JPH09270258A - Nickel-cobalt hydroxide for nonaqueous electrolyte battery active material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive active material of lithium composite nickel cobalt oxide with excellent cycle characteristics and high rate discharge characteristics by using nickel-cobalt hydroxide whose physical property such as a particle shape and particle size is controlled. SOLUTION: When a positive active material for a nonaqueous electrolyte battery, Lix Niy CO2 , (0.90<=x<=1.05, 0.7<=y<=0.9, y+z=1) is synthesized, nickel - cobalt hydroxide represented by Niv Cow (OH)2 (v+w=1) is used as a nickel - cobalt source, and Co substitution amount (w value) is controlled to the range of 0.1 to 0.3. Nickel-cobalt hydroxide obtained forms secondary particles by aggregation of myriad primary particles having a rice grain shape as observed by SEM photograph, and the mean particle size of the secondary particles is controlled to 1.5-10μm.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to Li _x Ni _y Co _z O ₂ (0.90 ≦ x ≦) of a positive electrode active material of a non-aqueous electrolyte secondary battery.
1.05, 0.7 ≦ y ≦ 0.9, y + z = 1) and a nickel-cobalt hydroxide used as a raw material for the synthesis of a lithium composite nickel-cobalt oxide.

[0002]

2. Description of the Related Art In recent years, portable electronic devices have become more portable.
Cordless use is rapidly progressing. Currently, nickel-cadmium storage batteries or sealed small lead-acid batteries play a role as driving power sources for these electronic devices, but as they become more portable and cordless, they become the driving power sources. Higher energy density of secondary battery,
The demand for smaller and lighter is increasing. Further, in recent years, a secondary battery has been attracting attention as a power source for mobile phones, and along with the rapid expansion of the market, there is a great demand for extending the call time and improving the cycle life.

Under such circumstances, a lithium composite transition metal oxide showing a high charge / discharge voltage, such as LiCoO 2.
₂ (for example, Japanese Patent Laid-Open No. 63-59507) and LiNiO ₂ aiming at higher capacity (for example, US Pat.
No. 02518) has been reported. Especially LiNiO
₂ is expected to have a higher energy density than LiCoO ₂ ,
Development is progressing in various fields. However, LiNiO ₂
However, since the polarization during charging was large and the oxidative decomposition voltage of the electrolytic solution was reached before Li could be sufficiently taken out, the expected large capacity could not be obtained.

In order to solve such a problem, a non-aqueous electrolyte secondary battery has been proposed in which a part of nickel element is replaced by cobalt is used as a positive electrode active material and insertion / extraction of lithium ion is utilized. There is. For example, JP-A-62-25
In 6371, a lithium composite nickel-cobalt oxide is synthesized by mixing lithium carbonate, cobalt carbonate and nickel carbonate and firing at 900 ° C.
Further, JP-A-63-299056 reports a method of mixing hydroxides of lithium with cobalt and nickel, and oxides. Furthermore, JP-A-1-294364
In the gazette, an example of synthesizing a lithium composite nickel-cobalt oxide by coprecipitating nickel ion and cobalt ion as a carbonate from an aqueous solution containing nickel ion and cobalt ion and then mixing with lithium carbonate is reported. Has been done.

[0005]

However, as reported so far, Li _x Ni _y Co _z O ₂ (0.90 ≦ x ≦
1.05, 0.7 ≦ y ≦ 0.9, y + z = 1) in the lithium composite nickel-cobalt oxide, the substitution C
Although the discharge capacity gradually increased as the o amount (z value) increased, it became clear that the cycle deterioration problem that the battery discharge capacity gradually decreased when the charge / discharge cycle was repeated. As a result of thorough investigations by the present inventors, it has been found that such characteristic deterioration is caused by the following. In other words, disassemble a battery that has undergone cycle deterioration,
As a result of observing the electrode plate, it was found that the crystal structure of the positive electrode active material was changed in the positive electrode plate that was repeatedly charged and discharged.

It has been reported that the lattice constant of LiNiO ₂ changes as the battery is charged and discharged (W. Li, JN Reimers and J.
R. Dahn, Solid State Ionic
s, 67 , 123 (1993)), and the crystal phase is changed from hexagonal (Hexagonal) to monoclinic (Monoclini) with the elimination of Li.
c), second hexagonal (Hexagonal), third hexagonal (He
xagonal) has been reported. Such a crystal phase change is poor in reversibility, and it is considered that the site where Li can be inserted / released is gradually lost during repeated charge / discharge reactions. By substituting a part of Ni with Co, such a change in the crystal phase is remarkably alleviated. This is because the binding force of Co with oxygen is N
Since it is stronger than i, it is considered that the crystal structure is more stabilized, and the change of the crystal phase unlike in the case where Co substitution is not performed (z = 0) does not occur. Therefore, Co substitution amount (z value)
It is considered that the larger the value becomes, the more stable the crystal phase becomes and the more the discharge capacity and the cycle characteristics are improved.

However, in practice, Japanese Unexamined Patent Publication No. 62-25637
Cobalt and nickel carbonates and hydroxides as reported in Japanese Patent Application Laid-Open No. 1 and Japanese Patent Application Laid-Open No. 63-299056.
The lithium composite nickel-cobalt oxide synthesized by mixing the respective compounds such as oxides is C
o When the substitution amount (z value) becomes large (z ≧ 0.1), nickel and cobalt are not actually uniformly dispersed, and it is clear that the mixture is partially LiNiO ₂ and LiCoO _2. became. Therefore, in such an active material, although the discharge capacity is large to some extent, when charge and discharge are repeated, the crystal structure is destroyed by the above-described crystal phase change in the portion where Co is not sufficiently replaced, and as a result, the discharge capacity is increased. It decreased and was not sufficient as a battery active material. Further, when nickel ions and cobalt ions are coprecipitated as carbonates as in JP-A-1-294364, nickel and cobalt are uniformly dispersed and good cycle characteristics are secured. However, in this case, since it precipitates as a basic carbonate, it actually has an undefined content of Ni.
(OH) ₂ has a double salt NiCO ₃ · XNI (OH) ₂ containing, non-uniform synthesis process of lithium. For this reason, there was a large variation in the battery characteristics, and there was a problem in actual use.

[0008] In addition, since the load on the battery increases with the high added value of portable equipment in recent years, improvement of the high rate discharge characteristics of discharging with a particularly large current is a major issue. All of the batteries using No. 1 were insufficient. An object of the present invention is to solve the above-mentioned problems relating to the conventional positive electrode, and nickel as a raw material for synthesizing a lithium composite nickel-cobalt oxide that provides a non-aqueous electrolyte secondary battery having excellent charge / discharge characteristics. -To provide a cobalt hydroxide.

[0009]

In order to solve such problems, the present inventors have used a hydroxide produced by coprecipitation as a source of nickel and cobalt which are raw materials of a positive electrode active material, and The physical properties are carefully studied,
Nickel in the particle, arrangement of cobalt atoms, particle shape, particle diameter, specific surface area, tap density, spatial volume of pores,
By controlling the occupancy rate of the pores, we have succeeded in preventing the cycle deterioration and obtaining a battery having good high rate discharge characteristics. That is, the present invention relates to Li _x Ni _y Co.
_z O ₂ (0.90 ≦ x ≦ 1.05, 0.7 ≦ y ≦ 0.9,
y + z = 1) as a nickel-cobalt source when synthesizing as a positive electrode active material, Ni _v Co _w (OH) ₂ (v + w = 1)
The nickel substitution amount (w value) is controlled in the range of 0.1 to 0.3 by using the nickel-cobalt hydroxide represented by, and the obtained nickel-cobalt hydroxide is observed by the SEM photograph. A large number of primary particles of rice grains are aggregated to form secondary particles, and the average particle diameter of the secondary particles is 1.5.
It is controlled so as to be 10 μm. This nickel-cobalt hydroxide is a liquid that continuously supplies an aqueous solution of nickel salt, an aqueous solution of cobalt salt and an aqueous solution of caustic alkali while controlling the concentration and flow rate in a tank whose pH and temperature are adjusted, and overflows from the tank. The physical properties can be controlled by collecting the product from.

[0010]

DETAILED DESCRIPTION OF THE INVENTION The nickel - cobalt hydroxide has the formula _{Ni v Co w (OH) 2} (0.7 ≦ v ≦ 0.9,
v + w = 1), and in the SEM photograph observation, numerous primary particles of rice grains are aggregated to form secondary particles,
The average particle size of the secondary particles is in the range of 1.5 to 10 μm. Since the particle shape of the nickel-cobalt hydroxide is spherical or elliptical, high packing property can be realized.
More desirable. Further, in order to sufficiently satisfy the high rate discharge characteristic, nickel-cobalt hydroxide has a BET specific surface area measured by adsorption of nitrogen gas of 8 to 35 m ² / g.
It is desirable that Further, the nickel-cobalt hydroxide preferably has a tap density of 1.4 to 2.3 g / cm ³ . Further, nickel-cobalt hydroxide has a pore space volume of 0.010 to 0.10 cm ³ /
g is desirable. Further, the nickel-cobalt hydroxide preferably has a pore occupancy in the range of 5 to 40%.

Such a method of coprecipitating nickel and cobalt as hydroxides has been reported as a method for producing nickel hydroxide used for a positive electrode for nickel-cadmium batteries. For example, in JP-A-63-16556 and JP-A-64-42330, as a method for producing nickel hydroxide, a nickel salt aqueous solution, a cobalt salt aqueous solution, and a caustic alkaline aqueous solution are placed in a bath whose pH and temperature are adjusted. Is continuously supplied while controlling its concentration and flow rate,
The method of collection is reported. Further, JP-A-63-
No. 152866, JP-A-5-41212, and JP-A-7-73877 report a method of solid-dissolving various metal elements containing Co in nickel hydroxide in a reaction tank by a coprecipitation method. There is. However, the addition of Co in these inventions is aimed at improving the characteristics of alkaline storage batteries such as aqueous solution nickel-cadmium batteries or nickel-hydrogen storage alloy batteries, and is carried out for the following reasons.

Γ-N that causes a decrease in the discharge capacity of the battery
Suppress the production of iOOH. (For example, M. Oshitani,
K. Takashima, and Y. Matsumara, Proceedings of the S
ymp.on Nickel Hydroxide Electrodes, Volume 90-4 / T
he Electrochemical Soc., 197 (1989), JP-A-5-4
No. 1212)

Improving the ionization rate of hydrogen on the surface of nickel hydroxide, the utilization rate by promoting proton conduction in nickel hydroxide, and the high rate charge / discharge efficiency. (For example I. Matsum
oto, M.Ikeyama, T.Iwaki, Y.Umeo and Y.Ogawa, Denkikaga
ku, 54,159〜164 (1986) etc.)

As described above, the role of Co in these inventions is not intended to be added as an active material in the nickel hydroxide crystal matrix, for the purpose of catalytic action. For this reason, if the amount of Co added increases too much, the utilization factor of the active material decreases. Therefore, the amount usually added is _{w in} Ni _v Co _w (OH) ₂ (v + w = 1).
In most cases, ≦ 0.1. The present invention is intended to improve the characteristics of a non-aqueous electrolyte battery, and includes the active material Li _x Ni _y Co _z O ₂ (0.90 ≦ x ≦ 1.05, 0.7
≤ y ≤ 0.9, y + z = 1) nickel-cobalt hydroxide Ni _v Co _w (OH) ₂ (0.7) used as a raw material for the synthesis of the lithium composite nickel-cobalt oxide
≦ v ≦ 0.9, v + w = 1) is controlled. As a matter of course, Co is solid-dissolved in the crystal matrix of the active material and acts as an active material, which is completely different from the above-mentioned characteristic improvement of the alkaline storage battery.

The reaction of synthesizing LiNiO ₂ proceeds in a form in which lithium atoms are diffused in the nickel salt crystal by heat treatment, and LiNiO ₂ is synthesized. Conventionally reported nickel carbonate, nickel oxide, etc. are in a so-called polycrystal state in which crystals in particles are randomly arranged. Therefore, LiNiO ₂ using them as a raw material is used.
Becomes a similar polycrystalline state. When a rechargeable battery is constructed by using LiNiO ₂ having such a polycrystal structure and charging / discharging is carried out, the site capable of accommodating Li is destroyed due to repeated crystal phase transition accompanying charging / discharging, Such crystals repeatedly expand and contract, resulting in finer particles, and detachment from the battery current collector. As a result, the discharge capacity of the battery is reduced and cycle deterioration is caused. When cobalt oxide, cobalt carbonate, or cobalt hydroxide is added at the time of synthesis as a method of adding Co, solid solution at the atomic level as obtained by the coprecipitation method cannot be realized, and LiNiO ₂ or Li is partially added.
Since it exists as CoO _2, it causes cycle deterioration for the same reason.

When the method for producing nickel-cobalt hydroxide according to the present invention is used, fine crystals produced in the bath grow by controlling the cobalt concentration, bath temperature, stirring speed, pH and the like. Since nickel-cobalt hydroxide particles are formed, even if the Co substitution amount (w value) is as large as 0.1 or more, nickel and cobalt are solid-solved at the atomic level, and the crystals are very well aligned in the same direction. To do. Moreover, the crystal structure is the same hexagonal as _{Li x Ni y Co z O 2} , even if the mixture is combined with lithium salt, the atomic arrangement is maintained. If the Co substitution amount (w value) exceeds 0.3, it becomes difficult to grow crystals, and polycrystalline Ni _v Co _w
(OH) ₂ is produced. Therefore, the Co substitution amount is 0.
It is desirable that 1 ≦ w ≦ 0.3.

As a result, Li _{x having} very few crystal grain boundaries
It becomes possible to synthesize Ni _y Co _z O ₂ . _{Ni v Co w (OH) 2} (0.7 ≦ v ≦ 0.9 having such a structure, v + w
= 1) was used as a synthetic raw material for Li _x Ni _y Co _z O ₂ (0.
90 ≦ x ≦ 1.05, 0.7 ≦ y ≦ 0.9, y + z =
When a secondary battery is constructed using 1) and charging / discharging is performed,
Addition of Co improves the crystal stability, eliminates the transition of the crystal phase due to charge and discharge, and has very few crystal grain boundaries that cause grain structure destruction, preventing grain refinement and dropping. Therefore, good cycle characteristics can be realized. Further, by controlling the particle size, BET specific surface area, tap density, pore spatial volume, and pore occupancy of the nickel-cobalt hydroxide particles according to the present invention, lithium ions are transferred when a battery is constructed. The contact area with the electrolyte is increased, and high efficiency discharge characteristics can be realized.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. << Example 1 >> FIG.
1 is a vertical cross-sectional view of a cylindrical battery used for evaluation of a non-aqueous secondary battery active material synthesized from cobalt hydroxide. Battery case 1 made of stainless steel sheet with organic electrolyte resistance
An electrode plate group 4 in which a positive electrode plate 5 and a negative electrode plate 6 are spirally wound via a separator 7 is housed therein with insulating plates 8 and 9 arranged vertically. The opening of the battery case 1 is sealed by an assembly sealing plate 2 provided with a safety valve and an insulating packing 3. An aluminum positive electrode lead 5a is drawn out from the positive electrode plate 5 and connected to the sealing plate 2, and a nickel negative electrode lead 6a is drawn out from the negative electrode plate 6 and connected to the bottom of the battery case 1.

The negative electrode plate 6, the electrolytic solution and the like will be described in detail below. The negative electrode plate 6 was manufactured as follows. First, 100 parts by weight of graphite powder was mixed with 10 parts by weight of a fluororesin-based binder, and this mixture was suspended in a carboxymethyl cellulose aqueous solution to form a paste. Then, this paste is applied to the surface of a copper foil having a thickness of 0.015 mm,
After dried, rolled to 0.2 mm, width 37 mm, length 28
It was cut into a size of 0 mm to obtain a negative electrode plate. For the electrolyte, use an equal volume mixed solvent of ethylene carbonate and diethyl carbonate,
What was melt | dissolved in the ratio of 1 mol / liter (L) of lithium hexafluorophosphate was used. After pouring this electrolytic solution into the electrode plate group 4, the battery was sealed and used as a test battery.

Next, the method for producing a lithium composite nickel-cobalt oxide using the nickel-cobalt hydroxide of the present invention will be described in detail. A tank having a volume of 100 L was used as a deposition tank for producing nickel-cobalt hydroxide. The amount of metallic nickel is 60 as the nickel salt aqueous solution.
An aqueous solution of nickel sulfate corresponding to g / L was used, and the molar ratio of cobalt to nickel was 0, 5, 10, 20, 3
Cobalt sulfate was added and dissolved so as to be 0% and 40% to prepare a nickel sulfate-cobalt mixed aqueous solution. Also,
A 25% by weight aqueous solution of sodium hydroxide was used as the caustic aqueous solution. The nickel-cobalt mixed aqueous solution was introduced into the above precipitation tank at a constant flow rate of 10 L / h, and the sodium hydroxide solution was introduced with sufficient stirring, and the nickel-cobalt hydroxide produced had an average particle size of 3 to The pH value of the reaction tank was controlled so as to be in the range of 5 μm. After washing the obtained nickel-cobalt hydroxide in water, 8
It was dried at 0 ° C. to obtain nickel-cobalt hydroxide.

The average particle size was measured by the laser method, and the value corresponding to a cumulative 50% was taken as the average particle size. Also,
The specific surface area was measured by the BET method using nitrogen. A graduated cylinder (weight Ag) with a tap density of 20 cm ³ was filled with nickel-cobalt hydroxide, and after tapping 200 times,
The weight (Bg) of the graduated cylinder and the volume of nickel-cobalt hydroxide (Dcm ³ ) were measured and determined by the following formula. Tap density (g / cm ³ ) = (B−A) / D

Regarding the pore distribution of nickel-cobalt hydroxide and the spatial volume of the pores, the pores in the range of 10 to 200 angstrom were measured by the BJH method using nitrogen adsorption. The pore size distribution of less than 10 Å is
The method using nitrogen gas adsorption is difficult to measure, and it is considered that there are actually spaces having pores of less than 10 angstroms. In addition, the pore occupancy of nickel-cobalt hydroxide is measured by the BJH method using nitrogen, and the space volume value of the pores (cm ³ / g) and the true density measured by the alcohol method using a pycnometer. (G / cm
^It was calculated from the value in ³ ) by the following formula. Pore occupancy (%) = pore volume value (cm ³ / g) ×
True density (g / cm ³ ) The amount of Co contained in nickel-cobalt hydroxide was analyzed by atomic absorption spectrometry. Table 1 shows the physical properties of the nickel-cobalt hydroxides A to F produced under the above conditions.

[0023]

[Table 1]

Next, a method of synthesizing Li _x Ni _y Co _z O ₂ will be described. The nickel-cobalt hydroxides A to F produced by the above method were mixed so that lithium hydroxide and (nickel + cobalt) had an atomic ratio of 1.05: 1.
Li after firing at 700 ° C. for 10 hours in an oxidizing atmosphere
_x Ni _y Co _z O ₂ (y + z = 1) was synthesized. Nickel-
The active materials obtained from cobalt hydroxides A to F are referred to as active materials A to F, respectively. As a comparative example, nickel-
Cobalt oxide was added to and mixed with cobalt hydroxide A such that the Co substitution amount (z value) was 0.2, and then lithium hydroxide and (nickel + cobalt) were in an atomic ratio of 1.05: 1.
And mixed under the same conditions to synthesize active material G
And Since the synthesized Li _x Ni _y Co _z O ₂ is obtained as an aggregated substance that is relatively easy to loosen, it was crushed using a mortar.

The method for manufacturing the positive electrode plate will be described below. First, the positive electrode active material Li _x Ni _y Co _z O ₂ (y + z =
100 parts by weight of the powder of 1) was mixed with 3 parts by weight of acetylene black and 5 parts by weight of a fluororesin binder, and the mixture was suspended in the solvent N-methyl-2-pyrrolidone of the binder to form a paste. I chose This paste is applied to both sides of an aluminum foil having a thickness of 0.020 mm and dried, and then a thickness of 0.130 mm, a width of 35 mm, and a length of 270 mm.
The positive electrode plate 5 of was produced. Then, the positive electrode plate and the negative electrode plate are spirally wound with a separator interposed therebetween to have a diameter of 13.8 mm,
It was stored in a battery case with a height of 50 mm. The electrolyte solution was dissolved in an equal volume mixed solvent of ethylene carbonate and diethyl carbonate at a ratio of 1 mol / L of lithium hexafluorophosphate, and was injected into the electrode plate group 4, and then the battery was sealed. The test battery was used. The batteries using the positive electrode active materials A to G were referred to as batteries A to G, respectively.

Tests were performed on these batteries under the following conditions. 4.2 at a current of 120 mA in an environment of 20 ° C
After charging to V, rest for 1 hour, then 120
It was discharged to 3 V with a current of mA. Charge and discharge 3 times with this method
Repeated three times, the discharge capacity at the third time was used as the initial capacity. In addition, the utilization rate (mAh / g) of the active material was calculated by dividing the initial capacity by the weight of the lithium composite nickel-cobalt oxide contained in the battery. Further, the capacity at the time of discharging at a current of 1200 mA after being charged to 4.2 V at a current of 120 mA is defined as the high rate discharge capacity, and the high rate discharge rate = 1
00 x (1200mA discharge capacity / 120mA discharge capacity)
The high rate discharge rate was calculated using the formula (%). Also, 20
After charging to 4.2V with 120mA current in the environment of ℃, rested for 1 hour, and then 3 hours with 120mA current.
The charging / discharging cycle of discharging to V was repeated, and the life was defined as the number of cycles until the discharge capacity decreased to half of the initial value. Table 2 shows the results of examining the 120 mA discharge capacity, the utilization rate of the active material, the high rate discharge rate and the life of each of the batteries A to G.

[0027]

[Table 2]

As is clear from Table 2, the battery A using the active material in which Co is not substituted and the battery B using the active material with a small amount of substitution change the crystalline phase as described above during charging and discharging. It is considered that the cycle characteristics are deteriorated due to the fact that such a crystal phase change is poorly reversible, and that sites for Li insertion / desorption are gradually lost during repeated charge / discharge reactions. To be On the other hand, battery C ~
Each of the lithium composite nickel-cobalt oxides of E showed a utilization rate of 170 mAh / g or more, and good results were obtained in both high rate discharge and cycle characteristics. This is because the change of the crystal phase was remarkably relaxed by substituting a part of Ni with Co. However, in the battery F in which the amount of Co added (w value) is 0.4, it can be seen that the life is deteriorated contrary to 250 cycles. This is the Co substitution amount (z value)
Of 0.4 or more, it becomes difficult to grow crystals of nickel-cobalt hydroxide, and polycrystalline Ni _v Co _w (O
H) ₂ is generated. For this reason, the lithium composite nickel-cobalt oxide obtained by the synthesis also became polycrystalline, and the grain boundaries grew due to repeated charge and discharge cycles, and the active material became fine powder and fell off from the electrode plate, leading to a decrease in capacity. It is considered to be a thing.

Further, when the Co addition amount (w value) is increased to 0.4 or more, nickel and cobalt are not uniformly dispersed even when such a coprecipitation method is used, and LiNi is partially dispersed.
It is considered to be a mixture of O ₂ and LiCoO ₂ , and it is considered that the crystal structure was destroyed by the above-mentioned crystal phase change in the portion where Co was not sufficiently replaced, and the discharge capacity was lowered. Moreover, even if the Co substitution amount is small,
When the coprecipitation method is not used like the active material G, cobalt is not uniformly dispersed, and the cycle characteristics are deteriorated for the same reason. From the above results, the nickel-cobalt hydroxide as the raw material of the lithium composite nickel-cobalt oxide is Ni _v Co _w (OH) ₂ (0.7 ≦ v ≦ 0.9,
When the nickel-cobalt hydroxide represented by v + w = 1), a non-aqueous electrolyte secondary battery having excellent discharge capacity and cycle characteristics can be obtained.

Example 2 The amount of metallic nickel is 60 g / L
Cobalt sulfate is added to a corresponding nickel sulfate aqueous solution so that the molar ratio of cobalt to nickel is 20%,
It melt | dissolved and the nickel sulfate-cobalt mixed aqueous solution was prepared. This nickel-cobalt mixed aqueous solution has a volume of 100 L.
Was introduced into the precipitation tank at a constant flow rate of 10 L / h, the temperature inside the tank was kept at 50 ° C., while sufficiently stirring, a 25 wt% sodium hydroxide solution was introduced to control the pH value of the reaction tank.
Nickel-cobalt hydroxides with various particle sizes were produced. This was washed with water and dried. All of the obtained nickel-cobalt hydroxides formed secondary particles in which primary particles were aggregated innumerable by SEM photograph observation, and the shape was spherical or elliptical spherical. Further, the average particle size of the obtained lithium composite nickel-cobalt oxide was almost the same as the particle size of the nickel-cobalt hydroxide as the raw material. Table 3 shows the physical properties of the produced nickel-cobalt hydroxide.
Shown in

[0031]

[Table 3]

A battery was prepared in the same manner as in Example 1 except that lithium composite nickel-cobalt oxides were synthesized using nickel-cobalt hydroxides H to L having different average particle diameters as raw materials. Batteries using nickel-cobalt hydroxides HL were designated as batteries HL, respectively. In Table 4, battery H ~
The results of examining the 120 mA discharge capacity of L, the utilization rate of the active material, the high rate discharge rate and the life are shown.

[0033]

[Table 4]

The particle size of the nickel-cobalt hydroxide has a correlation with the particle size of the lithium composite nickel-cobalt oxide, and also has a correlation with the tap density and the BET specific surface area. It is important because it has an impact. When the average particle diameter is small and the tap density is small like the active material H, the packing density of the lithium composite nickel-cobalt oxide into the electrode, that is, the capacity density is decreased, and the substantial battery capacity is decreased. Further, it can be seen that when the average particle diameter is larger than 10 μm, the fillability is sufficient, but the utilization rate of the active material and the high rate discharge rate are reduced.
This is because as the particle size of nickel-cobalt hydroxide increases, the specific surface area decreases, and lithium composite nickel-
It is considered that the reaction rate with lithium during the synthesis of cobalt oxide was low and the synthesis reaction did not proceed sufficiently. Furthermore, it is considered that since the synthesized lithium composite nickel-cobalt oxide also has a large particle diameter, the area of the reaction interface with the electrolytic solution is small and the high rate discharge characteristics are deteriorated.

As described above, it can be seen that the characteristics of the non-aqueous electrolyte secondary battery using the lithium composite nickel-cobalt oxide are significantly influenced by the physical properties of the nickel-cobalt hydroxide as the raw material. Therefore, Li _x Ni _y Co _z O ₂ (0.9%), which is a positive electrode active material for a non-aqueous electrolyte secondary battery,
0 ≦ x ≦ 1.05, 0.7 ≦ y ≦ 0.9, y + z = 1)
Ni _v Co _w (OH) ₂ (0.7 ≦) used as a raw material for the synthesis of the lithium composite nickel-cobalt oxide represented by
The nickel-cobalt hydroxide represented by v ≦ 0.9, v + w = 1) has an average particle diameter of 1.5 to 10 μm and a BET specific surface area measured by adsorption of nitrogen gas of 8 to 35 m.
² / g, the tap density is 1.4 to 2.3 g / cm ³ , the spatial volume of pores is 0.010 to 0.10 cm ³ / g, and the pore occupancy is in the range of 5 to 40%. desirable.

Comparative Example 1 A nickel-cobalt composite hydroxide having a lumpy particle shape was used as a raw material and Example 1 was used.
Similarly to lithium composite nickel-cobalt oxide M
Was synthesized. The chemical composition of the obtained nickel-cobalt composite oxide was LiNi _0.85 Co _0.15 O ₂ . The synthesized lithium composite nickel-cobalt oxide was obtained as massive particles having an average particle size of 4 μm. A battery was produced in the same manner as in Example 1 except that this lithium composite nickel-cobalt oxide M was used as the positive electrode active material. Table 5
The results of examining the initial discharge capacity, active material utilization rate, efficient discharge rate, and end-of-life cycle number of this battery are shown in FIG.

[0037]

[Table 5]

As is clear from Table 5, in the battery using the active material M in which the nickel-cobalt hydroxide as the raw material is in the form of lumps, the specific surface area is particularly small because of the lumpy particles, and the filling property in the electrode plate is good. Also becomes smaller. Further, since the polarization during charging / discharging is large, the utilization rate of the active material is also small. From the above results, it is desirable that the nickel-cobalt hydroxide, which is the raw material of the lithium composite nickel oxide, be spherical or elliptical spherical.

In the above embodiments, the method of using the nickel sulfate-cobalt mixed aqueous solution and the alkaline aqueous solution is shown as the method of producing the nickel-cobalt hydroxide, but the present invention is not limited to this. For example,
A complexing agent such as ammonium ion may be added in order to stabilize the metal ion, but the same effect can be obtained if the obtained nickel-cobalt hydroxide has similar physical properties. Further, in the above examples, the evaluation was performed using a cylindrical battery, but the same effect can be obtained even if the battery shape is different, such as a prismatic type or a coin type. Furthermore, although a carbonaceous material was used for the negative electrode in the above-mentioned examples, the effect of the present invention works on the positive electrode plate, and therefore oxidation of lithium metal, lithium alloys, Fe ₂ O ₃ , WO ₂ , WO _3, etc. The same effect can be obtained by using another negative electrode material such as a material. Although lithium hexafluorophosphate was used as the electrolyte in the above examples, other lithium-containing salts such as lithium perchlorate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, and hexafluoroarsenic acid were used. The same effect can be obtained with lithium or the like. Furthermore, although a mixed solvent of ethylene carbonate and diethyl carbonate was used in the above examples, other non-aqueous solvents such as cyclic esters such as propylene carbonate, cyclic ethers such as tetrahydrofuran, chain ethers such as dimethoxyethane, and propionic acid. The same effect can be obtained by using a non-aqueous solvent such as a chain ester such as methyl or a multi-component mixed solvent thereof.

[0040]

As is apparent from the above description, when the nickel-cobalt hydroxide having controlled physical properties such as particle shape and particle size according to the present invention is used, excellent cycle characteristics and high rate discharge characteristics can be obtained. It is possible to obtain a positive electrode active material lithium composite nickel-cobalt oxide that provides a water electrolyte secondary battery.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a cylindrical battery according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery case 2 Sealing plate 3 Insulating packing 4 Electrode plate group 5 Positive electrode plate 5a Positive electrode lead 6 Negative electrode plate 6a Negative electrode lead 7 Separator 8, 9 Insulation ring

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideyuki Kita, 45, Shirakata-cho, Fukui-shi, Fukui Prefecture 5-10 Sunamawari, Tanaka Chemical Research Institute (72) Inventor Takeshi Usui 45, Shirakata-cho, Fukui-shi, Fukui Prefecture Character sand beach 5-10 shares in Tanaka Chemical Research Institute (72) Inventor Yusumi Kameda 45 Shirakata-cho, Fukui City, Fukui Prefecture Character sand beach 5-10 shares in Tanaka Chemical Research Institute

Claims (6)

[Claims] 1. A non-aqueous electrolyte battery active material Li _x Ni _y Co _z
O ₂ (0.90 ≦ x ≦ 1.05, 0.7 ≦ y ≦ 0.9, y
+ Z = 1), which is a nickel-cobalt hydroxide used as a raw material for the synthesis of a lithium composite nickel-cobalt oxide, wherein Ni _v Co _w (OH) ₂ (0.7 ≦ v ≦
0.9, v + w = 1), and in the SEM photograph observation, primary particles are aggregated innumerably to form secondary particles,
A nickel-cobalt hydroxide for a non-aqueous electrolyte battery active material, wherein the secondary particles have an average particle diameter of 1.5 to 10 μm. 2. The nickel-cobalt hydroxide for a non-aqueous electrolyte battery active material according to claim 1, wherein the nickel-cobalt hydroxide has a spherical shape or an elliptic spherical shape. 3. The nickel-cobalt hydroxide has a BET specific surface area measured by adsorption of nitrogen gas of 8 to 35 m.
^The nickel-cobalt hydroxide for a non-aqueous electrolyte battery active material according to claim 1, which is ² / g. 4. The nickel-cobalt hydroxide for a non-aqueous electrolyte battery active material according to claim 1, wherein the nickel-cobalt hydroxide has a tap density of 1.4 to 2.3 g / cm ³ . 5. The nickel-cobalt hydroxide for a non-aqueous electrolyte battery active material according to claim 1, wherein the nickel-cobalt hydroxide has a pore volume of 0.010 to 0.10 cm ³ / g. . 6. The nickel-cobalt hydroxide for a non-aqueous electrolyte battery active material according to claim 1, wherein the nickel-cobalt hydroxide has a pore occupancy rate in the range of 5 to 40%.