JP2014220232A - Positive electrode active material for nonaqueous electrolyte secondary battery and method for producing the same, and nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery excellent in cycle characteristics while having a high operational potential.SOLUTION: In a positive electrode for a nonaqueous electrolyte secondary battery, a positive electrode active material is used, the positive electrode active material comprising a lithium composite oxide particle represented by general formula (1): LiMnNiABO(where, -0.2≤x≤0.2, 0.2≤y≤0.3, 0≤a≤0.05, 0≤b≤0.05, 0<a+b≤0.05, 0≤c≤0.05, 0≤d≤0.05 and 0≤c+d≤0.1 are satisfied; A represents W and/or Mo; and B represents at least one element selected from among Co, Cr, Fe, Ti and Cu), and having a spinel type crystal structure. A high concentration part of W and/or Mo exists on the surface and/or grain boundary of the lithium composite oxide particle. The lithium composite oxide particle has a specific surface area in the range of 0.1-0.3 m/g, and a product of a volume average grain size and the specific surface area of 1.0×10-3.0×10m/g.

Description

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

  In recent years, with the widespread use of portable electronic devices such as mobile phones and notebook computers, there is an increasing demand for small and lightweight secondary batteries having high energy density. In addition, development of a high-output secondary battery as a battery for a motor drive power supply, particularly a power supply for transportation equipment, is also strongly desired.

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

Research and development of such lithium ion secondary batteries is being actively conducted. Among these, a lithium ion secondary battery using a lithium metal composite oxide, particularly a lithium cobalt composite oxide (LiCoO ₂ ), which is relatively easy to synthesize, as a positive electrode material can obtain a high voltage of 4 V, and thus has high energy. Practical use is progressing as a battery having a high density. In the lithium ion secondary battery using this lithium cobalt composite oxide, many developments have been made so far to obtain excellent initial capacity characteristics and cycle characteristics, and various results have already been obtained.

  However, the lithium cobalt composite oxide uses a rare and expensive cobalt compound as a raw material, which increases the cost of the battery. For this reason, development of the positive electrode active material using the alternative material which can implement | achieve a high energy density while being cheaper than cobalt is calculated | required.

Newly proposed materials as positive electrode active materials for lithium ion secondary batteries include lithium manganese composite oxide (LiMn ₂ O ₄ ) using manganese and lithium nickel composite oxide (LiNiO ₂ ) using nickel. Can be mentioned. Among these, lithium manganese composite oxide is lithium cobalt because it is inexpensive and has excellent thermal stability, especially safety in terms of ignition, due to its crystal structure being a spinel structure. It is attracting attention as a powerful alternative material for complex oxides. Examples of such a spinel-type lithium manganese composite oxide include Li ₂ Mn ₄ O ₉ , Li ₄ Mn ₅ O ₁₂ , and LiMn ₂ O _{4. In} particular, LiMn ₂ O ₄ has a Li (lithium) potential. On the other hand, since charge and discharge are possible in the 4V region, research and development are actively conducted.

  By the way, when used as a power source for driving a motor of an electric vehicle or the like, a high potential of 300 V or more is required. However, in a secondary battery using a conventional lithium cobalt composite oxide, the operating potential is about 4.2 V. Therefore, there is a problem that the number of secondary batteries connected in series increases. For this reason, as an alternative material for the lithium cobalt composite oxide, it is required that the operating potential when the secondary battery is configured is higher than that of the lithium cobalt composite oxide. However, in the case of the above-described spinel type lithium manganese composite oxide, the operating potential is 4 V or less, and the above problem cannot be solved.

  Under such circumstances, higher potential is required in the research and development of lithium manganese composite oxides. For example, JP-A-9-147867 and JP-A-11-73962 disclose a positive electrode active material made of a spinel-type lithium-manganese composite oxide in which a part of a manganese site is substituted with nickel or chromium. Yes. According to these documents, in a secondary battery using this positive electrode active material, an operating potential of 4.5 V or more is obtained on the basis of metallic lithium. However, these spinel-type positive electrode active materials have a problem that the battery capacity decreases as charging and discharging are repeated, that is, the cycle characteristics are inferior.

  One of the causes of the decrease in battery capacity is considered to be decomposition of the electrolyte during charging. That is, since the decomposition of the electrolytic solution is an irreversible reaction, it is considered that the electrolytic solution that is a lithium ion carrier gradually decreases between the positive electrode and the negative electrode due to repeated charge and discharge, and as a result, the battery capacity decreases. . Note that the decomposed electrolytic solution serves as a source of gas mainly composed of hydrogen or the like, and may cause problems such as swelling of the secondary battery.

  Further, although this is not a problem inherent to the high-potential lithium-manganese composite oxide, it is considered that the elution of manganese in the electrolytic solution during charge / discharge is one of the causes for the decrease in battery capacity. In particular, when a carbon-based material is used as the negative electrode, manganese eluted from the positive electrode is deposited on the negative electrode and inhibits the battery reaction at the negative electrode.

  These phenomena are all caused by side reactions occurring at the interface between the positive electrode active material and the electrolytic solution. For this reason, in order to improve the cycle of the secondary battery using the high potential lithium manganese composite oxide as the positive electrode active material, it is considered important to control the surface state of the lithium manganese composite oxide.

  For example, Japanese Patent Laid-Open No. 2000-203842 discloses that the surface of spinel-type lithium manganese nickel composite oxide particles is coated with a metal halide, the amount of halogen present in the state of metal halide on the particle surface, and the inside of the particle A technique for suppressing elution of manganese into the electrolytic solution and decomposition of the electrolytic solution by controlling the amount of halogen present in the state of a solid solution substituted with oxygen atoms within a predetermined range is described. However, the technique described in this document has a problem that halogen is evaporated at the time of firing and the inside of the firing furnace is deteriorated.

  In contrast, JP-A-2006-36545 covers the surface of lithium manganese nickel composite oxide particles with a metal oxide containing at least one metal element selected from Mg, Al, Ti, Zr, and Zn. However, a technique for modifying the surface state is described.

  Japanese Patent Laid-Open No. 2008-305777 is mainly intended for those having a layered rock salt type crystal structure, but the main component material composed of a lithium compound and a transition metal compound such as nickel is calcined. A technique is described in which lithium nickel composite oxide particles having a large specific surface area are obtained by adding and firing an oxide of tungsten or molybdenum as an additive that suppresses grain growth and sintering at the time. The lithium-nickel composite oxide particles are characterized in that tungsten and molybdenum are concentrated on the surface of the primary particles.

  According to the techniques described in these documents, since it is not necessary to use halogen, problems such as the technique described in Japanese Patent Laid-Open No. 2000-203842 do not occur, and the cycle characteristics of the obtained secondary battery It is thought that various characteristics can be improved.

JP-A-9-147867 Japanese Patent Application Laid-Open No. 11-73962 JP 2000-203842 A JP 2006-36545 A JP 2008-305777 A

  An object of this invention is to provide the positive electrode active material which can implement | achieve the secondary battery excellent in cycling characteristics, while having a high operating potential. Moreover, an object of this invention is to provide the manufacturing method which can obtain such a positive electrode active material easily in industrial scale production. Furthermore, an object of this invention is to provide the secondary battery using such a positive electrode active material.

The positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention has a general formula (1): Li _{1 + x} Mn _{2 (1-yc) -a} Ni _{2 (yd) -b} A _{a + b} B _{2 (c + d)} O ₄ (however, −0.2 ≦ x ≦ 0.2, 0.2 ≦ y ≦ 0.3, 0 ≦ a ≦ 0.05, 0 ≦ b ≦ 0.05, 0 <a + b ≦ 0. 05, 0 ≦ c ≦ 0.05, 0 ≦ d ≦ 0.05, 0 ≦ c + d ≦ 0.1, A is selected from W and / or Mo, B is selected from Co, Cr, Fe, Ti, Cu The lithium manganese nickel composite oxide particles having a spinel type crystal structure, tungsten and / or at the surface and / or grain boundaries of the lithium manganese nickel composite oxide particles. There are concentrated portion of the molybdenum, there BET specific surface area in the range of 0.1m ² /g~0.3m ² / g, an ultrasonic dispersion treatment for 30 seconds And the volume average particle diameter obtained by measurement of particle size distribution using laser scattering particle size distribution analyzer after applying the product of the said BET specific surface area, 1.0 × 10 ^-6 m ³ /g~3.0× It is characterized by 10 ⁻⁶ m ³ / g.

  In the positive electrode active material, a peak group that can be attributed to the diffraction pattern of the spinel crystal structure of the space group Fd-3m or P4332 is observed in the diffraction pattern obtained by evaluation using XRD, and among the peak group, The peak position attributed to the (311) plane is preferably 36.40 ° or more at 2θ.

The concentrated portion of tungsten and / or molybdenum preferably contains a compound consisting of lithium and tungsten and / or molybdenum, and Li ₂ WO ₄ , Li ₄ WO ₅ , Li ₄ W ₂ O ₉ , Li ₂ MoO ₄ , More preferably, it is at least one selected from Li ₄ MoO ₅ and Li ₄ Mo ₂ O ₉ .

The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention includes a lithium compound, a precursor containing at least manganese and nickel, and a compound containing tungsten and / or molybdenum. _{1 + x} Mn _{2 (1-yc) -a} Ni _{2 (yd) -b} A _{a + b} B _{2 (c + d)} O ₄ (where −0.2 ≦ x ≦ 0.2, 0.2 ≦ y ≦ 0.3, 0 ≦ a ≦ 0.05, 0 ≦ b ≦ 0.05, 0 <a + b ≦ 0.05, 0 ≦ c ≦ 0.05, 0 ≦ d ≦ 0.05, 0 ≦ c + d ≦ 0.1, A is W and / or Mo, B is at least one element selected from Co, Cr, Fe, Ti, Cu), and the lithium mixture is mixed. And a baking step of baking the lithium mixture at 700 ° C. to 1000 ° C. for 10 hours to 20 hours in an oxidizing atmosphere. It is characterized in.

The precursor is represented by the general formula (2): Mn _1-yc Ni _yd B _{c + d} (OH) _{2 + α} (where 0.2 ≦ y ≦ 0.3, 0 ≦ c ≦ 0.05, 0 ≦ d ≦ 0.05, 0 ≦ c + d ≦ 0.1, 0 ≦ α ≦ 0.5, B is at least one element selected from Co, Cr, Fe, Ti, Cu) Composite hydroxide particles are preferred. Such manganese nickel composite hydroxide particles are prepared by continuously supplying an aqueous solution containing at least a manganese salt and a nickel salt and an aqueous alkaline solution into a reaction vessel at a constant rate, and the temperature of the aqueous reaction solution comprising these aqueous solutions. 30 to 80 ° C., pH value is maintained in the range of 10.5 to 12.5 based on the liquid temperature of 25 ° C., and the manganese nickel composite hydroxide represented by the general formula (2) is crystallized. Can be obtained by a crystallization process.

  It is preferable to further include a re-baking step of baking at 500 ° C. to 800 ° C. for 5 hours to 40 hours after the baking step.

  The lithium compound is preferably at least one selected from lithium hydroxide, lithium carbonate, and lithium acetate.

  The tungsten compound is preferably at least one selected from tungsten oxide, tungstic acid, and ammonium paratungstate, and the molybdenum compound is at least one selected from molybdenum oxide and ammonium paramolybdate. Preferably there is.

  The non-aqueous electrolyte secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, and the positive electrode active material for the non-aqueous electrolyte secondary battery is used as the positive electrode material of the positive electrode. It is characterized by.

  ADVANTAGE OF THE INVENTION According to this invention, the positive electrode active material which can implement | achieve the secondary battery excellent in cycling characteristics while having a high operating potential, and the nonaqueous electrolyte secondary battery using this positive electrode active material can be provided. . In addition, according to the present invention, it is possible to provide a production method capable of easily obtaining such a positive electrode active material in industrial scale production. For this reason, the industrial significance of the present invention is extremely large.

1 is a cross-sectional SEM image (observation magnification: 5000 times) of the positive electrode active material obtained in Example 1. FIG. FIG. 2 is a cross-sectional SEM image (observation magnification: 5000 times) of the positive electrode active material obtained in Example 6. FIG. 3 is a view showing a profile obtained by XRD measurement of the positive electrode active material obtained in Example 1. FIG. 4 is a schematic cross-sectional view of a 2032 type coin battery used for battery evaluation in Examples.

  In order to improve the cycle characteristics of a secondary battery using spinel-type lithium manganese nickel composite oxide particles (hereinafter referred to as “lithium composite oxide particles”), the present inventors have disclosed in JP-A-2006-36545. Based on the described technology, an attempt was made to coat the surface of the lithium composite oxide particles with a metal oxide such as magnesium or aluminum and to modify the surface state. However, with these metal oxides, it is difficult to uniformly coat the surface of the lithium composite oxide particles. With the technique described in this document, the decomposition of the electrolytic solution and the elution of manganese into the electrolytic solution are sufficient. It was concluded that the cycle characteristics could not be improved.

  In addition, the present inventors examined applying the technique described in Japanese Patent Application Laid-Open No. 2008-305777 to the production of spinel-type lithium composite oxide particles. In this case, the ratio of the obtained positive electrode active material Since the surface area increases and the contact area with the electrolytic solution increases, it was concluded that the decomposition of the electrolytic solution and the elution of manganese could not be suppressed.

  Based on these conclusions, as a result of repeated research, the present inventors have determined that the specific surface area should be improved in order to improve the cycle characteristics of a secondary battery using lithium composite oxide particles having a spinel structure as a positive electrode active material. The present inventors have found that it is effective to use small and relatively large particle size lithium composite oxide particles as the positive electrode active material.

On the other hand, in order to obtain such lithium composite oxide particles, it is necessary to increase the firing temperature in the production stage. In particular, according to the studies by the present inventors, in order to sufficiently improve the cycle characteristics of the secondary battery, the specific surface area of 0.1m ² /g~0.3m ² / g of the lithium composite oxide particles In order to do so, the firing temperature is required to exceed 1000 ° C. However, firing in such a high temperature region is not realistic because it consumes a large amount of energy and increases the burden on the firing furnace, assuming production on an industrial scale.

  Based on this point, the present inventors have conducted further research. As a result, when synthesizing lithium composite oxide particles, a predetermined amount of tungsten or molybdenum compound is mixed and fired at a temperature of 1000 ° C. or lower. Therefore, it is possible to obtain lithium composite oxide particles having a small specific surface area and a relatively large particle size because the growth can be promoted while suppressing the sintering of the primary particles. It was. The present invention has been completed based on these findings.

  Hereinafter, the present invention is divided into “1. a positive electrode active material for a non-aqueous electrolyte secondary battery”, “2. a positive electrode active material for a non-aqueous electrolyte secondary battery” and “3. a non-aqueous electrolyte secondary battery”. This will be described in detail.

1. Positive electrode active material for non-aqueous electrolyte secondary battery The positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention has a general formula (1): Li _{1 + x} Mn _{2 (1-yc) -a} Ni _{2 (yd)- b} A _{a + b} B _{2 (c + d)} O ₄ (where −0.2 ≦ x ≦ 0.2, 0.2 ≦ y ≦ 0.3, 0 ≦ a ≦ 0.05, 0 ≦ b ≦ 0.05, 0 <a + b ≦ 0.05, 0 ≦ c ≦ 0.05, 0 ≦ d ≦ 0.05, 0 ≦ c + d ≦ 0.1, A is W and / or Mo, B is Co, And at least one element selected from Cr, Fe, Ti, and Cu), and lithium composite oxide particles having a spinel crystal structure. The lithium composite oxide particles on its surface and / or the grain boundary, there is enrichment of the tungsten and / or molybdenum, in the range BET specific surface area of 0.1m ² /g~0.3m ² / g Yes, the product of the volume average particle size obtained by measuring the particle size distribution using a laser scattering particle size distribution meter after ultrasonic dispersion treatment for 30 seconds and the BET specific surface area is 1.0 × 10 ^−6. m ³ / g to 3.0 × 10 ⁻⁶ m ³ / g. In such lithium composite oxide particles, it is possible to suppress manganese from eluting into the electrolyte during charging and discharging, and it is possible to improve the cycle characteristics of a secondary battery using the same.

(1) Composition The value of x indicating the excess amount of lithium (Li) is −0.2 or more and 0.2 or less, preferably 0 or more and 0.2 or less, more preferably 0.1 or more and 0.2 or less. By regulating the value of x within the above range, lithium can be introduced into metal sites other than the lithium site, and the stability of the crystal can be improved. If the value of x is less than −0.2, such an effect cannot be obtained. On the other hand, if the value of x exceeds 0.2, the lithium itself is a metal that does not undergo oxidation-reduction reactions, leading to a decrease in battery capacity.

  Nickel (Ni) is an element that contributes to higher potential and higher capacity of the secondary battery. The value of y indicating the amount of nickel added to manganese (Mn) is 0.2 or more and 0.3 or less, preferably 0.225 or more and 0.275 or less, and more preferably 0.225 or more and 0.25 or less. By restricting the value of y to the above range, in the secondary battery using the lithium composite oxide particles of the present invention as the positive electrode active material, not only a 5V class potential is obtained, but also the charge / discharge capacity is high. can do. If the value of y is less than 0.2, the secondary battery cannot be increased in potential and capacity. On the other hand, if the value of y exceeds 0.3, nickel oxide that does not contribute to the Redox reaction is generated, and the charge / discharge capacity decreases.

  The value of a + b indicating the addition amount of tungsten (W) and / or molybdenum (Mo) is more than 0 and 0.05 or less, preferably more than 0 and 0.03 or less. Further, the value of a indicating the amount of tungsten and / or molybdenum added to manganese and the value of b indicating the amount of tungsten and / or molybdenum added to nickel are both 0 or more and 0.05 or less, preferably 0 or more. 0.03 or less. That is, tungsten and / or molybdenum need only exist at one of the manganese site and the nickel site, and does not necessarily need to exist at both sites. Further, in the positive electrode active material of the present invention, the growth of the primary particles is promoted without excessive sintering between the primary particles by regulating the value of a + b within such a range. It becomes possible to regulate the specific surface area within a desired range. On the other hand, if the value of a + b exceeds 0.05, the contents of manganese and nickel decrease, and the charge / discharge capacity of a secondary battery using this positive electrode active material decreases.

  In the positive electrode active material of the present invention, a predetermined amount of additive element B may be contained in addition to the metal element. Thereby, various characteristics of the secondary battery using the lithium composite oxide particles can be improved.

  As such an additive element B, at least one selected from cobalt (Co), chromium (Cr), iron (Fe), titanium (Ti), and calcium (Cu) can be used. These additive elements B are appropriately selected according to the use and required performance of the secondary battery in which the obtained positive electrode active material is used.

  The value of c + d indicating the amount of additive element B added to manganese and nickel is 0 or more and 0.1 or less, preferably 0 or more and 0.05 or less. Further, the value of c indicating the amount of additive element B added to manganese and the value of d indicating the amount of additive element B added to nickel are both 0 or more and 0.05 or less, preferably 0 or more and 0.025 or less. And When the value of c + d exceeds 0.1, the metal element that contributes to the Redox reaction decreases, so that the battery capacity decreases.

  The additive element B can be crystallized together with manganese and nickel in the crystallization step described later, and can be uniformly dispersed in manganese nickel composite hydroxide particles (hereinafter referred to as “composite hydroxide particles”). After the crystallization step, the additive element B may be coated on the surface of the composite hydroxide particles. Moreover, in a mixing process, it is also possible to mix with a lithium compound with a composite hydroxide particle, You may use these methods together. Regardless of which method is used, it is necessary to adjust the amount added so that the composition ratio of the general formula (1) is obtained.

  Note that oxygen (O) does not have to be strictly the stoichiometric ratio of 4. That is, in the lithium composite oxide particles, the composition ratio of oxygen is ideally a stoichiometric ratio of 4, but oxygen defects are generally generated due to the influence of synthesis conditions and additive elements. The general formula (1) is not intended to exclude a positive electrode active material having such oxygen defects from the scope of the present invention.

(2) Concentrated portion The positive electrode active material of the present invention has a concentrated portion (hereinafter referred to as “concentrated portion”) of tungsten and / or molybdenum on the surface of primary particles, the surface of secondary particles and / or the crystal grain boundary constituting the positive electrode active material. Is present). Here, the enrichment part means a part where the total number of atoms of tungsten and / or molybdenum with respect to the total number of atoms of manganese, nickel, tungsten, molybdenum and additive element B is 80 atomic% or more. The presence of such a concentrated portion can be confirmed by SEM observation of the lithium composite oxide particles. Specifically, the white portion of the cross-sectional SEM image of the positive electrode active material shown in FIGS. 1 and 2 corresponds to the concentrating portion.

  In this way, when the concentrated portion exists on the surface of the primary particles, the surface of the secondary particles and / or the grain boundaries constituting the positive electrode active material, the primary particles grow without excessive sintering in the firing step. Will be promoted. The reason for this is unknown, but the low melting point compound produced by the reaction of tungsten or molybdenum with lithium during the firing process functions as a kind of flux, and primary particle growth occurs in parts other than the concentrated part. This is considered to be promoted.

The compound constituting the concentration part is not particularly limited, and may be composed of an oxide or nitride of tungsten or molybdenum, or a solid solution with manganese, nickel or lithium. In particular, a compound of lithium and tungsten and / or molybdenum is preferable. Li ₂ WO ₄ , Li ₄ WO ₅ , Li ₄ W ₂ O ₉ etc. are used as the compound of lithium and tungsten, and Li ₂ MoO ₄ , Li ₄ MoO ₅ , Li ₄ Mo ₂ are used as the compound of lithium and molybdenum. Examples include O ₉ . Moreover, the concentration part may be comprised from 2 or more types of these compounds.

(3) In the lithium composite oxide particles having a BET specific surface area and a volume average particle diameter of the present invention, there BET specific surface area (S) is in the range of 0.1m ² /g~0.3m ² / g, of 30 seconds ultrasonic The product (S · MV) of the volume average particle size (MV) obtained by measuring the particle size distribution using a laser scattering particle size distribution meter after the sonic dispersion treatment and the BET specific surface area (S) is 1. characterized in that in the range of ^{0 × 10 -6 m 3 /g~3.0×10 -6} m 3 / g. When such lithium composite oxide particles of the present invention are used as the positive electrode active material, the interface (contact area) between the positive electrode active material and the electrolytic solution can be reduced, so that the electrolytic solution is decomposed and manganese is eluted. Suppression and cycle characteristics can be improved.

BET specific surface area of the lithium composite oxide particles (S) is, 0.1m ² /g~0.3m ² / g, preferably to 0.1m ² /g~0.25m ² / g. When the BET specific surface area (S) is less than 0.1 m ² / g, the resistance of the positive electrode active material is increased, and the charge / discharge capacity is also greatly reduced. On the other hand, if it exceeds 0.3 m ² / g, the cycle characteristics cannot be improved. The BET specific surface area (S) can be measured by the BET method by nitrogen gas adsorption.

  The BET specific surface area (S) in the above range can be achieved by increasing the firing temperature during firing without adding tungsten or molybdenum. However, in the lithium composite oxide particles obtained by firing at a high temperature, the primary particles are partially sintered and the secondary particles are also coarsened. In this case, it becomes difficult to mix with the conductive auxiliary agent at the time of manufacturing the secondary battery, and there is a possibility that conduction in the secondary battery cannot be secured.

In order to eliminate such coarse particles, the BET specific surface area (S) is regulated within the above range, and then the BET specific surface area (S) and laser scattering after performing ultrasonic dispersion treatment for 30 seconds. The product (S · MV) with the volume average particle size (MV) obtained by measuring the particle size distribution using a particle size distribution meter is 1.0 × 10 ⁻⁶ m ^{3 /} g to 3.0 × 10 ⁻⁶ m ^3. / g, preferably it is necessary to restrict the range of ^{1.5 × 10 -6 m 3 /g~3.0×10 -6} m 3 / g. When S · MV is less than 1.0 × 10 ⁻⁶ m ³ / g, the volume average particle size (MV) of the secondary particles is too small, and handling becomes difficult. On the other hand, if it exceeds 3.0 × 10 ⁻⁶ m ³ / g, it becomes difficult to mix with the conductive auxiliary agent as described above, and there is a possibility that conduction in the secondary battery cannot be secured.

  The volume average particle size (MV) is not particularly limited as long as S · MV is in the above range, but is preferably in the range of 3.3 μm to 30 μm, and in the range of 6.0 μm to 30 μm. More preferably.

(4) Crystal structure The positive electrode active material of the present invention has a spinel crystal structure, and in the diffraction pattern obtained by evaluation using XRD, the spinel crystal structure of the space group Fd-3m or P4332 A group of peaks that can be attributed to the diffraction pattern can be observed. Note that there is no problem even if the peak groups other than the space groups Fd-3m and P4332 are not observed unless they affect the battery characteristics.

  In particular, in the positive electrode active material of the present invention, in the spinel diffraction pattern, the peak attributed to the (311) plane is preferably 36.40 ° or more, and more preferably 36.43 ° or more. . Since the peak attributed to the (311) plane exists in the above range, the spacing between the planes can be controlled to an appropriate range, and the output characteristics of the secondary battery using this lithium composite oxide particle as the positive electrode active material Can be improved. On the other hand, the fact that the peak attributed to the (311) plane is less than 36.40 ° means that the plane spacing is increased. Such an increase in the interplanar spacing is considered to be because tungsten or molybdenum is excessively dissolved in the crystal lattice of the lithium composite oxide particles constituting the positive electrode active material. In this case, tungsten or molybdenum becomes a resistance component, The output characteristics may be degraded. In addition, according to experiments by the present inventors, no decrease in interplanar spacing due to solid solution of tungsten or molybdenum in the crystal lattice has been confirmed, and in the positive electrode active material of the present invention, it belongs to the (311) plane. There is no need to specify the upper limit of the peak to be generated. However, generally, when it exceeds 36.50 °, the interplanar spacing decreases, the movement of lithium during charging and discharging is hindered, and the output characteristics may be deteriorated. Therefore, considering this point, the upper limit of the peak attributed to the (311) plane is preferably 36.50 °, more preferably 36.47 °.

2. Method for producing positive electrode active material for non-aqueous electrolyte secondary battery The method for producing a positive electrode active material for non-aqueous electrolyte secondary battery according to the present invention includes a lithium compound, a precursor containing at least manganese and nickel, and tungsten and / or molybdenum. And a compound containing the general formula (1): Li _{1 + x} Mn _{2 (1-yc) -a} Ni _{2 (yd) -b} A _{a + b} B _{2 (c + d)} O ₄ (where −0 .2 ≦ x ≦ 0.2, 0.2 ≦ y ≦ 0.3, 0 ≦ a ≦ 0.05, 0 ≦ b ≦ 0.05, 0 <a + b ≦ 0.05, 0 ≦ c ≦ 0.05 0 ≦ d ≦ 0.05, 0 ≦ c + d ≦ 0.1, A is W and / or Mo, B is at least one element selected from Co, Cr, Fe, Ti, Cu) Mixing step to obtain a lithium mixture, and mixing the lithium mixture obtained in the mixing step in an oxidizing atmosphere at 700 ° C. At 1000 ° C., characterized in that it comprises a firing step of firing 10 hours to 20 hours.

  In the present invention, the precursor containing at least manganese and nickel is not particularly limited. For example, a granulated powder obtained by wet-mixing a manganese compound and a nickel compound and then spray-drying, Alternatively, composite hydroxide particles containing at least manganese and nickel, or manganese nickel composite oxide particles (hereinafter referred to as “composite oxide particles”) obtained by heat-treating granulated powder or composite hydroxide particles Can be used.

  Hereinafter, a case where composite hydroxide particles are obtained by a crystallization reaction and used as a precursor to produce a positive electrode active material will be mainly described as an example. In addition, in the manufacturing method of this invention, you may further provide a classification process, a grinding | pulverization process, etc. other than these processes as needed.

(1) Crystallization Step When composite hydroxide particles are used as the precursor of the positive electrode active material of the present invention, this precursor is represented by the general formula (2): Mn _1-yc Ni _yd B _{c + d} (OH) _{2 + α} (where 0.2 ≦ y ≦ 0.3, 0 ≦ c ≦ 0.05, 0 ≦ d ≦ 0.05, 0 ≦ c + d ≦ 0.1, 0 ≦ α ≦ 0.5, B is Composite hydroxide particles represented by (at least one element selected from Co, Cr, Fe, Ti, and Cu) are preferable. Such composite hydroxide particles, for example, continuously supply an aqueous solution containing at least a manganese salt and a nickel salt and an alkaline aqueous solution into the reaction vessel at a constant rate, and the temperature of the aqueous reaction solution composed of these aqueous solutions. Can be obtained by a crystallization process in which the pH value is maintained in the range of 10.5 to 12.5 on the basis of the liquid temperature of 25 ° C. At this time, it is preferable to sufficiently stir the reaction aqueous solution so that the generated composite hydroxide particles do not stay on the tank bottom and can be stably grown.

  In the crystallization process, when the amount of each aqueous solution introduced into the reaction tank and the amount of precipitate generated are constant, and when the amount of precipitate collected from the reaction tank through the overflow pipe is constant, the reaction tank It becomes a steady state in which the slurry concentration is constant. At this time, the collected precipitate is filtered, washed with water, and dried to obtain a spherical or substantially spherical manganese-nickel composite hydroxide.

(Raw material aqueous solution)
The raw material aqueous solution needs to contain at least a manganese salt and a nickel salt. Examples of nickel salts and manganese salts include sulfates, nitrates, and carbonates. Among these, sulfates are preferable from the viewpoint of cost and waste liquid treatment.

  The salt concentration in this raw material aqueous solution is preferably the sum of manganese salt and nickel salt, preferably 1.5 mol / L to 2.5 mol / L, more preferably 1.8 mol / L to 2.2 mol / L. When the salt concentration of the raw material aqueous solution is less than 1.5 mol / L, the crystals of the composite hydroxide particles may not grow sufficiently. On the other hand, if it exceeds 2.5 mol / L, the saturated concentration at room temperature is exceeded, so there is a risk that crystals will re-deposit and clog the piping. In addition, it is preferable to prepare the ratio of nickel salt and manganese salt in raw material aqueous solution so that the composition ratio of nickel and manganese contained in these salts may become a composition ratio represented by General formula (2).

(Alkaline aqueous solution)
The alkaline aqueous solution is not particularly limited, and a common alkaline metal hydroxide aqueous solution such as sodium hydroxide or potassium hydroxide can be used. The alkali metal hydroxide can be directly added to the reaction aqueous solution, but it is preferably added as an aqueous solution in view of easy pH control. In this case, the concentration of the alkali metal hydroxide aqueous solution is preferably 20% by mass to 50% by mass, and more preferably 20% by mass to 30% by mass. By restricting the concentration of the aqueous alkali metal solution to such a range, it is possible to prevent the pH value from being locally increased at the addition position while suppressing the amount of the solvent supplied to the reaction system. Composite hydroxide particles having a narrow particle size distribution can be obtained efficiently.

(PH value)
The pH value of the aqueous reaction solution needs to be maintained in the range of 10.5 to 12.5, preferably 10.7 to 12.0, more preferably 11.0 to 11.7 based on the liquid temperature of 25 ° C. Become. If the pH value is less than 10.5, the solubility of manganese and nickel is too high, and the composition of the resulting composite hydroxide particles may be shifted. On the other hand, when it exceeds 12.5, the produced | generated nucleus refines | miniaturizes and there exists a possibility that reaction aqueous solution may gelatinize. In addition, in order to supply an excessive amount of the aqueous alkaline solution, it is necessary to enlarge the reaction tank, which leads to deterioration in productivity.

(Temperature of reaction aqueous solution)
The temperature of the reaction aqueous solution needs to be maintained in the range of 30 ° C to 80 ° C, preferably 30 ° C to 70 ° C, more preferably 30 ° C to 60 ° C. If the temperature of the reaction aqueous solution is less than 30 ° C., the solubility of manganese and nickel is too low, and there is a possibility that composite hydroxide particles having the target composition ratio cannot be obtained. On the other hand, when it exceeds 80 ° C., energy for maintaining the temperature of the reaction aqueous solution increases, and the productivity may be deteriorated.

(Oxygen concentration)
The atmosphere in the reaction vessel is preferably introduced with an inert gas such as nitrogen or argon, whereby the oxygen concentration is preferably 1.0% by volume or less, more preferably 0.5% by volume or less, more preferably 0.2% by volume. It is necessary to do the following. If the oxygen concentration exceeds 1.0% by volume, manganese is oxidized, and the resulting composite hydroxide particles are refined, making it difficult to perform solid-liquid separation of the composite hydroxide particles.

(Aqueous solution containing ammonium ion donor)
In the crystallization step, an aqueous solution containing an ammonium ion supplier may be added in addition to the raw material aqueous solution and the alkaline aqueous solution. This makes it easy to control the solubility of the metal ions in the reaction aqueous solution within an appropriate range.

  The aqueous solution containing the ammonium ion donor is not particularly limited as long as it can form a nickel ammine complex in the reaction aqueous solution. For example, an aqueous solution of ammonia water, ammonium sulfate or ammonium chloride may be used. it can.

  When ammonia water is used as the ammonium ion supplier, the concentration is preferably 20% by mass to 30% by mass, more preferably 22% by mass to 28% by mass. By restricting the ammonia water concentration to such a range, loss of ammonia due to volatilization or the like can be suppressed to a minimum, so that production efficiency can be improved.

  In addition, when an aqueous solution containing an ammonium ion supplier is added, the ammonia concentration of the aqueous reaction solution is preferably 2 g / L to 15 g / L, more preferably 5 g / L to 13 g / L, and even more preferably 5 g / L to 10 g. Control within the range of / L. By controlling the ammonia concentration of the reaction aqueous solution in such a range, composite hydroxide particles having high sphericity can be obtained while preventing composition deviation.

(Composite hydroxide particles)
In the composite hydroxide particles obtained in the crystallization process as described above, manganese and nickel are uniformly dispersed at the molecular level, and therefore it is possible to effectively prevent deterioration of battery characteristics due to segregation of these elements. it can.

Note that according to the above-mentioned crystallization step, in the range of BET specific surface area of 10m ² / g~50m ² / g of the composite hydroxide particles obtained, to control the volume average particle size in the range of 1μm~8μm Can do. If the BET specific surface area and the volume average particle diameter of the composite hydroxide particles are within such ranges, a positive electrode active material having a desired BET specific surface area and volume average particle diameter can be easily obtained by the firing step described later. it can.

(2) Mixing step In the mixing step, the composite hydroxide particles obtained in the crystallization step, the lithium compound, and the compound of tungsten and / or molybdenum are represented by the general formula (1): Li _{1 + x} Mn _{2 ( 1-yc) -a} Ni _{2 (yd) -b} A _{a + b} B _{2 (c + d)} O ₄ (where −0.2 ≦ x ≦ 0.2, 0.2 ≦ y ≦ 0.3, 0 ≦ a ≦ 0.05, 0 ≦ b ≦ 0.05, 0 <a + b ≦ 0.05, 0 ≦ c ≦ 0.05, 0 ≦ d ≦ 0.05, 0 ≦ c + d ≦ 0.1, A is , W and / or Mo, B is a step of mixing at a composition ratio represented by at least one element selected from Co, Cr, Fe, Ti, and Cu to obtain a lithium mixture.

(Lithium compound)
The lithium compound is not particularly limited, and for example, at least one selected from lithium hydroxide, lithium carbonate, lithium acetate and the like can be used. Among these, considering the ease of handling and the stability of quality, it is preferable to use lithium hydroxide or lithium carbonate, and it is more preferable to use lithium hydroxide.

  Moreover, as a lithium compound, it is preferable to use that whose volume average particle diameter (MV) is 0.5 micrometer-40 micrometers from a viewpoint of obtaining a uniform lithium mixture, and it is more preferable to use a thing of 1.0 micrometer-30 micrometers. preferable.

(Tungsten compounds, molybdenum compounds)
Examples of the tungsten compound that can be mixed with the composite hydroxide particles and the lithium compound include tungsten oxide, tungstic acid, ammonia paratungstate, and the molybdenum compound includes molybdenum oxide, ammonia ammonium paramolybdate, and the like. . These compounds may be used alone or in combination of two or more. A composite compound of tungsten and molybdenum can also be used.

  As the tungsten compound or molybdenum compound, those having a volume average particle size (MV) of 0.1 μm to 3.5 μm are preferably used from the viewpoint of obtaining a uniform lithium mixture, and those of 0.1 μm to 1.0 μm are used. More preferably, is used.

  In the present invention, by adding a tungsten compound or a molybdenum compound to the composite hydroxide particles as described above and firing, the growth is promoted while suppressing the sintering of the primary particles. A positive electrode active material comprising secondary particles having a small surface area and a relatively large particle size is obtained. On the other hand, the technique described in Japanese Patent Application Laid-Open No. 2008-305777 described above similarly adds and burns a tungsten compound or a molybdenum compound. However, the technique described in this document uses these compounds. Is added to suppress the grain growth and sintering and to obtain a positive electrode active material composed of fine secondary particles having a large specific surface area. The reason why such a difference appears in both inventions is that the crystal structure is different, specifically, the positive electrode active material of the present invention has a spinel structure, whereas Japanese Patent Application Laid-Open No. 2008-305777. It is considered that the positive electrode active material described in the publication has a layered rock salt structure.

(Mixing method)
The mixing method is not particularly limited, and a general mixer can be used. For example, a shaker mixer, a V blender, a ribbon mixer, a Julia mixer, a Ladige mixer, or the like can be used, and it is sufficient that they are sufficiently mixed so that no fine powder is generated.

(3) Firing step The firing step is a step of firing the lithium mixture obtained in the mixing step at 700 ° C to 1000 ° C for 10 hours to 20 hours in an oxidizing atmosphere.

(Baking atmosphere)
Although the firing atmosphere is an oxidizing atmosphere, it is preferably performed in an atmosphere having an oxygen concentration of 18% by volume to 100% by volume, that is, in the atmosphere to an oxygen stream. preferable. When the oxygen concentration is less than 18% by volume, the oxidation reaction does not proceed sufficiently, and the resulting lithium composite oxide particles may not have sufficient crystallinity.

(Baking temperature)
The firing temperature is 700 ° C to 1000 ° C, preferably 800 ° C to 1000 ° C, more preferably 900 ° C to 1000 ° C. When the firing temperature is less than 700 ° C., the reaction between tungsten and molybdenum and lithium does not proceed, and the concentrated portion is not sufficiently formed. Further, manganese, nickel, and lithium cannot be sufficiently diffused, and the chemical composition tends to be locally uneven. Furthermore, the specific surface area of the positive electrode active material obtained is increased, the amount of manganese eluted into the electrolyte during charge / discharge is increased, and the cycle characteristics are degraded. On the other hand, when it exceeds 1000 ° C., tungsten and molybdenum are excessively dissolved, and not only the concentrated portion is not formed, but also the primary particles are partially sintered and the secondary particles are coarsened. . Moreover, not only does the energy consumption increase, but it is necessary to use a baking furnace that can withstand high temperatures, leading to an increase in production costs.

(Baking time)
The firing time is 10 hours to 20 hours, preferably 10 hours to 15 hours, more preferably 10 hours to 12 hours. When the firing time is less than 10 hours, the reaction between tungsten and molybdenum and lithium does not proceed, and the concentrated portion is not sufficiently formed. Further, manganese, nickel, and lithium cannot be sufficiently diffused, and the chemical composition tends to be locally uneven. On the other hand, when it exceeds 20 hours, tungsten and / or molybdenum is excessively dissolved, and not only the concentrated portion is not formed, but also the primary particles are partially sintered and the secondary particles are coarse. Turn into.

(Disintegration)
The lithium composite oxide particles after firing may be agglomerated or slightly sintered. In this case, it is preferable to crush the aggregate or sintered body of lithium composite oxide particles. Thereby, since the lithium composite oxide particles can be handled as a powder having an appropriate particle size, the filling property when used as a positive electrode active material can be improved. 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.

  By crushing the fired lithium composite oxide particles, the volume average particle size is preferably adjusted to 3.3 μm to 30 μm, more preferably 6.0 μm to 30 μm. By adjusting the volume average particle size of the lithium composite oxide particles to such a range, slurrying when producing the positive electrode is facilitated.

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

(4) Rebaking process The rebaking process is a process of baking the lithium composite hydroxide particles after the baking process at 500 ° C to 800 ° C for 5 hours to 40 hours in an oxidizing atmosphere. In this way, after the firing step, the oxygen defects in the lithium composite oxide particles can be recovered by firing again at a temperature lower than the firing temperature in the firing step, and the lithium composite oxide finally obtained The crystallinity of the particles can be improved.

(Baking atmosphere)
The firing atmosphere is an oxidizing atmosphere as in the firing step. Specifically, it is preferably performed in an atmosphere having an oxygen concentration of 18% by volume to 100% by volume, that is, in the atmosphere to an oxygen stream, and more preferably in an air stream in view of cost. When the oxygen concentration is less than 18% by volume, the oxidation reaction does not proceed sufficiently, and the resulting lithium composite oxide particles may not have sufficient crystallinity.

(Baking temperature)
As described above, the firing temperature is lower than the firing temperature in the firing step, specifically 500 ° C to 800 ° C, preferably 600 ° C to 800 ° C, more preferably 650 ° C to 750 ° C. It is. When the firing temperature is less than 500 ° C., oxygen defects cannot be sufficiently recovered. On the other hand, when it exceeds 800 ° C., oxygen defects are generated and the crystallinity of the lithium composite oxide particles is deteriorated.

(Baking time)
The firing time is 5 hours to 40 hours, preferably 10 hours to 40 hours, more preferably 20 hours to 40 hours. If the firing time is less than 5 hours, oxygen defects cannot be sufficiently recovered. On the other hand, even if it exceeds 40 hours, not only a further effect cannot be obtained, but also the production efficiency deteriorates.

3. Non-aqueous electrolyte secondary battery The non-aqueous electrolyte secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, a non-aqueous electrolyte solution, and the like, and includes the same components as those of a general non-aqueous electrolyte secondary battery. The embodiment described below is merely an example, and the nonaqueous electrolyte secondary battery of the present invention can be variously modified based on the knowledge of those skilled in the art based on the embodiment described in the present specification. It can be implemented in an improved form. Moreover, the use of the nonaqueous electrolyte secondary battery of the present invention is not particularly limited.

(1) Positive electrode Using the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention, for example, a positive electrode of a non-aqueous electrolyte secondary battery is produced as follows.

  First, a powdered positive electrode active material, a conductive material, and a binder are mixed, and activated carbon and a target solvent such as viscosity adjustment are added as necessary, and this is kneaded to prepare a positive electrode mixture paste. . At that time, the mixing ratio in the positive electrode mixture paste is also an important factor for determining the performance of the non-aqueous electrolyte secondary battery. When the solid content of the positive electrode mixture excluding the solvent is 100 parts by mass, the content of the positive electrode active material is 60 parts by mass to 95 parts by mass in the same manner as the positive electrode of a general non-aqueous electrolyte secondary battery. The content is preferably 1 part by mass to 20 parts by mass, and the content of the binder is preferably 1 part by mass to 20 parts by mass.

  The obtained positive electrode mixture paste is applied to, for example, the surface of a current collector made of aluminum foil and dried to disperse the solvent. If necessary, pressurization may be performed by a roll press or the like to increase the electrode density. In this way, a sheet-like positive electrode can be produced. The sheet-like positive electrode can be cut into an appropriate size according to the target battery and used for battery production. However, the method for manufacturing the positive electrode is not limited to the above-described examples, and other methods may be used.

  In producing the positive electrode, as the conductive material, for example, graphite (natural graphite, artificial graphite, expanded graphite and the like), and carbon black materials such as acetylene black and ketjen black (registered trademark) can be used.

  The binder plays a role of anchoring the active material particles. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluorine rubber, ethylene propylene diene rubber, styrene butadiene, cellulosic resin, and polyacrylic are used. An acid can be used.

  If necessary, a positive electrode active material, a conductive material, and activated carbon are dispersed, and a solvent that dissolves the binder is added to the positive electrode mixture. Specifically, an organic solvent such as N-methyl-2-pyrrolidone can be used as the solvent. Activated carbon can be added to the positive electrode mixture in order to increase the electric double layer capacity.

(2) Negative electrode The negative electrode composite material in which the negative electrode is made of metal lithium, lithium alloy, or the like, or a negative electrode active material capable of occluding and desorbing lithium ions, mixed with a binder, and added with an appropriate solvent to form a paste. Is applied to the surface of a metal foil current collector such as copper, dried, and compressed to increase the electrode density as necessary.

  As the negative electrode active material, for example, organic compound fired bodies such as natural graphite, artificial graphite and phenol resin, and powdery bodies of carbon materials such as coke can be used. In this case, a fluorine-containing resin such as PVDF can be used as the negative electrode binder, as in the case of the positive electrode, and an organic material such as N-methyl-2-pyrrolidone can be used as a solvent for dispersing these active materials and the binder. A solvent can be used.

(3) Separator A separator is interposed between the positive electrode and the negative electrode. The separator separates the positive electrode and the negative electrode and retains an electrolyte, and a thin film such as polyethylene or polypropylene and a film having many minute holes can be used.

(4) 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, and tetrahydrofuran, 2- One kind selected from ether compounds such as methyltetrahydrofuran and dimethoxyethane, sulfur compounds such as ethylmethylsulfone and butanesultone, phosphorus compounds such as triethyl phosphate and trioctyl phosphate, etc. are used alone or in admixture of two or more. be able to.

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.

  Furthermore, the non-aqueous electrolyte solution may contain a radical scavenger, a surfactant, a flame retardant, and the like.

(5) Shape and configuration of battery The non-aqueous electrolyte secondary battery of the present invention composed of the positive electrode, negative electrode, separator and non-aqueous electrolyte described above has various shapes such as a cylindrical shape and a laminated shape. Can be. In any case, the positive electrode and the negative electrode are laminated via a separator to form an electrode body, and the obtained electrode body is impregnated with a non-aqueous electrolyte, and the positive electrode current collector communicates with the outside. A non-aqueous electrolyte secondary battery is completed by connecting between the terminals and between the negative electrode current collector and the negative electrode terminal communicating with the outside using a current collecting lead or the like and sealing the battery case.

(6) Characteristics The nonaqueous electrolyte secondary battery using the positive electrode active material of the present invention has a high capacity and excellent cycle characteristics while having a high operating potential. Specifically, a positive electrode using the positive electrode active material of the present invention and a lithium foil as a negative electrode constitute a 2032 type coin battery, the current density is 0.1 mA / cm ² , and the cutoff voltage is up to 5.0V. When the battery is charged and discharged to a cutoff voltage of 3.0 V after a pause of 1 hour, a capacity (initial discharge capacity) of 100 mAh / g or more, preferably 110 mAh / g or more is obtained at a voltage of 4.6 V or more, Moreover, a capacity of 125 mAh / g or more, preferably 130 mAh / g or more is obtained at a voltage of 3.0 V or more.

In addition, a negative electrode active material made of carbon is used as the negative electrode to form a similar 2032 type coin battery, which is maintained at 60 ° C., the current density is 0.6 mA / cm ² , and the cutoff voltage is 4.9 V. The ratio of the discharge capacity of the 200th time (capacity maintenance ratio) to 70% or more of the discharge capacity of the second time when the operation of charging and discharging to a cutoff voltage of 3.5 V is repeated 200 times after a pause of 1 hour. , Preferably 75% or more.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

Example 1
[Crystalling process]
First, the temperature in the tank was set to 40 ° C. while stirring the reaction tank (5 L) with half the amount of water. The inside of the reaction vessel at this time was a nitrogen atmosphere (oxygen concentration: 1% by volume or less). Appropriate amounts of 25% by mass aqueous sodium hydroxide and 25% by mass aqueous ammonia are added to the water in the reaction vessel, the pH value in the reaction vessel is 11.5 based on the liquid temperature of 25 ° C., and the ammonia concentration is 5 g / L was prepared. Further, a hydrate of manganese sulfate and nickel sulfate was dissolved in pure water so that the molar ratio of manganese to nickel was Mn: Ni = 3: 1 to prepare a 2.0 mol / L raw material aqueous solution.

  This mixed aqueous solution was dropped into the reaction vessel at a constant rate to obtain a reaction aqueous solution. At the same time, 25% by mass aqueous ammonia and 25% by mass aqueous sodium hydroxide solution were also added dropwise at a constant rate, and the pH value of the aqueous reaction solution was maintained at 11.5 and the ammonia concentration at 5 g / L based on the liquid temperature of 25 ° C. The composite hydroxide particles were crystallized. Thereafter, the slurry containing the composite hydroxide particles was filtered and dried to obtain composite hydroxide particles.

As a result of analyzing the composition of the composite hydroxide particles using an ICP emission spectrophotometer (Varian, 725ES), it was confirmed that it was represented by the general formula: Mn _0.75 Ni _0.25 (OH) _2. It was done. Moreover, about this composite hydroxide particle, the BET specific surface area (S) measured using the fully automatic BET specific surface area measuring apparatus (the product made by MUNTEC Co., Ltd., Macsorb) is 30.0 m < ² > / g, and laser beam diffraction The volume average particle diameter (MV) measured using a scattering particle size analyzer (manufactured by Nikkiso Co., Ltd., Microtrac MT3000II) was 4.9 μm.

[Mixing process]
Tungsten oxide (volume average particle size (MV)) weighed so as to be 0.3 atomic% with respect to the total number of atoms of manganese and nickel in the obtained composite oxide particles and the composite hydroxide particles = 0.8 μm), and lithium hydroxide monohydrate weighed to be 50 atomic% with respect to the total number of atoms of manganese and nickel in the composite hydroxide particles and tungsten in tungsten oxide (Volume average particle size (MV) = 4.5 μm) was mixed using a tumbler shaker mixer (manufactured by Dalton, T2F) to obtain a lithium mixture.

[Baking process]
Using an atmosphere firing furnace (manufactured by Hiroki Co., Ltd., HAF-2020S), the lithium mixture was fired at 1000 ° C. for 12 hours in an air atmosphere, cooled to room temperature, and the resulting lithium composite oxide particles were And crushing using a hammer mill (MF10, manufactured by IKA Japan Co., Ltd.).

[Refiring process]
The lithium composite oxide particles obtained in the firing step were fired at 700 ° C. for 36 hours in an air atmosphere using an atmosphere firing furnace to obtain a positive electrode active material. As a result of analyzing the composition of this positive electrode active material using an ICP emission spectroscopic analyzer, it was confirmed that it was represented by the general formula: LiMn _1.499 Ni _0.496 W _0.005 O ₄ .

[Properties of positive electrode active material]
When the cross section of the positive electrode active material thus obtained was observed using SEM (manufactured by JEOL, JSM-7001F), as shown in FIG. 1, there were white sites on the surface of the secondary particles and the grain boundaries. confirmed. By energy dispersive X-ray analysis (EDS), it was confirmed that the number of atoms of tungsten in this portion relative to the total number of atoms of manganese, nickel, and tungsten was 82 atomic%.

In addition, the BET specific surface area (S) measured using a fully automatic BET specific surface area measurement device (manufactured by Mountec Co., Ltd., Macsorb) for this positive electrode active material is 0.20 m ² / g, and laser light diffraction The volume average particle diameter (MV) measured using a scattering type particle size analyzer (manufactured by Nikkiso Co., Ltd., Microtrac MT3000II) was 11.0 μm. From these results, the product (S · MV) of the BET specific surface area (S) and the volume average particle size (MV) was determined to be 2.2 × 10 ⁻⁶ m ³ / g.

  Furthermore, when the crystal structure of this positive electrode active material was measured using XRD (manufactured by PANALYTICAL, X'Pert, PROMRD), a peak group of a spinel crystal structure of the space group Fd-3m was detected. In this peak group, the peak position on the (311) plane was confirmed to be 36.45 ° at 2θ. A profile obtained by this XRD measurement is shown in FIG.

[Production of secondary battery]
For evaluation of the obtained positive electrode active material, a 2032 type coin battery 1 (hereinafter referred to as “coin type battery”) shown in FIG. 4 was used.

  The coin-type battery 1 includes a case 2 and an electrode 3 accommodated in the case 2. The case 2 has a positive electrode can 2a that is hollow and open at one end, and a negative electrode can 2b that is disposed in the opening of the positive electrode can 2a. When the negative electrode can 2b is disposed in the opening of the positive electrode can 2a, A space for accommodating the electrode 3 is formed between the negative electrode can 2b and the positive electrode can 2a. The electrode 3 includes a positive electrode 3a, a separator 3c, and a negative electrode 3b, which are stacked in this order. The positive electrode 3a contacts the inner surface of the positive electrode can 2a, and the negative electrode 3b contacts the inner surface of the negative electrode can 2b. It is accommodated in the case 2 so as to come into contact. The case 2 includes a gasket 2c, and relative movement is fixed by the gasket 2c so as to maintain a non-contact state between the positive electrode can 2a and the negative electrode can 2b. Further, the gasket 2c also has a function of sealing a gap between the positive electrode can 2a and the negative electrode can 2b to block the inside and outside of the case 2 in an airtight and liquid tight manner.

  Such a coin-type battery 1 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 and thinned to a mass of about 10 mg with a diameter of 10 mm, and the positive electrode 3a This was dried in a vacuum dryer at 120 ° C. for 12 hours.

Next, using the positive electrode 3a, the coin-type battery 1 was produced in a glove box in an Ar atmosphere in which the dew point was controlled at −80 ° C. At this time, as the negative electrode 3b, a lithium foil punched into a disk shape having a diameter of 14 mm, or a negative electrode sheet in which graphite powder having an average particle size of about 20 μm and polyvinylidene fluoride were applied to a copper foil was used. The separator 3c is a 25 μm thick polyethylene porous membrane, and the electrolyte is a 1: 7 mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) using 1M LiPF ₆ as a supporting electrolyte (Toyama Chemical). Kogyo Co., Ltd.) was used.

[Evaluation of secondary battery]
The initial discharge capacity indicating the performance of the coin-type battery 1 and the capacity retention rate of the cycle characteristics were evaluated as follows.

The initial discharge capacity is about 24 hours after the coin-type battery 1 using lithium foil as the negative electrode is manufactured, and after the open circuit voltage OCV (Open Circuit Voltage) is stabilized, the current density with respect to the positive electrode is 0.1 mA / Evaluation was made by measuring the capacity (initial discharge capacity) when charging to a cutoff voltage of 5.0 V as cm ² and discharging to a cutoff voltage of 3.0 V after a pause of 1 hour.

In addition, the cycle characteristics were as follows: a coin-type battery 1 using graphite powder as a negative electrode was produced, held at 60 ° C., charged at a current density of 0.6 mA / cm ² , and cut to a cutoff voltage of 4.9 V; After the rest for 1 hour, the operation of discharging to a cutoff voltage of 3.5 V was repeated 200 times, and the ratio of the 200th discharge capacity to the second discharge capacity (capacity maintenance ratio) was evaluated.

  As a result, the initial discharge capacity of the coin-type battery 1 of Example 1 was 139 mAh / g, and the capacity obtained up to 4.6 V was 132 mAh / g. Further, the capacity retention rate after 200 cycles was 75%.

(Example 2)
Except that the addition amount of tungsten in the mixing step was 0.5 atomic% with respect to the total number of manganese and nickel atoms in the composite hydroxide particles, the same as in Example 1, A positive electrode active material was obtained. This positive electrode active material was confirmed to be represented by the general formula: Li _1,01 Mn _1.493 Ni _0.495 W _0.012 O ₄ by analysis using an ICP emission spectrometer.

  When the cross section of this positive electrode active material was observed using SEM, white portions were confirmed on the surfaces of the secondary particles and the crystal grain boundaries. By EDS, it was confirmed that the number of tungsten atoms relative to the total number of manganese, nickel, and tungsten atoms at this site was 80 atomic%.

Further, when the BET specific surface area (S) and the volume average particle size (MV) were measured for this positive electrode active material in the same manner as in Example 1, the BET specific surface area (S) was 0.13 m ² / g. And the volume average particle size (MV) was 11.6 μm. From these results, the product (S · MV) of the BET specific surface area (S) and the volume average particle diameter (MV) was determined to be 1.5 × 10 ⁻⁶ m ³ / g.

  Furthermore, when the crystal structure of this positive electrode active material was measured using XRD, a peak group of spinel crystal structures of the space group Fd-3m was detected. In this peak group, the peak position on the (311) plane was confirmed to be 36.45 ° at 2θ.

  Finally, using this positive electrode active material, a coin-type battery 1 was produced in the same manner as in Example 1, and its performance was evaluated. As a result, the initial discharge capacity was 138 mAh / g, of which 4.6 V was reached. The capacity obtained was 131 mAh / g. Further, the capacity retention rate after 200 cycles was 75%.

Example 3
Except that the amount of tungsten added in the mixing step was 0.7 atomic% with respect to the total number of manganese and nickel atoms in the composite hydroxide particles, the same as in Example 1, A positive electrode active material was obtained. The positive electrode active material was confirmed to be represented by the general formula: LiMn _1.491 Ni _0.496 W _0.013 O ₄ by analysis using an ICP emission spectroscopic analyzer.

  When the cross section of this positive electrode active material was observed using SEM, white portions were confirmed on the surfaces of the secondary particles and the crystal grain boundaries. By EDS, it was confirmed that the number of tungsten atoms relative to the total number of manganese, nickel, and tungsten atoms at this site was 85 atomic%.

Further, when the BET specific surface area (S) and the volume average particle size (MV) were measured for this positive electrode active material in the same manner as in Example 1, the BET specific surface area (S) was 0.22 m ² / g. And the volume average particle size (MV) was 11.6 μm. From these results, the product (S · MV) of the BET specific surface area (S) and the volume average particle size (MV) was determined to be 2.6 × 10 ⁻⁶ m ³ / g.

  Furthermore, when the crystal structure of this positive electrode active material was measured using XRD, a peak group of spinel crystal structures of the space group Fd-3m was detected. In this peak group, the peak position on the (311) plane was confirmed to be 36.47 ° at 2θ.

  Finally, using this positive electrode active material, a coin-type battery 1 was produced in the same manner as in Example 1, and its performance was evaluated. As a result, the initial discharge capacity was 137 mAh / g, of which 4.6 V was reached. The capacity obtained was 131 mAh / g. Further, the capacity retention rate after 200 cycles was 75%.

Example 4
Except that the addition amount of tungsten in the mixing step was 1.5 atomic% with respect to the total number of manganese and nickel atoms in the composite hydroxide particles, the same as in Example 1, A positive electrode active material was obtained. Analysis using an ICP emission spectroscopic analyzer confirmed that this positive electrode active material was represented by the general formula: LiMn _1.482 Ni _0.490 W _0.028 O ₄ .

  When the cross section of this positive electrode active material was observed using SEM, white portions were confirmed on the surfaces of the secondary particles and the crystal grain boundaries. By EDS, it was confirmed that the number of tungsten atoms relative to the total number of manganese, nickel, and tungsten atoms at this site was 82 atomic%.

Further, when the BET specific surface area (S) and the volume average particle size (MV) were measured for this positive electrode active material in the same manner as in Example 1, the BET specific surface area (S) was 0.20 m ² / g. And the volume average particle diameter (MV) was 12.5 μm. From these results, the product (S · MV) of the BET specific surface area (S) and the volume average particle size (MV) was determined to be 2.5 × 10 ⁻⁶ m ³ / g.

Furthermore, when the crystal structure of this positive electrode active material was measured using XRD, a peak group of spinel crystal structure of the space group Fd-3m and a peak of Li ₂ WO ₄ were detected. Of the peak group of the spinel crystal structure of the space group Fd-3m, the peak position on the (311) plane was confirmed to be 36.46 ° at 2θ.

  Finally, using this positive electrode active material, a coin-type battery 1 was produced in the same manner as in Example 1, and its performance was evaluated. As a result, the initial discharge capacity was 133 mAh / g, of which 4.6 V was reached. The capacity obtained was 127 mAh / g. Further, the capacity retention rate after 200 cycles was 77%.

(Example 5)
Except that the addition amount of tungsten in the mixing step was 2.5 atomic% with respect to the total number of manganese and nickel atoms in the composite hydroxide particles, the same as in Example 1, A positive electrode active material was obtained. The positive electrode active material was confirmed to be represented by the general formula: Li _0.99 Mn _1.468 Ni _0.486 W _0.046 O ₄ by analysis using an ICP emission spectroscopic analyzer.

  When the cross section of this positive electrode active material was observed using SEM, white portions were confirmed on the surfaces of the secondary particles and the crystal grain boundaries. By EDS, it was confirmed that the number of tungsten atoms relative to the total number of manganese, nickel, and tungsten atoms at this site was 80 atomic%.

Further, when the BET specific surface area (S) and the volume average particle size (MV) were measured for this positive electrode active material in the same manner as in Example 1, the BET specific surface area (S) was 0.14 m ² / g. And the volume average particle diameter (MV) was 12.8 μm. From these results, the product (S · MV) of the BET specific surface area (S) and the volume average particle size (MV) was determined to be 1.8 × 10 ⁻⁶ m ³ / g.

Furthermore, when the crystal structure of this positive electrode active material was measured using XRD, a peak group of spinel crystal structure of the space group Fd-3m and a peak of Li ₂ WO ₄ were detected. Of the peak group of the spinel crystal structure of the space group Fd-3m, the position of the peak on the (311) plane was confirmed to be 36.44 ° at 2θ.

  Finally, using this positive electrode active material, a coin-type battery 1 was produced in the same manner as in Example 1, and its performance was evaluated. As a result, the initial discharge capacity was 127 mAh / g, of which 4.6 V was reached. The capacity obtained was 116 mAh / g. Further, the capacity retention rate after 200 cycles was 79%.

(Example 6)
In the mixing step, instead of tungsten oxide, molybdenum oxide (volume average particle diameter (MV)) weighed to be 0.3 atomic% with respect to the total number of manganese and nickel atoms in the composite hydroxide particles. = 0.8 μm) was used in the same manner as in Example 1 to obtain a positive electrode active material. This positive electrode active material was confirmed to be represented by the general formula: LiMn _1.498 Ni _0.496 Mo _0.006 O ₄ by analysis using an ICP emission spectroscopic analyzer.

  When the cross section of this positive electrode active material was observed using SEM, as shown in FIG. 2, a white part was confirmed on the surface of the secondary particle and the crystal grain boundary. By EDS, it was confirmed that the number of molybdenum atoms relative to the total number of manganese, nickel, and molybdenum atoms at this site was 83 atomic%.

Further, when the BET specific surface area (S) and the volume average particle size (MV) were measured for this positive electrode active material in the same manner as in Example 1, the BET specific surface area (S) was 0.25 m ² / g. The volume average particle size (MV) was 11.4 μm. From these results, the product (S · MV) of the BET specific surface area (S) and the volume average particle size (MV) was determined to be 2.9 × 10 ⁻⁶ m ³ / g.

  Furthermore, when the crystal structure of this positive electrode active material was measured using XRD, a peak group of spinel crystal structures of the space group Fd-3m was detected. In this peak group, the peak position on the (311) plane was confirmed to be 36.45 ° at 2θ.

  Finally, using this positive electrode active material, a coin-type battery 1 was produced in the same manner as in Example 1, and its performance was evaluated. The initial discharge capacity was 139 mAh / g, of which 4.6 V The capacity obtained was 132 mAh / g. Further, the capacity retention rate after 200 cycles was 75%.

(Example 7)
Except that the amount of molybdenum added in the mixing step was 0.7 atomic% with respect to the total number of manganese and nickel atoms in the composite hydroxide particles, the same as in Example 6, A positive electrode active material was obtained. Analysis using an ICP emission spectroscopic analyzer confirmed that the positive electrode active material was represented by the general formula: LiMn _1.492 Ni _0.494 Mo _0.014 O ₄ .

  When the cross section of this positive electrode active material was observed using SEM, white portions were confirmed on the surfaces of the secondary particles and the crystal grain boundaries. EDS confirmed that the number of molybdenum atoms relative to the total number of manganese, nickel, and molybdenum atoms at this site was 82 atomic%.

Further, when the BET specific surface area (S) and the volume average particle size (MV) were measured for this positive electrode active material in the same manner as in Example 1, the BET specific surface area (S) was 0.21 m ² / g. The volume average particle size (MV) was 11.5 μm. From these results, the product (S · MV) of the BET specific surface area (S) and the volume average particle size (MV) was determined to be 2.4 × 10 ⁻⁶ m ³ / g.

  Furthermore, when the crystal structure of this positive electrode active material was measured using XRD, a peak group of spinel crystal structures of the space group Fd-3m was detected. In this peak group, the peak position on the (311) plane was confirmed to be 36.45 ° at 2θ.

  Finally, using this positive electrode active material, a coin-type battery 1 was produced in the same manner as in Example 1, and its performance was evaluated. As a result, the initial discharge capacity was 134 mAh / g, of which 4.6 V was reached. The capacity obtained was 126 mAh / g. Further, the capacity retention rate after 200 cycles was 73%.

(Example 8)
Except that the amount of molybdenum added in the mixing step was 1.5 atomic% with respect to the total number of manganese and nickel atoms in the composite hydroxide particles, the same as in Example 6, A positive electrode active material was obtained. Analysis using an ICP emission spectroscopic analyzer confirmed that the positive electrode active material was represented by the general formula: LiMn _1.480 Ni _0.490 Mo _0.030 O ₄ .

  When the cross section of this positive electrode active material was observed using SEM, white portions were confirmed on the surfaces of the secondary particles and the crystal grain boundaries. EDS confirmed that the number of molybdenum atoms relative to the total number of manganese, nickel, and molybdenum atoms at this site was 82 atomic%.

Further, when the BET specific surface area (S) and the volume average particle size (MV) were measured for this positive electrode active material in the same manner as in Example 1, the BET specific surface area (S) was 0.24 m ² / g. And the volume average particle diameter (MV) was 11.7 μm. From these results, the product (S · MV) of the BET specific surface area (S) and the volume average particle size (MV) was determined to be 2.8 × 10 ⁻⁶ m ³ / g.

  Furthermore, when the crystal structure of this positive electrode active material was measured using XRD, a peak group of spinel crystal structures of the space group Fd-3m was detected. Of the peak group of the spinel crystal structure of the space group Fd-3m, the peak position on the (311) plane was confirmed to be 36.47 ° at 2θ.

  Finally, using this positive electrode active material, a coin-type battery 1 was produced in the same manner as in Example 1, and its performance was evaluated. As a result, the initial discharge capacity was 132 mAh / g, of which 4.6 V was reached. The capacity obtained was 124 mAh / g. Further, the capacity retention rate after 200 cycles was 75%.

Example 9
A positive electrode active material was obtained in the same manner as in Example 1 except that the firing temperature in the firing step was 900 ° C. This positive electrode active material was confirmed to be represented by the general formula: LiMn _1.499 Ni _0.496 W _0.005 O ₄ by analysis using an ICP emission spectroscopic analyzer.

  When the cross section of this positive electrode active material was observed using SEM, white portions were confirmed on the surfaces of the secondary particles and the crystal grain boundaries. By EDS, it was confirmed that the number of tungsten atoms relative to the total number of manganese, nickel, and tungsten atoms at this site was 81 atomic%.

Further, when the BET specific surface area (S) and the volume average particle size (MV) were measured for this positive electrode active material in the same manner as in Example 1, the BET specific surface area (S) was 0.29 m ² / g. And the volume average particle size (MV) was 6.9 μm. From these results, the product (S · MV) of the BET specific surface area (S) and the volume average particle size (MV) was determined to be 2.0 × 10 ⁻⁶ m ³ / g.

  Furthermore, when the crystal structure of this positive electrode active material was measured using XRD, a peak group of spinel crystal structures of the space group Fd-3m was detected. Of the peak group of the spinel crystal structure of the space group Fd-3m, the peak position on the (311) plane was confirmed to be 36.45 ° at 2θ.

  Finally, using this positive electrode active material, a coin-type battery 1 was produced in the same manner as in Example 1, and its performance was evaluated. The initial discharge capacity was 139 mAh / g, of which 4.6 V The capacity obtained was 132 mAh / g. Further, the capacity retention rate after 200 cycles was 75%.

(Example 10)
A positive electrode active material was obtained in the same manner as in Example 1 except that the firing time in the firing step was 20 hours. This positive electrode active material was confirmed to be represented by the general formula: LiMn _1.499 Ni _0.496 W _0.005 O ₄ by analysis using an ICP emission spectroscopic analyzer.

  When the cross section of this positive electrode active material was observed using SEM, white portions were confirmed on the surfaces of the secondary particles and the crystal grain boundaries. By EDS, it was confirmed that the number of tungsten atoms relative to the total number of manganese, nickel, and tungsten atoms at this site was 87 atomic%.

Further, when the BET specific surface area (S) and the volume average particle diameter (MV) were measured for this positive electrode active material in the same manner as in Example 1, the BET specific surface area (S) was 0.19 m ² / g. And the volume average particle size (MV) was 11.0 μm. From these results, the product (S · MV) of the BET specific surface area (S) and the volume average particle size (MV) was determined to be 2.1 × 10 ⁻⁶ m ³ / g.

  Furthermore, when the crystal structure of this positive electrode active material was measured using XRD, a peak group of spinel crystal structures of the space group Fd-3m was detected. Of the peak group of the spinel crystal structure of the space group Fd-3m, the peak position on the (311) plane was confirmed to be 36.45 ° at 2θ.

  Finally, using this positive electrode active material, a coin-type battery 1 was produced in the same manner as in Example 1, and its performance was evaluated. The initial discharge capacity was 139 mAh / g, of which 4.6 V The capacity obtained was 132 mAh / g. Further, the capacity retention rate after 200 cycles was 75%.

(Example 11)
A positive electrode active material was obtained in the same manner as in Example 1 except that the firing temperature in the refiring step was 500 ° C. This positive electrode active material was confirmed to be represented by the general formula: LiMn _1.499 Ni _0.496 W _0.005 O ₄ by analysis using an ICP emission spectroscopic analyzer.

  When the cross section of this positive electrode active material was observed using SEM, white portions were confirmed on the surfaces of the secondary particles and the crystal grain boundaries. By EDS, it was confirmed that the number of tungsten atoms in this portion relative to the total number of manganese, nickel, and tungsten atoms was 83 atomic%.

Further, when the BET specific surface area (S) and the volume average particle size (MV) were measured for this positive electrode active material in the same manner as in Example 1, the BET specific surface area (S) was 0.20 m ² / g. And the volume average particle size (MV) was 11.0 μm. From these results, the product (S · MV) of the BET specific surface area (S) and the volume average particle size (MV) was determined to be 2.2 × 10 ⁻⁶ m ³ / g.

  Furthermore, when the crystal structure of this positive electrode active material was measured using XRD, a peak group of spinel crystal structures of the space group Fd-3m was detected. Of the peak group of the spinel crystal structure of the space group Fd-3m, the peak position on the (311) plane was confirmed to be 36.45 ° at 2θ.

  Finally, using this positive electrode active material, a coin-type battery 1 was produced in the same manner as in Example 1, and its performance was evaluated. The initial discharge capacity was 139 mAh / g, of which 4.6 V The capacity obtained was 132 mAh / g. Further, the capacity retention rate after 200 cycles was 75%.

(Example 12)
A positive electrode active material was obtained in the same manner as in Example 1 except that the firing temperature in the refiring step was 800 ° C. This positive electrode active material was confirmed to be represented by the general formula: LiMn _1.499 Ni _0.496 W _0.005 O ₄ by analysis using an ICP emission spectroscopic analyzer.

  When the cross section of this positive electrode active material was observed using SEM, white portions were confirmed on the surfaces of the secondary particles and the crystal grain boundaries. By EDS, it was confirmed that the number of tungsten atoms relative to the total number of manganese, nickel, and tungsten atoms at this site was 82 atomic%.

Further, when the BET specific surface area (S) and the volume average particle size (MV) were measured for this positive electrode active material in the same manner as in Example 1, the BET specific surface area (S) was 0.20 m ² / g. And the volume average particle size (MV) was 11.0 μm. From these results, the product (S · MV) of the BET specific surface area (S) and the volume average particle size (MV) was determined to be 2.2 × 10 ⁻⁶ m ³ / g.

  Furthermore, when the crystal structure of this positive electrode active material was measured using XRD, a peak group of spinel crystal structures of the space group Fd-3m was detected. Of the peak group of the spinel crystal structure of the space group Fd-3m, the peak position on the (311) plane was confirmed to be 36.45 ° at 2θ.

  Finally, using this positive electrode active material, a coin-type battery 1 was produced in the same manner as in Example 1, and its performance was evaluated. The initial discharge capacity was 139 mAh / g, of which 4.6 V The capacity obtained was 132 mAh / g. Further, the capacity retention rate after 200 cycles was 75%.

(Example 13)
A positive electrode active material was obtained in the same manner as in Example 1 except that the firing time in the refiring step was 5 hours. This positive electrode active material was confirmed to be represented by the general formula: LiMn _1.499 Ni _0.496 W _0.005 O ₄ by analysis using an ICP emission spectroscopic analyzer.

  When the cross section of this positive electrode active material was observed using SEM, white portions were confirmed on the surfaces of the secondary particles and the crystal grain boundaries. By EDS, it was confirmed that the number of tungsten atoms relative to the total number of manganese, nickel, and tungsten atoms at this site was 85 atomic%.

Further, when the BET specific surface area (S) and the volume average particle size (MV) were measured for this positive electrode active material in the same manner as in Example 1, the BET specific surface area (S) was 0.20 m ² / g. And the volume average particle size (MV) was 11.0 μm. From these results, the product (S · MV) of the BET specific surface area (S) and the volume average particle size (MV) was determined to be 2.2 × 10 ⁻⁶ m ³ / g.

  Furthermore, when the crystal structure of this positive electrode active material was measured using XRD, a peak group of spinel crystal structures of the space group Fd-3m was detected. Of the peak group of the spinel crystal structure of the space group Fd-3m, the peak position on the (311) plane was confirmed to be 36.45 ° at 2θ.

  Finally, using this positive electrode active material, a coin-type battery was produced in the same manner as in Example 1, and its performance was evaluated. The initial discharge capacity was 139 mAh / g, of which 4.6 V was obtained. The capacity obtained was 132 mAh / g. Further, the capacity retention rate after 200 cycles was 75%.

(Example 14)
A positive electrode active material was obtained in the same manner as in Example 1 except that the firing time in the refiring step was 40 hours. This positive electrode active material was confirmed to be represented by the general formula: LiMn _1.499 Ni _0.496 W _0.005 O ₄ by analysis using an ICP emission spectroscopic analyzer.

  When the cross section of this positive electrode active material was observed using SEM, white portions were confirmed on the surfaces of the secondary particles and the crystal grain boundaries. By EDS, it was confirmed that the number of tungsten atoms with respect to the total number of manganese, nickel, and tungsten atoms at this site was 86 atomic%.

Further, when the BET specific surface area (S) and the volume average particle size (MV) were measured for this positive electrode active material in the same manner as in Example 1, the BET specific surface area (S) was 0.20 m ² / g. And the volume average particle size (MV) was 11.0 μm. From these results, the product (S · MV) of the BET specific surface area (S) and the volume average particle size (MV) was determined to be 2.2 × 10 ⁻⁶ m ³ / g.

  Furthermore, when the crystal structure of this positive electrode active material was measured using XRD, a peak group of spinel crystal structures of the space group Fd-3m was detected. Of the peak group of the spinel crystal structure of the space group Fd-3m, the peak position on the (311) plane was confirmed to be 36.45 ° at 2θ.

  Finally, using this positive electrode active material, a coin-type battery 1 was fabricated and its performance was evaluated. The initial discharge capacity was 139 mAh / g, of which the capacity obtained up to 4.6 V was 132 mAh / g. Met. Further, the capacity retention rate after 200 cycles was 75%.

(Comparative Example 1)
In the mixing step, a positive electrode active material was obtained in the same manner as in Example 1 except that neither tungsten nor molybdenum was added. By analysis using ICP emission spectrometer, the positive electrode active material has the general formula: Li _1.01 Mn _1.503 Ni _0.497 that O is ₄ in those represented was confirmed.

  When the cross section of the positive electrode active material was observed using an SEM, no white portion was observed on the surface of the secondary particles and the crystal grain boundaries.

Further, when the BET specific surface area (S) and the volume average particle size (MV) were measured for this positive electrode active material in the same manner as in Example 1, the BET specific surface area (S) was 0.75 m ² / g. And the volume average particle diameter (MV) was 8.3 μm. From these results, the product (S · MV) of the BET specific surface area (S) and the volume average particle diameter (MV) was determined to be 6.2 × 10 ⁻⁶ m ³ / g.

Furthermore, when the crystal structure of this positive electrode active material was evaluated using XRD, the peak of LiMn ₂ O ₄ belonging to the diffraction pattern of the spinel crystal structure of the space group Fd-3m was obtained in the obtained diffraction pattern. A group was observed. Among these peak groups, the position of the peak attributed to the (311) plane was confirmed to be 36.45 ° in 2θ.

  Finally, using this positive electrode active material, a coin-type battery 1 was produced in the same manner as in Example 1, and its performance was evaluated. As a result, the initial discharge capacity was 141 mAh / g, of which 4.6 V was reached. The capacity obtained was 137 mAh / g. Further, the capacity retention rate after 200 cycles was 60%.

(Comparative Example 2)
Except that the addition amount of tungsten in the mixing step was 3.0 atomic% with respect to the total number of manganese and nickel atoms in the composite hydroxide particles, the same as in Example 1, A positive electrode active material was obtained. This positive electrode active material was confirmed to be represented by the general formula: Li _0.98 Mn _1.455 Ni _0.481 W _0.064 O ₄ by analysis using an ICP emission spectroscopic analyzer.

  When the cross section of this positive electrode active material was observed using SEM, white portions were confirmed on the surfaces of the secondary particles and the crystal grain boundaries. By EDS, it was confirmed that the number of atoms of tungsten with respect to the total number of atoms of manganese, nickel, and tungsten at this portion was 84 atomic%.

Further, when the BET specific surface area (S) and the volume average particle size (MV) were measured for this positive electrode active material in the same manner as in Example 1, the BET specific surface area (S) was 0.22 m ² / g. And the volume average particle size (MV) was 16.8 μm. From these results, the product (S · MV) of the BET specific surface area (S) and the volume average particle size (MV) was determined to be 3.7 × 10 ⁻⁶ m ³ / g.

Furthermore, when the crystal structure of this positive electrode active material was measured using XRD, a peak group of spinel crystal structure of the space group Fd-3m and a peak of Li ₂ WO ₄ were detected. Among the peak groups of the spinel crystal structure of the space group Fd-3m, the peak position on the (311) plane was confirmed to be 36.34 ° at 2θ.

  Finally, using this positive electrode active material, a coin-type battery 1 was produced in the same manner as in Example 1, and its performance was evaluated. As a result, the initial discharge capacity was 111 mAh / g, of which 4.6 V was reached. The capacity obtained was 86 mAh / g. Further, the capacity retention rate after 200 cycles was 85%.

(Comparative Example 3)
Except that the amount of molybdenum added in the mixing step was 3.0 atomic% with respect to the total number of manganese and nickel atoms in the composite hydroxide particles, the same as in Example 6, A positive electrode active material was obtained. This positive electrode active material was confirmed to be represented by the general formula: Li _0.98 Mn _1.455 Ni _0.481 Mo _0.064 O ₄ by analysis using an ICP emission spectrometer.

  When the cross section of this positive electrode active material was observed using SEM, white portions were confirmed on the surfaces of the secondary particles and the crystal grain boundaries. EDS confirmed that the number of molybdenum atoms relative to the total number of manganese, nickel, and molybdenum atoms at this site was 82 atomic%.

Further, when the BET specific surface area (S) and the volume average particle size (MV) were measured for this positive electrode active material in the same manner as in Example 1, the BET specific surface area (S) was 0.26 m ² / g. And the volume average particle diameter (MV) was 13.4 μm. From these results, the product (S · MV) of the BET specific surface area (S) and the volume average particle diameter (MV) was determined to be 3.5 × 10 ⁻⁶ m ³ / g.

Further, when the crystal structure of the positive electrode active material was measured using XRD, a peak group of spinel crystal structure of the space group Fd-3m and a peak of Li ₂ MoO ₄ were detected. Among the peak groups of the spinel crystal structure of the space group Fd-3m, the peak position on the (311) plane was confirmed to be 36.38 ° at 2θ.

  Finally, using this positive electrode active material, a coin-type battery 1 was produced in the same manner as in Example 1, and its performance was evaluated. As a result, the initial discharge capacity was 105 mAh / g. The capacity obtained was 74 mAh / g. Further, the capacity retention rate after 200 cycles was 85%.

(Comparative Example 4)
A positive electrode active material was obtained in the same manner as in Example 1 except that the firing temperature in the firing step was 1050 ° C. This positive electrode active material was confirmed to be represented by the general formula: Li _0.98 Mn _1.499 Ni _0.496 W _0.005 O ₄ by analysis using an ICP emission spectrometer.

  When the cross section of this positive electrode active material was observed using SEM, white portions were confirmed on the surfaces of the secondary particles and the crystal grain boundaries. By EDS, it was confirmed that the number of tungsten atoms relative to the total number of manganese, nickel, and tungsten atoms at this site was 82 atomic%.

Further, when the BET specific surface area (S) and the volume average particle size (MV) were measured for this positive electrode active material in the same manner as in Example 1, the BET specific surface area (S) was 0.15 m ² / g. And the volume average particle diameter (MV) was 22.0 μm. From these results, the product (S · MV) of the BET specific surface area (S) and the volume average particle size (MV) was determined to be 3.3 × 10 ⁻⁶ m ³ / g.

  Furthermore, when the crystal structure of this positive electrode active material was measured using XRD, a peak group of spinel crystal structures of the space group Fd-3m was detected. Of the peak group of the spinel crystal structure of the space group Fd-3m, the peak position on the (311) plane was confirmed to be 36.45 ° at 2θ.

  Finally, using this positive electrode active material, a coin-type battery 1 was produced in the same manner as in Example 1, and its performance was evaluated. As a result, the initial discharge capacity was 120 mAh / g. The capacity obtained was 104 mAh / g. Moreover, the capacity retention rate after 200 cycles was 80%.

(Comparative Example 5)
A positive electrode active material was obtained in the same manner as in Example 1 except that the firing temperature in the refiring step was 850 ° C. This positive electrode active material was confirmed to be represented by the general formula: Li _0.98 Mn _1.499 Ni _0.496 W _0.005 O ₄ by analysis using an ICP emission spectrometer.

  When the cross section of this positive electrode active material was observed using SEM, white portions were confirmed on the surfaces of the secondary particles and the crystal grain boundaries. By EDS, it was confirmed that the number of tungsten atoms relative to the total number of manganese, nickel, and tungsten atoms at this site was 85 atomic%.

Further, when the BET specific surface area (S) and the volume average particle size (MV) were measured for this positive electrode active material in the same manner as in Example 1, the BET specific surface area (S) was 0.18 m ² / g. The volume average particle size (MV) was 11.4 μm. From these results, the product (S · MV) of the BET specific surface area (S) and the volume average particle size (MV) was determined to be 2.1 × 10 ⁻⁶ m ³ / g.

  Furthermore, when the crystal structure of this positive electrode active material was measured using XRD, a peak group of spinel crystal structures of the space group Fd-3m was detected. Of the peak group of the spinel crystal structure of the space group Fd-3m, the peak position on the (311) plane was confirmed to be 36.45 ° at 2θ.

  Finally, using this positive electrode active material, a coin-type battery 1 was produced in the same manner as in Example 1, and its performance was evaluated. As a result, the initial discharge capacity was 123 mAh / g, of which 4.6V was reached. The capacity obtained was 100 mAh / g. Moreover, the capacity retention rate after 200 cycles was 80%.

[Evaluation]
From Table 1 and Table 2, although the positive electrode active materials of Examples 1 to 14 have a concentrated portion of tungsten or molybdenum on the surface of the secondary particles and the grain boundaries, and were fired at a temperature of 1000 ° C. or lower, It is confirmed that the specific surface area is small and the average particle size is relatively large. Further, in the secondary battery using such a positive electrode active material, the initial discharge capacity can be 125 mAh / g or more and the capacity obtained up to 4.6 V can be 115 mAh / g or more, and after 200 cycles. It is confirmed that the capacity maintenance rate can be 75% or more.

1 coin cell battery 1
2 Case 2
2a Positive electrode can 2b Negative electrode can 2c Gasket 3 Electrode 3a Positive electrode 3b Negative electrode 3c Separator

Claims (12)

Formula _{(1): Li 1 + x} Mn 2 (1-yc) -a Ni 2 (yd) -b A a + b B 2 (c + d) O 4 ( provided that, -0.2 ≦ x ≦ 0 .2, 0.2 ≦ y ≦ 0.3, 0 ≦ a ≦ 0.05, 0 ≦ b ≦ 0.05, 0 <a + b ≦ 0.05, 0 ≦ c ≦ 0.05, 0 ≦ d ≦ 0 .05, 0 ≦ c + d ≦ 0.1, A is W and / or Mo, B is at least one element selected from Co, Cr, Fe, Ti, Cu) Consisting of lithium manganese nickel composite oxide particles having a structure,
On the surface and / or the grain boundary of the lithium-manganese-nickel composite oxide particles, there is enrichment of the tungsten and / or molybdenum, in the range BET specific surface area of 0.1m ² /g~0.3m ² / g Yes, the product of the volume average particle size obtained by measuring the particle size distribution using a laser scattering particle size distribution meter after ultrasonic dispersion treatment for 30 seconds and the BET specific surface area is 1.0 × 10 ^{− 6 m 3 /g~3.0×10 -6 m 3 /} g is, the positive electrode active material for a non-aqueous electrolyte secondary battery.   In the diffraction pattern obtained by the evaluation using XRD, a peak group that can be attributed to the diffraction pattern of the spinel crystal structure of the space group Fd-3m or P4332 is observed, and among the peak group, the peak group belongs to the (311) plane. The positive electrode active material for nonaqueous electrolyte secondary batteries according to claim 1, wherein the peak position is 36.40 ° or more at 2θ.   3. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the tungsten and / or molybdenum concentration portion contains a compound composed of lithium and tungsten and / or molybdenum. The compound composed of lithium and tungsten and / or molybdenum is selected from Li ₂ WO ₄ , Li ₄ WO ₅ , Li ₄ W ₂ O ₉ , Li ₂ MoO ₄ , Li ₄ MoO ₅ , Li ₄ Mo ₂ O _9. The positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 3, wherein the positive electrode active material is at least one kind. A lithium compound, a precursor containing at least manganese and nickel, and a compound containing tungsten and / or molybdenum are represented by a general formula (1): Li _{1 + x} Mn _{2 (1-yc) -a} Ni _{2 (yd)- b} A _{a + b} B _{2 (c + d)} O ₄ (where −0.2 ≦ x ≦ 0.2, 0.2 ≦ y ≦ 0.3, 0 ≦ a ≦ 0.05, 0 ≦ b ≦ 0.05, 0 <a + b ≦ 0.05, 0 ≦ c ≦ 0.05, 0 ≦ d ≦ 0.05, 0 ≦ c + d ≦ 0.1, A is W and / or Mo, B is Co, Cr , At least one element selected from Fe, Ti, Cu) and a mixing step of obtaining a lithium mixture by mixing so as to have a composition ratio represented by:
The manufacturing method of the positive electrode active material for non-aqueous electrolyte secondary batteries including the baking process which bakes the said lithium mixture at 700 to 1000 degreeC for 10 to 20 hours by oxidizing atmosphere. The precursor is represented by the general formula (2): Mn _1-yc Ni _yd B _{c + d} (OH) _{2 + α} (where 0.2 ≦ y ≦ 0.3, 0 ≦ c ≦ 0.05, 0 ≦ d ≦ 0.05, 0 ≦ c + d ≦ 0.1, 0 ≦ α ≦ 0.5, B is at least one element selected from Co, Cr, Fe, Ti, Cu) The manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries of Claim 5 which is composite hydroxide particle | grains.   An aqueous solution containing at least a manganese salt and a nickel salt and an aqueous alkaline solution are continuously supplied into the reaction tank at a constant rate, and the temperature of the aqueous reaction solution composed of these aqueous solutions is 30 ° C. to 80 ° C. The temperature is maintained in a range of 10.5 to 12.5 based on a temperature of 25 ° C, and further includes a crystallization step of crystallizing the manganese nickel composite hydroxide represented by the general formula (2). The manufacturing method of the positive electrode active material for non-aqueous electrolyte secondary batteries.   The non-aqueous electrolyte secondary battery according to any one of claims 5 to 7, further comprising a re-baking step of baking at 500 to 800 ° C for 5 to 40 hours in an oxidizing atmosphere after the baking step. A method for producing a positive electrode active material.   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 5 to 8, wherein the lithium compound is at least one selected from lithium hydroxide, lithium carbonate, and lithium acetate.   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 5 to 9, wherein the tungsten compound is at least one selected from tungsten oxide, tungstic acid, and ammonium paratungstate. .   The said molybdenum compound is a manufacturing method of the positive electrode active material for non-aqueous electrolyte secondary batteries in any one of Claims 5-9 which is at least 1 sort (s) selected from a molybdenum oxide and paramolybdate ammonia.   A positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte are provided, and the positive electrode active material for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 4 is used as a positive electrode material of the positive electrode. Non-aqueous electrolyte secondary battery.