JP2010080394A - Positive electrode active material for nonaqueous electrolyte secondary battery and manufacturing method therefor, and nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive electrode active material for a nonaqueous electrolyte secondary battery, which is made of lithium nickel composite oxide to compatibly attain two characteristics, namely, high charging/discharging heat capacity and high cycle durability. <P>SOLUTION: The positive electrode active material is made of secondary particles formed by agglomeration of primary particles of the lithium nickel composite oxide. The composition of the primary particles is represented by chemical formula: Li<SB>z</SB>Ni<SB>1-x-y</SB>Co<SB>x</SB>M<SB>y</SB>O<SB>2</SB>, and coating layers of an inorganic lithium compound exist on the surfaces of the primary particles or cavities exist inside the secondary particles and the area occupancy of the coating layers or the cavities is 2.5-9% of the cross sections of the secondary particles, where M is at least one element selected from Mn, Mg, Nb, Ti, Al and Zn, and x, y and z satisfy relations of 0.10≤x≤0.21, 0.01≤y≤0.08, 0.97≤z≤1.10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a positive electrode active material used in 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.

  In recent years, with the widespread use of portable electronic devices such as mobile phones and notebook computers, development of non-aqueous electrolyte secondary batteries having high energy density, small size and light weight is strongly desired. As such a secondary battery, there is a lithium ion secondary battery. A lithium ion secondary battery includes a negative electrode, a positive electrode, an electrolyte solution, and the like, and a material capable of desorbing or inserting lithium is used as an active material of the negative electrode and the positive electrode.

In particular, for lithium ion secondary batteries using lithium cobalt-based composite oxide (LiCoO ₂ ) as a positive electrode active material, many developments have been made to obtain excellent initial capacity characteristics and cycle characteristics. Results have been obtained. Specifically, since a high voltage of 4V class can be obtained, it is expected as a secondary battery having a high energy density, and is being put to practical use in fields such as portable electronic devices.

  Recently, not only small secondary batteries for portable electronic devices but also expectations for applying lithium ion secondary batteries as large secondary batteries for power storage and electric vehicles are increasing. However, the lithium cobalt-based composite oxide, which is the positive electrode material, uses rare and expensive cobalt, so it must be expensive for a general-purpose inexpensive secondary battery. Therefore, manufacture of a lithium ion secondary battery using a cheaper positive electrode active material is strongly demanded.

In order to meet these demands, lithium manganese composite oxide (LiMn ₂ O ₄ ) using manganese, which is cheaper than cobalt, or lithium nickel composite oxide (LiNiO ₂ ) using nickel is used as the positive electrode active material. Lithium ion secondary batteries have been proposed.

  The lithium manganese composite oxide is an effective alternative to the lithium cobalt composite oxide because its raw material is inexpensive and has excellent thermal stability, particularly safety in terms of ignition. However, since the theoretical capacity is only about half that of the lithium cobalt based composite oxide, it has a drawback that it is difficult to meet the demand for higher capacity of the lithium ion secondary battery that is increasing year by year. In addition, the self-discharge is intense at 45 ° C. or higher, and the charge / discharge life is also reduced.

  Moreover, the said lithium nickel type complex oxide has the theoretical capacity | capacitance substantially the same as a lithium cobalt type complex oxide, and shows a battery voltage a little lower than a lithium cobalt type complex oxide. For this reason, decomposition due to oxidation of the electrolytic solution is less likely to be a problem, and although higher capacity can be expected, there is a problem that cycle characteristics are inferior. In order to solve this problem, a lithium ion secondary battery using a lithium nickel composite oxide in which a part of nickel is substituted with another element as a positive electrode active material has been proposed.

  For example, Non-Patent Document 1 proposes a method in which a part of nickel in a lithium nickel composite oxide is replaced with cobalt in order to improve cycle characteristics. This method is based on the property that the expansion and contraction associated with lithium desorption / insertion in lithium cobalt complex oxide is opposite to that of the unit cell of lithium nickel complex oxide. Suppresses the repeated expansion and contraction of the unit cell of the lithium nickel composite oxide, reduces the conductivity in the secondary particles due to the occurrence of cracks at the grain boundaries between the primary particles due to the expansion and contraction, and further secondary It is intended to prevent the increase in resistance due to the decrease in conductivity between the active material and the electrode plate due to the refinement of the particles, thereby improving the cycle characteristics.

Patent Document 1 discloses Li _w Ni _x Co _y B _z O ₂ (provided that 0.05 ≦ w) as a positive electrode active material capable of maintaining good battery performance during storage and use in a high temperature environment. ≦ 1.10, 0.5 ≦ x ≦ 0.995, 0.005 ≦ z ≦ 0.20, x + y + z = 1), that is, cobalt and boron were added. Lithium nickel composite oxides have been proposed.

In Patent Document 2, for the purpose of improving the self-discharge characteristics and cycle characteristics of a lithium ion secondary battery, Li _x Ni _a Co _{b McO 2} (where M is Al, V, Mn, Fe, It is at least one element selected from Cu and Zn, and 0.8 ≦ x ≦ 1.2, 0.01 ≦ a ≦ 0.99, 0.01 ≦ b ≦ 0.99, 0.01 ≦ c ≦ 0.3 and 0.8 ≦ a + b + c ≦ 1.2) have been proposed.

  When a lithium nickel composite oxide in which a part of nickel is replaced with other elements is used as the positive electrode active material, both the charge capacity and the discharge capacity are higher than the lithium cobalt composite oxide, and the cycle characteristics are also improved. The However, it is impossible to completely eliminate the expansion and contraction of the crystal lattice due to the lithium insertion / extraction due to charging / discharging, and there is a limit to improving the cycle characteristics.

  On the other hand, a technique for trying to improve the characteristics of the lithium composite oxide in terms of the particle structure has also been proposed. For example, in Patent Literature 3, Patent Literature 4, Patent Literature 5 and Patent Literature 6, secondary particles in which primary particles having a particle size of about 0.1 μm to 2 μm are aggregated to about 5 to 30 μm have high capacity and cycle durability. It is disclosed that it is suitable as a positive electrode active material for a non-aqueous electrolyte secondary battery in that it can be compatible with each other and in addition, it is excellent in handling in industrial production.

  However, as disclosed in Patent Document 7, the secondary particles described above have a site occupancy rate of 3% or less due to metal ions other than lithium at the 3a site obtained from the Rietveld analysis of the X-ray diffraction pattern, It is indispensable to design a particle having both a crystal structure and a powder structure, such as a positive electrode active material in which a plurality of primary particles having a particle diameter of 0.1 to 1 μm are aggregated to form secondary particles.

  In addition, there is a growing demand for higher capacity for small secondary batteries used in portable electronic devices and the like, and positive electrode active material powders having a high packing density per unit volume and high properties are required. For that purpose, the shape of the secondary particles is spherical or elliptical, and the high tap density is also an important characteristic.

  Based on a basic structure consisting of primary particles with a particle size of 0.1 to 1 μm and secondary particles that are aggregates of these particles, as a proposal to improve cycle characteristics, etc., pore distribution and voids in the secondary particles Technology to control rates is also publicly available. However, this technology was developed with a focus on the diffusion of the electrolyte solution into the secondary particles, and was not made from the viewpoint of suppressing the influence caused by the expansion and contraction of the primary particles accompanying the lithium desorption. .

For example, in Patent Document 8, the primary particles are LiNiO ₂ or LiNi _1-x Co _x O _{2 in} which a part of Ni is substituted with Co (where x = 0.05 to 0.10). Nonaqueous lithium having a secondary particle size in the range of 3 to 30 μm, 80% or more of the pore volume having a pore radius of 50 nm or less, and an average pore radius in the range of 3 to 10 nm It has been proposed to be used as a positive electrode active material for secondary batteries. Thereby, the reproducibility of the initial capacity can be ensured, and the capacity decrease due to the cycle can be suppressed.

However, as far as it has been reported so far, a non-aqueous electrolyte secondary battery using the above LiNiO ₂ or LiNi _1-x Co _x O ₂ as a positive electrode active material should be subjected to a high-temperature storage test in the charged state of the battery. It has been pointed out that the problem that the battery performance is significantly deteriorated due to the above has not been sufficiently solved.

In order to solve this problem, Patent Document 9 discloses that a conductive material comprising a lithium nickel composite oxide as a main component, a carbon material, a binder, and a lithium nickel composite oxide is supported. In the positive electrode plate for a non-aqueous electrolyte battery composed of a flat plate for providing Li _x Ni _y M _1-y O ₂ (where M is one or more of Co, Mn, Cr, Fe, Mg, Al). 1.10 ≧ x ≧ 0.98, y: 0.95 ≧ y ≧ 0.7), and a lithium nickel system that is a spherical or elliptical spherical particle in which primary particles having a particle size of 2 μm or less are aggregated It has been proposed to use a composite oxide as a positive electrode active material.

Note that the lithium nickel composite oxide, which is the positive electrode active material of Patent Document 9, is provided with the following physical properties. That is, 1) the space volume having a pore radius of 30 mm or less is 10% or less with respect to the total space volume, 2) the total volume of the space having a pore radius of 30 mm or less is 0.002 cm ³ / g or less, 3) BET specific surface area measured by nitrogen gas adsorption is 0.15 to 0.3 m ² / g, 4) Average particle diameter is 10 to 16 μm, 5) Tap density is 2.0 to 3.0 g / cm ³ , 6) The space volume of the pores is 0.0015 to 0.06 cm ³ / g.

  However, in the lithium ion secondary battery of Patent Document 9 in which the above-described lithium nickel-based composite oxide is used as the positive electrode active material, the initial capacity per 1 g of the active material (indicated as the active material utilization rate in Patent Document 9). Is as low as 170 mAh / g and does not meet the recent demand for higher capacity.

Further, in Patent Document 10, a plurality of primary particles are aggregated to form secondary particles, and the length in which the primary particles are bonded to each other in the cross section of the secondary particles is the entire circumference in the cross section of the primary particles. Li _a Mn _x Ni _y Co _z O ₂ (where 10 ≦ 70%), and the porosity of the secondary particles is 2.5 to 35% (where 1 ≦ a ≦ 1.2, 0 A positive electrode material made of a crystal having a layer structure of a composite oxide of ≦ x ≦ 0.65, 0.35 ≦ y <0.5, 0 ≦ z ≦ 0.65, x + y + z = 1) is disclosed.

  However, according to the Example of patent document 10, the discharge capacity of a battery is about 150 mAh / g at 25 degreeC, and cannot respond to the recent request. In the above-mentioned patent document 10, if Ni exceeds 50% among metal elements other than Li, it is said that the influence of expansion and contraction cannot be suppressed.

JP-A-8-45509 Japanese Patent Laid-Open No. 8-213015 Japanese Patent Laid-Open No. 7-183047 JP 9-129230 A JP-A-10-72219 JP 2006-310181 A JP 2000-30893 A JP-A-8-7894 JP 11-135119 A Japanese Patent Laid-Open No. 2005-5105 A. Ueda and T. Ohzuka, J. Electrochem. Soc., 141, No. 8, 2010 (1994)

  In recent years, the demand for higher capacity and longer life for small secondary batteries used in portable electronic devices and the like has been increasing, and as described above, there has been an active movement to use lithium ion secondary batteries for large secondary batteries. In particular, there is great expectation as a power source for hybrid vehicles and electric vehicles. When used as a power source for automobiles, the battery also requires a life characteristic corresponding to the service life of the automobile. Therefore, a non-aqueous electrolyte secondary battery that has both higher capacity and higher cycle durability is desired. .

  The present invention has been made in view of such conventional circumstances, and is a positive electrode active material capable of realizing a non-aqueous electrolyte secondary battery having both high charge / discharge heat capacity and high cycle durability characteristics, In particular, it is an object of the present invention to provide a positive electrode active material composed of a lithium nickel composite oxide and a method for producing the same.

  In order to achieve the above object, the present inventor has made various studies, and as a result, the positive electrode active material developed by paying attention to the diffusion of the electrolyte into the secondary particles is provided with a specific compound layer on the surface thereof. It has been found that a positive electrode active material in which secondary particles having a specific pore structure are formed by primary particles has higher cycle durability and higher initial discharge capacity than before. In addition, the positive electrode active material, in which the positive electrode active material is washed with water to remove the compound layer and the pore structure of the secondary particles is further improved, has higher cycle characteristics and initial discharge capacity. It has been completed.

  That is, the first positive electrode active material (hereinafter referred to as positive electrode active material A) provided by the present invention is a hexagonal lithium nickel composite oxide primary particle having a layered structure with an average particle size of 0.1 to 2 μm. A positive electrode active material of a non-aqueous electrolyte secondary battery composed of secondary particles formed by agglomeration of the lithium nickel-based composite oxide, wherein the composition of primary particles of the lithium nickel composite oxide is represented by the following chemical formula 3, and the primary particles The surface ratio of the inorganic lithium compound has a coating layer, and the area ratio of the coating layer is 2.5 to 9% of the cross-sectional area of the secondary particles.

（但し、ＭはＭｎ、Ｍｇ、Ｎｂ、Ｔｉ、Ａｌ、Ｚｎから選ばれた少なくとも１種の元素であり、０.１０≦ｘ≦０.２１、０.０１≦ｙ≦０.０８、０.９７≦ｚ≦１.１０である）

(However, M is at least one element selected from Mn, Mg, Nb, Ti, Al, Zn, and 0.10 ≦ x ≦ 0.21, 0.01 ≦ y ≦ 0.08, 0.0. 97 ≦ z ≦ 1.10)

  In the positive electrode active material A of the present invention, the inorganic lithium compound forming the coating layer is preferably lithium sulfate. Moreover, the positive electrode active material A of the present invention preferably has a tap density of 2.0 to 2.5 g / cc.

  In the method for producing the positive electrode active material A provided by the present invention, Ni, Co, and M (wherein M is at least one element selected from Mn, Mg, Nb, Ti, Al, and Zn) are in a molar form. In the metal composite oxide which is solid-solved so that the ratio is 1-xy: x: y (where 0.10 ≦ x ≦ 0.21, 0.01 ≦ y ≦ 0.08) The sulfuric acid compound is mixed so that the ratio of the lithium-containing compound and the sulfate group is 1.6 to 4.3 wt%, and the mixture is held at 700 to 800 ° C. for 4 to 50 hours. Here, the sulfate compound is preferably a sulfate or sulfate hydrate of at least one metal selected from Li, Ni, Co, Mn, Mg, Nb, Ti, Al, and Zn.

  Another method for producing the positive electrode active material A provided by the present invention is Ni, Co, and M (where M is at least one element selected from Mn, Mg, Nb, Ti, Al, and Zn). ) With a molar ratio of 1-xy: x: y (provided that 0.10 ≦ x ≦ 0.21, 0.01 ≦ y ≦ 0.08) and sulfuric acid A lithium-containing compound is mixed with a metal composite oxide containing a group in a proportion of 1.6 to 4.3% by weight, and the mixture is held at 700 to 800 ° C. for 4 to 50 hours.

  Next, the second positive electrode active material provided by the present invention (hereinafter referred to as positive electrode active material B) is a primary hexagonal lithium nickel composite oxide having a layered structure with an average particle size of 0.1 to 2 μm. A positive electrode active material of a non-aqueous electrolyte secondary battery composed of secondary particles formed by agglomeration of particles, wherein the composition of primary particles of the lithium nickel composite oxide is represented by the following chemical formula 4, There is a void inside the secondary particle, and the area ratio occupied by the void is 2.5 to 9% of the cross-sectional area of the secondary particle.

（但し、ＭはＭｎ、Ｍｇ、Ｎｂ、Ｔｉ、Ａｌ、Ｚｎから選ばれた少なくとも１種の元素であり、０.１０≦ｘ≦０.２１、０.０１≦ｙ≦０.０８、０.９７≦ｚ≦１.１０である）

(However, M is at least one element selected from Mn, Mg, Nb, Ti, Al, Zn, and 0.10 ≦ x ≦ 0.21, 0.01 ≦ y ≦ 0.08, 0.0. 97 ≦ z ≦ 1.10)

  In the positive electrode active material B of the present invention, the tap density is preferably 2.2 to 2.7 g / cc. The method for producing the positive electrode active material B of the present invention is characterized in that the positive electrode active material B of the present invention described above is brought into contact with a polar solvent, and the coating layer of the inorganic lithium compound is dissolved and removed. In this case, water is preferably used as the polar solvent.

  The present invention also provides a non-aqueous electrolyte secondary battery using the positive electrode active material A or the positive electrode material B described above.

  ADVANTAGE OF THE INVENTION According to this invention, the positive electrode active material for nonaqueous electrolyte secondary batteries which is excellent in cycle durability while having high charge / discharge initial capacity, ie, positive electrode material A and B, can be provided. In particular, the positive electrode active material B of the present invention is suitable for a power source of a small portable electronic device such as a notebook personal computer or a mobile phone terminal, or a power source of an electric vehicle. The electric vehicle includes not only an electric vehicle that is driven purely by electric energy but also a so-called hybrid vehicle that is used in combination with a combustion engine such as a gasoline engine or a diesel engine.

  The positive electrode active material A of the present invention is also an intermediate product for obtaining the positive electrode active material B, but can be used alone as a positive electrode active material for a non-aqueous electrolyte secondary battery at the same time. Although it does not reach B, it has a charge / discharge capacity higher than that of a conventional positive electrode active material and is excellent in cycle characteristics. Therefore, it is suitable as a power source for small portable electronic devices.

  First, the positive electrode active material B of the present invention will be described. The positive electrode active material B is composed of secondary particles formed by agglomeration of hexagonal lithium nickel composite oxide primary particles having a layered structure represented by the following chemical formula 5 and having an average particle diameter of 0.1 to 1 μm. Has been. Moreover, the positive electrode active material B has voids in the secondary particles, and the area ratio of the voids in the cross-sectional electron microscope image of the secondary particles is 2.5 to 9% of the cross-sectional area of the secondary particles. It is a feature.

（但し、ＭはＭｎ、Ｍｇ、Ｎｂ、Ｔｉ、Ａｌ、Ｚｎから選ばれた少なくとも１種の元素であり、０.１０≦ｘ≦０.２１、０.０１≦ｙ≦０.０８、０.９７≦ｚ≦１.１０である）

(However, M is at least one element selected from Mn, Mg, Nb, Ti, Al, Zn, and 0.10 ≦ x ≦ 0.21, 0.01 ≦ y ≦ 0.08, 0.0. 97 ≦ z ≦ 1.10)

In order for the lithium nickel-based composite oxide to function well as a positive electrode active material, it is important that lithium is inserted and removed smoothly. For this purpose, the crystal structure is required to approach a perfect layered structure, and the lithium site occupancy at the 3a site is desirably 98% or more. In order to achieve this crystallinity, the composition of the lithium nickel composite oxide is Li _z Ni _1-xy Co _x M _y O ₂ (where M is Mn, Mg, Nb, At least one element selected from Ti, Al, and Zn, and satisfying the following conditions: 0.10 ≦ x ≦ 0.21, 0.01 ≦ y ≦ 0.08, 0.97 ≦ z ≦ 1.10. A composition is preferred.

  In lithium ion secondary batteries, lithium desorbs from the crystal lattice of the positive electrode active material upon charging and the primary particles shrink, and during discharge, lithium is inserted into the crystal lattice of the positive electrode active material and the primary particles expand. To do. If this contraction and expansion are repeated, the primary particles are dissociated, eventually leading to cracking of the secondary particles, leading to deterioration of battery characteristics. In the present invention, by providing voids in the secondary particles of the positive electrode active material B, the expansion and contraction during the charge and discharge are alleviated, and the complete dissociation between the primary particles is suppressed, and the secondary particles are cracked. Can be prevented.

  However, when voids are introduced into the secondary particles of the positive electrode active material, the density of the secondary particles decreases and the tap density also decreases, resulting in a decrease in the active material filling amount when configuring the secondary battery, There is a risk of reducing the charge / discharge capacity of the lithium ion secondary battery. Therefore, in order to achieve a tap density of 2.2 g / cc or more which is preferable as the positive electrode active material, the area ratio of the voids determined by the cross-sectional electron microscope image of the secondary particles is 9% or less of the secondary particle cross-sectional area. It is preferable to do. However, if the area ratio of the voids is too small, the expansion and contraction of the particles cannot be absorbed sufficiently, so the area ratio occupied by the voids is preferably 2.5% or more of the secondary particle cross-sectional area. The density is 2.7 g / cc or less.

  Next, the positive electrode active material A of the present invention will be described. The positive electrode active material A is composed of secondary particles formed by agglomeration of primary particles of a hexagonal lithium nickel composite oxide having a layered structure with an average particle diameter of 0.1 to 2 μm, and the lithium nickel composite oxide The composition of the product primary particles is represented by the following chemical formula 6. The positive electrode active material A has a coating layer of an inorganic lithium compound on the surface of the primary particles, and the area ratio of the coating layer in the cross-sectional electron microscope image of the secondary particles is 2. It is characterized by being 5 to 9%.

（但し、ＭはＭｎ、Ｍｇ、Ｎｂ、Ｔｉ、Ａｌ、Ｚｎから選ばれた少なくとも１種の元素であり、０.１０≦ｘ≦０.２１、０.０１≦ｙ≦０.０８、０.９７≦ｚ≦１.１０である）

(However, M is at least one element selected from Mn, Mg, Nb, Ti, Al, Zn, and 0.10 ≦ x ≦ 0.21, 0.01 ≦ y ≦ 0.08, 0.0. 97 ≦ z ≦ 1.10)

  As described above, the positive electrode active material A is an intermediate product in the process of manufacturing the positive electrode active material B. However, although the lithium ion secondary battery produced using the positive electrode active material A is not as good as the lithium ion secondary battery using the positive electrode active material B, the charge / discharge capacity is higher than that of the conventional lithium ion secondary battery. Therefore, the positive electrode active material A can also be said to be an excellent positive electrode active material.

  The role of the coating layer of the inorganic lithium compound in the positive electrode active material A is to relieve the expansion and contraction of the primary particles of the positive electrode active material due to the repetition of lithium insertion / desorption described above, and suppress dissociation between the primary particles, It prevents cracking of secondary particles and improves cycle durability characteristics. However, it can be said that the expansion / contraction relaxation function of the positive electrode active material A does not reach the voids of the positive electrode material B.

  As for the form of the coating layer formed on the surface of the primary particles, it is desirable that the primary particles constituting the secondary particles and the primary particles have a thickness of about several nanometers to several tens of nanometers and are present almost uniformly. However, if the coating layer is too thick, it is not preferable because the primary particles are completely blocked from each other and the diffusion of lithium ions is inhibited. Moreover, if it is too thin, the effect as a coating layer cannot be expected. Therefore, in the case of the lithium nickel composite oxide having excellent battery characteristics in which the average particle diameter of the primary particles is about 0.1 μm to 2 μm, the area ratio occupied by the coating layer is the cross-sectional electron microscope image of the secondary particles. The secondary particle cross-sectional area is preferably controlled in the range of 2.5 to 9%.

  Moreover, when using the positive electrode active material A which has a coating layer, in order to prevent the fall of the charge / discharge capacity of a secondary battery, it is desirable that the tap density of the positive electrode active material A is 2 to 2.5 g / cc. . If the area ratio of the coating layer in the positive electrode active material A is controlled within the range of 2.5 to 9% of the cross-sectional area of the secondary particles as described above, the tap density of the positive electrode active material A is 2 to 2.5 g / It can be within the range of cc.

  As a chemical form of the coating layer, a form that does not inhibit lithium desorption as a positive electrode active material is desirable, and inorganic lithium compounds such as lithium oxide, lithium hydroxide, and lithium sulfate are preferable. Among these, lithium sulfate is most preferable from the viewpoint of ease of production and from the viewpoint of control of crystallinity.

  The reason for using the primary particles of the hexagonal lithium nickel composite oxide having a layered structure with an average particle diameter of 0.1 to 2 μm in the positive electrode material A and the positive electrode material B is that lithium having a good characteristic is easily used. This is because an ion secondary battery can be obtained.

  Next, a method for producing the positive electrode active materials A and B described above will be described. First, the first method for producing the positive electrode active material A is Ni, Co, and M (where M is at least one element selected from Mn, Mg, Nb, Ti, Al, and Zn). Production of a metal composite oxide which is solid-solved so that the molar ratio is 1-xy: x: y (provided that 0.10 ≦ x ≦ 0.21 and 0.01 ≦ y ≦ 0.08). (Step 1a), a lithium-containing compound as a lithium source and a sulfuric acid compound are mixed with the metal composite oxide, and the mixture is held at 700 to 800 ° C. for 4 to 50 hours (Step 2a).

  The area ratio of the coating layer of the obtained positive electrode active material A can be adjusted with the addition amount of a sulfuric acid compound. Specifically, although depending on the firing conditions and the like, in order to control the area ratio of the coating layer to 2.5 to 9% of the secondary particle cross-sectional area, the addition amount of the sulfate compound is set to 0.7 as the sulfate group. It is preferable to adjust within the range of -3.1%.

  Further, as a second production method of the positive electrode material A, Ni, Co, and M (wherein M is at least one element selected from Mn, Mg, Nb, Ti, Al, and Zn) are in a molar ratio. 1-x-y: x: y (provided that 0.10 ≦ x ≦ 0.21, 0.01 ≦ y ≦ 0.08), and the sulfate group is 1.6 to 4 A metal composite oxide containing 3 wt% is manufactured (step 1b), a lithium-containing compound as a lithium source is mixed with the metal composite oxide containing sulfate groups, and the mixture is heated at 700 to 800 ° C. It can also hold | maintain for 4 to 50 hours (2b process).

  Also in this second manufacturing method, the area ratio of the coating layer of the positive electrode active material A can be adjusted by the addition amount of the sulfuric acid compound. In this method, the sulfate group in the metal composite oxide is 1. By adjusting within the range of 6 to 4.3%, the area ratio of the coating layer can be set to 2.5 to 9%.

  As said lithium containing compound, what is conventionally used as a lithium source for manufacture of lithium nickel type complex oxide may be used, for example, lithium hydroxide, lithium carbonate, lithium nitrate, lithium peroxide etc. are used suitably. Can do. The sulfuric acid compound is selected from compounds having metal ions forming a lithium nickel composite oxide as cations, specifically, Li, Ni, Co, Mn, Mg, Nb, Ti, Al, Zn. Furthermore, at least one metal sulfate or sulfate hydrate is preferred.

  A hexagonal lithium nickel composite oxide having a layered structure with an average particle diameter of 0.1 to 2 μm and having the above chemical formula 6 by the first or second manufacturing method, and having an inorganic lithium compound on the surface thereof A positive electrode material A composed of secondary particles obtained by agglomerating primary particles having a coating layer is obtained.

  Further, the positive electrode active material A is brought into contact with a polar solvent, and the coating layer of the inorganic lithium compound is dissolved and removed (third step), whereby a hexagonal system having a layered structure with an average particle size of 0.1 to 2 μm. And a positive electrode active material B that is composed of secondary particles obtained by agglomerating primary particles having the above chemical formula 5 and having voids in the secondary particles. Moreover, it is preferable to use water as the polar solvent. In addition, the area ratio of the space | gap of the positive electrode active material B is substantially the same as the area ratio of the coating layer of the positive electrode active material A used for the manufacture.

  Further, a specific manufacturing method will be described by taking as an example a case where the inorganic lithium compound coating layer is composed of lithium sulfate. According to the general neutralization crystallization method, in the first method, Ni, Co, and M (where M is at least one element selected from Mn, Mg, Nb, Ti, Al, Zn) A metal composite hydroxide having a molar ratio of 1-xy: x: y (where 0.10 ≦ x ≦ 0.21, 0.01 ≦ y ≦ 0.08) was synthesized and roasted. To obtain a metal composite oxide.

  To this metal composite oxide, a sulfate or sulfate hydrate having a metal ion forming a predetermined amount of lithium nickel-based composite oxide such as lithium sulfate or nickel sulfate as a cation, and lithium hydroxide as a lithium source, Mix. By heat-treating the mixture, a positive electrode material A having a lithium sulfate coating layer on the primary particle surface is obtained. In addition, although it is preferable to hold | maintain the said heat processing conditions at 700 to 800 degreeC for 4 hours or more, it is still more preferable to hold | maintain at 730 to 760 degreeC for 16 to 48 hours.

  Thereafter, the obtained positive electrode active material A is poured into water at room temperature and stirred for 30 minutes to 1 hour to dissolve and remove the lithium sulfate coating layer, followed by solid-liquid separation and drying to obtain positive electrode active material B. . The temperature range and contact time for dissolving the coating layer described above are preferable conditions that allow the lithium compound coating layer in the positive electrode active material A to be efficiently and reliably removed, and that a predetermined void is obtained.

  Further, when the metal composite oxide is produced, in the second method, a sulfate and sulfate hydrate having a metal ion forming a lithium nickel composite oxide such as nickel sulfate as a cation is used as a raw material. By using it, a metal composite oxide having a sulfate group can be obtained. Since this metal complex oxide already contains a sulfate group, the positive electrode active material A can be similarly obtained by adding only a lithium-containing compound as a lithium source and heat-treating it without adding a sulfate compound. Further, the positive electrode material B can be obtained by bringing the positive electrode material A into contact with water.

  The positive electrode active materials A and B of the present invention thus obtained have a lithium site occupancy of 3a site of 98% or more, and have a coating layer or voids in a predetermined area ratio in the secondary particles. The lithium secondary battery has a high charge / discharge capacity and a high cycle durability.

  Next, a nonaqueous electrolyte secondary battery using the positive electrode active materials A and B of the present invention, specifically, a lithium ion secondary battery will be described with reference to FIG. In the lithium ion secondary battery, a positive electrode 1 and a negative electrode 2 are laminated via a separator 3 to form an electrode body, and this electrode body is impregnated with a nonaqueous electrolyte. The positive electrode current collector 4 is brought into contact with the positive electrode can 5, the negative electrode current collector 6 is brought into contact with the negative electrode can 7, and the positive electrode can 5 and the negative electrode can 7 are sealed through a gasket 8. In some cases, the positive electrode current collector 4 and the negative electrode current collector 6 are connected using a terminal current collecting lead or the like that communicates with the outside. In addition to the coin type shown in FIG. 1, there are various types of lithium secondary batteries such as a cylindrical type and a laminated type.

  The positive electrode is produced, for example, as follows. First, a powdery positive electrode active material, a conductive material, and a binder are mixed, and if necessary, a target solvent such as activated carbon and viscosity adjustment is added and kneaded to prepare a positive electrode mixture paste. Each mixing ratio in the positive electrode composite material is also an important factor that determines the performance of the lithium ion secondary battery. When the total mass of the solid content of the positive electrode mixture excluding the solvent is 100% by mass, the content of the positive electrode active material is 60 to 95% by mass, the content of the conductive material is 1 to 20% by mass, and the binder The content is preferably 1 to 20% by mass.

  The obtained positive electrode mixture paste is applied to the surface of a current collector made of, for example, aluminum foil, and dried to scatter 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 is 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.

  Examples of the conductive agent used for producing the positive electrode include graphite (natural graphite, artificial graphite, expanded graphite, etc.), carbon black materials such as acetylene black and ketjen black. In addition, the binder plays a role of holding the active material particles, such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluorine rubber, ethylene propylene diene rubber, styrene butadiene, and cellulose resin. Polyacrylic acid or the like 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.

  The negative electrode is produced by mixing a metallic lithium, a lithium alloy, and the like with a negative electrode active material capable of inserting and extracting lithium ions, and adding an appropriate solvent to obtain a paste-like negative electrode mixture. This negative electrode mixture is applied to the surface of a metal foil current collector such as copper, dried, and compressed as necessary to increase the electrode density to obtain a negative electrode.

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

  The separator separates the positive electrode and the negative electrode and retains the electrolyte, and a thin film such as polyethylene or polypropylene and having many minute holes can be used. A thin film made of fibers can also be used.

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

  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; tetrahydrofuran, 2-methyltetrahydrofuran Ether compounds such as dimethoxyethane; sulfur compounds such as ethyl methyl sulfone and butane sultone; phosphorus compounds such as triethyl phosphate and trioctyl phosphate may be used alone or in admixture of two or more. it can.

[Example 1]
Mix nickel sulfate hydrate, cobalt sulfate hydrate and aluminum sulfate so that the molar ratio of Ni: Co: Al is 0.82: 0.15: 0.03, and dissolve in water. A mixed metal sulfate solution was prepared. The mixed metal sulfate solution was stirred together with an alkaline neutralized solution prepared from an aqueous caustic soda solution and aqueous ammonia, while quantitatively supplying the alkaline neutralized solution to a reaction vessel having a stirrer, A slurry was obtained. The obtained slurry was subjected to solid-liquid separation, and the collected mixed metal hydroxide was roasted at 700 ° C. for 6 hours in the air to obtain a Ni—Co—Al-based metal composite oxide.

  The obtained Ni—Co—Al-based metal composite oxide was mixed with lithium hydroxide powder added to the lithium oxide after calcining lithium sulfate so as to have a sulfate group content of 0.9 wt%, By firing for 16 hours at 745 ° C. in an oxygen atmosphere, a Li—Ni-based composite oxide of Sample 1 having a lithium sulfate coating layer on the primary particle surface was produced.

  About the obtained Li-Ni complex oxide of Sample 1, the composition was confirmed by chemical analysis, and the tap density was measured. Further, XRD measurement was performed to confirm that a hexagonal layered compound was formed, and fitting was performed by the Rietveld analysis method to calculate the lithium seat occupancy.

  Further, a small amount of the Li—Ni-based composite oxide of the sample 1 was sampled and embedded in a resin, and a cross section polisher (SM-09010, manufactured by JEOL Ltd.), which is a cross-section processing apparatus using argon ions. After performing the cross section of the powder, the cross section is observed with an electron beam with an acceleration voltage of 3 kV using a high-resolution field emission scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, S-4700) to determine the primary particle diameter, The area occupation ratio of the coating layer was calculated by image analysis.

Next, the initial discharge capacity evaluation as the positive electrode active material A was performed on the Li—Ni-based composite oxide of Sample 1. That is, 70% by mass of the positive electrode active material A powder was mixed with 20% by mass of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd.) and 10% by mass of PTFE (manufactured by Daikin Kogyo Co., Ltd.). 11 mm, pressure 100 MPa) was prepared and used as a positive electrode. Lithium metal was used as the negative electrode, and an equivalent mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) (made by Toyama Pharmaceutical Co., Ltd.) using 1M LiClO ₄ as a supporting salt was used as the electrolyte. A 2032 type coin-type lithium ion secondary battery as shown in FIG. 1 was produced in a glove box in an Ar atmosphere in which the dew point was controlled at −80 ° C.

The produced battery is left for about 24 hours, and after the open circuit voltage (OCV) is stabilized, the current density with respect to the positive electrode is set to 0.5 mA / cm ² and charged to a cutoff voltage of 4.3 V to obtain an initial charge capacity. The capacity when discharging to a cut-off voltage of 3.0 V after 1 hour of rest was defined as the initial discharge capacity. Furthermore, the capacity retention rate after repeating this charge / discharge cycle 100 times was determined and evaluated as cycle durability. The above results are summarized in Table 1 below as Sample 1.

[Example 2]
A Li—Ni-based composite oxide was produced in the same manner as in Example 1, except that the amount of lithium sulfate added was 1.2% by weight (sample 2) of the sulfate group in the lithium oxide after firing. The amount was changed to 9% by weight (sample 3) and 2.6% by weight (sample 4).

  About each Li-Ni type complex oxide of the obtained samples 2-4, while performing a chemical analysis, a XRD measurement, and cross-sectional observation similarly to the said Example 1, the battery evaluation as the positive electrode active material A was performed, The results are summarized in Table 1 below.

[Example 3]
A Li—Ni based composite oxide was produced in the same manner as in Example 1, but the sulfuric acid compound to be added was changed to nickel sulfate. About the Li-Ni type complex oxide of the obtained sample 5, while performing a chemical analysis, a XRD measurement, and cross-sectional observation similarly to the said Example 1, the battery evaluation as the positive electrode active material A was performed, and the result was shown below. Table 1 summarizes the results.

[Example 4]
Mix nickel sulfate hydrate, cobalt sulfate hydrate and aluminum sulfate so that the molar ratio of Ni: Co: Al is 0.82: 0.15: 0.03, and dissolve in water. A mixed metal sulfate solution was prepared. This mixed metal sulfuric acid solution is stirred together with an alkaline neutralized solution prepared from an aqueous caustic soda solution and aqueous ammonia, while quantitatively supplying the alkaline neutralized solution to a reaction vessel having a stirrer, and a slurry of mixed metal hydroxide Got.

  The obtained slurry was subjected to solid-liquid separation, and a predetermined amount of a nickel sulfate aqueous solution was added to and impregnated into the collected mixed metal hydroxide, followed by roasting in the atmosphere at 700 ° C. for 6 hours to thereby form sulfate groups. A Ni—Co—Al-based metal composite oxide was obtained.

  The obtained Ni—Co—Al-based metal composite oxide was mixed with lithium hydroxide powder, and then calcined at 730 ° C. for 48 hours in an oxygen atmosphere, whereby a sample 6 having a lithium sulfate coating layer on the primary particle surface was obtained. Li-Ni-based composite oxide was produced. The obtained Li—Ni-based composite oxide of Sample 6 was subjected to chemical analysis, XRD measurement, and cross-sectional observation in the same manner as in Example 1 above, and battery evaluation as the positive electrode active material A was performed. Table 1 summarizes the results.

[Comparative Example 1]
Mix nickel sulfate hydrate, cobalt sulfate hydrate and aluminum sulfate so that the molar ratio of Ni: Co: Al is 0.82: 0.15: 0.03, and dissolve in water. A mixed metal sulfate solution was prepared. This mixed metal sulfuric acid-assisted solution is stirred together with an alkaline neutralized solution prepared from an aqueous caustic soda solution and aqueous ammonia, while quantitatively supplying the alkaline neutralized solution to a reaction vessel having a stirrer, and mixed metal hydroxide A slurry was obtained. The obtained slurry was subjected to solid-liquid separation, and the collected mixed metal hydroxide was roasted at 700 ° C. for 6 hours in the air to obtain a Ni—Co—Al-based metal composite oxide.

  The obtained Ni—Co—Al-based composite oxide was mixed with lithium hydroxide powder, and then fired at 745 ° C. for 16 hours in an oxygen atmosphere to produce a Li—Ni-based composite oxide of Sample 7. . The obtained Li—Ni-based composite oxide of Sample 7 was subjected to chemical analysis, XRD measurement, and cross-sectional observation in the same manner as in Example 1 above, and battery evaluation as a positive electrode active material was performed. 1 is shown collectively.

[Comparative Example 2]
A Li—Ni-based composite oxide was produced in the same manner as in Example 1, but the amount of lithium sulfate added was excessively added to the fired lithium oxide so that the amount of sulfate group was 3.5% by weight. did. About the Li-Ni type complex oxide of the obtained sample 8, as in Example 1 above, chemical analysis, XRD measurement, and cross-sectional observation were performed, and a battery evaluation as a positive electrode active material was performed. 1 is shown collectively.

  As can be seen from Table 1 above, the Li—Ni-based composite oxides (positive electrode active material A) of Samples 1 to 6 according to the present invention each have a high charge / discharge initial capacity and excellent cycle durability. Yes. On the other hand, the Li—Ni-based composite oxide of the comparative example has a low capacity retention rate after 100 cycles because the coating layer of the inorganic lithium compound is small in the sample 7, and the area occupation rate of the coating layer of the inorganic lithium compound is low in the sample 8. Therefore, both initial charge / discharge capacity and cycle durability are slightly reduced.

[Example 5]
Mix nickel sulfate hydrate, cobalt sulfate hydrate and aluminum sulfate so that the molar ratio of Ni: Co: Al is 0.82: 0.15: 0.03, and dissolve in water. A mixed metal sulfate solution was prepared. The mixed metal sulfate solution was stirred together with an alkaline neutralized solution prepared from an aqueous caustic soda solution and aqueous ammonia, while quantitatively supplying the alkaline neutralized solution to a reaction vessel having a stirrer, A slurry was obtained. The obtained slurry was subjected to solid-liquid separation, and the collected mixed metal hydroxide was roasted at 700 ° C. for 6 hours in the air to obtain a Ni—Co—Al-based metal composite oxide.

  The obtained Ni—Co—Al-based metal composite oxide was mixed with lithium hydroxide powder added to the lithium oxide after calcining lithium sulfate so as to have a sulfate group content of 0.9 wt%, By baking for 16 hours at 745 ° C. in an oxygen atmosphere, a Li—Ni-based composite oxide having a lithium sulfate coating layer on the primary particle surface was produced. Water was added to this Li—Ni composite oxide to form a slurry, and the mixture was stirred at room temperature to dissolve and remove the coating layer. Then, solid-liquid separation was performed to obtain a lithium nickel composite oxide of Sample 10.

  About the Li-Ni type complex oxide of Sample 10 having voids inside the obtained secondary particles, the composition was confirmed by chemical analysis, and the tap density was measured. Further, XRD measurement was performed to confirm that a hexagonal layered compound was formed, and fitting was performed by the Rietveld analysis method to calculate the lithium seat occupancy.

  Further, a small amount of the Li—Ni-based composite oxide of the sample 10 was sampled and embedded in a resin, and a cross section polisher (SM-09010, manufactured by JEOL Ltd.), which is a cross-section processing apparatus using argon ions. After the cross section of the powder is obtained, the cross section is observed with an electron beam with an acceleration voltage of 3 kV using a high resolution field emission scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, S-4700) to obtain the primary particle diameter. At the same time, the area occupation ratio of the voids was calculated by image analysis.

Next, the initial discharge capacity evaluation as the positive electrode active material B was performed on the Li—Ni based composite oxide of the sample 10. That is, 70% by mass of the positive electrode active material B powder was mixed with 20% by mass of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd.) and 10% by mass of PTFE (manufactured by Daikin Kogyo Co., Ltd.). 11 mm, pressure 100 MPa) was prepared and used as a positive electrode. Lithium metal was used as the negative electrode, and an equivalent mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) (made by Toyama Pharmaceutical Co., Ltd.) using 1M LiClO ₄ as a supporting salt was used as the electrolyte. A 2032 type coin battery as shown in FIG. 1 was produced in an Ar atmosphere glove box whose dew point was controlled at −80 ° C.

The produced battery is left for about 24 hours, and after the open circuit voltage (OCV) is stabilized, the current density with respect to the positive electrode is set to 0.5 mA / cm ² and charged to a cutoff voltage of 4.3 V to obtain an initial charge capacity. The capacity when discharging to a cut-off voltage of 3.0 V after 1 hour of rest was defined as the initial discharge capacity. Furthermore, the capacity retention rate after repeating this charge / discharge cycle 100 times was determined and evaluated as cycle durability. The above results are summarized in Table 2 below as Sample 10.

[Example 6]
A Li—Ni-based composite oxide was produced in the same manner as in Example 5, except that the amount of lithium sulfate to be added was 1.2% by weight (sample 11) of the sulfate group in the lithium oxide after firing. The amount was changed to 9% by weight (sample 12) and 2.6% by weight (sample 13).

  About each Li-Ni type complex oxide of the obtained samples 11-13, while performing a chemical analysis, XRD measurement, and cross-sectional observation similarly to the said Example 5, the battery evaluation as the positive electrode active material B was performed, The results are summarized in Table 2 below. Moreover, the cross-sectional observation photograph by the electron microscope about the secondary particle of the positive electrode active material B of the sample 13 was shown in FIG.

[Example 7]
A Li—Ni composite oxide was produced in the same manner as in Example 5 above, but the sulfuric acid compound to be added was changed to nickel sulfate. About the Li-Ni type complex oxide of the obtained sample 14, while performing a chemical analysis, XRD measurement, and cross-sectional observation similarly to the said Example 5, the battery evaluation as the positive electrode active material B was performed, and the result was shown below. Table 2 summarizes the results.

[Example 8]
Mix nickel sulfate hydrate, cobalt sulfate hydrate and aluminum sulfate so that the molar ratio of Ni: Co: Al is 0.82: 0.15: 0.03, and dissolve in water. A mixed metal sulfate solution was prepared. The mixed metal sulfate solution was stirred together with an alkaline neutralized solution prepared from an aqueous caustic soda solution and aqueous ammonia, while quantitatively supplying the alkaline neutralized solution to a reaction vessel having a stirrer, A slurry was obtained.

  The obtained slurry was subjected to solid-liquid separation, and a predetermined amount of a nickel sulfate aqueous solution was added to and impregnated into the collected mixed metal hydroxide, followed by roasting in the atmosphere at 700 ° C. for 6 hours to thereby form sulfate groups. A Ni—Co—Al-based metal composite oxide was obtained.

  The obtained Ni—Co—Al-based metal composite oxide was mixed with lithium hydroxide powder and then calcined at 730 ° C. for 48 hours in an oxygen atmosphere, whereby Li— having a lithium sulfate coating layer on the primary particle surface. A Ni-based composite oxide was produced. Water was added to this Li—Ni-based composite oxide to form a slurry, which was stirred at room temperature to dissolve and remove the coating layer, followed by solid-liquid separation to obtain a lithium nickel-based composite oxide of Sample 15.

  The obtained Li—Ni composite oxide of Sample 15 having voids inside the secondary particles was subjected to chemical analysis, XRD measurement, and cross-sectional observation in the same manner as in Example 5 above, and a battery as positive electrode active material B Evaluation was performed and the results are summarized in Table 2 below.

[Comparative Example 3]
Mix nickel sulfate hydrate, cobalt sulfate hydrate and aluminum sulfate so that the molar ratio of Ni: Co: Al is 0.82: 0.15: 0.03, and dissolve in water. A mixed metal sulfate solution was prepared. This mixed metal sulfuric acid-assisted solution is stirred together with an alkaline neutralized solution prepared from an aqueous caustic soda solution and aqueous ammonia, while quantitatively supplying the alkaline neutralized solution to a reaction vessel having a stirrer, and mixed metal hydroxide A slurry was obtained. The obtained slurry was subjected to solid-liquid separation, and the collected mixed metal hydroxide was roasted at 700 ° C. for 6 hours in the air to obtain a Ni—Co—Al-based metal composite oxide.

  The obtained Ni—Co—Al-based metal composite oxide was mixed with lithium hydroxide powder and then fired at 745 ° C. for 16 hours in an oxygen atmosphere to produce a Li—Ni-based composite oxide. Water was added to this Li—Ni composite oxide to form a slurry, which was stirred and then solid-liquid separated to obtain a Li—Ni composite oxide of Sample 16.

  The obtained Li—Ni-based composite oxide of Sample 16 was subjected to chemical analysis, XRD measurement, and cross-sectional observation in the same manner as in Example 5 above, and battery evaluation as a positive electrode active material was performed. 2 collectively.

[Comparative Example 4]
A Li—Ni-based composite oxide was produced in the same manner as in Example 5, but the amount of lithium sulfate to be added was excessively added to the fired lithium oxide so that the amount of sulfate group was 3.5% by weight. did. The obtained Li—Ni-based composite oxide of Sample 17 was subjected to chemical analysis, XRD measurement, and cross-sectional observation in the same manner as in Example 5 above, and battery evaluation as a positive electrode active material was performed. 2 collectively.

  As can be seen from Table 2 above, the Li—Ni-based composite oxides (positive electrode active material B) of Samples 10 to 15 according to the present invention both have a high charge / discharge initial capacity and excellent cycle durability. Yes. On the other hand, in the Li—Ni-based composite oxide of the comparative example, the capacity retention rate after 100 cycles is low because the sample 16 has too little space area occupancy, and the sample 17 has too much space area occupancy. Both initial charge / discharge capacity and cycle durability are slightly reduced.

In Examples 1 to 8 of the present invention described above, the cathode material of the lithium nickel composite oxide in which a part of nickel (Ni) is replaced with cobalt (Co) and aluminum (Al) has been described. Lithium nickel composite oxide positive electrode material substituted with manganese (Mn), magnesium (Mg), niobium (Nb), titanium (Ti), zinc (Zn), or two or more elements including Al and Al In addition, it was possible to produce the same as described above, and it was possible to obtain the initial charge / discharge capacity and cycle durability substantially the same as described above.

It is sectional drawing which showed the general lithium ion secondary battery typically. 6 is a cross-sectional observation photograph of secondary particles of a positive electrode active material B made of a Li—Ni-based composite oxide of Sample 13 obtained in Example 6 using an electron microscope.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Positive electrode 5 Positive electrode can 6 Negative electrode collector 7 Negative electrode can 8 Gasket

Claims (11)

A positive electrode active material for a non-aqueous electrolyte secondary battery comprising secondary particles formed by agglomeration of hexagonal lithium nickel composite oxide primary particles having a layered structure with an average particle size of 0.1 to 2 μm. The composition of the primary particles of the lithium nickel composite oxide is represented by the following chemical formula 1, and the surface of the primary particles has a coating layer of an inorganic lithium compound, and the area ratio occupied by the coating layer is secondary particle breakage. A positive electrode active material characterized by being 2.5 to 9% of the area.

(However, M is at least one element selected from Mn, Mg, Nb, Ti, Al, Zn, and 0.10 ≦ x ≦ 0.21, 0.01 ≦ y ≦ 0.08, 0.0. 97 ≦ z ≦ 1.10)   The positive electrode active material according to claim 1, wherein the inorganic lithium compound forming the coating layer is lithium sulfate.   The positive electrode active material according to claim 1, wherein the tap density is 2.0 to 2.5 g / cc.   It is a manufacturing method of the positive electrode active material in any one of Claims 1-3, Comprising: Ni, Co, and M (However, M is at least 1 sort (s) chosen from Mn, Mg, Nb, Ti, Al, Zn) Is a solid solution in a molar ratio of 1-xy: x: y (provided that 0.10 ≦ x ≦ 0.21, 0.01 ≦ y ≦ 0.08). A mixed metal oxide is mixed with a sulfuric acid compound so that the ratio of the lithium-containing compound and the sulfate group is 1.6 to 4.3 wt%, and the mixture is held at 700 to 800 ° C. for 4 to 50 hours. And a method for producing a positive electrode active material.   The sulfate compound is a sulfate or sulfate hydrate of at least one metal selected from Li, Ni, Co, Mn, Mg, Nb, Ti, Al, and Zn. The manufacturing method of the positive electrode active material of description.   It is a manufacturing method of the positive electrode active material in any one of Claims 1-3, Comprising: Ni, Co, and M (However, M is at least 1 sort (s) chosen from Mn, Mg, Nb, Ti, Al, Zn) Is a solid solution in a molar ratio of 1-xy: x: y (provided that 0.10 ≦ x ≦ 0.21, 0.01 ≦ y ≦ 0.08). In addition, a lithium-containing compound is mixed with a metal composite oxide containing a sulfate group in a proportion of 1.6 to 4.3% by weight, and the mixture is held at 700 to 800 ° C. for 4 to 50 hours. A method for producing a positive electrode active material. A positive electrode active material for a non-aqueous electrolyte secondary battery comprising secondary particles formed by agglomeration of hexagonal lithium nickel composite oxide primary particles having a layered structure with an average particle size of 0.1 to 2 μm. The composition of the primary particles of the lithium nickel-based composite oxide is represented by the following chemical formula 2, and there are voids in the secondary particles, and the area ratio occupied by the voids is 2.5 of the cross-sectional area of the secondary particles. A positive electrode active material, which is ˜9%.

(However, M is at least one element selected from Mn, Mg, Nb, Ti, Al, Zn, and 0.10 ≦ x ≦ 0.21, 0.01 ≦ y ≦ 0.08, 0.0. 97 ≦ z ≦ 1.10)   The positive electrode active material according to claim 7, wherein the tap density is 2.2 to 2.7 g / cc.   It is a manufacturing method of the positive electrode active material of Claim 7 or 8, Comprising: The positive electrode active material in any one of Claims 1-3 is made to contact with a polar solvent, and the coating layer of an inorganic lithium compound is dissolved and removed. A method for producing a positive electrode active material.   The method for producing a positive electrode active material according to claim 9, wherein water is used as the polar solvent.   A non-aqueous electrolyte secondary battery using the positive electrode active material according to claim 1 or claim 7 or 8.

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