State estimation method, state estimation device, and program

Abstract

To estimate a state of a secondary battery which uses a solid electrolyte.SOLUTION: A state estimation device comprises: a first acquisition unit that acquires measurement data being impedance for each frequency which impedance is measured by an impedance method before and after a test of progressing degradation, and a predetermined state, for a secondary battery for reference; a derivation unit that calculates a peak frequency from a circular curve in a graph in which impedance represented by measurement data for each frequency is plotted, and obtains a model representing a relationship between the peak frequency and the state before and after the test; a second acquisition unit that acquires measurement data being impedance for each frequency which is measured by the impedance method, for a secondary battery of an estimation object; a calculation unit that calculates the peak frequency from the circular curve in the graph in which impedance for each frequency represented by the measurement data is plotted; and an estimation unit that estimates a state of the secondary battery of the estimation object using the model from the peak frequency for the secondary battery of the estimation object.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a state estimation method, a state estimation device, and a program. [Background technology]

[0002] In recent years, the use of secondary batteries in electric vehicles and the like has rapidly expanded. However, from the perspective of effective resource utilization, it is becoming increasingly important to reuse secondary batteries after their use in vehicles as secondary batteries for stationary applications and the like. When reusing batteries, it is necessary to correctly understand their degradation state in order to determine whether they can be reused. Techniques for estimating the degradation state of lithium-ion batteries have been disclosed (for example, Patent Document 1, Patent Document 2, and Patent Document 3).

[0003] Patent Document 1 discloses a method for analyzing the degradation state of an all-solid-state battery from a voltage change after current interruption. Patent Documents 2 and 3 disclose methods for analyzing the degradation state using an AC impedance method.

[0004] In recent years, all-solid-state batteries, which use solid electrolytes as the electrolyte, have been expected to replace liquid lithium-ion batteries as high-performance secondary batteries. As with conventional liquid lithium-ion batteries, it is important to reuse used batteries effectively in all-solid-state batteries.

[0005] Deterioration of secondary batteries due to charging and discharging can be classified into two types: chemical deterioration, in which battery performance is reduced due to chemical side reactions of constituent materials such as active materials and solid electrolytes, and physical deterioration, in which battery performance is reduced due to reduced contact between constituent materials caused by expansion and contraction of active materials, etc. In the deterioration of all-solid-state batteries, physical deterioration is an important factor, such as the occurrence of cracks between active materials and solid electrolytes, and between solid electrolytes. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2021-140991 [Patent Document 2] Japanese Patent Application Publication No. 2020-167069 [Patent Document 3] WO2012 / 095913 Summary of the Invention [Problem to be solved by the invention]

[0007] The method described in Patent Document 3 discloses that the degradation state is estimated from a resistance value obtained by an AC impedance method. Generally, it is assumed that the higher the resistance value, the lower the battery capacity. However, the correlation between the resistance value and the battery capacity is not necessarily clear, and it cannot be said that the battery capacity can be estimated with high accuracy, particularly for all-solid-state batteries.

[0008] Furthermore, Patent Document 1 discloses a method for estimating the state of degradation using a voltage change after current interruption, and Patent Document 2 discloses a method for estimating the state of degradation using resistance measurement by an AC impedance method, but there is no mention of physical degradation in all-solid-state batteries, and no method for easily isolating and determining physical degradation is disclosed.

[0009] As described above, Patent Documents 1 to 3 do not take into consideration physical deterioration specific to all-solid-state batteries, such as cracks occurring between the active material and the solid electrolyte, or between the solid electrolytes.

[0010] An object of the present invention is to provide a state estimation method, a state estimation device, and a program that can estimate the state of a secondary battery using a solid electrolyte while taking physical deterioration into consideration. [Means for solving the problem]

[0011] A state estimation method according to claim 1 is a state estimation method for estimating a state of a secondary battery using a solid electrolyte, comprising the steps of: acquiring measurement data, which is impedance for each frequency measured by an impedance method, and a predetermined state for the reference secondary battery before and after a test in which deterioration progresses; calculating a peak frequency from an arc-shaped curve in a graph in which the impedance for each frequency represented by the measurement data is plotted before and after the test; determining a model representing the relationship between the peak frequency and the state based on the peak frequency calculated before and after the test and the predetermined state; acquiring measurement data, which is impedance for each frequency measured by an impedance method, for the secondary battery to be estimated; calculating a peak frequency from the arc-shaped curve in a graph in which the impedance for each frequency represented by the measurement data is plotted; and estimating the state of the secondary battery to be estimated using the model from the peak frequency for the secondary battery to be estimated.

[0012] In the state estimation method described in claim 1, measurement data, which is impedance for each frequency measured by an impedance method, and a predetermined state are obtained for the reference secondary battery before and after a test that accelerates deterioration. Here, examples of the "test that accelerates deterioration" include a cycle test in which the secondary battery is repeatedly charged and discharged under predetermined conditions, and a test in which the battery is maintained in a constant state of charge.

[0013] Then, a peak frequency is calculated from the arc-shaped curve in a graph plotting the impedance for each frequency represented by the measurement data before and after the test. Here, the "graph" refers to a graph plotting the impedance for each frequency with the real component of the impedance on the horizontal axis and the imaginary component on the vertical axis. The "peak frequency" is the frequency that gives the peak where the absolute value of the imaginary number is maximum in the arc-shaped curve on the graph.

[0014] Then, a model expressing the relationship between the peak frequency and the state is calculated based on the peak frequency calculated before and after the test and the previously determined state. Then, measurement data representing impedance for each frequency measured by an impedance method is obtained for the secondary battery to be estimated, and the peak frequency is calculated from an arc-shaped curve in a graph plotting the impedance for each frequency represented by the measurement data. Then, the state of the secondary battery to be estimated is estimated using the model from the peak frequency for the secondary battery to be estimated.

[0015] In this state estimation method, a model expressing the relationship between the peak frequency and the state is calculated based on the peak frequency calculated before and after a test in which the deterioration of a reference secondary battery is accelerated and the state is determined in advance, and the state of the secondary battery to be estimated is estimated using the model from the peak frequency calculated from an arc-shaped curve in a graph plotting impedance for each frequency represented by measurement data obtained for the secondary battery to be estimated. This makes it possible to estimate the state of a secondary battery using a solid electrolyte, taking physical deterioration into consideration.

[0016] A state estimation method according to a second aspect of the present invention is the state estimation method according to the first aspect of the present invention, wherein the state is a capacity.

[0017] In the state estimation method described in claim 2, a model expressing the relationship between the peak frequency and capacity is calculated based on the peak frequency calculated before and after a test in which the deterioration of a reference secondary battery is accelerated and the capacity calculated in advance, and the capacity of the secondary battery to be estimated is estimated using the model from the peak frequency calculated from an arc-shaped curve in a graph plotting impedance for each frequency represented by measurement data acquired for the secondary battery to be estimated. This makes it possible to estimate the capacity of a secondary battery using a solid electrolyte, taking physical deterioration into consideration.

[0018] A state estimation method according to a third aspect of the present invention is the state estimation method according to the second aspect, wherein the model is a relational expression w=F(x) that expresses the relationship between a peak frequency x and a capacity w.

[0019] In the state estimation method described in claim 3, a relational expression w=F(x) expressing the relationship between the peak frequency x and the capacity w is calculated based on the peak frequency calculated before and after a test that accelerates the deterioration of a reference secondary battery and the state determined in advance, and the state of the secondary battery to be estimated is estimated using the relational expression w=F(x) from the peak frequency calculated from an arc-shaped curve in a graph plotting impedance for each frequency represented by measurement data acquired for the secondary battery to be estimated. Therefore, the state of a secondary battery using a solid electrolyte can be accurately estimated using the relational expression w=F(x) expressing the relationship between the peak frequency x and the capacity w.

[0020] A state estimation method according to a fourth aspect of the present invention is the state estimation method according to the third aspect, wherein the relational expression w=F(x) includes a term of a·log x and a term of b, where a and b are constants.

[0021] In the state estimation method according to claim 4, the relational expression w=F(x) expressing the relationship between the peak frequency x and the capacity w includes the term a·log x and the term b, which allows for more accurate estimation of the state of a secondary battery using a solid electrolyte.

[0022] A state estimation method according to claim 5 is a state estimation method for estimating a state of a secondary battery using a solid electrolyte, comprising the steps of: obtaining measurement data for the reference secondary battery, which is impedance for each frequency measured by an impedance method, before and after a test in which deterioration progresses; calculating a peak frequency and a diameter of the arc from an arc-shaped curve in a graph in which the impedance for each frequency represented by the measurement data is plotted before and after the test; determining a model representing the relationship between the peak frequency and the diameter of the arc based on the peak frequency and the diameter of the arc calculated before and after the test; obtaining measurement data for the secondary battery to be estimated, which is impedance for each frequency measured by an impedance method; calculating a peak frequency and a diameter of the arc from the arc-shaped curve in the graph in which the impedance for each frequency represented by the measurement data is plotted; and estimating the state of the secondary battery to be estimated using the model from the peak frequency and the diameter of the arc for the secondary battery to be estimated.

[0023] In the state estimation method described in claim 5, measurement data is obtained for the reference secondary battery, which is impedance measured for each frequency by an impedance method before and after a test to accelerate deterioration. Then, a peak frequency and a diameter of the arc are calculated from an arc-shaped curve in a graph plotting the impedance for each frequency represented by the measurement data before and after the test. Here, the "diameter of the arc" does not need to be a strict mathematical diameter, and can be, for example, approximately the difference between the real components of the points closest to the real axis on each end of the arc-shaped curve on the graph.

[0024] Then, a model expressing the relationship between the peak frequency and the diameter of the circular arc is obtained based on the peak frequency and the diameter of the circular arc calculated before and after the test. Measurement data, which is impedance for each frequency measured by an impedance method, is obtained for the secondary battery to be estimated.

[0025] Then, a peak frequency and a diameter of the arc are calculated from an arc-shaped curve in a graph plotting impedance for each frequency represented by the measurement data, and the state of the secondary battery is estimated using the model from the peak frequency and the diameter of the arc for the secondary battery.

[0026] In this state estimation method, a model expressing the relationship between the peak frequency and the arc diameter is calculated based on the peak frequency and the arc diameter calculated before and after a test in which the deterioration of a reference secondary battery is accelerated, and the state of the secondary battery to be estimated is estimated using the model from the peak frequency and the arc diameter calculated from an arc-shaped curve in a graph plotting impedance for each frequency represented by measurement data obtained for the secondary battery to be estimated. This makes it possible to estimate the state of a secondary battery using a solid electrolyte, taking physical deterioration into consideration.

[0027] A state estimation method according to claim 6 is the state estimation method according to claim 5, wherein the test is a test that progresses deterioration accompanied by chemical changes, the state is a degree of physical deterioration, the model is a relational expression y=F(x) that expresses the relationship between a peak frequency x and a diameter y of an arc, and the degree of physical deterioration of the secondary battery to be estimated is estimated based on a comparison of the peak frequency and the diameter y of the arc for the secondary battery to be estimated with the relational expression y=F(x).

[0028] In the state estimation method described in claim 6, a relational expression y=F(x) expressing the relationship between the peak frequency x and the arc diameter y is calculated based on the peak frequency and the arc diameter calculated before and after a test in which a reference secondary battery is subjected to deterioration accompanied by chemical changes, and the degree of physical deterioration of the secondary battery to be estimated is estimated based on a comparison of the peak frequency and the arc diameter calculated from an arc-shaped curve in a graph plotting impedance for each frequency represented by measurement data obtained for the secondary battery to be estimated with the relational expression y=F(x). This makes it possible to estimate the degree of physical deterioration of a secondary battery using a solid electrolyte.

[0029] A state estimation method according to a seventh aspect of the present invention is the state estimation method according to the sixth aspect, wherein estimating the degree of physical deterioration comprises estimating the degree of physical deterioration of the secondary battery to be estimated based on a comparison between a diameter y1 of an arc for the secondary battery to be estimated and a diameter y2 of an arc obtained by substituting a peak frequency x1 for the secondary battery to be estimated into the relational expression y=F(x).

[0030] In the state estimation method according to claim 7, the degree of physical deterioration of the secondary battery to be estimated is estimated based on a comparison between a diameter y1 of an arc for the secondary battery to be estimated and a diameter y2 of an arc obtained by substituting a peak frequency x1 for the secondary battery to be estimated into the relational expression y=F(x). Therefore, the degree of physical deterioration of a secondary battery using a solid electrolyte can be estimated with high accuracy.

[0031] The state estimation method according to claim 8 is the state estimation method according to claim 7, wherein the relational expression y=F(x) is ax b where a and b are constants.

[0032] In the state estimation method according to claim 8, the relational expression y=F(x) representing the relationship between the vertex frequency x and the diameter y of the arc is expressed as ax b where a and b are constants. Therefore, the degree of physical deterioration of a secondary battery using a solid electrolyte can be estimated with higher accuracy.

[0033] A state estimating method according to claim 9 is a state estimating method according to any one of claims 6 to 8, wherein the test that accelerates the deterioration accompanied by the chemical change is a test that maintains a constant voltage in a charged state.

[0034] In the state estimation method described in claim 9, a test is performed on a reference secondary battery, maintaining it at a constant voltage in a charged state and allowing deterioration accompanied by chemical changes to progress, and measurement data is obtained that is impedance for each frequency measured by an impedance method. This makes it possible to accurately determine the relational expression y=F(x) that expresses the relationship between the apex frequency x and the diameter y of the arc.

[0035] a calculation unit that calculates the peak frequency from the arc-shaped curve in the graph that plots the impedance for each frequency represented by the measurement data; and an estimation unit that estimates the state of the secondary battery that uses a solid electrolyte from the peak frequency for each frequency measured by the impedance method.

[0036] In the state estimation device described in claim 10, the first acquisition unit acquires measurement data, which is impedance for each frequency measured by an impedance method, and a pre-determined state of the reference secondary battery before and after a test that causes deterioration to progress.

[0037] Then, the derivation unit calculates a peak frequency from an arc-shaped curve in a graph plotting impedance for each frequency represented by the measurement data before and after the test, and determines a model that represents the relationship between the peak frequency and the state based on the peak frequency calculated before and after the test and the state that was determined in advance.

[0038] A second acquisition unit acquires measurement data representing impedance at each frequency measured by an impedance method for the secondary battery to be estimated. A calculation unit calculates a peak frequency from an arc-shaped curve in a graph plotting the impedance at each frequency represented by the measurement data. An estimation unit estimates the state of the secondary battery to be estimated using the model from the peak frequency for the secondary battery to be estimated.

[0039] In this state estimation method, a model expressing the relationship between the peak frequency and the state is calculated based on the peak frequency calculated before and after a test in which the deterioration of a reference secondary battery is accelerated and the state is determined in advance, and the state of the secondary battery to be estimated is estimated using the model from the peak frequency calculated from an arc-shaped curve in a graph plotting impedance for each frequency represented by measurement data obtained for the secondary battery to be estimated. This makes it possible to estimate the state of a secondary battery using a solid electrolyte, taking physical deterioration into consideration.

[0040] a calculation unit that calculates the peak frequency and the arc diameter from an arc-shaped curve in a graph that plots the impedance for each frequency represented by the measurement data before and after the test; and an estimation unit that estimates the state of the secondary battery that uses a solid electrolyte using the measurement unit; a first acquisition unit that acquires measurement data that is the impedance for each frequency measured by an impedance method for the reference secondary battery before and after a test that progresses degradation; a derivation unit that calculates an apex frequency and an arc diameter from an arc-shaped curve in a graph that plots the impedance for each frequency represented by the measurement data before and after the test, and obtains a model that represents the relationship between the apex frequency and the arc diameter based on the apex frequency and the arc diameter calculated before and after the test; a second acquisition unit that acquires measurement data that is the impedance for each frequency measured by the impedance method for the secondary battery that is to be estimated; a calculation unit that calculates the apex frequency and the arc diameter from the arc-shaped curve in the graph that plots the impedance for each frequency represented by the measurement data; and an estimation unit that estimates the state of the secondary battery that is to be estimated using the model from the apex frequency and the arc diameter for the secondary battery that is to be estimated.

[0041] In the state estimation device described in claim 11, the first acquisition unit acquires measurement data, which is impedance for each frequency measured by an impedance method, for the reference secondary battery before and after a test that causes deterioration to progress.

[0042] The derivation unit then calculates the apex frequency and the diameter of the arc from an arc-shaped curve in a graph in which the impedance for each frequency represented by the measurement data is plotted before and after the test, and obtains a model that represents the relationship between the apex frequency and the diameter of the arc based on the apex frequency and the diameter of the arc calculated before and after the test.

[0043] A second acquisition unit acquires measurement data representing impedance for each frequency measured by an impedance method for the secondary battery to be estimated. A calculation unit calculates a peak frequency and a diameter of the arc from an arc-shaped curve in a graph plotting the impedance for each frequency represented by the measurement data. An estimation unit uses the model to estimate the state of the secondary battery to be estimated from the peak frequency and the diameter of the arc for the secondary battery to be estimated.

[0044] The state estimation device calculates a model representing the relationship between the peak frequency and the arc diameter based on the peak frequency and the arc diameter calculated before and after a test in which the deterioration of a reference secondary battery is accelerated, and estimates the state of the secondary battery to be estimated using the model from the peak frequency and the arc diameter calculated from an arc-shaped curve in a graph plotting impedance for each frequency represented by measurement data obtained for the secondary battery to be estimated. This makes it possible to estimate the state of a secondary battery using a solid electrolyte, taking physical deterioration into consideration.

[0045] A program according to claim 12 is a program for estimating a state of a secondary battery using a solid electrolyte, the program causing a computer to execute the following processes: acquire measurement data, which is impedance for each frequency measured by an impedance method, and a predetermined state, for the reference secondary battery before and after a test of progressing deterioration; calculate a peak frequency from an arc-shaped curve in a graph in which the impedance for each frequency represented by the measurement data is plotted before and after the test; obtain a model representing the relationship between the peak frequency and the state based on the peak frequency calculated before and after the test and the predetermined state; acquire measurement data, which is impedance for each frequency measured by an impedance method, for the secondary battery to be estimated; calculate a peak frequency from the arc-shaped curve in the graph in which the impedance for each frequency represented by the measurement data is plotted; and estimate the state of the secondary battery to be estimated using the model from the peak frequency for the secondary battery to be estimated.

[0046] A computer executing the program according to claim 12 acquires measurement data, which is impedance at each frequency measured by an impedance method, for the reference secondary battery before and after a test that accelerates deterioration, and a predetermined state. The computer calculates a peak frequency from an arc-shaped curve in a graph that plots the impedance at each frequency represented by the measurement data before and after the test, and determines a model that represents the relationship between the peak frequency and the state based on the peak frequency calculated before and after the test and the predetermined state. The computer acquires measurement data, which is impedance at each frequency measured by an impedance method, for the secondary battery to be estimated. The computer calculates the peak frequency from the arc-shaped curve in the graph that plots the impedance at each frequency represented by the measurement data. The computer estimates the state of the secondary battery to be estimated using the model from the peak frequency for the secondary battery to be estimated.

[0047] The program calculates a model representing the relationship between the peak frequency and the state based on the peak frequency calculated before and after a test to accelerate the deterioration of a reference secondary battery and the state determined in advance, and estimates the state of the secondary battery to be estimated using the model from the peak frequency calculated from an arc-shaped curve in a graph plotting impedance for each frequency represented by measurement data obtained for the secondary battery to be estimated. This makes it possible to estimate the state of a secondary battery using a solid electrolyte, taking physical deterioration into consideration.

[0048] A program according to claim 13 is a program for estimating a state of a secondary battery using a solid electrolyte, the program causing a computer to execute a process of acquiring measurement data, which is impedance for each frequency measured by an impedance method, for the reference secondary battery before and after a test of progressing deterioration, calculating a peak frequency and a diameter of an arc from an arc-shaped curve in a graph in which the impedance for each frequency represented by the measurement data is plotted before and after the test, and determining a model expressing the relationship between the peak frequency and the diameter of the arc based on the peak frequency and the diameter of the arc calculated before and after the test, acquiring measurement data, which is impedance for each frequency measured by the impedance method, for the secondary battery to be estimated, calculating a peak frequency and a diameter of the arc from the arc-shaped curve in the graph in which the impedance for each frequency represented by the measurement data is plotted, and estimating the state of the secondary battery to be estimated using the model from the peak frequency and the diameter of the arc for the secondary battery to be estimated.

[0049] A computer executing the program according to claim 13 acquires measurement data of the reference secondary battery, which is impedance at each frequency measured by an impedance method, before and after a test for advancing deterioration. The computer calculates a peak frequency and a diameter of the arc from an arc-shaped curve in a graph plotting the impedance at each frequency represented by the measurement data before and after the test, and obtains a model representing the relationship between the peak frequency and the diameter of the arc based on the peak frequency and the diameter of the arc calculated before and after the test. The computer acquires measurement data of the impedance at each frequency measured by an impedance method for the secondary battery to be estimated. The computer calculates the peak frequency and the diameter of the arc from the arc-shaped curve in the graph plotting the impedance at each frequency represented by the measurement data. The computer estimates the state of the secondary battery to be estimated using the model based on the peak frequency and the diameter of the arc for the secondary battery to be estimated.

[0050] The program calculates a model representing the relationship between the peak frequency and the arc diameter based on the peak frequency and the arc diameter calculated before and after a test to accelerate the deterioration of a reference secondary battery, and estimates the state of the secondary battery to be estimated using the model from the peak frequency and the arc diameter calculated from an arc-shaped curve in a graph plotting impedance for each frequency represented by measurement data obtained for the secondary battery to be estimated. This makes it possible to estimate the state of a secondary battery using a solid electrolyte, taking physical deterioration into consideration. [Effects of the Invention]

[0051] According to the present invention, it is possible to estimate the state of a secondary battery using a solid electrolyte, taking physical deterioration into consideration. [Brief explanation of the drawings]

[0052] [Figure 1] FIG. 2 is a schematic block diagram of an example of a computer that functions as the state estimation device of the present embodiment. [Figure 2] 1 is a block diagram showing a functional configuration of a state estimation device according to an embodiment of the present invention; [Figure 3] FIG. 10 is a diagram showing an example of a graph in which impedance for each frequency is plotted. [Figure 4] FIG. 10 is a diagram for explaining a peak frequency. [Figure 5] 10 is a graph showing the relationship between peak frequency and capacitance. [Figure 6] 3 is a flowchart showing the flow of a state estimation process executed in the state estimation device of the first embodiment. [Figure 7] 10 is a graph showing the relationship between peak frequency and capacitance in Example 1. [Figure 8] 10 is a graph showing the relationship between the diameter of the arc and the capacity in Example 1. [Figure 9] 10 is a graph showing the relationship between peak frequency and capacitance in Example 1. [Figure 10] FIG. 2 is a diagram schematically illustrating an interface between an active material and a solid electrolyte. [Figure 11] FIG. 10 is a diagram illustrating a simulated state in which the contact rate between the active material and the solid electrolyte is reduced. [Figure 12] FIG. 2 is a diagram showing an equivalent circuit of impedance at the interface between an active material and a solid electrolyte. [Figure 13] 10 is a graph showing the relationship between apex frequency and arc diameter. [Figure 14] 10 is a diagram for explaining a method of estimating the degree of physical deterioration by comparing with a straight line that represents the relationship between the apex frequency and the diameter of a circular arc. FIG. [Figure 15] FIG. 10 is a diagram showing an example of a graph plotting impedance for each frequency at each total holding time. [Figure 16] 1 is a graph showing the relationship between frequency and the imaginary component of impedance. [Figure 17] 10 is a graph showing the relationship between apex frequency and arc diameter. [Figure 18] 10 is a flowchart showing the flow of a state estimation process executed in a state estimation device according to a second embodiment. [Figure 19] 10 is a graph showing the relationship between the apex frequency and the diameter of the circular arc in Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0053] [First embodiment] <Overall structure> FIG. 1 is a block diagram showing the hardware configuration of a state estimating device 10 according to the first embodiment.

[0054] 1, the state estimation device 10 includes a CPU (Central Processing Unit) 11, a ROM (Read Only Memory) 12, a RAM (Random Access Memory) 13, a storage 14, an input unit 15, a display unit 16, and a communication interface (I / F) 17. Each component is connected to each other via a bus 19 so as to be able to communicate with each other.

[0055] The CPU 11 is a central processing unit that executes various programs and controls each component. That is, the CPU 11 reads programs from the ROM 12 or the storage 14 and executes the programs using the RAM 13 as a work area. The CPU 11 controls the above components and performs various arithmetic processing in accordance with the programs stored in the ROM 12 or the storage 14. In this embodiment, a state estimation program 100 is stored in the storage 14. The state estimation program 100 may be a single program, or may be a group of programs configured by multiple programs or modules.

[0056] The ROM 12 stores various programs and various data. The RAM 13 temporarily stores programs or data as a working area. The storage 14 is configured with an HDD (Hard Disk Drive) or SSD (Solid State Drive) and stores various programs including the operating system and various data.

[0057] The input unit 15 includes a pointing device such as a mouse and a keyboard, and is used to perform various inputs.

[0058] The input unit 15 receives as input a combination of measurement data, which is the impedance for each frequency measured by an impedance method before and after a test to accelerate deterioration of a reference all-solid-state battery, and a previously determined capacity of the all-solid-state battery.

[0059] Specifically, first, an all-solid-state battery composed of a positive electrode, a solid electrolyte layer, and a negative electrode layer as shown below is fabricated.

[0060] The positive electrode layer is LiNi 0.5 Co 0.2 Mn 0.3 The cathode is composed of O2, a sulfide solid electrolyte with an argyrodite structure, conductive carbon, and a binder. The solid electrolyte layer is composed of a sulfide solid electrolyte with an argyrodite structure and a binder. The anode layer is composed of graphite, a sulfide solid electrolyte with an argyrodite structure, and a binder.

[0061] A slurry of the positive electrode layer constituent material dispersed in an organic solvent is applied to an aluminum foil and then dried to produce a positive electrode sheet. A slurry of the solid electrolyte layer constituent material dispersed in an organic solvent is applied to a metal foil and then dried to produce a solid electrolyte sheet. A slurry of the negative electrode layer constituent material dispersed in an organic solvent is applied to a metal foil and then dried to produce a negative electrode sheet.

[0062] Next, the coated surfaces of the solid electrolyte sheet and the negative electrode sheet are placed face-to-face and pressed together to transfer the solid electrolyte layer onto the negative electrode layer. The negative electrode sheet and positive electrode sheet with the transferred solid electrolyte layer are then stacked together in the order of positive electrode layer, solid electrolyte layer, and negative electrode layer, and pressed together to bond the layers together and densify the positive electrode layer, solid electrolyte layer, and negative electrode layer. This is then sealed with a laminate film to obtain an all-solid-state battery. To ensure the performance of the all-solid-state battery, the electrode surfaces are restrained with a jig to apply a specified surface pressure.

[0063] Then, a charge-discharge test is performed on the all-solid-state battery prepared as described above, in which the battery is charged and discharged under predetermined conditions (for example, at 25°C and 0.1 C), and the capacity of the all-solid-state battery is calculated. After that, the SOC (State Of Charge) is adjusted to 50%, and AC impedance measurement is performed at 25°C to obtain measurement data.

[0064] Next, this all-solid-state battery is subjected to a cycle test in which it is charged and discharged at 60°C and 1C. After 100 cycles and 200 cycles, the all-solid-state battery is removed and a charge-discharge test is performed at 25°C and 0.1C to calculate the capacity of the all-solid-state battery. In addition, AC impedance measurement is performed at SOC 50% to obtain measurement data.

[0065] In this way, a combination of measurement data, which is the impedance for each frequency measured by the impedance method, before and after the test to accelerate deterioration and the previously determined capacity of the all-solid-state battery is prepared for the reference all-solid-state battery. Then, the input unit 15 accepts the combination of the measurement data and the capacity before and after the test to accelerate deterioration for the reference all-solid-state battery.

[0066] Furthermore, the input unit 15 receives as input measurement data that is the impedance for each frequency measured by an impedance method for the all-solid-state battery whose capacity is unknown and is the estimation target.

[0067] Specifically, a charge-discharge test is carried out on an all-solid-state battery to be estimated, which is produced in the same manner as the above-mentioned reference all-solid-state battery, in which the battery is charged and discharged under predetermined conditions (for example, conditions of 25°C and 0.1C), and then the battery is adjusted to have an SOC of 50%, and AC impedance measurement is carried out at 25°C to obtain measurement data.

[0068] The display unit 16 is, for example, a liquid crystal display, and displays various information. The display unit 16 may also function as the input unit 15 by adopting a touch panel system.

[0069] The communication interface 17 is an interface for communicating with other devices, and uses standards such as Ethernet (registered trademark), FDDI (Fiber Distributed Data Interface), and Wi-Fi (registered trademark).

[0070] In a Cole-Cole plot obtained by measuring the AC impedance of an all-solid-state battery, the horizontal axis represents the real component Z', and the vertical axis represents the imaginary component Z", resulting in an arc-shaped curve caused by the resistance of the battery's charge / discharge reactions. As the all-solid-state battery deteriorates, the diameter of this arc increases, and the frequency at which the arc apex (the point at which the absolute value of the imaginary number is maximum) (hereinafter referred to as the apex frequency) decreases. Furthermore, the capacity of the all-solid-state battery decreases with deterioration. The inventors have found that the relationship between the apex frequency x, which changes with the progression of deterioration, and the capacity w can be expressed mathematically as w = F(x), regardless of the charge / discharge conditions that lead to deterioration, and further that a good approximation can be obtained in the form of w = a log x + b (a and b are constants). In order to improve the accuracy of the approximation, a correction term may be included, such as w = a log x + b + D (D is a correction term).

[0071] Theoretically, this can be interpreted as follows.

[0072] Generally, the practical battery capacity depends on the capacity of the active material itself and the battery resistance. The reason why the battery capacity is affected by the battery resistance is that if the resistance is large, the overvoltage during charging and discharging increases, and the upper limit voltage during charging and the lower limit voltage during discharging are reached before the limit capacity of the active material is reached.

[0073] The AC impedance method is a simple method for measuring battery resistance. A Cole-Cole plot, in which the real component of the impedance obtained by this method is plotted on the horizontal axis and the imaginary component on the vertical axis, produces an arc-shaped curve due to the resistance of the battery reaction, and the diameter of this arc can be used as an index of the resistance of the battery reaction. However, because the measurement conditions are different from the actual battery resistance during charging and discharging, the measured resistance does not generally match the resistance during charging and discharging, and does not necessarily correlate with the battery capacity.

[0074] Here, for a degraded battery, the resistance expressed as the diameter of the arc includes the effects of increased charge transfer resistance due to the formation of a resistive layer at the interface between the active material and electrolyte, a decrease in the contact area between the active material and electrolyte, and an increase in ionic conduction resistance in the electrode thickness direction. Among these factors, the peak frequency decreases as the charge transfer resistance increases, but it is theoretically known that the peak frequency remains nearly constant even when the contact area or ionic conduction resistance fluctuates. The strong correlation between capacity and peak frequency is thought to be due to the significant impact of the increase in charge transfer resistance due to the formation of a resistive layer on capacity reduction, and the strong correlation between charge transfer resistance and peak frequency.

[0075] Therefore, in this embodiment, as shown in FIG. 2, in the state estimation device 10, the CPU 11 executes the state estimation program 100 to function as a first acquisition unit 150, a derivation unit 160, a second acquisition unit 170, a calculation unit 180, and an estimation unit 190.

[0076] The first acquiring unit 150 acquires measurement data, which is the impedance for each frequency measured by an impedance method, and a previously determined capacity of the reference all-solid-state battery before and after a test that accelerates deterioration.

[0077] The derivation unit 160 calculates the peak frequency from an arc-shaped curve in a graph plotting impedance for each frequency represented by the measurement data acquired by the first acquisition unit 150, and obtains a relational expression w=F(x) that expresses the relationship between the peak frequency x and capacitance q. Here, the relational expression w=F(x) includes a term a·log x and a term b, where a and b are constants.

[0078] Specifically, Figure 3 shows the Cole-Cole plot obtained from the AC impedance measurement before the cycle test. Figure 4 shows the relationship between the apex frequency of the arc and the imaginary component of the impedance. In Figure 3, the relationship between the logarithm of the frequency (f) and the absolute value of the imaginary component Z" is

[0079] |Z”|=k(log f) 2+l(log f)+m (k, l, m are constants)

[0080] When expressed in this form, the coefficients k, l, and m are found using the least squares method, and the frequency f that gives the maximum value of |Z″| is found as the peak frequency x, which is defined as the peak frequency before the cyclic test. In addition, in Figure 3, the difference between the real components of the points closest to the real axis on each end of the arc is calculated as the diameter y of the arc, which is defined as the diameter of the arc before the cyclic test.

[0081] The diameter of the circular arc and the apex frequency after the cycle test are also calculated in the same manner.

[0082] The peak frequency x and its logarithm, the arc diameter y and its logarithm, and the capacity w obtained by the above method are shown in Table 1 as relative values, with the value before the cycle test taken as 1.

[0083] [Table 1]

[0084] The correspondence relationship between the relative value of the logarithm log x of the peak frequency x and the relative value of the capacitance w is expressed by a straight line as shown in FIG. 5, and the following relational expression 1 is obtained by the least squares method, for example.

[0085] w=a·log x+b (Equation 1)

[0086] The second acquisition unit 170 acquires measurement data, which is the impedance for each frequency measured by an impedance method, for the all-solid-state battery that is the estimation target.

[0087] The calculation section 180 calculates the peak frequency from an arc-shaped curve in a graph plotting impedance for each frequency represented by the measurement data acquired by the second acquisition section 170.

[0088] The estimation unit 190 substitutes the peak frequency for the all-solid-state battery to be estimated into Relational Expression 1 to estimate the capacity of the all-solid-state battery to be estimated, and displays the estimated capacity on the display unit 16.

[0089] <Operation of the state estimation device according to the first embodiment> Next, the operation of the state estimating device 10 according to the first embodiment will be described.

[0090] 6 is a flowchart showing the flow of the state estimation process by the state estimation device 10. The state estimation process is performed by the CPU 11 reading the state estimation program 100 from the storage 14, expanding it into the RAM 13, and executing it. In addition, a combination of measurement data, which is the impedance for each frequency measured by the impedance method before and after a test to accelerate deterioration of a reference all-solid-state battery, and a previously determined capacity is input to the state estimation device 10 and stored in the storage 14.

[0091] Furthermore, measurement data, which is the impedance for each frequency measured by an impedance method for the all-solid-state battery to be estimated, is input to the state estimation device 10 and stored in the storage 14.

[0092] In step S100, the CPU 11, as the first acquisition unit 150, acquires measurement data, which is the impedance for each frequency measured by the impedance method, and the previously determined capacity of the reference all-solid-state battery before and after a test to accelerate deterioration.

[0093] In step S102, the CPU 11 functions as the derivation unit 160 to calculate the peak frequency from the arc-shaped curve in the graph plotting the impedance for each frequency represented by the measurement data acquired in step S100.

[0094] In step S104, the CPU 11 functions as the derivation unit 160 to obtain a relational expression w=F(x) that represents the relationship between the peak frequency and the capacity.

[0095] In step S106, the CPU 11 functions as the second acquisition unit 170 to acquire measurement data that is the impedance for each frequency measured by the impedance method for the all-solid-state battery that is the estimation target.

[0096] In step S108, the CPU 11 functions as the calculation unit 180 to calculate the peak frequency from the arc-shaped curve in the graph plotting the impedance for each frequency represented by the measurement data acquired in step S106.

[0097] In step S110, the CPU 11, as the estimation unit 190, estimates the capacity of the all-solid-state battery to be estimated from the peak frequency of the all-solid-state battery to be estimated by using Relational Expression 1, displays the estimated capacity on the display unit 16, and ends the state estimation process.

[0098] Example 1 An example in which the capacity is estimated using the state estimating device 10 according to the first embodiment will be described.

[0099] For cells having the same specifications as the reference all-solid-state battery, a cycle test at 60°C and 1C was carried out for 300 cycles (condition 1), and another cycle test at 25°C and 1C was carried out for 300 cycles (condition 2). These were used as the all-solid-state batteries to be estimated, and the capacity w1, the apex frequency x1, and the arc diameter y1 were obtained by the same method as described in the first embodiment.

[0100] Furthermore, in order to simulate deterioration due to a decrease in the interparticle contact area caused by the expansion and contraction of the active material, a cell was fabricated in which the interfacial contact of the constituent materials was intentionally reduced by lowering the electrode pressing pressure during battery fabrication, and the capacity w1, apex frequency x1, and arc diameter y1 were obtained in the same manner as described in the first embodiment above (condition 3) without performing a cycle test.

[0101] Next, using Relational Expression 1, the estimated capacitance w2 at each peak frequency x1 obtained under Conditions 1 to 3 was calculated. Table 2 shows the results.

[0102] [Table 2]

[0103] The relationship between the peak frequency and the actually measured value of capacitance, and the relationship between the peak frequency and the estimated value of capacitance are shown in Figure 7. As can be seen from Figure 7, the estimated values ​​are close to the actually measured values, and the capacitance can be estimated with high accuracy.

[0104] Next, we will explain the relationship between the arc diameter and capacity. Generally, high battery resistance tends to result in low capacity, so it is possible that capacity can be estimated from the arc diameter, which is associated with the battery's resistance component. Figure 8 shows the relationship between the logarithm of the arc diameter and capacity for all of the data described above in this example. While a generally linear relationship is observed, some data deviates from this linear relationship (see the arrows in Figure 8). This deviating data corresponds to Condition 3, in which the pressing pressure was low, and it can be seen that accurate capacity estimation may not be possible for degradation that reduces physical contact within the electrodes.

[0105] On the other hand, the relationship between the logarithm of the peak frequency and the capacitance is shown in Figure 9, which shows that the capacitance can be estimated with high accuracy even when the physical contact deteriorates.

[0106] <Summary of the embodiment> The state estimation device 10 of this embodiment calculates a relational expression that expresses the relationship between the peak frequency and the capacity based on the peak frequency calculated before and after a test that progresses the deterioration of a reference all-solid-state battery and the capacity that has been calculated in advance, and estimates the capacity of the all-solid-state battery to be estimated using the relational expression from the peak frequency calculated from an arc-shaped curve in a graph that plots the impedance for each frequency represented by measurement data acquired for the all-solid-state battery to be estimated. In this way, the capacity of the all-solid-state battery can be estimated taking physical deterioration into consideration.

[0107] [Second embodiment] The state estimating device according to the second embodiment has the same configuration as that of the first embodiment, and therefore will be described using the same reference numerals.

[0108] <Overall structure> FIG. 1 is a block diagram showing the hardware configuration of a state estimating device 10 according to the second embodiment.

[0109] As shown in FIG. 2, the state estimating device 10 of the second embodiment includes a CPU 11, a ROM 12, a RAM 13, a storage 14, an input unit 15, a display unit 16, and a communication interface (I / F) 17, similarly to the first embodiment.

[0110] The input unit 15 receives as input measurement data that is the impedance for each frequency measured by an impedance method for a reference all-solid-state battery before and after a test that progresses deterioration accompanied by chemical changes.

[0111] Specifically, first, an all-solid-state battery composed of a positive electrode, a solid electrolyte layer, and a negative electrode layer is fabricated in the same manner as in the first embodiment.

[0112] The produced battery is then conditioned by charging and discharging under predetermined conditions, and adjusted to an SOC of 50%, after which AC impedance measurement at 25°C is carried out.

[0113] Next, this battery is charged to 100% SOC at 60°C and held at a voltage of 100% SOC for 48 hours, after which the SOC is adjusted to 50% and AC impedance is measured at 25°C. This same method is repeated to measure AC impedance after holding times of 120 hours and 240 hours.

[0114] In this way, measurement data, which is the impedance for each frequency measured by the impedance method before and after the test of progressing the deterioration accompanied by chemical changes, is prepared for the reference all-solid-state battery, and the input unit 15 receives the measurement data for the reference all-solid-state battery before and after the test of progressing the deterioration accompanied by chemical changes.

[0115] Furthermore, the input unit 15 receives as input measurement data that is the impedance for each frequency measured by an impedance method for the all-solid-state battery whose capacity is unknown and is the estimation target.

[0116] Specifically, a charge-discharge test is carried out on an all-solid-state battery to be estimated, which is produced in the same manner as the above-mentioned reference all-solid-state battery, in which the battery is charged and discharged under predetermined conditions. Thereafter, the battery is adjusted to have an SOC of 50%, and AC impedance measurement is carried out at 25°C to obtain measurement data.

[0117] In a Cole-Cole plot, in which the real component of the results obtained by measuring the AC impedance of an all-solid-state battery is plotted on the horizontal axis and the imaginary component on the vertical axis, an arc-shaped curve appears due to the resistance of the battery's charge / discharge reaction. As the all-solid-state battery deteriorates, the diameter y of this arc increases, and the apex frequency x at the apex of the arc (the point at which the absolute value of the imaginary number is maximum) decreases. The inventors have found that when deterioration is advanced by changing only the time or number of cycles under the same conditions, the relationship between the apex frequency x, which changes with the progression of deterioration, and the diameter y of the arc can be expressed mathematically as y = F(x), and furthermore, y = ax b (a, b are constants) to obtain a good approximation. b A correction term D may be included, such as +D (D is a correction term).

[0118] The reason why the apex frequency of the arc decreases with deterioration is thought to be chemical deterioration of the interface between the active material and the solid electrolyte, which is the site of the charge transfer reaction, and can be theoretically explained as follows.

[0119] Generally, the impedance resulting from the charge transfer reaction at the interface between the active material and solid electrolyte can be thought of as an equivalent circuit consisting of a parallel circuit with resistance R and capacitance C, as shown in Figure 10, which schematically illustrates the interface. The diameter of the arc is R, and the peak frequency is equivalent to 1 / (2πRC) (this frequency is called the characteristic frequency). R corresponds to the resistance associated with the charge transfer reaction and is part of the battery resistance. As chemical degradation progresses at the interface, the interfacial resistance R increases, and as a result, the peak frequency 1 / (2πRC) decreases. Note that C may also change as the chemical state at the interface changes, but since experimental data show that the peak frequency changes only slightly with degradation, the impact of changes in C is thought to be limited.

[0120] On the other hand, the influence of physical deterioration on impedance can be theoretically considered as follows: Specific phenomena of physical deterioration include a decrease in the contact area at the interface between the active material and the solid electrolyte due to expansion and contraction of the active material, and a decrease in ionic conductivity due to the formation of voids in the solid electrolyte in the electrode layer.

[0121] Figure 11 shows a simulated state where the contact rate at the interface between the active material and solid electrolyte is reduced. For example, if the contact area is halved, the resistance R in the equivalent circuit doubles. Meanwhile, the capacitance C of the capacitor is halved. As a result, the peak frequency 1 / (2πRC) remains unchanged, but the diameter of the arc doubles.

[0122] Figure 12 shows an image of the decrease in ionic conductivity due to the formation of voids in the solid electrolyte in the electrode layer. Generally, the electrode layer is made by mixing active material particles and solid electrolyte particles and pressing them together, so that the active material is dispersed in the solid electrolyte, which forms a three-dimensional network. In some cases, conductive materials such as conductive carbon are included to improve electronic conductivity, and binders are included to improve binding strength. In this case, the equivalent circuit of the impedance at the interface between the electrode and solid electrolyte is shown in Figure 12, where resistance r CT , capacitor capacitance c is connected in a ladder shape in the thickness direction, and lithium ion resistance r i In this case, too, an arc due to charge transfer resistance appears on the Cole-Cole plot, and the diameter of the arc reflects the charge transfer resistance and lithium ion resistance. Here, as shown in Figure 12, if voids are generated in the electrolyte due to physical deterioration, the lithium ion resistance r i can be considered to be large, in which case the diameter of the arc is r i The peak frequency becomes almost constant in the calculation, although it increases with increasing

[0123] The relationship between the apex frequency x and the arc diameter y for chemical and physical degradation can be summarized as shown in the image in Figure 13. In the degradation of the all-solid-state battery to be estimated, both chemical and physical degradation progress simultaneously, so it is plotted between the two arrows in Figure 13. From the above explanation, by comparing this point with the line representing chemical degradation and quantifying the degree of deviation, it can be used as an index of physical degradation.

[0124] The plot of the target solid-state battery (denoted as (x1, y1)) is compared with the line representing chemical degradation by comparing y1 and F(x1) in Figure 14. If the initial diameter of the arc is y0, the difference between F(x1) and y0 can be theoretically interpreted as the contribution of chemical degradation, and the difference between y1 and F(y1) as the contribution of physical degradation, allowing for a more theoretically reliable assessment. For example, y1 / F(x1), obtained by dividing y1 by F(x1), can be considered an indicator of how much the resistance has increased due to physical degradation. Furthermore, because physical degradation can potentially be reversed by repressing the battery to reconnect the separated interfaces, it can be said that the resistance that has risen to y1 can potentially be reduced to F(x1).

[0125] To make the above comparison, it is desirable that the test for promoting deterioration accompanied by chemical changes (chemical deterioration) should include as little physical deterioration as possible and be as close to chemical deterioration as possible, i.e., the slope of the line y = F(x) in Figure 14 should be as horizontal as possible. As a result of conducting experiments under various conditions, it was found that a method of maintaining a constant voltage in a charged state exhibits deterioration behavior that is closest to chemical deterioration alone. Therefore, in this embodiment, a test for maintaining a constant voltage in a charged state is used as a test for promoting deterioration accompanied by chemical changes.

[0126] Figure 15 shows a Cole-Cole plot of the impedance obtained for each retention time in this test, with the real component on the horizontal axis and the imaginary component on the vertical axis. Figure 16 shows a plot of the impedance with frequency on the horizontal axis and the imaginary component on the vertical axis. Figure 15 shows an arc-shaped curve, likely due to the charge / discharge reaction, with the arc becoming larger with retention time. Figure 16 shows that the peak frequency decreases with retention time. The charge / discharge reactions contributing to the arc include reactions at both the positive and negative electrodes. The reactions at the positive and negative electrodes are also composed of multiple elementary reactions, and the arc is considered to be the sum of these reactions. However, in this invention, the arc can be considered as a single pseudo-arc. In this case, the degree of physical deterioration of the positive and negative electrodes as a whole is estimated. Depending on the electrode material, the arcs may be clearly separated. In such cases, the degree of physical deterioration for each elementary reaction can be estimated by performing the same operation on each arc.

[0127] Therefore, in this embodiment, as shown in FIG. 2 above, in the state estimation device 10, the CPU 11 executes the state estimation program 100 to function as a first acquisition unit 150, a derivation unit 160, a second acquisition unit 170, a calculation unit 180, and an estimation unit 190.

[0128] The first acquiring unit 150 acquires measurement data, which is the impedance for each frequency measured by an impedance method, for the reference all-solid-state battery before and after a test in which deterioration accompanied by chemical changes is advanced.

[0129] The derivation unit 160 calculates the apex frequency and the diameter of the arc from the arc-shaped curve in the graph plotting the impedance for each frequency represented by the measurement data acquired by the first acquisition unit 150, and obtains the relational expression y=F(x) that expresses the relationship between the apex frequency x and the diameter y of the arc. Here, the relational expression y=F(x) is expressed as ax b where a and b are constants.

[0130] Specifically, as in the first embodiment, the coefficients k, l, and m of the relational expression between the logarithm of frequency f and the absolute value of the imaginary component Z" are found by the least squares method, and the frequency f that gives the maximum value of |Z"| is found as the apex frequency x. Also, in FIG. 3, the difference between the real components of the points closest to the real axis at each end of the arc is calculated as the diameter y of the arc.

[0131] The diameter of the circular arc and the apex frequency after the cycle test are also calculated in the same manner.

[0132] The apex frequency x and its logarithm, and the arc diameter y and its logarithm, obtained by the above method, are shown in Table 3 as relative values, with the value before voltage application set to 1.

[0133] [Table 3]

[0134] Log x and log y have a linear relationship (Figure 17), and the following relationship can be obtained by the least squares method.

[0135] log y=b log x+c

[0136] By modifying this equation, we obtain relational expression 2.

[0137] y=ax b (Equation 2)

[0138] The second acquisition unit 170 acquires measurement data, which is the impedance for each frequency measured by an impedance method, for the all-solid-state battery that is the estimation target.

[0139] The calculation section 180 calculates the apex frequency and the diameter of the arc from the arc-shaped curve in a graph plotting impedance for each frequency represented by the measurement data acquired by the second acquisition section 170.

[0140] The estimation unit 190 estimates the degree of physical deterioration of the all-solid-state battery to be estimated from the apex frequency and the diameter of the arc for the all-solid-state battery to be estimated by using Relational Formula 2, and displays the estimated degree of physical deterioration on the display unit 16.

[0141] Specifically, the degree of physical deterioration of the secondary battery to be estimated is estimated based on a comparison between the diameter y1 of the arc for the secondary battery to be estimated and the diameter y2 of the arc obtained by substituting the peak frequency x1 for the secondary battery to be estimated into the relational equation y=F(x).

[0142] More specifically, the value y1 / y2 obtained by dividing y1 by y2 is calculated as the degree of physical deterioration. If y1 / y2 is equal to or greater than a predetermined reference value, it is determined that re-pressing is necessary, and if it is less than the reference value, it is determined that re-pressing is not necessary. The result of this determination is displayed on the display unit 16.

[0143] <Operation of the state estimating device according to the second embodiment> Next, the operation of the state estimating device 10 according to the second embodiment will be described.

[0144] 18 is a flowchart showing the flow of the state estimation process by the state estimation device 10. The state estimation process is performed by the CPU 11 reading the state estimation program 100 from the storage 14, expanding it into the RAM 13, and executing it. In addition, measurement data, which is the impedance for each frequency measured by an impedance method for a reference all-solid-state battery before and after a test, is input to the state estimation device 10 and stored in the storage 14.

[0145] Furthermore, measurement data, which is the impedance for each frequency measured by an impedance method for the all-solid-state battery to be estimated, is input to the state estimation device 10 and stored in the storage 14.

[0146] In step S200, the CPU 11, as the first acquisition unit 150, acquires measurement data, which is the impedance for each frequency measured by the impedance method, for a reference all-solid-state battery before and after a test in which deterioration accompanied by chemical changes is advanced.

[0147] In step S202, the CPU 11, functioning as the derivation unit 160, calculates the apex frequency and the diameter of the arc from the arc-shaped curve in the graph plotting the impedance for each frequency represented by the measurement data acquired in step S200.

[0148] In step S204, the CPU 11 functions as the derivation unit 160 to obtain a relational expression y=F(x) that represents the relationship between the vertex frequency x and the diameter y of the arc.

[0149] In step S206, the CPU 11 functions as the second acquisition unit 170 to acquire measurement data that is the impedance for each frequency measured by the impedance method for the all-solid-state battery that is the estimation target.

[0150] In step S208, the CPU 11, functioning as the calculation unit 180, calculates the apex frequency and the diameter of the arc from the arc-shaped curve in the graph plotting the impedance for each frequency represented by the measurement data acquired in step S206.

[0151] In step S210, the CPU 11, as the estimation unit 190, estimates the degree of physical deterioration of the all-solid-state battery to be estimated from the apex frequency and the diameter of the arc for the all-solid-state battery to be estimated by using Relational Expression 2, displays the estimated degree of physical deterioration on the display unit 16, and ends the state estimation process.

[0152] <Example 2> An example in which the capacity is estimated using the state estimating device 10 according to the second embodiment will be described.

[0153] A cell with the same specifications as the reference all-solid-state battery was used as the all-solid-state battery to be estimated, and cycle tests were conducted under various conditions simulating repeated charging and discharging in practice. After the cycle tests, the diameter y1 of the circular arc and the apex frequency x1 were calculated for the cell.

[0154] The cycle test conditions, arc diameter y1, and apex frequency x1 are shown in Table 4. These are also shown in a graph in Figure 19. Note that, as with Table 3, x1 and y1 are shown as relative values, with the value before voltage application set to 1.

[0155] [Table 4]

[0156] In Figure 19, all of the points after the cycle test are plotted above the line of Relational Formula 2. This shows that the accelerated degradation test conducted to obtain Relational Formula 2 by maintaining a constant voltage in a charged state resulted in a state that was as close to chemical degradation as possible, with as little physical degradation as possible, as intended.

[0157] By substituting the peak frequency x1 obtained above for each condition into relational expression 2, the diameter y2 of the arc caused by chemical degradation (y2 = F(x1)) was calculated (Table 5). This is equivalent to calculating the diameter of the arc at points E', F', G', etc. in Figure 19. Next, y1 / y2 was calculated by dividing y1 by y2 (Table 5). y1 / y2 is a value that indicates how many times the resistance component has increased due to physical degradation; the larger the value, the greater the contribution of physical degradation.

[0158] [Table 5]

[0159] The larger the y1 / y2 ratio, the greater the contribution of physical deterioration, meaning that performance recovery can be expected by re-pressing. For example, by setting the judgment criterion value to 1.2, it is possible to narrow down the cells that require re-pressing (Table 5).

[0160] <Summary of the embodiment> The state estimation device 10 of this embodiment calculates a relational expression that expresses the relationship between the apex frequency and the arc diameter based on the apex frequency and the arc diameter calculated before and after a test that progresses the deterioration of a reference all-solid-state battery, and estimates the state of the all-solid-state battery to be estimated using the relational expression from the apex frequency and the arc diameter calculated from an arc-shaped curve in a graph that plots impedance for each frequency represented by measurement data acquired for the all-solid-state battery to be estimated. In this way, it is possible to estimate the degree of physical deterioration of the all-solid-state battery, taking physical deterioration into consideration.

[0161] [remarks] In the above embodiment, the capacity and physical deterioration level of an all-solid-state battery are estimated as an example, but this is not limiting. A secondary battery using a solid electrolyte may be used instead of an all-solid-state battery. For example, the capacity and physical deterioration level of a semi-solid-state battery may be estimated.

[0162] In the first embodiment, a relational expression representing the relationship between the peak frequency and the capacity is calculated, and the capacity of the all-solid-state battery to be estimated is estimated using the relational expression. However, the present invention is not limited to this. For example, a trained model such as a neural network that inputs the peak frequency and outputs the capacity may be calculated, and the trained model may be used to estimate the capacity of the all-solid-state battery to be estimated.

[0163] In the second embodiment, a relational expression representing the relationship between the apex frequency and the diameter of the arc is calculated, and the degree of physical deterioration of the all-solid-state battery to be estimated is estimated using the relational expression. However, the present invention is not limited to this. For example, a trained model such as a neural network that inputs the apex frequency and outputs the diameter of the arc may be calculated, and the trained model may be used to estimate the degree of physical deterioration of the all-solid-state battery to be estimated.

[0164] Furthermore, various processes executed by the CPU 11 after reading software (programs) in the above embodiment may be executed by various processors other than a CPU. Examples of such processors include programmable logic devices (PLDs) whose circuit configuration can be changed after fabrication, such as field-programmable gate arrays (FPGAs), and dedicated electrical circuits, such as application-specific integrated circuits (ASICs), which are processors with circuit configurations specifically designed to execute specific processes. Each of the above processes may be executed by one of these various processors, or by a combination of two or more processors of the same or different types (e.g., multiple FPGAs, or a combination of a CPU and an FPGA). The hardware structure of these various processors is, more specifically, an electrical circuit that combines circuit elements such as semiconductor devices.

[0165] In the above embodiment, each program has been described as being stored (installed) in advance on a computer-readable non-transitory recording medium. For example, the state estimation program 100 in the state estimation device 10 is stored in advance in the storage 14. However, the present invention is not limited to this. Each program may be provided in a form recorded on a non-transitory recording medium such as a CD-ROM (Compact Disc Read Only Memory), a DVD-ROM (Digital Versatile Disc Read Only Memory), or a USB (Universal Serial Bus) memory. Furthermore, the program may be downloaded from an external device via a network.

[0166] The processing flow described in the above embodiment is an example, and unnecessary steps may be deleted, new steps may be added, or the processing order may be changed within the scope of the gist of the invention. [Explanation of symbols]

[0167] 10 State Estimation Device 11 CPU 14. Storage 100 State Estimation Program (Program) 150 Acquisition Department 160 Derivation part 170 Acquisition Department 180 Calculation Unit 190 Estimation Department

Claims

1. 1. A state estimation method for estimating a degree of physical deterioration of a secondary battery using an active material and a solid electrolyte, the degree of physical deterioration being a decrease in contact area at the interface between the active material and the solid electrolyte due to expansion and contraction of the active material, or a decrease in ionic conductivity due to formation of voids in the solid electrolyte, the method comprising: For the reference secondary battery, measurement data is obtained which is impedance for each frequency measured by an impedance method before and after a test for progressing deterioration; Calculating a peak frequency and a diameter of an arc from a curve in a graph plotting impedance for each frequency represented by the measurement data before and after the test; A model expressing a relationship between the apex frequency and the diameter of the circular arc is obtained based on the apex frequency and the diameter of the circular arc calculated before and after the test; Acquire measurement data for the secondary battery to be estimated, the measurement data being impedance for each frequency measured by an impedance method; Calculating a peak frequency and a diameter of a circular arc from a circular arc-shaped curve in a graph in which impedance for each frequency represented by the measurement data is plotted; Using the model, the degree of physical deterioration of the secondary battery is estimated from the apex frequency and the diameter of the arc for the secondary battery. State estimation methods.

2. The test is a test in which the battery is held at a constant voltage in a charged state, The model is a relational expression y=F(x) that expresses a relationship between a vertex frequency x and a diameter y of a circular arc, The state estimation method according to claim 1 , further comprising: estimating a degree of physical deterioration of the secondary battery to be estimated based on a comparison of the peak frequency and the diameter of the arc for the secondary battery to be estimated with the relational expression y = F(x).

3. In the estimation of the degree of physical deterioration, A diameter y1 of the arc for the secondary battery to be estimated; 3. The state estimation method according to claim 2, further comprising estimating a degree of physical deterioration of the secondary battery to be estimated based on a comparison with a diameter y2 of an arc obtained by substituting a peak frequency x1 of the secondary battery to be estimated into the relational expression y = F(x).

4. The above relational expression y=F(x) is ax ｂ 3. The state estimation method according to claim 2, further comprising the terms: a and b being constants.

5. 1. A state estimation device for estimating a degree of physical deterioration of a secondary battery using an active material and a solid electrolyte, the degree of physical deterioration being a decrease in a contact area at an interface between the active material and the solid electrolyte due to expansion and contraction of the active material, or a decrease in ionic conductivity due to formation of voids in the solid electrolyte, the device comprising: a first acquisition unit that acquires measurement data of impedance for each frequency measured by an impedance method before and after a test for progressing deterioration of the reference secondary battery; Calculating a peak frequency and a diameter of an arc from a curve in a graph plotting impedance for each frequency represented by the measurement data before and after the test; A derivation unit that obtains a model that represents a relationship between the apex frequency and the diameter of the circular arc based on the apex frequency and the diameter of the circular arc calculated before and after the test; A second acquisition unit that acquires measurement data of the secondary battery as an estimation target, the measurement data being impedance for each frequency measured by an impedance method; a calculation unit that calculates a peak frequency and a diameter of a circular arc from a circular arc-shaped curve in a graph in which impedance for each frequency represented by the measurement data is plotted; an estimation unit that estimates the degree of physical deterioration of the secondary battery that is the estimation target, using the model, from the apex frequency and the diameter of the arc for the secondary battery that is the estimation target; A state estimator comprising:

6. 1. A program for estimating a degree of physical deterioration of a secondary battery using an active material and a solid electrolyte, the degree of physical deterioration being a decrease in contact area at the interface between the active material and the solid electrolyte due to expansion and contraction of the active material, or a decrease in ionic conductivity due to formation of voids in the solid electrolyte, the program comprising: For the reference secondary battery, measurement data is obtained which is impedance for each frequency measured by an impedance method before and after a test for progressing deterioration; Calculating a peak frequency and a diameter of an arc from a curve in a graph plotting impedance for each frequency represented by the measurement data before and after the test; A model expressing a relationship between the apex frequency and the diameter of the circular arc is obtained based on the apex frequency and the diameter of the circular arc calculated before and after the test; Acquire measurement data for the secondary battery to be estimated, the measurement data being impedance for each frequency measured by an impedance method; Calculating a peak frequency and a diameter of a circular arc from a circular arc-shaped curve in a graph in which impedance for each frequency represented by the measurement data is plotted; Using the model, the degree of physical deterioration of the secondary battery is estimated from the apex frequency and the diameter of the arc for the secondary battery. A program that causes a computer to carry out processing.

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