JPH117958A - Method for producing positive electrode active material and non-aqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a positive electrode active material having high capacity, excellent cycle characteristics under a high temperature environment, and excellent high load discharge, and a non-aqueous electrolyte secondary battery. SOLUTION: A cobalt salt, a lithium salt and aluminum hydroxide are mixed, and the mixture is calcined to obtain Li _x Co
_(1-y) Al _y O ₂ (provided that 0.05 ≦ x ≦ 1.10.
01 ≦ y <0.10. To obtain a positive electrode active material represented by the following formula:

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a positive electrode active material suitable for use in a non-aqueous electrolyte secondary battery, and to a non-aqueous electrolyte secondary battery.

[0002]

2. Description of the Related Art In recent years, with the advance of electronic technology, the performance, size, and portability of electronic devices have been advanced, and the demand for high energy density batteries used in these electronic devices has increased. Under such circumstances, a lithium ion secondary battery using LiCoO ₂ as a positive electrode material and a carbon material capable of doping and undoping lithium as a negative electrode material has been commercialized, such as a camcorder, a mobile phone, and a notebook personal computer. Has been adopted in various portable electronic devices.

[0003] At present, improvement of LiCoO ₂ is being promoted in order to further improve the characteristics of this lithium ion secondary battery.

For example, in order to exhibit excellent cycle characteristics in deep charge and discharge, Japanese Patent Application Laid-Open No. 4-253162 discloses that LiCoO ₂ is partially replaced with at least one element from Pb, Bi and B. It has been proposed to use such a material as a positive electrode active material. Here, a target positive electrode active material is obtained by firing a mixture obtained by pulverizing and mixing lithium carbonate, cobalt carbonate, lead dioxide, bismuth oxide, or boron oxide with a ball mill in the air.
Also, Japanese Patent Publication No. Hei 4-24831, Japanese Patent Application Laid-Open No. 7-176
302 discloses, in Japanese Patent Laid-Open 7-176303 _{discloses, A x M y N z O} 2 ( where, A is at least one selected from alkali metal, M is a transition metal, N represents A
1, at least one selected from In, Sn,
x, y, z are 0.05 ≦ x ≦ 1.10, 0.85 ≦ y
≤ 1.00, 0.001 ≤ z ≤ 0.10. It has been proposed to use a complex oxide represented by the following formula: Li _1.03 Co _0.95 Sn _0.042 O ₂ , Li
_1.01 Co _0.95 In _0.04 O ₂ , Li _1.02 Co _0.96 In _0.04
O _{2 and the} like are mentioned. Here, a target positive electrode active material is obtained by mixing lithium carbonate, cobalt oxide, stannic oxide, indium oxide, or aluminum oxide and firing in air.

[0005]

By the way, recently,
2. Description of the Related Art Lithium ion secondary batteries are increasingly used in electronic devices used not only in a normal temperature environment but also in various environments from a low temperature to a high temperature. Particularly in notebook computers, which have been increasingly adopted recently, the temperature inside the personal computer increases with the speed of the central processing unit, and the built-in lithium ion secondary battery is used for a long time in a high temperature environment. The battery characteristics below are important.

However, lithium ion secondary batteries using the above-described lithium cobalt oxide as a positive electrode active material exhibit excellent cycle characteristics in deep charge / discharge, but have been used or stored in a high temperature environment. In some cases, it has been found that the battery capacity is relatively easily damaged.

[0007] As described above, it is generally difficult for lithium cobalt oxide containing multiple elements to replace cobalt with other elements and to form a solid solution uniformly while maintaining a layered structure. It was also found that the performance of the active material greatly changed depending on the mixing state of the starting materials and the like.

Accordingly, the present invention provides a method for producing a positive electrode active material having a high capacity, having a small capacity deterioration even when used or stored in a high-temperature environment, and having excellent high-load characteristics. It is intended to provide a battery.

[0009]

In order to achieve the above object, a method for producing a positive electrode active material according to the present invention comprises mixing a cobalt salt, a lithium salt and aluminum hydroxide, and firing the mixture. , Li _x Co _(1-y) Al _y O ₂ (provided that
0.05 ≦ x ≦ 1.10 and 0.01 ≦ y <0.10. ) Is obtained.

In the present invention, the general formula Li _x Co _(1-y)
Al _y O ₂ (however, 0.05 ≦ x ≦ 1.10, 0.01 ≦
y <0.10. Since the positive electrode active material shown in (2) uses aluminum hydroxide as the aluminum source, the crystal stability of the positive electrode active material is improved as compared with the case where aluminum oxide is used as the aluminum source, and the positive electrode active material is high even in a high temperature environment. The capacity is maintained and high load characteristics are excellent.

As a result, when a non-aqueous electrolyte secondary battery is formed using this positive electrode active material, it has a high capacity, suppresses capacity deterioration at high temperatures, and has excellent high load characteristics.

That is, the non-aqueous electrolyte secondary battery according to the present invention has the general formula Li _x Co _(1-y) Al _y O ₂ (0.05
≤ x ≤ 1.10, 0.01 ≤ y <0.10. ), A negative electrode made of a non-graphitizable carbon material capable of doping / de-doping lithium, and a non-aqueous electrolyte solution. A ratio obtained by dividing the discharge capacity after the cycle is repeated by the initial capacity is 80% or more.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

In the method for producing a positive electrode active material according to the present invention, a cobalt salt, a lithium salt and aluminum hydroxide are mixed, and the mixture is calcined to obtain Li _x Co _(1-y) Al _y O
₂ (However, 0.05 ≦ x ≦ 1.10, 0.01 ≦ y <
0.10. ) Is obtained.

LiCoO ₂ has a crystal structure having a hexagonal layered structure, but when aluminum is not dissolved, in a charged state, that is, a state in which lithium is dedoped from the positive electrode active material, The crystal itself becomes unstable. Therefore, when LiCoO ₂ is repeatedly subjected to such a state (during charge / discharge cycles) or subjected to thermal stress in a charged state (during high-temperature storage), the crystal structure is broken and lithium doping / dedoping is performed normally. And the performance as a positive electrode active material is impaired.

[0016] In contrast, the lithium composite oxide of aluminum is solid-solved in the present invention _{(Li x Co (1-y} ) Al y O 2)
Can stably maintain its performance as a positive electrode active material even when lithium is doped or undoped under a high temperature environment as well as under a normal temperature environment. This is because the solid solution of aluminum stabilizes the hexagonal crystal structure during charging and maintains the crystal structure even in a high-temperature environment.

Further, there are three types of crystal structures of lithium-containing aluminum oxide (LiAlO ₂ ).
Those having a crystal structure similar to iCoO ₂ are α-LiAl
O ₂ . Therefore, it is desirable synthesis from the alpha-LiAlO easily generate ₂ Al (OH) _3. Al (O
By synthesizing Li _x Co _(1-y) Al _y O ₂ from H) _3, the stability of the crystal structure can be improved as compared with that synthesized using Al ₂ O ₃ .

As described above, in the present invention, by using aluminum hydroxide as the aluminum source, the crystal stability of the synthesized lithium composite oxide at high temperatures is improved.
As a result, this lithium composite oxide is used as a positive electrode active material,
When a non-aqueous electrolyte secondary battery is formed using a material capable of doping and undoping lithium as a negative electrode active material, high capacity is maintained and good high load characteristics are obtained even in a high temperature environment.

The ratio y of Al in Li _x Co _(1-y) Al _y O ₂ Al is 0.01 ≦ y <0.10. A
When the ratio y of 1 is less than 0.01, the effect of improving the capacity retention rate in a high-temperature environment described above is small, and when it is 0.1 or more, the battery capacity is rather reduced, which is not preferable.

Considering the specific firing conditions, it is preferable to use aluminum hydroxide having a particle size of 10 μm or less. If the particle size exceeds 10 μm, the crystal stability decreases, and the capacity retention under a high temperature environment decreases. This is because the synthesis reaction of the positive electrode active material proceeds by a solid-phase reaction, so that the use of aluminum hydroxide having a large particle size makes it difficult to synthesize homogeneous Li _x Co _(1-y) Al _y O _2. Conceivable.

The firing temperature for a mixture of a cobalt salt, a lithium salt and aluminum hydroxide is preferably in the range of 700 to 1100 ° C. in an atmosphere containing oxygen. If the firing temperature exceeds 1100 ° C., the lithium composite oxide itself is decomposed, which is not preferable.

As described above, the production using the aluminum hydroxide as the aluminum source (Li _x Co _(1-y) Al
_y O ₂ (however, 0.05 ≦ x ≦ 1.10, 0.01 ≦ y <
0.10. ) Is a lithium composite oxide,
The positive electrode active material has excellent crystal stability and is less likely to deteriorate in a high-temperature environment.

Since the lithium composite oxide in which aluminum is dissolved is low in electronic conductivity, when the particle size of the active material is too large, the load characteristics are reduced due to the decrease in electronic conductivity, and the high load side , The discharge capacity is reduced.
Therefore, the particle diameter of the positive electrode active material, that is, the obtained lithium composite oxide, is preferably 1 to 50 μm.

In the present invention, when the above-described lithium composite oxide is used as a positive electrode active material and a battery is formed by combining with an appropriate negative electrode active material, the battery has a high capacity and maintains a high capacity even at a high temperature. As a result, the high-load discharge characteristics are also excellent.

The negative electrode active material used here is not particularly limited as long as it can be doped with lithium metal or lithium and can be undoped. For example, a lithium alloy of lithium with aluminum, lead, indium or the like can be used. Other carbon materials capable of doping / dedoping lithium, or polymers such as polyacetylene and polypyrrole are preferably used.

The carbon material used for the negative electrode is not particularly limited, but includes pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke, etc.), graphites, glassy carbons, and organic carbonaceous materials. A molecular compound fired body (a phenol resin, a furan resin or the like fired at an appropriate temperature), carbon fiber, activated carbon, or the like can be used.

In particular, non-graphitizable carbons are preferably used because of their high charge / discharge capacity per weight and excellent cycle characteristics. Among them, the (002) plane spacing is 0.370 nm or more, and the true density is 1.70 g / cm ^3.
And in differential thermal analysis in an air stream of 70
A carbonaceous material having no exothermic peak at 0 ° C. or higher is used.

Examples of the material having such properties include a carbonaceous material obtained by carbonizing an organic material by a method such as firing, and the starting material for carbonization is furfuryl alcohol or a homopolymer of furfural, Furan resins consisting of copolymers are preferred. In particular,
Furfural + phenol, furfuryl alcohol + dimethylol urea, furfuryl alcohol, furfuryl alcohol + formaldehyde, furfuryl alcohol +
Polymers composed of furfural, furfural + ketones and the like are preferably used.

Alternatively, as a raw material, a hydrogen / carbon atomic ratio of 0.6
Using a petroleum pitch of ~ 0.8, a functional group containing oxygen is introduced into this, and a so-called oxygen cross-link is applied to obtain an oxygen content of 10 ~
A carbonaceous material obtained by baking after forming a precursor of 20% by weight is also suitable.

Further, a carbonaceous material having a large doping amount with respect to lithium by adding a phosphorus compound or a boron compound when carbonizing the above-mentioned furan resin or petroleum pitch can be used.

The graphite material needs to have a true specific gravity of at least 2.10 g / cm ³ , and preferably at least 2.18 g / cm ^{3 in} order to obtain a higher negative electrode mixture filling property. Used for In order to obtain such a true specific gravity, the plane spacing obtained by the X-ray diffraction method needs to be 0.335 nm or more and 0.34 nm or less.
More preferably, it is 35 nm or more and 0.337 nm or less. The crystal thickness in the c-axis direction is preferably at least 16.0 nm, more preferably at least 24.0 nm.

As described above, the above-mentioned negative electrode material can be suitably used. However, a lithium composite oxide using aluminum hydroxide as an aluminum source is used as a positive electrode active material, and a non-graphitizable carbon material which can be doped and dedoped with lithium is used. When the nonaqueous electrolyte secondary battery is configured as the negative electrode, the ratio of the nonaqueous electrolyte secondary battery in which the discharge capacity is divided by the initial capacity after repeating 200 cycles in an environment of 60 ° C. becomes 80% or more is 80% or more. The following battery can be obtained.

Here, after charging for 2.5 hours under the conditions of a charging voltage of 4.20 V and a charging current of 1 A, a discharging current of 250 m
A, a charge / discharge cycle in which discharge is performed under the condition of a final voltage of 2.50 V is defined as one cycle, and the initial capacity indicates the discharge capacity in the second cycle.

Since the nonaqueous electrolyte secondary battery according to the present invention uses a lithium composite oxide using aluminum hydroxide as an aluminum source as a positive electrode active material, the crystal structure of the positive electrode active material can be maintained even in a high temperature environment. , And excellent in cycle characteristics and high-load discharge.

As described above, the particle size of the positive electrode active material is preferably 1 to 50 μm. If the particle size of the positive electrode active material is too large, the load characteristics will decrease due to a decrease in electron conductivity, and the discharge capacity on the high load side will decrease.

By the way, the following components can be used as other components constituting the above-mentioned non-aqueous electrolyte secondary battery, for example, a non-aqueous electrolyte, a separator and the like.

As the non-aqueous electrolyte, for example, an electrolyte obtained by dissolving a lithium salt in an organic solvent as an electrolyte is used. As the organic solvent, although not particularly limited, propylene carbonate, ethylene carbonate,
1,2-dimethoxyethane, γ-butyrolactone, diethyl ether, tetrahydrofuran, 2-methyl-tetrahydrofuran, 1,3-dioxolan, sulfolane,
A single solvent or a mixture of two or more solvents such as acetonitrile, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, and methyl propyl carbonate is used.

The separator is not particularly limited, and examples thereof include a woven fabric, a nonwoven fabric, and a microporous synthetic resin membrane. In particular, a synthetic resin microporous membrane is preferably used,
Among them, a polyolefin-based microporous film is suitably used in terms of thickness, film strength, film resistance and the like. Specifically, a microporous membrane made of polyethylene and polypropylene or a microporous membrane obtained by combining these is used.

The shape of the current collector of the electrode is not particularly limited, but a foil shape or a mesh shape such as a mesh or expanded metal is used. As a material used for the positive electrode current collector, for example, aluminum, stainless steel, nickel, or the like is preferably used. A thickness of 10 to 50 μm is suitably used. As a material used for the negative electrode current collector, for example, copper, stainless steel, nickel, or the like is preferably used. A thickness of 5 to 30 μm is preferably used.

Further, in order to obtain a sealed non-aqueous electrolyte secondary battery with higher safety, a device such as a safety valve which operates by an increase in battery internal pressure and shuts off current when an abnormality such as overcharging occurs is provided. It is desirable that

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments to which the present invention is applied will be described. However, the present invention is not limited to the embodiments, and the present invention is implemented by appropriately changing the gist of the present invention. It is possible.

Example 1 First, as shown in FIG. 1, a positive electrode 1 was produced as follows.

Li / C in a molar ratio of lithium carbonate, cobalt oxide and aluminum hydroxide having an average particle size of 5 μm
o / Al = 1.01 / 0.97 / 0.03, mixed with a ball mill, calcined in air at 600 ° C for 1 hour, and further calcined at 900 ° C for 10 hours,
A positive electrode active material was synthesized. This positive electrode active material was pulverized and classified to obtain a positive electrode active material having an average particle size of 5.1 μm. The average particle size was measured with a laser diffraction type particle size distribution measuring device (LA-500, manufactured by Horiba, Ltd.). Here, the average particle diameter means a median diameter of a volume average diameter.

A positive electrode mixture was prepared by mixing 91% by weight of the obtained positive electrode active material, 6% by weight of graphite as a conductive agent, and 3% by weight of polyvinylidene fluoride as a binder.
The mixture was dispersed in N-methyl-2-pyrrolidone to obtain a positive electrode mixture slurry. Then, the positive electrode mixture slurry was applied to an aluminum foil serving as the positive electrode current collector 10, dried, and then compression-molded with a roller press to produce a belt-shaped positive electrode 1.

Next, the negative electrode 2 was manufactured as follows.

After using petroleum pitch as a starting material and introducing a functional group containing oxygen by 10 to 20% (oxygen crosslinking),
It was calcined at a temperature of 1000 ° C. in an inert gas to obtain a negative electrode active material. The obtained negative electrode active material is a non-graphitizable carbon material close to a glassy carbon material. 90% by weight of this carbonaceous material and 10% by weight of polyvinylidene fluoride as a binder were mixed to prepare a negative electrode mixture, and dispersed in N-methyl-2-pyrrolidone to prepare a negative electrode mixture slurry. Then, the negative electrode mixture slurry was applied to both surfaces of a copper foil serving as the negative electrode current collector 11, dried, and then compression-molded with a roll press to obtain a strip-shaped negative electrode 2.

The positive electrode 1 and the negative electrode 2 produced as described above
Were sequentially laminated via a separator 3 made of a microporous polypropylene film having a thickness of 25 μm and wound many times to produce a spiral electrode body. In this spiral electrode body, the dimensions were set such that the width and length of the negative electrode 2 were larger than those of the positive electrode 1.

The spirally wound electrode body thus manufactured was housed in a nickel-plated iron battery can 5 and insulating plates 4 were arranged on both upper and lower surfaces of the spirally wound electrode body. Then, in order to collect the current of the positive electrode 1 and the negative electrode 2, the aluminum lead 12 is led out from the positive electrode current collector 10, and the battery cover 7 and the PTC
The battery can 5 is welded to the safety valve device 8 connected via the element 9, the nickel lead 13 is led out from the negative electrode current collector 11, and
Welded. Then, into the battery can 5, an electrolytic solution in which 1 mol of LiPF ₆ was dissolved in a mixed solvent of 50% by volume of propylene carbonate and 50% by volume of diethyl carbonate was injected. Next, the battery cover 7 was fixed by caulking the battery cover 7 and the battery can 5 through the sealing gasket 6 coated with asphalt, and the diameter 18 mm and the height 65 m shown in FIG.
m was prepared.

EXAMPLE 2 Li / Co / Al = molar ratio of lithium carbonate, cobalt oxide and aluminum hydroxide having an average particle size of 5 μm.
The mixture was mixed in a ball mill so as to be 1.01 / 0.98 / 0.02, calcined in air at 600 ° C. for 1 hour, and further calcined at 900 ° C. for 10 hours to synthesize a positive electrode active material. . By grinding and mixing this positive electrode active material, a positive electrode active material having a particle size of 4.8 μm was obtained.

Hereinafter, using this positive electrode active material, Example 1
A cylindrical battery was manufactured in the same manner as in the above.

Example 3 Lithium carbonate, cobalt oxide, and aluminum hydroxide having an average particle size of 5 μm were formed in a molar ratio of Li / Co / Al =
The mixture was mixed in a ball mill so as to be 1.01 / 0.99 / 0.01, calcined in air at 600 ° C. for 1 hour, and then calcined at 900 ° C. for 10 hours to synthesize a positive electrode active material. . The positive electrode active material having a particle size of 4.7 μm was obtained by pulverizing and mixing this positive electrode active material. Hereinafter, a cylindrical battery was manufactured using this positive electrode active material in the same manner as in Example 1.

Example 4 Li / Co / Al = molar ratio of lithium carbonate, cobalt oxide and aluminum hydroxide having an average particle size of 5 μm.
The mixture was mixed in a ball mill so as to be 1.01 / 0.93 / 0.07, calcined in air at 600 ° C. for 1 hour, and further calcined at 900 ° C. for 10 hours to synthesize a positive electrode active material. . The positive electrode active material having a particle size of 5.0 μm was obtained by pulverizing and mixing the positive electrode active material. Hereinafter, a cylindrical battery was manufactured using this positive electrode active material in the same manner as in Example 1.

Example 5 Li / Co / Al = molar ratio of lithium carbonate, cobalt oxide and aluminum hydroxide having an average particle size of 5 μm.
The mixture was mixed in a ball mill so as to be 1.01 / 0.90 / 0.10, calcined in air at 600 ° C. for 1 hour, and then calcined at 900 ° C. for 10 hours to synthesize a positive electrode active material. . The positive electrode active material having a particle size of 4.6 μm was obtained by pulverizing and mixing the positive electrode active material. Hereinafter, a cylindrical battery was manufactured using this positive electrode active material in the same manner as in Example 1.

COMPARATIVE EXAMPLE 1 Lithium carbonate and cobalt oxide were used in a molar ratio of Li / Co.
= 1.01 / 1.00 and then calcined in air at 600 ° C. for 1 hour.
By baking at 0 ° C. for 10 hours, a positive electrode active material was synthesized. By grinding and mixing this positive electrode active material, a positive electrode active material having a particle size of 4.9 μm was obtained. Hereinafter, a cylindrical battery was manufactured using this positive electrode active material in the same manner as in Example 1.

Comparative Example 2 Li / Co / Al = molar ratio of lithium carbonate, cobalt oxide and aluminum hydroxide having an average particle size of 5 μm.
After mixing with a ball mill to be 1.01 / 0.995 / 0.005 and calcining in air at 600 ° C for 1 hour,
Further, by baking at 900 ° C. for 10 hours, a positive electrode active material was synthesized. By grinding and mixing this positive electrode active material, a positive electrode active material having a particle size of 4.8 μm was obtained. Hereinafter, a cylindrical battery was manufactured using this positive electrode active material in the same manner as in Example 1.

Comparative Example 3 Li / Co / Al = molar ratio of lithium carbonate, cobalt oxide and aluminum hydroxide having an average particle size of 5 μm.
A positive electrode active material was synthesized by mixing with a ball mill so as to be 1.01 / 0.88 / 0.12, calcining in air at 600 ° C. for 1 hour, and further calcining at 900 ° C. for 10 hours. . By grinding and mixing this positive electrode active material, a positive electrode active material having a particle size of 4.9 μm was obtained. Hereinafter, a cylindrical battery was manufactured using this positive electrode active material in the same manner as in Example 1.

Comparative Example 4 Li / Co / Al = 1. Lithium carbonate, cobalt oxide and aluminum oxide having an average particle size of 5 μm in a molar ratio of 1.
After mixing with a ball mill so as to be 01 / 0.97 / 0.03 and calcining in air at 600 ° C. for 1 hour, 9
By baking at 00 ° C. for 10 hours, a positive electrode active material was synthesized. By grinding and mixing this positive electrode active material,
A positive electrode active material having a particle size of 4.8 μm was obtained. Hereinafter, a cylindrical battery was manufactured using this positive electrode active material in the same manner as in Example 1.

With respect to the cylindrical batteries of the examples and comparative examples manufactured as described above, the initial capacity and the capacity retention rate under a high temperature environment were measured. Further, the discharge capacity at the time of performing a high load discharge was measured.

Note that the initial capacity is a charging voltage of 4.20 V,
After charging for 2.5 hours under the condition of a charging current of 1 A and then discharging under a condition of a discharging current of 250 mA and a cut-off voltage of 2.50 V, a charge-discharge cycle of two cycles is repeated.
The discharge capacity at the cycle is shown. The capacity retention rate in a high-temperature environment is calculated by measuring the discharge capacity when the battery whose initial capacity has been investigated is further repeated 200 cycles in an environment of 60 ° C., and dividing the discharge capacity at the 200th cycle by the initial capacity. Is the ratio of

The discharge capacity of the high-load discharge is determined by charging the battery whose initial capacity has been investigated under the conditions of a charging voltage of 4.20 V and a charging current of 1 A for 2.5 hours, and then discharging the battery with a discharging current of 1.5
A: Discharge capacity when discharging was performed under the condition of a final voltage of 2.50 V.

Table 1 shows the results of Examples and Comparative Examples.

[0062]

[Table 1]

From the results shown in Table 1, the cylindrical battery of Example 1 synthesized using aluminum hydroxide was compared with the cylindrical battery of Comparative Example 1 using a lithium composite oxide containing no solid solution of Al. Although the initial capacity is the same, the capacity maintenance rate under a high temperature environment is improved. The initial capacity of the cylindrical battery of Example 1 was the same as that of the cylindrical battery of Comparative Example 4 in which a lithium composite oxide was synthesized by a conventional method using aluminum oxide, but the capacity was maintained under a high temperature environment. Rate, 1.5 A discharge capacity is improved. Thus, by synthesizing a lithium composite oxide using aluminum hydroxide as a raw material, the crystal stability of the synthesized positive electrode active material at high temperatures is improved, and a battery having a high discharge capacity retention rate of 87% can be obtained. You can see that.

Next, comparing the initial capacity of the battery with the Co / Al composition ratio changed and the capacity retention rate under a high-temperature environment, the capacity in the range where the Al ratio y is 0.01 ≦ y <0.10 is obtained. It can be seen that the maintenance ratio shows an excellent value of 80% or more. On the other hand, when the Al ratio is less than 0.01, the effect of improving the capacity retention rate in a high-temperature environment is small, and when the Al ratio is 0.1 or more, the initial capacity is 13%.
Below 00 mAh. Therefore, in order to suppress the deterioration of the capacity under a high-temperature environment while maintaining the initial capacity, the ratio y of Al needs to be in the range of 0.01 ≦ y <0.10.

Next, in Experimental Examples 1 to 5, Co / A
With the composition ratio of 1 fixed at 0.97 / 0.03, the particle size of aluminum hydroxide used as a raw material is examined.

EXPERIMENTAL EXAMPLE 1 Lithium carbonate, cobalt oxide, and aluminum hydroxide having an average particle size of 1 μm were used in a molar ratio of Li / Co / Al =
The mixture was mixed with a ball mill so as to be 1.01 / 0.97 / 0.03, calcined in air at 600 ° C. for 1 hour, and further calcined at 900 ° C. for 10 hours to synthesize a positive electrode active material. . By grinding and mixing this positive electrode active material, a positive electrode active material having a particle size of 4.9 μm was obtained. Hereinafter, a cylindrical battery was manufactured using this positive electrode active material in the same manner as in Example 1.

Experimental Example 2 Li / Co / Al = molar ratio of lithium carbonate, cobalt oxide and aluminum hydroxide having an average particle size of 3 μm.
The mixture was mixed with a ball mill so as to be 1.01 / 0.97 / 0.03, calcined in air at 600 ° C. for 1 hour, and further calcined at 900 ° C. for 10 hours to synthesize a positive electrode active material. . By grinding and mixing this positive electrode active material, a positive electrode active material having a particle size of 4.8 μm was obtained. Hereinafter, a cylindrical battery was manufactured using this positive electrode active material in the same manner as in Example 1.

Experimental Example 3 Li / Co / Al = molar ratio of lithium carbonate, cobalt oxide and aluminum hydroxide having an average particle size of 7 μm.
The mixture was mixed with a ball mill so as to be 1.01 / 0.97 / 0.03, calcined in air at 600 ° C. for 1 hour, and further calcined at 900 ° C. for 10 hours to synthesize a positive electrode active material. . The positive electrode active material having a particle size of 5.2 μm was obtained by pulverizing and mixing this positive electrode active material. Hereinafter, a cylindrical battery was manufactured using this positive electrode active material in the same manner as in Example 1.

Experimental Example 4 Lithium carbonate, cobalt oxide and an average particle size of 10 μm
Of aluminum hydroxide in a molar ratio of Li / Co / Al =
The mixture was mixed with a ball mill so as to be 1.01 / 0.97 / 0.03, calcined in air at 600 ° C. for 1 hour, and further calcined at 900 ° C. for 10 hours to synthesize a positive electrode active material. . By grinding and mixing this positive electrode active material, a positive electrode active material having a particle size of 4.8 μm was obtained. Hereinafter, a cylindrical battery was manufactured using this positive electrode active material in the same manner as in Example 1.

Experimental Example 5 Lithium carbonate, cobalt oxide and an average particle size of 12 μm
Of aluminum hydroxide in a molar ratio of Li / Co / Al =
The mixture was mixed with a ball mill so as to be 1.01 / 0.97 / 0.03, calcined in air at 600 ° C. for 1 hour, and further calcined at 900 ° C. for 10 hours to synthesize a positive electrode active material. . The positive electrode active material having a particle size of 5.0 μm was obtained by pulverizing and mixing the positive electrode active material. Hereinafter, a cylindrical battery was manufactured using this positive electrode active material in the same manner as in Example 1.

With respect to the cylindrical battery of the experimental example manufactured as described above, the initial capacity and the capacity retention rate under a high temperature environment were measured in the same manner as in Example 1. Table 2 shows the results.

[0072]

[Table 2]

From the results in Table 2, it can be seen that as the particle size of the aluminum hydroxide used increases, the capacity retention in a high-temperature environment tends to decrease. When the particle size exceeds 10 μm, the capacity retention is more than 80%. It can be seen that it has decreased. Therefore, in order to obtain an excellent capacity retention rate even in a high temperature environment, the particle size of aluminum hydroxide should be 10 μm.
m or less.

Next, in Experimental Examples 6 to 12, Co /
With the Al composition ratio fixed at 0.97 / 0.03, the particle size of the lithium composite oxide used as the active material will be examined. In Comparative Example 13, a lithium composite oxide having a particle size of 68.8 μm without dissolving aluminum was used as a target for comparison.

Experimental Example 6 Li / Co / Al = molar ratio of lithium carbonate, cobalt oxide and aluminum hydroxide having an average particle size of 5 μm.
The mixture was mixed with a ball mill so as to be 1.01 / 0.97 / 0.03, calcined in air at 600 ° C. for 1 hour, and further calcined at 900 ° C. for 10 hours to synthesize a positive electrode active material. . The positive electrode active material having a particle diameter of 0.6 μm was obtained by pulverizing and mixing the positive electrode active material. Hereinafter, a cylindrical battery was manufactured using this positive electrode active material in the same manner as in Example 1.

Experimental Example 7 Li / Co / Al = molar ratio of lithium carbonate, cobalt oxide and aluminum hydroxide having an average particle size of 5 μm.
The mixture was mixed with a ball mill so as to be 1.01 / 0.97 / 0.03, calcined in air at 600 ° C. for 1 hour, and further calcined at 900 ° C. for 10 hours to synthesize a positive electrode active material. . The positive electrode active material having a particle size of 1.0 μm was obtained by pulverizing and mixing this positive electrode active material. Hereinafter, a cylindrical battery was manufactured using this positive electrode active material in the same manner as in Example 1.

Experimental Example 8 Li / Co / Al = molar ratio of lithium carbonate, cobalt oxide and aluminum hydroxide having an average particle size of 5 μm.
The mixture was mixed with a ball mill so as to be 1.01 / 0.97 / 0.03, calcined in air at 600 ° C. for 1 hour, and further calcined at 900 ° C. for 10 hours to synthesize a positive electrode active material. . The positive electrode active material having a particle size of 3.2 μm was obtained by pulverizing and mixing this positive electrode active material. Hereinafter, a cylindrical battery was manufactured using this positive electrode active material in the same manner as in Example 1.

Experimental Example 9 Li / Co / Al = molar ratio of lithium carbonate, cobalt oxide and aluminum hydroxide having an average particle size of 5 μm.
The mixture was mixed with a ball mill so as to be 1.01 / 0.97 / 0.03, calcined in air at 600 ° C. for 1 hour, and further calcined at 900 ° C. for 10 hours to synthesize a positive electrode active material. . By grinding and mixing this positive electrode active material, a positive electrode active material having a particle size of 10.9 μm was obtained. Hereinafter, a cylindrical battery was manufactured using this positive electrode active material in the same manner as in Example 1.

Experimental Example 10 Li / Co / Al = molar ratio of lithium carbonate, cobalt oxide and aluminum hydroxide having an average particle size of 5 μm.
The mixture was mixed with a ball mill so as to be 1.01 / 0.97 / 0.03, calcined in air at 600 ° C. for 1 hour, and further calcined at 900 ° C. for 10 hours to synthesize a positive electrode active material. . This positive electrode active material was pulverized and mixed to obtain a positive electrode active material having a particle size of 29.5 μm. Hereinafter, a cylindrical battery was manufactured using this positive electrode active material in the same manner as in Example 1.

Experimental Example 11 Li / Co / Al = molar ratio of lithium carbonate, cobalt oxide and aluminum hydroxide having an average particle size of 5 μm.
The mixture was mixed with a ball mill so as to be 1.01 / 0.97 / 0.03, calcined in air at 600 ° C. for 1 hour, and further calcined at 900 ° C. for 10 hours to synthesize a positive electrode active material. . By grinding and mixing this positive electrode active material, a positive electrode active material having a particle size of 49.7 μm was obtained. Hereinafter, a cylindrical battery was manufactured using this positive electrode active material in the same manner as in Example 1.

Experimental Example 12 Li / Co / Al = molar ratio of lithium carbonate, cobalt oxide and aluminum hydroxide having an average particle size of 5 μm.
The mixture was mixed with a ball mill so as to be 1.01 / 0.97 / 0.03, calcined in air at 600 ° C. for 1 hour, and further calcined at 900 ° C. for 10 hours to synthesize a positive electrode active material. . This positive electrode active material was pulverized and mixed to obtain a positive electrode active material having a particle diameter of 71.3 μm. Hereinafter, a cylindrical battery was manufactured using this positive electrode active material in the same manner as in Example 1.

Experimental Example 13 Li / Co = 1.01 in molar ratio of lithium carbonate, cobalt oxide, and aluminum hydroxide having an average particle size of 5 μm.
/1.00, and calcined in air at 600 ° C. for 1 hour, and then calcined at 900 ° C. for 10 hours to synthesize a positive electrode active material. By grinding and mixing this positive electrode active material, a particle size of 68.8 μm is obtained.
m of the positive electrode active material was obtained. Hereinafter, a cylindrical battery was manufactured using this positive electrode active material in the same manner as in Example 1.

The initial capacity, the capacity retention rate in a high-temperature environment, and the discharge capacity under high-load discharge were measured for the cylindrical battery of the experimental example manufactured as described above in the same manner as in Example 1. Table 3 shows the results.

[0084]

[Table 3]

From the results shown in Table 3, the batteries of Experimental Examples 8 to 12 in which the lithium composite oxide containing aluminum as a solid solution was used as the positive electrode active material were compared with the batteries of Experimental Example 13 at any average particle diameter. As a result, the capacity retention under a high temperature environment is improved. However, the average particle size of the positive electrode active material is 1.0 μm.
If it is less than m, the volume of the positive electrode active material decreases due to a decrease in the volume density of the electrode, and the initial capacity becomes 1300.
The result is less than mAh. When the average particle diameter of the positive electrode active material exceeds 50 μm, the initial capacity does not change much, but the 1.5 A discharge capacity becomes 11
The value was lower than 50 mAh. In Experimental Example 13 in which a lithium composite oxide in which aluminum did not form a solid solution was used as the positive electrode active material, even if the average particle diameter exceeded 50 μm, 1.5
Since the A discharge capacity is almost the same as that of Example 1 (average particle diameter: 5 μm), it is understood that the average particle diameter of the positive electrode active material in which aluminum is dissolved is preferably 1 to 50 μm.

Although lithium carbonate was used as a lithium salt for synthesis in this example and experimental examples, similar results can be obtained with other lithium salts such as lithium hydroxide and lithium nitrate. Furthermore, in this example, cobalt oxide was used as the cobalt salt used for the synthesis, but similar results can be obtained with other cobalt hydroxide, cobalt carbonate, and cobalt nitrate salts.

In the present embodiment and the experimental example, the case where the present invention is applied to a cylindrical battery has been described. However, the shape is not particularly limited. It can be applied to non-aqueous electrolyte secondary batteries of various shapes such as a mold, a button type, and a paper type battery.

[0088]

As is apparent from the above description, according to the present invention, when obtaining a lithium composite oxide, aluminum hydroxide is used as an aluminum source, so that it has a high capacity and a high temperature environment. It is possible to obtain a positive electrode active material and a non-aqueous electrolyte secondary battery which are excellent in cycle characteristics under high pressure and discharge under high load.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a cylindrical battery to which the present invention is applied.

[Explanation of symbols]

1 positive electrode, 2 negative electrode, 3 separator, 4 insulating plate, 5
Battery can, 6 Seal gasket, 7 Battery lid, 8 Safety valve device, 9 PTC element, 10 Positive current collector, 11 Negative current collector, 12 Positive electrode lead, 13 Negative electrode lead

──────────────────────────────────────────────────の Continuing on the front page (51) Int.Cl. ⁶ Identification symbol FI H01M 10/40 C04B 35/44 (72) Inventor Hironao Takagishi 1 Shimosugishita, Takakura, Hiwadacho, Koriyama-shi, Fukushima Sony Energy Tech

Claims (5)

[Claims] 1. A method according to claim 1, wherein a cobalt salt, a lithium salt and aluminum hydroxide are mixed, and the mixture is calcined to obtain Li _x Co
_(1-y) Al _y O ₂ (provided that 0.05 ≦ x ≦ 1.10.
01 ≦ y <0.10. A method for producing a positive electrode active material, comprising obtaining a lithium composite oxide represented by the formula (1). 2. The aluminum hydroxide has a particle size of 10 μm.
2. The method for producing a positive electrode active material according to claim 1, wherein m is equal to or less than m. 3. The lithium composite oxide has a particle size of 1 to 5.
The method for producing a positive electrode active material according to claim 1, wherein the thickness is 0 µm. 4. The general formula Li _x Co _(1-y) Al _y O ₂ (provided that
0.05 ≦ x ≦ 1.10 and 0.01 ≦ y <0.10. ), A negative electrode made of a non-graphitizable carbon material capable of doping and undoping lithium, and a non-aqueous electrolyte, and repeating 200 cycles in an environment of 60 ° C. Wherein the ratio obtained by dividing the discharge capacity at the time of discharge by the initial capacity is 80% or more. 5. The lithium composite oxide having a particle size of 1 to 5
The non-aqueous electrolyte secondary battery according to claim 4, wherein the thickness is 0 µm.