JP2015162322A - Precursor of positive electrode active material for nonaqueous electrolyte secondary battery and method for producing the same, and method for producing positive electrode active material for nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a precursor of a positive electrode active material for a nonaqueous electrolyte secondary battery, the positive electrode active material comprising a lithium-nickel-cobalt-manganese composite oxide particle less in an amount of residual impurities, high in capacity and excellent in coulomb efficiency and reaction resistance; a method for producing the precursor; and a method for producing a positive electrode active material using the precursor.SOLUTION: A precursor of a positive electrode active material for a nonaqueous electrolyte secondary battery can be obtained by cleaning a nickel-cobalt-manganese composite hydroxide particle with an aqueous solution of a carbonate, the nickel-cobalt-manganese composite hydroxide particle containing nickel, cobalt and manganese, as a main component, and further one or more of other elements, as an optimal element.

Description

  The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery. More specifically, the present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery that can be used as a positive electrode material to 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 secondary battery, there is a lithium ion secondary battery using lithium, a lithium alloy, a metal oxide, or carbon as a negative electrode, and 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 lithium cobalt complex oxide uses a rare and expensive cobalt compound as a raw material, it causes an increase in the cost of the active material and the battery, and an alternative to the active material is desired. Lowering the cost of the active material and making it possible to manufacture a cheaper lithium ion secondary battery has a significant industrial significance in terms of reducing the weight and size of portable devices that are currently in widespread use.

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, the lithium nickel composite oxide has inferior cycle characteristics as compared with the lithium cobalt composite oxide, and has a drawback that battery performance is relatively easily lost when used or stored in a high temperature environment.

  Therefore, lithium nickel cobalt manganese composite oxide having the same thermal stability and durability as the cobalt compound is a promising candidate as an alternative to the cobalt compound.

For example, Patent Document 1 discloses composite hydroxide particles substantially having a manganese: nickel ratio of 1: 1, an average particle diameter of 5 to 15 μm, a tap density of 0.6 to 1.4 g / ml, Manganese nickel composite hydroxide particles having a bulk density of 0.4 to 1.0 g / ml, a specific surface area of 20 to 55 m ² / g, and a sulfate content of 0.25 to 0.45% by mass have been proposed. . As its production method, the atomic ratio of manganese and nickel is substantially 1: 1 in an aqueous solution having a pH value of 9 to 13 in the presence of a complexing agent while controlling the degree of oxidation of manganese ions within a certain range. It is disclosed to coprecipitate particles produced by reacting a mixed aqueous solution of manganese salt and nickel salt, which is 1, with an alkaline solution under appropriate stirring conditions.
However, in Patent Document 1, although the structure of the manganese nickel composite oxide particles has been studied, no study has been made on the reduction of impurities.

JP 2004-210560 A

  Lithium nickel cobalt manganese composite oxide obtained by a conventional manufacturing method contains impurities that do not contribute to charge / discharge reactions such as sulfate radicals and chlorine derived from raw materials. Therefore, when configuring a battery, the irreversible capacity of the positive electrode material is reduced. A corresponding amount of negative electrode material must be used in the battery, resulting in a smaller capacity per unit weight and volume, and the extra lithium stored in the negative electrode as irreversible capacity is safe. It becomes a problem from the aspect of sex.

  Chlorine remaining as an impurity may volatilize in the firing process, corrode the firing furnace and surrounding equipment, and may cause contamination of metallic foreign matter into the product leading to a short circuit of the battery. It is done.

  The object of the present invention is to reduce the amount of impurities that do not contribute to the charge / discharge reaction and further corrode the firing furnace and peripheral equipment, thereby making it possible to obtain a non-aqueous electrolyte secondary battery excellent in battery characteristics and safety. It is to provide a precursor of a positive electrode active material and a method for producing the same.

  As a result of deepening research on the reduction of the amount of impurities in order to solve the above problems, the present inventor has washed nickel nickel cobalt manganese composite hydroxide with an aqueous carbonate solution, thereby reducing nickel cobalt manganese composite hydroxide with less impurities. It was found that by using this as a raw material, a lithium nickel cobalt manganese composite oxide with few impurities can be produced, and the present invention has been completed.

That is, the method for producing a precursor of the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is a non-aqueous electrolyte secondary battery comprising nickel cobalt manganese composite hydroxide particles represented by the following general formula (1). A method for producing a precursor of a positive electrode active material for use, wherein the nickel cobalt manganese composite hydroxide particles are washed with a carbonate aqueous solution having a carbonate concentration of 0.1 mol / L or more.
General formula: Ni _x Co _y Mn _z M _t (OH) ₂ (1)
(In the formula, M represents at least one element selected from Mg, Ca, Ba, Sr, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W, and 0.3 ≦ x ≦ 0.4, 0.3 ≦ y ≦ 0.4, 0.3 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, and x + y + z + t = 1.)

  The carbonate aqueous solution is at least one aqueous solution selected from potassium carbonate, sodium carbonate, potassium hydrogen carbonate and sodium hydrogen 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 liquid temperature range of 15-50 degreeC.

The nickel-cobalt-manganese composite hydroxide particles are mixed in an aqueous solution containing nickel, cobalt and manganese and, if necessary, a metal compound containing the element M, and an aqueous solution containing an ammonium ion supplier. It is preferable to obtain by neutralization crystallization by appropriately supplying an aqueous solution of an alkali metal hydroxide sufficient to keep the reaction solution alkaline.
Furthermore, the metal compound is preferably at least one metal chloride or metal chloride solution.

The precursor of the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is composed of nickel cobalt manganese composite hydroxide particles represented by the following general formula (1), and the sulfate group content is 0.20% by mass or less. The sodium content is 0.018% by mass or less.
General formula: Ni _x Co _y Mn _z M _t (OH) ₂ (1)
(In the formula, M represents at least one element selected from Mg, Ca, Ba, Sr, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W, and 0.3 ≦ x ≦ 0.4, 0.3 ≦ y ≦ 0.4, 0.3 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, and x + y + z + t = 1.)
The precursor of the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention preferably has a chlorine content of 0.1% by mass or less.

The manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries of this invention is the positive electrode active material for nonaqueous electrolyte secondary batteries which consists of lithium nickel cobalt manganese complex oxide particle represented by following General formula (2). A manufacturing method comprising mixing a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery with a lithium compound to obtain a lithium mixture; and the lithium mixture in an oxidizing atmosphere in a range of 800 to 1100 ° C. And firing to obtain lithium nickel cobalt manganese composite oxide particles.
General formula: Li _a Ni _x Co _y Mn _z M _t O ₂ (2)
(In the formula, M represents at least one element selected from Mg, Ca, Ba, Sr, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W, and 0.3 ≦ x ≦ 0.4, 0.3 ≦ y ≦ 0.4, 0.3 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, x + y + z + t = 1, a is 0.95 ≦ a ≦ 1.20 is there.)
The lithium compound is preferably at least one selected from the group consisting of lithium hydroxide, oxyhydroxide, oxide, carbonate, nitrate and halide.

According to the present invention, a precursor capable of obtaining a positive electrode active material for a non-aqueous electrolyte secondary battery having a small amount of residual impurities, a high capacity, a small irreversible capacity, and excellent coulomb efficiency and reaction resistance, and a method for producing the same Is provided. The production method of the present invention is easy and highly productive, and can reduce the impurity quality of the precursor. Therefore, it is possible to reduce damage such as corrosion on the production equipment due to components that volatilize during firing, and to reduce the amount of metallic foreign matter. Mixing can be suppressed.
Furthermore, the method for producing a positive electrode active material using the precursor of the present invention easily obtains 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 its industrial value is extremely high.

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

  Hereinafter, a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, a method for producing the same, and a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery using the precursor will be described in detail. The embodiments described below are merely examples, and the present invention can be implemented in various modifications and improvements based on the knowledge of those skilled in the art, including the following embodiments.

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 cobalt manganese composite hydroxide particles represented by the formula (1) are washed with an aqueous carbonate solution having a concentration of 0.1 mol / L or more.
General formula: Ni _x Co _y Mn _z M _t (OH) ₂ (1)
(In the formula, M represents at least one element selected from Ca, Ba, Sr, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W, and 0.3 ≦ x ≦ 0 .4, 0.3 ≦ y ≦ 0.4, 0.3 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, and x + y + z + t = 1.)

  X indicating the content of nickel in the precursor is 0.3 ≦ x ≦ 0.4, preferably 0.32 ≦ x ≦ 0.4, more preferably 0.33 ≦ x ≦ 0.4. is there. By using a positive electrode active material obtained from a precursor having a nickel content in the above range, a secondary battery having an excellent discharge capacity can be obtained.

  Y indicating the content of cobalt in the precursor is 0.3 ≦ y ≦ 0.4, preferably 0.3 ≦ y ≦ 0.35, more preferably 0.3 ≦ y ≦ 0.34. is there. By using a positive electrode active material obtained from a precursor having a cobalt content in the above range, a secondary battery having excellent discharge capacity and cycle characteristics can be obtained.

  Z indicating the content of manganese in the precursor is 0.3 ≦ z ≦ 0.4, preferably 0.3 ≦ y ≦ 0.35, more preferably 0.3 ≦ y ≦ 0.34. By using a positive electrode active material obtained from a precursor having a manganese content in the above range, a secondary battery having excellent cycle characteristics and thermal stability can be obtained.

Further, t indicating the content of the element M in the precursor is 0 ≦ t ≦ 0.1, preferably 0 ≦ t ≦ 0.07, and more preferably 0 ≦ t ≦ 0.05. By using a positive electrode active material obtained from a precursor whose M content is in the above range, a secondary battery excellent in cycle characteristics and thermal stability can be obtained while ensuring a discharge capacity.
In addition, the composition ratio of nickel, cobalt, manganese, and element M in the precursor is maintained in lithium nickel manganese composite oxide particles (positive electrode active material) described later.

(1) Method for Producing Nickel Cobalt Manganese Composite Hydroxide Particles As a method for producing nickel cobalt manganese composite hydroxide particles (hereinafter also simply referred to as “composite hydroxide particles”) used in the present invention, the above formula is used. If what satisfy | fills (1) is obtained, it will not specifically limit, A conventionally well-known method can be used, for example, nickel, cobalt, and manganese, and Ca, Ba, Sr, Al, Ti, V, as needed. A mixed aqueous solution of a metal compound containing at least one element M selected from Cr, Zr, Nb, Mo, Hf, Ta, and W and an aqueous solution of an alkali metal hydroxide are appropriately mixed and crystallized. It is done.

  Among them, in the heated reaction vessel, at least selected from nickel, cobalt and manganese and, if necessary, Ca, Ba, Sr, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W A mixed aqueous solution of a metal compound containing one element and an aqueous solution containing an ammonium ion supplier are supplied, and at that time, an alkali metal hydroxide in an amount sufficient to keep the reaction solution alkaline. It is preferable from the viewpoint of productivity, particle size stability, and the like to appropriately supply an aqueous solution and obtain nickel cobalt manganese composite hydroxide particles by neutralization crystallization.

  The metal compound containing nickel, cobalt, and manganese is not particularly limited. For example, sulfides, nitrates, and chlorides of the respective metals can be used. In view of the above, sulfides and chlorides are preferable, and among them, it is preferable to include at least one metal chloride.

  The metal compound containing at least one element M selected from Mg, Ca, Ba, Sr, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W is not particularly limited and is publicly known. Can be used, for example, magnesium sulfate, calcium sulfate, sodium aluminate, aluminum sulfate, titanium sulfate, ammonium peroxotitanate, potassium oxalate, vanadium sulfate, ammonium vanadate, chromium sulfate, potassium chromate, Zirconium sulfate, zirconium nitrate, niobium oxalate, ammonium molybdate, sodium tungstate, ammonium tungstate, and the like can be used.

Moreover, it does not specifically limit as an alkali metal hydroxide, For example, 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 of the reaction solution 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) Cleaning with carbonate aqueous solution In the method for producing a precursor of the present invention, the concentration of the composite hydroxide particles is 0.1 mol / L or more, preferably 0.15 to 2.00 mol / L, more preferably 0.8. It is characterized by washing with 20 to 1.50 mol / L carbonate aqueous solution. By using a carbonate aqueous solution having a concentration of 0.1 mol / L or more when washing, impurities in the composite hydroxide particles, 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 (K ₂ CO ₃ ), sodium carbonate (Na ₂ CO ₃ ), potassium hydrogen carbonate, and sodium hydrogen carbonate. 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 1.50 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 15 ° 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 composite hydroxide particles, 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 particularly limited as long as it can be sufficiently washed so that the sulfate content of the nickel cobalt manganese composite hydroxide is 0.2 mass% or less and the sodium content is 0.018 mass% or less. Although it is not, it is usually 0.5 to 2 hours.

The cleaning method includes adding the composite hydroxide particles to the carbonate aqueous solution, slurrying and cleaning, followed by filtration, or the usual cleaning method or composite hydroxide particles generated by neutralization crystallization. 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 is derived from nickel cobalt manganese composite hydroxide particles represented by the following general formula (1). The sulfate radical content is 0.20% by mass or less, and the Na content is 0.018% by mass or less.
General formula: Ni _x Co _y Mn _z M _t (OH) ₂ (1)
(M represents at least one element selected from Mg, Ca, Ba, Sr, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W, and 0.3 ≦ x ≦ 0. 4, 0.3 ≦ y ≦ 0.4, 0.3 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, and x + y + z + t = 1.)

  Sulfate radicals are slightly reduced in the firing step in the production of the positive electrode active material, and remain in the positive electrode active material, so it is necessary to sufficiently reduce it in the precursor. By making the sulfate radical content 0.20% by mass or less, preferably 0.15% by mass or less, more preferably 0.10% by mass or less, the resulting positive electrode active material also has a sulfate radical content of 0.20% by mass. % Or less, preferably 0.15% by mass or less, more preferably 0.10% by mass or less, and the positive electrode active material obtained can have a small irreversible capacity and a high capacity. Moreover, damage to equipment such as a firing furnace due to volatilization in the firing step can be suppressed.

  The sodium content also does not decrease in the firing step, but rather increases due to the lithium salt that is the mixed raw material, so 0.018% by mass or less, preferably 0.015% by mass or less, more preferably 0.012% by mass or less. Thus, it is necessary to sufficiently reduce the precursor.

  Furthermore, the chlorine content is preferably 0.1% by mass or less, more preferably 0.05% by mass or less, and further preferably 0.02% by mass or less. Although chlorine tends to decrease in the firing step and has less influence on the positive electrode active material than sulfate radicals, it is preferable to reduce it sufficiently in the precursor because it adversely affects the firing furnace during the production of the positive electrode active material.

  The sulfate, sodium, and chlorine contents in the precursor are within the above ranges by appropriately adjusting the concentration of the carbonate aqueous solution, the amount of the carbonate aqueous solution, the temperature, and the like when the composite hydroxide particles are washed with the carbonate aqueous solution. It can be.

3. Method for producing positive electrode active material for non-aqueous electrolyte secondary battery The method for producing a positive electrode active material for non-aqueous electrolyte secondary battery according to the present invention is as follows: 1) Mixing to obtain a lithium mixture by mixing the precursor and lithium compound Step 2) The lithium mixture is fired in an oxidizing atmosphere in the range of 850 to 1050 ° C., and lithium nickel cobalt manganese composite oxide particles represented by the following general formula (2) (hereinafter simply referred to as “lithium composite”). And a firing step for obtaining “oxide particles”.
General formula: Li _a Ni _x Co _y Mn _z M _t O ₂ (2)
(In the formula, M represents at least one element selected from Mg, Ca, Ba, Sr, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W, and 0.3 ≦ x ≦ 0.4, 0.3 ≦ y ≦ 0.4, 0.3 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, x + y + z + t = 1, and a is 0.95 ≦ a ≦ 1. 20)

Hereinafter, each step will be described.
(1) Mixing Step As a mixing ratio of the precursor and the lithium compound, lithium (Li) and a metal element (Me) other than lithium are 0.95 to 1.20 in molar ratio (Li / Me), preferably 1 It is preferable to adjust so that it may become 0.00-1.15. 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 0.95, it causes a large decrease in the battery capacity during the charge / discharge cycle. The internal resistance of the positive electrode will increase.
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. And carbonates are more preferably used.

  The precursor can be mixed with a lithium compound in a hydroxide state, but a roasting step may be added before the mixing step to remove residual moisture from the precursor, and It may be converted to an oxide form.

  By the roasting process, the ratio of lithium and metal elements other than lithium can be controlled more easily, the composition of the obtained lithium composite oxide particles can be stabilized, and the composition nonuniformity during firing can be suppressed. it can. That is, the roasting step is performed in an oxidizing atmosphere at a temperature of 150 to 1000 ° C., preferably 400 to 900 ° C., more preferably 400 to 800 ° C. in order to obtain an oxide form.

  At this time, if the roasting temperature is less than 150 ° C., residual moisture in the precursor may not be sufficiently removed. On the other hand, when the roasting temperature exceeds 1000 ° C., the primary particles constituting the particles rapidly grow and the reaction area on the precursor side after roasting is too small in the production of the subsequent lithium composite oxide particles. The reactivity with lithium may decrease, and the crystallinity of the lithium composite oxide particles may decrease. When the roasting temperature is 300 ° C. or lower, it can be carried out in combination with drying in the crystallization step for obtaining nickel cobalt manganese composite hydroxide particles.

(2) Firing step In the oxidizing step, the lithium mixture is calcined in the range of 800 to 1100 ° C, preferably in the range of 850 to 1050 ° C, more preferably in the range of 900 to 1000 ° C. That is, nickel cobalt lithium manganate is produced when heat-treated at a temperature exceeding 800 ° C., but below 800 ° C., the crystal is undeveloped and structurally unstable, and is easily caused by phase transition due to charge / discharge. The structure will be destroyed. On the other hand, when the temperature exceeds 1100 ° C., abnormal grain growth occurs, causing the layered structure to collapse and the specific surface area to decrease, making it difficult to insert and desorb lithium ions. In addition, since the reaction of the nickel cobalt manganese compound and the lithium compound is almost completed at about 700 ° C., baking up to 700 ° C. and baking at 700 ° C. or more may be divided into different facilities and processes. By dividing into two, gas components such as water vapor and carbon dioxide generated by the reaction between the nickel cobalt manganese compound and the lithium compound can be prevented from being brought into firing at 700 ° C. or higher for improving crystallinity, and higher crystallinity. Lithium composite oxide particles can be obtained. Moreover, in order to make it react uniformly in the temperature range which crystal growth advances after removing the crystal water etc. of a lithium compound, even if it hold | maintains at 600-900 degreeC and temperature lower than a calcination temperature for 1 hour or more, Good.

  By using the precursor of the present invention as a raw material and using the above production method, the sulfate radical content is 0.2% by mass or less, preferably 0.15% by mass or less, more preferably 0.10% by mass or less, containing sodium. A positive electrode active material for a non-aqueous electrolyte secondary battery comprising lithium composite oxide particles having an amount of 0.025% by mass or less, preferably 0.020% by mass or less, and a chlorine content of preferably 0.01% by mass or less is obtained. be able to.

  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. In addition, the analysis method and evaluation method of the metal of lithium nickel complex oxide used by the Example and the comparative example 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. Charge to 3V, after 1 hour of rest, discharge capacity to 3.0V cut-off voltage, discharge capacity, ratio of discharge capacity to charge capacity (discharge capacity / charge capacity) at this time Coulomb efficiency (%) It was.
(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.

Example 1
The temperature in the reaction vessel was set to 40 ° C., and 25 mass% ammonia water was added to the mixed aqueous solution containing nickel sulfate, cobalt chloride, and manganese sulfate in the reaction vessel to obtain a reaction solution. By maintaining the reaction solution at a pH of 11.5 based on a liquid temperature of 25 ° C. with a 20 mass% sodium hydroxide solution (neutralization crystallization method), a plurality of primary particles of 1 μm or less are aggregated to form spherical secondary particles. Thus, nickel-cobalt-manganese composite hydroxide particles formed by solid solution with a molar ratio of nickel, cobalt and manganese of 40:30:30 were produced.
The impurity content after sampling, washing and drying the composite hydroxide particles is 0.73% by mass for sulfate radical, 0.013% by mass for Na, and 0.35% by mass for chlorine. % (Reference example).
The obtained composite hydroxide particles are subjected to solid-liquid separation using a filter press filter, and 0.28 mol / L sodium carbonate aqueous solution at 25 ° C. and pH 11.5 (25 ° C. standard) is added to 1000 g of nickel cobalt manganese composite oxide. Washing was conducted by passing through the filter press filter at a rate of 3000 mL, and pure water was passed through for washing. Table 1 shows the evaluation results of the composition, the cleaning conditions, the amount of impurities, etc. of the nickel cobalt manganese composite hydroxide particles (precursor) after the cleaning.
In the obtained composite hydroxide particles (precursor), the molar ratio of each metal component of the lithium compound to the lithium nickel composite oxide is Ni: Co: Mn: Li = 0.40: 0.30: 0.30: The composite hydroxide particles and lithium hydroxide monohydrate (manufactured by Wako Pure Chemical Industries, Ltd.) were weighed and mixed so as to be 1.08. The obtained mixture was baked at 920 ° C. for 9 hours in an air atmosphere using an electric furnace. Then, after cooling in a furnace to room temperature, pulverization treatment was performed to obtain a positive electrode active material composed of spherical lithium nickel cobalt manganese composite oxide particles in which primary particles were aggregated. Table 2 shows the evaluation results of the composition and impurity amount of the obtained positive electrode active material.

[Battery preparation method]
90 parts by weight of the positive electrode active material powder was mixed with 5 parts by weight of acetylene black and 5 parts by weight of polyvinylidene fluoride, and n-methylpyrrolidone was added to form a paste. The paste was applied to the active material weight after drying in an aluminum foil of 20μm thickness is 0.05 g / cm ^2, and vacuum dried at 120 ° C., then the positive electrode and punched than this into a disk form having a diameter of 1cm 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 evaluation results of each characteristic (discharge capacity, coulomb efficiency, reaction resistance) of the obtained battery.

(Example 2)
A positive electrode active material was produced and evaluated in the same manner as in Example 1 except that the sodium carbonate aqueous solution was changed to 0.47 mol / L and washed. The evaluation results are shown in Tables 1 and 2.

(Example 3)
A positive electrode active material was produced and evaluated in the same manner as in Example 1 except that the aqueous sodium carbonate solution was changed to 1.12 mol / L and washed. The evaluation results are shown in Tables 1 and 2.

Example 4
A positive electrode active material was produced and evaluated in the same manner as in Example 1 except that Ni: Co: Mn: Li = 0.34: 0.33: 0.33. The evaluation results are shown in Tables 1 and 2.

(Comparative Example 1)
A positive electrode active material was produced and evaluated in the same manner as in Example 1 except that the aqueous sodium carbonate solution was changed to 0.09 mol / L and washed. The evaluation results are shown in Tables 1 and 2.

(Comparative Example 2)
A positive electrode active material was produced and evaluated in the same manner as in Example 1 except that the aqueous sodium carbonate solution was changed to a 1.60 mol / L sodium hydroxide aqueous solution and washed. The evaluation results are shown in Tables 1 and 2.

(Comparative Example 3)
A positive electrode active material was produced and evaluated in the same manner as in Example 1 except that the sodium hydroxide aqueous solution was changed to a 3.39 mol / L sodium hydroxide aqueous solution and washed. The evaluation results are shown in Tables 1 and 2.

From Table 1, in Examples 1 to 4 that satisfy all the requirements of the present invention, the amount of impurities of the obtained hydroxide is low, the positive electrode active material has a high capacity, and is excellent in Coulomb efficiency and reaction resistance. I understand.
On the other hand, in Comparative Examples 1 to 3 that do not satisfy some or all of the requirements of the present invention, the amount of hydroxide impurities increases and the reaction resistance increases. Moreover, in Comparative Examples 2 and 3 in which washing with a sodium hydroxide solution is performed, the concentration of the sodium hydroxide solution is increased, so that the amount of sulfate radicals is reduced but the sodium remains, so that the reaction resistance is reduced. It is high.

  As is clear from the above, the positive electrode active material for the non-aqueous electrolyte secondary battery of the present invention is composed of a lithium nickel cobalt manganese composite oxide having a high capacity and extremely reduced impurities. A non-aqueous electrolyte secondary battery having a high capacity and excellent battery characteristics can be obtained, and is particularly suitable as a chargeable / dischargeable secondary battery used in the field of small electronic devices. Very 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 nickel cobalt manganese composite hydroxide particles represented by the following general formula (1):
A method for producing a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the nickel cobalt manganese composite hydroxide particles are washed with a carbonate aqueous solution having a carbonate concentration of 0.1 mol / L or more.
General formula: Ni _x Co _y Mn _z M _t (OH) ₂ (1)
(In the formula, M represents at least one element selected from Mg, Ca, Ba, Sr, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W, and 0.3 ≦ x ≦ 0.4, 0.3 ≦ y ≦ 0.4, 0.3 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, and x + y + z + t = 1.)   2. The carbonate aqueous solution is at least one aqueous solution selected from potassium carbonate, sodium carbonate, potassium bicarbonate, and sodium bicarbonate, and the pH of the carbonate aqueous solution is 11 or more. The manufacturing method of the precursor of the positive electrode active material for nonaqueous electrolyte secondary batteries as described.   The method for producing a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the washing is performed in a liquid temperature range of 15 to 50 ° C.   In the heated reaction vessel, the nickel cobalt manganese composite hydroxide particles are mixed with an aqueous solution of a metal compound containing nickel, cobalt and manganese and, if necessary, the element M, an aqueous solution containing an ammonium ion supplier, In that case, an aqueous solution of an alkali metal hydroxide sufficient to keep the reaction solution alkaline is appropriately supplied and obtained by neutralization crystallization. The manufacturing method of the precursor of the positive electrode active material for nonaqueous electrolyte secondary batteries in any one.   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 mixed aqueous solution of the metal compound contains at least one metal chloride. It consists of nickel cobalt manganese composite hydroxide particles represented by the following general formula (1), characterized in that the sulfate radical content is 0.20 mass% or less and the sodium content is 0.018 mass% or less. A precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery.
General formula: Ni _x Co _y Mn _z M _t (OH) ₂ (1)
(In the formula, M represents at least one element selected from Mg, Ca, Ba, Sr, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W, and 0.3 ≦ x ≦ 0.4, 0.3 ≦ y ≦ 0.4, 0.3 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, and x + y + z + t = 1.)   The precursor of the positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 6, wherein the chlorine content is 0.1% by mass or less. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery comprising lithium nickel cobalt manganese composite oxide particles represented by the following general formula (2):
A mixing step of mixing the precursor of the positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 6 or 7 with a lithium compound to obtain a lithium mixture;
A firing step of firing the lithium mixture in an oxidizing atmosphere in the range of 800 to 1100 ° C. to obtain lithium nickel cobalt manganese composite oxide particles;
The manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries characterized by including this.
General formula: Li _a Ni _x Co _y Mn _z M _t O ₂ (2)
(In the formula, M represents at least one element selected from Mg, Ca, Ba, Sr, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W, and 0.3 ≦ x ≦ 0.4, 0.3 ≦ y ≦ 0.4, 0.3 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, x + y + z + t = 1, a is 0.95 ≦ a ≦ 1.20 is there.)   The non-aqueous composition according to claim 8, wherein the lithium compound is at least one selected from the group consisting of lithium hydroxide, oxyhydroxide, oxide, carbonate, nitrate, and halide. A method for producing a positive electrode active material for an electrolyte secondary battery.

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