JP2003045423A - Positive active material for alkaline secondary battery, alkaline secondary battery, hybrid car and electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive active material for a secondary battery enhancing the charging efficiency at high temperature in initial charging/discharging cycles. SOLUTION: Nickel hydroxide particles containing 1.5% or more Li to Ni in weight ratio is contained in the positive active material.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a positive electrode active material for an alkaline secondary battery containing nickel hydroxide, an alkaline secondary battery including a positive electrode containing the positive electrode active material, and a hybrid using the alkaline secondary battery. It relates to cars and electric vehicles. Further, the alkaline secondary battery can be mounted on a portable electronic device or the like in addition to a hybrid car and an electric vehicle.

[0002]

2. Description of the Related Art Nickel-hydrogen secondary batteries, which are an example of alkaline secondary batteries, are widely used as power sources for various mobile devices such as mobile phones and batteries for hybrid electric vehicles. Also, although nickel-cadmium batteries are mainly used as the power source for electric tools, demand for environmentally friendly batteries that can replace these nickel-cadmium batteries is also expected.

In the nickel-hydrogen secondary battery, nickel hydroxide (Ni (OH) ₂ ) is used as in the nickel-cadmium battery.
Is used as the positive electrode active material, and unlike the nickel-cadmium battery, a hydrogen storage alloy is used as the negative electrode material. To date, each company has made great efforts to improve the characteristics of the hydrogen storage alloy that is the negative electrode material, and as a result, the hydrogen storage alloys currently in use have reached capacities close to the theoretical values, and further higher capacity In order to improve battery characteristics, it is essential to improve the performance of the positive electrode.

When nickel hydroxide is used as the positive electrode active material, the charging efficiency of the positive electrode is usually increased to a predetermined value by activation by charging / discharging. The reason why the charging efficiency is improved by charging and discharging is that the nickel hydroxide particles take in alkali metal ions and water in the electrolyte into the lattice by repeating the initial charging and discharging, and the state gradually changes. Seem.

In particular, Li ions in the alkaline electrolyte are easily taken into the active material, and it is said to be effective for improving the conductivity of the active material and the charge acceptability at high temperature.

However, since lithium hydroxide has a low solubility, it is likely to precipitate in the electrolytic solution, and from the viewpoint of maintaining the conductivity of the electrolytic solution, the amount of Li ions in the total amount of alkali ions in the electrolytic solution is naturally limited. . In addition, in the sealed battery, the amount of electrolyte injected is limited in order to smoothly recombine the generated gas during overcharge. Therefore, even if all of the Li ions in the injected electrolytic solution were taken into the nickel hydroxide, the weight ratio of Li to Ni was 1.
The Li content could only be increased to about 0%. Therefore, in this method, a large amount of Li is contained in the nickel hydroxide particles.
It is difficult to add OH. In addition, since it is necessary to repeatedly charge and discharge until the amount of alkali ions present in the positive electrode active material reaches a steady state, there is a problem that sufficient characteristics cannot be obtained at the beginning of the cycle.

From the above, Japanese Patent Application Laid-Open No. 8-4550
No. 6 publication discloses that a mixed aqueous solution of an acidic lithium salt and an acidic nickel salt and an alkaline aqueous solution are used to measure the pH in a reaction tank.
While controlling the introduction amount of each aqueous solution so that is maintained at a predetermined value, by gradually introducing and mixing in the reaction tank, it has been proposed to precipitate nickel hydroxide crystals containing lithium. There is. According to such a method, a method described in JP-A-60-211767, that is, a method of causing lithium to be contained in aggregate particles of nickel hydroxide by causing an alkali metal containing lithium to act on a nickel salt solution. In comparison with the above, since it is easy to take lithium ions into the nickel hydroxide crystal lattice, it is possible to improve the battery capacity in the initial stage of charge / discharge at room temperature.

However, according to the method described in Japanese Patent Laid-Open No. 8-45506, paragraphs [0014] to
As described in [0016], the lithium content in the nickel hydroxide particles is as low as 1% by weight, which makes it difficult to obtain high initial charging efficiency at high temperatures. That is, since the process of oxidizing the nickel hydroxide particles to widen the distance between the crystal planes is not performed, Li cannot be incorporated at a high concentration of 1.5% by weight or more. In addition, the lithium concentration in the mixed aqueous solution of the acidic lithium salt and the acidic nickel salt is naturally limited for the purpose of avoiding increasing the concentration of residual sulfate groups and the like. Therefore, the lithium content in the nickel hydroxide particles can only be increased to about 1% by weight.

[0009]

DISCLOSURE OF THE INVENTION The present invention is directed to a positive electrode active material for an alkaline secondary battery and an alkaline secondary battery capable of improving the charging efficiency at high temperature in the initial stage of a charge / discharge cycle, and the alkaline secondary battery. It is an object to provide a hybrid car and an electric vehicle using the.

[0010]

The positive electrode active material for an alkaline secondary battery according to the present invention has a weight ratio to Ni of 1.5%.
It is characterized by containing the nickel hydroxide particles containing Li described above.

The alkaline secondary battery according to the present invention is an alkaline secondary battery including a positive electrode containing a positive electrode active material, a negative electrode, and an alkaline electrolyte, wherein the positive electrode active material has a weight ratio to Ni of 1.5. % Of Li is included in the nickel hydroxide particles.

The hybrid car according to the present invention is a hybrid car provided with an electric drive means and a power source for the electric drive means including an alkaline secondary battery, wherein the alkaline secondary battery includes a positive electrode containing a positive electrode active material, It is characterized in that it comprises a negative electrode and an alkaline electrolyte, and that the positive electrode active material contains nickel hydroxide particles containing Li in a weight ratio of 1.5% or more with respect to Ni.

The electric vehicle according to the present invention is an electric vehicle including a driving power source including an alkaline secondary battery, wherein the alkaline secondary battery includes a positive electrode containing a positive electrode active material, a negative electrode, and an alkaline electrolyte. And the positive electrode active material,
It is characterized by containing nickel hydroxide particles containing Li in a weight ratio of 1.5% or more with respect to Ni.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION First, the positive electrode active material for an alkaline secondary battery according to the present invention will be described.

The positive electrode active material for an alkaline secondary battery is N
It is characterized by containing nickel hydroxide particles containing Li in a weight ratio of 1.5% or more with respect to i.

Li can be present in the crystal lattice of nickel hydroxide. The existence form of Li is an atom,
It may take the form of an ion, a compound or the like. The Li content is 1.
If it is less than 5% by weight, the charging efficiency at high temperature at the beginning of the charge / discharge cycle is lowered. Further, even if the Li content is more than 3% by weight, not only a large improvement in charging efficiency at high temperature cannot be expected, but also a high positive electrode utilization rate and excellent charge / discharge cycle characteristics may not be obtained. Therefore, the Li content is preferably in the range of 1.5 to 3% by weight. A more preferable range is 2.5 to 2.7% by weight.

In addition to Li, the nickel hydroxide particles contain Z from the viewpoint of further improving the positive electrode utilization rate and cycle life.
One or more kinds of elements selected from the group consisting of n, Co, Mg and Y can be contained.

A conductive layer containing cobalt oxyhydroxide (CoOOH) may be formed on the surface of the nickel hydroxide particles. The nickel hydroxide particles having the conductive layer formed on the surface thereof can improve the conductivity of the positive electrode, and thus can improve the positive electrode utilization rate and the cycle life.

The nickel hydroxide particles have an average particle size of 4 to 1
It is preferably within the range of 8 μm. A more preferable range is 7 to 12 μm.

The positive electrode active material according to the present invention is obtained, for example, by oxidizing at least a part of nickel hydroxide particles in a solution containing lithium ions until the state of Ni (II) is changed to Ni (III). . At least a part of nickel hydroxide is oxidized to Ni (III) state and N
By using iOOH, the distance between crystal planes can be widened, so that Li ions are easily incorporated into the crystal lattice. As a result, the weight ratio to Ni is 1.5%
The nickel hydroxide particles containing Li described above can be produced. A specific manufacturing method will be described below.

First, by stirring and mixing an aqueous solution containing lithium hydroxide, nickel hydroxide particles and an oxidizing agent,
The target nickel hydroxide particles are obtained. Part or all of the obtained nickel hydroxide is nickel oxyhydroxide (Ni
Since it has been oxidized to the (OOH) state, it is desirable to carry out a reduction treatment if necessary.

The nickel hydroxide particles as a raw material include, for example,
Nickel hydroxide particles in which at least one metal of Zn and Co is eutectic, or non-eutectic nickel hydroxide particles can be used.

The concentration of lithium hydroxide (LiOH) in the aqueous solution is 1 M (mol / L) or more and 4 M (mol / L)
The following is preferable. This is due to the following reasons. When the LiOH concentration is less than 1 M, it may be difficult to set the Li content in nickel hydroxide to 1.5% by weight or more. Moreover, since the solubility of lithium hydroxide in water is low, it is almost difficult to prepare an aqueous solution having a LiOH concentration of more than 4M. By setting the LiOH concentration to 1 M or more and 4 M or less, the Li content in the nickel hydroxide particles can be in the range of 1.5 to 3% by weight. The more preferable range of the LiOH concentration is
1.5M or more and 3.5M or less, more preferable range is 2
It is M or more and 3M or less.

The aqueous solution containing lithium hydroxide contains KOH
Other alkali metal hydroxides such as

As the oxidizer, for example, at least one selected from the group consisting of perchlorates, chlorates and ozone can be used. Of these, perchlorate is preferable. Examples of perchlorates include KClO and the like.

The temperature at the time of stirring and mixing is 45 ° C. or higher, 75
It is preferable to keep the temperature within the range of ℃ or less. This is due to the following reasons. Stir mixing temperature 45 ° C
When it is less than 1, the Li content in the nickel hydroxide particles may be less than 1.5% by weight. On the other hand, if the temperature at the time of stirring and mixing exceeds 75 ° C., the surface of the nickel hydroxide particles may become rough, and it may be difficult to prepare the positive electrode paste. The more preferable stirring temperature is 50 ° C. or higher and 70 ° C. or lower.

As the reducing agent used in the reduction treatment,
For example, hydrogen peroxide water can be used. Also,
The amount of the reducing agent is preferably within the range of 30 to 120% of the amount that can be stoichiometrically reduced in the oxidized positive electrode active material. The reduction treatment can be performed by stirring and mixing the oxidized positive electrode active material in a reducing agent. The temperature of stirring and mixing is preferably room temperature or higher and 45 ° C. or lower.

At least a part of the nickel hydroxide particles is Ni in a solution containing zinc ions, cobalt ions, magnesium ions or yttrium ions.
When the target element is contained in the nickel hydroxide particles by oxidizing from (II) to the state of Ni (III), a positive electrode active material capable of improving the positive electrode utilization rate and charge / discharge cycle life is obtained. Obtainable.

Hereinafter, an alkaline secondary battery having a positive electrode containing the positive electrode active material according to the present invention will be described.

The alkaline secondary battery according to the present invention comprises an electrode group having a positive electrode containing the positive electrode active material and a negative electrode, an alkaline electrolyte, and a container accommodating the electrode group and the alkaline electrolyte. Prepare Moreover, in the alkaline secondary battery according to the present invention, a separator can be interposed between the positive electrode and the negative electrode.

The positive electrode, negative electrode, separator, alkaline electrolyte and container will be described below.

1) Positive Electrode This positive electrode has a Li / Ni content of 1.5% or more by weight.
It contains a positive electrode active material containing nickel hydroxide particles containing.

The positive electrode is prepared by, for example, preparing a paste containing a positive electrode active material, a conductive material, a polymer binder and water, filling the conductive substrate with the paste, drying and then press-molding. To be done.

Examples of the conductive material include cobalt oxide (for example, cobalt monoxide, cobalt oxyhydroxide), cobalt hydroxide, metallic cobalt, metallic nickel, carbon and the like. This conductive material is
It may be added as a powder separate from the positive electrode active material, or the surface of the positive electrode active material may be coated with a conductive material.

Examples of the polymer binder include carboxymethyl cellulose, methyl cellulose, sodium polyacrylate, polytetrafluoroethylene, styrene butadiene rubber and the like.

As the conductive substrate, for example, a two-dimensional porous substrate or a three-dimensional porous substrate can be used. Examples of the two-dimensional porous substrate include punched metal, expanded metal, nickel net and the like. Further, a two-dimensional porous substrate having irregularities formed on its surface may be used as the conductive substrate. On the other hand, examples of the three-dimensional porous body substrate include a felt-like metal porous body, a sponge-like metal porous body, and a nickel fiber sintered body. Examples of the material for forming these conductive substrates include nickel and metallic materials having nickel on the surface thereof (eg, stainless steel, iron). It is desirable to use a three-dimensional porous substrate as the conductive substrate.

2) Negative Electrode In this negative electrode, for example, a conductive material is added to powder of a hydrogen storage alloy, and the mixture is kneaded with a polymer binder and water to prepare a paste, and the paste is filled in a conductive material substrate, It is produced by pressing after drying.

As the hydrogen storage alloy, for example,
(a) a rare earth-nickel-based hydrogen storage alloy having a CaCu ₅ type structure (for example, LaNi ₅ , MmNi ₅ (Mm represents misch metal), LmNi ₅ (Lm represents lanthanum-enriched misch metal), or these Part of Ni in Al, Mn, Co, Ti, Cu, Zn, Zr, C
(Multi-element system substituted with elements such as r and B), (b)
Rare earth-magnesium-nickel hydrogen storage alloy, (c)
Ti-Ni-based hydrogen storage alloy, (d) Ti-Fe-based hydrogen storage alloy, (e) Ti-Ni-based hydrogen storage alloy, (f) Zr-V-
Examples include Ni-based hydrogen storage alloys, (g) Mg-based hydrogen storage alloys, (h) Laves phase hydrogen storage alloys, and the like. As the hydrogen storage alloy, a single phase alloy composed of the alloy phases shown in (a) to (h) above may be used, but the alloy phase shown in (a) to (h) above is mainly used. It is also possible to use multiphase alloys which contain as phases.

Of these, rare earth-nickel based hydrogen storage alloys and rare earth-magnesium-nickel based hydrogen storage alloys are preferable. As a rare earth-nickel-based hydrogen storage alloy, a general formula LnNi _5-xy Co _x My (where Ln is at least one element selected from rare earth elements including Y, M is Mn, Al, Cu, Fe and Cr) One or more elements selected from the group consisting of atomic ratios x and y of 0.2 ≦ x ≦ 0.
8, 0.2 ≦ y ≦ 1) is preferable. Further, in the rare earth-magnesium-nickel-based hydrogen storage alloy, in particular, the general formula R _1-ab Mg _a T _b Ni _zx M
_x (wherein R is at least one element selected from rare earth elements including Y, T is at least one element selected from the group consisting of Ca, Ti, Zr and Hf, M
Is Co, Mn, Fe, Al, Ga, Zn, Sn, Cu,
At least one element selected from the group consisting of Si, B, Nb, W, Mo, V, Cr, Ta, P and S, and the atomic ratio a, b, x and z is 0.15 ≦ a ≦ 0.35. , 0 ≦ b
≦ 0.3, 0 ≦ x ≦ 2, 3 ≦ z ≦ 3.8) are preferable.

In particular, the general formula R _1-ab Mg _a T _b Ni _zx M _x
Since the negative electrode containing the hydrogen storage alloy having the composition represented by the above formula has a rapid initial activation, the discharge capacity of the secondary battery can be improved.

As the binder, the same binders as described for the positive electrode can be used.

Examples of the conductive material include nickel powder and carbon black.

In the paste, Y ₂ O ₃ , Er ₂ O ₃ , Y
b ₂ O ₃ , Sm ₂ O ₃ , Mn ₃ O ₄ , LiMn ₂ O ₄ , Nb
An oxide such as ₂ O ₅ or SnO ₂ may be added. By including the oxide in the negative electrode, the cycle life at high temperature can be improved. Further, the type of oxide to be added can be one type or two or more types. The amount of oxide added is preferably in the range of 0.2 to 5 wt% with respect to the hydrogen storage alloy. A more preferable range is 0.4 to 2 wt%.

A two-dimensional porous substrate or a three-dimensional porous substrate can be used as the conductive substrate. Examples of the two-dimensional porous substrate include punched metal, expanded metal, nickel net and the like. Further, a two-dimensional porous substrate having irregularities formed on its surface may be used as the conductive substrate. On the other hand, examples of the three-dimensional porous body substrate include a felt-like metal porous body, a sponge-like metal porous body, and a nickel fiber sintered body. Examples of the material for forming these conductive substrates include nickel and metallic materials having nickel on the surface thereof (eg, stainless steel, iron). It is desirable to use a two-dimensional porous substrate as the conductive substrate.

3) Separator As the separator, for example, a polymer non-woven fabric such as a polypropylene non-woven fabric, a nylon non-woven fabric, or a non-woven fabric obtained by mixing polypropylene fibers and nylon fibers can be mentioned. In particular, a polypropylene nonwoven fabric whose surface is hydrophilized is suitable as a separator.

4) Alkaline Electrolyte This alkaline electrolyte is, for example, an aqueous solution of sodium hydroxide (NaOH) or lithium hydroxide (LiOH).
Aqueous solution of potassium hydroxide (KOH), NaO
H and LiOH mixture, KOH and LiOH mixture, K
A mixed solution of OH, LiOH, and NaOH can be used. Further, the positive electrode active material according to the present invention can be applied to an alkaline secondary battery using a gelled product obtained by adding a polymer or the like to an alkaline electrolyte.

5) Container This container can be formed from, for example, nickel, a metal such as nickel-plated stainless steel, a synthetic resin, a laminated film including a metal layer and a resin layer, or the like.

FIG. 1 shows a cylindrical alkaline secondary battery as an example of the alkaline secondary battery according to the present invention.

As shown in FIG. 1, an electrode group 5 made by stacking a positive electrode 2, a separator 3 and a negative electrode 4 and spirally winding them is housed in a bottomed cylindrical container 1. ing. The negative electrode 4 is disposed on the outermost periphery of the electrode group 5 and is in electrical contact with the container 1. The alkaline electrolyte is contained in the container 1. Hole 6 in the center
A circular sealing plate 7 having a is arranged in the upper opening of the container 1. The ring-shaped insulating gasket 8 is disposed between the peripheral edge of the sealing plate 7 and the inner surface of the upper opening of the container 1, and the sealing plate is attached to the container 1 by caulking to reduce the diameter of the upper opening inward. 7 is airtightly fixed via the gasket 8. The positive electrode lead 9 has one end connected to the positive electrode 2 and the other end connected to the lower surface of the sealing plate 7. The positive electrode terminal 10 having a hat shape is the sealing plate 7
It is attached so as to cover the hole 6 above. The rubber safety valve 11 is arranged so as to close the hole 6 in the space surrounded by the sealing plate 7 and the positive electrode terminal 10.
A circular holding plate 12 made of an insulating material having a hole in the center
Is arranged on the positive electrode terminal 10 such that the protrusion of the positive electrode terminal 10 projects from the hole of the holding plate 12. The outer tube 13 is a peripheral edge of the pressing plate 12,
The side surface of the container 1 and the peripheral edge of the bottom of the container 1 are covered.

The secondary battery according to the present invention includes, in addition to the cylindrical alkaline secondary battery as shown in FIG. 1, an electrode group having a structure in which positive electrodes and negative electrodes are alternately laminated with separators, and an alkaline group. A rectangular alkaline secondary battery having a structure in which an electrolytic solution is housed in a rectangular tubular container with a bottom, and an electrode group having a structure in which positive electrodes and negative electrodes are alternately laminated with a separator surrounded by a laminate film or resin. The same can be applied to a sealed thin alkaline secondary battery.

The positive electrode active material according to the present invention described above is
It includes nickel hydroxide particles containing 1.5% by weight or more of Li with respect to Ni. Such nickel hydroxide particles have a large crystal lattice distortion and can reach an equilibrium state in a short time after the start of charge / discharge. Therefore, since the alkaline secondary battery provided with the positive electrode containing the positive electrode active material according to the present invention can obtain high charging efficiency from the beginning of the charge / discharge cycle, it is possible to obtain high capacity from the beginning even in a high temperature environment. it can.

Further, by setting the Li content in the nickel hydroxide particles within the range of 1.5 to 3% by weight ratio with respect to Ni, a high battery capacity can be secured from the initial stage in a high temperature environment while using the positive electrode. Rate and the charge / discharge cycle life of the secondary battery can be improved.

In addition, nickel hydroxide particles containing 1.5% or more of Li in a weight ratio with respect to Ni were mixed with Ni (II) to Ni (III) in a solution containing lithium ions. When obtained by oxidizing until the state of (1), a large amount of lithium can be introduced into the crystal lattice while maintaining the crystal strain at an appropriate level. Therefore, it is possible to realize an alkaline secondary battery that simultaneously satisfies the positive electrode utilization rate, charge / discharge cycle life, and charge efficiency at high temperatures.

Next, a hybrid car and an electric vehicle according to the present invention will be described.

The hybrid car according to the present invention comprises an external combustion engine or an internal combustion engine, an electric drive means such as a motor, and a power supply for the electric drive means. The power source includes the alkaline secondary battery according to the present invention.

The "hybrid car" referred to here is one in which an external combustion engine or internal combustion engine drives a generator, and electric drive means drives wheels by the generated power and the power from the secondary battery. The driving force of both the combustion engine or the internal combustion engine and the electric driving means is used to drive the wheels.

The electric vehicle according to the present invention includes the alkaline secondary battery according to the present invention as a driving power source.

The hybrid car and electric vehicle equipped with the alkaline secondary battery according to the present invention can have high running performance such as fuel consumption.

[0059]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the above-mentioned drawings.

Example 1 <Preparation of Positive Electrode> 500 g of nickel hydroxide particles, 500 cc of a KClO solution having an effective chlorine concentration of 5%, and 1500 cc of a 0.3 M lithium hydroxide aqueous solution were kept at 60 ° C. By mixing with stirring for 5 hours, lithium was contained in the nickel hydroxide particles. Then, reduction treatment was performed to obtain lithium-containing nickel hydroxide particles. Regarding the obtained nickel hydroxide particles, in order to determine the overall composition of the particles including the inside, after dissolving the nickel hydroxide particles in dilute hydrochloric acid, the nickel hydroxide particles were analyzed by inductively coupled plasma emission spectroscopy (ICP). N in
The Li concentration (% by weight) with respect to i was measured, and the results are shown in Table 1 below as the Li concentration of the nickel hydroxide particles before assembly.

90 parts by weight of the lithium-containing nickel hydroxide particles thus obtained was used, and N of carboxymethyl cellulose was added.
0.25 part by weight of salt a, polytetrafluoroethylene 3
A paste was prepared by adding parts by weight and further adding water and kneading. This paste was filled in a foamed nickel substrate, dried, and then roll-molded by a roll press to obtain a positive electrode. The size of the positive electrode was 40 mm × 70 mm.
Regarding the amount of nickel hydroxide particles filled in the positive electrode,
Assuming that nickel hydroxide has a capacity of 289 mAh / g, the amount of nickel in the nickel hydroxide particles based on the ICP analysis value was set to correspond to 1300 mAh.

<Preparation of Negative Electrode> Composition is MmNi _3.7 Co
_A paste is prepared by adding a binder and water to a powder of a hydrogen storage alloy represented by _0.6 Mn _0.4 Al _0.3 (Mm represents a misch metal), and kneading the resulting paste, and the obtained paste is a punched metal substrate. On, dry
By pressing, a negative electrode having dimensions of 41 mm × 107 mm was produced.

<Battery Assembly> An electrode group was constructed by spirally winding the positive electrode and the negative electrode with a separator interposed therebetween. Insert the obtained electrode group into a battery can and
1 / l KOH and 1 mol / l NaOH and 0.5mo
A cylindrical nickel-hydrogen secondary battery of AA size having a structure of 1300 mAh and having the structure shown in FIG. Assembled

Examples 2 to 13 and Comparative Examples 1 to 6 In the process of introducing lithium into the nickel hydroxide particles, the concentration of the lithium hydroxide aqueous solution, the stirring and mixing time, and the temperature during stirring and mixing are shown in Table 1 below. Except change to
Lithium-containing nickel hydroxide particles were obtained in the same manner as in Example 1 described above. Comparative Example 1 is an example in which nickel hydroxide particles were treated with only an oxidizing agent. With respect to the obtained nickel hydroxide particles, the Li concentration (% by weight) with respect to Ni in the nickel hydroxide particles was measured in the same manner as described in Example 1 above, and the result was measured. Table 1 below shows the Li concentration.

A cylindrical nickel-hydrogen secondary battery was assembled from these nickel hydroxide particles in the same manner as in Example 1 described above.

The obtained Examples 1 to 13 and Comparative Examples 1 to 1
Regarding the secondary battery of No. 6, as initial charge / discharge, 150% charge was performed at room temperature for 15 hours at 0.1 C, and then discharge was performed at 0.2 C until the voltage reached 1V. Then 4
150% charge at 0.1C at 5 ° C, 0.5C
The charging / discharging was performed for 3 cycles in which discharging was performed up to 1 V. The discharge capacity of the battery at the third cycle was divided by the rated capacity of the battery to obtain the initial charging efficiency (%). Table 1 shows the relative initial charging efficiency of each example, where the initial charging efficiency at 45 ° C. of Comparative Example 1 is 1.

[0067]

[Table 1]

As is clear from Table 1, the secondary batteries of Examples 1 to 13 containing nickel hydroxide particles containing Li in a weight ratio of 1.5% or more with respect to Ni were the initial charging efficiency at 45 ° C. However, it can be seen that the Li content is higher than in Comparative Examples 1 to 6 including nickel hydroxide particles having a Li content lower than 1.5%.

In order to investigate the influence of lithium hydroxide contained in the alkaline electrolyte, Examples 1 to 13 were used.
Regarding the secondary batteries of Comparative Examples 1 to 6, after initial charge and discharge under the conditions described above, the nickel hydroxide particles were decomposed and dissolved in dilute hydrochloric acid, and then the inductively coupled plasma emission spectroscopy (ICP) was performed.
To measure the Li concentration (% by weight) with respect to Ni in the nickel hydroxide particles, and use the result as the Li of nickel hydroxide particles contained in the positive electrode of the nickel-hydrogen secondary battery at the time of shipment.
The content (Li concentration at shipping) is also shown in Table 1 described above.

As is clear from these results, the Li content in the nickel hydroxide particles may increase slightly after the secondary battery is assembled due to the influence of lithium hydroxide in the electrolytic solution. .

Next, the following experiment was conducted to investigate the relationship between the nickel hydroxide particles containing no Li and the lithium hydroxide concentration in the alkaline electrolyte.

Comparative Examples 7 to 9 Cylindrical nickel-hydrogen secondary batteries were prepared in the same manner as in Comparative Example 1 described above, except that the lithium hydroxide concentration in the alkaline electrolyte was changed as shown in Table 2 below. Assembled

The secondary batteries of Comparative Examples 7 to 9 thus obtained were subjected to initial charge / discharge under the same conditions as described in Example 1 above. Then, the initial charging efficiency (%) was determined in the same manner as described in Example 1 above. Comparative Example 1
Table 2 shows the relative initial charging efficiency of each comparative example, with the initial charging efficiency at 45 ° C. of 1 being 1. In addition, in Table 2, the results of Examples 1, 2, 5, 7 and Comparative Example 1 described above are also shown.

Regarding the secondary batteries of Comparative Examples 7 to 9,
After the initial charge and discharge under the above-mentioned conditions, the nickel hydroxide particles were decomposed, dissolved in dilute hydrochloric acid, and then the Li concentration (% by weight) relative to Ni in the nickel hydroxide particles was measured by inductively coupled plasma emission spectroscopy (ICP). The measurement results are shown in Table 2 as the Li content (Li concentration at the time of shipment) of the nickel hydroxide particles contained in the positive electrode of the nickel-hydrogen secondary battery at the time of shipment. In addition, in Table 2, the results of Examples 1, 2, 5, 7 and Comparative Example 1 described above are also shown.

[0075]

[Table 2]

As is clear from Table 2, the higher the concentration of lithium hydroxide in the alkaline electrolyte is, the more lithium can be contained in the nickel hydroxide particles, but the water in the alkaline electrolyte is increased. Lithium oxide concentration 2mo
Even if the concentration is as high as 1 / l, the Li content is at most 1.3% by weight.
You can see that it is nothing more than a degree.

Comparative Example 10 A positive electrode active material was synthesized according to the method described in paragraphs [0014] to [0016] of JP-A-8-45506.

First, a mixed aqueous solution containing 2.2 mol / L nickel sulfate and 0.03 mol / L lithium sulfate was prepared.

Then, pH 8 was placed in a reaction vessel equipped with a stirrer.
A suitable amount of the sodium hydroxide aqueous solution is put into the reaction tank, and the mixed aqueous solution is introduced into the reaction tank at a constant flow rate. In parallel with this, a pH meter or the like is used to maintain the solution in the reaction tank inside the tank. 6 mol while monitoring pH
/ L sodium hydroxide aqueous solution was introduced into the reaction tank.
When the 6 mol / L sodium hydroxide aqueous solution was introduced, the pH in the reaction vessel fluctuated as the acid-alkali reaction proceeded. Therefore, the introduction flow rate of the 6 mol / L sodium hydroxide aqueous solution was adjusted accordingly. The reaction tank was heated to about 40 ° C., and the solution in the reaction tank was constantly stirred.

Thus, the Ni / Li mixed aqueous solution and the sodium hydroxide aqueous solution were mixed to precipitate nickel hydroxide, and the precipitate was collected, washed with water, and dried to obtain a lithium-containing nickel hydroxide powder. It was

The lithium content of this lithium-containing nickel hydroxide powder was measured by atomic absorption spectrometry and found to be 1% by weight.

A cylindrical nickel-hydrogen secondary battery was assembled in the same manner as in Example 1 except that such lithium-containing nickel hydroxide powder was used as the positive electrode active material.

Regarding the obtained secondary battery of Comparative Example 10,
Initial charging / discharging was performed under the same conditions as described in Example 1 above. Then, the initial charging efficiency (%) was determined in the same manner as described in Example 1 above. Comparative Example 1-4
When the initial charging efficiency at 5 ° C. was set to 1, the relative initial charging efficiency of Comparative Example 10 was 1.01.

[0084]

As described above in detail, according to the present invention, a positive electrode active material for an alkaline secondary battery and an alkaline secondary battery, which achieve high charging efficiency from the beginning of a charge / discharge cycle, and this alkaline secondary battery are provided. A hybrid car and an electric vehicle to be used can be provided.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing a cylindrical alkaline secondary battery as an example of the alkaline secondary battery according to the present invention.

[Explanation of symbols]

1 ... container, 2 ... Positive electrode 3 ... separator, 4 ... Negative electrode, 5 ... electrode group, 7 ... Seal plate, 8 ... Insulation gasket.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masaaki Yamamoto             8th Shinsugita Town, Isogo Ward, Yokohama City, Kanagawa Prefecture             Ceremony company Toshiba Yokohama office F term (reference) 5H028 AA05 EE05 HH01 HH03                 5H050 AA02 BA11 CA03 CB16 EA02                       EA23 EA24 HA01 HA10 HA14                 5H115 PC06 PG04 PI16

Claims (10)

[Claims] 1. L of 1.5% or more by weight ratio to Ni
A positive electrode active material for an alkaline secondary battery, comprising nickel hydroxide particles containing i. 2. The positive electrode active material for an alkaline secondary battery according to claim 1, wherein the nickel hydroxide particles contain 1.5 to 3% by weight of Li of Ni. 3. The nickel hydroxide particles are obtained by oxidizing at least a part of the nickel hydroxide particles in a solution containing lithium ions until the state becomes Ni (II) to Ni (III). The positive electrode active material for an alkaline secondary battery according to claim 1. 4. An alkaline secondary battery comprising a positive electrode containing a positive electrode active material, a negative electrode, and an alkaline electrolyte, wherein the positive electrode active material contains water containing 1.5% or more by weight of Li with respect to Ni. An alkaline secondary battery comprising nickel oxide particles. 5. The alkaline secondary battery according to claim 4, wherein the nickel hydroxide particles contain Li in a weight ratio of 1.5 to 3% with respect to Ni. 6. The alkaline secondary battery according to claim 4, wherein the nickel hydroxide particles contain Li in a weight ratio of 2.5 to 2.7% with respect to Ni. 7. The nickel hydroxide particles are obtained by oxidizing at least a part of the nickel hydroxide particles in a solution containing lithium ions until the state becomes Ni (II) to Ni (III). The alkaline secondary battery according to claim 4, which is characterized in that. 8. The nickel hydroxide particles are 1 to 4 mo.
The secondary alkali solution according to claim 4, which is obtained by stirring and mixing an aqueous solution containing 1 / L of lithium hydroxide, a mixture containing an oxidizing agent and nickel hydroxide particles while maintaining the temperature at 45 to 75 ° C. battery. 9. A hybrid car comprising an electric driving means and a power source for the electric driving means including an alkaline secondary battery, wherein the alkaline secondary battery comprises a positive electrode containing a positive electrode active material, a negative electrode, and an alkaline electrolyte. And the positive electrode active material contains nickel hydroxide particles containing 1.5% or more of Li in a weight ratio with respect to Ni. 10. An electric vehicle including a driving power source including an alkaline secondary battery, wherein the alkaline secondary battery includes a positive electrode containing a positive electrode active material, a negative electrode, and an alkaline electrolyte, and the positive electrode active material is , An electric vehicle comprising nickel hydroxide particles containing 1.5% by weight or more of Li with respect to Ni.