Control method and control device for alkaline secondary battery

Abstract

A control method of an alkaline secondary battery having a positive electrode of which active material is nickel hydroxide, a negative electrode containing a hydrogen storage alloy, and an electrolyte solution composed of an alkaline aqueous solution, the control method comprising: a positive electrode potential estimation step (S2) of calculating and obtaining the potential of the positive electrode at a certain timing; an internal pressure estimation step (S4) of calculating and obtaining the internal pressure of the alkaline secondary battery in synchronization with the timing; a loss amount calculation step (S7) of accumulating the residence time of a state in which the potential of the positive electrode is below a threshold value a and the internal pressure is above a threshold value b, thereby calculating a loss amount; and a positive electrode protection step (S9) of protecting the positive electrode at a time when the loss amount calculated by the loss amount calculation step reaches a threshold value c (S8: Yes). Thus, the generation of Ni2O3H, which causes capacity reduction, can be fundamentally suppressed under appropriate conditions, and the capacity degradation of the positive electrode can be effectively suppressed.

Description

Technical Field

[0001] This invention relates to a control method and control apparatus for alkaline secondary batteries, and more specifically, to a control method and control apparatus for vehicle alkaline secondary batteries suitable for suppressing the degradation of the positive electrode. Background Technology

[0002] Electric vehicles (including hybrid vehicles) equipped with electric motors use electricity stored in secondary batteries to drive the motors. Among these secondary batteries, alkaline batteries such as nickel-metal hydride batteries are capable of high-current charging and discharging, and are therefore widely used in vehicles.

[0003] In such alkaline secondary batteries, side reactions may occur at the positive electrode when the positive electrode potential is below a predetermined lower limit or above a predetermined upper limit, potentially leading to electrode degradation. Similarly, the negative electrode may also degrade due to its potential falling outside the predetermined range. Therefore, to suppress degradation of both the positive and negative electrodes, it is preferable to calculate (monitor) the positive and negative electrode potentials separately and control the charging and discharging of the secondary battery according to the variation of the positive and negative electrode potentials within predetermined potential ranges.

[0004] Therefore, Patent Document 1 discloses the following invention, which can accurately estimate the potential of the positive electrode and suppress the occurrence of side reactions. In a battery system incorporating an alkaline secondary battery, the memory effect is preferably considered to improve the accuracy of the positive electrode potential calculation. Therefore, the battery system includes a single cell as a nickel-metal hydride battery, and an ECU that controls the charging and discharging of the single cell using its positive electrode potential V1 and negative electrode potential V2. The ECU takes the single cell's terminal voltage V, positive electrode opening potential U1, and negative electrode opening potential U2 as inputs, and uses a battery model to estimate the internal behavior of the single cell to calculate the internal hydrogen concentration of the positive electrode active material. The ECU calculates the storage capacity M (which is the potential change caused by the memory effect of the initial potential E1 based on the positive electrode opening potential U1) based on the hydrogen concentration, and uses the initial potential E1 and the storage capacity M to calculate the positive electrode opening potential U1.

[0005] According to this invention, the potential of the positive electrode can be accurately estimated, and the occurrence of side reactions can be suppressed. Furthermore, in side reactions, particularly in battery systems containing nickel-metal hydride batteries, there is a problem that if the amount of Ni₂O₃H generated in the positive electrode increases, the battery capacity will irreversibly decrease. Therefore, Patent Document 2 discloses the following invention for suppressing the generation of Ni₂O₃H.

[0006] The ECU performs control processing involving multiple steps. These steps include: obtaining voltage Vb, current Ib, and temperature Tb; calculating the positive electrode potential U+; calculating the upper limit Up of the positive electrode potential U+; controlling the PCU to limit the positive electrode potential U+ below a predetermined value when the positive electrode potential U+ exceeds the upper limit Up; and performing normal control when the positive electrode potential U+ is below the upper limit Up.

[0007] According to this invention, by appropriately suppressing the positive electrode potential, the generation of Ni2O3H can be expected to be suppressed. Existing technical documents Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2018-087785 Patent Document 2: Japanese Patent Application Publication No. 2018-10758 Summary of the Invention The problem that the invention aims to solve

[0009] However, the inventors have discovered that the formation of Ni2O3H cannot be completely suppressed by controlling the positive electrode potential alone, and there is a problem that controlling the positive electrode potential alone cannot sufficiently suppress the formation of Ni2O3H in alkaline secondary batteries.

[0010] Therefore, the problem to be solved by the present invention is to fundamentally suppress the formation of Ni2O3H that leads to capacity reduction and suppress the capacity degradation of the cathode under appropriate conditions. Methods for solving problems

[0011] To address the aforementioned issues, the present invention provides a control method for an alkaline secondary battery comprising a positive electrode with nickel hydroxide as the active material, a negative electrode containing a hydrogen storage alloy, and an electrolyte composed of an alkaline aqueous solution. The method includes the following steps: a positive electrode potential acquisition step, which calculates and acquires the potential of the positive electrode at a predetermined time; an internal pressure acquisition step, which calculates and acquires the internal pressure of the alkaline secondary battery synchronously with the aforementioned time; a loss calculation step, which accumulates the dwell time of a state where the positive electrode potential is below a first threshold (a) and the internal pressure is above a second threshold (b), thereby calculating the loss amount; and a positive electrode protection step, which protects the positive electrode when the loss amount calculated by the aforementioned loss calculation step reaches a third threshold (c).

[0012] In this case, in the above-mentioned positive electrode potential acquisition step, the OCV mapping diagram representing the relationship between the cell voltage and the negative electrode potential can be pre-stored according to temperature and current, respectively. The positive electrode potential is estimated by subtracting the negative electrode potential from the measured value of the cell voltage with reference to the above-mentioned OCV mapping diagram.

[0013] In addition, in the above internal pressure calculation steps, the internal pressure of the alkaline secondary battery can be estimated based on the voltage, temperature, and current values. The above-mentioned positive electrode protection steps can be controlled in a way that prevents the positive electrode potential from falling below the fourth threshold (d) corresponding to the loss amount.

[0014] The aforementioned alkaline secondary battery can be appropriately used in the case of nickel-metal hydride batteries. Furthermore, the aforementioned alkaline secondary battery is a vehicle-mounted battery for vehicle propulsion, and can be appropriately used when controlled by a battery control device that controls the battery.

[0015] The control device for an alkaline secondary battery of the present invention controls an alkaline secondary battery mounted in a vehicle, comprising a positive electrode with nickel hydroxide as the active material, a negative electrode containing a hydrogen storage alloy, and an electrolyte composed of an alkaline aqueous solution. The control device includes: a positive electrode potential acquisition device for calculating and acquiring the potential of the positive electrode at a predetermined time; an internal pressure acquisition device for calculating and acquiring the internal pressure of the alkaline secondary battery synchronously with the aforementioned time; a loss calculation device for accumulating the dwell time of a state where the positive electrode potential is below a first threshold a and the internal pressure is above a second threshold b, thereby calculating the loss amount; and a positive electrode protection device for protecting the positive electrode when the loss amount calculated by the loss calculation device reaches a third threshold c. The effects of the invention

[0016] The alkaline secondary battery control method and control device of the present invention can fundamentally suppress the generation of Ni2O3H that leads to capacity reduction under appropriate conditions and effectively suppress the capacity degradation of the positive electrode. Attached Figure Description

[0017] Figure 1 (a) is a schematic diagram showing the reaction on the particle surface of the positive electrode active material of a nickel-metal hydride battery during charging. Figure 1 (b) shows the reaction formulas of the normal positive electrode main reaction during discharge and the abnormal side reaction when oxygen is generated and local "electrolyte drying" occurs. Figure 2 This is a graph showing the range of conditions for the positive electrode potential [V] and internal pressure [Pa] to generate Ni2O3H. Figure 3 This is a graph comparing the total discharge capacity curve L1 of this embodiment (controlled in such a way that the internal pressure is above the threshold b and the positive electrode potential is not below the threshold a) with the total discharge capacity curve L2 of the prior art (without controlling whether the internal pressure is above the threshold b and the positive electrode potential is below the threshold a or not below the threshold a). Figure 4This is a graph showing the change in capacity retention rate [%] relative to total discharge capacity [Ah] in the experimental example. Figure 5 This is a partial cross-sectional view of the battery module of the nickel-metal hydride battery according to this embodiment. Figure 6 This is a block diagram of the control device for the nickel-metal hydride battery according to this embodiment. Figure 7 This is a flowchart illustrating the control method of the nickel-metal hydride battery according to this embodiment. Figure 8 This is a flowchart that details the process of estimating the positive electrode potential in this embodiment. Figure 9 This is a flowchart that details the process of estimating the internal pressure in this embodiment. Figure 10 This is a graph showing how the loss accumulates over time and reaches a threshold c. Detailed Implementation

[0018] The following is for reference Figures 1-10 An embodiment of the control method using a nickel-metal hydride battery 1 will be described to illustrate the control method of the alkaline secondary battery of the present invention. <Prerequisites for this implementation> The purpose of the nickel-metal hydride battery and its manufacturing method in this embodiment is to effectively suppress the formation of Ni2O3H. Therefore, the formation mechanism of Ni2O3H will be explained first.

[0019] <Surface of positive electrode active material particles> Figure 1 (a) is a schematic diagram showing the oxygen on the particle surface 2b of the positive electrode active material 2 of the nickel-metal hydride battery during the reaction of particles 2a during charging.

[0020] Figure 1 (b) shows the reaction formulas of the normal positive electrode main reaction during discharge and the abnormal side reaction when oxygen is generated and local "electrolyte drying" occurs. <Main Reactions at the Positive Electrode During Discharge> The particles 2a of the positive electrode active material 2 change between Ni(OH)2 and β-NiOOH during charging and discharging. It should be noted that, for ease of explanation, the positive electrode active material is sometimes described as Ni(OH)2. The normal main reaction of the nickel-metal hydride battery during discharge is shown in the following equation (1), which, in the presence of H2O, generates Ni(OH)2 and OH from β-NiOOH. - In this case, the H2O in the electrolyte is consumed and reduced. -It functions as an alkaline ion in alkaline electrolyte 4. In this case, oxygen (O2) and hydrogen (H2) gases are not produced through the exchange of ions and electrons.

[0021] β-NiOOH + H₂O + e - →Ni(OH)2+OH - ……(1) <Oxygen generation based on side reactions and the occurrence of "electrolyte drying"> The potential at the positive electrode may decrease. And when the electrolysis potential of H2O is reached, H2O electrolysis will occur as a side reaction. In the electrolysis of H2O, O2 is generated at the positive electrode through the reaction of the following formula (2).

[0022] 4OH - →O2 + 2H2O + 4e - ……(2) like Figure 1 As shown in (a), when the particle surface 2b of the positive electrode active material Ni(OH)2 / β-NiOOH, which serves as the positive electrode active material, becomes low potential through charging, the side reaction shown in equation (2) above occurs, generating O2 in the form of O2 bubbles A on the particle surface 2b of the positive electrode active material. During charging, O2 bubbles A adhere to the particle surface 2b of the positive electrode active material. These O2 bubbles A detach from the particle surface 2b of the positive electrode active material over time. Thus, the detached portion of bubble A comes into contact with the alkaline electrolyte 4, supplying H2O and OH-. - .

[0023] However, depending on the conditions, it may take time for the O2 generated on the surface 2b of the positive electrode active material particles, such as bubble B, to detach from the particle surface 2b. Thus, the O2 bubbles, such as bubble B, attached to the particle surface 2b of the positive electrode active material will block the alkaline electrolyte. As a result, the H2O and OH- ions on the particle surface 2b of the positive electrode active material will be unable to escape. - Physically excluded, this portion becomes a localized "electrolyte-drying" state. H2O, OH... - None of them exist here in a physical form.

[0024] <Generation of Ni2O3H based on "electrolyte drying"> Therefore, in a normal response, such as Figure 1 As shown in equation (1) of (b), H2O is required in the reaction, but in the case of “electrolyte drying out” without supplying H2O, an abnormal side reaction will occur during the discharge of the nickel-metal hydride battery, forming the reaction of equation (3) below.

[0025] 16β-NiOOH+4e -→8Ni₂O₃H⁺ + 2H₂O + O₂ + 4OH⁻ - ……(3) That is, the reaction occurs without the use of H2O, and instead produces H2O. Furthermore, Ni2O3H, O2, and OH are generated as products in this reaction. - O2 is steadily absorbed by the negative electrode (recombining reaction) over time as shown in equation (4), maintaining a closed system. - Return to alkaline electrolyte 4.

[0026] 4MH + O2 → 4M + 2H2O……(4) Here, Ni₂O₃H is an electrochemically inert product. Its formation involves irreversible accumulation, leading to increased battery resistance and decreased battery capacity. Therefore, the formation of Ni₂O₃H is generally discouraged as an undesirable reaction.

[0027] <Memory Effect of Nickel-Metal Hydrate Batteries> It is known that in nickel-metal hydride batteries, repeated charging and discharging at low state of charge (SOC) can produce a memory effect. In a battery system with a memory effect, the voltage shifts towards the higher potential side. Therefore, even at the same SOC, the voltage will increase during charging and decrease during discharging, making it particularly easy to generate O2. As a result, localized electrolyte drying occurs instantaneously at the oxygen-generated sites on the surface 2b of the positive electrode active material particles. Thus, as shown in equation (3) above, Ni2O3H is generated simultaneously with the insufficiently generated H2O. The generation of Ni2O3H leads to a sharp decrease in capacity.

[0028] <Mechanism of Ni2O3H formation in nickel-metal hydride batteries> As mentioned above, in nickel-metal hydride batteries, due to the positive electrode potential during charging, Ni₂O₃H produces oxygen (O₂) gas as a side reaction during charging, causing the internal pressure of the secondary battery to rise. The mechanism by which this O₂ causes "electrolyte drying" and the generation of Ni₂O₃H is analyzed.

[0029] In this Ni2O3H formation mechanism, even if the positive electrode potential is simply reduced, if no oxygen O2 is actually generated, the "electrolyte drying" will not occur, and therefore Ni2O3H will not be generated.

[0030] On the other hand, an increase in internal pressure does not necessarily mean the formation of Ni₂O₃H. The increase in internal pressure in a secondary battery is not always due to the formation of oxygen (O₂) gas; sometimes it is also due to the formation of hydrogen (H₂) gas. Even when the internal pressure increases due to the formation of hydrogen (H₂) gas, Ni₂O₃H will not be formed.

[0031] That is, the inventors presumed that when the decrease in the positive electrode potential during charging constitutes the oxygen evolution potential, and when the actual generation of oxygen O2 gas is in a state of high internal pressure, "electrolyte drying" will occur, and this has been confirmed.

[0032] <Memory Effect of Automotive Nickel-Metal Hydrate Batteries> Next, the memory effect of automotive nickel-metal hydride (NiMH) batteries will be explained. Electric vehicles (including hybrid vehicles) equipped with electric motors use electricity stored in secondary batteries to drive the motors. Alkaline secondary batteries, such as NiMH batteries, are widely used in vehicles because they can withstand high-current charging and discharging. These automotive NiMH batteries are sometimes exposed to harsh operating environments. For example, they are sometimes repeatedly charged and discharged at low SOC (State of Charge). It is known that a memory effect occurs under such operating conditions. When a memory effect occurs, the battery's charging curve shifts towards a higher potential. That is, even at the same SOC, the positive electrode potential increases. On the other hand, during discharge, the battery's discharge curve shifts towards a lower potential. That is, even at the same SOC, the positive electrode potential decreases. Thus, according to the above mechanism, the formation of Ni₂O₃H due to "electrolyte drying" is likely to occur.

[0033] The Necessity of Controlling On-board Nickel-Metal Hydrate Batteries During the formation of Ni₂O₃H, irreversible accumulation occurs, leading to a decrease in the capacity of nickel-metal hydride (NiMH) batteries. If this capacity reduction in NiMH batteries is not controlled, the degradation will continue.

[0034] <Principle of this implementation method> Therefore, in this embodiment, an example of a vehicle-mounted nickel-metal hydride battery is described, which has a positive electrode with nickel hydroxide as the active material, a negative electrode containing a hydrogen storage alloy, and an electrolyte composed of an alkaline aqueous solution.

[0035] Figure 2 This is a graph showing the range of positive electrode potential [V] and internal pressure [Pa] required for the formation of Ni₂O₃H. Threshold a [V], corresponding to the first threshold, is the boundary value of the positive electrode potential [V] at which oxygen (O₂) is easily formed, while threshold b [Pa], corresponding to the second threshold, is the boundary value used to determine whether gas has been generated within the nickel-metal hydride battery. For example, threshold a [V] can be shown to be around 0.3 [V] and threshold b [Pa] around 0.3 [Pa]. However, these values ​​can vary depending on the battery's shape, the materials used for active substances, etc., and are not specifically limited.

[0036] In the case of the lower left region VLPL, which is the "positive potential below threshold a" and not the "internal pressure above threshold b", the low internal pressure results in less oxygen (O2) generation and a low probability of Ni2O3H generation due to "electrolyte drying".

[0037] Furthermore, in the case of the upper right region VHPH, which is not "positive electrode potential below threshold a" but "internal pressure above threshold b", although the internal pressure is high, the positive electrode potential is high. Therefore, it is presumed that the generated gas is not oxygen O2, and the possibility of the above-mentioned generation of Ni2O3H due to "electrolyte drying" is low.

[0038] In the upper left region VHPL, which is neither "positive potential below threshold a" nor "internal pressure above threshold b", the low internal pressure results in less oxygen (O2) generation and a lower probability of Ni2O3H generation due to "electrolyte drying".

[0039] Furthermore, in the lower right region VLPH, where the positive electrode potential is below threshold a and the internal pressure is above threshold b, the positive electrode potential is one where oxygen (O2) is easily generated due to the aforementioned mechanism. Additionally, in region VLPH, it is presumed that the internal pressure is actually high, oxygen (O2) is generated, and the possibility of Ni2O3H formation due to electrolyte desiccation is extremely high. Therefore, the dwell time in this state of "positive electrode potential below threshold a" and "internal pressure above threshold b" is calculated. Regarding the positive electrode potential [V] and internal pressure [Pa], the control device 10 operating in the vehicle (see reference...) Figure 7 The measurements and calculations are performed simultaneously at a certain time interval (e.g., 1 second interval in this embodiment). That is, it is assumed that a predetermined amount of Ni2O3H is generated synchronously with the 1-second interval under the state of "positive electrode potential below threshold a" and "internal pressure above threshold b". In other words, the positive electrode potential [V] and internal pressure [Pa] measured and calculated simultaneously at a certain time interval represent the data on the extent to which the state of "positive electrode potential below threshold a" and "internal pressure above threshold b" where the probability of Ni2O3H generation is extremely high remains during the use time of the nickel-metal hydride battery.

[0040] In this embodiment, the focus is on the duration of residence in a state where the probability of Ni2O3H generation is extremely high, under conditions of "positive electrode potential below threshold a" and "internal pressure above threshold b". Therefore, it is practically possible to measure the residence time in such a state where the probability of Ni2O3H generation is extremely high. However, it can be presumed that the residence time in this state is extremely high, proportional to the number of times the process is detected ("frequency"), and the residence time is prolonged. Therefore, in this embodiment, from the perspective of simplifying the process, the "residence time" is expressed as "frequency", and this "frequency" is accumulated and considered as "loss amount".

[0041] By calculating the "frequency" of states where the probability of Ni2O3H formation is extremely high, the accumulation amount of Ni2O3H formed under such states is estimated and considered as the "loss amount." This "loss amount" is a variable representing the formation of Ni2O3H; in this embodiment, the unit is the number of counts. A threshold c, equivalent to the third threshold, is determined through experiments where the battery capacity deteriorates after accumulating a certain number of "loss amounts."

[0042] <The positive electrode potential in the experimental example is the frequency [%) below the threshold a> Figure 3 This graph compares the case where the positive electrode potential is controlled with and without such control. Curve L1 represents the total discharge capacity [Ah] controlled in a manner where the internal pressure [Pa] is above threshold b [Pa] and the positive electrode potential [V] is not below threshold a [V]. Curve L2 represents the total discharge capacity of the prior art without control where the internal pressure [Pa] is above threshold b [Pa] and the positive electrode potential [V] is below or not below threshold a [V].

[0043] The inventors compared the total discharge capacity in Experimental Example 1 and Experimental Example 2. In Experimental Example 1, control was performed so that the internal pressure [Pa] was above the threshold b [Pa] and the positive electrode potential [V] was not below the threshold a. Experimental Example 2 is a prior art method that did not perform the control of the internal pressure [Pa] being above the threshold b [Pa] and the positive electrode potential being below or not below the threshold a.

[0044] In Experiment 1, control was implemented so that the internal pressure [Pa] was above the threshold b [Pa] and the positive electrode potential [V] was not below the threshold a [V]. Therefore, as shown by curve L1, even if the total discharge capacity [Ah] increased, the frequency of the positive electrode potential [V] being below the threshold a [V] was zero. As a result, in the nickel-metal hydride battery of Experiment 1, the battery life was maintained until the total discharge capacity [Ah] significantly exceeded 6000 [Ah].

[0045] On the other hand, in Experimental Example 2 of the prior art, control was not performed where the internal pressure [Pa] was above threshold b [Pa] and the positive electrode potential [V] was below threshold a [V] or not below that threshold a. Therefore, as shown in curve L2, before the total discharge capacity [Ah] exceeded 2000 [Ah], the frequency [%] of the positive electrode potential [V] being below threshold a [V] was zero. However, after the total discharge capacity [Ah] exceeded 2000 [Ah], the frequency [%] of the positive electrode potential [V] being below threshold a [V] suddenly increased. Furthermore, when the total discharge capacity [Ah] approximately exceeded 3000 [Ah], the frequency reached over 80%, and the battery life was exhausted. It can be presumed that this is because once Ni2O3H is generated, the generated Ni2O3H further and rapidly causes the electrolyte to dry out, accelerating the generation of Ni2O3H.

[0046] <Battery life in the experimental example> Figure 4 This is a graph showing the change in capacity retention rate [%] relative to total discharge capacity [Ah] in the experimental example.

[0047] Capacity retention rate [%] is a value representing the percentage of battery capacity when the unused battery capacity is 100%. Here, for example, when it is below 70%, it is considered that the battery life has been exhausted. In the nickel-metal hydride battery of Experimental Example 1 represented by L3, when the total discharge capacity [Ah] is 2000 [Ah], the capacity retention rate [%] is below 90%. Furthermore, as the total discharge capacity [Ah] increases, the capacity retention rate [%] gradually decreases. And when the total discharge capacity [Ah] is approximately 6000 [Ah], the capacity retention rate [%] drops to 80%, which is still a usable capacity retention rate [%].

[0048] On the other hand, in Experimental Example 2 shown in L4, when the total discharge capacity [Ah] was 2000 [Ah], the capacity retention rate [%] was less than 90%, which was not significantly different from Experimental Example 1. However, when the total discharge capacity [Ah] is 3000 [Ah], the capacity retention rate [%) drops rapidly to around 70%. At this point, the battery needs to be replaced.

[0049] Furthermore, when the total discharge capacity [Ah] is greater than 3000 [Ah], the capacity retention rate [%) drops sharply to about 60%, indicating that the battery life is completely exhausted. <Reasons why the control method for nickel-metal hydride batteries in this embodiment can extend battery life> Depend on Figure 3 , Figure 4It can be inferred that in Experimental Example 2 of the prior art, the sharp decrease in battery capacity is due to the rapid drying of the electrolyte once Ni2O3H is generated, which accelerates the formation of Ni2O3H. Therefore, by setting the positive electrode voltage [V] and internal pressure [Pa] to a level that prevents the explosive accumulation of Ni2O3H due to such rapid electrolyte drying, the formation of Ni2O3H can be reliably suppressed.

[0050] In this embodiment, by managing the accumulation of Ni2O3H as a loss, the amount of Ni2O3H accumulated in the target nickel-metal hydride battery can be accurately estimated, and appropriate control can be performed corresponding to this loss. Such control can extend the capacity life of the positive electrode of the nickel-metal hydride battery.

[0051] <Control device for nickel-metal hydride battery in this embodiment> The following is a brief description of an example of a nickel-metal hydride battery and its control device, which are the premise of this embodiment.

[0052] Nickel-metal hydride batteries Figure 5 A partial cross-sectional view of the battery module 90 of the nickel-metal hydride battery according to this embodiment is shown. Figure 5 As shown, nickel-metal hydride (NiMH) batteries are sealed batteries used as on-board batteries for electric vehicles, hybrid vehicles, and other similar vehicles. To achieve the required electrical capacity, NiMH batteries installed in vehicles are known to be square, sealed secondary batteries composed of battery modules 90, which are formed by connecting multiple individual cells 110 in series.

[0053] The battery module 90 has a rectangular housing 300 in the shape of a cuboid. The housing consists of an integrated battery compartment 100 capable of housing multiple individual batteries 110 and a cover 200 that seals the integrated battery compartment 100. It should be noted that the housing 300 can be made of resin.

[0054] The integral battery tank 100 constituting the square casing 300 is made of a synthetic resin material (e.g., polypropylene, polyethylene, etc.) resistant to alkaline electrolytes. Furthermore, partitions 120 for separating multiple individual cells 110 are formed inside the integral battery tank 100, and the portions separated by these partitions 120 constitute the battery tank 130 for each individual cell 110. For example, the integral battery tank 100 has six battery tanks 130. Figure 5 The image shows four electrical tanks, representing a portion of the device.

[0055] The electrode assembly 140, along with the positive electrode current collector 150 and the negative electrode current collector 160 connected to its two sides, are housed together with the electrolyte in the thus separated electrode cell 130. The electrode assembly 140 is constructed by laminating rectangular positive electrode plates 141 and negative electrode plates 142 with a separator 143 in between. The direction in which the positive electrode plate 141, negative electrode plate 142, and separator 143 are laminated (perpendicular to the plane of the paper) is the lamination direction. The positive electrode plate 141 and negative electrode plate 142 of the electrode assembly 140 protrude from opposite sides in the direction of the plate surface (along the plane of the paper), thereby forming the lead-out portion 141a of the positive electrode plate 141 and the lead-out portion 142a of the negative electrode plate 142. Current collectors 150 and 160 are respectively engaged with the side edges of these leads-out portions 141a and 142a.

[0056] Additionally, a through hole 170 for connecting each of the electrical trays 130 is formed on the upper part of the partition wall 120. Regarding the through hole 170, two connecting protrusions 151 and 161, protruding from the upper part of the current collector plate 150 and the upper part of the current collector plate 160, are welded together through the through hole 170. This connects the electrode plate assemblies 140 of adjacent electrical trays 130 in series. A positive terminal 152 or a negative terminal (not shown) is installed above the end sidewall of the integral electrical tray 100 in the through hole 170 located at both ends of the electrical tray 130. The positive terminal 152 is welded to the connecting protrusion 151 of the current collector plate 150. The negative terminal is welded to the connecting protrusion 161 of the current collector plate 160. The total output of the electrode assembly 140, which is connected in series like this, i.e., multiple single cells 110, is taken out from the positive terminal 152 and the negative terminal.

[0057] On the other hand, the cover 200 constituting the square housing 300 is provided with an exhaust valve 210 to keep the internal pressure of the square housing 300 below the valve opening pressure, and a sensor mounting hole 220 for mounting a sensor for detecting the temperature of the electrode assembly 140. The sensor mounting hole 220 allows the temperature of the electrode assembly 140 to be measured through a hole extending from the electrode tank 130 to the vicinity of the electrode assembly 140.

[0058] The exhaust valve 210 is used to maintain the internal pressure within the integrated electric bath 100 below an acceptable threshold. When the internal pressure exceeds the valve opening pressure of the acceptable threshold, the valve is opened to release the gas generated inside the integrated electric bath 100. The internal pressure of the integrated electric bath 100 is homogenized throughout the electric bath 130 through a communication hole (not shown) formed in the partition wall 120. Thus, gas is released from the integrated electric bath 100 until the homogenized internal pressure throughout the electric bath 130 is lower than the valve opening pressure, maintaining its internal pressure below the acceptable valve opening pressure.

[0059] <Composition of the electrode assembly 140> <Positive Plate 141> In the positive electrode plate 141, the positive electrode substrate, which serves as the substrate, is a foamed nickel three-dimensional porous body composed of Ni or a Ni alloy, which is a porous metal. The positive electrode substrate has a framework portion containing a three-dimensional mesh structure and pore portions surrounded by the framework portion. The positive electrode substrate is manufactured, for example, by applying nickel plating to the surface of a foamed urethane framework and then burning off the foamed urethane. The positive electrode plate 141 has a positive electrode composite material layer containing Ni(OH)2 and Co as active materials. Specifically, granular nickel hydroxide is first processed into a paste by adding appropriate amounts of conductive agents such as cobalt hydroxide and metallic cobalt powder, as well as thickeners such as carboxymethyl cellulose and binders such as polytetrafluoroethylene, if necessary. Then, the paste-like processed material is filled into the mesh-like pore portions of the positive electrode substrate to form the positive electrode composite material layer. Then, it is dried, rolled, and cut to form a plate-shaped positive electrode plate 141.

[0060] <Negative electrode plate 142> The negative electrode plate 142 is constructed, for example, using a hydrogen storage alloy as the active material. This hydrogen storage alloy is composed of a mixture of rare earth metals, nickel, aluminum, cobalt, and manganese, which are mixtures of rare earth elements such as lanthanum, cerium, and neodymium. More specifically, a conductive agent such as carbon black, and, if necessary, a thickener such as carboxymethyl cellulose and a binder such as styrene-butadiene copolymer, are added to the hydrogen storage alloy, and it is first processed into a paste. Subsequently, after the hydrogen storage alloy, which has been processed into a paste, is coated or filled onto a core material such as a perforated metal (active material support), it is dried, rolled, and cut to form the negative electrode plate 142, which is also plate-shaped.

[0061] <Separator 143> As the spacer 143, a nonwoven fabric made of olefin resin such as polypropylene can be used, or a component obtained by subjecting it to hydrophilic treatment such as sulfonation as required.

[0062] The battery module 90 of the nickel-metal hydride battery in this embodiment has the above configuration. <Control device 10 for nickel-metal hydride batteries> Figure 6 This is a block diagram of the control device 10 of the nickel-metal hydride battery 1 according to this embodiment. Next, refer to... Figure 6 The control device 10 for the nickel-metal hydride battery 1 will be described. It should be noted that the description here refers to the case where the nickel-metal hydride battery 1 is controlled in the state of the battery pack 24 containing the battery module 90.

[0063] <Control Device 10> The control device 10, which serves as a battery control unit, is mounted on the vehicle and can control the vehicle's battery module 90 in real time or based on accumulated data, either on-board or so-called.

[0064] The control device 10 controls the inverter 20, which acts as a charging device for charging the battery module 90, to supply current from the motor generator 17, which acts as a generator, to the battery module 90, thereby charging the battery module 90. Additionally, the control device 10 controls the inverter 20, which acts as a power supply device, to discharge current from the battery module 90 to the drive motor, i.e., the motor generator 17, which acts as a load.

[0065] The control device 10 includes: a current detector 21 for measuring 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.

[0066] Temperature detector 23 is configured to Figure 5 The temperature sensor is located in the sensor mounting hole 220 shown. The temperature sensor measures the temperature near the electrode assembly 140 of the corresponding single cell 110 in the battery module 90 and outputs the measured temperature value as an electrical signal to the control device 10.

[0067] <Control Department 11> The control unit 11 of the control device 10 is configured as a computer equipped with a CPU, RAM, ROM, and interface for overall control of the control device 10. It should be noted that the control unit 11 functions as a loss calculation device and a positive electrode protection device.

[0068] <Information Acquisition Department 12> The information acquisition unit 12 successively obtains the charging current value from the current detector 21, the voltage value from the voltage detector 22, and the battery temperature from the temperature detector 23 and stores it.

[0069] <Storage Department 13> The storage unit 13 includes the program for the storage control device 10 and a storage medium for the necessary data. The program is equipped with storage for execution. Figures 7-9 The flowchart shown illustrates the program, for example, the execution of... Figures 7-9 The flowchart shown illustrates the following steps of the procedure. Storage unit 13, for example, stores... Figure 7 The program includes positive electrode potential estimation (S2), internal pressure estimation (S4), and positive electrode protection control (S9). Furthermore, the storage unit 13 stores... Figure 9 The process involves multiple steps. Figure 9The procedure includes several steps: obtaining the relationship between charging capacity and gas absorption rate (S401), measurement step (S402), calculation step of internal pressure increase rate (S403), charging capacity estimation step (S404), internal pressure decrease rate correction value calculation step (S405), internal pressure decrease rate calculation step (S406), correction internal pressure decrease rate calculation step (S407), estimation internal pressure calculation step (S408), negative electrode SOC estimation step (S409), hydrogen balance pressure calculation step (S410), correction negative electrode hydrogen balance pressure calculation step (S411), and correction estimation internal pressure calculation step (S412).

[0070] In addition, as data for control purposes, the storage unit 13 stores tabular data of "OCV mapping diagrams based on the relationship between cell voltage [V] and negative electrode potential [V]" according to the temperature [°C] and current [A] used in the positive electrode potential estimation unit 14. Furthermore, the storage unit 13 also stores mapping diagrams based on measured data of "relationship between charge capacity and gas absorption rate" used in the internal pressure estimation unit 15. Additionally, the storage unit 13 stores mapping diagrams of "relationship between temperature and internal pressure increase rate" and "relationship between temperature and internal pressure decrease rate". Furthermore, the storage unit 13 stores mapping diagrams of "relationship between battery voltage and negative electrode SOC". The storage unit 13 also stores mapping diagrams of "relationship between negative electrode SOC and hydrogen equilibrium pressure". Finally, the storage unit 13 stores mapping diagrams of "relationship between temperature and hydrogen equilibrium pressure".

[0071] In addition, the storage unit 13 also stores a mapping diagram of "the deterioration state of the battery estimated from the usage history of the nickel-metal hydride battery 1" and "the relationship between the deterioration state of the nickel-metal hydride battery 1 and the charge capacity". <Positive Potential Estimation Section 14> The positive electrode potential estimation unit 14 estimates the negative electrode potential based on the individual cell voltage measured by the voltage detector 22 and by referring to the "table data on the relationship between individual cell voltage and negative electrode potential" stored in the storage unit 13. Then, the positive electrode potential estimation unit 14 estimates the positive electrode potential based on the difference between the individual cell voltage and the negative electrode potential. This positive electrode potential estimation unit 14 enables the control device 10 to function as a positive electrode potential acquisition device.

[0072] <Internal Pressure Estimation Section 15> The internal pressure estimation unit 15 uses the temperature, voltage, current, and other data of the stored vehicle-mounted nickel-metal hydride battery obtained by the information acquisition unit 12 to... Figure 8 The process shown in the flowchart is used to estimate the internal pressure of the battery. Details are described below. This internal pressure estimation unit 15 enables the control device 10 to function as an internal pressure acquisition device.

[0073] <Charging and discharging control unit 16> The charge / discharge control unit 16 monitors the voltage of the battery module 90. When the state of charge (SOC) is below a threshold, it generates electricity using the electric generator 17 and charges the battery module 90 via the inverter 20. Conversely, during vehicle braking, regenerative current from the electric generator 17 is supplied via the inverter 20 to charge the battery module 90. In this case, if the current is too high or the SOC of the battery module 90 is too high, the charge / discharge control unit 16 limits the charging. The threshold values ​​at this time are stored in the storage unit 13. Furthermore, in... Figure 8 In the positive electrode protection control (S9) shown, charging and discharging are also controlled in such a way that the potential of the positive electrode is not lower than the threshold d, which is equivalent to the fourth threshold.

[0074] On the other hand, when the vehicle is driven, the charging and discharging control unit 16 uses instructions from the vehicle's ECU (Electronic Control Unit) to supply the necessary current from the battery module 90 to the electric generator 17 via the inverter 20.

[0075] <The process of the control method for the nickel-metal hydride battery in this embodiment> Figure 7 This is a flowchart illustrating the control method for the nickel-metal hydride battery according to this embodiment. (Refer to...) Figure 7 The process of the control method for the nickel-metal hydride battery of this embodiment will be described.

[0076] As described above, prior to implementing the control method for the nickel-metal hydride battery of this embodiment, the storage unit 13 of the control device 10 stores data such as table data and mapping diagrams used in positive electrode potential estimation (S2) and internal pressure estimation (S4).

[0077] When vehicle operation begins (start), it is first determined whether control is still continuing (S0). If control stops when vehicle operation stops (S0: Yes), the control method for the nickel-metal hydride battery also stops (stops). If control continues (S0: No), the voltage [V], current [A], temperature [°C], etc. of the nickel-metal hydride battery are measured (S1) at a predetermined time for positive electrode potential estimation (S2) and internal pressure estimation (S4). Regarding this timing, the measurement is performed at a certain time interval, for example, every 1 second, using a counter of the control device 10. Therefore, for example, it is determined every 100ms whether this measurement time is (S1), and before the measurement time (S1: No), there is a standby loop (S0: No → S1: No → S0). Subsequently, when the predetermined measurement time arrives (S1: Yes), the voltage [V], current [A], and temperature [°C] of the nickel-metal hydride battery are measured, and the processes of positive electrode potential estimation (S2) and internal pressure estimation (S4) are processed simultaneously in parallel.

[0078] <The process of estimating the positive electrode potential (S2)> Figure 8 This is a flowchart detailing the subroutine process for estimating the positive electrode potential (S2) in this embodiment. See below for reference. Figure 8 The flowchart shown provides a detailed explanation of the positive electrode potential estimation (S2) process.

[0079] When starting the positive electrode potential estimation (S2), the measured cell voltage [V], temperature [°C], and current [A] are first read in (S201). Next, the "table data on the relationship between cell voltage and negative electrode potential" stored in the storage unit 13 according to temperature [°C] and current [A] is read in (S202). Referring to the "table data on the relationship between cell voltage and negative electrode potential" for the corresponding temperature [°C] and current [A], the negative electrode potential [V] is estimated based on the read cell voltage [V] (S203). Then, using the estimated negative electrode potential, the positive electrode potential [V] is estimated based on the relationship that cell voltage [V] - negative electrode potential [V] = positive electrode potential [V] (S204).

[0080] Based on the above process, the positive electrode potential [V] is estimated, the positive electrode potential estimation process (S2) ends (end), and the process moves to... Figure 7 The process of determining whether the positive electrode potential [V] is below the threshold a [V] (S3).

[0081] <The process of determining whether the positive electrode potential [V] is below the threshold a [V] (S3)> Regarding the positive electrode potential [V] estimated during the positive electrode potential estimation process (S2), a threshold value [V] that may generate oxygen is pre-set as "threshold a [V]" in accordance with the characteristics of the nickel-metal hydride battery being targeted, and stored in the storage unit 13 of the control device 10. The control unit 11 reads the threshold value a [V] stored in the storage unit 13 and determines whether the positive electrode potential [V] estimated during the positive electrode potential estimation process (S2) is below the threshold value a [V] (S3). If the positive electrode potential [V] estimated during the positive electrode potential estimation process (S2) is not below the threshold value a [V] (S3: No), the system returns to S0 and determines whether to stop control (S0), and waits until the next measurement timing (S0: No → S1: No → S0).

[0082] On the other hand, if the positive electrode potential [V] estimated by the positive electrode potential estimation process (S2) is below the threshold a [V] (S3: Yes), a flag is set in the information acquisition unit 12 in order to perform the processing in S6.

[0083] <The process of estimating internal pressure (S4)> The control unit 11 performs the internal pressure estimation process (S4) in parallel with the positive electrode potential estimation process (S2).

[0084] Figure 9 This is a flowchart illustrating the details of the process (S4) for estimating the internal pressure in this embodiment. Refer to this... Figure 9 The flowchart shown illustrates the process of estimating internal pressure (S4).

[0085] First, control device 10 (see Figure 6 In the measurement step (S402), the voltage, current, and temperature of the nickel-metal hydride battery 1 are measured. Then, in the internal pressure drop rate calculation step (S406), the "internal pressure drop rate" is calculated based on the gas absorption rate of the negative electrode at the measured temperature. In parallel, in the charge capacity estimation step (S404), the "charge capacity" is estimated based on the measured voltage, current, and temperature. In the internal pressure drop rate correction value calculation step (S405), the "internal pressure drop rate correction value" is calculated based on the estimated "charge capacity." It should be noted that, in order to perform this estimation, the relationship between the charge capacity and the gas absorption rate of the negative electrode is read into the storage unit 13 of the control device 10 (see reference). Figure 6 (S401). Then, in the step of calculating the corrected internal pressure reduction rate (S407), the "internal pressure reduction rate" calculated by the step of calculating the internal pressure reduction rate correction value (S405) is corrected based on the "internal pressure reduction rate correction value" to calculate the "corrected internal pressure reduction rate" more accurately.

[0086] Next, through the estimated internal pressure calculation step (S408), the "estimated internal pressure" is calculated based on the "corrected internal pressure decrease rate" and the "internal pressure increase rate" calculated based on temperature. Furthermore, the negative electrode SOC is estimated in the negative electrode SOC estimation step (S409). Additionally, the "hydrogen balance pressure" of the negative electrode is calculated based on temperature in the hydrogen balance pressure calculation step (S410). On the other hand, the "corrected hydrogen balance pressure" is calculated based on the relationship between the negative electrode SOC and the negative electrode hydrogen balance pressure in the corrected hydrogen balance pressure calculation step (S411).

[0087] Subsequently, in the correction estimate internal pressure calculation step (S412), the "correction estimate internal pressure" is calculated more accurately based on the "hydrogen equilibrium pressure". After calculating the "corrected estimated internal pressure" in this way, the process of estimating the internal pressure ends (S4).

[0088] The internal pressure [Pa] is estimated through the above process, ending the internal pressure estimation (S4) process (end), and proceeding to... Figure 7 The process of determining whether the internal pressure [Pa] is above the threshold b [Pa] (S5). <The process of determining whether the internal pressure is above the threshold b (S5)> Regarding the internal pressure estimated by the internal pressure estimation process (S4), a threshold value ("threshold b [Pa]") is pre-set in the storage unit 13 of the control device 10, corresponding to the characteristics of the nickel-metal hydride battery being targeted, where the internal pressure [Pa] generated by gas may cause electrolyte drying. The control unit 11 reads the threshold value ("threshold b [Pa") stored in the storage unit 13 and determines whether the internal pressure [Pa] estimated by the internal pressure estimation process (S4) is above or below the threshold value ("threshold b [Pa") (S5). If the internal pressure [Pa] estimated by the internal pressure estimation process (S4) is not above the threshold value ("S5: No"), the system returns to S0 and determines whether to stop control ("S0"), and waits until the next measurement timing ("S0: No → S1: No → S0").

[0089] On the other hand, if the internal pressure [Pa] estimated by the internal pressure estimation process (S4) is above the threshold b [Pa] (S5: Yes), a flag is set in the information acquisition unit 12 in order to perform the processing in S6.

[0090] <Handling of cases where the positive electrode potential threshold a [V] is below and the internal pressure threshold b [Pa] is above (S6)> If the information acquisition unit 12 simultaneously sets a flag indicating that the positive electrode potential is below the threshold a [V] and the internal pressure is above the threshold b [Pa], the control unit 11 determines that the positive electrode potential is below the threshold a [V] and the internal pressure is above the threshold b [Pa]. Then, the measurement of this cycle is defined as "frequency 1" based on the assumption that Ni2O3H has been generated.

[0091] <Cumulative Frequency (S7)> The control unit 11 accumulates the "frequency" determined in S6 and stores it in the information acquisition unit 12 (S7) as a "frequency accumulation value". This "frequency accumulation value" is called "loss amount" in this embodiment. The unit is the number of times. That is, the "frequency accumulation value" is considered to be the total amount of Ni2O3H generated when the positive electrode potential threshold a [V] is below and the internal pressure threshold b [Pa] is above.

[0092] <Determination of whether the cumulative frequency value is greater than or equal to the threshold c (S8)> Regarding the frequency accumulation value accumulated in S7, the total amount of Ni2O3H that significantly shortens the lifespan of the target NiMH battery is pre-set as a threshold c through experiments, etc. Then, the frequency accumulation value calculated in S7 is compared with the threshold c (S8). Here, if the frequency accumulation value is not greater than or equal to the threshold c (S8: No), the positive electrode of the target NiMH battery is recorded as having no problem, and the process returns to S0, remaining in standby until the next measurement time (S0: No → S1: No → S0). In this case, it is determined that the current positive electrode potential control is not problematic, and the current positive electrode potential control is not changed; the current positive electrode potential control continues in this state.

[0093] Figure 10 This is a graph showing the irreversible accumulation of losses over time, reaching a threshold c. In the judgment (S8) regarding whether the cumulative frequency value is ≥ threshold c, it is determined whether "the cumulative frequency value ≥ threshold c". If the cumulative frequency value is above threshold c (S8: Yes), Ni₂O₃H accumulates in the positive electrode of the target nickel-metal hydride battery, indicating a problem with the current control of the positive electrode potential. That is, as... Figure 10 As shown, when controlled under this state, the loss amount, i.e., the accumulation of Ni2O3H, is close to causing... Figure 3 , Figure 4 Experimental Example 2 illustrates an avalanche-like capacity reduction state.

[0094] Furthermore, if the cumulative frequency value is greater than or equal to the threshold c (S8: Yes), a positive electrode protection control process is performed (S9). That is, the threshold c is the limit frequency at which the capacity of the nickel-metal hydride battery can be maintained within the normal range.

[0095] Positive electrode protection control (S9) In the positive electrode protection control process (S9), the positive electrode protection control process is changed. Under the current control, the amount of Ni2O3H accumulation is estimated to be low, which may allow unexpected Ni2O3H generation. Therefore, in order to further suppress Ni2O3H generation, the control benchmark is made more stringent. Specifically, the value of the threshold d[V] of the positive electrode potential [V] estimated for oxygen O2 generation is made higher than the current threshold d[V] of the positive electrode potential [V], and instead of the threshold d[V], it is made to be a higher threshold d+α[V] of the positive electrode potential [V]. Furthermore, the control device 10 controls the positive electrode potential [V] based on the set higher threshold d+α[V] of the positive electrode potential [V] in a way that the positive electrode potential [V] will not fall below the threshold d+α[V]. Specifically, the control unit 11 continuously monitors the individual cell voltage [V] of the battery module 90. Furthermore, the positive electrode potential [V] is estimated, and detection is performed for situations where the electric generator 17 consumes a large amount of power, or where the electric generator 17 has not generated power for a long time and the voltage of the individual cells [V] decreases due to power consumption from loads such as air conditioning or lighting. In such cases, the electric generator 17 is limited to generate power or output power in a way that ensures the estimated positive electrode potential [V] will not fall below the newly set threshold d+α [V], thereby preventing the positive electrode potential [V] from falling below the newly set threshold d+α [V]. This control effectively suppresses the formation of Ni2O3H, thereby extending the capacity life of the nickel-metal hydride battery. After the positive electrode protection control process (S9) is completed, the process returns to S0.

[0096] (The role of the implementation method) Because this embodiment has the above-described configuration, it is able to accurately estimate the capacity reduction caused by the generation and accumulation of Ni2O3H in the nickel-metal hydride battery installed in the vehicle as the amount of loss.

[0097] Regarding its specific function, the frequency of the state when the positive electrode potential is below threshold a [V] and the internal pressure is above threshold b [Pa] is accumulated (S7). By accumulating this frequency, the amount of Ni2O3H stored in the positive electrode of the nickel-metal hydride battery can be accurately estimated as the "loss amount".

[0098] The loss is monitored, and if it exceeds a predetermined threshold c (S8: Yes), a positive electrode protection step (S9) is implemented to prevent a sharp capacity reduction in the nickel-metal hydride battery. The positive electrode protection step (S9) is controlled in a manner that makes the positive electrode potential less likely to generate Ni2O3H, thus preventing a sharp capacity reduction in the nickel-metal hydride battery.

[0099] (Effects of the implementation method) The control method for nickel-metal hydride batteries in this embodiment has the following effects. (1) In the control method of the nickel-metal hydride battery of this embodiment, the generation of Ni2O3H that leads to capacity reduction can be fundamentally suppressed under appropriate conditions, and the capacity degradation of the positive electrode can be suppressed.

[0100] (2) In the control method for the nickel-metal hydride battery of this embodiment, the control device 10 is composed of a computer mounted on the vehicle, which is a system that is completed solely by the vehicle itself. Therefore, during vehicle operation, the control method for the nickel-metal hydride battery of this embodiment can be implemented autonomously to protect the vehicle-mounted nickel-metal hydride battery.

[0101] (3) Especially in vehicle operation, by drastically reducing the positive electrode capacity, it is possible to avoid the situation where the vehicle suddenly becomes inoperable. (4) It includes a positive electrode potential acquisition step for calculating and obtaining the potential of the positive electrode, and an internal pressure acquisition step for calculating and obtaining the internal pressure of the alkaline secondary battery. Since the conditions for the formation of Ni2O3H are analyzed and determined in a comprehensive manner based on these processes, the conditions for the formation of Ni2O3H can be accurately determined. Therefore, the formation of Ni2O3H can be reliably estimated.

[0102] (5) Since the conditions of positive electrode potential and internal pressure are determined based on threshold a and threshold b derived from experiments, accurate determination can be made. (6) In the positive electrode potential acquisition step, an OCV mapping diagram representing the relationship between the cell voltage and the negative electrode potential is provided according to temperature and current, respectively. Referring to the OCV mapping diagram, the positive electrode potential is estimated by subtracting the negative electrode potential from the measured value of the cell voltage. Therefore, it can also be processed quickly in the vehicle-mounted control device 10.

[0103] (7) In the internal pressure calculation step, the internal pressure of the alkaline secondary battery is estimated and calculated based on the voltage, temperature, and current values. Therefore, the internal pressure can be accurately estimated considering various conditions.

[0104] (8) By replacing the accumulation state of Ni2O3H with the amount of loss and using the threshold d for judgment, it is easy to infer that the battery is in a dangerous state of rapid deterioration and avoid the state of rapid generation of Ni2O3H.

[0105] (9) When the accumulation of Ni2O3H is large and the battery capacity is dangerous, the positive electrode protection step can prevent the accumulation of Ni2O3H from occurring. (10) By utilizing the positive electrode protection step, the positive electrode potential can be controlled in such a way that it does not fall below the threshold d corresponding to the loss amount. Therefore, it is possible to prevent the accumulation of Ni2O3H above this threshold.

[0106] (11) The control method for the nickel-metal hydride battery in this embodiment can be implemented using existing ECUs or similar devices for controlling the battery. Therefore, the control method for the nickel-metal hydride battery in this embodiment can be implemented using only software. Therefore, the control method for the nickel-metal hydride battery in this embodiment can be implemented without modifying existing vehicles.

[0107] (Modified Example) The above implementation method can also be implemented as follows. In this embodiment, the duration of residence in a state where the probability of Ni2O3H generation is extremely high ("positive electrode potential below threshold a" and "internal pressure above threshold b") is determined by the number of times the "frequency" is measured. However, the residence time in such a state with an extremely high probability of Ni2O3H generation can also be actually measured and accumulated regardless of the "frequency".

[0108] Additionally, in this embodiment, as... Figure 2 As shown, the system is divided into four regions based on thresholds a and b, indicating a state where the probability of Ni2O3H formation is extremely high for those with "positive electrode potential below threshold a" and "internal pressure above threshold b". However, multiple thresholds can also be set based on the probability of Ni2O3H formation, and the weighted values ​​obtained from each region can be accumulated.

[0109] In this embodiment, the "positive electrode potential" is estimated using a method defined by the cell voltage. However, it can also be estimated using other estimation methods. Furthermore, it is also possible to measure the "positive electrode potential" without estimation.

[0110] Furthermore, the "internal pressure" in this embodiment is estimated from information such as voltage, current, and temperature. This estimation method is just one example and can be further simplified; it can also be estimated from other data. Alternatively, a method of measuring the "internal pressure" without estimation can also be used.

[0111] · Figure 5 The battery module 90 of the nickel-metal hydride battery shown Figure 6 The control device 10 shown is an example, but is not limited to this configuration. The control device 10 can perform this function through the vehicle's ECU. Alternatively, it can be set up independently of the battery pack 24.

[0112] In this embodiment, the invention has been described using a nickel-metal hydride battery mounted in an electric vehicle as an example, but it can also be appropriately applied to batteries used in ships and aircraft. Furthermore, it can be applied to stationary batteries.

[0113] Alkaline secondary batteries are not limited to nickel-metal hydride batteries; they can also be implemented in other alkaline secondary batteries. · Figures 7-9The flowchart shown is one embodiment of this implementation method. It is self-evident that those skilled in the art can change the order of operations, add, remove, or modify the operations.

[0114] The numerical ranges illustrated in this embodiment are specific examples, and the present invention is not limited thereto. They can be appropriately optimized by those skilled in the art based on the alkaline secondary battery being the target.

[0115] In this invention, even if not described in the embodiments, it is self-evident that those skilled in the art can add, remove, or modify its components without departing from the scope of the claims. Explanation of symbols

[0116] 1…NiMH batteries 2…Positive electrode active material 2a…particles 2b…particle surface 4…Alkaline electrolyte 10…Control device for nickel-metal hydride batteries 11…Control Department 12…Information Acquisition Department 13… Storage section (programs, mapping diagrams, battery usage history, etc.) 14…Positive potential estimation section 15… Internal pressure estimation section 16…Charge and Discharge Control Department 17… Electric generator 20… Inverter 21… Current detector 22…Voltage Detector 23…Temperature detector 24… battery pack 90… Battery Module 100…Integrated Electric Sink 110…Single battery 120… next door 130…electrical tank 140…plate assembly 141… Positive plate 141a… Introduction 142… Negative electrode plate 142a… Introduction 143…spacer 150… collector board 151… Connecting protrusion 152…Connecting terminal 160… collector board 161…connecting protrusion 170…through hole 200… Cover 210…exhaust valve 220… Sensor mounting hole 300…square shell

Claims

1. A control method for an alkaline secondary battery, the alkaline secondary battery comprising a positive electrode using nickel hydroxide as the active material, a negative electrode containing a hydrogen storage alloy, and an electrolyte composed of an alkaline aqueous solution, wherein, The control method comprises the following steps: The positive electrode potential is obtained by calculating and obtaining the positive electrode potential at a certain timing. The internal pressure acquisition step involves calculating and obtaining the internal pressure of the alkaline secondary battery in sync with the timing step. The loss calculation steps involve accumulating the dwell time of the state when the positive electrode potential is below the first threshold (a) and the internal pressure is above the second threshold (b), thereby calculating the loss. as well as The positive electrode protection step involves protecting the positive electrode when the loss calculated in the loss calculation step reaches the third threshold (c). In the step of obtaining the positive electrode potential, an OCV mapping diagram representing the relationship between the cell voltage and the negative electrode potential is pre-stored according to temperature and current. The positive electrode potential is estimated by subtracting the negative electrode potential from the measured value of the cell voltage with reference to the OCV mapping diagram.

2. The control method for an alkaline secondary battery as described in claim 1, characterized in that, In the internal pressure acquisition step, the internal pressure of the alkaline secondary battery is estimated based on the voltage, temperature, and current values.

3. The control method for an alkaline secondary battery as described in claim 1 or 2, characterized in that, The positive electrode protection step is controlled in such a way that the positive electrode potential does not fall below the fourth threshold (d) corresponding to the loss.

4. The control method for an alkaline secondary battery as described in claim 1 or 2, characterized in that, The alkaline secondary battery is a nickel-metal hydride battery.

5. The control method for an alkaline secondary battery as described in claim 1 or 2, characterized in that, The alkaline secondary battery is an on-board battery used for vehicle propulsion. The alkaline secondary battery is controlled by a battery control device.

6. A control device for an alkaline secondary battery, comprising controlling an alkaline secondary battery mounted in a vehicle, having a positive electrode with nickel hydroxide as the active material, a negative electrode containing a hydrogen storage alloy, and an electrolyte composed of an alkaline aqueous solution, wherein... The control device has the following features: A positive electrode potential acquisition device calculates and obtains the positive electrode potential at a certain timing. An internal pressure obtaining device calculates and obtains the internal pressure of the alkaline secondary battery; The loss calculation device accumulates the dwell time of a state where the positive potential is below a first threshold (a) and the internal pressure is above a second threshold (b), thereby calculating the loss. as well as The positive electrode protection device protects the positive electrode when the loss calculated by the loss calculation device reaches the third threshold (c). In the step of obtaining the positive electrode potential, an OCV mapping diagram representing the relationship between the cell voltage and the negative electrode potential is pre-stored according to temperature and current. The positive electrode potential is estimated by subtracting the negative electrode potential from the measured value of the cell voltage with reference to the OCV mapping diagram.

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