KR20160041004A - Positive electrode active material for lithium ion secondary battery, and positive electrode for lithium ion secondary battery and lithium ion secondary battery comprising the same - Google Patents

Abstract

The purpose of the present invention is to provide a positive electrode active material for a lithium ion secondary battery which has low resistance and high capacity and shows excellent charge/discharge cycle characteristics. The positive electrode active material comprises primary particles represented by formula (1) of Li_(1+x)Ni_yCo_zM_(1-x-y-z)O_2 [wherein x is a number satisfying -0.12<=x<=0.2, y is a number satisfying 0.7<=y<=0.9, z is a number satisfying 0.05<=z<=0.3, and M is at least one element selected from the group consisting of Mg, Al, Ti, Mn, Zr, Mo and Nb], or secondary particles formed by agglomeration of the primary particles. The primary particles or secondary particles include a free lithium compound at a weight ratio of 0.1-2.0%, and the free lithium compound comprises lithium hydroxide in an amount of 60 wt% or less based on the weight of lithium carbonate in the free lithium compound.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive electrode active material for a lithium ion secondary battery, a positive electrode for a lithium ion secondary battery using the same, and a lithium ion secondary battery using the same. BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

The present invention relates to a positive electrode active material for a lithium ion secondary battery, a positive electrode for a lithium ion secondary battery using the same, and a lithium ion secondary battery.

The lithium ion secondary battery has a feature that the energy density is high and the memory effect is small as compared with other secondary batteries such as nickel-hydrogen storage batteries and nickel-cadmium storage batteries. Therefore, it is possible to supply power from a small power source such as a portable electronic device or a household electric device to a power source for a power storage device, an uninterruptible power source device, a power leveling device, a medium power source such as a driving power source for a ship, a railroad, a hybrid car, And the battery performance is required to be further improved. Particularly, for a lithium ion secondary battery developed as a medium to large-sized power source, it is required to have a high energy density capable of achieving a high capacity at a low capacity.

According to this request, LiMO ₂ having an α-NaFeO ₂ type layer structure (M is, refers to the elements such as Ni, Co, Mn) cathode active material, has been under development example because of the high charge-discharge capacity. On the other hand, the layered positive electrode active material having a high Ni content has a problem that the output characteristics are lowered depending on the charge-discharge cycle characteristics, particularly the cycle.

Therefore, a technique has been proposed in which the charging / discharging cycle characteristics of the layered positive electrode active material are improved by reducing the amount of impurities present on the particle surface of the positive electrode active material. For example, Patent Document 1, the particles washed with water (水洗) to be obtained by applying the technique for removing impurities, Li _{1 + x} Ni ₁ of _{-y- z Co y M z O 2} (M = B, Al , at least Wherein the particle surface of the lithium composite compound particle powder is at least one kind selected from the group consisting of at least one kind of fly ash type secondary ion Characterized in that the ionic strength ratio A (LiO ^- / NiO ₂ ^- ) is 0.3 or less and the ionic strength ratio B (Li ₃ CO ₃ ⁺ / Ni ⁺ ) is 20 or less when analyzed by a mass spectrometer An active material is disclosed. In addition, Patent Document 2 is a prior art disclosing a technique for washing particles.

Further, a technique has been proposed in which the output characteristic of the layered positive electrode active material is improved by adjusting the porosity or open pore ratio of the positive electrode active material. For example, Patent Document 3 discloses that secondary particles composed of a plurality of primary particles having an average particle size of not less than 0.01 탆 and not more than 5 탆 have a porosity of 3% or more and 30% or less and an open porosity of 70% As a cathode active material.

Japanese Patent Application Laid-Open No. 2010-155775 Japanese Patent Application Laid-Open No. 2013-026199 Japanese Patent Application Laid-Open No. 2014-67546

As disclosed in Patent Document 1, lowering the amounts of lithium hydroxide (LiOH) and lithium carbonate (Li ₂ CO ₃ ), which are impurities present on the surface of the layered positive electrode active material, can suppress the gelation of the coating It is possible to suppress the side reaction in the battery due to charging and discharging, thereby improving the charge-discharge cycle characteristics. However, if the layered positive electrode active material is dispersed and washed in water in order to reduce impurities present on the surface of the layered positive electrode active material, Li in the active material elutes and crystallinity of the surface of the active material decreases, have.

Further, as disclosed in Patent Document 3, when the ratio of the open pore occupying the voids is 70% or more, the electrolyte solution can more penetrate into the positive electrode active material particles, diffusion of lithium ions into the particles is promoted, And the positive electrode active material becomes large, it is expected that the charge / discharge characteristics, especially the output characteristics, are improved. However, simply increasing the open pore ratio increases the contact area between the electrolytic solution and the cathode active material, so that decomposition of the electrolytic solution is promoted, and the resistance may increase.

Accordingly, it is an object of the present invention to provide a positive electrode active material for a lithium ion secondary battery that is low in resistance, high in capacity, and excellent in charge-discharge cycle characteristics, and a positive electrode for a lithium ion secondary battery and a lithium ion secondary battery using the same.

In order to solve the above problems, a cathode active material for a lithium ion secondary battery according to the present invention comprises:

Li _{1 + x} Ni _y Co _z M _1-xyz O ₂ (1)

X is a number satisfying -0.12? X? 0.2, y is a number satisfying 0.7? Y? 0.9, z is a number satisfying 0.05? Z? 0.3, M is at least one element selected from the group consisting of Mg, Al, Ti, Mn, Zr, Mo and Nb.

, Or secondary particles aggregated with the primary particles,

Wherein the primary particles or the secondary particles contain a free lithium compound in a weight ratio of not less than 0.1% and not more than 2.0%, and the weight of lithium hydroxide in the free lithium compound is not more than Is not more than 60% of the weight of lithium carbonate.

The positive electrode for a lithium ion secondary battery according to the present invention includes the positive electrode active material for the lithium ion secondary battery.

Further, the lithium ion secondary battery according to the present invention is characterized by comprising the anode for the lithium ion secondary battery.

According to the present invention, it is possible to provide a positive electrode active material for a lithium ion secondary battery having a low resistance, a high capacity and a high charge / discharge cycle characteristic, a positive electrode for a lithium ion secondary battery using the same, and a lithium ion secondary battery using the same.

1 is a schematic cross-sectional view showing an embodiment of a lithium ion secondary battery according to the present invention.
2 is a view showing pore volume distribution of secondary particles of Example 1 measured by the mercury porosimetry;
3 is a graph showing the relationship between the capacity and charge-discharge cycle characteristics of a lithium ion secondary battery according to Examples and Comparative Examples;

Hereinafter, a cathode active material for a lithium ion secondary battery, a cathode for a lithium ion secondary battery, and a lithium ion secondary battery according to an embodiment of the present invention will be described in detail.

The positive electrode active material for a lithium ion secondary battery according to this embodiment is a positive electrode active material having a layered structure and includes primary particles or secondary particles in which primary particles are aggregated and includes primary particles or secondary particles Among the free lithium compounds, it is characterized by the weight ratio of lithium hydroxide and lithium carbonate. Here, the free lithium compound refers to a lithium-containing compound dissolved in water other than a compound functioning as a cathode active material. That is, in this specification, the primary particles or the secondary particles include a free lithium compound in addition to a compound functioning as a cathode active material. In the present specification, the term "composition" or "composition formula" for primary particles or secondary particles means that the composition or composition of only a compound functioning as a cathode active material, other than a free lithium compound, it means.

The positive electrode active material for a lithium ion secondary battery according to the present embodiment has the following composition formula (1)

Li _{1 + x} Ni _y Co _z M _1-xyz O ₂ (1)

X is a number satisfying -0.12? X? 0.2, y is a number satisfying 0.7? Y? 0.9, z is a number satisfying 0.05? Z? 0.3, M is at least one element selected from the group consisting of Mg, Al, Ti, Mn, Zr, Mo and Nb.

Wherein the primary particles or the secondary particles contain a free lithium compound in a weight ratio of not less than 0.1% and not more than 2.0% The weight of the lithium hydroxide in the free lithium compound is 60% or less of the weight of the lithium carbonate in the free lithium compound.

This layered positive electrode active material is capable of reversibly intercalating and deintercalating lithium ions upon charging and discharging, and is a cathode active material having a low resistance.

The layered positive electrode active material represented by the composition formula (1) has a feature that a high capacity can be expected and a charge-discharge cycle characteristic when Li is not less than a certain amount is not necessarily excellent. When the lithium ion secondary battery using this layered positive electrode active material is charged to a high voltage, charging / discharging cycle characteristics are largely deteriorated, so that the charging end voltage is usually suppressed to a low level, and a high theoretical capacity can not be fully utilized .

Examples of factors that lower the charge-discharge cycle characteristics of the layered positive electrode active material include free lithium compounds contained in the layered positive electrode active material. The free lithium compound is mainly composed of lithium carbonate and lithium hydroxide. Particularly, the decomposition of the electrolytic solution by contact between lithium hydroxide and the electrolyte solution can be considered. Since lithium hydroxide contains a hydroxyl group, it reacts with the fluorine-based electrolyte contained in the electrolyte to generate hydrofluoric acid (HF), which is a strong acid, and oxidative decomposition of the electrolytic solution is promoted by high voltage, .

Therefore, in the cathode active material for a lithium ion secondary battery according to the present embodiment, the ratio of Ni contributing to a high capacity is increased to maintain a high charge / discharge capacity, and progress of oxidative decomposition of the electrolytic solution due to contact between lithium hydroxide and the electrolytic solution is suppressed , The absolute amount of the free lithium compound contained in the primary particles or the secondary particles is suppressed and the weight of the lithium hydroxide is lower than the weight of lithium carbonate in particular to improve the charge-discharge capacity and the charge-discharge cycle characteristics .

In the composition formula (1), x represents the excess or deficiency of Li from the stoichiometric ratio (Li: M: O = 1: 1: 2) of the layered positive electrode active material (LiMO ₂ ). The higher the amount of Li, the higher the valence of the transition metal before charging, and the ratio of the change in the valence of the transition metal in Li removal is reduced, thereby improving the charge-discharge cycle characteristics. On the other hand, the larger the amount of Li, the lower the charge-discharge capacity of the layered positive electrode active material. Therefore, x is in the range of -0.12 to 0.2, preferably -0.1 to 0.2, particularly preferably -0.05 to 0.1. When x is -0.12 or more, sufficient amount of Li is enough to contribute to charge and discharge, and high capacity can be achieved. When x is 0.2 or less, the charge compensation due to the change in the valence of the transition metal can be sufficiently ensured, which is particularly effective for achieving both a high capacity and a high charge / discharge cycle characteristic.

In the composition formula (1), the content of Ni is in the range of 0.7 to 0.9. When the Ni content is 0.7 or more, sufficient Ni amount is sufficient to contribute to charging and discharging, and high capacity can be achieved. On the other hand, in the composition in which the Ni content exceeds 0.9, a part of the Li site is substituted by Ni, and the amount of Li sufficient to contribute to charge and discharge can not be ensured, and the charge / discharge capacity may decrease. More preferably 0.75 or more and 0.85 or less.

In the composition formula (1), the content of Co is in the range of 0.05 to 0.3. If the Co content is 0.05 or more, the layered structure can be maintained and excellent charge / discharge cycle characteristics can be obtained. On the other hand, in the case where the content of Co exceeds 0.3, the cost of Co is high, which is industrially disadvantageous. More preferably in the range of 0.1 to 0.2.

In the composition formula (1), M is at least one element selected from the group consisting of Mg, Al, Ti, Mn, Zr, Mo and Nb. In the composition formula (1), electrochemical activity in the layered positive electrode active material can be ensured by containing a transition metal element such as Ni or Co. By substituting these transition metal sites with at least one element selected from the group consisting of Mg, Al, Ti, Mn, Zr, Mo, and Nb as the element of M, the stability of the crystal structure and the stability of the layered positive electrode active material The electrochemical characteristics (such as cycle characteristics) can be improved.

The composition of the primary particles or the secondary particles of the cathode active material for a lithium ion secondary battery according to the present embodiment is not strictly limited to the stoichiometric ratio and the composition may have an inferior proportion insofar as the object of the present invention does not deviate , And may have substitution or deletion of sites on the crystal structure. That is, variation of the composition due to the difference in crystal composition within a range in which the layered compound structure can be maintained is allowed. Therefore, if the ideal composition is balanced, the amount of M is 1-x-y-z. However, the amount of M in the allowable range may deviate from the value of 1-x-y-z. The allowable range is about ± 0.06. The amount of oxygen may be either deficient or excessive if the layered structure is maintained.

The cathode active material for a lithium secondary battery according to the present embodiment includes primary particles having a predetermined composition or secondary particles in which primary particles are aggregated and the primary particles or secondary particles further contain a free lithium compound can do. The free lithium compound is not a compound capable of reversibly intercalating and deintercalating Li, and includes at least a compound selected from the group consisting of lithium carbonate, lithium hydroxide, lithium sulfate, lithium nitrate, and lithium chloride. In the positive electrode active material for a lithium secondary battery according to the present embodiment, the weight of lithium hydroxide in the free lithium compound is 60% or less of the weight of lithium carbonate.

As described above, lithium hydroxide reacts with the fluorine-based electrolyte contained in the electrolytic solution to generate hydrofluoric acid (HF), which is a strong acid, and oxidative decomposition of the electrolytic solution is accelerated by high voltage, It is difficult to obtain. Therefore, in the positive electrode active material for a lithium ion secondary battery according to the present embodiment, by suppressing the absolute amount of the free lithium compound and reducing the weight of lithium hydroxide in particular, the decomposition of the electrolytic solution due to contact between lithium hydroxide and the electrolyte is suppressed Thereby improving the charge-discharge cycle characteristics.

If the weight ratio of the free lithium compound is too large, the charge / discharge capacity tends to decrease. When Li ₂ CO ₃ is present in a small amount as a free lithium compound, reaction of Li ₂ CO ₃ + CO ₂ + ₂ LiHCO ₃ occurs, so that atmospheric CO ₂ or H ₂ O reacts with Li in the crystal, Can be suppressed. Therefore, in the primary particles or the secondary particles of the positive electrode active material for a lithium ion secondary battery according to the present embodiment, the weight ratio of the free lithium compound is 0.1% or more and 2.0% or less. More preferably, it is not less than 0.1% and not more than 1.0%. More preferably, it is 0.4% or more and 0.8% or less. Within this range, a high discharge capacity characteristic and a high charge / discharge cycle characteristic can be achieved at the same time. The content of lithium carbonate in the primary particles or the secondary particles of the positive electrode active material is preferably 0.07 wt% or more and 1.50 wt% or less.

Another factor for lowering the charging / discharging cycle characteristics of the layered positive electrode active material is the breakage of secondary particles due to expansion and contraction due to charging and discharging. If the secondary particles are broken, the contact area between the surface of the secondary particles and the electrolytic solution increases more than necessary, and the decomposition of the electrolytic solution is promoted, which may result in deterioration of battery performance.

Therefore, in the cathode active material for a lithium ion secondary battery according to the present embodiment, in order to suppress breakage of secondary particles due to expansion and contraction due to charging and discharging, open pores are formed in the secondary particles, , And the pore volume ratio in the range of not less than 0.1 μm and not more than 0.5 μm obtained by the mercury porosimetry (the ratio of the total volume of open pores having a pore size of not less than 0.1 μm and not more than 0.5 μm occupying the apparent volume of the secondary particles ) Is preferably not less than 7% and not more than 20%. When the void pore volume ratio is too small, it is difficult to suppress breakage of secondary particles due to charging and discharging. On the other hand, if the void pore volume ratio is too large, the ratio of the cathode active material in the electrode becomes small, and it is difficult to obtain a high charge / discharge capacity. Therefore, as described above, the open pore volume ratio of the secondary particles is preferably 7% or more and 20% or less, and more preferably 8% or more and 16% or less. Within this range, high charge / discharge capacity characteristics and high charge / discharge cycle characteristics can be achieved.

There are two types of pores in the secondary particles: open pores connected to the particle surface and waste pores not connected to the particle surface. Among these, it is effective to control the open porosity because it is difficult to participate in charging and discharging.

In the positive electrode active material for a lithium secondary battery according to the present embodiment, the Ni concentration on the surface of the primary particles or secondary particles is preferably lower than the Ni concentration in the vicinity of the center. Here, the term &quot; surface &quot; refers to a region from the outermost surface of the primary particle or secondary particle to a depth of 20 nm, and &quot; near the center &quot; means that when the diameter of the primary particle or secondary particle is 100% Quot; refers to a region of 50% of the central portion of the substrate. The Ni concentration is an average concentration in each of the above-mentioned regions. Ni is in an unstable charge state at the time of charging and promotes oxidative decomposition of the electrolytic solution to deteriorate battery performance. Therefore, it is preferable that the concentration of Ni is low only in the vicinity of the surface. Here, the concentration is "low" means that the value (atomic ratio) of Ni / (Ni + Co + M) on the surface is a value of Ni / (Ni + Co + M) ), Which is at least 0.01 lower.

The crystal structure of the particles of the cathode active material for a lithium secondary battery according to the present embodiment can be confirmed by X-ray diffraction (XRD) or the like. The average composition of particles of the cathode active material for a lithium secondary battery according to the present embodiment (in this case, an average composition of a compound functioning as a cathode active material and a free lithium compound) is measured by an inductively coupled plasma (ICP) , And Atomic Absorption Spectrometry (AAS). The elemental distributions of the particles of the cathode active material for a lithium secondary battery according to the present embodiment can be measured by a time-of-flight secondary ion mass spectrometer (TOF-SIMS), Auger Electron Spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and electron energy loss spectroscopy (TEM-EELS).

The open pore volume of the positive electrode active material for a lithium secondary battery according to the present embodiment is measured using a mercury porosimetry method. In the mercury infusion method, only pores (open pores) connected to the particle surface are initially measured, and the pores are not measured. In addition, since it is necessary that the measurement value does not include voids between the secondary particles, in this embodiment, the open pore volume in the range of 0.1 to 0.5 μm is measured. The open pore volume ratio can be calculated by multiplying the measured open pore volume (per unit weight) by the apparent density of the secondary particles.

The quantitative determination of the free lithium compound in the primary particles or the secondary particles of the cathode active material for a lithium secondary battery according to the present embodiment can be carried out by a titration method or a temperature-induced desorption-mass spectrometry (TPD- MS), ion chromatography (IC), and the like. Further, the value of "1 + x" in the composition formula (1) can be calculated from the average composition of the particles of the positive electrode active material for a lithium secondary battery measured by ICP and the like and the result of quantitative determination of the free lithium compound.

The average particle diameter of the primary particles of the cathode active material for a lithium secondary battery according to the present embodiment is preferably 0.1 占 퐉 or more and 2 占 퐉 or less. By setting the average particle diameter to 2 mu m or less, the filling performance of the positive electrode active material in the positive electrode is improved, and a satisfactory energy density can be achieved. Further, the cathode active material may be secondary granulated by granulating the produced primary particles by dry granulation or wet granulation. As the assembly means, for example, a granulator such as a spray dryer or an electric fluidized bed apparatus can be used. The average particle diameter of the secondary particles is preferably 5 탆 or more and 50 탆 or less.

The average particle diameter can be measured by observing with a scanning electron microscope (SEM) or a transmission electron microscope (TEM). By observation, ten primary particles or secondary particles are extracted in the order in which the particle diameters are close to the median value, and the weighted average of these particle diameters is calculated to obtain an average particle diameter. The particle diameter can be obtained as an average value of the long diameter and the short diameter of the particles in the observed electron microscopic image.

The BET specific surface area of the cathode active material for a lithium secondary battery according to the present embodiment is preferably 0.2 m2 / g or more and 1.5 m2 / g or less. Particularly preferably 0.2 m 2 / g or more and 1.0 m 2 / g or less. By setting the BET specific surface area to 1.5 m &lt; 2 &gt; / g or less, preferably 1.0 m &lt; 2 &gt; / g or less, the filling performance of the positive electrode active material in the positive electrode is improved and a satisfactory energy density can be achieved. The BET specific surface area can be measured using an automatic specific surface area measuring apparatus.

A method of manufacturing the positive electrode active material for a lithium ion secondary battery according to the present embodiment will be described. The cathode active material can be produced in accordance with a general method for producing a cathode active material. Examples of such a production method include a solid phase method, a coprecipitation method, a sol-gel method, a hydrothermal method, .

In the production of the positive electrode active material using the solid phase method, the Li-containing compound, Ni-containing compound, Co-containing compound and M-containing compound as raw materials are weighed at a ratio of a predetermined element composition and pulverized and mixed to prepare a raw material powder. As the Li-containing compound, for example, lithium acetate, lithium nitrate, lithium carbonate, lithium hydroxide, lithium chloride, lithium sulfate and the like can be used, but lithium carbonate and lithium hydroxide are preferably used. As the Ni and Co-containing compound, for example, oxides, hydroxides, carbonates, sulfates, and acetate salts can be used, but oxides, hydroxides and carbonates are preferably used. As the M-containing compound, for example, an acetate, a nitrate, a carbonate, a sulfate, an oxide, a hydroxide and the like can be used, but a carbonate, an oxide and a hydroxide are preferably used.

The pulverizing and mixing to prepare the raw material powder may be either dry pulverization or wet pulverization. As the grinding means, for example, a grinder such as a ball mill, a bead mill, a planetary ball mill, an attritor or a jet mill may be used.

The prepared raw material powder becomes primary particles of the cathode active material by calcination. It is preferable that the raw material powder is sintered by pyrolysis of the raw material compound by calcination. Also, it may be subjected to crushing and classification of the enemy before firing. The heating temperature in the plasticity is, for example, about 400 ° C to 700 ° C, and the heating temperature in the sintering is, for example, 700 ° C or more and 900 ° C or less, preferably 750 ° C or more and 850 ° C or less do. With such a temperature range, the crystallinity can be improved while avoiding decomposition of the cathode active material and volatilization of the components. The firing time in the plasticity is 2 hours to 24 hours, preferably 4 hours to 16 hours, and the firing time in the firing is 2 hours to 24 hours, preferably 4 hours or more 16 hours or less. The firing may be repeated a plurality of times. Further, in the present invention, washing with water after firing is unnecessary.

The firing atmosphere may be any of an inert gas atmosphere and an oxidizing gas atmosphere, but it is preferable that the atmosphere is an oxidizing gas atmosphere such as oxygen or air. By carrying out firing in an oxidizing gas atmosphere, impurities can be prevented from being mixed due to incomplete thermal decomposition of the raw material compound, and the crystallinity can be improved. The fired particles may be subjected to rapid cooling or air cooling, and may be quenched by using liquid nitrogen or the like.

Particularly, in the present invention, it is preferable that the content of the free lithium compound contained in the primary particles or the secondary particles is 0.1% or more and 2.0% or less, and the weight of the lithium hydroxide in the free lithium compound is 60% . In the production of the cathode active material for a lithium ion secondary battery according to the present embodiment, the above "0.1% to 2.0%" and "60% or less" can be realized by adjusting the composition of the raw material powder or changing the firing conditions. For example, in the case where lithium carbonate is used as the Li-containing compound, when the firing conditions are set to an oxygen atmosphere and lithium hydroxide is used as the Li-containing compound, the weight of the lithium hydroxide To 60% or less, but the present invention is not limited to this method. In the present invention, the quantitative value of the free lithium compound contained in the primary particle or the secondary particle shall be a value measured under the condition that the period of time left in the atmosphere after the calcination is within 10 hours. If it exceeds 10 hours, lithium hydroxide changes into lithium carbonate in the atmosphere, and the carbon content tends to increase.

The open pore volume ratio can be adjusted by arbitrarily setting the conditions of the firing temperature in the firing step and the assembling conditions when the primary particles are assembled by using a granulator such as a spray dryer or an electric fluidized bed apparatus. For example, by increasing the firing temperature, the sintering of the primary particles proceeds and the open pore volume ratio decreases. On the other hand, the open pore volume ratio increases as the firing temperature is lowered. The assembly may be performed after the firing step, or may be performed after the raw powder is pulverized and mixed.

The positive electrode active material for a lithium ion secondary battery manufactured as described above is used as a material for a positive electrode for a lithium ion secondary battery.

The positive electrode for a lithium ion secondary battery according to the present embodiment mainly includes a positive electrode composite material layer including a positive electrode active material for a lithium ion secondary battery, a conductive material and a binder, and a positive electrode current collector coated with the positive electrode composite material layer.

As the conductive material, a conductive material used in general lithium ion secondary batteries can be used. Specific examples include graphite powder, carbon particles such as acetylene black, furnace black, thermal black and channel black, and carbon fibers. The conductive material may be used in an amount of, for example, 3 mass% or more and 10 mass% or less with respect to the total mass of the positive electrode composite material layer.

As the binder, a binder used in general lithium ion secondary batteries can be used. Specific examples thereof include polyvinylidene fluoride (PVDF), polytetrafluoroethylene, polyhexafluoropropylene, styrene-butadiene rubber, carboxymethylcellulose and the like. The binder may be used in an amount of, for example, 2 mass% or more and 10 mass% or less with respect to the mass of the whole positive electrode composite material layer.

As the positive electrode current collector, foil made of aluminum or aluminum alloy, expanded metal, punching metal, or the like can be used. The thickness of the foil may be, for example, about 8 μm or more and 20 μm or less.

The positive electrode for a lithium ion secondary battery according to the present embodiment can be produced by using a positive electrode active material for a lithium ion secondary battery according to a general method for producing a positive electrode. An example of a method for producing a positive electrode for a lithium ion secondary battery includes a positive electrode composite material preparing step, a positive electrode material coating step, and a forming step.

In the positive electrode mixture preparing step, the positive electrode active material, the conductive material, and the binder which are the materials are mixed in a solvent to prepare a slurry-like positive electrode mixture. The solvent may be selected from the group consisting of N, N-dimethylformamide, N, N-dimethylacetamide, methanol, ethanol, propanol, isopropanol, ethylene glycol, diethylene glycol, Glycerin, dimethyl sulfoxide, tetrahydrofuran and the like. Examples of the stirring means for mixing the materials include a planetary mixer, a disper mixer, and a rotation / revolution mixer.

In the anode composite coating process, the cathode composite material in slurry form prepared is coated on the cathode current collector, and then the solvent is dried by heat treatment to form the cathode composite material layer. Examples of the coating means for applying the positive electrode composite material include a bar coater, a doctor blade, and a roll transfer machine.

In the molding step, the dried positive electrode composite material layer is pressure-formed by a roll press or the like, and is cut together with a positive electrode current collector if necessary, thereby forming a positive electrode for a lithium ion secondary battery in a desired shape. The thickness of the positive electrode composite material layer formed on the positive electrode collector may be, for example, about 50 탆 to 300 탆.

The positive electrode for a lithium ion secondary battery manufactured as described above is used as a material for a lithium ion secondary battery. The lithium ion secondary battery according to the present embodiment mainly includes a positive electrode for a lithium ion secondary battery, a negative electrode for a lithium ion secondary battery, a separator, and a nonaqueous electrolyte solution, and has an outer shape of various shapes such as a cylindrical shape, a square shape, a button shape, As shown in Fig.

1 is a schematic cross-sectional view showing an example of a lithium ion secondary battery according to the present embodiment. Fig. 1 illustrates a cylindrical lithium ion secondary battery. The lithium ion secondary battery 10 includes a positive electrode 1 coated with a positive electrode material on both surfaces of a positive electrode collector, and a negative electrode 1 formed on both surfaces of the negative electrode collector. And a separator 3 interposed between the positive electrode 1 and the negative electrode 2. The negative electrode 2 includes a positive electrode 1 and a positive electrode 2, The positive electrode 1 and the negative electrode 2 are wound via a separator 3 and are accommodated in a cylindrical battery can 4. The positive electrode 1 is electrically connected to the sealing lid 6 via the positive electrode lead piece 7 and the negative electrode 2 is electrically connected to the battery can 4 via the negative electrode lead piece 5. [ An insulating plate 9 made of an epoxy resin or the like is disposed between the positive electrode lead piece 7 and the negative electrode 2 and between the negative electrode lead piece 5 and the positive electrode 1 to be electrically insulated have. Each lead piece is a current lead-out member made of the same material as each current collector, and is bonded to each current collector by spot welding or ultrasonic welding. The battery can 4 is structured such that the nonaqueous electrolyte is injected into the battery can 4 and then sealed with a sealant 8 such as rubber and the top portion is sealed with a sealing lid 6. [

The negative electrode for a lithium ion secondary battery can be composed of a negative electrode active material and a negative electrode collector used in a general lithium ion secondary battery.

As the negative electrode active material, for example, at least one of metal lithium, a carbon material, a metal material, and a metal oxide material can be used. Examples of the carbon material include graphite such as natural graphite and artificial graphite, carbonized materials such as coke and pitch, amorphous carbon, and carbon fiber. Examples of the metal material include metal oxides including lithium, silicon, tin, aluminum, indium, gallium, magnesium, alloys thereof, and metal oxide materials including tin and silicon.

The negative electrode for the lithium ion secondary battery may be selected from the same group as the binder and the conductive material used for the positive electrode for the lithium ion secondary battery. The binder may be, for example, an amount of about 5% by mass based on the mass of the entire negative electrode composite layer.

As the negative electrode current collector, a copper foil or nickel foil, expanded metal, punching metal or the like can be used. The thickness of the foil may be, for example, about 5 탆 or more and about 20 탆 or less.

The negative electrode for a lithium ion secondary battery is manufactured by coating a negative electrode mixture obtained by mixing a negative electrode active material and a binder with an anode current collector such as a positive electrode for a lithium ion secondary battery, The thickness of the negative electrode composite layer formed on the negative electrode collector may be, for example, about 20 μm or more and 150 μm or less.

As the separator, a polyolefin resin such as polyethylene, polypropylene or polyethylene-polypropylene copolymer, a microporous film such as a polyamide resin or an aramid resin, or a nonwoven fabric may be used.

As the non-aqueous _{electrolyte, LiClO 4, LiPF 6, LiBF} 4, LiAsF 6, LiSbF 6, LiCF 3 SO 3, LiC 4 F 9 SO 3, LiCF 3 CO 2, Li 2 C 2 F 4 (SO 3) 2, LiN ( CF ₃ SO ₂ ) ₂ , and LiC (CF ₃ SO ₂ ) ₃ in a non-aqueous solvent. The concentration of the lithium salt in the non-aqueous electrolyte solution is preferably 0.7 M or more and 1.5 M or less.

As the non-aqueous solvent, diethyl carbonate, dimethyl carbonate, ethylene carbonate, propylene carbonate, vinylene carbonate, ethylmethyl carbonate, methylpropyl carbonate, methyl acetate, dimethoxyethane and the like can be used. In addition, various additives may be added to the non-aqueous electrolyte for the purpose of suppressing oxidative decomposition and reduction decomposition of the electrolytic solution, preventing precipitation of metal elements, improving ionic conductivity, and improving flame retardancy. Examples of such additives include, for example, 1,3-propane sultone, 1,4-butane sultone and the like, which inhibit the decomposition of the electrolytic solution, insoluble polyadipic anhydride and hexahydrophthalic anhydride which improve the preservability of the electrolytic solution, And fluorine-substituted alkyl boron which improves the corrosion resistance.

The lithium ion secondary battery according to the present embodiment having the above configuration can be used as a power source for a small power source such as a portable electronic device or a household electric device, a power source for a power storage device, an uninterruptible power source device, a power leveling device, , Railroad cars, hybrid cars, electric vehicles, and the like.

[Example]

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the technical scope of the present invention is not limited thereto.

(Example 1)

The cathode active material for a lithium ion secondary battery according to Example 1 was produced in the following order. First, raw materials such as lithium carbonate, nickel carbonate, cobalt carbonate and manganese carbonate were weighed so that Li: Ni: Co: Mn had a molar concentration ratio of 1.03: 0.75: 0.15: 0.10, Powder was prepared. The obtained raw material powder was spray-dried with a spray dryer and then charged into a high-purity alumina vessel, and calcination was carried out at 600 占 폚 for 12 hours under an oxygen stream. Then, the obtained calcined body was air-cooled, pulverized, and then charged into a high-purity alumina vessel to carry out main firing at 780 ° C for 8 hours under an oxygen stream. Then, the obtained sintered body was air-cooled, crushed and classified.

The crystal structure of the obtained positive electrode active material was analyzed. Using a X-ray diffractometer (Rigaku RINTIII) and measuring with a CuK? Line, the peak of the layered structure attributable to R3-m was confirmed. The average composition was measured by ICP to find that Li: Ni: Co: Mn was 1.00: 0.75: 0.15: 0.10.

The total amount of free lithium compound was quantified using the titration method, and the amount of Li ₂ CO ₃ was quantitatively determined using the IC method. The amount of LiOH was determined assuming that the remainder were all LiOH. As a result, LiOH was 0.08 wt%, Li ₂ CO ₃ was 0.49 wt%, and the weight of LiOH was 16% of the weight of Li ₂ CO ₃ . And using the carbonate as a lithium source, Li ₂ CO _3, except since the highest potential present as LiOH formed by reaction with moisture in the air, the total free lithium compound of the above named both of Li ₂ CO _3, except LiOH assumption is valid . The composition formula calculated from the average composition measured by ICP and the quantitative determination of the free lithium compound was Li _0.984 Ni _0.75 Co _0.15 Mn _0.10 O ₂ .

Fig. 2 shows the pore volume distribution of the secondary particles measured by the mercury porosimetry. The measurement apparatus was a MicroPhysical Model 9520 manufactured by Micromeritics. It was found that the pore volume ratio within the range of the pore size of 0.1 mu m or more and 0.5 mu m or less was 0.404 mL / g, and the apparent density of the secondary particles was 3.58 g / mL, so that the open pore volume ratio was 14%.

The average particle diameter of the primary particles of the positive electrode active material was also calculated. SEM (Hitachi High-Technologies Corporation S-4300) was used and observed at an acceleration voltage of 5 kV and a magnification of 10 k, and the average particle diameter of the ten primary particles was calculated as the average particle diameter.

Further, the BET specific surface area of the positive electrode active material was measured. The specific surface area was calculated from the adsorption / desorption isotherm curve by the Langmuir method using an automatic specific surface area / pore distribution measuring device (BELSORP-mini manufactured by BEL). As a result, the BET specific surface area was 0.5 m 2 / g.

Next, a lithium ion secondary battery having a positive electrode containing the obtained positive electrode active material for a lithium ion secondary battery was produced. First, 90 parts by mass of the obtained positive electrode active material, 6 parts by mass of the conductive material and 4 parts by mass of the binder were mixed in a solvent and stirred with a planetary mixer for 3 hours to prepare a positive electrode mixture. In addition, powder of carbon particles was used as the conductive material, polyvinylidene fluoride was used as the binder, and N-methylpyrrolidone was used as the solvent. Subsequently, the resulting positive electrode composite material was applied to one side of a 15 占 퐉 -thick aluminum foil positive pole collector using a blade coater, and then pressed using a roll press so as to have a compound density of 2.70 g / Mm to form a positive electrode for a lithium ion secondary battery.

The cathode was made of metal lithium. As the non-aqueous electrolyte, a lithium ion secondary battery according to Example 1 was produced by using LiPF ₆ dissolved in a mixed solvent of ethylene carbonate and dimethyl carbonate having a volume ratio of 1: 2 at a concentration of 1.0 mol / L.

Next, the produced lithium ion secondary battery was subjected to a charge-discharge test to evaluate discharge capacity characteristics and charge-discharge cycle characteristics. The charge-discharge test was conducted at an environmental temperature of 25 ° C.

The discharge capacity characteristics were obtained in the following procedure. Charging and discharging conditions are as follows: constant current and low voltage charging up to an upper limit voltage of 4.3 V with a current equivalent to 0.2 C, and a discharge for 30 minutes after charging, and then to a lower limit voltage of 3.0 V with a constant current equivalent to 0.2 C As shown in FIG. This charge-discharge cycle was repeated two times in total. Then, the 0.2C discharge capacity of the second cycle was evaluated as the discharge capacity characteristic per the weight of the cathode active material.

The charging / discharging cycle characteristics were obtained in the following procedure. The discharge capacity characteristics were evaluated, and the battery was charged at a constant current and a low voltage up to an upper limit voltage of 4.3 V with a current equivalent to 1 C, and after 10 minutes of rest, discharged at a lower limit voltage of 3.0 V at a constant current equivalent to 1.0 C. This charge / discharge cycle was repeated 47 times in total, and then charged at a constant current and a low voltage up to an upper limit voltage of 4.3 V with a current equivalent to 0.2 C and after 30 minutes of rest, discharged to a lower limit voltage of 3.0 V at a constant current equivalent to 0.2 C. Then, the fraction of the 0.2C discharge capacity at the 50th cycle with respect to the discharge capacity characteristic was calculated as the cycle capacity retention rate, and the charge-discharge cycle characteristics were evaluated.

As a result, the discharge capacity characteristic of the lithium ion secondary battery according to Example 1 was 191 Ah / kg, and the charge-discharge cycle characteristic was 92%.

(Example 2)

A cathode active material for a lithium ion secondary battery according to Example 2 was produced in the following order. Initially, lithium carbonate, nickel carbonate, cobalt carbonate and manganese carbonate were weighed so that the molar ratio of Li: Ni: Co: Mn was 1.03: 0.80: 0.10: 0.10, A positive electrode active material was prepared.

As a result of analyzing the crystal structure of the obtained positive electrode active material, it was confirmed that the peak of the layered structure attributable to R3-m was confirmed.

The average composition of the positive electrode active material was measured and found to be Li: Ni: Co: Mn of 1.00: 0.80: 0.10: 0.10.

LiOH and Li ₂ CO ₃ were quantitatively determined in the same manner as in Example 1 to find that LiOH was 0.13% by weight, Li ₂ CO ₃ was 0.56% by weight and LiOH was 23% by weight of Li ₂ CO ₃ I could. The composition formula calculated from the average composition and the result of quantitative determination of the free lithium compound was Li _0.980 Ni _0.80 Co _0.10 Mn _0.10 O ₂ .

Also, the void volume ratio of the open pores was 16%. The primary particles had an average particle diameter of 0.6 mu m and a BET specific surface area of 0.5 m &lt; 2 &gt; / g.

Next, in the same manner as in Example 1, a lithium ion secondary battery according to Example 2 having a positive electrode containing the obtained positive electrode active material was produced, and discharge capacity characteristics and charge-discharge cycle characteristics were evaluated. As a result, the discharge capacity characteristic of the lithium ion secondary battery according to Example 2 was 198 Ah / kg and the charge / discharge cycle characteristic was 89%.

(Example 3)

A cathode active material was prepared in the same manner as in Example 2 except that the firing temperature was 760 캜.

The average composition of the positive electrode active material was measured and found to be Li: Ni: Co: Mn of 1.00: 0.80: 0.10: 0.10.

LiOH and Li ₂ CO ₃ were quantitatively determined in the same manner as in Example 1 to find that LiOH was 0.16 wt%, Li ₂ CO ₃ was 0.59 wt%, LiOH was 27 wt% of Li ₂ CO ₃ , I could. The composition formula calculated from the average composition and the quantitative determination of the free lithium compound was Li _0.978 Ni _0.80 Co _0.10 Mn _0.10 O ₂ .

Also, the pore volume ratio was 23%. The primary particles had an average particle diameter of 0.5 mu m and a BET specific surface area of 1.5 m &lt; 2 &gt; / g.

Next, in the same manner as in Example 1, a lithium ion secondary battery according to Example 3 having a positive electrode containing the obtained positive electrode active material was produced, and discharge capacity characteristics and charge-discharge cycle characteristics were evaluated. As a result, the discharge capacity characteristic of the lithium ion secondary battery according to Example 3 was 202 Ah / kg, and the charge / discharge cycle characteristic was 86%.

(Example 4)

A cathode active material for a lithium ion secondary battery according to Example 4 was produced in the following order. Initially, a cathode active material was prepared in the same manner as in Example 1, except that lithium carbonate, nickel carbonate and cobalt carbonate as raw materials were weighed so that Li: Ni: Co had a molar concentration ratio of 1.03: 0.85: 0.15.

As a result of analyzing the crystal structure of the obtained positive electrode active material, it was confirmed that the peak of the layered structure attributable to R3-m was confirmed.

The average composition of the positive electrode active material was measured, and Li: Ni: Co was 1.00: 0.85: 0.15.

LiOH and Li ₂ CO ₃ were quantitatively determined in the same manner as in Example 1 to find that LiOH was 0.20% by weight, Li ₂ CO ₃ was 0.60% by weight and LiOH was 33% by weight of Li ₂ CO ₃ I could. The composition formula calculated from the average composition and the result of quantitative determination of the free lithium compound was Li _0.976 Ni _0.85 Co _0.15 O ₂ .

Also, the void volume ratio of the open pores was 14%. The primary particles had an average particle diameter of 0.6 mu m and a BET specific surface area of 0.5 m &lt; 2 &gt; / g.

Next, in the same manner as in Example 1, a lithium ion secondary battery according to Example 4 having a positive electrode containing the obtained positive electrode active material was produced, and discharge capacity characteristics and charge-discharge cycle characteristics were evaluated. As a result, the discharge capacity characteristic of the lithium ion secondary battery according to Example 4 was 205 Ah / kg and the charge / discharge cycle characteristic was 85%.

(Example 5)

The cathode active material for a lithium ion secondary battery according to Example 5 was produced in the following order. Initially, a positive electrode active material was prepared in the same manner as in Example 1, except that lithium carbonate, nickel carbonate and cobalt carbonate as raw materials were weighed so that Li: Ni: Co was 1.13: 0.80: 0.10 by molar ratio.

As a result of analyzing the crystal structure of the obtained positive electrode active material, it was confirmed that the peak of the layered structure attributable to R3-m was confirmed.

The average composition of the cathode active material was measured, and Li: Ni: Co was 1.10: 0.80: 0.10.

LiOH and Li ₂ CO ₃ were quantitatively determined in the same manner as in Example 1 to find that LiOH was 0.20 wt%, Li ₂ CO ₃ was 0.80 wt%, LiOH was 25 wt% of Li ₂ CO ₃ , I could. The composition formula calculated from the average composition and the result of quantitative determination of the free lithium compound was Li _1.071 Ni _0.80 Co _0.10 O ₂ .

Also, the void volume ratio of the open pores was 8%. The primary particles had an average particle diameter of 1.0 mu m and a BET specific surface area of 0.2 m &lt; 2 &gt; / g.

Next, in the same manner as in Example 1, a lithium ion secondary battery according to Example 5 having a positive electrode containing the obtained positive electrode active material was produced, and discharge capacity characteristics and charge / discharge cycle characteristics were evaluated. As a result, the discharge capacity characteristic of the lithium ion secondary battery according to Example 5 was 186 Ah / kg and the charge-discharge cycle characteristic was 80%.

(Example 6)

The cathode active material for a lithium ion secondary battery according to Example 6 was produced in the following order. First, lithium carbonate, nickel carbonate, cobalt carbonate and aluminum hydroxide as raw materials were weighed so that the molar ratio of Li: Ni: Co: Al was 1.03: 0.70: 0.20: 0.10 in the same manner as in Example 1, A positive electrode active material was prepared.

As a result of analyzing the crystal structure of the obtained positive electrode active material, it was confirmed that the peak of the layered structure attributable to R3-m was confirmed.

The average composition of the cathode active material was measured and found to be Li: Ni: Co: Al of 1.00: 0.70: 0.20: 0.10.

LiOH and Li ₂ CO ₃ were quantitatively determined in the same manner as in Example 1 to find that LiOH was 0.04% by weight, Li ₂ CO ₃ was 0.36% by weight, LiOH was 11% by weight of Li ₂ CO ₃ , I could. The composition formula calculated from the average composition and the quantitative determination of the free lithium compound was Li _0.989 Ni _0.70 Co _0.20 Al _0.10 O ₂ .

Also, the void volume ratio of the open pores was 12%. The primary particles had an average particle diameter of 0.6 mu m and a BET specific surface area of 0.5 m &lt; 2 &gt; / g.

Next, in the same manner as in Example 1, a lithium ion secondary battery according to Example 6 including the obtained positive electrode active material-containing anode was manufactured, and the discharge capacity characteristics and the charge-discharge cycle characteristics were evaluated. As a result, the discharge capacity characteristic of the lithium ion secondary battery according to Example 6 was 187 Ah / kg, and the charge / discharge cycle characteristic was 92%.

(Example 7)

The cathode active material for a lithium ion secondary battery according to Example 7 was produced in the following order. Initially, lithium carbonate, nickel carbonate, cobalt carbonate and manganese carbonate were weighed so that the molar ratio of Li: Ni: Co: Mn was 0.98: 0.75: 0.20: 0.10, A positive electrode active material was prepared.

As a result of analyzing the crystal structure of the obtained positive electrode active material, it was confirmed that the peak of the layered structure attributable to R3-m was confirmed.

The average composition of the positive electrode active material was measured and found to be 0.95: 0.75: 0.20: 0.10 for Li: Ni: Co: Mn.

LiOH and Li ₂ CO ₃ were quantitatively determined in the same manner as in Example 1 to find that LiOH was 0.28% by weight, Li ₂ CO ₃ was 0.53% by weight and LiOH was 53% by weight of Li ₂ CO ₃ I could. The composition formula calculated from the average composition and the quantitative determination of the free lithium compound was Li _0.925 Ni _0.75 Co _0.20 Mn _0.10 O ₂ .

Also, the void volume ratio of the open pores was 11%. The primary particles had an average particle diameter of 0.4 mu m and a BET specific surface area of 0.7 m &lt; 2 &gt; / g.

Next, in the same manner as in Example 1, a lithium ion secondary battery according to Example 7 having a positive electrode containing the obtained positive electrode active material was prepared, and discharge capacity characteristics and charge / discharge cycle characteristics were evaluated. As a result, the discharge capacity characteristic of the lithium ion secondary battery according to Example 7 was 180 Ah / kg, and the charge-discharge cycle characteristic was 84%.

(Example 8)

The cathode active material for a lithium ion secondary battery according to Example 8 was produced in the following order. First, lithium carbonate, nickel carbonate, cobalt carbonate and magnesium hydroxide as raw materials were weighed so as to have a molar ratio of Li: Ni: Co: Mg of 1.03: 0.80: 0.19: 0.01 in the same manner as in Example 1, A positive electrode active material was prepared.

As a result of analyzing the crystal structure of the obtained positive electrode active material, it was confirmed that the peak of the layered structure attributable to R3-m was confirmed.

The average composition of the positive electrode active material was measured, and Li: Ni: Co: Mg was 1.00: 0.80: 0.19: 0.01.

LiOH and Li ₂ CO ₃ were quantitatively determined in the same manner as in Example 1 to find that LiOH was 0.15% by weight, Li ₂ CO ₃ was 0.53% by weight and LiOH was 28% by weight of Li ₂ CO ₃ I could. The composition formula calculated from the average composition and the quantitative determination of the free lithium compound was Li _0.980 Ni _0.80 Co _0.19 Mg _0.01 O ₂ .

Also, the void volume ratio of the open pores was 14%. The primary particles had an average particle diameter of 0.3 mu m and a BET specific surface area of 0.8 m &lt; 2 &gt; / g.

Next, in the same manner as in Example 1, a lithium ion secondary battery according to Example 8 having a positive electrode containing the obtained positive electrode active material was produced, and discharge capacity characteristics and charge / discharge cycle characteristics were evaluated. As a result, the discharge capacity characteristic of the lithium ion secondary battery according to Example 8 was 195 Ah / kg, and the charge-discharge cycle characteristic was 90%.

(Example 9)

A cathode active material for a lithium ion secondary battery according to Example 9 was produced in the following order. First, lithium carbonate, nickel carbonate, cobalt carbonate and titanium oxide as raw materials were weighed so that the molar ratio of Li: Ni: Co: Ti was 1.03: 0.80: 0.19: 0.01 in the same manner as in Example 1, A positive electrode active material was prepared.

As a result of analyzing the crystal structure of the obtained positive electrode active material, it was confirmed that the peak of the layered structure attributable to R3-m was confirmed.

The average composition of the positive electrode active material was measured, and Li: Ni: Co: Ti was 1.00: 0.80: 0.19: 0.01.

LiOH and Li ₂ CO ₃ were quantitatively determined in the same manner as in Example 1 to find that LiOH was 0.12 wt%, Li ₂ CO ₃ was 0.56 wt%, LiOH was 21 wt% of Li ₂ CO ₃ , I could. The composition formula calculated from the average composition and the result of quantitative determination of the free lithium compound was Li _0.980 Ni _0.80 Co _0.19 Ti _0.01 O ₂ .

Also, the void volume ratio of the open pores was 8%. The primary particles had an average particle diameter of 0.5 mu m and a BET specific surface area of 0.4 m &lt; 2 &gt; / g.

Next, in the same manner as in Example 1, a lithium ion secondary battery according to Example 9 having a positive electrode containing the obtained positive electrode active material was produced, and discharge capacity characteristics and charge / discharge cycle characteristics were evaluated. As a result, the discharge capacity characteristic of the lithium ion secondary battery according to Example 9 was 202 Ah / kg, and the charge-discharge cycle characteristic was 88%.

(Example 10)

The cathode active material for a lithium ion secondary battery according to Example 10 was produced in the following order. First, lithium carbonate, nickel carbonate, cobalt carbonate, and zirconium oxide were weighed in the same manner as in Example 1 except that Li: Ni: Co: Zr was molar ratio of 1.03: 0.80: 0.19: A positive electrode active material was prepared.

As a result of analyzing the crystal structure of the obtained positive electrode active material, it was confirmed that the peak of the layered structure attributable to R3-m was confirmed.

The average composition of the positive electrode active material was measured, and Li: Ni: Co: Zr was 1.00: 0.80: 0.19: 0.01.

LiOH and Li ₂ CO ₃ were quantitatively determined in the same manner as in Example 1 to find that LiOH was 0.17% by weight, Li ₂ CO ₃ was 0.55% by weight and LiOH was 31% by weight of Li ₂ CO ₃ I could. The composition formula calculated from the average composition and the quantitative determination of the free lithium compound was Li _0.979 Ni _0.80 Co _0.19 Zr _0.01 O ₂ .

Also, the void volume ratio of the open pores was 11%. The primary particles had an average particle diameter of 0.5 mu m and a BET specific surface area of 0.4 m &lt; 2 &gt; / g.

Next, in the same manner as in Example 1, a lithium ion secondary battery according to Example 10 having a positive electrode containing the obtained positive electrode active material was produced, and discharge capacity characteristics and charge-discharge cycle characteristics were evaluated. As a result, the discharge capacity characteristic of the lithium ion secondary battery according to Example 10 was 199 Ah / kg, and the charge-discharge cycle characteristic was 90%.

(Example 11)

The cathode active material for a lithium ion secondary battery according to Example 11 was produced in the following order. Initially, lithium carbonate, nickel carbonate, cobalt carbonate and molybdenum oxide were weighed so that the molar ratio of Li: Ni: Co: Mo was 1.03: 0.80: 0.19: 0.01 in the same manner as in Example 1, A positive electrode active material was prepared.

As a result of analyzing the crystal structure of the obtained positive electrode active material, it was confirmed that the peak of the layered structure attributable to R3-m was confirmed.

The average composition of the positive electrode active material was measured, and Li: Ni: Co: Mo was 1.00: 0.80: 0.19: 0.01.

LiOH and Li ₂ CO ₃ were quantified in the same manner as in Example 1 to find that LiOH was 0.23 wt%, Li ₂ CO ₃ was 0.72 wt%, LiOH was 32 wt% of Li ₂ CO ₃ , I could. The composition formula calculated from the average composition and the quantitative determination of the free lithium compound was Li _0.972 Ni _0.80 Co _0.19 Mo _0.10 O ₂ .

Also, the void volume ratio of the open pores was 14%. The primary particles had an average particle diameter of 0.4 mu m and a BET specific surface area of 0.7 m &lt; 2 &gt; / g.

Next, in the same manner as in Example 1, a lithium ion secondary battery according to Example 11 having a positive electrode containing the obtained positive electrode active material was manufactured, and discharge capacity characteristics and charge-discharge cycle characteristics were evaluated. As a result, the discharge capacity characteristic of the lithium ion secondary battery according to Example 11 was 193 Ah / kg, and the charge / discharge cycle characteristic was 86%.

(Example 12)

The cathode active material for a lithium ion secondary battery according to Example 12 was produced in the following order. First, lithium carbonate, nickel carbonate, cobalt carbonate, and niobium oxide were weighed in the same manner as in Example 1 except that Li: Ni: Co: Nb was molar ratio of 1.03: 0.80: 0.19: A positive electrode active material was prepared.

As a result of analyzing the crystal structure of the obtained positive electrode active material, it was confirmed that the peak of the layered structure attributable to R3-m was confirmed.

The average composition of the positive electrode active material was measured, and Li: Ni: Co: Nb was 1.00: 0.80: 0.19: 0.01.

LiOH and Li ₂ CO ₃ were quantitatively determined in the same manner as in Example 1 to find that LiOH was 0.15% by weight, Li ₂ CO ₃ was 0.60% by weight and LiOH was 25% by weight of Li ₂ CO ₃ I could. The composition formula calculated from the average composition and the quantitative determination of the free lithium compound was Li _0.978 Ni _0.80 Co _0.19 Nb _0.01 O ₂ .

Also, the void volume ratio of the open pores was 14%. The primary particles had an average particle diameter of 0.4 mu m and a BET specific surface area of 0.7 m &lt; 2 &gt; / g.

Next, in the same manner as in Example 1, the lithium ion secondary battery according to Example 12 having the positive electrode containing the obtained positive electrode active material was produced, and the discharge capacity characteristics and the charge-discharge cycle characteristics were evaluated. As a result, the discharge capacity characteristic of the lithium ion secondary battery according to Example 12 was 188 Ah / kg, and the charge / discharge cycle characteristic was 87%.

(Example 13)

The positive electrode active material for a lithium ion secondary battery according to Example 13 was produced in the following order. First, lithium carbonate, nickel carbonate, cobalt carbonate and manganese carbonate as raw materials were weighed so that Li: Ni: Co: Mn had a molar ratio of 1.00: 0.80: 0.10: 0.10, I made them in the same order. The average particle diameter of the core particles was 0.6 탆. Further, lithium carbonate, nickel carbonate and manganese carbonate were weighed so that the molar ratio of Li: Ni: Mn was 1.22: 0.2: 0.6, and these were subjected to wet pulverization and mixing to prepare raw material powders. The obtained raw material powder was dried, charged into a high-purity alumina vessel, and heat-treated at 700 ° C for 12 hours in the air. Then, the obtained calcined body was air-cooled and pulverized.

The average particle diameter of the primary particles of the calcined body was calculated as the core particles, and as a result, the average particle diameter was 0.05 탆. Next, the particles of the cathode active material core particles and the calcined body were weighed so as to have a weight ratio of 98: 2, and these were wet-mixed, and then sprayed and dried to adhere the particles of the calcined body to the surface of the core particles. Subsequently, the obtained particles were charged in a high-purity alumina vessel and heat-treated at 800 DEG C for one hour in an oxygen stream to prepare a cathode active material for lithium ion secondary batteries according to Example 13. [

As a result of analyzing the crystal structure of the obtained positive electrode active material, it was confirmed that the peak of the layered structure attributable to R3-m was confirmed.

The average composition of the positive electrode active material was measured, and Li: Ni: Co: Mn was 1.01: 0.78: 0.10: 0.11.

Next, elemental analysis was performed on the surface and near the center of the positive electrode active material. A sample of the prepared cathode active material was thinned by argon ion etching using a grinder (gatan 600 type), and then subjected to elemental analysis. Elemental analysis such as the concentration distribution of atoms on the surface was carried out by using a field emission type transmission electron microscope (HF-2000 (manufactured by Hitachi Seisakusho Co., Ltd.) equipped with energy loss spectroscopy (hereinafter abbreviated as EELS) Hereinafter abbreviated as TEM)) at an acceleration voltage of 200 kV. In addition, the elemental distribution can be confirmed by TEM-EDS combined with TEM and X-ray analysis (EDS), time-of-flight secondary ion mass spectrometry (TOF-SIMS) and Auger electron spectroscopy (AES) It is possible.

The Ni / (Ni + Co + Mn) concentration ratio (atomic ratio) is about 0.65 in the region from the outermost surface to the depth of 20 nm of the cathode active material, about 0.70 in the region from the depth of 20 nm to the depth of 60 nm, And about 0.80 in the region exceeding the depth of 90 nm from the outermost surface. The ratio of Ni / (Ni + Co + Mn) in the vicinity of the center is estimated to be about 0.80 because the Ni / (Ni + Co + Mn) concentration ratio becomes constant in the region exceeding the depth of 90 nm from the outermost surface. Therefore, it was confirmed that the surface ratio of Ni / (Ni + Co + Mn) was lower than that in the vicinity of the center.

LiOH and Li ₂ CO ₃ were quantitatively determined in the same manner as in Example 1 to find that LiOH was 0.02% by weight, Li ₂ CO ₃ was 0.08% by weight and LiOH was 25% by weight of Li ₂ CO ₃ I could. The composition formula calculated from the average composition and the quantitative determination of the free lithium compound was Li _1.007 Ni _0.78 Co _0.10 Mn _0.11 O ₂ .

Also, the void volume ratio of the open pores was 8%. The primary particles had an average particle diameter of 0.5 mu m and a BET specific surface area of 0.4 m &lt; 2 &gt; / g.

Next, in the same manner as in Example 1, a lithium ion secondary battery according to Example 13 having a positive electrode containing the obtained positive electrode active material was produced, and discharge capacity characteristics and charge-discharge cycle characteristics were evaluated. As a result, the discharge capacity characteristic of the lithium ion secondary battery according to Example 13 was 187 Ah / kg, and the charge-discharge cycle characteristic was 94%.

(Example 14)

A cathode active material for a lithium ion secondary battery according to Example 14 was produced in the following order. Initially, a positive electrode active material was prepared in the same manner as in Example 1, except that lithium carbonate, nickel carbonate and cobalt carbonate as raw materials were weighed so that Li: Ni: Co was 1.22: 0.70: 0.10 by molar ratio.

As a result of analyzing the crystal structure of the obtained positive electrode active material, it was confirmed that the peak of the layered structure attributable to R3-m was confirmed.

The average composition of the positive electrode active material was measured to find that Li: Ni: Co was 1.20: 0.70: 0.10.

LiOH and Li ₂ CO ₃ were quantitatively determined in the same manner as in Example 1 to find that LiOH was 0.22 wt%, Li ₂ CO ₃ was 1.1 wt%, LiOH was 20 wt% of Li ₂ CO ₃ , I could. The composition formula calculated from the average composition and the quantitative determination of the free lithium compound was Li _1.162 Ni _0.70 Co _0.10 O ₂ .

Also, the void volume ratio of the open pores was 10%. The primary particles had an average particle diameter of 0.2 mu m and a BET specific surface area of 1.0 m &lt; 2 &gt; / g.

Next, in the same manner as in Example 1, a lithium ion secondary battery according to Example 14 including the obtained positive electrode active material was produced, and the discharge capacity characteristics and the charge / discharge cycle characteristics were evaluated. As a result, the discharge capacity characteristic of the lithium ion secondary battery according to Example 14 was 175 Ah / kg and the charge-discharge cycle characteristic was 85%.

(Example 15)

A cathode active material for a lithium ion secondary battery according to Example 15 was produced in the following order. Initially, lithium carbonate, nickel carbonate, cobalt carbonate and manganese carbonate as raw materials were weighed so that the molar ratio of Li: Ni: Co: Mn was 0.92: 0.80: 0.20: 0.10, A positive electrode active material was prepared.

As a result of analyzing the crystal structure of the obtained positive electrode active material, it was confirmed that the peak of the layered structure attributable to R3-m was confirmed.

The average composition of the cathode active material was measured and found to be 0.90: 0.80: 0.20: 0.10 for Li: Ni: Co: Mn.

LiOH and Li ₂ CO ₃ were quantitatively determined in the same manner as in Example 1, and it was found that LiOH was 0.10 wt%, Li ₂ CO ₃ was 0.45 wt%, and the weight of LiOH was 22 wt% of Li ₂ CO ₃ I could. The composition formula calculated from the average composition and the quantitative determination of the free lithium compound was Li _0.884 Ni _0.80 Co _0.20 Mn _0.10 O ₂ .

Also, the void volume ratio of the open pores was 17%. The primary particles had an average particle diameter of 0.4 mu m and a BET specific surface area of 0.7 m &lt; 2 &gt; / g.

Next, in the same manner as in Example 1, a lithium ion secondary battery according to Example 15 including the obtained positive electrode active material was produced, and the discharge capacity characteristics and the charge / discharge cycle characteristics were evaluated. As a result, the discharge capacity characteristic of the lithium ion secondary battery according to Example 15 was 181 Ah / kg and the charge / discharge cycle characteristic was 83%.

(Example 16)

The cathode active material for a lithium ion secondary battery according to Example 16 was produced in the following order. Initially, a cathode active material was produced in the same manner as in Example 2 except that the firing temperature was set at 800 캜.

As a result of analyzing the crystal structure of the obtained positive electrode active material, it was confirmed that the peak of the layered structure attributable to R3-m was confirmed.

The average composition of the positive electrode active material was measured and found to be Li: Ni: Co: Mn of 1.00: 0.80: 0.10: 0.10.

LiOH and Li ₂ CO ₃ were quantitatively determined in the same manner as in Example 1 to find that LiOH was 0.31 wt%, Li ₂ CO ₃ was 1.50 wt%, LiOH was 21 wt% of Li ₂ CO ₃ , I could. The composition formula calculated from the average composition and the quantitative determination of the free lithium compound was Li _0.948 Ni _0.80 Co _0.10 Mn _0.10 O ₂ .

Also, the void volume ratio of the open pores was 20%. The primary particles had an average particle diameter of 0.1 mu m and a BET specific surface area of 1.8 m &lt; 2 &gt; / g.

Next, in the same manner as in Example 1, the lithium ion secondary battery according to Example 16 including the obtained positive electrode active material-containing anode was manufactured, and the discharge capacity characteristics and the charge-discharge cycle characteristics were evaluated. As a result, the discharge capacity characteristic of the lithium ion secondary battery according to Example 16 was 182 Ah / kg, and the charge / discharge cycle characteristic was 80%.

(Example 17)

The cathode active material for a lithium ion secondary battery according to Example 17 was produced in the following order. Initially, a cathode active material was produced in the same manner as in Example 2 except that the firing temperature was set at 900 캜.

As a result of analyzing the crystal structure of the obtained positive electrode active material, it was confirmed that the peak of the layered structure attributable to R3-m was confirmed.

The average composition of the positive electrode active material was measured and found to be Li: Ni: Co: Mn of 1.00: 0.80: 0.10: 0.10.

LiOH and Li ₂ CO ₃ were quantified in the same manner as in Example 1 to find that LiOH was 0.08 wt%, Li ₂ CO ₃ was 0.15 wt%, and LiOH was 53 wt% of Li ₂ CO ₃ I could. The composition formula calculated from the average composition and the quantitative determination of the free lithium compound was Li _0.993 Ni _0.80 Co _0.10 Mn _0.10 O ₂ .

Also, the void volume ratio of the open pores was 7%. The primary particles had an average particle diameter of 2.4 mu m and a BET specific surface area of 0.1 m &lt; 2 &gt; / g.

Next, in the same manner as in Example 1, a lithium ion secondary battery according to Example 17 having a positive electrode containing the obtained positive electrode active material was produced, and discharge capacity characteristics and charge-discharge cycle characteristics were evaluated. As a result, the discharge capacity characteristic of the lithium ion secondary battery according to Example 17 was 184 Ah / kg, and the charge / discharge cycle characteristic was 80%.

(Example 18)

The cathode active material for a lithium ion secondary battery according to Example 18 was produced in the following order. Initially, raw materials such as lithium hydroxide, nickel carbonate, cobalt carbonate and manganese carbonate were weighed so that the molar ratio of Li: Ni: Co: Mn was 1.05: 0.80: 0.10: 0.10, A positive electrode active material was produced in the same manner as in Example 1 except that the obtained fired body was air-cooled in a CO ₂ atmosphere.

As a result of analyzing the crystal structure of the obtained positive electrode active material, it was confirmed that the peak of the layered structure attributable to R3-m was confirmed.

The average composition of the positive electrode active material was measured and found to be Li: Ni: Co: Mn of 1.00: 0.80: 0.10: 0.10.

LiOH and Li ₂ CO ₃ were quantitatively determined in the same manner as in Example 1 to find that LiOH was 0.24 wt%, Li ₂ CO ₃ was 0.65 wt%, LiOH was 37 wt% of Li ₂ CO ₃ , I could. The composition formula calculated from the average composition and the quantitative determination of the free lithium compound was Li _0.973 Ni _0.80 Co _0.10 Mn _0.10 O ₂ .

Also, the void volume ratio of the open pores was 11%. The primary particles had an average particle diameter of 1.0 mu m and a BET specific surface area of 0.2 m &lt; 2 &gt; / g.

Next, in the same manner as in Example 1, the lithium ion secondary battery according to Example 18 having the positive electrode containing the obtained positive electrode active material was produced, and the discharge capacity characteristics and the charge-discharge cycle characteristics were evaluated. As a result, the discharge capacity characteristic of the lithium ion secondary battery according to Example 18 was 196 Ah / kg, and the charge / discharge cycle characteristic was 85%.

(Comparative Example 1)

The positive electrode active material for a lithium ion secondary battery according to Comparative Example 1 was produced in the following order. The positive electrode active material for a lithium ion secondary battery according to Comparative Example 1 has a composition in which the ratio of Ni is low as compared with the embodiment.

First, lithium carbonate, nickel carbonate, cobalt carbonate, and manganese carbonate were weighed in the same manner as in Example 1, except that the molar ratio of Li: Ni: Co: Mn was 1.02: 0.60: 0.20: A positive electrode active material was prepared.

As a result of analyzing the crystal structure of the obtained positive electrode active material, it was confirmed that the peak of the layered structure attributable to R3-m was confirmed.

The average composition of the positive electrode active material was measured and found to be Li: Ni: Co: Mn of 1.00: 0.60: 0.20: 0.20.

LiOH and Li ₂ CO ₃ were quantitatively determined in the same manner as in Example 1 to find that LiOH was 0.05% by weight, Li ₂ CO ₃ was 0.12% by weight and LiOH was 42% by weight of Li ₂ CO ₃ I could. The composition formula calculated from the average composition and the result of quantitative determination of the free lithium compound was Li _0.995 Ni _0.60 Co _0.20 Mn _0.20 O ₂ .

Also, the void volume ratio of the open pores was 5%. The primary particles had an average particle diameter of 0.6 mu m and a BET specific surface area of 0.5 m &lt; 2 &gt; / g.

Next, in the same manner as in Example 1, a lithium ion secondary battery according to Comparative Example 1 having a positive electrode containing the obtained positive electrode active material was produced, and discharge capacity characteristics and charge / discharge cycle characteristics were evaluated. As a result, the discharge capacity characteristic of the lithium ion secondary battery according to Comparative Example 1 was 170 Ah / kg and the charge / discharge cycle characteristic was 93%.

(Comparative Example 2)

A cathode active material for a lithium ion secondary battery according to Comparative Example 2 was produced in the following order. The cathode active material for a lithium ion secondary battery according to Comparative Example 2 has a higher composition ratio of Ni than the embodiment. Further, lithium hydroxide was used as the Li source.

First, a cathode active material was prepared in the same manner as in Example 1, except that lithium hydroxide and nickel carbonate as raw materials were weighed so that the molar ratio of Li: Ni was 1.05: 1.00, and the firing temperature was changed to 730 캜 .

As a result of analyzing the crystal structure of the obtained positive electrode active material, it was confirmed that the peak of the layered structure attributable to R3-m was confirmed.

The average composition of the positive electrode active material was measured, and Li: Ni was 1.00: 1.00.

LiOH and Li ₂ CO ₃ were quantified in the same manner as in Example 1 to find that LiOH was 1.80 wt%, Li ₂ CO ₃ was 0.25 wt%, LiOH was 720 wt% of Li ₂ CO ₃ , I could. The composition formula calculated from the average composition and the result of quantitative determination of the free lithium compound was Li _0.920 Ni _1.00 O ₂ .

Also, the void volume ratio of the open pores was 1%. The primary particles had an average particle diameter of 2.1 mu m and a BET specific surface area of 0.1 m &lt; 2 &gt; / g.

Next, in the same manner as in Example 1, a lithium ion secondary battery according to Comparative Example 2 having a positive electrode containing the obtained positive electrode active material was produced, and discharge capacity characteristics and charge / discharge cycle characteristics were evaluated. As a result, the discharge capacity characteristic of the lithium ion secondary battery according to Comparative Example 2 was 135 Ah / kg and the charge / discharge cycle characteristic was 61%.

(Comparative Example 3)

The positive electrode active material for a lithium ion secondary battery according to Comparative Example 3 was produced in the following order. The positive electrode active material for a lithium ion secondary battery according to Comparative Example 3 is composed of particles having a free lithium compound amount and a weight ratio of LiOH higher than those of Examples.

Initially, raw materials such as lithium hydroxide, nickel carbonate, cobalt carbonate and manganese carbonate were weighed so that the molar ratio of Li: Ni: Co: Mn was 1.05: 0.75: 0.15: 0.10, A positive electrode active material was prepared in the same manner as in Example 1 except for the above.

As a result of analyzing the crystal structure of the obtained positive electrode active material, it was confirmed that the peak of the layered structure attributable to R3-m was confirmed.

The average composition of the positive electrode active material was measured and found to be Li: Ni: Co: Mn of 1.00: 0.75: 0.15: 0.10.

LiOH and Li ₂ CO ₃ were quantitatively determined in the same procedure as in Example 1 to find that LiOH was 0.72 wt%, Li ₂ CO ₃ was 0.19 wt%, LiOH was 379 wt% of Li ₂ CO ₃ , I could. The composition formula calculated from the average composition and the quantitative determination of the free lithium compound was Li _0.966 Ni _0.75 Co _0.15 Mn _0.10 O ₂ .

Also, the void volume ratio of the open pores was 3%. The primary particles had an average particle diameter of 1.6 mu m and a BET specific surface area of 0.1 m &lt; 2 &gt; / g.

Next, in the same manner as in Example 1, a lithium ion secondary battery according to Comparative Example 3 having a positive electrode containing the obtained positive electrode active material was produced, and discharge capacity characteristics and charge / discharge cycle characteristics were evaluated. As a result, the discharge capacity characteristic of the lithium ion secondary battery according to Comparative Example 3 was 192 Ah / kg, and the charge / discharge cycle characteristic was 75%.

Table 1 shows the discharge capacity characteristics (Ah / kg) and charge / discharge cycle characteristics (%) of the lithium ion secondary batteries according to Examples 1 to 18 and Comparative Examples 1 to 3, The amount of the lithium compound, the open pore volume ratio, the average particle diameter of the primary particles, and the BET specific surface area.

In the examples, the composition formula was calculated as follows. Since the cathode active material according to the present invention has a layered structure, LiM'O ₂ (M 'is a metal element). Therefore, when the respective molar concentration ratios are determined from the mass% of the measured values of Li, Ni, Co and M and the proportion of the obtained molar concentration ratios is proportionally distributed, the composition ratios of the elements other than oxygen can be calculated. _{1 + x} Ni _y Co _z M _{1 -xy- z} The coefficients x, y, z of O ₂ can be calculated and evaluated.

The respective coefficients in the examples of the present specification are obtained by proportionally allocating the sum of the molar concentration ratios of Li, Ni, Co, and M to 2 before quantifying the lithium amount according to the free lithium compound, As shown in FIG. The values of the correct coefficients x, y, and z can be obtained by proportionally dividing the sum of the coefficients of the embodiment to be 2 again.

[Table 1]

3 is a graph showing the relationship between discharge capacity characteristics and charge-discharge cycle characteristics of lithium ion secondary batteries according to Examples and Comparative Examples. As shown in Fig. 3, the lithium ion secondary batteries according to Examples 1 to 18 have excellent characteristics in discharge capacity characteristics and charge / discharge cycle characteristics at a high level. On the other hand, in the lithium ion secondary batteries according to Comparative Examples 1 to 3, at least one of the discharge capacity characteristic and the charge / discharge cycle characteristic is insufficient to the level of the embodiment, and therefore the discharge capacity characteristic and the charge / discharge cycle characteristic are not compatible.

Particularly, in Comparative Example 1 in which the ratio (y) of Ni was low and Comparative Example 2 in which the ratio (y) of Ni was high, the discharge capacity characteristics were as low as 135 Ah / kg to 170 Ah / kg as shown in Table 1. On the other hand, in Example 1 in which the ratio (y) of Ni was appropriate, the discharge capacity characteristics were improved. Also, discharge capacity characteristics showed improvement tendency in Examples 2 to 18 as well.

In Comparative Examples 2 and 3 in which the proportion of LiOH in the free lithium compound was high, the charge-discharge cycle characteristics were as low as 61% to 75%. In Comparative Examples 2 and 3, it is considered that the charge-discharge cycle characteristics deteriorated due to the decomposition of the electrolyte caused by the contact between LiOH and the electrolyte solution. On the other hand, in Examples 1 to 18, charge-discharge cycle characteristics showed improvement tendency. Therefore, by lowering the weight ratio of LiOH in the free lithium compound to 60% or less of Li ₂ CO ₃ , the progress of decomposition of the electrolytic solution due to contact between LiOH and the electrolytic solution is suppressed without lowering the discharge capacity of the cathode active material Thereby contributing to improvement of discharge capacity characteristics and charge / discharge cycle characteristics.

1 anode
2 cathode
3 Separator
4 battery cans
5 cathode lead piece
6 Sealing lid
7 Positive electrode lead piece
8 Seals
9 insulating plate
10 Lithium ion secondary battery

Claims (8)

The following composition formula (1)
Li _{1 + x} Ni _y Co _z M _1-xyz O ₂ (1)
X is a number satisfying -0.12? X? 0.2, y is a number satisfying 0.7? Y? 0.9, z is a number satisfying 0.05? Z? 0.3, M is at least one element selected from the group consisting of Mg, Al, Ti, Mn, Zr, Mo and Nb.
, Or secondary particles aggregated with the primary particles,
Wherein the primary particles or the secondary particles contain a free lithium compound in a weight ratio of not less than 0.1% and not more than 2.0%, and the weight of lithium hydroxide in the free lithium compound is not more than The positive electrode active material for a lithium ion secondary battery, which is not more than 60% by weight of lithium carbonate. The method according to claim 1,
Wherein the secondary particle has an open pore and a void pore volume ratio in a range of not less than 0.1 m and not more than 0.5 m obtained by mercury porosimetry is 7% or more and 20% or less. The method according to claim 1,
Wherein the weight ratio of the primary particles or the free lithium compound contained in the secondary particles is 0.1% or more and 1.0% or less. The method according to claim 1,
Wherein the Ni concentration on the surfaces of the primary particles or the secondary particles is lower than the Ni concentration in the vicinity of the center of the primary particles or the secondary particles. The method according to claim 1,
Wherein the primary particles have an average particle diameter of 0.1 占 퐉 or more and 2 占 퐉 or less. The method according to claim 1,
And a BET specific surface area of 0.2 m 2 / g or more and 1.5 m 2 / g or less. A positive electrode for a lithium ion secondary battery comprising the positive electrode active material for a lithium ion secondary battery according to any one of claims 1 to 6. A lithium ion secondary battery comprising the positive electrode for a lithium ion secondary battery according to claim 7.

Images