JPH09251854A - Manufacture of positive active material for non-aqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive active material for a non-aqueous electrolyte secondary battery with its large capacity capable of easily milling to a particle size of its prescribed range. SOLUTION: Manufacture of a positive active material for a non-aqueous electrolyte secondary battery to obtain oxide expressed by formula LIx NI(1-y) COy O2 (0.95<=x<=1.2, 0<=y<=0.5) using a mixture of nickel hydroxide and lithium salt in which at least nickel hydroxide or Co forms a solid solution, as a raw material, comprises a baking process at a first step for sintering at a temperature ranging from 300 deg.C to 650 deg.C for 2 to 20 hours, a process of milling and mixing after cooling to 100 deg.C or less, and a baking process at a second step for sintering at a temperature ranging from 700 deg.C to 900 deg.C for 2 to 30 hours.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to an improvement in a method for producing a positive electrode active material thereof.

[0002]

2. Description of the Related Art In recent years, portable electronic devices and cordless electronic devices have been rapidly developed, and there is a great demand for secondary batteries having small size, light weight and high energy density as their power sources.
Among them, non-aqueous electrolyte secondary batteries, especially lithium secondary batteries, are attracting attention as batteries having high voltage and high energy density. Conventionally, L has been used as a positive electrode active material for lithium secondary batteries.
iCoO ₂ , LiNiO ₂ , LiMnO _{2 and the} like are known. Batteries using LiCoO ₂ have already been commercialized. On the other hand, LiNiO ₂ and LiMnO ₂ are LiC
Since it is lower in cost and higher in capacity than oO ₂ , research and development has been actively conducted.

For example, by heating a raw material composed of a salt of metal M and a lithium salt in an air atmosphere at a temperature of 600 to 800 ° C., LiMO ₂ (M is Co, N
It has been proposed that one or more elements selected from i, Fe, and Mn) be obtained, and that it is preferable to perform the treatment twice preferably at 800 ° C. for 6 hours ( JP-A-4-181660). Also, L
i _y Ni _1-x Mn _x O ₂ (0 ≦ x ≦ 0.3, 1.0 ≦ y ≦
As a synthetic method of 1.3), the raw material was previously prepared in 150
After drying at ℃ for 15 hours, heat in air or oxygen atmosphere at 550 to 750 ℃ for 15 to 20 hours (first heating), and heat at 700 to 900 ℃ for 20 to 25 hours via normal temperature. (Second heating) or heating at 700-900 ° C for 20-25 hours (first heating) and heating at 250-350 ° C for 10-15 hours via normal temperature (second heating) A method of doing so has been proposed (JP-A-6-096768).

Li _x M _y1 N _y2 O _z (M is Co or Ni, N is any element of Ni, V, Fe, Mn, Ti and Cu, M ≠ N, y1 = 0.6 ~ 1.0, y2
= 0 to 0.4, y1 + y2 = 1, x = 0.8 to 1.0,
z = 1.5-3.0), a synthetic method of 450-800
Heating at a temperature of ℃ for 3 to 100 hours (first heating), and then at a temperature 50 to 600 ℃ higher than the first temperature, 0.5.
~ 50 hours heating (second heating), 0.1 ~ 25 ℃ / m
After cooling at a rate of in, a method of pulverizing into coarse powder having an average particle size of 10 to 80 μm and further pulverizing into fine powder having an average particle size of 0.5 to 9.0 μm has been proposed (JP-A-7- 11
4915).

[0005]

When the positive electrode active material is synthesized by one-step firing as described above, or when the positive electrode active material is synthesized by two-step firing without an intermediate crushing step, lithium salt is contained in the active material. However, there is a problem in that the synthetic reaction does not proceed sufficiently due to segregation and the utilization rate per weight of the active material decreases. In addition, the lithium salt segregated in the active material is 70
By firing at a high temperature of about 0 ° C. or higher, it is strongly sintered with the produced cobalt solid solution lithium composite nickel oxide. Therefore, when the active material is pulverized after the synthesis is completed, there is a problem that the particle size variation becomes large and the yield after classification is reduced. If there are many coarse particles in the positive electrode active material, for example, 3
If the weight ratio of particles of 0 μm or more is 20% or more of the whole, it becomes difficult to uniformly apply the positive electrode active material mixture to the electrode plate, or the active material falls off from the electrode plate as the charge / discharge cycle progresses. There is a problem such as doing. Further, when the positive electrode active material has many fine particles, for example, when the weight ratio of particles of 1 μm or less is 20% or more of the whole, the specific surface area of the active material becomes large, and thus a large amount of solvent is required at the time of preparing the paste, so that the paste coating is performed. There is a problem that it takes time to dry the electrode plate after the work. Therefore, it is necessary to remove coarse particles and fine particles by a classification process after crushing the positive electrode active material.

Further, even if the positive electrode active material is synthesized by two-step firing in which a crushing step is inserted in the middle, if the pulverization after the first-step firing is insufficient, for example, particles of 40 μm or more are entirely mixed in a weight ratio. 5% or more, the lithium salt segregated in the active material is not sufficiently crushed and dispersed, and the synthesis reaction does not proceed sufficiently, so that there is a problem that the utilization rate per weight of the active material is low. If the pulverization after the first-stage firing is excessively pulverized, particles having a particle size of, for example, 1 μm or less are contained in a total weight ratio of 20.
If it is more than 100%, the fine particles increase in the crushing step after the synthesis is completed, and the specific surface area of the active material increases, so a large amount of solvent is required when preparing the paste, and it takes time to dry the electrode plate after applying the paste. There's a problem. Therefore, it is necessary to remove coarse particles and fine particles by a classification process after crushing the positive electrode active material.

The present invention solves such a problem, and can be easily pulverized to a particle size in a predetermined range and has a high yield after classification, which is a positive electrode active material for a non-aqueous electrolyte secondary battery. It is an object of the present invention to provide a manufacturing method for giving

[0008]

The present invention uses a mixture of at least nickel hydroxide or nickel in which Co is solid-solved with nickel hydroxide and a lithium salt as a raw material, and has the general formula Li _x Ni.
_(1-y) Co _y O ₂ (0.95 ≦ x ≦ 1.2, 0 ≦ y ≦ 0.
5) In the method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, which obtains an oxide represented by 5), a first-step firing step of firing at a temperature range of 300 ° C to 650 ° C for 2 to 20 hours, and then 100 The method is characterized by having a step of pulverizing and mixing after cooling to below ℃, and a second step of calcination of the mixture obtained in the above step in the temperature range of 700 ° C to 900 ° C for 2 to 30 hours.

In the step of pulverizing and mixing, it is preferable that the active material has an average particle diameter of 1 to 20 μm and particles having a particle diameter of 40 μm or more account for 5% or less of the total weight of the active material. Further, it is preferable that after the second-step firing, the active material is pulverized so that 70% or more of the total weight thereof has a particle diameter of 1 to 15 μm. The nickel hydroxide preferably forms spherical or ellipsoidal secondary particles. The present invention also kneads the positive electrode active material synthesized by the above manufacturing method and a carbon-based conductive agent together with a N-methylpyrrolidone solution containing a binder of a fluorine-based compound, and coats the aluminum foil with a paste, Provided is a method for manufacturing a positive electrode plate for a non-aqueous electrolyte secondary battery which is dried and rolled.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the method of the present invention, as described above, in the first step, the temperature is within the range of 300 ° C to 650 ° C.
It is assumed that the firing is performed for 20 hours, the second step is performed in the temperature range of 700 ° C. to 900 ° C. for 2 hours for 30 hours, and the step of pulverizing and mixing is performed between the first step and the second step. In the synthesis of this positive electrode active material, the basic structure of the crystal of the cobalt solid solution lithium composite nickel oxide is generated by the first step firing, and the crystallinity of the lithium composite nickel oxide is improved by the second step firing. If the firing temperature is lower than 300 ° C. or the firing time is shorter than 2 hours in the first stage, the synthesis reaction of the lithium composite nickel oxide does not proceed sufficiently. When the firing temperature exceeds 650 ° C. or the firing time exceeds 20 hours, lithium is contained in the nickel portion of the cobalt solid solution lithium composite nickel oxide and nickel is contained in the lithium portion during the second stage firing. It becomes a structure, and the crystal structure changes from the hexagonal type to the rock salt type structure. Therefore, the discharge capacity is reduced.

In the second stage firing, the firing temperature is 70
When the temperature is lower than 0 ° C. or the firing time is shorter than 2 hours, the crystal growth of the cobalt solid solution lithium composite nickel oxide is insufficient. Further, when the firing temperature exceeds 900 ° C. or the firing time exceeds 30 hours, the lithium composite nickel oxide has a structure in which lithium is contained in the nickel portion and nickel is contained in the lithium portion, and the crystal structure is hexagonal. Change from type to rock salt type structure. Therefore, the discharge capacity is reduced. By pulverizing and mixing after the first-step firing, the segregated lithium salt in the cobalt solid solution lithium composite nickel oxide produced by the first-step firing can be pulverized and dispersed. The salt reacts sufficiently and the utilization rate per active material weight increases. In addition, by pulverizing and dispersing the segregated lithium salt in the cobalt solid solution lithium composite nickel oxide,
It is possible to prevent the segregated lithium salt from being strongly sintered with the cobalt solid solution lithium composite nickel oxide when fired at a high temperature of about 700 ° C. or higher. Therefore, when the powder is pulverized after the synthesis is completed, the particle size variation is reduced, and the classification efficiency is improved.

If the positive electrode active material has a large amount of coarse particles, for example, 15
If the weight ratio of particles of μm or more is 20% or more of the whole,
The coating property of the positive electrode active material on the electrode plate and the binding property of the electrode plate due to the battery cycle test become poor. Further, when the positive electrode active material has many fine particles, for example, when the weight ratio of particles of 1 μm or less is 20% or more of the whole, the specific surface area of the active material becomes large, and thus a large amount of solvent is required at the time of preparing the paste, so that the paste coating is performed. It takes time to dry the electrode plate after processing. Therefore, it is necessary to remove coarse particles and fine particles by a classification step after crushing the active material. The average particle size after classification is 1 to obtain better properties
It is desirable that the thickness be 15 μm.

Even if the synthesis of the positive electrode active material is carried out by two-stage firing having an intermediate pulverization step, the pulverization after the first-stage firing is insufficient, and for example, particles of 40 μm or more account for 5% by weight of the whole. When it is above, the lithium salt segregated in the active material is not sufficiently pulverized and dispersed, and the synthesis reaction does not proceed sufficiently, so that the utilization rate per weight of the active material becomes low. Alternatively, the pulverization after the first-stage firing is over-pulverization, for example, 1 μm
When the weight ratio of the following particles is 20% or more of the whole, the fine particles increase in the pulverizing step after the synthesis is completed, and the specific surface area of the active material increases, so that a large amount of solvent is required at the time of making the paste and the paste coating There is a problem that it takes time to dry the electrode plate later. Therefore, in the pulverization after the first-stage firing, it is desirable that the average particle diameter of the active material is in the range of 1 to 15 μm.

[0014]

Embodiments of the present invention will be described below. Example 1 Lithium hydroxide, nickel hydroxide and cobalt hydroxide were mixed so that the atomic ratio of lithium, nickel and cobalt was 1.0: 0.8: 0.2 and the temperature was raised in an oxygen atmosphere. The temperature was raised to 500 ° C. at a rate of 5 ° C./min, and firing was performed at the same temperature for 7 hours (first stage firing). The product was cooled to below 100 ° C. and ground in a grinding mill.
The average particle diameter was 15 μm, and the weight ratio of particles having a particle diameter of 40 μm or more was 0.07%. Next, in an oxygen atmosphere, the temperature was raised to 800 ° C. at a heating rate of 5 ° C./min, and firing was carried out at the same temperature for 15 hours (second stage firing). The product was cooled to below 100 ° C. and ground in a grinding mill. After crushing, it was classified with a sieve shaker. 88% of the total weight of the active material thus obtained had a particle size of 1 to 15 μm. The particle size and weight were measured with a laser diffraction type particle size distribution measuring device (Shimadzu SALD-1000). The compound obtained by this synthesis is referred to as active material 1.

Next, a positive electrode plate was prepared using the active material 1,
A cylindrical battery having the structure shown in FIG. 1 was assembled. The structure of this battery will be described. In a battery case 6 made of stainless steel, a positive electrode plate and a negative electrode plate are spirally wound with a separator between them, and an electrode plate group 3 has insulating plates 4 and 5 arranged vertically. It is stored. The opening of the case 6 is sealed by an assembly sealing plate 7 having a safety valve and an insulating packing 8. The positive electrode lead 1 pulled out from the positive electrode plate is connected to the sealing plate 7, and the negative electrode lead 2 pulled out from the negative electrode is the battery case 6.
Attached to the bottom of. The positive electrode plate and the negative electrode plate were produced as follows. An N-methylpyrrolidone solution in which 4 parts by weight of acetylene black as a conductive agent and 4 parts by weight of polyvinylidene fluoride as a binder were dissolved was added to 100 parts by weight of the positive electrode active material, and kneaded to form a paste. This paste was applied to both sides of an aluminum foil, dried, and then rolled to obtain a positive electrode plate having a thickness of 0.144 mm, a width of 37 mm, and a length of 250 mm.

On the other hand, the negative electrode used was a graphitized mesophase small sphere (hereinafter referred to as mesophase graphite).
100 parts by weight of this mesophase graphite was mixed with 3 parts by weight of styrene / butadiene rubber as a binder, and an aqueous carboxymethyl cellulose solution was added and kneaded to form a paste. Then, this paste is applied to both sides of a copper foil, dried and rolled to a thickness of 0.21 mm, a width of 39 mm, and a length of 2
It was a negative electrode plate of 80 mm. Aluminum lead is attached to the positive electrode plate, and nickel lead is attached to the negative electrode plate. The thickness is 0.025 mm, the width is 45 mm, and the length is 740 m.
It was spirally wound through a polyethylene separator having a diameter of m and stored in a battery case having a diameter of 14.0 mm and a height of 50 mm. The electrolyte used was a solvent prepared by mixing ethylene carbonate and ethyl methyl carbonate in a volume ratio of 20:80 and dissolving 1 mol / l of lithium hexafluorophosphate. After injecting this electrolytic solution, it was sealed. This battery is referred to as battery 1.

<< Examples 2 to 9 >> Active materials were synthesized in the same manner as in Example 1 except that the firing temperature in the first step and / or the second step was changed. The obtained compounds are referred to as active materials 2 to 9.

Examples 10 to 15 Active materials were synthesized in the same manner as in Example 1 except that the firing time in the first step and / or the second step was changed. The obtained compound is used as the active material 10 to
Set to 15.

<Examples 16 to 19> Active materials were synthesized in the same manner as in Example 1 except that the products after the first-stage baking were pulverized into various particle sizes. The obtained compound was used as the active material 16 to 19.
And

These active materials were synthesized 10 times under the same conditions. In addition, a cylindrical battery was manufactured using each active material. Batteries manufactured using the active materials 2 to 19 are referred to as batteries 2 to 19, respectively.

Comparative Example 1 Lithium hydroxide, nickel hydroxide and cobalt hydroxide were mixed so that the atomic ratio of lithium, nickel and cobalt was 1.0: 0.8: 0.2 and the mixture was placed in an oxygen atmosphere. At a heating rate of 5 ° C / min of 50
The temperature was raised to 0 ° C., and firing was performed at the same temperature for 7 hours (first stage firing). Next, without a pulverizing step, the temperature was raised to 800 ° C. at a temperature rising rate of 5 ° C./min in an oxygen atmosphere, and the mixture was baked at the same temperature for 15 hours (second-stage baking). Then 100
The mixture was cooled to below ℃, pulverized with a grinding mill, and classified with a sieve shaker. The compound obtained by this synthesis is referred to as Comparative Example 1.

Comparative Example 2 After the first and second steps of firing were carried out in the same manner as in Comparative Example 1, the particles were pulverized with an pulverizer to an average particle size of 40 μm, and further pulverized with an pulverizer. It was pulverized to an average particle size of 5 μm and classified by a sieve shaker. The compound obtained by this synthesis is referred to as Comparative Example 2. Each comparative example was synthesized 10 times under the same conditions. In addition, a cylindrical battery was manufactured using each active material.
The batteries produced by using Comparative Examples 1 and 2 are respectively referred to as Battery 20.
-21.

A charging / discharging test was conducted on each of the above batteries 1 to 21 under the following conditions. Charged at 4.2V for 2 hours with constant voltage charging, until the battery voltage reaches 4.2V, 42
It was set to be a constant current charge of 0 mA. 61 discharge
It was carried out by constant current discharge of 0 mA, and the discharge end voltage was set to 3.0V. Such charging / discharging was performed in an environment of 20 ° C. Table 1 shows the results. In the table, the number of accepted lots is 70 of the total weight of the active material in each of the 10 synthetic lots.
% Represents the number of lots having a particle diameter in the range of 1 to 15 μm. In addition, the average yield (%) is the weight% of particles having a particle diameter of 1 to 15 μm in the total weight of the active material.
Is represented by the average value of 10 synthetic lots. The discharge capacity (mAh) of the battery represents the discharge capacity of the battery after repeating charging and discharging 5 times.

[0024]

[Table 1]

From the active material 1 and the comparative examples 1 and 2, it can be seen that the number of passing lots, the average yield, and the discharge capacity are remarkably improved by including the crushing step after the first-stage firing. The number of passing lots and the average yield are high because the segregated lithium salt in the cobalt solid solution lithium nickel oxide produced by the first-step firing can be dispersed by pulverizing and mixing after the first-step firing. This is because the strong sintering after the two-step firing can be prevented and the pulverization / classification efficiency after the completion of the synthesis is improved. In addition, the reason why the discharge capacity is high is that the segregated lithium salt reacts sufficiently by the second-stage firing, and the utilization rate per active material weight increases.

Further, according to the active materials 1 to 10 to 11, the firing time is in the range of 2 to 20 hours in the first step and 2 to in the second step.
It can be seen that the number of accepted lots, the average yield, and the discharge capacity are almost the same even if the firing is performed by changing the range within 30 hours. Further, from the active materials 1 and 16 to 17, it can be seen that the number of acceptable lots, the average yield, and the discharge capacity are almost the same even after the first step firing and pulverizing to an average particle size of 1 to 20 μm.

From comparison between active material 1 and active materials 2 to 4 and 12, it can be seen that when the firing temperature in the first step is low or the firing time is short, both the acceptable lot and the average yield are significantly reduced. This is because when the firing temperature in the first step is less than 300 ° C. or the firing time is less than 2 hours, the synthesis reaction of the cobalt solid solution lithium nickel oxide does not proceed sufficiently and the synthesis in the second step is also performed. This is because the reaction proceeds and the lithium salt segregates and strongly sinters in the process, so that the pulverization / classification efficiency after the completion of the synthesis decreases. Further, the discharge capacity also decreases, but this is because the lithium salt segregates during the second-stage firing, and the synthesis reaction becomes insufficient.

From the comparison between the active material 1 and the active materials 5 and 14, when the firing temperature in the second stage is low or the firing time is short, the number of acceptable lots and the average yield are almost the same, but the discharge capacity is It can be seen that it will decrease. This is because if the firing temperature in the second stage is less than 700 ° C. or the firing time is less than 2 hours, the crystals of the cobalt solid solution lithium nickel oxide do not grow sufficiently. Active material 1 and active material 4,
From the comparison of Nos. 6, 9, and 15, it can be seen that the number of accepted lots, the average yield, and the discharge capacity are remarkably reduced when the firing temperature in the second stage is high or the firing time is long. The number of passed lots and the average yield are decreased because the lithium in the nickel portion of the cobalt solid solution lithium composite nickel oxide is increased when the firing temperature in the second step exceeds 900 ° C or the firing time exceeds 30 hours. In addition, nickel is contained in each lithium portion, and since it is strongly sintered, there is a large variation in particle size in the pulverizing step after completion of synthesis. The discharge capacity is lowered because the crystal structure of the cobalt solid solution lithium composite nickel oxide is changed from the hexagonal type to the rock salt type structure.

Further, comparing active material 1 and active material 7, when the firing temperature in the first stage is high and the firing temperature in the second stage is low, the number of accepted lots and the average yield are almost the same, but the discharge It can be seen that the capacity decreases. This is because not only the cobalt solid solution lithium composite nickel oxide is produced by the first-stage firing but also crystallization proceeds, but the second-stage firing temperature is 7%.
This is because if the temperature is less than 00 ° C., the crystals of the cobalt solid solution lithium nickel oxide do not grow sufficiently. In addition, comparing active material 1 with active materials 8 and 13, it can be seen that the number of accepted lots, the average yield, and the discharge capacity are significantly reduced when the firing temperature in the first stage is high or the firing time is long. The number of passing lots and the average yield are decreased because the solid solution of lithium nickel oxide containing cobalt is dissolved in the first stage when the first stage firing temperature exceeds 650 ° C or the firing time exceeds 20 hours. Since not only formation but also crystallization progresses, the crystal grows too much by the second-step firing, resulting in a structure in which lithium is contained in the nickel portion of the cobalt solid solution lithium composite nickel oxide and nickel is contained in the lithium portion. The reason is that since it is strongly sintered, the variation in particle size in the crushing step after the completion of synthesis becomes large. The discharge capacity is lowered because the crystal structure of the cobalt solid solution lithium composite nickel oxide is changed from the hexagonal type to the rock salt type structure.

From the comparison between the active material 1 and the active material 18, it can be seen that when the pulverization after the first-stage firing is fine, the discharge capacity is almost the same, but both the number of passed lots and the average yield are significantly reduced. This is because if the average particle size after the calcination and pulverization in the first step is 1 μm or less, the proportion of fine particles in the pulverization after the completion of synthesis remarkably increases. This is because the weight% occupied by those falling within the range of 15 μm is reduced. If the positive electrode active material contains a large amount of fine particles of 1 μm or less, the specific surface area becomes large. Therefore, if the active material is used without classification, a large amount of solvent is required when preparing the paste, and it takes time to dry the electrode plate after applying the paste. The problem arises. Therefore, it is necessary to remove fine particles from the positive electrode active material by a classifying process after crushing. From the comparison between the active material 1 and the active material 19, when the pulverization after the first-stage firing is coarse,
It can be seen that both the number of passed lots and the average yield decrease. This is because the segregated lithium salt generated by the first-step firing is not sufficiently grounded when the average particle size after the first-step firing exceeds 20 μm. This is because the pulverization / classification efficiency after the completion of the synthesis is reduced. Further, the discharge capacity also decreases, but this is because the lithium salt segregates and the synthesis reaction becomes insufficient.

From the above, according to the present invention, the segregated lithium salt is pulverized and dispersed by adding the step of pulverization and mixing after the calcination of the first step in the synthesis of the positive electrode active material, so that the solidification after the calcination of the second step is strengthened. It is possible to provide a positive electrode active material having a high yield by preventing such sintering and by sufficiently reacting the lithium salt segregated by the first-step firing.

In the above embodiment, LiNi
_{Although 0.8} Co _0.2 O ₂ was explained, Li _x Ni _(1-y) C
The same effect can be obtained for the compound represented by o _y O ₂ (0.95 ≦ x ≦ 1.2, 0 ≦ y ≦ 0.5). Also,
Although lithium hydroxide, nickel hydroxide, and cobalt hydroxide were used as the raw materials of LiNi _0.8 Co _0.2 O _{2 in} the above-mentioned examples, lithium salts such as lithium nitrate, lithium oxide, and lithium carbonate, CoO, Co ₂ O ₂ , and the like. ₃ , Co
The same effect can be obtained by using cobalt oxide represented by ₃ O ₄ , cobalt salts such as cobalt carbonate, and nickel hydroxide in which Co is dissolved. Further, in the above examples, the crushing was carried out by a grinding type crusher, but other crushers, for example, mortar, ball mill, vibrating ball mill, satellite ball mill, tube mill, pebble mill, conical mill, rod mill, vibrating mill, pin mill. The same effect can be obtained by using a jet mill or the like.

Further, in the above embodiment, the classification was carried out by a sieving shaker, but other classifying machines such as a sonic sieving machine, an electromagnetic sieving machine, a circular center sieving machine, an inertia classifier, a cyclone, a circular center The same effect can be obtained by using a classifier or the like. Further, in the above-mentioned examples, the synthesis was carried out in an oxygen atmosphere, but either the first step or the second step,
Alternatively, the same effect was obtained by performing both in an air atmosphere. In the above examples, the evaluation was performed using a cylindrical battery, but it goes without saying that similar effects can be obtained even if the battery shape is different, such as a prismatic battery. Furthermore, in the above example, a mixed solvent of ethylene carbonate and ethyl methyl carbonate was used as a solvent for the electrolyte,
Other non-aqueous solvent, for example, cyclic ether such as propylene carbonate, chain ether such as dimethoxyethane, non-aqueous solvent such as chain ester such as methyl propionate,
The same effect can be obtained by using these multi-component mixed solvents.

[0034]

As described above, according to the present invention, the segregated lithium salt is pulverized and dispersed by adding the step of pulverization and mixing after the first-step firing in the synthesis of the positive electrode active material,
As a result, it is possible to provide a positive electrode active material having a high yield by preventing strong sintering during the second-step firing and by sufficiently reacting the segregated lithium salt produced during the first-step firing.

[Brief description of drawings]

FIG. 1 is a front view showing a cross section of a main part of a cylindrical battery according to an embodiment of the present invention.

[Explanation of symbols]

 1 Positive electrode lead 2 Negative electrode lead 3 Electrode plate group 4, 5 Insulation plate 6 Battery case 7 Sealing plate 8 Insulation packing

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeo Kobayashi 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. A compound of the general formula Li _x Ni _(1-y) Co _y O ₂ (0.95 ≦ x
≦ 1.2, 0 ≦ y ≦ 0.5), which is a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, which comprises:
70% of the mixture obtained in the first stage baking step of baking in the temperature range of 00 ° C to 650 ° C for 2 to 20 hours, then cooling to 100 ° C or less and pulverizing and mixing, and the above step.
A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising a second-step firing step of firing in a temperature range of 0 ° C to 900 ° C for 2 to 30 hours. 2. In the step of pulverizing and mixing, the active material has an average particle diameter of 1 to 20 μm, and particles having a particle diameter of 40 μm or more account for 5% or less of the total weight of the active material.
A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery as described above. 3. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein after the second-step firing, the active material is pulverized so that 70% or more of the total weight thereof has a particle size of 1 to 15 μm. Production method. 4. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the nickel hydroxide forms spherical or ellipsoidal secondary particles. 5. The positive electrode active material synthesized by the method according to claim 1 and a carbon-based conductive agent are kneaded together with an N-methylpyrrolidone solution containing a binder of a fluorine-based compound, A method for producing a positive electrode plate for a non-aqueous electrolyte secondary battery, which comprises applying to an aluminum foil in the form of a paste, drying, and rolling.