WO2016013674A1 - Nickel manganese compound hydroxide particles and method for producing same - Google Patents

Abstract

[Problem] To provide nickel manganese compound hydroxide particles which can be used as a precursor for a cathode active material in which sodium content is reduced and for which reduction of and variation in battery characteristics are prevented. [Solution] A slurry including nickel manganese compound hydroxide particles is obtained by a crystallization reaction using sodium hydroxide as a neutralizer, the nickel manganese compound hydroxide particles being represented by general formula (A): Ni_xMn_yCo_zM_t(OH)_2+a (x+y+z+t=1, 0.3≤x≤0.7, 0.1≤y≤0.55, 0≤z≤0.4, 0≤t≤0.1, 0≤a≤0.5, where M is one or more elements selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W). The nickel manganese compound hydroxide particles are washed in a state in which an average valence of the metallic elements in the nickel manganese compound hydroxide particles is controlled at 2.4 or less.

Description

Nickel-manganese composite hydroxide particles and method for producing the same

The present invention relates to nickel manganese composite hydroxide particles, which are precursors of a positive electrode active material for a non-aqueous electrolyte secondary battery, and a method for producing the same.

In recent years, with the widespread use of portable electronic devices such as mobile phones and notebook computers, there is an increasing demand for small and lightweight secondary batteries having high energy density. In addition, development of a high output secondary battery is strongly desired as a power source for electric vehicles such as hybrid vehicles.

As a secondary battery that satisfies such requirements, there is a lithium ion secondary battery that is a kind of non-aqueous electrolyte secondary battery. This lithium ion secondary battery is composed of a negative electrode, a positive electrode, an electrolytic solution, and the like, and a material capable of desorbing and inserting lithium is used as an active material used as a material for the negative electrode and the positive electrode.

Currently, research and development of lithium-ion secondary batteries are being actively carried out. Among them, lithium using a positive electrode active material composed of layered or spinel type lithium transition metal composite oxide particles as a positive electrode material. Since an ion secondary battery can obtain a high voltage of 4 V class, it is being put to practical use as a material having a high energy density.

As such a positive electrode active material, lithium cobalt composite oxide (LiCoO ₂ ), which is currently relatively easy to synthesize, lithium nickel composite oxide (LiNiO ₂ ) using nickel which is cheaper than cobalt with a small amount of reserves, Lithium manganese composite oxide (LiMn ₂ O ₄ ), lithium nickel manganese composite oxide (LiNi _0.5 Mn _0.5 O ₂ ), lithium nickel cobalt manganese composite oxide (LiNi _{1 /} Lithium transition metal composite oxides such as ₃ Co _1/3 Mn _1/3 O ₂ ) have been proposed.

Among these positive electrode active materials, as a positive electrode material, lithium nickel manganese composite oxide having excellent thermal stability and high capacity without using cobalt, or good cycle characteristics, low resistance and high output can be obtained. Lithium nickel manganese cobalt composite oxide, which can be used, is currently attracting attention.

In order to obtain such lithium ion secondary battery with good performance, specifically battery characteristics of high cycle characteristics, low resistance, and high output, a lithium transition metal composite oxide used as a positive electrode active material It is required to strictly control the powder properties such as the average particle size, particle size distribution, specific surface area, and crystallite size, and the crystallinity thereof.

Various methods have been proposed as a method for producing a positive electrode active material. Among them, the method of using the transition metal composite hydroxide particles obtained by the crystallization reaction as the precursor of the positive electrode active material has a uniform composition at the atomic level by appropriately controlling the crystallization conditions, and There is an advantage that a positive electrode active material excellent in powder characteristics can be obtained.

Moreover, since the impurity component contained in the lithium transition metal composite oxide particles may cause a decrease in battery characteristics, it becomes an important management item in production, as with the above-described powder characteristics and crystallinity. . That is, it is necessary to reduce the amount of impurities contained in the transition metal composite hydroxide particles that are precursors of the positive electrode active material and to optimize the impurities.

In JP2013-171743A and JP2013-171744A, transition metal composite hydroxide particles are obtained by crystallization reaction, and the obtained transition metal composite hydroxide particles are filtered or filtered. Prior to this, it is described that excess base and ammonia contained in the transition metal composite hydroxide particles are removed by washing with a centrifugal separator, a suction filter, or the like.

In the production method using such a crystallization reaction, an inexpensive sodium hydroxide aqueous solution is used as a neutralizing agent. For this reason, sodium resulting from the sodium hydroxide aqueous solution is mixed as an impurity in the transition metal composite hydroxide particles obtained by the crystallization reaction. Such sodium can be removed to some extent by long-time washing with a large amount of water as described above. However, it is difficult to sufficiently remove all of the sodium contained in various states in the particles.

By the way, in International Publication No. WO2012 / 1318181, the aqueous solution for nucleation is controlled so that the pH value on the basis of the liquid temperature of 25 ° C. is 12.0 to 14.0, and the oxygen concentration is 1% by volume. A nucleation step in which nucleation is performed in an oxidizing atmosphere that exceeds the above, and an aqueous solution for particle growth containing nuclei formed in the nucleation step, having a pH value of 10.5 to 12.0 at a liquid temperature of 25 ° C. And a mixed atmosphere of oxygen and inert gas having an oxygen concentration of 1% by volume or less from an oxidizing atmosphere in the range of 0% to 40% with respect to the whole particle growing process from the beginning of the particle growing process. And a crystallization step comprising a particle growth step for growing the nuclei, and having a central portion made of fine primary particles and comprising plate-like primary particles larger than the fine primary particles outside the central portion. Having an outer shell, The Kkerumangan composite hydroxide particles, it is disclosed that obtained by industrial-scale mass production.

By using nickel-manganese composite hydroxide particles having such a structure as a precursor, a hollow structure comprising an outer shell portion in which aggregated primary particles are sintered and a hollow portion existing inside thereof is provided. Thus, a positive electrode active material having excellent powder characteristics can be obtained.

However, in the case of nickel-manganese composite hydroxide particles having such a structure, sodium contained in the central part consisting of fine primary particles, particularly by simply washing the obtained nickel-manganese composite hydroxide particles. Is extremely difficult to remove.

In such an industrial-scale mass production process, even when the transition metal composite hydroxide particles obtained by the crystallization reaction are washed, two positive electrode active materials using the transition metal composite hydroxide particles as a precursor are used. In secondary batteries, battery characteristics such as charge / discharge capacity and output characteristics are degraded and varied due to sodium in the particles. Thus, in the field of non-aqueous electrolyte secondary batteries, the presence of sodium in the positive electrode active material, which affects the battery characteristics of the secondary battery, has become a major problem.

JP 2013-171743 A JP 2013-171744 A International Publication No. WO2012 / 131818

The present invention is a positive electrode active material capable of producing a non-aqueous electrolyte secondary battery in which deterioration and variation in battery characteristics are suppressed, particularly in mass production on an industrial scale, and transition metal composite hydroxide particles that are precursors thereof, particularly An object of the present invention is to provide nickel manganese composite hydroxide particles.

Method for producing a nickel-manganese composite hydroxide particles of the present invention, the crystallization reaction with sodium hydroxide as a neutralizing agent, the general formula _{(A): Ni x Mn y} Co z M t (OH) 2 + a (X + y + z + t = 1, 0.3 ≦ x ≦ 0.7, 0.1 ≦ y ≦ 0.55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, 0 ≦ a ≦ 0.5, M Is a slurry containing nickel-manganese composite hydroxide particles represented by one or more elements selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W). A crystallization step to be obtained, and a washing step for washing the nickel manganese composite hydroxide particles in a state where the average valence of the metal element in the nickel manganese composite hydroxide particles is controlled to 2.4 or less. It is characterized by that.

It is preferable that the slurry is held in a non-oxidizing atmosphere in which the oxygen partial pressure is controlled to 10 Pa or less from the end of the crystallization process to the start of the cleaning process.

Alternatively or additionally, the slurry is controlled to have a pH value in the range of 10.5 to 13.0 based on a liquid temperature of 25 ° C. from the end of the crystallization step to the start of the washing step. It is preferable to hold at.

In addition, when holding the slurry in an air atmosphere while controlling the pH value from the end of the crystallization process to the start of the washing process, the holding time is preferably 10 hours or less. .

The method for producing nickel manganese composite hydroxide particles of the present invention is for producing nickel manganese composite hydroxide particles composed of secondary particles formed by agglomeration of a plurality of primary particles obtained by a crystallization reaction. Although applied, in particular, the nickel manganese composite hydroxide particles have a central portion made of fine primary particles, and are made of plate-like primary particles larger than the fine primary particles outside the central portion. It is suitably applied to the production of nickel manganese composite hydroxide particles composed of secondary particles having an outer shell portion. In this case, specifically, in the crystallization step, the aqueous solution for nucleation is controlled so that the pH value on the basis of the liquid temperature of 25 ° C. is 12.0 to 14.0, and the oxygen concentration is 1 volume. A nucleation step in which nucleation is performed in an oxidizing atmosphere exceeding 50%, and an aqueous solution for particle growth containing the nuclei formed in the nucleation step, the pH value at a liquid temperature of 25 ° C. is 10.5 to 12.2. A mixture of oxygen and inert gas with an oxygen concentration of 1% by volume or less from an oxidizing atmosphere in the range of 0% to 40% of the entire particle growth process from the start of the particle growth process. And a particle growth step for growing the nucleus by switching to an atmosphere.

Nickel manganese composite hydroxide particles of the present invention have the general formula _{(A): Ni x Mn y} Co z M t (OH) 2 + a (x + y + z + t = 1,0.3 ≦ x ≦ 0.7,0.1 ≦ y ≦ 0.55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, 0 ≦ a ≦ 0.5, M is Mg, Ca, Al, Ti, V, Cr, Zr, Nb, One or more elements selected from Mo, Hf, Ta, and W), secondary particles formed by aggregation of a plurality of primary particles, and an alkali metal content of 500 mass ppm or less It is characterized by being.

The nickel manganese composite hydroxide particles of the present invention have a central portion made of fine primary particles, and an outer shell portion made of plate-like primary particles larger than the fine primary particles outside the central portion. It is preferably composed of secondary particles.

Incidentally, nickel manganese composite hydroxide particles of the present invention have the general formula _{(B): Ni x Mn y} Co z M t (OH) 2 + a (x + y + z + t = 1,0.3 ≦ x ≦ 0.6,0 .2 ≦ y ≦ 0.4, 0.1 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.02, 0 ≦ a ≦ 0.5, M is Mg, Ca, Al, Ti, V, Cr, It is preferable to have a composition represented by one or more elements selected from Zr, Nb, Mo, Hf, Ta, and W.

The positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is characterized by comprising lithium nickel manganese composite oxide particles having the nickel manganese composite hydroxide particles as precursors.

According to the present invention, particularly in mass production on an industrial scale, when nickel manganese composite hydroxide particles containing manganese as a constituent metal element are obtained by a crystallization reaction using inexpensive sodium hydroxide as a neutralizing agent However, the alkali metal content, particularly the sodium content, can be reduced. In the positive electrode active material for a non-aqueous electrolyte secondary battery obtained using such nickel manganese composite hydroxide particles as a precursor, the positive electrode active material is used as the positive electrode in order to inherit the powder characteristics of low alkali metal content. By using it as a material, a non-aqueous electrolyte secondary battery in which deterioration and variation in battery characteristics due to the presence of alkali metal are suppressed is provided. For this reason, the industrial significance of the present invention is extremely large.

In view of the problems described above, the present inventors have used a transition metal composite hydroxide particle, in particular, a positive electrode active material containing nickel manganese composite hydroxide particles as a precursor, containing manganese as a constituent metal element. When the secondary battery was configured, we conducted intensive research on the cause of the deterioration and variation in battery characteristics.

As a result, the inventors have obtained knowledge that the oxidation state of nickel manganese composite hydroxide particles during washing affects the removal of alkali metals, particularly sodium, and have reached the present invention.

1. Method for Producing Nickel Manganese Composite Hydroxide Particles The method for producing nickel manganese composite hydroxide particles of the present invention comprises a general formula (A): Ni _x M _{y y} by a crystallization reaction using sodium hydroxide as a neutralizing agent. Co _z M _t (OH) _{2 + a} (x + y + z + t = 1, 0.3 ≦ x ≦ 0.7, 0.1 ≦ y ≦ 0.55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1 , 0 ≦ a ≦ 0.5, M is one or more elements selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W) A crystallization step of obtaining a slurry containing manganese composite hydroxide particles, and the nickel manganese composite hydroxide in a state in which the average valence of metal elements in the nickel manganese composite hydroxide particles is controlled to 2.4 or less. And a cleaning step for cleaning the particles.

Nickel-manganese composite hydroxide particles (hereinafter simply referred to as “composite hydroxide particles”) obtained by crystallization reaction are usually composed of secondary particles formed by aggregation of a plurality of primary particles. Most of the alkali metal salt adhering to the primary particle surface during crystallization is removed by washing with water after crystallization. However, the alkali metal contained as an impurity exists not only in the alkali metal salt adhering to the surface of the primary particle, but also in a state in which a part is incorporated in the crystal of the composite hydroxide particle. Such an alkali metal is difficult to remove by washing with water after crystallization, and when the alkali metal taken into the crystal increases, the content of the alkali metal as an impurity increases.

Although the details are unknown, the present inventor has obtained knowledge that an alkali metal, particularly sodium, is taken into the crystals of the composite hydroxide particles with the oxidation of manganese in the composite hydroxide particles. That is, manganese in the composite hydroxide particles is easily oxidized, and when the composite hydroxide particles obtained by the crystallization reaction are placed in an atmosphere in which oxygen is present, the composite hydroxide particles are oxidized. Along with this, in particular, the degree to which manganese is oxidized increases. As the degree of oxidation of manganese increases in this way, the content of alkali metal taken into the crystal increases accordingly. Thus, even if it wash | cleans with water after the crystallization process about the alkali metal taken in in the crystal | crystallization, the removal will become very difficult.

Therefore, by controlling the degree of oxidation of the composite hydroxide particles in advance, specifically, the average valence of the metal element in the composite hydroxide particles at the start of the cleaning process is controlled to 2.4 or less. By this, it becomes possible to suppress the alkali metal taken into the crystal.

Hereinafter, the method for producing composite hydroxide particles of the present invention is divided into (1) a crystallization step, (2) from the end of the crystallization step to the start of the cleaning step, and (3) the cleaning step. explain.

(1) Crystallization step The crystallization step is a step of obtaining composite hydroxide particles by a crystallization reaction. More specifically, nickel (Ni) and manganese (Mn), which are main metal elements, or a mixed aqueous solution containing nickel, manganese, and cobalt (Co) and an additive element M, water as a neutralizing agent. This is a step of forming a reaction aqueous solution by supplying an aqueous solution of sodium oxide and a complexing agent such as aqueous ammonia, crystallizing the composite hydroxide particles, and obtaining a slurry containing the composite hydroxide particles.

[Crystallization conditions]
In the present invention, the conditions in the crystallization step are not particularly limited, and are appropriately selected according to the composition, particle structure or powder characteristics of the target composite hydroxide particles.

Formula _{(A): Ni x Mn y} Co z M t (OH) 2 + a (x + y + z + t = 1,0.3 ≦ x ≦ 0.7,0.1 ≦ y ≦ 0.55,0 ≦ z ≦ 0 .4, 0 ≦ t ≦ 0.1, 0 ≦ a ≦ 0.5, M is selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W In the case of obtaining composite hydroxide particles represented by an element of more than species, the ratio of the metal compounds is adjusted so that the composition is the same as the composition of the composite hydroxide particles, and these metal compounds are dissolved in water. To produce a mixed aqueous solution.

In addition, by controlling the pH of the reaction aqueous solution (pH value based on a liquid temperature of 25 ° C.), the crystallization process grows mainly from the nucleation process in which nucleation occurs and the nuclei generated in the nucleation process as particles. It is preferable to divide into the particle growth process to be performed. By such a process, the composite hydroxide has a uniform composition at the atomic level and is composed of secondary particles obtained by agglomeration of primary particles, and has excellent powder characteristics such as a narrow particle size distribution. Particles are obtained.

In particular, a composite hydroxide particle having a particle structure composed of a central part composed of fine primary particles and an outer shell part formed outside the central part and composed of plate-like primary particles larger than the fine primary particles. In the case of obtaining, for example, as described in International Publication No. WO2012 / 131881, the aqueous solution for nucleation has a pH value of 12.0 to 14.0 based on a liquid temperature of 25 ° C. A nucleation step for performing nucleation in an oxidizing atmosphere with an oxygen concentration exceeding 1% by volume, and an aqueous solution for particle growth containing nuclei formed in the nucleation step at a liquid temperature of 25 ° C. The pH value is controlled to be 10.5 to 12.0, and the oxygen concentration is 1 volume from the oxidizing atmosphere in the range of 0% to 40% with respect to the whole particle growth process from the start of the particle growth process. % Oxygen and inert Switch to scan a mixed atmosphere of, by the particle growth step of growing the nucleus to form a crystallization step.

However, in the crystallization process, the atmosphere in the reaction vessel including the reaction field (in the reaction aqueous solution) during the crystallization reaction (hereinafter referred to as “reaction atmosphere”) is required unless an oxidizing atmosphere needs to be selected. A non-oxidizing atmosphere is preferable, and a nitrogen atmosphere is more preferable. Specifically, the oxygen partial pressure in the reaction atmosphere is preferably 1013 Pa or less, more preferably 1000 Pa or less, and even more preferably 990 Pa or less. However, in the present invention, it is preferable to hold the slurry containing nickel manganese composite hydroxide particles in a non-oxidizing atmosphere in which the oxygen partial pressure is controlled to 10 Pa or less between the end of crystallization and the start of washing. When such conditions are employed, the non-oxidizing atmosphere in the crystallization process can also be adjusted so that the oxygen partial pressure is 10 Pa or less. By performing the crystallization step in such a reaction atmosphere, it is possible to suppress the oxidation of manganese during the crystallization reaction and further reduce the alkali metal, particularly sodium, taken into the crystal.

(2) From the end of the crystallization process to the start of the washing process The composite hydroxide particles obtained by the crystallization reaction in the crystallization process are subjected to the washing process. However, in general, it is retained in the slurry to stabilize the composite hydroxide particles. Further, in industrial scale production, the transition from the crystallization process to the washing process is not smoothly performed, and usually, the transition requires a time from several hours to over 24 hours.

Therefore, after completion of the crystallization process, it is not immediately subjected to the washing process. During this time, for example, in the batch crystallization method, in order to suppress aggregation of the composite hydroxide particles in the retained slurry, The slurry obtained in the deposition process is stirred at a constant speed. Moreover, in the collection | recovery in a continuous crystallization method, after collect | recovering this slurry to the tank prepared separately, the slurry is hold | maintained, stirring at a fixed speed | rate.

[Average valence of metal elements]
At the end of the crystallization step, the average valence of the metal elements constituting the composite hydroxide particles obtained by the crystallization reaction is generally in the range of 2.00 to 2.15. However, as described above, in industrial scale mass production, the composite hydroxide particles are held in a slurry state, usually in an air atmosphere. In addition, this slurry is held while being stirred from the viewpoint of preventing aggregation of the composite hydroxide particles. In an atmosphere such as an air atmosphere where oxygen is present, the composite hydroxide particles are easily oxidized, and this is affected by the degree of stirring of the slurry and the contact state with the air atmosphere. Average valence increases. When this average valence exceeds 2.4, the degree of oxidation of manganese constituting the composite hydroxide particles increases, and along with this, more alkali metals are incorporated into the crystal. The alkali metal taken into the crystal is difficult to remove even by washing with water after crystallization, and the content of the alkali metal remaining in the composite hydroxide particles cannot be reduced.

Thus, by controlling the average valence of the metal element in the composite hydroxide particles to 2.4 or less, the alkali metal incorporated in the crystal is suppressed, and the primary particles are mainly washed by washing after crystallization. The alkali metal existing on the surface is removed. Thus, specifically, the content of alkali metal remaining in the composite hydroxide particles, particularly the content of sodium, can be reduced to 500 ppm by mass or less.

The average valence of the metal element in the composite hydroxide particles means the arithmetic average value of the valences of nickel, cobalt, manganese, and additive element M contained in the composite hydroxide particles, and the composite hydroxide It can be obtained by redox titration of a solution obtained by dissolving particles in hydrochloric acid.

Between the end of the crystallization process and the start of the washing process, the average valence of the metal element in the composite hydroxide particles is preferably controlled to 2.2 or less, more preferably 2.15 or less.

[Atmosphere control]
The atmosphere from the end of the crystallization process to the start of the cleaning process (hereinafter referred to as “holding atmosphere”) is preferably a non-oxidizing atmosphere, and more preferably a nitrogen atmosphere. That is, it is preferable to control the oxygen partial pressure in the holding atmosphere to 10 Pa or less, preferably 5 Pa or less. By controlling the holding atmosphere in such a range, even if the time from the end of the crystallization reaction to the start of the washing process is a long time, for example, 12 hours or more, the average of the main metal element M The valence can be kept below 2.4. On the other hand, when the oxygen partial pressure in the holding atmosphere exceeds 10 Pa, when the time from the completion of the crystallization reaction to the start of the washing step is long, for example, 12 hours or more, The average valence of the metal element may exceed 2.4.

In order to perform such atmosphere control, an inert gas, preferably nitrogen gas, is introduced into the closed space in which the composite hydroxide particles or the slurry containing the composite hydroxide particles is held during this time. Thus, the oxygen partial pressure may be 10 Pa or less from the oxygen partial pressure (for example, 1013 Pa or less) at the end of the crystallization reaction. Alternatively, the atmosphere during the crystallization reaction may be set as a non-oxidizing atmosphere in advance so that the non-oxidizing atmosphere is maintained even after the crystallization process is completed. Furthermore, even when the composite hydroxide particles are continuously separated by solid-liquid separation due to overflow, the composite hydroxide particles directly come into contact with the atmosphere. It is effective to maintain an atmosphere of 10 Pa or less.

In the present invention, an air atmosphere (oxygen partial pressure: 21273 Pa) can be selected as the holding atmosphere. In this case, the average valence of the metal element in the composite hydroxide particles is 2.4 or less. To control. For example, in the case where the slurry is stirred and held to an extent that prevents aggregation without involving an atmospheric atmosphere, the time from the end of the crystallization process to the start of the washing process is within 12 hours, preferably within 10 hours, More preferably, it must be within 8 hours. Stirring involving air atmosphere promotes oxidation of metal elements, so it is necessary to further reduce the retention time in the slurry state, and the average valence of metal elements depending on stirring conditions can be controlled to 2.4 or less. It is sufficient to confirm the appropriate holding time by a preliminary test.

When producing a large amount of composite hydroxide particles in industrial scale production, it usually takes a long time from the end of the crystallization process to the start of the washing process, and in the air atmosphere while controlling the stirring state, Since it is difficult to maintain the average valence of the metal element at 2.4 or less, it is preferable to maintain the holding atmosphere in a non-oxidizing atmosphere.

[PH value of slurry]
The higher the pH value of the slurry containing the composite hydroxide particles obtained in the crystallization step, the easier the oxidation proceeds. For this reason, the pH value based on the liquid temperature of the slurry at 25 ° C. is preferably 13.0 or less, more preferably 12.5 or less, and even more preferably 12.0 or less. By controlling the pH value of the slurry in such a range, oxidation of the composite hydroxide particles can be suppressed, and incorporation of alkali metal into crystals due to oxidation of manganese can be reduced. However, the pH value of the slurry is preferably 10.5 or more, more preferably 11.0 or more, based on the liquid temperature of 25 ° C. By controlling the lower limit of the pH value of the slurry within such a range, damage to the composite hydroxide particles in the slurry can be suppressed.

(3) Washing step As described above, since the composite hydroxide particles obtained in the crystallization step have a high pH value, oxidation proceeds immediately in an atmosphere containing oxygen. In particular, in an atmosphere containing oxygen at a high concentration or in a high temperature atmosphere, the oxidation rate is fast, and the degree of oxidation of the composite hydroxide particles increases rapidly. For this reason, at the time of starting the cleaning step, the average valence of the metal elements constituting the composite hydroxide particles can be controlled to 2.4 or less, preferably 2.2 or less, more preferably 2.15 or less. is important. As a result, the oxidation of manganese in the composite hydroxide particles subjected to the washing process is suppressed, the amount of alkali metal taken into the crystal along with the oxidation of manganese is reduced, and the alkali metal is on the surface of the primary particles. Stays present. The alkali metal remaining on the surface of the primary particles of such composite hydroxide particles can be removed sufficiently and easily by washing.

The method for cleaning the composite hydroxide particles is not particularly limited, and for example, a method of adding an appropriate amount of cleaning water to the slurry containing the composite hydroxide particles and stirring the slurry can be employed. At this time, as washing water, it is preferable to use pure water such as ion-exchanged water or distilled water having as little impurity content as possible from the viewpoint of preventing contamination of impurities. Further, it is preferable to perform the cleaning in a plurality of times rather than only once. In addition, the composite hydroxide particles can be washed using a filter press or the like. Furthermore, after the slurry is filtered or before it is filtered, it can be washed using a centrifugal separator, a suction filter, or the like. In any case, it is necessary to appropriately adjust the cleaning conditions according to the characteristics of the apparatus to be used, the amount of composite hydroxide particles to be cleaned, and the like.

2. Composite hydroxide particles of the transition metal complex hydroxide particles present invention is obtained by the production method of the present invention described above, the general formula _{(A): Ni x Mn y} Co z M t (OH) 2 + a (x + y + z + t = 1, 0.3 ≦ x ≦ 0.7, 0.1 ≦ y ≦ 0.55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, 0 ≦ a ≦ 0.5, M is Secondary element formed by agglomeration of a plurality of primary particles represented by Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W). It consists of particle | grains, and content of an alkali metal is 500 mass ppm or less, It is characterized by the above-mentioned. In the composite hydroxide particles of the present invention, the average valence of the metal element is in the range of 2.4 or less at the end of the washing step, but thereafter, the oxidation proceeds with time, so that the average valence is not necessarily limited. The numbers are not in this range.

(1) Composition [Main metal elements]
The composite hydroxide particles of the present invention contain at least nickel (Ni) and manganese (Mn) as main metal elements, and preferably contain nickel, manganese, and cobalt (Co). The present invention can be suitably applied to composite hydroxide particles containing manganese in which y in general formula (A) is 0.1 or more and 0.55 or less, indicating the composition of manganese. .

Nickel is an element that contributes to improving battery capacity. Therefore, the ratio of the number of nickel atoms to the total number of atoms of the metal element (Ni / total metal elements) is preferably 0.3 to 0.7, more preferably 0.3 to 0.6, and even more preferably 0. 3 to 0.5. When the value of Ni / all metal elements is less than 0.3, a secondary battery using a positive electrode active material having the composite hydroxide particles as a precursor does not have a high capacity. On the other hand, if the Ni / M ratio exceeds 0.7, the content of cobalt and manganese decreases, and the effect of addition cannot be sufficiently obtained.

Manganese is an element that contributes to improved thermal stability. Therefore, the ratio of the number of manganese atoms to the total number of atoms of metal elements (Mn / total metal elements) is preferably 0.1 to 0.55, more preferably 0.2 to 0.4, and even more preferably. 0.2 to 0.35. If the value of Mn / all metal elements is less than 0.1, the thermal stability cannot be sufficiently improved. On the other hand, if the value of Mn / all metal elements exceeds 0.55, the elution amount of manganese increases at high temperature operation, and the cycle characteristics may be deteriorated.

Cobalt is an element that contributes to improved cycle characteristics. In the present invention, addition of cobalt is optional, but when cobalt is added, the ratio of the number of cobalt atoms to the total number of atoms of the metal element (Co / total metal elements) is preferably 0.05 to 0.00. 4, more preferably 0.1 to 0.4, and still more preferably 0.2 to 0.35. When adding cobalt, if the value of Co / all metal elements is less than 0.05, the effect of addition cannot be sufficiently obtained. On the other hand, if the value of Co / all metal elements exceeds 0.4, the initial discharge capacity may be reduced.

[Additive elements]
The composite hydroxide particles of the present invention can contain an additive element M in addition to the main metal element. By containing the additive element M, the charge / discharge capacity, the output characteristics, and the like of the secondary battery using the positive electrode active material having the composite hydroxide particles as a precursor can be improved. Examples of the additive element M include magnesium (Mg), calcium (Ca), aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), zirconium (Zr), niobium (Nb), and molybdenum. At least one selected from the group consisting of (Mo), hafnium (Hf), tantalum (Ta), and tungsten (W) can be used.

The value of t in the general formula (A) indicating the content of the additive element M is 0.1 or less, preferably 0.05 or less, more preferably 0.02 or less. If the value of t exceeds 0.1, the metal element that contributes to the Redox reaction decreases, and the battery capacity decreases.

[Hydroxyl group]
The value of a in the general formula (A) indicating the content of the hydroxyl group (OH) contained in the composite hydroxide particles of the present invention is the average value of the metal elements in the composite hydroxide at the end of the crystallization process. Controlled by number. That is, a is expressed as 1 × average valence of metal element−2. When the average valence of metal element at the end of the crystallization process is 2.1, a is 0.1.

[Preferred examples of composition]
Nickel manganese composite hydroxide particles of the present invention have the general formula _{(B): Ni x Mn y} Co z M t (OH) 2 + a (x + y + z + t = 1,0.3 ≦ x ≦ 0.6,0.2 ≦ y ≦ 0.4, 0.1 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.02, 0 ≦ a ≦ 0.5, M is Mg, Ca, Al, Ti, V, Cr, Zr, One or more elements selected from Nb, Mo, Hf, Ta, and W) are preferable.

With such a composition, when used as a positive electrode active material, it can function as a positive electrode material with better cycle characteristics, low resistance and high output when used as a positive electrode active material. Further, in such a composition, the effect of the production method of the present invention is sufficiently exerted, and the improvement of the characteristics is sufficiently achieved while suppressing the deterioration of the characteristics as the positive electrode material due to the suppression of the alkali metal content. Can do.

(2) Content of alkali metal The content of alkali metal contained in the composite hydroxide particles of the present invention is 500 ppm by mass or less, preferably 400 ppm by mass or less, more preferably 270 ppm by mass or less. is there.

Alkali metal is used as a neutralizing agent in the crystallization process, and industrially, sodium (Na), potassium (K) or the like is used and contained as an impurity in the obtained composite hydroxide particles. Is done.

When the content of alkali metal in the composite hydroxide particles increases, in the positive electrode active material obtained using such composite hydroxide particles as a precursor, the output characteristics deteriorate due to a decrease in battery capacity or an increase in reaction resistance. Will result. Therefore, by making the content of the alkali metal contained in the composite hydroxide particles 500 mass ppm or less, the positive electrode active material obtained using this as a precursor can function as a positive electrode material having excellent battery characteristics. It becomes possible.

In particular, when sodium is used as the neutralizing agent, sodium remains in the composite hydroxide particles, resulting in a decrease in battery capacity and output characteristics, so the sodium content is 500 mass ppm or less. And is preferably 400 mass ppm or less, and more preferably 250 mass ppm or less.

Moreover, since potassium also reduces battery capacity and output characteristics, the potassium content is preferably 100 ppm by mass or less, more preferably 50 ppm by mass or less, and further preferably 20 ppm by mass or less. preferable.

(3) Particle Structure The particle structure of the composite hydroxide particle of the present invention is not limited as long as it is composed of secondary particles formed by aggregation of a plurality of primary particles. However, in order to further improve the output characteristics of the secondary battery using the positive electrode active material having the composite hydroxide particles as a precursor, the composite hydroxide particles have a central portion constituted by fine primary particles and It is preferable that a particle structure including an outer shell portion composed of plate-like primary particles larger than the fine primary particles is provided outside the center portion. In other words, the positive electrode active material having a composite hydroxide particle having such a particle structure as a precursor has a hollow structure, and a sufficient contact area with the electrolyte is ensured when a secondary battery is configured. Therefore, the output characteristics can be greatly improved.

By applying the present invention, it is possible to effectively reduce the content of alkali metal contained in crystals in the composite hydroxide particles having such a structure and the positive electrode active material obtained using the composite hydroxide particles as a precursor. It becomes possible.

(3) Powder characteristics The powder characteristics of the composite hydroxide particles can be adjusted according to the conditions in the crystallization process described above. The powder characteristics are inherited by the positive electrode active material having the composite hydroxide particles as a precursor. That is, the powder characteristics of the composite hydroxide particles can be controlled by adjusting the conditions in the crystallization process according to the powder characteristics required for the target positive electrode active material. For example, when obtaining a positive electrode active material having an average particle size of 3 μm to 20 μm, it is preferable to control the average particle size to 3 μm to 20 μm in the composite hydroxide particles that are precursors thereof. It is more preferable to control. Thereby, the positive electrode active material whose average particle diameter is in the above-described range can be easily obtained. In the present invention, the average particle diameter means an average particle diameter based on volume, and can be determined by, for example, a laser diffraction scattering method.

3. Positive electrode active material for non-aqueous electrolyte secondary battery (1) Positive electrode active material for non-aqueous electrolyte secondary battery The positive electrode active material for non-aqueous electrolyte secondary battery of the present invention (hereinafter referred to as “positive electrode active material”) is the present invention. It is characterized by comprising lithium nickel manganese composite oxide particles obtained by the production method of the present invention and using the nickel manganese composite hydroxide particles of the present invention as a precursor.

Specifically, the positive electrode active material of the present invention have the general formula _{(C): Li u Ni x} Mn y Co z M t (OH) 2 + a (0.95 ≦ u ≦ 1.50, x + y + z + t = 1, 0.3 ≦ x ≦ 0.7, 0.1 ≦ y ≦ 0.55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, 0 ≦ a ≦ 0.5, M is Mg, Ca 1 or more elements selected from Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W), and secondary particles formed by aggregating a plurality of primary particles. It is comprised by lithium nickel manganese complex oxide particle, and sodium content in lithium nickel manganese complex oxide particle is 500 mass ppm or less.

In the above general formula (C), the value of u indicating the content of lithium (Li) is 0.95 to 1.50, preferably 1.00 to 1.35, more preferably 1.00 to 1. It is controlled in the range of 20. If the value of u is less than 0.95, the positive electrode resistance of the secondary battery using this positive electrode active material will increase, and the output of the battery will decrease. On the other hand, when the value of u exceeds 1.50, the initial discharge capacity of the secondary battery using this positive electrode active material is lowered.

The composition of the positive electrode active material of the present invention, preferably, the general formula _{(D): Li u Ni x} Mn y Co z M t (OH) 2 + a (0.95 ≦ u ≦ 1.50, x + y + z + t = 1, 0.3 ≦ x ≦ 0.6, 0.2 ≦ y ≦ 0.4, 0.1 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.02, 0 ≦ a ≦ 0.5, M is Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W.

Further, the particle structure and powder characteristics of the present invention basically inherit the particle structure and powder characteristics of the composite oxide particles of the present invention. That is, the positive electrode active material of the present invention is not limited in its particle structure as long as it is composed of secondary particles formed by aggregating a plurality of primary particles. However, when a secondary battery having excellent output characteristics is to be obtained, the positive electrode active material preferably has a hollow particle structure. The powder characteristics of the positive electrode active material of the present invention are adjusted according to the intended use of the secondary battery and the required performance, and are not particularly limited. In order to obtain a high-capacity secondary battery, the average particle diameter of the positive electrode active material is preferably adjusted to a volume-based average particle diameter of 3 μm to 20 μm by the laser diffraction scattering method. It is preferable to adjust to a range of ˜15 μm.

The method for producing the positive electrode active material of the present invention is the same as that of the prior art, except that the composite hydroxide particles of the present invention described above are used as a precursor. That is, the non-aqueous electrolyte secondary battery of the present invention is obtained by firing the obtained lithium mixture (firing step) after mixing the composite hydroxide particles and the lithium compound described above (mixing step) (firing step). Process). In addition, in such a method for producing a positive electrode active material, in addition to the above steps, a heat treatment step, a calcination step, a crushing step, and the like can be appropriately performed as necessary.

[Heat treatment process]
The heat treatment step is a step of heating the composite hydroxide particles at 105 ° C. to 750 ° C. in an oxidizing atmosphere to remove moisture contained in the composite hydroxide particles to obtain heat treated particles. Here, the heat treated particles include not only the composite hydroxide particles from which excess moisture has been removed in the heat treatment step, but also transition metal composite oxide particles converted by the heat treatment step (hereinafter referred to as “composite oxide particles”), Alternatively, a mixture thereof is also included. By performing such a heat treatment step, moisture remaining in the particles until the firing step can be reduced to a certain amount, so that the ratio of the number of metal atoms and the number of lithium atoms in the obtained positive electrode active material Variations can be prevented from occurring.

[Mixing process]
The mixing step is a step of mixing the lithium compound with the composite hydroxide particles or the heat-treated particles to obtain a lithium mixture. The lithium compound is not particularly limited, but lithium hydroxide, lithium nitrate, lithium carbonate, or a mixture thereof can be used in consideration of availability. Among these, it is preferable to use lithium hydroxide, lithium carbonate, or a mixture thereof in consideration of ease of handling and quality stability.

In addition, it is preferable that the lithium mixture is sufficiently mixed before firing. When mixing is insufficient, Li / Me varies among individual particles, and sufficient battery characteristics may not be obtained.

Moreover, a general mixer can be used for mixing, for example, a shaker mixer, a V blender, a ribbon mixer, a Julia mixer, a Ladige mixer, or the like can be used. In using any mixer, the composite hydroxide particles or the heat-treated particles and the lithium compound may be sufficiently mixed so that the shape of the composite hydroxide particles or the heat-treated particles is not destroyed.

[Calcination process]
When lithium hydroxide or lithium carbonate is used as the lithium compound, the lithium mixture is lower than the firing temperature and is 350 ° C. to 800 ° C., preferably 450 ° C. to 780 ° C. after the mixing step and before the firing step. That is, calcination may be performed at a reaction temperature (calcination temperature) between lithium hydroxide or lithium carbonate and the composite oxide particles. Thereby, the diffusion of lithium into the composite hydroxide particles is promoted, and more uniform lithium composite oxide particles can be obtained.

[Baking process]
The firing step is a step in which the lithium mixture obtained in the mixing step is fired at a predetermined temperature to synthesize a positive electrode active material composed of lithium transition metal composite oxide particles (hereinafter referred to as “lithium composite oxide particles”). .

The atmosphere in the firing step is an oxidizing atmosphere, but it is preferably performed in an atmosphere having an oxygen concentration of 18% by volume to 100% by volume, that is, in the air to an oxygen stream. Is more preferable. If the oxygen concentration is less than 18% by volume, the oxidation reaction does not proceed sufficiently, and the crystallinity of the positive electrode active material may not be sufficient.

On the other hand, the firing temperature needs to be appropriately adjusted depending on the composition of the composite hydroxide particles or heat-treated particles in the lithium mixture, particularly the composition ratio of the main metal element M. For example, when using composite hydroxide particles having the composition of the present invention, the firing temperature is preferably 800 ° C. to 1100 ° C., more preferably 800 ° C. to 950 ° C. Moreover, it is preferable that baking time shall be 3 hours or more. By adopting such a firing temperature and firing time, a positive electrode active material with high crystallinity can be obtained.

[Crushing process]
In order to remove aggregation or light sintering in the positive electrode active material after the firing step, the aggregate or sintered body can be crushed to adjust the powder characteristics of the positive electrode active material to a suitable range. . Note that pulverization means that mechanical energy is applied to an aggregate composed of a plurality of secondary particles generated by sintering necking between secondary particles during firing, and the secondary particles themselves are hardly destroyed. An operation of separating secondary particles and loosening aggregates.

As the crushing method, known means can be used, for example, a pin mill or a hammer mill can be used. At this time, it is preferable to adjust the crushing force to an appropriate range so as not to destroy the secondary particles.

4). Non-aqueous electrolyte secondary battery The non-aqueous electrolyte secondary battery to which the positive electrode active material of the present invention is applied as a positive electrode material is a general non-aqueous electrolyte secondary battery such as a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte solution. It is comprised by the same component.

In the non-aqueous electrolyte secondary battery in which the positive electrode active material of the present invention is applied as a positive electrode material, the content of sodium in the positive electrode active material constituting the positive electrode material is reduced, and the thermal stability, charge / discharge capacity, and output characteristics are reduced. Thus, the battery characteristics are prevented from being deteriorated, and the variation is small.

Hereinafter, the present invention will be described in detail using examples and comparative examples, but the present invention is not limited to the embodiments.

(Example 1)
First, after supplying 1/3 of the volume of water to the reaction tank (60 L), the temperature in the tank was heated to 50 ° C. In this state, nitrogen was circulated in the reaction vessel, and the oxygen partial pressure was adjusted to 5 Pa. At the same time, nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in ion-exchanged water so that the molar ratio was Ni: Co: Mn = 1: 1: 1 to prepare a 2.0 mol / L mixed aqueous solution. .

Next, while stirring the water in the reaction vessel, the reaction aqueous solution is formed by supplying the above-described mixed aqueous solution, 20% by mass sodium hydroxide aqueous solution, and 25% by mass ammonia water into the reaction vessel. The composite hydroxide particles were crystallized. At this time, the supply amounts of the mixed aqueous solution, the aqueous sodium hydroxide solution, and the aqueous ammonia were adjusted so that the pH value on the basis of the liquid temperature of 25 ° C. was maintained at 11.5 and the ammonia concentration was maintained at 10 g / L. In this example, the reaction atmosphere was maintained in a nitrogen atmosphere having an oxygen partial pressure of 5 Pa and the temperature of the reaction aqueous solution was maintained at 50 ° C. through the crystallization reaction.

At the time of completion of the crystallization reaction, when oxidation-reduction titration was performed on an aqueous solution obtained by dissolving the obtained composite hydroxide particles with hydrochloric acid, the average valence of the metal element constituting the composite hydroxide particles was 2 .11.

The slurry containing the composite hydroxide particles obtained as described above was dispensed in a separately prepared container in an air atmosphere (oxygen partial pressure: 21273 Pa), and then washed without being retained. Specifically, the operation of solid-liquid separation of the slurry containing the composite hydroxide particles was repeated twice while being washed with pure water (ion exchange water) using 5C quantitative filter paper. The composite hydroxide particles thus washed and solid-liquid separated were subjected to a vacuum drying treatment at 120 ° C. for 12 hours to obtain powdered composite hydroxide particles.

As a result of analyzing the composition of the obtained composite hydroxide particles using an ICP emission spectrometer (Seiko Instruments Inc., Plasma Spectrometer SPS3000), the general formula: Ni _0.33 Mn _0.33 Co _0.334 (OH) _2.11 . It was confirmed that Moreover, sodium content was 170 mass ppm and potassium content was less than 20 mass ppm. Furthermore, as a result of measuring the volume-based average particle diameter by a laser diffraction scattering method using a particle size distribution measuring apparatus (manufactured by Nikkiso Co., Ltd., Microtrac HRA), the average particle diameter MV was 9.6 μm. The results are shown in Table 1.

(Example 2)
From the end of the crystallization process to the start of the washing process, the slurry containing the composite hydroxide particles is stirred for 2 hours in an atmospheric atmosphere (oxygen partial pressure: 21273 Pa). Using a magnetic stirrer HSD-6), composite hydroxide particles were obtained in the same manner as in Example 1 except that the atmospheric atmosphere was not entangled and maintained while stirring at a rotation speed of 500 rpm. The same measurement was performed. As a result of the oxidation-reduction titration after the holding, the average valence of the metal element constituting the composite hydroxide particles is 2.11, and the sodium content in the composite hydroxide particles after washing is 240 mass ppm, The potassium content was less than 20 mass ppm (Example 3)
The composite hydroxide particles are obtained in the same manner as in Example 2 except that the slurry containing the composite hydroxide particles is held with stirring for 4 hours from the end of the crystallization process to the start of the washing process. At the same time, the same measurement was performed. As a result of the oxidation-reduction titration after the holding, the average valence of the metal element constituting the composite hydroxide particles is 2.15, and the sodium content in the composite hydroxide particles after washing is 260 mass ppm, The potassium content was less than 20 ppm by mass.

Example 4
The composite hydroxide particles are obtained in the same manner as in Example 2 except that the slurry containing the composite hydroxide particles is held with stirring for 8 hours from the end of the crystallization process to the start of the washing process. At the same time, the same measurement was performed. As a result of the oxidation-reduction titration after the holding, the average valence of the metal element constituting the composite hydroxide particles is 2.22, and the sodium content in the composite hydroxide particles after washing is 280 mass ppm, The potassium content was less than 20 ppm by mass.

(Comparative Example 1)
The composite hydroxide particles are obtained in the same manner as in Example 2 except that the slurry containing the composite hydroxide particles is maintained with stirring for 16 hours from the end of the crystallization process to the start of the washing process. At the same time, the same measurement was performed. As a result of the oxidation-reduction titration after the holding, the average valence of the metal element constituting the composite hydroxide particles is 2.41, and the sodium content in the composite hydroxide particles after washing is 510 mass ppm, The potassium content was less than 20 ppm by mass, and the potassium content was less than 20 ppm by mass.

(Comparative Example 2)
The composite hydroxide particles are obtained in the same manner as in Example 2 except that the slurry containing the composite hydroxide particles is maintained with stirring for 24 hours from the end of the crystallization process to the start of the washing process. At the same time, the same measurement was performed. As a result of the oxidation-reduction titration after the holding, the average valence of the metal element constituting the composite hydroxide particles is 2.44, and the sodium content in the composite hydroxide particles after washing is 520 mass ppm, The potassium content was less than 20 ppm by mass.

(Comparative Example 3)
The composite hydroxide particles are obtained in the same manner as in Example 2 except that the slurry containing the composite hydroxide particles is held with stirring for 32 hours from the end of the crystallization step to the start of the washing step. At the same time, the same measurement was performed. As a result of the oxidation-reduction titration after the holding, the average valence of the metal element constituting the composite hydroxide particles is 2.51, and the sodium content in the composite hydroxide particles after washing is 520 mass ppm. The potassium content was less than 20 ppm by mass.

(Comparative Example 4)
The composite hydroxide particles are obtained in the same manner as in Example 2 except that the slurry containing the composite hydroxide particles is maintained with stirring for 96 hours from the end of the crystallization process to the start of the washing process. At the same time, the same measurement was performed. As a result of the oxidation-reduction titration after the retention, the average valence of the metal element constituting the composite hydroxide particles is 2.66, and the sodium content in the composite hydroxide particles after washing is 980 mass ppm, Potassium content was less than 20 ppm by weight (Example 5)
From the end of the crystallization process to the start of the washing process, except that the slurry containing the composite hydroxide particles was maintained with stirring for 4 hours while maintaining the nitrogen atmosphere (oxygen partial pressure: 5 Pa). In the same manner as in Example 2, composite hydroxide particles were obtained and the same measurement was performed. As a result of the oxidation-reduction titration after the holding, the average valence of the metal element constituting the composite hydroxide particles is 2.08, and the sodium content in the composite hydroxide particles after washing is 210 mass ppm, The potassium content was less than 20 ppm by mass.

(Example 6)
The composite hydroxide particles are obtained in the same manner as in Example 5 except that the slurry containing the composite hydroxide particles is maintained with stirring for 24 hours from the end of the crystallization process to the start of the washing process. At the same time, the same measurement was performed. As a result of the oxidation-reduction titration after the holding, the average valence of the metal element constituting the composite hydroxide particles is 2.07, and the sodium content in the composite hydroxide particles after washing is 220 mass ppm, The potassium content was less than 20 ppm by mass.

(Example 7)
The composite hydroxide particles are obtained in the same manner as in Example 5 except that the slurry containing the composite hydroxide particles is maintained with stirring for 32 hours from the end of the crystallization step to the start of the washing step. At the same time, the same measurement was performed. As a result of the oxidation-reduction titration after the holding, the average valence of the metal element constituting the composite hydroxide particles is 2.08, and the sodium content in the composite hydroxide particles after washing is 220 mass ppm, The potassium content was less than 20 ppm by mass.

(Example 8)
The composite hydroxide particles are obtained in the same manner as in Example 5 except that the slurry containing the composite hydroxide particles is maintained with stirring for 96 hours from the end of the crystallization process to the start of the washing process. At the same time, the same measurement was performed. As a result of the oxidation-reduction titration after the holding, the average valence of the metal element constituting the composite hydroxide particles is 2.08, and the sodium content in the composite hydroxide particles after washing is 240 mass ppm, The potassium content was less than 20 ppm by mass.

(Examples 9 to 12, Comparative Examples 5 to 8, Examples 13 to 16)
The atmosphere in the reaction vessel was an atmospheric atmosphere (oxygen partial pressure: 21273 Pa), the pH value of the aqueous reaction solution was maintained at 13.0 on the basis of the liquid temperature of 25 ° C., and the ammonia concentration was maintained at 15 g / L for 2 minutes and 30 seconds. After crystallization and nucleation (nucleation step), the supply of 25% by mass aqueous sodium hydroxide is stopped until the pH value of the reaction aqueous solution becomes 11.6 based on the liquid temperature of 25 ° C. Then, the supply was resumed, the pH value of the reaction aqueous solution was maintained at 11.6 on the basis of the liquid temperature of 25 ° C., the ammonia concentration was maintained at 15 g / L, crystallization was carried out for 30 minutes, and the liquid supply was temporarily stopped. Then, nitrogen gas was circulated until the atmosphere in the reaction tank became a nitrogen atmosphere (oxygen partial pressure; 200 Pa), and then the liquid supply was started, and crystallization was performed for a total of 2 hours from the start of growth (particle growth process) Circulate nitrogen gas after the grain growth process The composite hydroxide particles were obtained in the same manner as in Examples 1 to 4, Comparative Examples 1 to 4, and Examples 5 to 8, except that the oxygen partial pressure in the atmosphere was changed to 5 Pa. Went. The measurement results are shown in Table 2.

(Comparative Example 9, Example 17, Comparative Examples 10 and 11)
From the end of the crystallization step to the start of the washing step, the oxygen partial pressure was set to 10 Pa in the same manner as in Example 12 except that the pH value of the slurry was 13.5 on the basis of 25 ° C. (Comparative Example 9). (Example 17) Except that the oxygen partial pressure was 50 Pa and 200 Pa (Comparative Examples 10 and 11), the composite hydroxide particles were obtained in the same manner as in Example 16 and the same measurement was performed. went. The measurement results are shown in Table 2.

In Examples 9 to 12, Comparative Examples 5 to 9, and Examples 13 to 17, the potassium content was less than 20 ppm by mass.

(Comprehensive evaluation)
From Table 1 and Table 2, as the average valence of the metal element constituting the composite hydroxide particles at the start of the washing step increases, the content of alkali metal in the finally obtained composite hydroxide particles, particularly It is understood that the sodium content is increased. In particular, when the average valence exceeds 2.4, it is understood that the content of sodium alone exceeds 500 ppm.

Therefore, at the start of the cleaning process, by washing the composite hydroxide particles in a state where the average valence of the metal element is controlled to 2.4 or less, alkali metal, particularly sodium can be sufficiently removed, and composite hydroxide It is understood that the content of alkali metal remaining in the product particles can be reduced.

Therefore, according to the present invention, composite hydroxide particles are provided as a precursor for obtaining a positive electrode active material with a small content of alkali metal remaining in the crystal, and the composite hydroxide of the present invention It is understood that by using a positive electrode active material having a product particle as a precursor as a positive electrode material, it is possible to manufacture a secondary battery in which deterioration and variation in battery characteristics are suppressed.

Claims (9)

1. The crystallization reaction using sodium hydroxide as a neutralizing agent, the general formula _{(A): Ni x Mn y} Co z M t (OH) 2 + a (x + y + z + t = 1,0.3 ≦ x ≦ 0.7, 0.1 ≦ y ≦ 0.55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, 0 ≦ a ≦ 0.5, M is Mg, Ca, Al, Ti, V, Cr, Zr Crystallization step of obtaining a slurry containing nickel manganese composite hydroxide particles represented by Nb, Mo, Hf, Ta, W).
   A washing step of washing the nickel manganese composite hydroxide particles in a state where the average valence of the metal element in the nickel manganese composite hydroxide particles is controlled to 2.4 or less;
   A method for producing nickel manganese composite hydroxide particles, comprising:
2. 2. The nickel manganese composite hydroxide according to claim 1, wherein the slurry is maintained in a non-oxidizing atmosphere in which an oxygen partial pressure is controlled to 10 Pa or less from the end of the crystallization step to the start of the cleaning step. Particle manufacturing method.
3. 2. The slurry is maintained in a state in which the pH value based on a liquid temperature of 25 ° C. is controlled in the range of 10.5 to 13.0 from the end of the crystallization step to the start of the washing step. Or the manufacturing method of the nickel manganese composite hydroxide particle | grains of 2 or 2.
4. From the end of the crystallization process to the start of the washing process, the slurry is maintained in an air atmosphere in a state where the pH value based on a liquid temperature of 25 ° C. is controlled within the range of 10.5 to 13.0. And the manufacturing method of the nickel manganese composite hydroxide particle | grains of Claim 1 which makes this holding time 10 hours or less.
5. In the crystallization step, the aqueous solution for nucleation is controlled so that the pH value on the basis of a liquid temperature of 25 ° C. is 12.0 to 14.0, in an oxidizing atmosphere in which the oxygen concentration exceeds 1% by volume. A nucleation step for nucleation and an aqueous solution for particle growth containing nuclei formed in the nucleation step are controlled so that the pH value at a liquid temperature of 25 ° C. is 10.5 to 12.0. The nuclei are switched from an oxidizing atmosphere to a mixed atmosphere of oxygen and inert gas having an oxygen concentration of 1% by volume or less in the range of 0% to 40% with respect to the whole of the particle growth process from the start of the particle growth process. The nickel-manganese composite hydroxide particles have a central part composed of fine primary particles, and the plate-like primary larger than the fine primary particles outside the central part. Secondary particle having outer shell made of particles And get method of nickel-manganese composite hydroxide particles according to any one of claims 1-4.
6. Formula _{(A): Ni x Mn y} Co z M t (OH) 2 + a (x + y + z + t = 1,0.3 ≦ x ≦ 0.7,0.1 ≦ y ≦ 0.55,0 ≦ z ≦ 0 .4, 0 ≦ t ≦ 0.1, 0 ≦ a ≦ 0.5, M is selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W Nickel manganese composite water characterized by comprising secondary particles formed by agglomerating a plurality of primary particles and having an alkali metal content of 500 ppm by mass or less. Oxide particles.
7. Formula _{(A): Ni x Mn y} Co z M t (OH) 2 + a (x + y + z + t = 1,0.3 ≦ x ≦ 0.7,0.1 ≦ y ≦ 0.55,0 ≦ z ≦ 0 .4, 0 ≦ t ≦ 0.1, 0 ≦ a ≦ 0.5, M is selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W 2) having a central portion in which fine primary particles are aggregated and an outer shell portion in which plate-like primary particles larger than the fine primary particles are aggregated outside the central portion. Nickel-manganese composite hydroxide particles comprising secondary particles and having an alkali metal content of 500 ppm by mass or less.
8. Formula _{(B): Ni x Mn y} Co z M t (OH) 2 + a (x + y + z + t = 1,0.3 ≦ x ≦ 0.6,0.2 ≦ y ≦ 0.4,0.1 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.02, 0 ≦ a ≦ 0.5, M is selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W The nickel manganese composite hydroxide particles according to claim 6 or 7, represented by: one or more elements.
9. A positive electrode active material for a non-aqueous electrolyte secondary battery, comprising lithium nickel manganese composite oxide particles having the nickel manganese composite hydroxide particles according to any one of claims 5 to 8 as a precursor.