Estimation device, estimation method, and estimation program

Abstract

To provide an estimation device, an estimation method and an estimation program with which it is possible to improve the accuracy of estimating the salt concentration of a secondary cell.SOLUTION: An estimation device 10 comprises: a boundary salt concentration identification unit 131 for identifying a first boundary salt concentration and a second boundary salt concentration on the basis of the correspondence between the SOC and temperature of a secondary cell and a first boundary salt concentration that represents a salt concentration at a first boundary between an anode and an anode collector plate in the thickness direction of the secondary cell, as well as the correspondence between the SOC and temperature and a second boundary salt concentration that represents a salt concentration at a second boundary between a cathode and a cathode collector plate in the thickness direction; a liquid phase diffusion model for deriving the salt concentration of the secondary cell; and a salt concentration calculation unit 132 for calculating the salt concentration in the thickness direction using the first and second boundary salt concentrations identified by the boundary salt concentration identification unit. The first and second boundary salt concentrations can change in accordance with the movement of salt in the surface direction of the secondary cell at the first and second boundaries, respectively.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an estimation device, an estimation method, and an estimation program for estimating the salt concentration of a secondary battery. [Background technology]

[0002] Currently, secondary batteries such as lithium-ion batteries and nickel-metal hydride batteries are used in vehicles that use electric power as a driving force, such as electric vehicles, hybrid vehicles, and plug-in hybrid vehicles. When such secondary batteries are charged and discharged at high rates, salt concentration variations occur in the electrolyte of the secondary battery, causing an increase in the internal resistance of the secondary battery. The increase in the internal resistance of the secondary battery reduces the available charge / discharge power and increases the risk of precipitation of salts such as lithium. Therefore, various techniques have been proposed for estimating the salt concentration of secondary batteries.

[0003] As an example of such a technique, Patent Document 1 estimates the battery current density using measured values ​​of a secondary battery, and calculates the difference in electrolyte salt concentration between electrodes based on the battery current density. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-60406 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the monitoring device disclosed in Patent Document 1 calculates the difference in electrolyte salt concentration between electrodes based only on the battery current density, and therefore cannot estimate salt concentration variations in the surface direction of the secondary battery (Figure 1), resulting in low accuracy in estimating the salt concentration of the secondary battery.

[0006] The present invention is intended to solve such problems, and has an object to provide an estimation device, an estimation method, and an estimation program that can improve the accuracy of estimating the salt concentration of a secondary battery. [Means for solving the problem]

[0007] An estimation device for estimating a salt concentration of a secondary battery according to one aspect of the present invention includes: a boundary salt concentration specifying unit that specifies a first boundary salt concentration and a second boundary salt concentration based on a correspondence relationship between the SOC (State of Charge) and temperature of the secondary battery and a first boundary salt concentration, which is the salt concentration at a first boundary between the negative electrode and the negative electrode current collector plate in the thickness direction of the secondary battery, and a correspondence relationship between the SOC and temperature and a second boundary salt concentration, which is the salt concentration at a second boundary between the positive electrode and the positive electrode current collector plate in the thickness direction; a salt concentration calculation unit that calculates the salt concentration in the thickness direction by using a liquid phase diffusion model that derives the salt concentration of the secondary battery and the first boundary salt concentration and the second boundary salt concentration that are identified by the boundary salt concentration identification unit; The first boundary salt concentration and the second boundary salt concentration are characterized in that they can change according to the migration of salt in the in-plane direction of the secondary battery at the first boundary and the second boundary, respectively.

[0008] Furthermore, an estimation device for estimating a salt concentration of a secondary battery according to an aspect of the present invention includes: a boundary salt concentration specifying unit that specifies the first boundary salt concentration and the second boundary salt concentration based on a correspondence relationship between the SOC and temperature of the secondary battery and a first boundary salt concentration, which is the salt concentration at a first boundary between the negative electrode and the negative electrode current collector plate in the thickness direction of the secondary battery, and a correspondence relationship between the SOC and temperature and a second boundary salt concentration, which is the salt concentration at a second boundary between the positive electrode and the positive electrode current collector plate in the thickness direction; a salt concentration calculation unit that calculates the salt concentration in the thickness direction by using a liquid phase diffusion model that derives the salt concentration of the secondary battery and the first boundary salt concentration and the second boundary salt concentration that are identified by the boundary salt concentration identification unit; The first boundary salt concentration and the second boundary salt concentration are characterized by being correlated with the SOC and temperature of the secondary battery.

[0009] The correspondence when charging the secondary battery is as follows: When the SOC is large and the temperature is high, the first boundary salt concentration and the second boundary salt concentration are set to be high; When the SOC is small and the temperature is low, the first boundary salt concentration and the second boundary salt concentration can be defined to be low.

[0010] The corresponding relationship when discharging the secondary battery is as follows: When the SOC is small and the temperature is high, the first boundary salt concentration and the second boundary salt concentration are set to be high; When the SOC is large and the temperature is low, the first boundary salt concentration and the second boundary salt concentration can be defined to be low.

[0011] The estimation device also includes a voltage calculation unit that calculates an estimated voltage value of the secondary battery using a current measurement value and a temperature measurement value of the secondary battery and the salt concentration calculated by the salt concentration calculation unit; The device includes a boundary salt concentration correction unit that corrects the first boundary salt concentration and the second boundary salt concentration identified by the boundary salt concentration identification unit based on the error between the voltage estimation value calculated by the voltage calculation unit and the voltage measurement value of the secondary battery.

[0012] Furthermore, the salt concentration calculation unit can calculate the salt concentration of the secondary battery using the first boundary salt concentration and the second boundary salt concentration corrected by the boundary salt concentration correction unit.

[0013] Furthermore, the estimation device may include a limit derivation unit that derives maximum time and power within which an average salt concentration, which is an average value of the salt concentrations calculated by the salt concentration calculation unit, falls within a predetermined range.

[0014] A method for estimating a salt concentration of a secondary battery according to one aspect of the present invention includes: determining the first boundary salt concentration and the second boundary salt concentration based on a correspondence relationship between the SOC and temperature of the secondary battery and a first boundary salt concentration, which is the salt concentration at a first boundary between the negative electrode and the negative electrode current collector plate in the thickness direction of the secondary battery, and a correspondence relationship between the SOC and temperature and a second boundary salt concentration, which is the salt concentration at a second boundary between the positive electrode and the positive electrode current collector plate in the thickness direction; calculating a salt concentration in the thickness direction using a liquid phase diffusion model for deriving a salt concentration of the secondary battery and the identified first boundary salt concentration and second boundary salt concentration; The first boundary salt concentration and the second boundary salt concentration are characterized in that they can change according to the migration of salt in the in-plane direction of the secondary battery at the first boundary and the second boundary, respectively.

[0015] Further, a method for estimating a salt concentration of a secondary battery according to an aspect of the present invention includes: determining the first boundary salt concentration and the second boundary salt concentration based on a correspondence relationship between the SOC and temperature of the secondary battery and a first boundary salt concentration, which is the salt concentration at a first boundary between the negative electrode and the negative electrode current collector plate in the thickness direction of the secondary battery, and a correspondence relationship between the SOC and temperature and a second boundary salt concentration, which is the salt concentration at a second boundary between the positive electrode and the positive electrode current collector plate in the thickness direction; calculating a salt concentration in the thickness direction using a liquid phase diffusion model for deriving a salt concentration of the secondary battery and the identified first boundary salt concentration and second boundary salt concentration; The first boundary salt concentration and the second boundary salt concentration are characterized by being correlated with the SOC and temperature of the secondary battery.

[0016] An estimation program for estimating a salt concentration of a secondary battery according to one aspect of the present invention includes: identifying a first boundary salt concentration and a second boundary salt concentration based on a correspondence relationship between the SOC and temperature of the secondary battery and a first boundary salt concentration, which is the salt concentration at a first boundary between the negative electrode and the negative electrode current collector plate in the thickness direction of the secondary battery, and a correspondence relationship between the SOC and temperature and a second boundary salt concentration, which is the salt concentration at a second boundary between the positive electrode and the positive electrode current collector plate in the thickness direction; calculating a salt concentration in a thickness direction using a liquid phase diffusion model for deriving a salt concentration of the secondary battery and the identified first boundary salt concentration and second boundary salt concentration; The first boundary salt concentration and the second boundary salt concentration are characterized in that they can change according to the migration of salt in the in-plane direction of the secondary battery at the first boundary and the second boundary, respectively.

[0017] Further, an estimation program for estimating a salt concentration of a secondary battery according to an aspect of the present invention includes: identifying a first boundary salt concentration and a second boundary salt concentration based on a correspondence relationship between the SOC and temperature of the secondary battery and a first boundary salt concentration, which is the salt concentration at a first boundary between the negative electrode and the negative electrode current collector plate in the thickness direction of the secondary battery, and a correspondence relationship between the SOC and temperature and a second boundary salt concentration, which is the salt concentration at a second boundary between the positive electrode and the positive electrode current collector plate in the thickness direction; calculating a salt concentration in a thickness direction using a liquid phase diffusion model for deriving a salt concentration of the secondary battery and the identified first boundary salt concentration and second boundary salt concentration; The first boundary salt concentration and the second boundary salt concentration are characterized by being correlated with the SOC and temperature of the secondary battery. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide an estimation device, an estimation method, and an estimation program that can improve the accuracy of estimating the salt concentration of a secondary battery. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram illustrating an example of a secondary battery. [Figure 2] 1 is a diagram illustrating a configuration of an estimation device according to an embodiment of the present invention. [Figure 3] 1 is a conceptual diagram showing a method for identifying a boundary salt concentration and a method for calculating a salt concentration according to an embodiment of the present invention. [Figure 4] FIG. 10 is a diagram showing the relationship between the SOC and the restraining pressure of the secondary battery during charging and discharging of the secondary battery. [Figure 5] FIG. 10 is a diagram showing an example of a boundary salt concentration map according to an embodiment of the present invention. [Figure 6] FIG. 10 is a diagram showing an example of salt concentration in the thickness direction of a secondary battery. [Figure 7] FIG. 4 is a diagram illustrating an example of a battery model for calculating an estimated voltage value of a secondary battery. [Figure 8]4 is a flowchart illustrating an example of processing executed by an estimation device according to an embodiment of the present invention. [Figure 9] 10 is a flowchart illustrating another example of processing executed by the estimation device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] An embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a diagram showing an example of a secondary battery whose state is estimated by an estimation device according to an embodiment of the present invention. As shown in Fig. 1, the secondary battery has a thickness direction and a surface direction. Within the secondary battery, a negative electrode current collector plate, a negative electrode sheet, a separator, a positive electrode sheet, and a positive electrode current collector plate are stacked in the thickness direction. The surface direction is a direction perpendicular to the thickness direction and approximately parallel to the ground.

[0021] 2 is a block diagram showing the configuration of an estimation device 10 according to one embodiment of the present invention. The estimation device 10 is a device that estimates the salt concentration of a secondary battery installed in a vehicle. A specific example of the estimation device 10 is an ECU (Electronic Control Unit) installed in a vehicle.

[0022] The estimation device 10 includes a communication interface (I / F) 11, a storage device 12, and a calculation device 13. The communication I / F 11 is an interface for transmitting and receiving signals between the estimation device 10 and a secondary battery and other devices installed in the vehicle.

[0023] The storage device 12 is a storage device that stores the estimation program executed by the calculation device 13 and various information processed by the calculation device 13.

[0024] The calculation device 13 is a calculation device such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The calculation device 13 executes an estimation program stored in the storage device 12 to perform an estimation method defined by the estimation program. The estimation program includes a measurement value acquisition unit 130, a boundary salt concentration identification unit 131, a salt concentration calculation unit 132, a voltage calculation unit 133, an error calculation unit 134, a boundary salt concentration correction unit 135, and a limit derivation unit 136. Note that these programs may be executed by an integrated circuit such as an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0025] The measurement value acquiring unit 130 is a program that acquires measurement values ​​of the secondary battery, which are current measurement values, voltage measurement values, and temperature measurement values. The measurement value acquiring unit 130 can acquire the current measurement value of the secondary battery from a current sensor (not shown) that detects the current of the secondary battery via the communication I / F 11. The measurement value acquiring unit 130 can also acquire the voltage measurement value of the secondary battery from a voltage sensor (not shown) that detects the voltage of the secondary battery via the communication I / F 11. The measurement value acquiring unit 130 can also acquire the temperature measurement value of the secondary battery from a temperature sensor (not shown) that detects the temperature of the secondary battery via the communication I / F 11.

[0026] The boundary salt concentration identifying unit 131 is a program that identifies the salt concentration at the boundary between the negative electrode and the negative electrode current collector plate in the thickness direction of the secondary battery, and the salt concentration at the boundary between the positive electrode and the positive electrode current collector plate in the thickness direction. Hereinafter, the boundary between the negative electrode and the negative electrode current collector plate will be referred to as the "first boundary," and the salt concentration at the first boundary will be referred to as the "first boundary salt concentration." Furthermore, the boundary between the positive electrode and the positive electrode current collector plate in the thickness direction will be referred to as the "second boundary," and the salt concentration at the second boundary will be referred to as the "second boundary salt concentration."

[0027] As shown in FIG. 3 , the boundary salt concentration identification unit 131 can identify the first boundary salt concentration and the second boundary salt concentration using the estimated SOC value and the measured temperature value of the secondary battery and a boundary salt concentration map. The boundary salt concentration map defines the correspondence relationship between the estimated SOC value and the measured temperature value of the secondary battery and the first boundary salt concentration and the second boundary salt concentration, respectively. The estimated SOC value can be derived by correcting the current-integrated SOC obtained by integrating the current value. An adaptive filter such as an extended Kalman filter can be used to correct the current-integrated SOC. The adaptive filter can correct the current-integrated SOC based on the error between the estimated voltage value and the measured voltage value of the secondary battery. The estimated voltage value of the secondary battery can be calculated using a mathematical model (hereinafter referred to as the “battery model”) that derives the estimated voltage value of the secondary battery. The battery model will be described later.

[0028] FIG. 4 shows the relationship between the SOC and the confining pressure of a secondary battery during charging and discharging. During discharge, the active material contracts, causing the confining pressure of the secondary battery to decrease. At this time, the electrolyte penetrates into the spaces created by the contraction of the active material. On the other hand, during charging, the active material expands, causing the confining pressure of the secondary battery to decrease. The expansion of the active material pushes the electrolyte that has penetrated into the spaces in the planar direction. Since the amount of electrolyte moving in the planar direction differs in each part of the secondary battery, uneven salt concentration occurs in the planar direction.

[0029] The first boundary salt concentration and the second boundary salt concentration may change depending on the migration of salt in the plane direction of the secondary battery at the first boundary and the second boundary, respectively. The migration of salt in the plane direction of the secondary battery at the first boundary and the second boundary may change depending on the SOC and temperature of the secondary battery. Therefore, the first boundary salt concentration and the second boundary salt concentration are correlated with the SOC and temperature of the secondary battery, respectively. This relationship can be defined by a boundary salt concentration map.

[0030] 5 is a diagram showing an example of a boundary salt concentration map. The boundary salt concentration maps include a boundary salt concentration map for specifying a first boundary salt concentration during charging of a secondary battery, a boundary salt concentration map for specifying the first boundary salt concentration during discharging, a boundary salt concentration map for specifying a second boundary salt concentration during charging, and a boundary salt concentration map for specifying the second boundary salt concentration during discharging. The boundary salt concentration map for specifying the first boundary salt concentration and the boundary salt concentration map for specifying the second boundary salt concentration have the following common characteristics.

[0031] The boundary salt concentration map during charging is defined so that the first and second boundary salt concentrations are high when the SOC is high and the temperature is high, and the first and second boundary salt concentrations are low when the SOC is low and the temperature is low.

[0032] The boundary salt concentration map during discharge is defined so that the first and second boundary salt concentrations are high when the SOC is low and the temperature is high, and the boundary salt concentration map during discharge is defined so that the first and second boundary salt concentrations are low when the SOC is high and the temperature is low.

[0033] The boundary salt concentration identification unit 131 determines whether the secondary battery is being charged or discharged based on the trend of change in the secondary battery's most recent SOC, and uses the boundary salt concentration map corresponding to the current state of the secondary battery from among the boundary salt concentration map during charging and the boundary salt concentration map during discharging.

[0034] The salt concentration calculation unit 132 is a program that calculates the salt concentration in the thickness direction of the secondary battery using a liquid phase diffusion model that derives the salt concentration of the secondary battery, the first boundary salt concentration, the second boundary salt concentration, the current value, and the temperature measurement value, as shown in Fig. 3. The salt concentration calculated by the salt concentration calculation unit 132 corresponds to the estimated state value of the secondary battery.

[0035] The following equation 1 shows a liquid phase diffusion equation, which is an example of a liquid phase diffusion model. Using this liquid phase diffusion equation, the salt concentration in the electrolyte in the thickness direction of the secondary battery is derived, as shown in FIG.

number

[0036] D e,i eff a represents the effective liquid phase diffusion coefficient of each of the negative electrode, separator, and positive electrode. The effective liquid phase diffusion coefficient is determined by a map in which the temperature measurement value of the secondary battery is associated with these effective liquid phase diffusion coefficients. s,i represents the specific surface area of ​​the active material of each of the negative and positive electrodes. + 0 represents the transference number of lithium ions. i Li (x, t) represents the flux of lithium ions in the negative electrode and the positive electrode at position x in the thickness direction and time t. The flux of lithium ions can be calculated using the current value I based on Equation 2.

number

[0037] The following equations 3 to 8 represent the boundary conditions of the liquid phase diffusion equation of equation 1. The boundary conditions are the conditions at the boundaries between the negative electrode current collector plate, negative electrode, separator, positive electrode, and positive electrode current collector plate. Equation 3 represents the boundary condition at the first boundary.

number

[0038] Equation 4 shows the boundary condition at the second boundary.

number

[0039] Equations 5 and 6 represent the boundary conditions at the boundary between the negative electrode and the separator.

number

number

[0040] Equations 7 and 8 represent the boundary conditions at the boundary between the separator and the positive electrode.

number

number

[0041] The voltage calculation unit 133 is a program that calculates an estimated voltage value of the secondary battery using the current value and temperature measurement value of the secondary battery and the salt concentration calculated by the salt concentration calculation unit 132. FIG. 7 is a diagram showing an example of a battery model that calculates an estimated voltage value of the secondary battery. The voltage calculation unit 133 can calculate an estimated voltage value using the battery model shown in FIG. 7. The estimated voltage value in the secondary battery calculated by the voltage calculation unit 133 corresponds to an estimated state value of the secondary battery.

[0042] The battery model includes a negative electrode solid-phase diffusion model 21, a negative electrode potential map 22, a negative electrode reaction overvoltage model 23, a positive electrode solid-phase diffusion model 31, a positive electrode potential map 32, a positive electrode reaction overvoltage model 33, a liquid-phase diffusion model 41, a liquid-phase potential difference equation 42, a component resistance model 51, a liquid resistance model 52, and a film resistance model 53.

[0043] The negative electrode solid-phase diffusion model 21 is a mathematical model that derives the Li concentration on the negative electrode surface using the current value and temperature measurement values ​​of the secondary battery. The negative electrode potential map 22 defines the correspondence relationship between the Li concentration on the negative electrode surface and the negative electrode potential. The negative electrode reaction overvoltage model 23 is a mathematical model that derives the negative electrode reaction overvoltage, which is an overvoltage that can occur at the negative electrode, using the current value and temperature measurement values ​​of the secondary battery.

[0044] The voltage calculation unit 133 calculates the Li concentration on the negative electrode surface based on the measured current value and temperature value of the secondary battery using the negative electrode solid-phase diffusion model 21. Next, the voltage calculation unit 133 identifies the negative electrode potential corresponding to the Li concentration on the negative electrode surface using the negative electrode potential map 22. Furthermore, the voltage calculation unit 133 calculates the negative electrode reaction overvoltage based on the measured current value and temperature value of the secondary battery using the negative electrode reaction overvoltage model 23. Then, the voltage calculation unit 133 calculates an estimated negative electrode potential value by adding the identified negative electrode potential and the calculated negative electrode reaction overvoltage.

[0045] The positive electrode solid-phase diffusion model 31 is a mathematical model that derives the Li concentration on the positive electrode surface using the measured current value and temperature value of the secondary battery. The positive electrode potential map 32 defines the correspondence relationship between the Li concentration on the positive electrode surface and the positive electrode potential. The positive electrode reaction overvoltage model 33 is a mathematical model that derives the positive electrode reaction overvoltage, which is an overvoltage that can occur at the positive electrode, using the measured current value and temperature value of the secondary battery.

[0046] The voltage calculation unit 133 calculates the Li concentration on the positive electrode surface based on the measured current value and temperature value of the secondary battery using the positive electrode solid-phase diffusion model 31. Next, the voltage calculation unit 133 identifies the positive electrode potential corresponding to the Li concentration on the positive electrode surface using the positive electrode potential map 32. Furthermore, the voltage calculation unit 133 calculates the positive electrode reaction overvoltage based on the measured current value and temperature value of the secondary battery using the positive electrode reaction overvoltage model 33. Then, the voltage calculation unit 133 calculates an estimated positive electrode potential value by adding the identified positive electrode potential and the calculated positive electrode reaction overvoltage.

[0047] The liquid phase diffusion model 41 is a mathematical model that derives the salt concentration in the electrolyte in the thickness direction of the secondary battery using the current value and temperature measurement values ​​of the secondary battery. The liquid phase diffusion equation shown in the above formula 1 can be used as the liquid phase diffusion model 41. The liquid phase potential difference formula 42 is a formula that derives the liquid phase potential difference, which is the potential difference in the electrolyte in the thickness direction, using the salt concentration in the electrolyte in the thickness direction of the secondary battery.

[0048] When calculating the liquid phase potential difference, first, a boundary salt concentration identification unit 131 uses a boundary salt concentration map to identify a first boundary salt concentration and a second boundary salt concentration corresponding to an estimated SOC value based on a current value of the secondary battery and a measured temperature value. Next, a salt concentration calculation unit 132 uses the current value and the measured temperature value to calculate the salt concentration in the electrolyte in the thickness direction of the secondary battery based on a liquid phase diffusion model 41 that uses the first boundary salt concentration and the second boundary salt concentration as boundary conditions. Then, a voltage calculation unit 133 calculates a liquid phase potential difference based on the salt concentration in the electrolyte using a liquid phase potential difference equation 42.

[0049] The component resistance model 51 is a mathematical model that derives the amount of potential decrease (hereinafter referred to as the "first potential decrease amount") due to the component resistance of the secondary battery using the current value and temperature measurement values ​​of the secondary battery. The solution resistance model 52 is a mathematical model that derives the amount of potential decrease (hereinafter referred to as the "second potential decrease amount") due to the electrolytic solution. The film resistance model 53 is a mathematical model that derives the amount of potential decrease (hereinafter referred to as the "third potential decrease amount") due to the film formed on the surface of the negative electrode.

[0050] The voltage calculation unit 133 calculates a first potential decrement amount using the current value and temperature measurement value of the secondary battery and the component resistance model 51. Next, the voltage calculation unit 133 calculates a second potential decrement amount using the first potential decrement amount and the liquid resistance model 52. Then, the voltage calculation unit 133 calculates a third potential decrement amount using the second potential decrement amount and the film resistance model 53. Then, the voltage calculation unit 133 can calculate the estimated voltage value by subtracting the estimated negative electrode potential value and the third potential decrement amount from the sum of the estimated positive electrode potential value and the liquid phase potential difference.

[0051] The error calculation unit 134 is a program that calculates an error ΔV, which is the difference between the voltage measurement value and the voltage estimation value calculated by the voltage calculation unit 133. Specifically, the error calculation unit 134 can calculate the error ΔV by subtracting the voltage estimation value from the voltage measurement value.

[0052] The boundary salt concentration correction unit 135 is a program that corrects the first boundary salt concentration and the second boundary salt concentration identified by the boundary salt concentration identification unit 131 based on the error ΔV calculated by the error calculation unit 134. Specifically, the boundary salt concentration correction unit 135 calculates correction coefficients for the first boundary salt concentration and the second boundary salt concentration to minimize the error ΔV, and can correct the first boundary salt concentration and the second boundary salt concentration using the correction coefficients.

[0053] For example, the boundary salt concentration correction unit 135 can calculate the correction coefficient using the recursive least squares method. Alternatively, the boundary salt concentration correction unit 135 can calculate the correction coefficient using an adaptive filter such as an extended Kalman filter. The salt concentration calculation unit 132 calculates the salt concentration of the secondary battery using the first boundary salt concentration and the second boundary salt concentration corrected in this manner.

[0054] The limit derivation unit 136 is a program that derives a time limit, which is the remaining time for continuous charging and / or discharging from the current point in time until a reduction in power (electric power and / or current) occurs due to salt concentration unevenness of the secondary battery, and a power limit, which is the upper limit of the secondary battery's power that can be used until then. Specifically, the limit derivation unit 136 derives the maximum time and power for which the average value of the salt concentration calculated by the salt concentration calculation unit 132 (hereinafter referred to as the "average salt concentration") falls within a predetermined range. The time limit corresponds to the maximum time for which the average salt concentration falls within the predetermined range. The power limit corresponds to the maximum power for which the average salt concentration falls within the predetermined range. The processing executed by the limit derivation unit 136 will be described later with reference to FIG. 9.

[0055] 8 is a flowchart showing an example of processing executed by the estimation device 10. In step S101, the measurement value acquisition unit 130 acquires the current measurement value, voltage measurement value, and temperature measurement value of the secondary battery. In step S102, the boundary salt concentration identification unit 131 identifies the boundary salt concentration corresponding to the SOC estimated value and temperature measurement value based on the current measurement value of the secondary battery, using the boundary salt concentration map during charging or the boundary salt concentration map during discharging. In step S103, the salt concentration calculation unit 132 calculates the salt concentration in the thickness direction of the secondary battery using the identified boundary salt concentration.

[0056] In step S104, the voltage calculation unit 133 calculates an estimated voltage value of the secondary battery. In step S105, the error calculation unit 134 calculates the error between the measured voltage value acquired in step S101 and the estimated voltage value calculated in step S105. In step S106, the boundary salt concentration correction unit 135 corrects the boundary salt concentration identified in step S102 based on the error calculated by the error calculation unit 134.

[0057] In step S107, the salt concentration calculation unit 132 calculates the salt concentration in the thickness direction of the secondary battery using the corrected boundary salt concentration. In step S108, the voltage calculation unit 133 calculates an estimated voltage value of the secondary battery using the salt concentration calculated based on the corrected boundary salt concentration, and the processing in FIG. 8 ends.

[0058] 9 is a flowchart showing an example of processing executed by the limit deriving unit 136. In step S201, the limit deriving unit 136 determines whether or not the processing of steps S202 to S208 has been completed for all time levels. The time level refers to a continuous charging and / or discharging time (e.g., 0.5 seconds, 1 second, 10 seconds, etc.) that is assumed in advance depending on the use of the battery. Note that a number of time levels can be adopted according to the number of uses of the battery.

[0059] If the above process has not been completed for all time levels (NO), the process branches to step S202. In step S202, the limit deriving unit 136 selects the shortest continuous charge and / or discharge time among the predetermined continuous charge and / or discharge times that have not yet been selected. Therefore, in step S202, the continuous charge and / or discharge times are selected in order starting from the shortest.

[0060] In step S203, the limit derivation unit 136 determines whether the processes of steps S204 to S208 have been completed for all current levels. The current level refers to a charging and / or discharging current value (e.g., 5 A, 50 A, 150 A, etc.) that is assumed in advance depending on the intended use of the battery. Note that a number of current levels can be adopted depending on the number of intended uses of the battery.

[0061] If the above process has been completed for all current levels (YES), the process returns to step S201. On the other hand, if the above process has not been completed for all current levels (NO), the process branches to step S204. In step S204, the limit derivation unit 136 selects the smallest charge and / or discharge current value among the predetermined charge and / or discharge current values ​​that have not yet been selected. Therefore, in step S204, the charge and / or discharge current values ​​are selected in order starting from the smallest.

[0062] In step S205, the limit deriving unit 136 calculates the average salt concentration in the thickness direction of the secondary battery using the time selected in step S202, the current value selected in step S204, and the current temperature measurement value of the secondary battery. More specifically, the boundary salt concentration identifying unit 131 identifies the SOC estimate based on the current value selected in step S204 and the first boundary salt concentration and the second boundary salt concentration corresponding to the current temperature measurement value of the secondary battery. Next, the salt concentration calculating unit 132 calculates the salt concentration in the thickness direction based on a liquid-phase diffusion equation with the identified first boundary salt concentration and second boundary salt concentration as boundary conditions, using the time selected in step S202, the current value selected in step S204, and the current temperature measurement value of the secondary battery. The limit deriving unit 136 then calculates the average salt concentration from the salt concentrations in the thickness direction calculated by the salt concentration calculating unit 132.

[0063] In step S206, the limit deriving unit 136 determines whether the calculated average salt concentration is within a predetermined range. The predetermined range may be the range of the average salt concentration in a state where no salt concentration unevenness occurs in the secondary battery.

[0064] If the calculated average salt concentration is outside the predetermined range (NO), i.e., if it is estimated that salt concentration variations will occur in the secondary battery within the time selected in step S202, the process returns to step S203. On the other hand, if the calculated average salt concentration is within the predetermined range (YES), i.e., if it is estimated that salt concentration variations will not occur in the secondary battery within the time selected in step S202, the process branches to step S207.

[0065] In step S207, the limit derivation unit 136 determines whether the absolute value of the current value, i.e., the current value selected in step S204, is greater than the absolute value of the allowable current value. The allowable current value is a current value at which the average salt concentration in the thickness direction of the secondary battery is within a predetermined range for a predetermined time, i.e., a current value at which salt concentration unevenness does not occur in the secondary battery. Note that the minimum of the above-mentioned charge and / or discharge current levels can be used as the initial value of the allowable current value.

[0066] If the absolute value of the selected current value is equal to or less than the absolute value of the allowable current value (NO), the process returns to step S203. On the other hand, if the absolute value of the selected current value is greater than the absolute value of the allowable current value (YES), the process branches to step S208. In step S208, the limit derivation unit 136 sets the current value selected in step S204 as the allowable current value, and the process returns to step S203. Through the processes of steps S207 and S208, the current value at which the average salt concentration in the thickness direction of the secondary battery is within a predetermined range, i.e., the maximum current value among the current values ​​at which it is estimated that no salt concentration unevenness will occur in the secondary battery, is set as the allowable current value.

[0067] If it is determined in step S201 that the above processing has been completed for all time levels (YES), the process branches to step S209. In step S209, the limit derivation unit 136 calculates a power limit, and the processing of FIG. 9 ends. More specifically, the voltage calculation unit 133 calculates a voltage estimate using the allowable current value last set in step S208, i.e., the maximum current value among current values ​​estimated not to cause salt concentration unevenness in the secondary battery, the temperature measurement value of the secondary battery, and the battery model. Next, the limit derivation unit 136 calculates a power limit by integrating the allowable current value and the voltage estimate. Furthermore, the limit derivation unit 136 specifies, as a time limit, the continuous charge and / or discharge time associated with the allowable current value last set in step S208, i.e., the continuous charge and / or discharge time used to calculate the allowable current value.

[0068] In the above-described embodiment, the boundary salt concentration identifying unit 131 identifies the first boundary salt concentration and the second boundary salt concentration based on the correspondence relationship between the SOC and temperature of the secondary battery and the first boundary salt concentration and the second boundary salt concentration. Then, the salt concentration calculation unit 132 calculates the salt concentration in the thickness direction using a liquid phase diffusion model that derives the salt concentration of the secondary battery and the first boundary salt concentration and the second boundary salt concentration identified by the boundary salt concentration identifying unit 131. The first boundary salt concentration and the second boundary salt concentration can change depending on the movement of salt in the plane direction of the secondary battery at the first boundary and the second boundary, respectively.

[0069] This allows the salt concentration of the secondary battery to be calculated based on the first boundary salt concentration and the second boundary salt concentration that reflect the movement of salt in the surface direction of the secondary battery at the first boundary and the second boundary, thereby improving the accuracy of estimating the salt concentration of the secondary battery.

[0070] Generally, salt concentration variations in the in-plane direction of a secondary battery due to high-rate degradation require a model that performs complex processing, such as predicting the expansion of the active material, resulting in a large amount of data processing. Therefore, such models are not suitable for implementation in an ECU or the like. On the other hand, salt concentration variations in the in-plane direction appear as an increase in the average salt concentration in the thickness direction. In the above-described embodiment, a liquid phase diffusion model is used to calculate the salt concentration in the thickness direction of a secondary battery. Calculating the salt concentration using the liquid phase diffusion model does not require complex processing, such as predicting the expansion of the active material, and reduces the amount of data processing, making it suitable for implementation in an ECU or the like. Furthermore, by calculating the salt concentration in the thickness direction using the liquid phase diffusion model and identifying changes in the average salt concentration, it is possible to estimate the occurrence and elimination of salt concentration variations in the in-plane direction.

[0071] Furthermore, in the above-described embodiment, the voltage calculation unit 133 calculates an estimated voltage value of the secondary battery using the measured current value and temperature value of the secondary battery and the salt concentration calculated by the salt concentration calculation unit 132. Then, the boundary salt concentration correction unit 135 corrects the first boundary salt concentration and the second boundary salt concentration identified by the boundary salt concentration identification unit 131 based on the error between the estimated voltage value calculated by the voltage calculation unit 133 and the measured voltage value. This makes it possible to reduce the error between the actual first boundary salt concentration and the second boundary salt concentration of the secondary battery and the first boundary salt concentration and the second boundary salt concentration identified by the boundary salt concentration identification unit 131.

[0072] Furthermore, in the above-described embodiment, the salt concentration calculation unit 132 calculates the salt concentration of the secondary battery using the first boundary salt concentration and the second boundary salt concentration corrected by the boundary salt concentration correction unit 135. This reduces the error between the actual salt concentration of the secondary battery and the salt concentration of the secondary battery calculated by the salt concentration calculation unit 132, thereby improving the accuracy of estimating the salt concentration of the secondary battery.

[0073] Furthermore, in the above-described embodiment, the limit derivation unit 136 derives the maximum time and power for which the average salt concentration, which is the average value of the salt concentrations calculated by the salt concentration calculation unit 132, falls within a predetermined range. This makes it possible to derive the remaining time for continuous charging and / or discharging from the current state and the upper limit of available power before a reduction in power and / or current occurs due to uneven salt concentration in the secondary battery.

[0074] As described above, by estimating the salt concentration of the secondary battery with high accuracy, the state of the secondary battery can be accurately grasped, and thus the charging and discharging of the secondary battery can be appropriately controlled. For example, excessive restriction on the discharge of the secondary battery can be prevented, and the power of the secondary battery can be effectively used. As a result, the fuel efficiency of a vehicle driven by power from the secondary battery can be improved and a decrease in the drivability of the vehicle can be prevented.

[0075] The above-described estimation program includes a set of instructions (or software code) that, when loaded into a computer, causes the computer to perform one or more functions described in the embodiments. The program may be stored in a non-transitory computer-readable medium or a tangible storage medium. Examples of computer-readable media or tangible storage media include, but are not limited to, random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technologies, CD-ROM, digital versatile disk (DVD), Blu-ray (registered trademark) disk or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage device. The program may be transmitted on a transient computer-readable medium or a communication medium. Examples of transient computer-readable media or communication media include electrical, optical, acoustic, or other forms of propagated signals. Computers include various devices, such as ECUs, PCs (Personal Computers), servers, CPUs, MPUs, FPGAs, ASICs, etc.

[0076] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in other embodiments, the corrected boundary salt concentration, salt concentration, and / or voltage estimated value may be used to calculate other state estimated values ​​in addition to the salt concentration, voltage estimated value, power limit, and time limit of the secondary battery. [Explanation of symbols]

[0077] 10 Estimation device 11 Communication Interface 12 Storage device 13 Arithmetic unit 130 Measurement value acquisition unit 131 Boundary salt concentration identification part 132 Salt concentration calculation unit 133 Voltage calculation unit 134 Error calculation section 135 Boundary salt concentration correction unit 136 Limit Derivation Section

Claims

1. An estimation device for estimating a salt concentration of a secondary battery, a boundary salt concentration specifying unit that specifies the first boundary salt concentration and the second boundary salt concentration based on a correspondence relationship between a state of charge (SOC) and temperature of the secondary battery and a first boundary salt concentration, which is the salt concentration at a first boundary between a negative electrode and a negative electrode current collector plate in a thickness direction of the secondary battery, and a correspondence relationship between the SOC and the temperature and a second boundary salt concentration, which is the salt concentration at a second boundary between a positive electrode and a positive electrode current collector plate in the thickness direction; a salt concentration calculation unit that calculates the salt concentration in the thickness direction by using a liquid phase diffusion model that derives the salt concentration of the secondary battery and the first boundary salt concentration and the second boundary salt concentration that are specified by the boundary salt concentration specifying unit; Including, The estimation device is characterized in that the first boundary salt concentration and the second boundary salt concentration can change depending on the movement of salt in a surface direction of the secondary battery at the first boundary and the second boundary, respectively.

2. An estimation device for estimating a salt concentration of a secondary battery, a boundary salt concentration specifying unit that specifies the first boundary salt concentration and the second boundary salt concentration based on a correspondence relationship between an SOC and a temperature of the secondary battery and a first boundary salt concentration, which is a salt concentration at a first boundary between the negative electrode and the negative electrode current collector plate in a thickness direction of the secondary battery, and a correspondence relationship between the SOC and the temperature and a second boundary salt concentration, which is a salt concentration at a second boundary between the positive electrode and the positive electrode current collector plate in the thickness direction; a salt concentration calculation unit that calculates the salt concentration in the thickness direction by using a liquid phase diffusion model that derives the salt concentration of the secondary battery and the first boundary salt concentration and the second boundary salt concentration that are specified by the boundary salt concentration specifying unit; Including, The estimation device, wherein the first boundary salt concentration and the second boundary salt concentration are correlated with an SOC and a temperature of the secondary battery.

3. The correspondence relationship during charging of the secondary battery is the first boundary salt concentration and the second boundary salt concentration are defined to be high when the SOC is large and the temperature is high; The estimation device according to claim 1 or 2, wherein the first boundary salt concentration and the second boundary salt concentration are defined to be low when the SOC is small and the temperature is low.

4. The correspondence relationship during discharge of the secondary battery is: the first boundary salt concentration and the second boundary salt concentration are defined to be high when the SOC is small and the temperature is high; 4. The estimation device according to claim 1, wherein the first boundary salt concentration and the second boundary salt concentration are defined to be low when the SOC is high and the temperature is low.

5. a voltage calculation unit that calculates an estimated voltage value of the secondary battery using the current measurement value and temperature measurement value of the secondary battery and the salt concentration calculated by the salt concentration calculation unit; a boundary salt concentration correcting unit that corrects the first boundary salt concentration and the second boundary salt concentration identified by the boundary salt concentration identifying unit based on an error between the voltage estimated value calculated by the voltage calculating unit and a voltage measurement value of the secondary battery; The estimation device according to any one of claims 1 to 4, comprising:

6. The estimation device according to claim 5 , wherein the salt concentration calculation unit calculates the salt concentration in the secondary battery using the first boundary salt concentration and the second boundary salt concentration corrected by the boundary salt concentration correction unit.

7. The estimation device according to any one of claims 1 to 6, further comprising a limit derivation unit that derives the maximum time and power at which the average salt concentration, which is the average value of the salt concentrations calculated by the salt concentration calculation unit, falls within a predetermined range.

8. A method for estimating a salt concentration of a secondary battery, comprising: identifying the first boundary salt concentration and the second boundary salt concentration based on a correspondence relationship between the SOC and temperature of the secondary battery and a first boundary salt concentration, which is the salt concentration at a first boundary between the negative electrode and the negative electrode current collector plate in a thickness direction of the secondary battery, and a correspondence relationship between the SOC and the temperature and a second boundary salt concentration, which is the salt concentration at a second boundary between the positive electrode and the positive electrode current collector plate in the thickness direction; calculating a salt concentration in the thickness direction using a liquid phase diffusion model for deriving a salt concentration of the secondary battery and the identified first boundary salt concentration and second boundary salt concentration; The estimation method, wherein the first boundary salt concentration and the second boundary salt concentration can change depending on the movement of salt in a plane direction of the secondary battery at the first boundary and the second boundary, respectively.

9. A method for estimating a salt concentration of a secondary battery, comprising: identifying the first boundary salt concentration and the second boundary salt concentration based on a correspondence relationship between the SOC and temperature of the secondary battery and a first boundary salt concentration, which is the salt concentration at a first boundary between the negative electrode and the negative electrode current collector plate in a thickness direction of the secondary battery, and a correspondence relationship between the SOC and the temperature and a second boundary salt concentration, which is the salt concentration at a second boundary between the positive electrode and the positive electrode current collector plate in the thickness direction; calculating a salt concentration in the thickness direction using a liquid phase diffusion model for deriving a salt concentration of the secondary battery and the identified first boundary salt concentration and second boundary salt concentration; The estimation method, wherein the first boundary salt concentration and the second boundary salt concentration are correlated with an SOC and a temperature of the secondary battery.

10. An estimation program for estimating a salt concentration of a secondary battery, the program comprising: identifying the first boundary salt concentration and the second boundary salt concentration based on a correspondence relationship between the SOC and temperature of the secondary battery and a first boundary salt concentration, which is the salt concentration at a first boundary between the negative electrode and the negative electrode current collector plate in a thickness direction of the secondary battery, and a correspondence relationship between the SOC and the temperature and a second boundary salt concentration, which is the salt concentration at a second boundary between the positive electrode and the positive electrode current collector plate in the thickness direction; calculating a salt concentration in the thickness direction using a liquid phase diffusion model for deriving a salt concentration of the secondary battery and the specified first boundary salt concentration and second boundary salt concentration; the first boundary salt concentration and the second boundary salt concentration can change depending on the movement of salt in the surface direction of the secondary battery at the first boundary and the second boundary, respectively. Estimation program.

11. An estimation program for estimating a salt concentration of a secondary battery, the program comprising: identifying the first boundary salt concentration and the second boundary salt concentration based on a correspondence relationship between the SOC and temperature of the secondary battery and a first boundary salt concentration, which is the salt concentration at a first boundary between the negative electrode and the negative electrode current collector plate in a thickness direction of the secondary battery, and a correspondence relationship between the SOC and the temperature and a second boundary salt concentration, which is the salt concentration at a second boundary between the positive electrode and the positive electrode current collector plate in the thickness direction; calculating a salt concentration in the thickness direction using a liquid phase diffusion model for deriving a salt concentration of the secondary battery and the specified first boundary salt concentration and second boundary salt concentration; the first boundary salt concentration and the second boundary salt concentration are correlated with the SOC and temperature of the secondary battery. Estimation program.

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