JP2019003818A - Positive electrode active material precursor for nonaqueous electrolyte secondary battery, positive electrode active material for nonaqueous electrolyte secondary battery, method for manufacturing positive electrode active material precursor for nonaqueous electrolyte secondary battery, and method for manufacturing positive electrode active material for nonaqueous electrolyte secondary battery - Google Patents

Abstract

To provide a positive electrode active material precursor for a nonaqueous electrolyte secondary battery, which enables the formation of a positive electrode active material including porous particles for a nonaqueous electrolyte secondary battery.SOLUTION: A positive electrode active material precursor for a nonaqueous electrolyte secondary battery is provided, which comprises: a nickel cobalt manganese carbonate compound represented by the general formula, NiCoMnMCO(where x+y+z+t=1, 0.05≤x≤0.3, 0.1≤y≤0.4, 0.55≤z≤0.8 and 0≤t≤0.1 are satisfied, and M is at least one additive element selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo and W); and a hydrogen-containing functional group. In the positive electrode active material precursor, the substance amount ratio H/Me of hydrogen H included therein and metal component Me included therein is 1.60 or more and 1.65 or less.SELECTED DRAWING: Figure 2

Description

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

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

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

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

As a positive electrode material of the lithium ion secondary battery, lithium cobalt composite oxide (LiCoO ₂ ), which is currently relatively easy to synthesize, lithium nickel composite oxide (LiNiO ₂ ) using nickel cheaper than cobalt, lithium Nickel cobalt manganese composite oxide (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ), lithium manganese composite oxide (LiMn ₂ O ₄ ) using manganese, lithium nickel manganese composite oxide (LiNi _0.5 Mn _0.5 O _2), lithium-rich nickel-cobalt-manganese composite oxide _{(Li 2 MnO 3 -LiNi x Mn} y Co z O 2) lithium composite oxide or the like is proposed.

  Among these positive electrode active materials, in recent years, lithium-excess nickel cobalt manganese composite oxides with high capacity and excellent thermal stability have attracted attention. This composite oxide is a layered compound like lithium cobalt composite oxide, lithium nickel composite oxide, and the like (see, for example, Non-Patent Document 1).

  And the manufacturing method of the precursor for obtaining the lithium excess nickel cobalt manganese complex oxide is disclosed by patent document 1 and patent document 2, for example.

JP2011-028999A JP 2011-146392 A

“High performance lithium-ion batteries: solid solution cathode materials”, FB Technical News, No. 66, January 2011, pages 3-10

  By the way, in order to increase the output of the lithium ion secondary battery, it is effective to shorten the movement distance of the lithium ion between the positive electrode and the negative electrode. It is useful to use a positive electrode material containing porous particles having pores. However, in order to improve the battery characteristics per unit volume, it is preferable to reduce the number of pores as much as possible.

  However, in Patent Documents 1 and 2, although the method for producing a precursor and the composition of the positive electrode active material produced using the precursor are disclosed, the structure of the particles of the positive electrode active material is referred to. In particular, the internal structure of secondary particles has not been studied.

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

In order to solve the above problems, according to one aspect of the present invention,
General formula Ni _x Co _y Mn _z M _t CO ₃ (where x + y + z + t = 1, 0.05 ≦ x ≦ 0.3, 0.1 ≦ y ≦ 0.4, 0.55 ≦ z ≦ 0 .8, 0 ≦ t ≦ 0.1, and M is one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W). A nickel cobalt manganese carbonate composite represented,
A functional group containing hydrogen,
Non-aqueous system in which H / Me, which is a substance amount ratio between hydrogen H to be contained and metal component Me to be contained, is 1.60 or more and 1.65 or less and a specific surface area is 30 m ² / g or more and 60 m ² / g or less Provided is a positive electrode active material precursor for an electrolyte secondary battery.

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

The flowchart of the manufacturing method of the positive electrode active material precursor for non-aqueous electrolyte secondary batteries of embodiment of this invention. The SEM observation image of the positive electrode active material precursor for nonaqueous electrolyte secondary batteries obtained in Example 1 which concerns on this invention. The SEM observation image of the positive electrode active material for nonaqueous electrolyte secondary batteries obtained in Example 1 which concerns on this invention. Explanatory drawing of the cross-sectional structure of the coin-type battery produced in Example 1 which concerns on this invention. The SEM observation image of the positive electrode active material for nonaqueous electrolyte secondary batteries obtained in the comparative example 2.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and the following embodiments are not departed from the scope of the present invention. Various modifications and substitutions can be made.
[Positive electrode active material precursor for non-aqueous electrolyte secondary battery]
In the present embodiment, first, a configuration example of a positive electrode active material precursor for a nonaqueous electrolyte secondary battery will be described.

The positive electrode active material precursor for a non-aqueous electrolyte secondary battery of this embodiment has a general formula Ni _x Co _y Mn _z M _t CO ₃ (where x + y + z + t = 1, 0.05 ≦ x ≦ 0.3 0.1 ≦ y ≦ 0.4, 0.55 ≦ z ≦ 0.8, 0 ≦ t ≦ 0.1, and M is Mg, Ca, Al, Ti, V, Cr, Zr, Nb, 1 or more additional elements selected from Mo and W.) and a nickel-cobalt-manganese carbonate composite represented by (2) and a functional group containing hydrogen.

And H / Me which is a substance amount ratio of the hydrogen H to contain and the metal component Me to contain can be 1.60 or more and 1.65 or less. Further, the specific surface area can be ^{30 m} 2 / g or more ^{60 m} 2 / g or less.

  As described above, the positive electrode active material precursor for a non-aqueous electrolyte secondary battery of the present embodiment (hereinafter, also simply referred to as “precursor”) includes a nickel-cobalt-manganese carbonate composite and a functional group containing hydrogen. Can be included. In addition, a precursor can also be comprised from the nickel cobalt manganese carbonate composite and the functional group containing hydrogen.

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

  The precursor of this embodiment, which includes a nickel cobalt manganese carbonate composite and a functional group containing hydrogen, has a highly uniform particle size and is a fine crystal, and is a positive electrode for a non-aqueous electrolyte secondary battery. It can be used as a raw material of the active material, that is, a precursor.

Below, the precursor of this embodiment is demonstrated concretely.
(composition)
As described above, the nickel cobalt manganese carbonate composite is a nickel cobalt manganese composite in the form of a basic carbonate represented by the general formula: Ni _x Co _y Mn _z M _t CO ₃ .

  However, in the above general formula, x + y + z + t = 1, 0.05 ≦ x ≦ 0.3, 0.1 ≦ y ≦ 0.4, 0.55 ≦ z ≦ 0.8, 0 ≦ t ≦ 0.1. Satisfying, M is one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W.

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

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

  One or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W are uniformly distributed in the secondary particles within a predetermined atomic ratio t. The distribution and / or the surface of the secondary particles are preferably uniformly coated.

  However, in the nickel-cobalt-manganese carbonate composite, when the atomic ratio t of the additive elements exceeds 0.1, the metal elements contributing to the oxidation-reduction reaction (Redox reaction) are reduced, and the battery capacity may be reduced. .

  Further, even when the nickel cobalt manganese carbonate composite does not contain an additive element, the positive electrode active material produced using the precursor of the present embodiment has sufficient battery characteristics such as cycle characteristics and output characteristics. It has characteristics. For this reason, it is not necessary to contain an additive element.

  For this reason, it is preferable to adjust an additional element so that it may become in the range of 0 <= t <= 0.1 by atomic number ratio t.

As the additive element, one or more selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W can be used as described above. In particular, the additive element is molybdenum. It is preferable to include. That is, it is preferable that the additive element M in the above-described general formula: Ni _x Co _y Mn _z M _t CO ₃ contains Mo (molybdenum). According to the study by the inventors of the present invention, when the additive element contains molybdenum, the initial discharge capacity is reduced in the nonaqueous electrolyte secondary battery using the positive electrode active material prepared using the precursor. It is because it can increase especially.

  Furthermore, the nickel cobalt manganese carbonate composite is a metal component in the nickel cobalt manganese carbonate composite, that is, Ni, Co, Mn, and the additive element M, the molybdenum content is 0.5 at% or more and 5 at% or less. It is more preferable that This is because the above-described effect of increasing the initial discharge capacity can be particularly expressed by setting the molybdenum content in the metal component of the nickel cobalt manganese carbonate composite to 0.5 at% or more. Molybdenum has the effect of accelerating sintering during firing, but an excessively large crystal can be formed by setting the molybdenum content in the metal component of the nickel cobalt manganese carbonate composite to 5 at% or less. This is preferable because it is possible to reliably prevent an increase in resistance and a decrease in discharge capacity in a battery produced using the precursor.

Further, according to the study by the inventors of the present invention, it was confirmed that when the additive element contains molybdenum, the specific surface area of the positive electrode active material produced using the precursor can be reduced. This is because the fine vacancies in the positive electrode active material are structurally changed to large vacancies due to the addition of molybdenum. Furthermore, according to the study of the inventors of the present invention, the positive electrode active material paste can be manufactured by controlling the specific surface area of the positive electrode active material in the range of 1.5 m ² / g or more and 15.0 m ² / g or less. Can be easily. Therefore, also from the viewpoint of controlling the specific surface area within the above range, the additive element preferably contains molybdenum.

  It is preferable that the additive element is uniformly distributed and / or uniformly coated on the surface of the secondary particles contained in the precursor (hereinafter also simply referred to as “precursor particles”).

In the nickel cobalt manganese carbonate composite, the state of the additive element is not particularly limited. However, it is preferable that the additive element is uniformly distributed and / or uniformly coated on the surface inside the nickel cobalt manganese carbonate composite as described above. This is because the additive element is distributed (covered) inside and / or on the surface of the nickel cobalt manganese carbonate composite, so that the battery characteristics are improved when the precursor of this embodiment is used as the precursor of the positive electrode active material. This is because it can be particularly improved.

  In addition, in the nickel cobalt manganese carbonate composite, even when the addition amount of one or more kinds of additional elements is particularly small, in order to sufficiently enhance the effect of improving battery characteristics, the surface of the carbonate composite is more than the inside. It is preferable to increase the concentration of one or more kinds of additive elements.

  As described above, in the nickel cobalt manganese carbonate composite, even if the addition amount of one or more kinds of additional elements is small, the effect of improving the battery characteristics can be obtained and the decrease in the battery capacity can be suppressed. it can.

  Moreover, the precursor of this embodiment can contain the functional group containing hydrogen as stated above. Examples of the functional group containing hydrogen include a hydrogen group and a hydroxyl group. The functional group containing hydrogen is mixed in in the production process, and H / Me, which is a substance amount ratio between the hydrogen H contained in the precursor of the present embodiment and the contained metal component Me, is 1.60 or more. Therefore, when the positive electrode active material is used, porous particles can be obtained, which is preferable. Further, it is preferable that H / Me is 1.65 or less because when the precursor of this embodiment is used as a positive electrode active material and applied to a secondary battery, battery characteristics per unit volume can be improved. .

  The metal component Me contained in the precursor mentioned here includes Ni, Co, Mn, and M which is an additive element mentioned in the above general formula.

  Moreover, the precursor of this embodiment can also contain components other than the nickel cobalt manganese carbonate composite and the functional group containing hydrogen, but contains the nickel cobalt manganese carbonate composite and hydrogen. It can also consist of functional groups. In addition, even if the precursor of this embodiment is a case where it is comprised from the group containing a nickel cobalt manganese carbonate composite and hydrogen, it does not exclude containing an inevitable component in a manufacturing process or the like. Absent.

Furthermore, the specific surface area of the precursor of this embodiment is preferably 30 m ² / g or more and 60 m ² / g or less. This is because when the specific surface area of the precursor is 30 m ² / g or more, when the precursor is used as a positive electrode active material, the positive electrode active material includes porous particles having uniform pores inside the particles. Because it can be. In addition, when the specific surface area of the precursor is set to 60 m ² / g or less, when the precursor is used as a positive electrode active material, the number of pores in the particles contained in the positive electrode active material is excessively increased. This is because it can prevent and increase the energy density.
[Method for producing positive electrode active material precursor for non-aqueous electrolyte secondary battery]
Next, a configuration 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 “a precursor production method”) will be described.

  In addition, since the precursor mentioned above can be manufactured with the manufacturing method of the precursor of this embodiment, description is partially abbreviate | omitted about the already demonstrated content.

  In the precursor production method of the present embodiment, a precursor can be obtained by a crystallization reaction, and the obtained precursor can be washed and dried as necessary.

Specifically, the method for producing the precursor of the present embodiment has a general formula Ni _x Co _y Mn _z M _t CO ₃ (where x + y + z + t = 1, 0.05 ≦ x ≦ 0.3, 0 0.1 ≦ y ≦ 0.4, 0.55 ≦ z ≦ 0.8, 0 ≦ t ≦ 0.1, and M is Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, And a nickel-cobalt-manganese carbonate composite represented by the following formula: and a functional group containing hydrogen, and a positive electrode active material precursor for a non-aqueous electrolyte secondary battery. With respect to the manufacturing method, the following steps can be included.

An initial aqueous solution containing an alkaline substance and / or an ammonium ion supplier in the presence of carbonate ions, an aqueous solution containing nickel as a metal component, an aqueous solution containing cobalt as a metal component, and an aqueous solution containing manganese as a metal component And a nucleation step of generating nuclei in the mixed aqueous solution.
Particle growth process for growing nuclei formed in the nucleation process.
In the nucleation step, the pH value of the mixed aqueous solution can be controlled to 7.5 or less on the basis of the reaction temperature of 40 ° C.

  In addition, the particle growth process can be switched from an oxygen-free atmosphere having an oxygen content of less than 0.1% by volume to an oxygen-containing atmosphere having an oxygen content of 2% by volume or more in the middle of the process.

  A configuration example of the flow of the precursor manufacturing method of the present embodiment shown in FIG. 1 will be described below. As shown in FIG. 1, the precursor manufacturing method of this embodiment includes (A) a nucleation step, and after performing the nucleation step, particles of the precursor are generated by a coprecipitation method (B) particle growth. Process.

  In the conventional continuous crystallization method, since the nucleation reaction and the particle growth reaction proceed simultaneously in the same reaction tank, the particle size distribution of the obtained compound particles has become wide.

  In contrast, the precursor manufacturing method of the present embodiment clearly separates mainly the time at which the nucleation reaction occurs (nucleation process) and the time at which the particle growth reaction mainly occurs (particle growth process). . Thereby, even if both processes are performed in the same reaction vessel, precursor particles having a narrow particle size distribution can be obtained. In addition, between both processes, the nuclear disintegration process which stops addition of a raw material and only stirs can be included.

Hereafter, each process of the manufacturing method of the precursor of this embodiment is demonstrated concretely.
(1) Nucleation process A nucleation process is demonstrated with reference to FIG.

  As shown in FIG. 1, in the nucleation step, first, ion-exchanged water (water), an alkaline substance and / or an ammonium ion supplier are mixed in a reaction tank to prepare an initial aqueous solution.

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

  Moreover, although it does not specifically limit about an alkaline substance, It is preferable that it is 1 or more types selected from sodium carbonate, sodium hydrogencarbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide.

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

  Therefore, it is preferable to add an acidic substance to the initial aqueous solution as necessary to adjust the pH value (40 ° C. standard) to 5.4 or more and 7.5 or less, and 6.4 or more and 7.4 or less. More preferably. In particular, the pH value is more preferably adjusted to 6.4 or more and 7.0 or less.

  During the nucleation step, the mixed aqueous solution preferably has a pH value in the above range.

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

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

  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).

  In the nucleation step, first, an atmosphere control is performed in which oxygen mixing is suppressed by blowing an oxygen-free gas having an oxygen content of less than 0.1% by volume, such as nitrogen gas, into the reaction vessel in which the initial aqueous solution is prepared. Is preferred. After that, an aqueous solution containing a metal component such as an aqueous solution containing nickel as a metal component described later can be supplied at a constant flow rate, for example, and the pH value of the mixed aqueous solution can be controlled to fall within a predetermined range.

  In this way, an oxygen-free gas such as nitrogen gas is blown into the reaction tank, and the nucleation step is performed in an environment in which the mixing of oxygen is suppressed and blocked, thereby suppressing the reaction between oxygen and the crystallized product. Fine particles close to a single crystal of salt are produced.

  In the nucleation step, oxygen-free gas such as nitrogen gas is continuously supplied into the reaction tank while an aqueous solution containing a metal component such as an aqueous solution containing nickel as a metal component is added to the initial aqueous solution. You can also. As the oxygen-free gas, a gas similar to the gas blown into the reaction tank in which the above-described initial aqueous solution is prepared can be used.

  When supplying an oxygen-free gas into the reaction vessel, the supply amount of the oxygen-free gas can be confirmed by measuring the dissolved oxygen concentration in the mixed aqueous solution. Since dissolved oxygen in the mixed aqueous solution is consumed during the nucleation step, if the amount of dissolved oxygen in the mixed aqueous solution is 5% or less of the saturation amount, mixing of oxygen can be sufficiently suppressed.

  As the oxygen-free gas, for example, an inert gas such as nitrogen gas or argon gas, carbon dioxide gas, or the like can be used.

  In the nucleation step, mixing is performed by adding and mixing an aqueous solution containing nickel as the metal component, an aqueous solution containing cobalt as the metal component, and an aqueous solution containing manganese as the metal component into the initial aqueous solution in the reaction vessel. An aqueous solution can be formed.

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

  Further, in order to control the pH of the mixed aqueous solution, the pH adjusting aqueous solution can be dropped together with the dropping of the aqueous solution containing a metal component such as an aqueous solution containing nickel as the metal component. In this case, the pH adjusting aqueous solution is not particularly limited, and for example, an aqueous solution containing an alkaline substance and / or an ammonium ion supplier can be used. In addition, although it does not specifically limit as an alkaline substance and an ammonium ion supply body, The substance similar to what was demonstrated in initial stage aqueous solution can be used. The method for supplying the pH-adjusted aqueous solution into the reaction vessel is not particularly limited. For example, a pump capable of controlling the flow rate such as a metering pump while sufficiently stirring the obtained mixed aqueous solution, What is necessary is just to add so that pH value may be kept in a predetermined range.

  Then, as described above, particles serving as the core of the precursor can be generated in the mixed aqueous solution obtained by adding an aqueous solution containing a metal component such as an aqueous solution containing nickel as a metal component to the initial aqueous solution. . Whether or not a predetermined amount of nuclei is generated in the mixed aqueous solution can be determined by the amount of the metal salt contained in the mixed aqueous solution.

  Here, an aqueous solution containing nickel as the metal component, an aqueous solution containing cobalt as the metal component, and an aqueous solution containing manganese as the metal component, which are added to the initial aqueous solution in the nucleation step, will be described.

  In the aqueous solution containing nickel as a metal component, the aqueous solution containing cobalt as a metal component, and the aqueous solution containing manganese as a metal component, a metal compound containing each metal component can be contained. That is, for example, in the case of an aqueous solution containing cobalt as a metal component, a metal compound containing cobalt can be included.

  And as a metal compound, it is preferable to use a water-soluble metal compound, and a nitrate, sulfate, hydrochloride, etc. are mentioned as a water-soluble metal compound. Specifically, for example, nickel sulfate, cobalt sulfate, manganese sulfate and the like can be suitably used.

  The aqueous solution containing nickel as the metal component, the aqueous solution containing cobalt as the metal component, and the aqueous solution containing manganese as the metal component are mixed partly or in advance, and the mixed aqueous solution containing metal components Can be added to the initial aqueous solution.

  The composition ratio of each metal in the obtained precursor is substantially the same as the composition ratio of each metal in the metal component-containing mixed aqueous solution. For this reason, for example, a dissolved metal is added so that the composition ratio of each metal contained in the mixed aqueous solution containing metal components added to the initial aqueous solution in the nucleation step is equal to the composition ratio of each metal in the precursor to be produced. It is preferable to prepare a mixed aqueous solution containing a metal component by adjusting the ratio of the compound.

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

  When the aqueous solution containing each metal component is not mixed and added individually to the initial aqueous solution, the composition ratio of each metal contained in the entire precursor solution containing the added metal component is the composition of each metal in the precursor to be generated. It is preferable to prepare an aqueous solution containing each metal component so as to be equal to the ratio.

As described above, the precursor manufactured by the precursor manufacturing method of the present embodiment has a general formula Ni _x Co _y Mn _z M _t CO ₃ (where x + y + z + t = 1, 0.05 ≦ x ≦ 0.3, 0.1 ≦ y ≦ 0.4, 0.55 ≦ z ≦ 0.8, 0 ≦ t ≦ 0.1, M is Mg, Ca, Al, Ti, V, Cr, A nickel-cobalt-manganese carbonate composite represented by Zr, Nb, Mo, or W.) and a functional group containing hydrogen.

  That is, in addition to nickel, cobalt, and manganese, an additive element can be further contained.

  For this reason, in the nucleation step, one or more additional elements selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W (hereinafter simply referred to as “additive elements”) as necessary. An aqueous solution containing (described below) (hereinafter also simply referred to as “an aqueous solution containing an additive element”) can be added to the initial aqueous solution. Since the additive element preferably contains Mo (molybdenum) as described above, an aqueous solution containing molybdenum as at least a metal component is preferably used as the aqueous solution containing the additive element.

  In addition, when adding an aqueous solution containing nickel as a metal component and adding it to the initial aqueous solution after preparing a mixed aqueous solution containing a metal component, an aqueous solution containing an additive element is added to and mixed with the mixed aqueous solution containing metal component. You can leave it.

  In addition, when an aqueous solution containing nickel as a metal component is added individually to the initial aqueous solution without mixing, an aqueous solution containing an additive element can be individually added to the initial aqueous solution.

  Here, the aqueous solution containing the additive element can be prepared using, for example, a compound containing the additive element. Examples of the compound containing the additive element include titanium sulfate, ammonium peroxotitanate, potassium potassium oxalate, vanadium sulfate, ammonium vanadate, chromium sulfate, potassium chromate, zirconium sulfate, zirconium nitrate, niobium oxalate, molybdenum. Ammonium acid, sodium tungstate, ammonium tungstate and the like can be mentioned, and a compound can be selected according to the element to be added.

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

  And by adding the aqueous solution containing the above-mentioned additive element to the mixed aqueous solution, the additive element can be uniformly dispersed inside the core particles contained in the precursor.

  Moreover, in order to coat | cover the surface of the secondary particle of a precursor uniformly with an additional element, the coating process which coat | covers with an additional element can be implemented after completion | finish of the particle growth process mentioned later, for example. The coating step will be described later in the particle growth step.

  In the nucleation step, an aqueous solution containing nickel as a metal component is added to and mixed with the initial aqueous solution in the presence of carbonate ions to form a mixed aqueous solution, and nuclei can be generated in the mixed aqueous solution. At this time, the method for supplying carbonate ions is not particularly limited. For example, carbonate ions are supplied to the mixed aqueous solution by supplying carbon dioxide gas (carbon dioxide gas) together with or as an oxygen-free gas in the reaction vessel. Can be supplied. Also, carbonate ions can be supplied using a carbonate when preparing an initial aqueous solution or a pH-adjusted aqueous solution.

  As explained so far, in the nucleation step, an aqueous solution containing nickel as a metal component is added to the initial aqueous solution in the presence of carbonate ions and mixed to form a mixed aqueous solution, which generates nuclei in the mixed aqueous solution. it can.

  At this time, the concentration of the metal compound in the mixed aqueous solution is preferably 1 mol / L or more and 2.6 mol / L or less, and more preferably 1.5 mol / L or more and 2.2 mol / L or less.

  This is because if the concentration of the metal compound in the mixed aqueous solution is less than 1 mol / L, the amount of crystallized material per reaction tank decreases, which is not preferable because the productivity is lowered. On the other hand, if the concentration of the metal compound in the mixed aqueous solution exceeds 2.6 mol / L, it may exceed the saturation concentration at room temperature, and crystals may reprecipitate and clog the equipment piping. is there.

  The concentration of the metal compound refers to an aqueous solution containing nickel as a metal component, an aqueous solution containing cobalt as a metal component, an aqueous solution containing manganese as a metal component, and an addition added in some cases. It means the concentration of the metal compound derived from the aqueous solution containing the element.

  In the nucleation step, 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 in the nucleation step is not particularly limited, but is preferably 70 ° C. or lower, and more preferably 50 ° C. or lower, for example.

  This is because, in the nucleation step, when the temperature of the mixed aqueous solution is less than 20 ° C., the solubility is low, so that nucleation is likely to occur and control may be difficult.

  On the other hand, in the nucleation step, when the temperature of the mixed aqueous solution exceeds 70 ° C., the primary crystal may be distorted and the tap density may be lowered.

  In the nucleation step, the ammonium ion concentration in the mixed aqueous solution is not particularly limited, but is preferably, for example, 0 g / L or more and 20 g / L or less, and particularly preferably maintained at a constant value.

  The pH value, other ammonium ion concentration, dissolved oxygen amount, etc. in the mixed aqueous solution can be measured by a general pH meter, ion meter, and dissolved oxygen meter, respectively.

After completion of the nucleation step, that is, after the addition to the initial aqueous solution, such as a mixed aqueous solution containing a metal component, is completed, it is preferable to continue stirring in the mixed aqueous solution and crush the produced nuclei (nuclear crushing). Process). When the nuclear disintegration step is performed, the time is preferably 1 minute or longer, more preferably 3 minutes or longer. By carrying out the nuclear crushing step, the produced nuclei can be aggregated, and the coarsening of the particle diameter and the density reduction inside the particles can be more reliably suppressed.
(2) Particle Growth Step Next, the particle growth step will be described with reference to FIG.

  In the particle growth process, the nuclei generated in the nucleation process can be grown.

  Specifically, for example, as shown in FIG. 1, in the particle growth step, first, the pH value of the mixed aqueous solution obtained in the nucleation step can be adjusted.

  At this time, the pH value of the mixed aqueous solution can be adjusted to be 6.0 or more and 9.0 or less, for example, on the basis of the reaction temperature of 40 ° C. At this time, 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 a pH adjusting solution described later.

  This is because the impurity cation can be prevented from remaining by setting the pH value of the mixed aqueous solution to 6.0 or more and 9.0 or less.

  In the particle growth step, the mixed aqueous solution after the nucleation step is an aqueous solution containing nickel as a metal component, an aqueous solution containing cobalt as a metal component, and an aqueous solution containing manganese as a metal component in the presence of carbonate ions. Can be added and mixed.

  In addition, it is preferable that the mixed aqueous solution after a nucleation process here is the mixed aqueous solution which adjusted pH after the nucleation process as mentioned above.

  In addition, an aqueous solution containing nickel as a metal component, an aqueous solution containing cobalt as a metal component, and an aqueous solution containing manganese as a metal component are mixed in part or in the same manner as in the nucleation step. The metal component-containing mixed aqueous solution may be added to the mixed aqueous solution. Moreover, when a specific metal compound reacts and an unnecessary compound is produced | generated by mixing several metal compounds, the aqueous solution containing each metal component is added separately to mixed aqueous solution, for example. Also good.

  Furthermore, when an aqueous solution containing nickel as a metal component is added to the mixed aqueous solution, an aqueous solution containing an additive element can also be added in the same manner as in the nucleation step. As described above, an aqueous solution containing an additive element may be mixed and added to the metal component-containing mixed aqueous solution. Moreover, when adding the aqueous solution containing each metal component separately to mixed aqueous solution, the aqueous solution containing an additional element can also be added individually to mixed aqueous solution.

  As the aqueous solution containing nickel as the metal component, the aqueous solution containing cobalt as the metal component, and the aqueous solution containing manganese as the metal component, the same aqueous solution as in the nucleation step can be used. Further, the density and the like may be adjusted separately.

  When an aqueous solution containing nickel as a metal component is added to the mixed aqueous solution, the pH value of the obtained mixed aqueous solution is preferably controlled within a predetermined range as described later. For this reason, the aqueous solution etc. which contain nickel as a metal component can be gradually dripped at mixing aqueous solution instead of adding at once. Therefore, the solution containing these metal components or the mixed aqueous solution containing the metal components can be supplied to the reaction tank, for example, at a constant flow rate.

  In the particle growth step, an aqueous solution containing a metal component such as an aqueous solution containing nickel as the metal component can be added to the mixed aqueous solution after adjusting the pH value as described above. Also in this case, for the same reason that the pH value was adjusted before the start of the particle growth process, the pH value of the mixed aqueous solution was in the same range as that of the mixed aqueous solution after adjusting the pH value, that is, 6 based on the reaction temperature of 40 ° C. It is preferably maintained at 0.0 or more and 9.0 or less, more preferably 6.4 or more and 8.0 or less, and further preferably 7.1 or more and 8.0 or less. preferable.

  In the particle growth step, a precursor having a small amount of remaining impurities can be obtained by controlling the pH value of the mixed aqueous solution within the above range.

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

  In particular, during the particle growth process, it is preferable to control the fluctuation range of the pH value of the mixed aqueous solution 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 is large, the growth of the particles contained in the precursor is not constant, and uniform particles with a narrow particle size distribution range may not be obtained. .

  When supplying an aqueous solution containing a metal component or a mixed aqueous solution containing a metal component as described above, it is preferable to add a pH-adjusted aqueous solution together so that the pH of the mixed aqueous solution can be maintained within a predetermined range. As the pH adjustment aqueous solution, the same pH adjustment aqueous solution as in the nucleation step can be used, and the pH adjustment aqueous solution at this time is not particularly limited. For example, an aqueous solution containing an alkaline substance and / or an ammonium ion supplier is used. Can be used. In addition, although it does not specifically limit as an alkaline substance and an ammonium ion supply body, The substance similar to what was demonstrated in initial stage aqueous solution can be used. The method for supplying the pH-adjusted aqueous solution into the reaction vessel is not particularly limited. For example, a pump capable of controlling the flow rate such as a metering pump while sufficiently stirring the obtained mixed aqueous solution, What is necessary is just to add so that pH value may be kept in a predetermined range.

  In the particle growth step, the ammonium ion concentration in the mixed aqueous solution is preferably 0 g / L or more and 20 g / L or less, particularly preferably maintained at a constant value.

  This is because by setting the ammonium ion concentration to 20 g / L or less, the nuclei of the precursor particles can be uniformly grown. Further, in the particle growth step, the ammonium ion concentration is maintained at a constant value, so that the solubility of metal ions can be stabilized and the particle growth of uniform precursor particles can be promoted.

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

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

  In the particle growth process, the metal component is controlled while controlling the atmosphere so as to suppress the mixing of oxygen by blowing oxygen-free gas having an oxygen content of less than 0.1% by volume into the reaction vessel at the start of the particle growth process. For example, an aqueous solution containing a metal component such as an aqueous solution containing nickel can be supplied at a constant flow rate. In addition, when a certain period of time has elapsed after the start of supplying oxygen-free gas, the oxygen-containing gas is switched from oxygen-free gas having an oxygen content of 2% by volume or more and nickel is added as a metal component while blowing oxygen-containing gas. For example, an aqueous solution containing a metal component such as an aqueous solution containing can be supplied at a constant flow rate.

  That is, in the particle growth process, an oxygen content (oxygen concentration) of less than 0.1% by volume is changed from an oxygen content (oxygen concentration) of 2% by volume or more in the middle of the process. Can be switched.

  By supplying oxygen-free gas for a certain period after the start of the particle growth process, it is possible to suppress oxidation by oxygen in the growing precursor particles. Further, fine crystals can be further aggregated to generate large secondary particles.

  Then, oxygen is contained in the oxygen-containing gas supplied to the reaction vessel by the surface of the growing precursor particles by supplying an oxygen-containing gas instead of the oxygen-free gas when a certain period of time has elapsed since the start of the particle growth process. It can react with. Then, irregular fine particles that are not single crystals of carbonate are further aggregated, and larger secondary particles can be generated.

  As described above, by switching from oxygen-free gas to oxygen-containing gas in the middle of the particle growth process, the positive electrode has uniform pores inside the particles and has as few pores as possible to increase the energy density It becomes possible to obtain a positive electrode active material precursor from which an active material can be obtained.

  Further, by blowing an oxygen-containing gas from the middle of the particle growth process, it is possible to easily mix a functional group containing hydrogen with respect to the precursor as compared with the case of an inert gas atmosphere, and the obtained precursor H / Me, which is the substance amount ratio between the hydrogen contained in and the metal component Me contained, can be set to 1.60 or more and 1.65 or less.

  The timing for switching from the oxygen-free gas to the oxygen-containing gas is not particularly limited, and can be arbitrarily selected according to the energy density required for the positive electrode active material. For example, when the time of the grain growth process is T, the time for the oxygen-free atmosphere in the time T is preferably 1 / 5T or more and 1 / 2T or less. This is because the energy density of the positive electrode active material produced from the obtained precursor can be sufficiently increased by setting the time for an oxygen-free atmosphere to 1/5 T or more. Moreover, uniform pores can be formed inside the particles by setting the time of the oxygen-free atmosphere to 1 / 2T or less.

  The particle growth step time T refers to the time during which an aqueous solution containing nickel as a metal component is dropped into the mixed aqueous solution.

  When supplying oxygen-free gas or oxygen-containing gas into the reaction vessel in the particle growth step, the supply amount of the oxygen-free gas or oxygen-containing gas can be confirmed by measuring the dissolved oxygen concentration in the mixed aqueous solution. . For example, when oxygen-free gas is supplied, oxygen mixing can be sufficiently suppressed if the amount of dissolved oxygen in the mixed aqueous solution is 5% or less of the saturation amount.

  In addition, when an oxygen-containing gas is supplied, if the amount of dissolved oxygen in the mixed aqueous solution is half or more of the saturation amount, sufficient dissolved oxygen / oxygen can be supplied for the reaction.

  As the oxygen-free gas, for example, an inert gas such as nitrogen gas or argon gas, carbon dioxide gas, or the like can be used.

  For example, air or the like can be used as the oxygen-containing gas.

  The particle size of the secondary particles contained in the precursor can be controlled by the reaction time in the particle growth process.

  That is, in the particle growth step, a precursor having secondary particles having a desired particle diameter can be obtained by continuing the reaction until the particle has grown to a desired particle diameter.

  And after obtaining a precursor by a particle growth process, it can also have the coating process which coat | covers the surface of the particle | grains of the precursor obtained as mentioned above with an additional element. That is, the precursor manufacturing method of the present embodiment may further include a coating step of coating the precursor particles (secondary particles) obtained in the particle growth step with an additive element.

  The coating step can be any of the following steps, for example.

  For example, first, an aqueous solution containing an additive element is added to a slurry in which precursor particles are suspended, and the additive element is precipitated on the surface of the precursor particles by a crystallization reaction.

  The slurry in which the precursor particles are suspended is preferably slurried using an aqueous solution containing an additive element. Moreover, when adding the aqueous solution containing the additive element 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 is 6.0 or more and 9.0 or less. It is preferable to control. This is because the surface of the precursor particles can be particularly uniformly coated with the additive element by controlling the pH of the mixed aqueous solution of the slurry and the aqueous solution containing the additive element within the above range.

  Moreover, a coating process can also be made into the process of spraying and drying the aqueous solution or slurry containing an additional element with respect to precursor particle | grains.

  In addition, the coating step may be a step of spray drying a slurry in which the precursor particles and the compound containing the additive element are suspended.

  Moreover, it can also be set as the process of mixing a precursor particle and the compound containing an additional element by a solid-phase method.

  In addition, about the aqueous solution containing the additional element demonstrated here, the aqueous solution similar to what was demonstrated at the nucleation process can be used. In the coating step, an alkoxide solution containing the additive element may be used instead of the aqueous solution containing the additive element.

  As described above, when an aqueous solution containing an additive element is added to the mixed aqueous solution in the nucleation step, and the surface of the precursor particles is coated with the additional element in the particle growth step, it is added to the mixed aqueous solution in the nucleation step. It is preferable to reduce the amount of additive element ions by the amount to be coated. This is because the atomic ratio between the additive element contained in the obtained precursor and other metal components is desired by reducing the amount of the aqueous solution containing the additive element to be added to the mixed aqueous solution by an amount that covers the amount. It is because it can be set as the value of.

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

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

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

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

  In the particle growth process, adjust the pH value of the mixed aqueous solution obtained in the nucleation process to be within the specified range, and add an aqueous solution containing a metal component such as an aqueous solution containing nickel as the metal component to the mixed aqueous solution. By doing so, uniform precursor particles can be obtained.

By carrying out the above particle growth step, an aqueous solution of precursor particles, which is a slurry containing precursor particles, is obtained. And after finishing a particle growth process, a washing process and a drying process can be carried out.
(3) Cleaning Step In the cleaning step, the slurry containing the precursor particles obtained in the above-described particle growth step can be cleaned.

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

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

  The washing with water may be performed by a commonly performed method as long as it can remove excess raw materials contained in the precursor particles.

The water used in the water washing is preferably water having as little impurity content as possible, and more preferably pure water, in order to prevent contamination of impurities.
(4) Drying Step In the drying step, the precursor particles washed in the washing step can be dried.
First, in the drying step, for example, the dried precursor particles can be dried at a drying temperature of 80 ° C. or higher and 230 ° C. or lower.

  A precursor can be obtained after a drying process.

  According to the method for producing a precursor of this embodiment, a precursor that contains porous particles and can form a positive electrode active material for a non-aqueous electrolyte secondary battery with high energy density can be obtained.

  In addition, according to the method for producing a precursor of the present embodiment, by clearly separating the time mainly when the nucleation reaction occurs (nucleation process) and the time when the particle growth reaction mainly occurs (particle growth process), Even if both steps are performed in the same reaction vessel, precursor particles (secondary particles) having a narrow particle size distribution can be obtained.

  In addition, in the precursor manufacturing method of the present embodiment, the crystal size of the precursor particles obtained by the crystallization reaction can be controlled.

  Therefore, according to the precursor manufacturing method of the present embodiment, it is possible to obtain a precursor having a small primary particle size, high secondary particle size uniformity, and high density (tap density). it can.

In the precursor production method of the present embodiment, the nucleation step and the particle growth step can be performed separately in one reaction tank only by adjusting the pH of the reaction solution. Therefore, the precursor production method of the present embodiment is easy and suitable for large-scale production, so that it can be said that its industrial value is extremely large.
[Positive electrode active material for non-aqueous electrolyte secondary battery]
Next, a configuration example of the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present embodiment (hereinafter also simply referred to as “positive electrode active material”) will be described.

The positive electrode active material of this embodiment is related with the positive electrode active material for nonaqueous electrolyte secondary batteries containing a lithium metal complex oxide.
The lithium metal composite oxide has a general formula of Li _{1 + α} Ni _x Co _y Mn _z M _t O ₂ (0.25 ≦ α ≦ 0.55, x + y + z + t = 1, 0.05 ≦ x ≦ 0.3, 0. 1 ≦ y ≦ 0.4, 0.55 ≦ z ≦ 0.8, 0 ≦ t ≦ 0.1, M is an additive element, Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo , One or more elements selected from W).

  The positive electrode active material of the present embodiment can include porous secondary particles in which a plurality of primary particles are aggregated. In the porous secondary particles, the number ratio of the secondary particles having a porosity of 10% or more and 20% or less in the secondary particles can be set to 80% or more. Furthermore, the positive electrode active material of the present embodiment can have an energy density that is a product of the tap density and the initial discharge capacity of 580 mAh / cc or more.

The positive electrode active material of this embodiment is a lithium metal composite oxide in which two types of layered compounds represented by Li ₂ M1O ₃ and LiM2O ₂ are solid-solved, more specifically, a lithium-excess nickel cobalt manganese composite oxide. Can be included. In addition, the positive electrode active material of this embodiment can also be comprised from the said lithium metal complex oxide.

  In the above formula, M1 is a metal element containing at least Mn adjusted to be tetravalent on average, and M2 is a metal element containing at least Ni, Co, and Mn adjusted to be trivalent on average. is there.

It is assumed that the composition ratio of Ni, Co, and Mn shown in the above-described precursor is established as M1 + M2. Moreover, since the abundance ratio of Li ₂ M1O ₃ and LiM2O ₂ is excess of lithium, Li ₂ M1O ₃ is not 0%.

  As described above in the precursor, in order to further improve battery characteristics such as cycle characteristics and output characteristics of the positive electrode active material of the non-aqueous electrolyte secondary battery, the lithium metal composite oxide is Mg, as described above. One or more kinds of additive elements selected from Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W can be contained. The content of the additive element is preferably adjusted so that the atomic ratio t falls within the range of 0 ≦ t ≦ 0.1 in the precursor for the reasons already described.

As the above-mentioned additive element, one or more kinds selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W can be used as described above. In particular, the additive element includes molybdenum. It is preferable. That is, the additive element M in the above-described general formula: Li _{1 + α} Ni _x Co _y Mn _z M _t O ₂ preferably contains Mo (molybdenum). This is because, according to the study by the inventors of the present invention, when the positive electrode active material contains molybdenum as an additive element, the initial discharge capacity can be particularly increased in a battery using the positive electrode active material. It is.

  Furthermore, the lithium metal composite oxide is a metal component excluding Li in the lithium metal composite oxide, that is, Ni, Co, Mn, and the additive element M having a molybdenum content of 0.5 at% to 5 at%. More preferably. This is because the above-described effect of increasing the initial discharge capacity can be particularly expressed by setting the molybdenum content in the metal component excluding Li in the lithium metal composite oxide to 0.5 at% or more. Molybdenum has the effect of accelerating sintering during firing, but a large crystal is formed by setting the molybdenum content in the metal component excluding Li in the lithium metal composite oxide to 5 at% or less. This is preferable because it is possible to reliably prevent an increase in resistance and a decrease in discharge capacity in a battery manufactured using the lithium metal composite oxide.

Moreover, according to examination of the inventors of this invention, the effect that the specific surface area of a positive electrode active material can be reduced was confirmed by the addition element containing molybdenum. This is because the fine vacancies in the positive electrode active material are structurally changed to large vacancies due to the addition of molybdenum. Furthermore, according to the study of the inventors of the present invention, the positive electrode active material paste can be manufactured by controlling the specific surface area of the positive electrode active material in the range of 1.5 m ² / g or more and 15.0 m ² / g or less. The output characteristics can be improved. Therefore, also from the viewpoint of controlling the specific surface area within the above range, the additive element preferably contains molybdenum.

  The positive electrode active material of the present embodiment can have porous secondary particles having a structure having uniform pores up to the center of the secondary particles, and by using such a porous structure, the reaction The surface area can be increased. In addition, the electrolyte enters from the grain boundaries or pores between the primary particles of the outer shell, and lithium is inserted and desorbed at the reaction interface inside the particles, so that the movement of Li ions and electrons is not hindered, Output characteristics can be improved.

  The positive electrode active material of the present embodiment can contain porous secondary particles as described above, and the porous secondary particles have a porosity inside the secondary particles of 10% or more and 20% or less. It is preferable to contain the porous secondary particle which is. In addition, the positive electrode active material of the present embodiment includes 80% of secondary particles having a porosity of 10% or more and 20% or less of the secondary particles among the porous secondary particles contained. It is preferable to contain above. The porosity of the secondary particles contained in the positive electrode active material can be calculated by, for example, observing the cross-sectional structure of the positive electrode active material with an SEM and performing image processing or the like. For example, particles having a calculated porosity exceeding 3% can be made into porous secondary particles, that is, porous particles. And the ratio of the porous secondary particle which a positive electrode active material contains is not specifically limited, For example, it can be 85% or more and 100% or less in a number ratio.

  In addition, the number ratio of the porous secondary particles and the number ratio of the secondary particles having a porosity inside the secondary particles of 10% or more and 20% or less of the porous secondary particles are determined by, for example, SEM. This can be determined by observing the cross-sectional structure of a plurality of, for example, 100 or more positive electrode active materials, and counting the proportion of secondary particles having a porosity in a predetermined range.

The positive electrode active material of this embodiment can increase the specific surface area by having secondary particles having a porous structure. 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 may be, for example, 1.5 m ² / g or more. preferable. This is because, by setting the specific surface area of the positive electrode active material of the present embodiment to 1.5 m ² / g or more, the positive electrode mixture paste can be easily manufactured and the output characteristics can be improved. It is.

The positive electrode active upper limit of the specific surface area of material of the present embodiment is not particularly limited, for example, preferably to 15.0 m 2 / ^g or less, and more preferably less 13.0m 2 / ^g.

However, the specific surface area of the positive electrode active material of the present embodiment is 5.0 m ² / g or more and 15.0 m ² / g or less, particularly when the reaction surface area is increased and the output characteristics are particularly required to be increased. Is preferred. In particular, when it is required to make the production of the positive electrode mixture paste particularly easy, the specific surface area of the positive electrode active material of the present embodiment is 1.5 m ² / g or more and 5.0 m ² / g or less. It is preferable.

  Further, according to the positive electrode active material of the present embodiment, the porous material contains porous secondary particles, and the porosity inside the secondary particles is 10% or more and 20% or less among the porous secondary particles. By having the secondary particles of at least a certain ratio, it is possible to improve the output characteristics in the case of a battery and to increase the tap density.

  The tap density of the positive electrode active material of the present embodiment is not particularly limited, but is preferably 1.7 g / cc or more, and more preferably 2.0 g / cc or more.

  The positive electrode active material of this embodiment preferably has a high initial discharge capacity of 250 mAh / g or more when used for the positive electrode of a 2032 type coin-type battery, for example. Further, the discharge capacity under the high discharge rate condition (2C) is preferably 195 mAh / g or more.

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

  Moreover, when the positive electrode active material of this embodiment is used for the positive electrode of a 2032 type coin type battery, for example, it is preferable that the energy density is high. Specifically, for example, 550 mAh / cc or more is preferable, and 600 mAh / cc or more is more preferable. Since the higher energy density is preferable, the upper limit value is not particularly limited.

  The energy density can be calculated by multiplying the tap density by the initial discharge capacity.

The initial discharge capacity is 2032 type coin type battery using the positive electrode active material of this embodiment as the positive electrode, the current density with respect to the positive electrode is 0.05 C (270 mA / g is 1 C), and the cut-off voltage 4 The capacity can be obtained when the battery is charged to .65 V and discharged to a cut-off voltage of 2.35 V after a pause of 1 hour.
[Method for producing positive electrode active material for non-aqueous electrolyte secondary battery]
Next, one structural example of the method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery of the present embodiment (hereinafter also simply referred to as “method for producing a positive electrode active material”) will be described.

  The method for producing the positive electrode active material according to 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. Since an active material can be manufactured more reliably, it is preferable.

  The manufacturing method of the positive electrode active material of this embodiment can have the following processes.

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

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

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

  In the heat treatment step, the heat treatment temperature is set to 80 ° C. or more because when the heat treatment temperature is less than 80 ° C., excess moisture in the particles of the precursor cannot be removed, and the above variation may not be suppressed. is there.

  On the other hand, the heat treatment temperature is set to 600 ° C. or less 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. .

  In addition, the metal component contained in the precursor particles obtained when the heat treatment is performed under the predetermined heat treatment conditions is analyzed, and the correspondence between the heat treatment conditions and the metal components in the precursor particles obtained thereby You can also seek relationships. And the said dispersion | variation can also be suppressed by determining the ratio of the particle | grains of the precursor obtained by predetermined heat processing conditions, and a lithium compound.

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

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

The equipment used for the heat treatment is not particularly limited as long as the precursor particles can be heated in a non-reducing atmosphere, preferably in an air stream, such as an electric furnace that does not generate gas. Preferably used.
(2) Mixing step The mixing step is a step of forming a lithium mixture by adding and mixing a lithium compound to the heat-treated particles obtained by heating in the heat treatment step.

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

  The heat-treated particles and the lithium compound are the number of atoms of metals other than lithium in the lithium mixture, that is, the sum of the number of atoms of nickel, cobalt, manganese and additive elements (Me) and the number of atoms of lithium (Li). Mixing is preferably performed so that the ratio (Li / Me) is 1.1 or more and 1.8 or less. At this time, it is more preferable to mix so that Li / Me is 1.3 or more and 1.5 or less.

  That is, since Li / Me hardly changes before and after the firing step, Li / Me mixed in this mixing step becomes Li / Me in the positive electrode active material. Therefore, Li / Me in the lithium mixture becomes the positive electrode active to be obtained. Mixed to be the same as Li / Me in the material.

  The lithium compound used to form the lithium mixture is not particularly limited, but is preferably one or more selected from, for example, lithium hydroxide, lithium nitrate, and lithium carbonate because it is easily available. Can be used.

  In particular, in view of ease of handling and quality stability, it is more preferable to use at least one selected from lithium hydroxide and lithium carbonate as the lithium compound used in forming the lithium mixture.

For mixing, a general mixer can be used. For example, a shaker mixer, a Laedige mixer, a Julia mixer, a V blender, or the like may be used.
(3) Firing step The firing step is a step in which the lithium mixture obtained in the mixing step is fired to obtain a positive electrode active material. When the mixed powder is fired in the firing step, lithium in the lithium compound diffuses into the heat-treated particles, so that a lithium nickel cobalt manganese composite oxide is formed.

  The firing temperature of the lithium mixture at this time is not particularly limited, but is preferably, for example, 600 ° C. or higher and 1000 ° C. or lower.

  This is because when the firing temperature is set to 600 ° C. or higher, the diffusion of lithium into the heat-treated particles is sufficiently promoted, and the remaining of excess lithium and unreacted particles is suppressed and used in a battery. This is because sufficient battery characteristics can be obtained.

  However, if the firing temperature exceeds 1000 ° C., intense sintering occurs between the composite oxide particles and abnormal grain growth may occur, and the particles after firing become coarse and fine pores are formed inside the particles. This is because there is a possibility that it becomes impossible. Since such a positive electrode active material has a reduced specific surface area, when used in a battery, there arises a problem that the resistance of the positive electrode increases and the battery capacity decreases.

Since the firing temperature of the lithium mixture also affects the specific surface area of the positive electrode active material obtained, it can be selected from the temperature ranges described above according to the specific surface area required for the positive electrode active material. For example, when it is particularly required to suppress the specific surface area of the positive electrode active material, the firing temperature is preferably set to a higher temperature, for example, 900 ° C. or higher and 950 ° C. or lower. According to the study of the inventors of the present invention, the specific surface area of the positive electrode active material obtained can be 1.5 m ² / g or more and 5.0 m ² / g or less by firing in such a temperature range. The production of the composite paste can be made particularly easy. Moreover, when it is set as a non-aqueous electrolyte secondary battery using this positive electrode active material, battery capacity can be kept high and it is preferable.

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

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

  Of the firing time, the holding time at the firing temperature is preferably 1 hour or longer, and more preferably 2 hours or longer and 24 hours or shorter.

  This is because the generation of the lithium nickel cobalt manganese composite oxide can be sufficiently promoted by holding at the firing temperature for 2 hours or more.

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

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

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

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

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

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

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

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

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

  The particles of the lithium nickel cobalt manganese composite oxide obtained by the firing step may be aggregated or slightly sintered.

  In this case, it may be crushed. Thereby, the positive electrode active material of this embodiment containing a lithium nickel cobalt manganese composite oxide can be obtained.

Note that pulverization means that mechanical energy is applied to an aggregate composed of a plurality of secondary particles generated by sintering necking between secondary particles during firing, and the secondary particles themselves are hardly destroyed. This is an operation of separating the secondary particles and loosening the aggregates.
[Nonaqueous electrolyte secondary battery]
Next, a configuration example of the non-aqueous electrolyte secondary battery of the present embodiment will be described. The non-aqueous electrolyte secondary battery of this embodiment can have a positive electrode using the positive electrode active material described above.

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

  The nonaqueous electrolyte secondary battery of the present embodiment (hereinafter also simply referred to as “secondary battery”) is a general nonaqueous electrolyte secondary battery except that the positive electrode active material described above is used as the positive electrode material. And substantially the same structure.

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

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

  In addition, it cannot be overemphasized that the structure of the secondary battery of this embodiment is not limited to the said example, Moreover, the external shape can employ | adopt various shapes, such as a cylinder shape and a laminated form.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Hereinafter, sample preparation conditions and evaluation results in each example and comparative example will be described.
[Example 1]
1. Production and Evaluation of Precursor First, a precursor was produced by the following procedure.

Throughout all the examples and comparative examples, the Wako Pure Chemical Industries, Ltd. reagent grade samples are used for the preparation of the precursor, the positive electrode active material, and the secondary battery unless otherwise specified.
(Nucleation process)
(1) Preparation of initial aqueous solution First, in a reaction tank (5 L), water is added to an amount of about 1.2 L, and the temperature in the tank is set to 40 ° C. while stirring. The mixed aqueous solution was controlled to 40 ° C. in the crushing step and the particle growth step. The temperature of the initial aqueous solution and the mixed aqueous solution was controlled by adjusting the temperature of the warming water for the reaction vessel provided around the reaction vessel.

  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.

  64% sulfuric acid was further added to the initial aqueous solution to adjust the pH to 6.4.

Then, nitrogen gas having an oxygen concentration of 9 ppm is supplied from the nitrogen gas cylinder at 4 L / min as an oxygen-free gas for blocking oxygen, and the inside of the reaction vessel is purged, and the oxygen concentration is 0.1 volume. The oxygen-free atmosphere was less than or equal to%. The supply of the nitrogen gas is continued until a certain time has elapsed after the start of the particle growth process, and the inside of the reaction vessel is maintained in a nitrogen gas atmosphere that is the same atmosphere as the nitrogen gas, that is, an oxygen-free atmosphere that suppresses the mixing of oxygen Has been.
(2) Preparation of metal component-containing mixed aqueous solution Next, nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in water to prepare a metal component-containing mixed aqueous solution having a metal ion concentration of 2.0 mol / L. In this metal component-containing mixed aqueous solution, the element molar ratio of each metal was adjusted to be Ni: Co: Mn = 0.165: 0.165: 0.67.
(3) Adjustment of pH adjustment aqueous solution Sodium carbonate and ammonium carbonate were dissolved in water to prepare a pH adjustment aqueous solution having a carbonate ion concentration of 2.2 mol / L. The sodium carbonate and ammonium carbonate in the pH-adjusted aqueous solution were added so that the molar ratio was 9: 2.
(4) Addition and mixing of metal component-containing mixed aqueous solution to initial aqueous solution Add metal component-containing mixed aqueous solution to the initial aqueous solution in the reaction vessel at 10.3 ml / min. To obtain a mixed aqueous solution.

  In addition, when adding the metal component-containing mixed aqueous solution, a pH adjusting aqueous solution is added at the same time, and the pH value of the mixed aqueous solution in the reaction vessel is controlled so as not to exceed 6.4 (nucleation pH value) for 4 minutes. A nucleation step was carried out by crystallization.

In the nucleation step, the pH value is controlled by adjusting the supply flow rate of the pH adjusting aqueous solution with a pH controller, and the fluctuation range of the pH value of the mixed aqueous solution is 0.2 above and below the center value (set pH value) 6.2. It was within the range.
(5) Nuclear crushing process Then, stirring was continued for 5 minutes and the nucleus was crushed.
(Particle growth process)
In the particle growth step, the same metal component-containing mixed aqueous solution and pH adjustment aqueous solution as in the nucleation step were used. The experimental procedure of the particle growth process will be described below.
(1) Adjustment of pH of mixed aqueous solution In the particle growth step, first, the pH value is adjusted by adding the pH adjusted aqueous solution to the mixed aqueous solution obtained in the nucleation step while blowing the same nitrogen gas into the reaction vessel as in the nucleation step. It was set to 7.4 (liquid temperature 40 ° C. standard).
(2) Addition of metal component-containing mixed aqueous solution to mixed aqueous solution, mixing To the mixed aqueous solution after pH adjustment, 10.3 ml / min. The ratio was added.

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

  After this state was continued for 50 minutes, the nitrogen gas blown into the reaction vessel was replaced with air having an oxygen content of 21% by volume, and the reaction was further continued for 143 minutes to stop stirring, and the crystallization was completed. It was.

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

  In the particle growth step, the pH value is controlled by adjusting the supply flow rate of the pH adjusting aqueous solution by a pH controller, and the fluctuation range of the pH value of the mixed aqueous solution is 0 above and below the center value (set pH value) 7.2. .2 within the range.

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

(Evaluation of precursor)
The obtained precursor was dissolved in an inorganic acid and then subjected to chemical analysis by ICP emission spectroscopy. The composition was Ni: Co: Mn = 15.8 at%: 16.6 at%: 67.6 at%. It was confirmed that the carbonate was composed of Furthermore, using an elemental analysis device (Thermo Fisher Scientific model: FlashEA 1112), the amount of elements of hydrogen (H) is measured, and the mass ratio of metal (Ni + Co + Mn) is calculated to be 1.61. It was confirmed that hydrogen was contained. Moreover, it has confirmed that it had a functional group containing hydrogen.

Further, the particles of the precursor, the average particle diameter D _50, a laser diffraction scattering particle size distribution analyzer (manufactured by Nikkiso Co., Ltd., Microtrac HRA) result of measurement with a mean particle size is 10.7μm I was able to confirm.

  Next, SEM (manufactured by Hitachi High-Technologies Corporation, Scanning Electron Microscope S-4700) observation (magnification: 3000 times) of the obtained precursor particles was performed. As a result, the obtained precursor particles were approximately It was spherical and it was confirmed that the particle diameters were almost uniform. In the case of such a shape, the sphericity of the precursor particles shown in Table 2 is judged as ◯.

  The SEM observation results are shown in FIG.

Moreover, when the specific surface area of the obtained precursor particles was evaluated using Max Soap (manufactured by Mountec Co., Ltd.), it was 40.5 m ² / g.
2. Production and Evaluation of Positive Electrode Active Material Next, production and evaluation of the positive electrode active material were performed using the obtained precursor.

(Manufacture of positive electrode active material)
The precursor was heat-treated at 500 ° C. for 2 hours in an air stream (oxygen: 21 vol%) to convert to the composite oxide particles as heat-treated particles, and recovered.

  Next, the heat-treated particles and the lithium compound were mixed to obtain a lithium mixture.

  Specifically, lithium carbonate was weighed so that Li / Me = 1.5 of the obtained lithium mixture and mixed with the heat-treated particles to prepare a lithium mixture.

  Mixing was performed using a shaker mixer apparatus (manufactured by Willy et Bacofen (WAB), TURBULA Type T2C).

  The obtained lithium mixture was calcined in the atmosphere (oxygen: 21% by volume) at 500 ° C. for 5 hours, then calcined at 950 ° C. for 2 hours, cooled, and crushed to obtain a positive electrode active material. .

In addition, the composition of the obtained positive electrode active material is expressed as Li _1.5 Ni _0.158 Co _0.166 Mn _0.676 O ₂ .

(Evaluation of positive electrode active material)
When the particle size distribution of the obtained positive electrode active material was measured in the same manner as in the case of the precursor particles, it was confirmed that the average particle size was 9.8 μm.

  Moreover, cross-sectional SEM observation of the positive electrode active material was performed.

  In performing SEM observation of the cross section of the positive electrode active material, secondary particles of a plurality of positive electrode active material particles were embedded in a resin, and the cross section polisher process was performed to enable observation of the cross section of the particles. .

  3A and 3B show cross-sectional SEM observation results of the positive electrode active material. FIG. 3B is a partially enlarged view of FIG. 3A, and is an enlarged view of particles surrounded by a dotted line in FIG.

  As shown in FIG. 3A and FIG. 3B, it was confirmed that the obtained positive electrode active material was substantially spherical. In this case, the sphericity is evaluated as ◯ in Table 3. It was also confirmed that the structure had uniform pores up to the central part inside the secondary particles.

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

  The average porosity of the porous particles was 15%. Further, among the porous particles, the proportion of the porous particles having a porosity of 10% or more and 20% or less was 100%.

  Table 3 shows the average porosity of the porous particles among the above arbitrarily selected particles as the porosity of the porous particles. Further, the ratio of the number of porous particles to the number of porous particles in the observed particles is shown. Furthermore, the number ratio of the porous particles whose porosity is 10% or more and 20% or less among the porous particles is also shown.

  The same applies to Comparative Examples 1 and 2 below.

  Furthermore, when the tap density was measured, it was confirmed that it was 2.1 g / cc.

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

Further, when the specific surface area of the obtained positive electrode active material was determined by a flow method gas adsorption method specific surface area measurement device (manufactured by Yuasa Ionics Co., Ltd., Multisorb), it was confirmed to be 2.5 m ² / g.

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

  The configuration of the manufactured coin battery will be described with reference to FIG. FIG. 4 schematically shows a cross-sectional configuration diagram of the coin-type battery.

  As shown in FIG. 4, the coin-type battery 10 includes a case 11 and an electrode 12 accommodated in the case 11.

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

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

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

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

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

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

  The initial discharge capacity is left for about 24 hours after the coin-type battery 10 is manufactured, and after the open circuit voltage OCV (open circuit voltage) is stabilized, the current density with respect to the positive electrode is 0.05 C (270 mA / g is 1 C). ) To a cut-off voltage of 4.65 V, the capacity when discharged to a cut-off voltage of 2.35 V after a pause of 1 hour was defined as the initial discharge capacity.

  When a battery evaluation was performed on a coin-type battery having a positive electrode formed using the positive electrode active material, the initial discharge capacity was 290 mAh / g. In addition, in order to evaluate the high discharge rate characteristics, the charge / discharge capacity was measured at 0.01 C, and then the charge / discharge capacity was measured three times at 0.2 C, 0.5 C, and 1.0 C, and then 3 at 2.0 C. The average value measured once was taken as the discharge capacity at a high discharge rate. The value was 205 mAh / g.

  The energy density, which is the product of the initial discharge capacity and the tap density, was 609 mAh / cc.

Table 1 summarizes the manufacturing conditions of this example, Table 2 shows the characteristics of the precursor obtained in this example, and the characteristics of the positive electrode active material and the coin-type battery manufactured using this positive electrode active material. Each evaluation is shown in Table 3, respectively. The same contents are also shown in the same table for the following Comparative Example 1 and Comparative Example 2.
[Comparative Example 1]
Except for the point that all the gases blown into the reaction vessel during production of the precursor were changed to air gas having an oxygen concentration of 21% by volume, and the time of the particle growth step was changed to 196 minutes, Example 1 and Similarly, a precursor, a positive electrode active material, and a secondary battery were prepared and evaluated. The results are shown in Tables 1 to 3.

  In addition, about the obtained positive electrode active material, the cross-sectional SEM image observation was performed similarly to Example 1, and the porosity of the secondary particle was computed with image analysis software. Among 100 arbitrarily selected secondary particles, the number ratio of porous particles was 100%. Furthermore, the average porosity of the porous particles was 23%.

And although all the secondary particles of the positive electrode active material which were observed were porous particles, many of the porous particles have a porosity of over 20%. Among the porous particles, the porosity is 10%. The proportion of porous particles that are not less than 20% and not more than 20% was 30%.
[Comparative Example 2]
The point that all the gases blown into the reaction tank during the production of the precursor were nitrogen gas having an oxygen concentration of 9 ppm, the point of the particle growth step was changed to 196 minutes, and the firing temperature was 850 ° C. Except for the points, a precursor, a positive electrode active material, and a secondary battery were produced and evaluated in the same manner as in Example 1. The results are shown in Tables 1 to 3.

  The obtained positive electrode active material was subjected to cross-sectional SEM observation in the same manner as in Example 1.

  FIG. 5A and FIG. 5B show cross-sectional images of typical particles. Note that FIG. 5A shows an overall view, and FIG. 5B is an enlarged view of particles surrounded by a dotted line in FIG. 5A.

  For the obtained positive electrode active material, the porosity of the secondary particles was calculated from the cross-sectional SEM image using image analysis software in the same manner as in Example 1. Among 100 arbitrarily selected secondary particles, the number ratio of porous particles was 30%. Furthermore, the average porosity of the porous particles was 18%.

  Furthermore, among the porous particles, the proportion of porous particles having a porosity of 10% or more and 20% or less was 30%.

From the results shown in Table 2, it was confirmed that the precursor of Example 1 had the target composition. Furthermore, it was confirmed that the positive electrode active material obtained from the precursor contains porous particles, and among the porous particles, the number ratio of the porous particles having a porosity of 10% to 20% is also 100%. It was.

  It was confirmed that the initial discharge capacity and the discharge capacity under high discharge rate conditions can be sufficiently increased by using the positive electrode active material. It was also confirmed that the energy density was as high as 609 mAh / cc.

  On the other hand, in the comparative example 1, H / Me exceeded 1.65 about the precursor, and it has confirmed that the precursor of the target composition was not obtained. Moreover, although it was confirmed that the positive electrode active material obtained using such a precursor contains porous particles, the porosity of many porous particles exceeds 20%, and among the porous particles, It was confirmed that the number ratio of the porous particles having a porosity of 10% to 20% is as low as 30%. For this reason, it was confirmed that the tap density of the positive electrode active material was low and the energy density was small.

  Moreover, in Comparative Example 2, H / Me was less than 1.6 for the precursor, and it was confirmed that the precursor having the target composition was not obtained. Moreover, although the positive electrode active material obtained using such a precursor contains porous particles, among the porous particles, the number ratio of porous particles having a porosity of 10% or more and 20% or less is 30%. It was confirmed to be lower. That is, it was confirmed that when a positive electrode active material was produced using the precursor, porous particles having a porosity of 10% or more and 20% or less were hardly obtained.

  And in the secondary battery manufactured using the positive electrode active material, it can be confirmed that the initial discharge capacity, the discharge capacity under the high discharge rate condition, and the energy density are both inferior to those in Example 1. It was.

Claims (15)

General formula Ni _x Co _y Mn _z M _t CO ₃ (where x + y + z + t = 1, 0.05 ≦ x ≦ 0.3, 0.1 ≦ y ≦ 0.4, 0.55 ≦ z ≦ 0 .8, 0 ≦ t ≦ 0.1, and M is one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W). A nickel cobalt manganese carbonate composite represented,
A functional group containing hydrogen,
H / Me, which is a substance amount ratio between the hydrogen H contained and the metal component Me contained, is 1.60 or more and 1.65 or less,
A positive electrode active material precursor for a non-aqueous electrolyte secondary battery having a specific surface area of 30 m ² / g or more and 60 m ² / g or less. The additive element M in the general formula of the nickel cobalt manganese carbonate composite contains Mo,
2. The positive electrode active material precursor for a non-aqueous electrolyte secondary battery according to claim 1, wherein a content ratio of Mo is 0.5 at% or more and 5 at% or less in the metal component in the nickel cobalt manganese carbonate composite. A positive electrode active material for a non-aqueous electrolyte secondary battery containing a lithium metal composite oxide,
The lithium metal composite oxide has a general formula of Li _{1 + α} Ni _x Co _y Mn _z M _t O ₂ (0.25 ≦ α ≦ 0.55, x + y + z + t = 1, 0.05 ≦ x ≦ 0.3, 0.1 ≦ y ≦ 0.4, 0.55 ≦ z ≦ 0.8, 0 ≦ t ≦ 0.1, M is an additive element, Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, One or more elements selected from W),
Including porous secondary particles in which a plurality of primary particles are aggregated,
Among the porous secondary particles, the number ratio of secondary particles having a porosity of 10% or more and 20% or less in the secondary particles is 80% or more,
A positive electrode active material for a non-aqueous electrolyte secondary battery, wherein an energy density, which is a product of the tap density and the initial discharge capacity, is 580 mAh / cc or more. The additive element M in the general formula of the lithium metal composite oxide contains Mo,
4. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 3, wherein the content ratio of molybdenum is 0.5 at% or more and 5 at% or less among Ni, Co, Mn, and additive element M in the lithium metal composite oxide. Active material. 5. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 3, wherein the specific surface area is 1.5 m ² / g or more.   The positive electrode active material for a nonaqueous electrolyte secondary battery according to any one of claims 3 to 5, wherein the tap density is 2.0 g / cc or more.   The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 3 to 6, wherein a discharge capacity under a high discharge rate condition (2C) is 195 mAh / g or more. General formula Ni _x Co _y Mn _z M _t CO ₃ (where x + y + z + t = 1, 0.05 ≦ x ≦ 0.3, 0.1 ≦ y ≦ 0.4, 0.55 ≦ z ≦ 0 .8, 0 ≦ t ≦ 0.1, and M is one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W). A method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery, comprising: a nickel cobalt manganese carbonate composite represented; and a functional group containing hydrogen,
An initial aqueous solution containing an alkaline substance and / or an ammonium ion supplier in the presence of carbonate ions, an aqueous solution containing nickel as a metal component, an aqueous solution containing cobalt as a metal component, and an aqueous solution containing manganese as a metal component A nucleation step of generating nuclei in the mixed aqueous solution,
A particle growth step for growing nuclei formed in the nucleation step, and
In the nucleation step, the pH value of the mixed aqueous solution is controlled to 7.5 or less based on a reaction temperature of 40 ° C.,
The particle growth step is for a non-aqueous electrolyte secondary battery that switches from an oxygen-free atmosphere having an oxygen content of less than 0.1% by volume to an oxygen-containing atmosphere having an oxygen content of 2% by volume or more during the process. A method for producing a positive electrode active material precursor. The ammonium ion supplier is one or more selected from ammonium carbonate aqueous solution, ammonia water, ammonium chloride aqueous solution, ammonium sulfate aqueous solution,
9. The positive electrode active material precursor for a non-aqueous electrolyte secondary battery according to claim 8, wherein the alkaline substance is at least one selected from sodium carbonate, sodium hydrogen carbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide. Production method. In the particle growth step, in the mixed aqueous solution after the nucleation step, an aqueous solution containing nickel as a metal component, an aqueous solution containing cobalt as a metal component, and an aqueous solution containing manganese as a metal component in the presence of carbonate ions Adding and mixing
The method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery according to claim 8 or 9, wherein an ammonium ion concentration in the mixed aqueous solution is 0 g / L or more and 20 g / L or less during the particle growth step. .   11. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 8, wherein a time period for which an oxygen-free atmosphere is used is 1 / 5T or more and 1 / 2T or less of the time T of the particle growth process. A method for producing a precursor.   The method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery according to any one of claims 8 to 11, wherein in the nucleation step, the temperature of the mixed aqueous solution is maintained at 30 ° C or higher.   13. The non-aqueous electrolyte 2 according to claim 8, further comprising a coating step of coating the positive electrode active material precursor for a non-aqueous electrolyte secondary battery obtained in the particle growth step with the additive element. A method for producing a positive electrode active material precursor for a secondary battery. The coating step includes
An aqueous solution containing the additive element is added to the slurry in which the positive electrode active material precursor for the non-aqueous electrolyte secondary battery is suspended, and the additive element is added to the surface of the positive electrode active material precursor for the non-aqueous electrolyte secondary battery. The step of precipitating
Spray drying a slurry in which the positive electrode active material precursor for a non-aqueous electrolyte secondary battery and the compound containing the additive element are suspended; and the positive electrode active material precursor for the non-aqueous electrolyte secondary battery; The method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery according to claim 13, which is any one selected from a step of mixing a compound containing an additive element with a solid phase method. A positive electrode active material precursor for a non-aqueous electrolyte secondary battery obtained by the method for producing a positive electrode active material precursor for a non-aqueous electrolyte secondary battery according to any one of claims 8 to 14 is 80 ° C or higher and 600 ° C. A heat treatment step for heat treatment at a temperature of ℃ or less;
A mixing step of adding a lithium compound to the particles obtained by the heat treatment step and mixing to form a lithium mixture;
A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising: a firing step of firing the lithium mixture at a temperature of 600 ° C. or higher and 1000 ° C. or lower in an oxidizing atmosphere.