rays. Provided is a method for producing a nickel composite hydroxide in which the half-value width of the peak of the (101) plane in X-ray diffraction as a radiation source is 0.35 ° or more and 1.4 ° or less.

Further, as the alkaline aqueous solution, it is preferable to use at least one aqueous solution selected from sodium hydroxide, sodium carbonate, sodium hydrogencarbonate, sodium sesquicarbonate, potassium hydroxide, potassium carbonate, and potassium hydrogencarbonate. Further, the concentration of the alkaline aqueous solution is preferably 1 g / L or more and 100 g / L or less.

In the third aspect of the present invention, lithium, nickel, cobalt, and optionally the metal element M are contained, and the atomic number ratio of each metal element is Li: Ni: Co: M = c: (1-). ab): a: b (where 0.05 ≦ a ≦ 0.35, 0 ≦ b ≦ 0.10, 0.95 ≦ c ≦ 1.20, M is Mn, V, Mg, Ti and Al. A method for producing a positive electrode active material containing a lithium metal composite oxide represented by (at least one element selected from), wherein the nickel composite hydroxide is heat-treated to obtain a nickel composite hydroxide and a nickel composite oxide. The lithium metal is obtained by mixing at least one of the nickel composite hydroxide and the nickel composite oxide after heat treatment with a lithium compound to obtain a lithium mixture, and firing the lithium mixture. Provided is a method for producing a positive electrode active material, comprising obtaining a composite oxide.

Further, the BET specific surface area of the positive electrode active material obtained by the above manufacturing method is 0.35 m ² / g or more and 1.6 m ² / g or less, and the tap density is 2.0 g / cm ³ or more and 3.1 g / cm ³ The following is preferable.

When the nickel composite hydroxide of the present invention is used as a precursor of a positive electrode active material, it is possible to obtain a positive electrode active material having both a high tap density and a high specific surface area. When this positive electrode active material is used for the positive electrode of a secondary battery, both high battery capacity and excellent output characteristics can be achieved at the same time. Further, in the method for producing a nickel composite hydroxide and a positive electrode active material of the present invention, a positive electrode active material having such excellent battery characteristics and a precursor thereof can be easily produced with high productivity, and it is industrialized. The target value is extremely large.

FIG. 1 is a diagram showing an example of a method for producing a nickel composite hydroxide according to the present embodiment. FIG. 2 is a diagram showing an example of a method for producing a nickel composite hydroxide according to the present embodiment. FIG. 3 is a diagram showing an example of a method for producing a nickel composite hydroxide according to the present embodiment. FIG. 4 is a diagram showing an example of a method for producing a lithium metal double hydroxide according to the present embodiment.

Hereinafter, the present invention will be described with reference to the drawings. However, the present invention is not limited to this. Further, in the drawings, in order to explain the embodiment, the scale is appropriately changed and expressed, for example, a part thereof is described in a large or emphasized manner.

1. 1. Nickel Composite Hydroxide The nickel composite hydroxide according to the present embodiment contains, for example, nickel, cobalt, and optionally the metal element M, and the atomic number ratio (1) of each metal element is Ni :. Co: M = (1-ab): a: b (However, 0.05 ≦ a ≦ 0.35, 0 ≦ b ≦ 0.10, and the metal element M is Mn, V, Mg, Ti and Al. (At least one element selected from), the chlorine content is more than 0.1% by mass and 1.0% by mass or less, and the (101) plane in X-ray diffraction using CuKα ray as a radiation source. The half price range of the peak is 0.35 ° or more and 1.4 ° or less. The nickel composite hydroxide according to the present embodiment can be suitably used as a precursor of a lithium metal composite oxide (positive electrode active material) for a secondary battery.

[cobalt]
In the above ratio (atomic number ratio (1)), a indicating the cobalt content is 0.05 ≦ a ≦ 0.35. When the cobalt content is in this range, the cycle characteristics of the secondary battery can be improved, and the expansion / contraction behavior of the crystal lattice due to the removal / insertion of Li due to the charging / discharging of the positive electrode active material can be reduced. If a is less than 0.05, the cobalt content may be too low to obtain the expected effect. On the other hand, when a exceeds 0.35, the cobalt content is too high, and the initial discharge capacity of the secondary battery is significantly lowered, which may be disadvantageous in terms of cost. Further, a, which indicates the cobalt content in the above ratio, is preferably 0.07 ≦ a ≦ 0.25, more preferably 0.10 ≦ a ≦ 0.20, from the viewpoint of battery characteristics and cost.

[Metal element M]
In the above ratio, the metal element M is at least one element selected from Mn, V, Mg, Ti and Al. In the above ratio, b indicating the content of the metal element M is 0 ≦ b ≦ 0.1, preferably 0.01 ≦ b ≦ 0.1. When the metal element M is contained in this range, the durability characteristics and thermal stability of the secondary battery can be improved. When b is less than 0.01, the amount of the metal element M may be too small to obtain the expected effect. On the other hand, when b exceeds 0.1, the amount of the metal element M may be too large, the amount of other metal elements contributing to the redox reaction in the positive electrode active material may decrease, and the battery capacity may decrease. ..

[nickel]
In the above ratio, (1-ab) indicating the nickel content is 0.55 ≦ a ≦ 0.95. When the nickel content is in this range, a high battery capacity can be obtained. Further, from the viewpoint of further improving the battery capacity, the lower limit of a is preferably 0.65 or more, more preferably 0.7 or more. The nickel content is appropriately adjusted by the above-mentioned content of cobalt and the metal element M.

The nickel composite hydroxide according to the present embodiment may contain a small amount of elements other than nickel, cobalt, and the metal element M as long as the effects of the present invention are not impaired. The nickel composite hydroxide has a general formula (1): Ni _1-ab Co _a M _b (OH) _{2 + α} (however, 0.05 ≦ a ≦ 0.35, 0 ≦ b ≦ 0.10. 0 ≦ α ≦ 0.2, and the metal element M may be represented by at least one element selected from Mn, V, Mg, Ti and Al). The a, b, and M in the general formula (1) may be in the same range as a, b, and M in the above ratio. Further, α in the above general formula (1) may be 0.

[chlorine]
The nickel composite hydroxide according to this embodiment contains chlorine. Chlorine contained in the nickel composite hydroxide has an effect of suppressing the growth of primary particles of the lithium metal composite oxide in the firing step (step S50) described later, and by containing a specific amount of chlorine, the lithium metal composite is formed. A high BET specific surface area can be obtained while maintaining the high crystallinity of the oxide.

The chlorine content in the nickel composite hydroxide is preferably more than 0.1% by mass and 1.0% by mass or less with respect to the entire nickel composite hydroxide. When the chlorine content in the nickel composite hydroxide is 0.1% by mass or less, the primary particles grow too much when the lithium metal composite oxide is obtained in the firing step (step S50), which is the target. It may not be possible to obtain a high BET specific surface area.

On the other hand, when the chlorine content exceeds 1.0% by mass, the reaction between lithium and the nickel composite hydroxide is inhibited in the firing step (step S50), and the crystallinity of the lithium metal composite oxide having a layered structure is lowered. May cause you to. When the crystallinity of the lithium metal composite oxide is low, when a secondary battery is configured as a positive electrode material, there is a problem that Li diffusion in the solid phase (inside the particles of the positive electrode active material) is inhibited and the capacity is reduced. Occurs.

Further, when the nickel composite hydroxide contains an excessive amount of impurities containing chlorine (substances that do not contribute to the charge / discharge reaction and improvement of battery characteristics), some of the impurities are thermally decomposed in the firing step (step S50). However, it may remain in the lithium metal composite oxide even after firing. Impurities do not contribute to the charge / discharge reaction, so when constructing the battery, the negative electrode material must be used in the battery as much as the irreversible capacity of the positive electrode material. As a result, the capacity per weight and volume of the secondary battery as a whole becomes small, and the excess lithium accumulated in the negative electrode as an irreversible capacity may cause a problem in terms of thermal stability.

The chlorine content in the nickel composite hydroxide can be appropriately adjusted within the above range, and for example, even if it is 0.15% by mass or more and 0.5% by mass or less with respect to the entire nickel composite hydroxide. It may be 0.2% by mass or more and 0.5% by mass or less. When the content of chlorine in the nickel composite hydroxide is in this range, it is possible to achieve both a high BET specific surface area while maintaining high crystallinity of the lithium metal composite oxide.

For example, in the case of producing a nickel composite hydroxide by a method including a crystallization step (step S10) described later, nickel composite hydroxylation is performed by containing chlorine in the reaction aqueous solution in the crystallization step (step S10). Chlorine may be contained in the substance. For example, as will be described later, when a compound containing chlorine is used as a compound that is a raw material for nickel and / or cobalt, a nickel composite hydroxide containing chlorine can be easily obtained. Further, the chlorine content can be adjusted to the above-mentioned specific range in the cleaning step (step S10) described later. It is preferable that chlorine in the crystallization product (nickel composite hydroxide) obtained by crystallization is adjusted so that at least a part thereof remains in the nickel composite hydroxide after the washing step (step S20).

[Sulfuric acid root]
The nickel composite hydroxide may contain sulfate roots. The content of sulfuric acid root in the nickel composite hydroxide is preferably 0.01% by mass or more and 1.0% by mass or less, preferably 0.01% by mass or more and 0.5% by mass, based on the entire nickel composite hydroxide. The following is more preferable, and 0.01% by mass or more and 0.1% by mass or less is further preferable. Further, it is preferable that the content of sulfuric acid root is lower than the content of chlorine in the nickel composite hydroxide. If the sulfate root content in the nickel composite hydroxide is less than 0.01% by mass, the composite oxide particles having the desired high BET specific surface area may not be obtained. On the other hand, when the sulfuric acid root content in the nickel composite hydroxide exceeds 1.0% by mass, the amount of impurities increases as described above, and the battery capacity and thermal stability of the secondary battery decrease. Sometimes.

[Half price range of the peak on the (101) plane]
The nickel composite hydroxide preferably has a half-value width of the peak of the (101) plane of 0.35 ° or more and 1.4 ° or less, and 0.4 ° or more and 1.2 ° in X-ray diffraction using CuKα ray as a radiation source. ° or less is more preferable, and 0.4 ° or more and 1.0 ° or less is more preferable. The nickel composite hydroxide contains secondary particles composed of a plurality of primary particles, and the half-value width of the peak of the (101) plane in X-ray diffraction is negative with the particle size of the primary particles of the nickel composite hydroxide. There is a correlation of. That is, when the half-value width is small, the primary particles of the nickel composite hydroxide tend to be large, and when the half-value width is large, the primary particles of the nickel composite hydroxide tend to be small.

When the half-value width of the peak on the (101) plane is less than 0.35 °, the primary particle size of the nickel composite hydroxide is too large, and the lithium metal composite oxide obtained in the firing step (step S50) The primary particles grow too much, and the desired BET specific surface area cannot be obtained. On the other hand, when the half-value width of the peak on the (101) plane exceeds 1.4 °, the primary particle size of the nickel composite hydroxide is too small, so that the lithium metal composite oxide obtained in the firing step (step S50) The primary particles may not grow sufficiently, and as a result, voids may be formed inside the secondary particles of the lithium metal composite oxide, resulting in a low tap density of the lithium metal composite oxide.

The nickel composite hydroxide according to the present embodiment is a lithium metal composite oxide obtained after the firing step (step S50) when the chlorine content and the half-value range of the peak on the (101) plane are within the above ranges. In the positive electrode active material), both high tap density and high BET specific surface area can be achieved at the same time.

2. 2. Method for Producing Nickel Composite Hydroxide The method for producing a nickel composite hydroxide according to the present embodiment is in a reaction aqueous solution containing a nickel salt, a cobalt salt, a salt containing optionally a metal element M, and a neutralizing agent. Then, a crystallization of the nickel composite hydroxide is obtained by crystallization (step S10), and the cake obtained by filtering the slurry containing the crystallization is washed with an alkaline aqueous solution to obtain a nickel composite hydroxide. To obtain (step S20). Further, at least one of the nickel salt and the cobalt salt may be chloride (nickel chloride and / or cobalt chloride), for example, as shown in FIGS. 1 to 3. The method for producing a nickel composite hydroxide according to the present embodiment can easily and highly productively produce the above-mentioned nickel composite hydroxide.

The nickel composite hydroxide obtained by the production method of the present embodiment preferably has the same atomic number ratio of metal elements as the above-mentioned nickel composite hydroxide, for example, nickel, cobalt, and optionally metal elements. M is contained, and the atomic number ratio of each metal element is Ni: Co: M = (1-ab): a: b (however, 0.05 ≦ a ≦ 0.35, 0 ≦ b ≦ 0.10, M is preferably represented by at least one element selected from Mn, V, Mg, Ti and Al). Further, the obtained nickel composite hydroxide preferably contains secondary particles formed by aggregating a plurality of primary particles, and is preferably mainly composed of secondary particles. The nickel composite hydroxide may contain a small amount of a single primary particle. Hereinafter, each step will be described in detail.

[Crystalization step (step S10)]
In the production method according to the present embodiment, the nickel composite hydroxide is preferably obtained by crystallization, and in particular, the following crystallization step (step S10) can be preferably used. That is, as shown in FIGS. 1 to 3, the crystallization step (step S10) includes at least one of nickel chloride and cobalt chloride, optionally the element M, an ammonium ion feeder, and a neutralizing agent. A crystallization of nickel composite hydroxide may be obtained by crystallization in the reaction aqueous solution.

When a nickel composite hydroxide is obtained by crystallization, for example, an ammonium ion feeder is added to a mixed aqueous solution containing a nickel (Ni) salt, a cobalt (Co) salt, and optionally a metal element M while maintaining a predetermined temperature. The nickel composite hydroxide (crystallized product) is co-precipitated by adding an aqueous solution containing the above solution and controlling the reaction aqueous solution to a specific pH with a neutralizing agent (alkaline solution) to a specific gas atmosphere. May be good. Further, a nickel composite hydroxide may be obtained by filtering the obtained slurry of nickel hydroxide (crystallized product), washing the cake obtained with an alkaline aqueous solution, and then filtering and drying.

In the crystallization step (step S10), for example, chlorine can be contained in the reaction aqueous solution, and a salt containing chlorine is used as a metal raw material (nickel salt, cobalt salt, and a salt of any metal element M). Is preferable. Further, the metal raw material (nickel salt, cobalt salt, salt of any metal element M) preferably contains chloride, and more preferably contains at least one of nickel chloride and cobalt chloride. By containing chlorine in the reaction aqueous solution, chlorine can be left in the nickel composite hydroxide in the subsequent step (step S20 or later), and the BET specific surface area and tap density of the finally obtained lithium metal composite oxide can be left. Can be controlled within a suitable range.

The metal raw material (nickel salt, cobalt salt, salt of any metal element M) used in the crystallization step (step S10) has each metal element (nickel compound hydroxide) so as to match the composition of the obtained nickel composite hydroxide. Nickel, cobalt, sulfates of any metal element M), chlorides, nitrates and the like can be used, and as described above, it is preferable to contain at least one kind of chloride.

Further, in the crystallization step (step S10), an aqueous solution containing an ammonium ion feeder and a neutralizing agent (alkali solution) are added to a mixed aqueous solution containing a nickel salt, a cobalt salt, and optionally a metal element M prepared in advance. The reaction aqueous solution may be used and the crystallization step (step S10) may be performed. Further, the salt containing the metal element M may be mixed with the reaction aqueous solution separately from the mixed aqueous solution containing the nickel salt and the cobalt salt, and may be added to the mixed aqueous solution together with the nickel salt and the cobalt salt. May be good. If there is no solution of the metal element M suitable for crystallization, an aqueous solution of a salt of each metal element may be prepared separately and added to the reaction aqueous solution at the same time as the mixed aqueous solution.

The concentration of the mixed aqueous solution is preferably 1 mol / L or more and 2.6 mol / L or less in total of the salts of nickel, cobalt and the metal element M, and more preferably 1 mol / L or more and 2.2 mol / L. When the concentration of the mixed aqueous solution is less than 1 mol / L, the slurry concentration of the obtained nickel composite hydroxide (crystallized product) is low, and the productivity may be inferior. On the other hand, if it exceeds 2.6 mol / L, crystal precipitation or freezing may occur at a low temperature, which may clog the piping of the equipment, and it may be necessary to keep or heat the piping, or it may be costly.

The amount of the mixed aqueous solution supplied to the reaction vessel (reaction aqueous solution) is preferably such that the concentration of the crystallized product (nickel composite hydroxide) at the time when the crystallization reaction is completed is, for example, 30 g / L or more and 250 g / L or less. Is preferably adjusted to be 80 g / L or more and 150 g / L or less. If the concentration of the crystallized product is less than 30 g / L, the aggregation of the primary particles of the nickel composite hydroxide may be insufficient. On the other hand, when the concentration of the crystallized product exceeds 250 g / L, the mixed aqueous solution to be added may not be sufficiently diffused in the reaction vessel, and the particle growth may be biased.

Further, in the above reaction aqueous solution, the ammonium ion donor may not be present, but it is preferable that ammonium ions are present in the reaction aqueous solution. In the presence of ammonium ions, metal ions, especially Ni ions, form an ammine complex. As a result, the solubility of the metal ion is increased, the growth of the primary particles of the nickel composite hydroxide is promoted, and the particles of the dense nickel composite hydroxide are obtained. Further, since the solubility of metal ions is stable, a nickel composite hydroxide having a uniform shape and particle size can be obtained.

The ammonia concentration in the reaction aqueous solution is preferably 3 g / L or more and 25 g / L or less. When the ammonia concentration in the reaction aqueous solution is in this range, nickel composite hydroxide particles having a finer shape and a uniform particle size can be obtained. If the ammonia concentration in the reaction aqueous solution is less than 3 g / L, the solubility of metal ions may become unstable, primary particles with a uniform shape and particle size may not be formed, and gel-like nuclei may be formed. The particle size distribution may be wide. On the other hand, when the ammonia concentration exceeds 25 g / L, the solubility of the metal ions becomes too large, the amount of the metal ions remaining in the reaction aqueous solution increases, and the composition may be displaced. Further, when the ammonia concentration fluctuates, the solubility of metal ions fluctuates and a uniform nickel composite hydroxide is not formed. Therefore, it is preferable to keep the ammonia concentration at a constant value. For example, the ammonia concentration is preferably maintained at a desired concentration with the upper and lower limits set to about 5 g / L. The ammonia concentration in the reaction aqueous solution can be measured with an ammonia ion meter.

The type of the ammonium ion feeder that supplies the ammonium ion is not particularly limited, and for example, ammonia, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, and the like can be used.

The pH of the reaction aqueous solution to which the ammonium ion feeder is added is preferably controlled to 11.1 to 13.0 based on the liquid temperature of 25 ° C. with a neutralizing agent. When the pH of the reaction aqueous solution is less than 11.1. Nickel composite hydroxides with a metal ratio may not be obtained. On the other hand, when the pH of the reaction aqueous solution exceeds 13.0, the primary particles of the nickel composite hydroxide become finer, and the density of the obtained nickel composite hydroxide particles is lowered. Further, since the sphericality of the nickel composite hydroxide particles is also lowered, the filling property of the obtained positive electrode active material in the positive electrode may be lowered. Further, when the pH of the reaction aqueous solution fluctuates, the particle size and shape of the obtained nickel composite hydroxide fluctuate, so that it is preferable to keep the pH of the reaction aqueous solution at a constant value. For example, the pH of the reaction aqueous solution is preferably set to a median value and the pH fluctuation range is preferably suppressed to 0.3 or less.

As the neutralizing agent, an alkaline solution can be used, and for example, a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, or the like may be used.

The temperature of the reaction aqueous solution is preferably maintained in the range of 40 ° C. or higher and 60 ° C. or lower. When the temperature of the reaction aqueous solution is less than 40 ° C., the solubility of Ni decreases, nickel composite hydroxide particles having a uniform shape and particle size are not formed, and gel-like nuclei are likely to be formed, so that the particle size distribution is also large. It spreads and may deteriorate its characteristics when used in a secondary battery. On the other hand, when the temperature of the reaction aqueous solution exceeds 60 ° C., the solubility of the metal ions becomes too large, the amount of the metal ions remaining in the reaction aqueous solution increases, and the composition may be displaced.

The atmosphere of the crystallization step (step S10) is preferably, for example, an oxygen concentration of 5% by volume or less, preferably 4% by volume or less. When the oxygen concentration in the atmosphere is in the above range, the obtained nickel composite hydroxide particles are composed of secondary particles in which the primary particles are densely aggregated. When such a nickel composite hydroxide is mixed with a lithium compound (step S40) and fired (step S50), particles of a lithium composite oxide having a low porosity in the particles, a high density and a high filling property are obtained. be able to. That is, when the oxygen concentration in the atmosphere at the time of crystallization is 5% by volume or less, the oxidation of metal ions in the reaction aqueous solution is suppressed, the primary particles constituting the nickel composite hydroxide grow, and the structure is dense. Secondary particles of the nickel composite hydroxide having the above are obtained. Further, the lithium metal composite oxide obtained after the firing step (step S50) using the obtained nickel composite hydroxide as a precursor also has a high density and high filling property. On the other hand, when the oxygen concentration in the atmosphere at the time of crystallization exceeds 5% by volume, the oxidation of metal ions in the reaction aqueous solution is promoted and the growth of primary particles is suppressed, so that the nickel composite hydroxide having a dense structure Particles may not be obtained.

From the viewpoint of increasing the density of the nickel composite hydroxide particles and further improving the filling property of the lithium metal composite oxide particles, the oxygen concentration in the atmosphere at the time of crystallization may be 4% by volume or less. It is preferably 1% by volume or less, and more preferably 1% by volume or less. The lower limit of the oxygen concentration is not particularly limited, but may exceed 0% by volume or 0.5% by volume or more, for example. The oxygen concentration in the atmosphere at the time of crystallization may be controlled, for example, by passing an inert gas or a reducing gas through the space in the reaction vessel where the crystallization is performed. Further, the inert gas may be bubbled in the reaction aqueous solution. The gas used for controlling the oxygen concentration is preferably an inert gas from the viewpoint of ease of handling, and more preferably nitrogen gas from the viewpoint of cost.

[Washing step (step S20)]
In the washing step (step S20), as shown in FIG. 1, the cake obtained by filtering the slurry containing the crystallization of the nickel composite hydroxide is washed with an alkaline aqueous solution, and the nickel composite hydroxide is washed. Is the process of obtaining. The slurry of the crystallization of the nickel composite hydroxide obtained by crystallization contains a large amount of excess chlorine and sulfuric acid roots mainly derived from the raw materials, and causes particle growth in the subsequent firing step (step S50). It is preferable to control the content of the nickel composite hydroxide to a specific range at the stage of the nickel composite hydroxide because it can be excessively inhibited.

Specifically, the obtained slurry of the crystallization of the nickel composite hydroxide is once filtered to form a cake, and then dispersed in an alkaline aqueous solution by mixing and stirring for washing. Further, the nickel composite hydroxide after washing may be filtered again and dried.

As the alkaline aqueous solution used for washing, at least one aqueous solution selected from sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, and sodium sesquicarbonate can be used. Since these alkaline aqueous solutions have a high pH and have an ion exchange ability, impurities such as chlorine and sulfuric acid roots excessively remaining in the particles of the nickel composite hydroxide can be removed.

The concentration of the alkaline aqueous solution used for washing is not particularly limited, but is preferably 1 g / L or more and 100 g / L or less. If the concentration of the alkaline cleaning solution is less than 1 g / L, impurities in the nickel composite hydroxide may not be sufficiently removed. On the other hand, when the concentration of the alkaline aqueous solution exceeds 100 g / L, it can be sufficiently washed, but the alkali metal contained in the alkaline aqueous solution remains as an impurity and inhibits particle growth in the subsequent firing step (step S50). It may become a factor to do.

As a method for filtering the nickel composite hydroxide after cleaning, heavy pressure filtration using the difference in specific gravity of the solid liquid in the undiluted solution, vacuum filtration using the vacuum differential pressure obtained by the vacuum mechanism, and addition obtained by the pressurizing mechanism. A method such as pressure filtration with differential pressure can be used. Further, as the equipment (device) for filtration, a centrifuge, a nutche, a Moore filter, a disc filter, a drum filter, an Oliver filter, a filter press, a closed leaf filter, a closed multi-stage filter and the like can be used.

The nickel composite hydroxide after washing may be dried. By drying, at least a part of the water contained in the nickel composite hydroxide after washing may be removed. As a drying method, general hot air drying, vacuum drying, steam drying, suction drying and the like can be performed. The nickel composite hydroxide after washing can be dried, for example, at a temperature of 90 ° C. or higher and 160 ° C. or lower for about 24 hours or shorter.

The nickel composite hydroxide after washing preferably has a chlorine content of more than 0.1% by mass and 1.0% by mass or less. When the chlorine content is in the above range, the growth of the primary particles of the lithium metal composite oxide in the firing step (step S50) is adjusted in a suitable range, and the finally obtained lithium metal composite oxide (positive electrode active material) is adjusted. ) Can improve the BET specific surface area. The cleaning conditions described above can be appropriately adjusted so that the nickel composite hydroxide after cleaning has a chlorine content within the above range.

Further, in the nickel composite hydroxide after washing, the half-value width of the peak of the (101) plane in X-ray diffraction using CuKα ray as a radiation source is preferably 0.35 ° or more and 1.4 ° or less. It is more preferably 0.4 ° or more and 1.2 ° or less, and further preferably 0.4 ° or more and 1.0 ° or less. When the half-value width of the peak of the (101) plane of the nickel composite hydroxide is in the above range, the tap density of the lithium metal composite hydroxide obtained after the firing step (step S50) can be improved. The half-value range of the peak on the (101) plane is set within the above range by appropriately adjusting the composition of the nickel composite hydroxide, the pH at the time of crystallization, the temperature, the atmosphere, etc. within the above range. be able to.

3. 3. Method for Producing Positive Active Material In the method for producing a positive electrode active material according to the present embodiment, as shown in FIG. 4, the nickel composite hydroxide obtained by the above-mentioned manufacturing method is heat-treated to obtain nickel composite hydroxide and nickel. A step of obtaining at least one of the composite hydroxides (step S30), a step of mixing at least one of the nickel composite hydroxide and the nickel composite hydroxide with a lithium compound, and a step of obtaining a lithium mixture (step S40). A step (step S50) of calcining the lithium mixture to obtain a lithium metal composite oxide is provided. The method for producing a positive electrode active material according to the present embodiment can easily produce a positive electrode active material having both a high tap density and a high BET specific surface area with high productivity. Hereinafter, each step will be described in detail.

[Heat treatment step (step S30)]
As shown in FIG. 4, the nickel composite hydroxide obtained by the above-mentioned production method (steps S10 to S20) may be heat-treated to obtain at least one of the nickel composite hydroxide and the nickel composite oxide (. Step S30). Hereinafter, at least one of the nickel composite hydroxide and the nickel composite oxide is collectively referred to as a “precursor”.

By heat-treating the nickel composite hydroxide, the water content in the precursor remaining until the firing step (step S50) can be reduced. Further, when heat-treated, at least a part of the nickel composite hydroxide can be converted into a nickel composite oxide, and the number of atoms of metal elements other than lithium in the finally obtained lithium metal composite oxide and lithium can be obtained. It is possible to suppress the variation in the ratio of the number of atoms of. In the heat treatment step (step S30), it is sufficient that water can be removed to the extent that the ratio of the number of atoms of the metal element (lithium, nickel, cobalt, metal element M, etc.) in the lithium metal composite oxide does not vary. It is not always necessary to convert all nickel composite hydroxides to nickel composite oxides.

The temperature of the heat treatment is preferably 105 ° C. or higher and 800 ° C. or lower, and more preferably 300 ° C. or higher and 600 ° C. or lower. When the heat treatment temperature is less than 105 ° C., it takes a long time to remove the residual water, which is not industrially suitable. On the other hand, when the heat treatment temperature exceeds 800 ° C., the particles converted into the nickel composite oxide may be sintered and aggregated, and the reactivity with the lithium compound may be lowered. In addition, the heat treatment time is within a range in which at least a part of the water contained in the nickel composite hydroxide is removed and the ratio of the number of atoms of the metal element in the obtained lithium metal composite oxide does not vary. It can be adjusted as appropriate, but for example, it is 2 hours or more and 24 hours or less.

[Mixing step (step S40)]
Next, at least one of the nickel composite hydroxide and the nickel composite oxide (precursor) after the heat treatment is mixed with the lithium compound to obtain a lithium mixture (step S40). The precursor and the lithium compound are Li / Me ratios in the lithium mixture (Li here represents the number of moles of Li, and Me represents the total number of moles of Ni, Co and the metal element M. (Sometimes abbreviated as “Li / Me”) is mixed so as to be 0.95 or more and 1.20 or less. That is, the Li / Me ratio in the lithium mixture is the same as the Li / Me ratio in the finally obtained lithium metal composite oxide (positive electrode active material). The Li / Me ratio is the atomic number ratio of the metal elements constituting the lithium metal composite oxide, that is, Li: Ni: Co: M = c: (1-ab): a: b (however). , 0.05 ≦ a ≦ 0.35, 0 ≦ b ≦ 0.10, 0.95 ≦ c ≦ 1.20, M is at least one element selected from Mn, V, Mg, Ti and Al) Corresponds to the value of c. This is because Li / Me does not change before and after the firing step (step S50), so that the Li / Me of the lithium mixture obtained in the mixing step (step S40) is Li / Me in the lithium metal composite oxide (positive electrode active material). This is because it becomes Me.

The lithium compound is not particularly limited, and a known compound containing lithium can be used. For example, lithium hydroxide, lithium nitrate, lithium carbonate, or a mixture thereof is preferable from the viewpoint of easy availability. In particular, it is more preferable to use lithium hydroxide in consideration of ease of handling, stability of quality, reactivity in the firing step (step S50), and the like.

It is preferable that the lithium mixture is sufficiently mixed before the firing step (step S50). If the mixing is not sufficient, problems such as variations in Li / Me among the individual particles and insufficient battery characteristics may occur. In addition, a general mixer can be used for mixing, for example, a shaker mixer, a Ladyge mixer, a Julia mixer, a V blender, or the like can be used, and a precursor (nickel composite hydroxide / nickel composite) can be used. The precursor and the lithium compound may be sufficiently mixed with each other to the extent that the morphology of the oxide) or the lithium compound is not destroyed.

[Baking step (step S50)]
The lithium mixture is then calcined to give a lithium metal composite oxide (step S50). When the lithium mixture is fired in the firing step (step S50), the lithium in the lithium compound diffuses into the primary particles in the precursor (at least one of the nickel composite hydroxide and the nickel composite oxide) to oxidize the lithium metal composite. Things are formed.

The firing temperature is, for example, 650 ° C. or higher and 850 ° C. or lower, and preferably 720 ° C. or higher and 820 ° C. or lower. If the calcination temperature is less than 650 ° C., lithium is not sufficiently diffused into the nickel composite oxide, excess lithium and unreacted particles remain, and the crystal structure is not sufficiently arranged, which is sufficient. There is a problem that battery characteristics cannot be obtained. Further, when the firing temperature exceeds 850 ° C., sintering of the primary grain particles of the lithium metal composite oxide proceeds, and severe sintering may occur between the secondary particles, which may cause abnormal grain growth.

The firing time is preferably at least 1 hour or more, more preferably 3 hours or more and 24 hours or less. If the calcination time is less than 1 hour, the lithium metal composite oxide may not be sufficiently produced.

The atmosphere at the time of firing is preferably an oxidizing atmosphere, and more preferably an atmosphere having an oxygen concentration of 18% by volume or more and 100% by volume or less. That is, firing is preferably performed in the atmosphere or in an air flow having a higher oxygen partial pressure than the atmosphere. When the oxygen concentration is less than 18% by volume, the reaction between the nickel composite hydroxide / nickel composite oxide and the lithium compound may not be sufficiently performed, and the crystallinity of the lithium metal composite oxide may not be sufficient. .. In particular, from the viewpoint of further improving the battery characteristics, it is preferable to perform the operation in an oxygen stream.

The furnace used for firing is not particularly limited as long as it can heat the lithium mixture in the atmosphere or an air flow having a higher oxygen partial pressure than the atmosphere, but an electric furnace that does not generate gas is preferable. Further, as the furnace used for firing, either a batch type or a continuous type may be used.

The lithium metal composite oxide obtained in the firing step (step S50) may be used as it is as a positive electrode active material, or may be used as a positive electrode active material after being crushed and / or washed with water. good. Further, a lithium metal composite oxide other than the lithium metal composite oxide obtained in the firing step (step S50) may be mixed as long as the effect of the present invention is not impaired.

4. Positive Electrode Active Material The composition, characteristics, and the like of the positive electrode active material obtained by the above-mentioned production method of the present embodiment will be described below.

[composition]
The positive electrode active material contains lithium, nickel, cobalt, and optionally the element M, and the atomic number ratio of each metal element is Li: Ni: Co: M = c :( 1-ab) :. a: b (where 0.05 ≦ a ≦ 0.35, 0 ≦ b ≦ 0.10, 0.95 ≦ c ≦ 1.20, M is at least 1 selected from Mn, V, Mg, Ti and Al. Includes lithium metal composite oxides represented by (species element). Further, the lithium metal composite oxide preferably contains secondary particles formed by aggregating a plurality of primary particles, and is preferably mainly composed of secondary particles. The lithium metal composite oxide may contain a small amount of a single primary particle.

The positive electrode active material may contain a small amount of elements other than nickel, cobalt, and the metal element M as long as the effects of the present invention are not impaired. Further, the general formula (2): Li _c Ni _1-a-b Co _a M _b O _{2 + β} (provided that 0.05 ≦ a ≦ 0.35, 0 ≦ b ≦ 0.10, 0.95 ≦ c ≦ 1 .20, 0 ≦ β ≦ 0.2, M may be represented by at least one element selected from Mn, V, Mg, Ti and Al). The a, b, and M in the general formula (1) may be in the same range as a, b, and M in the ratio of the above-mentioned metal elements. Further, β in the above general formula (2) may be 0.

(Tap density)
The tap density of the positive electrode active material is preferably 2.0 g / cm ³ or more. When the tap density of the positive electrode active material is less than 2.0 g / cm ³ , the amount of the solvent required for producing the positive electrode mixture paste described later increases, and the required amount of the conductive material and the binder increases. However, the filling rate of the active material in the positive electrode active material layer is restricted, and a high battery capacity may not be obtained. In the positive electrode of a secondary battery, most of the positive electrode active material layer is usually composed of a lithium metal composite oxide. Therefore, by using a lithium metal composite oxide having a high tap density, a high-density positive electrode active material layer is formed. can do. On the other hand, the upper limit of the tap density of the positive electrode active material is not particularly limited, and the larger the tap density is, the more preferable, but if it is too large, the diffusion of lithium ions through the electrolytic solution in the positive electrode active material layer becomes the rate-determining factor. , Load characteristics may deteriorate. Therefore, the upper limit of the tap density of the positive electrode active material can be, for example, 3.1 g / cm ³ or less.

(BET specific surface area)
The BET specific surface area of the positive electrode active material is not particularly limited and varies greatly depending on the composition ratio and the contained elements, but is preferably 0.35 m ² / g or more and 1.6 m ² / g or less. When the BET specific surface area of the positive electrode active material is smaller than this lower limit, it means that the primary particle size of the lithium metal composite oxide is large, and the rate characteristics tend to deteriorate. Further, if the specific surface area is too large, the amount of the solvent required for producing the positive electrode mixture paste increases, the required amount of the conductive material and the binder increases, and the filling rate of the active material in the positive electrode plate increases. May be constrained and battery capacity may be constrained.

(Characteristics other than the above)
The chlorine content of the lithium metal composite oxide may be more than 0.1% by mass and 1.0% by mass or less, and 0.15% by mass or more and 0.5 by mass, based on the total lithium metal composite oxide. It may be 0% by mass or less, and may be 0.2% by mass or more and 0.5% by mass or less. Further, the lithium metal composite oxide may contain sulfate roots. The content of sulfate roots in the lithium metal composite oxide may be 0.01% by mass or more and 1.0% by mass or less with respect to the entire lithium metal composite oxide, and 0.01% by mass or more and 0. It may be 5% by mass or less, and may be 0.01% by mass or more and 0.1% by mass or less. The content of impurities (chlorine, sulfuric acid root) in the lithium metal composite oxide may be reduced by a calcination step (step S50), washing with water after the calcination step (step S50), or the like.

5. Secondary battery An embodiment of a secondary battery using the positive electrode active material obtained by the present invention will be described in detail for each component. The secondary battery is composed of the same components as a general secondary battery, such as a positive electrode, a negative electrode, and a non-aqueous electrolyte. A secondary battery using a non-aqueous electrolyte is also referred to as a non-aqueous electrolyte secondary battery. Further, the non-aqueous electrolyte may be a non-aqueous electrolyte solution or a solid electrolyte. The following describes an example of a secondary battery using a non-aqueous electrolyte solution. It should be noted that the embodiments described below are merely examples, and the secondary battery can be implemented in various modifications and improvements based on the knowledge of those skilled in the art, including the following embodiments. Further, the secondary battery is not particularly limited in its use.

(1) Positive Electrode A positive electrode mixture forming a positive electrode and each material constituting the same material will be described. The powdery positive electrode active material of the present invention is mixed with a conductive material and a binder, and if necessary, activated carbon, a solvent for viscosity adjustment, etc. is added, and the mixture is kneaded to form a positive electrode mixture paste. To make. The mixing ratio of each in the positive electrode mixture is also an important factor in determining the performance of the lithium secondary battery.

When the total mass of the solid content of the positive electrode mixture excluding the solvent is 100% by mass, the content of the positive electrode active material is 60 to 95% by mass and the conductive material is the same as the positive electrode of a general lithium secondary battery. It is desirable that the content is 1 to 20% by mass and the content of the binder is 1 to 20% by mass.

The obtained positive electrode mixture paste is applied to the surface of a current collector made of aluminum foil, for example, and dried to disperse the solvent. If necessary, pressurization may be performed by a roll press or the like in order to increase the electrode density. In this way, a sheet-shaped positive electrode can be manufactured. The sheet-shaped positive electrode can be cut into an appropriate size according to the target battery and used for manufacturing the battery. However, the method for producing the positive electrode is not limited to the above-exemplified one, and other methods may be used.

In producing the positive electrode, for example, graphite (natural graphite, artificial graphite, expanded graphite, etc.), carbon black materials such as acetylene black, and Ketjen black can be used as the conductive agent. Further, as the binder, for example, polyvinylidene fluoride, polytetrafluoroethylene, ethylene propylene diene rubber, fluororubber, styrene butadiene, cellulose resin, polyacrylic acid and the like can be used.

The binder plays a role of binding the active material particles, and for example, a fluororesin such as polytetrafluoroethylene, polyvinylidene fluoride, or fluororubber, a thermoplastic resin such as polypropylene, or polyethylene can be used. If necessary, the positive electrode active material, the conductive material, and the activated carbon are dispersed, and a solvent for dissolving the binder is added to the positive electrode mixture. As the solvent, specifically, an organic solvent such as N-methyl-2-pyrrolidone can be used. In addition, activated carbon can be added to the positive electrode mixture in order to increase the electric double layer capacity.

(2) Negative electrode For the negative electrode, a negative electrode mixture made into a paste by mixing a binder with a negative electrode active material that can occlude and desorb lithium ions, such as metallic lithium and lithium alloy, and adding an appropriate solvent. , Copper or other metal leaf A metal leaf, which is applied to the surface of a current collector, dried, and compressed to increase the electrode density as necessary, is used.

As the negative electrode active material, for example, an organic compound fired body such as natural graphite, artificial graphite, or phenol resin, or a powdery body of a carbon substance such as coke can be used. In this case, as the negative electrode binder, a fluororesin such as polyvinylidene fluoride can be used as in the positive electrode, and as a solvent for dispersing these active substances and the binder, N-methyl-2-pyrrolidone or the like can be used. Organic solvents can be used.

(3) Separator A separator is sandwiched between the positive electrode and the negative electrode. The separator separates the positive electrode and the negative electrode to retain the electrolyte, and a thin film such as polyethylene or polypropylene, which has a large number of minute holes, can be used.

(4) Non-aqueous electrolyte solution The non-aqueous electrolyte solution is obtained by dissolving a lithium salt as a supporting salt in an organic solvent. Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate and trifluoropropylene carbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate and dipropyl carbonate, and tetrahydrofuran and 2-. One selected from ether compounds such as methyl tetrahydrofuran and dimethoxyethane, sulfur compounds such as ethylmethyl sulfone and butane sulton, and phosphorus compounds such as triethyl phosphate and trioctyl phosphate is used alone or in combination of two or more. be able to.

As the supporting salt, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , etc., and a composite salt thereof can be used. Further, the non-aqueous electrolyte solution may contain a radical catching agent, a surfactant, a flame retardant and the like.

(5) Shape and configuration of the battery The shape of the lithium secondary battery according to the present invention, which is composed of the positive electrode, the negative electrode, the separator and the non-aqueous electrolyte solution described above, may be various, such as a cylindrical type and a laminated type. be able to.
Regardless of which shape is adopted, the positive electrode and the negative electrode are laminated via a separator to form an electrode body, and the electrode body is impregnated with the non-aqueous electrolytic solution. The positive electrode current collector and the positive electrode terminal leading to the outside, and the negative electrode current collector and the negative electrode terminal leading to the outside are connected by using a current collector lead or the like. The battery can be completed by sealing the above configuration in a battery case.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited to these Examples.

(Example 1)
A mixed aqueous solution of nickel chloride and cobalt chloride is prepared so that the nickel: cobalt molar ratio is 84.5: 15.5, and the nickel: cobalt: aluminum molar ratio is 82.0: 15.0: 3. An aqueous solution of sodium aluminate was prepared so as to be 0.0 and added to the reaction vessel. The total concentration of nickel chloride, cobalt chloride and sodium aluminate was 1.5 mol / L. 25% by mass of aqueous ammonia was added so that the concentration of ammonia in the reaction solution was 10 g / L, and a 25% by mass sodium hydroxide solution was added to the reaction vessel to bring the reaction temperature to 50 ° C. and pH 11.3. The composite hydroxide was prepared by the co-precipitation method. The oxygen concentration inside the reaction vessel was adjusted to 1% by volume by supplying nitrogen gas to the space inside the reaction vessel. Then, the entire amount of the slurry containing the nickel composite hydroxide (crystallized product) in the reaction vessel was recovered, filtered through a suction filter, and then the obtained nickel composite hydroxide cake was subjected to a 50 g / L sodium hydroxide aqueous solution. After mixing and stirring, the mixture was filtered again with a suction filter, and the obtained cake was dried at 120 ° C. with a stationary dryer to obtain dried particles of nickel composite hydroxide.

The composition of the nickel composite hydroxide was measured by a high frequency inductively coupled plasma (ICP) emission spectrophotometer (ICPS-8100, manufactured by Shimadzu Corporation) after dissolving the sample in nitrate. For the sulfuric acid root content, after dissolving the sample in nitrate, the sulfur element is measured by an ICP emission spectroscopic analyzer (ICPS-8100, manufactured by Shimadzu Corporation), and the measured amount of sulfur element is converted to _SO4 . I asked for it. The chlorine content was measured with an automatic titrator (COM-1600, manufactured by Hiranuma Sangyo Co., Ltd.). Further, the obtained nickel composite hydroxide was measured by using an X-ray diffractometer (X'Pett PRO manufactured by PANalytical Co., Ltd.) to measure the half-value width of the peak of the (101) plane using CuKα ray as a radiation source.

100 g of the obtained nickel composite hydroxide is inserted into a firing container made of alumina of 15 cm × 15 cm × 4 cm, and held at 700 ° C. for 6 hours in an air stream having a flow rate of 10 L / min using a closed electric furnace. By doing so, particles of nickel composite oxide were obtained.

After weighing this nickel composite oxide and commercially available lithium hydroxide so that Li / Me is 1.02, the shaker mixer device (Willie) is strong enough to maintain the morphology of spherical secondary particles. -Mixed well using TURBULA Type T2C manufactured by E. Bacoffen (WAB). 60 g of this mixture is inserted into a firing container made of magnesia of 5 cm × 12 cm × 3 cm, and the calcined particles are held at 760 ° C. for 12 hours in an oxygen stream with a flow rate of 6 L / min using a closed electric furnace. Lithium metal composite oxide) was obtained.

The BET specific surface area of the lithium metal composite oxide was determined by a flow method gas adsorption method specific surface area measuring device (Multisorb, manufactured by Yuasa Ionics Co., Ltd.). The tap density of the lithium metal composite oxide was calculated by placing a predetermined amount of the lithium metal composite oxide in a 20 ml glass graduated cylinder and tapping the volume 500 times. Table 1 shows the chlorine content and sulfate root content in the nickel composite hydroxide as a precursor, (101) half-value range, and the BET specific surface area and tap density of the final lithium metal composite oxide.

(Example 2)
A nickel composite hydroxide and a lithium metal composite oxide were prepared in the same manner as in Example 1 except that potassium hydroxide was used as the alkaline cleaning solution.

(Example 3)
A nickel composite hydroxide and a lithium metal composite oxide were prepared in the same manner as in Example 1 except that cobalt sulfate was used as a cobalt raw material.

(Example 4)
A nickel composite hydroxide and a lithium metal composite oxide were prepared in the same manner as in Example 1 except that nickel sulfate was used as the nickel raw material.

(Example 5)
A nickel composite hydroxide and a lithium metal composite oxide were prepared in the same manner as in Example 1 except that sodium carbonate having a concentration of 1 g / L was used as the alkaline washing solution.

(Example 6)
A nickel composite hydroxide and a lithium metal composite oxide were prepared in the same manner as in Example 1 except that the concentration of the alkaline washing solution was 100 g / L.

(Comparative Example 1)
A nickel composite hydroxide and a lithium metal composite oxide were prepared in the same manner as in Example 1 except that nickel sulfate was used as the nickel raw material and cobalt sulfate was used as the cobalt raw material.

(Comparative Example 2)
A nickel composite hydroxide and a lithium metal composite oxide were prepared in the same manner as in Example 5 except that the concentration of the alkaline washing solution was 0.5 g / L.

(Comparative Example 3)
A nickel composite hydroxide and a lithium metal composite oxide were prepared in the same manner as in Example 1 except that the concentration of the alkaline washing solution was 150 g / L.

The nickel composite hydroxide of the example has a chlorine content of more than 0.1% by mass and 1.0% by mass or less, and the peak of the (101) plane in X-ray diffraction using CuKα ray as a radiation source. The half price range was 0.35 ° or more and 1.0 ° or less. The BET specific surface area of the lithium metal composite oxide (positive electrode active material) obtained using the nickel composite hydroxide as a precursor is 0.35 m ² / g or more and 1.6 m ² / g or less, and is tapped. The density was 2.0 g / cm ³ or more and 3.1 g / cm ³ or less, and it was shown that the positive electrode active material obtained in the examples had a high specific surface area and a high tap density.

On the other hand, the nickel composite hydroxide of Comparative Example 1 has a low chlorine content because it does not use chloride as a nickel raw material and a cobalt raw material, and has a peak half-value range of 1.1 on the (101) plane, and is crystallized. The sex was bad. When a lithium metal composite oxide was produced using this nickel composite hydroxide as a precursor, particle growth during firing did not proceed sufficiently, and the obtained lithium metal composite oxide had a small BET specific surface area. The nickel composite hydroxide of Comparative Example 2 had a high chlorine content of 1.2% by mass because the concentration of the alkaline cleaning solution was too low. When a lithium metal composite oxide was produced using this nickel composite hydroxide as a precursor, particle growth during firing did not proceed sufficiently, and the obtained lithium metal composite oxide had a tap density of 1.8 g / cm. It became as low as ³ . As for the nickel composite hydroxide of Comparative Example 3, when 150 g / L of sodium hydroxide was used as the alkaline cleaning solution, the tap density was as low as 1.9 g / cm ³ . When a lithium metal composite oxide was produced using this nickel composite hydroxide as a precursor, it was confirmed that the quality of residual sodium was high due to excessive cleaning, even though the chlorine content of the precursor was low. It is considered that this is because the particle growth during firing was inhibited.

The technical scope of the present invention is not limited to the embodiments described in the above-described embodiments. One or more of the requirements described in the above embodiments and the like may be omitted. Further, the requirements described in the above-described embodiments and the like can be appropriately combined. In addition, to the extent permitted by law, the disclosure of all documents cited in the above-mentioned embodiments and the like shall be incorporated as part of the description in the main text.

Since the positive electrode active material of the present invention has a high tap density and a high specific surface area, it is possible to achieve both high capacity and high output when used as a positive electrode of a secondary battery. Therefore, it is suitable for use as a power source for power tools that require both high capacity and high output. Further, it can also be suitably used as a stationary storage battery used as a power source for an electric vehicle or for stabilizing renewable energy. The power source for an electric vehicle includes not only an electric vehicle driven by purely electric energy but also a power source for a so-called hybrid vehicle used in combination with a combustion engine such as a gasoline engine or a diesel engine.

Claims (6)

Nickel, cobalt, and optionally the metal element M are contained, and the atomic number ratio of each metal element is Ni: Co: M = (1-ab): a: b (where 0.05 ≦). a ≦ 0.35, 0 ≦ b ≦ 0.10, M is a nickel composite hydroxide represented by at least one element selected from Mn, V, Mg, Ti and Al).
The chlorine content is more than 0.1% by mass and 1.0% by mass or less, the sulfuric acid root content is less than the chlorine content, and 0.01% by mass or more and 1.0% by mass or less.
A nickel composite hydroxide having a half-value width of the peak of the (101) plane of 0.35 ° or more and 1.4 ° or less in X-ray diffraction using CuKα ray as a radiation source. Nickel, cobalt, and optionally the metal element M are contained, and the atomic number ratio of each metal element is Ni: Co: M = (1-ab): a: b (where 0.05 ≦). a ≦ 0.35, 0 ≦ b ≦ 0.10, M is at least one element selected from Mn, V, Mg, Ti and Al), which is a method for producing a nickel composite hydroxide.
A crystallization of a nickel composite hydroxide is obtained by crystallization in a reaction aqueous solution containing a salt containing nickel, a salt containing cobalt, and optionally a salt containing the metal element M, and a neutralizing agent.
The cake obtained by filtering the slurry containing the crystallization product is washed with an alkaline aqueous solution to obtain a nickel composite hydroxide.
At least one of the nickel-containing salt and the cobalt-containing salt contains chloride and
The nickel composite hydroxide after washing has a chlorine content of more than 0.1% by mass and 1.0% by mass or less, an acid root content of less than the chlorine content, and 0.01% by mass. % Or more and 1.0% by mass or less, and the half-value width of the peak of the (101) plane in X-ray diffraction using CuKα ray as a radiation source is 0.35 ° or more and 1.4 ° or less. How to make things. The nickel composite according to claim 2 , wherein the alkaline aqueous solution uses at least one aqueous solution selected from sodium hydroxide, sodium carbonate, sodium hydrogencarbonate, sodium sesquicarbonate, potassium hydroxide, potassium carbonate, and potassium hydrogencarbonate. Method for producing hydroxide. The method for producing a nickel composite hydroxide according to claim 2 or 3, wherein the concentration of the alkaline aqueous solution is 1 g / L or more and 100 g / L or less. It contains lithium, nickel, cobalt, and optionally the metal element M, and the atomic number ratio of each metal element is Li: Ni: Co: M = c: (1-ab): a: b ( However, 0.05 ≦ a ≦ 0.35, 0 ≦ b ≦ 0.10, 0.95 ≦ c ≦ 1.20, M is at least one element selected from Mn, V, Mg, Ti and Al) A method for producing a positive electrode active material containing a lithium metal composite oxide represented by.
The nickel composite hydroxide according to claim 1 is heat-treated to obtain at least one of the nickel composite hydroxide and the nickel composite oxide.
At least one of the nickel composite hydroxide and the nickel composite oxide after the heat treatment is mixed with a lithium compound to obtain a lithium mixture.
A method for producing a positive electrode active material, comprising firing the lithium mixture to obtain the lithium metal composite oxide. 5. Claim 5 that the BET specific surface area of the positive electrode active material is 0.35 m ² / g or more and 1.6 m ² / g or less, and the tap density is 2.0 g / cm ³ or more and 3.1 g / cm ³ or less. The method for producing a positive electrode active material according to.

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