JP2017226576A - Lithium-nickel-containing composite oxide and nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode active material capable of improving cycle characteristics without impairing charge-discharge capacity.SOLUTION: There is provided a positive electrode active material which is composed of a lithium-nickel-containing composite oxide mainly containing nickel as a transition metal obtained by baking a mixture of a precursor and a lithium compound at a temperature of 650 to 800°C using a compound of an alkali metal other than lithium as a flux and has a layered-rock-salt type crystal structure, where the ratio between the peak strengths attributed to (003) plane and (104) plane as determined by an X-ray powder diffraction using a Cu-Kα ray as an X-ray source is 1.20 or more, the ratio of integrated intensity between the peaks attributed to (003) plane and (104) plane is 1.15 or more, octahedral primary particles are contained, and the ratio of the number of the octahedral primary particles to the total number of the primary particles is 1.0% or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a lithium nickel-containing composite oxide used as a positive electrode active material for a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery using the lithium nickel-containing composite oxide as a positive electrode material.

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

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

As a positive electrode active material of such a non-aqueous electrolyte secondary battery, lithium cobalt composite oxide (LiCoO ₂ ) that is currently relatively easy to synthesize, and lithium nickel composite oxide (LiNiO ₂ ) using nickel that is cheaper than cobalt. ), Lithium nickel cobalt manganese composite oxide (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ), lithium manganese composite oxide using manganese (LiMn ₂ O ₄ ), lithium nickel manganese composite oxide (LiNi Lithium transition metal-containing composite oxides such as _0.5 Mn _0.5 O ₂ ) have been proposed.

  In these lithium transition metal-containing composite oxides, the influence of the primary particle shape on various battery characteristics is large. For example, when the primary particles of the lithium transition metal-containing composite oxide have a particle shape such that a specific crystal plane appears on the particle surface, the positive electrode active material is caused by such particle shape and high crystallinity. It is known that good battery characteristics can be obtained.

  For example, in Japanese Patent Application Laid-Open No. 2001-210324, when a lithium manganese composite oxide having an octahedral shape and a spinel crystal structure is used as a positive electrode active material, the cycle characteristics are improved. Is disclosed. This is because, by making the particle shape of the primary particles octahedral, the expansion and contraction of the crystal lattice that accompanies charging / discharging is easily absorbed between the particles, and therefore the conductive material that is one of the components of the positive electrode This is considered to be because the decrease in conductivity of the positive electrode active material due to poor contact is suppressed.

  On the other hand, even in a lithium nickel-containing composite oxide having a layered rock salt type crystal structure, its primary particles are made into self-shaped particle shapes, that is, particle shapes with unique crystal planes developed to enhance the crystallinity. Is considered to contribute to improving the cycle characteristics.

In fact, in the positive electrode active material having a layered rock salt type crystal structure, the primary particles can have a self-shaped particle shape. For example, “Denis Kramer and Gerbrand Ceder,“ Tailoring the Morphology of LiCoO ₂ : A First Principles Study ”, Chemistry of Materials, 2009, 21 (16), pp3799-3809” In a lithium cobalt composite oxide having a crystal structure, the possibility that primary particles having a particle shape close to an octahedral shape from a hexagonal plate shape is generated is disclosed.

  In the case of a positive electrode active material having a layered rock salt type crystal structure, the surface from which Li ions can move during charging / discharging is only a plane parallel to the c plane, and the movement of Li ions in the c-axis direction is substantial. Is difficult. That is, in the positive electrode active material having a hexagonal plate shape as the particle shape, the ratio of the (003) plane where Li ions cannot be inserted and desorbed is large as the ratio of the primary particles in contact with the electrolyte to the entire surface area. ) Since the ratio of the surfaces capable of inserting / desorbing Li ions other than the surface becomes small, it becomes difficult to insert and desorb Li ions as a whole, and it is difficult to improve the output characteristics and charge / discharge characteristics.

  On the other hand, in the positive electrode active material in which the particle shape is an octahedral shape, the proportion of the (003) plane in the entire surface area of the primary particles is smaller than in the positive electrode active material in which the particle shape is a hexagonal plate shape. It is considered that the surface area on which Li ions can be inserted and desorbed increases, and that the shape has an advantageous effect on the output characteristics, charge / discharge characteristics, and cycle characteristics.

  As an example of a lithium nickel-containing composite oxide having a layered rock salt type crystal structure in which the primary particles have an octahedral shape, WO 2012/164141 (Japanese Patent Publication No. 2014-523383) discloses a cobalt solution, In a crystallization process in which a substance containing ammonia and an alkali hydroxide are simultaneously reacted, cobalt hydroxide particles containing octahedral primary particles are obtained by controlling the cobalt concentration and pH, and the cobalt hydroxide particles are fired. Cobalt oxide particles are obtained, and further, the cobalt oxide particles and the lithium compound are mixed and fired, thereby comprising a layered rock salt type crystal structure and comprising lithium cobalt oxide containing octahedral primary particles. A positive electrode active material is disclosed.

  However, lithium cobalt oxide has a lower charge / discharge capacity than lithium nickel oxide, and cannot be said to have a sufficient charge / discharge capacity from the viewpoint of increasing the capacity of the battery. Moreover, it is difficult to synthesize lithium nickel oxide having a layered rock salt structure by a similar process for cation mixing described later.

Also, “Yongseon Kim,“ Lithium Nickel CobaltManganese Oxide Synthesized Using Alkali Chloride Flux: Morphology and Performance As a Cathode Material for Lithium Ion Batteries ”, ACS Applied Materials & Interfaces, 2012, 4 (5), pp 2329-2333 LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811) containing octahedral primary particles synthesized by a flux method using NaCl as a flux is disclosed.

However, although it can be confirmed by SEM that the particle shape of the primary particles is an octahedral shape, the powder X-ray diffraction pattern shows that the ratio of the X-ray diffraction intensity attributed to the (003) plane and the (104) plane is “ “(003) / (104)” is as small as about 0.9. For this reason, cation mixing, that is, Ni that should enter the 3b site of the layered rock salt type crystal structure (α-NaFeO ₂ type) due to the approximation of the ionic radii of Ni ²⁺ and Li ⁺ , is Li It is suggested that there is a phenomenon of mixing into the 3a site to be entered, and as a result, in the secondary battery using such a lithium nickel-containing composite oxide, its charge / discharge capacity is originally assumed. It is lower than the value.

JP 2001-210324 A WO2012 / 164141 (Special Table 2014-523383)

Denis Kramer and Gerbrand Ceder, “Tailoringthe Morphology of LiCoO2: A First Principles Study”, Chemistry of Materials, 2009, 21 (16), pp3799-3809 Yongseon Kim, “Lithium Nickel CobaltManganese Oxide Synthesized Using Alkali Chloride Flux: Morphology and Performance As a Cathode Material for Lithium Ion Batteries”, ACS Applied Materials & Interfaces, 2012, 4 (5), pp 2329-2333

  The present invention improves the cycle characteristics without impairing the excellent charge / discharge capacity of the positive electrode active material excellent in both charge / discharge characteristics and cycle characteristics, more specifically, the lithium nickel-containing composite oxide. Another object of the present invention is to provide a lithium nickel-containing composite oxide having octahedral primary particles and having a layered rock salt type crystal structure.

  One embodiment of the present invention relates to a lithium nickel-containing composite oxide mainly containing nickel (Ni) as a transition metal, and the lithium nickel-containing composite oxide has a layered rock salt type crystal structure and Cu as an X-ray source. The ratio of the height of the peak attributed to the (003) plane and the (104) plane obtained from powder X-ray diffraction using -Kα ray is 1.20 or more, and the (003) plane and the (104) plane are The ratio of the integrated intensity of the peak to which it belongs is 1.15 or more, and includes octahedral-shaped primary particles, and the ratio of the number of primary particles in the octahedral shape to the number of all primary particles is 1.0% or more. It is characterized by being.

  In the lithium nickel-containing composite oxide of the present invention, it is preferable that an average particle size of all the primary particles is in a range of 0.8 μm to 15 μm.

  The lithium nickel-containing composite oxide of the present invention preferably has a Li seat occupancy of 96.0% or more at the 3a site of the layered rock salt type crystal structure, which is determined by the Rietveld analysis method.

The lithium nickel-containing composite oxide of the present invention preferably contains cobalt (Co) or aluminum (Al) as an additive element. Further, the lithium nickel-containing composite oxide has a general formula: Li _{1 + u} Ni _x Co _y Al _z M _t O ₂ (where −0.03 ≦ u ≦ 0.10, x + y + z + t = 1, 0.65 ≦ x ≦ 1.00, 0 ≦ y ≦ 0.35, 0 ≦ z ≦ 0.10, 0 ≦ t ≦ 0.15, where M is Mn, Fe, Ti, V, Mg, Zr, Sr, Si, W 1 or more elements selected from the group consisting of Mo, Cr, and Nb).

Another aspect of the present invention relates to a method for producing a lithium-nickel-containing composite oxide, which has a layered rock salt type crystal structure and contains nickel (Ni) mainly as a transition metal. Mixing a hydroxide or nickel-containing composite oxide, a lithium compound, and an alkali metal compound other than lithium to obtain a mixed powder;
Firing the mixed powder at a temperature in the range of 650 ° C. to 800 ° C. to obtain sintered particles;
A cleaning step of cleaning the sintered particles, removing a lithium component derived from the lithium compound and acting as a flux, and a component derived from an alkali metal compound other than lithium acting as the flux;
With
Mainly containing nickel (Ni) as a transition metal, having a layered rock salt type crystal structure, and belonging to (003) plane and (104) plane obtained from powder X-ray diffraction using Cu—Kα ray as an X-ray source The ratio of the peak height to be 1.20 or more, the ratio of the integrated intensity of the peaks belonging to the (003) plane and the (104) plane is 1.15 or more, and octahedral primary particles A lithium nickel-containing oxide having a ratio of the number of primary particles of the octahedral shape to the number of all primary particles is 1.0% or more,
It is characterized by that.

  In the mixing step, the nickel-containing composite hydroxide or the metal element in the nickel-containing composite oxide, that is, the total material of atoms of nickel (Ni), cobalt (Co), aluminum (Al), and additive element M The alkali metal compound is mixed so that the ratio of the substance amount of the alkali metal element other than lithium in the alkali metal compound other than lithium to the amount is in the range of 0.04 to 1.0. It is preferable to do.

  In this case, in the mixing step, as the alkali metal compound other than lithium, one or more alkali metals selected from sodium (Na) and potassium (K) are contained, chlorides, carbonates, sulfates, Alternatively, it is preferable to use a mixture thereof.

  In the mixing step, the ratio of the amount of Li atoms in the lithium compound to the amount of atoms of metal elements in the nickel-containing composite hydroxide or nickel-containing composite oxide is 0.98 to 2 The lithium compound is preferably mixed so that the range is 0.00.

  The firing time in the firing step is preferably in the range of 1 hour to 72 hours.

  Yet another embodiment of the present invention relates to a non-aqueous electrolyte secondary battery, the secondary battery comprising a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte. The lithium nickel-containing composite oxide is used.

  According to the present invention, in the lithium nickel-containing composite oxide having a layered rock salt type crystal structure, the shape of a part of the primary particles is obtained without impairing the excellent charge / discharge capacity of the lithium nickel-containing composite oxide. By adopting an octahedral shape, it is possible to provide a positive electrode active material having improved cycle characteristics while maintaining excellent charge / discharge capacity.

  Moreover, according to the present invention, a method capable of efficiently producing such a lithium nickel-containing composite oxide even in industrial scale production can be provided.

  For this reason, the industrial significance of the present invention is extremely large.

FIG. 1 is an SEM photograph (10,000 times) showing primary particles of octahedral shape of the lithium nickel-containing composite oxide obtained in Example 1 of the present invention. FIG. 2 is an SEM photograph (1000 times) of the lithium nickel-containing composite oxide obtained in Example 1 of the present invention. FIG. 3 is a flowchart showing the production process of the lithium nickel-containing composite oxide of the present invention. FIG. 4 is an SEM photograph (5,000 times) showing secondary particles of a lithium nickel-containing composite oxide having a conventional particle shape. FIG. 5 is a schematic cross-sectional view of a 2032 type coin battery used for battery evaluation.

  As described above, in the lithium nickel-containing composite oxide having a layered rock salt type crystal structure, the shape of the primary particles is the octahedral shape in the same manner as the lithium manganese-containing composite oxide having a spinel type crystal structure. This suggests that the cycle characteristics can be improved. However, in the lithium-nickel-containing composite oxide having a layered rock salt type crystal structure containing the octahedral primary particles obtained so far, in a non-aqueous electrolyte secondary battery using this as a positive electrode material, The problem that the charge / discharge capacity becomes low cannot be solved.

  The present inventors diligently investigated the relationship between the flux in the flux method and the primary particle shape, crystallinity, charge / discharge capacity, and cycle characteristics of the lithium nickel-containing composite oxide having a layered rock salt type crystal structure. . As a result, by adding a specific flux to the nickel-containing composite hydroxide or nickel-containing composite oxide, which is a precursor, together with a lithium compound and firing, the primary structure contains octahedral-shaped primary particles. It was found that a lithium-nickel-containing composite oxide having a lamellar rock salt type crystal structure with small disturbance, high crystallinity, and large primary particle size can be obtained.

  The present invention has been completed based on this finding. Hereinafter, embodiments of the present invention will be described in detail.

(1) Lithium nickel-containing composite oxide The present invention relates to a lithium nickel-containing composite oxide mainly containing nickel (Ni) as a transition metal. In particular, the lithium nickel-containing composite oxide of the present invention has a layered rock salt type crystal structure, and is obtained from powder X-ray diffraction using Cu—Kα rays as an X-ray source on the (003) plane and the (104) plane. The ratio of the peak height to which it belongs is 1.20 or more, the ratio of the integrated intensity of the peaks to the (003) plane and (104) plane is 1.15 or more, and the octahedral shape is primary. A ratio of the number of primary particles of the octahedral shape to the number of all primary particles is 1.0% or more.

[composition]
The present invention is widely applied to lithium nickel-containing composite oxides having a layered rock salt type crystal structure and mainly containing nickel (Ni) as a transition metal. Note that “mainly including nickel” means that nickel is included in a ratio of 0.5 or more in terms of the number of atoms with respect to the total amount of transition metal and additive metal elements excluding lithium. In particular, the present invention is suitably applied to a positive electrode active material made of a lithium nickel-containing composite oxide containing cobalt (Co) or aluminum (Al) as an additive element.

More specifically, the lithium nickel-containing composite oxide of the present invention has a general formula: Li _{1 + u} Ni _x Co _y Al _z M _t O ₂ (where −0.03 ≦ u ≦ 0.10, x + y + z + t = 1, 0.65 ≦ x ≦ 1.00, 0 ≦ y ≦ 0.35, 0 ≦ z ≦ 0.10, 0 ≦ t ≦ 0.15, where M is Mn, Fe, Ti, V, Mg, Zr , Sr, Si, W, Mo, Cr, and Nb).

  In the present invention, the value of u indicating the amount of lithium (Li) is in the range of −0.03 to 0.10, preferably −0.02 to 0.05, more preferably 0 to 0.04. Adjusted. Thereby, in a secondary battery using the lithium nickel-containing composite oxide as a positive electrode material, sufficient charge / discharge capacity and output characteristics can be ensured. On the other hand, when the value of u is less than −0.03, the positive electrode resistance of the secondary battery increases and the output characteristics deteriorate. On the other hand, if the value of u exceeds 0.10, the charge / discharge capacity and output characteristics of the secondary battery will be degraded.

  Nickel (Ni) is an element that contributes to increasing the potential and capacity of the secondary battery, and the value of x indicating the content thereof is 0.65 or more and 1.00 or less, preferably 0.75 or more and 0. .90 or less, more preferably 0.80 or more and 0.85 or less. In the present invention, if the value of x is less than 0.65, the charge / discharge capacity of a secondary battery using this positive electrode active material cannot be sufficiently improved.

  Cobalt (Co) is an element that contributes to improving the charge / discharge cycle characteristics of the secondary battery, and the value of y indicating the content thereof is 0.35 or less, preferably 0.10 or more and 0.30 or less. Preferably, it is adjusted to a range of 0.10 or more and 0.20 or less. In the present invention, if the value of y exceeds 0.35, in the secondary battery using this positive electrode active material, the charge / discharge capacity cannot be sufficiently improved while improving the cycle characteristics.

  Aluminum (Al) is an element that contributes to improving thermal stability, and the value of z indicating the content thereof is 0.10 or less, preferably 0.01 or more and 0.08 or less, more preferably 0.01. It is adjusted to a range of 0.05 or less. When the value of z exceeds 0.10, the metal element contributing to the Redox reaction is decreased, and the charge / discharge capacity is decreased.

  Also in the lithium nickel-containing composite oxide of the present invention, in order to further improve the durability and output characteristics of the secondary battery, it is also possible to contain an additional additive element in addition to nickel, cobalt, and aluminum. . Such additive elements include manganese (Mn), iron (Fe), titanium (Ti), vanadium (V) magnesium (Mg), zirconium (Zr), strontium (Sr), silicon (Si), W (tungsten). ), Mo (molybdenum), Cr (chromium), and Nb (niobium) can be used.

  When these are contained, the content of the additive element is preferably adjusted to an atomic ratio with respect to the total amount of the transition metal and the additive element of 0.15 or less, preferably 0.10 or less.

  Aluminum and the additional additive element may be uniformly dispersed inside the primary particles and / or secondary particles of the lithium nickel-containing composite oxide, or may be coated on the particle surfaces. Furthermore, the particle surface may be coated after being uniformly dispersed inside the particle.

  The contents of lithium, nickel, cobalt, aluminum, and additional additive elements can be measured by ICP emission spectroscopy.

[Crystal structure and lithium seat occupancy]
The lithium nickel-containing composite oxide of the present invention has a layered rock salt type crystal structure and high crystallinity. Specifically, each site of 3a, 3b, and 6c in the particles constituting the lithium nickel-containing composite oxide of the present invention is represented by [Li _{1 + u} ] _3a [Ni _x Co _y Al _z ] _3b [O ₂ ] _6c . In this case, the lithium site occupancy of the 3a site obtained from Rietveld analysis of powder X-ray diffraction is 96.0% or more, preferably 96.5% or more, more preferably 97.0% or more, and further preferably 98.0. % Or more. By having such a high lithium seat occupancy, a high charge / discharge capacity can be realized in a secondary battery using this lithium nickel-containing composite oxide as a positive electrode material.

[Peak height ratio]
In the layered rock salt type crystal structure of the lithium nickel-containing composite oxide of the present invention, the peaks attributed to the (003) plane and the (104) plane obtained from powder X-ray diffraction using Cu—Kα rays as the X-ray source The ratio ((003) / (104)) of the height (the value obtained by subtracting the background from the maximum value of the peak) is 1.20 or more. It is considered that the larger the peak height ratio, the larger the crystallite size in the (003) direction (c-axis direction). As a result, the (003) plane in which Li is difficult to insert and desorb. It is considered that self-shaped crystals with a small ratio of γ are obtained, which contributes to improvement of battery characteristics.

  The peak height ratio is preferably 1.50 or more, and more preferably 2.00 or more.

[Peak intensity ratio]
In the layered rock salt type crystal structure of the lithium nickel-containing composite oxide of the present invention, the peaks attributed to the (003) plane and the (104) plane obtained from powder X-ray diffraction using Cu—Kα rays as the X-ray source The integral intensity ratio of “(003) / (104)” is 1.15 or more. The disorder of the crystal structure can be determined from the ratio of the peak intensities. For example, when cation mixing occurs, that is, when the crystal structure approaches from a layered rock salt type to a rock salt type, the X-ray diffraction intensity attributed to the (003) plane becomes small. At this time, the ratio value of the peak intensity becomes small. Therefore, it means that the larger the ratio of peak intensities is, the less the layered rock salt structure is.

  In the present invention, this peak intensity ratio is preferably 1.20 or more, and more preferably 1.25 or more.

[Particle properties]
The lithium nickel-containing composite oxide of the present invention is characterized by containing octahedral primary particles. Here, the octahedron shape includes not only a complete octahedron shape but also a shape lacking a part of the apex or side if it can be confirmed that the octahedron shape is substantially formed. For example, a shape close to an octahedron in which smooth crystal planes intersect each other and a clear ridge line is formed, or a vertex formed by intersecting four sides of the octahedron is not completely formed, but a shape of a surface or a ridge The shape formed by the above, the shape in which other crystal planes appear in the ridge portion formed by intersecting two faces of the octahedron, and the shape lacking a part of these shapes are also the octahedrons of the present invention. Included in the shape.

  The primary particle having a self-shaped shape derived from a layered rock salt structure is considered to indicate that the particle has high crystallinity, and the primary particle is caused by insertion and desorption of lithium ions accompanying charge and discharge. Since it is difficult for the crystal structure to change, it is considered that it contributes to the improvement of charge / discharge cycle characteristics. As described above, the self-shaped particle shape other than the octahedral shape may be a hexagonal plate shape. Compared with the octahedral shape and this hexagonal flat plate shape, the surface area of the Li ion insertion / desorption plane other than the plane parallel to the c-plane increases. The shape is considered to have an advantageous effect on the discharge characteristics and cycle characteristics.

  The octahedral shape can be confirmed and judged by microscopic observation using a scanning electron microscope (SEM) or the like and other known means.

  In the present invention, the primary particles of the above shape share a crystal plane, or when other primary particle crystals grow from a part of the surface of the primary particle, and the primary particles have a complicated crystal plane. In the case where secondary particles composed of a polyhedron having an octahedron as a structural unit are formed in common, the primary particles are assumed to have an octahedral shape.

  The particle property in the lithium nickel-containing composite oxide of the present invention is preferably mainly composed of relatively large primary particles without grain boundaries, but the lithium nickel of the present invention also includes secondary particles. Included in the composite oxide.

[Ratio of primary particles in octahedral shape]
Furthermore, in the lithium nickel-containing composite oxide of the present invention, not all primary particles must have an octahedral shape. That is, in the primary particles constituting the lithium nickel-containing composite oxide of the present invention, the higher the abundance ratio of primary particles having an octahedral shape, the more preferable, but even if the amount of primary particles having an octahedral shape is small, the output characteristics. In addition to the improvement in charge and discharge characteristics, due to the high crystallinity, the effect of improving the cycle characteristics of the entire positive electrode active material made of a lithium nickel-containing composite oxide containing octahedral primary particles is produced. In view of such characteristics, the abundance ratio of the octahedral primary particles in the present invention needs to be 1.0% or more (range of 1.0% to 100%) of the entire primary particles. . The abundance ratio is preferably 2.0% or more, and more preferably 2.5% or more. Although the upper limit is not limited, if the abundance ratio is in the range of 1.0% to 5.0%, the effect of improving the cycle characteristics of the positive electrode active material can be sufficiently obtained.

  The abundance ratio of the octahedral primary particles can also be measured by observation using a scanning electron microscope (SEM). Specifically, after taking an SEM photograph of one field of view or more, the number of all primary particles per unit area and the number of primary particles in the octahedral shape is counted, and the number of primary particles in the number of primary particles in the octahedral shape is counted. Find the ratio to the number.

[Average particle size]
In the lithium nickel-containing composite oxide of the present invention, the average particle size of all primary particles including the octahedral primary particles is preferably in the range of 0.8 μm to 15 μm, more preferably in the range of 1.2 μm to 15 μm. More preferably, it is in the range of 2.0 μm to 15 μm. By making the average particle size of the primary particles 0.8 μm or more, the positive electrode active material can be composed of relatively large primary particles having no grain boundary, thereby improving its cycle characteristics and storage. The characteristics can also be improved. However, when the average particle size of the primary particles exceeds 15 μm, the specific surface area becomes too small, and the output characteristics are significantly deteriorated.

  The average particle diameter of the primary particles can be measured by observation using a scanning electron microscope (SEM). Specifically, after taking SEM photographs of one field of view or more, the maximum diameter of a total of 200 or more primary particles is measured, and the average value (arithmetic mean) of these measured values is calculated. be able to.

(2) Method for Producing Lithium Nickel-Containing Composite Oxide The method for producing a lithium nickel-containing composite oxide of the present invention comprises: a) a nickel having a layered rock salt type crystal structure and mainly containing nickel (Ni) as a transition metal A mixed powder is obtained by mixing a lithium-containing composite hydroxide or nickel-containing composite oxide, a lithium compound, and a compound of an alkali metal other than lithium (hereinafter sometimes abbreviated as “alkali metal D”). B) firing the mixed powder at a temperature in the range of 650 ° C. to 800 ° C. in an oxygen atmosphere to obtain sintered particles; c) washing the sintered particles; And a cleaning step of removing the element D.

  Through these steps, the transition metal mainly contains nickel (Ni), has a layered rock salt type crystal structure, includes octahedral primary particles, and uses Cu-Kα rays as an X-ray source. Lithium nickel in which the ratio of peak heights attributed to (003) plane and (104) plane obtained from powder X-ray diffraction is 1.20 or more, and preferably the integrated intensity ratio of this peak is 1.15 or more A contained oxide can be obtained.

  In order to maintain an appropriate peak height ratio, an appropriate peak intensity ratio, and a high Li seat occupancy, it is necessary to perform firing at a temperature of 650 ° C. or higher and 800 ° C. or lower. When firing at a temperature exceeding 800 ° C., cation mixing proceeds as described above, and an appropriate peak height ratio, an appropriate peak intensity ratio, and a high Li seat occupancy can be maintained. Can not. On the other hand, when firing is performed at a temperature lower than 650 ° C., crystal growth does not proceed sufficiently, so that a self-shaped crystal as shown in the present invention cannot be obtained.

  In the present invention, instead of conventional NaCl, an alkali metal D compound is used as a flux, so that it can be dissolved between crystals (solute) and flux (solvent) even at a firing temperature of 800 ° C. or lower. In addition, since reprecipitation occurs, it is possible to obtain primary particles having a self-shaped octahedral shape in which crystal growth is promoted and a specific crystal plane is exposed on the surface.

Note that the lithium nickel-containing composite oxide finally obtained is Li _{1 + u} Ni _x Co _y Al _z M _t O ₂ (where −0.03 ≦ u ≦ 0.10, x + y + z + t = 1, 0.65 ≦ x ≦ 1.00, 0 ≦ y ≦ 0.35, 0 ≦ z ≦ 0.10, 0 ≦ t ≦ 0.15, where M is Mn, Fe, Ti, V, Mg, Zr, Sr, Si, Nickel-containing composite hydroxide or nickel-containing oxide mixed in the mixing step so as to have a composition represented by one or more elements selected from the group consisting of W, Mo, Cr, and Nb), and It is preferable to adjust the input amount of each lithium compound.

[precursor]
As the precursor of the lithium nickel-containing composite oxide of the present invention, a nickel-containing composite hydroxide containing mainly nickel (Ni) as a transition metal is used.

  Any known method can be employed for the apparatus, process, means, conditions, etc. for crystallization of the nickel-containing hydroxide by the coprecipitation method.

  Typically, a raw material aqueous solution composed of a mixed aqueous solution containing nickel salt, cobalt salt and other metal salt, alkaline solution such as sodium hydroxide solution as pH adjuster, and ammonia as ammonium ion supplier. By adding water or the like, the temperature of the reaction solution is maintained at 40 ° C. to 60 ° C., the pH is maintained at 11.1 to 13.0 based on the liquid temperature of 25 ° C., and the ammonia concentration is maintained at 3 g / L to 25 g / L. Meanwhile, the nickel-containing composite hydroxide is coprecipitated.

  Prior to the mixing step, the nickel-containing composite hydroxide is preferably heat-treated in a temperature range of 105 ° C to 800 ° C, more preferably in a temperature range of 300 ° C to 600 ° C. Such heat treatment can reduce the moisture remaining in the nickel-containing composite hydroxide up to the firing step. In other words, since the nickel-containing composite hydroxide can be converted to the nickel-containing composite oxide, it is possible to prevent the ratio of the number of metal atoms and the number of lithium atoms in the produced positive electrode active material from being varied. . However, all the nickel-containing composite hydroxides are necessarily converted to nickel-containing composite oxides, as long as moisture can be removed to such an extent that the ratio of the number of metal atoms and the number of lithium atoms in the positive electrode active material does not vary. There is no need.

[Mixing process]
The mixing method in the mixing step is not particularly limited as long as they can be mixed uniformly. For example, mixing using a mortar, shaker mixer, readyge mixer, Julian mixer, V blender, etc. It is possible to mix using a mixer.

(A) Mixing ratio of alkali metal D compound in the mixing step The mixing ratio of the alkali metal D compound in the mixing step is the metal element in the nickel-containing composite hydroxide or nickel-containing composite oxide, ie, nickel (Ni ), Cobalt (Co), aluminum (Al), and the total amount of atoms (or number of atoms) of the additive element M, the amount (or number of atoms) of alkali metal D atoms in the alkali metal D compound. Is set to be in the range of 0.04 to 1.0.

  The compound of the alkali metal D is a flux containing a nickel-containing composite hydroxide or a mixture of a nickel-containing composite oxide and a lithium compound, or a lithium nickel-containing composite oxide obtained by synthesis thereof as a solute ( And the primary particles of the lithium-nickel-containing composite oxide become an octahedral shape.

  When conventional NaCl is used as the flux, the occupancy rate of lithium in the positive electrode active material is reduced due to cation mixing. On the other hand, as described above, the present invention prevents the cation mixing in the firing step by using an alkali metal D compound as the flux, and has primary particles having a self-shaped octahedral shape by promoting crystal growth. Can be obtained.

  The mixing ratio of the alkali metal D compound is such that the octahedral shape of the primary particles of the lithium nickel-containing composite oxide, the abundance ratio of the primary particles of the octahedral shape in the entire primary particles, and further the promotion of crystal growth of the solute, etc. Considering the control factor of the flux method, etc., it is appropriately set within the above range. This mixing ratio is preferably set to be in the range of 0.04 to 1.0, more preferably in the range of 0.10 to 0.50.

(B) Substance type of flux used in the mixing step As the alkali metal D compound, compounds such as sodium (Na), potassium (K), rubidium (Rb) can be widely applied, but they are easily available. From the viewpoint of ease of handling and handling, it is preferable to use a hydroxide, chloride, carbonate, sulfate, or a mixture thereof containing one or more alkali metals selected from sodium and potassium. Since sodium and potassium are less likely to enter the layered rock salt type crystal structure as compared with lithium, the amount of impurities due to flux in the target lithium nickel-containing composite oxide can be suppressed.

  Of these compounds, they are highly soluble in water, easy to be removed by washing in the washing process, have a relatively low melting point, and contain impurities other than alkali metals (for example, chlorine and sulfur constituting the compounds). Therefore, it is preferable to use an alkali metal hydroxide.

(C) Mixing ratio of lithium compound in the mixing step The mixing ratio of the lithium compound in the mixing step depends on the mixing ratio of the alkali metal D compound, and the metal element in the nickel-containing composite hydroxide or nickel-containing composite oxide That is, the mass of lithium (Li) atoms in the lithium compound (or the total mass of atoms of nickel (Ni), cobalt (Co), aluminum (Al), and additive element M) (or the number of atoms) (or The ratio of the number of atoms) is preferably set to be in the range of 0.98 to 2.00, preferably in the range of 1.00 to 1.50. A part of the lithium compound is considered to act as a flux together with the alkali metal D compound. Therefore, the final lithium content is preferably in the range of 0.97 to 1.10 with respect to the total content of nickel, cobalt, aluminum, and additive element M in the lithium nickel-containing composite oxide. More preferably, it is in the range of 0.98 to 1.05, more preferably in the range of 1.00 to 1.04, and in consideration of the lithium component that volatilizes in the firing step, preferably a preliminary test , The mixing ratio of the lithium compound is appropriately determined. The lithium compound serving as the lithium source is selected from hydroxides, chlorides, oxides, other inorganic salts, or any organic salt from the viewpoint of ease of handling and availability.

[Baking process]
In the firing step, the mixed powder of the nickel-containing composite hydroxide or nickel-containing composite oxide, the lithium compound, and the alkali metal D compound obtained in the mixing step is at a temperature in the range of 650 ° C to 800 ° C. It is a step of firing to obtain sintered particles (sintered lithium nickel-containing composite oxide).

  The furnace used in the firing step is not particularly limited as long as the mixed powder obtained in the mixing step can be fired in the atmosphere or in an oxygen stream, and either a batch type or continuous type furnace is used. Can be used.

(A) Firing atmosphere The atmosphere in the firing step is preferably an oxidizing atmosphere including an air atmosphere because cation mixing is less likely to occur. More specifically, an atmosphere having an oxygen concentration of 18% by volume to 100% by volume, that is, a mixed atmosphere of oxygen having the above oxygen concentration and an inert gas (including an air atmosphere) can be employed. Usually, firing is performed in an air stream or an oxygen stream, but it is particularly preferable to perform the firing in an oxygen stream in view of battery characteristics.

(B) Firing temperature The firing temperature in the first firing step is in the range of 650 ° C to 800 ° C, preferably in the range of 700 ° C to 800 ° C. When the firing temperature is less than 650 ° C., the flux composed of the alkali metal D compound is not sufficiently melted, and as a result, the crystal growth of the lithium nickel composite oxide serving as the solute may not be promoted. On the other hand, when the firing temperature exceeds 800 ° C., the primary particles can be enlarged, but cation mixing occurs and the crystallinity thereof decreases. Further, excessive volatilization of the lithium component occurs from the lithium nickel composite oxide, and the deviation from the predetermined composition becomes large, which may adversely affect the characteristics.

(C) Firing time In the firing step, the time (firing time) maintained at the firing temperature is preferably in the range of 1 hour to 72 hours, more preferably in the range of 5 hours to 48 hours. When firing for more than 72 hours, the particle size increases, but volatilization of the lithium component from the lithium-nickel composite oxide proceeds excessively, which may lead to a decrease in crystallinity. On the other hand, when the firing time is less than 1 hour, crystal growth does not proceed sufficiently, and it is considered difficult to obtain primary particles of self-shaped octahedral shape.

[Washing process]
The cleaning step is to wash the sintered particles obtained in the firing step and is derived from the lithium compound added in the mixing step, but does not constitute a lithium nickel-containing composite oxide, but a lithium component that acts as a flux, and In this step, the component derived from the alkali metal D compound added as a flux in the mixing step, that is, the alkali metal D present in the elemental state is removed.

  The cleaning method is not particularly limited, and a known method can be used. For example, a lithium component acting as a flux and a liquid capable of dissolving the alkali metal D component, specifically, the sintered particles are put into water and alcohol and stirred to dissolve the residue of the alkali metal D component. Thereafter, a method of filtering and drying the sintered particles by a known method can be employed. However, regardless of the method used, the sintered particles may be washed so that the content of alkali metal D contained in the sintered particles after the washing step is 0.5% by mass or less. Necessary.

  In addition, the conditions for controlling the content of the alkali metal D contained in the sintered particles after the cleaning step to be within the above range vary depending on the amount of the sintered particles to be cleaned and their properties, and are uniquely determined. I can't. For this reason, it is preferable to appropriately select the cleaning conditions after carrying out a preliminary test.

Similarly to the alkali metal D, since lithium has high solubility in water and alcohol, lithium existing on the surface of the sintered particles is eluted during the cleaning process and is replaced with hydrogen ions (H ⁺ ) in the solvent. Proton exchange reaction may occur. In order to prevent such a proton exchange reaction, it is preferable to use an aqueous solution containing lithium ions in which a lithium compound such as lithium hydroxide or lithium carbonate is dissolved.

  In the conventional method for producing a lithium nickel-containing composite oxide, remixing with a lithium compound after the cleaning step and refiring may be performed. This is because a proton exchange reaction may occur during the washing process, and the amount of lithium in the sintered particles may be insufficient. However, in the method for producing a lithium nickel-containing composite oxide of the present invention, such remixing and refiring steps are not provided. This is to prevent the octahedral structure of some of the primary particles from being destroyed by such a process.

(3) Non-aqueous electrolyte secondary battery The non-aqueous electrolyte secondary battery of the present invention includes the same components as a general non-aqueous electrolyte secondary battery, such as a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte solution. The embodiment described below is merely an example, and the nonaqueous electrolyte secondary battery of the present invention is applied to various modified and improved embodiments based on the embodiment described in the present specification. It is also possible to do.

[Components]
a) Positive electrode Using the positive electrode active material for a non-aqueous electrolyte secondary battery obtained by the present invention, for example, a positive electrode of a non-aqueous electrolyte secondary battery is produced as follows.

  First, a conductive material and a binder are mixed with the powdered positive electrode active material obtained according to the present invention, and activated carbon and a solvent such as viscosity adjustment are added as necessary, and these are kneaded and mixed. A material paste is prepared. 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. For example, when the solid content of the positive electrode mixture excluding the solvent is 100 parts by mass, the content of the positive electrode active material is 60 parts by mass to 95 parts by mass as in the case of the positive electrode of a general non-aqueous electrolyte secondary battery. The content of the material can be 1 part by mass to 20 parts by mass, and the content of the binder can be 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 in order to increase the electrode density. In this way, a sheet-like positive electrode can be produced. This positive electrode can be cut into a suitable size according to the intended 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.

  The conductive material is added to give an appropriate conductivity to the electrode. As the conductive material, for example, graphite (natural graphite, artificial graphite, expanded graphite, etc.), and carbon black materials such as acetylene black and ketjen black can be used.

  The binder plays a role of tethering the positive electrode active material particles. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluoro rubber, ethylene propylene diene rubber, styrene butadiene, cellulose resin, poly Acrylic acid or the like can be used.

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

b) Negative electrode The negative electrode is made of metal lithium, lithium alloy or the like, or a negative electrode active material capable of absorbing and desorbing lithium ions mixed with a binder and added with a suitable solvent to form a paste. It is applied to the surface of a metal foil current collector such as copper, dried, and compressed to increase the electrode density as necessary.

  Examples of the negative electrode active material include lithium-containing materials such as metallic lithium and lithium alloys, natural graphite capable of occluding and desorbing lithium ions, sintered organic compounds such as artificial graphite and phenolic resins, and carbon materials such as coke. A powdery body 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.

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

d) 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, ethylmethyl carbonate, and dipropyl carbonate, and tetrahydrofuran, 2-methyltetrahydrofuran. And one kind selected from ether compounds such as dimethoxyethane, sulfur compounds such as ethyl methyl sulfone and butane sultone, phosphorus compounds such as triethyl phosphate and trioctyl phosphate, or a mixture of two or more kinds. it can.

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.

[Nonaqueous electrolyte secondary battery]
The non-aqueous electrolyte secondary battery of the present invention composed of the positive electrode, the negative electrode, the separator, and the non-aqueous electrolyte can be formed into various shapes such as a cylindrical shape and a laminated shape.

  In any case, the positive electrode and the negative electrode are laminated via a separator to form an electrode body, which is impregnated with a non-aqueous electrolyte solution, and the positive electrode current collector and the positive electrode terminal connected to the outside And a negative electrode current collector and a negative electrode terminal leading to the outside are connected using a current collecting lead or the like, and then sealed in a battery case to complete a non-aqueous electrolyte secondary battery.

[Characteristics of non-aqueous electrolyte secondary battery]
Since the non-aqueous electrolyte secondary battery of the present invention uses the positive electrode active material of the present invention as the positive electrode material as described above, it is excellent in both charge / discharge capacity and cycle characteristics.

  For example, when a 2032 type coin battery as shown in FIG. 5 is configured using the positive electrode active material of the present invention, an initial discharge capacity of 180 mAh / g or more, preferably 185 mAh / g or more, and 85% or more, Preferably, a 500 cycle discharge capacity maintenance ratio of 90% or more can be achieved simultaneously.

[Usage]
Since the nonaqueous electrolyte secondary battery of the present invention is excellent in both charge / discharge capacity and cycle characteristics as described above, the power source for small portable electronic devices (such as notebook personal computers and cellular phone terminals) and motor drive It is suitable for any power source.

  Hereinafter, the present invention will be described in more detail using examples and comparative examples. In addition, a present Example is one of the illustrations of this invention, and unless it deviates from the summary of this invention, it is not limited to these.

Example 1
(1) Preparation of precursor (nickel-containing composite hydroxide) First, nickel sulfate hexahydrate and cobalt sulfate heptahydrate are dissolved in water at an atomic ratio of Ni: Co = 82: 15, A 1.9 mol / L raw material aqueous solution was prepared. While the aqueous solution of sodium hydroxide as a pH adjusting agent and ammonia water as an ammonium ion supplier are dropped into this raw material aqueous solution, the liquid temperature is adjusted to 50 ° C. and the pH value (liquid temperature based on 25 ° C.) is adjusted to 12.0. Then, nickel-cobalt composite hydroxide was coprecipitated.

  Next, water was added to the obtained nickel cobalt composite hydroxide to form a slurry. While stirring the slurry, a 1.7 mol / L sodium aluminate aqueous solution and 64% by mass sulfuric acid as a pH adjuster were added at an atomic ratio of Ni: Co: Al = 82: 15: 3, and pH was adjusted. The value (liquid temperature 25 ° C. standard) was adjusted to 9.5, and stirring was further continued for about 1 hour to coat the nickel cobalt composite hydroxide particle surface with aluminum.

Thereafter, the slurry was washed with water, filtered, and dried to obtain a powdery aluminum-coated nickel-cobalt composite hydroxide (hereinafter referred to as “composite hydroxide”). As a result of analysis of Ni, Co, and Al components by ICP emission spectroscopy, it is confirmed that this composite hydroxide is represented by the general formula: Ni _0.82 Co _0.15 Al _0.03 (OH) ₂ It was done.

(2) Preparation of lithium nickel-containing composite oxide This composite hydroxide and lithium hydroxide monohydrate as a lithium compound (manufactured by Wako Pure Chemical Industries, Ltd., purity: 98.0% to 102.0%) Potassium hydroxide (manufactured by Kanto Chemical Co., Inc., purity 86%) as an alkali metal D compound in terms of atomic ratio (Me = Ni + Co + Al): Li: K = 1.00: 1.33: 0.348 Then, each was weighed and mixed using a mortar to obtain a mixed powder (mixing step).

  Next, the obtained mixed powder was fired in an oxygen atmosphere at a temperature of 730 ° C. for 24 hours to obtain sintered particles (firing step).

  Subsequently, the obtained sintered particles were put into a beaker, and an aqueous solution in which lithium hydroxide was dissolved in water at a concentration of 0.47 mol / L was added to perform washing and filtration (washing step).

Then, it vacuum-dried at 200 degreeC for 10 hours, and obtained lithium nickel containing complex oxide (lithium nickel cobalt aluminum complex oxide) as a positive electrode active material. As a result of measuring the element fraction (atomic ratio) of this positive electrode active material by ICP emission spectroscopy, this positive electrode active material has a general formula: Li _1.056 Ni _0.815 Co _0.145 Al _0.037 O It was confirmed that it consists of lithium nickel containing complex oxide represented by ₂ . In this positive electrode active material, a significant amount of potassium was not measured.

Moreover, as a result of analysis by powder X-ray diffraction measurement (equipment used: X'pert Pro MPD manufactured by Spectris Co., Ltd., measurement conditions: Cu-Kα ray, acceleration voltage: 45 kV), this positive electrode active material has a layered rock salt structure. (Alpha) -NaFeO ₂ structure), and the ratio of the height of peaks attributed to the (003) plane and the (104) plane is 2.16, and the (003) plane and the (104) plane It was confirmed that the ratio of the integrated intensity of the peaks belonging to is 1.30. The Li seat occupancy calculated by Rietveld analysis was 99.4%.

  Furthermore, using SEM (equipment used: JSM-7001F manufactured by JEOL Ltd.), SEM photographs of 3 fields of view were taken, and a total of 1154 primary particles were observed from the imaging, and finally obtained. In the powder of the positive electrode active material, it was confirmed that the octahedral primary particles were present without excessive aggregation. The abundance ratio of the primary particles in the octahedral shape was 3.93%. Moreover, the average particle diameter of the entire primary particles including the octahedral primary particles was 2.94 μm. FIG. 1 shows an SEM photograph (10,000 times) showing the octahedral primary particles obtained in Example 1. Moreover, the SEM photograph (1000 times) which shows the lithium nickel containing complex oxide obtained by Example 1 is shown in FIG.

  About Example 1, it shows in Table 1 about a flux seed | species, mixing ratio, baking conditions, and the composition of the obtained lithium nickel containing complex oxide. Further, in the obtained lithium nickel-containing composite oxide, the abundance ratio of the primary particles of the octahedron, the ratio of the peak height attributed to the (003) plane and the (104) plane, the ratio of the integrated intensity of the peak, the Li seat The occupation ratio is shown in Table 2.

(3) Production and Evaluation of Secondary Battery Using the obtained positive electrode active material comprising a lithium nickel-containing composite oxide as a positive electrode material for a secondary battery, evaluation of the battery characteristics, specifically charge / discharge characteristics (discharge) Capacity) and cycle characteristics (discharge capacity retention ratio) were measured and evaluated as characteristics of the obtained positive electrode active material.

  Specifically, using the obtained positive electrode active material as a positive electrode material, a 2032 type coin battery 1 as shown in FIG. 5 was produced. The 2032 type coin 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. As shown in FIG.

  The case 2 includes a gasket 2c, and the gasket 2c fixes the positive electrode can 2a and the negative electrode can 2b so as to maintain an electrically insulated state. Further, the gasket 2c also has a function of sealing the gap between the positive electrode can 2a and the negative electrode can 2b so that the inside and the outside of the case 2 are hermetically and liquid-tightly blocked.

This 2032 type coin battery 1 was produced as follows. First, 85% by mass of the positive electrode active material described above, 10% by mass of acetylene black, and 5% by mass of PVDF were weighed and mixed, and then an appropriate amount of NMP (n-methylpyrrolidone) was added to form a paste. did. This positive electrode mixture paste was applied onto an aluminum foil so that the surface density of the positive electrode active material after drying was 7 mg / cm ² , vacuum-dried at 120 ° C., and then into a disk shape having a diameter of 13 mm. The positive electrode 3a was produced by punching. In addition, lithium metal is used for the negative electrode 3b, and an equivalent mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) using 1M LiClO ₄ as a supporting salt is used for the electrolyte, and the dew point is −80 ° C. A 2032 type coin battery 1 was assembled in a controlled Ar atmosphere glove box.

[Charge / discharge characteristics]
After the 2032 type coin battery 1 is manufactured, it is left for about 24 hours, and after the open circuit voltage OCV (Open Circuit Voltage) is stabilized, the current density with respect to the positive electrode is set to 9 mA / g with respect to the weight of the positive electrode active material at 25 ° C. The battery is charged until the cut-off voltage becomes 4.3 V, and after a pause of 1 hour, a charge / discharge test is performed to measure the discharge capacity when discharged until the cut-off voltage reaches 3.0 V, and the initial discharge capacity is obtained. Thus, charge / discharge characteristics were evaluated. At this time, a multi-channel voltage / current generator (manufactured by Advantest Corporation, R6741A) was used for measuring the discharge capacity.

[Cycle characteristics]
The cycle characteristics are as follows: 85% by mass of the above positive electrode active material, 10% by mass of acetylene black, and 5% by mass of PVDF, and after mixing these, an appropriate amount of NMP (n-methylpyrrolidone) is added to the paste. I made it. By applying this positive electrode mixture paste on the aluminum foil so that the surface density of the positive electrode active material after drying is 7 mg / cm ² , vacuum drying at 120 ° C., and then cutting out to 30 mm × 50 mm, A positive electrode film was prepared. Carbon is used for the negative electrode, and a laminate cell is used for the electrolyte by using a mixed solution in which ethylene carbonate (EC) and diethyl carbonate (DEC) with 1M LiPF6 as a supporting salt are mixed at a volume ratio of 3: 7. Produced. The discharge capacity and initial discharge capacity after 500 cycles of a cycle of charging to 4.1 V and discharging to 3.0 V with a temperature of 60 ° C. and a current density with respect to the positive electrode of 360 mA / g based on the weight of the positive electrode active material The cycle characteristics were evaluated by calculating the ratio and determining the discharge capacity retention rate (500 cycle capacity retention rate).

  Table 2 shows the discharge capacity and discharge capacity retention rate of the positive electrode active material obtained in Example 1.

  Hereinafter, also in Example 2, Example 3, and Comparative Example 1, the same evaluation was made on the positive electrode active material made of the obtained lithium nickel-containing composite oxide and the secondary battery using this positive electrode active material as the positive electrode material. Went. Similarly, measurement results and evaluation results are shown in Tables 1 and 2.

(Example 2)
In the mixing step, the composite hydroxide, lithium hydroxide monohydrate, and potassium hydroxide have an atomic ratio of (Ni + Co + Al): Li: K = 1.00: 1.15: 0.174. Thus, the positive electrode active material was produced like Example 1 except having mixed. As a result of measurement by ICP emission spectroscopic analysis, this positive electrode active material is composed of a lithium nickel-containing composite oxide represented by the general formula: Li _1.010 Ni _0.818 Co _0.146 Al _0.036 O ₂ Was confirmed. Further, in this positive electrode active material, a significant amount of potassium was not measured. In addition, when 517 primary particles in total were observed from the two-view SEM photographs, the abundance ratio of the octahedral primary particles was 2.95%. Moreover, the average particle diameter of the whole primary particles including the octahedral primary particles was 2.10 μm.

(Example 3)
In the mixing step, the composite hydroxide, lithium hydroxide monohydrate, and potassium hydroxide are in the atomic ratio (Me = Ni + Co + Al): Li: K = 1.00: 1.09: 0.087. Thus, a positive electrode active material was produced in the same manner as in Example 1 except that mixing was performed. This positive electrode active material was confirmed to be composed of a lithium nickel-containing composite oxide represented by the general formula: Li _1.000 Ni _0.818 Co _0.146 Al _0.036 O ₂ . Further, in this positive electrode active material, a significant amount of potassium was not measured. In addition, when 879 primary particles in total were observed from SEM photographs of two fields of view, the abundance ratio of the octahedral primary particles was 2.19%. Moreover, the average particle diameter of the entire primary particles including the octahedral primary particles was 1.43 μm.

(Comparative Example 1)
In the mixing step, potassium hydroxide is not added, and only the composite hydroxide and lithium hydroxide monohydrate are in an atomic ratio (Me = Ni + Co + Al): Li: K = 1.00: 1.03: 0 A positive electrode active material was produced in the same manner as in Example 1 except that the subsequent washing and filtration steps were not performed. This positive electrode active material was confirmed to be composed of a lithium nickel-containing composite oxide represented by the general formula: Li _1.019 Ni _0.815 Co _0.149 Al _0.036 O ₂ . As shown in FIG. 4, from the SEM observation, the octahedral primary particles could not be confirmed, and the particles were formed by secondary particles in which the primary particles were aggregated. Note that a total of 205 primary particles were observed from an SEM photograph of one field of view. As a result, the average particle diameter of the primary particles in Comparative Example 1 was 0.48 μm.

  As a result of the above evaluation, the positive electrode active material composed of the lithium nickel-containing composite oxide having the octahedral primary particles of Examples 1 to 3 contains lithium nickel that does not have the octahedral primary particles of Comparative Example 1. It can be understood that, as compared with the positive electrode active material made of the composite oxide, the discharge capacity is maintained at the same level, the excellent cycle characteristics are exhibited, and the discharge capacity retention rate is sufficiently improved.

Further, a layered rock salt type compound LiNi _0.8 Co _0.1 Mn _0.1 O ₂ powder containing octahedral particles synthesized at 900 ° C. using the NaCl flux described in Non-Patent Document 2 ( Even when the discharge capacity of the positive electrode active material composed of [(003) / (104)] is 176 mAh / g (4.5 V-3.0 V)), the positive electrode active material of the present invention has a high discharge. In the lithium nickel-containing composite oxide of the present invention, the ratio of the height of the peak and the ratio of the intensity of the (003) plane to the (104) plane by the X-ray diffraction is high. This is probably due to the fact that the lithium seat occupancy is sufficiently high.

DESCRIPTION OF SYMBOLS 1 Coin type battery 2 Case 2a Positive electrode can 2b Negative electrode can 2c Gasket 3 Electrode 3a Positive electrode 3b Negative electrode 3c Separator

Claims (11)

  Peaks attributed to (003) plane and (104) plane obtained from powder X-ray diffraction containing mainly nickel as a transition metal, having a layered rock salt type crystal structure, and using Cu-Kα ray as an X-ray source The height ratio is 1.20 or more, the ratio of the integrated intensity of the peaks belonging to the (003) plane and the (104) plane is 1.15 or more, and includes octahedral-shaped primary particles, A lithium-nickel-containing composite oxide, wherein a ratio of the number of primary particles of the octahedral shape to the number of all primary particles is 1.0% or more.   2. The lithium nickel-containing composite oxide according to claim 1, wherein an average particle diameter of all the primary particles is in a range of 0.8 μm to 15 μm.   The lithium nickel-containing composite oxide according to claim 1 or 2, wherein the Li site occupancy at the 3a site of the layered rock salt type crystal structure is 96.0% or more, which is determined by a Rietveld analysis method.   The lithium nickel-containing composite oxide according to any one of claims 1 to 3, further comprising cobalt as the transition metal.   The lithium nickel-containing composite oxide according to claim 1, further comprising an additive element, wherein the additive element is aluminum. Li _{1 + u} Ni _x Co _y Al _z M _t O ₂ (where −0.03 ≦ u ≦ 0.10, x + y + z + t = 1, 0.65 ≦ x ≦ 1.00, 0 ≦ y ≦ 0.35, 0 ≦ z ≦ 0.10, 0 ≦ t ≦ 0.15, where M is selected from the group consisting of Mn, Fe, Ti, V, Mg, Zr, Sr, Si, W, Mo, Cr, and Nb The lithium nickel containing complex oxide in any one of Claims 1-5 which has a composition represented by the element more than a seed | species. Mixing a nickel-containing composite hydroxide or nickel-containing composite oxide, which has a layered rock salt type crystal structure and contains mainly nickel as a transition metal, a lithium compound, and an alkali metal compound other than lithium. Obtaining a powder, mixing step;
Firing the mixed powder at a temperature in the range of 650 ° C. to 800 ° C. to obtain sintered particles;
A cleaning step of cleaning the sintered particles, removing a lithium component derived from the lithium compound and acting as a flux, and a component derived from an alkali metal compound other than lithium acting as the flux;
With
Peaks attributed to (003) plane and (104) plane obtained from powder X-ray diffraction containing mainly nickel as a transition metal, having a layered rock salt type crystal structure, and using Cu-Kα ray as an X-ray source The height ratio is 1.20 or more, the ratio of the integrated intensity of the peaks belonging to the (003) plane and the (104) plane is 1.15 or more, and includes octahedral-shaped primary particles, A lithium nickel-containing oxide having a ratio of the number of primary particles of the octahedral shape to the number of all primary particles of 1.0% or more is obtained.
A method for producing a lithium nickel-containing composite oxide.   In the mixing step, the amount of atomic elements of alkali metal elements other than lithium in the alkali metal compound other than lithium in the amount of atomic elements of metal elements in the nickel-containing composite hydroxide or nickel-containing composite oxide The method for producing a lithium-nickel-containing composite oxide according to claim 7, wherein the alkali metal compound other than lithium is mixed so that the ratio of the lithium is in the range of 0.04 to 1.0.   In the mixing step, as the alkali metal compound other than lithium, a chloride, carbonate, sulfate, or a mixture thereof containing one or more alkali metals selected from sodium and potassium is used. Item 9. A method for producing a lithium nickel-containing composite oxide according to Item 7 or 8.   In the mixing step, a ratio of a substance amount of Li atoms in the lithium compound to a substance amount of metal element atoms in the nickel-containing composite hydroxide or nickel-containing composite oxide is 0.98 to 2.00. The method for producing a lithium nickel-containing composite oxide according to any one of claims 7 to 9, wherein the lithium compound is mixed so as to satisfy the following range. A non-aqueous electrolyte comprising a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, wherein the lithium nickel-containing composite oxide according to claim 1 is used as a positive electrode material of the positive electrode. Next battery.