Method for manufacturing nonaqueous secondary battery

Abstract

To detect organic foreign matter mixed in a battery and determine shipment for each cell battery of a nonaqueous secondary battery.SOLUTION: The method includes an initial charging dQ / dV calculation step of calculating an initial charging dQ / dV curve L2, an unknown peak detection step of obtaining a reference dQ / dV curve L1 of a nonaqueous electrolytic solution assumed in advance, comparing the reference dQ / dV curve L1 with the initial charging dQ / dV curve L2, and detecting an unknown peak not assumed in the reference dQ / dV, and a peak position recording step of recording voltages [V] of the detected peaks PA and PB when the peaks PA and PB are detected in the unknown peak detection step.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a non-aqueous secondary battery, and more particularly to a method for manufacturing a non-aqueous secondary battery characterized by detecting organic foreign matter mixed in the battery and determining whether the battery should be shipped. [Background technology]

[0002] During the manufacturing process of non-aqueous secondary batteries, such as lithium-ion secondary batteries, various unwanted substances may be generated or remain. Furthermore, during the manufacturing process, organic foreign matter such as resin or grease may be introduced from the outside for various reasons.

[0003] Once the battery elements are assembled, a conditioning process is performed on lithium-ion secondary batteries, which involves at least one precisely controlled initial charge / discharge cycle to activate the active materials. The initial charge in the conditioning process forms a solid electrolyte interface (SEI) on the negative electrode. SEI formation protects the negative electrode and is important for the life of the lithium-ion battery or cell. This is followed by a high-temperature aging process to eliminate micro-short circuits and stabilize the SEI.

[0004] The invention disclosed in Patent Document 1 utilizes the initial charge in this conditioning process to confirm the amount of additive reaction from dQ / dV up to the aging process. Here, "dQ / dV" is the ratio of the rate of change dQ / dt of discharge capacity (amount of discharged electricity) to the rate of change dV / dt of voltage, and has no unit. "dQ / dV" indicates the change in discharge capacity per unit voltage and can be used to determine the deterioration of each cell battery. By calculating dQ / dV in this way during the conditioning process, it was possible to determine whether foreign matter had been mixed into the lithium-ion secondary battery.

[0005] The lithium-ion secondary battery manufacturing method disclosed in Patent Document 1 contains an additive consisting of LiFSO3. LiFSO3 is important for stable generation of the SEI but is unnecessary in the completed battery, and it is desirable for it to be completely consumed during the initial charge. Therefore, in the confirmation discharge procedure, after the initial charge, the battery is discharged to 2.85 V, which is sufficiently lower than the 2.92 V voltage at which the LiFSO3 film forms. Next, in the LiFSO3 film formation confirmation charge, the battery is charged to 3.43 V, which is sufficiently higher than 2.92 V. In this case, the disappearance of LiFSO3 during the initial charge can be confirmed by calculating dQ / dV. Even if LiFSO3 remains, because the charge rate is lower than that of the initial charge, any LiFSO3 present will be consumed by film formation.

[0006] In this way, by calculating the dQ / dV of the initial charge, it is possible to confirm whether a specific substance such as LiFSO3 remains or disappears. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2022-140953 Summary of the Invention [Problem to be solved by the invention]

[0008] LiFSO3 is not the only substance unnecessary for lithium-ion secondary batteries. During the cell assembly process, organic substances such as grease applied to resin parts and sliding parts used in many types of production equipment can become mixed into the battery. In the invention disclosed in Patent Document 1, the object of confirmation is specified to be LiFSO3 only. Therefore, by calculating dQ / dV at the voltage at which LiFSO3 reacts, it is possible to confirm its remaining amount and its consumption. Furthermore, because LiFSO3 is added in a specified amount, it was sufficient to check it on a production lot basis.

[0009] However, during the cell assembly process, various organic substances, such as those used in production equipment and grease applied to sliding parts, can unintentionally become mixed into the battery. In such cases, even if abnormal wear of the resin parts or adhesion of organic substances is discovered during a visual inspection of the battery cells, it is difficult to identify the cells that have actually become mixed into the battery and the amount of the mixed substances. This results in extremely complicated work, such as suspending all cells in a lot suspected of contamination and conducting outline tests to confirm the impact of the contamination on battery quality before deciding whether to ship the battery.

[0010] Therefore, the problem to be solved by the method for manufacturing a nonaqueous secondary battery of the present invention is to make it possible to detect organic foreign matter that has become mixed into each cell battery and determine whether it should be shipped. [Means for solving the problem]

[0011] In order to solve the above problems, a method for manufacturing a nonaqueous secondary battery of the present invention is a method for manufacturing a nonaqueous secondary battery comprising a positive electrode, a negative electrode, and a nonaqueous electrolyte, and includes an initial charge dQ / dV calculation step of calculating an initial charge dQ / dV, which is a change in charge capacity relative to a change in voltage, during initial charge; an unknown peak detection step of comparing a predetermined reference dQ / dV of the nonaqueous electrolyte with the initial charge dQ / dV measured in the initial charge dQ / dV calculation step to detect an unknown peak not expected in the reference dQ / dV; and a peak position recording step of recording the voltage at the position of each of the detected unknown peaks when the unknown peaks are detected; a test charging step of charging from a voltage lower than the lowest voltage among the peak positions after the initial charging; a test dQ / dV calculation step of calculating the test dQ / dV in the test charging; and an unknown peak disappearance determination step of determining whether or not the unknown peaks detected in the unknown peak detection step have disappeared in the test dQ / dV calculated in the test dQ / dV calculation step.

[0012] The method may further comprise a cause identification step of identifying a causal substance of each of the unknown peaks based on the voltage at the position of each of the unknown peaks recorded in the peak position recording step.

[0013] After the initial charging is completed, a high-temperature aging step may be performed, and after the high-temperature aging step, the test charging step may be performed. After the high-temperature aging step, an inspection step may be performed in which at least one of a battery capacity inspection and an internal resistance inspection is performed.

[0014] The step of determining whether the unknown peak has disappeared may compare the test dQ / dV with the initial charging dQ / dV to determine whether the unknown peak has disappeared. The step of determining whether the unknown peak has disappeared may compare the test dQ / dV with the reference dQ / dV to determine whether the unknown peak has disappeared.

[0015] The test charging step may involve charging up to a set SOC. The present invention can also be suitably implemented when the nonaqueous secondary battery is a lithium ion secondary battery. [Effects of the Invention]

[0016] The method for manufacturing a non-aqueous secondary battery of the present invention has the advantage that it is possible to detect organic foreign matter mixed into each cell battery and determine whether the battery is ready for shipping. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a perspective view of a cell battery of a lithium ion secondary battery according to an embodiment of the present invention. [Figure 2] FIG. 1 is a block diagram showing the configuration of a manufacturing device that constitutes part of a manufacturing line for lithium ion secondary batteries. [Figure 3] 2 is a flowchart showing a method for manufacturing a lithium ion secondary battery according to the present embodiment. [Figure 4] 10 is a flowchart showing a procedure for determining whether a foreign object is present in the present embodiment. [Figure 5] 4 is a time chart showing a change in voltage of the lithium ion secondary battery of the present embodiment. [Figure 6] 10 is a graph showing the reference dQ / dV and the initial charge dQ / dV of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] 1 to 5, a method for manufacturing a nonaqueous secondary battery of the present invention will be described using one embodiment of a method for manufacturing a lithium ion secondary battery 10 as an example. (Outline of this embodiment) As mentioned in the section on conventional technology, various organic substances, such as resin parts used in production equipment and grease applied to sliding parts, can unintentionally get mixed into the battery during the cell assembly process. Conventional technology has not been able to address such cases.

[0019] To address this problem, in the method for manufacturing the lithium ion secondary battery 10 of this embodiment, organic foreign matter that has become mixed into each cell battery is detected and shipping is determined. Specifically, to detect unexpected contamination, the "reference dQ / dV" of a non-aqueous electrolyte without contaminants is measured in advance. The potential at which the contaminants change in the contaminated non-aqueous electrolyte is also measured in advance. Of course, the potential at which the contaminants change can be theoretically derived without experimental testing. The "initial charge dQ / dV" and the "reference dQ / dV" are compared during the initial charge of the cell battery under test. When contaminants are present, an unknown dQ / dV peak not present in the "reference dQ / dV" appears in the "initial charge dQ / dV." This peak occurs because the power that should be contributing to charging is consumed in the decomposition of the contaminants, preventing the voltage from increasing relative to the amount of power charged. The decomposition of the contaminants has a specific potential. The voltage at this unknown peak is then compared with the previously measured potential at which the contaminants change, allowing the contaminated contaminants to be identified.

[0020] Generally, organic foreign matter decomposes at a specific potential or heat, and may decompose during initial charging or high-temperature aging. Therefore, if there are no problems in tests of battery capacity or internal resistance after high-temperature aging, the product may be deemed to be satisfactory and passed.

[0021] Furthermore, when adjusting the SOC again in preparation for shipment after high-temperature aging, it is possible to test whether the unknown peak reappears by charging at a voltage that includes the voltage at the unknown peak and calculating the "test dQ / dV." This test makes it possible to check whether each type of foreign matter remains or has disappeared.

[0022] In this way, accurate testing is possible for each cell battery individually on the production line, and accurate product evaluation can be performed efficiently. (Configuration of this embodiment) <Lithium-ion secondary battery 10> First, a lithium-ion secondary battery 10 will be described with reference to FIG. 1 as an example of a nonaqueous secondary battery that is the premise of this embodiment. Needless to say, this embodiment does not limit the present invention. FIG. 1 is a perspective view of a cell battery of the lithium-ion secondary battery 10 of this embodiment. As shown in FIG. 1, the lithium-ion secondary battery 10 of this embodiment is configured as a cell battery. This cell battery is used in electric vehicles such as hybrid vehicles and fuel cell vehicles. A plurality of cell batteries are stacked and sealed in a resin case or the like, and a control device, measuring instrument, etc. are attached to form an in-vehicle battery pack.

[0023] The cell battery of the lithium-ion secondary battery 10 includes a rectangular parallelepiped battery case 11 with an opening on the top side. The battery case 11 includes a lid 12 that seals the battery case 11. A plate assembly 20 is housed inside the battery case 11. The plate assembly 20 is formed by winding long positive and negative electrode plates 14 and 15 with a separator 17 sandwiched between them and pressing them to form a wound body. A nonaqueous electrolyte 25 is injected into the battery case 11 through an injection hole (not shown). The battery case 11 and the lid 12 are made of a metal such as an aluminum alloy. The lithium-ion secondary battery 10 forms a sealed battery container by attaching and welding the lid 12 to the battery case 11. The lithium-ion secondary battery 10 also includes two external terminals 13 on the lid 12 that are used for charging and discharging power.

[0024] <Positive electrode plate 14> The positive electrode plate 14 has a positive electrode composite layer formed on the surface of a positive electrode substrate. The positive electrode composite layer contains a positive electrode active material. The positive electrode active material is a material capable of absorbing and releasing lithium, and examples of the positive electrode active material include lithium cobalt oxide (LiCoO), lithium manganese oxide (LiMnO), and lithium nickel oxide (LiNiO). Alternatively, a material in which LiCoO, LiMnO, and LiNiO are mixed in any ratio may be used.

[0025] The positive electrode mixture may also contain a conductive material, such as carbon nanotubes (CNTs), carbon nanofibers (CNFs), carbon black such as acetylene black (AB) or ketjen black, or graphite.

[0026] The positive electrode plate 14 is fabricated by, for example, kneading a positive electrode active material, a conductive material, a solvent, and a binder, applying the resulting kneaded positive electrode composite paste to a positive electrode substrate, and drying the mixture. For example, an NMP (N-methyl-2-pyrrolidone) solution can be used as the solvent. For example, polyvinylidene fluoride (PVdF), styrene butadiene rubber (SBR), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), or the like can be used as the binder. For the positive electrode substrate serving as a current collector, a thin film made of aluminum or an alloy primarily composed of aluminum can be used.

[0027] <Negative electrode plate 15> The negative electrode plate 15 has a negative electrode composite layer formed on the surface of a negative electrode substrate. The negative electrode plate 15 is produced, for example, by kneading a negative electrode active material, a conductive material, a solvent, and a binder, applying the kneaded negative electrode composite paste to the negative electrode substrate, and drying the paste.

[0028] In this embodiment, the negative electrode substrate is made of copper foil. The negative electrode active material of the negative electrode mixture layer is a material capable of absorbing and releasing lithium ions, and a powdered carbon material such as graphite is used.

[0029] <Separator 17> The separator 17 is a fine porous nonwoven fabric made of polypropylene or the like, which holds the nonaqueous electrolyte 25 between the positive electrode plate 14 and the negative electrode plate 15. Alternatively, the separator 17 may be a porous polymer membrane such as a porous polyethylene membrane, a porous polyolefin membrane, or a porous polyvinyl chloride membrane, or a lithium ion or ion conductive polymer electrolyte membrane, either singly or in combination. The electrode plate group 20 is immersed in the nonaqueous electrolyte 25.

[0030] Even if metallic Li precipitates on the negative electrode or if fine metal powder is mixed in as contamination, the presence of separator 17 prevents direct electrical connection between positive electrode plate 14 and negative electrode plate 15. If a physical short circuit occurs, self-discharge occurs, reducing the power of lithium-ion secondary battery 10. Since a minute short circuit dissolves and disappears due to self-heating, the high-temperature aging process eliminates such minute short circuits caused by Li deposition or fine metal powder. Of course, if metal components such as Fe ions subsequently dissolve into the non-aqueous electrolyte, it may be impossible to prevent the minute short circuit using separator 17.

[0031] <Nonaqueous electrolyte 25> The nonaqueous electrolyte 25 is a composition in which a supporting salt is contained in a nonaqueous solvent. Here, the nonaqueous solvent can be one or more materials selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), etc. The supporting salt can be one or more lithium compounds (lithium salts) selected from LiPF6, LiBF4, LiClO4, LiAsF6, LiCF3SO3, LiC4F9SO3, LiN(CF3SO2)2, LiC(CF3SO2)3, LiI, etc.

[0032] Furthermore, the lithium ion secondary battery 10 according to this embodiment employs ethylene carbonate (EC) as the nonaqueous solvent. Lithium bis(oxalato)borate (LiBOB) is added as a lithium salt to the nonaqueous electrolyte solution 25 as an additive. For example, LiBOB is added to the nonaqueous electrolyte solution 25 so that the concentration of LiBOB in the nonaqueous electrolyte solution 25 is 0.001 to 0.1 mol / L. Organic foreign matter mixed into the nonaqueous electrolyte solution 25 can be electrically or thermally reduced or eliminated by initial charging or high-temperature aging.

[0033] <Lithium-ion secondary battery manufacturing apparatus 200> 2 is a block diagram showing the configuration of a manufacturing apparatus 200 that constitutes part of a manufacturing line for lithium-ion secondary batteries 10. The manufacturing apparatus 200 can perform charging and discharging while monitoring the cell voltage and cell current and managing the temperature of the lithium-ion secondary batteries 10 being manufactured. The manufacturing apparatus 200 for lithium-ion secondary batteries 10 of this embodiment is configured to include a well-known charging and discharging device 203, a cell voltage measuring device 204, a cell current measuring device 205, a thermometer 206, and a heat retention device 207. It also includes a control device 208 that is a well-known computer equipped with an interface for controlling these devices. The control device 208 includes a CPU 281 and a memory 282. The memory 282 includes a RAM and a ROM.

[0034] These control the charging and discharging of the lithium-ion secondary battery 10 of this embodiment. They also monitor the cell voltage, monitor the cell current, and adjust the ambient temperature. Furthermore, based on this data, the SOC of the lithium-ion secondary battery 10 is estimated. A pulse current is applied to measure the voltage and the internal resistance. Furthermore, the difference dQ in the battery capacity [Ah] relative to the difference dV in the voltage [V] value within a time interval is measured, and dQ / dV is calculated.

[0035] <Method for manufacturing lithium-ion secondary battery according to this embodiment> 3 is a flowchart showing a method for manufacturing a lithium ion secondary battery according to this embodiment. First, a general outline of the overall flow of the method for manufacturing a lithium ion secondary battery according to this embodiment will be described with reference to FIG.

[0036] In the manufacturing method of the lithium-ion secondary battery 10 of this embodiment, a "cell battery assembly process (S1)" is performed. First, the positive electrode plates 14 and the negative electrode plates 15 are stacked with the separator 17 and wound to form the electrode plate assembly 20, which is then shaped into a flat shape. Then, a portion of each end of the positive electrode plates 14 and the negative electrode plates 15 is compressed, and the compressed portions of the positive electrode plates 14 and the negative electrode plates 15 are connected to the external terminals 13, respectively. This electrode plate assembly 20 is housed in the battery case 11, and after being sufficiently dried, the lid 12 is welded to the battery case 11.

[0037] Next, the "electrolyte injection (S2)" is performed. In this step, the non-aqueous electrolyte 25 is injected into the battery case 11 through the electrolyte injection hole (not shown) in the lid 12. Next, "sealing (S3)" is performed. Here, after the injection of the non-aqueous electrolyte 25 is completed, the electrolyte injection hole is welded and sealed.

[0038] In "initial charge and dQ / dV calculation (S4)", initial charge is performed. In initial charge, charging and discharging of the lithium ion secondary battery 10 are carried out as a conditioning step. In this initial charge, dQ / dV is calculated. Here, the calculated dQ / dV is referred to as "initial charge dQ / dV". This procedure corresponds to the "step of calculating the initial charge dQ / dV value" of the present invention. Details will be explained later.

[0039] Once the initial charge (S4) is complete and the SEI is formed, the aging step (S5) is performed. In the aging step (S5), the battery is stored at a high temperature (e.g., 100°C) for a certain period of time (e.g., several days) to dissolve metal foreign matter and stabilize the SEI.

[0040] Along with this aging step (S5), or after the aging step, the temperature is lowered and the battery is left for a certain period of time, and then a "cell self-discharge" step (S6) is carried out to measure the self-discharge of the cell. In the "inspection step (S7)", the lithium ion secondary battery 10 is actually inspected to see if it has the desired performance as a product.

[0041] Specifically, a pause is made to eliminate polarization in order to inspect OCV (open circuit voltage) and DC-IR (internal direct current resistance). Once polarization is eliminated, DC-IR and OCV are inspected. After the inspection process is completed, the battery is charged to a predetermined SOC before shipping (SOC adjustment), and during this charging, the inspection dQ / dV is calculated (S8). The details of this procedure will be described later.

[0042] In the "battery unit assembly process (S9)," multiple stabilized cell batteries are stacked and connected with bus bars to form a battery pack that self-discharges. Also, in the battery unit assembly process, various accessories such as control devices and measuring instruments are attached, and the battery unit is housed in a plastic case and shipped as a battery unit for vehicles.

[0043] The above is the procedure for manufacturing the lithium ion secondary battery of this embodiment. <Procedure for determining foreign matter contamination in this embodiment> 4 is a flowchart of the procedure for determining whether or not a foreign substance has been mixed in according to this embodiment. The method for manufacturing a lithium-ion secondary battery according to this embodiment is characterized in that the determination of whether or not a foreign substance has been mixed in is performed using dQ / dV. The procedure for determining whether or not a foreign substance has been mixed in according to this embodiment will be described below with reference to FIG. 4.

[0044] <Reference dQ / dV calculation (S10)> FIG. 6 is a graph showing the reference dQ / dV and initial charge dQ / dV of this embodiment. In FIG. 6, the horizontal axis represents the OCV voltage [V] during charging and discharging of the lithium-ion secondary battery 10, and the vertical axis represents the value of "dQ / dV" at that time. First, when starting the procedure for determining whether or not foreign matter has been mixed in (start), the procedure of "calculating the reference dQ / dV (S10)" is carried out as a prerequisite. Here, the "reference dQ / dV" is a design value. In other words, it refers to the value of dQ / dV when no foreign matter has been mixed in or generated in the nonaqueous electrolyte solution 25.

[0045] The graph indicated by curve L1 is the "reference dQ / dV," which is the value of dQ / dV when no foreign matter is mixed into or generated in non-aqueous electrolyte 25. In the procedure of "calculating reference dQ / dV (S10)," this curve L1 is obtained as the reference dQ / dV and stored in memory 282 of control device 208 of manufacturing apparatus 200 shown in FIG.

[0046] <First charge (S11)> This initial charge (S11) corresponds to the procedure of "initial charge dQ / dV calculation (S4)" in the flowchart shown in FIG.

[0047] FIG. 5 is a time chart showing the change in voltage [V] of the lithium-ion secondary battery 10 of this embodiment. The horizontal axis indicates the passage of time [sec]. However, this does not indicate the exact time. The vertical axis indicates the battery voltage [V]. As shown in FIG. 5, initial charging begins from 0 [V] and charging continues up to 4.2 [V], which is SOC 100 [%]. The graph is simplified and represented by a straight line.

[0048] <Initial charge dQ / dV calculation> Here, dQ / dV in the initial charge is calculated as shown in Fig. 6. When dQ / dV is calculated, as shown by curve L2 in Fig. 6, a peak P A and Peak P B This procedure corresponds to the "step of detecting unknown peaks" of the present invention. A The voltage [V] can be read as approximately A = 2.1 [V]. Also, the peak P B The voltage [V] of B can be read as approximately B = 2.6 [V]. In other words, the peak P of dQ / dV originating from foreign substance A A is electrically decomposed at approximately 2.1 [V]. Since energy is required to decompose this foreign substance A, the amount of power [Ah] required to increase the voltage [V] increases, and the peak P of dQ / dV occurs at 2.1 [V]. A Similarly, the peak P of dQ / dV due to foreign substance B occurs. B is electrically decomposed at approximately 2.6 [V]. Since energy is required to decompose this foreign substance B, the amount of power [Ah] required to increase the voltage [V] increases, and the peak P of dQ / dV occurs at 2.6 [V]. A In this way, in the procedure of "calculating initial charge dQ / dV (S12)", the peak P A , peak P B The voltage [V] is stored in the memory 282 of the control device 208 of the manufacturing apparatus 200 shown in Fig. 2. This procedure corresponds to the "peak position recording step" of the present invention.

[0049] <Whether or not a peak other than that of the electrolyte exists (S13)> The curve L1 of the reference dQ / dV obtained in the procedure of S10 is compared with the curve L2 of the initial charge dQ / dV obtained in the procedure of S12 to determine whether or not a peak other than that of the electrolyte exists. A and Peak P B Since the presence of the peaks other than the electrolyte is confirmed, it is determined that a peak other than the electrolyte exists (S13: Yes), and the process proceeds to step S18.

[0050] If no peak is confirmed, it is determined that no peak other than that of the electrolyte exists (S13: No), and the procedure proceeds to S14. In this case, it is determined that no foreign matter has been generated or mixed in, and the normal production processes of "high temperature aging and self-discharge (S14)," "capacity inspection and resistance inspection (S15)," and "SOC adjustment (S16)" are carried out. After that, lithium-ion secondary batteries 10 with no problems in the battery cells are shipped as products (S17), and the determination of foreign matter contamination is completed (END). Detailed explanations of each step will be omitted here.

[0051] <Record the peak position (S18)> If it is determined that a peak other than that of the electrolyte exists (S13: YES), the peak position is recorded (S18). In the procedure of calculating the initial charge dQ / dV (S12), this curve L2 is obtained as the initial charge dQ / dV and stored in the memory 282 of the control device 208 of the manufacturing apparatus 200 shown in FIG. 2. In this embodiment, the peak P A and Peak P B Since these voltages are detected, the respective voltages, in this case voltage A = 2.1 [V] and voltage B = 2.6 [V], are recorded.

[0052] At this time, based on voltage A = 2.1 [V] and voltage B = 2.6 [V], the resin constituting the lithium-ion secondary battery 10 and the grease of the manufacturing apparatus 200 are collated to analyze what the organic substance decomposed at such a potential is. Such a procedure corresponds to the "step of specifying the cause" of the present invention. Even if the causative substance is unknown, the response is possible, but if the causative substance is known, the response, for example, setting appropriate voltage, residence time, temperature, etc. can be done.

[0053] <High-temperature aging, self-discharge (S19)> Here, as in the case where no foreign matter is detected (S14), high-temperature aging and self-discharge are carried out. At this time, as shown in FIG. 5, the OCV voltage [V] gradually decreases due to self-discharge. Such a procedure corresponds to the "step of high-temperature aging" of the present invention.

[0054] <Capacity inspection, resistance inspection (S20)> When high-temperature aging and self-discharge (S19) are completed, capacity inspection and resistance inspection (S20) are performed. Here too, as in the case where no foreign matter is detected (S14), capacity inspection and resistance inspection are carried out. This is because capacity inspection and resistance inspection are basic performance inspections of the lithium-ion secondary battery 10. As shown in FIG. 5, once discharged, recharged, discharged again, the voltage is measured with respect to the applied current, and DC-IR is measured. This procedure corresponds to the "inspection step" of the present invention. Note that capacity inspection and resistance inspection (S20) may be carried out after inspection dQ / dV calculation (S23). Note that only any one of the inspections or other inspections may be carried out in combination.

[0055] <Discharge until less than the peak minimum voltage (voltage A) (S21)> Here, the setting of the start voltage of the inspection charge is made. Peak P A and peak P B At, since voltage A < B [V], the voltage [V] is discharged and lowered to less than voltage A [V].

[0056] <SOC adjustment (S22)> Once the voltage [V] has been discharged and reduced to below voltage A, inspection charging begins and the battery is charged to the SOC [%] set for shipping. This charging is for adjusting the SOC for shipping, but it is also inspection charging to confirm that foreign matter has disappeared, and this procedure corresponds to the "inspection charging step" of this invention.

[0057] <Test dQ / dV calculation (S23)> Here, charging is performed for SOC adjustment, but since the voltage [V] is discharged and lowered to below voltage A, charging is performed at voltage A. Therefore, by calculating dQ / dV during charging for SOC adjustment, if foreign object A remains, the peak P A should appear. Similarly, dQ / dV can be calculated for voltage B, which is higher than voltage A. This procedure corresponds to the "step of calculating test dQ / dV" of the present invention.

[0058] <Whether or not peaks other than those of the electrolyte have disappeared (S24)> Peak P due to foreign substance A during initial charging A and peak P originating from foreign substance B. B Even if the mark appears, foreign matter A or B may have electrically or chemically decomposed during the initial charge or subsequent high-temperature aging.

[0059] Therefore, the curve L1 of the reference dQ / dV and the curve L2 of the test dQ / dV in FIG. 6 are compared. In FIG. 6, the peak P A There is a difference of ΔA between the dQ / dV of curve L1 and the dQ / dV of curve L2 at the same A [V]. Also, peak P B At the same B [V], there is a difference of ΔB between the dQ / dV of curve L1 and the dQ / dV of curve L2. What this difference ΔA, ΔB means is that even if the same power is consumed at voltage A [V] and voltage B [V], curve L2 has a smaller dQ / dV. If foreign matter A and foreign matter B do not exist, these peaks PA and PB do not occur. In other words, if ΔA and ΔB disappear, foreign matter A and foreign matter B have disappeared. This procedure corresponds to the "step of determining whether the unknown peak has disappeared" of the present invention. In this case, peak P A , peak PB If the peak P has disappeared (S24: Yes), it can be determined that the foreign matter A and the foreign matter B have disappeared. A , peak P B Even if the charge has not completely disappeared, if it has decreased to a degree that does not affect the performance of the battery, a threshold value may be set to determine whether the battery is ready for shipment. In these cases, the battery is deemed ready for shipment (S17), and the process ends (END).

[0060] The test dQ / dV may be compared with the initial charging dQ / dV. In this case, complete disappearance cannot be determined, but the extent to which the foreign matter has decreased under certain conditions can be determined, making it possible to calculate the conditions for the disappearance of the foreign matter. By comparing this with curve L1, the state of foreign matter A and B becomes even clearer.

[0061] On the other hand, peak P A , peak P B If the foreign matter A and foreign matter B have not disappeared (S24: No), it is determined that foreign matter A and foreign matter B remain, and the product is disposed of as unshippable (S25), and the process ends (END).

[0062] (Operation of the embodiment) In the manufacturing method of the lithium ion secondary battery 10 of this embodiment, the reference dQ / dV of the non-aqueous electrolyte 25 without any foreign matter is calculated and recorded in advance (S10). Then, when manufacturing the lithium ion secondary battery 10, the initial charge dQ / dV is calculated for each individual cell battery in the initial charge (S11) (S12). In this initial charge dQ / dV, for example, a peak P that was not present in the reference dQ / dV is calculated. A , P B When this peak P is detected (S13: Yes), this means that a foreign substance has been generated or mixed in. A , P B Based on the voltage, it is possible to identify each of the foreign substances that have been generated or mixed in from the potential [V] at which they decompose. By identifying the type of foreign substance, it is possible to determine the optimal treatment method, such as the voltage, current, and temperature to be applied, allowing for effective and efficient treatment.

[0063] Next, after the initial charge, high temperature aging and self-discharge (S19) are performed, followed by a capacity test and a resistance test (S20). If there is a problem with the capacity test or resistance test, the product can be judged as defective. If there is no problem with the capacity test or resistance test, the peak P A In order to reproduce the peak P A The battery is discharged to a voltage A [V] (S21), and then charged for SOC adjustment (S22). During this charging for SOC adjustment, the test dQ / dV is calculated (S23). At this stage, foreign matter may have disappeared due to the initial charge (S11) or high-temperature aging (S19), and either or both of the peaks PA and PB may have disappeared or decreased. In such cases, by comparing the test dQ / dV with the reference dQ / dV, it is possible to accurately determine whether each foreign matter has disappeared or remains. This allows for easy, quick, and accurate decisions on whether or not to ship each product.

[0064] (Effects of the embodiment) (1) The method for manufacturing the lithium ion secondary battery 10 of this embodiment has the advantage that it is possible to detect organic foreign matter that has become mixed into each cell battery and determine whether the battery is ready for shipping.

[0065] (2) In step (S4) of calculating the initial charge dQ / dV, the initial charge dQ / dV, which is the change in discharge capacity relative to the change in voltage during the initial charge, is calculated. This has the effect of making it easy to determine the presence of organic foreign matter in the nonaqueous electrolyte solution 25.

[0066] (3) In the step of detecting unknown peaks (S13), the initial charging dQ / dV is compared with a predetermined reference dQ / dV of the nonaqueous electrolyte 25 to detect unknown peaks not expected in the reference dQ / dV. This has the effect of accurately determining the presence of organic foreign matter in the nonaqueous electrolyte 25.

[0067] (4) In the peak position recording step (S18), when an unknown peak is detected, the voltage at the position of each detected peak is recorded, which has the effect of enabling different foreign substances in the non-aqueous electrolyte 25 to be identified by separating them from their respective voltages.

[0068] (5) In the inspection charging step (S22), after the high-temperature aging step (S19), charging is performed from a voltage lower than the lowest voltage among the peak voltages. This has the effect of making it possible to calculate dQ / dV corresponding to all foreign matter.

[0069] (6) In the step of calculating the inspection dQ / dV, the dQ / dV corresponding to all foreign matter is calculated during the inspection charge, which has the effect of making it possible to determine whether the foreign matter has disappeared during the high-temperature aging process or the like.

[0070] (7) In the step of determining whether or not the unknown peak has disappeared (S24), it is determined whether or not the unknown peak has disappeared in the test dQ / dV. This has the effect of making it possible to reliably determine whether or not the foreign matter has disappeared in the high-temperature aging step (S19) or the like.

[0071] (8) Furthermore, in the step of identifying the cause (S18), the substance causing each peak is identified based on the voltage at the position of each peak, which has the effect of enabling the type of foreign matter to be analyzed and identified.

[0072] (9) In the inspection step (S20), after the initial charge is completed, a high-temperature aging process is performed, and at least one of a battery capacity inspection and an internal resistance inspection is performed. Therefore, if it is already determined that the foreign matter does not affect the capacity or internal resistance, the battery can be shipped as a product regardless of the amount of foreign matter remaining. This inspection step (S20), in conjunction with the unknown peak disappearance determination step (S24), allows the decision on product shipping to be made more safely, efficiently, and sufficiently.

[0073] (10) The step of determining whether the unknown peak has disappeared compares the test dQ / dV with the initial charging dQ / dV to determine whether the unknown peak has disappeared. This has the effect of making it possible to accurately determine the degree to which each foreign particle has been reduced individually.

[0074] (11) The step of determining whether or not the unknown peak has disappeared (S24) compares the test dQ / dV with the reference dQ / dV to determine whether or not the unknown peak has disappeared. This has the effect of enabling accurate determination of the amount of each foreign particle remaining individually.

[0075] (12) In the test charging step (S22), charging is performed up to the set SOC. Therefore, the test charging can be performed as charging for adjusting the SOC, which has the effect of eliminating waste in the manufacturing process.

[0076] (Another example) The above embodiment is an example of the present invention, and can be modified and implemented as follows. The manufacturing apparatus 200 is an example for carrying out the manufacturing method of the present invention, and the present invention is not limited to such an apparatus.

[0077] The various voltages, temperatures, times, etc. that are set are examples, and a person skilled in the art can optimize them as appropriate depending on the composition and configuration of the secondary battery in question. Although a lithium ion secondary battery is given as an example of a non-aqueous secondary battery, the invention can also be implemented with other non-aqueous secondary batteries as long as the invention is feasible.

[0078] Although the electrode plate assembly of the present embodiment is a wound type, it may be a stacked type. Also, the raw materials are merely examples and are not limited to these. The lithium ion secondary battery 10 shown as an example has a plate-shaped case, but the shape is not limited thereto and may be cylindrical or the like.

[0079] The flowcharts shown in Figures 3 and 4 are examples and can be implemented by adding, deleting, or changing the steps, or by changing the order. The method for manufacturing a lithium ion secondary battery according to the present embodiment is one embodiment of the invention, and it goes without saying that those skilled in the art can add, delete, or modify the configuration without being limited to the embodiment, as long as it does not deviate from the scope of the claims. [Explanation of symbols]

[0080] 10...Lithium-ion secondary battery 11...Battery case 12...lid body 13...External terminal 14...Positive electrode plate 15...Negative electrode plate 17...Separator 20...Electrode plate group 25…Nonaqueous electrolyte 200...Manufacturing equipment 203...Charging / discharging device 204...Cell voltage measuring instrument 205...Cell current measuring instrument 206…Thermometer 207…Heating device 208...Control device 281...CPU 282...Memory P A , P B …peak A, B [V]...Peak voltage

Claims

1. A method for manufacturing a non-aqueous secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte solution, comprising: a step of calculating an initial charge dQ / dV, which is a change in charge capacity relative to a change in voltage during initial charge; an unknown peak detection step of comparing a previously estimated reference dQ / dV of the non-aqueous electrolyte with the initial charge dQ / dV measured in the initial charge dQ / dV calculation step to detect an unknown peak not expected in the reference dQ / dV; a peak position recording step of recording a voltage at the position of each of the detected unknown peaks when the unknown peaks are detected in the unknown peak detection step; a test charging step of charging from a voltage lower than the lowest voltage among the peak voltages after the initial charging; a step of calculating a test dQ / dV in the test charge; an unknown peak disappearance determination step of determining whether or not the unknown peak detected in the unknown peak detection step has disappeared in the test dQ / dV calculated in the test dQ / dV calculation step; A method for manufacturing a non-aqueous secondary battery, comprising:

2. 2. The method for manufacturing a nonaqueous secondary battery according to claim 1, further comprising a step of identifying a cause of each of the unknown peaks based on the voltage at the position of each of the unknown peaks recorded in the peak position recording step.

3. a high-temperature aging step of performing a high-temperature aging process after the initial charging is completed; After the high-temperature aging step, the test charging step is performed. The method for producing a non-aqueous secondary battery according to claim 1 ,

4. After the high-temperature aging step, an inspection step is performed in which at least one of a battery capacity inspection and an internal resistance inspection is performed.

4. The method for producing a non-aqueous secondary battery according to claim 3,

5. 2. The method for manufacturing a nonaqueous secondary battery according to claim 1, wherein the step of determining whether the unknown peak has disappeared comprises comparing the test dQ / dV with the initial charging dQ / dV to determine whether the unknown peak has disappeared.

6. 2. The method for manufacturing a non-aqueous secondary battery according to claim 1, wherein the step of determining whether the unknown peak has disappeared comprises comparing the test dQ / dV with the reference dQ / dV to determine whether the unknown peak has disappeared.

7. 2. The method for manufacturing a non-aqueous secondary battery according to claim 1, wherein the test charging step involves charging the battery up to a set SOC.

8. 8. The method for producing a non-aqueous secondary battery according to claim 1, wherein the non-aqueous secondary battery is a lithium ion secondary battery.

Images