JPH11224668A - Nickel-cobalt hydroxide for active material of nonaqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide nickel-cobalt hydroxide which is a raw material for synthesizing a positive electrode active material enabling to provide a nonaqueous electrolyte secondary battery having an excellent cycle characteristic and excellent thermo-stability. SOLUTION: The nickel-cobalt hydroxide for an active material of a nonaqueous electrolyte battery represented by a chemical formula Niv Cow (OH)2 (0.7<=v<=0.9, v+w=1) forms secondary particles where innumerable primary particles coheres in SEM photo-observation. Here, the manufacturing method of the secondary particles is controlled such that the average diameter of the secondary particles is 10-18 μm, and the weight ratio of the secondary particles having diameter less than 1 μm is less than 7%, further BET specific surface measured by nitrogen gas absorption is 5-25 m<2> /g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to Li _x Ni _y Co _z O ₂ (0.90 ≦ x ≦) as a positive electrode active material of a non-aqueous electrolyte 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 devices and cordless devices have progressed and they have become established, they will become drive power sources. High energy density of secondary batteries,
The demand for smaller and lighter is increasing. In recent years, it has been drawing attention as a power source 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). In particular, LiN
iO ₂ compared to LiCoO _2, a high energy density is expected, but the development in various fields is proceeding, 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, there has been proposed a non-aqueous electrolyte secondary battery using a positive electrode active material in which a part of Ni element is replaced by Co and utilizing insertion and extraction of lithium ions. I have.

[0005] For example, in Japanese Patent Application Laid-Open No. 62-256371, lithium composite nickel-cobalt oxide is synthesized by mixing lithium carbonate, cobalt carbonate, and nickel carbonate and firing at 900 ° C.

[0006] JP-A-63-299056 reports a method of mixing hydroxides and oxides of lithium, cobalt and nickel.

Further, Japanese Patent Application Laid-Open No. 1-294364 discloses that nickel ions and cobalt ions are coprecipitated as carbonates from an aqueous solution containing nickel ions and cobalt ions and then mixed with lithium carbonate to form a lithium composite nickel-cobalt. An example of synthesizing an oxide has been reported.

[0008]

However, Li _x Ni _y C synthesized as reported so far.
_{o z O 2 (0.90 ≦ x} ≦ 1.05,0.7 ≦ y ≦ 0.
In the lithium composite nickel-cobalt oxide represented by (9, y + z = 1), the discharge capacity gradually increases as the amount of substituted Co (z value) increases, but the charge / discharge cycle is repeatedly performed. It became clear that there was a problem of cycle deterioration in which the charge / discharge capacity gradually decreased.

As a result of extensive studies by the present inventors, it has been found that such characteristic deterioration is caused by the following.

[0010] As a result of disassembling the cycle-degraded battery and observing the electrode plate, it was found that the crystal structure of the positive electrode active material had changed in the positive electrode subjected to repeated charge / discharge cycles. It has been reported that the lattice constant of LiNiO ₂ changes as the battery is charged and discharged (W.L.
i. N. Reimers and J.M. R. Dah
n, Solid State Ionics, 67, 1
23 (1993)), the crystal phase changes from hexagonal (Hexagonal) to monoclinic (Monocl) as Li is desorbed.
inic) and a second hexagonal crystal (Hexagona)
1) It is reported that the compound changes to a third hexagonal crystal (Hexagonal). Such a crystal phase change is poor in reversibility, and it is considered that the cause is that sites where Li can be inserted and desorbed gradually are lost during repeated charge / discharge reactions.

By replacing a part of Ni with Co, such a change in the crystal phase is remarkably reduced. This is considered to be because the crystal structure was further stabilized because the bonding force of Co with oxygen was stronger than that of Ni.
= 0), no change in crystal phase occurs. Therefore, it was considered that as the Co substitution amount (z value) increases, the crystal phase becomes more stable, and both the discharge capacity and the cycle characteristics are improved.

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) becomes large (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.

[0013] For this reason, although the discharge capacity of such an active material is large to some extent, when charge and discharge are repeated, the crystal structure is destroyed by the above-mentioned crystal phase change in the portion where Co is not sufficiently substituted, and the discharge capacity is reduced. It was not enough as a battery active material.

The portion where Co is not sufficiently substituted has an unstable crystal structure when the battery is fully charged, has low thermal stability when the battery in a fully charged state is heated or crushed, and has poor ignition, There was a fume. When the battery is crushed, the electrode plate physically collapses, causing a partial short circuit, causing a large current to flow and generating Joule heat. At this time, if the crystal structure of the battery active material is unstable, oxygen is easily released from the crystal, which may cause ignition.

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. In this case, since it precipitates as a basic carbonate, an indefinite amount of Ni
NiOH ₃ xNi (O) which is a double salt containing (OH) ₂
H) ₂ and the synthesis process with lithium is not uniform. For this reason, there are large variations in battery characteristics, and there is a problem in practical use.

The present invention has been made in view of the above-mentioned problems, and has been developed in view of the above problems. It is intended to provide cobalt hydroxide.

[0017]

SUMMARY OF THE INVENTION The nickel-cobalt hydroxide for a non-aqueous electrolyte battery active material according to the present invention comprises, as a source of nickel and cobalt as raw materials of a positive electrode active material, a hydroxide produced by coprecipitation. In addition to using it, the physical properties are studied diligently, and the arrangement of nickel and cobalt atoms in the particles, particle shape, particle size, specific surface area, tap density,
By controlling the spatial volume of the pores and the occupancy of the pores,
This has led to the development of a battery having good thermal stability while preventing cycle deterioration.

[0018] _{Specifically, Li x Ni y Co z O} 2 (y
+ Z = 1) when nickel is synthesized as a positive electrode active material.
As a cobalt _{source, Ni v Co w (OH)} 2 (v + w =
1), and its Co substitution amount (w value) is 0.1 to 0.1.
A nickel-cobalt hydroxide controlled in the range of 3 is used. The nickel-cobalt hydroxide is
In SEM photograph observation, secondary particles in which countless rice granular primary particles are aggregated are formed, and the average particle size of the secondary particles is 10 to 18 μm, and the particles having a secondary particle size of 1 μm or less are weight. The ratio was controlled to be 7% or less. In addition, BET measured by nitrogen gas adsorption
By setting the specific surface area to 5 to 25 m ² / g, sufficient thermal stability can be secured.

It is desirable that the particle shape of the nickel-cobalt hydroxide be spherical or elliptical, since high filling properties can be realized. Also, nickel-cobalt hydroxide,
Tap density is 1.6 to 2.6 g / cm ³ , pore volume is 0.008 to 0.10 cm ³ / g, and pore occupancy is 3
Desirably, it is about 40%.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The non-aqueous electrolyte battery active material Li
_{x Ni y Co z O 2 (} y + z = 1) according to the present invention as a raw material for synthesizing a nickel - cobalt hydroxide Ni _v
An embodiment of Co _w (OH) ₂ (v + w = 1) will be described.

[0021] In the present embodiment, the chemical formula Ni _v Co _w
Nickel-cobalt hydroxide represented by (OH) ₂ (0.7 ≦ v ≦ 0.9, v + w = 1) is mixed with nickel salt aqueous solution and cobalt salt aqueous solution in a tank whose pH and temperature are adjusted. The physical properties are controlled by continuously supplying and sampling the alkaline aqueous solution while controlling its concentration and flow rate.

The method of coprecipitating nickel and cobalt as a hydroxide as described above 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,
In JP-A-64-42330, as a method for producing nickel hydroxide, a nickel salt aqueous solution, a cobalt salt aqueous solution, and a caustic alkali aqueous solution are continuously introduced into a tank whose pH and temperature are adjusted while controlling the concentration and flow rate thereof. It has been reported how to supply and collect the water. Further, JP-A-63-15286
6, JP-A-5-41212, JP-A-7-7
Japanese Patent No. 3877 reports a method in which various metal elements including Co are dissolved in nickel hydroxide by a coprecipitation method in a reaction vessel.

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 carried out for the following reasons. .

(1) γ causing a decrease in the discharge capacity of the battery
-Suppress formation of NiOOH. (For example, M. Osh
itani, K .; Takashima, and Y. Matsumura, Proce
edingsof the Symp. on Nickel Hydroxide Electr
odes, Volume90-4, The Electrochemical Soc.,
197 (1989), Japanese Patent Application Laid-Open No. 5-41212) (2) Utilization rate and high rate charge / discharge efficiency are improved by promoting the ionization rate of hydrogen on the surface of nickel hydroxide and promoting proton conduction in nickel hydroxide. (For example, I. Matsu
moto, M. Ikeyama, T .; Iwaki, Y .; Umeo, and
Y. Ogawa, Denkikagaku, 54, 159-164 (1986) etc.) As described above, the role of Co in these inventions is to serve as a catalytic action, and is added as an active material in a nickel hydroxide crystal matrix. Not necessarily. For this reason, if the amount of Co is increased too much, the specific volume of the active material is reduced, and consequently the amount normally added is N
In _{i v Co w (OH) 2} (v + w = 1), w ≦
In most cases, it is 0.1.

An object of the present invention is to improve the characteristics of a non-aqueous electrolyte battery, and an 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 - cobalt hydroxide _{Ni v Co w (OH) 2} (0.7 ≦ v ≦ 0.
9, v + w = 1) and the production method thereof is controlled.

As a matter of course, Co is dissolved in the crystal matrix of the active material and acts as the active material, which is completely different from the characteristic improvement of the conventional alkaline storage battery.

The active material L of the non-aqueous electrolyte battery according to the present invention
The reaction for synthesizing iNiO ₂ proceeds by applying heat treatment so that lithium atoms diffuse into crystals of the nickel salt, whereby LiNiO ₂ is synthesized. Conventionally reported nickel carbonate, nickel oxide and the like are in a so-called polycrystalline state in which the crystals in the particles are randomly arranged, and therefore LiNiO ₂ using these as a raw material is in the same polycrystalline state.

LiNiO ₂ having such a polycrystalline structure
When a secondary battery is configured using and charged and discharged, sites capable of accommodating Li are destroyed due to repetition of transition of the crystal phase accompanying charge and discharge, and fine crystals repeat expansion and contraction, and particles Are miniaturized and detached from the battery current collector. As a result, the discharge capacity of the battery decreases, causing cycle deterioration.

When cobalt oxide, cobalt carbonate, or cobalt hydroxide is added during 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 And LiCoO ₂ , causing cycle deterioration for the same reason.

On the other hand, when the method for producing a nickel-cobalt hydroxide according to the present invention is used, by controlling the cobalt concentration, the tank temperature, the stirring speed, the PH, etc., the fine crystals formed in the tank are controlled. Grows to form nickel-cobalt hydroxide particles, so that the amount of Co substitution (w
Value) as large as 0.1 or more, nickel and cobalt form a solid solution at the atomic level, and crystals are very well arranged in the same direction. Moreover, the crystal structure is Li _x Ni _y Co
It is the same hexagonal and _z O _2, even if the synthesis is mixed with a lithium salt, arrangement of atoms is maintained.

If the Co substitution amount (w value) exceeds 0.3, crystal growth becomes difficult and polycrystalline Ni _v Co
_w (OH) ₂ grows. Therefore, it is desirable that the substitution amount of Co is 0.1 ≦ w ≦ 0.3.

As a result, Li _{x having} very few crystal grain boundaries was obtained.
Ni _y Co _z O ₂ becomes possible. _{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 = 1), when charging and discharging are performed, the stability of the crystal is improved by adding Co, the transition of the crystal phase accompanying the charging and discharging is eliminated, and the particle structure is destroyed. Very few grain boundaries that cause
Fine particles and falling off can be prevented, and good cycle characteristics can be realized.

Further, by adding Co, the stability of the crystal in the charged state is improved, and the fully charged battery is heated.
Alternatively, the thermal stability when crushed can be improved.

Further, by controlling the particle size, BET specific surface area, tap density, pore volume, and pore occupancy of the nickel-cobalt hydroxide particles, the lithium composite nickel-cobalt oxide after synthesis is controlled. Since the physical properties can be controlled to reduce the heat reaction area when a fully charged battery is heated or crushed, good thermal stability can be ensured when the battery is configured.

[0035]

EXAMPLES Examples of nickel-cobalt hydroxide, which is a raw material for synthesizing a non-aqueous electrolyte battery active material of the present invention, will be described below.

Example 1 FIG. 1 is a longitudinal sectional view of a cylindrical battery using an active material for a non-aqueous electrolyte secondary battery synthesized from nickel-cobalt hydroxide in this example and a comparative example. Show. In FIG. 1, reference numeral 1 denotes a battery case formed by processing a stainless steel sheet having resistance to organic electrolyte, 2 denotes a sealing plate provided with a safety valve, and 3 denotes an insulating packing. Reference numeral 4 denotes an electrode plate group, in which the positive electrode plate 5 and the negative electrode plate 6 are spirally wound a plurality of times via a separator 7 and housed in the battery case 1. A positive electrode aluminum lead 5 a is pulled out from the positive electrode plate 5 and connected to the sealing plate 2, and a negative electrode nickel lead 6
a is pulled out and connected to the bottom of the battery case 1. Reference numeral 8 denotes an insulating ring provided on the upper and lower portions of the electrode plate group 4, respectively.

Next, the negative electrode plate 6, the electrolyte and the like will be described in detail. 100 parts by weight of graphite powder to fluororesin binder 1
0 parts by weight were mixed and 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, dried, and dried.
It was rolled to 2 mm and cut into a size of 37 mm in width and 280 mm in length to obtain a negative electrode plate 6.

In the electrolyte, 1 mol / mol of lithium hexafluorophosphate was mixed in an equal volume mixed solvent of ethylene carbonate and diethyl carbonate.
What was dissolved at a ratio of 1 was used. After injecting this electrolytic solution into the electrode plate group 4, the battery was sealed and a test battery was obtained.

Next, a method for producing a lithium composite nickel-cobalt oxide using nickel-cobalt hydroxide will be described in detail. A tank is used as a precipitation tank for producing cobalt hydroxide, and a nickel salt solution is dissolved in a nickel sulfate solution in which nickel metal is dissolved so that the molar ratio of cobalt is 0, 5, 10, 20, 30, 40%. A mixed solution of nickel sulfate and cobalt in which a metal was added and dissolved, and a 25% by weight sodium hydroxide solution were used as a caustic alkali aqueous solution. Nickel in this tank
A cobalt mixed salt solution is introduced at a constant flow rate, and while sufficiently stirring, a sodium hydroxide solution is introduced, and the pH of the reaction vessel is adjusted so that the average particle size of the generated nickel-cobalt hydroxide is in the range of 12 to 14 μm. The value, salt concentration, and flow rate were controlled. The obtained nickel-cobalt hydroxide was washed with water and dried at 80 ° C. to obtain a nickel-cobalt hydroxide.

The average particle size and weight were measured by a laser diffraction type particle size distribution analyzer, and the value corresponding to a cumulative 50% was defined as the average particle size. The specific surface area is the BE using nitrogen.
It was measured by the T method. A 20 cm ³ graduated cylinder (weight Ag) is filled with nickel-cobalt hydroxide, and the tap density is 200 times.
g), volume of nickel-cobalt hydroxide (Dcm ³ )
Was measured and determined by the following equation.

Tap density (g / cm ³ ) = (BA) / D The pore distribution and the spatial volume of the pores of the nickel-cobalt hydroxide are 10 to 20 using the BJH method using nitrogen adsorption.
The pores in the range of 0 ° were measured. The pore distribution of 10 ° or less is difficult to measure by the method using nitrogen gas adsorption.
It is considered that a space having pores of 10 ° or less actually exists.

The pore occupancy of the nickel-cobalt hydroxide is measured by the value of the spatial volume of the pores (cm ³ / g) measured by the BJH method using nitrogen and the alcohol method using a pycnometer. True density (g / cm ³ )
Was calculated by the following equation.

Pore occupancy (%) = Space volume value of pore (c)
m ³ / g) × true density (g / cm ³ ) Further, the amount of Co contained in the nickel-cobalt hydroxides of Samples A to F was analyzed by atomic absorption analysis.

Table 1 shows the physical properties of the nickel-cobalt hydroxide prepared under the above conditions.

[0045]

[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 prepared by the above method are mixed such that lithium hydroxide and (nickel + cobalt) have an atomic ratio of 1.05 to 1, and are mixed at 750 ° C. in an oxidizing atmosphere. For 10 hours, Li _x
Active materials A to F of Ni _y Co _z O ₂ (y + z = 1) were synthesized.

As a comparative example, cobalt oxide was added to nickel-cobalt hydroxide A so that the amount of Co substitution (z value) was 0.2, mixed, and then lithium hydroxide and (nickel + cobalt) were added. Were mixed such that the atomic ratio became 1.05 to 1, and synthesis was performed under the same conditions to obtain an active material G.

The synthesized Li _x Ni _y Co _z O ₂ was obtained as an agglomerate that was relatively easy to loosen, and was ground using a mortar.

Next, a method for manufacturing the positive electrode plate will be described. First, the positive electrode plate is made of Li _x Ni _y Co _z O ₂ (y
+ Z = 1), 100 parts by weight of the powder, 3 parts by weight of acetylene black and 5 parts by weight of a fluororesin binder were mixed, and N-
Suspend in methylpyrrolidone solution to make a paste.
This paste was applied on both sides of an aluminum foil having a thickness of 0.020 mm, and after drying, a positive electrode plate 5 having a thickness of 0.130 mm, a width of 35 mm and a length of 270 mm was prepared.

Then, the positive electrode plate and the negative electrode plate are spirally wound via a separator, and have a diameter of 13.8 mm and a height of 50 mm.
In the battery case. As an electrolyte, a solution prepared by dissolving lithium hexafluorophosphate at a ratio of 1 mol / l in a mixed solvent of equal volumes of ethylene carbonate and ethyl methyl carbonate was injected into the electrode group 4, and then the battery was sealed. And used as a test battery.

The test batteries in Example 1 were referred to as batteries A to G, respectively, and tests were performed using these batteries under the following conditions.

Under an environment of 20 ° C., 4.2 V at 120 mA
After charging for 1 hour, pause for 1 hour.
Discharge to 3 V at 0 mA. Charge / discharge was repeated three times by this method, and the third discharge capacity was used as the initial capacity.

After charging to 4.2 V at 120 mA in an environment of 20 ° C., the battery was paused for 1 hour, and then similarly charged and discharged to discharge to 3 V at 120 mA.
The cycle in which the discharge was reduced to half of the initial period was defined as the end-of-life cycle.

Each of the batteries was charged at 120 mA to 4.2 V in an environment of 20 ° C., and a crush test was performed. In the crush test, a metal cylindrical rod having a diameter of 4 mm was pressed against the center of the battery so as to be parallel to a direction perpendicular to the direction in which the outer dimension of the battery was longest, and the thickness of the battery was measured. Crushed until it was halved. At this time, the average value of the maximum temperature of the battery and the presence or absence of smoke were measured.

Table 2 shows the results of examining the 120 mA discharge capacity, active material utilization (specific capacity of active material), end-of-life cycle, maximum temperature at the time of crushing, and the presence or absence of smoke of batteries A to G.

[0057]

[Table 2]

As is clear from Table 2, the battery A in which Co is not replaced and the battery B having a small replacement amount have a low end-of-life cycle. This is because the above-described crystal phase change is observed during charge and discharge, and such a crystal phase change is poor in reversibility, and sites where Li can be inserted and desorbed gradually during repeated charge and discharge reactions gradually disappear. It is considered that the cycle characteristics were degraded due to the deterioration.

The maximum temperature of the battery during the crush test is high, and the number of smoked batteries is large. It is considered that this is because Co is not substituted or the substitution amount is small, so that the crystal structure in the charged state becomes unstable and the thermal stability becomes low.

On the other hand, the specific capacities (active material utilization rates) of the lithium composite nickel-cobalt oxides in the batteries C to E were all 170 mAh / g or more, and both the cycle characteristics and the thermal stability were good. was gotten. This is because the change of the crystal phase was remarkably reduced by partially replacing Ni with Co.

However, it can be seen that the end-of-life cycle of the battery F in which the addition amount (w value) of Co is 0.4 is deteriorated, which is opposite to 276 cycles. This is because the amount of Co substitution (z
Value) is 0.4 or more, the crystal growth of nickel-cobalt hydroxide becomes difficult, and polycrystalline Ni _v Co
_w (OH) 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 conceivable that.

When the Co addition amount (w value) is increased to 0.4 or more, even if such a coprecipitation method is used, nickel and cobalt are not uniformly dispersed, and LiN
It is considered that it was a mixture of iO 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 substituted, and the discharge capacity was reduced.

At the time of the crush test, there was a smoked battery. This is probably because the crystal structure in the charged state of the portion where Co has not been sufficiently substituted is unstable, so that the thermal stability is lowered. Further, even when the Co substitution amount is small, when the coprecipitation method is not used unlike the active material G, cobalt is not uniformly dispersed, and the cycle characteristics and the thermal stability are deteriorated for the same reason.

From the above results, the lithium composite nickel-
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 supplied.

(Embodiment 2) Next, Embodiment 2 will be described. Using a tank as a precipitation tank to produce cobalt hydroxide, into a nickel sulfate solution with nickel metal dissolved,
A mixed solution of nickel sulfate and cobalt in which cobalt metal was added and dissolved so that cobalt became 20% in molar ratio, and a 25% by weight sodium hydroxide solution as a caustic aqueous solution were used. A nickel-cobalt mixed salt solution was introduced into the tank at a constant flow rate, and the temperature in the tank was reduced to 50 ° C.
The sodium hydroxide solution was introduced with sufficient stirring, and the pH value, salt concentration, and flow rate of the reaction tank were controlled to produce nickel-cobalt hydroxides HL having various particle sizes, and washed with water. And dried.

The obtained nickel-cobalt hydroxide H〜
All of L formed secondary particles in which primary particles were innumerably aggregated in SEM photograph observation, and their shapes were spherical or elliptical spherical. In addition, the average particle size of the obtained lithium composite nickel-cobalt oxide is determined by the raw material nickel-cobalt oxide.
It almost coincided with the particle size of cobalt hydroxide.

The prepared nickel-cobalt hydroxide H〜
Table 3 shows the physical properties of L.

[0068]

[Table 3]

Next, nickel-cobalt hydroxides H to L
Except that a lithium composite nickel-cobalt oxide was synthesized using as a raw material, batteries were prepared in the same manner as in Example 1, and batteries HL were obtained.

Table 4 shows the discharge capacity of the batteries H to L at 120 mA, the specific capacity of the active material (active material utilization rate), the end-of-life cycle, the maximum temperature at the time of crushing, and the presence or absence of smoke.
Table 4 shows the results.

[0071]

[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 diameter is small and the tap density is small as in the case of 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 substantial battery capacity is reduced.

The maximum temperature of the battery during the crush test is high, and the number of smoked batteries is large. This is probably because the smaller the particle size of the nickel-cobalt hydroxide, the larger the specific surface area, and the larger the thermal reaction area during the crush test, the lower the thermal stability.

When the average particle diameter is larger than 18 μm, the filling properties are sufficient, but the specific capacity of the active material is reduced. This is because the specific surface area decreases as the particle size of the nickel-cobalt hydroxide increases, the reaction rate with lithium during the synthesis of the lithium composite nickel-cobalt oxide decreases, and the synthesis does not proceed sufficiently. Can be considered.

As described above, the battery characteristics of the nonaqueous electrolyte secondary battery using the lithium composite nickel-cobalt oxide are as follows:
It can be seen that it is significantly affected by the physical properties of the nickel-cobalt hydroxide as the raw material.

[0076] Thus, the positive electrode active material for a nonaqueous electrolyte secondary battery _{Li x Ni y Co z O 2} (0.90 ≦ x ≦ 1.0
5,0.7 ≦ y ≦ 0.9, y + z = 1 lithium nickel composite represented _{by) - Ni v Co w (OH} ) 2 (0.7 ≦ v ≦ 0 used as a raw material for the synthesis of cobalt oxide. 9,
v + w = 1), the nickel-cobalt hydroxide has an average particle diameter of 10 to 18 μm, a BET specific surface area measured by nitrogen gas adsorption of 5 to 25 m ² / g, and a tap density of 1.6 to 1.6. 2.6 g / cm ^3, pore volume of the pores 0.008~0.10cm ³ / g, a pore occupancy 3-4
It is desirable to be in the range of 0%.

(Comparative Example) Next, a comparative example will be described. As a comparative example, nickel-
A lithium composite nickel-cobalt oxide M was synthesized in the same manner as in Example 1 using the cobalt composite hydroxide as a raw material.
The chemical composition of the obtained lithium composite nickel-cobalt oxide was LiNi _0.85 Co _0.15 O ₂ . In addition, the synthesized lithium composite nickel-cobalt oxide was obtained as massive particles having an average particle size of 14 μm. And
A battery (battery M) was prepared in the same manner as in Example 1 except that this lithium composite nickel-cobalt oxide M was used as a positive electrode active material.
It was created.

The battery M was examined for 120 mA discharge capacity, specific capacity of active material (active material utilization rate), end-of-life cycle, maximum temperature at the time of crushing and generation of smoke. Table 5 shows the results.

[0079]

[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 massive, the specific surface area is particularly small because of the massive particles.
The filling property of the electrode plate is also reduced. In addition, the specific capacity of the active material is also small due to large polarization at the time of charge and discharge.

From the above results, it is desirable that the nickel-cobalt hydroxide used as the raw material of the lithium composite nickel-cobalt oxide is spherical or elliptical spherical.

In the above embodiment, as an example of a method for producing a nickel-cobalt hydroxide, an example using a mixed solution of nickel sulfate-cobalt and a caustic alkali aqueous solution has been described.
For example, even if a complexing agent such as ammonium ion is added to stabilize metal ions, the same effect can be obtained if the obtained nickel-cobalt hydroxide has similar physical properties.

In the above embodiment, the evaluation was performed using a cylindrical battery. However, the same effect can be obtained even when the battery shape is different, such as a square battery or a coin battery.

Further, 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, lithium metal, lithium alloy, F
Similar effects can be obtained by using other negative electrode materials such as oxides such as e ₂ O ₃ , WO ₂ and WO ₃ .

Although lithium hexafluorophosphate was used as the electrolyte in the above embodiment, other lithium-containing salts such as lithium perchlorate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, and hexafluorophosphate were used. Similar effects can be obtained with lithium arsenate and the like.

In the above examples, a mixed solvent of ethylene carbonate and diethyl carbonate was used. However, other non-aqueous solvents such as cyclic esters such as propylene carbonate, cyclic ethers such as tetrahydrofuran, chain ethers such as dimethoxyethane, etc. Similar effects can be obtained by using a non-aqueous solvent such as a chain ester such as methyl propionate, or a multi-component mixed solvent thereof.

[0087]

According to the nickel-cobalt hydroxide for a non-aqueous electrolyte battery active material of the present invention, as is apparent from the above description, the physical properties such as the particle shape and the particle size are controlled. The cycle characteristics and thermal stability of a battery using a lithium composite nickel-cobalt oxide synthesized by using as a positive electrode active material can be improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a nonaqueous electrolyte battery to which a positive electrode active material synthesized using a nickel-cobalt hydroxide of the present invention is applied.

[Explanation of symbols]

 5 Positive electrode plate

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeo Kobayashi 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Inside Tanaka Chemical Research Laboratories (72) Inventor Takaaki Tanaka 45-10 Sunahama-cho, 45, Shirakatacho, Fukui City, Fukui Prefecture Inside Tanaka Chemical Laboratories Co., Ltd. 45 character sandy beach percent 5-10 Inside Tanaka Chemical Laboratory Co., Ltd.

Claims (5)

[Claims] 1. A chemical formula _{Li x Ni y Co z O 2} (0.9
0 ≦ x ≦ 1.05, 0.7 ≦ y ≦ 0.9, y + z = 1)
In the lithium nickel composite represented - nickel is used as a starting material for the synthesis of cobalt oxide - is cobalt hydroxide, formula _{Ni v Co w (OH) 2} (0.7 ≦ v ≦ 0.
9, v + w = 1), secondary particles formed by innumerable aggregation of primary particles in SEM photograph observation, and the following physical properties 1) Average particle diameter of secondary particles is 10 to 18 μm 2) Secondary particles 7% or less by weight of particles having a particle diameter of 1 μm or less 3) BET specific surface area measured by nitrogen gas adsorption of 5
Nonaqueous electrolyte battery active material for nickel, characterized in that it comprises a ~25m ² / g - cobalt hydroxide. 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 nonaqueous electrolyte battery active material according to claim 1, wherein the tap density of the nickel-cobalt hydroxide is 1.6 to 2.6 g / cm ³ . 4. The nickel-cobalt hydroxide for a non-aqueous electrolyte battery active material according to claim 1, wherein the spatial volume of the pores of the nickel-cobalt hydroxide is 0.008 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 of 3 to 40%.