JPH1079250A - Positive electrode active material, its manufacture, and nonaqueous solvent secondary battery using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode active material with high performance and high capacity excellent in the charging/discharging cycle and accomplish a secondary battery incorporating this positive electrode active material. SOLUTION: This positive electrode active material comprises a compound expressed by the chemical equation Li1- X-a AXNi1- Y-b BYO2 , where A is strontium or barium, B is at least one of transition metal elements, and X and Y should meet the conditions 0<X<=0.10 and 0<Y<=0.30 while a and b should meet the conditions -0.10<=a<=0.10 and -0.15<=b<=0.15, provided that X represents the total mol number of strontium or barium while Y represents the total mol number of all transition metal elements other than Ni in case B comprises two or more sorts of transition metal elements, wherein the positive electrode active material forms secondary particles as a coagulation of primary particles having mean particle size between 0.01 and 5.0μm, and the mean particle size of the secondary particles ranges from 5.0 to 50μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive electrode active material having a high capacity and good cycle characteristics, and a high-performance non-aqueous solvent secondary battery using such a positive electrode active material.

[0002]

2. Description of the Related Art In recent years, with the spread of portable devices such as video cameras and notebook personal computers, demand for small and high capacity secondary batteries has been increasing. Most of the secondary batteries currently used are nickel-based using alkaline electrolyte.
A cadmium battery has a low battery voltage of about 1.2 V, and it is difficult to improve the energy density. Therefore, a lithium secondary battery using lithium metal, which has a specific gravity of 0.534, which is the lightest among solid solids, has a very low potential, and has the largest current capacity per unit weight among metal negative electrode materials, has been studied. .

However, in a secondary battery using lithium metal for the negative electrode, dendritic lithium (dendrites) is recrystallized on the surface of the negative electrode at the time of discharging, and grows by a charge / discharge cycle. This dendrite growth not only degrades the cycle characteristics of the secondary battery, but in the worst case, breaks through a separator (separator) arranged so that the positive electrode and the negative electrode do not come into contact with each other, and electrically short-circuits with the positive electrode. Ignite and destroy battery. Thus, for example, as disclosed in Japanese Patent Application Laid-Open No. 62-90863, charge and discharge are performed by using a carbonaceous material such as coke as a negative electrode and doping and undoping alkali metal ions. A repetitive secondary battery has been proposed. As a result, it was found that the problem of deterioration of the negative electrode due to the repetition of charge and discharge as described above can be avoided. Further, such various carbonaceous materials can be used as a positive electrode by doping with an anion. As secondary batteries using electrodes based on the above-described principle of doping lithium ions or anions into carbonaceous materials, JP-A-57-20807, JP-A-58-93176, JP-A-58-93176, and -19
No. 2,266, Japanese Patent Application Laid-Open No. 62-90863, Japanese Patent Application Laid-Open No. 62-122066, Japanese Patent Application Laid-Open No. 3-66656, and the like are known.

Further, recently, in order to meet the demand for higher energy density, a battery having a battery voltage of around 4 V has appeared and has been receiving attention. Increasing the battery voltage has been promoted by searching for and developing an active material exhibiting a high potential at the positive electrode, and inorganic compounds such as transition metal oxides and transition metal chalcogens containing alkali metals are known. Above all, Li _X C
oO ₂ (0 <x ≦ 1.0), Li _x NiO ₂ (0 <x ≦
1.0) are considered most promising in terms of high potential, stability, and long life. Among them, LiNi
O ₂ is a raw material that is less expensive and has a more stable supply than LiCoO ₂ , and is a 4V-class active material. Research has been particularly vigorously pursued because of its advantages such as suppression of decomposition.

[0005]

However, LiN
In the case where iO ₂ is repeatedly charged and discharged at a relatively low discharge capacity of about 100 mAh / g, there is no particular problem in the cycle life characteristics. However, when the charge and discharge are repeatedly performed at a discharge capacity of about 100 mAh / g or more, However, there has been a problem that the capacity is remarkably deteriorated and cannot be used practically.

The relationship between the particle size of the positive electrode active material and the discharge capacity is described in JP-A-1-304664 and JP-A-4-3.
3260, JP-A-6-325991 and JP-A-7-1
83047.

First, Japanese Patent Application Laid-Open No. 1-304664 discloses that Li
_X MO ₂ (where M represents one or more transition metals;
05 ≦ x ≦ 1.10. It is described that in the positive electrode, the negative electrode, and the non-aqueous electrolyte secondary battery mainly composed of), the average particle size of the Li _X MO ₂ is preferably 10 to 150 μm. Here, what they mean is the average particle size of secondary particles in which so-called primary particles are agglomerated because the measurement is performed with a Microtrac particle size analyzer using scattering of laser light. It is considered to be the diameter. However, coatability and cycle characteristics were not at satisfactory levels.

Japanese Patent Application Laid-Open No. 6-325791 discloses that LiMNO (M is Co, Ni, etc., N is Ni,
V, Fe, etc.) and an average particle size of 0.01 to 5.0.
Average particle size of 0.1 to 15 μm in which primary particles aggregate
It is described that a non-aqueous secondary battery comprising a primary particle aggregate (secondary particle) is preferable.
The capacity is reduced to 60% of the initial value in about 0 to 300 charge / discharge cycles, and the cycle characteristics are not at a satisfactory level.

Japanese Patent Application Laid-Open No. 7-183047 discloses that a composite oxide of lithium and nickel has a particle size of 0.1 to 3 μm,
It is described that a non-aqueous electrolyte secondary battery in which the secondary particles have a particle size of 5 to 50 μm is preferable, but does not refer to the cycle characteristics but only to the self-discharge rate.

An object of the present invention is to solve the drawbacks of the prior art and to provide a high-performance positive electrode active material having a high capacity and an excellent charge / discharge cycle, and a secondary battery using the same. And

[0011]

SUMMARY OF THE INVENTION The present invention has the following arrangement to solve the above-mentioned problems.

"(1) Chemical formula Li _1-Xa A _X Ni _1-Yb B
_Y O ₂ (where A is strontium or barium, B is at least one transition metal element,
X and Y are 0 <X ≦ 0.10, 0 <Y ≦ 0.30, a,
b is -0.10≤a≤0.10, -0.15≤b≤
0.15; where X is the total number of moles of strontium or barium, and when B is composed of two or more transition metal elements, Y is the total number of moles of all transition metal elements other than Ni). And the average particle diameter of the positive electrode active material is not less than 0.01 μm and 5.0.
secondary particles that are aggregates of primary particles having a particle size of 5.0 μm or more and 50 μm or less.
A positive electrode active material having a size of not more than μm.

(2) Chemical formula Li _1-Xa A _X Ni _{1-Yb BY}
O ₂ (where A is at least two or more kinds of alkaline earth metal elements, B is at least one kind of transition metal element, and X and Y are 0 <X ≦ 0.10, 0 <Y ≦ 0.
30, a and b are -0.10≤a≤0.10, -0.1
5 ≦ b ≦ 0.15; where X is the total number of moles of alkaline earth metal elements, and when B is composed of two or more transition metal elements, Y is the total mole number of all transition metal elements other than Ni. Which is a compound represented by the following formula: wherein the positive electrode active material has an average particle diameter of 0.01 μm
As described above, an aggregate of primary particles having a size of 5.0 μm or less is formed, and the average particle size of the aggregate is 5.0 μm or more and 50 μm or less.
m or less.

(3) The starting material containing lithium and A is
The above (1) or (2), wherein the stoichiometric ratio of the starting materials containing nickel and B is 0.90 or more and less than 1.00, and the mixture is fired in an oxidizing atmosphere. The production method of the positive electrode active material according to the above. "

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The positive electrode active material of the present invention is preferably used for a positive electrode of a secondary battery. As a particularly preferred secondary battery, a secondary battery using a non-aqueous electrolyte containing an alkali metal salt as described above can be mentioned. Therefore, a lithium secondary battery will be described below as an example, and a detailed example will be described.

The inventors of the present invention have focused on the discharge capacity and the decrease in the discharge capacity associated with the charge / discharge cycle, and have intensively studied the improvement of the cycle life characteristics. It was found that when it was within the range, the capacity was high and the cycle characteristics were good. That is, the chemical formula Li
_{1-Xa A X Ni 1-} Yb B Y O 2 ( where, A is strontium or barium, B is composed of at least one transition metal element, wherein X, Y are, 0 <X ≦ 0.10 ,
0 <Y ≦ 0.30, a and b are −0.10 ≦ a ≦ 0.1
0, -0.15≤b≤0.15; where X is the total number of moles of strontium or barium, and when B is composed of two or more transition metal elements, Y is all transition metal elements other than Ni Is a compound represented by the following general formula: wherein the positive electrode active material has an average particle diameter of 0.01 μm or more and 5.0 μm or less. forms a Atsumaritai, average particle size of the aggregate is more than 5.0 .mu.m, the positive electrode active material to wherein a is 50μm or less, and the chemical formula Li _1-Xa a _X Ni
_1-Yb B _Y O ₂ (where, A is at least two or more alkaline earth metal elements, B comprises at least one or more transition metal elements, wherein X, Y are, 0 <X ≦ 0 .1
0, 0 <Y ≦ 0.30, a and b are −0.10 ≦ a ≦
0.10, -0.15 ≦ b ≦ 0.15; where X is the total number of moles of the alkaline earth metal element, and when B is composed of two or more transition metal elements, Y is other than Ni. Which is the total number of moles of all transition metal elements), and the positive electrode active material has an average particle size of 0.01 μm or more and 5.0 μm or less. An aggregate of primary particles is formed, and the average particle size of the aggregate is 5.
A positive electrode active material having a size of 0 μm or more and 50 μm or less.

Here, the transition metal element is not limited, but may be manganese, scandium, titanium,
Vanadium, chromium, iron, cobalt and the like are preferably used, and each has the same effect.

In the present invention, the amount of one or more alkaline earth metal elements to be replaced with lithium is set at 10
%, It is possible to achieve an improvement in cycle life characteristics while suppressing a decrease in capacity, and by replacing nickel with a transition metal element,
It is presumed that it became possible to maintain the layered structure, and to impart electron conductivity, to act synergistically with the effect of the alkaline earth metal element, and to obtain good cycle life characteristics. .

If X is larger than 0.10, the alkaline earth metal element substituted for lithium inhibits the diffusion of lithium ions as described above, and conversely becomes a resistance component, which greatly reduces the discharge capacity. I will. In order to suppress a decrease in discharge capacity, X is preferably smaller than 0.08, and more preferably smaller than 0.05.
On the other hand, when Y exceeds 0.3, the crystal structure becomes unstable and the cycle life characteristics deteriorate. Preferably, Y is less than 0.25, more preferably
Y is preferably smaller than 0.2. Further, a and b are
Indicates deviation from stoichiometry. If a is smaller than -0.10, the positive electrode paste gels during kneading, and if it is larger than 0.10, the discharge capacity decreases. In this respect, −0.05 ≦ a ≦ 0.05 is more preferable, and still more preferably −0.02 ≦ a ≦ 0.
02. When b is smaller than -0.15,
If the discharge capacity decreases, and if it exceeds 0.15, the positive electrode paste will gel during kneading. From this, −0.08 ≦ b ≦ 0.08 is more preferable, and further preferably −0.04 ≦ b ≦ 0.04.

Regarding the primary particles, the particle size of the primary particles is 0.1.
Particles smaller than 01 μm are difficult to synthesize, and cause clogging of the separator. Particles larger than 5.0 μm are hard to aggregate, and the expansion and contraction of the active material at the time of charging and discharging increases. This is inconvenient because the adhesion between the active material and the current collector is deteriorated, the ion transfer characteristics in the active material are inhibited, and the capacity of the battery is reduced.

Further, if the particle size of the secondary particles is less than 5.0 μm, the secondary particles are peeled off during pressing at the time of producing the positive electrode,
In addition, in order to increase the surface area of the active material, the amount of the conductive agent or the binder must be increased, the energy density per unit weight is reduced, and further, by increasing the water content, In general, the LiNiO ₂ -based active material which is unstable with respect to moisture is deteriorated, which is disadvantageous because the capacity of the battery is reduced. On the other hand, if it exceeds 50 μm, particles may penetrate the separator and cause a short circuit, which is inconvenient in terms of safety and yield.

Next, a method for producing the positive electrode active material of the present invention will be described. As the lithium compound as a raw material, general salts such as lithium carbonate, lithium nitrate, lithium sulfate and lithium hydroxide or hydrates thereof, or lithium oxide,
Examples thereof include oxides such as lithium peroxide and lithium iodide. Similar salts or hydrates and oxides of nickel can be mentioned, and similar starting materials can be used for other alkaline earth metals and transition metals.

As an example of the manufacturing method, the following method can be mentioned. The starting materials are prepared so that lithium and the alkaline earth metal element which is an additive element are insufficient by about 0.1 to 10 mol% with respect to a target stoichiometric ratio. That is, a starting material containing lithium and A is prepared at a stoichiometric ratio of 0.90 or more to less than 1.00 with respect to a starting material containing nickel and B. After the raw materials thus mixed are sufficiently mixed, if necessary, they are molded to facilitate a solid-phase reaction.
Pre-fire at ~ 800 ° C. Then, after the secondary particles are crushed using a ball mill or a crusher, the main particles are baked again at 500 to 900 ° C. in an oxidizing atmosphere, and the particle size is adjusted by a pulverization or classification operation to form a positive electrode active material. did. It has been confirmed by composition analysis that a more homogeneous and reproducible composition can be obtained by this operation.

Here, the adjustment of the average particle size of the primary particles is mainly determined by the average particle size of the primary particles of the starting material and the firing conditions.
The average particle size of the secondary particles is determined mainly by the average particle size of the secondary particles of the starting material and the grinding conditions. In the present invention, the average primary particle size was determined by taking a photograph of the particle morphology by SEM observation, measuring the particle size in the vertical and horizontal directions of a total of 30 primary particles, and determining the average value. Average secondary particle diameter The average particle diameter is a mode diameter obtained by measurement with a Microtrac particle size analyzer utilizing scattering of laser light.

There is also a method in which the operation of removing the strongly alkaline substance is not performed. First, lithium and the alkaline earth metal element, which is an additive element, are 0.9 to 0.9% less than all the transition metal elements.
The starting materials are prepared so as to have a molar ratio of 1.00, and then calcined in the same manner as described above, and then subjected to pulverization and classification operations to obtain a positive electrode active material. Further, an additional element may be added to the positive electrode active material of the present invention without impairing the electrode performance.

In the present invention, the material of the negative electrode is not particularly limited, but includes carbonaceous materials, alloys (eg, Li—Al), metal oxides (eg, SnO), metal nitrides (eg, Li ₃ N), and the like. Is used. The carbonaceous material is not particularly limited, and generally, a material obtained by firing an organic substance is used. When the electron conductivity of the carbonaceous material is not sufficient for the purpose of current collection, it is also preferable to add a conductive agent.

When the carbonaceous material is carbon fiber, the carbon fiber to be used is not particularly limited, and is generally obtained by firing an organic substance. Specifically, P obtained from polyacrylonitrile (PAN)
AN-based carbon fiber, pitch-based carbon fiber obtained from pitch such as coal or petroleum, cellulose-based carbon fiber obtained from cellulose, vapor-grown carbon fiber obtained from gas of low-molecular-weight organic substances, and the like, Carbon fibers obtained by firing polyvinyl alcohol, lignin, polyvinyl chloride, polyamide, polyimide, phenolic resin, furfuryl alcohol, and the like may be used.
Among these carbon fibers, carbon fibers satisfying the characteristics are appropriately selected according to the characteristics of the electrode and the battery in which the carbon fibers are used. When the carbon fiber is used for a negative electrode of a secondary battery using a non-aqueous electrolyte containing an alkali metal salt, a PAN-based carbon fiber, a pitch-based carbon fiber, and a vapor-grown carbon fiber are preferable. In particular, PAN-based carbon fibers and pitch-based carbon fibers are preferable in that doping of alkali metal ions, particularly lithium ions, is favorable,
Among them, PAN-based carbon fibers such as “Torayca” T series or “Torayca” M series manufactured by Toray Industries,
Pitch-based carbon fibers obtained by firing mesophase pitch coke are more preferably used.

When the carbon fiber is used as the electrode, any form may be used, but it is preferable to arrange the carbon fiber uniaxially, or to form a fabric-like or felt-like structure. Examples of the structure such as a fabric or a felt include a woven fabric, a knitted fabric, a braid, a lace, a net, a felt, a paper, a nonwoven fabric, a mat, and the like. Felt and the like are preferred. Further, the carbon fiber may be used by attaching it to a current collector such as a copper foil with a binder or the like, and a conductive agent such as carbon powder may be added. In view of operability and productivity, short fiber carbon fibers are more preferable. Like ordinary carbon powder, it can be used in the form of an electrode together with a conductive agent and a binder, and has structural characteristics unique to carbon fibers. An average length of 30 μm or less is more preferable because of easy handling and high bulk density.

The electrolyte of a secondary battery using the electrode of the present invention is not particularly limited, and a conventional non-aqueous solvent electrolyte can be used. Among these, propylene carbonate, ethylene carbonate, γ-butyrolactone, N-methylpyrrolidone, acetonitrile, and the like for the secondary battery electrolyte comprising the non-aqueous electrolyte containing the alkali metal salt described above.
N, N-dimethylformamide, dimethylsulfoxide, tetrahydrofuran, 1,3-dioxolan, methyl formate, sulfolane, oxazolidone, thionyl chloride,
1,2-dimethoxyethane, diethylene carbonate, derivatives and mixtures thereof, and the like are preferably used. As the electrolyte contained in the electrolytic solution, an alkali metal,
In particular, lithium halide, perchlorate, thiocyanate, borofluoride, phosphorus fluoride, arsenic fluoride, aluminum fluoride, trifluoromethyl sulfate, and the like are preferably used. Applications of the secondary battery using the electrode of the present invention include, for example, video cameras, notebook computers, word processors, radio-cassettes, and portable small electronic devices such as mobile phones, utilizing the features of light weight, high capacity, and high energy density. Widely available.

[0030]

EXAMPLES Specific embodiments of the present invention will be described below with reference to examples, but the present invention is not limited thereto.

Example 1 Commercially available high purity reagent lithium hydroxide (Li (OH)),
Nickel hydroxide (Ni (OH) ₂ ), strontium hydroxide octahydrate (Sr (OH) ₂ .8H ₂ O) and cobalt hydroxide (Co (OH) ₂ ) were converted to Li _0.99 Sr in terms of oxide.
_After being weighed to _0.02 Ni _0.90 Co _0.10 O ₂ and sufficiently mixed in an automatic mortar, the mixture was filled in an alumina crucible, and was placed in a pure oxygen gas stream (flow rate 1 liter / min) using an atmosphere firing furnace. It was kept at 650 ° C. for 16 hours and pre-baked. After cooling to room temperature, the mixture was pulverized again in an automatic mortar for 30 minutes to break up aggregation of secondary particles. Then, in the same atmosphere as in the preliminary firing, main firing was performed at 750 ° C. for 8 hours, cooled to room temperature, and then pulverized again with an automatic mortar to obtain a positive electrode active material powder of the present invention. By changing the pulverization time at this time, three types of powder having an average secondary particle size of 5 μm, 22 μm, and 47 μm were obtained. The average particle size of the secondary particles is measured by a laser diffraction type particle size distribution analyzer (wet type) SAL manufactured by Shimadzu Corporation.
It was measured by dispersing in water using D-2000A. The mode diameter of the obtained particle size distribution data was defined as the average particle diameter. The primary particle diameter measured by SEM observation was 0.1
μm. The obtained powder was analyzed by flame atomic absorption spectrometry for the alkali metal element and by ICP emission spectroscopy for the other metal elements, and was _subjected to quantitative composition analysis to find that Li _1.02 Sr _0.0019 Ni _0.89 Co
It was confirmed that the composition was _0.11 O ₂ . Next, a method for manufacturing a cell for evaluating charge and discharge characteristics will be described. The positive electrode mixture was prepared by mixing a polyvinylidene fluoride active material as a binder in an N-methylpyrrolidone (NMP) solution prepared so as to have a concentration of 10 wt%, and the above active material: conductive agent (acetylene black): binder was 89%. Parts by weight: 4 parts by weight: 7 parts by weight, and mixed in an automatic mortar for 30 minutes in a nitrogen stream. This was applied on an aluminum foil having a thickness of 13 μm, dried at 90 ° C. in a drier, applied on the back side, dried to form positive electrodes on both sides, and then pressed to obtain a 180 μm thick positive electrode material coated portion. A positive electrode having a width of 10 mm and a length of 20 mm was produced.

Next, the discharge capacity of the positive electrode manufactured as described above was evaluated. The electrolytic solution was propylene carbonate and dimethyl carbonate (each having a volume ratio of 1: 1) containing 1 M LiBF ₄ , and the evaluation was performed using a three-electrode cell using a lithium metal foil as a counter electrode and a reference electrode. The current density per active material was 4.2 V (vs. Li ⁺ / L) at a constant current of 130 mA / g.
i), a constant potential charge was performed at 4.2 V, and the charge was continued until the total charge time reached 5 hours. After charging, the battery was discharged at a current density of 30 mA / g to 3.0 V (vs. Li ⁺ / Li) to determine an initial capacity. Further, the same charging was performed with the charging time being 3 hours, and after charging, the charging was performed at the same current density as the charging, and the charging time was changed to 3.0.
The charge / discharge cycle of discharging at a constant current up to V (vs. Li ⁺ / Li) is repeated, and the discharge capacity at the 300th charge and discharge cycle at a current density of 130 mA / g is compared with the first discharge capacity. Table 1 shows the results of the obtained capacity retention rates.

Capacity retention (%) = {(300th discharge capacity) / (1st discharge capacity)} × 100 Comparative Example 1 The average particle diameter of the secondary particles was changed to 3 μm, 6
Two kinds of positive electrode active material powders were prepared in the same manner as in Example 1 except that the thickness was set to 1 μm, and the results of initial capacity and capacity retention were shown in Table 1.

Comparative Example 2 Nickel carbonate (Ni (CO ₃ ) ₂ )
In the same manner as in Example 1 except that the sintering temperature was set to 900 ° C., two kinds of positive electrode active material powders having an average primary particle diameter of 10 μm, an average secondary particle diameter of 28 μm, and 45 μm were prepared, and an initial capacity was set. Table 1 shows the results of determining the capacity retention rate.

Example 2 Three kinds of positive electrode active material powders having a primary particle diameter of 0.2 μm and an average secondary particle diameter of 6 μm, 24 μm and 44 μm were prepared in the same manner as in Example 1 except that barium was used instead of strontium. Table 1 shows the results of measuring the initial capacity and the capacity retention. The composition determined by the quantitative analysis was Li
_1.01 Ba _0.02 Ni _0.90 Co _0.10 O ₂ .

Comparative Example 3 The average particle size of the secondary particles was changed to 4 μm and 6
Two kinds of positive electrode active material powders were prepared in the same manner as in Example 2 except that the thickness was 5 μm, and the results of obtaining the initial capacity and the capacity retention were shown in Table 1.

Comparative Example 4 Nickel carbonate (Ni (CO ₃ ) ₂ )
In the same manner as in Example 1 except that the sintering temperature was set to 900 ° C., two kinds of positive electrode active material powders having an average primary particle diameter of 11 μm, an average secondary particle diameter of 25, and 43 μm were prepared, and an initial capacity was set. Table 1 shows the results of determining the capacity retention rate.

Example 3 Commercially available high purity reagent lithium hydroxide (Li (OH)),
Nickel hydroxide (Ni (OH) _2), strontium hydroxide octahydrate _{(Sr (OH) 2 · 8H} 2 O), barium hydroxide octahydrate _{(Ba (OH) 2 · 8H} 2 O), water Li _0.99 S in terms of oxide as cobalt oxide (Co (OH) ₂ )
r _0.01 Ba _0.01 Ni _0.90 Co _0.10 O _{2 In the same} manner as in Example 1 except for weighing the primary particles, the average particle diameter of the primary particles was 0.1 μm, and the average particle diameter of the secondary particles was 5 μm and 24 μm.
Table 1 shows the results obtained by preparing three types of positive electrode active material powders of m and 45 μm, and determining the initial capacity and capacity retention. The composition determined by the quantitative analysis was Li _1.01 Sr _0.01 Ba _0.01 Ni
_0.90 Co _0.10 O ₂ . Comparative Example 5 Two kinds of positive electrode active material powders were produced in the same manner as in Example 3 except that the average particle diameter of the secondary particles was changed to 4 μm and 67 μm by changing the pulverization time, and the initial capacity and the capacity retention were determined. The results are shown in Table 1.

Comparative Example 6 Nickel carbonate (Ni (CO ₃ ) ₂ )
In the same manner as in Example 3 except that the sintering temperature was set to 900 ° C., two kinds of positive electrode active material powders having an average primary particle diameter of 11 μm, an average secondary particle diameter of 27 μm, and 44 μm were prepared, and an initial capacity was set. Table 1 shows the results of determining the capacity retention rate. Further, Example 4 also shows a secondary battery manufactured by combining the positive electrode active material of the present invention and carbon fiber.

[0040]

[Table 1] Example 4 A commercially available PAN-based carbon fiber ("Treca" T-300, manufactured by Toray Industries, Inc.) was pulverized with a hammer mill and a roller mill so as to have an average length of 15 μm.
Milled fibers heat-treated for a period of time were used as negative electrode active materials. For the negative electrode mixture, 10 parts of polyvinylidene fluoride active material
wt-% N-methylpyrrolidone (N
MP) solution, the active material: a conductive agent (acetylene black): a binder was mixed in a proportion of 80 parts by weight: 5 parts by weight: 15 parts by weight, and mixed in an automatic mortar for 30 minutes in a nitrogen stream. did. This was applied on a copper foil having a thickness of 10 μm, dried at 90 ° C. in a dryer, applied to the back side, dried to form copper electrodes on both sides, and then pressed to produce a 180 μm thick negative electrode. . A battery positive electrode (average particle diameter of secondary particles of the positive electrode active material: 22 μm) prepared in the same manner as in Example 1 was applied to this negative electrode by a porous polyethylene film (25S, Mitsubishi Chemical Corporation). Was placed in a battery can with a separator interposed therebetween, and the electrolytic solution was injected and sealed to produce a 18650-size cylindrical secondary battery. As the electrolyte, propylene carbonate and dimethyl carbonate (each at a volume ratio of 1: 1) containing 1M LiPF6 were used. Using the secondary battery thus manufactured, the battery was charged at a constant current / constant potential (total charge time: 3 hours) at a current of 1 A and a charge cut-off voltage of 4.10 V, and then discharged at a constant current of 1 A. Discharged at 2.5V. Table 2 shows the results obtained for the initial capacity and capacity retention at this time.

Comparative Example 7 A secondary battery was prepared and evaluated in the same manner as in Example 4 except that the active material having an average particle diameter of 3 μm of the secondary particles prepared in Comparative Example 1 was used as the positive electrode active material. The results are shown in Table 2.

[0042]

[Table 2]

[0043]

According to the present invention, it is possible to provide a positive electrode active material having a high capacity and an excellent charge / discharge cycle and a high-performance secondary battery using the same.

Claims (12)

[Claims] 1. A chemical formula _{Li 1-Xa A X Ni 1} -Yb B Y O 2
(Where A is strontium or barium and B is
Is composed of at least one transition metal element, wherein X, Y
Are 0 <X ≦ 0.10, 0 <Y ≦ 0.30, a and b are
-0.10≤a≤0.10, -0.15≤b≤0.1
5; However, X is the total number of moles of strontium or barium, and when B is composed of two or more transition metal elements, Y is the total number of moles of all transition metal elements other than Ni.)
And forming secondary particles that are aggregates of primary particles having an average particle diameter of 0.01 μm or more and 5.0 μm or less, The average particle size of the secondary particles is 5.0 μm or more and 50 μm or more.
A positive electrode active material characterized by the following. 2. A non-aqueous solvent secondary battery using the positive electrode active material according to claim 1. 3. The non-aqueous solvent secondary battery according to claim 2, wherein a carbonaceous material is used as the negative electrode active material. 4. The non-aqueous solvent secondary battery according to claim 3, wherein said carbonaceous material is carbon fiber. 5. The non-aqueous solvent secondary battery according to claim 4, wherein said carbon fibers are in the form of short fibers having an average length of 30 μm or less. 6. A starting material containing lithium and A is added in a stoichiometric ratio of 0.1 to a starting material containing nickel and B.
The method for producing a positive electrode active material according to claim 1, wherein the mixture is prepared at a ratio of 90 or more and less than 1.00 and fired in an oxidizing atmosphere. 7. A chemical formula _{Li 1-Xa A X Ni 1} -Yb B Y O 2
(Where A is at least two or more alkaline earth metal elements, B is at least one transition metal element, and X and Y are 0 <X ≦ 0.10 and 0 <Y ≦ 0 .3
0, a, and b are -0.10≤a≤0.10, -0.15
≦ b ≦ 0.15; where X is the total number of moles of alkaline earth metal elements, and when B is composed of two or more transition metal elements, Y is the total number of moles of all transition metal elements other than Ni. Is a compound represented by the formula: wherein the positive electrode active material has an average particle diameter of 0.01 μm
As described above, an aggregate of primary particles having a size of 5.0 μm or less is formed, and the average particle size of the aggregate is 5.0 μm or more and 50 μm or less.
m or less. 8. A non-aqueous solvent secondary battery using the positive electrode active material according to claim 7. 9. The non-aqueous solvent secondary battery according to claim 8, wherein a carbonaceous material is used as the negative electrode active material. 10. The non-aqueous solvent secondary battery according to claim 9, wherein said carbonaceous material is carbon fiber. 11. The non-aqueous solvent secondary battery according to claim 10, wherein said carbon fibers are in the form of short fibers having an average length of 30 μm or less. 12. A starting material containing lithium and A is blended with a starting material containing nickel and B at a stoichiometric ratio of 0.90 or more and less than 1.00, and fired in an oxidizing atmosphere. The method for producing a positive electrode active material according to claim 7, wherein: