JP3189361B2 - Alkaline storage battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline storage battery,
In particular, the present invention relates to an improvement in an alkaline storage battery using a hydrogen storage alloy capable of electrochemically absorbing and releasing hydrogen as an active material for an electrode.

[0002]

2. Description of the Related Art Lead storage batteries and alkaline storage batteries are widely used as various power supplies. Among these, alkaline storage batteries can be expected to have high reliability and can be reduced in size and weight, so they have been used as small batteries for various portable devices and as large batteries for industrial use. In this alkaline storage battery, an air electrode, a silver oxide electrode, or the like is partially used as a positive electrode, but in most cases, a nickel electrode. This type of alkaline storage battery has been changed from a pocket type to a sintered type, the characteristics have been improved, the hermetic sealing has become possible, and the use has been expanded.

On the other hand, as the negative electrode, zinc, iron, hydrogen and the like are targeted in addition to cadmium. Recently, attention has been paid to alkaline storage batteries using a hydrogen storage alloy in order to achieve a higher energy density, and many proposals have been made for manufacturing methods and the like.

Among them, as a hydrogen storage alloy negative electrode, for example, the surface of alloy particles is plated with nickel or copper to improve the porosity by improving the oxidation resistance of the hydrogen storage alloy powder and the utilization factor and formability. A technique for forming a metal layer is known. Further, in order to improve the properties, a process has been proposed in which a heat treatment is performed in a vacuum after the production of the alloy, or an alloy powder is immersed in an alkaline solution. Further, when applied to a closed type, addition of a fluororesin or a catalyst has been attempted in order to improve the absorbability of oxygen gas generated from the positive electrode particularly during overcharge.

[0005]

In order to further improve the characteristics of the battery using the hydrogen storage alloy, it is necessary to reduce the internal pressure of the battery particularly during overcharge, to improve the high rate discharge characteristics, and to improve the characteristics at the beginning of the charge / discharge cycle. Improvement of charge / discharge characteristics, that is, initial activity is one of the issues. For example, La _0.8 Nd _0.2 N
In order to improve the performance of i _2.5 Co _2.4 Si _0.1 , La _0.8 Nd
By producing a deviation alloy from the stoichiometric composition, such as _{0.2 Ni 2.9 Co 2 .4 Si 0.1} , the grain boundary of the LaNi ₅ based alloys to precipitate MoCo _3, that it exhibits good electrochemical reactions known (P, H, L, Nott
em and P, Hookeling, J. Elec
trochem. Soc. , 137 (7), 199
1. ).

However, in this method, a hydrogen storage alloy electrochemically storing and releasing hydrogen and MoCo ₃ as a second phase are simultaneously formed during the synthesis of the alloy, and an intermetallic compound such as a LaNi ₅ base alloy is formed. Precipitating the second phase is considered to be effective in an alloy system having a relatively narrow composition range, but is not necessarily effective in an alloy system that forms a stable intermetallic compound in a wide composition range, and is not effective. Applying this technique to alloys has been difficult. Further, it has been very difficult to control the particle size of MoCo ₃ in relation to battery characteristics.

Further, in order to improve these characteristics, attempts have been made to add Pd black, which is well known as a catalyst material , and some effects have been recognized, but further improvements in characteristics have been desired. Attempts have been made to mix or plate Ni powder with hydrogen storage alloy powder. However, there is a slight effect on improving high-rate discharge characteristics, but a remarkable effect on improving initial activity and lowering battery internal pressure is recognized. I couldn't.

The present invention has been made to solve the above problems, and more effectively and inexpensively improves the internal pressure characteristics of batteries during overcharge, the high rate discharge characteristics, and the charge / discharge characteristics at the beginning of a charge / discharge cycle, that is, the initial activity. To provide an alkaline storage battery.

[0009]

In order to achieve this object, an alkaline storage battery according to the present invention has a mean particle size on the surface of a hydrogen storage alloy powder having a mean particle size of 10 to 40 μm, which is a main constituent material of a negative electrode. An alloy having a hexagonal structure represented by the general formula MoM ₃ (M = Co, Ni or a mixture thereof) of 10 μm or less, preferably 2 μm or less, Pd, Pt, Pd supported on carbon, and Pd supported on carbon A catalyst powder such as Pt is integrated. The hydrogen storage alloy used at this time is represented by the general formula AB _a (where A is Zr alone or 30 atomic% or less of Ti, Hf, Ta, Y, Ca, Mg,
Z containing La, Ce, Nd, Nb, Mo, Al, Si
r and B are Ni and Mg, Ca, Ti, Hf, V, N
b, Cr, Mo, Mn, Fe, Co, Pd, Cu, A
g, Zn, Cd, Al, Si, La, Ce, Pr, Nd
At least one element selected from the group consisting of α = 1.5 to 2.
5, A and B are different elements), and L of the intermetallic compound
aves phase, has at least one crystal structure of hexagonal symmetry C14 type and cubic symmetry C15 type, and when the lattice constant is C14 type, a = 4.8-5.2 °, c = 7.
9 to 8.3 °, a = 6.92 to 7.3 for C15 type
0 ° alloy or general formula MmNi _XYZ Co _Y M _Z (where 4.8 ≦ X ≦ 5.2, 0 <Y ≦ 2, 0 <Z ≦ 1.5
And M is Mn, Al, Cr, Fe, Cu, Sn, S
b, Mo, V, is at least one of Nb, Ta, Zn, Mg, Zr, Ti, Mm is represented by at least showing three or more of a mixture of rare earth metals), CaCu ₅
An alloy having a mold structure and having a La content of 2 to 25 wt% is preferable.

Further, even better results can be obtained by immersing the hydrogen storage alloy powder, which is the main constituent material of the negative electrode, in a basic solution in advance and then integrating the catalyst particles on the surface thereof by mechanochemical reaction.

[0011]

With this configuration, the hydrogen gas generated from the negative electrode during overcharge is gas-reacted and absorbed in the hydrogen storage alloy. At this time, if the catalyst particles are integrated on the surface of the hydrogen storage alloy, the hydrogen storage alloy The activation energy of the hydride formation reaction on the surface is reduced. That is, the gas absorption reaction speed is accelerated, and hydrogen gas in the battery is quickly absorbed. As a result, the internal pressure of the battery can be kept low. This is presumably because the catalyst particles themselves do not absorb much hydrogen but effectively diffuse hydrogen into the hydrogen storage alloy. At that time, it is extremely important to reduce the particle size of the catalyst particles. This is because a large surface area and a large contact area with the hydrogen storage alloy are required to function as a catalyst for the hydrogen gas absorption reaction. It is also important to control the amount of catalyst added. This is because if the addition amount is too small, the effect is not sufficiently exhibited, and if the addition amount is too large, the capacity of the negative electrode is reduced, and as a result, the battery characteristics are deteriorated.

Since the exchange current density increases due to the action of the catalyst, the discharge voltage during high-rate discharge increases, and the discharge capacity also increases. Further, the charge / discharge characteristics at the beginning of the charge / discharge cycle, that is, the initial activity is improved.

[0013]

Embodiment 1 An alkaline storage battery according to an embodiment of the present invention will be described below with reference to the drawings. As a hydrogen storage alloy, ZrMn _0.5 V _0.2 C whose main alloy phase is a C15-type Laves phase alloy
MoCo ₃ was used as the o _0.1 Ni _1.2 catalyst. First, electrode fabrication will be described . MoCo obtain an alloy powder mainly comprising MoCo ₃ phase ₃ composition alloy work made by a gas atomizing method in arc melting, crushing it, sieved to an average particle size of 5
μm. A hydrogen storage alloy powder having an average particle diameter of 20 μm was added to a KOH aqueous solution having a specific gravity of 1.3 and kept at a temperature of 80 ° C.
After immersion time, the MoCo ₃ above was added 2 wt%, MoCo ₃ by argon atmosphere mechanofusion method
The powder was integrated with the hydrogen storage alloy powder. Here, the hydrogen storage alloy base particles are immersed in the KOH aqueous solution because the surface of the base particles is intentionally made uneven to integrate the child particles into the recesses of the base particles so as to be as strong as possible. It is to have. When this state was observed with an electron microscope, it was observed that MoCo ₃ was scattered on the surface of the hydrogen storage alloy. The average particle size is 24
μm. Thereafter, this was kneaded with water to form a paste. This paste was filled into a foamed nickel plate having a porosity of 95% and a thickness of 0.8 mm, immersed in a 0.6 wt% aqueous solution of carboxymethylcellulose, dried under vacuum, and then pressed to obtain an electrode. The obtained electrode was made into a negative electrode having a width of 39 mm, a length of 97 mm, and a thickness of 0.33 mm, and was combined with the positive electrode and the separator into a three-layer spiral shape and stored in an AA-size cylindrical battery case. At this time, a known foamed nickel electrode was selected as the positive electrode, and a lead plate having a width of 39 mm, a length of 77 mm, and a thickness of 0.70 mm was used. Further, a polypropylene nonwoven fabric provided with hydrophilicity was used as the separator . As an electrolytic solution, 2.2 cc of a solution obtained by dissolving 40 g / l of lithium hydroxide in an aqueous solution of potassium hydroxide having a specific gravity of 1.30 was used. This was sealed to obtain a sealed battery. This is Example 1 of the present invention, and is referred to as Battery A.

In order to compare the characteristics of this battery, a battery according to a conventional method was also manufactured. That is, as a conventional method, similarly, a hydrogen storage alloy having a composition of ZrMn _0.6 V _0.2 Co _0.1 Ni _1.2 and an average particle diameter of 20 μm was formed into a battery in the same manner as described above without integrating MoCo ₃ . This is referred to as a battery B as a conventional method.

MoCo to be further added_ThreeAddition amount and particle size
Battery to examine the effect of battery on battery performance
Was prepared. That is, in the manufacturing method according to the battery A, Mo
Co _ThreeWas added to 0.01 wt% of the total alloy amount.
Were prepared at 20 wt%, and the batteries C and
Pond D. In addition, in the manufacturing method according to battery A, MoCo
_ThreeA battery E having an average particle size of 20 μm
Was. These batteries A to E have a capacity of 12
87 mAh.

These batteries were evaluated by a normal charge / discharge cycle test. Table 1 shows the results.

[0017]

[Table 1]

First, the initial discharge voltage and the capacity were compared. 2
The battery A was charged at a constant current of 150% at a rate of 5 hours at 0 ° C. and then discharged at a constant current of up to 1.0 V at a rate of 5 hours for 5 cycles. Was about 1287 mAh after 2 cycles. However, in battery B, the average discharge voltage was 1.22 V, the discharge capacity did not reach 1287 mAh in two cycles, and the discharge capacity increased with an increase in the number of cycles, and required four cycles to become substantially constant. In battery C, the result was the same as in battery B, and the effect of the addition of MoCo ₃ was not remarkably observed. Battery D has a discharge capacity of 2
It was constant at approximately 1200 mAh after the cycle. That is, although the initial activity was improved by the effect of the addition of MoCo _{3, the} amount of the addition was too large, so that the capacity of the negative electrode was reduced, and as a result, the discharge characteristics of the battery were deteriorated. From the results of the batteries A, C, and D, it can be seen that there is an optimum value for the amount of MoCo ₃ added. In the result of the battery E, the average discharge voltage was 1.26.
V, the discharge capacity was about 1270 mAh after 2 cycles. Since the particle size of the MoCo ₃ is not sufficiently small relative to that of the hydrogen-absorbing alloy powder, MoCo ₃ and contact area of the hydrogen storage alloy is reduced as compared with the battery A and MoCo ₃
It is considered that the effect as a MoCo ₃ catalyst is small because the surface area of the powder is small. Thereafter, charging was performed up to 200% at an hourly rate, and discharging was performed up to a final voltage of 1.0 V at an hourly rate, and a charge / discharge cycle at 20 ° C. was repeated. The discharge voltage at the 10th cycle, which is considered to be sufficient to activate the battery, is shown in Table 1 above, the charging voltage and the internal pressure of the battery are shown in FIG. 1, and the discharge curve is shown in FIG. Batteries A and D have an average discharge voltage of 1.25 V and a maximum internal pressure of 1 when overcharged, respectively.
0 and 14Kgcm ^-2 at a battery while B, C in the average discharge voltage 1.14V, the maximum battery internal pressure to about 30Kgcm ^-2, the average in the battery E discharge voltage 1.21V, the maximum cell internal pressure 25Kg
cm ^-2 , indicating that Battery A exhibited excellent charge / discharge characteristics even during resting charge / discharge. The average particle size of MoCo ₃ is 2
Further excellent results were obtained in the case where the thickness was set to be equal to or less than μm and the battery was prepared in the same manner as the battery A.

[0019] (Example 2) or more but is for the AB ₂ type Laves phase alloys, as a second embodiment, a MmNi ₅ based alloy _{MmNi 3.7 Mn 0.4 Al 0.3 Co 0.6} (La
(Content 14 wt%) will be described below.

As a hydrogen storage alloy, the main alloy phase is Ca
Cu_FiveMmNi with mold structure_3.7Mn _0.4Al_0.3C
o_0.6, MoCo as catalyst_ThreeWas used. First, electrode fabrication
Will be described. MoCo_ThreeArc melting of alloy of composition
MoCo by gas atomization method_ThreeMainly phase
An alloy powder was obtained, pulverized and sieved to an average particle size of 5 μm.
did. Heat the hydrogen storage alloy powder having an average particle size of 20 μm
Immersed in 1.3 KOH aqueous solution maintained at 80 ° C for 1 hour
After pickling, the above MoCo_Three2% by weight and argon
MoCo by atmosphere mechanofusion method_ThreePowder
It was integrated on the hydrogen storage alloy powder. Where hydrogen storage
The immersion of the gold base particles in the KOH aqueous solution
The intentional generation of irregularities causes the child particles to become
Integrated as if rubbing into the recess
This is to ensure a match. Observe this state with an electron microscope
Then, MoCo was added to the surface of the hydrogen storage alloy._ThreeAre scattered
Was seen. The particle size is about 23μm
Had become. Then knead it with water to make a paste
Was. This paste is foamed with a porosity of 95% and a thickness of 0.8 mm.
0.6wt% carboxymethyl cell filled in nickel plate
Immersed in a loin solution, vacuum-dried, and then pressurized.
Obtained. The obtained electrode was 39 mm wide, 97 mm long, and 0.3 mm thick.
Combine with a positive electrode and a separator by setting the anode to 33 mm
Into a three-layer spiral shape and stored in an AA-size cylindrical battery case
did. At this time, a well-known foamed nickel electrode is selected for the positive electrode.
And 39mm wide, 77mm long and 0.70mm thick.
A board was used for mounting. The separator is hydrophilic.
It is a polypropylene nonwoven fabric given. As the electrolyte,
Lithium hydroxide in potassium hydroxide aqueous solution with specific gravity 1.30
Was dissolved in an amount of 40 g / 1 and 2.2 cc was used. this
The sealed battery was sealed. This is Embodiment 2 of the present invention.
Yes, battery a.

In order to compare the characteristics of this battery, a battery according to a conventional method was also manufactured. That is, as a conventional method, similarly, a battery was formed in the same manner as above without integrating a hydrogen storage alloy MoCo ₃ having a composition of MmNi _3.7 Mn _0.4 Al _0.3 Co _0.6 and an average particle diameter of 20 μm. This is referred to as a battery b as a conventional method.

Further, a comparative battery was manufactured in order to examine the effects of the amount and particle size of MoCo ₃ to be added on the battery performance. That is, in the manufacturing method according to the battery a, the MoC
Although the addition amount of o ₃ was 0.01 wt% of the total alloy amount,
20 wt% were prepared, and battery c and battery d were prepared, respectively.
And In addition, these batteries a to e, which were prepared by preparing MnCo _{3 having} an average particle size of 20 μm in a manufacturing method according to battery a to obtain batteries e, had a capacity of 1,287 m
Ah.

These batteries were evaluated by a normal charge / discharge cycle test. Table 2 shows the results.

[0024]

[Table 2]

First, the initial discharge voltage and the capacity were compared. 2
When the battery was charged at a constant current of 150% at a rate of 5 hours at 0 ° C. and then subjected to 5 cycles of constant current discharge to 1.0 V at a rate of 5 hours, the average discharge voltage of the battery a was 1.30 V, and the discharge capacity was Was about 1287 mAh after 2 cycles. However, in battery b, the average discharge voltage was 1.23 V, the discharge capacity did not reach 1287 mAh in two cycles, and the discharge capacity increased with an increase in the number of cycles, and required four cycles to become substantially constant. In the case of the battery c, the result was the same as in the case of the battery b, and the effect of the addition of MoCo ₃ was not remarkably observed. Battery d has a discharge capacity of 2
It was constant at approximately 1200 mAh after the cycle. That is, although the initial activity was improved by the effect of the addition of MoCo _{3, the} amount of the addition was too large, so that the capacity of the negative electrode was reduced, and as a result, the discharge characteristics of the battery were deteriorated. It can be seen from the results of the batteries a, c, and d that there is an optimum value for the amount of MoCo ₃ added. In the result of the battery e, the average discharge voltage was 1.27.
V, the discharge capacity was approximately 1271 mAh after the second cycle. Since the particle size of the MoCo ₃ is not sufficiently small relative to that of the hydrogen-absorbing alloy powder, MoCo ₃ and contact area of the hydrogen storage alloy is reduced as compared with the battery a and MoCo ₃
It seems that MoCo ₃ has little effect as a catalyst because the surface area of the powder is small. Thereafter, the charging was performed up to 200% at a rate of 1 hour, and the discharge was performed up to a final voltage of 1.0 V at a rate of 1 hour. The discharge voltage and discharge capacity at the tenth cycle, which are considered to have sufficiently activated the battery, are shown in Table 2 above, the charging voltage and the internal pressure of the battery are shown in FIG. 3, and the discharge curve is shown in FIG. 4, respectively. Cell a, b is the average discharge voltage battery b while the maximum battery internal pressure during overcharge was respectively 12 and 17Kgcm ^-2 at 1.26V, c in the average discharge voltage 1.15V, the maximum battery internal pressure to about 36Kgcm ^{- 2. The} average discharge voltage of the battery e was 1.22 V and the maximum internal pressure of the battery was 30 Kgcm ^-2 , indicating that the battery a exhibited excellent charge / discharge characteristics even with rapid charge / discharge. MoCo
_Even more excellent results were obtained when the average particle diameter of No. ₃ was 2 μm or less and was prepared in the same manner as for battery a.

Further, MoNi ₃ instead of MoCo ₃ in the previous examples, Pb, Pt, supported on carbon P
b, excellent results were obtained using Pt supported on carbon. The synthesis of MoCo ₃ was performed by the gas atomizing method, but the same result was obtained by the quenching roll method. Further, in the above embodiment, the integration of the hydrogen storage alloy powder and the MoCo ₃ powder was performed by the mechanofusion method, but the same result could be obtained by the high-speed in-stream impact method. In this example, the size of the battery was AA, but a large effect was also observed in other sizes, large alkaline storage batteries and open batteries.

[0027]

As is clear from the above description of the embodiment, according to the alkaline storage battery of the present invention, the battery internal pressure at the time of overcharge, which has been a problem in the past, is reduced, and high-rate charge / discharge characteristics are obtained.
It is possible to provide a high-performance alkaline storage battery in which the charge and discharge characteristics in the initial stage of the charge and discharge cycle are improved at low cost.

[Brief description of the drawings]

FIG. 1 shows batteries A to A of an alkaline storage battery according to a first embodiment of the present invention.
Graph showing charging characteristics indicating charging voltage and battery internal pressure at the 10th cycle of E

FIG. 2 is a graph showing high-rate discharge characteristics.

FIG. 3 is a graph showing charging characteristics showing the charging voltage and the internal pressure of the alkaline storage batteries of Example 2 in the tenth cycle of the batteries a to e.

FIG. 4 is a graph showing high-rate discharge characteristics.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Yoshio Moriwaki 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Isao Matsumoto 1006 Kadoma Kadoma Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (56) References JP-A-1-267955 (JP, A) JP-A-63-195961 (JP, A) JP-A-2-256161 (JP, A) JP-A-62-291862 (JP, A) JP-A-63-284758 (JP, A) JP-A-2-223150 (JP, A) JP-A-64-57568 (JP, A) JP-A-3-269952 (JP, A) JP-A-5-234590 (JP, A) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H01M 10/24-4/30 H01M 10/34 H01M 4/24-4/26 H01M 4/38 H01M 4/62

Claims (9)

(57) [Claims] A positive electrode mainly composed of a metal oxide; a negative electrode mainly composed of a hydrogen storage alloy powder capable of electrochemically absorbing and releasing hydrogen as an active material; a separator; A battery provided with a power generating element comprising an electrolyte solution, wherein the hydrogen storage alloy base particles used for the negative electrode have an average particle size of 10 to 40 μm, and the surface of the base particles has an average particle size of 10 μm or less and has a catalytic function. Particles are mechanochemical
An alkaline storage battery in which the average particle size is larger than that of the hydrogen storage alloy base particles by being partially fused and firmly integrated by the reaction of the hydrogen storage alloy. (However, child particles having a catalytic function
In the case of an alloy having a hexagonal structure represented by MoCo ₃
except for. ) 2. The secondary particles having a catalytic function have an average particle size of 2
alkaline storage battery of claim 1, wherein at most mu. 3. The alkaline storage battery according to claim 1, wherein the amount of the secondary particles having a catalytic function is 0.1 to 10% by weight based on the weight of the battery. 4. A child particle having a catalytic function is represented by a general formula Mo
M ₃ and (M = Ni or Co and a mixture of Ni) alloy having a hexagonal structure represented by the main component claim 1-3 Neu
Alkaline storage battery according to any Re not. 5. The alkaline storage battery according to claim 1 to 3 or Re not gall the daughter particles having a catalytic function is at least one selected Pd, from Pt. 6. alkaline storage battery according to any Re without gall claim 1-3 daughter particles is at least one selected from Pt supported on supported Pd, carbon to carbon having a catalytic function. 7. A main hydrogen storage alloy is represented by a general formula AB _a (where A is Zr alone or 30 atomic% or less of Ti, H
f, Ta, Y, Ca, Mg, La, Ce, Nd, Nb,
Zr and B containing Mo, Al and Si are Ni and Mg, C
a, Ti, Hf, V, Nb, Cr, Mo, Mn, Fe,
Co, Pb, Cu, Ag, Zn, Cd, Al, Si, L
a, at least one element selected from the group consisting of Ce, Pr, and Nd, a = 1.5 to 2.5, and A and B are different elements), and the alloy phase substantially changes to the Laves phase of the intermetallic compound. belongs, is at least one of its C14 type crystal structure is hexagonal object and falling sides C15 type target, the lattice constants C14
In the case of the type, a = 4.8-5.2 °, c = 7.9-8.3.
The alkaline storage battery according to any one of claims 1 to 6 , wherein a = 6.92 to 7.30 in case of {, C15 type. 8. A main hydrogen storage alloy has a CaCu ₅ type structure, in the general formula MmNi _XYZ Co _Y M _Z (wherein, 4.8 ≦
X ≦ 5.2, 0 <Y ≦ 2, 0 <Z ≦ 1.5, and M is M
n, Al, Cr, Fe, Cu, Sn, Sb, Mo, V,
At least one of Nb, Ta, Zn, Mg, Zr, and Ti, and Mm represents a mixture of at least three or more rare earth metals).
Alkaline storage battery according to claim 1-6 Neu not Re or content of 2~25wt%. 9. The hydrogen storage alloy base particles are immersed in a basic solution to form many irregularities on the surface of the base particles before integrating the child particles having a catalytic function with the hydrogen storage alloy base particles. alkaline storage battery according to 1-8 or Re without noise.