JP2022095968A - Positive electrode active material for nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode active material precursor for a nonaqueous electrolyte secondary battery, capable of forming positive electrode active material for a nonaqueous electrolyte secondary battery containing porous particles.

SOLUTION: Provided is a positive electrode active material precursor for a nonaqueous electrolyte secondary battery, which comprises: a nickel manganese carbonate composite which has a composition represented by Ni:Mn:M=x:y:t in terms of material amount ratio (where x+y+t=1, 0.2≤x≤0.3, 0.7≤y≤0.8, and 0≤t≤0.2 are satisfied, and M represents one or more types of additive element selected from Mg, Ca, Al, Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo, and W); and a functional group including hydrogen. In the positive electrode active material precursor, material amount ratio H/Me of hydrogen H included therein and a metal component Me included therein is 1.60 or more.

SELECTED DRAWING: None

COPYRIGHT: (C)2022,JPO&INPIT

Description

INDUSTRIAL APPLICABILITY 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 for a battery.

In recent years, with the spread of small information terminals such as smartphones and tablet PCs, there is a strong demand for the development of small and lightweight non-aqueous electrolyte secondary batteries having high energy density. In addition, the development of a high-output secondary battery is strongly desired as a large-sized battery such as a power source for driving a motor.

As a secondary battery satisfying these requirements, there is a lithium ion secondary battery. The lithium ion secondary battery is composed of 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.

Currently, research and development of lithium-ion secondary batteries is being actively carried out. Among them, a lithium ion secondary battery using a layered or spinel type lithium metal composite oxide as a positive electrode material is being put into practical use as a battery having a high energy density because a high voltage of 4V class 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, 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) Lithium composite oxides such as _0.5 O ₂ ) and lithium excess nickel cobalt manganese composite oxide (Li ₂ MnO ₃ -LiNi _x Mn _{y Coz} O ₂ ) have been proposed.

Among these positive electrode active materials, a nickel-manganese composite oxide having a spinel-type structure has been attracting attention in recent years as a material that exhibits a charge / discharge voltage of 5 V class, which is higher than that of a conventional lithium ion battery.

Then, a method for producing a precursor for obtaining such a lithium excess nickel-cobalt-manganese composite oxide is disclosed in, for example, Patent Document 1.

Japanese Unexamined Patent Publication No. 2014-238976

By the way, during the charge / discharge reaction of the lithium ion secondary battery, the movement of lithium ions occurs between the positive electrode active material and the electrolytic solution. Therefore, in order to increase the output of the lithium ion secondary battery, it is preferable that the contact area between the positive electrode active material and the electrolytic solution is large, and the positive electrode activity including porous particles having uniform pores inside the particles. It is effective to use a substance.

However, although Patent Document 1 discloses a method for producing a precursor and the composition of a positive electrode active material produced using the precursor, the structure of particles of the positive electrode active material is referred to. In particular, the internal structure of the secondary particles has not been investigated.

Therefore, in view of the above-mentioned problems of the prior art, in one aspect of the present invention, a positive electrode active material precursor for a non-aqueous electrolyte secondary battery capable of forming a positive electrode active material for a non-aqueous electrolyte secondary battery containing porous particles can be formed. The purpose is to provide the body.

According to one aspect of the present invention in order to solve the above problems.
Ni: Mn: M = x: y: t (where x + y + t = 1, 0.2 ≦ x ≦ 0.3, 0.7 ≦ y ≦ 0.8, 0 ≦ t ≦ 0 in terms of substance amount ratio .2 is satisfied, and M is one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo, and W.) With the nickel-manganese carbonate complex, which is
With a functional group containing hydrogen,
Provided is a positive electrode active material precursor for a non-aqueous electrolyte secondary battery in which H / Me, which is the material amount ratio of the contained hydrogen H and the contained metal component Me, is 1.60 or more.

According to one aspect of the present invention, it is possible to provide a positive electrode active material precursor for a non-aqueous electrolyte secondary battery capable of forming a positive electrode active material for a non-aqueous electrolyte secondary battery containing porous particles.

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

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments and does not deviate from the scope of the present invention. Can be modified and substituted in various ways.

[Positive active material precursor for non-aqueous electrolyte secondary batteries]
An example of a configuration of a positive electrode active material precursor for a non-aqueous electrolyte secondary battery (hereinafter, also simply referred to as “precursor”) of the present embodiment will be described. The precursor of the present embodiment has a substance amount ratio (mol ratio) of Ni: Mn: M = x: y: t (provided that x + y + t = 1, 0.2 ≦ x ≦ 0.3, 0.7. Satisfying ≦ y ≦ 0.8 and 0 ≦ t ≦ 0.2, M is selected from Mg, Ca, Al, Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo, and W. It has a nickel-manganese carbonate complex which is one or more kinds of additive elements to be added, and a functional group containing hydrogen.

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

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

The precursor of the present embodiment can include substantially spherical secondary particles formed by agglomeration of a plurality of fine primary particles. The precursor of this embodiment can also be composed of the secondary particles.

The precursor of the present embodiment has high uniformity of 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.

Hereinafter, the precursor of the present embodiment will be specifically described.

(composition)
The nickel-manganese carbonate complex contained in the precursor of the present embodiment and the functional group containing hydrogen will be described.

As described above, the nickel-manganese carbonate complex is a nickel-manganese composite in the form of a basic carbonate having a composition of Ni: Mn: M = x: y: t in terms of substance amount ratio.

However, in the above substance amount ratio, x + y + t = 1, satisfying 0.2 ≦ x ≦ 0.3, 0.7 ≦ y ≦ 0.8, 0 ≦ t ≦ 0.2, and M is Mg, Ca. , Al, Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo, and W.

The additive element M in the substance amount ratio of the nickel-manganese carbonate complex preferably contains one or more elements selected from Ti, Fe, and Co, and is more preferably Ti. At this time, the content ratios of Ti, Fe, and Co are preferably 0.5 at% or more and 5 at% or less.

By using Ti as the additive element M, oxygen is strongly bonded to the crystal structure, so that the elution of metals such as Mn and Ni from the positive electrode active material due to oxygen desorption under high voltage is suppressed, resulting in this. Cycle characteristics are improved.

The precursor of the present embodiment is represented by the general formula 1: xMn ₂ (CO ₃ ) ₃ · yMn (OH) ₃ , the general formula 2: Ni ₄ CO ₃ (OH) ₆ (H ₂ O) ₄ , and the like. It can contain a compound having an indefinite composition mixed with a carbonate or a hydroxide.

When the precursor of the present embodiment is used as a precursor of the positive electrode active material of a non-aqueous electrolyte secondary battery, in order to further improve the battery characteristics such as cycle characteristics and output characteristics, a nickel manganese carbonate composite is used. Can also add one or more kinds of additive elements M as described above.

As a raw material for Ti, titanium organic compounds such as titanium tetraisopropoxide and titanium tetrabutoxide, titanium sulfate and the like can be used.

One or more kinds of additive elements M selected from Mg, Ca, Al, Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo, and W are within a predetermined substance amount ratio t. Therefore, it is preferable that the secondary particles are uniformly distributed inside and / or the surface of the secondary particles is uniformly covered.

However, in the nickel-manganese carbonate composite, if the substance amount ratio t of the additive element M exceeds 0.1, the metal elements that contribute to the redox reaction (Redox reaction) may decrease, and the battery capacity may decrease. be.

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

Further, the precursor of the present embodiment can contain the above-mentioned hydrogen-containing functional group. 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 the substance amount ratio of hydrogen H contained in the precursor of the present embodiment to the metal component Me is 1.60 or more. This makes it possible to obtain porous particles when used as a positive electrode active material. Further, by setting the H / Me to 1.7 or less, when the precursor of the present embodiment is used as the 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 Ni, Mn, and the additive element M mentioned in the above-mentioned substance amount ratio, as described above.

Further, the precursor of the present embodiment may contain a component other than the nickel-manganese carbonate complex and the hydrogen-containing functional group, but from the nickel-manganese carbonate complex and the hydrogen-containing functional group. It can also be configured. In this case, the precursor of the present embodiment does not exclude the inclusion of unavoidable components in the manufacturing process and the like.

[Manufacturing method of 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 according to the present embodiment (hereinafter, also simply referred to as “precursor manufacturing method”) will be described. In the method for producing a precursor of the present embodiment, a precursor can be obtained by a crystallization reaction, and the obtained precursor is washed and dried as needed.

Specifically, the method for producing the precursor of the present embodiment is Ni: Mn: M = x: y: t (where x + y + t = 1 and 0.2 ≦ x ≦ 0.3 in terms of substance amount ratio. , 0.7 ≦ y ≦ 0.8, 0 ≦ t ≦ 0.2, and M is Mg, Ca, Al, Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo. A positive electrode active material precursor for a non-aqueous electrolyte secondary battery having a nickel-manganese carbonate complex composed of one or more additive elements selected from and W) and a functional group containing hydrogen. It is a manufacturing method of, and includes the following steps.

In the presence of carbonate ions, an initial aqueous solution containing at least one of an ammonium ion feeder and an alkaline substance, an aqueous solution containing Ni as a metal component, and an aqueous solution containing Mn as a metal component (hereinafter, simply "Ni as a metal component"). A crystallization step of generating nuclei in a mixed aqueous solution mixed with (also referred to as "an aqueous solution containing, etc.") and growing the generated nuclei.

In the method for producing a precursor of the present embodiment, the crystallization step is carried out in an oxygen-containing atmosphere by controlling the pH value of the mixed aqueous solution to 9.0 or less based on a reaction temperature of 40 ° C.

FIG. 1 shows an example of the flow of the method for producing a precursor of the present embodiment. As shown in FIG. 1, the method for producing a precursor of the present embodiment includes a crystallization step.

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

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

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

If necessary, an acidic substance is added to the initial aqueous solution to adjust the reaction temperature to 9.0 or less based on the reaction temperature of 40 ° C. By setting the pH value of the initial aqueous solution within the above range, it is possible to suppress the residual impurities, so that a precursor having a small remaining amount of impurities can be obtained. At this time, the pH value of the initial aqueous solution is preferably adjusted to be 5.4 or more and 9.0 or less, more preferably 6.4 or more and 8.0 or less, and 7.1. It is more preferable to adjust the pH 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 step, the pH value of the mixed aqueous solution is preferably within the above range. Since the pH value of the mixed aqueous solution fluctuates slightly 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 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 the particles contained in the precursor of the present embodiment is not constant, and uniform particles having 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 or the like can be preferably used. As the acidic substance, it is preferable to use the same type of acid as the metal salt used when preparing the aqueous solution containing the metal component to be added to the initial aqueous solution.

In the crystallization step, the inside of the reaction vessel is in the presence of carbonate ions. The method for supplying carbonic acid ions is not particularly limited, and for example, carbon dioxide ions can be supplied to the mixed aqueous solution by supplying carbon dioxide gas together with the oxygen-containing gas described later in the reaction vessel. In addition, carbonate ions can be supplied by using a carbonate when preparing an initial aqueous solution or a pH-adjusting aqueous solution.

In the crystallization step, the atmosphere is controlled so as to have an oxygen-containing atmosphere by blowing an oxygen-containing gas into the reaction vessel in which the initial aqueous solution is prepared. After that, 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 vessel at a constant flow rate, for example, and the pH value of the mixed aqueous solution is controlled to be within a predetermined range. is 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 vessel, and the like. This produces amorphous fine particles (primary particles) that are not single crystals of carbonate. These particles become the nucleus of the precursor (nuclear particle). These nuclear particles aggregate and grow to generate large secondary particles. The particle size of the secondary particles can be controlled by the reaction time of the crystallization step.

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

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

When the oxygen-containing gas is supplied 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 the dissolved oxygen in the mixed aqueous solution is consumed during the crystallization step, if the amount of dissolved oxygen in the mixed aqueous solution is more than half of the saturated amount, sufficient oxygen for the reaction can be supplied.

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 even while the 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) that become the nuclei (nuclear particles) of the precursor are generated in the initial aqueous solution containing the metal component. As a result, a mixed aqueous solution containing primary particles as nuclear particles is obtained. Whether or not a predetermined amount of nuclear particles are produced can be determined by the amount of the metal salt contained in the mixed aqueous solution.

When 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, the pH value of the obtained mixed aqueous solution is preferably controlled within a predetermined range as described above. Therefore, it is preferable that the aqueous solution containing the metal component is gradually added dropwise to the initial aqueous solution rather than being added all at once. Thereby, the solution containing the metal component, the mixed aqueous solution containing the metal component described later, and the like can be supplied to the reaction vessel, for example, so as to have a constant flow rate.

Further, when supplying the aqueous solution containing the metal component or the mixed aqueous solution containing the metal component 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. The pH-adjusted aqueous solution is not particularly limited, and for example, an aqueous solution containing at least one of an ammonium ion feeder and an alkaline substance can be used. The method of supplying the pH-adjusted aqueous solution into the reaction vessel is not particularly limited. For example, a pump capable of controlling the flow rate while sufficiently stirring the obtained mixed aqueous solution, such as a metering pump, can be used to control the flow rate of the mixed aqueous solution. It may be added so that the pH value is maintained in a predetermined range.

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

The aqueous solution containing Ni as a metal component and the aqueous solution containing Mn as a metal component can contain a metal compound containing each metal component. For example, an aqueous solution containing Mn as a metal component can contain a metal compound containing manganese.

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

The aqueous solution containing Ni as a metal component and the aqueous solution containing Mn as a metal component may be partially or wholly mixed in advance and added to the initial aqueous solution as a mixed aqueous solution containing a metal component.

The composition ratio of each metal in the obtained precursor is the same as the composition ratio of each metal in the mixed aqueous solution containing a metal component. Therefore, for example, the composition ratio of each metal contained in the mixed aqueous solution containing a metal component added to the initial aqueous solution in the crystallization step is equal to the composition ratio of each metal in the precursor to be produced. It is preferable to adjust the ratio to prepare a mixed aqueous solution containing a metal component.

When a specific metal compound reacts with each other to generate an unnecessary compound by mixing a plurality of metal compounds, an aqueous solution containing each metal component is simultaneously converted into an initial aqueous solution at a predetermined ratio. It may be added.

The aqueous solution containing each metal component may not be mixed and may be individually added to the initial aqueous solution. In this case, an 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 generated precursor in the entire aqueous solution containing the metal component to be added. It is preferable to prepare.

As described above, the precursor produced by the method for producing a precursor of the present embodiment has a substance amount ratio of Ni: Mn: M = x: y: t (provided that x + y + t = 1 and 0.2. ≤x≤0.3, 0.7≤y≤0.8, 0≤t≤0.2, where M is Mg, Ca, Al, Ti, V, Cr, Fe, Co, Cu, Zn, It has a nickel-manganese carbonate complex composed of one or more additive elements selected from Zr, Nb, Mo, and W) and a functional group containing hydrogen.

That is, the precursor of the present embodiment may further contain the additive element M in addition to Ni and Mn.

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

When an aqueous solution containing Ni as a metal component is mixed to form a metal component-containing mixed aqueous solution and then the metal component-containing mixed aqueous solution is added to the initial aqueous solution, the metal component-containing 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, for example, by using a compound containing the additive element M. Examples of the compound containing the additive element M include magnesium sulfate, calcium sulfate, sodium aluminate, titanium sulfate, ammonium peroxotitanate, potassium titanium oxalate, vanadium sulfate, ammonium vanadate, chromium sulfate, and potassium chromate. , Iron sulfate, cobalt sulfate, copper sulfate, zinc sulfate, zirconium sulfate, zirconium nitrate, niobium oxalate, ammonium molybdate, sodium tungstate, ammonium tungstate, etc., and the compound is selected according to the element to be added. be able to.

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

Then, by adding the above-mentioned aqueous solution containing the additive element M to the precursor particle-containing aqueous solution, the additive element M can be uniformly dispersed inside the nuclear particles contained in the precursor.

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

The temperature of the mixed aqueous solution is preferably maintained at 20 ° C. or higher, more preferably 30 ° C. or higher. The upper limit of the temperature of the mixed aqueous solution is not particularly limited, but is preferably 70 ° C. or lower, more preferably 50 ° C. or lower, for example. 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 in the crystallization step exceeds 70 ° C., the primary crystal may be distorted and the tap density may be lowered.

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

The lower limit of the ammonium ion concentration can be appropriately adjusted as needed, 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 by, for example, using an ammonium ion feeder in the initial aqueous solution or the pH adjusting aqueous solution and adjusting the supply amount thereof. It is preferable to do so.

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.

As described above, in the crystallization step, fine particles (primary particles) which are precursor nuclei (nuclear particles) can be generated and grown in the precursor particle-containing aqueous solution. Then, the crystallization step is continuously performed until the nuclear particles grow to a desired particle size, and the nuclear particles are grown to obtain a precursor having porous secondary particles having a desired particle size. can.

The average particle size of the precursor is preferably 3.0 μm or more and 20.0 μm or less, and more preferably 5.0 μm or more and 15.0 μm or less. The average particle size of the positive electrode active material to be synthesized is close to the average particle size of the precursor. The desired average particle size of the positive electrode active material depends on the design of the target battery, etc., but in general, when the average particle size of the positive electrode active material is less than 3.0 μm, the coatability at the time of electrode manufacturing and the coating property in the positive electrode This is not desirable because it reduces the packing density of the positive electrode active material. On the other hand, if the average particle size of the positive electrode active material exceeds 20 μm, it becomes difficult to uniformly promote the synthesis of the positive electrode active material over the entire particles, and the battery characteristics are deteriorated. Therefore, the above range is preferable for the average particle size of the positive electrode active material. When the average particle size of the precursor is within the above range, the average particle size of the obtained positive electrode active material can also be controlled within the optimum range. The average particle size means a volume average particle size Mv based on an effective diameter, and the average particle size is measured by, for example, a laser diffraction / scattering method or a dynamic light scattering method.

Further, in order to uniformly coat the surface of the porous secondary particles, which are precursors, with the additive element M, for example, after the crystallization step is completed, a coating step of coating with the additive element M is performed. You may. The coating process will be described later.

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

Specifically, in the method for producing a precursor of the present embodiment, the crystallization step can include the following steps.
In the presence of carbonate ions, the nucleus is formed in a mixed aqueous solution in which an initial aqueous solution containing at least one of an ammonium ion feeder and an alkaline substance, an aqueous solution containing Ni as a metal component, and an aqueous solution containing Mn as a metal component are mixed. Nuclear generation step to generate.
A particle growth step for growing the nuclei generated in the nucleation step.

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

FIG. 2 shows another example of the flow of the method for producing the precursor of the present embodiment. As shown in FIG. 2, in the method for producing a precursor of the present embodiment, the crystallization step is a nucleation step and a particle growth step in which precursor particles are generated by a coprecipitation method after the nucleation step. And include. The nucleation step is a step in which a nucleation reaction mainly occurs, and the particle growth step is a step in which a particle growth reaction mainly occurs. By having the nucleation step and the particle growth step in the crystallization step, it is possible to obtain precursor particles having a narrower particle size distribution.

Hereinafter, each step of the method for producing the precursor of the present embodiment shown in FIG. 2 will be specifically described. A part of the description of the contents common to the crystallization step of the method for producing the precursor of the present embodiment shown in FIG. 1 will be omitted.

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

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

In the nucleation generation step, it is preferable to maintain the pH value of the mixed aqueous solution obtained by adding an aqueous solution containing a metal component such as an aqueous solution containing Ni as a metal component to the initial aqueous solution at a lower pH value than in the particle growth step described later. By keeping the pH value of the mixed aqueous solution low, the number of 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 obtained precursor can be reduced. Because it becomes.

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

During the nucleation step, the pH value of the mixed aqueous solution is also preferably in the above range. Since the pH value of the mixed aqueous solution fluctuates slightly during the nucleation step, the maximum pH value of the mixed aqueous solution during the nucleation step can be used 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 the acidic substance, the acidic substance described in the above-mentioned crystallization step can be preferably used.

In the nucleation step, an oxygen-containing gas is blown into a reaction vessel in which an initial aqueous solution is prepared to control the atmosphere, and then the above-mentioned aqueous solution containing a metal component is supplied at a constant flow rate, for example, and the pH value of the mixed aqueous solution is determined. Can be controlled to fall within the range of. 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 vessel, and the like to generate amorphous fine particles that are not single crystals of carbonate. Further, by blowing the oxygen-containing gas, it is possible to make it easier to mix the functional group containing hydrogen with the precursor as compared with the case of the inert gas atmosphere. Thereby, the substance amount ratio of 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 vessel even while the 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 the oxygen-containing gas is supplied 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 the dissolved oxygen in the mixed aqueous solution is consumed during the nucleation generation step, if the amount of dissolved oxygen in the mixed aqueous solution is more than half of the saturated amount, sufficient oxygen for the reaction can be supplied.

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

In the nucleation step, a mixed aqueous solution can be formed by adding and mixing an aqueous solution containing Ni as a metal component and an aqueous solution containing Mn as a metal component to the initial aqueous solution in the reaction vessel.

When an aqueous solution containing Ni as a metal component is added to the initial aqueous solution, the pH value of the obtained mixed aqueous solution is preferably controlled to 7.5 or less based on the reaction temperature of 40 ° C. It is more preferably controlled to 4 or less, and even more preferably to be controlled to 7.0 or less. Therefore, it is preferable that the aqueous solution containing a metal component, such as an aqueous solution containing Ni as a metal component, is gradually added dropwise to the initial aqueous solution rather than being added all at once.

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

Then, as described above, it becomes a precursor nucleus (nuclear particles) in the mixed aqueous solution obtained by adding an aqueous solution containing a metal component such as an 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 nuclear particles are generated in the mixed aqueous solution can be determined by the amount of the metal salt contained in the mixed aqueous solution.

The aqueous solution containing Ni as a metal component and the aqueous solution containing Mn as a metal component to be added to the initial aqueous solution in the nucleation generation step contain Ni as the same metal component as in the above-mentioned crystallization step. An aqueous solution or the like can be preferably used.

As described above, the precursor produced by the method for producing a precursor of the present embodiment has a substance amount ratio of Ni: Mn: M = x: y: t (provided that x + y + t = 1 and 0.2. ≤x≤0.3, 0.7≤y≤0.8, 0≤t≤0.2, where M is Mg, Ca, Al, Ti, V, Cr, Fe, Co, Cu, Zn, It has a nickel-manganese carbonate complex composed of one or more additive elements selected from Zr, Nb, Mo, and W) and a functional group containing hydrogen.

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

Therefore, in the nucleation step, one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo, and W as needed. An aqueous solution containing M (an aqueous solution containing the additive element M) can also be added to the initial aqueous solution. As for the method of adding the aqueous solution containing the additive element M and the aqueous solution containing the additive element M to the initial aqueous solution, the same method as in the case of the crystallization step described above can be used.

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

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

Further, 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 completion of the particle growth step described later. .. The coating process will be described later.

Further, in the nucleation generation step, as in the crystallization step of the method for producing a precursor 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 can be mixed to form a mixed aqueous solution, and nuclei can be generated in the mixed aqueous solution.

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

The temperature of the mixed aqueous solution in the nucleation step is preferably maintained at 20 ° C. or higher, more preferably 30 ° C. or higher. 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 lower, more preferably 50 ° C. or lower, for example. This is because when the temperature of the mixed aqueous solution in the nucleation 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 in the nucleation step exceeds 70 ° C., 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 the same range as in the case of the crystallization step described above, for example. As for the method for measuring the pH value, the ammonium ion concentration, and the dissolved oxygen amount in the mixed aqueous solution, the same method as in the above-mentioned crystallization step can be preferably used.

After the completion of the nucleation step, that is, after the addition to the initial aqueous solution such as the mixed aqueous solution containing a metal component is completed, it is preferable to continue stirring to the mixed aqueous solution to crush the generated nuclei (nucleation crushing). Process). When the nuclear crushing step is performed, the time is preferably 1 minute or longer, more preferably 3 minutes or longer. By performing the nuclear crushing step, it is possible to more reliably suppress the agglomeration of the generated nuclei, the coarsening of the particle size, and the decrease in the density inside the particles.

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

At this time, the pH value of the mixed aqueous solution can be adjusted to be 6.0 or more and 9.0 or less based on the reaction temperature of 40 ° C., for example. By setting the pH value of the mixed aqueous solution to 6.0 or more and 9.0 or less, it is possible to suppress the residual impurity cations. 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-mentioned pH adjusting aqueous solution.

Since the pH value of the mixed aqueous solution fluctuates slightly during the particle growth step, the maximum pH value of the mixed aqueous solution during the particle growth step can be used as the pH value of the mixed aqueous solution in the particle growth step. It is preferable that the pH value of the mixed aqueous solution is in the above range.

In particular, it is preferable to control the fluctuation range of the pH value of the mixed aqueous solution to be within 0.2 above and below the center value (set pH value) during the particle growth step. 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 having a narrow particle size distribution range may not be obtained. ..

The particle growth step is a step of adding and mixing an aqueous solution containing Ni as a metal component and an aqueous solution containing Mn as a metal component in the presence of carbonate ions to the mixed aqueous solution after the nucleation generation step. be able to.

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

Further, the aqueous solution containing Ni as a metal component and the aqueous solution containing Mn as a metal component are partially or wholly mixed as in the case of the nucleation step to form a mixed aqueous solution as a mixed aqueous solution containing a metal component. It may be added. 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 individually added to the mixed aqueous solution. May be good.

Further, when an aqueous solution containing Ni as a metal component is added to the mixed aqueous solution, the aqueous solution containing the additive element M can be added at the same time as in the case of the nucleation step. As described above, an aqueous solution containing the additive element M can be mixed with the mixed aqueous solution containing a metal component and added. 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 a metal component and the aqueous solution containing Mn as a metal component, the same aqueous solution as in the case of the above-mentioned nucleation step can be used. Further, the concentration 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. Therefore, an aqueous solution containing Ni as a metal component can be gradually added dropwise to the mixed aqueous solution instead of being added all at once. Therefore, a solution containing these metal components, a mixed aqueous solution containing the metal component, or the like can be supplied to the reaction vessel, for example, so as to have 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 adjusting the pH value. Also in this case, for the same reason that the pH value was adjusted before the start of the particle growth step, 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. It is preferably maintained at 9.0 or less. In the particle growth step, by controlling the pH value of the mixed aqueous solution within the above range, a precursor having a small amount of impurities remaining can be obtained. 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 7.1 or more and 8.0 or less.

During the particle growth step, the pH value of the mixed aqueous solution after adjusting the pH value fluctuates slightly. Therefore, the maximum value of the pH value of the mixed aqueous solution after adjusting the pH value during the particle growth step is set as the pH value of the mixed aqueous solution in the particle growth step, and the maximum value of the pH value of the mixed aqueous solution after adjusting the pH value is in the above range. It is preferable to be in.

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 as to be 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 after adjusting the pH value is large, the growth of the particles contained in the precursor is not constant, and uniform particles having a narrow particle size distribution range cannot be obtained. Because there is.

As described above, when an aqueous solution containing a metal component or a mixed aqueous solution containing a mixed metal component is supplied to the mixed aqueous solution, a pH-adjusted aqueous solution is also added so that the pH of the mixed aqueous solution can be maintained within a predetermined range. Is preferable. As the pH-adjusted aqueous solution, the same pH-adjusted aqueous solution as in the case of the above-mentioned nucleation step can be used. As a method of supplying the pH-adjusted aqueous solution into the reaction vessel, the method described above in the above-mentioned nucleation step can be preferably used.

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

The lower limit of the ammonium ion concentration can be appropriately adjusted as needed, 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 by, for example, using an ammonium ion feeder in the initial aqueous solution or the pH adjusting aqueous solution and adjusting the supply amount thereof. Is preferable.

Further, 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 and mixed with the mixed aqueous solution in the presence of carbonate ions. At this time, the method of supplying carbonic acid ions is not particularly limited, and for example, carbonic acid ions can be supplied to the mixed aqueous solution by supplying carbon dioxide gas together with the oxygen-containing gas described later in the reaction vessel. Further, when preparing the above-mentioned initial aqueous solution or pH-adjusted aqueous solution, carbonate ions can be used to supply carbonate ions.

In the particle growth step, an oxygen-containing gas is blown into the reaction vessel to control the atmosphere so as to create an oxygen-containing atmosphere, and an aqueous solution containing a metal component such as an aqueous solution containing Ni as a metal component is flowed at a constant flow rate, for example. Can be supplied at. As a result, it reacts with dissolved oxygen contained in the mixed aqueous solution and oxygen contained in the oxygen-containing gas supplied to the reaction vessel, and atypical fine particles that are not single crystals of carbonate are further aggregated. It is possible to generate large secondary particles. Further, by blowing the oxygen-containing gas, it is possible to make it easier to mix the functional group containing hydrogen with the precursor as compared with the case of the inert gas atmosphere. Thereby, the H / Me, which is the substance amount ratio of the hydrogen H contained in the obtained precursor and the metal component Me contained in the obtained precursor, can be more reliably set to 1.60 or more.

When oxygen-containing gas is supplied into the reaction vessel in the particle growth step, the supply amount of the oxygen-containing gas can be confirmed by measuring the dissolved oxygen concentration in the mixed aqueous solution. Since the 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 saturated amount, sufficient oxygen for the reaction can be supplied.

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 of the particle growth step. That is, in the particle growth step, if the reaction is continued until the particles grow to a desired particle size, a precursor having a desired particle size and porous secondary particles can be obtained.

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

In the method for producing a precursor of the present embodiment, it is preferable to use an apparatus in which the precursor, which is a product, is not recovered until the reaction in the crystallization step is completed. Examples of such an apparatus include a commonly used batch reaction tank equipped with a stirrer. By adopting such an apparatus, the particle size distribution is narrow because there is no problem that growing particles are recovered at the same time as the overflow liquid, unlike a continuous crystallization device that recovers products by a general overflow. It is preferable because particles having a uniform particle size can be obtained.

Further, in order to control the atmosphere of the reaction vessel, it is preferable to use a device capable of controlling the atmosphere, such as a closed type device.

By using a device capable of controlling the atmosphere of the reaction vessel, the particles containing the precursor can have the structure as described above, and the coprecipitation reaction can be promoted almost uniformly, so that the particle size can be adjusted. It is possible to obtain particles having an excellent distribution, that is, particles having a narrow range of particle size distribution.

In the particle growth step, the pH value of the mixed aqueous solution obtained in the nucleation generation 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 added to the mixed aqueous solution. By doing so, uniform precursor particles can be obtained.

(Coating process)
Further, in the method for producing a precursor of the present embodiment, after obtaining particles (secondary particles) of the precursor of the present embodiment in the crystallization step, the surface of the obtained particles of the precursor of the present embodiment is displayed. It is also possible to further have a coating step of coating with the additive element M.

The coating step can be, for example, any of the following steps.
A step of adding an aqueous solution containing an additive element M to a slurry in which 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 an aqueous solution or slurry containing the additive element M onto the precursor particles to dry them.
A step of spraying and drying a slurry in which precursor particles and a compound containing an additive element M are suspended.
A step of mixing the precursor particles and the compound containing the additive element M by the solid phase method.

It is assumed that the coating step is, for example, 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, for the slurry in which the precursor particles are suspended, it is preferable to use an aqueous solution containing the additive element M to make the precursor particles into a slurry. Further, when an 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 becomes 6.0 or more and 9.0 or less. It is preferable to control such a method. 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.

As the aqueous solution containing the additive element M used in the coating step, the same aqueous solution as in the above-mentioned nucleation step can be used. Further, 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 that the amount of the additive element ion added to the initial aqueous solution or the mixed aqueous solution in the crystallization step is reduced by the amount to be coated. By reducing the amount of the aqueous solution containing the additive element M to be added to the mixed aqueous solution by the amount to be covered, the atomic number ratio of the additive element M contained in the obtained precursor to other metal components is reduced. Is 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 precursor particles after heating after the completion of the crystallization step.

Next, after completing the crystallization step shown in FIG. 1 or 2, a washing step or a drying step can be performed. Hereinafter, the cleaning step and the drying step 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 FIG. 2 can be washed.

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

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

Further, the washing with water may be carried out by a method usually used, and it is sufficient that excess raw materials and the like contained in the particles of the precursor can be removed.

As the water used for washing with water, it is preferable to use water having as little impurity content as possible, and more preferably pure water, in order to prevent impurities from being mixed.

(3) Drying process The drying process will be described. 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 washed precursor particles can be dried by setting the drying temperature to 80 ° C. or higher and 230 ° C. or lower.

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

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

Further, in the method for producing a precursor of the present embodiment, the crystal size of the particles of the precursor obtained by the crystallization reaction can be controlled. Therefore, according to the method for producing a precursor of the present embodiment, a precursor having a small particle size of the primary particles, a high uniformity of the particle size of the secondary particles, and a high density (tap density) can be obtained. Can be done.

Further, according to the method for producing a precursor of the present embodiment shown in FIG. 2, the time when the nucleation reaction mainly occurs (nucleation step) and the time when the particle growth reaction mainly occurs (particle growth step) are separated. Can be done. As a result, precursor particles (secondary particles) having a narrow particle size distribution can be obtained even if both steps are performed in the same reaction vessel.

Further, in the method for producing a precursor of the present embodiment shown in FIG. 2, the nucleation step and the particle growth step can be separated in one reaction vessel only by mainly adjusting the pH of the reaction solution. can.

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

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

The positive electrode active material of the present embodiment relates to a positive electrode active material for a non-aqueous electrolyte secondary battery containing a lithium metal composite oxide. The lithium metal composite oxide has Li: Ni: Mn: M ₌ α: x: y: t (0.48 ≦ α ≦ 0.65, x + y + t = 1 and 0.2 ≦ x in terms of material amount ratio. ≤0.3, 0.7≤y≤0.8, 0≤t≤0.1, M is Mg, Ca, Al, Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, It is one or more additive elements selected from Mo and W) and has a spinel structure.

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

The positive electrode active material of the present embodiment can include a lithium metal composite oxide having a spinel-type crystal structure represented by LiA ₂ O ₄ , more specifically, a lithium nickel-manganese composite oxide. The positive electrode active material of the present embodiment can also be composed of the above-mentioned lithium metal composite oxide.

In the above substance amount ratio, A ₂ is a metal element containing at least Ni and Mn adjusted to have an average valence of 3.5.

In the precursor of the present embodiment, as described above, in order to further improve the battery characteristics such as the cycle characteristics and the output characteristics of the positive electrode active material of the non-aqueous electrolyte secondary battery, the lithium metal composite oxide is described above. Can contain one or more additive elements M selected from Mg, Ca, Al, Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo, and W. The content of the additive element M is preferably adjusted so that the substance amount ratio t is within the range of 0 ≦ t ≦ 0.1 in the 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 of 10% by volume or more inside the secondary particles. Contains porous secondary particles that are less than or equal to the volume. The positive electrode active material of the present embodiment contains 80% or more of the secondary particles having a porosity inside the secondary particles of 10% by volume or more and 30% by volume or less among the porous secondary particles contained therein. contains. The porosity of the porous secondary particles contained in the positive electrode active material can be calculated, for example, by observing the cross-sectional structure of the positive electrode active material with SEM and performing image processing or the like. For example, particles having a calculated porosity of more than 3% are referred to as porous secondary particles (porous particles). The porous particles can be particles having pores up to the center. The ratio of the porous secondary particles contained in the positive electrode active material is not particularly limited, but can be, for example, 50% or more and 100% or less in terms of the number ratio.

Calculation of the number ratio of porous secondary particles and the number ratio of porous secondary particles whose porosity inside the secondary particles is 10% by volume or more and 30% by volume or less among the porous secondary particles. The method is not particularly limited. In the calculation method, for example, first, the cross-sectional structure of a plurality of, for example, 100 or more positive electrode active material secondary particles is first observed by SEM, and the number ratio of the control secondary particles among the secondary particles is counted. It can be obtained by doing.

The positive electrode active material of the present embodiment can have a large 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 for the positive electrode active material and is not particularly limited, but is, for example, 0.5 m ² / g or more. Is preferable. This is because by setting the specific surface area of the positive electrode active material of the present embodiment to 0.5 m ² / g or more, it is possible to facilitate the production of the positive electrode mixture paste and to improve the output characteristics. Is.

The upper limit of the specific surface area of the positive electrode active material of the present embodiment is not particularly limited, but is preferably 3.0 m ² / g or less, and more preferably 2.0 m ² / g or less, for example. However, when it is required to particularly increase the reaction surface area and the output characteristics, the specific surface area of the positive electrode active material of the present embodiment shall be 1.0 m ² / g or more and 2.0 m ² / g or less. Is preferable. Further, when it is particularly required to 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. Is preferable.

Further, according to the positive electrode active material of the present embodiment, the porous secondary particles are contained, and the porosity inside the secondary particles among the porous secondary particles is 10% by volume or more and 30% by volume or less. By having a certain proportion or more of porous secondary particles, it is possible to improve the output characteristics of a battery and also to increase the tap density.

The tap density of the positive electrode active material of the present embodiment is preferably 1.5 g / cm ³ or more, and more preferably 1.7 g / cm ³ or more. When the tap density of the positive electrode active material is high, it is possible to increase the packing density of the positive electrode active material in the positive electrode when the positive electrode constituting the secondary battery is manufactured. When the packing density of the positive electrode active material in the positive electrode is high, it is possible to realize a larger charge / discharge capacity with a positive electrode having the same volume.

The average particle size of the positive electrode active material is preferably 3.0 μm or more and 20.0 μm or less, and more preferably 5.0 μm or more and 15.0 μm or less, similar to the average particle size of the precursor. As described above, in general, when the average particle size of the positive electrode active material is less than 3.0 μm, the coatability at the time of electrode production and the packing density of the positive electrode active material in the positive electrode are lowered. On the other hand, if the average particle size of the positive electrode active material exceeds 20 μm, it becomes difficult to uniformly promote the synthesis of the positive electrode active material over the entire particles, and the battery characteristics are deteriorated. The average particle size is the volume average particle size Mv based on the effective diameter, similar to the average particle size of the precursor described above.

When the positive electrode active material of the present embodiment is used for the positive electrode of a 2032 type coin cell battery, for example, it preferably has a high initial discharge capacity of 135 mAh / g or more. Further, it is preferable that the discharge capacity under high discharge rate conditions (current density: 2C) is 120 mAh / g or more.

For the discharge capacity under the high discharge rate condition (current density: 2C), the current density is 2C, charging and discharging are repeated a plurality of times (for example, 3 times), and then the measurement is performed a plurality of times (for example, 3 times). It can be the average value of multiple measurements obtained in.

When the positive electrode active material of the present embodiment is used for the positive electrode of a laminated battery, for example, it is preferable that the positive electrode active material has a high cycle capacity retention rate of 60% or more as a cycle characteristic. The cycle capacity maintenance rate is calculated as follows. The laminated battery is charged to a cutoff voltage of 4.3 V in a constant temperature bath maintained at 25 ° C. with a current density of 0.33 mA / cm ² , and discharged to a cutoff voltage of 3.0 V after a one-hour rest. Conditioning is performed by repeating the cycle of 5 cycles. Next, in a constant temperature bath maintained at 60 ° C., the current density is 2.7 mA / cm ² , the cutoff voltage is charged to 4.3 V, and after a one-hour pause, the cycle is discharged to a cutoff voltage of 3.0 V. Is repeated for 200 cycles, and the discharge capacity of each cycle is measured. The cycle capacity retention rate is the discharge capacity obtained in the first cycle after conditioning of the laminated battery, and is a value obtained by dividing the discharge capacity obtained in the 200th cycle after conditioning (obtained in the 200th cycle after conditioning). Discharge capacity / Discharge capacity obtained in the first cycle after conditioning).

[Manufacturing method of 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 according to the present embodiment (hereinafter, also simply referred to as “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 used. It is preferable because the substance can be produced more reliably.

The method for producing a positive electrode active material of the present embodiment can have the following steps.
A heat treatment step of heat-treating the positive electrode active material precursor for a non-aqueous electrolyte secondary battery obtained by the above-mentioned 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 of adding and mixing a lithium compound to the particles obtained by the heat treatment step to form a lithium mixture.
A firing step in which a lithium mixture is calcined 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 above-mentioned precursor can be heat-treated at a temperature of 80 ° C. or higher and 600 ° C. or lower. By performing the heat treatment, the water content contained in the precursor can be removed, and it is possible to prevent the number of metal atoms and the ratio of the number of lithium atoms in the finally obtained positive electrode active material from fluctuating.

It is not necessary to convert all the precursors to nickel-manganese composite oxides as long as the water can be removed to the extent that the number of metal atoms and the ratio of lithium atoms in the positive electrode active material do not vary. However, in order to further reduce the above variation, it is preferable to convert all the precursor particles into composite oxide particles at a heating temperature of 500 ° C. or higher.

The reason why the heat treatment temperature is set to 80 ° C. or higher in the heat treatment step is that if the heat treatment temperature is less than 80 ° C., excess water in the particles of the precursor cannot be removed and the above variation may not be suppressed. 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. be.

The above variation can be suppressed by determining the metal component contained in the particles of the precursor corresponding to the heat treatment conditions in advance by analysis and determining the ratio with the lithium compound.

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

The heat treatment time is not particularly limited, but if it is less than 1 hour, the excess water of the precursor particles may not be sufficiently removed. Therefore, 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 it can heat the precursor particles in a non-reducing atmosphere, preferably in an air stream, and an electric furnace that does not generate gas is preferable. Used.

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

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

The heat-treated particles and the lithium compound are the sum of the atomic numbers of the metal component Me other than lithium in the lithium mixture, that is, the sum of the atomic numbers of Ni, Mn and the additive element M (Me), and the atomic number of lithium (Li). It is preferable to mix so that the ratio (Li / Me) of the above is 0.48 or more and 0.65 or less. At this time, it is more preferable to mix so that Li / Me is 0.50 or more and 0.60 or less.

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

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

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

(3) Firing step The firing step is a step of calcining the lithium mixture obtained in the above mixing step 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-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, the residual of excess lithium and unreacted particles is suppressed, and the battery is used. This is because sufficient battery characteristics can be obtained. However, if the firing temperature exceeds 1000 ° C, the composite oxide particles may be violently sintered and abnormal grain growth may occur, and the grains after firing become coarse and fine pores 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.

Since the firing temperature of the lithium mixture also affects the specific surface area of the obtained positive electrode active material, it can be selected from the above temperature ranges according to the specific surface area required for the positive electrode active material. For example, when it is required to particularly suppress the specific surface area of the positive electrode active material, it is preferable to set the firing temperature to a higher temperature, for example, 900 ° C. or higher and 950 ° C. or lower. According to the study of the inventor of the present invention, the specific surface area of the obtained positive electrode active material can be set to 1.5 m ² / g or more and 8.0 m ² / g or less by firing in such a temperature range, and the positive electrode can be obtained. The production of the mixture paste can be particularly facilitated. Further, when the positive electrode active material is used as a non-aqueous electrolyte secondary battery, the battery capacity can be kept high, which is preferable.

From the viewpoint of uniformly reacting the heat-treated particles with the lithium compound, it is preferable to raise the temperature to the above temperature by setting the temperature rise rate to 3 ° C./min or more and 10 ° C./min or less.

Furthermore, the reaction can be more uniformly carried out by holding the lithium compound at a temperature near the melting point for about 1 hour or more and 5 hours or less. When the temperature is maintained near the melting point of the lithium compound, the temperature can be subsequently raised to a predetermined firing temperature.

Of the firing times, the holding time at the firing temperature is preferably 1 hour or more, and more preferably 2 hours or more and 24 hours or less. This is because the formation of the lithium nickel-manganese composite oxide can be sufficiently promoted by holding the lithium nickel manganese composite oxide at the calcination temperature for 2 hours or more.

After the holding time at the firing temperature is completed, the descent rate is not particularly limited, but when the lithium mixture is loaded in the sack and fired, the descent rate is set to 2 ° C./min or more in order to suppress the deterioration of the sack. It is preferable to cool the atmosphere to 200 ° C. or lower at ° C./min or lower.

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

As described above, it is preferable to have an atmosphere with an oxygen concentration of 18% by volume or more. By setting the oxygen concentration to 18% by volume or more, the crystallinity of the lithium nickel-manganese composite oxide can be sufficiently enhanced. Because.

In particular, considering the battery characteristics, it is preferable to perform the operation in an oxygen stream.

The furnace used for firing is not particularly limited as long as it can heat the lithium mixture in the atmosphere or oxygen-containing gas, but gas generation is generated from the viewpoint of keeping the atmosphere in the furnace uniform. No electric furnace is preferred. Further, either a batch type or a continuous type furnace can be used.

When lithium hydroxide or lithium carbonate is used as the lithium compound, it is preferable to perform calcining after the mixing step and before the firing step. The calcination temperature is preferably lower than the firing temperature and 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 1 hour or more and 10 hours or less, and more preferably 3 hours or more and 6 hours or less.

It is preferable that the calcining is held at the calcining temperature and then calcined. In particular, it is preferable to perform calcining at the reaction temperature of lithium hydroxide or lithium carbonate and the heat-treated particles.

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

The particles of the lithium nickel-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 the present embodiment containing the lithium nickel-manganese composite oxide can be obtained.

In addition, crushing means that mechanical energy is applied to an agglomerate composed of a plurality of secondary particles generated by sintering necking between secondary particles during firing, and the secondary particles themselves are hardly destroyed. It is an operation to separate secondary particles and loosen aggregates.

[Non-aqueous electrolyte secondary battery]
Next, a configuration example of the non-aqueous electrolyte secondary battery (hereinafter, also simply referred to as “secondary battery”) of the present embodiment will be described. The non-aqueous electrolyte secondary battery is also referred to as a lithium ion secondary battery. The secondary battery of the present embodiment can have a positive electrode using the above-mentioned positive electrode active material.

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

The secondary battery of the present embodiment can have substantially the same structure as a general non-aqueous electrolyte secondary battery except that the positive electrode active material of the present embodiment is used as the positive electrode material. ..

The secondary battery of the present embodiment can have, for example, a case and a structure including 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 laminated via a separator. Then, the electrode body is impregnated with a non-aqueous electrolyte to collect electricity 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. It can be connected using a lead or the like to form a structure sealed in a case.

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

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

The positive electrode is appropriately processed according to the battery 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 for increasing the electrode density, and the like are performed.

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

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

The binder serves to hold the positive electrode active material particles together. The binder used for this positive electrode mixture is not particularly limited, and for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluororubber, ethylene propylene diene rubber, styrene butadiene, cellulose-based resin, and the like. Alternatively, polyacrylic acid or the like can be used.

Activated carbon or the like may be added to the positive electrode mixture, and the electric double layer capacity of the positive electrode can be increased by adding activated carbon or the like.

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

Further, 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, and the conductivity is similar to that of the positive electrode of a general non-aqueous 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 leaf current collector such as copper and drying it. This negative electrode is formed by substantially the same method as the positive electrode, although the components constituting the negative electrode mixture paste, their composition, the material of the current collector, etc. are different, and various treatments are required as required, as with the positive electrode. Is done.

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

As the negative electrode active material, for example, a substance containing lithium such as metallic lithium or a lithium alloy, or an occlusion substance capable of storing and desorbing lithium ions can be adopted.

The storage substance is not particularly limited, and for example, a calcined body of an organic compound such as natural graphite, artificial graphite, and phenol resin, and a powdery body of a carbon substance such as coke can be used. When the storage material is used as the negative electrode active material, a fluororesin such as PVDF can be used as the binder as in the case of the positive electrode, and the solvent for dispersing the negative electrode active material in the binder can be used. An organic solvent such as N-methyl-2-pyrrolidone can be used.

(Separator)
The separator is arranged 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 an electrolyte. The separator may be, for example, a thin film such as polyethylene or polypropylene, and a film having a large number of fine pores may be used, but the separator is not particularly limited as long as it has the above-mentioned 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; and chain carbonates such as diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate and dipropyl carbonate; further, tetrahydrofuran and 2-. Ether compounds such as methyl tetrahydrofuran and dimethoxyethane; sulfur compounds such as ethylmethyl sulfone and butane sulton; phosphorus compounds such as triethyl phosphate and trioctyl phosphate may be used alone or in admixture of two or more. Can be done.

Supporting salts include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , and LiN (CF ₃ ).
SO ₂ ) ₂ , and complex salts thereof, etc. can be used.

The non-aqueous electrolyte may contain a radical scavenger, a surfactant, a flame retardant, or the like in order to improve the battery characteristics.

(Characteristics of the secondary battery of this embodiment)
The secondary battery of the present embodiment can have, for example, the above configuration and has a positive electrode using the above-mentioned positive electrode active material, so that a high initial discharge capacity and a low positive electrode resistance can be obtained, and the capacity is high. High output. Further, the secondary battery of the present embodiment has a high cycle capacity retention rate.

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

Further, the secondary battery of the present embodiment is also suitable for a battery as a power source for driving a motor, which requires high output. As the size of the battery increases, it becomes difficult to ensure safety, and an expensive protection circuit is indispensable. However, the secondary battery of the present embodiment has excellent safety, so that safety is ensured. Not only is it easier, but it also simplifies expensive protection circuits and makes them cheaper. Further, since it is possible to reduce the size and increase the output, it is suitable as a power source for transportation equipment whose mounting space is restricted.

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

The sample preparation conditions and evaluation results of each example and comparative example will be described below.

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

Through all the examples and comparative examples, the precursor, the positive electrode active material, and the secondary battery are prepared by using each sample of special grade reagent manufactured by Wako Pure Chemical Industries, Ltd. unless otherwise specified. ..

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

(Nucleation process)
(1) Preparation of initial aqueous solution First, the temperature in the tank was set to 40 ° C. by putting water in the reaction tank (5 L) up to an amount of about 1.2 L and stirring, and the following nuclear formation step and nuclear solution. The temperature of 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 heated water for the reaction tank provided around the reaction tank.

Then, an appropriate amount of 25% by mass ammonia water was added to the water in the reaction vessel to adjust the ammonium ion concentration in the initial aqueous solution to 5 g / L. Further 64% sulfuric acid was added to the initial aqueous solution to adjust the pH to 6.4.

Then, as an oxygen-containing gas, air gas was supplied from an air compressor at 4 L / min 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 inside of 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 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 mixed aqueous solution containing a metal component, the element molar ratio of each metal was adjusted to be Ni: Mn = 0.25: 0.75.

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

(4) Addition of the mixed aqueous solution containing a metal component to the initial aqueous solution, and the mixed aqueous solution containing the mixed metal component was added to the initial aqueous solution in the reaction vessel at 10.3 ml / min. Was added to prepare a mixed aqueous solution.

When the mixed aqueous solution containing a metal component is added, a pH adjusting aqueous solution is added at the same time to control the pH value of the mixed aqueous solution in the reaction vessel so as not to exceed 6.4 (nucleation pH value). The nucleation step was carried out by crystallization for a minute. 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 step After that, stirring was continued for 5 minutes to crush the nucleus.

(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, the pH adjusted aqueous solution was first added to the mixed aqueous solution obtained in the nucleation step to set the pH value to 7.4 (based on liquid temperature of 40 ° C.). The maximum pH value of the mixed aqueous solution in the particle growth step was 7.4.
(2) Addition of the mixed aqueous solution containing a metal component to the mixed aqueous solution, mixing The mixed aqueous solution containing a metal component was added at a ratio of 10.3 ml / min to the mixed aqueous solution after adjusting the pH value.

At this time, the addition amounts of the mixed aqueous solution containing a metal component and the pH adjusting aqueous solution were controlled so that the pH value of the mixed aqueous solution did not exceed 7.4 based on the reaction temperature of 40 ° C.

After continuing this state for 196 minutes, stirring was stopped and crystallization was completed.

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

The pH value in the particle growth step is controlled by adjusting the supply flow rate of the pH-adjusted 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 in the range of 0.2.

In addition, 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 precursor]
The obtained precursor was dissolved with an inorganic acid and then chemically analyzed by ICP emission spectroscopy. As a result, it was confirmed that the composition was a carbonate composed of Ni: Mn = 0.25: 0.75. did it. Furthermore, the elemental amount of hydrogen (H) was measured using an elemental analyzer (Thermo Fisher Scientific, model: FlashEA 1112), and the amount of substance ratio with the metal (Ni + Co + Mn) was as high as 1.63. It was confirmed that it contained hydrogen. It was also confirmed that it had a functional group containing hydrogen.

Further, regarding the volume average particle size Mv of the particles of this precursor, the average particle size _D50 was measured using a laser diffraction scattering type particle size distribution measuring device (Microtrac HRA manufactured by Nikkiso Co., Ltd.). It was confirmed that the volume average particle size Mv was about 9.9 μm.

Next, SEM (scanning electron microscope S-4700, manufactured by Hitachi High-Technologies Co., Ltd.) of the obtained precursor particles was observed (magnification: 3000 times), and the obtained precursor particles were abbreviated. It was confirmed that it was spherical and the particle size was almost uniform.

2. 2. Manufacture and evaluation of positive electrode active material Next, the positive electrode active material was manufactured and evaluated using the obtained precursor.

[Manufacturing of positive electrode active material]
The precursor was heat-treated at 500 ° C. for 2 hours in an air (oxygen: 21% by volume) air stream to convert it into composite oxide particles which were 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 = 0.5 of the obtained lithium mixture, and mixed with the heat-treated particles to prepare a lithium mixture. Mixing was performed using a shaker mixer device (TURBULA Type T2C, manufactured by Willy et Bacoffen (WAB)). The obtained lithium mixture was calcined in the air (oxygen: 21% by volume) at 500 ° C. for 5 hours, then calcined at 950 ° C. for 2 hours, and cooled. Then, it was crushed to obtain a positive electrode active material. The composition of the obtained positive electrode active material is represented as Li: Ni: Mn = 0.50: 0.25: 0.75.

[Evaluation of positive electrode active material]
As a result of measuring the particle size distribution of the obtained positive electrode active material and measuring the average particle size _D50 by the same method as in the case of the precursor particles, the volume average particle size Mv of the positive electrode active material was about 9. It was confirmed that it was 1 μm.

Moreover, the cross section of the positive electrode active material was observed by SEM. In observing the cross section of the positive electrode active material by SEM, the secondary particles of a plurality of positive electrode active material particles were embedded in the resin, and the cross section of the particles could be observed by cross-section polisher processing, and then the observation was performed by SEM. .. As a result, it was confirmed that the structure had uniform pores up to the center inside the secondary particles.

In addition, 100 or more particles of these cross-sectional SEM images were observed, and the void ratio of the secondary particles was calculated using image analysis software (ImageJ, software developed by the National Institutes of Health). When the porosity of each of the 100 arbitrarily selected secondary particles was calculated using the above image analysis software, the number ratio of the particles having pores up to the center (porous particles) was 100%. .. The porous particles mean particles in which the porosity of the secondary particles exceeds 3% by volume. The non-porous secondary particles are dense particles having a porosity of 3% by volume or less. The average porosity of the porous particles was 24% by volume. Among the porous particles, the number ratio of the porous particles having a porosity inside the porous particles of 10% by volume or more and 30% by volume or less was 100%.

Table 2 shows the average porosity of the porous particles among the above-mentioned arbitrarily selected particles as the porosity of the porous particles. In addition, as the number ratio of the porous particles, the ratio of the porous particles to the observed particles is shown. Further, among the porous particles, the number ratio of the porous particles in which the porosity inside the porous particles is 10% by volume or more and 30% by volume or less is also shown. The same applies to the following Comparative Example 1.

Furthermore, when the tap density was measured, it was confirmed that the tap density was about 1.7 g / cm ³ .

The tap density was measured after filling a 20 ml graduated cylinder with the obtained positive electrode active material and then tightly filling the graduated cylinder with a method of repeating free fall from a height of 2 cm 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 measuring device (manufactured by Yuasa Ionics Co., Ltd., Multisorb), it was confirmed that the specific surface area was about 1.2 m ² / g. ..

3. 3. Manufacture and evaluation of non-aqueous electrolyte secondary batteries [Manufacturing of non-aqueous electrolyte secondary batteries]
Using the obtained positive electrode active material, a 2032 type coin type battery and a laminated type battery were produced as a non-aqueous electrolyte secondary battery.

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

The case 11 has a positive electrode can 111 that is hollow and has one end open, and a negative electrode can 112 that is arranged at the opening of the positive electrode can 111. The case 11 is configured so that when the negative electrode can 112 is arranged 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 is composed of a positive electrode 121, a separator 122, and a negative electrode 123, and is laminated so as to be arranged in this order so that the positive electrode 121 contacts the inner surface of the positive electrode can 111 and the negative electrode 123 contacts the inner surface of the negative electrode can 112. It is housed in the case 11.

The case 11 is provided with a gasket 113, and the gasket 113 is fixed between the positive electrode can 111 and the negative electrode can 112 so as to maintain an electrically insulating state. Further, the gasket 113 also has a function of sealing the gap between the positive electrode can 111 and the negative electrode can 112 to airtightly block the inside and the outside of the case 11.

The coin-type battery 10 was manufactured as follows. A slurry obtained by dispersing 20.0 g of the obtained positive electrode active material, 2.35 g of acetylene black, and 1.18 g of polyvinylidene fluoride in N-methyl-2-pyrrolidone (NMP) was placed on an Al foil with positive electrode activity per 1 cm ² . After applying so that 5.0 mg of the substance was present, it was dried in the air at 120 ° C. for 30 minutes to remove NMP. The Al foil coated with the positive electrode active material was cut into strips having a width of 66 mm and rolled and pressed with a load of 1.2 tons to prepare a positive electrode 121. The positive electrode 121 was punched into a circle having a diameter of 13 mm and dried in a vacuum dryer at 120 ° C. for 12 hours.

Next, using the positive electrode 121, the coin-type battery 10 was manufactured in a glove box having an Ar atmosphere in which the dew point was controlled to −80 ° C. At this time, as the negative electrode 123, a lithium foil punched into a disk shape having a diameter of 14 mm was used.

The configuration of the manufactured laminated battery will be described with reference to FIG. 4. FIG. 4 is a diagram schematically showing the configuration of a laminated battery. As shown in FIG. 4, the laminated battery 100 has a positive electrode 110, a negative electrode 120, a separator 130, and a laminated film 140.

The laminated battery 100 was manufactured as follows. A positive electrode 110 was prepared in the same manner as in a coin cell, cut out into a rectangle having a size of 50 mm × 30 mm, and dried in a vacuum dryer at 120 ° C. for 12 hours. Next, using the positive electrode 110, the laminated battery 100 was produced in a dry room controlled to have a dew point of −80 ° C. At this time, as the negative electrode 120, a negative electrode sheet in which a negative electrode mixture paste, which is a mixture of graphite powder having an average particle diameter of about 20 μm and polyvinylidene fluoride, was applied to a copper foil was used. The separator 130 is a polyethylene porous membrane having a thickness of 25 μm, and the electrolytic solution is an equal amount mixed solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) using 1M LiClO ₄ as a supporting electrolyte (Tomiyama Pure Chemical Industries, Ltd.). Made by Co., Ltd.) was used. As the laminated film 140, a known one can be used.

[Evaluation of battery characteristics]
The battery characteristics of the lithium ion secondary battery manufactured using the obtained positive electrode active material are the initial discharge capacity of the lithium ion secondary battery and the high discharge rate conditions using the coin-type battery 10 shown in FIG. The high discharge rate characteristics were evaluated, and the cycle characteristics of the lithium ion secondary battery were evaluated using the laminated cell type battery 100 shown in FIG.

(Initial discharge capacity)
Using the coin-type battery 10 shown in FIG. 3, the initial discharge capacity of the obtained coin-type battery 10 was measured, and the performance of the lithium ion secondary battery was evaluated. The initial discharge capacity was defined as follows.

The initial discharge capacity is such that the manufactured coin-type battery 10 is left for about 24 hours, the open circuit voltage OCV (open circuit voltage) stabilizes, and then the current density with respect to the positive electrode is 0.05 C (270 mA / g is 1 C). , The cutoff voltage was charged to 5.0V. After 1 hour of rest, the battery was discharged at 0.05 C to a cutoff 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 by using the positive electrode active material, the initial discharge capacity was about 139 mAh / g.

(High discharge rate characteristics)
Next, using the coin-type battery 10 shown in FIG. 3, the discharge capacity of the high discharge rate was measured as the high discharge rate characteristic of the coin-type battery 10, and the performance of the lithium ion secondary battery was evaluated. In order to evaluate the high discharge rate characteristics, first, the current density was set to 0.01 C, and the battery was charged and discharged under the same conditions as above, and the discharge capacity was measured. After that, the current densities were set to 0.2C, 0.5C, and 1.0C, and charging and discharging were repeated 3 times under the same conditions as above, and the discharge capacity was measured 3 times. After that, the current density was set to 2.0 C, charging and discharging were repeated 3 times under the same conditions as above, and the discharge capacity was measured 3 times. This average value was taken as the discharge capacity of a high discharge rate. The value was about 123 mAh / g.

(Cycle characteristics)
Using the laminated battery 100 shown in FIG. 4, the cycle capacity retention rate was measured as the cycle characteristic of the laminated battery 100, and the performance of the lithium ion secondary battery was evaluated. The cycle characteristics were evaluated by measuring the capacity retention rate after 200 cycles of charging and discharging. Specifically, a laminated battery using a negative electrode produced by using a sheet in which a mixture of graphite powder and polyvinylidene fluoride is coated on a copper foil is first placed in a constant temperature bath kept at 25 ° C. for a current density. Conditioning was performed by repeating a cycle of charging to a cutoff voltage of 4.3 V at 0.33 mA / cm ² and discharging to a cutoff voltage of 3.0 V after a one-hour rest. Next, in a constant temperature bath maintained at 60 ° C., the current density is 2.7 mA / cm ² , the cutoff voltage is charged to 4.3 V, and after a one-hour pause, the cycle is discharged to a cutoff voltage of 3.0 V. Was repeated 200 cycles and evaluated by measuring the discharge capacity of each cycle.

Then, the value obtained by dividing the discharge capacity obtained in the first cycle after conditioning of the laminated battery of Example 1 by the discharge capacity obtained in the 200th cycle after conditioning (obtained in the 200th cycle after conditioning). The cycle capacity retention rate, which is the discharge capacity / the discharge capacity obtained in the first cycle after conditioning), was 60%.

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

[Example 2]
In the preparation of the (2) metal component-containing mixed aqueous solution in the nuclear production step in Example 1, titanium sulfate was added and the elemental molar ratio of each metal was Ni: Mn: Ti = 0.25: 0.725: 0. A precursor, a positive electrode active material, and a secondary battery were prepared and evaluated in the same manner as in Example 1 except that the temperature was adjusted to .025. The results are shown in Tables 1 to 3.

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

With respect to the obtained positive electrode active material, SEM observation of a cross section of the positive electrode active material was carried out in the same manner as in Example 1, and the porosity of the secondary particles was calculated by image analysis software. Of the 100 arbitrarily selected secondary particles, the number ratio of the porous particles was about 45%. The average porosity of the porous particles was 7%. Among the porous particles, the number ratio of the porous particles having a porosity inside the porous particles of 10% by volume or more and 30% by volume or less was 0%.

From the results in Table 1, it was confirmed that all the particles of the precursor of Example 1 had the target composition. Furthermore, from the results in Table 2, it was confirmed that the positive electrode active material obtained from the precursor had a porosity of 10% or more and a ratio of the number of porous particles of 100%. Was done. From the results in Table 3, it was confirmed that the battery manufactured using the positive electrode active material can have a sufficiently high initial discharge capacity and a discharge capacity under high discharge rate conditions.

From the results in Table 1, it was confirmed that all the precursors of Example 2 had the target composition. Furthermore, from the results in Table 2, it was confirmed that the positive electrode active material obtained from the precursor had a porosity of 10% or more and a ratio of the number of porous particles of 100%. Was done. From the results in Table 3, it was confirmed that the battery manufactured using the positive electrode active material can obtain higher cycle characteristics than in Example 1.

On the other hand, from the results in Table 1, it was confirmed that in Comparative Example 1, the H / Me was less than 1.6 for the precursor, and the precursor having the target composition was not obtained. Therefore, from the results in Table 2, it was confirmed that when the positive electrode active material was produced using the precursor, almost no porous particles were obtained, and the porosity of the porous particles was also small. Then, from the results of Table 3, the initial discharge capacity of the secondary battery manufactured by using the positive electrode active material and the discharge capacity under high discharge rate conditions are both as compared with the cases of Examples 1 and 2. I was able to confirm that it was inferior.

10 Coin-type battery 11 Case 12 Electrode 111 Positive electrode can 112 Negative electrode can 113 Gasket 121 Positive electrode (evaluation electrode)
122 Separator 123 Negative electrode (lithium metal)
100 Laminated battery 110 Positive electrode 120 Negative electrode 130 Separator 140 Laminate film

Claims (4)

A positive electrode active material for a non-aqueous electrolyte secondary battery containing a lithium metal composite oxide.
The lithium metal composite oxide has Li: Ni: Mn: M = α: x: y: t (0.48 ≦ α ≦ 0.65, x + y + t = 1 and 0.2 ≦ x in terms of material amount ratio. ≤0.3, 0.7≤y≤0.8, 0≤t≤0.1, M is Mg, Ca, Al, Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, One or more additive elements selected from Mo and W).
And has a spinel-type crystal structure,
Containing porous secondary particles in which multiple primary particles are aggregated,
Among the porous secondary particles, the number ratio of the secondary particles having a porosity inside the porous secondary particles of 10% by volume or more and 30% by volume or less is the total number of the porous secondary particles. A positive electrode active material for a non-aqueous electrolyte secondary battery having a content of 80% or more. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein M is Ti. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the specific surface area is 0.5 m ² / g or more. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 to 3, wherein the tap density is 1.5 g / cm ³ or more.

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