JP2023123905A - Method for manufacturing nonaqueous secondary battery, device for inspecting nonaqueous secondary battery, and method for inspecting nonaqueous secondary battery - Google Patents

Abstract

To provide a method for manufacturing a nonaqueous secondary battery, a device for inspecting the nonaqueous secondary battery, and a method for inspecting the nonaqueous secondary battery, capable of determining whether an effective specific surface area of a negative electrode active material in the nonaqueous secondary battery is within an appropriate range or not.SOLUTION: A method for manufacturing a nonaqueous secondary battery includes: a charging step of charging a lithium ion secondary battery 10 that includes a positive electrode plate, a negative electrode plate including a negative electrode mixture layer containing a negative electrode active material, and an electrolyte; and a determination step of determining whether an effective specific surface area per weight in the negative electrode active material is an appropriate size or not. In the determination step, a charge electricity amount Q and a voltage V of the lithium ion secondary battery 10 during the charging step are acquired every predetermined time; a specific value of the charge electricity amount Q at which the amount of slope reduction is maximum in a Q-V curve representing the value of the voltage V relative to the charge electricity amount Q is calculated; and if the specific value is within a pre-set appropriate range, it is determined that the specific surface area is an appropriate size, while if the specific value is outside the appropriate range, it is determined that the specific surface area is not an appropriate size.SELECTED DRAWING: Figure 1

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 an inspection method for a non-aqueous secondary battery.

Electric vehicles and hybrid vehicles use a lithium-ion secondary battery, which is an example of a non-aqueous secondary battery, as their power source. A lithium ion secondary battery includes an electrode body having a positive plate and a negative plate. A negative electrode plate of a lithium ion secondary battery includes a negative electrode base material, which 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 contains a negative electrode active material that is a material capable of intercalating and deintercalating lithium ions. Carbon materials such as graphite, non-graphitizable carbon, and graphitizable carbon are used as the negative electrode active material, for example.

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

JP-A-10-11604

The effective specific surface area of the negative electrode active material in the negative electrode mixture layer depends on the specific surface area of the negative electrode active material in the raw material state before forming the negative electrode mixture layer and the manufacturing process when forming the negative electrode mixture layer. do. Therefore, the effective specific surface area of the negative electrode active material differs from lithium ion secondary battery to lithium ion secondary battery due to variations in manufacturing conditions. Therefore, at the manufacturing site, there is a demand for means for determining whether or not the effective specific surface area of the negative electrode active material in the manufactured lithium ion secondary battery is within the appropriate range.

A method for manufacturing a non-aqueous secondary battery for solving the above-mentioned problems includes assembling a non-aqueous secondary battery using a positive electrode plate, a negative electrode plate having a negative electrode mixture layer containing a negative electrode active material, and an electrolytic solution. an assembling step, a charging step of charging the non-aqueous secondary battery, and a determining step of determining whether or not the effective specific surface area per weight of the negative electrode active material is an appropriate size; acquires the charged quantity of electricity Q and voltage V of the non-aqueous secondary battery in the charging step at predetermined time intervals, and decreases the slope of the QV curve showing the value of the voltage V with respect to the charged quantity of electricity Q A specific value of the charged quantity of electricity Q that maximizes the amount is calculated, and if the specific value is within a preset appropriate range, it is determined that the specific surface area is an appropriate size, and the specific value is If it is out of the appropriate range, it is determined that the specific surface area is not an appropriate size.

According to the manufacturing method described above, in the first period at the beginning of charging in the charging process, the amount of increase in the voltage V is greater than the amount of increase in the amount of charge Q, and the QV curve shows a sharp rise. In the second period in which the charging process progresses and the charged quantity of electricity Q reaches a specific value, the amount of increase in the voltage V with respect to the amount of increase in the charged quantity of electricity Q becomes moderate, and the slope of the QV curve greatly decreases. Therefore, in the determination step, the value of the charged quantity of electricity Q at the boundary between the first period and the second period is calculated as the specific value. Further, in the charging process, part of the charged quantity of electricity Q is consumed to form the SEI film on the negative electrode mixture layer. The amount of the SEI coating formed on the negative electrode mixture layer has a positive correlation with the effective specific surface area of the negative electrode active material. Therefore, when the SEI film is formed on the negative electrode mixture layer during charging, the rise of the QV curve and the specific value in the first period change according to the effective specific surface area of the negative electrode active material. Therefore, by calculating the specific value in the charging process, it is possible to determine whether or not the effective specific surface area of the negative electrode active material is an appropriate size. In addition, by judging the size of the effective specific surface area of the negative electrode active material from the QV curve in the charging process, it is possible to judge all non-aqueous secondary batteries in the manufacturing process of non-aqueous secondary batteries. Become.

In the above manufacturing method, the specific value is ^{a Q-d 2 V/dQ 2 curve indicating a value of d 2 V /} dQ ² obtained by second-order differentiating the QV curve with respect to the charged quantity of electricity Q. It is preferably calculated as the value of the charged quantity of electricity Q at which a peak appears in the -d ² V/dQ ² curve. According to the above manufacturing method, in calculating the specific value, by using the Q-d ² V/dQ ² curve, it is possible to easily determine whether the effective specific surface area of the negative electrode active material is an appropriate size. can.

In the manufacturing method described above, the charging performed in the charging step is preferably the initial charging of the non-aqueous secondary battery assembled in the assembling step. According to the above manufacturing method, by performing the determination step when the non-aqueous secondary battery is charged for the first time, the effective negative electrode active material can be obtained without including changes in the non-aqueous secondary battery due to repeated charging and discharging. A determination can be made about the specific surface area. Therefore, the precision of determination can be improved.

In the manufacturing method described above, the appropriate range is preferably set based on a calibration curve derived from the specific values calculated for each of a plurality of prefabricated non-aqueous secondary batteries having different specific surface areas. . According to the above manufacturing method, in setting the appropriate range, by using a calibration curve derived from specific values calculated from a plurality of non-aqueous secondary batteries having different specific surface areas, the actual composition and An appropriate range can be set in consideration of the influence of the manufacturing process. Therefore, the precision of determination can be improved.

A non-aqueous secondary battery inspection apparatus for solving the above problems inspects a non-aqueous secondary battery including a positive electrode plate, a negative electrode plate having a negative electrode mixture layer containing a negative electrode active material, and an electrolytic solution. An inspection device, comprising: an acquisition unit that acquires a charged quantity of electricity Q and a voltage V of the non-aqueous secondary battery at predetermined time intervals when the non-aqueous secondary battery is charged; A first process of calculating a specific value of the charged quantity of electricity Q that maximizes the amount of decrease in the slope of the QV curve indicating the value of the voltage V, and a case where the specific value is within a preset appropriate range. and determining that the effective specific surface area per weight of the negative electrode active material is an appropriate size, and determining that the specific surface area is not an appropriate size when the specific value is outside the appropriate range. and a control unit that executes a second process.

A non-aqueous secondary battery inspection method for solving the above problems inspects a non-aqueous secondary battery including a positive electrode plate, a negative electrode plate having a negative electrode mixture layer containing a negative electrode active material, and an electrolytic solution. In the inspection method, when charging the non-aqueous secondary battery, the charged quantity of electricity Q and voltage V of the non-aqueous secondary battery are obtained at predetermined time intervals, and the voltage V with respect to the charged quantity of electricity Q is measured. In the QV curve showing the value, the specific value of the charged quantity of electricity Q that maximizes the amount of decrease in the slope is calculated, and when the specific value is within a preset appropriate range, the weight in the negative electrode active material It is determined that the effective specific surface area per area is an appropriate size, and if the specific value is outside the appropriate range, it is determined that the specific surface area is not an appropriate size.

In the non-aqueous secondary battery inspection method, the specific value is calculated for each of a plurality of pre-fabricated non-aqueous secondary batteries having different specific surface areas to derive a calibration curve, and based on the calibration curve It is preferable to set the appropriate range by

According to the present invention, it can be determined whether or not the effective specific surface area of the negative electrode active material in the non-aqueous secondary battery is within the appropriate range.

FIG. 1 is a schematic diagram showing the configuration of a non-aqueous secondary battery inspection system. FIG. 2 is a partially developed view of the electrode body. FIG. 3 is a cross-sectional view of the electrode assembly in an unfolded state. FIG. 4 is a block diagram showing the configuration of the inspection device. FIG. 5 is a flow chart showing a method for manufacturing a lithium ion secondary battery. FIG. 6 is a flow chart showing the processing of the determination step. FIG. 7 is a diagram showing the correspondence between the charged quantity of electricity Q, the voltage V, and d ² V/dQ ² of the lithium ion secondary battery in the charging process. FIG. 8 is a diagram showing the behavior of QV curves when the effective specific surface area of the negative electrode active material is different. FIG. 9 is a diagram showing the relationship between the effective specific surface area of the negative electrode active material and the specific value.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 9. FIG.
[Non-aqueous secondary battery inspection system]
As shown in FIG. 1, the non-aqueous secondary battery inspection system 1 charges the non-aqueous secondary battery in the manufacturing process of the non-aqueous secondary battery, and also measures the effectiveness of the negative electrode active material in the non-aqueous secondary battery. It is determined whether or not the specific surface area is an appropriate size. A nonaqueous secondary battery inspection system 1 includes a lithium ion secondary battery 10 , a charging device 30 , and an inspection device 40 .

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 supply 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 charge quantity 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 enclosed in a resin or metal case to form a battery pack. Battery packs are used in hybrid vehicles and electric vehicles.

A lithium ion secondary battery 10 includes a battery case 11 and a lid body 12 . Battery case 11 has a rectangular parallelepiped shape with an opening on the upper side. Lid 12 seals the opening of battery case 11 . Battery case 11 and lid 12 are made of metal such as aluminum or an aluminum alloy. Lithium ion secondary battery 10 is configured as a sealed container by attaching lid 12 to battery case 11 .

The lid 12 is provided with two external terminals 13A and 13B. The external terminals 13A and 13B are used for charging and discharging electric power. In the nonaqueous secondary battery inspection system 1 , the external terminals 13A and 13B are electrically connected to the charging device 30 and the inspection device 40 .

The lithium ion secondary battery 10 accommodates an electrode assembly 20 inside a battery case 11 . A positive electrode-side current collecting portion 20A, which is an end portion of the electrode assembly 20 on the positive electrode side, is electrically connected to the positive electrode external terminal 13A via a positive electrode-side current collecting member 14A. A negative electrode current collecting portion 20B, which is the end portion of the electrode body 20 on the negative electrode side, is electrically connected to the negative external terminal 13B via the negative electrode current collecting member 14B. A non-aqueous electrolyte is injected into the battery case 11 through 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 laminated body in which a long positive electrode plate 21 and a long negative electrode plate 24 are laminated with a separator 27 interposed therebetween. The positive electrode plate 21, the negative electrode plate 24, and the separator 27 are laminated such that their longitudinal directions are aligned 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 substrate 22 and a positive electrode mixture layer 23 . The positive electrode base material 22 is an elongated foil-like electrode base material. The positive electrode mixture layer 23 is provided on each of the two opposing surfaces of the positive electrode substrate 22 . The positive electrode base material 22 has, at one end in the width direction, a positive electrode side exposed portion 22A in which the positive electrode material mixture layer 23 is not formed and the positive electrode base material 22 is exposed.

A metal foil composed of aluminum or an alloy containing aluminum as a main component is used for the positive electrode base material 22 . The positive electrode base material 22 functions as a current collector in the positive electrode. The positive electrode side exposed portion 22A included in the positive electrode base material 22 constitutes the positive electrode side current collector portion 20A by pressing the facing surfaces to each other in the state of the wound body.

The positive electrode mixture layer 23 is a hardened liquid positive electrode mixture paste. The positive electrode mixture paste contains 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. Accordingly, the positive electrode mixture layer 23 includes a positive electrode active material, a positive electrode conductive material, and a positive electrode binder.

A lithium-containing composite metal oxide capable of intercalating and deintercalating lithium ions, which are charge carriers in the lithium ion secondary battery 10, is used as the positive electrode active material. A lithium-containing composite oxide is an oxide containing lithium and a metal element other than lithium. Metal elements other than lithium are selected from the group consisting of, for example, nickel, cobalt, manganese, vanadium, magnesium, molybdenum, niobium, titanium, tungsten, aluminum, and iron contained as iron phosphate in lithium-containing composite oxides. at least one type of

For example, lithium-containing composite oxides are lithium cobaltate (LiCoO ₂ ), lithium nickelate (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 lithium nickel-cobalt-manganese oxide (LiNiCoMnO ₂ ). For example, the lithium-containing composite oxide is lithium iron phosphate ( _LiFePO4 ).

An NMP (N-methyl-2-pyrrolidone) solution, which is an example of an organic solvent, is used as the positive electrode solvent. As the positive electrode conductive material, for example, carbon black such as acetylene black and ketjen black, carbon fiber such as carbon nanotube and carbon nanofiber, and graphite are used. 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), styrene-butadiene rubber (SBR), and the like.

In addition, 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 contains an insulating inorganic component and a resin component that functions as a binder. The inorganic component is at least one selected from the group consisting of powdery boehmite, titania, and alumina. The resin component is at least one selected from the group consisting of PVDF, PVA and acryl.

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

A metal foil composed of copper or an alloy containing copper as a main component is used for the negative electrode base material 25 . The negative electrode base material 25 functions as a current collector in the negative electrode. The negative electrode-side exposed portion 25A forms the negative electrode-side collector portion 20B in the state of the wound body, with the surfaces facing each other being pressed against each other.

The negative electrode mixture layer 26 is a hardened liquid negative electrode mixture paste. The negative electrode mixture paste contains 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 evaporating 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. The negative electrode mixture layer 26 may further contain an additive such as a conductive material.

A negative electrode active material is a material capable of intercalating and deintercalating lithium ions. As the negative electrode active material, for example, carbon materials such as graphite, non-graphitizable carbon, graphitizable carbon, and carbon nanotubes are used. 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 retains the non-aqueous electrolyte between the positive electrode plate 21 and the negative electrode plate 24 . When the electrode body 20 is immersed in the non-aqueous electrolyte, the non-aqueous electrolyte permeates the separator 27 from the ends toward the center.

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

[Non-aqueous electrolyte]
The non-aqueous electrolyte is a composition containing a supporting salt in a non-aqueous solvent. As the non-aqueous solvent, one or two or more materials selected from the group consisting of propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate and the like can be used. Support 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 1 or 2 or more lithium compounds (lithium salts) selected from the above can be used.

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

[Inspection device]
As shown in FIG. 4 , the inspection device 40 includes a control unit 41 , a storage unit 42 , a charge quantity acquisition unit 43 and a voltage acquisition unit 44 . 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 charged electricity quantity acquisition unit 43 acquires the charged electricity quantity Q supplied to the lithium ion secondary battery 10 being charged by the charging device 30 . The voltage acquisition unit 44 acquires the voltage V of the lithium ion secondary battery 10 being charged by the charging device 30 .

The control unit 41 causes the charged quantity of electricity acquisition unit 43 to acquire the charged quantity of electricity Q and causes the voltage acquisition unit 44 to acquire the voltage V at predetermined time intervals. The charged quantity of electricity acquisition unit 43 and the voltage acquisition unit 44 are an example of an acquisition unit that acquires the charged quantity of electricity Q and the voltage V at predetermined time intervals when the lithium ion secondary battery 10 is charged. The control unit 41 causes the storage unit 42 to store the charge quantity Q acquired by the charge quantity acquisition unit 43 and the voltage V acquired by the voltage acquisition unit 44 in association with each other.

The control unit 41 includes a calculation unit 41A and a determination unit 41B. The calculation unit 41A obtains a QV curve that indicates the value of the voltage V with respect to the charged quantity of electricity Q when the lithium ion secondary battery 10 is charged. The calculation unit 41A calculates a specific value Q1, which is the value of the charged quantity of electricity Q that maximizes the amount of decrease in the slope of the QV curve.

Based on the specific value Q1 calculated by the calculation unit 41A, the determination unit 41B determines whether or not the effective specific surface area per weight of the negative electrode active material is an appropriate size. Make pass/fail judgment. The determination unit 41B determines that the specific surface area is an appropriate size when the specific value Q1 is within the appropriate range. The determination unit 41B determines that the specific surface area is not an appropriate size when the specific value Q1 is out of the appropriate range.

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, and the like of the inspection device 40 . The data storage section 42B stores data for executing various processes in the control section 41 . 42 C of program storage parts memorize|store the program for performing various processes in the control part 41. FIG.

[Method for producing lithium ion secondary battery]
As shown in FIG. 5, 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 the positive electrode plate 21 and the negative electrode plate 24, respectively. In the manufacturing process of the positive electrode plate 21 , the positive electrode material mixture paste is applied to both sides of the positive electrode base material 22 so as to form the positive electrode side exposed portions 22</b>A at both ends in the width direction. After that, 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 substrate 22 . After that, the positive electrode substrate 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 , the negative electrode mixture paste is applied to both surfaces of the negative electrode base material 25 so as to constitute the negative electrode side exposed portions 25</b>A at both ends in the width direction. After that, 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 surfaces of the negative electrode substrate 25 . After that, 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.

In the negative electrode mixture layer 26, since the negative electrode active material is covered with the negative electrode binder, the effective specific surface area of the negative electrode active material that contributes to the charge/discharge reaction is reduced. In addition, in the step of pressing the negative electrode mixture layer 26, the particles of the negative electrode active material are cracked, thereby increasing the effective specific surface area of the negative electrode active material. Therefore, the effective 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 .

Step S1-2 is an assembly process for assembling the lithium ion secondary battery 10. FIG. In the assembly process, the electrode body 20 is manufactured first. Specifically, first, the positive electrode plate 21 and the negative electrode plate 24 are laminated with the separator 27 interposed therebetween, then wound and pressed flat. After that, the positive electrode side exposed portion 22A is pressed to form the positive electrode side collector portion 20A, and the negative electrode side exposed portion 25A is pressed to form the negative electrode side collector portion 20B. The electrode body 20 is manufactured by the above procedure.

Next, the electrode body 20 is housed inside the battery case 11 . At this time, the positive electrode current collecting portion 20A is electrically connected to the positive electrode external terminal 13A via the positive electrode current collecting member 14A. The negative current collector 20B is electrically connected to the negative external terminal 13B via the negative current collector 14B. The upper portion of battery case 11 is closed with lid 12 . Then, after removing water from the electrode assembly 20 by heat treatment, a non-aqueous electrolyte 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 step of charging the lithium-ion secondary battery 10 assembled in the assembling step with the charging device 30. FIG. The charging performed in the charging process is, for example, the initial charging of the lithium ion secondary battery 10 assembled in the assembling process. In the charging process, the external terminals 13A and 13B of the lithium ion secondary battery 10 are connected to the charging device 30 and the inspection device 40 .

Step S1-4 is a determination step of determining whether or not the effective specific surface area of the negative electrode active material is an appropriate size based on the behavior of the charge quantity Q and voltage V in the charging process by the inspection device 40. . In the manufacturing process of the lithium ion secondary battery 10, only the lithium ion secondary battery 10 determined in the determination process that the size of the effective specific surface area of the negative electrode active material is within the appropriate range is a post-process step. Proceed to S1-5.

Step S1-5 is an aging step in which the lithium-ion secondary battery 10 that has undergone the charging step and the determination step is allowed to stand at a high temperature for a certain period of time. The aging process dissolves metallic foreign matter in the lithium ion secondary battery 10 and stabilizes the SEI film.

[Determination process]
The determination step (step S1-4) will be described in detail below with reference to FIGS.
As shown in FIG. 6, in the determination process, the inspection device 40 executes the processes of steps S2-1 to S2-6, which are an example of the method for inspecting the lithium ion secondary battery 10. FIG. At step S2-1, the inspection device 40 acquires a QV curve that indicates the value of the voltage V with respect to the charged quantity of electricity Q in the charging process. First, in the charging process, the control unit 41 of the inspection device 40 executes a process of causing the charged quantity of electricity acquiring unit 43 to acquire the charged quantity of electricity Q at predetermined time intervals. At the same time, the control unit 41 executes a process of causing the voltage acquisition unit 44 to acquire the voltage V at predetermined time intervals in the charging process. The timing at which the charged quantity of electricity acquisition unit 43 acquires the charged quantity of electricity Q and the timing at which the voltage acquisition unit 44 acquires the voltage V are the same. The acquired charged quantity of electricity Q and voltage V are associated with each other and stored in the data storage unit 42B. The calculation unit 41A derives a QV curve based on the charged quantity of electricity Q obtained by the charged quantity of electricity obtaining unit 43 and the voltage V obtained by the voltage obtaining unit 44 .

As shown in FIG. 7, curve 101 in graph 100 is an example of a QV curve. In the first period 101A at the beginning of charging in the charging process, the amount of increase in the voltage V is greater than the amount of increase in the amount of charge Q, so the curve 101 rises steeply. In the second period 101B when the charging process progresses and the charged quantity of electricity Q reaches the specific value Q1, the amount of increase in the voltage V relative to the amount of increase in the charged quantity of electricity Q becomes moderate, and the slope of the QV curve greatly decreases. The specific value Q1 is the value of the charged quantity of electricity Q that maximizes the amount of decrease in the slope of the curve 101 .

In the charging process, part of the charged quantity of electricity Q is consumed to form the SEI film 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 effective specific surface area of the negative electrode active material. Therefore, when the SEI film is formed 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 according to the effective specific surface area of the negative electrode active material. Therefore, by calculating the specific value Q1 in the charging process, it is possible to determine whether or not the effective specific surface area of the negative electrode active material is an appropriate size.

In step S2-2, the calculation unit 41A calculates the value of d ² V/dQ ² obtained by second-order differentiation of the QV curve. A curve 102 in the graph 100 shown in FIG. 7 is a Q−d ² V/dQ ² curve showing the value of d ² V/dQ ² with respect to the amount of charge Q. FIG. Curve 102 has a peak 102P at a particular value Q1.

In step S2-3, the calculation unit 41A sets the value of the charged quantity of electricity Q at the peak 102P of the curve 102 as a specific value Q1 that is the value of the charged quantity of electricity Q at the boundary between the first period 101A and the second period 101B. calculate. The process of calculating the specific value Q1 in step S2-3 is an example of the first process executed in the inspection device 40. FIG.

In step S2-4, the determination unit 41B determines whether or not the specific value Q1 calculated in step S2-3 is within a preset appropriate range. The appropriate range used in step S2-4 is saved in the data storage section 42B provided in the storage section 42. FIG. The process of determining whether or not the specific value Q1 is within the proper range in step S2-4 is an example of the second process executed in the inspection device 40. FIG.

If the specific value Q1 is within the proper range, the process proceeds to step S2-5. After proceeding to step S2-5, the lithium-ion secondary battery 10 is judged to have an appropriate effective specific surface area of the negative electrode active material, and proceeds to the subsequent aging step.

If the specific value Q1 is out of the proper range, go to step S2-6. The lithium ion secondary battery 10 that proceeded to step S2-6 is excluded from the production line because it is determined that the effective specific surface area of the negative electrode active material is not an appropriate size.

Moreover, the above processing is executed by the inspection program installed and stored in the program storage unit 42C. In step S2-1, the inspection program causes the charged quantity of electricity acquisition unit 43 to acquire the charged quantity of electricity Q at predetermined time intervals, and causes the voltage acquisition unit 44 to acquire the voltage V at predetermined time intervals. The inspection program causes the calculation unit 41A to execute processing for calculating the specific value Q1. The inspection program causes the determination unit 41B to perform processing for determining whether or not the specific value Q1 is within a preset proper range.

[Relationship between specific surface area and specific value]
Hereinafter, the relationship between the effective specific surface area of the negative electrode active material and the specific value Q1 of the QV curve will be described with reference to FIG.

As shown in FIG. 8, the curve 201 in the graph 200 indicates the open circuit potential (OCP) on the positive side with respect to the charge quantity Q in the charging process. A curve 202 in the graph 200 indicates the open circuit potential on the negative electrode side with respect to the charge quantity 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 charge quantity Q in the charging process. The voltage V coincides with a value obtained by subtracting the open circuit potential on the positive electrode side from the open circuit potential on the negative electrode side. That is, curve 203 is the difference between curve 201 and curve 202 .

In the graph 200, a dashed curve 202A indicates the open circuit potential on the negative electrode side with respect to the charged quantity of electricity Q in the charging process when the effective specific surface area of the negative electrode active material is smaller than the state of the curve 202. In graph 200, curve 203A indicated by a dashed line is an example of a QV curve when the effective specific surface area of the negative electrode active material is smaller than that of curve 203. FIG.

When the effective specific surface area of the negative electrode active material becomes relatively small, the amount of the SEI film formed on the negative electrode mixture layer 26 decreases. Then, the charge quantity Q consumed for forming the SEI film decreases, and the curve 202A as a whole 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 is also shifted to the right of the specific value Q1 on the curve 203. FIG.

In the graph 200, a dashed curve 202B indicates the open circuit potential on the negative electrode side with respect to the charged quantity of electricity Q in the charging process when the effective specific surface area of the negative electrode active material is larger than that of the curve 202. In the graph 200, a dashed curve 203B is an example of a QV curve when the effective specific surface area of the negative electrode active material is larger than that of the curve 203. FIG.

When the effective specific surface area of the negative electrode active material becomes relatively large, the amount of the SEI film formed on the negative electrode mixture layer 26 increases. Then, the amount of charged electricity Q consumed to form the SEI film increases, and the curve 202B as a whole shifts to the left of the curve 202 in the correspondence relationship with the curve 201 . In this case, the specific value Q1B on the curve 203B is also shifted to the left of the specific value Q1 on the curve 203. FIG.

As described above, the specific value Q1 in the QV curve changes depending on the size of the effective specific surface area of the negative electrode active material. Therefore, by determining whether or not the specific value Q1 in the QV curve is within the appropriate range, it is possible to evaluate whether or not the effective specific surface area of the negative electrode active material is an appropriate size.

[Appropriate range setting for specific values]
A procedure for setting the proper range of the specific value Q1 will be described below with reference to FIG. The proper range of the specific value Q1 is set before the steps S1-1 to S1-5 of manufacturing the lithium ion secondary battery 10. FIG.

First, a plurality of negative electrode plates 24 having different effective specific surface areas of the negative electrode active materials are produced by using a plurality of levels of negative electrode active materials having different specific surface areas in the raw material state. Next, for the negative electrode plate 24 of each level, the effective 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. Then, after assembling a plurality of levels of lithium ion secondary batteries 10 using each of a plurality of negative electrode plates 24 having different effective specific surface areas of the negative electrode active material, charging is performed and identification is performed in the same manner as in step S1-4. Calculate the value Q1. For example, by changing the manufacturing conditions of the negative electrode plate 24, the negative electrode plate 24 with different effective specific surface areas of the negative electrode active material may be manufactured.

As shown in FIG. 9, each of the plurality of points P plotted in the graph 300 corresponds to the specific surface area and specific value Q1 in each of the plurality of lithium ion secondary batteries 10 having different effective specific surface areas of the negative electrode active materials shows the correspondence with An approximation line 301 in the graph 300 is an approximation line derived from a plurality of points P, and is a calibration curve for setting the proper range of the specific value Q1. The approximation line 301 has a negative slope such that the specific value Q1 decreases as the effective specific surface area of the negative electrode active material increases.

For example, if the effective specific surface area of the negative electrode active material becomes excessively large, the life characteristics of the lithium ion secondary battery 10 deteriorate. On the other hand, when the effective specific surface area of the negative electrode active material becomes excessively small, lithium tends to deposit on the electrode body 20 . Therefore, the upper limit QU of the proper range of the specific value Q1 is set to a value corresponding to the specific surface area A1 to the extent that lithium is not excessively deposited on the electrode body 20 . Further, the lower limit QL of the proper range of the specific value Q1 is set to a value corresponding to the specific surface area A2 to the extent that the life characteristics of the lithium ion secondary battery 10 do not deteriorate excessively. The proper range of the specific value Q1 is set by the procedure described above. The proper range of the specific value Q1 is stored in the data storage section 42B.

[Effects of Embodiment]
According to the above embodiment, the following effects can be obtained.
(1) By determining whether or not the specific value Q1 in the charging process is within a preset appropriate range, it is possible to determine whether or not the effective specific surface area of the negative electrode active material is an appropriate size. Further, by determining the size of the effective specific surface area of the negative electrode active material from the QV curve in the charging process, determination can be made for all the lithium ion secondary batteries 10 in the manufacturing process of the lithium ion secondary batteries 10. It becomes possible.

(2) By using the Qd ² V/dQ ² curve in calculating the specific value Q1, it is possible to easily determine whether or not the effective specific surface area of the negative electrode active material is an appropriate size.
(3) By performing the determination step when the assembled lithium ion secondary battery 10 is charged for the first time, the negative electrode active material can be effectively used without including changes in the lithium ion secondary battery 10 due to repeated charging and discharging. It is possible to make a judgment about the specific surface area. Therefore, the precision of determination can be improved.

(4) 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, the actual composition and manufacturing of the negative electrode mixture layer 26 An appropriate range can be set taking into consideration the influence of the process. Therefore, the precision of determination can be improved.

[Change example]
It should be noted that the above embodiment can be implemented with the following modifications.
The case where the appropriate range of the specific value Q1 is set using the calibration curve derived from the specific value Q1 of the plurality of lithium ion secondary batteries 10 having different effective specific surface areas of the negative electrode active materials is illustrated. Instead of actually producing a plurality of lithium ion secondary batteries 10 having different effective specific surface areas of the negative electrode active material, it is possible to determine the appropriateness of the specific value Q1 through model simulation such as finite element analysis or numerical calculation. A range may be set.

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

・Calculation of the specific value Q1 is not limited to the method using the Qd ² V/dQ ² 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 value may be calculated as the specific value Q1. The threshold 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 or not the effective 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 be configured to include the positive electrode plate 21, the negative electrode plate 24, and the non-aqueous electrolyte.
- 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 interposed therebetween.

・The lithium-ion secondary battery 10 may be mounted on an automatic transport machine, a special vehicle for cargo handling, an electric vehicle, a hybrid vehicle, etc., a computer, or other electronic equipment. may be configured. For example, it may be provided in a moving body such as a ship or an aircraft, and it is a power supply system that supplies power from a power plant to a building or home in which a secondary battery is installed via a substation. good too.

DESCRIPTION OF SYMBOLS 1... Non-aqueous secondary battery inspection system 10... Lithium ion secondary battery 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 DESCRIPTION OF SYMBOLS 27... Separator 30... Charging device 40... Inspection apparatus 41... Control part 41A... Calculation part 41B... Judgment part 42... Storage part 42A... Memory part 42B... Data storage part 42C... Program storage part 43... Charged electric quantity acquisition part 44... Voltage acquisition part

Claims (7)

an assembling step of assembling a non-aqueous secondary battery using a positive electrode plate, a negative electrode plate having a negative electrode mixture layer containing a negative electrode active material, and an electrolytic solution;
a charging step of charging the non-aqueous secondary battery;
A determination step of determining whether the effective specific surface area per weight of the negative electrode active material is an appropriate size,
The determination step includes
acquiring the charged quantity of electricity Q and voltage V of the non-aqueous secondary battery in the charging step at predetermined time intervals;
Calculating a specific value of the charged quantity of electricity Q that maximizes the amount of decrease in slope in a QV curve showing the value of the voltage V with respect to the charged quantity of electricity Q,
When the specific value is within a preset proper range, it is determined that the specific surface area is a proper size, and when the specific value is outside the proper range, the specific surface area is not a proper size. A method for manufacturing a non-aqueous secondary battery. The specific value is a Qd ² V/dQ ² curve showing a value of d ² V/dQ ² obtained by second-order differentiating the QV curve with respect to the charged quantity of electricity Q, wherein the Qd ² V/ 2. The method of manufacturing a non-aqueous secondary battery according to claim 1, wherein the dQ is calculated as the value of the charged quantity of electricity Q at which a peak appears in the ² curve. 3. The method of manufacturing a non-aqueous secondary battery according to claim 1, wherein the charging performed in the charging step is the initial charging of the non-aqueous secondary battery assembled in the assembling step. The appropriate range is set based on a calibration curve derived from the specific values calculated for each of a plurality of prefabricated non-aqueous secondary batteries having different specific surface areas. 1. The method for manufacturing the non-aqueous secondary battery according to claim 1. An inspection device for inspecting a non-aqueous secondary battery comprising a positive electrode plate, a negative electrode plate having a negative electrode mixture layer containing a negative electrode active material, and an electrolytic solution,
an acquisition unit that acquires the charged quantity of electricity Q and the voltage V of the non-aqueous secondary battery at predetermined time intervals when the non-aqueous secondary battery is charged;
A first process of calculating a specific value of the charged quantity of electricity Q that maximizes the amount of decrease in slope in a QV curve showing the value of the voltage V with respect to the charged quantity of electricity Q, and the specific value is set in advance. If it is within the appropriate range, it is determined that the effective specific surface area per weight of the negative electrode active material is an appropriate size, and if the specific value is outside the appropriate range, the specific surface area is appropriate. A non-aqueous secondary battery inspection device, comprising: a second process for determining that the size is not the same; An inspection method for inspecting a non-aqueous secondary battery comprising a positive electrode plate, a negative electrode plate having a negative electrode mixture layer containing a negative electrode active material, and an electrolytic solution,
When charging the non-aqueous secondary battery, the charged quantity of electricity Q and voltage V of the non-aqueous secondary battery are obtained at predetermined intervals,
Calculating a specific value of the charged quantity of electricity Q that maximizes the amount of decrease in slope in a QV curve showing the value of the voltage V with respect to the charged quantity of electricity Q,
When the specific value is within a preset appropriate range, it is determined that the effective specific surface area per weight of the negative electrode active material is an appropriate size, and when the specific value is outside the appropriate range A non-aqueous secondary battery inspection method for determining that the specific surface area is not an appropriate size. Calculating the specific value for each of a plurality of prefabricated non-aqueous secondary batteries having different specific surface areas to derive a calibration curve,
The method for inspecting a non-aqueous secondary battery according to claim 6, wherein the appropriate range is set based on the calibration curve.

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