JP2023012835A - Control method for alkaline secondary battery, and control device - Google Patents

Abstract

To suppress capacity deterioration of a cathode by fundamentally suppressing, under proper conditions, generation of Ni2O3H that causes capacity reduction.SOLUTION: A control method for a nickel hydride storage battery includes: a step (S2) of cathode potential estimation for calculating and acquiring a potential of a cathode in fixed timing in an alkaline secondary battery comprising the cathode containing nickel hydroxide as an active material, an anode containing a hydrogen-storing alloy, and an electrolyte having an alkaline aqueous solution; a step (S4) of inner pressure estimation for calculating and acquiring an inner pressure of the alkaline secondary battery synchronously with the timing; a step (S7) of damage amount calculation for calculating a damage amount by integrating a residence time in a state of a cathode potential equal to or lower than a threshold (a) and an inner pressure equal to or higher than a threshold (b); and a step (S9) of cathode protection for protecting the cathode at a time point (S8: YES) when the damage amount calculated in the step of damage amount calculation reaches a threshold (c).SELECTED DRAWING: Figure 7

Description

The present invention relates to a control method and a control method for an alkaline secondary battery, and more particularly to a control method and a control device suitable for a vehicle alkaline secondary battery that suppresses deterioration of a positive electrode.

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.

In such an alkaline secondary battery, when the positive electrode potential of the secondary battery becomes lower than a predetermined lower limit potential or higher than a predetermined upper limit potential, a side reaction occurs at the positive electrode and the positive electrode deteriorates. can. Likewise, the negative electrode may be deteriorated when the negative electrode potential is out of the predetermined potential range. Therefore, in order to suppress deterioration of the positive electrode and the negative electrode, each of the positive electrode potential and the negative electrode potential is calculated (monitored), and the charge and discharge of the secondary battery is performed so that each of the positive electrode potential and the negative electrode potential changes within a predetermined potential range. is desired to be controlled.

Therefore, Patent Document 1 discloses the following invention that can accurately estimate the potential of the positive electrode and suppress the occurrence of side reactions.
In a battery system including alkaline secondary batteries, it is desired to improve the accuracy of calculating the positive electrode potential in consideration of the memory effect. Therefore, the battery system includes a unit cell, which is a nickel-metal hydride battery, and an ECU that controls charging and discharging of the unit cell using the positive electrode potential V1 and the negative electrode potential V2 of the cell. The ECU calculates the hydrogen concentration inside the positive electrode active material using a battery model for estimating the internal behavior of the single cell, which includes as inputs the voltage V across the terminals of the single cell, the positive electrode open-circuit potential U1, and the negative electrode open-circuit potential U2. calculate. From the hydrogen concentration, the ECU calculates a memory amount M, which is a potential change amount due to the memory effect of the positive electrode open-circuit potential U1 from the initial potential E1, and uses the initial potential E1 and the memory amount M to calculate the positive electrode open-circuit potential U1. .

According to such an invention, the potential of the positive electrode can be accurately estimated, and the occurrence of side reactions can be suppressed.
In addition, among the side reactions, particularly in a battery system including a nickel-metal hydride battery, an increase in the amount of Ni ₂ O ₃ H produced in the positive electrode causes an irreversible decrease in battery capacity. Therefore, Patent Document 2 discloses the following invention for suppressing the formation of Ni ₂ O ₃ H.

The ECU has the following steps. Obtaining voltage Vb, current Ib and temperature Tb. Calculating the positive electrode potential U+. A step of calculating the upper limit value Up of the positive electrode potential U+. Controlling the PCU to limit the positive electrode potential U+ to a predetermined value or less when the positive electrode potential U+ exceeds the upper limit value Up. A step of executing normal control when the positive electrode potential U+ is equal to or lower than the upper limit value Up. The ECU executes control processing including these steps.

With such an invention, suppression of the production of Ni ₂ O ₃ H can be expected by appropriately suppressing the positive electrode potential.

JP 2018-087785 A JP 2018-10758 A

However, the present inventors believe that the production of Ni ₂ O ₃ H cannot be completely suppressed only by controlling the positive electrode potential, and that the control of the positive electrode potential alone is sufficient to suppress the production of Ni ₂ O ₃ H in alkaline secondary batteries. It was found that there is a problem that generation cannot be suppressed.

Therefore, the problem to be solved by the present invention is to fundamentally suppress the formation of Ni ₂ O ₃ H, which causes a decrease in capacity, under appropriate conditions, thereby suppressing the deterioration of the capacity of the positive electrode.

In order to solve the above-mentioned problems, the method for controlling an alkaline secondary battery of the present invention provides an alkaline secondary 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. In the control method, a positive electrode potential acquisition step of calculating and acquiring the positive electrode potential at a constant timing, an internal pressure acquiring step of calculating and acquiring the internal pressure of the alkaline secondary battery in synchronization with the timing, and a threshold value a The damage amount calculation step of calculating the damage amount by accumulating the stay time in the state when the positive potential is the following and the internal pressure is equal to or higher than the threshold value b, and the damage amount calculated in the damage amount calculation step is A positive electrode protection step was provided to protect the positive electrode when the threshold value c was reached.

In this case, in the step of obtaining the positive electrode potential, an OCV map showing the relationship between the cell voltage and the negative electrode potential is prepared for each temperature and current, and the negative electrode potential is subtracted from the measured value of the cell voltage with reference to the OCV map. , the positive electrode potential may be estimated.

Further, in the step of calculating the internal pressure, the internal pressure of the alkaline secondary battery may be estimated and calculated from the voltage, temperature and current value.
In the step of protecting the positive electrode, the positive electrode potential can be controlled so as not to fall below a threshold value d according to the amount of damage.

The alkaline secondary battery can be suitably implemented in the case of a nickel-hydrogen storage battery. Also, the alkaline secondary battery is a vehicle-mounted battery for driving a vehicle, and can be suitably implemented when the battery is controlled by a battery control device that controls the battery.

A control device for controlling an alkaline secondary battery of the present invention is an alkaline secondary battery that has 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 and is mounted on a vehicle. A positive electrode potential acquisition device that calculates and acquires the potential of the positive electrode at a certain timing, an internal pressure acquisition device that calculates and acquires the internal pressure of the alkaline secondary battery in synchronization with the timing, and a positive electrode that is equal to or lower than the threshold value a. A damage amount calculation device that calculates the amount of damage by accumulating the residence time of the state when the potential is the same and the internal pressure is equal to or higher than the threshold value b, and the damage amount calculated by the damage amount calculation device reaches the threshold value c. A positive electrode protection device is provided to protect the positive electrode when the battery is turned on.

The control method and control device for an alkaline secondary battery of the present invention can fundamentally suppress the generation of Ni ₂ O ₃ H, which causes a decrease in capacity, under appropriate conditions, and effectively suppress the deterioration of the capacity of the positive electrode. can.

FIG. 1(a) is a schematic diagram showing the reaction during charging of the particle surface of the positive electrode active material of a nickel-metal hydride storage battery. FIG. 1(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 graph showing ranges of positive electrode potential [V] and internal pressure [Pa] for generating Ni ₂ O ₃ H. FIG. Graph L1 of the total amount of discharged electricity of the present embodiment, in which the internal pressure is above the threshold b and the positive electrode potential is not below the threshold a, and the internal pressure is above the threshold b and the positive electrode potential is below the threshold a. It is a graph comparing with the graph L2 of the total amount of discharged electricity of the prior art which did not control whether or not to become . 4 is a graph showing changes in capacity retention rate [%] with respect to total discharged electricity [Ah] in experimental examples. FIG. 2 is a cross-sectional view of part of the battery module of the nickel-metal hydride storage battery of the present embodiment; 1 is a block diagram of a control device for a nickel-metal hydride storage battery according to this embodiment; FIG. 4 is a flow chart showing a control method for the nickel-metal hydride storage battery of this embodiment. 4 is a flowchart showing in detail the procedure for estimating the positive electrode potential according to the present embodiment; 4 is a flow chart showing in detail a procedure for estimating internal pressure according to the present embodiment; It is a graph which shows that the amount of damage accumulates with progress of time, and reaches the threshold value c.

A method for controlling an alkaline secondary battery according to the present invention will be described below using an embodiment of a method for controlling a nickel-metal hydride storage battery 1 with reference to FIGS.
<Assumptions of this embodiment>
The purpose of the nickel _- metal hydride storage battery and the method for manufacturing the same of the present embodiment is to effectively suppress 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. 1(a) is a schematic diagram showing oxygen in the reaction during charging of the particle surfaces 2b of the particles 2a of the positive electrode active material 2 of the positive electrode of a nickel-metal hydride storage battery.

FIG. 1(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 2a of positive electrode active material 2 change between Ni(OH) ₂ and β-NiOOH due to charging and discharging. For convenience of explanation, the positive electrode active material may be described as Ni(OH) ₂ . 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>
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. 1(a), when the particle surface 2b 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) A side reaction occurs, and O ₂ bubbles A are generated on the particle surface 2b 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 2b of the positive electrode active material. The O ₂ bubbles A separate from the particle surface 2b 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 O ₂ generated on the particle surfaces 2b of the positive electrode active material to leave the particle surfaces 2b 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 2b of the positive electrode active material block the alkaline electrolyte. As a result, the H ₂ O and OH ⁻ on the particle surface 2b 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>
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 noble. That is, even if the SOC is the same, the voltage increases during charging and decreases during discharging, making it particularly easy for O ₂ to be generated. As a result, at the place where oxygen is generated on the particle surface 2b of the positive electrode active material, the liquid is locally dried up instantaneously, so that H ₂ O is generated in a shortage as shown in the above formula (3). 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.

According to such a mechanism for generating Ni ₂ O ₃ H, even if the positive electrode potential is simply lowered, if oxygen O ₂ is not actually generated, “liquid depletion” does not occur, so Ni ₂ O ₃ H is not generated.

On the other hand, Ni ₂ O ₃ H is not necessarily generated simply because the internal pressure is increased. The rise in the internal pressure of the _secondary battery is not necessarily caused by the generation of gaseous oxygen _O2 , but may be caused by the generation of gaseous hydrogen H2, for example. When the gas of hydrogen H ₂ is generated and the internal pressure is increased, Ni ₂ O ₃ H is also not generated.

That is, the present inventor believes that "liquid depletion" occurs when the decrease in positive electrode potential during charging becomes the potential for generating oxygen, and when oxygen _O2 gas is actually generated and the internal pressure is high. We have deduced and demonstrated 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 usage 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 "liquid depletion" by the mechanism described above.

<Necessity for control of in-vehicle nickel-metal hydride storage batteries>
When Ni ₂ O ₃ H is generated, it accumulates irreversibly, resulting in a decrease in the capacity of nickel-metal hydride storage batteries. The deterioration of the nickel-metal hydride storage battery whose capacity has decreased will progress further unless control is performed according to the deterioration.

<Principle of this embodiment>
Therefore, in the present embodiment, an automotive nickel-hydrogen 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 will be described as an example.

FIG. 2 is a graph showing ranges of positive electrode potential [V] and internal pressure [Pa] at which Ni ₂ O ₃ H is produced. The threshold value a [V] is a boundary value of the positive electrode potential [V] at which oxygen O ₂ is likely to be generated, and the threshold value b [Pa] is used to determine whether gas is generated in the nickel-metal hydride storage battery. Boundary value. For example, the threshold a [V] can be about 0.3 [V], and the threshold b [Pa] can be about 0.3 [Pa]. However, the value varies depending on the shape of the battery and the material such as the active material, and is not particularly limited.

In the case of the lower left region VLPL, which is “positive electrode potential equal to or lower than threshold value a” and not “internal pressure equal to or higher than threshold value b”, since the internal pressure is low, less oxygen O ₂ is generated and Ni ₂ O ₃ H due to “liquid dryness” generation is unlikely to occur.

In addition, in the case of the upper right region VHPH, which is not "the positive electrode potential equal to or lower than the threshold value a" but "the internal pressure equal to or higher than the threshold value b", although the internal pressure is high, the gas generated due to the high positive electrode potential is oxygen _O2 . Therefore, it is unlikely that Ni ₂ O ₃ H will be generated due to the above-mentioned "dryness".

_In the upper left region _{VHPL ,} which is neither “the positive electrode potential equal to or lower than the threshold value a” nor “the internal pressure equal to or higher than the threshold value b”, the internal pressure is low. less likely to occur.

In the lower right region VLPH in the state of "positive potential equal to or lower than threshold value a" and "internal pressure equal to or higher than threshold value b", the positive potential is a potential at which oxygen _O2 is likely to be generated by the mechanism described above. Moreover, it is presumed that the internal pressure is actually high and oxygen O ₂ is generated, and there is an extremely high possibility that Ni ₂ O ₃ H will be generated due to "liquid depletion". Therefore, the staying time in the state of "positive electrode potential equal to or less than threshold value a" and "internal pressure equal to or greater than threshold value b" is calculated. The positive electrode potential [V] and the internal pressure [Pa] are simultaneously measured and calculated at regular timings (for example, at intervals of 1 second in this embodiment) by the control device 10 (see FIG. 7) during operation of the vehicle. That is, it is assumed that a predetermined amount of Ni ₂ O ₃ H is generated in the state of "positive electrode potential equal to or lower than threshold value a" and "internal pressure equal to or higher than threshold value b" synchronized at intervals of one second. In other words, how long the nickel-metal hydride storage battery stays in a state where there is an extremely high possibility that Ni ₂ O ₃ H will be generated with a “positive electrode potential below threshold a” and “internal pressure above threshold b”. Data.

In the present embodiment, attention is focused on how long the user stays in a state in which there is an extremely high possibility that Ni ₂ O ₃ H will be generated with “positive electrode potential equal to or lower than threshold value a” and “internal pressure equal to or higher than threshold value b”. are doing. Therefore, it is also possible to measure the residence time in a state in which the possibility that such Ni ₂ O ₃ H is actually generated is extremely high. However, in proportion to the number of times of "frequency" which is the number of times of acquisition detected by the above procedure, it can be estimated that Ni ₂ O ₃ H is likely to be generated and stays for a long time. Therefore, in the present embodiment, "staying time" is represented by "frequency" for simplification of processing, and this "frequency" is accumulated, and this is considered as "amount of damage".

By calculating the "frequency" of the state in which the possibility of generating Ni ₂ O ₃ H is extremely _high , the _{Ni 2} The accumulated amount of O ₃ H is estimated and regarded as the “damage amount”. This "amount of damage" is a variable indicating the generation of _{Ni2O3H ,} and in this embodiment, the unit is the number of counts. The threshold value c is determined through an experiment to see how many times the "damage amount" is accumulated before the battery capacity deteriorates.

<Frequency [%] at which the positive electrode potential in the experimental example became equal to or lower than the threshold value a>
FIG. 3 is a graph comparing the case where the positive electrode potential is controlled and the case where it is not. A graph L1 shows the total amount of discharged electricity [Ah] controlled so that the internal pressure [Pa] is equal to or higher than the threshold b [Pa] and the positive electrode potential [V] is controlled to be equal to or lower than the threshold a [V]. Graph L2 shows the total amount of discharged electricity in the prior art that does not control whether the internal pressure [Pa] is equal to or higher than the threshold b [Pa] and the positive electrode potential [V] is equal to or lower than the threshold a [V].

The inventors compared the total amount of discharged electricity between Experimental Example 1 and Experimental Example 2. FIG. In Experimental Example 1, control was performed so that the internal pressure [Pa] is equal to or higher than the threshold value b [Pa] and the positive electrode potential [V] is not equal to or lower than the threshold value a. Experimental example 2 is a conventional technique that does not control whether the internal pressure [Pa] is equal to or higher than the threshold b [Pa] and the positive electrode potential is equal to or lower than the threshold a.

In Experimental Example 1, when the internal pressure [Pa] is equal to or higher than the threshold value b [Pa], the positive electrode potential [V] is controlled so as not to become equal to or lower than the threshold value a [V]. Therefore, as shown in the graph L1, even if the total amount of discharged electricity [Ah] increases, the frequency of the positive electrode potential [V] falling below the threshold value a [V] is zero. As a result, in the nickel-hydrogen storage battery of Experimental Example 1, the battery life could be maintained until the total amount of discharged electricity [Ah] greatly exceeded 6000 [Ah].

On the other hand, in Experimental Example 2 of the prior art, it was not controlled whether the internal pressure [Pa] is equal to or higher than the threshold value b [Pa] and the positive electrode potential [V] is equal to or lower than the threshold value a [V]. Therefore, as shown in graph L2, the frequency [%] at which the positive electrode potential [V] becomes equal to or lower than the threshold value a [V] is zero until the total amount of discharged electricity [Ah] exceeds 2000 [Ah]. there were. However, when the total amount of discharged electricity [Ah] exceeds 2000 [Ah], the frequency [%] at which the positive electrode potential [V] becomes equal to or lower than the threshold value a [V] suddenly increases. When the total amount of discharged electricity [Ah] exceeded approximately 3000 [Ah], the frequency exceeded 80%, and the battery life ended. It can be presumed that this is because once Ni ₂ O ₃ H is generated, the generated Ni ₂ O ₃ H further rapidly causes liquid drying, and Ni ₂ O ₃ H is generated at an accelerated rate.

<Battery life of experimental example>
FIG. 4 is a graph showing changes in the capacity retention rate [%] with respect to the total amount of discharged electricity [Ah] in the experimental example.

The capacity retention rate [%] is a value indicating the ratio of the battery capacity to 100% of the unused battery capacity. In the nickel-hydrogen storage battery of Experimental Example 1 indicated by L3, when the total amount of discharged electricity [Ah] is 2000 [Ah], the capacity retention rate [%] is less than 90%. Furthermore, as the total amount of discharged electricity [Ah] increases, the capacity retention rate [%] gradually decreases. Then, when the total amount of discharged electricity [Ah] reaches approximately 6000 [Ah], the capacity retention rate [%] drops below 80% at this point, but it is still a usable capacity retention rate [%].

On the other hand, in Experimental Example 2 indicated by L4, when the total amount of discharged electricity [Ah] is 2000 [Ah], the capacity retention rate [%] is less than 90%, and there is no big difference from Experimental Example 1.
However, when the total amount of discharged electricity [Ah] reaches 3000 [Ah], the capacity retention rate [%] rapidly decreases to about 70%. At this point, the capacity retention rate [%] has already reached the point at which battery replacement is required.

Furthermore, when the total amount of discharged electricity [Ah] exceeds 3000 [Ah], the capacity retention rate [%] drops sharply to about 60%, and the battery life is completely exhausted.
<Reason why the nickel-metal hydride storage battery control method of the present embodiment can prolong the battery life>
As can be seen from FIGS. 3 and 4, the rapid drop in battery capacity in Experimental Example 2 of the prior art is due to the fact that once Ni ₂ O ₃ H is generated, the liquid is rapidly depleted, and Ni ₂ O accelerates. It can be presumed that this is due to the generation of _3H . Therefore, by setting the positive electrode voltage [V] and the internal pressure [Pa] at which Ni _{2 O 3 H is not generated before the accumulated amount of Ni 2 O 3 H is} generated explosively due to such rapid liquid depletion, It reliably suppresses the generation of Ni ₂ O ₃ H.

In the present embodiment, by managing the accumulated amount of Ni ₂ O ₃ H as the amount of damage, the amount of Ni ₂ O ₃ H accumulated in the target nickel-metal hydride storage battery can be accurately estimated, and this Appropriate control is performed according to the amount of damage. Such control can extend the capacity life of the positive electrode of the nickel-hydrogen storage battery.

<Control Device for Nickel Metal Hydride Storage Battery of Present Embodiment>
An example of a nickel-metal hydride storage battery and its control device, which are prerequisites for the present embodiment, will be briefly described below.

<Nickel metal hydride storage battery>
FIG. 5 shows a cross-sectional view of part of the battery module 90 of the nickel-metal hydride storage battery of this embodiment. As shown in FIG. 5, the nickel-metal hydride storage battery is a sealed battery, and is an in-vehicle battery used as a power source for vehicles such as electric vehicles and hybrid vehicles. As a nickel-metal hydride storage battery mounted on a vehicle, there is known a prismatic sealed secondary battery comprising a battery module 90 configured by electrically connecting a plurality of cells 110 in series in order to obtain a required power capacity. ing.

The battery module 90 has a rectangular parallelepiped rectangular case 300 composed of an integrated battery case 100 capable of accommodating a plurality of cells 110 and a lid body 200 sealing the integrated battery case 100 . It should be noted that the prismatic case 300 can be made of resin.

The integrated battery case 100 that constitutes the rectangular case 300 is made of a synthetic resin material, such as polypropylene or polyethylene, that is resistant to an alkaline electrolyte. A partition wall 120 is formed inside the integrated battery case 100 to partition the plurality of unit cells 110 . The integrated battery case 100 has, for example, six battery cases 130, of which four are shown in FIG.

In the container 130 thus partitioned, the electrode plate group 140 and the positive electrode current collector plate 150 and the negative electrode current collector plate 160 joined to both sides of the electrode plate group 140 are housed together with the electrolyte.
The electrode plate group 140 is configured by stacking a rectangular positive electrode plate 141 and a rectangular negative electrode plate 142 with a separator 143 interposed therebetween. At this time, the direction in which the positive electrode plate 141, the negative electrode plate 142 and the separator 143 are stacked (the direction perpendicular to the paper surface) is the stacking direction. The positive electrode plate 141 and the negative electrode plate 142 of the electrode plate group 140 protrude to the opposite side portions in the direction of the plate surface (the direction along the plane of the drawing), so that the lead portion 141 a of the positive electrode plate 141 and the negative electrode plate 142 are projected. lead portion 142a is configured. Current collecting plates 150 and 160 are joined to the side edges of these lead portions 141a and 142a, respectively.

In addition, through holes 170 used for connecting the battery containers 130 are formed in the upper part of the partition wall 120 . The through-hole 170 is formed by two connection projections 151 and 161, a connection projection 151 projecting from the top of the current collector plate 150 and a connection projection 161 projecting from the top of the current collection plate 160. A weld connection is made through the through hole 170 . As a result, the electrode plate groups 140 of the battery containers 130 adjacent to each other are electrically connected in series. Of the through-holes 170 , the through-holes 170 located outside the battery containers 130 at both ends are fitted with the positive electrode connection terminal 152 or the negative electrode connection terminal (not shown) above the end sidewalls of the integrated battery container 100 . . The positive electrode connection terminal 152 is welded to the connection protrusion 151 of the current collector plate 150 . The negative electrode connection terminal is welded to the connection protrusion 161 of the current collector plate 160 . The electrode plate group 140 connected in series in this manner, that is, the total output of the plurality of cells 110 is taken out from the positive connection terminal 152 and the negative connection terminal.

On the other hand, the cover 200 constituting the prismatic case 300 has an exhaust valve 210 that reduces the internal pressure of the prismatic case 300 to the valve opening pressure or less, and a sensor mounting hole for mounting a sensor for detecting the temperature of the electrode plate group 140. 220 is provided. The sensor mounting hole 220 allows the temperature of the electrode plate group 140 to be measured by a hole extending through the battery case 130 to the vicinity of the electrode plate group 140 .

The exhaust valve 210 is for maintaining the internal pressure in the integrated battery case 100 below the permissible threshold, and when the internal pressure exceeds the permissible threshold and exceeds the valve opening pressure, , the gas generated inside the integrated battery case 100 is discharged by opening the valve. The internal pressure of the integrated battery container 100 is made uniform in all the battery containers 130 by communication holes (not shown) formed in the partition walls 120 . As a result, the integrated battery container 100 discharges gas until the internal pressure equalized in all battery containers 130 becomes less than the valve opening pressure, and the internal pressure is maintained below the permissible valve opening pressure. become.

<Structure of Electrode Group 140>
<Positive electrode plate 141>
The positive electrode plate 141 uses a foamed nickel three-dimensional porous body made of a porous metal Ni or a Ni alloy 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 electrode plate 141 includes a positive electrode mixture 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 b of the positive electrode substrate to form a positive electrode mixture layer. After that, by drying, rolling and cutting, the plate-like positive electrode plate 141 is formed.

<Negative Plate 142>
The negative electrode plate 142 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. Thereafter, 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 to form a plate-like negative electrode plate 142 . to form

<Separator 143>
As the separator 143, a nonwoven fabric made of an olefin resin such as polypropylene, or a nonwoven fabric subjected to hydrophilic treatment such as sulfonation as necessary, can be used.

The battery module 90 of the nickel-metal hydride storage battery of this embodiment has the configuration described above.
<Control device 10 for nickel-metal hydride storage battery>
FIG. 6 is a block diagram of the control device 10 of the nickel-metal hydride storage battery 1 of this embodiment. Next, referring to FIG. 6, the control device 10 of the nickel-hydrogen storage battery 1 will be described. Here, the case where the nickel-metal hydride storage battery 1 is controlled in the state of the battery pack 24 containing the battery module 90 will be described.

<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 arranged in the sensor mounting hole 220 shown in FIG. The temperature sensor measures the temperature near the electrode plate group 140 of the corresponding cell 110 of 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 . In addition, this control unit 11 functions as a damage amount calculation device and a positive electrode protection device.

<Information Acquisition Unit 12>
The information acquisition unit 12 successively acquires the charging current value from the current detector 21, acquires the voltage value from the voltage detector 22, acquires the 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 comprises a program for executing the following steps of the flow charts shown in FIGS. 7-9. For example, programs for positive electrode potential estimation (S2), internal pressure estimation (S4), and positive electrode protection control (S9) in FIG. 7 are stored. Furthermore, the following program of FIG. 9 is stored. A step of acquiring the relationship between the charge reserve and the gas absorption rate (S401). Measurement step (S402). A step for calculating the internal pressure increase rate (S403). A step of estimating the charge reserve amount (S404). A step for calculating an internal pressure decrease speed correction value (S405). Step (S406) for calculating the rate of decrease in internal pressure. A step for calculating the corrected internal pressure decrease rate (S407). Estimated internal pressure calculation step (S408). A negative electrode SOC estimation step (S409). A step for calculating the hydrogen equilibrium pressure (S410). A step for calculating the corrected negative electrode hydrogen equilibrium pressure (S411). A step of calculating the corrected estimated internal pressure (S412).

Further, in the storage unit 13, as data presupposed for control, for each temperature [°C] and current [A] used in the positive electrode potential estimating unit 14, "cell voltage [V] and negative electrode potential [V] Table data based on the OCV map from which the relationship was acquired" is stored. A map based on actual measurement data of "relationship between charge reserve and gas absorption rate" used in internal pressure estimating unit 15 is also stored. Maps of "relationship between temperature and internal pressure increase rate" and "relationship between temperature and internal pressure decrease rate" are also stored. In addition, a map of "relationship between battery voltage and negative electrode SOC" is also stored. A map of "relationship between negative electrode SOC and hydrogen equilibrium pressure" is also stored. A map of "relationship between temperature and hydrogen equilibrium pressure" is also stored.

In addition, a map of "deterioration state of the battery estimated from the usage history of the nickel-metal hydride storage battery 1" and "relationship between the deterioration state of the nickel-metal hydride storage battery 1 and the charge reserve amount" is also stored.
<Positive electrode potential estimation unit 14>
The positive electrode potential estimator 14 estimates the potential of the negative electrode from the cell voltage measured by the voltage detector 22 and the “table data for acquiring the relationship between the cell voltage and the negative electrode potential” stored in advance in the storage unit 13 . Then, the positive electrode potential estimation unit 14 estimates the positive electrode potential from the difference between the cell voltage and the negative electrode potential. This positive electrode potential estimation unit 14 causes the control device 10 to function as a positive electrode potential acquisition device.

<Internal pressure estimation unit 15>
The internal pressure estimation unit 15 estimates the internal pressure of the battery based on the temperature, voltage, current, etc. of the on-vehicle nickel-metal hydride storage battery acquired and accumulated by the information acquisition unit 12 according to the procedure of the flowchart shown in FIG. Details will be described later. The internal pressure estimator 15 causes the control device 10 to function as an internal pressure acquisition device.

<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 . Also, in the positive electrode protection control (S9) shown in FIG. 8, charging and discharging are controlled so that the potential of the positive electrode does not fall below the threshold value d.

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).

<Procedure of control method for nickel-metal hydride storage battery of the present embodiment>
FIG. 7 is a flow chart showing the procedure of the control method for the nickel-metal hydride storage battery of this embodiment. The procedure of the control method for the nickel-metal hydride storage battery of this embodiment will be described with reference to FIG.

As described above, before executing the procedure of the nickel-metal hydride storage battery control method of the present embodiment, the storage unit 13 of the control device 10 stores table data and Data such as maps are stored.

When the operation of the vehicle is started (start), first, it is determined whether or not the control is continued (S0). When the control ends (S0: YES) such as when the operation of the vehicle ends (S0: YES), the control method for the nickel-metal hydride storage battery also ends (end). If the control is continued (S0; NO), if it is the predetermined timing for estimating the positive electrode potential (S2) or estimating the internal pressure (S4), the voltage [V], current [A], Temperature [°C] and the like are measured (S1). This timing is measured by a counter of the control device 10, for example, at a fixed timing every one second. Therefore, whether or not it is the measurement timing is determined every 100 ms (S1), and before the measurement timing (S1: NO), a standby loop (S0: NO→S1: NO→S0) is established. Then, when a predetermined measurement timing arrives (S1: YES), the voltage [V], current [A], and temperature [°C] of the nickel-metal hydride storage battery are measured, and the positive electrode potential is estimated (S2) and the internal pressure is estimated (S4). ) are processed simultaneously in parallel.

<Positive electrode potential estimation procedure (S2)>
FIG. 8 is a flowchart showing in detail the subroutine of the positive electrode potential estimation (S2) procedure of this embodiment. The procedure for estimating the positive electrode potential (S2) will be described in detail below with reference to the flowchart shown in FIG.

When the positive electrode potential estimation (S2) is started, first, the measured cell voltage [V], temperature [°C], and current [A] are read (S201). Next, the “table data for acquiring the relationship between the cell voltage and the negative electrode potential” stored in the storage unit 13 for each temperature [° C.] and current [A] is read out (S202). Estimate the negative electrode potential [V] by referring to the "table data that acquired the relationship between the cell voltage and the negative electrode potential" for the read cell voltage [V] and the corresponding temperature [°C] and current [A]. (S203). Next, based on the estimated negative electrode potential,
Cell voltage [V] - negative electrode potential [V] = positive electrode potential [V]
Based on this relationship, the positive electrode potential [V] is estimated (S204).

The positive electrode potential [V] is estimated by the above procedure, the procedure of positive electrode potential estimation (S2) is completed (end), and whether or not the positive electrode potential [V] in FIG. Proceed to the determination procedure (S3).

<Procedure for Determining Whether Positive Electrode Potential [V] Is Below Threshold Value a [V] (S3)>
The positive electrode potential [V] estimated in the step of estimating the positive electrode potential (S2) is adjusted in advance to match the characteristics of the target nickel-metal hydride storage battery. , and stored in the storage unit 13 of the control device 10 . The control unit 11 reads out the threshold a [V] stored in the storage unit 13, and the positive electrode potential [V] estimated in the procedure of positive electrode potential estimation (S2) is equal to or less than the threshold a [V]. (S3). If the positive electrode potential [V] estimated in the procedure of positive electrode potential estimation (S2) is not equal to or lower than the threshold value a [V] (S3: NO), the process returns to S0, and it is determined whether or not the control is finished (S0). (S0: NO→S1: NO→S0).

On the other hand, if the positive electrode potential [V] estimated in the procedure of positive electrode potential estimation (S2) is equal to or less than the threshold value a [V] (S3: YES), the information acquiring unit 12 set a flag.

<Internal Pressure Estimation Procedure (S4)>
The control unit 11 executes the internal pressure estimation procedure (S4) in parallel with the positive electrode potential estimation procedure (S2).

FIG. 9 is a flowchart of a subroutine showing details of the procedure (S4) for estimating the internal pressure of this embodiment. The internal pressure estimation procedure (S4) will be described with reference to the flowchart shown in FIG.

First, the control device 10 (see FIG. 6) measures the voltage, current, and temperature of the nickel-hydrogen storage battery 1 in a measurement step (S402). Then, in the internal pressure decrease rate calculation step (S406), the "internal pressure decrease rate" based on the gas absorption rate of the negative electrode is calculated based on the measured temperature. In parallel, in the step of estimating the amount of charge reserve (S404), the "reserve charge amount" is estimated based on the measured voltage, current, and temperature. In the step (S405) of calculating the correction value of internal pressure decrease speed, the "correction value of internal pressure decrease rate" is calculated based on the estimated "charge reserve amount". For this estimation, the relationship between the charge reserve and the gas absorption rate of the negative electrode is read in advance into the storage unit 13 (see FIG. 6) of the control device 10 (S401). Then, in the corrected internal pressure decrease speed calculation step (S407), the "internal pressure decrease speed" calculated in the internal pressure decrease speed correction value calculation step (S405) is corrected based on the "internal pressure decrease speed correction value" to make it more accurate. Calculate the appropriate “corrected internal pressure decrease rate”.

Next, in the estimated internal pressure calculation step (S408), the "estimated internal pressure" is calculated from the "corrected internal pressure decrease rate" and the "internal pressure increase rate" calculated based on the temperature.
Furthermore, the negative electrode SOC is estimated in the negative electrode SOC estimation step (S409). Also, in the hydrogen equilibrium pressure calculation step (S410), the "hydrogen equilibrium pressure" of the negative electrode is calculated from the temperature. On the other hand, in the corrected hydrogen equilibrium pressure calculation step (S411), the "corrected hydrogen equilibrium pressure" is calculated from the relationship between the negative electrode SOC and the hydrogen equilibrium pressure of the negative electrode.

Then, in the step of calculating the corrected estimated internal pressure (S412), a more accurate "corrected estimated internal pressure" is calculated based on the "hydrogen equilibrium pressure".
After calculating the "corrected estimated internal pressure" in this manner, the procedure for estimating the internal pressure (S4) ends.

A procedure for estimating the internal pressure [Pa] according to the procedure described above, ending the procedure for estimating the internal pressure (S4) (end), and determining whether or not the internal pressure [Pa] in FIG. 7 is equal to or greater than the threshold value b [Pa]. Proceed to (S5).
<Procedure for determining whether the internal pressure is equal to or greater than the threshold value b (S5)>
The internal pressure estimated in the procedure of internal pressure estimation (S4) is the internal pressure [Pa] at which the internal pressure [Pa] due to gas generation may cause liquid dryness according to the characteristics of the target nickel-metal hydride storage battery in advance. Pa]” and stored in the storage unit 13 of the control device 10 . The control unit 11 reads the threshold value b [Pa] stored in the storage unit 13, and determines whether the internal pressure [Pa] estimated in the internal pressure estimation (S4) procedure is equal to or greater than the threshold value b [Pa]. (S5). If the internal pressure [Pa] estimated in the procedure of internal pressure estimation (S4) is not equal to or greater than the threshold value b [Pa] (S5: NO), the process returns to S0, where it is determined whether or not the control is finished (S0), and the next measurement is performed. Wait until timing (S0: NO→S1: NO→S0).

On the other hand, if the internal pressure [Pa] estimated in the procedure of internal pressure estimation (S4) is equal to or greater than the threshold value b [Pa] (S5: YES), a flag is set to the information acquisition unit 12 to carry out the processing in S6. stand up.

<Process when the positive electrode potential is equal to or lower than the threshold a [V] of the positive electrode potential and equal to or higher than the threshold b [Pa] of the internal pressure (S6)>
If the information acquisition unit 12 has a flag of the positive potential threshold value a [V] or less and a flag of the internal pressure value of the internal pressure threshold value b [Pa] or more set at the same time, the control unit 11 sets the positive potential threshold value a [V]. or less and equal to or greater than the internal pressure threshold value b [Pa]. Then, it is presumed that Ni ₂ O ₃ H is generated in the measurement of this cycle, and it is qualified as “one frequency”.

<Frequency Integration (S7)>
The control unit 11 accumulates the "frequency" certified in S6 to the information acquisition unit 12 and stores it as a "frequency integrated value" (S7). This "frequency integrated value" is referred to as a "damage amount" in the present embodiment. The unit is number of times. That is, it can be thought of as the accumulated total amount of Ni ₂ O ₃ H, which is estimated to be generated when the positive electrode potential threshold a [V] or less and the internal pressure threshold b [Pa] or more.

<Determination of whether or not integrated frequency value≧threshold value c (S8)>
The total accumulated amount of Ni ₂ O ₃ H that significantly shortens the life of the target nickel-metal hydride storage battery is set as the threshold value c through experiments or the like. Then, the frequency integrated value obtained in S7 is compared with the threshold value c (S8). Here, if the frequency integrated value≧threshold value c is not satisfied, that is, if the frequency integrated value is less than the threshold value c (S8: NO), it is assumed that there is no problem with the positive electrode of the target nickel-metal hydride storage battery, and the process returns to S0 to perform the next measurement. Wait until timing (S0: NO→S1: NO→S0). In this case, it is determined that there is no problem with the current positive electrode potential control, and the current positive electrode potential control is continued without changing the current positive electrode potential control.

FIG. 10 is a graph showing that the amount of damage accumulates irreversibly over time and reaches a threshold c. In the determination of whether or not the integrated frequency value≧threshold value c (S8), it is determined whether or not “integrated frequency value≧threshold value c”. If the frequency integrated value is equal to or greater than the threshold value c (S8: YES), it is determined that Ni ₂ O ₃ H is accumulated in the positive electrode of the target nickel-metal hydride storage battery and that there is a problem with the current positive electrode potential control. . That is, as shown in FIG. 10, under the control as it is, the amount of damage, that is, the accumulated amount of Ni ₂ O ₃ H will cause an avalanche-like capacity decrease as shown in Experimental Example 2 in FIGS. 3 and 4. indicates that it is approaching

Therefore, when the integrated frequency value≧threshold value c (S8: YES), the positive electrode protection control procedure (S9) is performed. That is, the threshold value c is the limit frequency at which the capacity of the nickel-hydrogen storage battery can be maintained within a normal range.

<Positive electrode protection control (S9)>
The positive electrode protection control procedure (S9) changes the positive electrode protection control procedure. Under the current control, the accumulated amount of Ni ₂ O ₃ H was underestimated, and unexpected production of Ni ₂ O ₃ H was permitted. Therefore, in order to further suppress the formation of Ni ₂ O ₃ H, the control standard is made stricter. Specifically, the threshold d [V] of the positive electrode potential [V] for generating oxygen O ₂ was raised from the current threshold d [V] of the positive electrode potential [V] to the threshold d [V]. Instead, a higher threshold d+α [V] of the positive electrode potential [V] is set. Then, the control device 10 controls the positive electrode potential [V] based on the threshold value d+α[V] of the positive electrode potential [V] set higher so that the positive electrode potential [V] does not become less than the threshold value d+α[V]. Specifically, the control unit 11 constantly monitors the cell voltage [V] of the battery module 90 . Then, the positive electrode potential [V] is estimated, and the cell voltage [V] is reduced when the motor generator 17 consumes a large amount of power, or when the motor generator 17 consumes power due to loads such as air conditioners and lights that do not generate power for a long time. Detect when it drops. In such a case, the positive electrode potential [V] is reduced by generating power or limiting the output of the motor generator 17 so that the estimated positive electrode potential [V] does not fall below the newly set threshold value d+α [V]. Make sure that it does not fall below the newly set threshold value d+α [V]. Such control effectively suppresses the formation of Ni ₂ O ₃ H, thereby extending the capacity life of the nickel-metal hydride storage battery. After completing the positive electrode protection control procedure (S9), the process returns to S0.

(Action of Embodiment)
Since the present embodiment has the configuration as described above, the Ni ₂ O ₃ H is generated and accumulated in the nickel-metal hydride storage battery mounted on the vehicle. There is

Specifically, the frequency of states when the positive electrode potential is equal to or lower than the threshold value a [V] and the internal pressure is equal to or higher than the threshold value b [Pa] is integrated (S7). By accumulating this frequency, the amount of Ni ₂ O ₃ H accumulated in the positive electrode of the nickel-metal hydride storage battery can be accurately estimated as the “damage amount”.

This amount of damage is monitored, and if it exceeds a predetermined threshold value c (S8: YES), the positive electrode protection step (S9) is performed so as not to cause a sudden drop in capacity of the nickel-metal hydride storage battery. . The action of the positive electrode protection step (S9) is to control the positive electrode potential to a potential at which Ni ₂ O ₃ H is less likely to be generated, thereby preventing a rapid decrease in capacity of the nickel-metal hydride storage battery. be.

(Effect of Embodiment)
The method for controlling a nickel-metal hydride storage battery according to this embodiment has the following effects.
(1) In the method for controlling a nickel-metal hydride storage battery according to the present embodiment, the production of Ni ₂ O ₃ H, which causes a decrease in capacity, can be fundamentally suppressed under appropriate conditions, and the capacity deterioration of the positive electrode can be suppressed.

(2) In the control method of the nickel-metal hydride storage battery of the present embodiment, the control device 10 is composed of a computer mounted on the vehicle, and is a so-called on-board system that is completed only by the configuration on the vehicle. Therefore, when the vehicle is operated, it is possible to autonomously implement the nickel-metal hydride storage battery control method of the present embodiment to protect the on-vehicle nickel-metal hydride storage battery.

(3) In particular, it is possible to avoid a situation in which the vehicle cannot be operated suddenly due to a sudden decrease in the positive electrode capacity during operation of the vehicle.
(4) The method includes a positive electrode potential obtaining step of calculating and obtaining the potential of the positive electrode, and an internal pressure obtaining step of calculating and obtaining the internal pressure of the alkaline secondary battery. Since the conditions under which Ni ₂ O ₃ H is produced are determined by comprehensively analyzing these procedures, the conditions under which Ni ₂ O ₃ H is produced can be specified accurately. Therefore, the generation of Ni ₂ O ₃ H can be reliably estimated.

(5) Since the condition of the positive electrode potential and the condition of the internal pressure are determined by the threshold a and the threshold b derived from experiments and the like, accurate determination can be made.
(6) In the step of obtaining the positive electrode potential, an OCV map showing the relationship between the cell voltage and the negative electrode potential is provided for each temperature and current, and the negative electrode potential is subtracted from the measured cell voltage with reference to the OCV map. Estimate the potential. Therefore, even in the in-vehicle control device 10, the processing can be performed quickly.

(7) In the internal pressure calculation step, the internal pressure of the alkaline secondary battery is estimated and calculated from the voltage, temperature, and current values. Therefore, the internal pressure can be accurately estimated by considering various conditions.

(8) By replacing the accumulation state of Ni ₂ O ₃ H with the amount of damage and judging by the threshold value d, it is possible to easily estimate that the battery is in a dangerous state of rapid deterioration, and Ni ₂ O ₃ H can be avoided from being generated all at once at an accelerated rate.

( ₉ ) When the accumulation of _Ni2O3H is large and the capacity of the battery is at risk _, the positive electrode protection step can prevent further accumulation of _Ni2O3H .
(10) According to the positive electrode protection step, the positive electrode potential is controlled so as not to fall below the threshold value d according to the amount of damage. Therefore, Ni ₂ O ₃ H can be prevented from accumulating any more.

(11) The control method for the nickel-metal hydride storage battery of the present embodiment can be implemented using an ECU or the like for controlling existing batteries. Therefore, the control method of the nickel-metal hydride storage battery of this embodiment can be implemented only with software. Therefore, the control method of the nickel-metal hydride storage battery of this embodiment can be implemented without modifying the existing vehicle.

(Modification)
The above embodiment can also be implemented as follows.
〇 In this embodiment, in the present embodiment, how much time stays in a state where there is an extremely high possibility that Ni ₂ O ₃ H is generated with “positive electrode potential equal to or lower than threshold value a” and “internal pressure equal to or higher than threshold value b” It is judged by the number of times of "frequency". However, regardless of the "frequency", it is also possible to measure and integrate the residence time in a state where the possibility of Ni ₂ O ₃ H being produced is extremely high.

〇In addition, in the present embodiment, as shown in FIG. 2, Ni 2 O 3 is divided into four regions according to the threshold a and the threshold b, and the Ni ₂ O ₃ is divided into four regions with a “positive electrode potential equal to or lower than the threshold a” and an “internal pressure equal to or higher than the threshold b”. It determines the state in which H is most likely to be generated. However, a plurality of thresholds may be set according to the possibility of Ni ₂ O ₃ H being generated, and the weighted values for each region may be integrated.

O In this embodiment, the "positive electrode potential" is estimated from the cell voltage by a predetermined method. However, it may be estimated by a method based on other estimation methods. Furthermore, of course, a method of actually measuring the "positive electrode potential" instead of estimating it may be used.

○In addition, the "internal pressure" in this embodiment is also estimated from information such as voltage, current, and temperature. This estimation method is an example, and a more simplified method or a method of estimating from other data may be used. Furthermore, of course, a method of actually measuring the "internal pressure" instead of estimating it may be used.

○ The battery module 90 of the nickel-metal hydride storage battery shown in FIG. 5 and the control device 10 shown in FIG. 6 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. Moreover, it can also be provided independently in the battery pack 24 .

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.

〇Alkaline secondary batteries are not limited to nickel-metal hydride storage batteries, and other alkaline secondary batteries can also be used.
○ The flowcharts shown in FIGS. 7 to 9 are examples 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 and implement them. stomach.

○ Numerical ranges exemplified in the present embodiment are specific examples, and the present invention is not limited to these, and can be appropriately optimized according to the target alkaline secondary battery by those skilled in the art. .

○ 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.

1 Nickel-metal hydride storage battery 2 Positive electrode active material 2a Particle 2b Particle surface 4 Alkaline electrolyte 10 Nickel-metal hydride storage battery control device 11 Control unit 12 Information acquisition unit 13 Storage unit (program, map, battery use history, etc.)
DESCRIPTION OF SYMBOLS 14... Positive electrode electric potential estimation part 15... Internal pressure estimation 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 100... Integral Battery case 110 Single battery 120 Partition wall 130 Battery case 140 Electrode plate group 141 Positive electrode plate 141a Lead portion 142 Negative electrode plate 142a Lead portion 143 Separator 150 Current collector 151 Connection protrusion 152 Connection DESCRIPTION OF SYMBOLS Terminal 160... Current collector plate 161... Connection protrusion 170... Through hole 200... Cover body 210... Exhaust valve 220... Sensor mounting hole 300... Square case

Claims (7)

In a control method for an alkaline secondary battery having a positive electrode using nickel hydroxide as an active material, a negative electrode containing a hydrogen storage alloy, and an electrolytic solution comprising an alkaline aqueous solution,
a positive electrode potential acquisition step of calculating and acquiring the potential of the positive electrode at a constant timing;
an internal pressure acquisition step of calculating and acquiring the internal pressure of the alkaline secondary battery in synchronization with the timing;
a damage amount calculation step of calculating the damage amount by accumulating the residence time in the state when the positive electrode potential is equal to or lower than the threshold value a and the internal pressure is equal to or higher than the threshold value b;
A control method for an alkaline secondary battery, comprising a positive electrode protection step of protecting a positive electrode when the damage amount calculated in the damage amount calculation step reaches a threshold value c. In the step of obtaining the positive electrode potential, an OCV map showing the relationship between the cell voltage and the negative electrode potential is prepared for each temperature and current, and the negative electrode potential is subtracted from the measured cell voltage value with reference to the OCV map, thereby obtaining the positive electrode potential. 2. The method for controlling an alkaline secondary battery according to claim 1, wherein .theta. 3. The method of controlling an alkaline secondary battery according to claim 1, wherein in the step of acquiring the internal pressure, the internal pressure of the alkaline secondary battery is estimated and calculated from voltage, temperature, and current values. 4. The method of controlling an alkaline secondary battery according to claim 1, wherein said positive electrode protection step controls the positive electrode potential so that it does not fall below a threshold value d according to the amount of damage. The method of controlling an alkaline secondary battery according to any one of claims 1 to 4, wherein the alkaline secondary battery is a nickel-metal hydride storage battery. The alkaline secondary battery is an in-vehicle battery for driving a vehicle,
6. The method for controlling an alkaline secondary battery according to claim 1, wherein the control is performed by a battery control device that controls the alkaline secondary battery. A control device for controlling an alkaline secondary battery mounted on a vehicle and 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 positive electrode potential acquisition device that calculates and acquires the potential of the positive electrode at a constant timing;
an internal pressure acquisition device that calculates and acquires the internal pressure of the alkaline secondary battery;
a damage amount calculation device that calculates the amount of damage by integrating the stay time in a state where the positive electrode potential is equal to or lower than the threshold value a and the internal pressure is equal to or higher than the threshold value b;
A control device for an alkaline secondary battery, comprising a positive electrode protection device for protecting a positive electrode when the damage amount calculated by the damage amount calculation device reaches a threshold value c.

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