JPH07135019A - Hydride secondary battery - Google Patents

Abstract

PURPOSE:To provide a hydride secondary battery excellent in a capacity holding characteristic by decreasing a self discharge. CONSTITUTION:A battery is manufactured by using a positive electrode, negative electrode, electrolyte and a separator not containing impurities such as causing self discharge reaction. As this concrete means, the electrolyte used in the battery and a preservation liquid of the positive electrode, negative electrode, separator, etc., (immersing condition: positive electrode is 1.5ml/g per active material weight, negative electrode is 1.0ml/g per active material weight, separator is 10ml/g per weight, preserved for 24 hours at 90 deg.C) are used as an electrolyte, to build a model cell with platinum serving as an operating electrode. Here in this current density-potential curve, after holding for 0.5hrs by -0.95V (vs. Hg/HgO) at 25 deg.C, the positive electrode, negative electrode, electrolyte and the separator with -0.5V to 0V peak anode current density in 0.05mA/cm<2> or less (0.02mA/cm<2> or less in the case of not holding by -0.95V) are used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydride secondary battery, and more particularly, to a hydride secondary battery having less self-discharge and excellent capacity retention characteristics.

[0002]

2. Description of the Related Art A hydride secondary battery using a hydrogen storage alloy as a negative electrode active material has the ability to store and release a large amount of hydrogen, and electrochemically stores and releases hydrogen even in an alkaline aqueous solution. When a nickel electrode is used for the positive electrode, a battery reaction occurs as in the following equation.

[Positive electrode] Ni (OH) ₂ + OH ⁻ ⇔ NiOOH + H ₂ O + e ⁻ (1) [Negative electrode] M + H ₂ O + e ⁻ ⇔ M (H) + OH ⁻ (2) M in the formula (2) is a hydrogen storage alloy. Indicates.

In the equations (1) and (2), the reaction proceeds to the right in charging. That is, as shown in the formula (2), the hydrogen storage alloy M of the negative electrode electrolyzes water (H ₂ O) in the alkaline aqueous solution and stores hydrogen to be in a state shown by M (H). (OH ⁻ ) is generated, and as shown in formula (1), the hydroxyl group (OH ⁻ ) reacts with nickel hydroxide [Ni (OH) ₂ ] of the positive electrode to become NiOOH, and water (H ₂ O) is generated. .

In the case of discharge, this reverse reaction occurs, and the reaction proceeds leftward in the equations (1) and (2).
That is, in the negative electrode, hydrogen is occluded by charging and hydrogen is released by discharging.

However, this hydride secondary battery is prone to self-discharging as described below during storage and tends to lose its capacity.

For example, impurities eluted from the separator into the electrolytic solution cause a shuttle reaction as shown in equations (3) and (4), resulting in loss of capacity. Therefore, the separator has been improved by, for example, subjecting the separator to sulfonation (Japanese Patent Laid-Open No. 64-57568).

[0008] [negative] ^{_{6M (H) + NO 2 -}} → 6M + NH 3 + H 2 O + OH - (3) [Positive Electrode _{6NiOOH + NH 3 + H 2 O} + OH - → 6Ni (OH) 2 + NO 2 - (4)

Further, such a nitrate ion nickel nitrate remaining as an impurity in nickel electrode (NO ₃ ^-)
Elute in the electrolyte, and the nitrate ions cause the battery to self-discharge.

Therefore, it has been attempted to reduce nitrate radicals remaining as impurities in the nickel electrode (Japanese Patent Laid-Open No. Sho 5).
0-31335).

The amount of impurities that elute in the electrolytic solution to cause self-discharge of the battery is determined by the ion chromatographic analysis of the electrolytic solution or the capacity retention characteristic of actually assembling the battery, that is, the capacity retention rate accompanying storage. It can be determined by measuring the change in

However, analysis of impurities (cations and anions) in an alkaline aqueous solution requires time for sample preparation, and the ionic species that can be analyzed are also limited. In particular, the cation analysis is liable to be erroneous because the aqueous alkali solution contains alkali metal ions (K ⁺ , Li ⁺ , Na ⁺ ).

Also, when measuring the capacity retention characteristics of a battery, a holding period must be provided, and therefore, there is a problem that a considerable time is required for the measurement.

[0014]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems that conventional hydride secondary batteries have, and provides a battery as a battery constituent member such as a positive electrode, a negative electrode, an electrolytic solution, and a separator. It is an object of the present invention to provide a hydride secondary battery that allows the capacity retention characteristics at that time to be easily estimated, has less self-discharge, and has excellent capacity retention characteristics.

[0015]

Means for Solving the Problems A positive electrode, a negative electrode, a separator and the like used in a battery are immersed in an alkaline aqueous solution which can be used as an electrolytic solution in advance, and stored under predetermined conditions as an electrolytic solution. By assembling a model cell using platinum and measuring its current density-potential curve, it is possible to easily and easily estimate the capacity retention characteristics when a battery is manufactured using them.

Further, regarding the electrolytic solution used for the battery,
By using it as an electrolyte and assembling a model cell with platinum as the working electrode and measuring the current density-potential curve, it is possible to easily and easily estimate the capacity retention characteristics when a battery is produced using the electrolyte. it can.

That is, the peak current in the potential range of −0.5 V to 0 V (vs. Hg / HgO) on the anode side in the above model cell causes oxidation of nitrogen compounds which cause self-discharge reaction of nitrate radicals, ammonium ions and the like. Therefore, the impurities can be identified.

By using a positive electrode, a negative electrode, an electrolytic solution, a separator and the like having a small oxidation current, it is possible to obtain a hydride secondary battery with less self-discharge and excellent capacity retention characteristics.

In order to obtain the above-described hydride secondary battery with less self-discharge and excellent capacity retention characteristics, the electrolytic solution, the positive electrode, the negative electrode, the separator and the like satisfy the following conditions. It is necessary.

That is, the electrolytic solution is the electrolytic solution,
When a model cell having platinum as a working electrode was assembled, its current density-potential curve showed -0.95 V at 25 ° C.
(Vs. Hg / HgO), after holding for 0.5 hour,
The peak anode current density in the range of 0.5V to 0V is 0.
It is necessary to be less than 05 mA / cm ² .

The positive electrode was prepared by adding an aqueous alkaline solution, which can be used as an electrolytic solution for a hydride secondary battery, in an amount of 1.
When a model cell having platinum as a working electrode was assembled by preserving the storage solution after being immersed at 5 ml / g for 24 hours at 90 ° C., its current density-potential curve was 25.
It is necessary that the peak anode current density in the range of -0.5V to 0V after holding for 0.5 hour at -0.95V (vs. Hg / HgO) at 0 ° C is 0.05 mA / cm ² or less. is there.

The negative electrode was prepared by adding an aqueous alkaline solution which can be used as an electrolytic solution for a hydride secondary battery, in an amount of 1.
When a model cell having platinum as a working electrode was assembled by preserving the electrolyte as a storage solution after soaking at 0 ml / g and holding it at 90 ° C. for 24 hours, the current density-potential curve showed a value of 25
It is necessary that the peak anode current density in the range of -0.5V to 0V after holding for 0.5 hour at -0.95V (vs. Hg / HgO) at 0 ° C is 0.05 mA / cm ² or less. is there.

The separator is used in an alkaline aqueous solution which can be used as an electrolytic solution of a hydride secondary battery in an amount of 10% by weight.
When a model cell having platinum as a working electrode was assembled by preserving the electrolyte as a preservative solution after being immersed in ml / g and held at 90 ° C for 24 hours, the current density-potential curve showed 25 ° C.
At -0.95V (vs. Hg / HgO) for 0.5 hour, the peak anode current density in the range of -0.5V to 0V needs to be 0.05 mA / cm ² or less. .

As described above, at −25 ° C., −0.95 V (v
s. Hg / HgO) is maintained for 0.5 hour to reduce the nitrogen-containing compound that causes self-discharge during storage of the battery and convert it to an ammonia component, thereby positive electrode, negative electrode, separator, and electrolyte solution. It is for facilitating the detection of the nitrogen-containing compound contained in the battery constituent member such as, and can be detected by such reduction when scanning without holding at −0.95V as described above. Since such a thing is not detected, it is necessary that the electrolytic solution, the positive electrode, the negative electrode, and the separator all have a peak anode current density in the range of −0.5 V to 0 V of 0.02 mA / cm ² or less. .

The positive electrode is made of, for example, a sintered type in which a nickel sintered body is used as a base material and nickel oxide or nickel hydroxide is held therein, or wire mesh, metal fiber, punching metal, expanded metal, metal foam or the like. A porous metal is used as a substrate, and nickel oxide or nickel hydroxide is attached or impregnated in a paste form into a sheet-shaped molded body by a paste method or the like. It is also possible to use a known nickel electrode produced by a binding method or a paste method.

However, this positive electrode is required to have a peak anode current density of not more than the specific value in the above model cell, and those which do not satisfy such conditions are immersed in an alkaline aqueous solution. It is necessary to use it for battery assembly after satisfying the conditions.

As the nickel oxide and nickel hydroxide used for the positive electrode, for example, nickel monoxide (N
iO), nickel dioxide (NiO ₂ ), nickel hydroxide [Ni (OH) ₂ ], and the like. However, these are cases where the positive electrode is in a discharged state, and when the positive electrode is in a charged state, the above nickel oxide and nickel hydroxide exist as other compounds.

The negative electrode uses a hydrogen storage alloy as an active material. As this hydrogen storage alloy, for example, V-Ti-Zr-Ni-Cr-Co-F used in Examples described later is used.
e-Mn-based hydrogen storage alloy, V-Ti-Zr-Ni-
Including Cr-Co-Fe based hydrogen storage alloys, Ti-N
i-based, Ti-Ni-Zr-based, (Ti _2-x Zr _x V _4-y N
i _y ) _1-Z Cr _Z (x: 0 to 1.5, y: 0.6 to 3.
5, z: 0.2 or less) (USP4728586) system, T
A hydrogen storage alloy such as i-Mn-based, Zr-Mn-based, and MmNi ₅ -based can be used.

This negative electrode may be manufactured by either a sintering method (compression bonding method) or a paste method.

The method of producing the negative electrode by the sintering method is, for example, to use a porous metal such as a wire net, a metal fiber, a punching metal, and an expanded metal as a base material, and press-bond the powder of the hydrogen storage alloy thereto and heat-treat. Is a method of producing a negative electrode by means of a paste method, in which a powder of a hydrogen storage alloy is made into a paste together with a binder and the like, and the paste is attached or impregnated on a substrate made of the above porous metal and dried. After that, it is a method of producing a negative electrode by pressing with a press or the like.

As in the case of the positive electrode, this negative electrode also requires that the peak anode current density in the model cell be less than or equal to the specific value. Those that do not meet such conditions are alkaline aqueous solutions. It is necessary to immerse it inside so that the above conditions can be satisfied before it is used for battery assembly.

As the material of the separator, for example, nylon non-woven fabric, polypropylene non-woven fabric or the like can be used.

However, similarly to the case of the positive electrode, the negative electrode, etc., this separator also needs to have the peak anode current density of the specific value or less in the above model cell, which does not satisfy such a condition. It is necessary to immerse the product in an alkaline aqueous solution so as to satisfy the conditions and then to use it for battery assembly.

As described above, since this separator also needs to satisfy the above-mentioned conditions, it is suitable to use a polypropylene nonwoven fabric treated with plasma, grafted or sulfonated, which easily satisfies such conditions. ing.

The electrolytic solution is composed of an alkaline aqueous solution,
As the alkaline aqueous solution, for example, an aqueous solution of an alkali metal hydroxide such as sodium hydroxide, potassium hydroxide or lithium hydroxide is used.

However, this electrolytic solution also requires that the peak anode current density be less than or equal to the specific value in the model cell as in the case of the positive electrode, the negative electrode, the separator, and the like. Those that do not satisfy the above condition must satisfy the above conditions before being used for battery assembly.

[0037]

EXAMPLES First, the negative electrode, positive electrode and separator used in the examples were prepared as follows.

Negative electrode: commercially available Ti, Zr, V, Ni, C
r, Co, Fe, Mn (all have a purity of 99.9% or more)
Each sample was blended so that the alloy composition would be the following composition, and heated and melted in a high frequency melting furnace to obtain a multiphase alloy.

V ₁₅ Ti ₁₅ Zr ₂₁ Ni ₂₉ Cr ₅ Co ₆ Fe
₁ Mn ₈ [ _NA alloy: (Ti _0.42 Zr _0.58 ) (V _0.23 Ni _0.45
Cr _0.08 Co _0.05 Fe _0.01 Mn _0.07 ) _1.78 ]

V ₁₅ Ti ₁₅ Zr ₂₁ Ni ₃₁ Cr ₆ Co ₆ Fe
₆ [NB alloy: (Ti _0.42 Zr _0.58 ) (V _0.23 Ni _0.48
Cr _0.09 Co _0.09 Fe _0.09 ) _1.78 ]

This alloy was evacuated to 10 ^-4 torr in a pressure vessel and purged with argon three times, then
By maintaining the hydrogen pressure at 14 kg / cm ² for 24 hours, exhausting the hydrogen and further heating at 400 ° C. to completely desorb the hydrogen, to obtain a hydrogen storage alloy powder having a particle size of 20 to 100 μm.

This hydrogen-absorbing alloy powder was pressure-bonded to a nickel current collector using a roll mill without using an organic binder, and in an atmosphere of Ar / H ₂ = 99/1, 875 ° C. × 12.
After holding for 30 minutes, cool to 30 ℃ and thickness 0.3mm
Thus, two types of negative electrodes (NA negative electrode and N-B negative electrode) were obtained in a sheet shape having a width of 38 mm and a length of 129 mm.

Positive electrode: Sintered nickel positive electrode is of a conventionally known type, that is, a nickel sintered body as a substrate is nickel nitrate [Ni (NO ₃ ) ₂ ] and cobalt nitrate [Co (NO ₃ ) ₂ ] It produced by the method of passing through the process of immersing in a mixed liquid of.

The produced positive electrode was washed with warm water at 90 ° C. for 8 hours. This sintered nickel positive electrode is indicated as P1-A positive electrode.
For comparison, a sintered nickel positive electrode manufactured in the same manner as above, which was not washed with warm water at 90 ° C., like the P1-A positive electrode, was designated as P1-0 electrode.

On the other hand, a paste type nickel positive electrode was prepared as follows. That is, nickel hydroxide (zinc 2%, cobalt 1% solid solution), nickel powder, cobalt powder, polytetrafluoroethylene dispersion (containing 60% polytetrafluoroethylene), and 2% carboxymethylcellulose aqueous solution in a weight ratio of 100. : 10:
The mixture was mixed at a ratio of 5: 5: 50, and the obtained paste-like material was impregnated into a nickel foam as a substrate.

Then, the nickel foam impregnated with the paste as described above is dried at 80 ° C. for 2 hours, and then 1 t.
on / cm ² and press at 80 ℃ alkali aqueous solution (3
After being dipped in 0% potassium hydroxide) for 2 hours, it is washed with warm water at 90 ° C. for 10 minutes to give a thickness of 0.60 mm and a width of 38.
A sheet-shaped positive electrode having a length of 88 mm and a length of 88 mm was produced. This is designated as P2-0 positive electrode.

Further, instead of rinsing with warm water of 90 ° C. for 10 minutes in the final step, a paste type nickel positive electrode was also prepared by rinsing with warm water of 90 ° C. for 1 hour.
A positive electrode was used.

Separator: The following five separators are used.
Types of non-woven fabrics, that is, commercially available nylon non-woven fabrics (S-
N), a commercially available polypropylene non-woven fabric having a wettability with a surfactant (SK), a commercially available polypropylene non-woven fabric subjected to plasma treatment (SP), and a commercially available polypropylene non-woven fabric graft-treated (S-). G), commercially available polypropylene non-woven fabric subjected to sulfonation treatment (S-
S) was used. The size of these five types of separators is
All have a thickness of 0.15 mm, a width of 40 mm, and a length of 235.
mm. The symbol in parentheses after each non-woven fabric is an abbreviation for each non-woven fabric constituting the separator.

The abbreviations of the negative electrodes, positive electrodes and separators and their outlines are summarized below.

N-A negative electrode: Composition is V ₁₅ Ti ₁₅ Zr ₂₁ N ₂₁
Negative electrode using hydrogen storage alloy of Cr ₅ Co ₆ Fe ₁ Mn ₈ as active material

N—B negative electrode: Composition is V ₁₅ Ti ₁₅ Zr ₂₁ Ni
₃₁ Negative electrode using hydrogen storage alloy of Cr ₆ Co ₆ Fe ₆ as active material

P1-A positive electrode: Sintered nickel positive electrode, which was produced and then washed with warm water at 90 ° C. for 8 hours.

P1-0 positive electrode: Sintered nickel positive electrode, which has not been washed with water after fabrication

P2-0 positive electrode: a paste-type nickel positive electrode that has been rinsed with warm water at 90 ° C. for 10 minutes after being prepared

P2-A positive electrode: a paste-type nickel positive electrode, which was prepared and washed with warm water at 90 ° C. for 1 hour.

Separator SN: Commercially available nylon non-woven fabric

Separator SK : Commercially available polypropylene non-woven fabric having wettability with a surfactant.

Separator SP : Commercial polypropylene non-woven fabric plasma-treated

Separator SG : Commercial polypropylene non-woven fabric graft-treated.

Separator S--S: Commercially available polypropylene non-woven fabric sulfonated

Example 1 50 m of each of the above-mentioned negative electrode, positive electrode and separator is 300 m
It was immersed in 1% aqueous 30% potassium hydroxide solution and stored at 90 ° C. for 24 hours.

Using this storage solution as an electrolyte, a platinum plate as a working electrode, a platinum plate as a counter electrode, and an Hg / Hg electrode as a reference electrode, the H-shaped model cell shown in FIG. 1 was assembled.
The current density-potential curve was measured at a scanning rate of 10 mV / sec at 0 ° C. The results are shown in FIGS. 2 to 5.

Prior to the description of FIGS. 2 to 5, FIG. 1 will be described. FIG. 1 is a schematic diagram schematically showing an H-shaped model cell. In FIG. 1, 1 is a working electrode made of a platinum plate, 2 is a counter electrode, and this counter electrode 2 is also made of a platinum plate.
3 is a reference electrode composed of an Hg / HgO electrode,
4 is a glass filter that functions as a separator, 5
Is an electrolytic solution containing the above-mentioned storage solution.

FIG. 2 is a current density-potential curve of a cell using a preserving solution of a sintered nickel positive electrode as an electrolytic solution, which is P1-0 [P1-0 positive electrode (calcined without washing treatment after fabrication. Preservative solution for positive electrode nickel)], -0.5
An anode peak is recognized in the range of V to 0V.

On the other hand, P1-A [sintered nickel positive electrode (P1-
A) storage solution], the current density in the range of −0.5 V to 0 V is the same as in the case of unused (30% potassium hydroxide aqueous solution in which a nickel-containing positive electrode such as a sintered nickel is not stored). It was 0.02 mA / cm ² or less, and almost no peak was observed.

FIG. 3 is a view showing a current density-potential curve of a cell using a paste type nickel positive electrode storage solution as an electrolytic solution.

As shown in FIG. 3, P2-A [after fabrication, 9
In a preservative solution of a paste-type nickel positive electrode (P2-A positive electrode) washed with warm water of 0 ° C. for 1 hour, the current density in the range of −0.5 V to 0 V was 0.02 m, as in the case of unused.
It was A / cm ² or less, and almost no peak was observed.

However, in P2-0 [a preservative solution of a paste-type nickel positive electrode (P2-0 positive electrode) which has been washed with warm water at 90 ° C. for 10 minutes after its preparation], -0.5 V to 0
An anode peak exceeding 0.5 mA / cm ² was observed in the V range.

FIG. 4 is a diagram showing a current density-potential curve of a cell using a negative electrode storage solution as an electrolytic solution.

As shown in FIG. 4, N-A (preserving liquid for N-A negative electrode) and N-B (preserving liquid for negative electrode N-B) appeared in the range of 0 mV or higher and were unused. No cobalt oxidation peak was observed, but no peak was observed in the -0.5V to 0V range.

FIG. 5 is a view showing a current density-potential curve of a cell using a separator storage solution as an electrolytic solution.

As shown in FIG. 5, S-N (a preservative solution for a separator S-N made of commercially available nylon nonwoven fabric) and S-K
(Separator S- made of commercially available polypropylene nonwoven fabric
The storage solution of K) is 0.5 m in the range of -0.5V to 0V.
An anode peak above A / cm ² was observed.

On the other hand, the storage solution (S
-P, S-G, and S-S), the current density in the range of -0.5 V to 0 V was 0.02 mA / cm ² or less, and no peak was observed.

FIG. 6 shows that the cell using the preservation solution of various separators as an electrolytic solution has a voltage of -0.95 V (Hg / HgO) of 0.
The current density-potential curve when hold | maintaining for 5 hours is shown.

As shown in FIG. 6, SN and SK are 0.05 in the range of -0.5V to 0V, as in the case of FIG.
A high anode peak above mA / cm ² was observed.

On the other hand, the storage solution (S
-P, S-G and S-S), no anode peak was observed in the range of -0.5V to 0V.

Example 2 A spirally wound electrode body was prepared by combining the N-A negative electrode, the positive electrode and the separator used in Example 1, and the spirally wound electrode body was placed in a metal battery container and made of a 30% potassium hydroxide aqueous solution. The electrolyte solution was injected, the positive electrode tab was spot-welded to the resin sealing body, the outermost peripheral portion of the negative electrode was brought into contact with the side surface of the battery container, and then sealed, to prepare an AA size hydride secondary battery. .

After the battery was manufactured, it was stored at 60 ° C. for 17 hours,
Charged at 0.1C (110mA) for 15 hours, then 0.2C
It was discharged to 1.0 V at (220 mA). This cycle was repeated until the discharge capacity became constant.

After the discharge capacity became constant, 0.1 C (1
It was charged at 10 mA) for 15 hours, stored at 20 ° C. for 30 days, and the remaining capacity was measured. The capacity before storage was set to 100%, and the capacity retention rate after storage was determined. The results are shown in Table 1.

[0080]

[Table 1]

As shown in Table 1, batteries (H1, I) using a combination of battery constituent members having no anode peak were used.
1, J1, R1, S1, T1) all showed a high capacity retention rate of 75% or more.

However, batteries (A1, B1, C1, D) having an anode peak in any one of the battery constituent members
1, E1, F1, G1, K1, L1, M1, N1, O
1, P1, Q1) all had a capacity retention of 60% or less.

As is clear from the results shown in Table 1,
It can be easily and easily inferred that a hydride secondary battery with less self-discharge and excellent capacity retention characteristics can be produced by using a battery constituent member having no anode peak.

Example 3 An AA size hydride secondary battery was produced in the same manner as in Example 2 by combining the N—B negative electrode, the positive electrode and the separator used in Example 1, and the capacity retention after storage was similarly performed. I checked the rate. The results are shown in Table 2.

[0085]

[Table 2]

As shown in Table 2, batteries (H2, J) using a combination of battery constituent members having no anode peak were used.
2, R2, S2, T2) all showed a high capacity retention rate of 80% or more, and had a higher capacity retention rate than when the N-A negative electrode was used.

Also in the case of the third embodiment, as in the case of the second embodiment, the batteries (A2, B2, C2, D2, E2, F2, G) having the anode peak as one of the battery constituent members are also included.
2, K2, L2, M2, N2, O2, P2, Q2)
The capacity retention was lower than the battery without anode peak.

As is clear from the results shown in Table 2,
It can be easily and easily estimated that a hydride secondary battery with less self-discharge and excellent capacity retention characteristics can be produced by using a battery constituent member having no anode peak.

Example 4 When the discharge capacities of the batteries of Examples 2 and 3 became constant, the sealing body of the battery was removed, and the electrolytic solution in the battery was taken out with a microsyringe.

Using the electrolytic solution in this battery, a cell similar to that of Example 1 was assembled, and its current density-potential curve was measured. Representative examples of the results are shown in FIGS. 7 and 8.

FIG. 7 is a current density-potential curve after holding at -0.95 V for 0.5 hours. As shown in FIG. 7, the unused electrolytic solution and H1 (no anode peak in the battery constituent member: capacity retention rate 82%) had a current density of 0.05 mA / cm ^{2 in} the range of −0.5 V to 0 V. Lower, no anodic peak was observed.

However, Al having a capacity retention rate of 31% (there is an anode peak in the positive electrode and separator of the battery constituent member).
, A strong peak exceeding 0.05 mA / cm ² was observed in the range of −0.5 V to 0 V.

As is clear from the results shown in FIG.
In order to obtain a hydride secondary battery with less self-discharge and excellent capacity retention characteristics, in the current density-potential curve after holding at -0.95V for 0.5 hours, -0.5V to 0V is obtained.
It is necessary that the current density in the range is 0.05 mA / cm ² or less.

FIG. 8 is a current density-potential curve when the voltage was not held at -0.95V. As shown in FIG. 8, the current density in the range of −0.5 V to 0 V was 0.02 mA / cm ² between the unused electrolyte solution and S2 (no anode peak in the battery constituent member: 81% capacity retention). Below,
No anode peak was observed.

However, for B2 having a capacity retention of 36% (there were anode peaks in the positive electrode and the separator), a strong peak exceeding 0.2 mA / cm ² was observed in the vicinity of −0.3V.

As is clear from the results shown in FIG.
In order to obtain a hydride secondary battery with less self-discharge and excellent capacity retention characteristics, in the current density-potential curve,
Current density in the range of 0.5V to 0V is 0.02mA / cm
Must be ² or less.

It can be inferred from these Examples 1 to 4 that the anode peak in the range of -0.5 V to 0 V is caused by the self-discharge reaction of the hydride secondary battery. Whether or not there is a coloration indicating the presence of an ammonia compound by adding a Nessler reagent (ammonia compound indicator) to the electrolytic solution of Example 4 (the current density-potential curves are shown in FIGS. 7 and 8) I checked. The results are shown in Table 3.

[0098]

[Table 3]

As shown in Table 3, in the batteries (A1, B2) in which the battery constituent members had an anode peak, a coloration indicating the presence of an ammonia compound in the Nessler indicator was recognized.
Then, the battery (A
1, B2) had a capacity retention rate of about 30 to 40% lower than that of the batteries (H1, S2) which had no color.

The ammonia compounds that cause the coloration of this Nessler indicator are NH ₄ OH, CH ₃ NH ₂ and C _{2
H 6 NH 2, (CH 3} ) 2 NH, (C 2 H 5) 2 -N
It is considered to be a compound containing a nitrogen group such as H and (CH ₃ ) ₃ N.

It is clear from the results of the color test shown in Table 3 that the oxidation of these ammonia compounds shows an anode peak on the current density-potential curve and causes a self-discharge reaction in the battery. .

In the above example, V-Ti-Zr-Ni-Cr-Co-Fe- was used as the hydrogen storage alloy for the negative electrode.
Mn-based and V-Ti-Zr-Ni-Cr-Co-
Although the description has been made by taking the case of using the Fe-based alloy as an example, the hydrogen storage alloy is not limited to these, and may be, for example, Ti-Ni-based, Ti-Ni-Zr-based, (Ti _2-x Z
r _x V _4-y Ni _y ) _1-z Cr _z (x: 0 to 1.5, y:
0.6 to 3.5, z: 0.2 or less) (USP47285)
86), Ti-Mn-based, Zr-Mn-based, and MmNi ₅ -based hydrogen storage alloys, the same effects are observed, so these are also used in the same manner as those exemplified in the examples. be able to.

Although only the negative electrode manufactured by the sintering method is shown, the negative electrode manufactured by the paste method has the same effect. It can be used as well. Therefore, the present invention does not limit the manufacturing method of the electrode.

[0104]

As described above, according to the present invention, it is possible to provide a hydride secondary battery having less self-discharge and excellent capacity retention characteristics.

That is, in the present invention, a model cell having platinum as a working electrode is assembled by using an electrolyte solution used for a battery or a storage solution in which a positive electrode, a negative electrode, a separator, etc. are stored, and the current density-potential curve thereof is assembled. By inferring, the effect of battery constituent members on the capacity retention characteristics of the battery is estimated,
Since the battery is manufactured based on the result, it is possible to provide a hydride secondary battery with less self-discharge and excellent capacity retention characteristics.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an H-shaped model cell used for measuring a current density-potential curve in Examples.

FIG. 2 is a diagram showing a current density-potential curve of a model cell using a storage solution of a sintered nickel positive electrode as an electrolytic solution.

FIG. 3 is a view showing a current density-potential curve of a model cell in which a paste type nickel positive electrode storage solution is used as an electrolytic solution.

FIG. 4 is a diagram showing a current density-potential curve of a model cell using a storage solution of a hydrogen storage alloy negative electrode as an electrolytic solution.

FIG. 5 is a diagram showing a current density-potential curve of a model cell in which a stock solution of a separator is used as an electrolytic solution.

FIG. 6 is a current density of a model cell using a separator storage solution as an electrolyte after being held at −0.95 V for 0.5 hours.
It is a figure which shows an electric potential curve.

FIG. 7 is a diagram showing a current density-potential curve of a model cell in which an electrolytic solution taken out from a practical battery is used as an electrolytic solution after being held at −0.95 V for 0.5 hours.

FIG. 8 is a view showing a current density-potential curve of a model cell using an electrolytic solution taken out from a practical battery as an electrolytic solution.

[Explanation of symbols]

 1 Working electrode 2 Counter electrode 3 Reference electrode 4 Glass filter 5 Electrolyte

Claims (11)

[Claims] 1. A hydride secondary battery having a positive electrode containing nickel oxide or nickel hydroxide, a negative electrode containing a hydrogen storage alloy, an electrolytic solution containing an alkaline aqueous solution, and a separator made of non-woven fabric. And a hydride secondary battery in which the separator does not elute impurities in the electrolytic solution. 2. When an electrolyte solution of the hydride secondary battery according to claim 1 is assembled into a model cell using the electrolyte solution and platinum as a working electrode, the current density-potential curve of the model cell at 25 ° C. Hydrogen having a peak anode current density in the range of -0.5 V to 0 V after holding at -0.95 V (vs. Hg / HgO) for 0.5 hours is 0.05 mA / cm ² or less. Secondary battery. 3. The positive electrode of the hydride secondary battery according to claim 1,
Immersing it in an alkaline aqueous solution that can be used as an electrolyte of a hydride secondary battery at 1.5 ml / g of active material weight,
When a model cell having platinum as a working electrode was assembled using a storage solution after storing at 90 ° C. for 24 hours as an electrolytic solution, its current density-potential curve showed −0.95 V (v
s. Hg / HgO) after being held for 0.5 hour, −0.
The peak anode current density in the range of 5V to 0V is 0.05.
A hydride secondary battery having a current density of mA / cm ² or less. 4. The negative electrode of the hydride secondary battery according to claim 1,
Immerse it in an alkaline aqueous solution that can be used as an electrolyte of a hydride secondary battery at 1.0 ml / g of active material weight,
When a model cell having platinum as a working electrode was assembled using a storage solution after storing at 90 ° C. for 24 hours as an electrolytic solution, its current density-potential curve showed −0.95 V (v
s. Hg / HgO) after being held for 0.5 hour, −0.
The peak anode current density in the range of 5V to 0V is 0.05.
A hydride secondary battery having a current density of mA / cm ² or less. 5. The separator of the hydride secondary battery according to claim 1 is immersed in an alkaline aqueous solution which can be used as an electrolytic solution of the hydride secondary battery at 10 ml / g per weight, and 2
When a model cell having platinum as a working electrode was assembled using a storage solution after storage for 4 hours as an electrolytic solution, its current density-potential curve showed -0.95 V (vs. Hg /
HgO) -0.5V to 0V after holding for 0.5 hour
The peak anode current density in the range is 0.05 mA / cm
^A hydride secondary battery characterized by being ² or less. 6. The current density-potential curve according to claim 2, claim 3, claim 4 or claim 5, wherein -0.95.
A hydride secondary battery having a peak anode current density of 0.02 mA / cm ² or less in a range of −0.5 V to 0 V when scanned without being held at V. 7. The peak anode current according to claim 2, claim 3, claim 4, claim 5, or claim 6 is due to oxidation of impurities that cause a self-discharge reaction in the battery. And a hydride secondary battery. 8. A hydride secondary battery in which the separator of the hydride secondary battery according to claim 1 is a polypropylene nonwoven fabric that has been plasma-treated, grafted or sulfonated. 9. The hydride secondary battery according to claim 1, wherein the positive electrode of the hydride secondary battery is manufactured by a paste method or a sintering method. 10. A hydride secondary battery, wherein the hydrogen storage alloy of the negative electrode of the hydride secondary battery according to claim 1 is an AB ₂ type hydrogen storage alloy. 11. The AB ₂ type hydrogen storage alloy according to claim 10, wherein A contains at least one element selected from Ti and Zr, and B represents Ni, V, Cr, Co, Mn and Fe. A hydride secondary battery containing any one or more elements.