JPH11354151A - Nickel-hydrogen battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance charging efficiency at high temperatures, prevent corrosion/deterioration of a negative electrode, and extend the life of a battery, by combining a nickel electrode, as a positive electrode, made up by adding a specific amount of CaCO3 to Ni(OH)2 , with an electrode, as the negative electrode, of an LaNi5 hydrogen storage alloy made up by substituting Ce for a specific amount of La. SOLUTION: As for a positive electrode, powder of CaCO3 is added by 1 to 4 wt.% to, and mixed with, powder of a positive-electrode active material of Ni(OH)2 , a water solution of a viscosity improver is added to, and kneaded with, the mixture, and thus obtained positive-electrode active material mix paste is packed into a long, three-dimensional, net-like, porous metallic substrate. As for a negative electrode, a viscosity improver water solution is kneaded with powder of a hydrogen storage alloy, as an LaNi5 hydrogen storage alloy, expressed by a fixed expression and made up by substituting Ce for 5 to 20% of La and substituting Co and Al for part of Ni, and thus obtained negative- electrode active material slurry is spread over a long porous metallic substrate, such as punching metal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a nickel-metal hydride battery.

[0002]

2. Description of the Related Art Conventionally, nickel-metal hydride batteries have been widely used in portable equipment, emergency power supplies, and the like because of their high energy density, high durability against overcharge and overdischarge, and good life performance. In order to increase the high energy density as a negative electrode of a nickel-metal hydride battery, LaN having a large hydrogen storage amount is used.
i ₅ hydrogen storage alloy, particularly about 20% of Ni in order to suppress the pulverization of the practical alloy Co, at high temperature with an alloy of several percent of the Ni was replaced by Al in order to adjust the equilibrium pressure To enhance the charging efficiency, Ni (O
It has been proposed to use a material obtained by adding a small amount of calcium carbonate to H) ₂ . In addition, it is common to add a cobalt compound to the positive electrode in order to improve conductivity.

[0003]

However, as described above, when CaCO ₃ is added to the nickel electrode of a nickel-metal hydride battery, the deterioration of the negative electrode during charge and discharge is accelerated due to the influence of the carbonate group. It was found that there was an adverse effect of shortening the life. In view of this point, it is desired to develop a nickel-metal hydride battery that enhances charging efficiency at a high temperature, prevents corrosion of the negative electrode, and improves battery life.

[0004]

SUMMARY OF THE INVENTION Ni (OH) is used as a positive electrode.
_{A combination of a} nickel electrode obtained by adding 1 to 4% by weight of CaCO ₃ to ₂ and an electrode made of a LaNi ₅ -based hydrogen storage alloy obtained by replacing 5 to 20% of La with Ce as a negative electrode. Nickel-metal hydride battery.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be exemplified. As the positive electrode, a powder of a positive electrode active material Ni (OH) ₂ and 1 to 4% by weight of CaCO ₃ added thereto as a powder,
An aqueous solution of a thickener such as a CMC aqueous solution is added to the mixture, and the mixture is kneaded with 35 to 45% by weight of the mixture, and the obtained positive electrode active material mixture paste is mixed with a tertiary foamed nickel substrate or the like. The original reticulated porous metal substrate is filled, heated, dried, pressed, and cut to produce a large number of Ni plates having predetermined dimensions. In addition, powder of a cobalt compound such as cobalt oxide such as CoO of metallic cobalt may be added to the above-described mixture as needed in an amount of 5 to 10% by weight with respect to the positive electrode active material in order to improve the utilization rate of the active material. Preferred and general.

On the other hand, as a negative electrode, a LaNi ₅ -based hydrogen storage alloy having a general formula L in which 5 to 20% of La is replaced by Ce and a part of Ni is replaced by Co and Al.
_{a 1 Ce y Ni 5-ab} Co a Al b ( in茲y = 0.05
~ 0.20, a = 0.5 ~ 1.5, b = 0.1 ~ 1.
20% by weight of an aqueous solution of a thickener such as a 1% CMC aqueous solution is kneaded with the hydrogen storage alloy powder represented by 0), and the obtained negative electrode active material slurry is applied to a porous metal substrate such as a long punching metal. Then, heating, drying, pressing, and cutting are performed to produce a large number of hydrogen storage electrodes (MH plates) having predetermined dimensions.

[0007] The desired number of nickel electrodes and the predetermined number of hydrogen storage alloy electrodes thus obtained are laminated via a synthetic resin separator to form an electrode plate group, which is housed in a battery case, and is charged with KOH or KOH. A predetermined amount of an alkaline electrolytic solution composed of an aqueous solution containing KOH as a main component and a small amount of NaOH and / or LiOH added thereto, and a battery case lid was provided, thereby producing a sealed nickel-metal hydride battery. As a result, a nickel hydrogen battery having good discharge characteristics at high temperatures and a long life was obtained.

As will be described in detail below, when the addition amount of CaCO _{3 in} the nickel electrode is in the range of 0 to 4%, the discharge capacity at room temperature can be maintained satisfactorily.
Since the maximum discharge capacity at a high temperature can be obtained when the addition amount of aCO ₃ is 3%, it is preferable to limit the amount to 1 to 3% from an economic viewpoint. On the other hand, Ca for Na (OH) ₂
When a nickel electrode having an addition amount of CO ₃ in the range of 1 to 4% is used as a positive electrode, the charge and discharge of a nickel-metal hydride battery using the above-mentioned LaNi ₅ -based hydrogen storage alloy electrode as a negative electrode is affected by carbonate groups. In order to prevent the corrosion deterioration of the negative electrode, it is necessary to use C
It was found that the longest life was maintained when the substitution rate of e was in the range of 5 to 20%.

After all, in order to obtain a nickel-metal hydride battery having high discharge characteristics at a high temperature and preventing corrosion deterioration of the negative electrode and having improved life characteristics, 1 to 4% of CaCO with respect to Ni (OH) ₂ is used as the positive electrode. It has been found that the object can be achieved by combining an Ni electrode containing ₃ and an electrode made of a LaNi ₅ -based hydrogen storage alloy in which 5 to 20% of La is replaced with Ce as a negative electrode.

Next, a number of test examples in which the amount of CaCO ₃ added in the Ni electrode and the substitution ratio of Ce to La in the hydrogen storage alloy are varied are described in detail below. [Comparative Test Example] Ni (OH) 92.5-X parts by weight of ₂ powder, CaCO ₃ powder X-parts, 7.5 parts by weight of CoO powder (0 indicating the value of X in the following Table 1 in茲, 0.5, 1, 2,
3, 4) and 1.0% CMC
An aqueous solution of a thickening agent composed of an aqueous solution was added at 40% by weight, and kneaded to prepare six kinds of positive electrode active material mixture pastes having different addition amounts of CaCO _2.
m, filling into a long nickel foam substrate with a basis weight of 600 g / m ² , drying by heating, pressing and cutting, width 70 mm, length 1
A large number of six types of Ni plates each having a thickness of 60 mm and a thickness of 0.4 mm were produced. On the other hand, La _1-y Ce _y Ni _3.5 C
o _1.0 Al _0.5 (the value of the substitution rate y is shown in Table 1 below)
(2.5, 5, 10, 20, 30 shown in Table 1) were prepared as powders, and each paste was mixed with an aqueous solution of a thickener consisting of a 1.0% CMC aqueous solution.
0% by weight, kneaded, thickness 0.1 mm, porosity 40
% Of punching metal, heated and dried, pressed and cut to prepare a large number of six types of hydrogen storage alloy electrode plates having a width of 70 mm, a length of 160 mm and a thickness of 0.4 mm, that is, MH plates. As shown in Table 1, 36 types of Ni electrode plates having different addition amounts of CaCO ₃ and six types of MH electrode plates having different substitution amounts of Ce to La were obtained as shown in Table 1. Was manufactured.

[0011]

[Table 1]

The above-mentioned various nickel-metal hydride batteries were manufactured as follows, and the discharge characteristics at normal temperature of 20 ° C. and the high temperature of 50 ° C. and the charge / discharge cycle life test were performed as follows. That is, the 24 Ni plates and the 25 MH plates have a width of 170
The separator is laminated via a long zigzag sulfonated PP separator folded into a long zigzag shape, placed in a metal battery case, and hermetically sealed with a battery case lid.
200 cc of an alkaline electrolyte containing KOH as a main component was injected under reduced pressure, activated for several cycles, charged at 20 ° C. at 6 A for 24 hours, allowed to stand for 8 hours, and then charged at 24 A
, And the capacity at 20 ° C. was measured.
After charging at 6 A for 24 hours at an environmental temperature of 50 ° C., the battery was left at 20 ° C. for 8 hours.
At a temperature of 50 ° C. Furthermore, each battery has a capacity of 12 A × 12 at 20 ° C.
The battery was charged for 1 hour and discharged at 24 A to 1 V, and subjected to a cycle life test. The test results are shown in FIGS.
FIG. 1 shows the respective discharge characteristics at 20 ° C. and 50 ° C. when the substitution ratio of Ce to La is 10%, but as long as the substitution ratio is in the range of 5 to 20%, Whatever the value of the rate was changed, CaCO ₃
Since the relationship between the amount of addition and the value of the discharge capacity thereof has substantially the same discharge characteristics as that shown in FIG. 1, the relationship in the case where the substitution ratio of Ce is 10% is typical in the case where the substitution ratio of Ce is 10%. The illustration is omitted.

The following can be seen from Table 1, FIG. 1 and FIG. That is, as is clear from FIG.
In the case of, the discharge capacity is maximum when CaCO ₃ is not added, and the discharge capacity decreases as the added amount increases,
In order to maintain a discharge capacity of 100 AH or more, it is preferable that the addition amount of CaCO ₃ is limited to 4% or less. The addition amount of ₃ must be at least 1%, and then the discharge capacity also increases with the increase of the addition amount, shows a maximum value at the addition amount of 3%, and thereafter starts to decrease, so that the discharge capacity is maintained at 100 AH or more. It is found that it is preferable to set the upper limit to 4%, and in the end, when the amount of CaCO ₃ added is in the range of 1 to 4%, high discharge characteristics are obtained. On the other hand, as is apparent from FIG.
When the addition amount of aCO ₃ is in the range of 0 to 4%, the hydrogen storage alloy constituting the negative electrode has a Ce substitution ratio with respect to La of 5 to 20% and CaCO ₃ in the range of 0 to 4%. The charge / discharge cycle life also shows the maximum value of 1200 cycles. Therefore, when FIGS. 1 and 2 are summarized, it is necessary to use Na (OH) to improve the battery life as well as the discharge characteristics at high temperatures. A nickel-metal hydride battery comprising a combination of a nickel electrode having an addition amount X of calcium carbonate with respect to ₂ of 1 to 4% and an MH electrode made of a LaNi ₅ -based hydrogen storage alloy having a substitution ratio of Ce to La of 5 to 20%. It turned out to be a choice. If a nickel-metal hydride battery that achieves this purpose is selected from Table 1, Test Examples 15, 16, 17, 21, 22, 23, and 2
It can be seen that a combination of the Ni pole and the MH pole of 7, 28, 29, 33, 34 and 35 is an embodiment of the present invention. In the table, test examples corresponding to these examples are underlined for easy understanding.

[0014]

As described above, according to the present invention, CaC
In a nickel-metal hydride battery having a Ni electrode to which o ₃ is added as a positive electrode and a LaNi ₅ hydrogen storage alloy electrode as a negative electrode,
When combining an Ni electrode in which the addition amount of aCo ₃ is in the range of 1 to 4% with respect to Ni (OH) ₂ and an electrode composed of a LaNi ₅ -based hydrogen storage alloy electrode in which La is replaced with Ce by 5 to 20%. The present invention provides a nickel-metal hydride battery having improved charge-discharge cycle life by improving discharge characteristics particularly at high temperatures and preventing the negative electrode from being corroded by carbonate.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a change in the amount of CaCo ₃ added to a Ni electrode and a discharge capacity of a nickel-metal hydride battery.

FIG. 2 is a diagram showing the relationship between the cycle life of a nickel-metal hydride battery and the change in the substitution ratio of Ce to La in a LaNi ₅ hydrogen storage alloy electrode.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Shirai 23-6 Tsukubashicho, Iwaki-shi, Fukushima Pref. 23-6 Iwaki Furukawa Battery Co., Ltd. Chome 2-1 Tohoku Electric Power Co. R & D Center (72) Inventor Fumio Sato 7-2-1 Nakayama Aoba-ku Aoba-ku Sendai City Miyagi Prefecture Tohoku Electric Power Co. R & D Center (72) Inventor Ken Koyama Miyagi 7-2-1, Nakayama, Aoba-ku, Sendai-shi Tohoku Electric Power Company R & D Center

Claims (1)

[Claims] 1. A cathode comprising Ni (OH) _{2 and} CaC
A nickel electrode obtained by adding 1 to 4% by weight of O ₃ , and a LaNi obtained by replacing 5 to 20% of La with Ce as a negative electrode
A nickel-metal hydride battery, which is combined with an electrode made of a _5- system hydrogen storage alloy.