Method for manufacturing non-aqueous secondary battery, inspection device for non-aqueous secondary battery, and inspection method for non-aqueous secondary battery

Abstract

To provide a non-aqueous secondary battery manufacturing method, a non-aqueous secondary battery testing device, and a non-aqueous secondary battery testing method that make it possible to determine whether a non-aqueous secondary battery is normal or not according to the reduction reaction of a negative electrode mixture layer during a charging process.SOLUTION: In a determination step, the measured specific surface area of a negative electrode active material is obtained on the basis of the result measured from a negative electrode plate, and the amount of charge Q and voltage V of the non-aqueous secondary battery are obtained at predetermined intervals while the non-aqueous secondary battery is being charged, and in a Q-V curve that shows the value of a voltage V with respect to the amount of charge Q, the specific value of the amount of charge Q that maximizes the amount of decrease in the slope is calculated, and it is determined whether the non-aqueous secondary battery is normal on the basis of the measured specific surface area of the negative electrode active material and the specific value of the amount of charge Q.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a non-aqueous secondary battery, an inspection device for a non-aqueous secondary battery, and a method for inspecting a non-aqueous secondary battery. [Background technology]

[0002] Electric vehicles and hybrid vehicles use lithium ion secondary batteries, an example of nonaqueous secondary batteries, as their power source. A lithium ion secondary battery includes an electrode assembly having a positive electrode plate and a negative electrode plate. The negative electrode plate of a lithium ion secondary battery includes a negative electrode substrate, which is a metal plate such as a copper plate, and a negative electrode mixture layer formed on the negative electrode substrate. The negative electrode mixture layer includes a negative electrode active material, which is a material capable of absorbing and releasing lithium ions. Examples of the negative electrode active material include carbon materials such as graphite, non-graphitizable carbon, and easily graphitizable carbon.

[0003] The effective specific surface area (surface area per unit weight) of the negative electrode active material in the negative electrode plate affects various performance characteristics of the lithium-ion secondary battery, such as the life characteristics and discharge characteristics. For example, Patent Document 1 discloses a technology for achieving good discharge characteristics by defining the effective specific surface area of ​​the negative electrode active material in the negative electrode plate within a predetermined range. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-11604 Summary of the Invention [Problem to be solved by the invention]

[0005] However, with such technology, even if the effective specific surface area of ​​the negative electrode active material in the negative electrode plate is set within a predetermined range during the electrode plate manufacturing process, an unexpected SEI coating may be formed in the negative electrode mixture layer depending on the reduction reaction of the negative electrode mixture layer during the charging process. Therefore, there is a need for a means for determining whether a manufactured lithium-ion secondary battery is normal or not, based on the reduction reaction of the negative electrode mixture layer, at the manufacturing site. [Means for solving the problem]

[0006] A method for manufacturing a non-aqueous secondary battery that solves the above-mentioned problems includes: a plate manufacturing step of manufacturing a negative electrode plate having a negative electrode mixture layer containing a negative electrode active material, and a positive electrode plate; an assembly step of assembling a non-aqueous secondary battery using the negative electrode plate, the positive electrode plate, and an electrolyte; a charging step of charging the non-aqueous secondary battery; and a determination step of determining whether the non-aqueous secondary battery is normal. The determination step includes obtaining a measured specific surface area of ​​the negative electrode active material based on a result of measurement of the negative electrode plate manufactured in the plate manufacturing step; obtaining a charging quantity of electricity Q and a voltage V of the non-aqueous secondary battery at predetermined time intervals while the non-aqueous secondary battery is being charged in the charging step; calculating a specific value of the charging quantity of electricity Q that maximizes the decrease in slope of a Q-V curve that shows the voltage V versus the charging quantity of electricity Q; and determining whether the non-aqueous secondary battery is normal based on the measured specific surface area of ​​the negative electrode active material and the specific value of the charging quantity of electricity Q.

[0007] According to the above manufacturing method, in the first period of the charging process, the increase in voltage V is large relative to the increase in the quantity of charge electricity Q, and the QV curve shows a steep rise. As the charging process progresses and the quantity of charge electricity Q reaches a specific value in the second period, the increase in voltage V relative to the increase in the quantity of charge electricity Q becomes more gradual, and the slope of the QV curve decreases significantly. Therefore, in the determination process, the value of the quantity of charge electricity Q at the boundary between the first and second periods is calculated as a specific value. Furthermore, during the charging process, a portion of the quantity of charge electricity Q is consumed to form an SEI film on the negative electrode mixture layer. The amount of the SEI film formed on the negative electrode mixture layer has a positive correlation with the effective specific surface area of ​​the negative electrode active material in the negative electrode plate. Note that the effective specific surface area of ​​the negative electrode active material in the negative electrode plate does not refer to the effective specific surface area of ​​the negative electrode active material in the raw material state, but rather to the effective specific surface area of ​​the negative electrode active material in the state manufactured as a negative electrode plate. Therefore, the formation of an SEI film on the negative electrode mixture layer during charging changes the rise of the QV curve and the specific value in the first period depending on the effective specific surface area of ​​the negative electrode active material in the negative electrode plate. In addition, during the charging process, depending on the reduction reaction of the negative electrode mixture layer, an unexpected SEI film may be formed in the negative electrode mixture layer, resulting in an unexpected increase in the amount of SEI film formed on the negative electrode mixture layer. Therefore, the rise of the QV curve and the specific value in the first period also change. Therefore, by obtaining the measured specific surface area of ​​the negative electrode active material from the negative electrode plate manufactured in the electrode plate manufacturing process and calculating the specific value in the charging process, it is possible to determine whether a non-aqueous secondary battery is normal or not depending on the reduction reaction of the negative electrode mixture layer during the charging process. Furthermore, by determining whether a non-aqueous secondary battery is normal or not from the QV curve in the charging process, it is possible to determine the normality of all non-aqueous secondary batteries in the non-aqueous secondary battery manufacturing process.

[0008] In the above-described manufacturing method, it is preferable that the determining step determines whether or not the nonaqueous secondary battery is normal by determining whether or not an unexpected SEI coating has been formed in the negative electrode mixture layer in the charging step, based on the measured specific surface area of ​​the negative electrode active material and the specific value of the charged quantity of electricity Q.

[0009] In the above manufacturing method, it is preferable that the determination step calculates an appropriate range for the specific value of the charging quantity of electricity Q based on the measured specific surface area of ​​the negative electrode active material, and determines that the nonaqueous secondary battery is normal when the specific value of the charging quantity of electricity Q is within the appropriate range, and determines that the nonaqueous secondary battery is abnormal when the specific value of the charging quantity of electricity Q is outside the appropriate range.

[0010] In the above manufacturing method, it is preferable that the determining step calculates an appropriate range for the effective specific surface area of ​​the negative electrode active material in the negative electrode plate based on the measured specific surface area of ​​the negative electrode active material, estimates the effective specific surface area of ​​the negative electrode active material in the negative electrode plate based on the specific value of the charged quantity of electricity Q, and determines that the nonaqueous secondary battery is normal if the effective specific surface area of ​​the negative electrode active material in the negative electrode plate is within the appropriate range, and determines that the nonaqueous secondary battery is abnormal if the effective specific surface area of ​​the negative electrode active material in the negative electrode plate is outside the appropriate range.

[0011] In the above manufacturing method, the determining step preferably acquires a measured specific surface area of ​​the negative electrode active material based on a measurement result from some of the negative electrode plates manufactured in the same lot in the electrode plate manufacturing step, and determines whether the nonaqueous secondary battery is normal for the plurality of negative electrode plates manufactured in the same lot in the electrode plate manufacturing step based on the measured specific surface area of ​​the negative electrode active material and the specific value of the charged quantity of electricity Q. According to the above manufacturing method, the measured specific surface area of ​​the negative electrode active material is acquired based on a measurement result from some of the negative electrode plates manufactured in the same lot. This makes it possible to determine whether the nonaqueous secondary battery is normal for the plurality of negative electrode plates manufactured in the same lot, depending on the reduction reaction of the negative electrode mixture layer in the charging step.

[0012] In the above manufacturing method, the specific value of the charge electricity Q is calculated by second-order differentiation of the QV curve with respect to the charge electricity Q. 2 V / dQ 2 The value of Qd 2 V / dQ 2 In the curve, the Qd 2 V / dQ 2 It is preferable that the specific value is calculated as the value of the charged quantity of electricity Q at which a peak appears on the curve. 2 V / dQ 2 By using the curve, it is possible to easily determine whether the nonaqueous secondary battery is normal or not depending on the reduction reaction of the negative electrode mixture layer during the charging process.

[0013] A non-aqueous secondary battery inspection device for solving the above problems is an inspection device for a non-aqueous secondary battery including a negative electrode plate having a negative electrode mixture layer containing a negative electrode active material, a positive electrode plate, and an electrolyte, and includes: a first acquisition unit that acquires a measured specific surface area of ​​the negative electrode active material based on a result of measurement from the negative electrode plate; a second acquisition unit that acquires a charging quantity of electricity Q and a voltage V of the non-aqueous secondary battery at predetermined time intervals while the non-aqueous secondary battery is being charged; and a control unit that executes a first process that calculates a specific value of the charging quantity of electricity Q that maximizes the decrease in slope of a Q-V curve showing the voltage V versus the charging quantity of electricity Q; and a second process that determines whether the non-aqueous secondary battery is normal based on the measured specific surface area of ​​the negative electrode active material and the specific value of the charging quantity of electricity Q.

[0014] A method for testing a non-aqueous secondary battery that solves the above-described problems is a method for testing a non-aqueous secondary battery that includes a negative electrode plate having a negative electrode mixture layer containing a negative electrode active material, a positive electrode plate, and an electrolyte, and includes the steps of: obtaining a measured specific surface area of ​​the negative electrode active material based on a result of measurement of the negative electrode plate; obtaining a charging quantity of electricity Q and a voltage V of the non-aqueous secondary battery at predetermined time intervals while the non-aqueous secondary battery is being charged; calculating a specific value of the charging quantity of electricity Q that maximizes the decrease in slope of a QV curve showing the voltage V versus the charging quantity of electricity Q; and determining whether the non-aqueous secondary battery is normal based on the measured specific surface area of ​​the negative electrode active material and the specific value of the charging quantity of electricity Q. [Effects of the Invention]

[0015] According to the present invention, it is possible to determine whether or not a nonaqueous secondary battery is normal depending on the reduction reaction of the negative electrode mixture layer during the charging process. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a nonaqueous secondary battery inspection system. [Figure 2] FIG. 2 is a partially developed view of the electrode assembly. [Figure 3] FIG. 3 is a cross-sectional view of the electrode assembly in an expanded state. [Figure 4] FIG. 4 is a block diagram showing the configuration of the inspection device. [Figure 5] FIG. 5 is a diagram showing the correspondence relationship between the charged quantity of electricity Q, voltage V, and d2V / dQ2 of a lithium ion secondary battery in the charging process. [Figure 6] FIG. 6 is a diagram showing the behavior of the QV curve when the effective specific surface area of ​​the negative electrode active material in the negative electrode plate is different. [Figure 7] FIG. 7 is a flowchart showing a method for manufacturing a lithium ion secondary battery. [Figure 8] FIG. 8 is a flowchart showing the processing of the determination step. [Figure 9] FIG. 9 is a diagram showing the relationship between the effective specific surface area of ​​the negative electrode active material in the negative electrode plate and a specific value. [Figure 10] FIG. 10 is a flowchart showing the processing of the determination step. DETAILED DESCRIPTION OF THE INVENTION

[0017] [First embodiment] Hereinafter, one embodiment of the present invention will be described with reference to FIGS. [Non-aqueous secondary battery inspection system] 1, a non-aqueous secondary battery inspection system 1 charges a non-aqueous secondary battery during the manufacturing process of the non-aqueous secondary battery and determines whether the non-aqueous secondary battery is normal. The non-aqueous secondary battery inspection system 1 includes a lithium ion secondary battery 10, a charging device 30, and an inspection device 40.

[0018] The lithium ion secondary battery 10 is an example of a non-aqueous secondary battery. A charging device 30 is connected to the lithium ion secondary battery 10. The lithium ion secondary battery 10 is charged by receiving power from the charging device 30. An inspection device 40 determines whether the lithium ion secondary battery 10 is good or bad based on the behavior of the charged quantity of electricity Q and the voltage V of the lithium ion secondary battery 10 during charging.

[0019] [Lithium-ion secondary battery] The lithium-ion secondary battery 10 is a cell battery that is combined with a plurality of lithium-ion secondary batteries 10 and sealed in a resin or metal case to form a battery pack. The battery pack is used in hybrid vehicles and electric vehicles.

[0020] The lithium-ion secondary battery 10 includes a battery case 11 and a lid 12. The battery case 11 has a rectangular parallelepiped shape with an opening on the upper side. The lid 12 seals the opening of the battery case 11. The battery case 11 and the lid 12 are made of a metal such as aluminum or an aluminum alloy. The lithium-ion secondary battery 10 forms a sealed battery container by attaching the lid 12 to the battery case 11.

[0021] Two external terminals 13A and 13B are provided on the lid 12. The external terminals 13A and 13B are used for charging and discharging power. In the nonaqueous secondary battery inspection system 1, the external terminals 13A and 13B are electrically connected to a charging device 30 and an inspection device 40.

[0022] The lithium ion secondary battery 10 includes an electrode assembly 20. The electrode assembly 20 is housed inside a battery case 11. The electrode assembly 20 includes a positive electrode side current collector 20A and a negative electrode side current collector 20B. The positive electrode side current collector 20A is the positive electrode side end of the electrode assembly 20. The negative electrode side current collector 20B is the negative electrode side end of the electrode assembly 20. The positive electrode side current collector 20A is electrically connected to a positive electrode external terminal 13A via a positive electrode side current collector 14A. The negative electrode side current collector 20B is electrically connected to a negative electrode external terminal 13B via a negative electrode side current collector 14B.

[0023] The lithium ion secondary battery 10 includes a non-aqueous electrolyte solution 15. The non-aqueous electrolyte solution 15 is poured into the battery case 11 through a pouring hole (not shown). [Electrode body] As shown in Fig. 2, the electrode assembly 20 is a flat wound body formed by winding a laminate in which a long positive electrode plate 21 and a negative electrode plate 24 are stacked with a separator 27 interposed therebetween. Thus, the lithium-ion secondary battery 10 includes the negative electrode plate 24, the positive electrode plate 21, and the separator 27. The positive electrode plate 21, the negative electrode plate 24, and the separator 27 are stacked so that their respective longitudinal directions coincide with each other. In the laminate before winding, the positive electrode plate 21, the separator 27, the negative electrode plate 24, and the separator 27 are stacked in this order in the thickness direction.

[0024] [Positive electrode] As shown in Fig. 3, the positive electrode plate 21 includes a positive electrode substrate 22 and a positive electrode mixture layer 23. The positive electrode substrate 22 is a foil-like electrode substrate formed in a long shape. The positive electrode mixture layer 23 is provided on each of two opposing surfaces of the positive electrode substrate 22. The positive electrode substrate 22 includes, at one end in the width direction, a positive electrode-side exposed portion 22A where the positive electrode mixture layer 23 is not formed and the positive electrode substrate 22 is exposed.

[0025] A metal foil made of aluminum or an alloy mainly composed of aluminum is used for the positive electrode substrate 22. The positive electrode substrate 22 functions as a current collector for the positive electrode. When the positive electrode substrate 22 is wound, the opposing surfaces of the positive electrode side exposed portion 22A are pressed against each other to form the positive electrode side current collecting portion 20A.

[0026] The positive electrode mixture layer 23 is a hardened product of a liquid positive electrode mixture paste. The positive electrode mixture paste includes a positive electrode active material, a positive electrode solvent, a positive electrode conductive material, and a positive electrode binder. The positive electrode mixture layer 23 is formed by drying the positive electrode mixture paste and evaporating the positive electrode solvent. Therefore, the positive electrode mixture layer 23 includes a positive electrode active material, a positive electrode conductive material, and a positive electrode binder.

[0027] The positive electrode active material is a lithium-containing composite metal oxide capable of absorbing and releasing lithium ions, which are charge carriers in the lithium-ion secondary battery 10. The lithium-containing composite oxide is an oxide containing lithium and a metal element other than lithium. The metal element other than lithium is at least one selected from the group consisting of, for example, nickel, cobalt, manganese, vanadium, magnesium, molybdenum, niobium, titanium, tungsten, aluminum, and iron contained in the lithium-containing composite oxide as iron phosphate.

[0028] For example, the lithium-containing composite oxide is lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or lithium manganese oxide (LiMn2O4). For example, the lithium-containing composite oxide is a ternary lithium-containing composite oxide containing nickel, cobalt, and manganese, such as lithium nickel cobalt manganese oxide (LiNiCoMnO2). For example, the lithium-containing composite oxide is lithium iron phosphate (LiFePO4).

[0029] The positive electrode solvent is an NMP (N-methyl-2-pyrrolidone) solution, which is an example of an organic solvent. The positive electrode conductive material may be, for example, carbon black such as acetylene black or ketjen black, carbon fiber such as carbon nanotube or carbon nanofiber, or graphite. The positive electrode binder is an example of a resin component contained in the positive electrode mixture paste. Examples of the positive electrode binder include polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), and styrene butadiene rubber (SBR).

[0030] The positive electrode plate 21 may have an insulating layer at the boundary between the positive electrode exposed portion 22A and the positive electrode mixture layer 23. The insulating layer contains an inorganic component having insulating properties and a resin component that functions as a binder. The inorganic component is at least one selected from the group consisting of powdered boehmite, titania, and alumina. The resin component is at least one selected from the group consisting of PVDF, PVA, and acrylic.

[0031] [Negative electrode] The negative electrode plate 24 includes a negative electrode substrate 25 and a negative electrode mixture layer 26. The negative electrode substrate 25 is a foil-like electrode substrate formed in a long shape. The negative electrode mixture layer 26 is provided on each of two opposing surfaces of the negative electrode substrate 25. The negative electrode substrate 25 includes a negative electrode side exposed portion 25A at one end in the width direction, opposite the positive electrode side exposed portion 22A, where the negative electrode mixture layer 26 is not formed and the negative electrode substrate 25 is exposed.

[0032] A metal foil made of copper or an alloy mainly composed of copper is used for the negative electrode substrate 25. The negative electrode substrate 25 functions as a current collector for the negative electrode. When the negative electrode exposed portion 25A is wound, opposing surfaces of the negative electrode exposed portion 25A are pressed against each other to form the negative electrode current collecting portion 20B.

[0033] The negative electrode mixture layer 26 is a hardened product of a liquid negative electrode mixture paste. The negative electrode mixture paste includes a negative electrode active material, a negative electrode solvent, a negative electrode dispersant, and a negative electrode binder. The negative electrode mixture layer 26 is formed by drying the negative electrode mixture paste and evaporating the negative electrode solvent. Therefore, the negative electrode mixture layer 26 includes a negative electrode active material, a negative electrode dispersant, and a negative electrode binder. The negative electrode mixture layer 26 may further include an additive such as a conductive material.

[0034] The negative electrode active material is a material capable of absorbing and releasing lithium ions. Examples of the negative electrode active material include carbon materials such as graphite, non-graphitizable carbon, easily graphitizable carbon, and carbon nanotubes. One example of the negative electrode solvent is water. One example of the negative electrode dispersant is carboxymethyl cellulose (CMC). One example of the negative electrode binder is the same as the positive electrode binder. One example of the negative electrode binder is SBR.

[0035] [Separator] The separator 27 prevents contact between the positive electrode plate 21 and the negative electrode plate 24, and also holds the nonaqueous electrolyte 15 between the positive electrode plate 21 and the negative electrode plate 24. When the electrode body 20 is immersed in the nonaqueous electrolyte 15, the nonaqueous electrolyte 15 permeates from the ends of the separator 27 toward the center.

[0036] The separator 27 is a nonwoven fabric made of polypropylene, etc. Examples of the separator 27 that can be used include porous polymer membranes such as porous polyethylene membranes, porous polyolefin membranes, and porous polyvinyl chloride membranes, and ion-conductive polymer electrolyte membranes.

[0037] [Nonaqueous electrolyte] The nonaqueous electrolyte 15 is a composition in which a supporting salt is contained in a nonaqueous solvent. The nonaqueous solvent may be one or more materials selected from the group consisting of propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, etc. The supporting salt may be one or more lithium compounds (lithium salts) selected from LiPF6, LiBF4, LiClO4, LiAsF6, LiCF3SO3, LiC4F9SO3, LiN(CF3SO2)2, LiC(CF3SO2)3, LiI, etc.

[0038] In this embodiment, a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate is used as the nonaqueous solvent. Lithium bis(oxalato)borate (LiBOB) is added as a lithium salt to the nonaqueous electrolyte solution 15. For example, LiBOB is added to the nonaqueous electrolyte solution 15 so that the concentration of LiBOB in the nonaqueous electrolyte solution 15 is 0.001 to 0.1 mol / L.

[0039] [Inspection equipment] 4, the inspection device 40 includes a control unit 41, a memory unit 42, a specific surface area acquisition unit 43, a charged electricity amount acquisition unit 44, and a voltage acquisition unit 45. The control unit 41 is, for example, a CPU that controls the overall operation of the inspection device 40. The memory unit 42 includes, for example, a RAM that temporarily stores data, and a non-volatile memory such as an HDD or flash memory.

[0040] The specific surface area acquisition unit 43 acquires the effective specific surface area of ​​the negative electrode active material in the negative electrode plate 24 as the measured specific surface area of ​​the negative electrode active material based on the measurement results from the negative electrode plate 24. Note that the effective specific surface area of ​​the negative electrode active material in the negative electrode plate 24 does not refer to the effective specific surface area of ​​the negative electrode active material in a raw material state, but rather to the effective specific surface area of ​​the negative electrode active material in a state manufactured as the negative electrode plate 24. Hereinafter, the effective specific surface area of ​​the negative electrode active material in the negative electrode plate 24 will be simply referred to as the "specific surface area of ​​the negative electrode active material." Furthermore, the effective specific surface area of ​​the negative electrode active material based on the measurement results from the negative electrode plate 24 will be referred to as the "measured specific surface area of ​​the negative electrode active material." The measured specific surface area of ​​the negative electrode active material is the surface area per unit weight. The measured specific surface area of ​​the negative electrode active material is the specific surface area of ​​the negative electrode active material measured from a negative electrode plate 24 selected from multiple negative electrode plates 24 manufactured in the same lot.

[0041] The charging electricity quantity acquisition unit 44 acquires the charging electricity quantity Q supplied to the lithium ion secondary battery 10 in a state of being charged by the charging device 30. The voltage acquisition unit 45 acquires the voltage V of the lithium ion secondary battery 10 in a state of being charged by the charging device 30.

[0042] The control unit 41 causes the specific surface area acquisition unit 43 to acquire the measured specific surface area of ​​the negative electrode active material. The specific surface area acquisition unit 43 is an example of a first acquisition unit that acquires the measured specific surface area of ​​the negative electrode active material. The control unit 41 causes the charging electricity quantity acquisition unit 44 to acquire the charging electricity quantity Q and causes the voltage acquisition unit 45 to acquire the voltage V at predetermined time intervals. The charging electricity quantity acquisition unit 44 and the voltage acquisition unit 45 are examples of a second acquisition unit that acquires the charging electricity quantity Q and the voltage V of the lithium ion secondary battery 10 at predetermined time intervals while the lithium ion secondary battery 10 is being charged. The control unit 41 causes the charging electricity quantity Q acquired by the charging electricity quantity acquisition unit 44 and the voltage V acquired by the voltage acquisition unit 45 to be stored in the memory unit 42 in association with each other.

[0043] The control unit 41 includes a first calculation unit 41A, a second calculation unit 41B, and a determination unit 41C. The first calculation unit 41A calculates an appropriate range based on the measured specific surface area of ​​the negative electrode active material. The appropriate range is a range of a specific value Q1 for determining whether the lithium ion secondary battery 10 is normal.

[0044] The second calculation unit 41B acquires a QV curve that indicates the voltage V versus the charged quantity of electricity Q during charging of the lithium ion secondary battery 10. The second calculation unit 41B calculates a specific value Q1 that is the value of the charged quantity of electricity Q at which the amount of decrease in the slope of the QV curve is maximized.

[0045] The determination unit 41C determines whether the lithium ion secondary battery 10 is normal or not based on the appropriate range of the specific value Q1 calculated by the first calculation unit 41A and the specific value Q1 calculated by the second calculation unit 41B. In this way, the determination unit 41C determines whether the lithium ion secondary battery 10 is normal or not. If the specific value Q1 is within the appropriate range, the determination unit 41C determines that the lithium ion secondary battery 10 is normal. If the specific value Q1 is outside the appropriate range, the determination unit 41C determines that the lithium ion secondary battery 10 is abnormal.

[0046] The storage unit 42 includes a memory unit 42A, a data storage unit 42B, and a program storage unit 42C. The memory unit 42A temporarily stores data, programs, etc. of the inspection device 40. The data storage unit 42B stores data for executing various processes in the control unit 41. The program storage unit 42C stores programs for executing various processes in the control unit 41.

[0047] [Relationship between specific surface area of ​​negative electrode active material and specific value] Here, the relationship between the specific surface area of ​​the negative electrode active material and the specific value Q1 will be described with reference to FIGS.

[0048] 5, a curve 101 in the graph 100 is an example of a QV curve. A curve 102 in the graph 100 is a graph of d with respect to the amount of charged electricity Q. 2 V / dQ 2The value of Qd 2 V / dQ 2 This is an example of a curve.

[0049] As will be described in detail later, in a first period 101A at the beginning of charging in the charging process, the increase in voltage V is large relative to the increase in the quantity of charged electricity Q, so curve 101 shows a steep rise. As the charging process progresses, in a second period 101B when the quantity of charged electricity Q reaches a specific value Q1, the increase in voltage V relative to the increase in the quantity of charged electricity Q becomes gentler, and the slope of the QV curve decreases significantly. The specific value Q1 is the value of the quantity of charged electricity Q at which the decrease in the slope of curve 101 is greatest. In this case, curve 102 has a peak 102P at the specific value Q1.

[0050] In the charging process, a portion of the charged quantity of electricity Q is consumed to form an SEI (Solid Electrolyte Interphase) coating on the negative electrode mixture layer 26. The amount of the SEI coating formed on the negative electrode mixture layer 26 has a positive correlation with the specific surface area of ​​the negative electrode active material. Therefore, the formation of the SEI coating on the negative electrode mixture layer 26 during charging changes the rise of the curve 101 in the first period 101A and the specific value Q1 depending on the specific surface area of ​​the negative electrode active material.

[0051] In addition, depending on the reduction reaction of the anode mixture layer 26, an unexpected SEI coating may be formed in the anode mixture layer 26. As a specific example, a reduction reaction of the anode mixture layer 26 may result in the formation of an unexpected SEI coating due to moisture in the anode mixture layer 26 due to a high water content. In this case, the amount of SEI coating formed on the anode mixture layer 26 increases. Thus, even when an unexpected SEI coating is formed in the anode mixture layer 26, the rise of the curve 101 in the first period 101A and the specific value Q1 change. Therefore, by obtaining the measured specific surface area of ​​the anode active material and calculating the specific value Q1 during the charging process, it is possible to determine whether an unexpected SEI coating has been formed in the anode mixture layer 26 depending on the reduction reaction of the anode mixture layer 26. This allows the normality of the lithium-ion secondary battery 10 to be determined.

[0052] As shown in FIG. 6, curve 201 in graph 200 indicates the open circuit potential (OCP) of the positive electrode side versus the quantity of electricity Q charged during the charging process. Curve 202 in graph 200 indicates the open circuit potential of the negative electrode side versus the quantity of electricity Q charged during the charging process. Curve 203 in graph 200 is an example of a QV curve indicating the voltage V of lithium ion secondary battery 10 versus the quantity of electricity Q charged during the charging process. The voltage V is equal to the value obtained by subtracting the open circuit potential of the negative electrode side from the open circuit potential of the positive electrode side. In other words, curve 203 is the difference between curve 201 and curve 202.

[0053] In graph 200, dashed curve 202A indicates the open circuit potential of the negative electrode side versus the charged quantity of electricity Q when the specific surface area of ​​the negative electrode active material is smaller than that of curve 202. In graph 200, dashed curve 203A is an example of a QV curve when the specific surface area of ​​the negative electrode active material is smaller than that of curve 203.

[0054] When the specific surface area of ​​the negative electrode active material becomes relatively smaller, the amount of SEI coating formed in the negative electrode mixture layer 26 decreases. As a result, the amount of charged electricity Q consumed for forming the SEI coating decreases, and the entire curve 202A shifts to the right of the curve 202 in its correspondence with the curve 201. In this case, the specific value Q1A on the curve 203A also shifts to the right of the specific value Q1 on the curve 203.

[0055] In graph 200, dashed curve 202B indicates the open circuit potential of the negative electrode side relative to the charged quantity of electricity Q when the specific surface area of ​​the negative electrode active material is larger than that of curve 202. In graph 200, dashed curve 203B is an example of a QV curve when the specific surface area of ​​the negative electrode active material is larger than that of curve 203.

[0056] When the specific surface area of ​​the negative electrode active material becomes relatively larger, the amount of SEI coating formed in the negative electrode mixture layer 26 increases. As a result, the charged quantity of electricity Q consumed for forming the SEI coating increases, and the entire curve 202B shifts to the left of the curve 202 in its correspondence with the curve 201. In this case, the specific value Q1B on the curve 203B also shifts to the left of the specific value Q1 on the curve 203.

[0057] Furthermore, if an unexpected SEI coating is formed in the negative electrode mixture layer 26, the amount of the SEI coating formed increases in the negative electrode mixture layer 26. In such a case, the entire curve 202B shifts to the left of the curve 202, and the specific value Q1B shifts to the left of the specific value Q1.

[0058] As described above, the specific value Q1 in the QV curve changes depending on the specific surface area of ​​the negative electrode active material. Additionally, the specific value Q1 in the QV curve changes depending on the formation of an unexpected SEI film in the negative electrode mixture layer 26. Therefore, by determining whether the specific value Q1 in the QV curve is within an appropriate range corresponding to the measured specific surface area of ​​the negative electrode active material, it is possible to evaluate whether an unexpected SEI film is formed in the negative electrode mixture layer 26 in response to the reduction reaction of the negative electrode mixture layer 26. This allows the determination of whether the lithium-ion secondary battery 10 is normal.

[0059] [Method of manufacturing lithium-ion secondary batteries] 7, the method for manufacturing the lithium-ion secondary battery 10 includes steps S1-1 to S1-5. Step S1-1 is a source process for manufacturing each of the positive electrode plate 21 and the negative electrode plate 24. In particular, the source process includes a kneading process and an electrode plate manufacturing process. The kneading process includes a process for kneading a positive electrode material mixture paste and a process for kneading a negative electrode material mixture paste. The electrode plate manufacturing process is a process for manufacturing the positive electrode plate 21 and the negative electrode plate 24, and includes a process for manufacturing the positive electrode plate 21 and a process for manufacturing the negative electrode plate 24.

[0060] In the manufacturing process of the positive electrode plate 21, a positive electrode mixture paste is applied to both sides of the positive electrode substrate 22 so as to form the positive electrode-side exposed portions 22A at both ends in the width direction. The positive electrode mixture paste is then dried to form the positive electrode mixture layer 23. Next, the positive electrode mixture layer 23 formed on both sides of the positive electrode substrate 22 is pressed to adjust the thickness of the positive electrode mixture layer 23. Thereafter, the positive electrode substrate 22 is cut in the center in the width direction. By the above steps, two positive electrode plates 21 are manufactured at once.

[0061] In the manufacturing process of the negative electrode plate 24, a negative electrode mixture paste is applied to both sides of the negative electrode substrate 25 so as to form the negative electrode-side exposed portions 25A at both ends in the width direction. The negative electrode mixture paste is then dried to form the negative electrode mixture layer 26. Next, the negative electrode mixture layer 26 formed on both sides of the negative electrode substrate 25 is pressed to adjust the thickness of the negative electrode mixture layer 26. Thereafter, the negative electrode substrate 25 is cut in the center in the width direction. By the above steps, two negative electrode plates 24 are manufactured at once.

[0062] Step S1-2 is an assembly process in which the lithium-ion secondary battery 10 is assembled using the negative electrode plate 24, the positive electrode plate 21, and the nonaqueous electrolyte solution 15. In the assembly process, the electrode body 20 is first manufactured. Specifically, the positive electrode plate 21 and the negative electrode plate 24 are first stacked with the separator 27 interposed therebetween, then wound and pressed flat. Thereafter, the positive electrode side exposed portion 22A is pressed against the positive electrode side current collector 20A, and the negative electrode side exposed portion 25A is pressed against the negative electrode side current collector 20B. The electrode body 20 is manufactured by the above procedure.

[0063] Next, the electrode body 20 is housed in the battery case 11. At this time, the positive electrode side current collector 20A is electrically connected to the positive electrode external terminal 13A via the positive electrode side current collector 14A. The negative electrode side current collector 20B is electrically connected to the negative electrode external terminal 13B via the negative electrode side current collector 14B. The top of the battery case 11 is closed with the lid 12. Then, after removing moisture from the electrode body 20 by heat treatment, the nonaqueous electrolyte 15 is injected into the battery case 11. Through the above procedure, the lithium ion secondary battery 10 is assembled.

[0064] Step S1-3 is a charging process in which the lithium ion secondary battery 10 assembled in the assembly process is charged by the charging device 30. The charging performed in the charging process is, for example, the initial charging of the lithium ion secondary battery 10 assembled in the assembly process. In the charging process, the external terminals 13A, 13B of the lithium ion secondary battery 10 are connected to the charging device 30 and the inspection device 40.

[0065] Step S1-4 is a determination step in which the inspection device 40 determines whether the lithium-ion secondary battery 10 is normal based on the behavior of the charged quantity of electricity Q and the voltage V during the charging step. In particular, an unexpected SEI film may be formed in the negative electrode mixture layer 26 after the electrode plate manufacturing step is completed, depending on the reduction reaction during the charging step. In this way, whether the lithium-ion secondary battery 10 is normal can be determined based on the behavior of the charged quantity of electricity Q and the voltage V during the charging step, depending on whether an unexpected SEI film has been formed in the negative electrode mixture layer 26. In the manufacturing process for the lithium-ion secondary battery 10, only lithium-ion secondary batteries 10 determined to be normal in the determination step proceed to the subsequent step, step S1-5.

[0066] Step S1-5 is an aging step in which the lithium-ion secondary battery 10 that has been through the charging step and the evaluation step is left standing at a high temperature for a certain period of time. The aging step dissolves metallic foreign matter in the lithium-ion secondary battery 10 and stabilizes the SEI coating.

[0067] [Judgment process] The determination step (step S1-4) will be described in detail below with reference to FIGS. As shown in FIG. 8, in the determination step, the inspection device 40 executes the processes of steps S2-1 to S2-8, which are an example of a method for inspecting the lithium-ion secondary battery 10. In step S2-1, the inspection device 40 acquires a measured specific surface area of ​​the negative electrode active material. First, the control unit 41 of the inspection device 40 causes the specific surface area acquisition unit 43 to acquire the measured specific surface area of ​​the negative electrode active material. The measured specific surface area of ​​the negative electrode active material is the actual specific surface area of ​​the negative electrode active material measured from the negative electrode plates 24 manufactured in the electrode plate manufacturing process. Some of the negative electrode plates 24 manufactured as the same lot in the electrode plate manufacturing process are sampled and measured. In this way, the specific surface area acquisition unit 43 acquires the measured specific surface area of ​​the negative electrode active material based on the measurement results from the negative electrode plates 24 manufactured in the electrode plate manufacturing process. In particular, the specific surface area acquisition unit 43 acquires the measured specific surface area of ​​the negative electrode active material based on the results of measurements taken from some of the negative electrode plates 24 among a plurality of negative electrode plates 24 manufactured in the same lot during the electrode plate manufacturing process.

[0068] In step S2-2, the control unit 41 calculates an appropriate range for the specific value Q1 based on the measured specific surface area of ​​the negative electrode active material. The control unit 41 stores the calculated appropriate range for the specific value Q1 in the data storage unit 42B. In this way, the control unit 41 sets the calculated appropriate range for the specific value Q1.

[0069] [Setting the appropriate range for specific values] Here, a procedure for setting the appropriate range of the specific value Q1 will be described with reference to FIG. First, prior to the manufacturing process of the lithium-ion secondary battery 10, a plurality of negative electrode plates 24 with different specific surface areas of the negative electrode active material are fabricated using a plurality of levels of negative electrode active material with different specific surface areas in the raw material state. Next, the specific surface area of ​​the negative electrode active material contained in the negative electrode mixture layer 26 of each level of negative electrode plate 24 is measured using a measurement method such as the BET method. Then, a plurality of levels of lithium-ion secondary batteries 10 are assembled using each of the plurality of negative electrode plates 24 with different specific surface areas of the negative electrode active material, and then charging is performed, and the specific value Q1 is calculated in the same manner as in step S1-4. Note that a plurality of levels of negative electrode plates 24 with different specific surface areas of the negative electrode active material may be fabricated, for example, by changing the manufacturing conditions of the negative electrode plates 24.

[0070] 9, each of the multiple points P plotted in graph 300 indicates the correspondence relationship between the specific surface area of ​​the negative electrode active material and the specific value Q1 for each of multiple lithium-ion secondary batteries 10 having different specific surface areas of the negative electrode active material. Approximation line 301 in graph 300 is an approximation line derived from the multiple points P and is a calibration curve for setting an appropriate range for specific value Q1. Approximation line 301 has a negative slope such that the specific value Q1 decreases as the specific surface area of ​​the negative electrode active material increases.

[0071] Furthermore, an appropriate upper limit approximation line 302 in graph 300 is an approximation line derived from approximation line 301. The appropriate upper limit approximation line 302 is a calibration curve for setting the upper limit of the appropriate range of specific value Q1. An appropriate lower limit approximation line 303 in graph 300 is an approximation line derived from approximation line 301. The appropriate lower limit approximation line 303 is a calibration curve for setting the lower limit of the appropriate range of specific value Q1.

[0072] For example, the appropriate upper limit approximation line 302 and the appropriate lower limit approximation line 303 are ranges that take into consideration the measurement error of the specific value Q1, with the approximation line 301 as the reference. As a specific example, for the specific surface area AR of the negative electrode active material, an upper limit QRH is set as the upper limit of the appropriate range of the specific value Q1 from the appropriate upper limit approximation line 302, and a lower limit QRL is set as the lower limit of the appropriate range of the specific value Q1 from the appropriate lower limit approximation line 303. In this way, the appropriate range of the specific value Q1 is set for the specific surface area AR of the negative electrode active material. The appropriate range of the specific value Q1 is stored in the data storage unit 42B.

[0073] Next, in step S2-2 of the determination process of FIG. 8 , the control unit 41 determines an allowable range for the measured specific surface area of ​​the negative electrode active material based on the measured specific surface area of ​​the negative electrode active material. The allowable range for the measured specific surface area of ​​the negative electrode active material is a range based on the measured specific surface area of ​​the negative electrode active material, taking into consideration measurement errors in the measured specific surface area of ​​the negative electrode active material and manufacturing errors in the negative electrode plate 24. The allowable range for the measured specific surface area of ​​the negative electrode active material ranges from an allowable lower limit specific surface area to an allowable upper limit specific surface area. The allowable lower limit specific surface area may be the area obtained by subtracting a tolerance area from the measured specific surface area of ​​the negative electrode active material. The allowable upper limit specific surface area may be the area obtained by adding the tolerance area to the measured specific surface area of ​​the negative electrode active material.

[0074] The control unit 41 calculates the upper limit of the appropriate range of the specific value Q1 corresponding to the allowable lower limit specific surface area from the appropriate upper limit approximation line 302. The control unit 41 sets the calculation result as the upper limit of the appropriate range of the specific value Q1. The control unit 41 calculates the lower limit of the appropriate range of the specific value Q1 corresponding to the allowable upper limit specific surface area from the appropriate lower limit approximation line 303. The control unit 41 sets the calculation result as the lower limit of the appropriate range of the specific value Q1. In this way, the control unit 41 sets the appropriate range of the specific value Q1 so as to correspond to the allowable range of the measured specific surface area of ​​the negative electrode active material.

[0075] In this way, the control unit 41 can estimate the specific value Q1 corresponding to the measured specific surface area of ​​the negative electrode active material from the approximation line 301. The control unit 41 can also estimate an appropriate range of the specific value Q1 corresponding to the allowable range of the measured specific surface area of ​​the negative electrode active material from the appropriate upper limit approximation line 302 and the appropriate lower limit approximation line 303. In other words, the control unit 41 can set the appropriate range of the specific value Q1 based on the measured specific surface area of ​​the negative electrode active material actually measured from some of the negative electrode plates 24 among the multiple negative electrode plates 24 manufactured in the same lot in the electrode plate manufacturing process.

[0076] As a specific example, for a specific surface area AR of a negative electrode active material, the allowable range of the measured specific surface area of ​​the negative electrode active material ranges from an allowable lower limit specific surface area AL to an allowable upper limit specific surface area AH. An upper limit QH of the appropriate range of the specific value Q1 corresponding to the allowable lower limit specific surface area AL is calculated as the upper limit of the appropriate range of the specific value Q1. A lower limit QL of the appropriate range of the specific value Q1 corresponding to the allowable upper limit specific surface area AH is calculated as the lower limit of the appropriate range of the specific value Q1. As a result, an appropriate range of the specific value Q1 from the lower limit QL to the upper limit QH is calculated for the specific surface area AR of the negative electrode active material.

[0077] In step S2-3, the inspection device 40 acquires a QV curve showing the value of the voltage V versus the quantity of charged electricity Q during the charging process for a plurality of negative electrode plates 24 manufactured as the same lot during the electrode plate manufacturing process. First, the control unit 41 executes a process to cause the charging electricity quantity acquisition unit 44 to acquire the charging electricity quantity Q at predetermined time intervals while the lithium ion secondary battery 10 is being charged during the charging process. At the same time, the control unit 41 executes a process to cause the voltage acquisition unit 45 to acquire the voltage V at predetermined time intervals while the lithium ion secondary battery 10 is being charged during the charging process. The timing at which the charging electricity quantity acquisition unit 44 acquires the charging electricity quantity Q is the same as the timing at which the voltage acquisition unit 45 acquires the voltage V. The control unit 41 associates the acquired charging electricity quantity Q and voltage V and stores them in the data storage unit 42B. The second calculation unit 41B derives a QV curve based on the charging electricity quantity Q acquired by the charging electricity quantity acquisition unit 44 and the voltage V acquired by the voltage acquisition unit 45.

[0078] In step S2-4, the second calculation unit 41B calculates the second derivative d of the QV curve. 2 V / dQ 2 To give a specific example, the second calculation unit 41B calculates a curve 102 from a curve 101 shown in FIG.

[0079] In step S2-5, the second calculation unit 41B calculates d 2 V / dQ 2 As a specific example, the second calculation unit 41B calculates the value of the charged quantity of electricity Q at which the value of is maximum as the specific value Q1. As a specific example, the second calculation unit 41B calculates the value of the charged quantity of electricity Q at the peak 102P of the curve 102 shown in FIG. 5 as the specific value Q1, which is the value of the charged quantity of electricity Q at the boundary between the first period 101A and the second period 101B. In other words, the second calculation unit 41B calculates the specific value Q1 of the charged quantity of electricity Q at which the amount of decrease in slope is maximum in the QV curve showing the value of the voltage V with respect to the charged quantity of electricity Q. In addition, the specific value Q1 is calculated by second-order differentiation d of the QV curve with respect to the charged quantity of electricity Q. 2 V / dQ 2 Denote the value of d 2 V / dQ 2 In the curve, d 2 V / dQ 2 It can be said that the specific value Q1 is calculated as the value of the charged quantity of electricity Q at which a peak appears on the curve. The process of calculating the specific value Q1 in step S2-5 is an example of a first process executed by the inspection device 40.

[0080] In step S2-6, the determination unit 41C determines whether the specific value Q1 calculated in step S2-5 is within an appropriate range. The appropriate range used in step S2-6 is the applicable range calculated in step S2-2 and is stored in the data storage unit 42B included in the storage unit 42. That is, the determination unit 41C determines whether an unexpected SEI coating has been formed in the negative electrode mixture layer 26 based on the measured specific surface area of ​​the negative electrode active material acquired in step S2-1 and the specific value Q1 of the charged quantity of electricity Q calculated in step S2-5. This allows the determination unit 41C to determine whether the lithium-ion secondary battery 10 is normal. The process of determining whether the lithium-ion secondary battery 10 is normal in step S2-6 is an example of a second process executed by the inspection device 40.

[0081] If the specific value Q1 is within the appropriate range, the determination unit 41C determines that the lithium ion secondary battery 10 is normal, and proceeds to step S2-7. The lithium ion secondary battery 10 that has proceeded to step S2-7 is determined to be normal and proceeds to the subsequent aging step.

[0082] If the specific value Q1 is outside the appropriate range, the determination unit 41C determines that the lithium ion secondary battery 10 is abnormal, and proceeds to step S2-8. The lithium ion secondary battery 10 that proceeds to step S2-8 is determined to be abnormal and is removed from the production line.

[0083] In the determination process, steps S2-1 and S2-2 are performed on some of the negative electrode plates 24 manufactured in the same lot in the electrode plate manufacturing process. Meanwhile, steps S2-3 to S2-8 are performed on the negative electrode plates 24 manufactured in the same lot in the electrode plate manufacturing process. That is, determination unit 41C determines whether lithium-ion secondary battery 10 is normal or not based on the measured specific surface area of ​​the negative electrode active material and specific value Q1 of the charged quantity of electricity Q for the negative electrode plates 24 manufactured in the same lot in the electrode plate manufacturing process.

[0084] The above processing is executed by an inspection program installed and stored in program storage unit 42C. In step S2-1, the inspection program causes specific surface area acquisition unit 43 to acquire a measured specific surface area of ​​the negative electrode active material. In step S2-2, the inspection program causes first calculation unit 41A to execute processing to calculate an appropriate range. In step S2-3, the inspection program causes charged electricity quantity acquisition unit 44 to acquire charged electricity quantity Q at predetermined time intervals, and in step S2-4, causes voltage acquisition unit 45 to acquire voltage V at predetermined time intervals. In step S2-5, the inspection program causes second calculation unit 41B to execute processing to calculate specific value Q1. In step S2-6, the inspection program causes determination unit 41C to execute processing to determine whether lithium ion secondary battery 10 is normal.

[0085] [Operation of the first embodiment] The operation of the first embodiment will be described. In the source process, a plurality of negative electrode plates 24 and a plurality of positive electrode plates 21 are manufactured in the same lot. In particular, in the electrode plate manufacturing process, a plurality of negative electrode plates 24 and a plurality of positive electrode plates 21 are manufactured in the same lot. In the electrode plate manufacturing process, some negative electrode plates 24 are sampled as measurement targets from the plurality of negative electrode plates 24 manufactured in the same lot. The measured specific surface area of ​​the negative electrode active material is measured from the negative electrode plates 24 sampled as measurement targets. In this way, the measured specific surface area of ​​the negative electrode active material can be obtained based on the measurement results from the negative electrode plates 24 sampled as measurement targets. After the source process is completed, the assembly process is performed. After the assembly process is completed, the charging process is performed.

[0086] In the charging process, while the lithium ion secondary battery 10 is being charged, the charged quantity of electricity Q and the voltage V of the lithium ion secondary battery 10 are acquired at predetermined time intervals. As a result, a QV curve showing the value of the voltage V relative to the charged quantity of electricity Q is acquired. Based on the QV curve, the second-order differentiation d 2 V / dQ 2 The value of d is calculated. 2 V / dQ 2The value of the charged quantity of electricity Q at which the value of is maximum is calculated as the specific value Q1. As a result of the calculation, the specific value Q1 can be obtained.

[0087] After the charging step is completed, a determination step is performed. In the determination step, a measured specific surface area of ​​the negative electrode active material is acquired. An appropriate range of the specific value Q1 is calculated based on the acquired measured specific surface area of ​​the negative electrode active material. In the determination step, the specific value Q1 calculated in the charging step is acquired. If the acquired specific value Q1 is within the appropriate range of the calculated specific value Q1, it is determined that the lithium ion secondary battery 10 is normal. If the acquired specific value Q1 is outside the appropriate range of the calculated specific value Q1, it is determined that the lithium ion secondary battery 10 is abnormal.

[0088] [Effects of the first embodiment] The effects of the first embodiment will be described. (1) By obtaining the measured specific surface area of ​​the negative electrode active material from the negative electrode plate 24 manufactured in the electrode plate manufacturing process and calculating the specific value Q1 in the charging process, it is possible to determine whether the lithium ion secondary battery 10 is normal or not depending on the reduction reaction of the negative electrode mixture layer 26. In addition, by determining the size of the specific surface area of ​​the negative electrode active material from the QV curve in the charging process, it is possible to make a determination for all lithium ion secondary batteries 10 in the manufacturing process of the lithium ion secondary batteries 10.

[0089] (2) The specific surface area of ​​the negative electrode active material can be measured based on the results of measurements taken from some of the negative electrode plates 24 manufactured in the same lot. This makes it possible to determine whether the lithium-ion secondary battery 10 is normal or not based on the reduction reaction of the negative electrode mixture layer 26 for multiple negative electrode plates 24 manufactured in the same lot.

[0090] (3) In calculating the specific value Q1, Qd 2 V / dQ 2 By using the curve, it is possible to easily determine whether the lithium ion secondary battery 10 is normal or not depending on the reduction reaction of the negative electrode mixture layer 26.

[0091] (4) By performing the determination process when the assembled lithium-ion secondary battery 10 is initially charged, it is possible to determine whether the lithium-ion secondary battery 10 is normal without taking into account changes in the lithium-ion secondary battery 10 that occur as a result of repeated charging and discharging. This improves the accuracy of the determination.

[0092] (5) In setting the optimum range, a calibration curve derived from specific values ​​Q1 calculated from a plurality of lithium-ion secondary batteries 10 having different specific surface areas of the negative electrode active material is used, thereby making it possible to set the optimum range taking into account the influence of the actual composition of the negative electrode mixture layer 26 and the manufacturing process, thereby improving the accuracy of the determination.

[0093] [Second embodiment] Next, a second embodiment will be described. In the following description, the same components and control contents as those in the already described embodiment will be denoted by the same reference numerals, and redundant description thereof will be omitted or simplified.

[0094] In the first embodiment, the control unit 41 determined whether the lithium ion secondary battery 10 is normal based on whether the calculated specific value Q1 is within an appropriate range for the specific value Q1. In the second embodiment, the control unit 41 estimates the specific surface area of ​​the negative electrode active material based on the calculated specific value Q1. Then, the control unit 41 determines whether the lithium ion secondary battery 10 is normal based on whether the estimated specific surface area of ​​the negative electrode active material is within an appropriate range for the specific surface area of ​​the negative electrode active material.

[0095] As shown in FIG. 10 , in the second embodiment, after step S2-1 is completed, in step S2-9, the control unit 41 calculates an appropriate range for the specific surface area of ​​the negative electrode active material based on the measured specific surface area of ​​the negative electrode active material. The control unit 41 may calculate the allowable range of the measured specific surface area of ​​the negative electrode active material in the first embodiment as the appropriate range for the specific surface area of ​​the negative electrode active material. The control unit 41 stores the calculated appropriate range for the specific surface area of ​​the negative electrode active material in the data storage unit 42B. In this way, the control unit 41 sets the calculated appropriate range for the specific surface area of ​​the negative electrode active material.

[0096] After step S2-5 is completed, in step S2-10, control unit 41 estimates the specific surface area of ​​the negative electrode active material based on the calculated specific value Q1. Specifically, control unit 41 refers to approximation line 301 in graph 300 and calculates the specific surface area of ​​the negative electrode active material corresponding to the calculated specific value Q1.

[0097] In step S2-11, determination unit 41C determines whether the specific surface area of ​​the negative electrode active material estimated in step S2-6 is within an appropriate range. The appropriate range used in step S2-11 is the applicable range calculated in step S2-2 and is stored in data storage unit 42B included in storage unit 42. That is, determination unit 41C determines whether an unexpected SEI coating has been formed in negative electrode mixture layer 26 based on the measured specific surface area of ​​the negative electrode active material acquired in step S2-1 and specific value Q1 of the charged quantity of electricity Q calculated in step S2-5. This allows determination unit 41C to determine whether lithium-ion secondary battery 10 is normal. The process of determining whether lithium-ion secondary battery 10 is normal in step S2-11 is an example of a second process executed by inspection device 40.

[0098] If the estimated specific surface area of ​​the negative electrode active material is within the appropriate range, determination unit 41C determines that lithium ion secondary battery 10 is normal, and proceeds to step S2-7. If the estimated specific surface area of ​​the negative electrode active material is outside the appropriate range, determination unit 41C determines that lithium ion secondary battery 10 is abnormal, and proceeds to step S2-8.

[0099] The above processing is executed by an inspection program installed and stored in program storage unit 42C. In step S2-9, the inspection program causes first calculation unit 41A to execute processing to calculate an appropriate range. In step S2-10, the inspection program estimates the specific surface area of ​​the negative electrode active material based on specific value Q1. In step S2-11, the inspection program causes determination unit 41C to execute processing to determine whether lithium ion secondary battery 10 is normal.

[0100] [Example of change] The above embodiment can be modified as follows. Determination unit 41C may determine, for example, whether the measured specific surface area of ​​the negative electrode active material itself is within the appropriate range. If determination unit 41C determines that the measured specific surface area of ​​the negative electrode active material itself is within the appropriate range, it may perform a determination based on specific value Q1 in step S2-6 of Fig. 8 and step S2-11 of Fig. 10. If determination unit 41C determines that the measured specific surface area of ​​the negative electrode active material itself is not within the appropriate range, it may determine at that point that lithium-ion secondary battery 10 is abnormal.

[0101] In the negative electrode mixture layer 26, the negative electrode active material is covered with the negative electrode binder, thereby reducing the specific surface area of ​​the negative electrode active material that contributes to charge / discharge reactions. Furthermore, in the process of pressing the negative electrode mixture layer 26, the particles of the negative electrode active material are cracked, thereby increasing the specific surface area of ​​the negative electrode active material. Therefore, the specific surface area of ​​the negative electrode active material depends not only on the specific surface area of ​​the negative electrode active material in the raw material state, but also on the composition of the negative electrode mixture layer 26 and the manufacturing process for the negative electrode mixture layer 26.

[0102] For example, if the specific surface area of ​​the negative electrode active material is excessively large, the life characteristics of the lithium-ion secondary battery 10 will deteriorate. On the other hand, if the specific surface area of ​​the negative electrode active material is excessively small, lithium will be more likely to deposit on the electrode body 20. Therefore, the appropriate range of the measured specific surface area of ​​the negative electrode active material itself may be determined so that an upper limit does not cause excessive deposition of lithium on the electrode body 20, and a lower limit does not cause excessive deterioration of the life characteristics of the lithium-ion secondary battery 10.

[0103] For example, the control unit 41 may estimate an appropriate range of the specific value Q1 corresponding to the measured specific surface area of ​​the negative electrode active material from the appropriate upper limit approximation line 302 and the appropriate lower limit approximation line 303, without calculating the allowable range of the measured specific surface area of ​​the negative electrode active material. In this case, the control unit 41 may determine, for example, a range obtained by calculating a tolerance in the estimated appropriate range of the specific value Q1 as the appropriate range of the specific value Q1.

[0104] The control unit 41 may, for example, estimate the specific value Q1 corresponding to the measured specific surface area of ​​the negative electrode active material from the approximation line 301 without referring to the appropriate upper limit approximation line 302 and the appropriate lower limit approximation line 303. In this case, the control unit 41 may, for example, estimate a range obtained by calculating a tolerance for the estimated specific value Q1 as the appropriate range of the specific value Q1.

[0105] The measured specific surface area of ​​the negative electrode active material may be measured at any time, for example, after the electrode plate manufacturing process. The measured specific surface area of ​​the negative electrode active material may be obtained at any time, for example, after the electrode plate manufacturing process. The appropriate ranges of the specific value Q1 and the appropriate ranges of the specific surface area of ​​the negative electrode active material may be calculated at any time, for example, after the electrode plate manufacturing process.

[0106] The example shows a case where the appropriate range of the specific value Q1 is set using a calibration curve derived from the specific value Q1 of multiple lithium-ion secondary batteries 10 having different specific surface areas of the negative electrode active material. Alternatively, instead of actually fabricating multiple lithium-ion secondary batteries 10 having different specific surface areas of the negative electrode active material, the appropriate range of the specific value Q1 may be set by a model simulation such as finite element analysis or numerical calculation.

[0107] The determination step may be performed not during the first charge but during the second or subsequent charge. In this case, in order to set an appropriate range for the specific value Q1, multiple lithium-ion secondary batteries 10 having different specific surface areas of the negative electrode active material that have undergone similar charge-discharge cycles may be used. When the determination step is performed during the second or subsequent charge, the specific surface area of ​​the negative electrode active material can also be determined for lithium-ion secondary batteries 10 that have undergone charge-discharge cycles.

[0108] Calculation of specific value Q1 is Qd 2 V / dQ 2 The method is not limited to the method using a curve. For example, the value of the charged quantity of electricity Q at which the value of dV / dQ is equal to or less than a predetermined threshold may be calculated as the specific value Q1. In this case, the threshold is smaller than the value of dV / dQ in the first period 101A and larger than the value of dV / dQ in the second period 101B. Even with such a method, it is possible to determine whether the specific surface area of ​​the negative electrode active material is appropriate.

[0109] In the nonaqueous secondary battery inspection system 1, the nonaqueous secondary battery is not limited to the lithium ion secondary battery 10, but may be any battery having a positive electrode plate 21, a negative electrode plate 24, and a nonaqueous electrolyte solution 15.

[0110] The electrode assembly 20 may be, for example, a laminate in which a plurality of positive electrode plates 21 and a plurality of negative electrode plates 24 are alternately stacked with separators 27 interposed therebetween. The lithium-ion secondary battery 10 may be installed in an automatic transport vehicle, a special-purpose vehicle for loading and unloading, an electric vehicle, a hybrid vehicle, a computer, or other electronic device, or may be part of other systems. For example, it may be installed in a moving object such as a ship or an aircraft, or it may be a power supply system that supplies power from a power plant via a substation to a building or home where a secondary battery is installed.

[0111] The phrase "at least one" used herein means "one or more" of the desired options. As an example, the phrase "at least one" used herein means "only one option" or "both of two options" if there are two options. As another example, the phrase "at least one" used herein means "only one option" or "any combination of two or more options" if there are three or more options. The phrase "at least one type" is also similar to the phrase "at least one." [Explanation of symbols]

[0112] 1. Non-aqueous secondary battery inspection system 10...Lithium-ion secondary battery 15...Nonaqueous electrolyte 20...Electrode body 21...Positive electrode plate 22...Positive electrode substrate 23...Positive electrode mixture layer 24...Negative electrode plate 25...Anode substrate 26...Negative electrode mixture layer 27...Separator 30...Charging device 40...Inspection equipment 41...Control unit 41A...1st calculation section 41B…Second calculation section 41C...judgment section 42...Storage section 42A...Memory section 42B...Data storage section 42C...Program memory section 43…Specific surface area acquisition section 44...Charged electricity quantity acquisition unit 45...Voltage acquisition section

Claims

1. an electrode plate manufacturing process for manufacturing a negative electrode plate having a negative electrode mixture layer containing a negative electrode active material and a positive electrode plate; an assembly process of assembling a nonaqueous secondary battery using the negative electrode plate, the positive electrode plate, and an electrolyte; a charging step of charging the nonaqueous secondary battery; a determining step of determining whether the nonaqueous secondary battery is normal; The determination step includes: a measured specific surface area of ​​the negative electrode active material is obtained based on the measurement results of the negative electrode plate manufactured in the electrode plate manufacturing step; In the charging step, a charged quantity of electricity Q and a voltage V of the nonaqueous secondary battery are acquired at predetermined time intervals while the nonaqueous secondary battery is being charged; setting an appropriate range for the specific value of the charging quantity of electricity Q based on the measured specific surface area of ​​the negative electrode active material; Calculating a specific value of the charged quantity of electricity Q at which a decrease in slope is maximum in a Q-V curve showing the voltage V versus the charged quantity of electricity Q; determining that the nonaqueous secondary battery is normal when the specific value of the charging quantity of electricity Q is within an appropriate range based on the measured specific surface area of ​​the negative electrode active material and the specific value of the charging quantity of electricity Q, and determining that the nonaqueous secondary battery is abnormal when the specific value of the charging quantity of electricity Q is outside the appropriate range; the appropriate range of the specific value of the charged electricity Q includes a first appropriate range that is set when the measured specific surface area of ​​the negative electrode active material is a first measured specific surface area, and a second appropriate range that is set when the measured specific surface area of ​​the negative electrode active material is a second measured specific surface area that is smaller than the first measured specific surface area, The upper limit of the second appropriate range is greater than the upper limit of the first appropriate range, The lower limit of the second optimum range is greater than the lower limit of the first optimum range. A method for manufacturing a non-aqueous secondary battery.

2. an electrode plate manufacturing process for manufacturing a negative electrode plate having a negative electrode mixture layer containing a negative electrode active material and a positive electrode plate; an assembly process of assembling a nonaqueous secondary battery using the negative electrode plate, the positive electrode plate, and an electrolyte; a charging step of charging the nonaqueous secondary battery; a determining step of determining whether the nonaqueous secondary battery is normal; The determination step includes: a measured specific surface area of ​​the negative electrode active material is obtained based on the measurement results of the negative electrode plate manufactured in the electrode plate manufacturing step; determining an appropriate range of an effective specific surface area of ​​the negative electrode active material in the negative electrode plate based on the measured specific surface area of ​​the negative electrode active material; In the charging step, a charged quantity of electricity Q and a voltage V of the nonaqueous secondary battery are acquired at predetermined time intervals while the nonaqueous secondary battery is being charged; Calculating a specific value of the charged quantity of electricity Q at which a decrease in slope is maximum in a Q-V curve showing the voltage V versus the charged quantity of electricity Q; Estimating an effective specific surface area of ​​the negative electrode active material in the negative electrode plate based on the specific value of the charged electricity Q; determining that the nonaqueous secondary battery is normal when the effective specific surface area of ​​the negative electrode active material in the negative electrode plate is within an appropriate range of the effective specific surface area of ​​the negative electrode active material, based on the measured specific surface area of ​​the negative electrode active material and the specific value of the charged quantity of electricity Q; and determining that the nonaqueous secondary battery is abnormal when the effective specific surface area of ​​the negative electrode active material in the negative electrode plate is outside the appropriate range of the effective specific surface area of ​​the negative electrode active material, the appropriate range of the effective specific surface area of ​​the negative electrode active material includes a third appropriate range that is set when the measured specific surface area of ​​the negative electrode active material is a first measured specific surface area, and a fourth appropriate range that is set when the measured specific surface area of ​​the negative electrode active material is a second measured specific surface area that is smaller than the first measured specific surface area, the upper limit of the fourth optimum range is smaller than the upper limit of the third optimum range, The lower limit of the fourth optimum range is smaller than the lower limit of the third optimum range. A method for manufacturing a non-aqueous secondary battery.

3. The determination step includes: a measured specific surface area of ​​the negative electrode active material is obtained based on a measurement result from some of the negative electrode plates among the plurality of negative electrode plates manufactured in the same lot in the electrode plate manufacturing process; For a plurality of negative electrode plates manufactured in the same lot in the electrode plate manufacturing process, whether or not an unexpected SEI film has been formed in the negative electrode mixture layer in the charging process is determined based on the measured specific surface area of ​​the negative electrode active material and the specific value of the charged quantity of electricity Q, thereby determining whether or not the nonaqueous secondary battery is normal. The method for producing the nonaqueous secondary battery according to claim 1 or 2.

4. The specific value of the charge quantity of electricity Q is obtained by second-order differentiation of the Q-V curve with respect to the charge quantity of electricity Q. ２ V / dQ ２ The value of Q-d ２ V / dQ ２ In the curve, the Qd ２ V / dQ ２ The charge quantity Q is calculated as the value at which a peak appears on the curve. The method for producing the nonaqueous secondary battery according to any one of claims 1 to 3.

5. An inspection device for a non-aqueous secondary battery including a negative electrode plate having a negative electrode mixture layer containing a negative electrode active material, a positive electrode plate, and an electrolyte, a first acquisition unit that acquires a measured specific surface area of ​​the negative electrode active material based on a result of measurement from the negative electrode plate; a second acquisition unit that acquires a charged quantity of electricity Q and a voltage V of the nonaqueous secondary battery at predetermined time intervals while the nonaqueous secondary battery is being charged; a control unit that executes a setting process that sets an appropriate range for the specific value of the charging quantity of electricity Q based on the measured specific surface area of ​​the negative electrode active material; a first process that calculates the specific value of the charging quantity of electricity Q at which a decrease in slope is greatest in a Q-V curve that shows the voltage V versus the charging quantity of electricity Q; and a second process that determines, based on the measured specific surface area of ​​the negative electrode active material and the specific value of the charging quantity of electricity Q, that the non-aqueous secondary battery is normal if the specific value of the charging quantity of electricity Q is within the appropriate range for the specific value of the charging quantity of electricity Q, and determines that the non-aqueous secondary battery is abnormal if the specific value of the charging quantity of electricity Q is outside the appropriate range for the specific value of the charging quantity of electricity Q, the appropriate range of the specific value of the charged electricity Q includes a first appropriate range that is set when the measured specific surface area of ​​the negative electrode active material is a first measured specific surface area, and a second appropriate range that is set when the measured specific surface area of ​​the negative electrode active material is a second measured specific surface area that is smaller than the first measured specific surface area, The upper limit of the second appropriate range is greater than the upper limit of the first appropriate range, The lower limit of the second optimum range is greater than the lower limit of the first optimum range. Inspection equipment for non-aqueous secondary batteries.

6. An inspection device for a non-aqueous secondary battery including a negative electrode plate having a negative electrode mixture layer containing a negative electrode active material, a positive electrode plate, and an electrolyte, a first acquisition unit that acquires a measured specific surface area of ​​the negative electrode active material based on a result of measurement from the negative electrode plate; a second acquisition unit that acquires a charged quantity of electricity Q and a voltage V of the nonaqueous secondary battery at predetermined time intervals while the nonaqueous secondary battery is being charged; a control unit that executes the following processes: a setting process that sets an appropriate range of the effective specific surface area of ​​the negative electrode active material in the negative electrode plate based on the measured specific surface area of ​​the negative electrode active material; a first process that calculates a specific value of the charging quantity of electricity Q that maximizes the decrease in slope of a Q-V curve that shows the voltage V versus the charging quantity of electricity Q; an estimation process that estimates the effective specific surface area of ​​the negative electrode active material in the negative electrode plate based on the specific value of the charging quantity of electricity Q; and a second process that determines, based on the measured specific surface area of ​​the negative electrode active material and the specific value of the charging quantity of electricity Q, that the nonaqueous secondary battery is normal if the effective specific surface area of ​​the negative electrode active material in the negative electrode plate is within the appropriate range of the effective specific surface area of ​​the negative electrode active material, and determines that the nonaqueous secondary battery is abnormal if the effective specific surface area of ​​the negative electrode active material in the negative electrode plate is outside the appropriate range of the effective specific surface area of ​​the negative electrode active material, the appropriate range of the effective specific surface area of ​​the negative electrode active material includes a third appropriate range that is set when the measured specific surface area of ​​the negative electrode active material is a first measured specific surface area, and a fourth appropriate range that is set when the measured specific surface area of ​​the negative electrode active material is a second measured specific surface area that is smaller than the first measured specific surface area, the upper limit of the fourth optimum range is smaller than the upper limit of the third optimum range, The lower limit of the fourth optimum range is smaller than the lower limit of the third optimum range. Inspection equipment for non-aqueous secondary batteries.

7. A method for inspecting a nonaqueous secondary battery including a negative electrode plate having a negative electrode mixture layer containing a negative electrode active material, a positive electrode plate, and an electrolyte, comprising: obtaining a measured specific surface area of ​​the negative electrode active material based on the measurement results from the negative electrode plate; determining an appropriate range for a specific value of a charging quantity of electricity Q of the nonaqueous secondary battery based on the measured specific surface area of ​​the negative electrode active material; acquiring the charged quantity of electricity Q and the voltage V at predetermined time intervals while the nonaqueous secondary battery is being charged; Calculating a specific value of the charged quantity of electricity Q at which a decrease in slope is maximum in a Q-V curve showing the voltage V versus the charged quantity of electricity Q; determining that the nonaqueous secondary battery is normal when the specific value of the charging quantity of electricity Q is within an appropriate range based on the measured specific surface area of ​​the negative electrode active material and the specific value of the charging quantity of electricity Q, and determining that the nonaqueous secondary battery is abnormal when the specific value of the charging quantity of electricity Q is outside the appropriate range; the appropriate range of the specific value of the charged electricity Q includes a first appropriate range that is set when the measured specific surface area of ​​the negative electrode active material is a first measured specific surface area, and a second appropriate range that is set when the measured specific surface area of ​​the negative electrode active material is a second measured specific surface area that is smaller than the first measured specific surface area, The upper limit of the second appropriate range is greater than the upper limit of the first appropriate range, The lower limit of the second optimum range is greater than the lower limit of the first optimum range. Inspection method for non-aqueous secondary batteries.

8. A method for inspecting a nonaqueous secondary battery including a negative electrode plate having a negative electrode mixture layer containing a negative electrode active material, a positive electrode plate, and an electrolyte, comprising: obtaining a measured specific surface area of ​​the negative electrode active material based on the measurement results from the negative electrode plate; determining an appropriate range of an effective specific surface area of ​​the negative electrode active material in the negative electrode plate based on the measured specific surface area of ​​the negative electrode active material; acquiring a charged quantity of electricity Q and a voltage V of the nonaqueous secondary battery at predetermined time intervals while the nonaqueous secondary battery is being charged; Calculating a specific value of the charged quantity of electricity Q at which a decrease in slope is maximum in a Q-V curve showing the voltage V versus the charged quantity of electricity Q; Estimating an effective specific surface area of ​​the negative electrode active material in the negative electrode plate based on the specific value of the charged electricity Q; determining that the nonaqueous secondary battery is normal when the effective specific surface area of ​​the negative electrode active material in the negative electrode plate is within an appropriate range of the effective specific surface area of ​​the negative electrode active material, based on the measured specific surface area of ​​the negative electrode active material and the specific value of the charged quantity of electricity Q; and determining that the nonaqueous secondary battery is abnormal when the effective specific surface area of ​​the negative electrode active material in the negative electrode plate is outside the appropriate range of the effective specific surface area of ​​the negative electrode active material, the appropriate range of the effective specific surface area of ​​the negative electrode active material includes a third appropriate range that is set when the measured specific surface area of ​​the negative electrode active material is a first measured specific surface area, and a fourth appropriate range that is set when the measured specific surface area of ​​the negative electrode active material is a second measured specific surface area that is smaller than the first measured specific surface area, the upper limit of the fourth optimum range is smaller than the upper limit of the third optimum range, The lower limit of the fourth optimum range is smaller than the lower limit of the third optimum range. Inspection method for non-aqueous secondary batteries.

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