JP6237229B2 - Precursor of positive electrode active material for nonaqueous electrolyte secondary battery and method for producing the same, and positive electrode active material for nonaqueous electrolyte secondary battery and method for producing the same - Google Patents

Description

  The present invention relates to a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery, a method for producing the same, a positive electrode active material for a non-aqueous electrolyte secondary battery, and a method for producing the same. More specifically, the present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery that can increase the capacity of the battery.

  In recent years, with the widespread use of portable devices such as mobile phones and notebook computers, development of small and lightweight secondary batteries with high energy density is strongly desired. As such a lithium ion secondary battery using lithium, a lithium alloy, a metal oxide, or carbon as a negative electrode, research and development are actively performed.

A lithium ion secondary battery using a lithium composite oxide, particularly a lithium cobalt composite oxide (LiCoO ₂ ), which is relatively easy to synthesize, as a positive electrode material has a high energy density because a high voltage of 4V can be obtained. Is expected to be put to practical use. A battery using a lithium cobalt composite oxide has been developed so far to obtain excellent initial capacity characteristics and cycle characteristics, and various results have already been obtained.

  However, since the lithium cobalt composite oxide uses a rare and expensive cobalt compound as a raw material, it increases the cost of the active material and further the battery. Lowering the cost of active materials and making it possible to manufacture cheaper lithium-ion secondary batteries has significant industrial significance in reducing the weight and size of portable devices that are currently in widespread use, replacing cobalt compounds. A cheaper active material is desired.

New materials for the positive electrode active material for lithium ion secondary batteries include lithium manganese composite oxide (LiMn ₂ O ₄ ) using manganese, which is cheaper than cobalt, and lithium nickel composite oxide (LiNiO ₂ ) using nickel. ).
Lithium-manganese composite oxide is an inexpensive alternative and has excellent thermal stability, so it can be said to be a powerful alternative to lithium-cobalt composite oxide, but its theoretical capacity is only about half that of lithium-cobalt composite oxide. Therefore, it has a drawback that it is difficult to meet the demand for higher capacity of lithium ion secondary batteries, which is increasing year by year.

  On the other hand, since lithium nickel composite oxide has a lower electrochemical potential than lithium cobalt composite oxide, decomposition due to oxidation of the electrolytic solution is less likely to be a problem, and higher capacity can be expected. Therefore, development is actively conducted. However, when a lithium-ion secondary oxide is produced using a material synthesized purely of nickel alone as the positive electrode active material, the lithium-nickel composite oxide is inferior to the cobalt type in cycle characteristics and is used in a high-temperature environment. When stored, the battery performance is relatively easily lost.

In order to solve such a drawback, a lithium nickel composite oxide in which a part of nickel is substituted with cobalt or the like has also been proposed. For example, Patent Document 1, in order to improve the self-discharge characteristics and cycle characteristics of the lithium ion secondary _{battery, Li x Ni a Co b M} c O 2 (0.8 ≦ x ≦ 1.2,0. 01 ≦ a ≦ 0.99, 0.01 ≦ b ≦ 0.99, 0.01 ≦ c ≦ 0.3, 0.8 ≦ a + b + c ≦ 1.2, M is Al, V, Mn, Fe, Cu and A lithium-containing composite oxide represented by at least one element selected from Zn), and Patent Document 2 discloses a positive electrode capable of maintaining good battery performance during storage and use in a high-temperature environment. As the active material, Li _w Ni _x Co _y B _z O ₂ (0.05 ≦ w ≦ 1.10, 0.5 ≦ x ≦ 0.995, 0.005 ≦ z ≦ 0.20, x + y + z = 1) Lithium-containing composite oxides and the like that have been proposed have been proposed.

Japanese Patent Laid-Open No. 8-213015 JP-A-8-045509

  However, in the lithium nickel composite oxide obtained by the conventional manufacturing method, both the charge capacity and the discharge capacity are higher than those of the lithium cobalt composite oxide, and the cycle characteristics are improved, but only for the first charge / discharge, There is a problem that the discharge capacity is small compared to the charge capacity, and the so-called irreversible capacity defined by the difference between the two is considerably large compared to the cobalt-based composite oxide.

One of the reasons for the increase in the irreversible capacity is that the conventional lithium nickel composite oxide contains impurities that do not contribute to the charge / discharge reaction such as sulfate radicals (SO ₄ ²⁻ ) and Cl derived from raw materials. Since these impurities do not contribute to the charge / discharge reaction, when the battery is constructed, the negative electrode material must be used in the battery by an amount corresponding to the irreversible capacity of the positive electrode material. The capacity per weight and volume is reduced, and excess lithium is accumulated in the negative electrode as an irreversible capacity, which is a problem in terms of safety.

  Accordingly, an object of the present invention is to reduce the amount of impurities that do not contribute to the charge / discharge reaction, thereby making it possible to obtain a non-aqueous electrolyte secondary battery that has high capacity, low irreversible capacity, and excellent coulomb efficiency and reaction resistance. The object is to provide a precursor of a positive electrode active material and a method for producing the same.

  As a result of further research by the inventors to solve the above problems, a nickel composite hydroxide with less impurities can be obtained by washing the nickel composite hydroxide with an aqueous carbonate solution. It has been found that the above problem can be avoided by using a lithium nickel composite oxide produced from a hydroxide as a positive electrode material, and the present invention has been completed.

That is, the method for producing a precursor of a positive electrode active material for a nonaqueous electrolyte secondary battery according to the present invention is a positive electrode active material for a nonaqueous electrolyte secondary battery comprising a nickel composite hydroxide represented by the following general formula (1). The precursor composite manufacturing method is characterized in that the nickel composite hydroxide is washed with a carbonate aqueous solution having a concentration of 0.06 mol / L or more.
The general _{formula: Ni 1-x-y Co} x M y (OH) 2 ··· (1)
(In the formula, M represents at least one element selected from Al, Ti, Mn, and W, x is 0 <x ≦ 0.20, and y is 0 <y ≦ 0.07.)

  The carbonate aqueous solution is at least one aqueous solution selected from potassium carbonate and sodium carbonate, and the pH of the carbonate aqueous solution is preferably 11 or more.

  Moreover, it is preferable to perform the said washing | cleaning in the range of 10-50 degreeC of liquid temperature.

  In addition, the nickel composite hydroxide contains an aqueous solution of a metal compound containing nickel and cobalt and at least one element selected from Al, Ti, Mn and W in a heated reaction vessel, and an ammonium ion supplier. It is preferable to obtain by neutralization crystallization by supplying an appropriate amount of an aqueous solution of an alkali metal hydroxide sufficient to keep the reaction solution alkaline.

Further, the precursor obtained after washing, 0.1% by weight sulfate ion content less and a Na content of 0.01 mass% or less.

Moreover, it is preferable that the precursor obtained after washing | cleaning has a chlorine content of 0.1 mass% or less.

The manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries of this invention is a manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries which consists of lithium nickel complex oxide represented by following General formula (2). A roasting step of obtaining a nickel composite oxide by oxidizing and calcining a precursor of the positive electrode active material for a non-aqueous electrolyte secondary battery in an oxidizing atmosphere at 400 to 800 ° C .; and the nickel composite oxide and lithium A mixing step of mixing a compound to obtain a lithium mixture; and a baking step of baking the lithium mixture in an oxygen atmosphere in a range of 650 to 850 ° C. to obtain a lithium nickel composite oxide.
General formula: Li _a Ni _{1-x′-y ′} Co _{x ′} M _{y ′} O ₂ (2)
(In the formula, M represents at least one element selected from Al, Ti, Mn and W, a is 0.85 ≦ a ≦ 1.05, and x ′ is 0 <x ′ ≦ 0.20. , Y ′ is 0 <y ′ ≦ 0.07.)

  After the firing step, the lithium nickel composite oxide is 0.10% by mass with respect to the total amount of lithium compound present at a temperature of 10 to 40 ° C. and on the surface of the lithium nickel composite oxide. It is preferable to include a water washing step of filtering and drying after washing with water at a slurry concentration sufficient to become the following.

  The lithium compound is preferably at least one selected from the group consisting of lithium hydroxide, oxyhydroxide, oxide, carbonate, nitrate, and halide.

Also, the positive electrode active material, 0.1% by weight sulfate ion content less and a Na content of 0.01 mass% or less.

The present invention provides a precursor capable of obtaining a positive electrode active material for a non-aqueous electrolyte secondary battery that has a high capacity, a small irreversible capacity, and excellent coulomb efficiency and reaction resistance, and a method for producing the same. Further, the production method of the present invention is easy and has high productivity, and its industrial value is extremely large.
Furthermore, the method for producing a positive electrode active material using the precursor of the present invention provides a positive electrode active material for a non-aqueous electrolyte secondary battery that has a high capacity, a small irreversible capacity, and excellent coulomb efficiency and reaction resistance. .

FIG. 1 is a cross-sectional view of a coin battery used for battery evaluation.

  Hereinafter, the present invention will be described in detail.

1. Method for Producing Precursor of Positive Electrode Active Material for Nonaqueous Electrolyte Secondary Battery A method for producing a precursor of a positive electrode active material for a nonaqueous electrolyte secondary battery of the present invention (hereinafter also simply referred to as “precursor”) is described below. The nickel composite hydroxide represented by the formula (1) is washed with a carbonate aqueous solution having a concentration of 0.1 mol / L or more.
The general _{formula: Ni 1-x-y Co} x M y (OH) 2 ··· (1)
(In the formula, M represents at least one element selected from Al, Ti, Mn, and W, x is 0 <x ≦ 0.20, and y is 0 <y ≦ 0.07.)

X indicating the content of cobalt in the nickel composite hydroxide is 0 <x ≦ 0.20, preferably 0.03 ≦ x ≦ 0.20, more preferably 0.10 ≦ x ≦ 0.20. It is. When the cobalt content is in the above range, excellent discharge capacity, cycle characteristics, and thermal stability can be obtained.
Further, y indicating the content of at least one element M selected from Al, Ti, Mn and W is 0 <y ≦ 0.07, and preferably 0.01 ≦ y ≦ 0.05. . When the content of M is in the above range, excellent cycle characteristics and thermal stability can be obtained.

(1) Method for producing nickel composite hydroxide The method for producing the nickel composite hydroxide used in the present invention is not particularly limited as long as a material satisfying the above formula (1) is obtained. For example, an aqueous solution of a metal compound and an aqueous solution of an alkali metal hydroxide containing nickel and cobalt and at least one element M selected from Al, Ti, Mn, and W are appropriately mixed, and crystallized. And so on.

  Among them, an aqueous solution of a metal compound containing nickel and cobalt and at least one element selected from Al, Ti, Mn and W and an aqueous solution containing an ammonium ion supplier are supplied into a heated reaction vessel, In that case, it is possible to obtain a nickel composite hydroxide by neutralized crystallization by appropriately supplying an aqueous solution of an alkali metal hydroxide sufficient to keep the reaction solution alkaline. From the viewpoint of properties and the like.

Although it does not specifically limit as a metal compound containing nickel and cobalt, For example, a sulfate , nitrate, chloride, etc. of nickel or cobalt can be used, From the viewpoint of the ease of waste water treatment, and an environmental burden among these. Nickel or cobalt sulfate and chloride are preferred.
The metal compound containing at least one element M selected from Al, Ti, Mn and W is not particularly limited, and examples thereof include aluminum sulfate, sodium aluminate, titanium sulfate, ammonium peroxotitanate, potassium oxalate titanium, Manganese sulfate, ammonium tungstate, or the like can be used.
Moreover, it does not specifically limit as an alkali metal hydroxide, For example, well-known sodium hydroxide, potassium hydroxide, etc. can be used.

  Although it does not specifically limit as an ammonium ion supplier, For example, ammonia, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride etc. can be used.

  The temperature in the reaction vessel is preferably 40 to 60 ° C., and the pH is preferably 10 to 14. When the temperature at the time of crystallization exceeds 60 ° C. or the pH exceeds 14, the priority of nucleation increases in the liquid, and crystal growth does not proceed and only a fine powder can be obtained. On the other hand, when the temperature is less than 40 ° C. or pH is less than 10, the generation of nuclei in the liquid is small, and the crystal growth of the particles becomes preferential, so that very large particles are generated so that irregularities are generated during electrode production. Or the remaining amount of metal ions in the reaction solution may be high and the reaction efficiency may be very poor.

(2) Washing with aqueous carbonate solution In the method for producing a precursor of the present invention, the nickel composite hydroxide has a concentration of 0.06 mol / L or more, preferably 0.08 to 1.00 mol / L, more preferably 0.8. It is characterized by washing with 10 to 0.60 mol / L carbonate aqueous solution. By using a carbonate aqueous solution with a concentration of 0.06 mol / L or more when washing, impurities in the nickel composite hydroxide, particularly sulfate radicals and chlorine, are efficiently exchanged with carbonic acid in the carbonate aqueous solution. Can be removed well.

  In that case, it is preferable that pH is 11 or more on a 25 degreeC reference | standard. By setting the pH to 11 or more, sulfate radicals and chlorine that form acids can be more efficiently removed. Although the upper limit of pH is not specifically limited, since carbonate aqueous solution is used, about 12.5 becomes an upper limit by pH of 25 degreeC reference | standard.

The carbonate aqueous solution is preferably at least one aqueous solution selected from potassium carbonate and sodium carbonate (Na ₂ CO ₃ ). Since lithium carbonate, calcium carbonate, and barium carbonate have low solubility in water, an aqueous solution in which a sufficient amount is dissolved may not be obtained.

  For example, when sodium carbonate is used as the carbonate, the aqueous solution concentration is preferably 0.2 mol / L or more, and more preferably 0.25 to 0.60 mol / L. Since sodium carbonate has high solubility in water, impurities such as sulfate radicals and chlorine can be more efficiently removed by setting the concentration of the aqueous solution to 0.2 mol / L or more.

The water temperature of the carbonate aqueous solution is preferably 10 ° C to 50 ° C. When the water temperature is in the above range, the ion exchange reaction becomes active and the impurity removal proceeds efficiently.
Moreover, 1000 mL or more is preferable with respect to 1000 g of nickel composite hydroxide, and, as for the amount of sodium carbonate aqueous solution, 2000-5000 mL is more preferable. If it is 1000 mL or less, the impurity ions and carbonate ions may not be sufficiently substituted, and the cleaning effect may not be sufficiently obtained.
The washing time with the carbonate aqueous solution is not particularly limited as long as it can be sufficiently washed so that the sulfate content of the nickel composite hydroxide is 0.1% by mass or less and the Na content is 0.01% by mass or less. Usually, 0.5 to 2 hours.

  As a cleaning method, a nickel composite hydroxide is added to a carbonate aqueous solution, and after slurrying and cleaning, filtration is performed, or a normal cleaning method or nickel composite hydroxide generated by neutralization crystallization is included. The slurry can be supplied to a filter such as a filter press and subjected to washing with water through which an aqueous carbonate solution is passed. Washing with water is preferable because it has high impurity removal efficiency, and filtration and washing can be performed continuously in the same facility and productivity is high.

After washing with an aqueous carbonate solution, washing is then performed with pure water as necessary. In order to remove cationic impurities such as sodium, it is preferable to perform washing with pure water.
For washing with pure water, a method that is usually performed can be used. However, when washing with a carbonate aqueous solution is performed, water washing with pure water is continuously performed after washing with the carbonate aqueous solution. Preferably it is done.

2. Precursor of positive electrode active material for non-aqueous electrolyte secondary battery The precursor of the positive electrode active material for non-aqueous electrolyte secondary battery of the present invention comprises a nickel composite hydroxide represented by the following general formula (1), and sulfuric acid. The root content is 0.1% by mass or less, and the Na content is 0.01% by mass or less.
The general _{formula: Ni 1-x-y Co} x M y (OH) 2 ··· (1)
(In the formula, M represents at least one element selected from Al, Ti, Mn, and W, x is 0 <x ≦ 0.20, and y is 0 <y ≦ 0.07.)

The sulfate radical does not decrease in the firing step in the production of the positive electrode active material, and remains in the positive electrode active material, so that it needs to be sufficiently reduced in the precursor. By setting the sulfate group content to 0.1% by mass or less, preferably 0.08% by mass or less, the sulfate group content of the obtained positive electrode active material can also be set to 0.1% by mass or less. The positive electrode active material can have a small irreversible capacity and a high capacity.
Similarly, the Na content needs to be sufficiently reduced in the precursor so as to be 0.01% by mass or less, preferably 0.008% by mass or less, more preferably 0.005% by mass or less. .

  Furthermore, the chlorine content is preferably 0.1% by mass or less, more preferably 0.05% by mass or less, and further preferably 0.01% by mass or less. Although chlorine has less influence on the positive electrode active material than sulfate radical, it is preferable to sufficiently reduce it in the precursor because it adversely affects the firing furnace during the production of the positive electrode active material.

  The sulfate radical, Na, and chlorine contents in the precursor are within the above ranges by appropriately adjusting the concentration of carbonate aqueous solution, the amount of carbonate aqueous solution, the temperature, etc. when washing the nickel composite hydroxide with the carbonate aqueous solution. It can be.

3. Method for Producing Positive Electrode Active Material for Nonaqueous Electrolyte Secondary Battery The method for producing a positive electrode active material for a nonaqueous electrolyte secondary battery according to the present invention is as follows: 1) The nickel composite hydroxide for precursor in an oxidizing atmosphere 400 A roasting step of oxidative roasting at ˜800 ° C. to obtain a nickel composite oxide, 2) a mixing step of mixing the nickel composite oxide and a lithium compound to obtain a lithium mixture, and 3) oxygenation of the lithium mixture. And firing in a range of 650 to 850 ° C. in an atmosphere to obtain a lithium nickel composite oxide represented by the following general formula (2).
General formula: Li _a Ni _{1-x′-y ′} Co _{x ′} M _{y ′} O ₂ (2)
(In the formula, M represents at least one element selected from Al, Ti, Mn and W, a is 0.85 ≦ a ≦ 1.05, and x ′ is 0 <x ′ ≦ 0.20. , Y ′ is 0 <y ′ ≦ 0.07.)
Moreover, it is preferable to include the water washing process which filters and dries after performing the water washing process of the said lithium nickel composite oxide after the said baking process.
Hereinafter, each step will be described.

(1) Roasting step The roasting step is a step of roasting nickel composite hydroxide to obtain nickel composite oxide. As a result, the ratio of lithium to a metal element other than lithium can be easily controlled. Roasting is performed at a temperature of 400 to 800 ° C., more preferably 500 to 720 ° C. in an oxidizing atmosphere.

  At this time, if the roasting temperature is less than 400 ° C., it is difficult to stabilize the quality of the lithium nickel composite oxide obtained by using this, and the composition tends to be non-uniform during synthesis. On the other hand, when the roasting temperature exceeds 800 ° C., the primary particles constituting the particles rapidly grow and the reaction area on the nickel compound side is too small in the subsequent production of the lithium nickel composite oxide. There is a problem that the specific gravity separation between the nickel compound having a large specific gravity in the lower layer and the lithium compound in the molten state in the upper layer is caused without being able to react.

(2) Mixing step As a mixing ratio of the nickel composite oxide and the lithium compound, a molar ratio (Li / Me) of metal elements (Me) other than lithium (Li) and lithium is preferably 0.85 to 1.05. Is preferably adjusted to 0.95 to 1.04. That is, mixing is performed so that the molar ratio (Li / Me) in the lithium mixture is the same as the molar ratio (Li / Me) in the positive electrode active material of the present invention. This is because the molar ratio (Li / Me) does not change before and after the firing step, and thus Li / Me mixed in this mixing step becomes the molar ratio (Li / Me) in the positive electrode active material.
When the molar ratio (Li / Me) of the obtained positive electrode active material is less than 0.85, it causes a large decrease in the battery capacity during the charge / discharge cycle. The internal resistance of the positive electrode will increase.

As will be described later, when the lithium nickel composite oxide is washed with water after the firing step, the molar ratio (Li / Me) is preferably 0.95 to 1.13.
That is, when the molar ratio is less than 0.95, the molar ratio of the obtained fired powder is also less than 0.95, the crystallinity is very poor, and the molar ratio between lithium and a metal other than lithium when washed with water. (Li / Me) is less than 0.85. On the other hand, if the molar ratio exceeds 1.13, the molar ratio of the calcined powder obtained also exceeds 1.13, and a large amount of excess lithium compound is present on the surface, which is difficult to remove by washing with water. For this reason, when this is used as a positive electrode active material, not only a large amount of gas is generated during charging of the battery, but also a slurry that reacts with a material such as an organic solvent used in electrode preparation because it is a powder exhibiting a high pH. Causes gelation and causes problems. Moreover, the molar ratio (Li / Me) after washing exceeds 1.05.

  For the mixing, a dry blender such as a V blender or a mixing granulator is used, and for the firing, an oxygen concentration of 20% by mass in an oxygen atmosphere, a dry air atmosphere subjected to dehumidification and decarboxylation, or the like. A firing furnace such as an electric furnace, kiln, tubular furnace or pusher furnace adjusted to the above gas atmosphere is used.

  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.

(3) Firing step In this step, the lithium mixture is baked in an oxygen atmosphere in the range of 650 to 850 ° C. As a calcination temperature, the range of 650-800 degreeC, Preferably the range of 730-790 degreeC is used. In other words, lithium nickelate is produced if heat treatment is performed at a temperature exceeding 500 ° C., but if the temperature is lower than 650 ° C., the crystal is undeveloped and structurally unstable, and the structure is easily formed by phase transition due to charge / discharge. It will be destroyed. On the other hand, when the temperature exceeds 800 ° C., cation mixing is likely to occur, the layered structure is destroyed, lithium ion insertion or desorption becomes difficult, and nickel oxide or the like is generated by decomposition. Further, in order to remove the crystallization water of the lithium compound and perform a uniform reaction in the temperature range in which crystal growth proceeds, the reaction is performed at a temperature of 400 to 600 ° C for 1 hour or longer, and subsequently at a temperature of 650 to 800 ° C. It is particularly preferable to calcinate in two stages over time.

(4) Rinsing step The lithium transition metal composite oxide obtained by the firing step is used as the positive electrode active material as it is, but the surface area that can be brought into contact with the electrolytic solution by removing excess lithium on the particle surface. It is preferable to perform a water washing step after firing since the increase in charge / discharge capacity can be achieved. Moreover, since the weak part formed in the particle | grain surface is fully removed, a contact with electrolyte solution can increase and charge / discharge capacity can be improved.

  When washing with water, the slurry concentration is sufficient so that the lithium amount of the lithium compound existing on the surface of the lithium nickel composite oxide is 0.10% by mass or less with respect to the total amount at a temperature of 10 to 40 ° C. Then, it is preferable to wash with water, and then filter and dry.

  In the water washing treatment, by setting the temperature to 10 to 40 ° C., the amount of lithium existing on the surface of the lithium nickel composite oxide powder can be reduced to 0.10% by mass or less, and gas generation at the time of holding at a high temperature is suppressed. be able to. In addition, a positive electrode active material capable of achieving high capacity and high output can be obtained, and high safety can be achieved at the same time.

  The amount of lithium present on the surface of the lithium nickel composite oxide was determined by adding ultrapure water to 10 g of lithium nickel composite oxide powder up to 100 ml and stirring, followed by titration with 1 mol / liter hydrochloric acid until the second neutralization point. Measure and obtain as alkali content neutralized with hydrochloric acid.

  Further, the washing time is not particularly limited, but it is necessary that the washing time is sufficient for the lithium amount of the lithium compound present on the surface of the lithium nickel composite oxide to be 0.10% by mass or less based on the total amount. Yes, depending on the washing temperature, it is generally not 20 minutes to 2 hours.

  As the slurry concentration when washing with water, the amount (g) of the calcined powder with respect to 1 L of water contained in the slurry is preferably 500 to 2000 g / L. That is, as the slurry concentration increases, the amount of powder increases. When the slurry concentration exceeds 2000 g / L, the viscosity is very high and stirring becomes difficult. However, it becomes difficult to separate the powder from the powder even when peeling occurs. On the other hand, if the slurry concentration is less than 500 g / L, the amount of lithium elution is large and the amount of lithium on the surface is small because the solution is too dilute, but lithium is desorbed from the crystal lattice of the positive electrode active material. Not only tends to collapse, but the aqueous solution having a high pH absorbs carbon dioxide in the atmosphere and reprecipitates lithium carbonate. In consideration of productivity from an industrial point of view, the slurry concentration is preferably in the above range from the viewpoint of facility capacity and workability.

  The filtration method after washing with water may be a commonly used method, and for example, a suction filter, a filter press, a centrifuge, or the like can be used.

The drying temperature after filtration is not particularly limited and is preferably 80 to 350 ° C. If the temperature is less than 80 ° C., the drying of the positive electrode active material after washing with water becomes slow, so that a gradient of lithium concentration occurs between the particle surface and the inside of the particle, and the battery characteristics may deteriorate. On the other hand, near the surface of the positive electrode active material, it is expected that it is very close to the stoichiometric ratio, or slightly desorbed lithium and close to the charged state. As a result, the crystal structure close to 1 may be destroyed, and the battery characteristics may be deteriorated.
Although it does not specifically limit as drying time, Preferably it is 2 to 24 hours.

4). Positive electrode active material for nonaqueous electrolyte secondary battery The positive electrode active material for a nonaqueous electrolyte secondary battery of the present invention comprises a lithium nickel composite oxide represented by the following general formula (2), and has a sulfate group content of 0. .1 mass% or less, Na content is 0.01 mass% or less.
General formula: Li _a Ni _{1-x′-y ′} Co _{x ′} M _{y ′} O ₂ (2)
(In the formula, M represents at least one element selected from Al, Ti, Mn and W, a is 0.85 ≦ a ≦ 1.05, x ′ is 0 <x ′ ≦ 0.20, y 'Is 0 <y' ≦ 0.07.)

In the positive electrode active material of the present invention, the sulfate group content is 0.1% by mass or less, preferably 0.08% by mass or less, more preferably 0.05% by mass or less, and further preferably 0.01% by mass or less. Thus, the obtained positive electrode active material can have a small irreversible capacity and a high capacity.
Similarly, good battery characteristics can be obtained by setting the Na content to 0.01% by mass or less, preferably 0.008% by mass or less, and more preferably 0.006% by mass or less.
Furthermore, the chlorine content is preferably 0.1% by mass or less, more preferably 0.05% by mass or less, and further preferably 0.01% by mass or less.

  The sulfate radical, Na, and chlorine content in the positive electrode active material can be adjusted as appropriate by adjusting the concentration of carbonate aqueous solution, the amount of carbonate aqueous solution, the temperature, etc. when washing the nickel composite hydroxide with the carbonate aqueous solution. By performing the water washing step, the above range can be obtained.

  Hereinafter, the present invention will be described in more detail by way of examples and comparative examples of the present invention, but the present invention is not limited to these examples. The metal analysis method and the specific surface area evaluation method of the lithium nickel composite oxide used in the examples and comparative examples are as follows.

1. Analysis and evaluation method (1) Composition analysis: Measured by ICP emission spectrometry.
(2) Sulfate radical content: Sulfur was quantitatively analyzed by an ICP emission analysis method, and the sulfur content was determined by multiplying a coefficient by assuming that all sulfur was oxidized to become sulfate radicals (SO ₄ ²⁻ ).
(3) Na, Cl content: measured by atomic absorption spectrometry.
(4) Charge / discharge capacity, irreversible capacity, coulomb efficiency:
The charge / discharge capacity is allowed to stand for about 24 hours after the coin-type battery is produced, and after the open circuit voltage OCV (open circuit voltage) is stabilized, the current density with respect to the positive electrode is set to 0.5 mA / cm ² and the cut-off voltage is 4. The capacity when charging up to 3V, after 1 hour of rest and discharging up to a cutoff voltage of 3.0V is the discharge capacity, and the difference between the charge capacity and the discharge capacity at this time (charge capacity-discharge capacity) is the irreversible capacity. . The ratio of the discharge capacity to the charge capacity (discharge capacity / charge capacity) was defined as the coulomb efficiency (%).
(5) Reaction resistance:
For the reaction resistance, a coin-type battery was charged at a charging potential of 4.1 V, an AC impedance method Nyquist plot was created using a frequency response analyzer and a potento-galvanostat (manufactured by Solartron, 1255B), and fitting was performed using an equivalent circuit. The value of the positive electrode resistance was calculated by calculation.

2. Examples and Comparative Examples (Example 1)
[Production of nickel composite hydroxide]
An aqueous solution containing nickel sulfate, cobalt sulfate, and sodium aluminate, a 25 mass% sodium hydroxide solution, and 25 mass% aqueous ammonia are added to the reaction vessel so that the molar ratio of nickel, cobalt, and aluminum is 82: 15: 3. At the same time, a nickel composite hydroxide was produced by a coprecipitation method while maintaining the pH at 12.8 based on 25 ° C. and the ammonia concentration at 10 g / L.
The obtained nickel composite hydroxide is composed of spherical secondary particles in which a plurality of primary particles of 1 μm or less are aggregated, and nickel, cobalt, and aluminum are dissolved. The obtained nickel composite hydroxide was subjected to solid-liquid separation with a filter press filter. Thereafter, a 0.28 mol / L sodium carbonate aqueous solution at 20 ° C. and pH 11.5 (25 ° C. standard) was washed by passing through the filter press filter at a rate of 3000 mL with respect to 1000 g of the nickel composite oxide. Further, pure water was passed through and washed. Table 1 shows the results of the composition, impurity amount, etc. of the nickel composite hydroxide (precursor) after washing.

[Production of lithium nickel composite oxide]
The obtained nickel composite hydroxide was roasted at 700 ° C. in an air atmosphere using an electric furnace to obtain a nickel composite oxide. Lithium nickel composite hydroxide and water so that the molar ratio of each metal component of the lithium nickel composite oxide is Ni: Co: Al: Li = 0.85: 0.12: 0.03: 1.03. Lithium oxide monohydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was weighed and mixed. The obtained mixture was calcined at 500 ° C. for 3 hours in an atmosphere having an oxygen concentration of 30% or more using an electric furnace, and then main-fired at 750 ° C. for 20 hours. Then, after cooling in a furnace to room temperature, pulverization was performed to obtain a spherical fired powder in which primary particles were aggregated.
A slurry was prepared by mixing the obtained spherical calcined powder with pure water so that the slurry concentration was 1500 g / L, and the mixture was washed with water at room temperature for 30 minutes using a stirrer and then filtered. After filtration, it was kept at 190 ° C. for 14 hours using a vacuum dryer and cooled to room temperature to obtain a positive electrode active material having a volume-based average particle diameter of 10.8 μm by laser diffraction scattering method. Table 2 shows the composition and impurity amount of the obtained positive electrode active material.

[Production of battery]
90 parts by weight of the spherical fired powder (positive electrode active material powder) obtained above was mixed with 5 parts by weight of acetylene black and 5 parts by weight of polyvinylidene fluoride, and added with n-methylpyrrolidone to form a paste. This was applied to a 20 μm-thick aluminum foil so that the weight of the active material after drying was 0.05 g / cm ² , vacuum-dried at 120 ° C., and then punched into a disk shape having a diameter of 1 cm. did.
Lithium metal was used as the negative electrode, and an equivalent mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) using 1M LiClO ₄ as a supporting salt was used as the electrolyte. Further, a 2032 type coin battery was manufactured in a glove box in an Ar gas atmosphere in which a separator made of polyethylene was impregnated with an electrolytic solution and the dew point was controlled at −80 ° C. FIG. 1 shows a schematic structure of a 2032 type coin battery. Here, the coin battery includes a positive electrode (evaluation electrode) 1 in a positive electrode can 5, a lithium metal negative electrode 3 in a negative electrode can 6, an electrolyte-impregnated separator 2, and a gasket 4.
Table 2 shows the characteristics of the obtained battery (discharge capacity, irreversible capacity, coulomb efficiency, reaction resistance).

(Example 2)
A positive electrode active material was produced in the same manner as in Example 1 except that the sodium carbonate aqueous solution of Example 1 was changed to 0.47 mol / L and washed, and a battery was produced using the obtained positive electrode active material. did. The results are shown in Table 1.

(Example 3)
A positive electrode active material was produced in the same manner as in Example 1, except that the sodium carbonate aqueous solution of Example 1 was changed to 0.09 mol / L and washed, and a battery was produced using the obtained positive electrode active material. did. The results are shown in Table 1.

Example 4
A positive electrode active material was produced in the same manner as in Example 1 except that the spherical fired powder was washed with water and not vacuum dried after firing, and a battery was fabricated using the obtained positive electrode active material. The results are shown in Table 1.
(Comparative Example 1)
The positive electrode active material was prepared in the same manner as in Example 1 except that the sodium carbonate aqueous solution of Example 1 was washed with 1.6 mol / L sodium hydroxide aqueous solution, and the spherical fired powder was washed with water and not vacuum dried after firing. A battery was produced using the positive electrode active material obtained. The results are shown in Table 1.

(Comparative Example 2)
A positive electrode active material was prepared in the same manner as in Example 1 except that the sodium carbonate aqueous solution of Example 1 was washed with a 3.39 mol / L sodium hydroxide aqueous solution, and the spherical fired powder was washed with water and not vacuum dried after firing. A battery was produced using the positive electrode active material obtained. The results are shown in Table 1.

(Comparative Example 3)
A positive electrode active material was produced in the same manner as in Example 1 except that washing with an aqueous solution of sodium carbonate was not performed, only washing with pure water was performed, and that the spherical fired powder was washed with water and not vacuum dried after firing. And the battery was produced using the obtained positive electrode active material. The results are shown in Table 1.

From Tables 1 and 2, it can be seen that in Examples 1 to 4, which satisfy all the requirements of the present invention, the amount of impurities in the obtained hydroxide is low, and the positive electrode active material has a high capacity.
On the other hand, in Comparative Example 1 that does not satisfy some or all of the requirements of the present invention, the amount of hydroxide impurities is large and the capacity is reduced. In Comparative Example 2, the concentration of the sodium hydroxide solution was increased, but the amount of sulfate radical (SO ₄ ) was reduced, but the sodium root remained, resulting in a reduction in capacity. Furthermore, in Comparative Example 3, since the nickel composite hydroxide was washed with pure water only, the amount of sulfate radicals was high, and the discharge capacity and coulomb efficiency were reduced.

  As is clear from the above, the positive electrode active material for a non-aqueous electrolyte secondary battery obtained by the present invention and the non-aqueous electrolyte secondary battery using the same have a low irreversible capacity and a high capacity, particularly in the field of small electronic devices. Since it is suitable as a chargeable / dischargeable secondary battery, its industrial applicability is extremely large.

1 Positive electrode (Evaluation electrode)
2 Separator (electrolyte impregnation)
3 Lithium metal negative electrode 4 Gasket 5 Positive electrode can 6 Negative electrode can

Claims (9)

A method for producing a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery comprising a nickel composite hydroxide represented by the following general formula (1):
An aqueous solution of a metal compound containing nickel and cobalt and at least one element selected from Al, Ti, Mn and W and an aqueous solution containing an ammonium ion supplier are supplied into a heated reaction vessel. Supplying an aqueous solution of an alkali metal hydroxide sufficient to keep the reaction solution alkaline, and obtaining a nickel composite hydroxide by neutralization crystallization;
Washing the nickel composite hydroxide with an aqueous carbonate solution having a concentration of 0.06 mol / L or more ,
The method for producing a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the metal compound containing nickel and cobalt contains at least one of sulfate and chloride .
The general _{formula: Ni 1-x-y Co} x M y (OH) 2 ··· (1)
(In the formula, M represents at least one element selected from Al, Ti, Mn, and W, x is 0 <x ≦ 0.20, and y is 0 <y ≦ 0.07.)   The non-aqueous electrolyte secondary battery according to claim 1, wherein the carbonate aqueous solution is at least one aqueous solution selected from potassium carbonate and sodium carbonate, and the pH of the carbonate aqueous solution is 11 or more. For producing a precursor of a positive electrode active material for use.   The said washing | cleaning is performed in the range of 10-50 degreeC of liquid temperature, The manufacturing method of the precursor of the positive electrode active material for nonaqueous electrolyte secondary batteries of Claim 1 or 2 characterized by the above-mentioned. The precursor obtained after washing, according to one of claims 1 to 3, wherein the sulfate ion content of 0.1 wt% or less, Na content of 0.01 mass% or less The manufacturing method of the precursor of the positive electrode active material for nonaqueous electrolyte secondary batteries. The method for producing a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 4 , wherein the precursor obtained after the washing has a chlorine content of 0.1% by mass or less. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery comprising a lithium nickel composite oxide represented by the following general formula (2):
A roasting step of obtaining a nickel composite oxide by oxidizing and baking the precursor of the positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 4 or 5 in an oxidizing atmosphere at 400 to 800 ° C;
A mixing step of mixing the nickel composite oxide and the lithium compound to obtain a lithium mixture;
A baking step of baking the lithium mixture in an oxygen atmosphere in a range of 650 to 850 ° C. to obtain a lithium nickel composite oxide;
The manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries characterized by including this.
General formula: Li _a Ni _{1-x′-y ′} Co _{x ′} M _{y ′} O ₂ (2)
(In the formula, M represents at least one element selected from Al, Ti, Mn and W, a is 0.85 ≦ a ≦ 1.05, x ′ is 0 <x ′ ≦ 0.20, y 'Is 0 <y' ≦ 0.07.) After the firing step, the lithium nickel composite oxide is 0.10% by mass with respect to the total amount of lithium compound present at a temperature of 10 to 40 ° C. and on the surface of the lithium nickel composite oxide. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 6 , further comprising a water washing step of filtering and drying after washing with water at a slurry concentration sufficient to become: The lithium compound, a hydroxide of lithium, oxyhydroxide, oxide, carbonate, according to claim 6 or 7, characterized in that at least one selected from the group consisting of nitrates and halides A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery. 9. The non-aqueous solution according to claim 6 , wherein the positive electrode active material has a sulfate radical content of 0.1% by mass or less and an Na content of 0.01% by mass or less. A method for producing a positive electrode active material for an electrolyte secondary battery.

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