JP2019021424A - Positive electrode active material precursor for nonaqueous electrolyte secondary battery, positive electrode active material for nonaqueous electrolyte secondary battery, method for manufacturing the positive electrode active material precursor for nonaqueous electrolyte secondary battery, and method for manufacturing the positive electrode active material for nonaqueous electrolyte secondary battery - Google Patents

Abstract

To provide a positive electrode active material precursor for a nonaqueous electrolyte secondary battery, by which a positive electrode active material for a nonaqueous electrolyte secondary battery, including porous particles can be formed.SOLUTION: Provided is a positive electrode active material precursor for a nonaqueous electrolyte secondary battery, which comprises: a nickel cobalt manganese carbonate composite; and a functional group including hydrogen, provided that the nickel cobalt manganese carbonate composite has a composition represented by Ni:Mn:Co:M=x:y:z:t (where x+y+z+t=1, 0.25<x<0.60, 0<y<0.70, 0<z<0.70 and 0≤t≤0.10, and M represents one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo and W). In the positive electrode active material precursor, the substance amount ratio H/Me of the hydrogen H and a metal component Me included therein is 1.60 or more.SELECTED DRAWING: None

Description

  The present invention relates to a positive electrode active material precursor for a non-aqueous electrolyte secondary battery, a positive electrode active material for a non-aqueous electrolyte secondary battery, a method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery. The present invention relates to a method for producing a positive electrode active material.

  In recent years, with the widespread use of portable electronic devices such as mobile phones and laptop computers, development of small and lightweight non-aqueous electrolyte secondary batteries having high energy density is strongly desired. In addition, development of a high-power secondary battery is strongly desired as a large battery such as a motor drive power source.

  As a secondary battery that satisfies these requirements, there is a lithium ion secondary battery. A lithium ion secondary battery includes a positive electrode, a negative electrode, an electrolytic solution, and the like, and a material capable of desorbing and inserting lithium is used as the positive electrode active material and the negative electrode active material.

  Research and development of lithium-ion secondary batteries are currently being actively conducted. Among them, a lithium ion secondary battery using a layered or spinel type lithium metal composite oxide as a positive electrode material can be used as a battery having a high energy density because a high voltage of 4V can be obtained.

Currently, lithium cobalt composite oxide (LiCoO ₂ ), which is relatively easy to synthesize, lithium nickel composite oxide (LiNiO ₂ ) using nickel, which is cheaper than cobalt, and lithium nickel are used as positive electrode materials for lithium ion secondary batteries. Cobalt manganese composite oxide (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ), lithium manganese composite oxide using manganese (LiMn ₂ O ₄ ), lithium nickel manganese composite oxide (LiNi _0.5 Mn) _0.5 O _2), lithium-rich nickel-cobalt-manganese composite oxide _{(Li 2 MnO 3 -LiNi x Mn} y Co z O 2) lithium composite oxide such as have been proposed.

  Among these positive electrode active materials, in recent years, an inexpensive lithium nickel cobalt manganese composite oxide has attracted attention. This composite oxide is a layered rock salt type compound like the lithium cobalt composite oxide.

  And the manufacturing method of the precursor for obtaining the lithium nickel cobalt manganese complex oxide is disclosed by patent document 1, for example.

JP-A-2015-191847

  By the way, in order to increase the output of the lithium ion secondary battery, it is effective to shorten the movement distance between the positive electrode and the negative electrode of the lithium ion. It is useful to use a positive electrode material containing particles.

  However, Patent Document 1 discloses a method for producing a precursor and a composition of a positive electrode active material produced using the precursor, but does not mention the structure of the particles of the positive electrode active material. In particular, the internal structure of secondary particles has not been studied.

  Accordingly, in view of the above-described problems of the prior art, in one aspect of the present invention, a positive electrode active material precursor for a nonaqueous electrolyte secondary battery that can form a positive electrode active material for a nonaqueous electrolyte secondary battery containing porous particles is provided. The purpose is to provide a body.

In order to solve the above problems, according to one aspect of the present invention,
Ni: Mn: Co: M = x: y: z: t (where x + y + z + t = 1, 0.25 <x <0.60, 0 <y <0.70, 0 <z) <0.70, 0 ≦ t ≦ 0.10 is satisfied, and M is one type selected from Mg, Ca, Al, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, and W A nickel cobalt manganese carbonate composite composed of the above additive elements),
A functional group containing hydrogen,
Provided is a positive electrode active material precursor for a non-aqueous electrolyte secondary battery, wherein H / Me, which is a mass ratio of the contained hydrogen H and the contained metal component Me, is 1.60 or more.

  According to one embodiment of the present invention, a positive electrode active material precursor for a non-aqueous electrolyte secondary battery that can form a positive electrode active material for a non-aqueous electrolyte secondary battery containing porous particles can be provided.

It is a figure which shows an example of the flow of the manufacturing method of the positive electrode active material precursor for non-aqueous electrolyte secondary batteries of embodiment of this invention. It is a figure which shows another example of the flow of the manufacturing method of the positive electrode active material precursor for non-aqueous electrolyte secondary batteries of embodiment of this invention. It is explanatory drawing of the cross-sectional structure of the coin-type battery produced in Example 1 which concerns on this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and the following embodiments are not departed from the scope of the present invention. Various modifications and substitutions can be made.

[Positive electrode active material precursor for non-aqueous electrolyte secondary battery]
One structural example of the positive electrode active material precursor for a non-aqueous electrolyte secondary battery of the present embodiment (hereinafter also simply referred to as “precursor”) will be described. The precursor of this embodiment is Ni: Mn: Co: M = x: y: z: t (provided that x + y + z + t = 1, and 0.25 <x <0.60) in a mass ratio (mol ratio). 0 <y <0.70, 0 <z <0.70, 0 ≦ t ≦ 0.10, M is Mg, Ca, Al, Ti, V, Cr, Fe, Cu, Zn, Zr, A nickel cobalt manganese carbonate composite composed of one or more additional elements selected from Nb, Mo, and W.) and a functional group containing hydrogen.

  In the precursor of the present embodiment, H / Me, which is a substance amount ratio between the hydrogen H contained and the metal component Me contained, is set to 1.60 or more.

  In the present embodiment, the metal component Me contained in the precursor includes Ni, Mn, Co, and the additive element M mentioned in the substance ratio.

  The precursor of this embodiment can include substantially spherical secondary particles formed by aggregation of a plurality of fine primary particles. The precursor of this embodiment can also be comprised with this secondary particle.

  The precursor of the present embodiment has high uniformity in particle size and is a fine crystal, and can be used as a raw material for a positive electrode active material for a non-aqueous electrolyte secondary battery.

  Below, the precursor of this embodiment is demonstrated concretely.

(composition)
The nickel cobalt manganese carbonate composite contained in the precursor of this embodiment and the functional group containing hydrogen will be described.

  As described above, the nickel cobalt manganese carbonate composite is a nickel carbonate manganese composite in the form of a basic carbonate having a composition of Ni: Mn: Co: M = x: y: z: t. is there.

  However, in the above substance amount ratio, x + y + z + t = 1, and 0.25 <x <0.60, 0 <y <0.70, 0 <z <0.70, 0 ≦ t ≦ 0.10, M is one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, and W.

In addition, the precursor of this embodiment has a general formula 1: xMn ₂ (CO ₃ ) ₃ .yMn (OH) ₃ , a general formula 2: xCo (CO ₃ ) ₂ .yCo (OH) ₂ .zH ₂ O, and General formula 3: Ni ₄ CO ₃ (OH) ₆ (H ₂ O) _{4 and the} like can contain a compound of indefinite composition in which a carbonate or a hydroxide represented by a mixture is mixed.

  In order to further improve battery characteristics such as cycle characteristics and output characteristics when the precursor of this embodiment is used as a precursor of a positive electrode active material of a non-aqueous electrolyte secondary battery, a nickel cobalt manganese carbonate composite is used. As described above, one or more kinds of additive elements M can be added.

  One or more additive elements M selected from Mg, Ca, Al, Ti, V, Fe, Cr, Cu, Zn, Zr, Nb, Mo, and W are within a predetermined mass ratio t. It is preferable that the particles are uniformly distributed inside the secondary particles and / or the surfaces of the secondary particles are uniformly coated.

  However, in the nickel-cobalt-manganese carbonate composite, when the material amount ratio t of the additive element M exceeds 0.1, the metal element contributing to the oxidation-reduction reaction (Redox reaction) decreases, and the battery capacity may decrease. There is.

  Further, even when the nickel cobalt manganese carbonate composite does not contain the additive element M, the positive electrode active material produced using the precursor of this embodiment has sufficient battery characteristics such as cycle characteristics and output characteristics. It has characteristics. For this reason, it is not necessary to contain the additive element M. Therefore, the additive element M is adjusted so that the substance amount ratio t falls within the range of 0 ≦ t ≦ 0.1.

  Moreover, the precursor of this embodiment can contain the functional group containing the above-mentioned hydrogen. Examples of the functional group containing hydrogen include a hydrogen group and a hydroxyl group. The functional group containing hydrogen is mixed in the manufacturing process, and H / Me, which is the mass ratio of hydrogen H contained in the precursor of this embodiment and the metal component Me, is 1.60 or more. Thus, when the positive electrode active material is used, porous particles can be obtained. Moreover, when H / Me is 1.70 or less, when the precursor of this embodiment is a positive electrode active material, the strength of the positive electrode active material can be particularly increased, and the shape can be reliably maintained.

  In the present embodiment, the metal component Me contained in the precursor includes, as described above, Ni, Mn, Co, and the additive element M mentioned in the substance amount ratio.

  In addition, the precursor of the present embodiment may contain components other than the nickel cobalt manganese carbonate composite and the functional group containing hydrogen, but the nickel cobalt manganese carbonate composite and the functional containing hydrogen. It can also consist of groups. In this case, the precursor of this embodiment does not exclude containing an inevitable component in a manufacturing process or the like.

[Method for producing positive electrode active material precursor for non-aqueous electrolyte secondary battery]
Next, an example of a method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery of the present embodiment (hereinafter, also simply referred to as “precursor production method”) will be described. In the precursor manufacturing method of the present embodiment, a precursor can be obtained by a crystallization reaction, and the obtained precursor is washed and dried as necessary.

  Specifically, the precursor production method according to the present embodiment is made of Ni: Mn: Co: M = x: y: z: t (where x + y + z + t = 1 and 0.25 <x <0.60, 0 <y <0.70, 0 <z <0.70, 0 ≦ t ≦ 0.10, M is Mg, Ca, Al, Ti, V, Cr, Fe, Cu, A non-aqueous electrolyte having a nickel-cobalt-manganese carbonate composite composed of Zn, Zr, Nb, Mo, and W, and a functional group containing hydrogen. It is a manufacturing method of the positive electrode active material precursor for secondary batteries, Comprising: The following processes are included.

  In the presence of carbonate ions, an initial aqueous solution containing at least one of an ammonium ion supplier and an alkaline substance, an aqueous solution containing nickel (Ni) as a metal component, an aqueous solution containing cobalt (Co) as a metal component, and a metal Crystallization in which nuclei are generated in a mixed aqueous solution mixed with an aqueous solution containing manganese (Mn) as a component (hereinafter also simply referred to as “an aqueous solution containing Ni as a metal component”) and the generated nuclei are grown. Process.

  In the precursor production method of the present embodiment, the crystallization step is performed in an oxygen-containing atmosphere by controlling the pH value of the mixed aqueous solution to 9.0 or less on the basis of the reaction temperature of 40 ° C.

  In FIG. 1, an example of the flow of the manufacturing method of the precursor of this embodiment is shown. As shown in FIG. 1, the precursor manufacturing method of the present embodiment includes a crystallization step.

(1) Crystallization Step As shown in FIG. 1, in the crystallization step, first, ion exchange water (water) is mixed with at least one of an ammonium ion supplier and an alkaline substance in a reaction tank to prepare an initial aqueous solution. it can.

  The ammonium ion supplier is not particularly limited, but is preferably one or more selected from an ammonium carbonate aqueous solution, ammonia water, an ammonium chloride aqueous solution, and an ammonium sulfate aqueous solution.

  The alkaline substance is not particularly limited, but is preferably at least one selected from sodium carbonate, sodium hydrogen carbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide.

  An acidic substance is added to the initial aqueous solution as necessary, and the initial aqueous solution is adjusted to 9.0 or less based on a reaction temperature of 40 ° C. By setting the pH value of the initial aqueous solution within the above range, it is possible to prevent impurities from remaining, and thus a precursor with a small amount of impurities can be obtained. At this time, the pH value of the initial aqueous solution is preferably adjusted to be 5.4 to 9.0, more preferably 6.4 to 8.0, and 7.1. It is more preferable to adjust so as to be 7.4 or less. The pH at this time can be adjusted, for example, by adding a pH adjusting aqueous solution described later.

  During the crystallization process, it is preferable that the mixed aqueous solution also has a pH value within the above range. Since the pH value of the mixed aqueous solution slightly fluctuates during the crystallization step, the maximum pH value of the mixed aqueous solution during the crystallization step can be set as the pH value of the mixed aqueous solution in the crystallization step.

  During the crystallization step, the fluctuation range of the pH value of the mixed aqueous solution is preferably controlled so as to be within 0.2 above and below the center value (set pH value), for example. This is because, when the fluctuation range of the pH value of the mixed aqueous solution is large, the growth of particles contained in the precursor of this embodiment is not constant, and uniform particles with a narrow particle size distribution range may not be obtained. Because there is.

  The pH value in the initial aqueous solution and the mixed aqueous solution can be measured by a known pH meter.

  The acidic substance is not particularly limited, and for example, sulfuric acid can be preferably used. In addition, it is preferable to use the same kind of acid as the metal salt used when preparing the aqueous solution containing the metal component added to initial stage aqueous solution as an acidic substance.

  In the crystallization process, the inside of the reaction vessel is set in the presence of carbonate ions. The supply method of carbonate ions is not particularly limited. For example, carbonate ions can be supplied to the mixed aqueous solution by supplying carbon dioxide gas together with an oxygen-containing gas described later in the reaction tank. Further, when preparing the initial aqueous solution or the pH adjusting aqueous solution, carbonate ions can be supplied using carbonate.

  In the crystallization step, the atmosphere is controlled so as to obtain an oxygen-containing atmosphere by blowing an oxygen-containing gas into the reaction vessel in which the initial aqueous solution is prepared. Thereafter, as will be described later, an aqueous solution containing a metal component such as an aqueous solution containing Ni as a metal component is supplied into the reaction tank at a constant flow rate, for example, so that the pH value of the mixed aqueous solution falls within a predetermined range. doing. The metal component reacts with dissolved oxygen contained in the mixed aqueous solution, oxygen contained in the oxygen-containing gas supplied to the reaction tank, or the like. As a result, amorphous fine particles (primary particles) that are not single crystals of carbonate are generated. These particles become precursor nuclei (nuclear particles). The core particles aggregate and grow to generate large secondary particles. The particle size of the secondary particles can be controlled by the reaction time in the crystallization process.

  Further, by blowing an oxygen-containing gas, it is possible to easily mix a functional group containing hydrogen into the precursor as compared with an inert gas atmosphere. Thereby, the obtained precursor can make H / Me which is a substance amount ratio of the hydrogen H to contain and the metal component Me to be 1.60 or more.

  As the oxygen-containing gas, for example, various gases containing oxygen such as air can be used.

  When supplying the oxygen-containing gas into the reaction vessel, the supply amount of the oxygen-containing gas can be confirmed by measuring the dissolved oxygen concentration in the mixed aqueous solution. Since dissolved oxygen in the mixed aqueous solution is consumed during the crystallization process, if the amount of dissolved oxygen in the mixed aqueous solution is half or more of the saturation amount, sufficient oxygen can be supplied to the reaction.

  The amount of dissolved oxygen in the mixed aqueous solution can be measured by a known dissolved oxygen meter or the like.

  In the crystallization step, the oxygen-containing gas may be continuously supplied into the reaction vessel while an aqueous solution containing a metal component such as an aqueous solution containing Ni as a metal component is added to the initial aqueous solution.

  Next, in the crystallization step, an aqueous solution containing the metal component such as an aqueous solution containing Ni as a metal component is added to and mixed with the initial aqueous solution in the reaction vessel. As a result, fine particles (primary particles) serving as precursor nuclei (core particles) are generated in the initial aqueous solution containing the metal component. As a result, a mixed aqueous solution containing primary particles serving as core particles is obtained. Whether or not a predetermined amount of core particles has been generated can be determined by the amount of metal salt contained in the mixed aqueous solution.

  When adding an aqueous solution containing a metal component such as an aqueous solution containing Ni as a metal component to the initial aqueous solution, the pH value of the resulting mixed aqueous solution is preferably controlled within a predetermined range as described above. For this reason, it is preferable that the aqueous solution containing the metal component is gradually added to the initial aqueous solution instead of being added at once. Thereby, the solution containing the said metal component or the metal component containing mixed aqueous solution mentioned later etc. can be supplied so that it may become a fixed flow volume to a reaction tank, for example.

  Moreover, when supplying the aqueous solution containing the metal component or the metal component-containing mixed aqueous solution described later, it is preferable to drop the pH-adjusted aqueous solution together so that the pH of the mixed aqueous solution can be maintained within a predetermined range. Although it does not specifically limit as pH adjustment aqueous solution, For example, the aqueous solution containing at least one of an ammonium ion supply body and an alkaline substance can be used. The method for supplying the pH-adjusted aqueous solution into the reaction vessel is not particularly limited. For example, a pump capable of controlling the flow rate, such as a metering pump, while sufficiently stirring the obtained mixed aqueous solution, What is necessary is just to add so that pH value may be kept in a predetermined range.

  Here, in the crystallization step, an aqueous solution containing Ni as the metal component, an aqueous solution containing Co as the metal component, and Mn as the metal component in the aqueous solution containing the metal component added to the initial aqueous solution The aqueous solution to be used will be described.

  The aqueous solution containing Ni as the metal component, the aqueous solution containing Co as the metal component, and the aqueous solution containing Mn as the metal component can contain a metal compound containing each metal component. For example, if it is the aqueous solution containing Mn as a metal component, the metal compound containing manganese can be included.

  As the metal compound, a water-soluble metal compound is preferably used, and examples of the water-soluble metal compound include nitrates, sulfates, and hydrochlorides. Specifically, for example, nickel sulfate, cobalt sulfate, manganese sulfate and the like can be suitably used.

  These aqueous solutions containing Ni as a metal component, an aqueous solution containing Co as a metal component, and an aqueous solution containing Mn as a metal component are mixed in advance in part or as a metal component-containing mixed aqueous solution. You may add to aqueous solution.

  The composition ratio of each metal in the obtained precursor is the same as the composition ratio of each metal in the metal component-containing mixed aqueous solution. For this reason, the composition ratio of each metal contained in the metal component-containing mixed aqueous solution added to the initial aqueous solution in the crystallization step is equal to the composition ratio of each metal in the generated precursor, for example, the dissolved metal compound It is preferable to adjust the ratio to prepare a mixed aqueous solution containing metal components.

  In addition, when a plurality of metal compounds are mixed and specific metal compounds react with each other to generate an unnecessary compound, an aqueous solution containing each metal component is simultaneously made into an initial aqueous solution at a predetermined ratio. It may be added.

  The aqueous solution containing each metal component may be added individually to the initial aqueous solution without mixing. In this case, the aqueous solution containing each metal component so that the composition ratio of each metal component contained in the aqueous solution is equal to the composition ratio of each metal component in the precursor to be generated in the entire aqueous solution containing the metal component to be added. Is preferably prepared.

  As described above, the precursor manufactured by the precursor manufacturing method of the present embodiment is Ni: Mn: Co: M = x: y: z: t (provided that x + y + z + t = 1) as described above. 0.25 <x <0.60, 0 <y <0.70, 0 <z <0.70, 0 ≦ t ≦ 0.10, and M is Mg, Ca, Al, Ti, V, A nickel cobalt manganese carbonate composite composed of one or more additive elements selected from Cr, Fe, Cu, Zn, Zr, Nb, Mo, and W. and a functional group containing hydrogen Have

  That is, the precursor of this embodiment can further contain the additive element M in addition to Ni, Mn, and Co.

  For this reason, in the crystallization step, one or more additive elements M selected from Mg, Ca, Al, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, and W are selected as necessary. An aqueous solution containing (hereinafter also simply referred to as “aqueous solution containing additive element M”) can be added to the initial aqueous solution.

  In addition, after mixing the aqueous solution containing Ni as a metal component, etc. to make a metal component-containing mixed aqueous solution, when adding the metal component-containing mixed aqueous solution to the initial aqueous solution, the metal component containing the aqueous solution containing the additive element M is added. The mixed aqueous solution may be added to the initial aqueous solution.

  When an aqueous solution containing Ni as a metal component is individually added to the initial aqueous solution, the aqueous solution containing the additive element M may be individually added to the initial aqueous solution.

  Here, the aqueous solution containing the additive element M can be prepared using, for example, a compound containing the additive element M. Examples of the compound containing the additive element M include, for example, magnesium sulfate, calcium sulfate, sodium aluminate, titanium sulfate, ammonium peroxotitanate, potassium oxalate, vanadium sulfate, ammonium vanadate, chromium sulfate, and potassium chromate. , Iron sulfate, copper sulfate, zinc sulfate, zirconium sulfate, zirconium nitrate, niobium oxalate, ammonium molybdate, sodium tungstate, or ammonium tungstate. The compound can be selected according to the element to be added. .

  As described above, the additive element M is preferably uniformly distributed and / or uniformly coated on the surface of the core particles contained in the precursor.

  And the additive element M can be uniformly disperse | distributed inside the core particle which a precursor contains by adding aqueous solution containing the additive element M mentioned above to precursor particle | grain containing aqueous solution.

  In order to uniformly coat the surface of the secondary particles of the precursor with the additive element M, for example, a coating step of coating with the additive element M can be performed after the crystallization process is completed. The coating process will be described later.

  The temperature of the mixed aqueous solution is preferably maintained at 20 ° C. or higher, and more preferably maintained at 30 ° C. or higher. In addition, although the upper limit of the temperature of mixed aqueous solution is not specifically limited, For example, it is preferable that it is 70 degrees C or less, and it is more preferable that it is 50 degrees C or less. This is because, when the temperature of the mixed aqueous solution in the crystallization step is less than 20 ° C., the solubility is low, so that nucleation is likely to occur and control may be difficult. On the other hand, if the temperature of the mixed aqueous solution exceeds 70 ° C. in the crystallization step, the primary crystal may be distorted and the tap density may be lowered.

  Although the ammonium ion concentration in the mixed aqueous solution in the crystallization step is not particularly limited, for example, it is preferably 0 g / L or more and 20 g / L or less, and particularly preferably maintained at a constant value. By setting the ammonium ion concentration to 20 g / L or less, fine particles (primary particles) that are the cores (nuclear particles) of the precursor can be grown uniformly. Further, since the ammonium ion concentration is maintained at a constant value, the solubility of metal ions can be stabilized, and the growth of uniform precursor nuclei (core particles) can be promoted.

  The lower limit value of the ammonium ion concentration can be appropriately adjusted as necessary, and is not particularly limited. Therefore, the ammonium ion concentration in the mixed aqueous solution is adjusted to be 0 g / L or more and 20 g / L or less, for example, by using an ammonium ion supplier in the initial aqueous solution or the pH adjusting aqueous solution and adjusting the supply amount. It is preferable to do.

  The ammonium ion concentration in the precursor particle-containing aqueous solution can be measured by a known ion meter or the like.

  When the addition to the initial aqueous solution such as the metal component-containing mixed aqueous solution is completed, the mixed aqueous solution can be a precursor particle-containing aqueous solution containing sufficiently grown precursor particles.

  Thus, in the crystallization step, fine particles (primary particles) that are the cores (nuclear particles) of the precursor can be generated and grown in the aqueous solution containing the precursor particles. Then, the crystallization process is continued until the core particles grow to a desired particle size, and the core particles are grown to obtain a precursor having porous secondary particles having a desired particle size. it can.

  Further, in order to uniformly coat the surface of the porous secondary particles as the precursor with the additive element M, for example, a coating step of coating with the additive element M is performed after the completion of the crystallization process. May be. The covering process will be described later.

(Other aspects of crystallization process)
In the precursor manufacturing method of the present embodiment, as shown in FIG. 1, the crystallization process is composed of one process, but is not limited thereto. For example, the crystallization process can include a nucleation process and a particle growth process.

Specifically, in the precursor manufacturing method of the present embodiment, the crystallization step can include the following steps.
In the presence of carbonate ions, an initial aqueous solution containing at least one of an ammonium ion supplier and an alkaline substance, an aqueous solution containing Ni as a metal component, an aqueous solution containing Co as a metal component, and Mn as a metal component A nucleation step of generating nuclei in a mixed aqueous solution mixed with an aqueous solution.
A particle growth step for growing the nuclei generated in the nucleation step.

  The nucleation step is preferably performed in an oxygen-containing atmosphere by controlling the pH value of the mixed aqueous solution to 7.5 or less on the basis of the reaction temperature of 40 ° C.

  In FIG. 2, another example of the flow of the manufacturing method of the precursor of this embodiment is shown. As shown in FIG. 2, in the precursor manufacturing method of the present embodiment, the crystallization step includes a nucleation step and a particle growth step of generating precursor particles by a coprecipitation method after performing the nucleation step. Including. In the nucleation step, a nucleation reaction mainly occurs, and the particle growth step is a step in which a particle growth reaction mainly occurs. Since the crystallization process includes a nucleation process and a particle growth process, precursor particles having a narrower particle size distribution can be obtained.

  Hereafter, each process of the manufacturing method of the precursor of this embodiment shown in FIG. 2 is demonstrated concretely. A part of the content common to the crystallization step of the precursor manufacturing method of the present embodiment shown in FIG. 1 is partially omitted.

(1-1) Nucleation Step The nucleation step will be described with reference to FIG. As shown in FIG. 2, in the nucleation step, first, ion-exchanged water (water) and at least one of an ammonium ion supplier and an alkaline substance can be mixed in a reaction tank to prepare an initial aqueous solution.

  As the ammonium ion supplier and the alkaline substance, the same ammonium ion supplier and alkaline substance as in the crystallization step described above can be preferably used.

  In the nucleation step, it is preferable to maintain a mixed aqueous solution in which an aqueous solution containing a metal component such as an aqueous solution containing Ni as a metal component is added to the initial aqueous solution at a lower pH value than the particle growth step described later. This is because by keeping the pH value of the mixed aqueous solution low, the nuclei in the mixed aqueous solution can be reduced and the number can be increased, and the particle size of the secondary particles contained in the resulting precursor can be reduced. Because it becomes.

  Therefore, it is preferable to add an acidic substance to the initial aqueous solution as necessary to adjust the pH value to 7.5 or less, more preferably 5.4 to 7.5, and 6.4. It is more preferable to adjust to 7.4 or less. The pH value is particularly preferably adjusted to 6.4 or more and 7.0 or less.

  During the nucleation step, the mixed aqueous solution preferably has a pH value in the above range. Since the pH value of the mixed aqueous solution slightly fluctuates during the nucleation step, the maximum pH value of the mixed aqueous solution during the nucleation step can be set as the pH value of the mixed aqueous solution in the nucleation step.

  During the nucleation step, the pH value of the mixed aqueous solution is preferably controlled within 0.2 above and below the center value (set pH value), for example.

  As for the acidic substance, the acidic substance described in the above crystallization step can be preferably used.

  In the nucleation step, an oxygen-containing gas is blown into the reaction tank in which the initial aqueous solution has been prepared, and the atmosphere is controlled. Then, the aqueous solution containing the above-described metal components is supplied at a constant flow rate, for example, so that the pH value of the mixed aqueous solution is predetermined. Can be controlled to fall within the range of Thereby, it reacts with dissolved oxygen contained in the mixed aqueous solution, oxygen contained in the oxygen-containing gas supplied to the reaction tank, or the like to produce amorphous fine particles that are not single crystals of carbonate. In addition, by blowing an oxygen-containing gas, it is possible to easily mix a functional group containing hydrogen with respect to the precursor as compared with an inert gas atmosphere. Thereby, H / Me which is a substance amount ratio of the hydrogen H contained in the obtained precursor and the metal component Me contained can be set to 1.60 or more.

  In the nucleation step, the oxygen-containing gas can be continuously supplied into the reaction tank while an aqueous solution containing a metal component such as an aqueous solution containing Ni as a metal component is added to the initial aqueous solution.

  When supplying the oxygen-containing gas into the reaction vessel, the supply amount of the oxygen-containing gas can be confirmed by measuring the dissolved oxygen concentration in the mixed aqueous solution. Since dissolved oxygen in the mixed aqueous solution is consumed during the nucleation step, if the amount of dissolved oxygen in the mixed aqueous solution is half or more of the saturation amount, sufficient oxygen can be supplied to the reaction.

  As the oxygen-containing gas, for example, various gases containing oxygen such as air can be used.

  In the nucleation step, an aqueous solution containing Ni as a metal component, an aqueous solution containing Co as a metal component, and an aqueous solution containing Mn as a metal component are added to and mixed with the initial aqueous solution in the reaction vessel. A mixed aqueous solution can be formed.

  In addition, when adding the aqueous solution etc. which contain Ni as a metal component to initial stage aqueous solution, it is preferable that the pH value of the mixed aqueous solution obtained is controlled to 7.5 or less on the reaction temperature 40 degreeC reference | standard. It is more preferably controlled to 4 or less, and further preferably controlled to 7.0 or less. For this reason, it is preferable that an aqueous solution containing a metal component such as an aqueous solution containing Ni as a metal component is not added all at once but gradually dropped into the initial aqueous solution.

  Further, in order to control the pH of the mixed aqueous solution, the pH adjusting aqueous solution can be dropped together with the dropping of the aqueous solution containing a metal component such as an aqueous solution containing Ni as the metal component. As the pH-adjusted aqueous solution, the same pH-adjusted aqueous solution as in the crystallization step described above can be suitably used.

  And as above-mentioned, it becomes the nucleus (nuclear particle) of a precursor in the mixed aqueous solution obtained by adding the aqueous solution containing metal components, such as the aqueous solution containing Ni as a metal component, to the initial aqueous solution. Fine particles (primary particles) can be generated. Whether or not a predetermined amount of core particles is generated in the mixed aqueous solution can be determined by the amount of the metal salt contained in the mixed aqueous solution.

  Regarding the aqueous solution containing Ni as the metal component, the aqueous solution containing Co as the metal component, and the aqueous solution containing Mn as the metal component, which are added to the initial aqueous solution in the nucleation step, An aqueous solution containing Ni as a metal component similar to the above can be suitably used.

  As described above, the precursor manufactured by the precursor manufacturing method of the present embodiment is Ni: Mn: Co: M = x: y: z: t (provided that x + y + z + t = 1). 0.25 <x <0.60, 0 <y <0.70, 0 <z <0.70, 0 ≦ t ≦ 0.10, and M is Mg, Ca, Al, Ti, V, A nickel cobalt manganese carbonate composite composed of one or more additive elements selected from Cr, Fe, Cu, Zn, Zr, Nb, Mo, and W. and a functional group containing hydrogen Have

  That is, in addition to Ni, Mn, and Co, the additive element M can be further contained.

  For this reason, in the nucleation step, one or more additional elements M selected from Mg, Ca, Al, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, and W are selected as necessary. An aqueous solution containing (an aqueous solution containing the additive element M) can also be added to the initial aqueous solution. About the addition method to the initial aqueous solution of the aqueous solution containing the additive element M and the aqueous solution containing the additive element M, the same method as the case of the crystallization process described above can be used.

  As described above, it is preferable that the additive element M is uniformly distributed and / or uniformly coated on the surface of the core particles contained in the precursor.

  By adding the aqueous solution containing the additive element M described above to the mixed aqueous solution, the additive element M can be uniformly dispersed inside the core particles contained in the precursor.

  In order to uniformly coat the surface of the secondary particles of the precursor with the additive element M, for example, a coating step of coating with the additive element M may be performed after the particle growth step described later. . The covering process will be described later.

  In the nucleation step, as in the crystallization step of the precursor production method of the present embodiment shown in FIG. 1, an aqueous solution containing Ni as a metal component is added to the initial aqueous solution in the presence of carbonate ions. It mixes and it is set as mixed aqueous solution, A nucleus can be produced | generated in this mixed aqueous solution.

  At this time, the method for supplying carbonate ions is not particularly limited. For example, carbonate ions can be supplied to the mixed aqueous solution by supplying carbon dioxide gas together with an oxygen-containing gas described later in the reaction vessel. . Further, when preparing the initial aqueous solution or the pH adjusting aqueous solution, carbonate ions can be supplied using carbonate.

  The temperature of the mixed aqueous solution in the nucleation step is preferably maintained at 20 ° C. or higher, and more preferably maintained at 30 ° C. or higher. In addition, the upper limit of the temperature of the mixed aqueous solution in the nucleation step is not particularly limited, but is preferably 70 ° C. or less, and more preferably 50 ° C. or less, for example. This is because in the nucleation step, when the temperature of the mixed aqueous solution is less than 20 ° C., the solubility is low, so that nucleation is likely to occur and control may be difficult. On the other hand, if the temperature of the mixed aqueous solution exceeds 70 ° C. in the nucleation step, the primary crystal may be distorted and the tap density may be lowered.

  The range of the ammonium ion concentration in the mixed aqueous solution in the nucleation step is preferably set to the same range as in the crystallization step described above, for example. About the measuring method of pH value in mixed aqueous solution, ammonium ion concentration, and dissolved oxygen amount, the method similar to the case of the crystallization process described above can be used suitably.

  After completion of the nucleation step, that is, after the addition to the initial aqueous solution, such as a mixed aqueous solution containing metal components, is completed, it is preferable to continue stirring in the mixed aqueous solution and crush the produced nuclei (nuclear crushing) Process). When performing the nuclear disintegration step, the time is preferably 1 minute or longer, and more preferably 3 minutes or longer. By performing the nuclear disintegration step, the produced nuclei can be aggregated, and the coarsening of the particle diameter and the density reduction inside the particles can be more reliably suppressed.

(1-2) Particle Growth Step Next, the particle growth step will be described with reference to FIG. In the particle growth process, the nuclei generated in the nucleation process can be grown. Specifically, for example, as shown in FIG. 2, in the particle growth step, first, the pH value of the mixed aqueous solution obtained in the nucleation step can be adjusted.

  At this time, the pH value of the mixed aqueous solution can be adjusted, for example, to be 6.0 or more and 9.0 or less on the basis of the reaction temperature of 40 ° C. It can suppress that an impurity cation remains by making pH value of mixed aqueous solution 6.0 or more and 9.0 or less. The pH value of the mixed aqueous solution is more preferably adjusted to be 6.4 or more and 8.0 or less, and further preferably adjusted to be 7.1 or more and 8.0 or less. The pH at this time can be adjusted, for example, by adding the above-described pH adjusting aqueous solution.

  Since the pH value of the mixed aqueous solution slightly fluctuates during the particle growth step, the maximum pH value of the mixed aqueous solution during the particle growth step can be set as the pH value of the mixed aqueous solution in the particle growth step. The pH value of the mixed aqueous solution is preferably in the above range.

  In particular, during the particle growth process, it is preferable to control the fluctuation range of the pH value of the mixed aqueous solution so that it is within 0.2 above and below the center value (set pH value). This is because when the fluctuation range of the pH value of the mixed aqueous solution is large, the growth of the particles contained in the precursor is not constant, and uniform particles with a narrow particle size distribution range may not be obtained. .

  In the particle growth step, in the mixed aqueous solution after the nucleation step, in the presence of carbonate ions, an aqueous solution containing Ni as a metal component, an aqueous solution containing Co as a metal component, and an aqueous solution containing Mn as a metal component Can be added and mixed.

  Here, the mixed aqueous solution after the nucleation step is preferably a mixed aqueous solution whose pH is adjusted after the nucleation step as described above.

  Further, an aqueous solution containing Ni as a metal component, an aqueous solution containing Co as a metal component, and an aqueous solution containing Mn as a metal component are mixed partly or entirely, as in the case of the nucleation step, The mixed aqueous solution containing metal components may be added to the mixed aqueous solution. In addition, when a plurality of metal compounds are mixed to produce an unnecessary compound due to a reaction between specific metal compounds, an aqueous solution containing each metal component is added individually to the mixed aqueous solution. Also good.

  Furthermore, when an aqueous solution containing Ni as a metal component is added to the mixed aqueous solution, an aqueous solution containing the additive element M can also be added in the same manner as in the nucleation step. As described above, an aqueous solution containing the additive element M can be mixed and added to the mixed aqueous solution containing metal components. In addition, when the aqueous solution containing each metal component is individually added to the mixed aqueous solution, the aqueous solution containing the additive element M can also be individually added to the mixed aqueous solution.

  As the aqueous solution containing Ni as the metal component, the aqueous solution containing Co as the metal component, and the aqueous solution containing Mn as the metal component, the same aqueous solution as in the nucleation step described above can be used. Further, the density and the like may be adjusted separately.

  When an aqueous solution containing Ni as a metal component is added to the mixed aqueous solution, the pH value of the obtained mixed aqueous solution is preferably controlled within a predetermined range as described later. For this reason, the aqueous solution containing Ni as a metal component can be gradually dropped into the mixed aqueous solution, not added at once. Therefore, a solution containing these metal components or a mixed aqueous solution containing the metal components can be supplied to the reaction tank, for example, at a constant flow rate.

  In the particle growth step, as described above, an aqueous solution containing a metal component such as an aqueous solution containing Ni as a metal component can be added to the mixed aqueous solution after adjustment of the pH value. Also in this case, the pH value of the mixed aqueous solution after adjusting the pH value is in the same range as that of the mixed aqueous solution, that is, 6.0 or more, for the same reason that the pH value was adjusted before the start of the particle growth step. It is preferably maintained at 9.0 or less. In the particle growth step, a precursor having a small amount of remaining impurities can be obtained by controlling the pH value of the mixed aqueous solution within the above range. The pH value of the mixed aqueous solution is more preferably maintained at 6.4 or more and 8.0 or less, and further preferably at 7.1 or more and 8.0 or less.

  In addition, since the pH value of the mixed aqueous solution after the pH value adjustment slightly fluctuates during the particle growth step, the maximum pH value of the mixed aqueous solution after the pH value adjustment during the particle growth step is set as the mixing value in the particle growth step. The pH value of the aqueous solution can be set, and the pH value of the mixed aqueous solution after the pH value adjustment is preferably in the above range.

  In particular, during the particle growth step, it is preferable to control the fluctuation range of the pH value of the mixed aqueous solution after adjusting the pH value so that it is within 0.2 above and below the center value (set pH value). This is because when the pH value of the mixed aqueous solution after adjusting the pH value is large, the growth of particles contained in the precursor is not constant, and uniform particles with a narrow particle size distribution range cannot be obtained. Because there is.

  As described above, when supplying an aqueous solution containing a metal component or a mixed aqueous solution containing a metal component to the mixed aqueous solution, a pH adjusting aqueous solution is added so that the pH of the mixed aqueous solution can be maintained within a predetermined range. It is preferable. As the pH adjustment aqueous solution, the same pH adjustment aqueous solution as in the above-described nucleation step can be used. As the method for supplying the pH-adjusted aqueous solution into the reaction vessel, the above-described method can be suitably used in the above-described nucleation step.

  In the particle growth step, the ammonium ion concentration in the mixed aqueous solution is preferably 0 g / L or more and 20 g / L or less, and particularly preferably maintained at a constant value. This is because by setting the ammonium ion concentration to 20 g / L or less, the nuclei of the precursor particles can be uniformly grown. In addition, since the ammonium ion concentration in the particle growth step is maintained at a constant value, the solubility of metal ions can be stabilized, and the particle growth of uniform precursor particles can be promoted.

  The lower limit value of the ammonium ion concentration can be appropriately adjusted as necessary, and is not particularly limited. Therefore, the ammonium ion concentration in the mixed aqueous solution is adjusted to be 0 g / L or more and 20 g / L or less, for example, by using an ammonium ion supplier for the initial aqueous solution or the pH adjusting aqueous solution and adjusting the supply amount. It is preferable.

  In the particle growth step, an aqueous solution containing a metal component such as an aqueous solution containing Ni as a metal component can be added to and mixed with the mixed aqueous solution in the presence of carbonate ions. At this time, the method for supplying carbonate ions is not particularly limited. For example, carbonate ions can be supplied to the mixed aqueous solution by supplying carbon dioxide gas together with an oxygen-containing gas described later in the reaction vessel. Further, when preparing the above-mentioned initial aqueous solution and pH-adjusted aqueous solution, carbonate ions can be supplied using carbonate.

  In the particle growth process, an aqueous solution containing a metal component such as an aqueous solution containing Ni as a metal component is controlled at a constant flow rate while controlling the atmosphere so as to become an oxygen-containing atmosphere by blowing an oxygen-containing gas into the reaction vessel. Can be supplied at. As a result, it reacts with dissolved oxygen contained in the mixed aqueous solution, oxygen contained in the oxygen-containing gas supplied to the reaction tank, etc. to further agglomerate amorphous fine particles that are not single crystals of carbonate. It is possible to generate large secondary particles. Further, by blowing an oxygen-containing gas, it is possible to easily mix a functional group containing hydrogen with respect to the precursor as compared with the case of an inert gas atmosphere. Thereby, H / Me, which is a substance amount ratio between the hydrogen H contained in the obtained precursor and the metal component Me contained, can be more reliably set to 1.60 or more.

  In addition, when supplying oxygen-containing gas in a reaction tank in a particle growth process, supply_amount | feed_rate of this oxygen-containing gas can be confirmed by measuring the dissolved oxygen concentration in mixed aqueous solution. Since dissolved oxygen in the mixed aqueous solution is consumed during the particle growth step, if the amount of dissolved oxygen in the mixed aqueous solution is more than half of the saturation amount, sufficient oxygen can be supplied to the reaction.

  As the oxygen-containing gas, for example, various gases containing oxygen such as air can be used.

  The particle size of the secondary particles contained in the precursor can be controlled by the reaction time in the particle growth process. That is, in the particle growth step, a precursor having porous secondary particles having a desired particle diameter can be obtained by continuing the reaction until the particle has grown to a desired particle diameter.

  As described above, by performing the crystallization step shown in FIG. 1 or 2, a precursor particle aqueous solution that is a slurry containing the precursor particles is obtained.

  In addition, in the precursor manufacturing method of the present embodiment, it is preferable to use an apparatus that does not collect the precursor as a product until the reaction in the crystallization process is completed. Examples of such an apparatus include a normally used batch reaction tank equipped with a stirrer. By adopting such a device, unlike the continuous crystallization device that recovers the product by a general overflow, there is no problem that the growing particles are recovered simultaneously with the overflow liquid, so the particle size distribution is narrow, Particles having a uniform particle size can be obtained, which is preferable.

  In order to control the atmosphere of the reaction tank, it is preferable to use an apparatus capable of controlling the atmosphere, such as a sealed apparatus.

  By using an apparatus capable of controlling the atmosphere of the reaction vessel, the particles contained in the precursor can be made to have the structure as described above, and the coprecipitation reaction can be advanced almost uniformly. Particles having an excellent distribution, that is, particles having a narrow particle size distribution range can be obtained.

  In the particle growth step, the pH value of the mixed aqueous solution obtained in the nucleation step is adjusted to be within a predetermined range, and an aqueous solution containing a metal component such as an aqueous solution containing Ni as a metal component is further added to the mixed aqueous solution. By doing so, uniform precursor particles can be obtained.

(Coating process)
Further, in the method for producing the precursor of the present embodiment, after obtaining the particles (secondary particles) of the precursor of the present embodiment in the crystallization step, the surface of the obtained precursor particles of the present embodiment is obtained. Further, a coating step of coating with the additive element M can be further included.

The coating process can be, for example, any of the following processes.
A step of adding an aqueous solution containing the additive element M to the slurry in which the precursor particles are suspended, and precipitating the additive element M on the surface of the precursor particles by a crystallization reaction.
A step of spraying and drying an aqueous solution or slurry containing the additive element M on the precursor particles.
A step of spraying and drying a slurry in which the precursor particles and the compound containing the additive element M are suspended.
A step of mixing the precursor particles and the compound containing the additive element M by a solid phase method.

  For example, the coating step is a step of adding an aqueous solution containing the additive element M to a slurry in which the precursor particles are suspended and precipitating the additive element M on the surface of the precursor particles by a crystallization reaction. In this case, the slurry in which the precursor particles are suspended is preferably slurried using an aqueous solution containing the additive element M. Further, when the aqueous solution containing the additive element M is added to the slurry in which the precursor particles are suspended, the pH of the mixed aqueous solution of the slurry and the aqueous solution containing the additive element M is 6.0 or more and 9.0 or less. It is preferable to control as described above. This is because the surface of the precursor particles can be particularly uniformly coated with the additive element M by controlling the pH of the mixed aqueous solution of the slurry and the aqueous solution containing the additive element M within the above range.

  In addition, about the aqueous solution containing the additional element M used at a coating process, the same aqueous solution as the case of the nucleation process mentioned above can be used. In the coating step, an alkoxide solution containing the additive element M may be used instead of the aqueous solution containing the additive element M.

  As described above, the surface of the precursor particles can be coated with the additive element M by adding the aqueous solution containing the additive element M to the initial aqueous solution or the mixed aqueous solution in the crystallization step and performing the coating step. In this case, it is preferable to reduce the amount of additive element ions added to the initial aqueous solution or the mixed aqueous solution in the crystallization step by the amount to be coated. This is because the addition ratio of the aqueous solution containing the additive element M added to the mixed aqueous solution is reduced by an amount covering the atomic ratio between the additive element M contained in the obtained precursor and other metal components. This is because can be set to a desired value.

  As described above, the coating step of coating the surface of the precursor particles with the additive element M may be performed on the heated precursor particles after the completion of the crystallization step.

  Next, after the crystallization process shown in FIG. 1 or FIG. 2 is finished, a washing process or a drying process may be performed. Hereinafter, the cleaning process and the drying process will be described.

(2) Cleaning process The cleaning process will be described. In the washing step, the slurry containing the precursor particles obtained in the crystallization step shown in FIG. 1 or 2 can be washed.

  In the washing step, first, the slurry containing the precursor particles can be filtered, then washed with water, and filtered again.

  Filtration may be performed by a commonly used method. For example, a centrifuge or a suction filter is used.

  Washing with water may be performed by a commonly performed method as long as excessive raw materials contained in the precursor particles can be removed.

  The water used in the water washing is preferably water having as little impurity content as possible, and more preferably pure water, in order to prevent contamination of impurities.

(3) Drying process A drying process is demonstrated. In the drying step, the particles of the precursor of the present embodiment washed in the washing step can be dried. First, in the drying step, for example, the dried precursor particles can be dried at a drying temperature of 80 ° C. or higher and 230 ° C. or lower.

  After the drying step, the precursor of this embodiment can be obtained.

  According to the method for producing a precursor of this embodiment, a precursor capable of forming a positive electrode active material for a nonaqueous electrolyte secondary battery containing porous particles can be obtained.

  In the precursor manufacturing method of the present embodiment, the crystal size of the precursor particles obtained by the crystallization reaction can be controlled. Therefore, according to the precursor manufacturing method of the present embodiment, a primary particle is a small particle size, a secondary particle size is highly uniform, and a high density (tap density) precursor is obtained. Can do.

  In addition, according to the precursor manufacturing method of the present embodiment shown in FIG. 2, the time during which the nucleation reaction mainly occurs (nucleation process) and the time during which the particle growth reaction mainly occurs (particle growth process) are separated. Can do. Thereby, even if both processes are performed in the same reaction vessel, precursor particles (secondary particles) having a narrow particle size distribution are obtained.

  Furthermore, in the method for producing a precursor of this embodiment shown in FIG. 2, the nucleation step and the particle growth step can be performed separately in one reaction tank mainly by adjusting the pH of the reaction solution. it can.

  Therefore, the precursor production method of the present embodiment is easy and suitable for large-scale production, so that it can be said that its industrial value is extremely large.

[Positive electrode active material for non-aqueous electrolyte secondary battery]
Next, a configuration example of the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present embodiment (hereinafter also simply referred to as “positive electrode active material”) will be described.

  The positive electrode active material of this embodiment is related with the positive electrode active material for nonaqueous electrolyte secondary batteries containing a lithium metal complex oxide. The lithium metal composite oxide is Li: Ni: Mn: Co: M = α: x: y: z: t (1.00 ≦ α ≦ 1.30, x + y + z + t = 1) in terms of mass ratio, 0 .25 <x <0.60, 0 <y <0.70, 0 <z <0.70, 0 ≦ t ≦ 0.10, M is Mg, Ca, Al, Ti, V, Cr, Fe, And one or more additive elements selected from Cu, Zn, Zr, Nb, Mo, and W.

  The positive electrode active material of the present embodiment can include porous secondary particles in which a plurality of primary particles are aggregated. And among the porous secondary particles, the number ratio of the secondary particles having a porosity inside the secondary particles of 10% or more and 30% or less can be 80% or more.

The positive electrode active material of the present embodiment can include a lithium metal composite oxide having a layered rock salt type crystal structure represented by LiAO ₂ , more specifically, a lithium nickel cobalt manganese composite oxide. In addition, the positive electrode active material of this embodiment can also be comprised from the said lithium metal complex oxide.

  In the above substance amount ratio, A is a metal element containing at least Ni, Co, and Mn adjusted to be trivalent on average.

  In the precursor of the present embodiment, as described above, in order to further improve battery characteristics such as cycle characteristics and output characteristics of the positive electrode active material of the non-aqueous electrolyte secondary battery, the lithium metal composite oxide is as described above. In addition, one or more additive elements M selected from Mg, Ca, Al, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, and W can be contained. About the content of the additive element M, it is preferable to adjust so that it may become in the range of 0 <= t <= 0.1 by substance amount ratio t in a precursor for the above-mentioned reason.

  As described above, the positive electrode active material of the present embodiment can contain porous secondary particles, and the porous secondary particles have a porosity inside the secondary particles of 10% or more and 30%. Contains porous secondary particles that are: The positive electrode active material of this embodiment contains 80% or more of secondary particles having a porosity of 10% or more and 30% or less of the secondary particles among the porous secondary particles contained. . The porosity of the porous secondary particles contained in the positive electrode active material can be calculated by, for example, observing the cross-sectional structure of the positive electrode active material with an SEM and performing image processing or the like. For example, particles having a calculated porosity exceeding 3% are defined as porous secondary particles (porous particles). The porous particles can be particles having pores up to the center. And the ratio of the porous secondary particle which a positive electrode active material contains is although it does not specifically limit, For example, it can be 30% or more and 100% or less by a number ratio.

  The calculation method of the number ratio of the porous secondary particles and the number ratio of the porous secondary particles whose porosity is 10% or more and 30% or less among the porous secondary particles is as follows. There is no particular limitation. In the calculation method, for example, first, a cross-sectional structure of a plurality of, for example, 100 or more positive electrode active materials is observed with an SEM, and the number of secondary particles serving as a reference among the secondary particles is counted. You can ask for it.

The positive electrode active material of this embodiment can enlarge the specific surface area by having porous secondary particles. The specific surface area of the positive electrode active material of the present embodiment can be arbitrarily selected depending on the characteristics required of the positive electrode active material, and is not particularly limited, but is, for example, 1.0 m ² / g or more. Is preferred. This is because, by setting the specific surface area of the positive electrode active material of the present embodiment to 1.0 m ² / g or more, the production of the positive electrode mixture paste can be facilitated and the output characteristics can be improved. It is.

The positive electrode active upper limit of the specific surface area of material of the present embodiment is not particularly limited, for example, preferably to 3.0 m 2 / ^g or less, and more preferably to 2.0 m 2 / ^g or less. However, the specific surface area of the positive electrode active material of the present embodiment is 1.0 m ² / g or more and 2.0 m ² / g or less, particularly when the reaction surface area is increased and the output characteristics are particularly required to be increased. Is preferred. In particular, when it is required to particularly facilitate the production of the positive electrode mixture paste, the specific surface area of the positive electrode active material of the present embodiment is 0.5 m ² / g or more and 1.5 m ² / g or less. It is preferable.

  Moreover, according to the positive electrode active material of the present embodiment, the porous material contains porous secondary particles, and the porosity inside the secondary particles is 10% or more and 30% or less among the porous secondary particles. By having the secondary particles of at least a certain ratio, it is possible to improve the output characteristics in the case of a battery and to increase the tap density.

  The tap density of the positive electrode active material of the present embodiment is not particularly limited, but is preferably 1.5 g / cc or more, and more preferably 1.7 g / cc or more.

  For example, when the positive electrode active material of this embodiment is used for the positive electrode of a 2032 type coin-type battery, when charged at a current of 0.05 C, the capacity of the discharge current of 2.0 C relative to the capacity at the discharge current of 0.05 C (discharge) The capacity retention ratio is preferably 85% or more.

  Note that the discharge capacity under the high discharge rate condition (2C) can be measured at 2C a plurality of times, for example, three times, and can be an average value of the plurality of times of measurement.

[Method for producing positive electrode active material for non-aqueous electrolyte secondary battery]
Next, an example of a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery of the present embodiment (hereinafter, also simply referred to as “a method for producing a positive electrode active material”) will be described.

  The method for producing the positive electrode active material of the present embodiment is not particularly limited as long as the positive electrode active material can be produced so as to have the particle structure of the positive electrode active material described above, but if the following method is adopted, the positive electrode active material is produced. This is preferable because the substance can be produced more reliably.

The manufacturing method of the positive electrode active material of this embodiment can have the following processes.
A heat treatment step of heat-treating the positive electrode active material precursor for a non-aqueous electrolyte secondary battery obtained by the above-described method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery at a temperature of 80 ° C. or higher and 600 ° C. or lower.
A mixing step in which a lithium compound is added to and mixed with the particles obtained by the heat treatment step to form a lithium mixture.
A firing step of firing the lithium mixture at a temperature of 600 ° C. or higher and 1000 ° C. or lower in an oxidizing atmosphere.

  Hereinafter, each step will be described.

(1) Heat treatment step In the heat treatment step, the precursor described above can be heat treated at a temperature of 80 ° C or higher and 600 ° C or lower. By performing the heat treatment, moisture contained in the precursor can be removed, and variation in the ratio of the number of metal atoms and the number of lithium atoms in the finally obtained positive electrode active material can be prevented.

  It should be noted that all the precursors need not be converted into nickel-cobalt-manganese composite oxides, as long as moisture can be removed to such an extent that variations in the number of metal atoms and the number of lithium atoms in the positive electrode active material do not occur. However, in order to reduce the variation, it is preferable to convert all the precursor particles into composite oxide particles by setting the heating temperature to 500 ° C. or higher.

  In the heat treatment step, the heat treatment temperature is set to 80 ° C. or higher because when the heat treatment temperature is less than 80 ° C., excess moisture in the particles of the precursor cannot be removed and the above variation may not be suppressed. It is. On the other hand, the heat treatment temperature is set to 600 ° C. or lower because if the heat treatment temperature exceeds 600 ° C., the particles may be sintered by roasting and composite oxide particles having a uniform particle size may not be obtained. is there.

  By previously determining the metal component contained in the precursor particles corresponding to the heat treatment conditions by analysis and determining the ratio with the lithium compound, the above-described variation can be suppressed.

  The heat treatment atmosphere is not particularly limited and may be a non-reducing atmosphere, but is preferably performed in an air stream that can be easily performed.

  In addition, the heat treatment time is not particularly limited, but if it is less than 1 hour, excess moisture from the precursor particles may not be sufficiently removed, it is preferably at least 1 hour or more and more preferably 2 hours or more and 15 hours or less. preferable.

  The equipment used for the heat treatment is not particularly limited, as long as the precursor particles can be heated in a non-reducing atmosphere, preferably in an air stream, and an electric furnace that does not generate gas is suitable. Used.

(2) Mixing step The mixing step is a step of forming a lithium mixture by adding and mixing a lithium compound to the heat-treated particles obtained by heating in the heat treatment step.

  The heat-treated particles obtained by heat treatment in the heat treatment step include nickel cobalt manganese carbonate composite particles and / or nickel cobalt manganese composite oxide particles.

  The heat-treated particles and the lithium compound are the number of atoms of the metal component Me other than lithium in the lithium mixture, that is, the sum of the number of atoms of Ni, Co, Mn, and the additive element M (Me), and the number of lithium atoms (Li It is preferable to mix so that a ratio (Li / Me) to 1.0 or more and 1.3 or less. At this time, it is more preferable to mix so that Li / Me is 1.05 or more and 1.15 or less.

  That is, since Li / Me does not change before and after the firing step, Li / Me mixed in this mixing step becomes Li / Me in the positive electrode active material, so that Li / Me in the lithium mixture is to be obtained. To be the same as Li / Me.

  The lithium compound used to form the lithium mixture is not particularly limited, but is preferably one or more selected from, for example, lithium hydroxide, lithium nitrate, and lithium carbonate because it is easily available. Can be used. In particular, in view of ease of handling and quality stability, it is more preferable to use at least one selected from lithium hydroxide and lithium carbonate as the lithium compound used in forming the lithium mixture.

  For mixing, a general mixer can be used, and for example, a shaker mixer, a Laedige mixer, a Julia mixer, a V blender, or the like may be used.

(3) Firing step The firing step is a step in which the lithium mixture obtained in the mixing step is fired to obtain a positive electrode active material. When the mixed powder is fired in the firing step, lithium in the lithium compound diffuses into the heat-treated particles, so that a lithium nickel cobalt manganese composite oxide is formed.

  The firing temperature of the lithium mixture at this time is not particularly limited, but is preferably 600 ° C. or higher and 1000 ° C. or lower, for example. This is because when the firing temperature is set to 600 ° C. or higher, the diffusion of lithium into the heat-treated particles is sufficiently promoted, and the remaining of excess lithium and unreacted particles is suppressed and used in a battery. This is because sufficient battery characteristics can be obtained. However, if the firing temperature exceeds 1000 ° C., intense sintering occurs between the composite oxide particles and abnormal grain growth may occur, and the particles after firing become coarse and fine pores are formed inside the particles. This is because there is a possibility that it will not be possible. Since such a positive electrode active material has a reduced specific surface area, when used in a battery, the resistance of the positive electrode may increase and the battery capacity may decrease.

  In addition, from the viewpoint of uniformly performing the reaction between the heat-treated particles and the lithium compound, it is preferable to raise the temperature to the above temperature with a rate of temperature increase of 3 ° C./min to 10 ° C./min.

  Furthermore, the reaction can be performed more uniformly by maintaining at a temperature near the melting point of the lithium compound for about 1 hour to 5 hours. When the temperature is maintained near the melting point of the lithium compound, the temperature can be raised to a predetermined firing temperature.

  Of the firing time, the holding time at the firing temperature is preferably 1 hour or longer, and more preferably 2 hours or longer and 24 hours or shorter. This is because the generation of the lithium nickel cobalt manganese composite oxide can be sufficiently promoted by holding at the firing temperature for 2 hours or more.

  After completion of the holding time at the firing temperature, there is no particular limitation. However, when the lithium mixture is loaded on the sagger and baked, the rate of descent is 2 ° C./min to 10 ° C. to suppress deterioration of the sachet. It is preferable that the atmosphere is cooled to 200 ° C. or lower as the temperature / ° C. or lower.

  The atmosphere during firing is preferably an oxidizing atmosphere, more preferably an oxygen concentration of 18% by volume to 100% by volume, and a mixed atmosphere of oxygen and an inert gas having the oxygen concentration. Is particularly preferred. That is, the firing is preferably performed in the atmosphere or an oxygen-containing gas.

  As described above, an atmosphere having an oxygen concentration of 18% by volume or more is preferable because the crystallinity of the lithium nickel cobalt manganese composite oxide can be sufficiently increased by setting the oxygen concentration to 18% by volume or more. Because it can.

  Considering battery characteristics in particular, it is preferably performed in an oxygen stream.

  The furnace used for firing is not particularly limited as long as the lithium mixture can be heated in the atmosphere or an oxygen-containing gas. However, from the viewpoint of maintaining a uniform atmosphere in the furnace, gas generation is not caused. No electric furnace is preferred. In addition, either a batch type or continuous type furnace can be used.

  Further, when lithium hydroxide or lithium carbonate is used as the lithium compound, it is preferably calcined after the mixing step and before the firing step. The calcination temperature is lower than the firing temperature and is preferably 350 ° C. or higher and 800 ° C. or lower, and more preferably 450 ° C. or higher and 780 ° C. or lower.

  The calcination time is preferably about 1 hour to 10 hours, more preferably 3 hours to 6 hours.

  Note that the calcination is preferably carried out while maintaining the calcination temperature. In particular, it is preferable to calcine at a reaction temperature between lithium hydroxide or lithium carbonate and the heat-treated particles.

  When calcination is performed, lithium is sufficiently diffused into the heat-treated particles, and a uniform lithium nickel cobalt manganese composite oxide can be obtained, which is preferable.

  The particles of the lithium nickel cobalt manganese composite oxide obtained by the firing step may be aggregated or slightly sintered. In this case, it may be crushed. Thereby, the positive electrode active material of this embodiment containing a lithium nickel cobalt manganese composite oxide can be obtained.

  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. This is an operation of separating the secondary particles and loosening the aggregates.

[Nonaqueous electrolyte secondary battery]
Next, a configuration example of the non-aqueous electrolyte secondary battery of the present embodiment will be described. The non-aqueous electrolyte secondary battery of this embodiment can have a positive electrode using the positive electrode active material described above.

  First, the structure of the nonaqueous electrolyte secondary battery of this embodiment will be described.

  The non-aqueous electrolyte secondary battery of the present embodiment (hereinafter also simply referred to as “secondary battery”) is a general non-aqueous system except that the positive electrode active material of the present embodiment is used as the positive electrode material. It can have substantially the same structure as the electrolyte secondary battery.

  The secondary battery of this embodiment can have a structure including, for example, a case and a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator housed in the case.

  More specifically, the secondary battery of the present embodiment can have an electrode body in which a positive electrode and a negative electrode are stacked via a separator. Then, the electrode body is impregnated with a non-aqueous electrolyte, and the current is collected between the positive electrode current collector of the positive electrode and the positive electrode terminal communicating with the outside, and between the negative electrode current collector of the negative electrode and the negative electrode terminal communicating with the outside, respectively. It can be connected with a lead or the like and sealed in a case.

  Note that the structure of the secondary battery of the present embodiment is not limited to the above example, and various shapes such as a cylindrical shape and a laminated shape can be adopted as the outer shape.

(Positive electrode)
First, the positive electrode that is a feature of the secondary battery of this embodiment will be described. The positive electrode is a sheet-like member, and is formed by applying and drying a positive electrode mixture paste containing the above-described positive electrode active material on the surface of a current collector made of aluminum foil, for example.

  In addition, a positive electrode is suitably processed according to the battery to be used. For example, a cutting process for forming an appropriate size according to a target battery, a pressure compression process using a roll press or the like to increase the electrode density, and the like are performed.

  The positive electrode mixture paste can be formed by adding and kneading a solvent to the positive electrode mixture. The positive electrode mixture can be formed by mixing the above-described positive electrode active material in a powder form, a conductive material, and a binder.

  The conductive material is added to give an appropriate conductivity to the electrode. The conductive material is not particularly limited, and for example, graphite (natural graphite, artificial graphite, expanded graphite, and the like), and carbon black materials such as acetylene black and ketjen black can be used.

  The binder plays a role of tethering the positive electrode active material particles. The binder used in this positive electrode mixture is not particularly limited. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluorine rubber, ethylene propylene diene rubber, styrene butadiene, cellulose resin, Alternatively, polyacrylic acid or the like can be used.

  In addition, activated carbon etc. may be added to a positive electrode compound material, and the electric double layer capacity | capacitance of a positive electrode can be increased by adding activated carbon etc.

  The solvent dissolves the binder and disperses the positive electrode active material, the conductive material, activated carbon, and the like in the binder. The solvent is not particularly limited, and for example, an organic solvent such as N-methyl-2-pyrrolidone can be used.

  Moreover, the mixing ratio of each substance in the positive electrode mixture paste is not particularly limited. For example, when the solid content of the positive electrode mixture excluding the solvent is 100 parts by mass, the content of the positive electrode active material is 60 parts by mass or more and 95 parts by mass or less, as in the case of the positive electrode of a general nonaqueous electrolyte secondary battery. The content of the material can be 1 part by mass or more and 20 parts by mass or less, and the content of the binder can be 1 part by mass or more and 20 parts by mass or less.

(Negative electrode)
The negative electrode is a sheet-like member formed by applying a negative electrode mixture paste to the surface of a metal foil current collector such as copper and drying it. The negative electrode is formed by substantially the same method as the positive electrode, although the components constituting the negative electrode mixture paste, the composition thereof, and the current collector material are different. Is done.

  The negative electrode mixture paste is a paste obtained by adding an appropriate solvent to a negative electrode mixture in which a negative electrode active material and a binder are mixed.

  As the negative electrode active material, for example, a material containing lithium, such as metallic lithium or a lithium alloy, or an occlusion material that can occlude and desorb lithium ions can be employed.

  The occlusion material is not particularly limited, and for example, natural graphite, artificial graphite, an organic compound fired body such as phenol resin, and a carbon material powder such as coke can be used. When such an occlusion material is employed as the negative electrode active material, a fluorine-containing resin such as PVDF can be used as the binder, as with the positive electrode, and as a solvent for dispersing the negative electrode active material in the binder, An organic solvent such as N-methyl-2-pyrrolidone can be used.

(Separator)
The separator is disposed so as to be sandwiched between the positive electrode and the negative electrode, and has a function of separating the positive electrode and the negative electrode and holding the electrolyte. As such a separator, for example, a thin film such as polyethylene or polypropylene and a film having a large number of fine pores can be used. However, the separator is not particularly limited as long as it has the above function.

(Non-aqueous electrolyte)
The non-aqueous electrolyte is obtained by dissolving a lithium salt as a supporting salt in an organic solvent.

  Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and trifluoropropylene carbonate; chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and dipropyl carbonate; Ether compounds such as methyltetrahydrofuran and dimethoxyethane; sulfur compounds such as ethyl methyl sulfone and butane sultone; phosphorus compounds such as triethyl phosphate and trioctyl phosphate used alone or in admixture of two or more Can do.

As the supporting salt, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , and complex salts thereof can be used.

  The non-aqueous electrolyte may contain a radical scavenger, a surfactant, a flame retardant, or the like for improving battery characteristics.

(Characteristics of the non-aqueous electrolyte secondary battery of this embodiment)
The nonaqueous electrolyte secondary battery of the present embodiment can have the above-described configuration, for example, and has a positive electrode using the above-described positive electrode active material, so that a high initial discharge capacity and a low positive electrode resistance are obtained. High capacity and high output.

(Use of secondary battery of this embodiment)
Since the secondary battery of this embodiment has the above properties, it is suitable for the power source of small portable electronic devices (such as notebook personal computers and mobile phone terminals) that always require high capacity.

  Further, the secondary battery of the present embodiment is also suitable for a battery as a motor driving power source that requires a high output. When the battery size increases, it becomes difficult to ensure safety, and an expensive protection circuit is indispensable. However, the secondary battery of this embodiment has excellent safety, so ensuring safety Not only becomes easy, but also an expensive protection circuit can be simplified and the cost can be reduced. And since it can be reduced in size and increased in output, it is suitable as a power source for transportation equipment subject to restrictions on the mounting space.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

  The sample preparation conditions and evaluation results in each example and comparative example are described below.

[Example 1]
1. Precursor production and evaluation [Precursor production]
First, a precursor was prepared by the following procedure.

  Throughout all examples and comparative examples, the preparation of the precursor, the positive electrode active material, and the secondary battery use each reagent-grade sample manufactured by Wako Pure Chemical Industries, Ltd. unless otherwise specified. .

(Crystallization process)
As shown in FIG. 2, the crystallization process was performed in a process including a nucleation process and a particle growth process. Hereinafter, the nucleation step and the particle growth step will be described.

(Nucleation process)
(1) Preparation of initial aqueous solution First, in a reaction tank (5 L), water is added to an amount of about 1.2 L, and the temperature in the tank is set to 40 ° C. while stirring. The mixed aqueous solution was controlled to 40 ° C. in the crushing step and the particle growth step. The temperatures of the initial aqueous solution and the mixed aqueous solution were controlled by adjusting the temperature of the warming water for the reaction vessel provided around the reaction vessel.

  And the appropriate amount of 25 mass% ammonia water was added to the water in a reaction tank, and the ammonium ion concentration in initial stage aqueous solution was adjusted to 5 g / L. 64% sulfuric acid was further added to the initial aqueous solution to adjust the pH to 6.4.

  Then, air gas was supplied from the air compressor at 4 L / min as an oxygen-containing gas into the reaction tank, and the inside of the tank was purged to create an atmosphere containing oxygen. The supply of air gas is continued until the particle growth step is completed, and the reaction vessel is maintained in an air atmosphere, that is, an oxygen-containing atmosphere.

(2) Preparation of metal component-containing mixed aqueous solution Next, nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in water to prepare a metal component-containing mixed aqueous solution having a metal ion concentration of 2.0 mol / L. In this metal component-containing mixed aqueous solution, the element molar ratio of each metal was adjusted to be Ni: Co: Mn = 0.334: 0.333: 0.333.

(3) Adjustment of pH adjustment aqueous solution Sodium carbonate and ammonium carbonate were dissolved in water to prepare a pH adjustment aqueous solution having a carbonate ion concentration of 2.2 mol / L. The sodium carbonate and ammonium carbonate in the pH-adjusted aqueous solution were added so that the molar ratio was 9: 2.

(4) Addition and mixing of metal component-containing mixed aqueous solution to initial aqueous solution Add metal component-containing mixed aqueous solution to the initial aqueous solution in the reaction vessel at 10.3 ml / min. To obtain a mixed aqueous solution.

  In addition, when adding the metal component-containing mixed aqueous solution, a pH adjusting aqueous solution is added at the same time, while controlling the pH value of the mixed aqueous solution in the reaction tank so as not to exceed 6.4 (nucleation pH value). A nucleation step was performed by crystallization for minutes. Further, during the nucleation step, the fluctuation range of the pH value of the mixed aqueous solution was within the range of 0.2 above and below the center value (set pH value) 6.2. The maximum pH value of the mixed aqueous solution in the nucleation step was 6.4.

(5) Nuclear crushing process Then, stirring was continued for 5 minutes and the nucleus was crushed.

(Particle growth process)
In the particle growth step, the same metal component-containing mixed aqueous solution and pH adjusted aqueous solution as in the nucleation step were used. The experimental procedure of the particle growth process will be described below.
(1) Adjustment of pH of mixed aqueous solution In the particle growth step, first, a pH adjusted aqueous solution was added to the mixed aqueous solution obtained in the nucleation step to adjust the pH value to 7.4 (based on a liquid temperature of 40 ° C). The maximum pH value of the mixed aqueous solution in the particle growth step was 7.4.
(2) Addition and mixing of metal component-containing mixed aqueous solution to mixed aqueous solution The metal component-containing mixed aqueous solution was added to the mixed aqueous solution after adjusting the pH value at a rate of 10.3 ml / min.

  At this time, the addition amount of the metal component-containing mixed aqueous solution and the pH adjusting aqueous solution was controlled so that the pH value of the mixed aqueous solution did not exceed 7.4 on the basis of the reaction temperature of 40 ° C.

  After this state was continued for 196 minutes, stirring was stopped and crystallization was terminated.

  And the product obtained by the particle growth process was washed with water, filtered, and dried to obtain precursor particles (washing and drying process).

  In the particle growth process, the pH value is controlled by adjusting the supply flow rate of the pH adjusting aqueous solution with a pH controller, and the fluctuation range of the pH value of the mixed aqueous solution is above and below the center value (set pH value) 7.2. It was within the range of 0.2.

  Further, the ammonium ion concentration in the mixed aqueous solution in the nucleation step and the particle growth step was maintained at 5 g / L.

[Evaluation of precursors]
The obtained precursor was dissolved in an inorganic acid and then subjected to chemical analysis by ICP emission spectroscopy. As a result, the composition was carbonic acid consisting of Ni: Co: Mn = 0.334: 0.333: 0.333. It was confirmed to be a salt. Furthermore, using an elemental analyzer (Model: FlashEA 1112 manufactured by Thermo Fisher Scientific), the amount of hydrogen (H) was measured, and the mass ratio of metal (Ni + Co + Mn) was calculated to be 1.64. It was confirmed that hydrogen was contained. Moreover, it has confirmed that it had a functional group containing hydrogen.

Further, the particles of the precursor, the average particle diameter D _50, a laser diffraction scattering particle size distribution analyzer (manufactured by Nikkiso Co., Ltd., Microtrac HRA) result of measurement with a mean particle size of about 8.6μm It was confirmed that there was.

  Next, SEM (manufactured by Hitachi High-Technologies Corporation, Scanning Electron Microscope S-4700) observation (magnification: 3000 times) of the obtained precursor particles was performed. As a result, the obtained precursor particles were approximately It was spherical and it was confirmed that the particle diameters were almost uniform.

2. Production and Evaluation of Positive Electrode Active Material Next, production and evaluation of the positive electrode active material were performed using the obtained precursor.

[Production of positive electrode active material]
The precursor was heat-treated at 500 ° C. for 2 hours in an air stream (oxygen: 21 vol%) to convert to the composite oxide particles as heat-treated particles, and recovered. Next, the heat-treated particles and the lithium compound were mixed to obtain a lithium mixture. Specifically, lithium carbonate was weighed so that Li / Me = 1.10 of the obtained lithium mixture and mixed with the heat-treated particles to prepare a lithium mixture. Mixing was performed using a shaker mixer apparatus (manufactured by Willy et Bacofen (WAB), TURBULA Type T2C). The obtained lithium mixture was calcined at 500 ° C. for 5 hours in the atmosphere (oxygen: 21% by volume), then calcined at 910 ° C. for 10 hours and cooled. Thereafter, it was pulverized to obtain a positive electrode active material. The composition of the obtained positive electrode active material is expressed as Li: Ni: Co: Mn = 1.10: 0.334: 0.333: 0.333.

[Evaluation of positive electrode active material]
When the particle size distribution of the obtained positive electrode active material was measured by the same method as in the case of the precursor particles, it was confirmed that the average particle size was about 7.9 μm.

  Moreover, the cross section of the positive electrode active material was observed by SEM. In performing SEM observation of the cross section of the positive electrode active material, secondary particles of a plurality of positive electrode active material particles were embedded in a resin, and the cross section polisher process was performed to enable observation of the cross section of the particles. . As a result, it was confirmed that the structure had uniform pores up to the central part inside the secondary particles.

  In addition, 100 or more particles of these cross-sectional SEM images were observed, and the porosity of the secondary particles was calculated using image analysis software (Development software of National Institutes of Health, ImageJ). When the porosity of each of 100 arbitrarily selected secondary particles was calculated using the above-described image analysis software, the number ratio of particles having pores to the center (porous particles) was 100%. . The porous particles mean particles in which the porosity of the secondary particles exceeds 3%. Non-porous secondary particles are dense particles having a porosity of 3% or less. The average porosity of the porous particles was 22%. Among the porous particles, the number ratio of porous particles having a porosity of 10% or more and 30% or less inside the porous particles was 100%.

  Table 2 shows the average porosity of the porous particles among the above arbitrarily selected particles as the porosity of the porous particles. Further, the ratio of the number of porous particles to the number of porous particles in the observed particles is shown. Furthermore, the ratio of the number of porous particles having a porosity of 10% or more and 30% or less among the porous particles is also shown. The same applies to Comparative Example 1 below.

  Furthermore, when the tap density was measured, it was confirmed that the density was about 1.9 g / cc.

  The tap density was measured after the obtained positive electrode active material was filled into a 20 ml graduated cylinder, and then the graduated cylinder was closely packed by a method in which free fall from a height of 2 cm was repeated 500 times.

Further, when the specific surface area of the obtained positive electrode active material was determined by a flow method gas adsorption method specific surface area measurement device (manufactured by Yuasa Ionics Co., Ltd., Multisorb), it was confirmed to be about 1.1 m ² / g. .

3. Manufacture and evaluation of secondary batteries [Manufacture of secondary batteries]
Using the obtained positive electrode active material, a 2032 type coin-type battery was prepared and evaluated.

  The structure of the manufactured coin type battery will be described with reference to FIG. FIG. 3 schematically shows a cross-sectional configuration diagram of the coin-type battery. As shown in FIG. 3, the coin-type battery 10 includes a case 11 and an electrode 12 accommodated in the case 11.

  The case 11 has a positive electrode can 111 that is hollow and has one end opened, and a negative electrode can 112 that is disposed in the opening of the positive electrode can 111. The case 11 is configured such that when the negative electrode can 112 is disposed in the opening of the positive electrode can 111, a space for accommodating the electrode 12 is formed between the negative electrode can 112 and the positive electrode can 111.

  The electrode 12 includes a positive electrode 121, a separator 122, and a negative electrode 123, which are stacked in this order, so that the positive electrode 121 is in contact with the inner surface of the positive electrode can 111 and the negative electrode 123 is in contact with the inner surface of the negative electrode can 112. In the case 11.

  The case 11 includes a gasket 113, and the gasket 113 is fixed so as to maintain an electrically insulated state between the positive electrode can 111 and the negative electrode can 112. In addition, the gasket 113 has a function of sealing the gap between the positive electrode can 111 and the negative electrode can 112 and blocking the inside and outside of the case 11 in an airtight and liquidtight manner.

  This coin-type battery 10 was produced as follows. First, 52.5 mg of the obtained positive electrode active material, 15 mg of acetylene black, and 7.5 mg of polytetrafluoroethylene (PTFE) were mixed with a solvent (N-methyl-2-pyrrolidone), and the diameter was 11 mm at a pressure of 100 MPa, the thickness was 11 mm. The positive electrode 121 was manufactured by press molding to a thickness of 100 μm. The produced positive electrode 121 was dried in a vacuum dryer at 120 ° C. for 12 hours. Using the positive electrode 121, the negative electrode 123, the separator 122, and the electrolytic solution, the coin-type battery 10 was produced in a glove box in an Ar atmosphere in which the dew point was controlled at −80 ° C.

As the negative electrode 123, a negative electrode sheet in which graphite powder having an average particle diameter of about 20 μm punched into a disk shape having a diameter of 14 mm and polyvinylidene fluoride were applied to a copper foil was used. The separator 122 was a polyethylene porous film with a film thickness of 25 μm. As the electrolytic solution, an equivalent mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) using 1M LiClO ₄ as a supporting electrolyte (manufactured by Toyama Pharmaceutical Co., Ltd.) was used.

[Battery evaluation]
The initial discharge capacity for evaluating the performance of the obtained coin-type battery 10 was defined as follows.

  The initial discharge capacity is that the produced coin-type battery 10 is left for about 24 hours, and the open circuit voltage OCV (open circuit voltage) is stabilized, and then the current density with respect to the positive electrode is set to 0.05 C (270 mA / g is assumed to be 1 C). The battery was charged to a cutoff voltage of 4.3V. After 1 hour of rest, the battery was discharged at 0.05 C to a cut-off voltage of 3.0 V. The discharge capacity at this time was defined as the initial discharge capacity. When a battery evaluation was performed on a coin-type battery having a positive electrode formed using the positive electrode active material, the initial discharge capacity was about 167 mAh / g.

  Next, in order to evaluate the high discharge rate characteristics, first, the current density was set to 0.01 C, and charging / discharging was performed under the same conditions as described above, and the discharge capacity was measured. Then, charging / discharging was repeated 3 times on the same conditions as the above, respectively with current density set to 0.2C, 0.5C, and 1.0C, and the discharge capacity was measured 3 times. Thereafter, charge and discharge were repeated three times under the same conditions as described above at a current density of 2.0 C, and the discharge capacity was measured three times. This average value was taken as the discharge capacity at a high discharge rate. The value was about 147 mAh / g.

At this time, the discharge capacity retention rate (discharge capacity retention rate) was about 88%. The discharge capacity retention rate is the ratio of the discharge capacity at a high discharge rate to the initial discharge capacity, and was obtained by the following formula (1).
Discharge capacity retention rate (%) = discharge capacity at high discharge rate / initial discharge capacity × 100 (1)

  Table 1 shows the characteristics of the precursor obtained in this example, Table 2 shows the characteristics of the positive electrode active material, and Table 3 shows the evaluations of the coin-type battery manufactured using this positive electrode active material. The same contents are also shown in the same table for Comparative Example 1 below.

[Comparative Example 1]
A precursor, a positive electrode active material, and a secondary battery were produced and evaluated in the same manner as in Example 1 except that the gas blown into the reaction vessel during the production of the precursor was changed to nitrogen gas. . The results are shown in Tables 1 to 3.

  About the obtained positive electrode active material, it carried out similarly to Example 1, SEM observation of the cross section of the positive electrode active material was performed, and the porosity of the secondary particle was computed with image analysis software. Among 100 arbitrarily selected secondary particles, the number ratio of porous particles was 29%. The average porosity of the porous particles was 7%. Among the porous particles, the number ratio of the porous particles having a porosity of 10% or more and 30% or less inside the porous particles was 0%.

  It was confirmed from the results shown in Table 1 that the precursors of Example 1 had the target composition. Further, it was confirmed that the positive electrode active material obtained from the precursor had a porosity of the porous particles of 10% or more, and the ratio of the number of the porous particles was also 100%. It was confirmed that the battery using such a positive electrode active material can sufficiently increase the initial discharge capacity and the discharge capacity under a high discharge rate condition.

  On the other hand, in Comparative Example 1, H / Me was less than 1.60 for the precursor, and it was confirmed that the precursor having the target composition was not obtained. For this reason, when a positive electrode active material was manufactured using this precursor, it was confirmed that almost no porous particles were obtained and the porosity of the porous particles was small. And in the secondary battery manufactured using the positive electrode active material, it was confirmed that both the initial discharge capacity and the discharge capacity under the high discharge rate condition were inferior to those in Example 1.

Claims (12)

Ni: Mn: Co: M = x: y: z: t (where x + y + z + t = 1, 0.25 <x <0.60, 0 <y <0.70, 0 <z) <0.70, 0 ≦ t ≦ 0.10 is satisfied, and M is one type selected from Mg, Ca, Al, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, and W A nickel cobalt manganese carbonate composite composed of the above additive elements),
A functional group containing hydrogen,
A positive electrode active material precursor for a non-aqueous electrolyte secondary battery, wherein H / Me, which is a material amount ratio between the hydrogen H contained and the metal component Me contained, is 1.60 or more. A positive electrode active material for a non-aqueous electrolyte secondary battery containing a lithium metal composite oxide,
The lithium metal composite oxide is Li: Ni: Mn: Co: M = α: x: y: z: t (1.00 ≦ α ≦ 1.30, x + y + z + t = 1) in terms of mass ratio, 0 .25 <x <0.60, 0 <y <0.70, 0 <z <0.70, 0 ≦ t ≦ 0.10, M is Mg, Ca, Al, Ti, V, Cr, Fe, One or more additive elements selected from Cu, Zn, Zr, Nb, Mo, and W.)
Including porous secondary particles in which a plurality of primary particles are aggregated,
Non-aqueous electrolyte secondary battery in which the number ratio of secondary particles having a porosity of 10% to 30% among the porous secondary particles is 80% or more Positive electrode active material. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim ² , wherein the specific surface area is 1.0 m ² / g or more.   The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 2 or 3, wherein the tap density is 1.5 g / cc or more. Ni: Mn: Co: M = x: y: z: t (where x + y + z + t = 1, 0.25 <x <0.60, 0 <y <0.70, 0 <z) <0.70, 0 ≦ t ≦ 0.10, M is one or more selected from Mg, Ca, Al, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, and W A nickel cobalt manganese carbonate composite composed of an additive element) and a functional group containing hydrogen, and a method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery,
In the presence of carbonate ions, an initial aqueous solution containing at least one of an ammonium ion supplier and an alkaline substance, an aqueous solution containing Ni as a metal component, an aqueous solution containing Co as a metal component, and Mn as a metal component A crystallization step of generating nuclei in a mixed aqueous solution mixed with an aqueous solution and growing the generated nuclei,
The said crystallization process is a manufacturing method of the positive electrode active material precursor for non-aqueous electrolyte secondary batteries performed by controlling pH value of the said mixed aqueous solution to 9.0 or less on the reaction temperature of 40 degreeC reference | standard in oxygen-containing atmosphere. The crystallization process includes
In the presence of carbonate ions, nuclei are generated in a mixed aqueous solution obtained by mixing the initial aqueous solution, an aqueous solution containing Ni as a metal component, an aqueous solution containing Co as a metal component, and an aqueous solution containing Mn as a metal component. A nucleation process;
A particle growth step for growing the nuclei generated in the nucleation step;
Including
The method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery according to claim 5, wherein in the nucleation step, the pH value of the mixed aqueous solution is controlled to 7.5 or less based on a reaction temperature of 40 ° C. In the particle growth step, in the mixed aqueous solution after the nucleation step, in the presence of carbonate ions, an aqueous solution containing Ni as a metal component, an aqueous solution containing Co as a metal component, and an aqueous solution containing Mn as a metal component Adding and mixing,
The method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery according to claim 6, wherein an ammonium ion concentration in the mixed aqueous solution is 0 g / L or more and 20 g / L or less during the particle growth step.   The method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery according to claim 6 or 7, wherein in the nucleation step, the temperature of the mixed aqueous solution is maintained at 30 ° C or higher. The ammonium ion supplier is one or more selected from ammonium carbonate aqueous solution, ammonia water, ammonium chloride aqueous solution, and ammonium sulfate aqueous solution,
The non-aqueous electrolyte secondary according to any one of claims 5 to 8, wherein the alkaline substance is at least one selected from sodium carbonate, sodium bicarbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide. A method for producing a positive electrode active material precursor for a battery.   The positive electrode active material precursor for a nonaqueous electrolyte secondary battery according to any one of claims 5 to 9, further comprising a coating step of coating the positive electrode active material precursor for the nonaqueous electrolyte secondary battery with the additive element. Body manufacturing method. The coating step includes
An aqueous solution containing the additive element is added to the slurry in which the positive electrode active material precursor for the non-aqueous electrolyte secondary battery is suspended, and the additive element is added to the surface of the positive electrode active material precursor for the non-aqueous electrolyte secondary battery. The step of precipitating
A step of spraying and drying a slurry in which the positive electrode active material precursor for a non-aqueous electrolyte secondary battery and the compound containing the additive element are suspended; or the positive electrode active material precursor for the non-aqueous electrolyte secondary battery; The method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery according to claim 10, which is a step of mixing the compound containing the additive element with a solid phase method. A positive electrode active material precursor for a non-aqueous electrolyte secondary battery obtained by the method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery according to any one of claims 5 to 11, A heat treatment step for heat treatment at a temperature of ℃ or less;
A mixing step of adding and mixing a lithium compound to the particles obtained by the heat treatment step to form a lithium mixture;
A baking step of baking the lithium mixture at a temperature of 600 ° C. or higher and 1000 ° C. or lower in an oxidizing atmosphere;
The manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries containing.

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