Method for estimating state of secondary battery

Abstract

This invention provides a method for rapidly and accurately estimating the state of a secondary battery. The UKF calculation unit obtains the positive electrode OCP curve (OCP curve) before processing. p and negative electrode OCP curve OCP n Differentiate the positive and negative OCP curves separately. For the standard deviation Q... Cs,ave,p Standard deviation Q Cs,ave,n Set an initial value (S1). Then, based on θ p θ n Calculate dV p,abs / dθ(θ p ) and dV n,abs / dθ(θ n (S2). Make the standard deviation Q Cs,ave,p Multiply by dV p / dθ(θ p Additionally, make Q Cs,ave,n Multiply by dV n / dθ(θ n (S3). Using a nonlinear Kalman filter to apply C s,ave,p and C s,ave,n Make corrections (S4). Then use the corrected parameters to calculate SOC and FCC (S5).

Description

Technical Field

[0001] This invention relates to a method for estimating the state of a secondary battery, specifically a method for estimating the state of a secondary battery rapidly and with good accuracy. Background Technology

[0002] In secondary batteries, such as lithium-ion batteries, the full charge capacity (FCC) [Ah] (hereinafter referred to as "FCC") decreases due to degradation caused by use. Here, "FCC" is the capacity [Ah] that can be fully charged, expressed as the product of current [A] and time [h] [Ah]. In other words, the full charge capacity (FCC) is the capacity [Ah] that can be discharged until the fully charged battery is completely discharged. When the fully charged battery is discharged, the ratio of the remaining capacity (RC) [Ah] to the full charge capacity (FCC) [Ah) is expressed as the charge rate (SOC) [%] (hereinafter referred to as "SOC"). If the capacity of FCC [Ah] decreases, the SOC [%] will change even at the same voltage [V]. Since the charging and discharging of secondary batteries is usually controlled based on SOC [%], it is important to accurately estimate FCC [Ah] in order to accurately estimate SOC [%].

[0003] The battery management device described in Patent Document 1 includes an electrical circuit model of a battery and includes: a controller that calculates battery-related parameters; and an arithmetic unit that uses a filter with variable gain to estimate the parameters of the electrical circuit model based on the time-varying current of the battery current flowing through the battery and the battery temperature.

[0004] In the apparatus and method for estimating the state of charge of a battery as described in Patent Document 2, the processor adjusts the value of the process noise covariance used by the extended Kalman filter based on the battery's operating characteristics. The state of charge of the battery is then estimated based on the adjusted value of the process noise covariance.

[0005] In the method for estimating the state of a battery described in Patent Document 3, the Kalman filter calculation unit uses the measured values ​​of a voltage sensor, a current sensor, and a temperature sensor installed on the battery, as well as a battery equivalent circuit model recorded in the battery equivalent circuit model recording unit. It includes steps for successively estimating the battery's charge rate and capacity degradation rate, the current offset of the current sensor, and the battery's internal resistance set by the battery equivalent circuit model. It also includes a step for the system noise covariance calculation unit to change the set value used in the Kalman filter calculation unit, i.e., the system noise covariance value, according to the battery degradation.

[0006] In estimating the state of these batteries, extended Kalman filters and similar methods can be used. Existing technical documents Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2023-030328 Patent Document 2: Japanese Patent Application Publication No. 2020-508442 Patent Document 3: Japanese Patent Publication No. 2023-541417 Summary of the Invention The problem that the invention aims to solve

[0008] However, the characteristics of lithium-ion secondary batteries differ in regions such as high SOC and low SOC. Therefore, the contribution rate of the filter's process noise parameter settings may differ in the high SOC region and the low SOC region.

[0009] Therefore, there are problems that cannot be addressed simply by setting and correcting the parameters of existing filters to reduce process noise. This problem exists in a wide range of secondary batteries, not just lithium-ion secondary batteries.

[0010] The problem to be solved by the secondary battery state estimation method of the present invention is to estimate the battery state quickly and with good accuracy. Methods for solving problems

[0011] To address the aforementioned issues, the state estimation method for a secondary battery of the present invention utilizes an adaptive filter via a computer-equipped control device to converge the voltage error of the secondary battery. The method is characterized in that, in the aforementioned adaptive filter, there exists a component that participates in the average ion concentration C of the positive electrode solid phase. s,ave,p The standard deviation Q of the correction process noise p and the standard deviation R of the observation noise p And the average ion concentration C of the negative electrode solid phase. s,ave,n The standard deviation Q of the correction process noise n and the standard deviation R of the observation noise n As a parameter, θ represents the proportion of the average ion concentration in the positive electrode solid phase. p Positive open circuit potential V p [V] Positive OCP curve OCP p And θ represents the proportion of average ion concentration in the negative electrode solid phase. n The negative open circuit potential V at that time n [V] Negative OCP curve OCP n In this process, the above positive electrode OCP curve is obtained. p The differential value dV p / dθp The absolute value multiplied by the above standard deviation Q p The standard deviation R mentioned above p The ratio of the above negative electrode OCP curves to the OCP ratio. n The differential value dV n / dθ n The absolute value multiplied by the above standard deviation Q n The standard deviation R mentioned above n The ratio of the two values ​​causes the average solid-phase ion concentration C at the positive electrode to vary accordingly with the state of charge (SOC) of the secondary battery. s,ave,p and the average ion concentration C of the negative electrode solid phase s,ave,n The correction sensitivity changed respectively.

[0012] The following process can be performed to determine the above-mentioned average ion concentration C of the positive electrode solid phase by correction. s,ave,p And the above-mentioned average ion concentration C of the negative electrode solid phase s,ave,n The process; based on the determined average ion concentration C of the positive electrode solid phase. s,ave,p And the above-mentioned average ion concentration C of the negative electrode solid phase s,ave,n Calculate the average ion concentration ratio θ of the above positive electrode solid phase. p The ratio θ of the average ion concentration in the negative electrode solid phase mentioned above n The process; in the above positive electrode OCP curve OCP p And the above negative electrode OCP curve OCP n In the above positive electrode OCP curve, OCP p OCP curve of the negative electrode mentioned above n The spacing is staggered to achieve the above-mentioned average ion concentration ratio θ of the positive electrode solid phase. p The ratio θ of the average ion concentration in the negative electrode solid phase mentioned above n A consistent process; and obtaining the above-mentioned positive open-circuit potential V p [V] and the above negative open circuit potential V n The difference [V] is used to explore the voltage ratio θ of the above-mentioned average ion concentration in the positive electrode solid phase, which is the set minimum voltage VL[V] and maximum voltage VH[V]. p The ratio θ of the average ion concentration in the negative electrode solid phase mentioned above n Let the concentration ratio corresponding to the lowest voltage VL[V] be θ0, and let the concentration ratio corresponding to the highest voltage VH[V] be θ0. 100 The process, in representing the above-mentioned average ion concentration ratio θ of the positive electrode solid phase, p The above positive open-circuit potential V p The above positive electrode OCP curve of [V] OCP p And θ represents the ratio of the average ion concentration in the negative electrode solid phase mentioned above. n The above negative open circuit potential V n[V] Negative OCP curve OCP n In this context, SOC[%] can be calculated using the formula shown in Mathematical Formula 1 below.

[0013] [Mathematical Expression 1]

[0014] Furthermore, θ represents the ratio of the average ion concentration in the positive electrode solid phase mentioned above. p The above positive open-circuit potential V p The above positive electrode OCP curve of [V] OCP p And θ represents the ratio of the average ion concentration in the negative electrode solid phase. n The above negative open circuit potential V n The above negative electrode OCP curve of [V] OCP n In this context, the average ion concentration ratio θ of the positive electrode solid phase is based on the above-mentioned average ion concentration of the positive electrode solid phase and the above-mentioned average ion concentration of the negative electrode solid phase. p and the above-mentioned average ion concentration ratio θ of the negative electrode solid phase. n , will "ε s,p "Set as positive electrode volume fraction, and set "L" p "Set as the thickness of the positive electrode active material, and set "A" s When “F” is set as the area of ​​the coated part and “F” is set as the Faraday constant, FCC[Ah] can be calculated using the formula shown in Mathematical Formula 2 below.

[0015] [Mathematical Expression 2]

[0016] This can be implemented particularly well when the adaptive filter described above is a Kalman filter. This method can also be appropriately implemented when the secondary battery is a lithium-ion secondary battery and the ion is Li ion. Invention Effects

[0017] The secondary battery state estimation method according to the present invention can quickly and accurately estimate the battery state. Attached Figure Description

[0018] Figure 1 This is a block diagram of the main parts of the state estimation device for a lithium-ion secondary battery according to this embodiment. Figure 2 This is a flowchart of the state estimation method for lithium-ion secondary batteries according to this embodiment. Figure 3 (a) is a graph showing the relationship between the average solid-phase ion concentration ratio θ and the open-circuit potential OCP [V]. Figure 3(b) is a graph showing the relationship between the solid-phase average ion concentration ratio θ and the absolute value of the differential value dV / dθ of the open-circuit potential OCP[V]. Figure 4 It is a graph showing the relationship between the average solid-phase ion concentration ratio θ and the open-circuit potential OCP[V]. Figure 5 It is a schematic diagram of a single-particle model assuming that the positive or negative active material is a single positive sphere. Detailed Implementation

[0019] The following is for reference Figures 1-4 To use lithium-ion Li + An embodiment of the method for estimating the FCC [Ah] and SOC [%] of a lithium-ion secondary battery, which serves as the carrier ion, will be described as an example to illustrate the state estimation method for the secondary battery of the present invention. However, the present invention is not to be limited by this embodiment.

[0020] (Summary of this implementation method) In the estimation methods of FCC[Ah] and SOC[%], as described in the background art, the method of using adaptive filters such as extended Kalman filters for estimation is well known. Various adaptive filters can be used in the estimation method of FCC and SOC of the lithium-ion secondary battery of the present invention, but in this embodiment, the well-known unscented Kalman filter (hereinafter referred to as "UKF") is used. The UKF is a high-level recursive algorithm used to estimate the state of a nonlinear dynamic system. Unlike existing extended Kalman filters that rely on linear approximations, the UKF uses a deterministic sampling method to obtain the mean and covariance of the state distribution. One of the main advantages of the UKF is its ability to process nonlinear systems more effectively than linear filters. It should be noted that a detailed description of the UKF itself is omitted in this application.

[0021] Figure 1 This is a block diagram of the main parts of the state estimation device 1 for a lithium-ion secondary battery according to this embodiment. In the method for estimating the FCC and SOC of the lithium-ion secondary battery according to this embodiment, the following method is used: Figure 1 The open-circuit voltage OCV [V] of a single cell is calculated and estimated using the battery model 2 of the state estimation device 1 as shown. Based on the estimated voltage E, the open-circuit voltage OCV [V] is calculated. est [V]”, and the measured voltage E obtained using a sensor. meas [V]” calculates the voltage error ΔV[V].

[0022] Based on the voltage error ΔV[V], the average ion concentration C of the positive electrode solid phase is calculated using the UKF calculation unit 3. s,ave,pand the average ion concentration C of the negative electrode solid phase s,ave,n Corrections can reduce the voltage error ΔE[V]. Here, this is based on the corrected average ion concentration C of the cathode solid phase. s,ave,p and the average ion concentration C of the negative electrode solid phase s,ave,n The estimated voltage E est [V]” is used to presuppose SOC[%] and FCC[Ah].

[0023] <Principle of this implementation method> The UKF (Upper Limit Factor) settings include the standard deviation of process noise (Q) and the standard deviation of observation noise (R). These are typically fixed values ​​set based on the ease with which the target parameter changes. In this embodiment, the parameter targeted for correction by the UKF is the average ion concentration C of the cathode solid phase. s,ave,p and the average ion concentration C of the negative electrode solid phase s,ave,n Both of these. Furthermore, UKF possesses the ability to participate in the average ion concentration C of the positive electrode solid phase. s,ave,p The standard deviation Q of the correction process noise p and the standard deviation R of the observation noise p As a parameter. Additionally, regarding UKF, as a parameter, the average ion concentration C of the participating negative electrode solid phase is... s,ave,n The standard deviation Q of the correction process noise n and the standard deviation R of the observation noise n As a parameter. It should be noted that, in the description of this application, process noise is sometimes expressed relative to the average ion concentration C of the positive electrode solid phase. s,ave,p Standard deviation Q Cs,ave,p Abbreviated as standard deviation Q p Additionally, process noise is sometimes compared to the average ion concentration C of the negative electrode solid phase. s,ave,n Standard deviation Q Cs,ave,n Abbreviated as standard deviation Q n Additionally, sometimes the "standard deviation Q" is used... p and standard deviation Q n This is collectively referred to as the standard deviation Q.

[0024] In this embodiment, the standard deviation R of the observation noise at the positive electrode p The standard deviation R of the observation noise of the negative electrode n Keep the value constant. On the other hand, regarding the standard deviation Q of the positive electrode in this embodiment p and the standard deviation Q of the negative electrode n This causes its value to change. This adjustment method has the characteristics of this embodiment.

[0025] For example, based on conditions such as SOC, the average ion concentration C of the positive electrode solid phase... s,ave,pand the average ion concentration C of the negative electrode solid phase s,ave,n The contribution of the error to the overall error changes. Therefore, the initially set standard deviation Q... p Q n The value may not be appropriate.

[0026] Here, Figure 3 (a) is a graph showing the relationship between the solid-phase average ion concentration ratio θ and the open-circuit potential OCP [V]. Figure 3 (b) is a graph showing the relationship between the solid-phase average ion concentration ratio θ and the absolute value of the differential value dV / dθ of the open-circuit potential OCP[V].

[0027] Figure 3 (a) is the positive electrode OCP curve. p and negative electrode OCP curve OCP n It should be noted that in this application, "positive electrode OCP curve OCP" is sometimes used. p and negative electrode OCP curve OCP n These are collectively referred to as "OCP curves". Additionally, sometimes the "positive open-circuit potential Vp and negative open-circuit potential Vn" are collectively referred to as "open-circuit potential OCP [V]". Based on these positive OCP curves... p and negative electrode OCP curve OCP n Derive the open-circuit voltage OCV [V]. The horizontal axis represents the proportion of average ion concentration in the negative electrode solid phase, θ. n It is approximately equal to the SOC [%]. The upper positive electrode OCP curve OCP p V represents the open circuit potential of the positive electrode. p [V]. Additionally, the lower negative electrode OCP curve OCP... n V represents the open circuit potential of the negative electrode. n [V]. Here, "θ" represents the "solid-phase average ion concentration C" as shown in the following mathematical formula 3. s,ave "Compared to "the maximum ion concentration in the solid phase C" s,MAX The proportion of "".

[0028] It should be noted that "θ" p "This indicates the average ion concentration C of the positive electrode solid phase" s,ave.p "Compared to "the maximum ion concentration C in the positive electrode solid phase" s,MAX.p The proportion of "θ". n "This indicates the average ion concentration C of the negative electrode solid phase" s,ave.n "Compared to "the maximum ion concentration C of the negative electrode solid phase" s,MAX.n The proportion of "".

[0029] “C s,MAX.n "It is a material that can accumulate negative electrode active material EMP as a physical property." n Lithium ion Li+ The total amount. "C" s,MAX.p "It is an active material EMP that can accumulate as a positive electrode." p Lithium ion Li + The total amount. It should be noted that in this embodiment, the "solid-phase average ion concentration" in the positive electrode is determined by "C". s,ave,p The symbol "" indicates polarity. In the subscripts indicating polarity, the positive terminal is represented by "". p "Indicates that the negative electrode is composed of " n "Indicates". Additionally, the "average ion concentration of the positive electrode solid phase" at time step k is determined by "C". s,ave,p (k) indicates this. The same applies below.

[0030] [Mathematical Expression 3]

[0031] Therefore, in the case of the negative electrode, θ=0.0 means that the active material EMP at the negative electrode... n Lithium ions (Li) are completely absent in the medium. + The state is SOC=0 [%]. On the other hand, θ=1.0 refers to the state of lithium ions Li. + In the negative electrode active material EMP n The state is reached when the accumulation reaches the limit of what can be accumulated, i.e., SOC = 100%. Therefore, Figure 3 The portion to the right of (a) enclosed by the double-dotted line can be referred to as the high SOC region of the battery. On the other hand, Figure 3 The part to the left of (a) that is surrounded by a double-dotted line can be called the low SOC region of the battery.

[0032] like Figure 3 As shown in (a), regarding the OCP curve from the positive electrode... p and negative electrode OCP curve OCP n The voltage error ΔE[V] caused by the curve characteristics differs between the low SOC region on the left and the high SOC region on the right. Specifically, when shifting to the left in the direction of decreasing open-circuit voltage OCV[V] and decreasing SOC[%], firstly, the negative open-circuit potential V... n [V] Negative OCP curve OCP n First, a significant change occurs. Therefore, in the accurate estimation of the open-circuit voltage OCV[V], the average ion concentration C of the negative electrode solid phase... s,ave,n Its contribution has increased.

[0033] On the other hand, when the open-circuit voltage OCV[V] increases in the direction of rightward shift and SOC[%] increases, firstly, the positive open-circuit potential Vp[V] changes from the positive OCP curve OCP. pFirst, a significant change occurs. Therefore, in the accurate estimation of the open-circuit voltage OCV[V], the average ion concentration C of the positive electrode solid phase... s,ave,p Its contribution has increased.

[0034] Here, through observation Figure 3 The dV / dθ curve shown in (b) can be used to determine the positive open-circuit potential Vp[V] and the negative open-circuit potential V. n Which one in [V] contributes more? Figure 3 of (a) Figure 3 (b) is based on the inventor's actual measurements. Here, the horizontal axis is... Figure 3 (a) also represents the ratio of average ion concentration θ in the negative electrode solid phase. n The "dV / dθ curve" represents the ratio of the average ion concentration θ in the negative electrode solid phase. n The relationship between the differential value dV / dθ and the value of dθ in the figure. The dV / dθ curve in the positive electrode is derived from the curve d... p This indicates that the dV / dθ curve in the negative electrode is derived from the curve d n express. Figure 3 In (b), when migrating to the right and falling into the high SOC region, firstly, the dV / dθ curve in the positive electrode, i.e., curve d... p First, it exhibits significant variation. Therefore, in the accurate estimation of the open-circuit voltage OCV[V], the average ion concentration C of the positive electrode solid phase... s,ave,p Its contribution has increased. On the other hand, in Figure 3 In (b), when migrating to the left and falling into the low SOC region, firstly, the dV / dθ curve in the negative electrode, i.e., curve d... n First, it exhibits significant variation. Therefore, in the accurate estimation of the open-circuit voltage OCV[V], the average ion concentration C of the negative electrode solid phase... s,ave,n The contribution increases. As mentioned above, according to Figure 3 The graph shown in (b) confirms that in the high SOC region, curve d p The changes are significant, and the contribution rate of the positive electrode is high. On the other hand, this confirms that in the low SOC region, curve d... n The changes are significant, and the contribution rate of the negative electrode is high.

[0035] In UKF, the larger the standard deviation Q of the process noise, the greater the correction. Therefore, the average ion concentration C in the cathode solid phase will be affected. s,ave,p The standard deviation Q of the correction process noise p With the positive open circuit potential V p Multiply by the dV / dθ values. Additionally, the average ion concentration C in the negative electrode solid phase will be considered. s,ave,n The standard deviation Q of the correction process noise n With the negative open circuit potential V nThe dV / dθ values ​​are multiplied together. This allows for a greater correction to the parameter that contributes more significantly.

[0036] Therefore, in the state estimation method for lithium-ion secondary batteries of this embodiment, the standard deviation Q of the positive and negative electrodes is appropriately changed according to conditions such as SOC. p Q n The value of . The average ion concentration C of the positive electrode solid phase of the object to be corrected s,ave,p and the average ion concentration C of the negative electrode solid phase s,ave,n It is a parameter closely related to the open-circuit voltage OCV [V]. Therefore, the positive electrode OCP curve OCP... p The differential value dV p / dθ p The absolute value multiplied by the standard deviation Q p With standard deviation R p The ratio of the negative electrode OCP curve to the OCP ratio. n The differential value dV n / dθ n The absolute value multiplied by the standard deviation Q n With standard deviation R n The ratio. This causes the average solid-phase ion concentration C of the cathode to vary accordingly with SOC [%]. s,ave,p and the average ion concentration C of the negative electrode solid phase s,ave,n The correction sensitivity changes accordingly. This reflects the contribution of the error to the variation in conditions. As a result, based on the corrected average ion concentration C of the cathode solid phase... s,ave,p and the average ion concentration C of the negative electrode solid phase s,ave,n More accurately estimate SOC[%] and FCC[Ah].

[0037] As described above, the standard deviation Q is changed according to conditions such as SOC [%]. The average ion concentration C of the positive electrode solid phase is the target of correction. s,ave,p and the average ion concentration C of the negative electrode solid phase s,ave,n This is a parameter closely related to the open-circuit potential OCP [V]. Therefore, the positive electrode OCP curve is... p The differential value dV p / dθ p The absolute value multiplied by the standard deviation Q p With standard deviation R p The ratio of the negative electrode OCP curve to the OCP ratio. n The differential value dV n / dθ n The absolute value multiplied by the standard deviation Q n With standard deviation R nThe ratio reflects the contribution of the error to changes in conditions such as SOC [%]. Therefore, the state estimation method for lithium-ion secondary batteries according to this embodiment can quickly and accurately estimate the state of the battery.

[0038] (Structure of this embodiment) <Lithium-ion secondary battery state estimation device 1> Figure 1 This is a block diagram of the main parts of the lithium-ion secondary battery state estimation device 1 according to this embodiment. It should be noted that... Figure 1 Only the main parts are shown, and illustrations of known parts that are not required in the description of this embodiment, such as the control device that controls the state estimation device 1, the storage device that stores data or programs, and the charging and discharging device that charges and discharges the battery, are omitted.

[0039] The state estimation device 1 receives the measured current I from a galvanometer (not shown). meas [A] Input the lithium-ion secondary battery to be inspected into battery model 2, and measure the temperature T. meas [℃] Input the thermometer (not shown) into Battery Model 2.

[0040] <Battery Model 2> Battery Model 2 based on measured current I meas [A] and measured temperature T meas The [℃] is used to simulate the internal voltage E[V] of an actual lithium-ion secondary battery. The estimated voltage E is based on the simulation results. est [V] The circuit used for estimation. Battery model 2 includes circuits such as solid-phase diffusion model 21 for the positive electrode, reaction overvoltage model 23, solid-phase diffusion model 24 for the negative electrode, reaction overvoltage model 26, liquid-phase diffusion model 27, internal resistance 29, and hysteresis 30.

[0041] Figure 5 It is assumed that the positive electrode active material is EAM. p This is a schematic diagram of a single-particle model for a single positive sphere. The "Solid-phase diffusion model 21" estimates the average solid-phase ion concentration C in the positive electrode. s,ave,p The average ion concentration C in the positive electrode solid phase s,ave,p The definition, using Figure 5 The assumed positive electrode active material EAM as shown p The concept is based on a single-particle model (SM) of a single, positive sphere. If the battery is charged, lithium ions (Li)... + From the positive electrode active material EAM p It is released internally. On the other hand, if discharge occurs, lithium ions (Li) are released. + In the positive electrode active material EAM pInternal accumulation. Positive electrode active material EAM p The concentration of positive solid phase ions C within the electrode s,p Uneven. The concentration C of the positive electrode solid phase ions... s,p The average value is defined as the average ion concentration C of the positive electrode solid phase. s,ave,p .

[0042] [Mathematical Expression 4]

[0043] Here, mathematical formula 4 above is used to calculate the average ion concentration C of the positive electrode solid phase. s,ave,p The calculation formula is shown in mathematical formula 4. Based on this formula, the average ion concentration C of the cathode solid phase at time step k can be theoretically estimated. s,ave,p .

[0044] However, the positive open circuit potential V p [V] Due to the ion concentration C on the positive electrode solid phase surface s,surf,p The change is directly influenced by the effect of [the material / mechanism]. Therefore, based on the estimated average ion concentration C of the positive electrode solid phase... s,ave,p Calculate the ion concentration C on the positive electrode solid surface. s,surf,p Here, mathematical formulas 5 and 6 shown below are based on the average ion concentration C of the positive electrode solid phase at time step k. s,ave,p Calculate the ion concentration C on the positive electrode solid surface. s,surf,p The conversion formula.

[0045] [Mathematical Expression 5]

[0046] [Mathematical Expression 6]

[0047] Here, "potential diagram 22" is used to determine the ion concentration C on the positive electrode solid surface. s,surf,p Converted to the concentration of ions C on the positive electrode solid surface s,surf,p The corresponding positive open circuit potential V p The diagram [V] is pre-stored in the storage device of the control computer of the state estimation device 1. The positive electrode solid-phase surface ion concentration C is calculated using mathematical formula 6. s,surf,p The positive open-circuit potential V is calculated by referring to potential diagram 22. p [V].

[0048] "Reaction Overvoltage Model 23" is the estimated input measurement current I. meas The voltage decrease associated with the internal reaction in [A] is the reaction overvoltage η. p The model of [V] is used. The reaction overvoltage η is calculated using the reaction overvoltage model 23. p[V].

[0049] The positive open-circuit potential V obtained in this way p [V] and reaction overvoltage η p [V] are added together. The "Solid-Phase Diffusion Model of the Negative Electrode 24" estimates the average solid-phase ion concentration C in the negative electrode. s,ave,n In the negative electrode, similarly to the positive electrode, the average solid-phase ion concentration C is... s,ave,n Definition, use and Figure 5 The assumed negative electrode active material EAM as shown n The concept is the same as that of a single-particle model SM for a single sphere. If the battery discharges, lithium ions (Li)... + From the negative electrode active material EAM n Lithium ions are released from the lithium. On the other hand, if charging is performed, lithium ions (Li) are released. + In the negative electrode active material EAM n Internal accumulation. Negative electrode active material EAM n The concentration of negative electrode solid phase ions C s,n Non-uniform. The concentration C of the negative electrode solid phase ions... s,n The average value is defined as the average ion concentration C of the negative electrode solid phase. s,ave,n This can be theoretically deduced in the same way as the positive electrode using mathematical formula 4.

[0050] However, the negative open circuit potential V n [V] Due to the ion concentration C on the surface of the negative electrode solid phase s,surf,n The change is directly influenced by the effect of [the material / mechanism]. Therefore, based on the estimated average ion concentration C of the negative electrode solid phase... s,ave,n The ion concentration C on the surface of the negative electrode solid phase was calculated. s,surf,n .

[0051] "Potential Diagram 25" is used to determine the ion concentration C on the surface of the negative electrode solid phase. s,surf,n Converted to the concentration of ions C on the surface of the negative electrode solid phase s,surf,n The corresponding negative open circuit potential V n The diagram [V] is pre-stored in the storage device of the control computer of the state estimation device 1. In the negative electrode, similarly to the positive electrode, the ion concentration C on the solid surface of the negative electrode, calculated using mathematical formulas 5 and 6, is... s,surf,n The open-circuit potential V of the negative electrode is calculated by referring to potential diagram 25. n [V].

[0052] "Reaction Overvoltage Model 26" is the estimated input measurement current I. meas The voltage decrease associated with the internal reaction in [A] is the reaction overvoltage η. n[V] model. The reaction overvoltage η is calculated by the reaction overvoltage model 26 n [V].

[0053] The negative electrode open-circuit potential V obtained in this way n [V] is added to the reaction overvoltage η n [V]. The "liquid phase diffusion model 27" calculates the voltage drop originating from lithium ions Li diffusing in the non-aqueous electrolyte + . Here, the voltage drop is estimated based on the negative electrode liquid phase ion concentration C e,n , the separator liquid phase ion concentration C e,s , and the positive electrode liquid phase ion concentration C e,p through the "liquid phase potential difference formula 28 (detailed illustration omitted)".

[0054] The "internal resistance 29" estimates the voltage drop caused mainly by the resistance of metal parts such as terminals in the positive electrode and the negative electrode. The internal resistance 29 includes component resistance 29a of terminals, current collectors and the like, liquid resistance 29b of the non-aqueous electrolyte, and coating resistance 29c of SEI and the like.

[0055] The "hysteresis 30" estimates the voltage change caused by the hysteresis of the battery. In secondary batteries, there is known a hysteresis phenomenon in which the open-circuit voltage OCV [V] as an electromotive force is affected by the past current value I [A]. In "hysteresis 30", an equivalent circuit is formed by an RC circuit. This hysteresis is reproduced to estimate the variation of the open-circuit voltage OCV [V] based on the hysteresis.

[0056] Thus, in the present embodiment, the battery model 2 is provided with circuits such as the positive electrode solid phase diffusion model 21, the reaction overvoltage model 23, the negative electrode solid phase diffusion model 24, the reaction overvoltage model 26, the liquid phase diffusion model 27, the internal resistance 29, and the hysteresis 30. Then, based on the measured current I ob [A] and the measured temperature T ob [°C], the estimated voltage E inside the actual lithium ion secondary battery is calculated est [V].

[0057] After that, in the voltage error calculator 31, the difference between the measured voltage E actually measured at time step k meas [V] and the estimated voltage E estimated by the battery model 2 est [V] is output as the voltage error ΔE [V].

[0058] The voltage error ΔE [V] output from the voltage error calculator 31 is input to the UKF operation unit 3. <UKF operation unit 3> The UKF computation unit 3 makes predictions based on the voltage error ΔE[V] by reducing the voltage error ΔE[V] at time steps k.

[0059] Figure 2 This is a flowchart of the state estimation method for lithium-ion secondary batteries according to this embodiment. The following explains the processing of the UKF arithmetic unit 3. According to... Figure 2 The flowchart shown illustrates the processing procedure of the UKF arithmetic unit 3.

[0060] <Preparation> Before processing, such as Figure 3 The positive electrode OCP curve is shown in (a). p and negative electrode OCP curve OCP n Additionally, such as Figure 3 As shown in (a), the obtained positive electrode OCP curve is OCP. p and negative electrode OCP curve OCP n Perform differentiation separately. The pre-obtained average ion concentration ratio θ of the negative electrode solid phase is then calculated. n dV p The curve d / dθ p and dV n The curve d / dθ n The two-dimensional graph. It should be noted that the form in which the differential curve is obtained can be either a calculation formula or a two-dimensional graph, as long as it can be calculated.

[0061] <Standard deviation Q Cs,ave,p Standard deviation Q Cs,ave,n Set initial value (S1) >

[0062] [Mathematical Expression 7]

[0063] Regarding the standard deviation Q Cs,ave,p "and standard deviation Q" Cs,ave,n Set the initial value (S1). It should be noted that in the description of this application, the standard deviation Q is sometimes referred to as... Cs,ave,p Abbreviated as standard deviation Q p The standard deviation Q Cs,ave,n Abbreviated as standard deviation Q n Here, as shown in Equation 7 above, the process noise in the extended Kalman filter at time step k is related to the average ion concentration C of the positive electrode solid phase. s,ave,p The standard deviation Q of the process noise related to the correction p (k) sets the initial value Q. p＿ini"In addition, regarding the average ion concentration C of the negative electrode solid phase..." s,ave,n The standard deviation Q of the process noise related to the correction n (k) sets the initial value Q. n＿ini Here, "k" represents the time step used for observation. "k+1" represents the next time step, and "k-1" represents the previous time step. Regarding the initial value Q... p＿ini "and initial value Q" n＿ini The value of is determined during the design of the extended Kalman filter. An appropriate value is set based on the target object.

[0064] Based on θ p and θ n Calculate dV p,abs / dθ(θ p ) and dV n,abs / dθ(θ n S2)> First, the "average ion concentration C of the positive electrode solid phase" is extracted from battery model 2. s,ave,p (k)” and “Average ion concentration C of negative electrode solid phase” s,ave,n (k)”. Battery model 2 in this embodiment uses Figure 5 The single-particle model SM is shown. Additionally, based on the known average ion concentration C of the negative electrode solid phase... s,ave,n And the maximum ion concentration C of the positive electrode solid phase. s,max,p θ can be calculated from the mathematical formula shown in equation 8 below. p (k), θ n (k). Additionally, here, the subscript " abs "" indicates absolute value.

[0065] [Mathematical Expression 8]

[0066] Based on the differential curve obtained in the prior preparation, and "θ" p (k)” and “θ” n (k)”, derive “dV” through the calculation formula of mathematical formula 9. p / dθ(θp(k))” and “dV n / dθ(θn(k))”. Then obtain their absolute values ​​abs.

[0067] [Mathematical Expression 9]

[0068] <Make the standard deviation Q Cs,ave,p With dV p / dθ(θ p Multiply by Q. Additionally, make Q... Cs,ave,nWith dV n / dθ(θ n Multiplication (S3) >

[0069] [Mathematical Expression 10]

[0070] Next, the standard deviation Q is calculated using the mathematical formula shown in equation 10 above. Cs,ave,p "and "dV p,abs / dθ p Multiplying (k) by each other, we derive the standard deviation Q′p(k). Similarly, we make the standard deviation Q′p(k) equal to the standard deviation Q′p(k). Cs,ave,n "and "dV n,abs / dθ n Multiply by (k) to derive the standard deviation Q′. n (k)”.

[0071] The standard deviation Q′ exported here p (k) and "standard deviation Q′" n (k)” becomes the standard deviation Q of the process noise used in UKF when the step size is k. <Using a nonlinear Kalman filter to apply C> s,ave,p and C s,ave,n Make corrections (S4) > Here, the UKF, acting as a nonlinear Kalman filter, is used to measure the average ion concentration C of the positive electrode solid phase. s,ave,p and the average ion concentration C of the negative electrode solid phase s,ave,n Make corrections (S4). The "Q'" obtained by multiplying during S3 will be... p (k)” and “Q′ n (k) is set as the standard deviation of the process noise of UKF, "Q′". i (k)”.

[0072] Here, "C" s,offset,p "and "C s,offset,n "These represent the changes caused by the correction of the average solid-phase ion concentration at the positive and negative electrodes, respectively." Therefore, the discrete-time internal parameter update formula is the calculation formula shown in the following mathematical formula 11.

[0073] [Mathematical Expression 11]

[0074] Furthermore, the output update formula is made to be the calculation formula of the following mathematical formula 12.

[0075] [Mathematical Expression 12]

[0076] Here, "V" cell "" indicates the estimated voltage value of a single cell [V]. This is known as the estimated voltage E. est [V]. Because the object parameter is "C" s,ave,p "and "C s,ave,n Therefore, the state variable x(k) in the UKF calculation becomes the calculation formula shown in the following mathematical formula 13.

[0077] [Mathematical Expression 13]

[0078] Here, "g(k)" is the Kalman gain, derived from UKF. Additionally, "y(k)" represents the measured voltage, and "y^-(k)" represents the estimated single-cell voltage. Therefore, the formula for calculating the UKF state estimate becomes the formula shown in mathematical formula 14 below.

[0079] [Mathematical Expression 14]

[0080] <Calculate SOC and FCC (S5) using the revised parameters> Figure 4 This is a graph showing the relationship between the average solid-phase ion concentration ratio θ and the open-circuit potential OCP [V]. The horizontal axis represents the average solid-phase ion concentration ratio θ, and the vertical axis represents the potential [V].

[0081] As described above, based on the corrected standard deviation Q′ as a parameter corrected in S4 p (k) Corrected standard deviation Q′ n (k) Estimated “Estimated voltage E” est [V]”, calculate SOC and FCC (S5).

[0082] In this case, because the object parameter is "C" s,ave,p "and "C s,ave,n Therefore, these parameters are appropriately corrected in S4. Thus, the ratio of the average ion concentration in the positive electrode solid phase θ... p The ratio of the average ion concentration in the negative electrode solid phase to θ n All were accurately estimated. Therefore, as Figure 4 As shown, the OCP curve at the positive electrode... p and negative electrode OCP curve OCP n In the process, the average ion concentration ratio θ of the positive electrode solid phase can be increased. p The ratio of the average ion concentration to the negative electrode solid phase θ n The positions are accurately aligned. Therefore, θ0 and θ can also be accurately derived. 100 The value of .

[0083] The SOC[%] is determined by performing the following procedure. First, the average ion concentration C of the positive electrode solid phase is determined by correction. s,ave,p and the average ion concentration C of the negative electrode solid phase s,ave,n Based on the determined average ion concentration C of the positive electrode solid phase. s,ave,p and the average ion concentration C of the negative electrode solid phase s,ave,n Calculate the average ion concentration ratio θ of the positive electrode solid phase. p The ratio of the average ion concentration in the negative electrode solid phase to θ n At the positive electrode, the OCP curve shows OCP... p and negative electrode OCP curve OCP n In the middle, the positive electrode OCP curve OCP p OCP curve with negative electrode n Staggered to achieve an average ion concentration ratio θ in the positive electrode solid phase p The ratio of the average ion concentration in the negative electrode solid phase to θ n Consistent. Obtain the positive open-circuit potential V. p [V] and the negative open circuit potential V n The difference [V]. Explore the ratio θ of the average solid-phase ion concentration at the cathode for the set minimum voltage VL[V] and maximum voltage VH[V]. p The ratio of the average ion concentration in the negative electrode solid phase to θ n Let the concentration ratio corresponding to the lowest voltage VL[V] be θ0, and let the concentration ratio corresponding to the highest voltage VH[V] be θ0. 100 .

[0084] θ represents the proportion of average ion concentration in the positive electrode solid phase. p Positive open circuit potential V p [V] Positive OCP curve OCP p θ represents the ratio of average ion concentration in the negative electrode solid phase. n The negative open circuit potential V at that time n [V] Negative OCP curve OCP n In the above calculation, SOC[%] is calculated using the mathematical formula shown in Formula 1 below.

[0085] [Mathematical Expression 1]

[0086] Here, mathematical formula 1 is based on the ratio of the average ion concentration θ of the positive electrode solid phase. p Find the formula for calculating SOC [%]. (Based on the positive electrode OCP curve) p and negative electrode OCP curve OCP n In the process, the average ion concentration C of the positive electrode solid phase is calculated based on the correction.s,ave,p The ratio of average ion concentration in the positive electrode solid phase θ p Additionally, the average ion concentration C of the negative electrode solid phase was calculated based on the correction. s,ave,n The ratio of average ion concentration in the negative electrode solid phase θ n Therefore, θ0 and θ can be accurately estimated. 100 ,θ p The value of θp. Based on the same positions of θp and θn, SOC[%] is calculated. This is achieved by accurately estimating θ0, θ... 100 ,θ p Substituting the value into the calculation formula shown in Mathematical Formula 1 above allows for a more accurate calculation of SOC.

[0087] [Mathematical Expression 2]

[0088] Furthermore, the calculation formula shown in mathematical formula 2 above is the formula for calculating the FCC. "ε" s,p "L" represents the positive electrode volume fraction. p "A" indicates the thickness of the positive electrode active material. s "" represents the area of ​​the coated portion, and "F" represents the Faraday constant. Therefore, the terms on the right-hand side are considered constants. Since θ0, θ 100 Since it is known, the FCC can be easily and accurately calculated.

[0089] (The function of this implementation method) The UKF computing unit 3 processes the positive OCP curve before it is applied. p and negative electrode OCP curve OCP n For the positive electrode OCP curve, OCP... p and negative electrode OCP curve OCP n Perform differentiation separately. For the standard deviation Q... Cs,ave,p Standard deviation Q Cs,ave,n Set an initial value (S1). Then, based on θ p θ n Calculate dV p,abs / dθ(θ p ) and dV n,abs / dθ(θ n (S2). Make the standard deviation Q Cs,ave,p With dV p / dθ(θ p Multiply by Q. Additionally, make Q... Cs,ave,n With dV n / dθ(θ n Multiply by (S3). Use a nonlinear Kalman filter to apply C s,ave,p and C s,ave,nMake corrections (S4). Then calculate the SOC and FCC using the corrected parameters (S5). Through this process, appropriately change the standard deviation Q values ​​of the positive and negative electrodes according to the conditions of SOC, etc.

[0090] (Effects of this implementation method) (1) According to the state estimation method of the lithium-ion secondary battery of the present invention in this embodiment, the voltage error ΔE[V] of the lithium-ion secondary battery is converged by using a state estimation device 1 equipped with a computer and a UKF. By appropriately adjusting the process noise parameter of the UKF, the state of the battery can be estimated quickly and with good accuracy. Therefore, the correction amount can be appropriately varied. Therefore, the convergence time can be shortened and the estimation can be performed with good accuracy. In addition, it has the effect of making full use of the performance of the target battery.

[0091] (2) Specifically, the average ion concentration C of the cathode solid phase is used as a parameter for the process noise of UKF. s,ave,p The standard deviation Q of the correction process noise Cs,ave,p Additionally, the average ion concentration C of the negative electrode solid phase was used. s,ave,n The standard deviation Q of the correction process noise Cs,ave,n Calculate θ, which represents the proportion of average ion concentration in the positive electrode solid phase. p Positive open circuit potential V p [V] Positive OCP curve OCP p Calculate θ, which represents the proportion of average ion concentration in the negative electrode solid phase. n The negative open circuit potential V at that time n [V] Negative OCP curve OCP n The positive electrode OCP curve is shown. p The differential value dV p / dθ p The absolute value multiplied by the standard deviation Q p With standard deviation R p The ratio. The negative electrode OCP curve OCP. n The differential value dV n / dθ n The absolute value multiplied by the standard deviation Q n With standard deviation R n The ratio. This causes the average solid-phase ion concentration C of the cathode to vary accordingly with SOC [%]. s,ave,p and the average ion concentration C of the negative electrode solid phase s,ave,n The correction sensitivity changes accordingly. Therefore, the correction amount can be appropriately varied based on the contribution. Thus, it has the effect of making estimations with good accuracy.

[0092] (3) The ratio of the average ion concentration θ of the positive electrode solid phase p Positive open circuit potential Vp [V] OCP curve at the positive electrode p The figure shows the ratio of average ion concentration θ in the negative electrode solid phase. n The negative open circuit potential V at that time n [V] OCP curve at the negative electrode n The OCP curve of the positive electrode is shown in the figure. p and negative electrode OCP curve OCP n The SOC[%] is calculated from this. Therefore, it has the effect of estimating the SOC[%] with good accuracy.

[0093] (4) In Figure 4 The figure shows the ratio of average ion concentration θ in the positive electrode solid phase. p Positive open circuit potential V p [V] Positive OCP curve OCP p Additionally, θ represents the ratio of average ion concentration in the negative electrode solid phase. n The negative open circuit potential V at that time n [V] Negative OCP curve OCP n The OCP curve of the positive electrode is shown. p and negative electrode OCP curve OCP n In the process, the average ion concentration C of the positive electrode solid phase is calculated based on the correction. s,ave,p The ratio of average ion concentration in the positive electrode solid phase θ p Additionally, the average ion concentration C of the negative electrode solid phase was calculated based on the correction. s,ave,n The ratio of average ion concentration in the negative electrode solid phase θ n FCC[Ah] is calculated based on the same positions of θp and θn. Therefore, it has the effect of accurately estimating FCC[Ah].

[0094] (5) In this embodiment, the UKF is used as an adaptive filter. Therefore, it has the effect of estimating the state of the battery with higher accuracy compared to extended Kalman filters, etc. In addition, it has the effect of estimating the state of the battery with lower load compared to particle Kalman filters, etc.

[0095] (6) In this embodiment, the secondary battery is a lithium-ion secondary battery, and the ions are Li ions. + This embodiment has the effect of accurately estimating the state of the battery, even in such a battery.

[0096] (Other examples) Adaptive filters can be exemplified by, for example, the Kalman filter. In this embodiment, the UKF is used as the adaptive filter, but it is not limited to this. Instead, Kalman filters, extended Kalman filters, particle Kalman filters, error state Kalman filters, etc., can also be used to estimate the state of the secondary battery.

[0097] In this embodiment, the average ion concentration C of the cathode solid phase is used as a parameter for the process noise of the adaptive filter. s,ave,p The standard deviation Q of the correction process noise p Additionally, the average ion concentration C of the negative electrode solid phase was used. s,ave,n The standard deviation Q of the correction process noise n However, in addition to these, other parameters can also be added to implement this invention.

[0098] In this embodiment, lithium-ion Li32O3 in a lithium-ion secondary battery is exemplified as a secondary battery. + However, in the secondary battery of the present invention, there are no limitations on its structure, composition, shape, purpose, etc., as long as the present invention can be implemented. For example, it can also be implemented in other non-aqueous electrolyte secondary batteries. In addition, it can also be applied to alkaline secondary batteries such as nickel-metal hydride secondary batteries.

[0099] That is, the invention disclosed in this application is not limited to the specific implementation. It can be implemented by using an adaptive filter and correcting the average carrier concentrations of the positive and negative electrode solid phases based on the voltage error ΔE[V]. In this case, among the ions acting as electron carriers, for example in a secondary battery, there are ions such as Li used for the main reaction. + Ni + Na + SO4 2-、 H + Plasma. And based on this correction, SOC[%] and FCC[Ah] are estimated.

[0100] In this embodiment, for ease of explanation, the differential value dV / dθ is displayed as a two-dimensional graph, but it is not limited to this. It can also be obtained and stored in the form of a calculation formula.

[0101] In this embodiment, two battery models are illustrated. Figure 1 The battery model shown is not limited to this. For example, the form and elements of the equivalent circuit, state-based circuit, etc., are not restricted. In this embodiment, for example, the average ion concentration C of the positive electrode solid phase s,ave,p The definition adopts Figure 5 The assumed positive electrode active material EAM as shown pThe concept is based on a single, spherical "single-particle model." If the battery discharges, lithium ions (Li)... + In the positive electrode active material EAM p Internal storage. If charging is performed, lithium ions (Li) will accumulate. + Towards the positive electrode active material EAM p External release. Positive electrode active material EAM p The ion concentration within the cathode is not uniform; the average value of this concentration is defined as the average ion concentration C of the cathode solid phase. s,ave,p Furthermore, the mathematical formulas shown in Formulas 5 and 6 are used to estimate the average ion concentration C relative to the positive electrode solid phase. s,ave,p C of positive electrode solid phase surface ion concentration s,surf,p .

[0102] However, these can also be considered relative to the average ion concentration C of the positive electrode solid phase. s,ave,p C of positive electrode solid phase surface ion concentration s,surf,p Actual measurements were conducted, and conversions were performed using graphs, tables, and approximations.

[0103] The accompanying drawings are for the purpose of understanding the invention, but due to their schematic and simplified nature, they may not be accurate and do not limit the invention. The numerical values, ranges, and compositions used in this embodiment are illustrative and do not limit the scope of the invention. It can be implemented with appropriate optimization by those skilled in the art.

[0104] Figure 2 The flowchart shown is an example of implementation, and the process can be added, deleted, replaced, or modified. Regarding this invention, as long as it does not depart from the claims, it can be implemented by those skilled in the art by adding, deleting, or modifying elements.

Claims

1. A method for estimating the state of a secondary battery, characterized in that it uses an adaptive filter through a computer-controlled device to converge the voltage error of the secondary battery, and is further described as follows: In the adaptive filter, the parameters are: The average ion concentration C in the positive electrode solid phase s,ave,p The standard deviation Q of the correction process noise p and the standard deviation R of the observation noise p ; as well as The average ion concentration C in the negative electrode solid phase s,ave,n The standard deviation Q of the correction process noise n and the standard deviation R of the observation noise n , θ represents the proportion of average ion concentration in the positive electrode solid phase. p Positive open circuit potential V p Positive electrode OCP curve OCP p And θ represents the proportion of average ion concentration in the negative electrode solid phase. n The negative open circuit potential V at that time n Negative electrode OCP curve OCP n middle, By the positive electrode OCP curve OCP p The differential value dV p / dθ p The absolute value multiplied by the standard deviation Q p With the standard deviation R p The ratio, The negative electrode OCP curve OCP n The differential value dV n / dθ n The absolute value multiplied by the standard deviation Q n With the standard deviation R n The ratio, The average solid-phase ion concentration C of the positive electrode that varies accordingly with the SOC of the secondary battery. s,ave,p and the average ion concentration C of the negative electrode solid phase s,ave,n The correction sensitivity changed respectively.

2. The method for estimating the state of a secondary battery according to claim 1, characterized in that, This method performs the following procedure: The average ion concentration C of the positive electrode solid phase is determined by correction. s,ave,p and the average ion concentration C of the negative electrode solid phase s,ave,n The process; Based on the determined average ion concentration C of the positive electrode solid phase s,ave,p and the average ion concentration C of the negative electrode solid phase s,ave,n Calculate the average ion concentration ratio θ of the positive electrode solid phase respectively. p The ratio θ of the average ion concentration in the negative electrode solid phase n The process; The positive electrode OCP curve OCP p and the negative electrode OCP curve OCP n In the process, the positive electrode OCP curve is... p OCP curve of the negative electrode n The staggered arrangement ensures that the average ion concentration ratio θ of the positive electrode solid phase is... p The ratio θ of the average ion concentration in the negative electrode solid phase n A consistent process; as well as Obtain the positive open-circuit potential V p With respect to the negative open circuit potential V n The difference between the voltages is explored by the ratio θ of the average ion concentration in the positive electrode solid phase to the set minimum voltage VL and maximum voltage VH. p The ratio θ of the average ion concentration in the negative electrode solid phase n The concentration ratio corresponding to the lowest voltage VL is set as θ0, and the concentration ratio corresponding to the highest voltage VH is set as θ. 100 The process, θ represents the ratio of the average ion concentration in the positive electrode solid phase. p The positive open-circuit potential V at that time p The positive electrode OCP curve OCP p And θ represents the ratio of the average ion concentration in the negative electrode solid phase. n The negative open circuit potential V at that time n The negative electrode OCP curve OCP n In this process, the SOC is calculated using the following formula. 。 3. The method for estimating the state of a secondary battery according to claim 1, characterized in that, θ represents the ratio of the average ion concentration in the positive electrode solid phase. p The positive open-circuit potential V at that time p The positive electrode OCP curve OCP p And θ represents the average ion concentration ratio of the negative electrode solid phase. n The negative open circuit potential V at that time n The negative electrode OCP curve OCP n middle, Based on the ratio θ of the average ion concentration of the positive electrode solid phase to the average ion concentration of the negative electrode solid phase. p and the ratio of average ion concentration θ of the negative electrode solid phase. n , ε s,p "Set as positive electrode volume fraction, and set "L p "Set as the thickness of the positive electrode active material, and set "A" s When the area of ​​the coated portion is set as F, and F is set as the Faraday constant, the FCC is calculated using the following formula. 。 4. The method for estimating the state of a secondary battery according to claim 1, wherein, The adaptive filter is a Kalman filter.

5. The method for estimating the state of a secondary battery according to claim 1, characterized in that, The secondary battery is a lithium-ion secondary battery, and the ions are Li ions.

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