JP2019009046A - Method for manufacturing positive electrode active material for lithium ion secondary battery, and positive electrode active material for lithium ion secondary battery - Google Patents

Abstract

To provide: a method for manufacturing a positive electrode active material for a lithium ion secondary battery, which enables the manufacturing of a high-capacity, nickel-containing positive electrode active material for a lithium ion secondary battery by use of an inexpensive raw material; and a positive electrode active material for a lithium ion secondary battery.SOLUTION: A method for manufacturing a positive electrode active material for a lithium ion secondary battery according to the present invention is one for manufacturing a positive electrode active material to be used for a positive electrode of a lithium ion secondary battery. The method comprises: a mixing step S21 of mixing a lithium-containing compound and a nickel-containing composition; and a sintering step S22 of sintering a mixture obtained by the mixing step S21 under an oxidizing atmosphere to obtain a lithium composite compound. The nickel-containing composition is a composition obtained by going through a roasting step S11 of roasting a neutralized precipitate recovered by a neutralization treatment from a waste solution of an electroless nickel plating solution at a temperature of 900°C or higher and 1000°C or lower; and a water-rinse step S12 of rinsing, with water, a roasted product obtained by the roasting step.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for producing a positive electrode active material used for a positive electrode of a lithium ion secondary battery, and a positive electrode active material produced thereby.

  Lithium ion secondary batteries are widely used as small and lightweight secondary batteries having high energy density. The lithium ion secondary battery has a feature that it has a high energy density as compared with other secondary batteries such as a lead storage battery, a nickel (Ni) / hydrogen storage battery, and a nickel / cadmium storage battery. Therefore, from small power sources such as portable electronic devices and household electric appliances, stationary power sources such as power storage devices, uninterruptible power supply devices, power leveling devices, ships, rail vehicles, hybrid rail vehicles, hybrid vehicles, electric vehicles Applications are expanding to medium and large power supplies such as drive power supplies.

One type of positive electrode active material for a lithium ion secondary battery is a lithium (Li) composite compound having a layered rock salt crystal structure (hereinafter sometimes referred to as a layered structure) belonging to the space group R-3m. . A typical lithium composite compound having a layered structure is LiCoO _2, but LiNi _1/3 Co _1/3 Mn _1/3 O ₂ whose stability has been improved by diversification is also known. Furthermore, in recent years, lithium composite compounds having a high nickel content, such as LiNi _0.8 Co _0.1 Mn _0.1 O ₂ and LiNi _0.8 Co _0.2 O ₂ , are highly charged and discharged. It is expected as a next-generation positive electrode active material showing capacity.

  Generally, a nickel source used as a raw material for a positive electrode active material is more expensive than a manganese (Mn) source or the like. For this reason, the higher the nickel content contained in the positive electrode active material, the higher the production cost of the positive electrode active material. Therefore, the development of an inexpensive nickel source that can be used as a raw material for the positive electrode active material is an extremely important elemental technology for increasing the manufacturing cost and productivity of the positive electrode active material. Conventionally, electroless nickel plating waste liquid that is often disposed of in landfills is regarded as a promising nickel source that meets such requirements. Techniques for purifying and recovering nickel from electroless nickel plating waste liquid and the like are described in, for example, Patent Document 1 and Patent Document 2.

  Patent Document 1 discloses a method for preparing a purified nickel solution from a nickel salt obtained by neutralizing an electric nickel plating waste liquid or an electroless nickel plating waste liquid to produce high-purity nickel metal or nickel carbonate. ing. Specifically, in Patent Document 1, the electroless nickel plating waste liquid is neutralized with an alkali such as sodium carbonate to obtain a nickel neutralized precipitate, and then dissolved in an inorganic acid such as sulfuric acid to obtain a nickel sulfate solution. Impurities such as phosphorus, copper, iron, zinc and cobalt are separated as precipitates to obtain a purified nickel solution.

  In Patent Document 2, nickel ions are extracted from the electroless nickel plating waste solution by a solvent extraction method, and a release agent such as dilute sulfuric acid is added thereto to isolate and recover nickel.

  Conventionally, nickel has been widely used as a raw material for alloy steel including stainless steel. At present, a recycling system for collecting nickel from ores and scraps containing iron, cobalt, etc. together with nickel, refining it to high purity and reusing it has been established.

  For example, Patent Document 3 discloses a method for producing a ferronickel raw material that forms a ferronickel raw material from nickel sulfide or a mixed sulfide containing nickel sulfide and cobalt sulfide. In Patent Document 3, nickel hydroxide obtained in the hydroxylation step is roasted in a temperature range of 230 ° C. or more and 870 ° C. or less to form nickel oxide, and washed with water having a water temperature of 50 ° C. or more. After that, it is described that the baking is performed at a temperature of 50 ° C. or higher.

JP 2012-140668 A JP 2011-052250 A JP 2012-031446 A

  A nickel neutralized precipitate obtained by neutralizing nickel sulfate or the like contained in an electroless nickel plating waste liquid contains nickel as a main component, is inexpensive, and has excellent procurement properties. Therefore, if nickel recovered from electroless nickel plating waste liquid can be used as a raw material for a positive electrode active material for a lithium ion secondary battery, the manufacturing cost of the positive electrode active material can be reduced, and the amount of nickel resources supplied can be reduced. Since it becomes difficult to receive influence, the manufacturing cost and productivity of a positive electrode active material can be improved.

However, nickel-neutralized precipitates useful as a nickel source are often recovered from electroless nickel plating waste liquid in a composition containing a large amount of impurities. According to the techniques disclosed in Patent Documents 1 and 2, although the purity of nickel as a metal is improved, there is a possibility that a sulfur content or the like derived from sulfuric acid added by neutralization or the like may remain. When a raw material containing such impurities is used as it is when firing a lithium composite compound, a heterogeneous phase such as lithium sulfate (Li ₂ SO ₄₎ or lithium sodium sulfate (LiNaSO ₄ ) is generated, and charge and discharge capacities are begun. There is a problem that the electrode performance is greatly impaired.

Further, as disclosed in Patent Document 3, when using a method in which nickel hydroxide obtained in the hydroxylation step is roasted into an inert or oxygen partial pressure of 10 ⁻⁸ atm or less to obtain nickel oxide, Equipment for making the atmospheric conditions as described above is required. Furthermore, in the technique disclosed in Patent Document 3, roasting is performed at a temperature range of 230 ° C. or higher and 870 ° C. or lower. However, phosphorus cannot be efficiently removed from those roasted within this temperature range. That is, with such a treatment method, it is difficult to produce a positive electrode active material for a lithium ion secondary battery that is inexpensive and has a high charge / discharge capacity using a nickel neutralized precipitate as a raw material.

  The present invention has been made in view of the above circumstances, and can produce a high-capacity positive electrode active material for lithium ion secondary batteries containing nickel using inexpensive raw materials. And a positive electrode active material for a lithium ion secondary battery manufactured thereby.

  The present inventor has obtained a sulfur content, a phosphorus content and a sodium content contained as impurities in a nickel neutralized precipitate recovered from the waste liquid of the electroless Ni plating solution (hereinafter sometimes referred to as a neutralized precipitate). We have intensively studied to apply nickel neutralized precipitates originating from plating waste liquid as a raw material for the positive electrode active material. In addition, the sulfur and phosphorus remaining in the nickel neutralized precipitate form a slightly water-soluble compound, and the knowledge that it is difficult to remove by water washing alone makes the sulfur and phosphorus content easily water-soluble. The present invention has been completed by finding that a method of pre-conversion to a water-soluble compound and removal by washing with water is effective.

  The method for producing a positive electrode active material for a lithium ion secondary battery according to the present invention that has solved the above problems is obtained by a mixing step of mixing a compound containing lithium and a composition containing nickel, and the mixing step. A firing step of firing the mixture in an oxidizing atmosphere to obtain a lithium composite compound, and the nickel-containing composition is a neutralized precipitate recovered from a waste solution of an electroless nickel plating solution by a neutralization treatment The composition was obtained through a roasting step of roasting at a temperature of 900 ° C. to 1000 ° C. and a water washing step of washing the roasted product obtained in the roasting step.

Moreover, the positive electrode active material for a lithium ion secondary battery according to the present invention includes a lithium composite oxide represented by the following formula (1) and a compound containing phosphorus, and contains phosphorus with respect to nickel in the positive electrode active material. The concentration was 0.01% by mass or more and 1.0% by mass or less.
_{Li 1 + a Ni b Mn c} Co d M e O 2 + α ··· (1)
[In the formula (1), M is one or more elements selected from the group consisting of Mg, Al, Ti, Zr, Mo and Nb, and a, b, c, d, e and α are: −0.1 ≦ a ≦ 0.2, 0.7 <b ≦ 1.0, 0 ≦ c <0.3, 0 ≦ d <0.3, 0 ≦ e ≦ 0.3, b + c + d + e = 1, − It is a number that satisfies 0.2 ≦ α ≦ 0.2. ]

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the positive electrode active material for lithium ion secondary batteries which can manufacture the high capacity | capacitance positive electrode active material for lithium ion secondary batteries containing nickel using an inexpensive raw material, and this are manufactured. In addition, a positive electrode active material for a lithium ion secondary battery can be provided.

It is a flowchart explaining the processing method of the electroless nickel plating waste liquid. It is a flowchart explaining the processing method of nickel neutralization deposit. It is a flowchart explaining the manufacturing method of the positive electrode active material for lithium ion secondary batteries which concerns on one Embodiment of this invention. It is a fragmentary sectional view showing typically an example of a lithium ion secondary battery.

  Hereinafter, a positive electrode active material for a lithium ion secondary battery according to an embodiment of the present invention (hereinafter sometimes simply referred to as a positive electrode active material) and a method for producing the same will be described in detail with reference to the drawings as appropriate. In addition, the following description shows the specific example of the content of this invention, and this invention is not limited to these. The present invention can be variously modified by those skilled in the art within the scope of the technical idea disclosed in the present specification.

[Positive electrode active material]
The positive electrode active material according to the present embodiment includes a lithium transition metal composite oxide (referred to herein as a lithium composite compound) composed of lithium (Li) and a metal element such as a transition metal, phosphorus, and the like. And a compound containing. Further, the positive electrode active material according to the present embodiment may include a compound containing sulfur. The positive electrode active material according to the present embodiment is capable of reversibly inserting and extracting lithium ions by applying a voltage, and is preferably used as a positive electrode material for a lithium ion secondary battery.

  The aforementioned lithium composite compound has a composition containing at least nickel (Ni) as a metal element other than lithium (Li). Since the above lithium composite compound contains nickel, high energy density and high charge / discharge capacity are exhibited by including the lithium composite compound in the positive electrode active material. In this way, in this embodiment, since the lithium composite compound contained in the positive electrode active material contains nickel, it is important to reduce the cost of the raw nickel source. As a raw material nickel source, as described later, a nickel neutralized precipitate recovered from a waste liquid of an electroless nickel plating solution is used.

The above-described lithium composite compound may be a composition containing only nickel (Ni) as a transition metal, or contains at least one of manganese (Mn) and cobalt (Co) in addition to nickel (Ni). It may be a composition. Specific examples of such a lithium composite compound include LiNiO ₂ , a layered rock salt type lithium composite compound in which a part of Ni is substituted with Mn and Co, LiNi _z Mn _2−z O ₄ (wherein 0 Spinel type lithium composite compounds represented by <z <0.5). Further, other lithium composite compounds doped with Ni, such as olivine type, polyanion type, and reverse spinel type, may be used.

The above-mentioned lithium composite compound has a general formula; LiNi _x Mn _y Co _1-xy O ₂ (where 0 <x <1, 0 ≦ y <1) and a space group R-3m It has a layered rock salt type crystal structure belonging to It is preferable that the lithium composite compound in this embodiment is mainly comprised from Li, Ni, Co, Mn, and O, and it is especially preferable that it is the structure represented by following formula (1).
_{Li 1 + a Ni b Mn c} Co d M e O 2 + α ··· (1)
[In the formula (1), M is one or more elements selected from the group consisting of Mg, Al, Ti, Zr, Mo and Nb, and a, b, c, d, e and α are: −0.1 ≦ a ≦ 0.2, 0.7 <b ≦ 1.0, 0 ≦ c <0.3, 0 ≦ d <0.3, 0 ≦ e ≦ 0.3, b + c + d + e = 1, − It is a number that satisfies 0.2 ≦ α ≦ 0.2. ]
In addition, since c, d, and e may be 0 as described above, when the corresponding one is 0, the formula (1) is expressed as Li _{1 + a} Ni _b Co _{d Me} O _{2 + α} , Li _{1 + a Ni b Mn c M e O 2} + α, Li 1 + a Ni b Mn c Co d O 2 + α, Li 1 + a Ni b Mn c O 2 + α, Li 1 + a Ni b Co d O 2 + α, Li 1 + a Ni b M e O 2 + α and _{Li 1} + a Ni _b O _{2 + α} can be expressed as such.

  The lithium composite compound represented by the formula (1) has a composition in which the proportion of nickel (Ni) per metal element (Ni, Mn, Co and M) other than lithium (Li) exceeds 70 atomic%. . If it does in this way, since it is set as the composition which contains nickel which can extract more lithium in a high ratio, an energy density and a charge / discharge capacity can be improved more.

  Here, the significance of numerical ranges of a, b, c, d, e, and α in Equation (1) will be described.

A in the formula (1) is set to −0.1 or more and 0.2 or less. a represents the stoichiometric ratio of the lithium composite compound represented by the general formula; LiM′O ₂ , that is, the excess or deficiency of lithium from Li: M ′: O = 1: 1: 2. Here, M ′ represents a metal element (Ni, Mn, Co, and M) other than lithium (Li) in the formula (1). When lithium (Li) is insufficient, the valence of the transition metal before charging becomes high, the rate of change in valence of the transition metal when lithium is desorbed is reduced, and the charge / discharge cycle of the positive electrode active material Improved characteristics. On the other hand, when lithium (Li) is excessive, the charge / discharge capacity of the positive electrode active material decreases. Therefore, by defining a within the above numerical range, it is possible to achieve both high charge / discharge capacity and good charge / discharge cycle characteristics.

  a may be −0.05 or more and 0.10 or less. If “a” is −0.05 or more, a sufficient amount of lithium to contribute to charging and discharging is secured, so that the capacity of the positive electrode active material can be increased. In addition, when a is 0.10 or less, charge compensation due to a change in the valence of the transition metal is sufficiently performed, so that both high charge / discharge capacity and good charge / discharge cycle characteristics can be achieved.

  B in the formula (1) exceeds 0.7 and is 1.0 or less. The higher the proportion of nickel (Ni) per metal element other than lithium (Ni, Mn, Co and M), the more effective charge compensation is achieved by nickel that pulls more lithium, which is advantageous for higher capacity. is there. Therefore, by defining b in the above numerical range, it is possible to effectively increase the capacity of the positive electrode active material.

  b may be 0.75 or more and 0.90 or less. If b is 0.75 or more, the positive electrode active material has a higher capacity. Further, if b is 0.90 or less, the crystal structure of the positive electrode active material is kept relatively stable, so that the charge / discharge cycle characteristics, thermal stability, and the like of the positive electrode active material are not easily impaired.

  C in the formula (1) is 0 or more and less than 0.3. When manganese (Mn) is added, the layered structure is stably maintained even when lithium is desorbed by charging. On the other hand, when manganese (Mn) is excessive, the ratio of other transition metals such as nickel is decreased, and the charge / discharge capacity of the positive electrode active material is decreased. Therefore, by defining c within the above numerical range, it is possible to stably maintain the crystal structure of the positive electrode active material even when lithium insertion and desorption are repeated by charging and discharging, and high charge and discharge are possible. Good charge / discharge cycle characteristics, thermal stability, and the like can be obtained together with the discharge capacity.

  c may be 0.05 or more and 0.25 or less. If c is 0.05 or more, the crystal structure of the positive electrode active material is further stabilized. Moreover, since the ratio of other transition metals, such as nickel, will become high if c is 0.25 or less, it becomes difficult to impair the charging / discharging capacity | capacitance of a positive electrode active material.

  In the formula (1), d is 0 or more and less than 0.3. When cobalt (Co) is added, the charge / discharge cycle characteristics are improved without significantly impairing the charge / discharge capacity. On the other hand, when cobalt (Co) is excessive, the procurement of raw materials is deteriorated and the raw material costs are also expensive, which may be disadvantageous in industrial production of the positive electrode active material. Therefore, by defining d within the above numerical range, it is possible to achieve both high charge / discharge capacity and good charge / discharge cycle characteristics with good productivity.

  d may be 0.10 or more and 0.25 or less. When d is 0.10 or more, the charge / discharge capacity and the charge / discharge cycle characteristics are further improved. Moreover, if d is 0.25 or less, the procurement of the raw material is further improved and the raw material cost is further reduced, so that the productivity of the positive electrode active material is further improved.

  E in the formula (1) is 0 or more and 0.3 or less. When one or more elements (M) selected from the group consisting of magnesium (Mg), aluminum (Al), titanium (Ti), zirconium (Zr), molybdenum (Mo) and niobium (Nb) are added, While maintaining the electrochemical activity of the positive electrode active material, electrode performance including charge / discharge cycle characteristics can be improved. On the other hand, when M is excessive, the ratio of other transition metals such as nickel is decreased, and the charge / discharge capacity of the positive electrode active material is decreased. Therefore, by defining e in the above numerical range, both high charge / discharge capacity and good electrochemical characteristics can be achieved.

  In the formula (1), b + c + d + e = 1. In this case, since the composition is appropriate, it is possible to effectively increase the capacity of the positive electrode active material. On the other hand, when b + c + d + e ≠ 1, since the composition is not appropriate, the charge / discharge capacity of the positive electrode active material is reduced.

Α in the formula (1) is set to −0.2 or more and 0.2 or less. α represents the excess or deficiency of oxygen (O) from the stoichiometric ratio of the positive electrode active material represented by the chemical formula LiM′O ₂ . If the coefficient of oxygen (O) is within the above numerical range, defects in the crystal structure of the positive electrode active material are reduced, and good electrochemical characteristics can be obtained. α is more preferably −0.1 or more and 0.1 or less.

Moreover, the positive electrode active material according to the present embodiment includes a compound containing phosphorus as described above. In the present embodiment, the concentration of phosphorus with respect to nickel in the positive electrode active material is 0.01 mass% or more and 1.0 mass% or less. Examples of the compound containing phosphorus include lithium sulfate (Li ₂ SO ₄ ), lithium phosphate (Li ₃ PO ₄ ), and lithium sodium sulfate (LiNaSO ₄ ). When the concentration of phosphorus with respect to nickel in the positive electrode active material is 0.01% by mass or more, an effect of suppressing side reaction between the positive electrode and the electrolytic solution can be expected without causing a reduction in discharge capacity. Moreover, since content of the compound containing above phosphorus is not too high as the density | concentration of the phosphorus with respect to nickel in a positive electrode active material is 1.0 mass% or less, high discharge capacity is obtained.

  Furthermore, the positive electrode active material according to the present embodiment may include a compound containing sulfur. In this case, the concentration of sulfur with respect to nickel in the positive electrode active material can be 0.01% by mass or more and 0.2% by mass or less. When the sulfur concentration with respect to nickel in the positive electrode active material is 0.01% by mass or more, an effect of suppressing a side reaction between the positive electrode and the electrolytic solution can be expected without causing a decrease in discharge capacity. Moreover, since content of the compound containing above sulfur is not too high as the density | concentration of sulfur with respect to nickel in a positive electrode active material composition is 0.2 mass% or less, high discharge capacity is obtained.

  The average particle diameter of primary particles of the positive electrode active material is preferably 0.1 μm or more and 2 μm or less. When the average particle size is within this range, the positive electrode active material filling property of the positive electrode is improved, so that a positive electrode having a high energy density can be manufactured. Moreover, since the scattering and aggregation of the powdered positive electrode active material are reduced, the handleability is improved. The positive electrode active material may form secondary particles. The average particle diameter of the secondary particles of the positive electrode active material can be, for example, 3 μm or more and 50 μm or less, depending on the specifications of the positive electrode.

The BET specific surface area of the positive electrode active material is preferably 0.2 m ² / g or more and 2.0 m ² / g or less. When the BET specific surface area of the powdered positive electrode active material composed of a collection of primary particles and secondary particles is within this range, a positive electrode having a higher energy density can be produced.

  The particle breaking strength of the positive electrode active material is preferably 30 MPa or more and 100 MPa or less. When the particle breaking strength is within this range, the positive electrode active material particles are not easily broken in the process of producing the electrode, and the positive electrode mixture layer is coated with a positive electrode mixture slurry containing the positive electrode active material on the positive electrode current collector. When forming the film, coating defects such as peeling are less likely to occur. The particle breaking strength of the positive electrode active material can be measured using, for example, a micro compression tester.

The crystal structure of the positive electrode active material can be confirmed by, for example, X-ray diffraction (XRD).
The composition of the positive electrode active material can be confirmed by high frequency inductively coupled plasma (ICP) emission spectroscopy, atomic absorption spectrometry (AAS), or the like.

[Method of treating electroless nickel plating waste liquid]
FIG. 1 is a flow diagram illustrating a method for treating electroless nickel plating waste liquid.
As shown in FIG. 1, the electroless nickel plating waste liquid treatment method includes a separation step S1, a neutralization treatment step S2, and a first solid-liquid separation step S3.

Here, the waste liquid (electroless nickel plating waste liquid) generated after electroless nickel plating is subjected to a recovery process for recovering nickel which is a valuable metal.
Electroless nickel plating is used for surface treatment of various metal members, precision equipment parts, electronic equipment parts, etc. including engine pistons, printer shafts, piping, and pumps. An electroless nickel plating solution used as a plating bath generally contains nickel sulfate, a pH adjusting agent such as sodium hypophosphite and sodium hydroxide as a reducing agent, a complexing agent, a surfactant, and the like. . Since the electroless nickel plating waste liquid contains a large amount of valuable metals, nickel (Ni) and phosphorus (P), these are separated from each other and recovered.

  In the separation step S1, nickel ions contained in the electroless nickel plating waste liquid are separated and concentrated. For example, the electroless nickel plating waste liquid is passed through a purification column packed with a chelate resin to adsorb nickel ions to the chelate resin. Thereafter, nickel ions are eluted from the chelate resin through an acidic solution such as dilute sulfuric acid through a purification column. By these operations, for example, a nickel solution in which the nickel ions are concentrated in the form of nickel sulfate or the like is recovered.

In the neutralization treatment step S2, the nickel solution recovered in the separation step S1 is neutralized. Specifically, sodium hydroxide is added to the nickel solution to cause precipitation of nickel compounds such as nickel hydroxide. For example, the neutralization treatment performed by adding sodium hydroxide to a nickel solution containing nickel sulfate is represented by the following reaction formula (I).
NiSO ₄ + 2NaOH → Ni (OH) ₂ + Na ₂ SO ₄ (I)

In the first solid-liquid separation step S3, the nickel compound precipitated in the neutralization treatment step S2 is solid-liquid separated by filtration. By this step, for example, Na ₂ SO ₄ can be removed. Through the above steps, a nickel neutralized precipitate containing a nickel compound as a main component is recovered from the electroless nickel plating waste liquid.

  Since the nickel neutralized precipitate recovered from the electroless nickel plating waste liquid undergoes such a process, it often contains sulfur, phosphorus, sodium, and the like as impurities together with nickel that can be a raw material for the lithium composite compound. In the electroless nickel plating waste liquid treatment step, nickel neutralized precipitates containing nickel hydroxide as a main component are recovered, but are recovered as nickel carbonate by adding carbonate as an alkali. Sometimes. Sulfur contained in the nickel neutralization precipitate is derived from nickel sulfate contained in the plating solution, sulfate as a by-product of the neutralization treatment reaction, pH adjuster used for elution, etc. ing. Sodium is derived from a neutralizing agent or a sodium salt produced by neutralization.

  Impurities such as sulfur, phosphorus and sodium contained in the nickel neutralized precipitate are mainly present as water-soluble sodium sulfate. However, some of these impurities form aggregates with complexing agents, surfactants added to the plating waste liquid, organic substances mixed in the processing process of the plating waste liquid, etc., and poorly water-soluble sulfur-containing organic substances, It exists in the nickel-neutralized precipitate as a phosphate-based nickel compound, a phosphorus-containing organic substance, or the like. Since these compounds present in the nickel neutralized precipitate are difficult to dissolve even if the sludge collected by the neutralization treatment is washed with water, the nickel neutralized precipitate contains sulfur, phosphorus, sodium, etc. at a certain concentration or more. Impurities remain. Usually, several tens of mass% of sulfur and sodium and several mass% of phosphorus are present with respect to nickel in the nickel neutralized precipitate.

When the nickel neutralized precipitate contains such a large amount of impurities, when the lithium composite compound is fired, lithium sulfate (Li ₂ SO ₄ ), lithium phosphate (Li ₃ PO ₄ ), lithium sodium sulfate Since a heterogeneous phase such as (LiNaSO ₄ ) is easily formed, the charge / discharge capacity of the lithium ion secondary battery is reduced.
Therefore, in the present embodiment, a nickel composition (composition containing nickel) obtained by subjecting to a predetermined treatment step (see FIG. 2) for removing impurities such as sulfur, phosphorus, and sodium from the nickel neutralized precipitate, Used as a raw material for lithium composite compounds.

[Method of treating nickel neutralized precipitate]
FIG. 2 is a flowchart illustrating a method for treating a nickel neutralized precipitate, that is, a method for removing impurities such as sulfur, phosphorus, and sodium from the nickel neutralized precipitate.
As shown in FIG. 2, the nickel neutralized precipitate treatment method includes a roasting step S11, a water washing step S12, a second solid-liquid separation step S13, and a drying step S14.

  In the roasting step S11, the nickel neutralized precipitate is roasted. The roasting temperature in the roasting step S11 is 900 ° C. or higher and 1000 ° C. or lower. By roasting at a roasting temperature of 900 ° C. or higher, it becomes possible to remove sulfur and phosphorus in the water washing step S12 described later. If the roasting temperature is less than 900 ° C., sulfur and phosphorus cannot be removed in the water washing step S12 described later, and if it exceeds 1000 ° C., the cost becomes high.

  Although the roasting time in the roasting step S11 is not particularly limited, for example, if it is 10 hours, the reaction for forming a water-soluble compound proceeds sufficiently. The atmosphere of the roasting step S11 is not particularly limited, and can be performed in an oxidizing atmosphere such as an oxygen atmosphere or an air atmosphere, or can be performed in a non-oxidizing atmosphere such as an inert atmosphere or a vacuum atmosphere. Note that when roasting is performed in an oxidizing atmosphere, special equipment or the like is not required, and thus cost reduction can be achieved. When roasted in an inert atmosphere, the content of phosphorus contained in the positive electrode active material can be reduced.

  In the water washing step S12, the roasted product obtained in the roasting step S11 is washed with water. By washing the roasted product with water, it is possible to wash away the water-soluble compound formed containing sulfur, phosphorus and sodium contained as impurities. Therefore, the sulfur, phosphorus and sodium concentrations of the nickel composition recovered after the treatment are reduced, and it becomes possible to produce a high capacity positive electrode active material for a lithium ion secondary battery.

  In the water washing step S12, the roasted product may be washed under still water or under a water flow. As a stirrer for stirring the roasted product, for example, various apparatuses such as a single-shaft stirrer, a multi-shaft stirrer, a ball mill, a bead mill, and a planetary mixer can be used. As water used for washing, ion exchange water, purified water, pure water, and the like are preferable.

  Although the temperature of the water used for water washing is not specifically limited, it is preferable to wash with water at 40 ° C. or higher, and more preferably with water at 70 ° C. or higher and less than 100 ° C. If water temperature is 40 degreeC or more, since solubility of a water-soluble impurity etc. will become high, the sulfur concentration and sodium concentration of the nickel composition collect | recovered can fully be reduced. Further, when the water temperature is 70 ° C. or higher, the solubility of impurities is further increased, and the effect of removing impurities is improved.

By performing the roasting step S11 described above, sulfur, phosphorus, and sodium contained as impurities in the neutralized precipitate become, for example, NiSO ₄ , Na ₃ PO ₄ , Na ₂ SO _{4, and the} like. Since these compounds are water-soluble, they can be removed from the neutralized precipitate by performing the washing step S12, and the amount of impurities in the nickel composition is sufficiently reduced. The removal rate of these compounds from the neutralized precipitate is, for example, 80% or more.

  About 2nd solid-liquid separation process S13 and drying process S14 which are demonstrated below, you may perform as needed.

  In the second solid-liquid separation step S13, the roasted product washed in the water washing step S12 is subjected to solid-liquid separation. For example, water in a state where the washed roasted product is suspended is subjected to a filtration treatment, and a solid component composed of nickel oxide, an alkali metal nickel composite oxide, or the like is separated by filtration and collected. As the filtration device, a suction filtration device, a filter press, a centrifugal separator, or the like can be used.

  In the drying step S14, the solid content filtered out in the second solid-liquid separation step S13 is dried until a fine moisture content is obtained. Drying may be performed by heat drying or by air drying with various gases. The drying temperature may be, for example, about 50 ° C. or more and about 200 ° C. or less, and other drying conditions such as drying time are not particularly limited. By drying the solid content separated in the second solid-liquid separation step S13, a nickel composition with a small amount of impurities suitable for a raw material for a positive electrode active material for a lithium ion secondary battery is obtained.

[Method for producing positive electrode active material]
Next, with reference to FIG. 3, a process for producing a positive electrode active material containing the above-described lithium composite compound using the nickel composition obtained as described above will be described.
FIG. 3 is a flowchart for explaining a method for producing a positive electrode active material for a lithium ion secondary battery according to an embodiment of the present invention (hereinafter also referred to as a method for producing a positive electrode active material).
As shown in FIG. 3, the manufacturing method of a positive electrode active material has mixing process S21 and baking process S22.

  In the production of the positive electrode active material, in the mixing step S21, a lithium compound (compound containing lithium) as a lithium source and a nickel composition (composition containing nickel) are mixed to obtain a mixture. As described above, the nickel composition is subjected to the first solid-liquid separation step S3, the roasting step S11, and the water washing step S12 from the separation step S1, and the second water washing step S12 as necessary. The solid-liquid separation step S13 and the drying step S14 are performed, and the concentration of impurities is reduced.

  As the lithium compound, for example, lithium carbonate, lithium acetate, lithium nitrate, lithium hydroxide, lithium chloride, lithium sulfate and the like can be used. Of these, lithium carbonate is particularly preferable as the lithium compound. Lithium carbonate is more procurable and less expensive than other lithium compounds. Further, since the melting point is high, damage to the heat treatment apparatus and the like can be reduced.

  The nickel composition may be used in combination with a high-purity nickel composition having a different origin from the nickel composition obtained as described above. When the composition of the lithium composite compound is made to contain manganese (Mn), cobalt (Co), other metal elements (M), etc., the manganese compound, cobalt compound, and other metal elements (M) are included. What is necessary is just to mix a compound with lithium carbonate, a nickel composition, etc. In the mixing step S21, the lithium compound, the nickel composition, and the like are weighed, pulverized, and mixed to obtain a powdery mixture.

The nickel composition preferably has a sulfur concentration relative to nickel of 0.2% by mass or less. Moreover, it is preferable that the density | concentration of the phosphorus with respect to nickel is 1.0 mass% or less. In such a case, when the lithium composite compound is included in the positive electrode active material of the lithium ion secondary battery, different phases such as lithium sulfate (Li ₂ SO ₄ ) and lithium phosphate (Li ₃ PO ₄ ) are hardly generated. Thus, a high discharge capacity can be obtained. Here, when the concentration of sulfur with respect to nickel is 0.01% by mass or more, or the concentration of phosphorus with respect to nickel is 0.01% by mass or more, the nickel composition does not cause a decrease in discharge capacity, The effect of suppressing the side reaction between the positive electrode and the electrolytic solution can be expected.

  Examples of manganese compounds, cobalt compounds, and nickel compounds that can be used include oxides, hydroxides, carbonates, and acetates. Among these, it is particularly preferable to use an oxide, a hydroxide, or a carbonate. Moreover, as a compound containing another metal element (M), an oxide, a hydroxide, carbonate, acetate, nitrate etc. can be used, for example. Among these, it is particularly preferable to use an oxide, a hydroxide, or a carbonate. These compounds may be coprecipitated by a coprecipitation method and mixed with the nickel composition or the like, or may be weighed separately and mixed with the nickel composition or the like.

  The pulverization and mixing of the raw materials in the mixing step S21 can be performed using a pulverizer. As such a pulverizer, for example, a general precision pulverizer such as a ball mill, a jet mill, or a sand mill can be used. The raw material is preferably pulverized by wet pulverization. From an industrial viewpoint, it is preferable to use water as a dispersion medium. The raw material slurry obtained by wet pulverization can be dried by, for example, a dryer. As the dryer, for example, a spray dryer (spray dryer), a fluidized bed dryer, an evaporator or the like can be used.

  In the mixing step S21, when the raw material is wet pulverized, the starting raw material is atomized by the pulverization and the viscosity of the raw material slurry is increased. From the viewpoint of uniformly mixing the raw materials, it is preferable to advance the atomization and thickening of the raw materials to a certain level or more. Specifically, the ratio (viscosity / d100) of the slurry viscosity (mPa · s) at room temperature (25 ° C.) of the raw material slurry to the maximum diameter d100 (μm) in the particle size distribution is preferably 500 or more. When the viscosity / d100 is 500 or more, since the raw materials are sufficiently mixed and the particle size becomes fine, the uniformity of the composition of the lithium composite compound to be fired can be increased. Viscosity / d100 may be 500 or more when the solid content ratio of the raw material slurry is in the range of 20% by mass or less, for example, when the solid content ratio is 20% by mass.

  In the firing step S22, the mixture obtained in the mixing step S21 is fired in an oxidizing atmosphere to obtain a lithium composite compound that is appropriately crystallized. As shown in FIG. 3, the firing step S22 includes a first heat treatment step S23 for forming a first precursor, a second heat treatment step S24 for forming a second precursor, and a third heat treatment step S25 which is a finishing heat treatment. It is preferable to have.

  In the first heat treatment step S23, the mixture obtained in the mixing step S21 is heat-treated at a heat treatment temperature of 200 ° C. or more and 400 ° C. or less for 0.5 hours or more and 5 hours or less to obtain the first precursor. obtain. The first heat treatment step S23 is performed mainly for the purpose of removing moisture and the like that hinder the synthesis reaction of the lithium composite compound from the mixture obtained in the mixing step S21. In the first heat treatment step S23, if the heat treatment temperature is 200 ° C. or higher, the combustion reaction of impurities and the thermal decomposition reaction of the starting material are unlikely to be insufficient. Further, if the heat treatment temperature is 400 ° C. or lower, it is unlikely to proceed to crystallization of the lithium composite compound in this step, and the formation of a crystal structure with many defects in the presence of a gas containing moisture, impurities, etc. is prevented. be able to.

  The heat treatment temperature in the first heat treatment step S23 is preferably 250 ° C. or higher and 400 ° C. or lower, and more preferably 250 ° C. or higher and 380 ° C. or lower. If the heat treatment temperature is within this range, the progress of crystallization in this step can be suppressed while efficiently removing moisture, impurities and the like. The heat treatment time in the first heat treatment step S23 is set to an appropriate time according to, for example, the heat treatment temperature, the amount of moisture and impurities contained in the mixture, the removal target of moisture and impurities, and the like. Can do.

  The first heat treatment step S23 may be performed in an oxidizing atmosphere, may be performed in a non-oxidizing atmosphere, or may be performed in a reduced pressure atmosphere. The oxidizing atmosphere may be either an oxygen gas atmosphere or an air atmosphere. The non-oxidizing atmosphere may be an inert gas atmosphere such as nitrogen gas or argon gas. Further, the reduced-pressure atmosphere may be a reduced-pressure condition with an appropriate degree of vacuum such as an atmospheric pressure or lower.

  The first heat treatment step S23 is preferably performed under an atmosphere gas flow or exhausted by a pump. By performing the heat treatment in such an atmosphere, the gas desorbed from the mixture can be efficiently eliminated. It is preferable that the flow rate of the atmospheric gas flow or the pump exhaust is larger than the volume of the gas desorbed from the mixture.

  In the second heat treatment step S24, the first precursor obtained in the first heat treatment step S23 is heat treated at a heat treatment temperature of 450 ° C. or higher and 900 ° C. or lower for 0.1 hour or more and 50 hours or less. Two precursors are obtained. The second heat treatment step S24 is performed mainly for oxidizing nickel in the first precursor from divalent to trivalent to crystallize a lithium composite compound having a layered structure. From the viewpoint of increasing the charge / discharge capacity of the positive electrode active material, the nickel in the first precursor is preferably oxidized from divalent to trivalent without omission. The divalent nickel easily occupies lithium sites in the layered structure, and contributes to a decrease in charge / discharge capacity of the positive electrode active material. Therefore, in the second heat treatment step S24, the first precursor is heat-treated in an oxidizing gas atmosphere to oxidize the nickel valence from divalent to trivalent without omission. In the second heat treatment step S24, when the heat treatment temperature is 450 ° C. or higher, crystallization of the lithium composite compound proceeds at a favorable rate, and lithium carbonate does not remain excessively. In addition, if the heat treatment temperature is 900 ° C. or lower, the grain growth does not proceed excessively, so that the charge / discharge capacity of the positive electrode active material can be increased.

  The heat treatment temperature in the second heat treatment step S24 is more preferably 600 ° C. or higher. If it is 600 degreeC or more, the reaction efficiency of lithium carbonate will improve more. The heat treatment temperature in the second heat treatment step S24 is more preferably 700 ° C. or lower. If it is 700 or less, the crystal grains are less likely to be coarsened, which is suitable for increasing the charge / discharge capacity of the positive electrode active material.

  The heat treatment time in the second heat treatment step S24 is more preferably 0.1 hour or longer and 15 hours or shorter. If the heat treatment time is 0.1 hour or longer, the first precursor can be sufficiently reacted with oxygen. If the heat treatment time is 15 hours or less, the valence of nickel can be oxidized from divalent to trivalent without any omission and productivity can be improved.

  The second heat treatment step S24 is preferably performed in an oxidizing atmosphere. The oxygen concentration in the atmosphere is preferably 80% or more, more preferably 90% or more, further preferably 95% or more, particularly preferably 99% or more, and most preferably 100%. By performing the heat treatment under an oxidizing gas stream having a high oxygen concentration, nickel can be reliably oxidized. In addition, carbon dioxide gas generated by thermal decomposition of lithium carbonate can be reliably removed from the second precursor.

  In the third heat treatment step S25, the second precursor obtained in the second heat treatment step S24 is heat-treated at a heat treatment temperature of 700 ° C. or higher and 900 ° C. or lower to obtain a lithium composite compound having a layered structure. The third heat treatment step S25 is performed mainly for the purpose of sufficiently oxidizing nickel in the second precursor from divalent to trivalent and growing crystal grains of a lithium composite compound having a layered structure. If the heat treatment temperature in the third treatment step S25 is less than 700 ° C., the crystallization of the second precursor may be difficult to proceed, and if it exceeds 900 ° C., the layered structure of the second precursor is decomposed. Divalent nickel is produced without being suppressed, and the capacity of the resulting lithium composite compound is reduced. Therefore, in this embodiment, the heat treatment temperature is set to 700 ° C. or more and 900 ° C. or less to promote the grain growth of the second precursor and to suppress the decomposition of the layered structure, thereby obtaining the lithium composite The capacity of the compound is improved.

  In the third heat treatment step S25, the heat treatment time is preferably 0.1 hours or more and 50 hours or less, and more preferably 0.5 hours or more and 15 hours or less. In the third heat treatment step S25, if the oxygen partial pressure is low, heat is required to promote the oxidation reaction of nickel. Therefore, when the oxygen supply to the second precursor is insufficient in the third heat treatment step S25, it is necessary to increase the heat treatment temperature. When the heat treatment temperature is raised, decomposition of the layered structure is inevitable in the obtained lithium composite compound, and good electrode characteristics of the positive electrode active material cannot be obtained. However, if the heat treatment time is 0.1 hour or longer, the second precursor can be sufficiently reacted with oxygen.

  The third heat treatment step S25 is performed in an oxidizing atmosphere. The oxygen concentration in the atmosphere is preferably 80% or more, more preferably 90% or more, further preferably 95% or more, particularly preferably 99% or more, and most preferably 100%. By performing the heat treatment in an atmosphere having a high oxygen concentration, nickel can be reliably oxidized.

The lithium composite compound obtained in the third heat treatment step S25 can be classified with a sieve as necessary. For example, a sieve having an aperture of 53 μm can be used.
As described above, the positive electrode active material for a lithium ion secondary battery according to this embodiment, which includes the above-described lithium composite compound and the compound containing phosphorus, can be manufactured.

[Lithium ion secondary battery]
Next, a lithium ion secondary battery using the positive electrode active material according to the embodiment will be described.
FIG. 4 is a partial cross-sectional view schematically showing an example of a lithium ion secondary battery.
As shown in FIG. 4, a lithium ion secondary battery 100 according to this embodiment includes a bottomed cylindrical battery can 101 that contains a non-aqueous electrolyte, and a roll-like battery that is housed inside the battery can 101. A wound electrode group 110 and a disk-shaped battery lid 102 that seals the opening at the top of the battery can 101 are provided.

  The battery can 101 and the battery lid 102 are made of a metal material such as stainless steel or aluminum. The battery can 101 is sealed by fixing the battery lid 102 by caulking or the like through a sealing material 106 made of an insulating resin material.

  The wound electrode group 110 is formed by winding a belt-like positive electrode 111 and a negative electrode 112 with a separator 113 interposed therebetween. The positive electrode 111 includes a positive electrode current collector 111a and a positive electrode mixture layer 111b formed on the surface of the positive electrode current collector 111a. The negative electrode 112 includes a negative electrode current collector 112a and a negative electrode mixture layer 112b formed on the surface of the negative electrode current collector 112a. The separator 113 is made of, for example, a polyolefin such as polypropylene or polyethylene.

  The positive electrode current collector 111 a is electrically connected to the battery lid 102 via the positive electrode lead piece 103. On the other hand, the negative electrode current collector 112 a is electrically connected to the bottom of the battery can 101 via the negative electrode lead piece 104. An insulating plate 105 that prevents a short circuit is disposed between the wound electrode group 110 and the battery lid 102 and between the wound electrode group 110 and the bottom of the battery can 101. The positive electrode lead piece 103 and the negative electrode lead piece 104 are respectively formed of the same material as the positive electrode current collector 111a and the negative electrode current collector 112a, and spot welding is performed on each of the positive electrode current collector 111a and the negative electrode current collector 112a. Joined by ultrasonic pressure welding or the like.

  The positive electrode current collector 111a is formed of, for example, a metal foil such as aluminum or an aluminum alloy, an expanded metal, a punching metal, or the like. The metal foil can have a thickness of about 15 μm or more and about 25 μm or less, for example. The positive electrode mixture layer 111b includes the positive electrode active material for a lithium ion secondary battery according to the present embodiment described above. The positive electrode mixture layer 111b is formed of a positive electrode mixture formed by kneading the above-described positive electrode active material and, for example, a conductive material, a binder, and the like.

  The negative electrode current collector 112a is formed of a metal foil such as copper, a copper alloy, nickel, or a nickel alloy, an expanded metal, a punching metal, or the like. The metal foil can have a thickness of about 7 μm or more and about 10 μm or less, for example. The negative electrode mixture layer 112b includes a general negative electrode active material for a lithium ion secondary battery. The negative electrode mixture layer 112b is formed of a negative electrode mixture formed by kneading a negative electrode active material and, for example, a conductive material, a binder, and the like.

  As a negative electrode active material, the appropriate | suitable kind used in a general lithium secondary battery can be used. Specific examples of the negative electrode active material include graphitized materials obtained from natural graphite, petroleum coke, pitch coke, etc., treated at a high temperature of 2500 ° C. or higher, mesophase carbon, amorphous carbon, and amorphous on the surface of graphite. Carbon material coated with carbonaceous material, carbon material whose surface crystallinity has been reduced by mechanically treating the surface of natural graphite or artificial graphite, material with organic matter such as polymer coated and adsorbed on the carbon surface, carbon fiber Lithium metal, alloys of lithium and aluminum, tin, silicon, indium, gallium, magnesium, etc., materials carrying metal on the surface of silicon particles or carbon particles, oxides of metals such as tin, silicon, iron, titanium, etc. Is mentioned. Examples of the metal to be supported include lithium, aluminum, tin, silicon, indium, gallium, magnesium, and alloys containing any one of these as a main component. In addition, the main component in an alloy means a component with most content in an alloy.

  As the conductive material used for the positive electrode mixture layer 111b and the negative electrode mixture layer 112b, for example, carbon particles such as graphite, carbon black, acetylene black, ketjen black, and channel black, carbon fibers, and the like can be used. One of these conductive materials may be used alone, or a plurality of these conductive materials may be used in combination. The amount of the conductive material is preferably 0.5% by mass or more and 20% by mass or less with respect to the positive electrode active material and the negative electrode active material, respectively. When the conductive material is in such a range, good conductivity can be obtained and high charge / discharge capacity can be secured.

  Examples of the binder used for the positive electrode mixture layer 111b and the negative electrode mixture layer 112b include polyvinylidene fluoride (PVDF), polytetrafluoroethylene, polychlorotrifluoroethylene, polypropylene, polyethylene, acrylic polymer, imide, and the like. An appropriate material such as a polymer having an amide group or a copolymer thereof can be used. These binders may be used individually by 1 type, and may use multiple types together. Further, a thickening binder such as carboxymethylcellulose may be used in combination.

  The lithium ion secondary battery 100 having the above configuration can store electric power supplied from the outside in the wound electrode group 110 using the battery lid 102 as a positive external terminal and the bottom of the battery can 101 as a negative external terminal. . Further, the electric power stored in the wound electrode group 110 can be supplied to an external device or the like. In addition, although this lithium ion secondary battery 100 is made into the cylindrical form, the shape of a lithium secondary battery is not specifically limited. The shape of the lithium secondary battery can be, for example, a square shape, a button shape, or a laminate sheet shape.

  The lithium ion secondary battery 100 is, for example, a small power source such as a portable electronic device or a household electric device, a stationary power source such as a power storage device, an uninterruptible power supply device, or a power leveling device, a ship, a rail vehicle, or a hybrid rail vehicle. It can be used as a drive power source for hybrid vehicles, electric vehicles and the like. Since the lithium ion secondary battery 100 has a configuration in which the positive electrode mixture layer 111b includes the positive electrode active material for a lithium ion secondary battery according to the present embodiment, the manufacturing cost is low, and the nickel neutralized precipitate originates. While using the nickel composition as a raw material, the secondary battery has a higher charge / discharge capacity than before.

  The embodiment according to the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like within a scope not departing from the gist of the present invention. They are also included in the present invention.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated concretely, the technical scope of this invention is not limited to this.

Example 1
The nickel neutralized precipitate recovered from the waste liquid of the electroless nickel plating solution by neutralization was roasted at 1000 ° C. for 10 hours (roasting step S11). The nickel neutralized precipitate was roasted in an oxidizing atmosphere having an oxygen concentration of 99% or more.
Next, the roasted product obtained by roasting was washed with ion exchange water at 70 ° C. (water washing step S12). In addition, 10 times the amount of ion-exchanged water was used for the roasted product. The roasted product was washed with water by immersing the roasted product in ion-exchanged water and stirring for 1 hour.

  Subsequently, the ion-exchanged water in which the roasted product was immersed was subjected to suction filtration to separate the roasted product from solid to liquid (second solid-liquid separation step S13). And the roasted material separated by filtration was dried by holding at 120 ° C. for 2 hours to obtain a nickel composition (drying step S14).

  Next, the nickel composition obtained from the nickel neutralized precipitate is analyzed for the amounts of nickel, sodium, and phosphorus using a high frequency inductively coupled plasma emission spectrometer (OPTIMA 8300 manufactured by Perkin Elmer), and a high frequency combustion infrared absorption analyzer. The amount of sulfur was analyzed by (CSLS-600 manufactured by LECO).

  Next, a lithium composition, a nickel composition obtained from a nickel neutralized precipitate, cobalt carbonate, and manganese carbonate are mixed at a mass ratio of Li: Ni: Co: Mn of 1.04: 0.80: 0. 15: 0.05, ion-exchanged water was added so that the solid content was 20% by mass, and the mixture was mixed while wet-pulverizing with a bead mill (mixing step S21).

  Subsequently, the slurry-like mixture thus obtained was dried by a spray dryer to obtain a mixture in which raw materials were mixed. The obtained powdery mixture was fired in an oxidizing atmosphere to obtain a lithium composite compound having a layered structure belonging to the space group R-3m (firing step S22). Specifically, the mixture in which the raw materials were mixed was fired in the order of the first heat treatment step S23, the second heat treatment step S24, and the third heat treatment step S25.

  In the first heat treatment step S23, 1 kg of the mixture is filled into an alumina container having a length of 300 mm, a width of 300 mm, and a height of 100 mm, and heat-treated at a heat treatment temperature of 350 ° C. for 1 hour in a continuous transfer furnace in an air atmosphere. 1 precursor powder was obtained. In the first heat treatment step S23, moisture derived from nickel hydroxide and carbon dioxide derived from cobalt carbonate and manganese carbonate were mainly desorbed.

  In the second heat treatment step S24, in the continuous transfer furnace in which the first precursor obtained in the first heat treatment step S23 is replaced with an oxidizing atmosphere having an oxygen concentration of 90% or more, the heat treatment temperature is 600 ° C. in an oxygen stream. Heat treatment was performed over time to obtain a second precursor powder. In the second heat treatment step S24, mainly carbon dioxide derived from lithium carbonate and carbon dioxide derived from undecomposed cobalt carbonate and manganese carbonate were desorbed.

  In the third heat treatment step S25, a continuous transfer furnace in which the second precursor obtained in the second heat treatment step S24 is replaced with an oxidizing atmosphere having an oxygen concentration of 90% or higher is set to 10 at a heat treatment temperature of 755 ° C. in an oxygen stream. Heat treatment was performed for a time to obtain a lithium composite compound powder. The obtained lithium composite compound powder was classified with a sieve having an opening of 53 μm or less to obtain a positive electrode active material for a lithium secondary battery.

(Example 2)
In the roasting step S11, a positive electrode active material according to Example 2 was obtained in the same procedure as in Example 1 except that the roasting temperature was changed from 1000 ° C to 900 ° C.

Example 3
A positive electrode active material according to Example 3 was obtained in the same procedure as in Example 1 except that the temperature of water was changed from 70 ° C. to 40 ° C. in the washing step S12.

(Example 4)
In the roasting step S11, the positive electrode active material according to Example 4 was obtained in the same procedure as in Example 1 except that the roasting atmosphere was changed from oxygen to air.

(Comparative Example 1)
The processing flow of the nickel neutralized precipitate shown in FIG. 2 is not carried out, and the nickel neutralized precipitate is used as it is for the mixing step S21, except that the nickel neutralized precipitate is used in the mixing step S21. A positive electrode active material was obtained.

(Comparative Example 2)
A positive electrode active material according to Comparative Example 2 was obtained in the same procedure as Example 1 except that the roasting step S11 was not performed and the water washing step S12 was used.

(Comparative Example 3)
A positive electrode active material according to Comparative Example 3 was obtained in the same procedure as in Example 1 except that the water washing step S12 was not performed and the mixture was subjected to the mixing step S21.

(Comparative Example 4)
A positive electrode active material according to Comparative Example 4 was obtained in the same procedure as in Example 1 except that the roasting temperature was changed from 1000 ° C. to 870 ° C. in the roasting step S11.

(Comparative Example 5)
In the roasting step S11, the roasting temperature is changed from 1000 ° C. to 870 ° C., and the roasting step S11 is changed from an oxygen atmosphere to an argon atmosphere according to the same procedure as in Example 1 according to Comparative Example 5. A positive electrode active material was obtained.

(Comparative Example 6)
A positive electrode active material according to Comparative Example 6 was obtained in the same procedure as in Example 1 except that the roasting temperature was changed from 1000 ° C. to 800 ° C. in the roasting step S11.

(Comparative Example 7)
A positive electrode active material according to Comparative Example 7 was obtained in the same procedure as in Example 1 except that the roasting temperature was changed from 1000 ° C. to 600 ° C. in the roasting step S11.

(Comparative Example 8)
A positive electrode active material according to Comparative Example 8 was obtained in the same procedure as in Example 1 except that the roasting temperature was changed from 1000 ° C. to 400 ° C. in the roasting step S11.

(Comparative Example 9)
In the roasting step S11, the roasting temperature is changed from 1000 ° C. to 600 ° C., and the roasting step S11 is changed from an oxygen atmosphere to an air atmosphere according to the same procedure as that of the first embodiment according to the comparative example 9. A positive electrode active material was obtained.

Next, using the obtained positive electrode active material, a positive electrode for a lithium ion secondary battery was produced by the following procedure. First, the positive electrode active material and the carbon-based conductive material were weighed so that the mass ratio was 90: 6 and mixed using a mortar. And the obtained mixture and the binder melt | dissolved in N-methyl-2-pyrrolidone (NMP) were mixed so that mass ratio might be set to 96: 4, and it was set as the slurry. The slurry was applied to an aluminum foil having a thickness of 15 μm, dried at 120 ° C., and then compression-molded with a press so that the electrode density was 2.7 g / cm ^3, and punched into a disk shape having a diameter of 15 mm. A positive electrode for a lithium ion secondary battery was obtained.

Then, the lithium ion secondary battery was produced using the positive electrode for lithium ion secondary batteries. As the negative electrode, metallic lithium was used. In addition, as the non-aqueous electrolyte, LiPF ₆ is adjusted to 1.0 mol / L in a solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) are mixed so that the volume ratio is 3: 7. The solution dissolved in was used. Then, the positive and negative electrodes for the lithium ion secondary battery are assembled to one side and the other side of the separator, respectively, and stored together with the non-aqueous electrolyte in the battery can, and the battery lid is crimped and sealed through a sealing material And it was set as the lithium ion secondary battery.

  Next, the discharge capacity of the obtained lithium ion secondary battery was measured. Charging was performed at a constant current and a constant voltage up to a charge end voltage of 4.3 V with a charging current of 0.2 CA. The discharge was performed at a constant current up to a discharge end voltage of 2.5 V with a discharge current of 0.2 CA. The measurement results of the discharge capacity (Ah / kg) are shown in Table 1.

In addition, Table 1 below is used in the roasting temperature (° C.) and roasting atmosphere of the roasting step S11 and the roasting step S12 for the positive electrode active material manufacturing methods according to Examples 1-4 and Comparative Examples 1-9. Shows the temperature (° C) of the water. Table 1 shows the results of measuring the sulfur (S) concentration, phosphorus (P) concentration, and sodium (Na) concentration (mass ratio) with respect to nickel (Ni) in the nickel composition and the positive electrode active material (mass ratio). % Vs. Ni). Table 1 shows the composition formula of the lithium composite compound. The concentrations of Ni, S, P, and Na in the positive electrode active material were analyzed in the same manner as the nickel composition was analyzed.
Components contained in the lithium composite compound were analyzed with a high-frequency inductively coupled plasma optical emission spectrometer (OPTIMA 8300, manufactured by Perkin Elmer).

  As shown in Table 1, in Examples 1 to 4, since the nickel neutralized precipitate was roasted under appropriate conditions (roasting temperature and roasting atmosphere) and then washed with water, sulfur, phosphorus and sodium were efficiently removed. We were able to. In Examples 1 to 4, the composition of the lithium composite compound also satisfied the requirements of the present invention. As a result, a high discharge capacity was obtained with the positive electrode synthesized using these materials.

Furthermore, when Examples 1 and 2 were compared, it was found that the higher the roasting temperature, the less sulfur, phosphorus and sodium, and the higher the discharge capacity. This is considered to be because sulfur, phosphorus, and sodium were efficiently removed because the reaction of forming a water-soluble compound was promoted as the roasting temperature increased. However, if the roasting temperature is too high, the production cost increases, and therefore, 1000 ° C. or less is preferable.
Moreover, when Example 1 and 3 were compared, it turned out that there are few sulfur and sodium, and discharge capacity is so high that the washing temperature is high. This is considered to be because sulfur and sodium were efficiently removed because the solubility of the compounds that form sulfur and sodium increased as the washing temperature increased.
As a result of comparing Examples 1 and 4, it was found that there was no particular problem even if the roasting atmosphere for roasting the nickel neutralized precipitate was changed from an oxygen atmosphere to an air atmosphere.
As described above, from Examples 1 to 4, it was found that a positive electrode having a high capacity can be obtained by reducing sulfur, phosphorus, and sodium. Even if impurities such as phosphorus and sulfur are contained in a trace amount, a positive effect such as suppression of a side reaction between the positive electrode and the electrolyte can be expected without causing a decrease in discharge capacity.

  On the other hand, in Comparative Examples 1 to 4, although the composition of the lithium composite compound satisfied the requirements of the present invention, the nickel neutralized precipitate was not roasted, washed with water, or roasted However, it was not set as an appropriate condition. Therefore, Comparative Examples 1 to 4 contained a large amount of at least one of sulfur, phosphorus, and sodium. And this caused the discharge capacity to be low.

Specifically, in Comparative Examples 1 and 3, since the water washing step S12 was not performed, the amounts of sulfur, phosphorus, and sodium in the nickel composition and the positive electrode active material were relatively high.
In Comparative Example 2, since the roasting step S11 was not performed, the amounts of sulfur and phosphorus in the nickel composition and the positive electrode active material were relatively high.
Although Comparative Examples 4-9 performed the baking process S11 and the water washing process S12, since the baking temperature was less than 900 degreeC, formation of a water-soluble compound did not fully advance, sulfur in nickel composition, Phosphorus could not be reduced sufficiently at the same time. Since Comparative Examples 4 to 9 were fired while a large amount of sulfur and phosphorus contained in the nickel neutralized precipitate remained, lithium sulfate (Li ₂ SO ₄ ), lithium phosphate (Li ₃ PO ₄ ) and other heterogeneous phases are considered, and it is considered that the number of crystal regions not showing electrochemical activity increased.
As a result, it is considered that all of Comparative Examples 1 to 9 resulted in a low positive electrode discharge capacity.

  From the above, it was found that both the roasting step S11 and the water washing step S12 are essential in order to effectively reduce impurities contained as impurities in the nickel neutralized precipitate.

DESCRIPTION OF SYMBOLS 100 Lithium ion secondary battery 101 Battery can 102 Battery cover 103 Positive electrode lead piece 104 Negative electrode lead piece 105 Insulating plate 106 Sealing material 110 Winding electrode group 111 Positive electrode 111a Positive electrode collector 111b Positive electrode mixture layer 112 Negative electrode 112a Negative electrode collector 112b Negative electrode mixture layer 113 Separator

Claims (7)

A mixing step of mixing a compound containing lithium and a composition containing nickel;
Firing the mixture obtained in the mixing step in an oxidizing atmosphere to obtain a lithium composite compound, and
The composition containing nickel is obtained by a roasting step of roasting a neutralized precipitate recovered from a waste solution of an electroless nickel plating solution by a neutralization process at 900 ° C. or higher and 1000 ° C. or lower, and the roasting step. A method for producing a positive electrode active material for a lithium ion secondary battery, wherein the composition is obtained through a water washing step of washing the roasted product.   2. The method for producing a positive electrode active material for a lithium ion secondary battery according to claim 1, wherein the composition containing nickel has a sulfur concentration relative to nickel of 0.2 mass% or less.   3. The method for producing a positive electrode active material for a lithium ion secondary battery according to claim 1, wherein the composition containing nickel has a phosphorus concentration with respect to nickel of 1.0% by mass or less. The lithium composite compound is represented by the following formula (1):
The mixing step is a step of mixing the compound containing lithium, the composition containing nickel, and a compound containing a metal element other than lithium and nickel in the following formula (1). The manufacturing method of the positive electrode active material for lithium ion secondary batteries as described in any one of Claim 1 thru | or 3.
_{Li 1 + a Ni b Mn c} Co d M e O 2 + α ··· (1)
[In the formula (1), M is one or more elements selected from the group consisting of Mg, Al, Ti, Zr, Mo and Nb, and a, b, c, d, e and α are: −0.1 ≦ a ≦ 0.2, 0.7 <b ≦ 1.0, 0 ≦ c <0.3, 0 ≦ d <0.3, 0 ≦ e ≦ 0.3, b + c + d + e = 1, − It is a number that satisfies 0.2 ≦ α ≦ 0.2. ]   The method for producing a positive electrode active material for a lithium ion secondary battery according to any one of claims 1 to 4, wherein the roasting in the roasting step is performed in an oxidizing atmosphere. A lithium composite oxide represented by the following formula (1) and a compound containing phosphorus,
A positive electrode active material for a lithium ion secondary battery, wherein a concentration of phosphorus with respect to nickel in the positive electrode active material is 0.01% by mass or more and 1.0% by mass or less.
_{Li 1 + a Ni b Mn c} Co d M e O 2 + α ··· (1)
[In the formula (1), M is one or more elements selected from the group consisting of Mg, Al, Ti, Zr, Mo and Nb, and a, b, c, d, e and α are: −0.1 ≦ a ≦ 0.2, 0.7 <b ≦ 1.0, 0 ≦ c <0.3, 0 ≦ d <0.3, 0 ≦ e ≦ 0.3, b + c + d + e = 1, − It is a number that satisfies 0.2 ≦ α ≦ 0.2. ]   The lithium ion secondary battery according to claim 6, comprising a compound containing sulfur, wherein the concentration of sulfur with respect to nickel in the positive electrode active material is 0.01 mass% or more and 0.2 mass% or less. Positive electrode active material for secondary battery.

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