JP3229544B2 - Nickel-cobalt hydroxide for non-aqueous electrolyte battery active material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a Li _x Ni _y Co _z O ₂ (0.90 ≦ x ≦) cathode active material for a non-aqueous electrolyte secondary battery.
The present invention relates to a nickel-cobalt hydroxide used as a raw material for synthesizing a lithium composite nickel-cobalt oxide represented by 1.05, 0.7 ≦ y ≦ 0.9, y + z = 1).

[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 batteries or sealed small lead-acid batteries play the role of power sources for driving these electronic devices. However, as portable and cordless devices have been developed and established, they will become power sources for driving. High energy density of secondary batteries,
The demand for smaller and lighter is increasing. In recent years, secondary batteries have been attracting attention as power sources for mobile phones. With the rapid market expansion, demands for longer talk time and improved cycle life have become extremely large.

Under such circumstances, a lithium composite transition metal oxide exhibiting a high charge / discharge voltage, for example, LiCoO
₂ (for example, JP-A-63-59507) or LiNiO ₂ (for example, US Pat.
02518) has been reported. Especially LiNiO
₂ is expected to have a higher energy density than LiCoO ₂ ,
Development is ongoing in various areas. However, LiNiO ₂
Has a large polarization at the time of charging, and reaches the oxidative decomposition voltage of the electrolytic solution before Li can not be sufficiently taken out, so that the expected large capacity could not be obtained.

In order to solve such a problem, a non-aqueous electrolyte secondary battery has been proposed which uses a material in which a part of nickel element is replaced with cobalt as a positive electrode active material and utilizes insertion / removal of lithium ions. I have. For example, JP-A-62-25
In US Pat. No. 6371, lithium composite nickel-cobalt oxide is synthesized by mixing lithium carbonate, cobalt carbonate, and nickel carbonate and firing at 900 ° C.
JP-A-63-299056 discloses a method of mixing lithium and cobalt and nickel hydroxides and oxides. Further, JP-A-1-294364
In this publication, an example was reported in which nickel ions and cobalt ions were coprecipitated as carbonates from an aqueous solution containing nickel ions and cobalt ions, and then mixed with lithium carbonate to synthesize a lithium composite nickel-cobalt oxide. Have been.

[0005]

[SUMMARY OF THE INVENTION However, heretofore, such as reported _{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 represented by
Although the discharge capacity gradually increases as the amount o (z value) increases, the problem of cycle deterioration in which the battery discharge capacity gradually decreases when charge / discharge cycles are repeated is evident. As a result of extensive studies by the present inventors, it has been found that such characteristic deterioration is caused by the following. That is, disassemble the cycle-degraded battery,
As a result of observing the electrode plate, it was found that a change in the crystal structure of the positive electrode active material occurred in the positive electrode plate after repeated charge / discharge cycles.

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. Amer.
R. Dahn, Solid State Ionic
s, 67 , 123 (1993)), and the crystal phase changes from hexagonal (Hexagonal) to monoclinic (Monoclini) as Li is desorbed.
c), second hexagonal (Hexagonal), third hexagonal (He
xagonal). It is considered that such a crystal phase change is poor in reversibility, and the sites where Li can be inserted and desorbed gradually are lost during repeated charge / discharge reactions. By substituting a part of Ni with Co, such a change in the crystal phase is remarkably reduced. This is because the bonding force of Co with oxygen is N
This is considered to be because the crystal structure was more stabilized because it was stronger than i, and a change in the crystal phase as in the case where Co substitution was not performed (z = 0) does not occur. For this reason, the amount of Co substitution (z value)
It is considered that the crystal phase becomes more stable and the discharge capacity and the cycle characteristics are improved as the value increases.

However, actually, Japanese Patent Application Laid-Open No. 62-25637
No. 1 and JP-A-63-299056, cobalt and nickel carbonates and hydroxides,
Lithium composite nickel-cobalt oxide synthesized by mixing each compound such as oxide,
When the o-substitution amount (z value) increases (z ≧ 0.1), it is apparent that nickel and cobalt are not actually uniformly dispersed but are partially a mixture of LiNiO ₂ and LiCoO _2. became. For this reason, 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 due to the above-described crystal phase change in a portion where Co is not sufficiently substituted, and as a result, the discharge capacity is reduced. It was not enough as a battery active material. Further, when nickel ions and cobalt ions are coprecipitated as carbonates as disclosed in JP-A-1-294364, good cycle characteristics are ensured because nickel and cobalt are uniformly dispersed. However, in this case, since it precipitates as a basic carbonate, indefinite amount of Ni
(OH) ₂ has a double salt NiCO ₃ · XNI (OH) ₂ containing, non-uniform synthesis process of lithium. For this reason, there is a large variation in battery characteristics, and there is a problem in practical use.

In addition, since the load on the battery increases with the recent added value of portable equipment, improvement of the high-rate discharge characteristics for discharging with a large current is a major problem. All of the batteries using were insufficient. An object of the present invention is to solve the above-described problems related to the conventional positive electrode, and to provide a nonaqueous electrolyte secondary battery having excellent charge / discharge characteristics, a nickel composite nickel-cobalt oxide raw material nickel. -To provide cobalt hydroxide.

[0009]

Means for Solving the Problems In order to solve such a problem, the present inventors have used hydroxide produced by co-precipitation as a source of nickel and cobalt which are raw materials of a positive electrode active material, After careful examination of its physical properties,
Arrangement of nickel and cobalt atoms in particles, particle shape, particle size, specific surface area, tap density, pore volume,
By controlling the occupation ratio of the pores, it was possible to prevent cycle deterioration and to obtain 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 in the synthesis as a positive active material _{Ni v Co w (OH) 2} (v + w = 1)
Using a nickel-cobalt hydroxide represented by the formula, the amount of Co substitution (w value) is controlled in the range of 0.1 to 0.3, and the obtained nickel-cobalt hydroxide is observed by SEM photograph observation. The primary particles of rice grains are innumerably aggregated to form secondary particles, and the secondary particles have an average particle diameter of 1.5.
It is controlled to be 10 to 10 μm. This nickel-cobalt hydroxide is a solution that continuously supplies a nickel salt aqueous solution, a cobalt salt aqueous solution, and a caustic alkali aqueous solution in a tank whose pH and temperature are adjusted while controlling the concentration and flow rate thereof, 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, the primary particles of rice grains are innumerably 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 spherical, high filling properties can be realized,
More desirable. In order to sufficiently satisfy the high-rate discharge characteristics, the nickel-cobalt hydroxide has a BET specific surface area of 8 to 35 m ² / g measured by nitrogen gas adsorption.
It is desirable that Further, the nickel-cobalt hydroxide desirably has a tap density of 1.4 to 2.3 g / cm ³ . Further, nickel-cobalt hydroxide has a pore 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 a hydroxide has been reported as a method for producing nickel hydroxide used for a positive electrode of a nickel-cadmium battery. For example, JP-A-63-16556 and JP-A-64-42330 disclose an aqueous nickel salt solution, an aqueous cobalt salt solution, and an aqueous caustic alkali solution in a tank whose pH and temperature are adjusted as a method for producing nickel hydroxide. Continuously while controlling its concentration and flow rate,
Methods for sampling have been reported. Further, JP-A-63-
JP-A-152866, JP-A-5-41212, and JP-A-7-73877 report a method in which various metal elements including Co are dissolved in nickel hydroxide by a coprecipitation method in a reaction vessel. I have. However, the addition of Co in these inventions is aimed at improving the characteristics of alkaline storage batteries such as aqueous nickel-cadmium batteries or nickel-hydrogen storage alloy batteries, and is performed for the following reasons.

Γ-N which causes a decrease in the discharge capacity of the battery
Suppress generation of iOOH. (Eg 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)

[0013] Improvement of 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 charging and discharging efficiency. (For example, I.Matsum
oto, M.Ikeyama, T.Iwaki, Y.Umeo and Y.Ogawa, Denkikaga
ku, 54, 159-164 (1986))

As described above, the role of Co in these inventions is all for the purpose of catalytic action, and is not necessarily added as an active material in the nickel hydroxide crystal matrix. For this reason, when the amount of Co added is too large, the utilization rate of the active material becomes conversely small. Therefore, the normally added amount is _{w in} Ni _v Cow (OH) ₂ (v + w = 1).
In most cases, ≤0.1. The present invention has the purpose of improving characteristics of the nonaqueous electrolyte battery, the active material _{Li x Ni y Co z O 2} (0.90 ≦ x ≦ 1.05,0.7
≦ y ≦ 0.9, y + z = 1 lithium nickel composite represented by) - Nickel is used as a raw material for the synthesis of cobalt oxide - cobalt hydroxide _{Ni v Co w (OH) 2} (0.7
.Ltoreq.v.ltoreq.0.9, v + w = 1). As a matter of course, Co is dissolved in the crystal matrix of the active material and acts as an active material, which is completely different from the above-described improvement in the characteristics of the alkaline storage battery.

The reaction for synthesizing LiNiO ₂ proceeds by applying heat treatment in such a manner that lithium atoms diffuse into crystals of the nickel salt, whereby LiNiO ₂ is synthesized. Nickel carbonate being reported conventionally, the nickel oxide or the like, crystals in the particles is a so-called polycrystalline state randomly arranged, LiNiO ₂ using this for them to feed
Is in the same polycrystalline state. When a secondary battery is formed by using LiNiO ₂ having such a polycrystalline structure and charging and discharging are performed, sites capable of accommodating Li are destroyed by repetition of transition of a crystal phase accompanying charging and discharging, and fine Such crystals are repeatedly expanded and contracted to make the particles finer and detached from the battery current collector. As a result, the discharge capacity of the battery decreases, causing cycle deterioration. Also, when cobalt oxide, cobalt carbonate, or cobalt hydroxide is added during synthesis as a Co addition method, solid solution at the atomic level as obtained by the coprecipitation method cannot be realized, and LiNiO ₂ or Li
Since it is present as CoO ₂ , cycle deterioration is caused for the same reason.

When the method for producing a nickel-cobalt hydroxide according to the present invention is used, by controlling the cobalt concentration, the bath temperature, the stirring speed, the pH, etc., fine crystals formed in the bath grow. 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 form a solid solution at the atomic level and crystals are very well aligned in the same direction. I do. In addition, since the crystal structure is hexagonal, which is the same as Li _x Ni _y Co _z O ₂ , the arrangement of atoms is maintained even when the mixture is mixed with a lithium salt for synthesis. If the Co substitution amount (w value) exceeds 0.3, crystal growth becomes difficult, and polycrystalline Ni _v Co _w
(OH) ₂ is produced. Therefore, the amount of Co substitution is 0.1.
It is desirable that 1 ≦ w ≦ 0.3.

As a result, Li _{x having} very few crystal grain boundaries is obtained.
Ni _y Co _z O ₂ can be synthesized. _{Ni v Co w (OH) 2} (0.7 ≦ v ≦ 0.9 having such a structure, v + w
= 1) was the synthesis of raw materials _{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 configured using 1) and charged and discharged,
The addition of Co improves the stability of the crystal, eliminates the transition of the crystal phase due to charge and discharge, and minimizes the grain refinement and dropout due to the very small number of crystal grain boundaries that cause the destruction of the particle structure. And good cycle characteristics can be realized. Further, by controlling the particle size, BET specific surface area, tap density, space volume of pores, and pore occupancy of the nickel-cobalt hydroxide particles according to the present invention, lithium ions are transferred when a battery is configured. The contact area with the electrolyte is increased, and high-efficiency discharge characteristics can be realized.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the drawings according to specific embodiments. << Example 1 >> FIG. 1 shows nickel-nickel in this example and a comparative example.
1 is a longitudinal sectional view of a cylindrical battery used for evaluating an active material for a non-aqueous secondary battery synthesized using cobalt hydroxide as a raw material. Battery case 1 processed from stainless steel sheet resistant to organic electrolyte
Inside, 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 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. Then, an aluminum positive electrode lead 5 a is pulled out from the positive electrode plate 5 and connected to the sealing plate 2, and a nickel negative electrode lead 6 a is pulled out from the negative electrode plate 6 and connected to the bottom of the battery case 1.

Hereinafter, the negative electrode plate 6, the electrolyte and the like will be described in detail. 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 binder, and this mixture was suspended in an aqueous solution of carboxymethyl cellulose to form a paste. Then, this paste is applied to the surface of a copper foil having a thickness of 0.015 mm,
After drying, rolling to 0.2 mm, width 37 mm, length 28
The negative electrode plate was cut out to a size of 0 mm. In the electrolyte, a mixed solvent of equal volume of ethylene carbonate and diethyl carbonate,
What was melt | dissolved at the ratio of lithium hexafluorophosphate 1 mol / liter (L) was used. After this electrolyte solution was injected into the electrode plate group 4, the battery was sealed and used as a test battery.

Next, a method for producing a lithium composite nickel-cobalt oxide using the nickel-cobalt hydroxide of the present invention will be described in detail. A 100 L tank was used as a precipitation tank for producing nickel-cobalt hydroxide. The amount of metallic nickel is 60 as a nickel salt aqueous solution.
g / L of an aqueous nickel sulfate solution having a molar ratio of cobalt to nickel of 0, 5, 10, 20, 3
Cobalt sulfate was added and dissolved at 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. A nickel-cobalt mixed aqueous solution is introduced into the above-mentioned precipitation tank at a constant flow rate of 10 L / h, and while sufficiently stirring, a sodium hydroxide solution is introduced to produce a nickel-cobalt hydroxide having an average particle size of 3 to 3. 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 a nickel-cobalt hydroxide.

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

The pore distribution and spatial volume of the pores of the nickel-cobalt hydroxide were measured for pores in the range of 10 to 200 angstroms using the BJH method using nitrogen adsorption. The pore distribution of less than 10 Å is
It is difficult to measure by the method using nitrogen gas adsorption, and it is considered that a space having pores smaller than 10 angstroms actually exists. In addition, the pore volume occupancy of the nickel-cobalt hydroxide was measured by the BJH method using nitrogen, the value of the space volume 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 of ³ ) by the following formula. Pore occupancy (%) = spatial volume value of pores (cm ³ / g) x
True density (g / cm ³ ) Further, the amount of Co contained in the nickel-cobalt hydroxide was analyzed by atomic absorption analysis. Table 1 shows the physical properties of the nickel-cobalt hydroxides A to F prepared under the above conditions.

[0023]

[Table 1]

Next, a method for synthesizing Li _x Ni _y Co _z O ₂ will be described. The nickel-cobalt hydroxides A to F produced by the above method are mixed such that lithium hydroxide and (nickel + cobalt) have an atomic ratio of 1.05 to 1,
Baking at 700 ° C. for 10 hours in an oxidizing atmosphere, Li
_{x Ni y Co z O 2 (} y + z = 1) was synthesized. Nickel-
Active materials obtained from cobalt hydroxides A to F are referred to as active materials A to F, respectively. As a comparative example, nickel-
After adding and mixing cobalt oxide to the cobalt hydroxide A so that the amount of Co substitution (z value) becomes 0.2, lithium hydroxide and (nickel + cobalt) have an atomic ratio of 1.05 to 1.
And then synthesized under the same conditions to obtain the active material G.
And Synthesized Li _x Ni _y Co _z O ₂ is is obtained as a relatively loose easily aggregate mass was pulverized using a mortar.

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

The batteries were tested under the following conditions. 4.2 mA at 120 mA in a 20 ° C. environment
After charging to V, pause for 1 hour and then
The battery was discharged to 3 V at a current of mA. Charge and discharge by this method
Repeated times, the third discharge capacity 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, after the battery was charged to 4.2 V with a current of 120 mA, the capacity when discharged at a current of 1200 mA was defined as a high-rate discharge capacity, and a high-rate discharge rate = 1.
00 × (1200 mA discharge capacity / 120 mA discharge capacity)
The high rate discharge rate was calculated using the formula of (%). Also, 20
Charged to 4.2 V at a current of 120 mA in an environment of 120 ° C., paused for 1 hour, and then charged at a current of 120 mA for 3 hours.
The charge / discharge cycle of discharging to V was repeated, and the life was defined as the number of cycles until the discharge capacity was reduced to half of the initial value. Table 2 shows the results of examining the 120 mA discharge capacity, active material utilization rate, high rate discharge rate, and life of batteries A to G.

[0027]

[Table 2]

As is clear from Table 2, the battery A using the active material without substitution of Co and the battery B using the active material with a small substitution amount have the above-mentioned crystal phase change during charge and discharge. It was considered that such a crystal phase change was poor in reversibility, and the cycle characteristics were degraded due to the gradual loss of sites where Li can be inserted and desorbed during repeated charge and discharge reactions. Can be On the other hand, batteries C ~
Each of the lithium composite nickel-cobalt oxides of E exhibited an availability 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 mitigated by partially replacing Ni with Co. However, it can be seen that the life of the battery F in which the Co addition amount (w value) is 0.4 is deteriorated, which is 250 cycles. This is the amount of Co substitution (z value)
When There increased to 0.4 or more, a nickel - crystal growth of the cobalt hydroxide becomes difficult, polycrystalline Ni _v Co _w (O
H) ₂ is generated. For this reason, the lithium composite nickel-cobalt oxide obtained by the synthesis also becomes polycrystalline, and the crystal grain boundaries grow by repeated charge / discharge cycles, and the active material is pulverized and drops from the electrode plate, resulting in a decrease in capacity. It is considered something.

When the amount of Co added (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 that the mixture was a mixture of O ₂ and LiCoO ₂ , and it is considered that the crystal structure was destroyed by the above-described crystal phase change in the portion where Co was not sufficiently substituted, and the discharge capacity was reduced. Also, even if the amount of Co substitution is small,
When the coprecipitation method is not used as in the case of the active material G, cobalt is not uniformly dispersed, and the cycle characteristics are deteriorated for the same reason. Above results, the lithium nickel composite - nickel as a raw material for cobalt oxide - cobalt _{hydroxide, Ni v Co w (OH)} 2 (0.7 ≦ v ≦ 0.9,
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 was 60 g / L
Cobalt sulfate was added to a considerable aqueous solution of nickel sulfate so that the molar ratio of cobalt to nickel was 20%.
The mixture was dissolved to prepare a nickel sulfate-cobalt mixed aqueous solution. This nickel-cobalt mixed aqueous solution has a volume of 100 L.
Into the precipitation tank at a constant flow rate of 10 L / h, and while maintaining the inside temperature of the tank at 50 ° C. and stirring sufficiently, a 25% by weight 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 the obtained nickel-cobalt hydroxides formed secondary particles in which primary particles were innumerably aggregated in 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 HL having different average particle sizes as raw materials. Batteries using nickel-cobalt hydroxides HL were designated as batteries HL, respectively. Table 4 shows that the batteries H to
5 shows the results of examining the L 120 mA discharge capacity, active material utilization rate, high rate discharge rate, and life.

[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. Important to influence. When the average particle size 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 reduced, and the actual battery capacity is reduced. Further, when the average particle size is larger than 10 μm, although the filling property is sufficient, the utilization rate of the active material and the high rate discharge rate are decreased.
This is because when the particle size of the nickel-cobalt hydroxide increases, the specific surface area decreases, and the lithium composite nickel
It is considered that the rate of reaction with lithium during the synthesis of the cobalt oxide was reduced, and the synthesis reaction did not proceed sufficiently. Furthermore, since the synthesized lithium composite nickel-cobalt oxide has a large particle size, it is considered that the area of the reaction interface with the electrolytic solution is small and the high-rate discharge characteristics are reduced.

Thus, it can be seen that the characteristics of the non-aqueous electrolyte secondary battery using the lithium composite nickel-cobalt oxide are significantly affected by the physical properties of the nickel-cobalt hydroxide as a raw material. Accordingly, Li _x Ni _y Co _z O ₂ (0.9%) which is a positive electrode active material for a non-aqueous electrolyte secondary battery is used.
0 ≦ x ≦ 1.05, 0.7 ≦ y ≦ 0.9, y + z = 1)
Ni _v Co _w (OH) ₂ is used as a raw material for the synthesis of in the lithium composite nickel-cobalt oxide represented by (0.7 ≦
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 of 8 to 35 m measured by nitrogen gas adsorption.
² / g, tap density is 1.4 to 2.3 g / cm ³ , pore space volume is 0.010 to 0.10 cm ³ / g, and pore occupancy is 5 to 40%. desirable.

Comparative Example 1 A nickel-cobalt composite hydroxide having a massive particle shape was used as a raw material in Example 1.
The 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 fabricated in the same manner as in Example 1, except that the lithium composite nickel-cobalt oxide M was used as a 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 below.

[0037]

[Table 5]

As is evident from Table 5, in the battery using the active material M in which the raw material nickel-cobalt hydroxide is a lump, the specific surface area is particularly small because the lump is a lump, and the filling property to the electrode plate is small. Is also smaller. Further, since the polarization at the time of charge and discharge is large, the utilization rate of the active material is low. From the above results, it is desirable that the nickel-cobalt hydroxide used as the raw material of the lithium composite nickel oxide be spherical or elliptical spherical.

In the above embodiment, as a method for producing a nickel-cobalt hydroxide, a method using a mixed aqueous solution of nickel sulfate-cobalt or an aqueous alkaline solution was described, but the present invention is not limited to this. For example,
A complexing agent such as ammonium ion or the like may be added 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 embodiment, the evaluation was performed using a cylindrical battery, but the same effect can be obtained even when the battery shape is different, such as a prismatic type or a coin type. Furthermore, in the above embodiment, a carbonaceous material was used for the negative electrode. However, since the effect of the present invention acts on the positive electrode plate, oxidation of lithium metal, lithium alloy, 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. Further, in the above embodiment, lithium hexafluorophosphate was used as the electrolyte, but other lithium-containing salts such as lithium perchlorate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, and hexafluoroarsenate were used. Similar effects can be obtained with lithium and the like. Furthermore, in the above examples, a mixed solvent of ethylene carbonate and diethyl carbonate was used, but other non-aqueous solvents, for example, cyclic esters such as propylene carbonate, cyclic ethers such as tetrahydrofuran, chain ethers such as dimethoxyethane, and propionic acid Similar effects can be obtained by using a non-aqueous solvent such as a chain ester such as methyl, or a mixed solvent of these non-aqueous solvents.

[0040]

As is evident from the above description, the use of the nickel-cobalt hydroxide of the present invention having controlled physical properties such as particle shape and particle size makes it possible to obtain a non-volatile metal having excellent cycle characteristics and high rate discharge characteristics. A positive electrode active material lithium composite nickel-cobalt oxide that provides a water electrolyte secondary battery can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal 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

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideyuki Kita 45 characters, Shirakata-cho, Fukui City, Fukui Prefecture 5-10 Sunahamari Research Institute, Inc. (72) Inventor Takeshi Takeshi 45 characters, Shirakata-cho, Fukui City, Fukui Prefecture 5-10 Sandy Beach Discount, Tanaka Chemical Laboratory Co., Ltd. (72) Inventor Yuzumi Kameda 45-10, Shirahama-cho, Shirakata-cho, Fukui City, Fukui Prefecture (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01M 4/58 C01G 53/00

Claims (5)

(57) [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) by the lithium nickel composite represented - nickel is used as a raw material for the synthesis of cobalt oxide - a cobalt _{hydroxide, Ni v Co w (OH)} 2 (0.7 ≦
v ≦ 0.9, v + w = 1), and in the SEM photograph observation, the primary particles are innumerably aggregated to form secondary particles, and the average particle size of the secondary particles is 1.5 to 10 μm. Ah
BET specific surface area measured by nitrogen gas adsorption
A nickel-cobalt hydroxide for a non-aqueous electrolyte battery active material, which has a mass of 8 to 35 m ² / g . 2. The nickel-cobalt hydroxide for a non-aqueous electrolyte battery active material according to claim 1, wherein the nickel-cobalt hydroxide is spherical or elliptical spherical. 3. 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 . 4. 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. . 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 occupancy in the range of 5 to 40% .