CN115621427A - Method and device for controlling alkaline secondary battery - Google Patents

Method and device for controlling alkaline secondary battery Download PDF

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Publication number
CN115621427A
CN115621427A CN202210145573.8A CN202210145573A CN115621427A CN 115621427 A CN115621427 A CN 115621427A CN 202210145573 A CN202210145573 A CN 202210145573A CN 115621427 A CN115621427 A CN 115621427A
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positive electrode
internal pressure
secondary battery
electrode potential
potential
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室田洋辅
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Primearth EV Energy Co Ltd
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Primearth EV Energy Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/24—Electrodes for alkaline accumulators
    • H01M4/26—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/24—Electrodes for alkaline accumulators
    • H01M4/32—Nickel oxide or hydroxide electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Secondary Cells (AREA)
  • Protection Of Static Devices (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)

Abstract

A method for controlling an alkaline secondary battery having a positive electrode containing nickel hydroxide as an active material, a negative electrode containing a hydrogen storage alloy, and an electrolyte solution composed of an alkaline aqueous solution, the method comprising: a positive electrode potential estimation step (S2) for calculating and obtaining the potential of the positive electrode at a fixed timing; an internal pressure estimation step (S4) for calculating and obtaining the internal pressure of the alkaline secondary battery in synchronization with the timing; a loss amount calculation step (S7) for calculating the retention time of the state when the positive electrode potential is less than or equal to a threshold value a and the internal pressure is greater than or equal to a threshold value bAccumulating to calculate the loss amount; and a positive electrode protection step (S9) for protecting the positive electrode when the loss calculated in the loss calculation step reaches a threshold value (c) (YES in S8). Thus, ni that may cause a decrease in capacity can be fundamentally suppressed under appropriate conditions 2 O 3 H is generated, and the capacity degradation of the positive electrode is effectively suppressed.

Description

Method and device for controlling alkaline secondary battery
Technical Field
The present invention relates to a control method and a control device for an alkaline secondary battery, and more particularly, to a control method and a control device for an alkaline secondary battery for a vehicle suitable for suppressing deterioration of a positive electrode.
Background
An electric vehicle (including a hybrid vehicle) equipped with an electric motor drives the electric motor by 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 vehicle applications because they can be charged and discharged with a large current.
In such an alkaline secondary battery, when the potential of the positive electrode of the secondary battery is lower than a predetermined lower limit potential or higher than a predetermined upper limit potential, a side reaction occurs in the positive electrode, and the positive electrode may be deteriorated. With respect to the negative electrode, deterioration may also occur due to the negative electrode potential being outside the predetermined potential range. Therefore, in order to suppress deterioration of the positive electrode and the negative electrode, it is preferable to calculate (monitor) the positive electrode potential and the negative electrode potential, respectively, and control charge and discharge of the secondary battery so that the positive electrode potential and the negative electrode potential change within predetermined potential ranges, respectively.
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 an alkaline secondary battery, it is preferable to improve the calculation accuracy of the positive electrode potential in consideration of the memory effect. Therefore, the battery system includes a battery cell as a nickel-metal hydride battery, and an ECU that controls charging and discharging of the battery cell using a positive electrode potential V1 and a negative electrode potential V2 of the battery cell. The ECU includes, as inputs, an inter-terminal voltage V, a positive open potential U1, and a negative open potential U2 of the cell, and calculates the hydrogen concentration inside the positive electrode active material using a battery model for estimating the internal behavior of the cell. The ECU calculates a storage amount M (which is an amount of potential change due to memory effect of the initial potential E1 based on the positive electrode open potential U1) from the hydrogen concentration, and calculates the positive electrode open potential U1 using the initial potential E1 and the storage amount M.
According to the present invention, the potential of the positive electrode can be accurately estimated, and the occurrence of side reactions can be suppressed.
In addition, in side reactions, particularly in battery systems including nickel-metal hydride batteries, there is a possibility that Ni in the positive electrode may be present 2 O 3 The problem is that the battery capacity irreversibly decreases as the amount of H produced increases. Therefore, patent document 2 discloses suppression of Ni 2 O 3 H production of the following invention.
The ECU executes a control process including a plurality of steps. The steps include the following steps: obtaining a voltage Vb, a current Ib and a temperature Tb; calculating the positive electrode potential U +; calculating an upper limit value Up of a positive electrode potential U +; a step of controlling the PCU so that the positive electrode potential U + is limited to a predetermined value or less when the positive electrode potential U + exceeds the upper limit value Up; and executing normal control when the positive electrode potential U + is less than or equal to the upper limit value Up.
According to the invention, ni can be expected by appropriately suppressing the positive electrode potential 2 O 3 Suppression of H production.
Documents of the prior art
Patent literature
Patent document 1: japanese patent laid-open publication No. 2018-087785
Patent document 2: japanese patent laid-open publication No. 2018-10758
Disclosure of Invention
Problems to be solved by the invention
However, the present inventors have found that Ni 2 O 3 The generation of H cannot be completely suppressed by controlling only the positive electrode potential, and Ni cannot be sufficiently suppressed in an alkaline secondary battery by controlling only the positive electrode potential 2 O 3 H is generated.
Therefore, an object to be solved by the present invention is to fundamentally suppress Ni that causes a decrease in capacity under appropriate conditions 2 O 3 H is generated, and deterioration of the positive electrode capacity is suppressed.
Means for solving the problems
In order to solve the above problems, a method for controlling an alkaline secondary battery according to the present invention is a method for controlling an alkaline secondary battery including a positive electrode containing nickel hydroxide as an active material, a negative electrode containing a hydrogen storage alloy, and an electrolyte solution composed of an alkaline aqueous solution, the method including the steps of: a positive electrode potential obtaining step of calculating and obtaining a positive electrode potential at a predetermined timing; an internal pressure obtaining step of calculating and obtaining an internal pressure of the alkaline secondary battery in synchronization with the timing; a loss amount calculation step of calculating a loss amount by integrating a retention time in a state where the retention time is an internal pressure equal to or less than a first threshold (a) and equal to or more than a second threshold (b); and a positive electrode protection step of protecting the positive electrode when the loss amount calculated in the loss amount calculation step reaches a third threshold value (c).
In this case, in the positive electrode potential obtaining step, an OCV map showing a relationship between the cell voltage and the negative electrode potential may be stored in advance for each of the temperature and the current, and the positive electrode potential may be estimated by subtracting the negative electrode potential from an actually measured value of the cell voltage with reference to the OCV map.
In the internal pressure calculation step, the internal pressure of the alkaline secondary battery may be estimated from the voltage, the temperature, and the current value.
The positive electrode protecting step may be controlled so that the positive electrode potential does not become equal to or lower than the fourth threshold (d) corresponding to the amount of loss.
The alkaline secondary battery can be suitably used in the case of a nickel-metal hydride storage battery. The alkaline secondary battery is a vehicle-mounted battery for driving a vehicle, and can be suitably used when the battery is controlled by a battery control device for controlling the battery.
A control device for an alkaline secondary battery according to the present invention controls an alkaline secondary battery mounted on a vehicle and having a positive electrode containing nickel hydroxide as an active material, a negative electrode containing a hydrogen storage alloy, and an electrolyte solution composed of an alkaline aqueous solution, the control device comprising: a positive electrode potential obtaining device for calculating and obtaining the potential of the positive electrode at a certain timing; an internal pressure obtaining device for calculating and obtaining the internal pressure of the alkaline secondary battery in synchronization with the timing; loss amount calculation means for calculating a loss amount by integrating the retention time of a state in which the positive electrode potential is equal to or lower than a first threshold value a and the internal pressure is equal to or higher than a second threshold value b; and a positive electrode protection device for protecting the positive electrode when the loss calculated by the loss calculation device reaches a third threshold value c.
ADVANTAGEOUS EFFECTS OF INVENTION
The alkaline secondary battery control method and control device of the present invention can fundamentally suppress Ni that may cause a decrease in capacity under appropriate conditions 2 O 3 H is generated, and the capacity degradation of the positive electrode is effectively suppressed.
Drawings
Fig. 1 (a) is a schematic diagram showing a reaction of the particle surface of the positive electrode active material of the nickel-metal hydride storage battery during charging, and fig. 1 (b) is a reaction equation showing a normal main reaction of the positive electrode during discharging and an abnormal side reaction when oxygen is generated to cause local "electrolyte dry".
FIG. 2 is a schematic diagram showing the generation of Ni 2 O 3 Positive electrode potential of H [ V ]]And internal pressure [ Pa]A graph of the range of conditions of (1).
Fig. 3 is a diagram comparing a curve L1 of the total discharge power amount (controlled so that the internal pressure is equal to or higher than the threshold value b and the positive electrode potential is not equal to or lower than the threshold value a) of the present embodiment with a curve L2 of the total discharge power amount (not controlled so that whether the internal pressure is equal to or higher than the threshold value b and the positive electrode potential is equal to or lower than the threshold value a) of the related art.
Fig. 4 is a graph showing changes in the capacity retention rate [% ] with respect to the total discharge capacity [ Ah ] of the experimental examples.
Fig. 5 is a partial sectional view of a battery module of the nickel-metal hydride storage battery according to the present embodiment.
Fig. 6 is a block diagram of a control device for a nickel-metal hydride storage battery according to the present embodiment.
Fig. 7 is a flowchart illustrating a method of controlling the nickel-metal hydride storage battery according to the present embodiment.
Fig. 8 is a flowchart showing the procedure of positive electrode potential estimation according to the present embodiment in detail.
Fig. 9 is a flowchart illustrating in detail the internal pressure estimation process according to the present embodiment.
Fig. 10 is a graph showing that the loss amount is accumulated with the elapse of time and reaches the threshold value c.
Detailed Description
A method for controlling an alkaline secondary battery according to an embodiment of the method for controlling a nickel-metal hydride storage battery 1 of the present invention will be described below with reference to fig. 1 to 10.
< premise of the present embodiment >
The purpose of the nickel-metal hydride storage battery of the present embodiment and the method for manufacturing the same is to effectively suppress Ni 2 O 3 And H is generated. Therefore, first to Ni 2 O 3 The mechanism of H formation will be described.
< surface of particles of Positive electrode active Material >
Fig. 1 (a) is a schematic diagram showing oxygen in a reaction at the time of charging on the particle surface 2b of the particles 2a of the positive electrode active material 2 of the nickel-hydrogen storage battery.
Fig. 1 (b) is a reaction formula showing a normal main reaction of the positive electrode at the time of discharge and an abnormal side reaction at the time of local "electrolyte dry" due to oxygen generation.
< Main reaction of Positive electrode during discharge >
The particles 2a of the positive electrode active material 2 are charged and discharged with Ni (OH) 2 And beta-NiOOH. For convenience of explanation, ni (OH) may be used 2 The form of (b) will be described with respect to the positive electrode active material. The normal main reaction of a nickel-metal hydride storage battery during discharge is represented by the following formula (1) and expressed as H 2 With the proviso that the presence of O produces Ni (OH) from beta-NiOOH 2 And OH - . In this case, H of the electrolyte 2 O is consumed and decreases. OH group - And functions as alkaline ions of the alkaline electrolyte 4. In this case, oxygen (O) is not generated by the exchange of ions and electrons 2 ) Hydrogen (H) 2 ) A gas.
β-NiOOH+H 2 O+e - →Ni(OH) 2 +OH - ……(1)
< production of oxygen by side reaction and occurrence of "drying of electrolyte >
The potential of the positive electrode may be lowered. And reaches H 2 H is generated as a side reaction at the electrolysis potential of O 2 And (4) electrolyzing O. H 2 In the electrolysis of O, O is generated at the positive electrode by the reaction of the following formula (2) 2 。
4OH - →O 2 +2H 2 O+4e - ……(2)
As shown in FIG. 1 (a), ni (OH) as a positive electrode active material 2 When the particle surface 2b of the positive electrode active material of/. Beta. -NiOOH becomes a low potential by charging, a side reaction represented by the above formula (2) occurs, and O is present on the particle surface 2b of the positive electrode active material 2 Form of bubble A of (2) to form O 2 . Positive electrode generation of O during charging 2 When is, O 2 The bubbles a of (2) are attached to the particle surface 2b of the positive electrode active material. The O is 2 The bubbles a are detached from the particle surface 2b of the positive electrode active material with the passage of time. Thus, the part from which the bubbles A are removed comes into contact with the alkaline electrolyte 4 to supply H 2 O、OH - 。
However, depending on the conditions, O is generated on the particle surface 2b of the positive electrode active material 2 It may take time to detach from the particle surface 2B of the positive electrode active material like the air bubbles B. Thus, O such as air bubbles B attached to the particle surface 2B of the positive electrode active material 2 The bubbles will block the alkaline electrolyte. As a result, H on the particle surface 2b of the positive electrode active material 2 O、OH - Physically excluded, this part becomes a local "electrolyte dry" state. H 2 O、OH - None are physically present here.
<Ni based on "electrolyte drying 2 O 3 Generation of H>
Thus, in the normal reaction, as shown in formula (1) of FIG. 1 (b), H is required in the reaction 2 O but not supplying H 2 When the "electrolyte of O dries out", an abnormal side reaction occurs at the time of discharge of the nickel-metal hydride storage battery, and the reaction of the following formula (3) is constituted.
16β-NiOOH+4e - →8Ni 2 O 3 H+2H 2 O+O 2 +4OH - ……(3)
I.e. without using H 2 O reacts with H to form H 2 And O. Ni was produced as a product in this case 2 O 3 H、O 2 And OH - . Wherein, O 2 As time passes, the negative electrode is smoothly absorbed (recombined) with the separator through the separator as shown in the following formula (4)Reaction), a closed system was maintained. OH group - And returned to the alkaline electrolyte 4.
4MH+O 2 →4M+2H 2 O……(4)
Here, ni 2 O 3 H is an electrochemically inert product, in the formation of Ni 2 O 3 When H is consumed, irreversible accumulation occurs, which causes problems such as an increase in battery resistance and a decrease in battery capacity. Thus, ni 2 O 3 The production of H is generally suppressed as an undesirable reaction.
< memory Effect of Nickel-Metal hydride storage Battery >
It is known that a nickel-metal hydride storage battery has a memory effect due to repeated charge and discharge at a low SOC. In a battery system in which a memory effect occurs, since the voltage shifts to the high potential side, even if the SOC is the same, the voltage increases during charging and decreases during discharging, and O is particularly easily generated 2 . As a result, local drying of the electrolyte occurs instantaneously at the site where oxygen is generated on the particle surface 2b of the positive electrode active material, and thus, as shown in the above formula (3), H is not sufficiently generated 2 Reaction of O with formation of Ni 2 O 3 H. When Ni is generated 2 O 3 H causes a rapid capacity decrease.
<Ni in nickel-hydrogen storage battery 2 O 3 Mechanism of H formation>
As described above, in the nickel-metal hydride storage battery, ni is generated by the potential of the positive electrode at the time of charging 2 O 3 H generates oxygen O due to a side reaction of charging 2 The internal pressure of the secondary battery is increased. For passing through the O 2 Thereby causing 'drying of the electrolyte' and generation of Ni 2 O 3 The mechanism of H was analyzed.
Such Ni 2 O 3 The mechanism of H formation is that even if the positive electrode potential is simply lowered, oxygen O is not actually formed 2 Then "drying of the electrolyte" does not occur, so that Ni is not generated 2 O 3 H。
On the other hand, ni is not necessarily generated only by the increase of the internal pressure 2 O 3 H. IIThe rise in the internal pressure of the secondary battery is not necessarily limited to oxygen O 2 Due to the formation of gases of (2), e.g. sometimes also due to hydrogen H 2 Is generated by the gas of (1). In the formation of hydrogen H 2 When the internal pressure is increased by the gas (2), ni is not generated 2 O 3 H。
That is, the present inventors estimated that the decrease in the positive electrode potential during charging constitutes an oxygen evolution potential, and oxygen O is actually generated 2 The gas (2) is in a state of high internal pressure, and "drying out of the electrolyte" occurs, and this is confirmed.
< memory Effect of Nickel-Hydrogen storage Battery for vehicle >
Next, the memory effect of the nickel-metal hydride storage battery mounted on a vehicle will be described. An electric vehicle (including a hybrid vehicle) equipped with an electric motor drives the electric motor by 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 vehicle applications because they can be charged and discharged with a large current. Such an in-vehicle nickel-metal hydride storage battery is sometimes exposed to a severe use environment. For example, charging and discharging may be repeated in a low SOC (State Of Charge) State. It is known that a memory effect occurs under such a use environment. When the memory effect occurs, the charging curve of the battery is shifted to the high potential side. That is, the positive electrode potential increases even at the same SOC. On the other hand, during discharge, the discharge curve of the battery shifts to the low potential side. That is, the positive electrode potential decreases even at the same SOC. Thus, according to the above mechanism, ni tends to occur easily due to "drying out of electrolyte 2 O 3 And H is generated.
< necessity of control for vehicle-mounted nickel-hydrogen storage Battery >
In the generation of Ni 2 O 3 When H is consumed, irreversible accumulation occurs, resulting in a decrease in the capacity of the nickel-metal hydride storage battery. In the nickel-metal hydride storage battery in which such a capacity decrease has occurred, if the control for the deterioration is not performed, the deterioration is further advanced.
< principle of the present embodiment >
In this embodiment, a nickel-metal hydride storage battery for vehicle use, which includes a positive electrode containing nickel hydroxide as an active material, a negative electrode containing a hydrogen storage alloy, and an electrolyte solution composed of an alkaline aqueous solution, will be described as an example.
FIG. 2 is a diagram showing the generation of Ni 2 O 3 Positive electrode potential of H [ V ]]With internal pressure [ Pa]A graph of the range of conditions (iv). Threshold a [ V ] corresponding to first threshold]To easily generate oxygen O 2 Positive electrode potential of]Is equivalent to the threshold b [ Pa ] of the second threshold]Is a boundary value for determining whether or not gas is generated in the nickel-metal hydride storage battery. For example, the threshold a [ V ] may be illustrated]Is 0.3[ v ]]Left and right, threshold b [ Pa]Is 0.3[ Pa ]]Left and right. However, the value varies depending on the shape of the battery, the material of the active material, and the like, and is not particularly limited.
In the case of the region VLPL below the left of "positive electrode potential not higher than threshold a" and not "internal pressure not lower than threshold b", the internal pressure is low, so that oxygen O is present 2 Less generation of Ni due to "drying of electrolyte" occurs 2 O 3 The probability of generation of H is low.
In the case where the positive electrode potential is not "the positive electrode potential at or below the threshold a" and the internal pressure is "the internal pressure at or above the threshold b" in the upper right region VHPH, it is estimated that the gas generated is not oxygen O because the positive electrode potential is high although the internal pressure is high 2 Ni caused by "drying out of electrolyte" as described above occurs 2 O 3 The probability of generation of H is low.
In the case where the internal pressure is not in the upper left region VHPL of "positive electrode potential not higher than threshold a" and "internal pressure not lower than threshold b", the internal pressure is low, and therefore oxygen O is present 2 Less generation of Ni due to "drying of electrolyte" occurs 2 O 3 The probability of generation of H is also low.
In the lower right region VLPH in the state of "positive electrode potential not higher than threshold a" and "internal pressure not lower than threshold b", the positive electrode potential is likely to generate oxygen O due to the above-described mechanism 2 The potential of (2). In the region VLPH, it is estimated that the internal pressure is substantially high and oxygen O is generated 2 Ni caused by "drying of electrolyte" occurs 2 O 3 The probability of generation of H is extremely high. Therefore, the retention time in the state of "positive electrode potential not higher than threshold a" and "internal pressure not lower than threshold b" is calculated. About anode potential [ V]And internal pressure [ Pa]The measurement and calculation are performed simultaneously at a fixed timing (for example, at 1 second intervals in the present embodiment) by the control device 10 (see fig. 7) operated in the vehicle. That is, it is assumed that a predetermined amount of Ni is generated in synchronization with the 1 second interval in a state of "positive electrode potential not higher than threshold a" and "internal pressure not lower than threshold b 2 O 3 H. That is, the positive electrode potential [ V ] is measured and calculated at the same time at a fixed timing]And internal pressure [ Pa]Indicates that Ni is generated at a positive electrode potential of not more than a threshold value a and an internal pressure of not less than a threshold value b during the use time of the nickel-hydrogen storage battery 2 O 3 Data on how much the state with a high probability of H stays.
In the present embodiment, attention is paid to the generation of Ni at "positive electrode potential not higher than threshold a" and "internal pressure not lower than threshold b 2 O 3 How long H stays in a state where the probability of H is extremely high. Therefore, it is also possible to actually measure the Ni produced 2 O 3 The residence time of the state where the probability of H is extremely high. However, it is presumed that Ni is being produced in proportion to the number of "frequencies" as the number of acquisitions detected by the above-described procedure 2 O 3 The very high probability of H remaining for a long period of time. Therefore, in the present embodiment, from the viewpoint of simplification of the process, "stay time" is expressed as "frequency", and the "frequency" is accumulated and regarded as "loss amount".
By calculating the occurrence of Ni 2 O 3 The "frequency" of a state in which the possibility of H generation is extremely high is estimated to be that Ni is generated in such a state 2 O 3 Ni produced in a state where the possibility of H production is extremely high 2 O 3 The amount of accumulated H is regarded as "the amount of loss". The "amount of loss" is represented by Ni 2 O 3 The variable for H generation is in units of counts in the present embodiment. The capacity of the battery is determined by an experiment in which the capacity of the battery is deteriorated when the "loss amount" is accumulated by how many timesA threshold value c corresponding to the third threshold value.
< frequency [% ] at which positive electrode potential of experimental example is not more than threshold a >
Fig. 3 is a diagram for comparing a case where the positive electrode potential is controlled with a case where the positive electrode potential is not controlled. The curve L1 represents the total discharge electric energy [ 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 not equal to or lower than the threshold a [ V ]. Curve L2 represents the total discharge electric energy in the related art in which the internal pressure [ Pa ] is not less than the threshold b [ Pa ] and the positive electrode potential [ V ] is not less than the threshold a [ V ] or not less.
The present inventors compared the total discharge capacity in experimental example 1 and experimental example 2. In experimental example 1, the internal pressure [ Pa ] was controlled to be not less than the threshold value b [ Pa ] and the positive electrode potential [ V ] was controlled not to be not less than the threshold value a. Experimental example 2 is a conventional technique in which control is not performed so that the internal pressure [ Pa ] is not less than the threshold b [ Pa ] and the positive electrode potential is not less than the threshold a or not less than the threshold a.
In experimental example 1, the internal pressure [ Pa ] is controlled to be not less than the threshold value b [ Pa ] and the positive electrode potential [ V ] is controlled not to be less than the threshold value a [ V ]. Therefore, as shown in the curve L1, even if the total discharge electric energy [ Ah ] increases, the frequency at which the positive electrode potential [ V ] is equal to or lower than the threshold value a [ V ] is zero. As a result, in the nickel-metal hydride storage battery of experimental example 1, the battery life was maintained until the total discharge electric energy [ Ah ] significantly exceeded 6000[ Ah ].
On the other hand, in the prior art experimental example 2, the internal pressure [ Pa ] was not performed]Is greater than or equal to a threshold value b [ Pa ]]And positive electrode potential [ V]Is a threshold value a [ V ]]Or below the threshold a or not. Therefore, as shown by the curve L2, at the total discharge capacity [ Ah]Above 2000[ 2 ], [ Ah ]]Front, anode potential [ V ]]Is a threshold value a [ V ]]Frequency [ ]]Is zero. However, at the total discharge capacity [ Ah]Above 2000[ 2 ], [ Ah ]]Then, the positive electrode potential [ V ]]Is a threshold value a [ V ]]Frequency [ ]]Suddenly increased in height. And, when the total discharge electric quantity [ Ah ]]Substantially exceeding 3000[ alpha ], [ Ah ]]At a frequency of more than 80%, the battery life is exhausted. This is presumably because Ni is once generated 2 O 3 H, then due to the generated Ni 2 O 3 H further causes the electrolyte to be further rapidlyDry to accelerate the formation of Ni 2 O 3 H。
< Battery Life of Experimental example >
Fig. 4 is a graph showing changes in the capacity retention rate [% ] with respect to the total discharge capacity [ Ah ] of the experimental examples.
The capacity retention rate [% ] is a value representing the proportion of the battery capacity when the unused battery capacity is 100%, and here, for example, when it is 70% or less, it is regarded as the battery life is exhausted. In the nickel-metal hydride storage battery of experimental example 1 represented by L3, the capacity retention rate [% ] is about less than 90% when the total discharge electric quantity [ Ah ] is 2000[ Ah ]. Further, as the total discharge electric power amount [ Ah ] increases, the capacity maintenance rate [% ] gradually decreases. Also, when the total discharge capacity [ Ah ] is approximately [ 6000 ] Ah ], the capacity maintenance rate [% ] is reduced to 80%, and remains a usable capacity maintenance rate [% ].
On the other hand, in experimental example 2 shown by L4, when the total discharge electric charge [ Ah ] is 2000[ Ah ], the capacity retention rate [% ] is about less than 90%, and there is not much difference from experimental example 1.
However, when the total discharge capacity [ Ah ] is 3000[ Ah ], the capacity retention rate [% ] is rapidly reduced to about 70%. At this time, the capacity maintenance rate [% ] requiring battery replacement is already present.
Further, when the total discharge capacity [ Ah ] is greater than 3000[ Ah ], the capacity maintenance rate [% ] is drastically reduced to about 60%, and the battery life is completely exhausted.
< reason why the method for controlling a nickel-metal hydride storage battery according to the present embodiment can extend the battery life >
As can be understood from fig. 3 and 4, in experimental example 2 of the conventional art, the battery capacity is drastically reduced because Ni is once generated 2 O 3 H will quickly cause the electrolyte to dry up and accelerate the generation of Ni 2 O 3 H. Therefore, ni is explosively generated by such rapid electrolyte drying 2 O 3 Making the accumulated amount of H before Ni generation 2 O 3 Positive electrode voltage [ V ] of H]And internal pressure [ Pa]Can surely suppress Ni 2 O 3 And H is generated.
In this embodiment modeBy applying such Ni 2 O 3 The accumulated amount of H is managed as a loss amount, and Ni accumulated in the target nickel-metal hydride storage battery can be accurately estimated 2 O 3 The amount of H is appropriately controlled in accordance with the amount of loss. The capacity life of the positive electrode of the nickel-metal hydride storage battery can be extended by such control.
< control device for Nickel-Metal hydride storage Battery of the present embodiment >
An example of a nickel-metal hydride storage battery and a control device therefor, which are the premise of the present embodiment, will be briefly described below.
< Nickel-hydrogen storage Battery >
Fig. 5 shows a partial sectional view of a battery module 90 of the nickel-metal hydride storage battery of the present 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, a prismatic sealed secondary battery including a battery module 90 is known, and the battery module 90 is configured by electrically connecting a plurality of battery cells 110 in series.
The battery module 90 includes a rectangular parallelepiped rectangular case 300 including an integrated electric tank 100 capable of housing a plurality of electric cells 110 and a lid 200 sealing the integrated electric tank 100. Note that, the square case 300 may be a case made of resin.
The integrated electric cell 100 constituting the square case 300 is made of a synthetic resin material (for example, polypropylene, polyethylene, etc.) having resistance to alkaline electrolyte. A partition wall 120 for partitioning the plurality of unit cells 110 is formed inside the integrated electric tank 100, and a portion partitioned by the partition wall 120 constitutes an electric tank 130 for each unit cell 110. The integrated cell 100 has, for example, 6 cells 130, of which a portion of 4 are shown in fig. 5.
The electrode plate group 140, and the positive electrode collector plate 150 and the negative electrode collector plate 160 joined to both sides thereof are housed in the electric cell 130 thus partitioned together with the electrolytic solution.
The electrode group 140 is formed by stacking rectangular positive and negative electrode plates 141 and 142 with a separator 143 interposed therebetween. In this case, 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 group 140 protrude from opposite sides in the plate surface direction (direction along the paper surface), thereby constituting a lead portion 141a of the positive electrode plate 141 and a lead portion 142a of the negative electrode plate 142. Collector plates 150 and 160 are joined to side end edges of the lead portions 141a and 142a, respectively.
Further, a through hole 170 for connecting each cell 130 is formed in an upper portion of the partition wall 120. The through-hole 170 is welded to the connection protrusion 151 protruding from the upper portion of the current collector plate 150 and the connection protrusion 161 protruding from the upper portion of the current collector plate 160, respectively, by the through-hole 170. Thereby electrically connecting the electrode plate groups 140 of respectively adjacent cells 130 in series. The positive connection terminal 152 or the negative connection terminal (not shown) is attached to the upper end side wall of the integrated electric cell 100 through the through-holes 170 located outside the electric cells 130 at both ends among the through-holes 170. The positive connection terminal 152 is welded to the connection protrusion 151 of the collector plate 150. The connection terminal of the negative electrode is welded to the connection projection 161 of the current collector plate 160. The total output of the electrode group 140, i.e., the plurality of cells 110 connected in series in this manner is taken out from the positive connection terminal 152 and the negative connection terminal.
On the other hand, the lid body 200 constituting the rectangular case 300 is provided with an exhaust valve 210 for setting the internal pressure of the rectangular case 300 to a valve opening pressure or less, and a sensor mounting hole 220 for mounting a sensor for detecting the temperature of the electrode group 140. The sensor mounting holes 220 enable the temperature of the electrode plate group 140 to be measured through holes extending to the vicinity of the electrode plate group 140 within the electric bath 130.
The exhaust valve 210 is used to maintain the internal pressure in the integrated electric tank 100 at or below a permissible threshold, and when the internal pressure is equal to or above a valve opening pressure that exceeds the permissible threshold, the exhaust valve opens to exhaust gas generated inside the integrated electric tank 100. The internal pressure of the integrated electric cell 100 is equalized throughout the electric cell 130 by the communication holes, not shown, formed in the partition wall 120. Thus, the gas in the integrated electric cell 100 is discharged until the internal pressure becomes uniform throughout the electric cell 130 and becomes lower than the valve opening pressure, and the internal pressure is maintained at a pressure lower than the allowable valve opening pressure.
< construction of electrode group 140 >
< Positive electrode plate 141>
In the positive electrode plate 141, a foamed nickel three-dimensional porous body made of Ni or a Ni alloy as a porous metal is used as a positive electrode base material as a base material. The positive electrode base material has a skeleton portion having a three-dimensional network structure, and a hole portion surrounded by the skeleton portion. The positive electrode base material is produced by, for example, performing nickel plating on the urethane skeleton surface of the foamed urethane, and then burning out the foamed urethane. The positive plate 141 contains Ni (OH) 2 And a positive electrode composite material layer containing Co as an active material. Specifically, a suitable amount of a conductive agent such as cobalt hydroxide or metal cobalt powder, and if necessary, a thickener such as carboxymethyl cellulose, or a binder such as polytetrafluoroethylene are added to granular nickel hydroxide, and the mixture is first processed into a paste. Then, the paste-like processed material is filled into the mesh-like holes of the positive electrode substrate to form a positive electrode composite material layer. Thereafter, the positive electrode plate 141 is dried, rolled, and cut to form a plate-like positive electrode plate.
< negative electrode plate 142>
The negative electrode plate 142 is formed, for example, with a hydrogen storage alloy containing, as a constituent element, a mixed rare earth metal that is a mixture of rare earth elements such as lanthanum, cerium, and neodymium, and nickel, aluminum, cobalt, and manganese as an active material. More specifically, the hydrogen absorbing alloy is first processed into a paste by adding a conductive agent such as carbon black, and if necessary, a thickener such as carboxymethyl cellulose, and a binder such as a styrene-butadiene copolymer. Then, the hydrogen storage alloy thus processed into a paste is applied or filled to a core material such as a punching metal (active material support), and then dried, rolled, and cut to form the negative electrode plate 142 similarly in a plate shape.
< spacers 143>
As the separator 143, a nonwoven fabric of an olefin resin such as polypropylene or a member obtained by subjecting the nonwoven fabric to hydrophilic treatment such as sulfonation as needed can be used.
The battery module 90 of the nickel-metal hydride storage battery of the present embodiment has the above configuration.
< 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 according to the present embodiment. Next, the control device 10 of the nickel-metal hydride storage battery 1 will be described with reference to fig. 6. Here, a case will be described in which the nickel-metal hydride storage battery 1 is controlled in a state of the battery assembly 24 in which the battery module 90 is housed.
< control device 10>
The control device 10 as a battery control device is mounted on a vehicle, and can control the battery module 90 of the vehicle in real time or based on accumulated data, so-called on-board (on-board).
The control device 10 controls the inverter 20 as a charging device for charging the battery module 90, and supplies a current from a motor generator (generator) 17 as a generator to the battery module 90, thereby charging the battery module 90. The control device 10 controls the inverter 20 as a power supply device to discharge the current from the battery module 90 to the motor generator 17 as a load driving motor.
The control device 10 includes: a current detector 21 that measures the current of the battery module 90; a voltage detector 22 for measuring the voltage between the terminals of the battery module 90; and a temperature detector 23 for measuring the temperature of the battery module 90.
The temperature detector 23 includes a temperature sensor disposed in the sensor mounting hole 220 shown in fig. 5. The temperature sensor measures the temperature near the electrode group 140 of the corresponding battery cell 110 in the battery module 90, and outputs the measured temperature value as an electrical signal to the control device 10.
< control section 11>
The 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. The control unit 11 functions as a loss amount calculation device and a positive electrode protection device.
< information acquisition section 12>
The information obtaining unit 12 obtains the charging current value by the current detector 21, obtains the voltage value by the voltage detector 22, and obtains and stores the battery temperature by the temperature detector 23.
< storage section 13>
The storage unit 13 includes a storage medium storing a program of the control device 10 and necessary data. The program includes a program for executing the flowcharts shown in fig. 7 to 9, for example, a program for executing the following steps of the flowcharts shown in fig. 7 to 9. The storage unit 13 stores programs of, for example, positive electrode potential estimation (S2), internal pressure estimation (S4), and positive electrode protection control (S9) in fig. 7. Further, the storage unit 13 stores a plurality of steps of the program of fig. 9. The various steps of the program of FIG. 9 include: a charge reserve-gas absorption rate relationship obtaining step (S401), a measurement step (S402), an internal pressure increase rate calculating step (S403), a charge reserve estimation step (S404), an internal pressure decrease rate correction value calculating step (S405), an internal pressure decrease rate calculating step (S406), a corrected internal pressure decrease rate calculating step (S407), an estimated internal pressure calculating step (S408), an anode SOC estimating step (S409), a hydrogen equilibrium pressure calculating step (S410), a corrected anode hydrogen equilibrium pressure calculating step (S411), and a corrected estimated internal pressure calculating step (S412).
As data to be a premise of the control, "table data based on an OCV map in which the relationship between the cell voltage [ V ] and the negative electrode potential [ V ] is obtained" is stored in the storage unit 13 for each of the temperature [ deg.c ] and the current [ a ] used in the positive electrode potential estimation unit 14. The storage unit 13 also stores a map based on measured data of the "relationship between the charge reserve and the gas absorption rate" used in the internal pressure estimating unit 15. The storage unit 13 also stores a map of "a relationship between temperature and internal pressure increase rate" and "a relationship between temperature and internal pressure decrease rate". In addition, the storage unit 13 stores a map of "relationship between the voltage of the battery and the negative electrode SOC". The storage unit 13 also stores a map of "relationship between negative electrode SOC and hydrogen equilibrium pressure". The storage unit 13 also stores a map of "relationship between temperature and hydrogen equilibrium pressure".
The storage unit 13 also stores a map of "the state of degradation of the battery estimated from the usage history of the nickel-metal hydride storage battery 1" and "the relationship between the state of degradation of the nickel-metal hydride storage battery 1 and the charge storage amount".
< Positive electrode potential estimating part 14>
The positive electrode potential estimating unit 14 estimates the potential of the negative electrode by referring to "table data for obtaining the relationship between the cell voltage and the negative electrode potential" stored in advance in the storage unit 13, based on the cell voltage measured by the voltage detector 22. Then, positive electrode potential estimating unit 14 estimates the positive electrode potential from the difference between the cell voltage and the negative electrode potential. The positive potential estimating unit 14 causes the control device 10 to function as a positive potential obtaining device.
< internal pressure estimating section 15>
The internal pressure estimating unit 15 estimates the internal pressure of the battery by using the procedure of the flowchart shown in fig. 8 based on the temperature, voltage, current, and the like of the stored in-vehicle nickel-metal hydride storage battery obtained by the information obtaining unit 12. Details are as follows. The internal pressure estimating unit 15 causes the control device 10 to function as an internal pressure obtaining 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 a threshold value, generates power by the motor generator 17 and charges the battery module 90 by the inverter 20. On the other hand, when the vehicle is braked, the regenerative current from the motor generator 17 is supplied by the inverter 20, and the battery module 90 is charged. In this case, when the current is too large and the SOC of the battery module 90 is too high, the charge/discharge control unit 16 restricts the charging. The threshold value and the like at this time are stored in the storage unit 13. In the positive electrode protection control (S9) shown in fig. 8, the charge and discharge are also controlled so that the potential of the positive electrode does not fall below the threshold value d corresponding to the fourth threshold value.
On the other hand, the charge/discharge Control Unit 16 supplies a necessary current from the battery module 90 to the motor generator 17 via the inverter 20 by a command from an ECU (Electronic Control Unit) of the vehicle when the vehicle is driven.
< Process of the method for controlling a Nickel-Metal hydride storage Battery of the present embodiment >
Fig. 7 is a flowchart showing the procedure of the method for controlling a nickel-metal hydride storage battery according to the present embodiment. The procedure of the method for controlling a nickel-metal hydride storage battery according to the present embodiment will be described with reference to fig. 7.
As described above, before the process of implementing the method for controlling a nickel-metal hydride storage battery according to the present embodiment, data such as table data and a map used for estimating the positive electrode potential (S2) and estimating the internal pressure (S4) is stored in the storage unit 13 of the control device 10.
When the operation of the vehicle is started (started), it is first determined whether or not the control is still being continued (S0). When the control is stopped when the operation of the vehicle is stopped (S0: yes), the control method for the nickel-metal hydride storage battery is also stopped (stopped). When the control is continued (S0; NO), the voltage [ V ], current [ A ], temperature [ DEG C ] and the like of the nickel-metal hydride storage battery are measured (S1) at predetermined timings for positive electrode potential estimation (S2) and internal pressure estimation (S4). This timing is measured at a constant timing, for example, every 1 second, by a counter of the control device 10. Therefore, for example, it is determined whether the measurement timing is the measurement timing every 100ms (S1), and a standby cycle (loop) is set before the measurement timing (S1: no) (S0: no → S1: no → S0). Then, when a predetermined measurement timing arrives (S1: YES), the voltage [ V ], the current [ A ], and the temperature [ DEG C ] of the nickel-metal hydride storage battery are measured, and the processes of the positive electrode potential estimation (S2) and the internal pressure estimation (S4) are simultaneously processed in parallel.
< Process (S2) of Positive electrode potential estimation >
Fig. 8 is a flowchart showing in detail a subroutine of the positive electrode potential estimation (S2) process according to the present embodiment. The process of the positive electrode potential estimation (S2) will be described in detail below with reference to a flowchart shown in fig. 8.
When the positive electrode potential estimation is started (S2), the measured cell voltage [ V ], temperature [ ° c ], and current [ a ] are read first (S201). Then, "table data for obtaining the relationship between the cell voltage and the negative electrode potential", which is stored in the storage unit 13 for each of the temperature [ deg.C ] and the current [ A ], is read (S202). The negative electrode potential [ V ] is estimated from the read cell voltage [ V ] by referring to "table data for obtaining the relationship between cell voltage and negative electrode potential" of the corresponding temperature [ deg.C ] and current [ A ] (S203). Next, using the estimated negative electrode potential, the positive electrode potential [ V ] is estimated based on the relation between the cell voltage [ V ] -the negative electrode potential [ V ] = the positive electrode potential [ V ] (S204).
The positive electrode potential [ V ] is estimated according to the above procedure, the procedure of the positive electrode potential estimation (S2) is ended (end), and the routine proceeds to the procedure of determining whether the positive electrode potential [ V ] is equal to or less than the threshold value a [ V ] (S3) in fig. 7.
< determination of whether or not the positive electrode potential [ V ] is equal to or less than the threshold value a [ V ] (S3) >
The positive electrode potential [ V ] estimated by the process of the positive electrode potential estimation (S2) is set in advance as a "threshold value a [ V ]" in accordance with the characteristics of the target nickel-hydrogen storage battery, and stored in the storage unit 13 of the control device 10. The control unit 11 reads the threshold value av stored in the storage unit 13, and determines whether or not the positive electrode potential V estimated in the positive electrode potential estimation (S2) is equal to or lower than the threshold value av (S3). When the positive electrode potential [ V ] estimated by the process of the positive electrode potential estimation (S2) is not equal to or less than the threshold value a [ V ] (S3: no), the process returns to S0, and determines whether to stop the control (S0), and waits until the next measurement timing (S0: no → S1: no → S0).
On the other hand, when the positive electrode potential [ V ] estimated by the process of the positive electrode potential estimation (S2) is equal to or less than the threshold value a [ V ] (S3: YES), the information obtaining unit 12 is provided with a Flag (Flag) for performing the process in S6.
< Process of estimating internal pressure (S4) >
The control unit 11 executes the internal pressure estimation process (S4) in parallel with the positive electrode potential estimation process (S2).
Fig. 9 is a flowchart showing a subroutine of the procedure (S4) of estimating the internal pressure according to the present embodiment in detail. The process of estimating the internal pressure (S4) will be described with reference to the flowchart shown in fig. 9.
First, the controller 10 (see fig. 6) measures the voltage, current, and temperature of the nickel-metal hydride storage battery 1 in the measurement step (S402). Then, in the internal pressure decrease speed calculation step (S406), "internal pressure decrease speed" is calculated from the gas absorption speed of the negative electrode based on the measured temperature. In parallel, in the charge storage amount estimation step (S404), "charge storage amount" is estimated based on the measured voltage, current, and temperature. In the internal pressure decreasing speed correction value calculating step (S405), "internal pressure decreasing speed correction value" is calculated based on the estimated "charge reserve". In order to perform this estimation, the relationship between the charge storage amount and the gas absorption rate of the negative electrode, etc. are read in advance into the storage unit 13 (see fig. 6) of the control device 10 (S401). Thereafter, in the corrected internal pressure reduction speed calculation step (S407), the "internal pressure reduction speed" calculated in the internal pressure reduction speed correction value calculation step (S405) is corrected based on the "internal pressure reduction speed correction value", and the "corrected internal pressure reduction speed" is calculated more accurately.
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.
In addition, the negative electrode SOC is estimated in the negative electrode SOC estimation step (S409). In addition, the "hydrogen equilibrium pressure" of the negative electrode is calculated from the temperature in the hydrogen equilibrium pressure calculation step (S410). On the other hand, in the corrected hydrogen equilibrium pressure calculating step (S411), "corrected hydrogen equilibrium pressure" is calculated from the relationship between the anode SOC and the hydrogen equilibrium pressure of the anode.
Thereafter, in the corrected estimated internal pressure calculation step (S412), the "corrected estimated internal pressure" is calculated more accurately based on the "hydrogen equilibrium pressure".
After "correction of the estimated internal pressure" is calculated in this manner, the internal pressure estimation process is ended (S4).
The internal pressure [ Pa ] is estimated by the above process, the process of estimating the internal pressure [ Pa ] (S4) is ended (end), and the process proceeds to the process of determining whether the internal pressure [ Pa ] is equal to or greater than the threshold b [ Pa ] (S5) in fig. 7.
< determination of whether or not the internal pressure is equal to or greater than threshold value b (S5) >
The internal pressure estimated by the process of the internal pressure estimation (S4) is stored in the storage unit 13 of the control device 10, with the internal pressure [ Pa ] that is generated based on the gas and in which the drying up of the electrolyte is likely to occur being set in advance in accordance with the characteristics of the target nickel-hydrogen storage battery as the "threshold value b [ Pa ]. The control unit 11 reads the threshold b [ Pa ] stored in the storage unit 13, and determines whether or not the internal pressure [ Pa ] estimated by the internal pressure estimation (S4) process is equal to or greater than the threshold b [ Pa ] (S5). If the internal pressure [ Pa ] estimated by the process of the internal pressure estimation (S4) is not equal to or greater than the threshold b [ Pa ] (S5: NO), the process returns to S0, determines whether or not to stop the control (S0), and waits until the next measurement timing (S0: NO → S1: NO → S0).
On the other hand, when the internal pressure [ Pa ] estimated by the process of the internal pressure estimation (S4) is equal to or higher than the threshold b [ Pa ] (S5: YES), a flag is provided in the information obtaining unit 12 in order to perform the processing in S6.
< Process (S6) for cases where threshold a [ V ] of positive electrode potential is not more than and threshold b [ Pa ] of internal pressure is not less than >
The information obtaining part 12 is provided with a threshold a [ V ] of the positive electrode potential]The following mark, and a threshold value b [ Pa ] of internal pressure]In the case of the above flag, the control unit 11 determines that the threshold a [ V ] of the positive potential is set]Below and a threshold value b [ Pa ] of the internal pressure]The above is the case. Then, the cycle was measured to estimate that Ni was produced 2 O 3 The form of H is considered to be "frequency 1 times".
< accumulation of frequency (S7) >
The control unit 11 integrates the "frequency" determined in S6, and stores the integrated value in the information obtaining unit 12 as an "integrated value of frequency" (S7). This "frequency integrated value" is referred to as "loss amount" in the present embodiment. The unit is the number of times. That is, the "frequency integrated value" is regarded as the positive potential threshold value a [ V ]]Below and internal pressure threshold b [ Pa]Estimating Ni produced in the above case 2 O 3 Total amount of H accumulated.
< determination (S8) whether the frequency integrated value is equal to or greater than the threshold value c >
With respect to the frequency integration value integrated in S7, ni which significantly shortens the life of the nickel-metal hydride storage battery to be subjected to the frequency integration is preliminarily set 2 O 3 The total amount of accumulated H is set as a threshold value c by an experiment or the like. Then, the frequency integrated value obtained in S7 is compared withThe threshold value c is compared (S8). If the frequency integrated value is not equal to or greater than the threshold value c, that is, if the frequency integrated value is smaller than the threshold value c (S8: no), the positive electrode of the target nickel-metal hydride storage battery returns to S0 to wait until the next measurement timing (S0: no → S1: no → S0), as long as there is no problem. In this case, it is determined that there is no problem in the current control of the positive electrode potential, and the current control of the positive electrode potential is continued while maintaining this state without changing the current control of the positive electrode potential.
Fig. 10 is a graph showing that accumulation of the amount of wear irreversibly occurs with the passage of time, and the threshold value c is reached. In the judgment (S8) whether the frequency integrated value is not less than the threshold c, it is judged whether "the frequency integrated value is not less than the threshold c". When the frequency integrated value is not less than the threshold value c (S8: YES), ni is accumulated in the positive electrode of the nickel-metal hydride storage battery as the target 2 O 3 H, it is judged that there is a problem in the control of the potential of the positive electrode which is currently performed. That is, as shown in fig. 10, when the control is performed in this state, the loss amount, that is, ni is shown 2 O 3 The accumulation amount of H approaches a state in which the avalanche capacity reduction shown in experimental example 2 of fig. 3 and 4 occurs.
And a step (S9) of performing positive protection control when the frequency integrated value is not less than the threshold value c (S8: yes). That is, the threshold value c is a limit frequency at which the capacity of the nickel-metal hydride storage battery can be maintained within a normal range.
< Positive electrode protection control (S9) >
In the positive electrode protection control process (S9), the positive electrode protection control process is changed. Under the control of present, ni 2 O 3 The accumulation of H is estimated to be small, which would allow for unexpected Ni 2 O 3 And H is generated. Therefore, to further suppress Ni 2 O 3 H is generated, and the control standard is stricter. Specifically, let the estimate be oxygen O 2 Generated positive electrode potential [ V ]]Threshold value d [ V ] of]Is higher than the present anode potential [ V ]]Threshold value d [ V ] of]Instead of the threshold d [ V ]]To a higher positive electrode potential [ V ]]D + alpha [ V ] of]. Then, the control device 10 sets the positive electrode potential [ V ] to be higher]Threshold value d + alpha [ V ] of]According to positive electrode potential [ V ]]Can notBelow a threshold value d + alpha V]The manner in which the above-described operation is performed. Specifically, the control unit 11 continuously monitors the cell voltage [ V ] of the battery module 90]. And estimating the positive electrode potential [ V ]]The motor generator 17 consumes a large amount of electric power, or the motor generator 17 consumes electric power due to a load such as an air conditioner or a lamp without generating electric power for a long time to make the unit voltage [ V]The reduced condition is detected. In this case, the estimated positive electrode potential [ V ] is used]Not lower than the newly set threshold d + alpha V]The positive electrode potential [ V ] is set by causing the motor generator 17 to generate power or to limit the output]Will not be lower than the newly set threshold value d + alpha V]. Ni can be effectively suppressed by such control 2 O 3 The generation of H can extend the capacity life of the nickel-metal hydride storage battery. After the process of the positive electrode protection control (S9) is completed, the process returns to S0.
(operation of the embodiment)
Since the present embodiment has the above-described configuration, it is possible to form Ni in the nickel-metal hydride storage battery mounted on the vehicle 2 O 3 The decrease in capacity due to the accumulation of H together acts as a loss amount to be accurately estimated.
As to the specific action, for a threshold value a [ V ]]A positive electrode potential of the following and a threshold value b [ Pa ]]The frequency of the above states of the internal pressure is integrated (S7). By integrating the frequency, ni accumulated in the positive electrode of the nickel-metal hydride storage battery can be accumulated 2 O 3 The amount of H is accurately estimated as "loss amount".
When the amount of loss is monitored and exceeds a threshold value c, which is a predetermined threshold value (S8: YES), a positive electrode protection step (S9) is performed so that the nickel-metal hydride storage battery does not undergo a sudden capacity decrease. The function of the positive electrode protecting step (S9) is to make Ni less likely to be generated by setting the positive electrode potential to be lower 2 O 3 The mode of the potential of H is controlled, and the nickel-metal hydride storage battery has the function of preventing the rapid capacity reduction.
(effects of the embodiment)
The method of controlling a nickel-metal hydride storage battery according to the present embodiment has the following effects.
(1) Nickel-metal hydride storage battery of the present embodimentIn the pool control method, ni which causes capacity reduction can be fundamentally suppressed under appropriate conditions 2 O 3 The generation of H can suppress the capacity degradation of the positive electrode.
(2) In the method for controlling a nickel-metal hydride storage battery according to the present embodiment, the control device 10 is a system constituted by a computer mounted on a vehicle, and is completed only by a configuration on the vehicle. Therefore, the method for controlling the nickel-metal hydride storage battery according to the present embodiment can be autonomously performed during operation of the vehicle, and the nickel-metal hydride storage battery mounted on the vehicle can be protected.
(3) Particularly, when the vehicle is operated, the positive electrode capacity is rapidly reduced, thereby avoiding a situation where the vehicle suddenly fails to operate.
(4) The method comprises a positive electrode potential obtaining step for calculating and obtaining the potential of the positive electrode, and an internal pressure obtaining step for calculating and obtaining the internal pressure of the alkaline secondary battery. Due to the reaction of Ni according to these processes 2 O 3 Since the conditions for generating H are compositely analyzed and determined, ni can be accurately determined 2 O 3 H is produced under the conditions described above. Therefore, ni can be estimated reliably 2 O 3 And H is generated.
(5) Since the conditions of the positive electrode potential and the conditions of the internal pressure are determined based on the threshold value a and the threshold value b, which are derived from experiments or the like, accurate determination can be performed.
(6) In the positive electrode potential obtaining step, an OCV map showing the relationship between the cell voltage and the negative electrode potential is provided for each of the temperature and the current, and the positive electrode potential is estimated by subtracting the negative electrode potential from the actual measurement value of the cell voltage with reference to the OCV map. Therefore, the processing can be performed quickly even in the in-vehicle control device 10.
(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 value. Therefore, the internal pressure can be accurately estimated in consideration of various conditions.
(8) Mixing Ni 2 O 3 By replacing the accumulated state of H with the amount of loss and determining the accumulated state by the threshold value d, it is possible to easily estimate that the battery is in a dangerous state of rapid deterioration, and avoid Ni 2 O 3 H plusQuickly generated state.
(9) In Ni 2 O 3 When the accumulation of H is large and the battery capacity is in a dangerous state, ni can be made to be Ni by the positive electrode protection step 2 O 3 No more accumulation of H occurs.
(10) In the positive electrode protection step, the positive electrode potential is controlled so as not to be equal to or lower than the threshold value d corresponding to the amount of loss. Thus, ni can be made to 2 O 3 No more accumulation of H occurs.
(11) The method for controlling the nickel-metal hydride storage battery according to the present embodiment can be implemented using an ECU or the like that is conventionally used to control a battery. Therefore, the method for controlling the nickel-metal hydride storage battery according to the present embodiment can be implemented by software alone. Therefore, the method for controlling the nickel-metal hydride storage battery according to the present embodiment can be implemented without modifying the existing vehicle.
(modification example)
The above embodiment can be implemented as follows.
In the present embodiment, the number of times of "frequency" is used to determine generation Ni of "positive electrode potential not higher than threshold a" and "internal pressure not lower than threshold b 2 O 3 How long H stays in a state where the probability of H is extremely high. However, such generated Ni may be actually measured and accumulated regardless of the "frequency 2 O 3 The residence time of a state where the probability of H is extremely high.
In the present embodiment, as shown in fig. 2, the threshold a and the threshold b are divided into 4 regions, and generation Ni of "positive electrode potential not higher than threshold a" and "internal pressure not lower than threshold b" is determined 2 O 3 A state in which the probability of H is extremely high. However, ni may be generated 2 O 3 The probability of H is set by setting a plurality of thresholds, and values obtained by weighting in each region are accumulated.
In the present embodiment, the "positive electrode potential" is estimated by a method defined by the cell voltage. However, the estimation may be performed by a method based on another estimation method. Needless to say, the "positive electrode potential" may be actually measured without estimation.
The "internal pressure" in the present embodiment is also estimated from information such as voltage, current, and temperature. This estimation method is an example, and may be further simplified, or may be a method of estimating from other data. Needless to say, the "internal pressure" may be measured without estimation.
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, but are not limited to such a configuration. The control device 10 may execute this function by an ECU of the vehicle. Alternatively, the battery pack 24 may be provided separately.
In the present embodiment, the present invention has been described by taking a nickel metal hydride storage battery mounted on an electric vehicle as an example, but the present invention can be suitably applied to batteries for ships and aircrafts. Further, the present invention can be applied to a stationary battery.
The alkaline secondary battery is not limited to the nickel-metal hydride storage battery, and may be implemented in other alkaline secondary batteries.
It is needless to say that the flowcharts shown in fig. 7 to 9 are an example of the present embodiment, and can be implemented by those skilled in the art by changing the order of operations, adding, deleting, or changing the operations.
The numerical ranges exemplified in the present embodiment are specific examples, and the present invention is not limited thereto, and can be optimized as appropriate by those skilled in the art according to the target alkaline secondary battery.
It is needless to say that, even when not described in the embodiments, the present invention can be implemented by adding, deleting, or modifying the components by those skilled in the art without departing from the scope of the claims.
Description of the symbols
1-8230and nickel-hydrogen accumulator
2 8230a positive electrode active material
2a 8230and particles
2b 8230am particle surface
4\8230alkalineelectrolyte
10-8230and controller for Ni-MH accumulator
11 \ 8230and control part
12 8230a information acquisition part
13 8230that a storage unit (program, map, battery use history, etc.)
14 8230a positive electrode potential estimating part
15 \ 8230and internal pressure estimating part
16 8230and a charge and discharge control part
17 \ 8230and motor generator
20 method 8230and inverter
21 \ 8230and current detector
22 \ 8230and voltage detector
23 8230a temperature detector
24-8230and battery pack
90-8230and battery module
100 \ 8230and integrated electric tank
110 \ 8230and single cell
120 \ 8230and partition wall
130 \ 8230and electric tank
140 of 8230and electrode plate group
141 8230a positive plate
141a 8230a lead-out part
142- (8230)' negative plate
142a 8230and a lead-out part
143 (8230); spacer
150 \ 8230and collector plate
151 \ 8230and connecting projection
152\8230andconnecting terminal
160 \ 8230and collector plate
161 \ 8230and connecting protrusion
170 \ 8230and through hole
200 \ 8230and cover
210\8230avent valve
220 \8230andsensor mounting hole
300 \ 8230and square shell

Claims (7)

1. A method for controlling an alkaline secondary battery having a positive electrode containing nickel hydroxide as an active material, a negative electrode containing a hydrogen storage alloy, and an electrolyte solution composed of an alkaline aqueous solution, comprising the steps of:
a positive electrode potential obtaining step of calculating and obtaining a positive electrode potential at a predetermined timing;
an internal pressure obtaining step of calculating and obtaining an internal pressure of the alkaline secondary battery in synchronization with the timing;
a loss amount calculation step of calculating a loss amount by integrating a retention time in a state where the positive electrode potential is equal to or lower than a first threshold (a) and the internal pressure is equal to or higher than a second threshold (b); and
and a positive electrode protection step of protecting the positive electrode when the loss amount calculated in the loss amount calculation step reaches a third threshold value (c).
2. The method of controlling an alkaline secondary battery according to claim 1, wherein in the positive electrode potential obtaining step, an OCV map showing a relationship between the cell voltage and the negative electrode potential is stored in advance for each of the temperature and the current, and the positive electrode potential is estimated by subtracting the negative electrode potential from an actually measured value of the cell voltage with reference to the OCV map.
3. The method of controlling an alkaline secondary battery according to claim 1 or 2, wherein in the internal pressure obtaining step, the internal pressure of the alkaline secondary battery is estimated from a voltage, a temperature, and a current value.
4. The method according to claim 1 or 2, wherein the positive electrode protecting step is performed so that the positive electrode potential does not become equal to or lower than a fourth threshold (d) corresponding to the amount of loss.
5. The method of controlling an alkaline secondary battery according to claim 1 or 2, wherein the alkaline secondary battery is a nickel-metal hydride storage battery.
6. The method of controlling an alkaline secondary battery according to claim 1 or 2,
the alkaline secondary battery is an on-vehicle battery for driving a vehicle,
the alkaline secondary battery is controlled by a battery control device for controlling the alkaline secondary battery.
7. A control device for an alkaline secondary battery, which controls an alkaline secondary battery mounted on a vehicle and having a positive electrode containing nickel hydroxide as an active material, a negative electrode containing a hydrogen storage alloy, and an electrolyte solution composed of an alkaline aqueous solution, wherein the control device comprises:
a positive electrode potential obtaining device for calculating and obtaining the potential of the positive electrode at a certain timing;
an internal pressure obtaining device that calculates and obtains an internal pressure of the alkaline secondary battery;
loss amount calculation means for calculating a loss amount by integrating the retention time in a state in which the positive electrode potential is equal to or lower than a first threshold (a) and the internal pressure is equal to or higher than a second threshold (b); and
and a positive electrode protection device for protecting the positive electrode when the loss calculated by the loss calculation device reaches a third threshold value (c).
CN202210145573.8A 2021-07-14 2022-02-17 Method and device for controlling alkaline secondary battery Pending CN115621427A (en)

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