JP2023141511A - Non-aqueous secondary battery manufacturing method, non-aqueous secondary battery testing device, and non-aqueous secondary battery testing method - Google Patents

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

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.

In electric vehicles and hybrid vehicles, a lithium ion secondary battery, which is an example of a non-aqueous secondary battery, is used as a power source. A lithium ion secondary battery includes an electrode body having a positive electrode plate and a negative electrode plate. A negative electrode plate of a lithium ion secondary battery includes a negative electrode base material that is a metal plate such as a copper plate, and a negative electrode mixture layer formed on the negative electrode base material. The negative electrode mixture layer includes a negative electrode active material that is a material capable of intercalating and deintercalating lithium ions. As the negative electrode active material, carbon materials such as graphite, non-graphitizable carbon, and easily graphitizable carbon are used, for example.

The effective specific surface area (surface area per unit weight) of the negative electrode active material in the negative electrode plate affects various performances such as life characteristics and discharge characteristics of the lithium ion secondary battery. For example, Patent Document 1 discloses a technique for achieving good discharge characteristics by defining the effective specific surface area of a negative electrode active material in a negative electrode plate within a predetermined range.

Japanese Patent Application Publication No. 10-11604

However, in such technology, even if the effective specific surface area of the negative electrode active material in the negative electrode plate is defined within a predetermined range in the electrode plate manufacturing process, depending on the reduction reaction of the negative electrode mixture layer in the charging process, An unexpected SEI film was sometimes formed on the negative electrode mixture layer. Therefore, there is a need for a means for determining whether a manufactured lithium ion secondary battery is normal or not according to the reduction reaction of the negative electrode mixture layer at the manufacturing site.

A method for manufacturing a non-aqueous secondary battery to solve the above problems includes an electrode plate manufacturing process of manufacturing a negative electrode plate having a negative electrode mixture layer containing a negative electrode active material, and a positive electrode plate, and a step of manufacturing the negative electrode plate and the positive electrode. An assembly process for assembling a non-aqueous secondary battery using a plate and an electrolyte, a charging process for charging the non-aqueous secondary battery, and a determining process for 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 the measurement result from the negative electrode plate manufactured in the electrode plate manufacturing step, and obtaining the measured specific surface area of the negative electrode active material in the charging step. The amount of charge Q and voltage V of the non-aqueous secondary battery are acquired at predetermined intervals while the rechargeable battery is being charged, and the slope of the Q-V curve showing the voltage V against the amount of charge Q is determined. A specific value of the amount of charged electricity Q at which the amount of decrease is maximum is calculated, and based on the measured specific surface area of the negative electrode active material and the specific value of the amount of charged electricity Q, it is determined that the non-aqueous secondary battery is normal. Determine whether or not.

According to the above manufacturing method, in the first period at the beginning of charging in the charging process, the amount of increase in voltage V is larger than the amount of increase in amount of charged electricity Q, and the QV curve shows a steep rise. In the second period when the charging process progresses and the charged electricity amount Q reaches a specific value, the amount of increase in the voltage V with respect to the increase in the charged electricity amount Q becomes gradual, and the slope of the QV curve decreases significantly. Therefore, in the determination step, the value of the amount of charged electricity Q at the boundary between the first period and the second period is calculated as the specific value. Further, in the charging process, a part of the charging electricity amount Q is consumed for forming the 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 on the negative electrode plate. Note that the effective specific surface area of the negative electrode active material in the negative electrode plate referred to here is not the effective specific surface area of the negative electrode active material in the raw material state, but the effective specific surface area of the negative electrode active material in the state of being manufactured as a negative electrode plate. It shows the specific surface area. Therefore, due to the formation of an SEI film on the negative electrode mixture layer during charging, the rise of the QV curve in the first period and the specific value vary depending on the effective specific surface area of the negative electrode active material on the negative electrode plate. change. In addition, in the charging process, an unexpected SEI film is formed on the negative electrode mixture layer due to the reduction reaction of the negative electrode mixture layer. The amount of SEI coating may increase unexpectedly. Therefore, even if an unexpected SEI film is formed on the negative electrode mixture layer, the rise of the QV curve and the specific value in the first period 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 respond to the reduction reaction of the negative electrode mixture layer in the charging process. It can be determined whether the non-aqueous secondary battery is normal or not. In addition, by determining whether a non-aqueous secondary battery is normal from the Q-V curve in the charging process, it is possible to make a determination for all non-aqueous secondary batteries in the manufacturing process of non-aqueous secondary batteries. Become.

In the above manufacturing method, the determining step is based on the measured specific surface area of the negative electrode active material and the specific value of the charged electricity amount Q, and determines whether an unexpected SEI film is formed in the negative electrode mixture layer in the charging step. It is preferable to determine whether or not the non-aqueous secondary battery is normal by determining whether or not the non-aqueous secondary battery is normal.

In the above manufacturing method, the determining step calculates an appropriate range of a specific value of the charged quantity of electricity Q based on the measured specific surface area of the negative electrode active material, and the specific value of the charged quantity of electricity Q is within the appropriate range. If so, it is determined that the non-aqueous secondary battery is normal, and if the specific value of the charged electricity amount Q is outside the appropriate range, it is determined that the non-aqueous secondary battery is not normal. It is preferable.

In the above manufacturing method, the determining step calculates 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, and determines the charged electricity amount Q. Based on the value, the effective specific surface area of the negative electrode active material on the negative electrode plate is estimated, and when the effective specific surface area of the negative electrode active material on the negative electrode plate is within the appropriate range, the non-aqueous It is preferable to determine that the nonaqueous secondary battery is not normal when the secondary battery is determined to be normal and the effective specific surface area of the negative electrode active material in the negative electrode plate is outside the appropriate range. .

In the above manufacturing method, the determining step is based on the measurement results of some of the negative electrode plates among the plurality of negative electrode plates manufactured in the same lot in the electrode plate manufacturing step, based on the measurement ratio of the negative electrode active material. The surface area is obtained, and based on the measured specific surface area of the negative electrode active material and the specific value of the charged electricity amount Q, the non-conventional surface area is determined for a plurality of negative electrode plates manufactured in the same lot in the electrode plate manufacturing process. It is preferable to determine whether the water secondary battery is normal. According to the above manufacturing method, the measured specific surface area of the negative electrode active material is obtained based on the results measured from some of the negative electrode plates manufactured in the same lot. Thereby, it can be determined whether a non-aqueous secondary battery is normal or not based on the reduction reaction of the negative electrode mixture layer in the charging process for a plurality of negative electrode plates manufactured in the same lot.

In the above manufacturing method, the specific value of the amount of charged electricity Q is Q-d ² V/dQ ² indicating a value of d ² V/dQ ² obtained by second-order differentiation of the QV curve with respect to the amount of charged electricity Q. In the curve, it is preferable to calculate the value of the charged electricity amount Q at which a peak appears on the Qd ² V/dQ ² curve. According to the above manufacturing method, by using the Q-d ² V/dQ ² curve in calculating the specific value, it is possible to determine whether the non-aqueous secondary battery is normal according to the reduction reaction of the negative electrode mixture layer in the charging process. It can be easily determined whether or not.

A non-aqueous secondary battery inspection device for solving the above problems is a non-aqueous secondary battery inspection device 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. a first acquisition unit that acquires a measured specific surface area of the negative electrode active material based on the measurement result from the negative electrode plate; and a first acquisition unit that acquires a measured specific surface area of the negative electrode active material, and a second acquisition unit that acquires the charged quantity of electricity Q and the voltage V at predetermined time intervals, and the charged quantity of electricity whose slope decreases at a maximum in a QV curve showing the voltage V with respect to the charged quantity of electricity Q; A first process of calculating a specific value of Q, and determining whether or not 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 charged electricity amount Q. and a control unit that executes the second process.

A method for testing a non-aqueous secondary battery to solve the above problem 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. Then, the measured specific surface area of the negative electrode active material is obtained based on the measurement result from the negative electrode plate, and the charged electricity amount Q of the non-aqueous secondary battery is determined while the non-aqueous secondary battery is being charged. and the voltage V at predetermined time intervals, calculate a specific value of the charged quantity of electricity Q that maximizes the amount of decrease in slope in the QV curve showing the voltage V with respect to the charged quantity of electricity Q, and Based on the measured specific surface area of the active material and the specific value of the amount of charged electricity Q, it is determined whether the non-aqueous secondary battery is normal.

According to the present invention, it can be determined whether the non-aqueous secondary battery is normal or not depending on the reduction reaction of the negative electrode mixture layer in the charging process.

FIG. 1 is a schematic diagram showing the configuration of a non-aqueous secondary battery testing system. FIG. 2 is an exploded view of a part of the electrode body. FIG. 3 is a cross-sectional view of the electrode body in an expanded state. FIG. 4 is a block diagram showing the configuration of the inspection device. FIG. 5 is a diagram showing the correspondence among the amount of electricity Q, voltage V, and d ² V/dQ ² of the lithium ion secondary battery in the charging process. 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. FIG. 7 is a flowchart showing a method for manufacturing a lithium ion secondary battery. FIG. 8 is a flowchart showing the processing of the determination step. 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. FIG. 10 is a flowchart showing the processing of the determination step.

[First embodiment]
An embodiment of the present invention will be described below with reference to FIGS. 1 to 9.
[Non-aqueous secondary battery inspection system]
As shown in FIG. 1, a non-aqueous secondary battery inspection system 1 charges a non-aqueous secondary battery and checks whether the non-aqueous secondary battery is normal in the manufacturing process of the non-aqueous secondary battery. Make a judgment. The non-aqueous secondary battery testing system 1 includes a lithium ion secondary battery 10, a charging device 30, and a testing device 40.

The lithium ion secondary battery 10 is an example of a non-aqueous secondary battery. Charging device 30 is connected to lithium ion secondary battery 10 . The lithium ion secondary battery 10 is charged by receiving power from the charging device 30. The inspection device 40 determines the quality of the lithium ion secondary battery 10 based on the behavior of the charged electricity amount Q and the voltage V during charging of the lithium ion secondary battery 10 .

[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 constitute a battery pack. Battery packs are used in hybrid cars and electric cars.

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 metal such as aluminum or an aluminum alloy. The lithium ion secondary battery 10 is configured as a sealed battery case by attaching a lid 12 to a battery case 11.

The lid body 12 is provided with two external terminals 13A and 13B. External terminals 13A and 13B are used for charging and discharging power. In the non-aqueous secondary battery testing system 1, the external terminals 13A and 13B are electrically connected to the charging device 30 and the testing device 40.

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

The lithium ion secondary battery 10 includes a non-aqueous electrolyte 15. The non-aqueous electrolyte 15 is injected into the battery case 11 from an injection hole (not shown).
[Electrode body]
As shown in FIG. 2, the electrode body 20 is a flat wound body obtained by winding a laminate in which a long positive electrode plate 21 and a negative electrode plate 24 are laminated with a separator 27 in between. Therefore, the lithium ion secondary battery 10 includes a negative electrode plate 24, a positive electrode plate 21, and a 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 laminated in this order in the thickness direction.

[Positive plate]
As shown in FIG. 3, the positive electrode plate 21 includes a positive electrode base material 22 and a positive electrode mixture layer 23. The positive electrode base material 22 is a foil-shaped electrode base material formed in an elongated shape. The positive electrode mixture layer 23 is provided on each of the two opposing surfaces of the positive electrode base material 22 . The positive electrode base material 22 includes, at one end in the width direction, a positive electrode side exposed portion 22A in which the positive electrode base material 22 is exposed without the positive electrode mixture layer 23 formed thereon.

As the positive electrode base material 22, a metal foil made of aluminum or an alloy containing aluminum as a main component is used. The positive electrode base material 22 functions as a current collector in the positive electrode. In the state of a wound body, the positive electrode side exposed portion 22A of the positive electrode base material 22 has opposing surfaces pressed against each other to constitute a positive electrode side current collecting portion 20A.

The positive electrode mixture layer 23 is a cured 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 vaporizing 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.

As the positive electrode active material, a lithium-containing composite metal oxide that can insert and release lithium ions, which are charge carriers in the lithium ion secondary battery 10, is used. A lithium-containing composite oxide is an oxide containing lithium and a metal element other than lithium. Other metal elements other than lithium are selected from the group consisting of nickel, cobalt, manganese, vanadium, magnesium, molybdenum, niobium, titanium, tungsten, aluminum, and iron contained in the lithium-containing composite oxide as iron phosphate. At least one type of

For example, lithium-containing composite oxides include lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), and lithium manganate (LiMn ₂ O ₄ ). For example, the lithium-containing composite oxide is a ternary lithium-containing composite oxide containing nickel, cobalt, and manganese, and is nickel cobalt lithium manganate (LiNiCoMnO ₂ ). For example, the lithium-containing composite oxide is lithium iron phosphate (LiFePO ₄ ).

As the positive electrode solvent, an NMP (N-methyl-2-pyrrolidone) solution, which is an example of an organic solvent, is used. As the positive electrode conductive material, for example, carbon black such as acetylene black and Ketjen black, carbon fibers such as carbon nanotubes and carbon nanofibers, and graphite are used. The positive electrode binder is an example of a resin component contained in the positive electrode mixture paste. As the positive electrode binder, for example, polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), styrene butadiene rubber (SBR), etc. are used.

Note that the positive electrode plate 21 may include an insulating layer at the boundary between the positive electrode side exposed portion 22A and the positive electrode mixture layer 23. The insulating layer includes an inorganic component having insulation 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.

[Negative electrode plate]
The negative electrode plate 24 includes a negative electrode base material 25 and a negative electrode mixture layer 26. The negative electrode base material 25 is a foil-shaped electrode base material formed in an elongated shape. The negative electrode mixture layer 26 is provided on each of the two opposing surfaces of the negative electrode base material 25. The negative electrode base material 25 has a negative electrode side exposed part 25A in which the negative electrode mixture layer 26 is not formed and the negative electrode base material 25 is exposed at one end in the width direction, which is opposite to the positive electrode side exposed part 22A. Equipped with

As the negative electrode base material 25, a metal foil made of copper or an alloy containing copper as a main component is used. The negative electrode base material 25 functions as a current collector in the negative electrode. In the state of a wound body, the negative electrode side exposed portion 25A has opposing surfaces pressed against each other to form a negative electrode side current collector 20B.

The negative electrode mixture layer 26 is a cured 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 dispersion material, and a negative electrode binder. The negative electrode mixture layer 26 is formed by drying the negative electrode mixture paste and vaporizing the negative electrode solvent. Therefore, the negative electrode mixture layer 26 includes a negative electrode active material, a negative electrode dispersion material, and a negative electrode binder. Note that the negative electrode mixture layer 26 may further contain an additive such as a conductive material.

The negative electrode active material is a material that can insert and release lithium ions. As the negative electrode active material, carbon materials such as graphite, non-graphitizable carbon, easily graphitizable carbon, carbon nanotubes, etc. are used, for example. An example of the negative electrode solvent is water. For example, carboxymethyl cellulose (CMC) can be used as the negative electrode dispersion material. As the negative electrode binder, the same material as the positive electrode binder can be used. An example of the negative electrode binder is SBR.

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

The separator 27 is a nonwoven fabric made of polypropylene or the like. As the separator 27, for example, a porous polymer membrane such as a porous polyethylene membrane, a porous polyolefin membrane, a porous polyvinyl chloride membrane, an ion conductive polymer electrolyte membrane, etc. can be used.

[Nonaqueous electrolyte]
The non-aqueous electrolyte 15 is a composition containing a supporting salt in a non-aqueous solvent. As the non-aqueous solvent, one or more materials selected from the group consisting of propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, etc. can be used. Supporting salts include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN(CF ₃ SO ₂ ) ₂ , LiC(CF ₃ SO ₂ ) ₃ , LiI One or more kinds of lithium compounds (lithium salts) selected from the following can be used.

In this embodiment, a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate is used as the nonaqueous solvent. Lithium bisoxalate borate (LiBOB) as a lithium salt as an additive is added to the non-aqueous electrolyte 15. For example, LiBOB is added to the non-aqueous electrolyte 15 so that the concentration of LiBOB in the non-aqueous electrolyte 15 is 0.001 or more and 0.1 or less [mol/L].

[Inspection equipment]
As shown in FIG. 4, the inspection device 40 includes a control section 41, a storage section 42, a specific surface area acquisition section 43, a charging electricity amount acquisition section 44, and a voltage acquisition section 45. The control unit 41 is, for example, a CPU that controls the overall operation of the inspection device 40. The storage unit 42 includes, for example, a RAM that temporarily stores data and a nonvolatile memory such as an HDD or flash memory.

The specific surface area acquisition unit 43 acquires the effective specific surface area of the negative electrode active material on 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 referred to here is not the effective specific surface area of the negative electrode active material in the raw material state, but the effective specific surface area of the negative electrode active material in the state of being manufactured as the negative electrode plate 24. Indicates the effective specific surface area. Hereinafter, the effective specific surface area of the negative electrode active material in the negative electrode plate 24 will be simply referred to as "specific surface area of the negative electrode active material." Further, the effective specific surface area of the negative electrode active material based on the results measured from the negative electrode plate 24 is referred to as "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 the negative electrode plates 24 extracted from among the plurality of negative electrode plates 24 manufactured in the same lot.

The charging amount of electricity acquisition unit 44 acquires the charging amount of electricity Q supplied to the lithium ion secondary battery 10 that is being charged by the charging device 30. The voltage acquisition unit 45 acquires the voltage V of the lithium ion secondary battery 10 being charged by the charging device 30.

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 amount acquisition unit 44 to acquire the charging electricity amount Q and causes the voltage acquisition unit 45 to acquire the voltage V at predetermined time intervals. The charging electricity amount acquisition unit 44 and the voltage acquisition unit 45 perform a second acquisition process to acquire the charging electricity amount Q and the voltage V of the lithium ion secondary battery 10 at predetermined intervals while the lithium ion secondary battery 10 is being charged. This is an example of the section. The control unit 41 causes the storage unit 42 to store 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 in association with each other.

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 the appropriate range based on the measured specific surface area of the negative electrode active material. The appropriate range is a range of specific values Q1 for determining whether the lithium ion secondary battery 10 is normal.

The second calculation unit 41B obtains a QV curve indicating the voltage V with respect to the amount of charged electricity Q when the lithium ion secondary battery 10 is being charged. The second calculation unit 41B calculates a specific value Q1, which is the value of the amount of charged electricity Q at which the amount of decrease in the slope of the QV curve is maximum.

The determination unit 41C determines whether the lithium ion secondary battery 10 is normal 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. Determine. Thereby, the determination unit 41C determines the quality of the lithium ion secondary battery 10. The determination unit 41C determines that the lithium ion secondary battery 10 is normal when the specific value Q1 is within the appropriate range. The determination unit 41C determines that the lithium ion secondary battery 10 is not normal when the specific value Q1 is outside the appropriate range.

The storage section 42 includes a memory section 42A, a data storage section 42B, and a program storage section 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.

[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 explained with reference to FIGS. 5 and 6.

As shown in FIG. 5, a curve 101 in a graph 100 is an example of a QV curve. Further, a curve 102 in the graph 100 is an example of a Q-d ² V/dQ ² curve indicating the value of d ² V/dQ ² with respect to the amount of charged electricity Q.

As will be described in detail later, in the first period 101A at the beginning of charging in the charging process, the amount of increase in the voltage V is larger than the amount of increase in the amount of charged electricity Q, so the curve 101 shows a steep rise. In the second period 101B when the charging process progresses and the charged electricity amount Q reaches the specific value Q1, the amount of increase in the voltage V with respect to the increase in the charged electricity amount Q becomes gradual, and the slope of the QV curve decreases significantly. The specific value Q1 is the value of the amount of charged electricity Q at which the amount of decrease in the slope of the curve 101 is maximum. In such a case, the curve 102 has a peak 102P at the specific value Q1.

In the charging process, a part of the charging electricity amount Q is consumed to form a SEI (Solid Electrolyte Interphase) film on the negative electrode mixture layer 26. The amount of the SEI film formed on the negative electrode mixture layer 26 has a positive correlation with the specific surface area of the negative electrode active material. Therefore, by forming an SEI film on the negative electrode mixture layer 26 during charging, the rise of the curve 101 in the first period 101A and the specific value Q1 change depending on the specific surface area of the negative electrode active material.

Additionally, depending on the reduction reaction of the negative electrode mixture layer 26, an unexpected SEI film may be formed on the negative electrode mixture layer 26. As a specific example, as a reduction reaction of the negative electrode mixture layer 26, the negative electrode mixture layer 26 may have a high water content and an unexpected SEI film derived from water may be formed. In this case, the amount of SEI coating formed on the negative electrode mixture layer 26 increases. In this way, even when an unexpected SEI film is formed in the negative electrode mixture layer 26, the rise of the curve 101 and the specific value Q1 in the first period 101A change. Therefore, by obtaining the measured specific surface area of the negative electrode active material and calculating the specific value Q1 in the charging process, it is possible to prevent unexpected SEI in the negative electrode mixture layer 26 according to the reduction reaction of the negative electrode mixture layer 26. It can be determined whether a film has been formed. Thereby, it can be determined whether the lithium ion secondary battery 10 is normal.

As shown in FIG. 6, a curve 201 in a graph 200 indicates the open circuit potential (OCP) on the positive electrode side with respect to the amount of charge Q in the charging process. A curve 202 in the graph 200 shows the open circuit potential on the negative electrode side with respect to the amount of charged electricity Q in the charging process. A curve 203 in the graph 200 is an example of a QV curve showing the voltage V of the lithium ion secondary battery 10 with respect to the amount of charged electricity Q in the charging process. The voltage V is equal to the value obtained by subtracting the open circuit potential of the negative electrode from the open circuit potential of the positive electrode. That is, curve 203 is the difference between curve 201 and curve 202.

In the graph 200, a curve 202A shown by a broken line indicates the open circuit potential on the negative electrode side with respect to the amount of charged electricity Q when the specific surface area of the negative electrode active material is smaller than the state of the curve 202. In the graph 200, a curve 203A indicated by a broken line is an example of a QV curve when the specific surface area of the negative electrode active material is smaller than the state of the curve 203.

When the specific surface area of the negative electrode active material becomes relatively small, the amount of SEI coating formed in the negative electrode mixture layer 26 decreases. Then, the amount of charged electricity Q consumed in forming the SEI film decreases, so that the entire curve 202A shifts to the right side of the curve 202 in relation to the curve 201. In this case, the specific value Q1A on the curve 203A also shifts to the right side of the specific value Q1 on the curve 203.

In the graph 200, a curve 202B shown by a broken line indicates the open circuit potential on the negative electrode side with respect to the amount of charged electricity Q when the specific surface area of the negative electrode active material is larger than the state of the curve 202. In the graph 200, a curve 203B indicated by a broken line is an example of a QV curve when the specific surface area of the negative electrode active material is larger than that of the curve 203.

When the specific surface area of the negative electrode active material becomes relatively large, the amount of SEI coating formed in the negative electrode mixture layer 26 increases. Then, as the amount of charged electricity Q consumed for forming the SEI film increases, the entire curve 202B shifts to the left side of the curve 202 in relation to the curve 201. In this case, the specific value Q1B on the curve 203B is also shifted to the left side of the specific value Q1 on the curve 203.

Furthermore, when an unexpected SEI coating is formed on the negative electrode mixture layer 26, the amount of SEI coating formed on the negative electrode mixture layer 26 increases. 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.

As described above, the specific value Q1 in the QV curve changes depending on the specific surface area of the negative electrode active material. In addition to this, the specific value Q1 in the QV curve changes due to the formation of an unexpected SEI film in the negative electrode mixture layer 26. Therefore, by determining whether or not the specific value Q1 in the QV curve is within the appropriate range corresponding to the measured specific surface area of the negative electrode active material, the negative electrode mixture layer In step 26, it can be evaluated whether an unexpected SEI film is formed. Thereby, it can be determined whether the lithium ion secondary battery 10 is normal.

[Method for manufacturing lithium ion secondary battery]
As shown in FIG. 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 a plate manufacturing process. The kneading step includes a step of kneading the positive electrode mixture paste and a step of kneading the negative electrode mixture paste. The electrode plate manufacturing process is a process of manufacturing the positive electrode plate 21 and the negative electrode plate 24, and includes a manufacturing process of the positive electrode plate 21 and a manufacturing process of the negative electrode plate 24.

In the manufacturing process of the positive electrode plate 21, a positive electrode mixture paste is applied to both sides of the positive electrode base material 22 so as to form positive electrode side exposed portions 22A at both ends in the width direction. Thereafter, the positive electrode mixture paste is dried to form the positive electrode mixture layer 23. Next, the thickness of the positive electrode mixture layer 23 is adjusted by pressing the positive electrode mixture layer 23 formed on both surfaces of the positive electrode base material 22 . Thereafter, the positive electrode base material 22 is cut at the center in the width direction. Through the above steps, two positive electrode plates 21 are manufactured at one time.

In the manufacturing process of the negative electrode plate 24, a negative electrode mixture paste is applied to both sides of the negative electrode base material 25 so as to form negative electrode side exposed portions 25A at both ends in the width direction. Thereafter, the negative electrode mixture paste is dried to form the negative electrode mixture layer 26. Next, the thickness of the negative electrode mixture layer 26 is adjusted by pressing the negative electrode mixture layer 26 formed on both sides of the negative electrode base material 25. Thereafter, the negative electrode base material 25 is cut at the center in the width direction. Through the above steps, two negative electrode plates 24 are manufactured at one time.

Step S1-2 is an assembly process for assembling the lithium ion secondary battery 10 using the negative electrode plate 24, the positive electrode plate 21, and the non-aqueous electrolyte 15. In the assembly process, the electrode body 20 is first manufactured. Specifically, first, the positive electrode plate 21 and the negative electrode plate 24 are laminated with the separator 27 in between, and then they are rolled up and further pressed flat. Thereafter, the positive electrode side exposed portion 22A is pressure-contacted to form the positive electrode side current collector portion 20A, and the negative electrode side exposed portion 25A is press-contacted to form the negative electrode side current collector portion 20B. The electrode body 20 is manufactured by the above procedure.

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 member 14A. The negative current collector 20B is electrically connected to the negative external terminal 13B via the negative current collector 14B. The upper part of the battery case 11 is covered with a lid 12. After removing moisture from the electrode body 20 by heat treatment, the non-aqueous electrolyte 15 is injected into the battery case 11. The lithium ion secondary battery 10 is assembled by the above procedure.

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 first charging of the lithium ion secondary battery 10 assembled in the assembly process. In the charging process, external terminals 13A and 13B of the lithium ion secondary battery 10 are connected to the charging device 30 and the testing device 40.

Step S1-4 is a determination step in which the inspection device 40 determines whether or not the lithium ion secondary battery 10 is normal based on the behavior of the charged electricity amount Q and voltage V in the charging process. In particular, in the negative electrode mixture layer 26, an unexpected SEI film may be formed depending on the reduction reaction in the charging process after the electrode plate manufacturing process is completed. In this way, it is possible to determine whether the lithium ion secondary battery 10 is normal or not depending on whether an unexpected SEI film is formed in the negative electrode mixture layer 26 based on the behavior of the amount of charged electricity Q and the voltage V in the charging process. It can be determined whether or not. In the manufacturing process of the lithium ion secondary battery 10, only the lithium ion secondary battery 10 determined to be normal in the determination process proceeds to step S1-5, which is a subsequent process.

Step S1-5 is an aging process in which the lithium ion secondary battery 10 that has undergone the charging process and the determination process is left at high temperature for a certain period of time. The aging process dissolves metal foreign substances in the lithium ion secondary battery 10 and stabilizes the SEI coating.

[Judgment process]
The determination step (step S1-4) will be described in detail below with reference to FIGS. 8 and 9.
As shown in FIG. 8, in the determination step, the inspection device 40 executes 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 obtains the 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 plate 24 manufactured in the electrode plate manufacturing process. Among the plurality of negative electrode plates 24 manufactured in the same lot in the electrode plate manufacturing process, some of the negative electrode plates 24 are sampled to be measured. In this manner, the specific surface area acquisition unit 43 acquires the measured specific surface area of the negative electrode active material based on the results of measurement from the negative electrode plate 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 measured from some of the negative electrode plates 24 among the plurality of negative electrode plates 24 manufactured in the same lot in the electrode plate manufacturing process. do.

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 of the specific value Q1 in the data storage unit 42B. Thereby, the control unit 41 sets an appropriate range for the calculated specific value Q1.

[Setting the appropriate range of specific values]
Here, with reference to FIG. 9, a procedure for setting the appropriate range of the specific value Q1 will be described.
First, before the manufacturing process of the lithium ion secondary battery 10, by using a plurality of levels of negative electrode active materials with different specific surface areas in the raw material state, a plurality of negative electrode active materials with different specific surface areas are used. A negative electrode plate 24 is produced. Next, in each level of the negative electrode plate 24, the specific surface area of the negative electrode active material contained in the negative electrode mixture layer 26 is measured using a measurement method such as the BET method. After assembling a plurality of levels of lithium ion secondary batteries 10 using each of the plurality of negative electrode plates 24 having different specific surface areas of the negative electrode active materials, charging is performed and the specific value Q1 is set as in step S1-4. calculate. Note that, for example, by changing the manufacturing conditions of the negative electrode plate 24, negative electrode plates 24 having a plurality of levels in which the specific surface area of the negative electrode active material is different may be produced.

As shown in FIG. 9, each of the plurality of points P plotted in the graph 300 indicates the specific surface area and specific value of the negative electrode active material in each of the plurality of lithium ion secondary batteries 10 in which the specific surface area of the negative electrode active material is different. The correspondence with Q1 is shown. An approximate line 301 in the graph 300 is an approximate line derived from a plurality of points P, and is a calibration curve for setting an appropriate range for the specific value Q1. The approximate line 301 has a negative slope such that the specific value Q1 becomes smaller as the specific surface area of the negative electrode active material becomes larger.

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

For example, the appropriate upper limit approximation line 302 and the appropriate lower limit approximation line 303 are ranges based on the approximation line 301 in consideration of the measurement error of the specific value Q1. 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 from the appropriate lower limit approximation line 303, A lower limit QRL is set as the lower limit of the appropriate range of the specific value Q1. In this way, an 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 section 42B.

Next, in the determination step of FIG. 8, in step S2-2, the control unit 41 determines an allowable range of 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 permissible range of the measured specific surface area of the negative electrode active material is a range that takes into account the measurement error of the measured specific surface area of the negative electrode active material and the manufacturing error of the negative electrode plate 24 based on the measured specific surface area of the negative electrode active material. The permissible range of the measured specific surface area of the negative electrode active material is from the minimum permissible specific surface area to the maximum permissible specific surface area. The allowable lower limit specific surface area may be the area obtained by subtracting the 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.

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. Thereby, the control unit 41 sets the appropriate range of the specific value Q1 so as to correspond to the permissible range of the measured specific surface area of the negative electrode active material.

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 approximate line 301. Further, the control unit 41 can estimate the 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 sets 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 plurality of negative electrode plates 24 manufactured in the same lot in the electrode plate manufacturing process. It is possible to set an appropriate range of

As a specific example, with respect to the specific surface area AR of the negative electrode active material, the allowable range of the measured specific surface area of the negative electrode active material is from the allowable lower limit specific surface area AL to the allowable upper limit specific surface area AH. The 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. The 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. Thereby, 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.

In step S2-3, the inspection device 40 examines a QV curve indicating the value of the voltage V with respect to the amount of charged electricity Q in the charging process for a plurality of negative plates 24 manufactured in the same lot in the plate manufacturing process. get. First, in the charging process, while the lithium ion secondary battery 10 is being charged, the control unit 41 executes a process of causing the charging electricity amount obtaining unit 44 to obtain the charging electricity amount Q at predetermined intervals. At the same time, in the charging process, the control unit 41 executes a process of causing the voltage acquisition unit 45 to acquire the voltage V at predetermined time intervals while the lithium ion secondary battery 10 is being charged. The timing at which the charging amount of electricity acquisition section 44 acquires the charging amount of electricity Q and the timing at which the voltage acquisition section 45 acquires the voltage V are the same. The control unit 41 stores the acquired amount of charged electricity Q and voltage V in association with each other 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.

In step S2-4, the second calculation unit 41B calculates the value of d ² V/dQ ² obtained by second-order differentiation of the QV curve. To give a specific example, the second calculation unit 41B calculates a curve 102 from a curve 101 shown in FIG.

In step S2-5, the second calculation unit 41B calculates, as the specific value Q1, the value of the amount of charged electricity Q at which the calculated value of d ² V/dQ ² becomes the maximum value. To give a specific example, the second calculation unit 41B converts the value of the charging amount Q at the peak 102P of the curve 102 shown in FIG. 5 into the charging amount Q at the boundary between the first period 101A and the second period 101B. It is calculated as a specific value Q1 which is the value of . That is, the second arithmetic unit 41B calculates a specific value Q1 of the amount of charged electricity Q that maximizes the amount of decrease in slope in the QV curve indicating the value of the voltage V with respect to the amount of charged electricity Q. In addition, the specific value Q1 has a peak on the d ² V/dQ ² curve in the d ² V/dQ ² curve that indicates the value of d ² V/dQ ² obtained by second-order differentiation of the QV curve with respect to the charging electricity quantity Q. It can be said that it is calculated as the value of the amount of charged electricity Q that appears. The process of calculating the specific value Q1 in step S2-5 is an example of the first process executed by the inspection device 40.

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. In other words, the determination unit 41C determines whether the negative electrode mixture layer 26 is It is determined whether an outer SEI film is formed. Thereby, the determination unit 41C can 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 the second process executed by the inspection device 40.

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 aging step, which is a subsequent process.

If the specific value Q1 is outside the appropriate range, the determination unit 41C determines that the lithium ion secondary battery 10 is not normal, and proceeds to step S2-8. The lithium ion secondary battery 10 that has proceeded to step S2-8 is determined to be not normal and is removed from the production line.

In the determination process, steps S2-1 and S2-2 target some of the negative plates 24 among the plurality of negative plates 24 manufactured in the same lot in the plate manufacturing process. On the other hand, steps S2-3 to S2-8 target a plurality of negative electrode plates 24 manufactured in the same lot in the electrode plate manufacturing process. In other words, the determination unit 41C determines whether lithium ion It is determined whether the secondary battery 10 is normal.

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

[Operation of the first embodiment]
The operation of the first embodiment will be explained.
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 extracted as measurement targets from a plurality of negative electrode plates 24 manufactured in the same lot. The specific surface area of the negative electrode active material is measured from the negative electrode plate 24 extracted as the measurement target. 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 plate 24 extracted as the measurement target. After the source process is completed, the assembly process is performed. A charging process is performed after the assembly process is completed.

While the lithium ion secondary battery 10 is being charged in the charging process, the charged electricity amount Q and voltage V of the lithium ion secondary battery 10 are acquired at predetermined intervals. As a result, a QV curve indicating the value of the voltage V with respect to the amount of charging electricity Q is obtained. Based on the QV curve, the value of d ² V/dQ ² is calculated by second-order differentiation of the QV curve. The value of the amount of charged electricity Q at which the value of d ² V/dQ ² becomes the maximum value is calculated as the specific value Q1. As a result of calculation in this manner, the specific value Q1 can be obtained.

After the charging process is completed, a determination process is performed. In the determination step, a measured specific surface area of the negative electrode active material is obtained. An appropriate range for the specific value Q1 is calculated based on the obtained 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 not normal.

[Effects of the first embodiment]
The effects of the first embodiment will be explained.
(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, the reduction reaction of the negative electrode mixture layer 26 is performed. Depending on this, it can be determined whether the lithium ion secondary battery 10 is normal or not. Furthermore, by determining the specific surface area of the negative electrode active material from the Q-V curve in the charging process, it becomes possible to perform the determination for all the lithium ion secondary batteries 10 in the manufacturing process of the lithium ion secondary batteries 10. .

(2) The measured specific surface area of the negative electrode active material can be obtained based on the results measured 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 a plurality of negative electrode plates 24 manufactured in the same lot.

(3) In calculating the specific value Q1, by using the Q-d ² V/dQ ² curve, it can be determined whether the lithium ion secondary battery 10 is normal or not depending on the reduction reaction of the negative electrode mixture layer 26. It can be easily determined.

(4) By performing the determination process during the first charge of the lithium ion secondary battery 10 after assembly, the lithium ion secondary battery 10 It is possible to determine whether or not it is normal. Therefore, the accuracy of determination can be improved.

(5) In setting the appropriate range, by using a calibration curve derived from the specific value Q1 calculated from a plurality of lithium ion secondary batteries 10 with different specific surface areas of negative electrode active materials, it is possible to It is possible to set an appropriate range that takes into account the influence of the composition and manufacturing process. Therefore, the accuracy of determination can be improved.

[Second embodiment]
Next, a second embodiment will be described. In the following description, the same configurations and the same control contents as those of the already described embodiments will be denoted by the same reference numerals, and overlapping descriptions will be omitted or simplified.

In the first embodiment, the control unit 41 determines whether the lithium ion secondary battery 10 is normal based on whether the calculated specific value Q1 is within the appropriate range of 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 depending on whether the estimated specific surface area of the negative electrode active material is within the appropriate range of the specific surface area of the negative electrode active material.

As shown in FIG. 10, in the second embodiment, after step S2-1 is completed, in step S2-9, the control unit 41 determines the specific surface area of the negative electrode active material based on the measured specific surface area of the negative electrode active material. Calculate the appropriate range of. 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 of the specific surface area of the negative electrode active material. The control unit 41 stores the calculated appropriate range of the specific surface area of the negative electrode active material in the data storage unit 42B. Thereby, the control unit 41 sets the appropriate range of the calculated specific surface area of the negative electrode active material.

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

In step S2-11, the 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 the data storage unit 42B included in the storage unit 42. In other words, the determination unit 41C determines whether the negative electrode mixture layer 26 is It is determined whether an outer SEI film is formed. Thereby, the determination unit 41C can 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 S2-11 is an example of the second process executed by the inspection device 40.

If the estimated specific surface area of the negative electrode active material 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. If the estimated specific surface area of the negative electrode active material is outside the appropriate range, the determination unit 41C determines that the lithium ion secondary battery 10 is not normal, and proceeds to step S2-8.

Further, the above processing is executed by an inspection program installed and stored in the program storage section 42C. In step S2-9, the inspection program causes the first calculation unit 41A to execute a process of calculating an appropriate range. In step S2-10, the inspection program estimates the specific surface area of the negative electrode active material based on the specific value Q1. In step S2-11, the test program causes the determination unit 41C to execute a process of determining whether the lithium ion secondary battery 10 is normal.

[Example of change]
Note that the above embodiment can be modified and implemented as follows.
- For example, the determination unit 41C may determine whether the measured specific surface area of the negative electrode active material itself is within an appropriate range. When determining that the measured specific surface area of the negative electrode active material itself is within the appropriate range, the determination unit 41C performs determination based on the specific value Q1 in step S2-6 of FIG. 8 and step S2-11 of FIG. Good too. If the 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 that the lithium ion secondary battery 10 is not normal at that point.

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. Further, in the process of pressing the negative electrode mixture layer 26, the particles of the negative electrode active material are broken, so that the specific surface area of the negative electrode active material increases. 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 of the negative electrode mixture layer 26.

For example, if the specific surface area of the negative electrode active material becomes excessively large, the life characteristics of the lithium ion secondary battery 10 will deteriorate. On the other hand, when the specific surface area of the negative electrode active material becomes excessively small, lithium tends to precipitate on the electrode body 20. Therefore, the appropriate range of the measured specific surface area of the negative electrode active material is an upper limit that does not excessively deposit lithium on the electrode body 20, and a lower limit that does not excessively deteriorate the life characteristics of the lithium ion secondary battery 10. may be determined.

- For example, the control unit 41 calculates 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. You may estimate the appropriate range of . Further, in this case, the control unit 41 may, for example, determine a range in which a tolerance is calculated for the estimated appropriate range of the specific value Q1 as the appropriate range of the specific value Q1.

- For example, the control unit 41 may estimate the specific value Q1 corresponding to the measured specific surface area of the negative electrode active material from the approximate line 301 without referring to the appropriate upper limit approximate line 302 and the appropriate lower limit approximate line 303. Further, in this case, the control unit 41 may estimate, for example, a range in which a tolerance is calculated for the estimated specific value Q1 as the appropriate range of the specific value Q1.

- The measurement specific surface area of the negative electrode active material may be measured at any timing, for example, after the electrode plate manufacturing process. The measured specific surface area of the negative electrode active material may be obtained at any timing, for example, after the electrode plate manufacturing process. The appropriate range of the specific value Q1 and the appropriate range of the specific surface area of the negative electrode active material may be calculated at any timing, for example, after the electrode plate manufacturing process.

- The case where the appropriate range of the specific value Q1 is set using a calibration curve derived from the specific values Q1 of a plurality of lithium ion secondary batteries 10 whose negative electrode active materials have different specific surface areas has been illustrated. Instead, instead of actually manufacturing multiple lithium ion secondary batteries 10 with different specific surface areas of negative electrode active materials, the appropriate range of the specific value Q1 is set by model simulation such as finite element analysis or numerical calculation. You may.

- The determination step may be performed not during the first charging but during the second and subsequent charging. In this case, in order to set the appropriate range of the specific value Q1, a plurality of lithium ion secondary batteries 10 having different specific surface areas of negative electrode active materials that have undergone similar charge/discharge cycles may be used. When performing the determination step at the time of second and subsequent charging, the size of the specific surface area of the negative electrode active material can also be determined for the lithium ion secondary battery 10 that has undergone a charge/discharge cycle.

- Calculation of the specific value Q1 is not limited to the method using the Q-d ² V/dQ ² curve. For example, a value of the amount of charged electricity Q at which the value of dV/dQ is equal to or less than a predetermined threshold value may be calculated as the specific value Q1. The threshold value in this case 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 an appropriate size.

- In the non-aqueous secondary battery inspection system 1, the non-aqueous secondary battery is not limited to the lithium ion secondary battery 10, and may have any configuration as long as it includes a positive electrode plate 21, a negative electrode plate 24, and a non-aqueous electrolyte 15. .

- The electrode body 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 laminated with separators 27 in between.
- The lithium ion secondary battery 10 may be installed in an automatic transport machine, a special vehicle for cargo handling, an electric vehicle, a hybrid vehicle, etc., as well as a computer or other electronic equipment, and may be used in other systems. It may be configured. For example, it may be installed in a moving body such as a ship or an aircraft, and is a power supply system that supplies power from a power plant to a building, home, etc. where a secondary battery is installed via a substation, etc. Good too.

- The expression "at least one" as used herein means "one or more" of the desired options. As an example, the expression "at least one" as used herein means "only one option" or "both of the two options" if the number of options is two. As another example, the expression "at least one" as used herein means "only one option" or "any combination of two or more options" if there are three or more options. means. Moreover, the expression "at least one type" is also the same as the expression "at least one."

1... Non-aqueous secondary battery inspection system 10... Lithium ion secondary battery 15... Non-aqueous electrolyte 20... Electrode body 21... Positive electrode plate 22... Positive electrode base material 23... Positive electrode mixture layer 24... Negative electrode plate 25... Negative electrode base material 26...Negative electrode mixture layer 27...Separator 30...Charging device 40...Inspection device 41...Control section 41A...First calculation section 41B...Second calculation section 41C...Judgment section 42...Storage section 42A...Memory section 42B...Data storage section 42C...Program storage unit 43...Specific surface area acquisition unit 44...Charging electricity amount acquisition unit 45...Voltage acquisition unit

Claims (8)

An electrode plate manufacturing process 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 nonaqueous secondary battery using the negative electrode plate, the positive electrode plate, and an electrolyte;
a charging step of charging the non-aqueous secondary battery;
a determination step of determining whether the non-aqueous secondary battery is normal;
The determination step includes:
Obtaining the measured specific surface area of the negative electrode active material based on the results measured from the negative electrode plate manufactured in the electrode plate manufacturing process,
In the charging step, while the non-aqueous secondary battery is being charged, the amount of electricity Q and the voltage V of the non-aqueous secondary battery are acquired at predetermined intervals;
In a QV curve showing the voltage V with respect to the charged quantity of electricity Q, calculate a specific value of the charged quantity of electricity Q at which the amount of decrease in slope is maximum,
A method for manufacturing a non-aqueous secondary battery, wherein it is determined 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 charged electricity amount Q. The determination step determines whether an unexpected SEI film is 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 electricity amount Q. The method for manufacturing a non-aqueous secondary battery according to claim 1, wherein it is determined whether or not the non-aqueous secondary battery is normal. The determination step includes:
Based on the measured specific surface area of the negative electrode active material, calculate an appropriate range of the specific value of the charged electricity amount Q,
It is determined that the non-aqueous secondary battery is normal when the specific value of the charged electricity amount Q is within the appropriate range, and when the specific value of the charged electricity amount Q is outside the appropriate range, The method for manufacturing a non-aqueous secondary battery according to claim 1 or 2, wherein the non-aqueous secondary battery is determined to be not normal. The determination step includes:
Based on the measured specific surface area of the negative electrode active material, calculate an appropriate range of the effective specific surface area of the negative electrode active material in the negative electrode plate,
Estimating the effective specific surface area of the negative electrode active material in the negative electrode plate based on the specific value of the charging electricity amount Q,
When the effective specific surface area of the negative electrode active material in the negative electrode plate is within the appropriate range, it is determined that the non-aqueous secondary battery is normal, and the effective specific surface area of the negative electrode active material in the negative electrode plate is determined to be normal. The method for manufacturing a non-aqueous secondary battery according to claim 1 or 2, wherein it is determined that the non-aqueous secondary battery is not normal when the specific surface area is outside the appropriate range. The determination step includes:
Obtaining the measured specific surface area of the negative electrode active material based on the results measured 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,
Based on the measured specific surface area of the negative electrode active material and the specific value of the charging electricity amount Q, the non-aqueous secondary battery is The method for manufacturing a non-aqueous secondary battery according to any one of claims 1 to 4, wherein it is determined whether or not it is normal. The specific value of the charged quantity of electricity Q is the value of the Q-d ² V/dQ ² curve, which indicates the value of d ² V/dQ ² obtained by second-order differentiation of the Q-V curve with respect to the charged quantity of electricity Q. The method for manufacturing a non-aqueous secondary battery according to any one of claims 1 to 5, wherein the value is calculated as the value of the amount of charged electricity Q at which a peak appears on the -d ² V/dQ ² curve. A non-aqueous secondary battery inspection device comprising 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 the results measured from the negative electrode plate;
a second acquisition unit that acquires the amount of electricity Q and the voltage V of the non-aqueous secondary battery at predetermined time intervals while the non-aqueous secondary battery is being charged;
A first process of calculating a specific value of the amount of charged electricity Q that maximizes the amount of decrease in slope in a QV curve showing the voltage V with respect to the amount of charged electricity Q; and a measured specific surface area of the negative electrode active material. a control unit that executes a second process of determining whether or not the non-aqueous secondary battery is normal based on the specific value of the charged electricity amount Q. . A method for testing a non-aqueous secondary battery comprising a negative electrode plate having a negative electrode mixture layer containing a negative electrode active material, a positive electrode plate, and an electrolyte, the method comprising:
Obtaining a measured specific surface area of the negative electrode active material based on the results measured from the negative electrode plate,
Obtaining the amount of charge Q and voltage V of the non-aqueous secondary battery at predetermined intervals while the non-aqueous secondary battery is being charged;
In a QV curve showing the voltage V with respect to the charged quantity of electricity Q, calculate a specific value of the charged quantity of electricity Q at which the amount of decrease in slope is maximum,
A method for testing a non-aqueous secondary battery, comprising: 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 charged quantity of electricity Q.

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