JPH03108273A - Manufacture of nickel hydrogen secondary battery - Google Patents

Abstract

PURPOSE:To obtain high battery voltage from the initial stage by filling an electrolyte into a container storing a hydrogen storage alloy electrode containing preset elements at the preset composition and an unsintered nickel oxide electrode, holding it at a preset temperature for a preset period, then initially charging it. CONSTITUTION:The composition of a hydrogen storage alloy is shown by ABX, where A is one kind of rare earth elements including La, B is one of Ni, Co, Mn, Al, B, Cu, Zr, and V, and X is 4.8-5.2. An electrode with this composition is used as a negative electrode, an unsintered nickel oxide electrode is used as a positive electrode, they are stored in a battery container, and an electrolyte is filled. lt is left intact at 35-70 deg.C for three hr or longer, the distribution of the electrolyte in a battery is unified, and the current distribution is unified at the time of initial charging. High voltage is obtained from the initial stage of the charge/discharge cycle, and the secondary battery with little rise of the internal pressure of the battery and no leakage of the electrolyte is obtained.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a nickel-metal hydride secondary battery, and in particular improves the process from injecting an electrolyte to initial charging. Pertains to a method for manufacturing a nickel-metal hydride secondary battery.

(Prior Art) In recent years, with advances in electronic technology, various electronic devices have become portable, and with advances in packaging technology, there has been an increasing demand for the use of batteries in large electronic devices. Accordingly, a high-capacity secondary battery is desired as a battery that can be used in the large-sized electronic devices.

As a secondary battery that can handle this increase in capacity, for example, L
A nickel-hydrogen secondary battery is known in which a hydrogen storage alloy electrode containing a hydrogen storage alloy having a composition such as aNi5 is used as a negative electrode, and a non-sintered nickel oxide electrode containing nickel hydroxide is used as a positive electrode. ing. Compared to nickel-cadmium secondary batteries that use a cadmium electrode for the negative electrode, this nickel-metal hydride secondary battery uses the hydrogen storage alloy electrode for the negative electrode, so it does not cause environmental pollution. 2) It has excellent battery characteristics, and 2) the negative electrode has a high energy density per unit weight and unit volume, and the capacity of the negative electrode can be increased, so it can respond to higher capacity.

Conventionally, in the manufacturing method of the nickel-metal hydride secondary battery, a hydrogen storage alloy electrode and a non-sintered nickel oxide electrode are housed in a battery container, an electrolyte is injected into the battery container, and the battery is sealed. After assembly, the first charge was performed to obtain a nickel-metal hydride secondary battery.

However, when nickel-metal hydride secondary batteries manufactured using conventional methods are repeatedly charged and discharged, the internal pressure of the battery increases significantly due to the generation of gas within the battery at a relatively early stage of the charge/discharge cycle. There was a problem in which liquid sometimes leaked from the safety valve.

For these reasons, there are two methods: ■ Adding a catalyst to the hydrogen storage alloy electrode to promote the gas absorption reaction; ■ Preventing surface deterioration by immersing the hydrogen storage alloy powder or hydrogen storage alloy electrode in an alkaline solution. A method for fabricating hydrogen storage alloy electrodes has been proposed.

However, even in nickel-metal hydride secondary batteries incorporating hydrogen storage alloy electrodes fabricated by this method, it is difficult to sufficiently prevent the rise in battery internal pressure due to gas generation inside the battery at a relatively early stage of the charge/discharge cycle. The problem was that it could not be suppressed. In addition, the method using the catalyst uses an expensive catalyst, which increases the manufacturing cost of the battery, and the method of treating the hydrogen storage alloy with an alkaline solution requires complicated treatment and is difficult to work in. There was a problem that the safety of

(Problems to be Solved by the Invention) The present invention has been made to solve the conventional problems, and it is an object of the present invention to suppress the large increase in battery internal pressure at a relatively early stage of the charge/discharge cycle, and to prevent the electrolyte from forming a safety valve. The purpose of the present invention is to provide a method for safely and inexpensively manufacturing a nickel-metal hydride secondary battery that can prevent leakage from the nickel-metal hydride secondary battery and can sufficiently handle increased capacity.

[Structure of the Invention] (Means for Solving the Problems) The present invention involves injecting an electrolytic solution into a battery container containing a hydrogen storage alloy electrode and a non-sintered nickel oxide electrode,
This is a method for manufacturing a nickel-metal hydride secondary battery, characterized in that initial charging is performed after leaving the battery at 5 to 70°C for 3 hours or more.

The hydrogen-absorbing alloy electrode has a structure in which a mixture of hydrogen-absorbing alloy powder, a polymer binder, and conductive powder is coated and fixed on a conductive core as a current collector. have

The hydrogen storage alloy to be added to the mixture is not particularly limited, and may be one that can store hydrogen electrochemically generated in the electrolyte and easily release the stored hydrogen during discharge. In particular, AB, (where A is at least one rare earth element including La,
B is Nis Co 5Mn5ADs B5Cu, Zr
It is at least one element selected from the group consisting of and, and X is 4.8 to 5.2. ) is preferably used.

Examples of the polymer binder blended in the mixture include sodium polyacrylate, polytetrafluoroethylene (
PTFE), carboxymethyl cellulose (CMC)
etc. can be mentioned. The blending ratio of the polymer binder is 0.5 to 100 parts by weight of the hydrogen storage alloy powder.
It is desirable that the amount is in the range of 5 parts by weight.

Examples of the conductive powder blended in the mixture include carbon black and graphite. The blending ratio of the conductive powder is 100% of the hydrogen storage alloy powder.
It is desirable that the amount is 0.1 to 4 parts by weight.

Examples of the conductive core that is the current collector include those with a two-dimensional structure such as punched metal, expanded metal, and wire mesh, and those with a three-dimensional structure such as foamed metal and reticulated sintered metal fiber. I can do it.

The non-sintered nickel oxide electrode is produced by, for example, filling a sintered fiber substrate, a foamed metal substrate, a nonwoven plated substrate, a bunched metal substrate, or the like with a paste containing nickel hydroxide.

The reason why the storage conditions are limited in the present invention is that if the storage time is less than 3 hours or the storage temperature is less than 35°C, the electrolyte will not be sufficiently dispersed inside the battery, whereas the storage temperature is 70°C. If it exceeds the hydrogen storage alloy surface, a film is formed on the surface of the hydrogen storage alloy, which prevents the gas absorption reaction inside the battery from occurring smoothly, resulting in a significant increase in the battery internal pressure at a relatively early stage of the charge/discharge cycle.

(Function) According to the present invention, by injecting the electrolyte into the battery container and performing the initial charge after leaving it at a temperature within the range of 35 to 70°C for 3 hours or more, the battery can be charged at a relatively early stage of the charge/discharge cycle. It is possible to obtain a nickel-metal hydride secondary battery in which a significant increase in battery internal pressure is suppressed.

In other words, the present inventors investigated the causes of a significant increase in battery internal pressure at a relatively early stage of the charge/discharge cycle in nickel-metal hydride secondary batteries manufactured using conventional methods. It was found that this is due to non-uniform current distribution due to non-uniform distribution of electrolyte inside the battery during charging. Furthermore, it has been found that even if the electrolyte distribution becomes uniform after the first charge and the current distribution becomes uniform during subsequent charging and discharging, the above-mentioned problem cannot be solved.

Therefore, in the present invention, by injecting the electrolyte into the battery container and leaving it for 3 hours or more at a temperature within the range of 35 to 70°C, the distribution of the electrolyte inside the battery becomes uniform, and the initial charging The current distribution at the time can be made uniform. As a result, gas absorption reactions occur smoothly at the positive and negative electrodes during subsequent charging and discharging, so that a significant increase in battery internal pressure at a relatively early stage of the charging and discharging cycle can be suppressed. Furthermore, the method of the present invention does not require the use of expensive catalysts or treatment with an alkaline solution, so that nickel-metal hydride secondary batteries can be produced safely, at low cost, and more easily.

In addition, ABX (However, A is at least one kind of rare earth element including La, B is NIS Co, Mn, A
At least one element selected from the group consisting of Ω, B s Cu s Z r, and X is 4.8 to 5
．． It is 2. ) By using a hydrogen storage alloy electrode containing a hydrogen storage alloy having the composition shown in (1), it is possible to more effectively suppress a significant increase in battery internal pressure at a relatively early stage of a charge/discharge cycle. This is considered to be because the wettability of the surface of the hydrogen storage alloy electrode with respect to the electrolytic solution is improved, and the distribution of the electrolytic solution inside the battery at the time of initial charging tends to be more uniform.

Furthermore, according to the present invention, a nickel-metal hydride secondary battery capable of increasing capacity can be obtained by using an elementary storage alloy electrode and a non-sintered nickel oxide electrode.

(Example) Examples of the nickel-metal hydride secondary battery of the present invention will be described in detail below.

First, L111Ni4.2CO0, 2Mno, 3AM
A hydrogen storage alloy having a composition of 0.3 (Lm; La-enriched metal) was made to absorb and release hydrogen twice and was pulverized, and 200 mesh baths of hydrogen storage alloy powder were used. Next, a paste was prepared by adding PTFE as a polymer binder, carbon black as a conductive powder, and water to the hydrogen storage alloy powder, and then this paste was applied to a bunched metal with a nickel-plated N4 temporary hole. A negative hydrogen storage alloy electrode was prepared by coating, drying, and pressing.

On the other hand, after preparing a paste whose main composition was nickel hydroxide and cobalt oxide, this paste was filled into a sintered fiber substrate, dried, and pressed to produce a non-sintered nickel oxide electrode as a positive electrode.

The hydrogen storage alloy electrode and the non-sintered nickel oxide electrode were made of polyamide with a thickness of 0.20m1I! An electrode group was prepared by winding the electrode through a thick nonwoven fabric. This electrode group was inserted into the AA size space of an acrylic resin container equipped with a pressure detector, and an electrolytic solution of 8N potassium hydroxide was poured into this space, the seal was sealed, and the space was sealed as shown in Figure 1. The test cell was assembled.

That is, this test cell includes a battery case consisting of the case body 1 and the cap 2 made of the acrylic resin. A space 3 having the same inner diameter and height as the metal container of an AA size battery is formed in the center of the case body 1, and an electrode group 4 is housed inside this space 3, and an electrolyte is also contained in the space 3. is accommodated. The cap 2 serves as a sealing plate, and a pressure detector 5 is attached to the cap 2 so that the internal pressure of the battery can be detected. The cap 2 is airtightly fixed onto the case body 1 with bolts 8 and nuts 9 via a rubber sheet 6 and an O-ring 7. A negative electrode lead 10 from the hydrogen storage alloy negative electrode and a positive electrode lead 11 from the non-sintered nickel positive electrode are led out through between the rubber sheet 6 and the O-ring 7.

This assembled test cell was tested at temperatures of 25°C, 35°C, and 45°C.
, placed in a thermostat at 70°C and 80°C for 0.5 hours, 1 hour, 2 hours, 3 hours, 6 hours, 12 hours, 24 hours, 4 hours.
It was left to stand for 8 hours, 72 hours, and 120 hours. Subsequently, after being left at room temperature (25°C) for 1 hour and cooling, 0.
Initial charging was performed for 15 hours using IC current.

Regarding the test cell that was initially charged, ■Discharge capacity until the discharge voltage becomes 1V or less when performing IC discharge, ■Battery voltage when half of its capacity is discharged, ■5C
When discharging, measure the discharge capacity until the discharge voltage becomes 1V or less, and ■ the maximum value of the battery internal pressure, and based on these measurement results, determine the rise characteristics of the battery voltage,
The battery life and battery internal pressure were examined. These results are shown in Tables 1 to 3 below. In addition, Table 4 also includes Tables 1 to 4.
Table 3 shows the overall evaluation. The rise characteristics, battery life, battery internal pressure, and overall evaluation were evaluated as follows.

(1) Rise characteristic 0: The battery voltage at the second cycle did not decrease by 20 mV or more compared to the battery voltage at the 10th cycle, and even at a large current discharge of 5C, it did not decrease significantly compared to IC discharge.

×...■The battery voltage at the 2nd cycle has decreased by 2 hV or more compared to the battery voltage at the 10th cycle, and at least one of the following has occurred: ■The battery voltage at the 2nd cycle has decreased by 2 hV or more compared to the battery voltage at the 10th cycle; Applicable.

(2) Battery life indicates the number of charging/discharging cycles when the discharge capacity decreases to 80% or less of the second cycle discharge capacity.

(3) Battery internal pressure O: The maximum value of the battery internal pressure was 15 kg/cm2 or less.

×...The maximum value of the battery internal pressure exceeded 15 kg/cm2.

(4) Overall rating: 0: 0 in Table 1, the number of cycles in Table 2 is approximately 500 cycles or more, and 0 in Table 3.

X...■×1 in Table 1■Number of cycles in Table 2 is 5
Significantly smaller than about 00 cycles, ■ × in Table 3,
At least one of the following applies.

Table 3 Table 4 Table 4 (Comprehensive evaluation) As is clear from Table 1, in order to generate a higher voltage than at the beginning of the cycle, it is better to keep the storage temperature at 70 degrees or lower and increase the storage time. I understand. In addition, it has been found that, in practice, satisfactory results can be obtained by leaving it for approximately 3 hours or more.

As is clear from Table 2, in order to obtain a life of about 500 cycles or more, which is the desired life for an alkaline secondary battery, it was found that it is only necessary to leave it at a temperature within the range of 35 to 70°C for 3 hours or more. . If the storage temperature is 25℃, the storage time will be longer (it is true that the lifespan will be extended, but 1
Even when left for 20 hours, only about 200 cycles were achieved. Furthermore, when the temperature was 80° C., the lifespan was extended up to 6 hours, but when left for longer than that, the lifespan was shortened. In order to investigate the cause of this, a battery that had been left at 80°C was disassembled and the charging and discharging behavior of the electrodes was examined by cyclic portamometry, and the formation of a film on the surface was observed. From this, it was found that if left at 80''C, some kind of reaction would occur between the electrode and the electrolyte, changing the capacity balance of the positive and negative electrodes and reducing the lifespan.

As is clear from Table 3, when the temperature at which the battery was left was 25°C or the time at which it was left for two hours or less, the internal pressure of the battery increased significantly. In addition, batteries with high internal pressure tend to operate the safety valve, which may stain the inside of the device that houses the battery with alkaline electrolyte, and also cause a decrease in battery capacity due to a lack of electrolyte, making it difficult to use for practical use. It's not something you can do.

As is clear from Table 4, which comprehensively evaluates the above results, in the method of the present invention, in which the initial charge is performed after injecting the electrolyte and leaving it for at least 3 hours in the temperature range of 35 to 70°C, the charge/discharge cycle It is possible to obtain a nickel-metal hydride secondary battery that can obtain a higher battery voltage than the initial one, has a sufficiently long battery life, and has a small increase in battery internal pressure as the charge/discharge cycle progresses, thereby preventing electrolyte leakage. I realized that.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to suppress a significant increase in battery internal pressure at a relatively early stage of a charge/discharge cycle, and prevent leakage of electrolyte from a safety valve. It is possible to provide a method for safely and inexpensively manufacturing a nickel-metal hydride secondary battery that can sufficiently handle increased capacity.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a test cell used in an example of the present invention. 1... Case body, 2... Cap, 4... Electrode group, 5... Pressure detector.

Claims (2)

[Claims] (1) Inject the electrolyte into the battery container containing the hydrogen storage alloy electrode and the non-sintered nickel oxide electrode, and
A method for manufacturing a nickel-metal hydride secondary battery, characterized in that the first charge is carried out after being left at 70°C for 3 hours or more. (2) The hydrogen storage alloy electrode is AB_X (where A is at least one rare earth element including La, and B is N
at least one element selected from the group consisting of i, Co, Mn, Al, B, Cu, Zr, and X is 4
．． 8 to 5.2. 2. The method for manufacturing a nickel-metal hydride secondary battery according to claim 1, further comprising a hydrogen storage alloy having a composition represented by: