JP2023062472A - Method for inspecting nickel-hydrogen storage battery - Google Patents

Abstract

To provide a method for inspecting a nickel-hydrogen storage battery that nondestructively estimates the generated amount of Ni2O3H that incurs a decrease in capacity and assesses the reuse of the nickel-hydrogen storage battery.SOLUTION: Provided is a method for inspecting a nickel-hydrogen storage battery having a cathode whose active material is nickel hydroxide, an anode that includes a hydrogen-storing alloy, and an electrolyte which is composed of an alkaline aqueous solution. This inspection method comprises: a charge-discharge step (S2) for charging and discharging a target battery at a set rate and acquiring a charge-discharge curve; a Q/dV conversion step (S3) for converting the charge-discharge curve to a dQ/dV curve; a damage index calculation step (S4) for adding the absolute value of a maximum peak at charge time and the absolute value of a minimum peak at discharge time in the dQ/dV curve and thereby calculating a damage index; and a determination step (S5) in which it is determined that the battery is acceptable when the damage index is greater than or equal to a given threshold, and it is determined that the battery is unacceptable when the damage index is less than the threshold.SELECTED DRAWING: Figure 3

Description

The present invention relates to an inspection method for nickel-metal hydride storage batteries, and more particularly to an inspection method suitable for nickel-metal hydride storage batteries for estimating the amount of Ni ₂ O ₃ H produced.

2. Description of the Related Art An electric vehicle (including a hybrid vehicle, etc.) equipped with an electric motor drives the electric motor with electric power stored in a secondary battery. Among such secondary batteries, alkaline secondary batteries such as nickel-metal hydride storage batteries are widely used for vehicles because they can charge and discharge large currents.

It is known that such a nickel-metal hydride storage battery has a memory effect depending on the usage conditions. Therefore, the positive electrode potential of the battery is likely to become lower than the predetermined lower limit potential or higher than the predetermined upper limit potential, so that a side reaction occurs at the positive electrode, which may deteriorate the positive electrode. Likewise, the negative electrode may be deteriorated when the negative electrode potential is out of the predetermined potential range.

FIG. 1 is a graph showing the relationship between the existence ratio (%) of Ni ₂ O ₃ H (nickel oxide) in the positive electrode and the capacity ratio (%) of the battery. As shown in FIG. 1, as pointed out in Patent Document 1, among the reactions, particularly in a nickel-hydrogen storage battery, when the abundance ratio (%) of Ni ₂ O ₃ H (nickel oxide) in the positive electrode increases, , there is a problem that the capacity ratio (%) of the battery is irreversibly lowered. Therefore, Patent Document 1 discloses the following invention for suppressing the formation of Ni ₂ O ₃ H.

In an alkaline storage battery using nickel hydroxide for the positive electrode, electrochemically inactive Ni ₂ O ₃ H may be generated depending on the conditions by performing charging and discharging under repeated charging and discharging conditions. Therefore, in the invention disclosed in Patent Document 1, the current density is 100 [A/m ² ], the SOC is within the range of 20 to 80 [%], and the total amount of electricity is 10 [kAh]. In this case, a battery has been proposed in which the positive electrode potential is appropriately controlled so that the Ni ₂ O ₃ H content is less than or equal to a specified amount.

Such an invention can be expected to suppress the formation of Ni ₂ O ₃ H.

JP 2011-233423 A

However, the present inventor believes that if a certain amount of Ni ₂ O ₃ H is produced, even if it is very small, the capacity of the battery will decrease, and if the battery is continuously used in a state where this Ni ₂ O ₃ H is produced, It was found that the battery capacity may drop rapidly. Therefore, it is necessary to accurately grasp the state in which Ni ₂ O ₃ H is produced.

Regarding the continuation of the use of a nickel-metal hydride storage battery with a certain usage history in the prior art, as a technique for confirming the formation of Ni ₂ O ₃ H, for example, structural analysis such as XRD of electrode plates after decomposition is common. However, since this method is a destructive test, there is a problem that reuse of the battery is substantially impossible. There is also a conventional dQ/dV detection technique for measuring the Co elution amount, which is a type of deterioration level. However, since it is a destructive inspection in the overdischarge region below 1 V of the cell, there is a problem that it is not suitable for judging reuse.

Therefore, the problem to be solved by the inspection method of the nickel-metal hydride storage battery of the present invention is to non-destructively estimate the amount of Ni ₂ O ₃ H that causes a decrease in capacity, and determine whether the nickel-metal hydride storage battery is to be reused. be.

In order to solve the above-mentioned problems, the method for inspecting a nickel-metal hydride storage battery of the present invention is a method for inspecting a nickel-metal hydride storage battery having a positive electrode using nickel hydroxide as an active material, a negative electrode containing a hydrogen-absorbing alloy, and an electrolytic solution composed of an alkaline aqueous solution. , a charging step of charging the target battery at a set rate and obtaining a charging curve, a dQ/dV conversion step of replacing the charging curve with a dQ/dV curve, and a maximum during charging in the dQ/dV curve a damage index calculation step of calculating a damage index from the absolute value of the peak; and a determination step of determining a non-defective product if the damage index is equal to or greater than a certain threshold, and determining a defective product if the damage index is less than the threshold. characterized by comprising A threshold value of the damage index may be set to 10 or more.

Further, the method for inspecting a nickel-metal hydride storage battery of the present invention is a method for inspecting a nickel-metal hydride storage battery having a positive electrode using nickel hydroxide as an active material, a negative electrode containing a hydrogen-absorbing alloy, and an electrolytic solution made of an alkaline aqueous solution, wherein the set rate A discharging step of discharging the target battery and obtaining a discharge curve, a Q/dV conversion step of replacing the discharge curve with a dQ/dV curve, and the absolute value of the minimum peak during discharging in the dQ/dV curve a step of calculating a damage index for calculating a damage index; It may be characterized. A threshold value of the damage index may be set to 10 or more.

Further, the method for inspecting a nickel-metal hydride storage battery of the present invention is a method for inspecting a nickel-metal hydride storage battery having a positive electrode that uses nickel hydroxide as an active material, a negative electrode that contains a hydrogen-absorbing alloy, and an electrolytic solution that is an alkaline aqueous solution. A charging and discharging step of charging and discharging the target battery and obtaining a charging and discharging curve, a Q / dV conversion step of replacing the charging and discharging curve with a dQ / dV curve, and a maximum peak during charging in the dQ / dV curve a damage index calculation step of calculating a damage index by adding the absolute value of the minimum peak during discharge to the absolute value of; If the product is defective, it may be determined to be defective. A threshold value of the damage index may be set to 20 or more.

In the test sample of the nickel-metal hydride storage battery to be inspected in the inspection method for the nickel-metal hydride storage battery, the relationship between the damage index and the amount of Ni ₂ O ₃ H produced is obtained in advance, and the damage in the determination step is determined based on this relationship. It is preferable to include a threshold setting step of setting a threshold for the index.

In the determination step, when the damage index is below the threshold, based on the relationship between the damage index obtained in the threshold setting step and the amount of Ni ₂ O ₃ H produced, It is also preferable to further include a step of calculating the amount of Ni ₂ O ₃ H produced by calculating the amount of Ni ₂ O ₃ H produced. In this case, if the production amount of Ni ₂ O ₃ H calculated in the step of calculating the production amount of Ni ₂ O ₃ H is equal to or less than the reference value, the nickel-metal hydride storage battery can be used under the set usage conditions. It is also preferred to have a use determination step of determining that

It is desirable that the rate set in the charging or discharging is 3C or less. The charging or discharging range may be 0 to 100% SOC.
The nickel-metal hydride storage battery is an in-vehicle battery for driving a vehicle, and the inspection method for the nickel-metal hydride storage battery can be implemented in the vehicle.

The method for inspecting a nickel-metal hydride battery according to the present invention can non-destructively estimate the amount of Ni ₂ O ₃ H that causes a decrease in capacity, and determine whether the nickel-metal hydride battery is to be reused.

1 is a graph showing the relationship between the abundance ratio (%) of Ni ₂ O ₃ H (nickel oxide) in a positive electrode and the capacity ratio (%) of a battery. (a) is a schematic diagram showing oxygen in a reaction during charging of the particle surfaces of the particles of the positive electrode active material 2 of the positive electrode of the nickel-metal hydride storage battery. (b) is a reaction formula showing a normal main reaction of the positive electrode during discharge and an abnormal side reaction when oxygen is generated and local "liquid depletion" occurs. 4 is a flow chart showing the procedure of a method for inspecting a nickel-metal hydride storage battery according to the present embodiment; 4 is a graph showing charge/discharge curves of a nickel-metal hydride storage battery. 4 is a graph showing the slope of the charging/discharging curve of the nickel-metal hydride storage battery as a dQ/dV curve. 4 is a graph showing the relationship between the damage index DI during charging and discharging and the amount of Ni ₂ O ₃ H produced. 1 is a block diagram of a control device 10 for a nickel-metal hydride storage battery according to this embodiment; FIG. 4 is a graph showing the relationship between the damage index DIc only during charging and the amount of Ni ₂ O ₃ H produced. 4 is a graph showing the relationship between the damage index DId only during discharge and the amount of Ni ₂ O ₃ H produced.

A method for inspecting a nickel-metal hydride storage battery according to the present invention will be described below using one embodiment with reference to FIGS. 1 to 9. FIG.
<Assumptions of this embodiment>
The method for inspecting a nickel-metal hydride storage battery according _to the present embodiment aims at detecting the formation of _Ni2O3H . Therefore, first, the mechanism of formation of Ni ₂ O ₃ H will be described.

<Surface of Particles of Positive Electrode Active Material>
FIG. 2(a) is a schematic diagram showing oxygen in reaction during charging of the particle surfaces 22b of the particles 22a of the positive electrode active material 2 of the positive electrode of the nickel-metal hydride storage battery. FIG. 2(b) is a reaction formula showing a normal main reaction of the positive electrode during discharge and an abnormal side reaction when oxygen is generated and local "liquid depletion" occurs.

<Main reaction at positive electrode during discharge>
Particles 22a of positive electrode active material 2 change between Ni(OH) ₂ and β-NiOOH due to charging and discharging. For convenience of explanation, Ni(OH) ₂ may be used as a representative positive electrode active material. A normal main reaction during discharge of a nickel-metal hydride storage battery is that Ni(OH) ₂ and OH ⁻ are produced from β-NiOOH on the premise of the presence of H ₂ O, as shown in the following equation (1). In this case, H ₂ O in the electrolyte is consumed and reduced. OH ⁻ acts as an alkali ion of the alkaline electrolyte 4 . In this case, the exchange of ions and electrons does not generate gases such as oxygen O ₂ and hydrogen H ₂ .

β-NiOOH+H ₂ O+e ⁻ →Ni(OH) ₂ +OH ⁻ (1)
<Generation of Oxygen and Occurrence of “Liquid Depletion” Due to Side Reaction>
Depending on the conditions of use, the potential of the positive electrode may become low. When the potential for electrolysis of H ₂ O is reached, electrolysis of H ₂ O occurs as a side reaction. In the electrolysis of H ₂ O, O ₂ is generated at the positive electrode by the reaction represented by the following formula (2).

4OH ⁻ →O ₂ +2H ₂ O+4e ⁻ (2)
As shown in FIG. 2(a), when the particle surface 22b of the positive electrode active material of Ni(OH) ₂ /β-NiOOH, which is the positive electrode active material, becomes a low potential due to charging, the potential as shown in the above equation (2) is reached. A side reaction occurs, and O ₂ bubbles A are generated on the particle surface 22b of the positive electrode active material. When O ₂ is generated at the positive electrode during charging, bubbles A of O ₂ adhere to the particle surface 22b of the positive electrode active material. The O ₂ bubbles A separate from the particle surface 22b of the positive electrode active material over time. Then, the place where the air bubble A has left comes into contact with the alkaline electrolyte 4, and H ₂ O and OH ^- are supplied.

However, depending on the conditions, it may take time for the O ₂ generated on the particle surfaces 22b of the positive electrode active material to leave the particle surfaces 22b of the positive electrode active material like the bubbles B. Thus, the O ₂ bubbles such as the bubbles B adhering to the particle surface 22b of the positive electrode active material block the alkaline electrolyte locally. As a result, the H ₂ O and OH ⁻ on the particle surface 22b of the positive electrode active material are physically removed, and the portion is locally “liquid dried”. Neither H ₂ O nor OH ^— are physically present here.

<Generation of Ni ₂ O ₃ H by “liquid drying”>
Then, in a normal reaction, H ₂ O is required for the reaction as shown in formula A _in FIG. A side reaction occurs, resulting in a reaction such as the following formula (3).

16β-NiOOH+4e ⁻ →8Ni ₂ O ₃ H+2H ₂ O+O ₂ +4OH ⁻ (3)
That is, it reacts without using H ₂ O and produces H ₂ O on the contrary. As products at that time, Ni ₂ O ₃ H, O ₂ and OH ⁻ are generated. Of these, O ₂ is smoothly absorbed by the negative electrode (recombination reaction) through the separator as shown in the following formula (4) over time, maintaining a closed system. OH ⁻ returns to the alkaline electrolyte 4 .

4MH+ _O2 →4M+ _2H2O (4)
Here, Ni ₂ O ₃ H is an electrochemically inactive product, and when Ni ₂ O ₃ H is generated, it accumulates irreversibly, causing an increase in battery resistance and a decrease in battery capacity. is at issue. Therefore, the generation of Ni ₂ O ₃ H is usually suppressed as undesirable.

<Memory effect of nickel metal hydride storage battery>
Next, the memory effect of the nickel-metal hydride storage battery will be explained. It is known that a memory effect occurs in a nickel-metal hydride storage battery when it is repeatedly charged and discharged at a low SOC. In a battery system with a memory effect, the voltage shifts to the noble side during charging. Therefore, ΔSOC increases. That is, even if the SOC is the same, the potential of the positive electrode becomes low during charging, and O ₂ is particularly likely to be generated. As a result, at the place where oxygen is generated on the particle surface 22b of the positive electrode active material, local _liquid depletion occurs instantaneously. Ni ₂ O ₃ H is produced simultaneously with the reaction. The formation of Ni ₂ O ₃ H causes a rapid capacity decrease.

<Mechanism of Ni ₂ O ₃ H Generation in Nickel Metal Hydride Battery>
As described above, in the nickel-hydrogen storage battery, Ni ₂ O ₃ H generates oxygen O ₂ gas as a side reaction of charging due to the potential of the positive electrode during charging, and the internal pressure of the secondary battery rises. The O ₂ causes "liquid depletion", and the mechanism by which Ni ₂ O ₃ H is produced was analyzed.

The present inventor presumes that "liquid depletion" occurs when the decrease in positive electrode potential during charging becomes the potential for oxygen generation, and when oxygen O ₂ gas is actually generated and the internal pressure is high. and proved this.

<Memory effect of in-vehicle nickel-metal hydride storage battery>
Next, the memory effect of the in-vehicle nickel-metal hydride storage battery will be described. 2. Description of the Related Art An electric vehicle (including a hybrid vehicle, etc.) equipped with an electric motor drives the electric motor with electric power stored in a secondary battery. Among such secondary batteries, alkaline secondary batteries such as nickel-metal hydride storage batteries are widely used for vehicles because they can charge and discharge large currents. Such in-vehicle nickel-metal hydride storage batteries may be exposed to harsh operating environments. For example, charging and discharging may be repeated in a low SOC (State Of Charge) state. It is known that a memory effect occurs in such a use environment. The memory effect causes a positive shift in the battery charge curve. That is, even if the SOC is the same, the positive electrode potential becomes higher. On the other hand, during discharge, the discharge curve of the battery shifts to the base. That is, even if the SOC is the same, the positive electrode potential becomes lower. Then, Ni ₂ O ₃ H is likely to be generated due to "dryness" due to the mechanism described above.

<Necessity for control of in-vehicle nickel-metal hydride storage batteries>
As shown in FIG. 2(b), once Ni ₂ O ₃ H is generated, it accumulates irreversibly, resulting in a decrease in the capacity of the nickel-metal hydride storage battery. The deterioration of the nickel-metal hydride storage battery whose capacity has decreased will progress further unless control is performed according to the deterioration. Therefore, as in Patent Document 1 cited in the description of the prior art, an invention has been proposed that suppresses the generation of Ni ₂ O ₃ H by controlling a nickel-metal hydride storage battery mounted on a vehicle.

<Generation of Ni ₂ O ₃ H and Decrease in Capacity of Nickel Metal Hydride Storage Battery>
However, once Ni ₂ O ₃ H is generated, it accumulates irreversibly. Then, coupled with the memory effect, the capacity decrease progresses more and more. As the capacity decrease progresses, the voltage further shifts to the noble side, creating an environment in which Ni ₂ O ₃ H is likely to be generated at an accelerated rate. Then, a rapid decrease in the capacity of the battery is caused. Therefore, it is necessary to detect the generation of Ni ₂ O ₃ H at the initial stage when Ni ₂ O ₃ H is generated, even if it is a small amount.

<Principle of this embodiment>
FIG. 3 is a flow chart showing the procedure of the inspection method for the nickel-metal hydride storage battery of this embodiment. Next, the principle by which Ni ₂ O ₃ H can be detected by the nickel-metal hydride storage battery inspection method of the present embodiment will be described with reference to the flow chart of FIG.

In the nickel-metal hydride battery inspection method of the present embodiment, first, the relationship between the damage index DI and the amount of Ni ₂ O ₃ H produced is acquired in advance in a test sample of the nickel-metal hydride storage battery to be inspected in the nickel-metal hydride storage battery inspection method. . A threshold value setting step (S1) is provided for setting the threshold value of the damage index DI in the determination step based on the relationship between the obtained damage index DI and the amount of Ni ₂ O ₃ H produced. The charging/discharging step (S2) of charging/discharging the target battery at the set rate and obtaining a charging/discharging curve is also provided. Further, there is provided a Q/dV conversion step (S3) for replacing the charge/discharge curve with a dQ/dV curve. Then, a damage index DI calculation step (S4) is provided for calculating the damage index DI by adding the absolute value of the maximum peak during charging to the absolute value of the minimum peak during discharging in the dQ/dV curve. Then, a judgment step (S5) is provided for judging that the product is non-defective if the damage index DI exceeds a certain threshold, and that the product is defective if the damage index DI is below the threshold.

<Threshold Setting Step (S1)>
In the threshold value setting step (S1), the relationship between the damage index DI and the amount of Ni ₂ O ₃ H produced is acquired in advance in a test sample of a nickel-metal hydride storage battery to be inspected in the nickel-metal hydride storage battery inspection method. Based on the obtained relationship between the damage index DI and the amount of Ni ₂ O ₃ H produced, the threshold value of the damage index DI in the determination step is set. The "damage index DI" will be described in detail later.

<Step of charging and discharging (S2)>
In the charging/discharging step (S2), the target battery is charged/discharged at the set rate and a charge/discharge curve is obtained. In this embodiment, charging and discharging are performed at a low rate of ⅓ C in order to improve measurement accuracy. In addition, charging and discharging at a low rate takes a long time, so a high rate may be used. A "charging curve" is a graph showing the battery capacity [Ah] when charged and the module voltage [V] at that time. A "discharge curve" is a graph showing the battery capacity [Ah] when discharged and the module voltage [V] at that time. In the present application, "charging curve" and "discharging curve" are collectively referred to as "charging/discharging curve".

FIG. 4 is a graph showing charge/discharge curves of a nickel-metal hydride storage battery. The horizontal axis represents changes in the battery capacity [Ah] of the nickel-metal hydride storage battery due to charging and discharging. The vertical axis indicates the voltage [V] of the module of the nickel-metal hydride storage battery. When the module voltage [V] is 6.0 [V], the SOC of the nickel-metal hydride storage battery is approximately 0 [%].

<Charging curve>
Here, the charging curve will be described with an example of the graph C0, which is the charging curve of an unused nickel-metal hydride storage battery with a usage history of 0 [Ah].

As shown in the graph C0, 0 [Ah], that is, an unused and undegraded nickel-metal hydride storage battery has a capacity of 0 [Ah], that is, an SOC of 0 [%], a module voltage of 6.0 [V] and a low rate, here Start charging at 1/3C. When charging is started, the module voltage first rises to around 7.5 [V] and continues to rise. The battery capacity [Ah] ranges from 0 [Ah] to 2 [Ah], and the module voltage rises to about 8.3 [V], but the slope of the graph C0 gradually decreases. In other words, "dQ/dV", that is, the degree of change in battery capacity [Ah] with respect to change in module voltage [V], gradually increases.

When the battery capacity is approximately 2.8 [Ah], the module voltage is approximately 8.35 [V]. With this point of inflection IPc as a boundary, the slope of the graph C0 gradually increases again. "dQ/dV", that is, the degree of increase of the battery capacity [Ah] with respect to the module voltage [V] gradually decreases. When the charging is continued, the battery capacity [Ah] is approximately 7.0 [Ah] and the module voltage [V] is approximately 8.9 [V], and the battery is fully charged.

<Discharge curve>
Next, the discharge curve will be described with reference to graph D0, which is the discharge curve of an unused nickel-metal hydride storage battery with a usage history of 0 [Ah].

As shown in graph D0, the fully charged nickel-metal hydride storage battery is discharged. The nickel-metal hydride storage battery has a usage history of 0 [Ah], that is, it is a brand new unused battery. The discharge starts at a low rate, here 1/3C. Graph D0 moves leftward from the rightmost point, but the battery capacity [Ah] at the start of discharge is approximately 6.75 [Ah], and the module voltage [V] is 8.6 [V]. From there, the module voltage [V] sharply drops to around 7.8 [V] until the battery capacity [Ah] reaches around 5 [Ah]. At this time, "dQ/dV", that is, the degree of increase in the battery capacity [Ah] with respect to the module voltage [V] gradually increases. Note that since the change in the module voltage [V] is negative during discharging, dQ/dV is a negative numerical value.

As the discharge continues, the slope of the graph D0 gradually decreases until the module voltage reaches about 7.85 [V]. "dQ/dV", that is, the degree of increase in the battery capacity [Ah] with respect to the module voltage [V] gradually increases.

Then, the slope of the graph D0 gradually increases again after the inflection point IPd at which the module voltage is approximately 7.85 [V]. The absolute value of "dQ/dV" becomes smaller and smaller.
<Step of conversion to dQ/dV (S3)>
FIG. 4 is a graph showing dQ/dV curves of the charge/discharge curves of FIG. The horizontal axis indicates the module voltage [V]. The vertical axis indicates the value of dQ/dV. During charging, the battery capacity [Ah] increases with respect to the amount of change in the module voltage [V], so the value is a positive value. On the other hand, during discharging, the battery capacity [Ah] decreases with respect to the amount of change in the module voltage [V], so the value becomes a negative number. Therefore, the vertical axis of the coordinates shown in FIG. 4 has a scale of dQ/dV [Ah/V]=0 at the center, positive upward and negative downward.

The dQ/dV conversion step (S3) is a step of replacing the charge/discharge curve with a dQ/dV curve.
Again, for example, the charging curve of the graph C0 shown in FIG. 3 will be described as an example. As shown in FIG. 3, in the graph C0 showing the charging curve, the slope becomes small when the module voltage [V] is approximately 8.35 [V]. That is, the battery capacity [Ah] with respect to the module voltage [V], that is, "dQ/dV" is maximized. In the graph RC0 showing the dQ/dV curve shown in FIG. 4, the peak is generally shown when the module voltage [V] is 8.35 [V]. At this time, dQ/dV=30 in general.

The reason why such a peak is shown is that during charging, the energy of the current is consumed for chemical changes, so even if the battery capacity [Ah] increases, it does not lead to an increase in the module voltage [V]. I think that the.

On the other hand, in the graph D0 showing the discharge curve, the slope becomes small when the module voltage [V] is approximately 7.84 [V]. That is, the absolute value of "dQ/dV" is maximum. The numbers in this case are negative numbers. Graph RD0 showing the dQ/dV curve shown in FIG. 4 shows a very small peak when the module voltage [V] is approximately 7.84 [V]. At this time, dQ/dV is approximately -28.

<Step of Calculating Damage Index DI (S4)>
The damage index DI calculation step (S4) calculates the damage index DI by adding the absolute value of the minimum peak during discharge to the maximum peak during charge in the dQ/dV curve.

In the dQ/dV converting step (S3), the charging curve graph C0 and the discharging curve graph D0 were converted into dQ/dV curves. By converting the charge curve graph C0 and the discharge curve graph D0 into dQ/dV curves, the maximum value in the dQ/dV curve of the charge curve graph C0 was detected. Similarly, the minimum value in the dQ/dV curve of the discharge curve graph D0 was detected. The magnitude of the absolute values of such minimum and maximum values can serve as an index indicating that the main reaction of the nickel-metal hydride storage battery is sufficiently carried out without damage.

<Damage index DI>
Therefore, in the present embodiment, the absolute value of the minimum peak during discharging is added to the absolute value of the maximum peak during charging in the dQ/dV curve. In this embodiment, the "damage index DI" refers to a value obtained by adding the absolute value of the maximum peak during charging to the absolute value of the minimum peak during discharging in the dQ/dV curve. In the damage index DI calculation step (S4), this "damage index DI" is calculated. This "damage index DI" indicates that the nickel-metal hydride storage battery is less deteriorated as the numerical value is larger. On the other hand, when the "damage index DI" is small, it indicates that the deterioration of the nickel-metal hydride storage battery is progressing.

<Determination Step (S5)>
In the determination step (S5), if the damage index DI is equal to or greater than a certain threshold, the product is determined to be non-defective, and if it is less than the threshold, the product is determined to be defective.

<Threshold Setting Step (S1)>
Here, the step (S1) of threshold value setting will be described, although the order will be changed. As described above, in the nickel-metal hydride battery inspection method of the present embodiment, the inventors found that the "damage index DI" can serve as an index of deterioration of the nickel-metal hydride battery. Then, in the determination step (S5), deterioration of the nickel-hydrogen storage battery is determined based on this "damage index DI". Here, the criterion for determination at this time is the "threshold". Here, a method for determining the threshold will be described.

<Deterioration of Ni-MH storage batteries due to use and charge/discharge curves>
With reference to FIG. 4, the graph C0 of the charge curve and the graph D0 of the discharge curve of a new nickel-metal hydride storage battery with no usage history have been described. This charge/discharge curve changes according to deterioration due to use.

<Degradation and charge curve>
In FIG. 4, graph C0 shows a charging curve during charging of an unused nickel-metal hydride storage battery. On the other hand, graph C1 shows a charging curve when charging a nickel-metal hydride storage battery using 1800 Ah. Graph C2 shows a charge curve during charging of a nickel-metal hydride storage battery that uses 2920 Ah. Graph C3 shows a charge curve during charging of a nickel-metal hydride storage battery using 3070 Ah. Graph C4 shows a charge curve during charging of a nickel-metal hydride storage battery using 3080 Ah.

Graph C1 shows a charge curve when a nickel-metal hydride storage battery with a usage history of 1800 [Ah] is charged. In all graphs C0 to C4, charging conditions are the same, from a completely discharged SOC 0[%] module voltage of 6.0[V] to a charging rate of 1/3C to SOC 100[%] full charge. The characteristics of the charged nickel-metal hydride storage battery change due to deterioration of the active material and the like due to use. Graph C1 is compared with the charging curve C0 of an unused nickel-metal hydride storage battery. By comparison, when charging is started from SOC 0 [%], the module voltage [V] is approximately 8.9 [V] and SOC 100 [%], which is not much different from graph C0. However, the change in module voltage [V] with respect to the increase in battery capacity [Ah] is different. When the battery capacity [Ah] is about 2.7 [Ah] immediately after the start of charging, the graph C1 shows that the module voltage [V] is lower than the graph C0, and when the battery capacity exceeds about 2.7 [Ah], the graph C1 , higher than the module voltage [V] from the graph C0.

Looking at the slope of the graph, the slope of the graph C0 is almost horizontal near the inflection point IPc. On the other hand, the graph C1 consistently maintains a constant slope or more.
FIG. 5 is a graph showing the slope of the charging/discharging curve of the nickel-metal hydride storage battery as a dQ/dV curve. As shown in FIG. 5, when these slopes are represented by dQ/dV curves, graph C0 becomes graph RC0 and graph C1 becomes graph RC1.

Here, in the graph RC0 based on the graph C0, as described above, the module voltage [V] was approximately 8.35 [V] and the value of dQ/dV showed a peak of approximately +30. On the other hand, in the graph RC1 based on the graph C1, the value of dQ/dV shows an extremely gentle peak of approximately dQ/dV=+7 near approximately 8.3 [V].

Graph C2 shown in FIG. 4 shows a charge curve when a nickel-metal hydride storage battery having a usage history of 2920 [Ah] is charged. In this case, the module voltage [V] is higher than the graph C1 at the early stage of charging. Further, graph C3 has a usage history of 3070 [Ah], but shows a higher module voltage [V] than graph C2 at the early stage of charging. Graph C4 shows a higher module voltage [V] than graph C3 at an earlier timing.

As described above, in the history of use, when charging and discharging were repeated at a large amount of current, the deterioration of the active material progressed, and the module voltage [V] increased with a small battery capacity [Ah]. I can confirm. This shows that even if the same battery capacity [Ah] is charged, the SOC [%] of the deteriorated nickel-metal hydride storage battery is higher. Also, a deteriorated nickel-metal hydride storage battery tends to have a higher SOC [%]. This means that the potential in the nickel-metal hydride storage battery is such that oxygen is likely to be generated, and the environment is such that Ni ₂ O ₃ H is likely to be generated.

For example, in the graphs C0 and C1, the usage history repeats many charges and discharges from 0 [Ah] to 1800 [Ah] and 1800 [Ah], but the module potential [V] at the same electric capacity [Ah] is not much different. However, in the graphs C3 and C4, a clear increase in the module voltage [V] can be confirmed even though the usage history is only 10 [Ah] from 3070 [Ah] to 3080 [Ah]. . In other words, it can be understood that once the deterioration of the nickel-metal hydride storage battery begins to progress as the usage history becomes longer, the deterioration progresses at an accelerated pace, causing a rapid capacity decrease.

<Degradation and discharge curve>
In FIG. 4, graph D0 shows a discharge curve during discharge of an unused nickel-metal hydride storage battery. Graph D1 shows a discharge curve during discharge of a nickel-metal hydride storage battery used for 1800 Ah. Graph D2 shows a discharge curve during discharge of a nickel-metal hydride storage battery that uses 2920 Ah. Graph D3 shows a discharge curve during discharge of a nickel-metal hydride storage battery that uses 3070 Ah. Graph D4 shows a discharge curve during discharge of a nickel-metal hydride storage battery that uses 3080 Ah.

Graph D1 shows a discharge curve when a nickel-metal hydride storage battery with a usage history of 1800 [Ah] is discharged. Graphs D0 to D4 all have the same discharge conditions from a fully charged SOC of 100 [%] to a discharge rate of 1/3 C, SOC of 0 [%], and module voltage of 6.0 [V]. The characteristics of the charged nickel-metal hydride storage battery change due to deterioration of the active material and the like due to use. Graph D1 with a usage history of 1800 [Ah] is compared with graph D0 of the discharge curve of an unused nickel-metal hydride storage battery.

Comparing the graph D0 and the graph D1, the battery capacity [Ah] at the start of discharge is around 6.8 [Ah] in the graph D0, while in the graph D1, around 5.9 [Ah] It can be seen that the battery capacity after that is greatly reduced. Also, the graph D0 shows a nearly horizontal slope near the module voltage [V]=7.8 [V]. On the other hand, the graph D1 does not have such a nearly horizontal portion, and it can be confirmed that the module voltage [V] gradually decreases according to the discharge. In the graph D2 with the usage history of 2920 [Ah], it is 4.9 [Ah] at the start of discharge. Furthermore, in the graph D3 with the usage history of 3070 [Ah], it becomes 4.9 [Ah] at the start of discharge. In graph D4 with a usage history of 3080 [Ah], it is approximately 4.2 [Ah].

Accordingly, the slope of the graph D0 is the smallest, followed by the slope of the graph D1. The slope increases in the order of graph D2, graph D3, and graph D4 where deterioration has progressed further. That is, as the discharge progresses, the module voltage [V] of the deteriorated nickel-metal hydride storage battery quickly drops.

<Degradation and dQ/dV>
As shown in FIG. 5, when these slopes are expressed as dQ/dV curves, graph C0 becomes graph RC0 and graph C1 becomes graph RC1. Graph C2 becomes graph RC2. Graph C3 becomes graph RC3. Graph C4 becomes graph RC4.

Here, in the graph RC0 based on the graph C0, as described above, the module voltage [V] was approximately 8.35 [V] and the value of dQ/dV showed a peak of approximately DIc=+30. On the other hand, none of the graphs RC1 to RC4 based on the graphs C1 to C4 show a sharp peak like the graph RC0.

Also, the graph D0 becomes the graph RD0, and the graph D1 becomes the graph RD1. Graph D2 becomes graph RD2. Graph D3 becomes graph RD3. Graph D4 becomes graph RD4.

Here, in the graph RD0 based on the graph D0, as described above, the module voltage [V] is approximately 7.8 [V] and the value of dQ/dV has a peak (bottom) of approximately DId=-30. Indicated. On the other hand, graphs RD1 to RD4 based on graphs D1 to D4 do not show steep peaks (bottoms) like graph RD0.

<Threshold setting>
The present inventors found that when the active material of a nickel-metal hydride storage battery deteriorates due to the history of use, as shown in FIG. . Also, a negative peak of DId=-30 appears in the value of dQ/dV during discharge. It was found that the absolute values of both the maximum peak and the minimum peak decreased with deterioration. Therefore, the relationship between the damage index DI and the amount of Ni ₂ O ₃ H produced is acquired in advance in a test sample having the same configuration as the nickel-metal hydride storage battery to be inspected. Here, the threshold value of the damage index DI in the determination step is set based on the relationship between the damage index DI obtained by DIc+DId and the amount of Ni ₂ O ₃ H produced.

<Relationship between Damage Index DI and Ni ₂ O ₃ H Production Amount>
FIG. 6 is a graph showing the relationship between the damage index DI during charging and discharging and the amount of Ni ₂ O ₃ H produced. The horizontal axis indicates "damage index DI". That is, it represents the sum of the absolute value of the maximum peak DIc during charging and the absolute value of the minimum peak DId during discharging in the dQ/dV curve. The vertical axis indicates the percentage of the amount of Ni ₂ O ₃ H produced in the positive electrode active material.

When the damage index DI was approximately dQ/dV≧20, the amount of Ni ₂ O ₃ H produced could not be detected. As will be described later, the peak DIc during charging satisfies dQ/dV≧10 as shown in FIG. 8, and the amount of Ni ₂ O ₃ H produced could not be detected. Moreover, as shown in FIG. 9, the peak DId during discharge satisfies |dQ/dV|≧10, and the amount of Ni ₂ O ₃ H produced could not be detected.

On the other hand, when the damage index DI is less than 20, the amount of Ni ₂ O ₃ H produced is recognized. Further, when the damage index DI was about 7, the proportion of Ni ₂ O ₃ H in the active material was about 72.5[%]. Conversely, when the amount of Ni ₂ O ₃ H produced is zero, the damage index DI must be 20 or more. That is, in the case _shown in FIG. 6, if the "threshold" of the damage index DI is set to "20 or more", the nickel-metal hydride storage battery in which _Ni2O3H is generated can be excluded by inspection.

<judgment>
In the nickel-metal hydride storage battery inspection method of the present embodiment, as described above, the threshold set in the threshold setting step (S1) is set prior to the inspection in the charge/discharge step (S2) to the determination step (S5). are doing.

Then, the damage index DI of the target nickel-metal hydride storage battery is calculated through the charging/discharging step (S2) to the damage index DI calculation step (S4). If the value is equal to or greater than a threshold value (for example, "20" here) (S5: YES), the product is determined to be non-defective (S6), and if the value is less than the threshold value (S5: NO), the product is determined to be defective (S7).

For the nickel-metal hydride storage battery determined to be defective (S7), the amount of _Ni2O3H produced is calculated from the _graph showing the relationship between the "damage index DI and the amount of _Ni2O3H produced" shown in _FIG . S8). Then, the degree of deterioration of the nickel-hydrogen storage battery is evaluated. In this way, even though the product is not determined to be completely non-defective, it is possible to use the product with slight deterioration by, for example, controlling the conditions of use according to the deterioration.

This completes the method for inspecting a nickel-metal hydride storage battery according to the present embodiment.
<Nickel metal hydride storage battery>
A nickel-metal hydride storage battery, which is the premise of this embodiment, will be briefly described below. The nickel-metal hydride storage battery of this embodiment is a sealed battery, and is a vehicle-mounted battery used as a power source for vehicles such as electric vehicles and hybrid vehicles. It is a prismatic sealed battery comprising a battery module configured by electrically connecting a plurality of single cells in series in order to obtain a required power capacity as a nickel-metal hydride storage battery mounted on a vehicle.

A battery module has a rectangular parallelepiped prismatic case composed of an integrated battery case capable of accommodating a plurality of cells and a lid body for sealing the integrated battery case. A resin-made case can be used for this rectangular case.

The integrated battery case that constitutes the rectangular case is made of a synthetic resin material, such as polypropylene or polyethylene, that is resistant to an alkaline electrolyte. A partition wall is formed inside the integrated battery case to partition a plurality of cells, and the portion partitioned by the partition wall serves as a battery case for each battery. The integrated battery case has, for example, six battery cases.

<Structure of Electrode Group>
In the compartmentalized container, an electrode plate group, and a positive electrode collector plate and a negative electrode collector plate joined to both sides of the electrode plate group are accommodated together with an electrolytic solution. The electrode plate group is configured by laminating a rectangular positive electrode plate and a negative electrode plate with a separator interposed therebetween. Electrode groups of adjacent battery cases are electrically connected in series. The total output of the series-connected electrode plate group, ie, the plurality of single cells, is taken out from the positive connection terminal and the negative connection terminal.

<Positive plate>
For the positive electrode plate, a foamed nickel three-dimensional porous body made of Ni or a Ni alloy, which is a porous metal, is used as a positive electrode base material. The positive electrode substrate has a bone portion having a three-dimensional network structure and a hole portion surrounded by the bone portion. The positive electrode substrate is manufactured, for example, by nickel-plating the surface of the urethane skeleton of foamed urethane and then burning off the foamed urethane. The positive plate comprises a positive composite layer containing Ni(OH) ₂ and Co as active materials. Specifically, to granular nickel hydroxide, add an appropriate amount of a conductive agent such as cobalt hydroxide or metallic cobalt powder, and if necessary, a thickener such as carboxymethyl cellulose or a binder such as polytetrafluoroethylene, and then paste it. processed into a shape. After that, the paste-like processed material is filled into the mesh-like holes of the positive electrode substrate to form a positive electrode mixture layer. After that, it is dried, rolled, and cut to form a plate-like positive electrode plate.

<Negative plate>
The negative electrode plate is made of, for example, a misch metal, which is a mixture of rare earth elements such as lanthanum, cerium, and neodymium, and a hydrogen storage alloy containing nickel, aluminum, cobalt, and manganese as constituent elements. In more detail, this hydrogen storage alloy is added with a conductive agent such as carbon black, and if necessary, a thickener such as carboxymethyl cellulose and a binder such as styrene-butadiene copolymer, and is first made into a paste. process. After that, the hydrogen-absorbing alloy thus processed into a paste is applied to or filled in a core material such as a punching metal (active material support), which is then dried, rolled, and cut into a plate-like negative electrode plate. Form.

<Separator>
As the separator, a nonwoven fabric made of an olefinic resin such as polypropylene, or a nonwoven fabric subjected to a hydrophilic treatment such as sulfonation as necessary, can be used.

The battery module of the nickel-metal hydride storage battery of this embodiment has the configuration described above.
<Control Device for Nickel Metal Hydride Storage Battery of Present Embodiment>
Next, an example of a nickel-metal hydride storage battery and its control device, which are prerequisites for this embodiment, will be briefly described. A typical example of the method for inspecting a nickel-metal hydride battery according to the present embodiment is an inspection method for reusing a used nickel-metal hydride battery that has been collected as a single unit. However, the inspection method of the present embodiment, which can detect signs of rapid deterioration of the nickel-metal hydride storage battery, can also be suitably applied to an in-vehicle nickel-metal hydride storage battery as a drive secondary battery. Therefore, one embodiment of a method for inspecting a nickel-metal hydride storage battery as such a vehicle-mounted secondary battery for driving will be briefly described here.

<Control device 10 for nickel-metal hydride storage battery>
FIG. 7 is a block diagram of the control device 10 for the nickel-metal hydride storage battery of this embodiment. The control device 10 for the nickel-metal hydride storage battery will be described with reference to FIG. Here, the nickel-metal hydride storage battery is controlled in the state of the battery pack containing the battery module 90 .

<Control device 10>
A control device 10, which is a battery control device, is mounted on a vehicle and can control a battery module 90 of the vehicle in real time or based on accumulated data so-called onboard.

The control device 10 controls and charges the inverter 20 as a charging device for charging the battery module 90 with current from the motor generator 17 as a power generator. Further, the control device 10 controls the inverter 20 as a power supply device to discharge current from the battery module 90 to the motor generator 17 as a drive motor serving as a load.

The control device 10 includes a current detector 21 that measures the current of the battery module 90, a voltage detector 22 that measures the voltage across the terminals of the battery module 90, and a temperature detector 23 that measures the temperature of the battery module 90. ing.

The temperature detector 23 has a temperature sensor. The temperature sensor measures the temperature in the vicinity of the electrode plate group of the corresponding unit cell in the battery module 90 and outputs the measured temperature value to the control device 10 as an electrical signal.

<Control unit 11>
A control unit 11 of the control device 10 is configured as a computer including a CPU, a RAM, a ROM, and an interface for controlling the entire control device 10 .

<Information Acquisition Unit 12>
The information acquisition unit 12 sequentially acquires charge/discharge current values from the current detector 21, voltage values from the voltage detector 22, and battery temperature from the temperature detector 23, and stores them.

<Storage unit 13>
The storage unit 13 includes a storage medium in which programs for the control device 10 and necessary data are stored. The program includes a program that executes the flowchart shown in FIG.

The storage unit 13 also pre-stores, as data on the premise of control, a " _threshold value" based on a map showing the relationship between the amount of damage and the amount of _Ni2O3H produced.
<Damage index calculator 14>
The damage index calculator 14 estimates a change in battery capacity [Ah] from the battery module 90 charged/discharged by the charge/discharge controller 16, and generates a charge curve from the module voltage [V]. In this case, since the battery capacity [Ah] is a vehicle-mounted battery, it is impossible to accurately measure the battery capacity [Ah] by charging and discharging from a fully discharged SOC of 0 [%] to a fully charged SOC of 100 [%]. Have difficulty. Therefore, the battery capacity [Ah] is estimated within the SOC [%] range in which problems in vehicle operation are unlikely to occur. dQ/dV [Ah/V] is calculated from the estimated charging curve, and the damage index DI is calculated.

It should be noted that the acquisition of the damage index DI is sufficient if the peak of dQ/dV [Ah/V] can be recognized. Therefore, not all dQ/dV [Ah/V] in the range of SOC 0 [%] to 100 [%] are necessary. The purpose is to find signs of the formation of Ni ₂ O ₃ H. To achieve this purpose, it is not always necessary to calculate dQ/dV [Ah/V] in the range of SOC 0 [%] to 100 [%].

<Determination unit 15>
The determination unit 15 compares the damage index DI calculated by the damage index calculation unit 14 with a pre-stored threshold to determine whether the onboard nickel-metal hydride storage battery is good or bad. Here, if the product is determined to be defective, a warning is given to the driver of the vehicle. In addition, the control unit 11 limits the charging and discharging conditions of the battery module 90 according to the amount of Ni ₂ O ₃ H produced estimated from the damage index DI, thereby suppressing rapid deterioration of the nickel-metal hydride storage battery. Control the vehicle so that it does not interfere with the operation of the vehicle.

<Charge/discharge control unit 16>
The charge/discharge control unit 16 monitors the voltage of the battery module 90 , and when the SOC is lower than the threshold, the motor generator 17 generates power to charge the battery module 90 via the inverter 20 . On the other hand, the battery module 90 is charged by supplying the regenerated current from the motor generator 17 through the inverter 20 when the vehicle is braked. In this case, the charge/discharge control unit 16 limits charging when the current is excessive or the SOC of the battery module 90 is too high. The threshold and the like at this time are stored in the storage unit 13 . Further, in the present embodiment, charging and discharging are controlled so that the potential of the positive electrode becomes a potential at which O ₂ is not generated so that Ni ₂ O ₃ H is not generated.

On the other hand, when the vehicle is driven, the charge/discharge control unit 16 supplies necessary current from the battery module 90 to the motor generator 17 via the inverter 20 in accordance with a command from the vehicle ECU (Electronic Control Unit).

In particular, when the determination unit 15 warns of deterioration of the nickel-metal hydride storage battery, the charge/discharge control unit 16 avoids rapid charge/discharge at low temperatures, etc., to prevent rapid generation of Ni ₂ O ₃ H. Suppress.

(Action of Embodiment)
Since the present embodiment has the configuration as described above, it is accurately estimated using the damage index DI whether or not Ni ₂ O ₃ H is generated in the nickel-metal hydride storage battery.

(Effect of Embodiment)
The method for controlling a nickel-metal hydride storage battery according to this embodiment has the following effects.
(1) It is possible to non-destructively estimate the amount of Ni ₂ O ₃ H that causes a decrease in capacity, and to determine whether the nickel-hydrogen storage battery is to be reused. Therefore, it is possible to reuse the nickel-metal hydride storage battery while ensuring its performance.

(2) Since the inspection is non-destructive, even nickel-metal hydride storage batteries whose use history is unknown can be reused by judging their deterioration.
(3) Since the inspection can be determined only by the battery capacity [Ah] and the module voltage [V], there is no need for a complicated inspection device.

(4) Since the generation of Ni ₂ O ₃ H, which causes a rapid capacity decrease, can be detected at the initial stage, the performance of the nickel-hydrogen storage battery after reuse can be ensured.
(5) Further, since the relationship between the damage index DI and the amount of Ni ₂ O ₃ H produced is obtained in advance and the determination is made using the threshold value based on this relationship, the determination can be made accurately.

(6) Furthermore, since the determination is made based on the relationship between the damage index DI and the amount of Ni ₂ O ₃ H produced, it is possible to estimate how much Ni ₂ O ₃ H is produced from the damage index DI. can.

(7) Since the damage index is determined by the dQ/dV curves during both charging and discharging, deterioration can be determined more accurately.
(8) In the judgment step (S5), if the damage index DI is less than the threshold value, the generation amount calculation step (S9) is further provided. Based on the relationship between the damage index and the Ni ₂ O ₃ H production amount obtained in the threshold setting step (S1), the production amount of Ni ₂ O ₃ H is calculated based on the damage index. Therefore, the production amount of Ni ₂ O ₃ H in the nickel-hydrogen storage battery can be estimated.

(9) If the amount of Ni ₂ O ₃ H produced in the nickel-metal hydride storage battery can be estimated, the service life can be extended by limiting the conditions of use if the deterioration is minor.
(10) In particular, the nickel-metal hydride storage battery inspection method of the present embodiment can also be performed in a vehicle. By doing this in a vehicle, it is possible to anticipate a case in which the nickel-metal hydride storage battery suddenly generates Ni ₂ O ₃ H, making it difficult to operate the vehicle.

(11) In such a case, by limiting the use conditions of the nickel-metal hydride storage battery, it is possible to avoid a sudden difficulty in operating the vehicle.
(Modification)
The above embodiment can also be implemented as follows.

<Modification 1>
FIG. 8 is a graph showing the relationship between the damage index DIc only during charging and the amount of Ni ₂ O ₃ H produced.

In the above embodiment, in the charging/discharging step (S2), the target battery is charged/discharged at a set rate and the charge/discharge curve is obtained. Next, in the Q/dV conversion step (S3), the charge/discharge curve is replaced with a dQ/dV curve. Then, in the damage index DI calculation step (S4), the damage index DI is calculated by adding the absolute value of the minimum peak during discharge to the maximum peak during charge in the dQ/dV curve. Based on the damage index DI calculated in this way, the acceptability of the target nickel-metal hydride storage battery is determined.

On the other hand, in Modification 1, in the charging/discharging step (S2), the target battery is charged at the set rate and only the charging curve is acquired. Next, in the Q/dV converting step (S3), the charging curve is replaced with a dQ/dV curve. Then, in the damage index DI calculation step (S4), the damage index DIc is calculated based only on the absolute value of the maximum peak during charging in the dQ/dV curve shown in FIG. Based on the damage index DIc calculated only for charging in this manner, the acceptability of the target nickel-metal hydride storage battery is determined in the determination step (S5).

Even with such a configuration, it was verified that the production amount of Ni ₂ O ₃ H could be accurately estimated based on the damage index DIc only during charging, as shown in FIG. In Modification 1, according to FIG. 8, the threshold is set to dQ/dV≧10.

Although the damage index DI based on both charging and discharging as in the above embodiment allows more accurate estimation, a simple method such as Modification 1 can also be implemented.
<Modification 2>
FIG. 9 is a graph showing the relationship between the damage index DId and the amount of Ni ₂ O ₃ H produced only during discharge.

In Modified Example 2, in the charging/discharging step (S2), the target battery is discharged at a set rate and only the discharge curve is acquired. Next, in the Q/dV conversion step (S3), the discharge curve is replaced with a dQ/dV curve. Then, in the damage index DI calculation step (S4), the damage index DId is calculated based only on the absolute value of the maximum peak (bottom) during discharge in the dQ/dV curve shown in FIG. Based on the damage index DId calculated only for discharge in this manner, the acceptability of the target nickel-metal hydride storage battery is determined in the determination step (S5).

Even with such a configuration, it was verified that the amount of Ni ₂ O ₃ H produced could be accurately estimated based on the damage index DId only during discharge, as shown in FIG. In modification 2, according to FIG. 9, the threshold is set to |dQ/dV|≧10.

Although the damage index DI based on both charging and discharging as in the above embodiment allows more accurate estimation, a simple method such as Modification 2 can also be implemented.
<Other Modifications>
○ Numerical ranges exemplified in this embodiment are specific examples, and the present invention is not limited to these, and can be appropriately optimized according to the configuration and characteristics of the target nickel-metal hydride storage battery by those skilled in the art. It is.

○ The threshold can be set with an appropriate margin in anticipation of safety.
○ The battery module 90 of the nickel-metal hydride storage battery shown in FIG. 5 and the control device 10 shown in FIG. 7 are examples, and are not limited to such configurations. The control device 10 may perform its functions by means of the ECU of the vehicle. It can also be provided independently within the battery pack.

Of course, the nickel-metal hydride storage battery to be inspected can be unloaded from the vehicle and collected, and the battery can be inspected alone at an inspection factory or the like.
In the present embodiment, the nickel-metal hydride storage battery mounted on an electric vehicle has been described as an example, but the present invention can also be suitably applied to batteries for ships and aircraft. Furthermore, it can also be applied to a stationary battery.

○ The flowchart shown in FIG. 3 is an example of implementation of this embodiment, and it goes without saying that a person skilled in the art can change the order of the procedures, add, delete, or change the procedures.

○ Needless to say, even if the present invention is not described in the embodiments, it is possible for those skilled in the art to add, delete, or change the configuration without departing from the scope of the claims.

A... Bubble B... Bubble 2... Positive electrode active material 22a... Particle 22b... Particle surface 4... Alkaline electrolytic solution 10... Control device 11... Control unit 12... Information acquisition unit 13... Storage unit (program, map, etc.)
DESCRIPTION OF SYMBOLS 14... Damage index calculation part 15... Judgment part 16... Charge/discharge control part 17... Motor generator 20... Inverter 21... Current detector 22... Voltage detector 23... Temperature detector 24... Battery pack 90... Battery module

Claims (12)

In a method for inspecting a nickel-metal hydride storage battery having a positive electrode using nickel hydroxide as an active material, a negative electrode containing a hydrogen storage alloy, and an electrolytic solution made of an alkaline aqueous solution,
a charging step of charging the target battery at a set rate and obtaining a charging curve;
a dQ/dV converting step of replacing the charging curve with a dQ/dV curve;
a damage index calculation step of calculating a damage index from the absolute value of the maximum peak during charging in the dQ/dV curve;
A method for inspecting a nickel-metal hydride storage battery, comprising: judging that the damage index is a non-defective product if the damage index is equal to or greater than a certain threshold value, and that the product is defective if the damage index is less than the threshold value. 2. The method of inspecting a nickel-metal hydride storage battery according to claim 1, wherein the threshold value of said damage index is set to 10 or more. In a method for inspecting a nickel-metal hydride storage battery having a positive electrode using nickel hydroxide as an active material, a negative electrode containing a hydrogen storage alloy, and an electrolytic solution made of an alkaline aqueous solution,
a discharging step of discharging the target battery at a set rate and acquiring a discharge curve;
a dQ/dV conversion step of replacing the discharge curve with a dQ/dV curve;
a damage index calculation step of calculating a damage index from the absolute value of the minimum peak during discharge in the dQ/dV curve;
A method for inspecting a nickel-metal hydride storage battery, comprising: judging that the damage index is a non-defective product if the damage index is equal to or greater than a certain threshold value, and that the product is defective if the damage index is less than the threshold value. 4. The method of inspecting a nickel-metal hydride storage battery according to claim 3, wherein the threshold value of said damage index is set to 10 or more. In a method for inspecting a nickel-metal hydride storage battery having a positive electrode using nickel hydroxide as an active material, a negative electrode containing a hydrogen storage alloy, and an electrolytic solution made of an alkaline aqueous solution,
a charge/discharge step of charging/discharging the target battery at a set rate and acquiring a charge/discharge curve;
a Q/dV conversion step of replacing the charge/discharge curve with a dQ/dV curve;
a damage index calculation step of calculating a damage index by adding the absolute value of the maximum peak during charging to the absolute value of the minimum peak during discharging in the dQ/dV curve;
A method for inspecting a nickel-metal hydride storage battery, comprising: judging that the damage index is a non-defective product if the damage index is equal to or greater than a certain threshold value, and that the product is defective if the damage index is less than the threshold value. 6. The method of inspecting a nickel-metal hydride storage battery according to claim 5, wherein a threshold value of said damage index is set to 20 or more. In the test sample of the nickel-metal hydride storage battery to be inspected in the inspection method for the nickel-metal hydride storage battery, the relationship between the damage index and the amount of Ni ₂ O ₃ H produced is obtained in advance, and the damage in the determination step is determined based on this relationship. 7. The method for inspecting a nickel-metal hydride storage battery according to claim 1, further comprising a threshold setting step of setting a threshold for the index. In the determination step, when the damage index is below the threshold, based on the relationship between the damage index obtained in the threshold setting step and the amount of Ni ₂ O ₃ H produced, 8. The inspection method for _a nickel-hydrogen storage battery according to claim 7, further comprising _a step of calculating the amount of _Ni2O3H produced by calculating the amount of _Ni2O3H produced. If the production amount of Ni ₂ O ₃ H calculated in the step of calculating the production amount of Ni ₂ O ₃ H is equal to or less than the reference value, it is determined that the nickel-metal hydride storage battery can be used under the set usage conditions. 9. The method for inspecting a nickel-metal hydride storage battery according to claim 8, further comprising a step of determining whether the battery is used. 10. The method for inspecting a nickel-metal hydride storage battery according to claim 1, wherein the rate set for said charging or said discharging is 3C or less. 11. The method for inspecting a nickel-metal hydride storage battery according to claim 1, wherein the SOC is 0 to 100% in the charging and discharging ranges. The nickel-metal hydride storage battery according to any one of claims 1 to 11, wherein the nickel-metal hydride storage battery is an in-vehicle battery for driving a vehicle, and the inspection method for the nickel-metal hydride storage battery is performed in the vehicle. inspection method.

Images