JP2019158448A - Electrode plate inspection apparatus and electrode plate inspection method - Google Patents

Abstract

To provide an electrode plate inspection apparatus and an electrode inspection method capable of more accurately and quickly inspecting a detailed state of an electrode plate of a secondary battery.SOLUTION: An electrode board inspection apparatus 20 includes an installation stand 108 which holds an electrode board 100 in an electrolysis solution; a probe 11 equipped with an opposite poles 114 in the electrolysis solution 116 of a measurement unit 118 opened wide toward the electrode board 100; an impedance measurement unit 13 which measures a complex impedance between the electrode board 100 and the opposite poles 114; a moving unit which performs relative displacement of the probe 11 to the electrode board 100; and the fitting part 141 which performs fitting of the complex impedance to a characteristic model of an electrode board. The moving unit moves the probe 11 to an adjoining point of measurement Tg. The impedance measurement unit 13 acquires complex impedance for every point of measurement Tg. The fitting result of the point of measurement which adjoins an initial value given to a characteristic model of the electrode board 100 at the point of measurement Tg is used for the fitting unit 141.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrode plate inspection apparatus and an electrode plate inspection method for inspecting an electrode plate of a secondary battery.

  A lithium ion secondary battery, which is one of non-aqueous electrolyte secondary batteries, has a high energy density and a high capacity, and is therefore used as a power source for driving an electric vehicle (EV), a hybrid vehicle (HV), etc. It has been. A lithium ion secondary battery has an electrode body obtained by winding or laminating a positive electrode plate having an active material layer on both surfaces of an electrode core and a negative electrode plate with a separator interposed therebetween. One of such secondary battery inspection techniques is an inspection based on complex impedance with respect to an electrode plate. For example, Patent Document 1 describes an example of a technique for measuring complex impedance.

  The technique for inspecting an electrode plate described in Patent Document 1 includes a measurement unit that is connected to a counter electrode disposed in an electrolytic solution and that acts on a part of an electrode active material layer that is opposed via the electrolytic solution. Prepare a probe. Moreover, the measurement part of a probe is made to act on a part of electrode active material layer which opposes, and the counter electrode in a probe and the to-be-measured part of an electrode active material layer are electrically connected through electrolyte solution. Further, the impedance is measured between the electrically connected counter electrode and the part to be measured, and the resistance of the electrode is calculated based on the measurement of the impedance. And the area of the counter electrode in a probe is 100 times or more larger than the operation area of the measurement part of this probe.

JP 2014-25850 A

According to this technique, the state of the electrode plate of the secondary battery is measured in detail, whereby the battery state of the secondary battery can be inspected.
By the way, in recent years, there is a strong demand for a technique capable of more accurately and quickly inspecting the detailed state of the electrode plate of the secondary battery so that the performance of the secondary battery can be sufficiently exhibited.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an electrode plate inspection apparatus and an electrode plate that can more accurately and quickly inspect the detailed state of the electrode plate of the secondary battery. To provide an inspection method.

  An electrode plate inspection apparatus that solves the above-described problems is provided in an electrolyte solution in a container having an electrode plate holding portion that holds an electrode plate of a secondary battery in the electrolyte solution, and a measurement window that opens toward the electrode plate. A probe having a counter electrode, a measuring unit connected to the electrode plate and the counter electrode to measure a complex impedance between the electrode plate and the counter electrode, and a movement for moving the probe relative to the electrode plate And a fitting unit for fitting the complex impedance to a characteristic model of the electrode plate, the moving unit moves the probe to an adjacent measurement point on the electrode plate, and the measuring unit is configured to perform the measurement. The complex impedance is obtained for each point, and when the fitting unit fits the complex impedance at the measurement point to the characteristic model of the electrode plate, Adopting fitting result for the measurement points adjacent to the measurement point to the initial value given to characteristic model of the plate.

  An electrode plate inspection method that solves the above problems is a method of inspecting an electrode plate with an electrode plate inspection apparatus, and is directed to an electrode plate holding portion that holds an electrode plate of a secondary battery in an electrolyte, and to the electrode plate A probe having a counter electrode in an electrolyte in a container having a measurement window that is opened, and a measurement unit connected to the electrode plate and the counter electrode to measure a complex impedance between the electrode plate and the counter electrode And a moving unit that moves the probe relative to the electrode plate, and a fitting unit that fits the complex impedance to a characteristic model of the electrode plate. A step of moving the probe to an adjacent measurement point; a step of acquiring a complex impedance for each measurement point by the measurement unit; and a complex input of the measurement point to be measured by the fitting unit. When fitting the-impedance to the characteristic model of the electrode plate, and a step of employing a fitting result for the measurement point adjacent to the measurement point of the measurement to an initial value to be given to characteristic model of the electrode plate.

  According to such a configuration or method, fitting can be suitably performed. Since adjacent measurement points on the electrode plate are likely to have similar characteristics, the measurement points can be fitted in a short time using the fitting result of the adjacent measurement points. Therefore, the detailed state of the electrode plate of the secondary battery can be inspected more accurately and quickly.

  As a preferred configuration, the electrode plate of the secondary battery includes a film resistance component and a reaction resistance component in complex impedance, and the characteristic model of the electrode plate includes model parts corresponding to the coating resistance component and the reaction resistance component, respectively. And the fitting unit fits each of the covering resistance component and the reaction resistance component to the corresponding model portion.

According to such a configuration, fitting can be performed quickly even if a plurality of components are included in the characteristic model.
As a preferred configuration, the fitting unit sequentially performs fitting on the measurement points after the measurement unit measures a plurality of measurement points on the electrode plate.

According to such a configuration, complex impedance can be measured quickly. Also, fitting of the characteristic model can be performed as appropriate.
As a preferred configuration, the fitting unit includes three intersections of an intersection with a real axis, an intersection between a film resistance component and a reaction resistance component, and an intersection changing from a reaction resistance to a diffusion resistance in the Nyquist plot of the complex impedance. The characteristic model of the electrode plate is fitted based on the three intersections, and the three intersections indicated by the fitting results of the adjacent measurement points are set as initial values, and the three intersections which are the initial values are set. Specify from the neighborhood.

According to such a configuration, fitting can be performed quickly. In addition, the number of complex impedance measurements can be reduced.
As a preferred configuration, the characteristic model of the electrode plate is an equivalent circuit.

According to such a configuration, the fitting based on the equivalent circuit is quickly performed.
As a preferred configuration, the characteristic model of the electrode plate is a figure fitting model.

According to such a configuration, fitting based on a figure is quickly performed.
An electrode plate inspection apparatus that solves the above-described problems is provided in an electrolyte solution in a container having an electrode plate holding portion that holds an electrode plate of a secondary battery in the electrolyte solution, and a measurement window that opens toward the electrode plate. A probe having a counter electrode, a measuring unit connected to the electrode plate and the counter electrode to measure a complex impedance between the electrode plate and the counter electrode, and a movement for moving the probe relative to the electrode plate And a fitting unit for fitting the complex impedance to a characteristic model of the electrode plate, the moving unit moves the probe to an adjacent measurement point on the electrode plate, and the measuring unit is configured to perform the measurement. The complex impedance is obtained for each point, the characteristic model of the electrode plate is a figure fitting model, and the fitting unit is configured to calculate the complex impedance of the measurement point. When the figure is fitted to the characteristic model of the electrode plate, among the complex impedance Nyquist plot, the intersection with the real axis, the intersection between the film resistance component and the reaction resistance component, and the intersection changing from the reaction resistance to the diffusion resistance Figure fitting is performed based on the three intersections.

  According to such a configuration, calculation is performed by performing figure fitting based on three intersections: the intersection with the real axis, the intersection between the film resistance component and the reaction resistance component, and the intersection changing from the reaction resistance to the diffusion resistance. The figure is reduced and figure fitting can be performed quickly. In addition, the number of complex impedance measurements can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the detailed state of the electrode plate of a secondary battery can be test | inspected more accurately and rapidly.

The schematic of the structure about 1st Embodiment of an electrode plate test | inspection apparatus. The graph which shows an example of the fitting of the embodiment. The circuit diagram which shows the characteristic model of the electrode plate of the embodiment. It is a graph which shows the battery state of the electrode plate of the embodiment, Comprising: (a) The graph which shows a film resistance component, (b) The graph which shows a reaction resistance component. The flowchart which shows the procedure which test | inspects the electrode plate of the embodiment. The graph explaining the fitting start of the measurement point of the embodiment. The graph explaining the end of fitting of the measurement point of the embodiment. The graph explaining the fitting start time of the next measurement point of the embodiment. The graph explaining the end of fitting of the next measurement point of the embodiment. The graph which shows an example of a Nyquist plot about 2nd Embodiment of an electrode plate test | inspection apparatus. The graph explaining fitting of the figure model of the embodiment.

(First embodiment)
1st Embodiment of an electrode plate inspection apparatus and an electrode plate inspection method is described according to FIGS.

  The electrode plate inspection apparatus 20 shown in FIG. 1 measures the complex impedance of the electrode plate 100 of the secondary battery. In the present embodiment, the secondary battery is a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery. The secondary battery is a sealed battery having a rectangular parallelepiped shape, and a plurality of secondary batteries are connected by a bus bar to constitute an assembled battery. The assembled battery is mounted on an electric vehicle or a hybrid vehicle, and supplies power to an electric motor or the like.

  In complex impedance measurement, an alternating voltage (or alternating current) signal is input to an inspection object (here, an electrode plate) while changing the frequency, and the response current (or response voltage) at that time is measured. Then, the transfer function (impedance) of the electrode reaction is obtained by comparing the input sine wave with the response signal. For example, the frequency is changed from a high frequency of about 10 kHz to a low frequency of about 0.1 Hz, and the impedance is obtained from the response current (or response voltage) at each frequency. In general, since there is a difference in moving speed between ions and electrons, complex impedance measurement is performed using the difference in moving speed. Specifically, in the high-frequency region, electrons can move in response to changes in the direction of voltage, but ions have a slow reaction and cannot keep up. For this reason, it is possible to extract and measure only the components related to the movement of electrons from the system. Thereafter, as the frequency is further lowered, the movement of ions corresponds to a change in the direction of the AC voltage. Therefore, it is possible to measure components related to ion movement in addition to electron movement. The frequency characteristic of this complex impedance is represented in a Nyquist plot or the like, and the resistance value or the like of each component can be obtained by analyzing this.

  As shown in FIG. 2, for example, the impedance characteristics of the Nyquist plot can be divided into a plurality of regions corresponding to the measurement frequency band. Specifically, it has “region a” corresponding to the circuit resistance and “region b” corresponding to the solution resistance in response to the band changing from the high frequency side toward the low frequency side. The impedance characteristics correspond to a “film resistance region c” corresponding to the complex impedance caused by the film resistance, a “reaction resistance region d” corresponding to the complex impedance caused by the reaction resistance, and a substantially linear diffusion resistance. It has “region e”. Hereinafter, the complex impedance is simply referred to as impedance.

(Electrode plate 100)
The electrode plate 100 of the secondary battery will be described with reference to FIG.
The electrode plate 100 is a positive electrode plate or a negative electrode plate in which an electrode active material layer is formed on a current collector. The electrode plate 100 is formed so that the current collector 104 is exposed without the electrode active material layer 102 being provided (or removed) at the end.

(Positive electrode)
The positive electrode includes a positive electrode current collector and a positive electrode active material layer including a positive electrode active material formed on the positive electrode current collector. In such a positive electrode, a paste-like or slurry-like composition in which a positive electrode active material and a conductive material or a binder used as necessary are dispersed in an appropriate solvent is applied to a sheet-like positive electrode current collector. It can be produced by drying the composition. For the positive electrode current collector, a conductive member made of a metal having good conductivity (for example, aluminum, nickel, titanium, stainless steel, etc.) is used. As the solvent, any of an aqueous solvent and an organic solvent can be used. For example, N-methyl-2-pyrrolidone (NMP) can be used.

(Positive electrode active material)
As the positive electrode active material, one kind or two or more kinds of various materials that can be used as the positive electrode active material of the lithium ion secondary battery can be used. For example, a lithium transition metal compound such as a layered structure or a spinel structure containing lithium and at least one transition metal element as a constituent metal element, a polyanion type (for example, olivine type) lithium transition metal compound, or the like can be used.

Preferably, general formula: LiMn _2−p M _p O ₄ (wherein p is 0 ≦ p <2, typically 0 ≦ p ≦ 1 (eg 0.2 ≦ p ≦ 0.6)) And a lithium transition metal compound (oxide) typically having a spinel structure. When p is greater than 0, M can be any metallic or non-metallic element other than Mn. A composition in which M contains at least one transition metal element (for example, one or more selected from Ti, Cr, Fe, Co, Ni, Cu, and Zn) is preferable. Specific examples include LiNi _0.5 Mn _1.5 O ₄ and LiCrMnO ₄ .

(Conductive material)
A carbon material can be used as the conductive material. Specifically, for example, selected from carbon materials such as various carbon blacks (for example, acetylene black, ketjen black), coke, activated carbon, graphite, carbon fibers (PAN-based carbon fibers, pitch-based carbon fibers), and carbon nanotubes. Can be one or more. Among them, it is preferable to use carbon black (for example, acetylene black) having a relatively small particle size and a large specific surface area.

(Binder)
As the binder, a polymer that can be dissolved or dispersed in a solvent to be used can be used. For example, in a positive electrode mixture composition using an aqueous solvent, cellulose polymers such as carboxymethylcellulose (CMC, for example, sodium salt), hydroxypropylmethylcellulose (HPMC), polyvinyl alcohol (PVA), polytetrafluoroethylene (PTFE), etc. Fluorine-based resins such as styrene-butadiene rubber (SBR) can be employed. In the positive electrode mixture composition using a non-aqueous solvent, polyvinylidene fluoride (PVdF), polyvinylidene chloride (PVdC), or the like can be employed.

  50 mass% or more is suitable for the ratio of the positive electrode active material to the whole positive electrode active material layer, and it is preferable that it is normally 70 mass% or more and 95 mass% or less. In the case of using a conductive material, the ratio of the conductive material in the entire positive electrode active material layer can be, for example, 2% by mass or more and 20% by mass or less, and preferably 2% by mass or more and 15% by mass or less. . When using a binder, the ratio of the binder to the whole positive electrode active material layer can be, for example, 0.5% by mass or more and 10% by mass or less, and usually 1% by mass or more and 5% by mass or less is preferable. .

The mass of the positive electrode active material layer provided per unit area of the positive electrode current collector can be, for example, about 5 mg / cm ^{2 to} 40 mg / cm ² (preferably 10 mg / cm ^{2 to} 20 mg / cm ² ). . The density of the positive electrode active material layer can be, for example, about 1.5 g / cm ³ or more and 4 g / cm ³ or less (preferably 1.8 g / cm ³ or more and 3 g / cm ³ or less). The thickness of is, for example, 40 μm or more (preferably 50 μm or more) and can be 100 μm or less (preferably 80 μm or less).

(Negative electrode)
The negative electrode includes a negative electrode current collector and a negative electrode active material layer including at least a negative electrode active material formed on the negative electrode current collector. Such a negative electrode includes a paste-like or slurry-like composition (a dispersion for forming a negative electrode active material layer) in which a negative electrode active material and a binder (binder) used as necessary are dispersed in a suitable solvent. ) Is applied to a sheet-like negative electrode current collector, and the composition is dried to form a negative electrode active material layer (negative electrode active material layer). As the negative electrode current collector, a conductive material made of a metal having good conductivity (for example, copper, nickel, titanium, stainless steel, etc.) is used. Moreover, as said solvent, both an aqueous solvent and an organic solvent can be used, for example, water can be used.

(Negative electrode active material)
As the negative electrode active material, one type or two or more types of materials conventionally used in lithium ion secondary batteries can be used. For example, natural graphite (graphite), artificial graphite, hard carbon (non-graphitizable carbon), soft carbon (graphitizable carbon), carbon materials such as carbon nanotubes, silicon oxide, titanium oxide, vanadium oxide, iron oxide, cobalt oxide Nickel oxide, niobium oxide, tin oxide, lithium silicon composite oxide, lithium titanium composite oxide (Lithium Titanium Composite Oxide: LTO, for example, Li ₄ Ti ₅ O ₁₂ , LiTi ₂ O ₄ , Li ₂ Ti ₃ O ₇ ), Metal oxide materials such as lithium vanadium composite oxide, lithium manganese composite oxide, lithium tin composite oxide, metal nitride materials such as lithium nitride, lithium cobalt composite nitride, lithium nickel composite nitride, tin, silicon, aluminum , Zinc, lithium and other metals or metal alloys mainly composed of these metal elements Or the like can be used Ranaru metallic material.

  As the binder, an appropriate material can be selected from the polymer materials exemplified as the binder for the positive electrode active material layer. Specifically, styrene butadiene rubber (SBR), polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE) and the like are exemplified. In addition, various additives such as a dispersant and a conductive material can be used as appropriate.

  The proportion of the negative electrode active material in the entire negative electrode active material layer is suitably 50% by mass or more, preferably 90% by mass or more and 99% by mass or less, more preferably 95% by mass or more and 99% by mass or less. . When using a binder, the ratio of the binder to the whole negative electrode active material layer can be, for example, 1% by mass or more and 10% by mass or less, and usually 1% by mass or more and 5% by mass or less is appropriate. is there.

The mass of the negative electrode active material layer provided per unit area of the negative electrode current collector is, for example, about 5 mg / cm ^{2 to} 20 mg / cm ² (preferably 5 mg / cm ^{2 to} 10 mg / cm ² ). It is. The density of the negative electrode active material layer can be set to, for example, about 0.5 g / cm ³ or more and 2 g / cm ³ or less (typically 1 g / cm ³ or more and 1.5 g / cm ³ or less). The thickness of is, for example, 40 μm or more (typically 50 μm or more), and can be 100 μm or less (typically 80 μm or less).

(Electrode plate inspection device 20)
As shown in FIG. 1, the electrode plate inspection apparatus 20 includes a probe 11 applied to the measurement point Tg of the electrode plate 100, an impedance measurement unit 13 that measures the impedance of the measurement point Tg, and a control unit 14 that controls the measurement process. And a placement portion 12 on which the electrode plate 100 is placed.

(Probe 11)
The probe 11 includes a probe main body 112 and a measurement unit 118 connected to the cylindrical probe main body 112. The probe main body 112 has a predetermined electrolytic solution 116 in a cylinder and a counter electrode 114 disposed in the electrolytic solution and provided with an electrode lead. The probe 11 is manufactured by injecting the electrolytic solution 116 after accommodating the counter electrode 114 in the probe main body 112 from the opening provided at the upper end of the probe main body 112. The probe main body 112 has a cylindrical shape with an open upper end, and has a measurement unit 118 that acts on a part of the inspection target (electrode active material layer 102) via the electrolytic solution 116 at the lower end. The upper end (opening) of the probe main body 112 can be covered with a lid or the like. The probe 11 moves up and down in the vertical direction Z based on a signal from the control unit 14 and can be electrically connected to an inspection target (a part of the electrode active material layer 102) installed on the mounting unit 12. It is configured as follows.

  Examples of the material of the probe main body 112 and the lid include metal materials such as aluminum and steel, and resin materials such as polyethylene (PE), polypropylene (PP), polyphenylene sulfide, and polyimide. The shape of the probe main body 112 (outer shape of the container) can be, for example, a cylindrical shape, a rectangular parallelepiped shape, a cubic shape, and a shape obtained by processing and deforming them. For example, a needleless syringe made of polypropylene can be used.

(Counter electrode 114)
As the counter electrode 114, a carbon material, various metal materials, and the like can be used as long as they are stable in the electrolytic solution to be used in a voltage (or current) region that is input during impedance measurement. If the resistance to be inspected is relatively low, or if you want to separate and measure the reaction resistance more precisely, the counter electrode 114 has a low electrical resistivity (specific resistance) and a highly stable material in the measurement atmosphere (in the electrolyte) Is preferably used. For example, the above-described positive electrode or negative electrode active material layer forming material can be used as a counter electrode. The resistance derived from the counter electrode can be reduced by using the counter electrode 114 made of a positive electrode or a negative electrode. Therefore, the resistance of the electrode active material layer 102 to be inspected can be measured with higher accuracy. In addition, since the positive electrode and the negative electrode are stable in the electrolyte even when a relatively high voltage (for example, 100 mV to 1000 mV) is input, changes in the surface state, associated measurement errors, and variations in measurement values are unlikely to occur. .

  The area of the counter electrode 114 is preferably changed as appropriate according to the area of the measurement window which is the horizontal sectional area of the measurement unit 118. In general, since the magnitude of the resistance is inversely proportional to the measurement area, when it is desired to separate the resistance of only the inspection target (electrode active material layer 102), the area of the counter electrode 114 with respect to the working area of the measurement unit 118 (area of the measurement window) Needs to be secured more widely. In the present invention, the area of the counter electrode 114 is set to be 100 times or more (for example, 200 times or more, preferably 300 times or more, more preferably 500 times or more) wider than the working area of the measurement unit 118. As a result, the reaction resistance of the counter electrode 114 can be made negligibly small. For example, the resistance of the counter electrode 114 is set to 1/50 or less (preferably 1/100 or less) of the inspection target (measurement point Tg). Therefore, only the resistance (for example, film resistance, reaction resistance, or diffusion resistance) derived from the electrode active material layer 102 to be inspected can be accurately measured.

(Electrolytic solution 116)
As the electrolytic solution 116, a solution containing a supporting salt in a non-aqueous solvent (organic solvent) is typically used. As the non-aqueous solvent, for example, one or more organic solvents used in the electrolyte solution of the lithium ion secondary battery can be appropriately selected and used. Examples of preferable non-aqueous solvents include carbonates such as ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), vinylene carbonate (VC), and propylene carbonate (PC). . For example, a mixed solvent containing EC, DMC, and EMC at a volume ratio of 3: 4: 3 can be used.

As the supporting salt, for example, one or more lithium salts used as a supporting salt in a lithium ion secondary battery can be appropriately selected and used. Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiEBF ₆ , Li (CF ₃ SO ₂ ) ₂ N, LiCF ₃ SO _{3 and the} like. A preferred example is LiPF ₆ . The concentration of the supporting salt in the nonaqueous electrolytic solution may be adjusted to be in the range of, for example, 0.7 mol / L or more and 1.3 mol / L or less (for example, 1.0 mol / L or more and 1.2 mol / L or less). preferable.

(Measurement unit 118)
The measurement unit 118 is connected to the probe main body 112 and electrically connects the counter electrode 114 in the probe and the measurement point Tg of the electrode active material layer 102 via the electrolytic solution 116. The smaller the working area (cross-sectional area) of the measurement unit 118 (measurement end portion that can be in contact with the measurement point Tg of the electrode active material layer 102), the more the influence of the resistance component derived from the counter electrode can be suppressed. On the other hand, if it is too small, the obtained result may vary depending on the state of the electrode active material layer 102 at the measurement point Tg. Thus, the active area of the measuring portion 118, for ^example, preferably be a 0.01cm ² ~0.1cm 2 (especially 0.02cm ² ~0.05cm ^2), where is about 0.03 cm ^2. Although the shape of the measurement part 118 is not specifically limited, A circular shape is preferable. In the case of a circular shape, the diameter of the measurement unit 118 (measurement end portion that can be in contact with the measurement point Tg of the electrode active material layer 102) is, for example, Φ1 mm to Φ10 mm (preferably Φ2 mm to Φ5 mm), and here is about Φ2 mm. .

(Placement part 12)
The mounting unit 12 includes a mounting table 108 as an electrode plate holding unit on which the electrode plate 100 to be inspected is mounted, and a jig (for example, a clamp) for fixing the electrode plate 100. And based on the signal from the control part 14, it is comprised so that it can move to a horizontal direction (the direction of the arrow of the direction X of FIG. 1, and the direction Y) by the drive motor which is not shown in figure. In the present embodiment, the moving unit is configured by a drive motor.

  Moreover, the mounting part 12 is a container in which the mounting table 108 can hold the electrolytic solution 106, and the electrode plate 100 is placed in the electrolytic solution 106 to be held. In addition, the electrolyte solution 106 of the mounting part 12 is the same as the electrolyte solution 116 of the probe 11. Therefore, the measurement unit 118 is immersed in the electrolytic solution 106 of the mounting unit 12, whereby the electrolytic solution 106 of the mounting unit 12 and the electrolytic solution 116 of the probe 11 are connected, and the measurement point Tg of the electrode plate 100 is connected. The counter electrode 114 is electrically connected with the working area (measurement window area) defined by the measurement unit 118.

(Impedance measurement unit 13)
The impedance measuring unit 13 electrically connects the counter electrode 114 in the probe 11 and the measurement point Tg of the electrode active material layer 102. The impedance measuring unit 13 can employ, for example, an analog method such as a Lissajous method or an AC bridge method, or a digital method such as a digital Fourier integration method or a fast Fourier transform method using noise application. For example, as the impedance measuring unit 13, a potentio / galvanostat (PS / GS) capable of controlling current and voltage and a frequency response analyzer (FRA) incorporating a sine wave oscillation circuit are combined. Can be used. And based on the signal from the control part 14, an alternating current or alternating voltage is input between the probe 11 electrically connected, and the measurement point Tg, and an impedance is measured. The obtained impedance measurement result is sent to the control unit 14 as an output of the impedance measurement unit 13.

(Control unit 14)
The control unit 14 controls impedance measurement, probe 11 adjustment, and the like based on predetermined information. For example, position adjustment of the measurement point Tg to be inspected installed on the placement unit 12, driving of the probe 11, control of impedance measurement and the like (resistance calculation of the measurement point Tg based on the measured impedance) are performed. The configuration of the control unit 14 includes at least a ROM (Read Only Memory) storing a program for performing such control, a CPU (Central Processing Unit) capable of executing the program, and an input / output port. . A signal (output) from the probe 11, the impedance measurement unit 13, or the like is input to the control unit 14 via an input port. The control unit 14 outputs a drive signal to the probe 11, the impedance measurement unit 13, and the like via an output port.

  In the present embodiment, the electrode plate inspection apparatus 20 uses the resistance value measured by the impedance measuring unit 13 as a characteristic model of the electrode plate, and the film resistance component and the reaction resistance component at each measurement point Tg of the electrode active material layer 102. Further, a fitting part 141 for fitting is provided. A measurement result of the measured impedance is sent to the fitting unit 141 via the control unit 14 (as a resistance value calculated by the control unit). The fitting unit 141 fits the characteristic model of the electrode plate based on the sent resistance measurement result. For example, the characteristic model of the electrode plate is defined as an equivalent circuit 30 (see FIG. 3) and stored in advance in a storage medium (for example, ROM, HDD, optical recording medium, magnetic recording medium, magneto-optical recording medium, flash memory, etc.). Keep it. Also, initial values of the parameters of the electrode plate characteristic model are determined and stored in advance in a storage medium. Then, the initial value of each parameter of the characteristic model of the electrode plate is fitted to the measured impedance. Thereby, the film resistance component and the reaction resistance component at the measurement point Tg are represented by the characteristic model of the electrode plate. By representing the characteristic model of the electrode plate, it is possible to simulate the characteristic of the electrode plate at the measurement point Tg.

  As shown in FIG. 3, the equivalent circuit 30 as a characteristic model of the electrode plate includes a resistor R0, a parallel circuit of a resistor R1 and a capacitor C1, and a parallel circuit of a resistor R2 and a capacitor C2 connected in series. It is shown by a characteristic model consisting of a circuit. Here, the resistor R0 is a model corresponding to the circuit resistance and the solution resistance, the parallel circuit of the resistor R1 and the capacitor C1 is a model corresponding to the film resistance, and the parallel circuit of the resistor R2 and the capacitor C2 is This is a model corresponding to reaction resistance.

  In the present embodiment, the characteristic model of the electrode plate is fitted to the measured impedance for each measurement point Tg. At this time, if the initial value of each parameter of the characteristic model of the electrode plate is fitted to the measured impedance, many calculations are often required each time. If the difference between the measured value and the initial value is large, the fitting may end abnormally, and the initial value may be changed and the fitting may have to be performed again. Therefore, for the fitting of the measurement point Tg adjacent to the already fitted measurement point Tg, the parameters of the characteristic model of the electrode plate specified for the fitted measurement point Tg are adopted and reset as initial values. Fitting from the reset initial value. Also in the electrode active material layer 102, if the measurement points Tg are adjacent to each other, there is a high probability that each parameter of the characteristic model of the electrode plate is approximated. Therefore, by using the reset initial value, there is a high possibility that the calculation required for the fitting can be reduced compared to the fitting from the predetermined initial value, and between the initial value and the measured value. The divergence can be suppressed to a small level, and the possibility that the fitting may be malfunctioning can be reduced.

  A graph L3 in FIG. 4A is a graph showing the film resistances measured at the measurement points Tg aligned in the direction X in the electrode active material layer 102 in the order of the measurement points Tg. As shown in the graph L3, the value of the film resistance at each measurement point Tg varies in the direction X so that the maximum value is about twice the minimum value. That is, if fitting of each measurement point Tg is performed from a predetermined initial value, the amount of calculation corresponding to the magnitude of variation is required for fitting to the film resistance characteristic model. Further, when the difference between the initial value and the measured resistance value is excessively large, the fitting may be malfunctioning.

  On the other hand, when only two adjacent measurement points Tg in the direction X are compared, the difference in film resistance value between the two measurement points Tg is sufficiently small. In other words, if the fitting of each measurement point Tg is performed using the value of the adjacent measurement point Tg as an initial value, the measured resistance value having a small difference with respect to the initial value is fitted, so that the calculation required for the fitting is reduced. Will be able to. In addition, since the difference between the initial value and the measured resistance value can be kept small, the difference between the measured value and the value at the start of the fitting can be kept small, and the possibility that the fitting will be out of order is reduced.

  A graph L4 in FIG. 4B is a graph showing reaction resistances measured at the measurement points Tg arranged in a line in the direction X in the electrode active material layer 102 in the order of the measurement points Tg. As shown in the graph L4, the value of the reaction resistance at each measurement point Tg varies in the direction X so that the maximum value is about 1.5 times the minimum value. In other words, if the fitting of each measurement point Tg is performed from a predetermined initial value, the fitting for the reaction resistance characteristic model requires a calculation amount corresponding to the magnitude of variation. Further, when the difference between the initial value and the measured resistance value is excessively large, the fitting may be malfunctioning.

  On the other hand, when only two measurement points Tg adjacent in the direction X are compared, the difference in the value of the reaction resistance between the two measurement points Tg is sufficiently small. In other words, if the fitting of each measurement point Tg is performed using the value of the adjacent measurement point Tg as an initial value, the measured resistance value having a small difference with respect to the initial value is fitted, so that the calculation required for the fitting is reduced. Will be able to. In addition, since the difference between the initial value and the measured resistance value can be kept small, the difference between the measured value and the value at the start of the fitting can be kept small, and the possibility that the fitting will be out of order is reduced.

Thus, fitting to the characteristic model of the film resistance and fitting to the characteristic model of the reaction resistance can be suitably performed.
With reference to FIG. 5, the procedure of the fitting process for fitting the electrical characteristic of each measurement point Tg to the characteristic model of the electrode plate based on the measurement value of each measurement point Tg by the electrode plate inspection apparatus 20 will be described.

  The fitting process includes an initial value setting process (step S11), a moving process (step S12), an impedance measurement process (step S13), a fitting process (step S14), an initial value changing process (step S15), Whether or not there is a measurement point Tg is determined (step S16).

  In the initial value setting step (step S11), the equivalent circuit 30 is selected as a characteristic model of the electrode plate including the film resistance region c and the reaction resistance region d. In addition, predetermined initial values are set for the parameters of the equivalent circuit 30. Further, the moving order (scanning order) of the first measurement point Tg and the measurement point Tg on the electrode plate 100 is determined.

  In the moving step (step S12), the probe 11 is sequentially moved from the first measurement point Tg as a starting point to the measurement points Tg on the electrode plate 100 in a predetermined movement order. At each measurement point Tg that is a movement destination, the measurement unit 118 of the probe 11 is allowed to act on a part of the electrode active material layer 102 facing the measurement point Tg, and the counter electrode 114 and the electrode active material layer 102 in the probe are measured via the electrolytic solution 116. The point Tg is electrically connected. Specifically, the probe 11 is moved in the vertical direction Z, and the mounting portion 12 is moved in the horizontal direction, so that the probe 11 is pressed against the measurement point Tg. As a result, the measurement point Tg of the electrode active material layer 102 is locally electrically connected to the counter electrode 114 in the probe via the electrolytes 116 and 106. In this embodiment, the measurement is performed in a state where the electrode plate 100 including the electrode active material layer 102 is placed in a container of a mounting table 108 filled with the same electrolyte solution 106 as the electrolyte solution 116 in the probe 11. In order to stably perform the measurement, it is preferable to proceed to the next step after holding the position of the probe 11 for several seconds to several minutes.

  In the impedance measurement process (step S13), the control unit 14 measures the impedance by inputting an alternating current or an alternating voltage between the electrically connected counter electrode 114 and the measurement point Tg. A current cable and a voltage cable are connected to the lead of the counter electrode 114 and the portion of the electrode plate 100 where the current collector 104 is exposed, and an alternating current or an alternating voltage is input. Then, based on the signal from the control unit 14, the impedance is measured.

  The frequency region to be measured in the impedance measurement may be a range in which a target resistance value (for example, a film resistance value and a reaction resistance value) can be calculated. For example, 100 kHz or less and 0.01 Hz or more (for example, 10 kHz or less 0 .1 Hz or higher, for example, 1 kHz or lower and 0.1 Hz or higher).

  An AC voltage of 100 mV to 1000 mV (for example, 200 mV to 1000 mV, or, for example, 300 mV to 1000 mV) is input between the electrically connected counter electrode 114 and the measurement point Tg. In general, in the impedance measurement of a non-aqueous electrolyte secondary battery, a voltage of about 5 mV to 10 mV is often input. However, in this embodiment, since the area of the measurement point Tg of the electrode active material layer 102 is very narrow, the influence of other resistance components (for example, solution resistance components) is large. Therefore, for example, in order to detect a response current related to a film resistance or a reaction resistance, it is preferable to input a voltage having a larger amplitude than in the past. By setting the input voltage within the above range, measurement noise can be suppressed, and highly accurate measurement can be performed. For the same reason, when measuring using an alternating current, an alternating current of, for example, 50 μA or more and 500 μA or less (for example, 100 μA or more and 500 μA or less) is input between the electrically connected counter electrode 114 and the measurement point Tg. It is preferable to measure the impedance.

  In the fitting step (step S14), the control unit 14 calculates a resistance value at the measurement point Tg of the electrode active material layer 102 based on the impedance measurement result. The film resistance and reaction resistance at the measurement point Tg can be read from the graph L2 (see FIG. 2) of the Nyquist plot. The fitting unit 141 of the control unit 14 analyzes the shape of the Nyquist plot against the appropriately selected equivalent circuit 30 (curve fitting), thereby analyzing each parameter value (for example, resistance R0, R1, R2, capacitances C1, C2) are obtained. The fitting unit 141 performs, for example, curve fitting by the least square method or the like.

  The impedance can be measured, for example, by measuring the impedance when the AC frequency is changed from 10 kHz to 0.1 Hz, but the necessary data is obtained from the obtained data. It can be extracted and analyzed.

  The equivalent circuit 30 has an initial shape of the Nyquist plot by setting an initial value set in advance for each parameter, and this corresponds to the shape of the Nyquist plot obtained based on the impedance measurement result by curve fitting analysis. Parameters to be determined. At this time, if the deviation between the shape of the Nyquist plot based on the preset initial value and the shape of the Nyquist plot obtained based on the impedance measurement result is large, a long time is required for fitting. If the deviation is too large, fitting may end abnormally, and the initial value may be changed and fitting may have to be performed again.

  In the initial value changing step (step S15), the initial value of each parameter set in the equivalent circuit 30 is changed (reset). Specifically, the initial value set for each parameter is reset to the parameter obtained by fitting. For example, the fitting result for the first measurement point Tg is set to an initial value when fitting the next measurement point Tg. Similarly, the fitting result for the second and subsequent measurement points Tg is set as an initial value when fitting the next measurement point Tg.

  As a result, when fitting the second and subsequent measurement points Tg, each parameter becomes a value closer to the characteristics of the electrode plate 100 than the preset initial value, and the deviation between the initial value and the measured value is reduced. be able to. Therefore, the time required for fitting can be shortened. In addition, since the deviation is reduced, the possibility of fitting failure occurring when the deviation is too large is reduced, and re-execution of the fitting is suppressed.

  Also, if the distance between the previous measurement point Tg and the current measurement point Tg is short, the characteristics of these two measurement points Tg are similar, and the probability that the parameters of the equivalent circuit 30 are close values increases. Therefore, by moving the probe 11 so as to sequentially scan the adjacent measurement points Tg, the scanning time can be shortened, the time required for fitting can be further shortened, and the fitting accuracy can be maintained high.

  It is determined whether or not the next measurement point Tg is present on the electrode plate 100 (step S16). If it is determined that the next measurement point Tg is present (YES in step S16), the fitting process returns to step S12, the probe 11 is moved to the next measurement point Tg in step S12, and then step S13. To S15 are executed.

  That is, the probe 11 is continuously scanned in a predetermined pattern on the electrode active material layer 102 while maintaining the electrical connection between the measurement unit 118 of the probe 11 and the measurement point Tg of the electrode active material layer 102. Thus, the resistance distribution in the plane of the electrode active material layer 102 is measured. Alternatively, the measurement unit 118 of the probe 11 and the measurement point Tg of the electrode active material layer 102 are intermittently electrically connected, and the probe 11 is scanned in a predetermined pattern on the electrode active material layer 102, whereby the electrode active material The resistance distribution in the plane of the layer 102 is measured.

If it is determined that there is no next measurement point Tg (NO in step S16), the fitting process is terminated.
By measuring the in-plane resistance distribution of the electrode active material layer 102 as described above, the local resistance distribution can be grasped. For example, it can be used for grasping the formation state of an oxide film on the electrode after the aging treatment, or for analyzing the change (deterioration) in resistance of the electrode after the durability test. Further, for example, in the resistance distribution in the surface of the electrode active material layer 102, the electrode plate 100 can be determined as a non-defective product when the highest value or the lowest value of the resistance is within a predetermined reference value.

(Function)
As shown in FIG. 6, a Nyquist plot graph W11 of the first measurement point Tg is obtained. At this time, the equivalent circuit 30 has model curves FC11 and FC21 based on the initial values of the parameters.

  As shown in FIG. 7, the fitting unit 141 changes each parameter of the equivalent circuit 30 to fit the model curves FC11 and FC21 to the film resistance region c and the reaction resistance region d of the graph W11 of the Nyquist plot, respectively. Thereby, fitted model curves FC12 and FC22 are obtained. Then, the initial values of the parameters of the equivalent circuit 30 are reset to values corresponding to the fitted model curves FC12 and FC22.

  Subsequently, as shown in FIG. 8, the position of the probe 11 is moved from the first measurement point Tg to the next measurement point Tg, the impedance is measured, and the graph W12 of the Nyquist plot is obtained. At this time, the initial values of the parameters of the equivalent circuit 30 are reset to values corresponding to the model curves FC12 and FC22.

  Therefore, as shown in FIG. 9, the fitting unit 141 changes each parameter of the equivalent circuit 30, and fits the model curves FC12 and FC22 to the film resistance region c and the reaction resistance region d of the graph W12 of the Nyquist plot, respectively. Thereby, fitted model curves FC13 and FC23 are obtained. Then, the initial values of the parameters of the equivalent circuit 30 are reset to values corresponding to the fitted model curves FC13 and FC23. That is, compared with the initial value set in advance, each parameter of the equivalent circuit 30 can be made smaller in deviation from the shape of the Nyquist plot obtained based on the impedance measurement result, and the time required for fitting can be shortened. Will be able to.

As described above, according to the present embodiment, the following effects can be obtained.
(1) Since the fitting result of the adjacent measurement point Tg is reset to the initial value of the fitting, the fitting can be suitably performed. Since the measurement points Tg adjacent to each other in the electrode plate 100 are likely to have close characteristics, the measurement points Tg can be fitted in a short time using the fitting result of the adjacent measurement points Tg. Therefore, the detailed state of the electrode plate 100 of the secondary battery can be inspected more accurately and quickly.

  (2) Since the fitting unit 141 fits each of the covering resistance component and the reaction resistance component to the corresponding model part of the equivalent circuit 30, the fitting is performed quickly even if the characteristic model includes a plurality of components. It becomes like this.

(Second Embodiment)
With reference to FIG.10 and FIG.11, 2nd Embodiment of an electrode plate test | inspection apparatus and an electrode plate test | inspection method is described.

  The electrode plate inspection apparatus 20 according to the present embodiment is equivalent to the equivalent circuit in the first embodiment in that the figure models FC31 and FC41 shown in FIG. 11 are fitted to the graph L5 of the Nyquist plot shown in FIG. It is different from the point of fitting to 30. Hereinafter, differences will be mainly described, and detailed description of other configurations will be omitted.

  As shown in FIG. 10, the electrode plate inspection apparatus 20 includes an intersection A between the fitting part 141 and the real axis of the graph L2 of the Nyquist plot, and an inflection point B between the film resistance region c and the reaction resistance region d. Then, three inflection points C between the reaction resistance region d and the diffusion resistance region e are acquired. The inflection point B is an intersection between the film resistance region c and the reaction resistance region d, and the inflection point C is an intersection between the reaction resistance region d and the region e related to diffusion resistance. In figure fitting, these three points are characteristic models of the electrode plate, that is, parameters of the figure model. These three points can be obtained by at least one of the following methods.

  As a first method, it may be acquired based on a Nyquist plot created from a large number of acquired impedances. As a second method, a point selected from three frequency ranges in which the existence of three points is estimated. Alternatively, the third method may be points at three frequencies where the existence of three points is estimated. The three points acquired by these methods have high accuracy according to the first method, and the accuracy decreases in the order of the second method and the third method. On the other hand, the time required for acquisition is short according to the third method, and becomes longer in the order of the second method and the first method.

  As a fourth method, three points to be measured are specified from the vicinity of each frequency of these three points, with the three points indicated by the fitting results of adjacent measurement points Tg being measured as initial values. You may do it. According to this, three points can be specified accurately and quickly.

  As shown in FIG. 11, the electrode plate inspection apparatus 20 performs graphic fitting of the graphic models FC31 and FC41 by the fitting unit 141. The electrode plate inspection apparatus 20 includes graphic models FC31 and FC41 having a film resistance region c and a reaction resistance region d. Therefore, the graphic models FC31 and FC41 also have points corresponding to the intersection A, the inflection point B, and the inflection point C. The electrode plate inspection apparatus 20 deforms the graphic model so that the three points of the graphic model coincide with the three points obtained from the graph L5 of the Nyquist plot.

  Here, for example, the figure model is deformed so that the size of the semicircle of the figure model FC31 matches the intersection A and the inflection point B, and the size of the semicircle of the figure model FC41 is inflection point B and the inflection point. The figure model is deformed so as to match the point C. As a result, the characteristics of the measurement point Tg having the film resistance region c and the reaction resistance region d can be acquired very quickly although the accuracy is not so high.

As described above, according to this embodiment, in addition to the effect (1) described in the first embodiment, the following effects can be obtained.
(3) Since the number of intersections used for fitting is three, fitting can be performed quickly. In addition, the number of impedance measurements can be reduced.

(4) By specifying the intersection A, the inflection point B, and the inflection point C from the vicinity indicated by the fitting result of the adjacent measurement point Tg, the fitting can be performed quickly.
(5) Since only three points are matched, fitting based on a figure is performed quickly.

(Other embodiments)
In addition, each said embodiment can also be implemented with the following aspects.
In the second embodiment, the case of performing figure fitting based on three points has been illustrated. However, the present invention is not limited to this. If fitting is possible with a relatively small number of three points or more than three points. The fitting may be performed on the equivalent circuit, or other fittings may be performed.

  In the first embodiment, the case where the fitting is performed on the equivalent circuit has been illustrated. However, the present invention is not limited to this, and the figure fitting may be performed or other fittings may be performed.

  In the second embodiment, the case where the sizes of the semicircles of the graphic models FC31 and FC41 are adjusted to the three points obtained from the Nyquist plot graph L5 is exemplified. However, the present invention is not limited to this, and four or more points may be obtained from the Nyquist plot graph, and the sizes of the semicircles of the graphic models FC31 and FC41 may be matched to the obtained four or more points.

  In each of the above embodiments, the case where the impedance of the measurement point Tg is fitted each time it is measured is illustrated. However, the present invention is not limited thereto, and the fitting may be performed after measuring the impedance of all or a plurality of measurement points. Good. As a result, the work can be performed separately for only the measurement process and the fitting process.

  In each of the above embodiments, the case where the electrode plate 100 is installed in a container filled with the electrolytic solution 106 is illustrated. However, the measurement is not limited thereto, and the measurement may be performed using an electrode plate in which the electrode active material layer is sufficiently impregnated with an electrolyte solution in advance. Alternatively, since the electrode active material layer to be inspected is porous and has a minute gap between the electrode active material and the conductive material particles, the probe including the electrolytic solution is connected to the electrode active material layer. By contact, the electrolytic solution may be immersed in a minute gap in the electrode active material layer.

  In each of the above embodiments, the case where the secondary battery is a lithium ion secondary battery has been illustrated, but the present invention is not limited thereto, and the secondary battery may be another nonaqueous electrolyte secondary battery, An alkaline secondary battery such as a nickel hydride secondary battery or a nickel cadmium secondary battery may be used.

  -The secondary battery may not be mounted on an electric vehicle or a hybrid vehicle. For example, the secondary battery may be mounted on a vehicle such as a gasoline vehicle or a diesel vehicle. In addition, the secondary battery may be used as a power source for a moving body such as a railway, a ship, and an aircraft, a robot, and an electrical product such as an information processing apparatus.

  DESCRIPTION OF SYMBOLS 11 ... Probe, 12 ... Mounting part, 13 ... Impedance measuring part, 14 ... Control part, 20 ... Electrode plate inspection apparatus, 30 ... Equivalent circuit, 100 ... Electrode plate, 102 ... Electrode active material layer, 104 ... Current collector DESCRIPTION OF SYMBOLS 106 ... Electrolyte solution 108 ... Mounting stand 112 ... Probe body 114 ... Counter electrode 116 ... Electrolyte solution 118 ... Measuring part 141 ... Fitting part C1, C2 ... Capacity | capacitance, R0, R1, R2 ... Resistance.

Claims (8)

An electrode plate holding part for holding the electrode plate of the secondary battery in the electrolyte solution;
A probe having a counter electrode in the electrolyte in a container having a measurement window opened toward the electrode plate;
A measuring unit connected to the electrode plate and the counter electrode to measure a complex impedance between the electrode plate and the counter electrode;
A moving unit for moving the probe relative to the electrode plate;
A fitting section for fitting the complex impedance to a characteristic model of the electrode plate,
The moving unit moves the probe to an adjacent measurement point on the electrode plate,
The measurement unit acquires the complex impedance for each measurement point,
The fitting unit adopts a fitting result for a measurement point adjacent to the measurement point as an initial value given to the characteristic model of the electrode plate when fitting the complex impedance of the measurement point to the characteristic model of the electrode plate. Inspection device. The electrode plate of the secondary battery includes a film resistance component and a reaction resistance component in complex impedance,
The characteristic model of the electrode plate has a model portion corresponding to a covering resistance component and a reaction resistance component,
The electrode plate inspection apparatus according to claim 1, wherein the fitting unit fits each of a covering resistance component and a reaction resistance component to a corresponding model portion. The electrode plate inspection apparatus according to claim 1, wherein the fitting unit sequentially performs fitting on the measurement points after the measurement unit measures a plurality of measurement points on the electrode plate. The fitting unit is based on three intersections of an intersection with a real axis, an intersection between a film resistance component and a reaction resistance component, and an intersection changing from a reaction resistance to a diffusion resistance in the Nyquist plot of the complex impedance. Fits the characteristic model of the electrode plate, and identifies the three intersections from the vicinity of the three intersections, which are the initial values, with the three intersections indicated by the fitting results of the adjacent measurement points as initial values. The electrode plate inspection apparatus according to any one of claims 1 to 3. The electrode plate inspection apparatus according to claim 1, wherein the characteristic model of the electrode plate is an equivalent circuit. The electrode plate inspection apparatus according to claim 1, wherein the characteristic model of the electrode plate is a figure fitting model. An electrode plate holding part for holding the electrode plate of the secondary battery in the electrolyte solution;
A probe having a counter electrode in the electrolyte in a container having a measurement window opened toward the electrode plate;
A measuring unit connected to the electrode plate and the counter electrode to measure a complex impedance between the electrode plate and the counter electrode;
A moving unit for moving the probe relative to the electrode plate;
A fitting section for fitting the complex impedance to a characteristic model of the electrode plate,
The moving unit moves the probe to an adjacent measurement point on the electrode plate,
The measurement unit acquires the complex impedance for each measurement point,
The characteristic model of the electrode plate is a figure fitting model,
The fitting unit is configured to graphically fit the complex impedance of the measurement point to the characteristic model of the electrode plate, among the Nyquist plot of the complex impedance, the intersection with the real axis, the intersection of the film resistance component and the reaction resistance component, And an electrode plate inspection device that performs figure fitting based on three intersections with the intersection changing from reaction resistance to diffusion resistance. A method for inspecting an electrode plate with an electrode plate inspection device,
An electrode plate holding section for holding the electrode plate of the secondary battery in the electrolyte; a probe having a counter electrode in the electrolyte in a container having a measurement window opened toward the electrode plate; and the electrode plate. A measuring unit connected to the counter electrode and measuring a complex impedance between the electrode plate and the counter electrode; a moving unit for moving the probe relative to the electrode plate; and the complex impedance of the electrode plate Applying to an electrode plate inspection device equipped with a fitting part for fitting to a characteristic model,
The moving unit moving the probe to an adjacent measurement point;
The measurement unit obtaining a complex impedance for each measurement point; and
When the fitting unit fits the complex impedance of the measurement point to be measured to the characteristic model of the electrode plate, an initial value given to the characteristic model of the electrode plate is a fitting result for a measurement point adjacent to the measurement point to be measured. An electrode plate inspection method comprising the steps of adopting.

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