Method for manufacturing a battery and method for inspecting a battery

Abstract

Provided are a battery manufacturing method and a battery inspection method. The battery manufacturing method includes the following steps: a step of performing an aging treatment on a plurality of batteries; a step of obtaining inter-terminal voltages of the plurality of batteries before the aging treatment; a step of obtaining inter-terminal voltages of the plurality of batteries after the aging treatment; and a step of determining whether each of the plurality of batteries is defective. In the step of determining, at least one of the differences in the inter-terminal voltages before and after the aging treatment of each of the plurality of batteries is excluded to set a threshold value.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a battery and a method for inspecting a battery. Background Technology

[0002] Japanese Patent Application Publication No. 2006-253027 discloses a method for manufacturing a secondary battery, which includes a step of judging the defects of the secondary battery and a step of judging the defects of the secondary battery again for other secondary batteries besides the secondary batteries judged to be defective.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2006-253027

[0004] During battery manufacturing, battery defects are sometimes determined based on the electrical characteristics of multiple batteries. Summary of the Invention

[0005] The battery manufacturing method disclosed herein includes the following steps: an aging process for multiple batteries; a process for obtaining the inter-terminal voltage of the multiple batteries before the aging process; a process for obtaining the inter-terminal voltage of the multiple batteries after the aging process; and a process for determining whether each of the multiple batteries is defective. In the determination step, a threshold is set by excluding at least one inter-terminal voltage difference from the inter-terminal voltage differences of each of the multiple batteries before and after the aging process. Based on this battery manufacturing method, the accuracy of determining battery defects is improved. Attached Figure Description

[0006] Figure 1 This is a flowchart of the battery manufacturing process.

[0007] Figure 2 It is a cross-sectional view schematically showing the internal structure of battery 1.

[0008] Figure 3 This is a schematic diagram of electrode 20.

[0009] Figure 4 This is the flowchart for the determination process S30.

[0010] Figure 5 This is a graph representing the voltage difference ΔV between terminals after aging treatment.

[0011] Figure 6 This is a graph representing the voltage difference ΔV between terminals after aging treatment.

[0012] Figure 7 This is a graph showing the voltage difference ΔV between terminals after removing defective battery 1.

[0013] Figure 8 This is a graph showing the voltage difference ΔV between terminals after removing defective battery 1.

[0014] Figure 9 This is a graph showing the terminal voltage difference ΔV after rejecting defective battery 1 in other embodiments. Detailed Implementation

[0015] Hereinafter, one embodiment of the technology disclosed herein will be described with reference to the accompanying drawings. The embodiments described herein are not intended to specifically limit the invention. The drawings are schematic and do not necessarily reflect the actual object. Furthermore, components and parts that perform the same function are appropriately labeled with the same reference numerals, and repeated descriptions are appropriately omitted. In this specification, unless specifically mentioned, descriptions such as "X~Y" indicating numerical ranges mean "X and above and Y and below".

[0016] Figure 1 This is a flowchart of the battery manufacturing process. (For example...) Figure 1 As shown, the battery manufacturing method includes a step S10 of preparing multiple batteries and a step S20 of judging battery defects. The battery manufacturing method may also include other steps. Hereinafter, the battery manufacturing method will be described using a lithium-ion secondary battery as an example. Furthermore, the technology disclosed herein is not limited to the manufacturing method of lithium-ion secondary batteries, and can also be applied to other known batteries (e.g., sodium-ion secondary batteries).

[0017] <Process S10 for preparing multiple batteries>

[0018] In step S10, which involves preparing multiple batteries, multiple batteries 1 are prepared according to a known method. For example... Figure 1 As shown, the process S10 for preparing multiple batteries includes a battery assembly preparation process S11 and an initial charging process S12.

[0019] <Battery Assembly Preparation Process S11>

[0020] In the battery assembly preparation process S11, the battery assembly 1 is prepared before initial charging. Figure 2 It is a cross-sectional view schematically showing the internal structure of battery 1. Figure 3 This is a schematic diagram of electrode body 20. In the battery assembly preparation process S11, the casing 10, electrode body 20, and non-aqueous electrolyte (illustration omitted) are prepared.

[0021] like Figure 2As shown, the housing 10 is a square container. For example, a metal material (aluminum, aluminum alloy, etc.) with constant strength is used for the housing 10. The housing 10 includes a housing body 12 with an opening at the top and a cover 14 that blocks the opening. An electrode body 20 and an electrolyte are housed in the housing 10. An injection port 15 for injecting the electrolyte is provided in the cover 14. An vent valve 19 is provided in the cover 14. A positive terminal 16 and a negative terminal 18 are mounted on the cover 14 via insulating components 16a and 18a. The positive terminal 16 and the negative terminal 18 are connected to the electrode body 20 via current collectors 26 and 28 respectively disposed inside the housing 10. Aluminum, aluminum alloy, etc., can be used as the positive terminal 16. Copper, copper alloy, etc., can be used as the negative terminal 18.

[0022] Electrode 20 is the power generation element of battery 1. For example... Figure 3 As shown, the electrode body 20 includes a positive electrode plate 30, a negative electrode plate 40, and a separator 50. In this embodiment, the electrode body 20 is a wound electrode body. The wound electrode body is manufactured by stacking and winding the positive electrode plate 30, the negative electrode plate 40, and the separator 50. The structure of the electrode body 20 is not particularly limited, and other known structures (such as stacked electrode bodies) may also be used.

[0023] The positive electrode plate 30 includes a positive electrode core 32 and a positive electrode active material layer 34 formed on the surface of the positive electrode core 32. The positive electrode core 32 is a conductive metal foil. Aluminum or similar materials can be used for the positive electrode core 32. The positive electrode active material layer 34 includes a positive electrode active material, a conductive material, and a binder. For example, a lithium transition metal composite oxide can be used as the positive electrode active material. Carbon materials such as acetylene black and graphite can be used as the conductive material. Resin materials such as polyvinylidene fluoride (PVdF) can be used as the binder.

[0024] The negative electrode plate 40 includes a negative electrode core 42 and a negative electrode active material layer 44 attached to the surface of the negative electrode core 42. The negative electrode core 42 is a conductive metal foil. Copper or similar materials can be used for the negative electrode core 42. The negative electrode active material layer 44 includes a negative electrode active material, a binder, a thickener, etc. Carbon materials such as graphite, hard carbon, and soft carbon can be used as the negative electrode active material. Resin materials such as styrene-butadiene rubber (SBR) can be used as the binder. Resin materials such as carboxymethyl cellulose (CMC) can be used as the thickener.

[0025] The separator 50 is an insulating sheet sandwiched between the positive electrode plate 30 and the negative electrode plate 40. For example, polyethylene (PE), polypropylene (PP), polyester, cellulose, polyamide, and other resin materials can be used as the separator 50. A heat-resistant layer containing inorganic fillers can also be formed on the surface of the separator 50.

[0026] The electrolyte comprises a non-aqueous solvent and a supporting salt. Examples of non-aqueous solvents include ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethylmethyl carbonate (EMC). Various lithium salts can be used as the supporting salt, such as LiPF6.

[0027] In the battery assembly preparation step S11, the battery assembly 1 is prepared by housing the electrode body 20 in the prepared casing 10 and injecting electrolyte (see reference). Figure 2 After the electrolyte is injected, the injection port 15 is sealed by the sealing component 15a. In the battery assembly preparation process S11, multiple battery assemblies 1 are prepared.

[0028] <Initial charging process S12>

[0029] In the initial charging step S12, multiple battery assemblies 1 are initially charged. In the initial charging step S12, the battery assemblies 1 are charged under predetermined conditions until they reach a predetermined voltage value. The initial charging can be performed using known methods. While not particularly limited, it can be performed at a voltage value that is 10% to 90% of the SOC (State of Charge) at full charge. While not particularly limited, the initial charging can be performed, for example, at a normal temperature environment of around 25°C (e.g., 20°C to 30°C) at a charging rate of 0.05C to 10C. Furthermore, the voltage value and charging conditions of the initial charging are set according to the type of battery. In the initial charging step S12, each of the multiple battery assemblies 1 is initially charged individually.

[0030] Multiple batteries 1 are prepared by initially charging multiple battery assemblies 1. If multiple batteries 1 are prepared, it is then determined whether any of the multiple batteries 1 is defective. Furthermore, the initial charging step S12 may also include a step of repeatedly charging and discharging the battery 1 under predetermined conditions. In this initial charging step S12, the battery 1 is activated.

[0031] <Process S20 for determining battery defects>

[0032] The process S20 for determining battery defects is performed based on the terminal voltage of battery 1 before and after aging. For example... Figure 1 As shown, the process S20 for determining battery defects includes a first terminal voltage acquisition process S21, an aging process S22, a second terminal voltage acquisition process S23, and a determination process S30.

[0033] <First Terminal Voltage Acquisition Process S21>

[0034] In the first inter-terminal voltage acquisition step S21, the inter-terminal voltage (first inter-terminal voltage) V1 of the plurality of batteries 1 before the aging treatment is acquired. At this time, the plurality of batteries 1 are charged in a manner that brings them to a predetermined voltage (or a voltage equivalent to a predetermined SOC). The voltage and SOC of the batteries 1 in the first inter-terminal voltage acquisition step S21 are not particularly limited. The batteries 1 may also be charged to a predetermined voltage in the initial charging step S12. The voltage of the batteries 1 may also be adjusted to reach a predetermined voltage after the initial charging step S12.

[0035] The first terminal voltage V1 can be measured by a voltage measuring device (not shown). The positive terminal 16 and negative terminal 18 of battery 1 are connected to the positive and negative terminals of the voltage measuring device, respectively, thereby enabling the measurement of the first terminal voltage V1. Furthermore, in the first terminal voltage acquisition step S21, if a battery has a first terminal voltage V1 that deviates from a predetermined range, that battery can be considered defective and rejected. The rejected battery 1 is also rejected in subsequent steps. After the first terminal voltage acquisition step S21, an aging process is performed on multiple batteries 1.

[0036] <Aging process S22>

[0037] In aging process S22, multiple batteries 1 are subjected to aging treatment. In aging process S22, the multiple batteries 1 are housed in an aging apparatus (not shown) and placed in an environment with a predetermined temperature for a predetermined period. The multiple batteries 1 can be aged in one aging apparatus or in different aging apparatuses. The aging conditions are set according to the type of battery, etc., and are therefore not particularly limited. The aging temperature can be set to a constant temperature selected between 20°C and 75°C. The aging period can be set to 5 to 15 days. After the aging treatment, the terminal voltage of the battery 1 is measured again.

[0038] <Second Terminal Voltage Acquisition Process S23>

[0039] In the second terminal voltage acquisition step S23, the terminal voltage (second terminal voltage) V2 of multiple batteries 1 after aging treatment is acquired. The method for acquiring the second terminal voltage V2 can also be the same as the method for acquiring the first terminal voltage V1. Furthermore, in the second terminal voltage acquisition step S23, if there is a battery whose second terminal voltage V2 deviates from a predetermined range, that battery can also be considered defective and rejected. The rejected battery 1 is also rejected in subsequent steps.

[0040] After aging, the inter-terminal voltage of multiple batteries 1 is lower than the inter-terminal voltage before aging. In other words, the second inter-terminal voltage V2 is lower than the first inter-terminal voltage V1. The individual batteries 1 are determined to be defective based on the first inter-terminal voltage V1 and the second inter-terminal voltage V2.

[0041] <Judgment Process S30>

[0042] In the judgment process S30, the voltage difference between terminals V1-V2 (ΔV) before and after the aging treatment of each battery 1 is used to determine whether each battery 1 is defective. Figure 4 This is the flowchart for the determination process S30. For example... Figure 4 As shown, the judgment process S30 includes a process S31 of calculating the voltage difference between terminals for multiple batteries, a process S32 of excluding at least one voltage difference between terminals, a process S33 of calculating the average value of the voltage differences between terminals, a process S34 of calculating the standard deviation of the voltage differences between terminals, a process S35 of judging the batteries as defective based on a threshold, a process S36 of rejecting the batteries judged as defective, and a process S37 of judging whether the defective judgment has been repeated a predetermined number of times. Here, N batteries are the judgment objects in the judgment process S30. Here, N is an integer. In addition, the number of batteries that are the judgment objects is not particularly limited.

[0043] Figure 5 and Figure 6 This is a graph representing the voltage difference ΔV between terminals after aging treatment. Figure 5 and Figure 6 In the example, for each battery 1 for which the inter-terminal voltage difference ΔV is calculated, the open circuit voltage OCV (OCV) and the inter-terminal voltage difference ΔV after aging treatment are shown. Figure 5 In the diagram, a circle represents the total voltage difference ΔV between the terminals of multiple batteries 1. Figure 7 and Figure 8 This is a graph showing the terminal voltage difference ΔV after removing defective battery 1. Figure 7 The graph shown represents the terminal voltage difference ΔV after the first rejection of defective battery 1. Figure 8 The graph shown represents the terminal voltage difference ΔV after the second rejection of defective battery 1. Figures 5-8 In the diagram, the average value ΔVa of the voltage difference ΔV between terminals is shown by a dashed line, and the threshold value Th, based on the average value ΔVa, is shown by a dashed line. Figures 6-8 In the diagram, the voltage differences between the terminals of multiple batteries 1 that are eliminated by process S32 are represented by triangles, while the voltage differences between the terminals that are not eliminated by process S32 are represented by circles.

[0044] <Process S31 for calculating the voltage difference between terminals of battery 1>

[0045] In step S31, which calculates the voltage difference between terminals for battery 1, the voltage difference ΔV between terminals is calculated based on the difference between the voltage V1 between the first terminals and the voltage V2 between the second terminals. Here, the voltage difference ΔV between terminals is calculated separately for each of the multiple batteries 1. In this embodiment, the voltage difference ΔV between terminals is calculated for N batteries 1 (refer to...). Figure 5 The voltage difference ΔV between terminals is the value obtained by dividing the difference between the voltage V1 between the first terminal and the voltage V2 between the second terminal by the aging period (number of days). However, the method for calculating the voltage difference ΔV between terminals is not necessarily limited to this method. For example, the voltage difference ΔV between terminals may not be obtained by dividing by the aging period, but rather as the difference between the voltage V1 between the first terminal and the voltage V2 between the second terminal.

[0046] <Step S32 for eliminating voltage difference between at least one terminal>

[0047] In step S32, which excludes at least one inter-terminal voltage difference, at least one inter-terminal voltage difference ΔV calculated for each of the plurality (N in this embodiment) batteries 1 that are to be judged is excluded from subsequent calculations (in this embodiment, the calculation of the average value (S33) and the calculation of the standard deviation (S34)).

[0048] exist Figure 5 In the illustrated embodiment, the average value of the voltage difference ΔV (mV / day) between the terminals of the plurality of batteries 1 is 0.0272, and the standard deviation is 0.0390. For example... Figure 6 As shown, the maximum value ΔVmax and minimum value ΔVmin among the inter-terminal voltage differences ΔV of multiple batteries 1 are excluded. Here, the maximum and minimum inter-terminal voltage differences ΔV among the N batteries 1 are excluded. A threshold Th for judging the defect of battery 1 is set based on the remaining N-2 inter-terminal voltage differences ΔV of batteries 1.

[0049] <Step S33: Calculating the average value of the voltage difference between terminals>

[0050] In step S33, which calculates the average value of the voltage difference between terminals, the average value ΔVa of the voltage difference ΔV between the terminals of battery 1 is calculated. Here, the average value of the voltage difference ΔV between the terminals of N-2 batteries 1, excluding the maximum value ΔVmax and the minimum value ΔVmin, is calculated. In this embodiment, the average value ΔVa is 0.0224.

[0051] <Step S34: Calculating the standard deviation of the voltage difference between terminals>

[0052] In step S34, which calculates the standard deviation of the voltage difference between terminals, the standard deviation σ of the voltage difference ΔV between the terminals of battery 1 is calculated. Here, similar to step S33, which calculates the average value, the standard deviation σ of the voltage difference ΔV between the terminals of N-2 batteries 1, excluding the maximum value ΔVmax and the minimum value ΔVmin, is calculated. In this embodiment, the standard deviation σ is 0.0257.

[0053] <Process S35 for determining the defect of battery 1 based on a threshold>

[0054] In step S35, which determines whether battery 1 is defective based on a threshold, a preset threshold Th is used to determine whether battery 1 is defective. In this embodiment, the threshold Th is set by excluding at least one inter-terminal voltage difference ΔV (maximum value ΔVmax and minimum value ΔVmin). Here, the determination of whether all N batteries 1, which are the objects of determination, are defective is performed.

[0055] The threshold Th is set based on the standard deviation σ calculated in step S34, which calculates the standard deviation. The threshold Th can be set as a value (nσ) obtained by multiplying the standard deviation σ by a predetermined value n. The value n can be predetermined through mass production tests or similar methods corresponding to the type of battery. In this embodiment, the threshold Th is set as three times the standard deviation σ (3σ). However, the threshold Th is not limited to this value.

[0056] Based on a threshold Th, it is determined whether all N batteries 1 are defective. Here, for each battery 1, it is determined whether the difference between the voltage difference ΔV between the terminals and the average value ΔVa calculated in step S33 (which calculates the average value) is below the threshold Th. Figure 6 As shown, among N-2 batteries 1 out of N batteries 1, the difference between the inter-terminal voltage difference ΔV and the average value ΔVa is below the threshold Th. Among the batteries 1 with the highest inter-terminal voltage difference ΔV and the second highest inter-terminal voltage difference ΔV, the difference between the inter-terminal voltage difference ΔV and the average value ΔVa is greater than the threshold Th. The batteries 1 with the highest inter-terminal voltage difference ΔV and the second highest inter-terminal voltage difference ΔV are determined to be defective. If a defective battery 1 is determined to exist (No), proceed to step S36.

[0057] <Process S36 for rejecting batteries deemed defective>

[0058] In step S36, where batteries deemed defective are rejected, two batteries 1 out of the N batteries 1 to be rejected are removed from the rejection list. After these two batteries 1 are removed from the rejection list, the process returns to step S32, where at least one voltage difference between terminals is eliminated.

[0059] <Step S32 for eliminating voltage difference between at least one terminal>

[0060] In the second step S32, where at least one inter-terminal voltage difference is excluded, similar to the first step S32, at least one inter-terminal voltage difference ΔV calculated for each of the multiple batteries 1 is excluded from subsequent calculations. In step S36, two batteries 1 are excluded from the judgment. Here, among the N-2 inter-terminal voltage differences ΔV, similar to the first step S32, the maximum and minimum inter-terminal voltage differences ΔV are excluded. A threshold Th for judging the defect of battery 1 is set based on the remaining N-4 inter-terminal voltage differences ΔV of the batteries 1.

[0061] like Figure 7 As shown, among the voltage differences ΔV between the terminals of multiple batteries 1, the maximum value ΔVmax and the minimum value ΔVmin are excluded. Here, among the voltage differences ΔV between the terminals of N-2 batteries 1, the maximum and minimum values ​​of the voltage differences ΔV are excluded. Based on the voltage differences ΔV between the terminals of the remaining N-4 batteries 1, a threshold Th for judging the defect of battery 1 is set again. Furthermore, the minimum value ΔVmin is the same as the minimum value excluded in the first process S32.

[0062] <Step S33: Calculating the average value of the voltage difference between terminals>

[0063] In the second step S33, which calculates the average value of the voltage difference between terminals, the average value of the voltage difference ΔV between the terminals of the N-4 batteries 1, excluding the maximum value ΔVmax and the minimum value ΔVmin, is calculated. In this embodiment, the average value ΔVa is 0.0171.

[0064] <Step S34: Calculating the standard deviation of the voltage difference between terminals>

[0065] In the second step S34, which calculates the standard deviation of the voltage difference between terminals, the same as in step S33 where the average value is calculated, the standard deviation σ of the voltage difference ΔV between the terminals of the N-4 batteries 1, excluding the maximum value ΔVmax and the minimum value ΔVmin, is calculated. In this embodiment, the standard deviation σ is 0.0060.

[0066] <Process S35 for determining the defect of battery 1 based on a threshold>

[0067] In the second step S35, which determines the defect of battery 1 based on a threshold, the same as in the first step S35 is used, and the maximum value ΔVmax and the minimum value ΔVmin are excluded. Here, it is determined whether the N-2 batteries 1 that were excluded from the first step S35 are defective.

[0068] Similar to the first step S35, the threshold Th is set based on the standard deviation σ calculated in step S34, which calculates the standard deviation. Similar to the first step S35, the threshold Th is set to a value that is three times the standard deviation σ (3σ). The threshold Th is not limited to this value.

[0069] The threshold Th is used to determine whether N-2 batteries are defective. For example... Figure 7 As shown, among N-3 batteries 1 out of N-2 batteries 1, the difference between the inter-terminal voltage difference ΔV and the average value ΔVa is below the threshold Th. Among the N-2 batteries 1, the battery 1 with the highest inter-terminal voltage difference ΔV has an inter-terminal voltage difference ΔV greater than the threshold Th. The battery 1 with the highest inter-terminal voltage difference ΔV is determined to be defective. If a defective battery 1 is determined to exist (No), the process proceeds again to step S36.

[0070] <Process S36 for rejecting batteries deemed defective>

[0071] In step S36, where batteries deemed defective are rejected, one battery 1 from the remaining N-2 batteries 1, after excluding the two previously rejected batteries, is further rejected from the judgment list. With one battery 1 rejected, the remaining N-3 batteries 1 become the judgment targets. The process then returns to step S32, where at least one voltage difference between terminals is eliminated.

[0072] <Step S32 for eliminating voltage difference between at least one terminal>

[0073] In the third step S32, the same processing as in the first and second steps S32 is performed. The maximum and minimum inter-terminal voltage differences ΔV among the N-3 inter-terminal voltage differences ΔV are excluded. A threshold Th for determining the defect of battery 1 is set based on the remaining N-5 inter-terminal voltage differences ΔV of battery 1. Figure 8 As shown, the maximum value ΔVmax and minimum value ΔVmin among the inter-terminal voltage differences ΔV of multiple batteries 1 are excluded. Here, the maximum and minimum inter-terminal voltage differences ΔV among N-3 batteries 1 are excluded. Based on the remaining N-5 inter-terminal voltage differences ΔV, a threshold Th for judging the defect of battery 1 is set again. Furthermore, the minimum value ΔVmin is the same as the minimum value excluded in the first process S32.

[0074] <Step S33: Calculating the average value of the voltage difference between terminals; Step S34: Calculating the standard deviation of the voltage difference between terminals>

[0075] In step S33, which calculates the average value of the voltage difference between terminals in the third step, the average value of the voltage difference ΔV between the terminals of the remaining N-5 batteries 1 after excluding the maximum value ΔVmax and the minimum value ΔVmin is calculated. In this embodiment, the average value ΔVa is 0.0167. In step S34, which calculates the standard deviation of the voltage difference between terminals in the third step, the same as in step S33, the standard deviation σ of the voltage difference ΔV between the terminals of the remaining N-5 batteries 1 after excluding the maximum value ΔVmax and the minimum value ΔVmin is calculated. In this embodiment, the standard deviation σ is 0.0055.

[0076] <Process S35 for determining the defect of battery 1 based on a threshold>

[0077] In the third step S35, which determines the defect of battery 1 based on a threshold, the maximum value ΔVmax and the minimum value ΔVmin are excluded, just like in the first and second steps S35. Here, it is determined whether the remaining N-3 batteries 1, which were excluded from the second step S35, are defective. Similar to the first and second steps S35, the threshold Th is set to three times the standard deviation σ (3σ).

[0078] The threshold Th is used to determine whether N-3 batteries are defective. For example... Figure 8 As shown, among all N-3 batteries 1 that are subject to judgment, the difference between the inter-terminal voltage difference ΔV and the average value ΔVa is below the threshold Th. If a battery 1 is determined to be without defects (yes), the process proceeds to step S37.

[0079] <Process S37: Determining whether a defect has been repeatedly detected a predetermined number of times>

[0080] In step S37, which determines whether a defective judgment has been made more than a predetermined number of times, it is determined whether the judgment in step S35 has reached the predetermined number of times. Although not specifically limited, the number of judgments in step S35 can be set to 5 to 10 times. Here, since the number of judgments in step S35 is 3, it is judged as not reaching the predetermined number (No), and thus the process returns to step S32.

[0081] The above steps S32 to S37 are repeated. In step S37, if the predetermined number of defect determinations has been reached (Yes), then step S30 ends. In other words, the determination of whether each of the multiple batteries 1 is defective is completed based on the voltage difference ΔV between the terminals before and after the aging process. In step S30, 3 out of the N batteries 1 that are subject to determination are determined to be defective.

[0082] The following describes the method when step S32, which eliminates the voltage difference between at least one terminal in the above-mentioned determination step S30, is not performed. Figure 9 This is a graph showing the terminal voltage difference ΔV after rejecting defective battery 1 in other embodiments.

[0083] As mentioned above, in Figure 5 In the illustrated embodiment, the average value ΔVa of the voltage difference ΔV between the terminals of the N batteries 1 is 0.0272, and the standard deviation σ is 0.0390. Without performing step S32, as... Figure 5 As shown, among the N batteries 1 in the evaluation criteria, the battery 1 with the highest inter-terminal voltage difference ΔV and the battery 1 with the second highest inter-terminal voltage difference ΔV are judged as defective. The two batteries 1 judged as defective are removed from the evaluation criteria.

[0084] The average value ΔVa of the voltage difference ΔV between the terminals of the remaining N-2 batteries 1 is 0.0175, and the standard deviation σ is 0.0073. Without performing step S32, as... Figure 9 As shown, among all N-2 batteries 1 subject to judgment, the difference between the inter-terminal voltage difference ΔV and the average value ΔVa is below the threshold Th. The judgment process ends when a battery 1 is determined to be without defects and the number of judgments reaches a predetermined number.

[0085] exist Figure 9 In the embodiment shown, the voltage difference ΔV between the terminals of one of the N-2 batteries 1 that is being judged (in...) Figure 9The voltage difference ΔV between the terminals of this battery 1 (represented by a square) deviates significantly compared to the voltage difference ΔV between the terminals of the other N-3 batteries 1. This voltage difference ΔV is 2.91 times higher than the standard deviation compared to the average value. This voltage difference ΔV is an extremely large value compared to the voltage differences ΔV between the terminals of the other N-3 batteries 1 (so-called deviation value). According to the inventors, when the voltage difference ΔV between the terminals of this battery 1 deviates significantly compared to the other batteries 1, a defect such as a minor short circuit may have occurred in this battery 1. When the voltage difference ΔV of the deviation value, which may indicate a defect, is included in the calculation of the threshold Th, it is difficult to appropriately set the threshold Th based on the voltage difference ΔV of the deviation value. For example, when determining the defect of battery 1 based on the average value ΔVa and the standard deviation σ of the voltage differences ΔV between the terminals of multiple batteries 1, the standard deviation σ becomes large, and the threshold Th may be set too wide. In this case, in the battery defect determination (step S35 in this embodiment), it is difficult to determine that the battery 1, which may have experienced a defect, is defective. To classify battery 1 as defective, consider setting a strict threshold Th. For example, when setting the threshold Th by multiplying the standard deviation σ by the value n, a smaller value can be chosen for n. However, if the threshold Th is set strictly, battery 1, even if it has no defective characteristics, may still be classified as defective.

[0086] In the above embodiment, the battery manufacturing method includes: a step of obtaining the inter-terminal voltage V1 of a plurality of batteries 1 before aging treatment (step S21); a step of performing aging treatment on the plurality of batteries 1 (step S22); a step of obtaining the inter-terminal voltage V2 of the plurality of batteries 1 after aging treatment (step S23); and a step of determining whether each of the plurality of batteries 1 is defective (step S30). In the step of determining whether each of the plurality of batteries 1 is defective, at least one inter-terminal voltage difference ΔV is excluded from the inter-terminal voltage differences ΔV of each of the plurality of batteries 1 before and after aging treatment to set a threshold Th. In this manufacturing method, in setting the threshold Th, it is possible to set the threshold Th in a state where inter-terminal voltage differences ΔV with large deviations compared with the inter-terminal voltage differences ΔV of other batteries 1 are excluded. As a result, it is possible to prevent the threshold Th (in this embodiment, the standard deviation σ) from being set too wide due to large deviations in inter-terminal voltage differences ΔV. As a result, it is easy to set the threshold Th appropriately. Because the threshold Th is set appropriately, batteries 1 that deviate from the standard value in terms of the voltage difference ΔV between their terminals compared to other batteries 1 (batteries 1 that may have experienced minor short circuits or other defects) are more easily identified as defective. As a result, the accuracy of identifying defective batteries 1 is improved.

[0087] In the above embodiment, at least one inter-terminal voltage difference ΔV is the maximum value ΔVmax and the minimum value ΔVmin among the inter-terminal voltage differences ΔV of the plurality of batteries 1. By excluding the maximum value ΔVmax and the minimum value ΔVmin among the inter-terminal voltage differences ΔV, large-deviation inter-terminal voltage differences ΔV are easily eliminated when setting the threshold Th. Furthermore, large-deviation inter-terminal voltage differences ΔV are easily eliminated in either the case of a battery 1 with a very large inter-terminal voltage difference ΔV compared to the other batteries 1, or in the case of a battery 1 with a very small inter-terminal voltage difference ΔV. As a result, the threshold Th can be easily and appropriately set.

[0088] Furthermore, in the above embodiment, the maximum value ΔVmax and the minimum value ΔVmin of the inter-terminal voltage difference ΔV are excluded. However, the inter-terminal voltage differences ΔV of multiple batteries 1 can also be excluded in a manner that includes the maximum value ΔVmax and the minimum value ΔVmin. For example, the maximum value ΔVmax and the second highest value among the multiple inter-terminal voltage differences ΔV can also be excluded. The minimum value ΔVmin and the second lowest value among the multiple inter-terminal voltage differences ΔV can also be excluded. The excluded inter-terminal voltage differences ΔV can also be three or more.

[0089] If the proportion of defective batteries 1 is known in advance, the number of terminal voltage differences ΔV to be excluded can also be determined based on this proportion (defect occurrence rate). Therefore, it is easy to appropriately exclude terminal voltage differences ΔV with large deviations, and it is easy to appropriately set the threshold Th. Furthermore, the number of terminal voltage differences ΔV to be excluded can, for example, be set by multiplying the number of batteries 1 subject to judgment by the defect occurrence rate. The defect occurrence rate can, for example, be obtained based on mass production tests, mass production performance, etc.

[0090] In the above embodiment, the process S20 for determining battery defects includes a process (process S36) of removing batteries 1 determined to be defective from a plurality of batteries 1. Furthermore, the process S20 for determining battery defects includes a process (processes S35, S36) that repeatedly performs the following steps: setting a threshold Th based on a standard deviation σ calculated by further excluding at least one inter-terminal voltage difference ΔV from the inter-terminal voltage differences ΔV of the plurality of batteries 1 that have been excluded from the defective batteries 1, and then determining the defective batteries. Since the threshold Th is set again in the state where the batteries 1 determined to be defective have been previously excluded, it is easy to appropriately set the threshold Th in stages. As a result, it is easy to appropriately set the threshold Th.

[0091] In the above embodiment, the number of batteries 1 to be judged is N. Preferably, the number of batteries 1 to be judged is 7 or more. Therefore, the threshold Th used to judge the defect of batteries 1 in the above method can be easily and appropriately set. Furthermore, the number of batteries 1 to be judged is not limited to the above number.

[0092] In the above implementation, the threshold Th is set based on the standard deviation σ. However, it is not limited to this method; the threshold Th can also be a predetermined value based on mass production testing, mass production performance, or the degree of a minor short circuit that should be judged as defective.

[0093] The battery manufacturing method described above can be applied to battery inspection methods if the terminal voltages before and after aging treatment have been obtained in advance. This inspection method improves the accuracy of identifying defective batteries.

[0094] The techniques disclosed herein have been described above. Unless specifically stated otherwise, the embodiments described herein are not intended to limit the invention. Furthermore, the techniques disclosed herein are capable of various modifications; unless specific problems arise, the constituent elements and processes mentioned herein can be appropriately omitted or combined. This specification also includes the disclosures described in the following items.

[0095] Item 1:

[0096] A method for manufacturing a battery, comprising the following steps:

[0097] A process for aging multiple batteries;

[0098] The process of obtaining the inter-terminal voltage of the aforementioned multiple batteries before the aforementioned aging treatment;

[0099] The process of obtaining the inter-terminal voltage of the aforementioned multiple batteries after the aforementioned aging treatment; and

[0100] The process of setting a threshold by excluding at least one inter-terminal voltage difference from the inter-terminal voltage differences before and after the aging treatment of each of the above-mentioned batteries, and determining whether each of the above-mentioned batteries is defective.

[0101] Item 2:

[0102] In the battery manufacturing method described in item 1,

[0103] The above-mentioned determination process also includes:

[0104] Batteries deemed defective will be removed from the aforementioned battery pool; and

[0105] The following steps are repeated a predetermined number of times: a threshold is set based on the standard deviation calculated by further excluding at least one inter-terminal voltage difference from the inter-terminal voltage differences of multiple batteries that have been excluded from being judged as defective, and defective batteries are judged.

[0106] Item 3:

[0107] In the battery manufacturing method described in item 1 or 2,

[0108] The voltage difference between at least one terminal includes the maximum and minimum values ​​among the voltage differences between the terminals of the plurality of batteries.

[0109] Item 4:

[0110] In any of the battery manufacturing methods described in items 1 to 3,

[0111] The aforementioned batteries consist of seven or more units.

[0112] Item 5:

[0113] In any of the battery manufacturing methods described in items 1 to 4,

[0114] The percentage of batteries that fail is obtained in advance, and the number of voltage differences between terminals that are excluded is determined based on this percentage.

[0115] Item 6:

[0116] A method for inspecting a battery, comprising the following steps:

[0117] A process for obtaining the inter-terminal voltage of multiple batteries before aging treatment;

[0118] The process of obtaining the inter-terminal voltage of the aforementioned multiple batteries after the aforementioned aging treatment; and

[0119] The process of setting a threshold by excluding at least one inter-terminal voltage difference from the inter-terminal voltage differences before and after the aging treatment of each of the above-mentioned batteries, and determining whether each of the above-mentioned batteries is defective.

[0120] Item 7:

[0121] In the battery inspection method described in item 6,

[0122] The above-mentioned determination process also includes:

[0123] Batteries deemed defective will be removed from the aforementioned battery pool; and

[0124] The following steps are repeated a predetermined number of times: a threshold is set based on the standard deviation calculated by further excluding at least one inter-terminal voltage difference from the inter-terminal voltage differences of multiple batteries that have been excluded from being judged as defective, and defective batteries are judged.

[0125] Item 8:

[0126] In the battery inspection method described in item 6 or 7,

[0127] The voltage difference between at least one terminal includes the maximum and minimum values ​​among the voltage differences between the terminals of the plurality of batteries.

[0128] Item 9:

[0129] In any of the battery inspection methods described in items 6-8,

[0130] The aforementioned batteries consist of seven or more units.

[0131] Item 10:

[0132] In any of the battery inspection methods described in items 6-9,

[0133] The percentage of batteries that fail is obtained in advance, and the number of voltage differences between terminals that are excluded is determined based on this percentage.

Claims

1. A method for manufacturing a battery, characterized in that, The process includes the following steps: A process for aging multiple batteries; The process of obtaining the inter-terminal voltage of the plurality of batteries before the aging treatment; The process of obtaining the inter-terminal voltage of the plurality of batteries after the aging treatment; as well as The process of setting a threshold by excluding at least one inter-terminal voltage difference from the inter-terminal voltage differences before and after the aging treatment of each of the plurality of batteries, and determining whether each of the plurality of batteries is defective.

2. The method for manufacturing a battery according to claim 1, characterized in that, The determination process also includes: Batteries deemed defective are removed from the plurality of batteries; and The following steps are repeated a predetermined number of times: a threshold is set based on the standard deviation calculated by further excluding at least one inter-terminal voltage difference from the inter-terminal voltage differences of a plurality of batteries that have been excluded from being judged as defective batteries, and defective batteries are judged.

3. The method for manufacturing a battery according to claim 1 or 2, characterized in that, The at least one inter-terminal voltage difference includes the maximum and minimum values ​​of the inter-terminal voltage differences among the plurality of batteries.

4. The method for manufacturing a battery according to claim 1 or 2, characterized in that, The number of batteries is seven or more.

5. The method for manufacturing a battery according to claim 1 or 2, characterized in that, The proportion of batteries that malfunction is predetermined, and the number of terminal voltage differences that are excluded is determined based on this proportion.

6. A method for inspecting a battery, characterized in that, The process includes the following steps: A process for obtaining the inter-terminal voltage of multiple batteries before aging treatment; The process of obtaining the inter-terminal voltage of the plurality of batteries after the aging treatment; and The process of setting a threshold by excluding at least one inter-terminal voltage difference from the inter-terminal voltage differences before and after the aging treatment of each of the plurality of batteries, and determining whether each of the plurality of batteries is defective.

7. The battery inspection method according to claim 6, characterized in that, The determination process also includes: Batteries deemed defective are removed from the plurality of batteries; and The following steps are repeated a predetermined number of times: a threshold is set based on the standard deviation calculated by further excluding at least one inter-terminal voltage difference from the inter-terminal voltage differences of a plurality of batteries that have been excluded from being judged as defective batteries, and defective batteries are judged.

8. The battery inspection method according to claim 6 or 7, characterized in that, The at least one inter-terminal voltage difference includes the maximum and minimum values ​​of the inter-terminal voltage differences among the plurality of batteries.

9. The battery inspection method according to claim 6 or 7, characterized in that, The number of batteries is seven or more.

10. The battery inspection method according to claim 6 or 7, characterized in that, The proportion of batteries that malfunction is predetermined, and the number of terminal voltage differences that are excluded is determined based on this proportion.

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