Method for inspecting an electric storage device, method for manufacturing an electric storage device, and method for manufacturing a device stack

Abstract

To provide a method for inspecting a power storage device capable of appropriately determining whether a short circuit exists between a metal case and a negative electrode plate in the power storage device, a method for manufacturing a power storage device using the inspection method, and a method for manufacturing a device stack using the inspection method.SOLUTION: A method for inspecting a battery 10 in which an electrode body 30 is accommodated in a case 11 so that the electrode body is insulated from the case by an insulation film 50 includes: a voltage adjustment step S4 for adjusting the battery to a first voltage VB1; a first measurement step S52 for measuring a first potential difference EF1 which is a case-to-negative electrode potential difference generated between the case and a negative electrode potential member 25 that is exposed outside the case and electrically connected to a negative electrode plate 32 to have a negative electrode potential PN; a second measurement step S55 for measuring a second potential difference EF2 which is a case-to-negative electrode potential difference after a lapse of a standby period IWT of 24 hours or more; and a case-to-negative electrode short circuit determination step S57 for determining whether a short circuit exists between the case and the negative electrode plate from magnitude of the first potential difference and the second potential difference and a change ΔF12 between the first potential difference and the second potential difference.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method for inspecting an electricity storage device, a method for manufacturing an electricity storage device, and a method for manufacturing a device stack. [Background technology]

[0002] When manufacturing an electricity storage device such as a secondary battery, it is sometimes necessary to inspect whether or not a micro-short circuit occurs between the metal case and the negative plate of the electrode body of the electricity storage device (for example, see Patent Document 1). This is because an electricity storage device in which a micro-short circuit occurs between the metal case and the negative plate may experience a significant decrease in capacity over a long period of use, which may cause a deterioration in quality. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-72059 A Summary of the Invention [Problem to be solved by the invention]

[0004] A method for determining whether or not there is a micro-short circuit between the metal case and the negative electrode plate is to measure the potential difference (hereinafter, referred to as the case-negative electrode potential difference) occurring between the metal case and the negative electrode plate. This is because when the two are short-circuited, the metal case and the negative electrode plate are at roughly the same potential. Specifically, a voltmeter (e.g., a digital multimeter) with a sufficiently high internal resistance (e.g., having an internal resistance of 1 MΩ or more) is connected to the metal case and the negative electrode terminal that is conductive to the negative electrode plate and exposed to the outside of the metal case, and the case-negative electrode potential difference is measured. If the measured case-negative electrode potential difference is equal to or less than a threshold value, specifically, for example, 0.4 V or less, it is determined that a micro-short circuit has occurred between the metal case and the negative electrode plate.

[0005] However, in such an electricity storage device, the metal case and the electrode body (its negative and positive plates) are insulated by an insulating film or the like, so the potential of the metal case is not determined relative to the negative electrode potential of the negative plate and the positive electrode potential of the positive plate, and is a floating potential. Therefore, when the case-negative electrode potential difference is measured as described above, if there is no short circuit between the metal case and the negative electrode terminal, the obtained case-negative electrode potential difference is likely to vary and may be an extremely small value, even below the threshold value (for example, 0.4 V or less). That is, even if there is no short circuit between the metal case and the negative electrode terminal, it may be erroneously determined that a micro-short circuit occurs between the metal case and the negative electrode plate.

[0006] The present invention has been made in consideration of the current situation, and provides an inspection method for an electricity storage device that can appropriately determine the presence or absence of a short circuit between a metal case and a negative electrode plate in an electricity storage device, a manufacturing method for an electricity storage device using this inspection method, and a manufacturing method for a device stack using this inspection method. [Means for solving the problem]

[0007] (1) One aspect of the present invention for solving the above problem is a method for inspecting an electricity storage device in which an electrode body, in which a negative electrode plate is arranged outside a positive electrode plate in a thickness direction, is housed within a metal case while being insulated from the metal case by an insulating film, the method comprising: a voltage adjustment step of charging or discharging the electricity storage device to adjust it to a first device voltage; a first measurement step of measuring a first potential difference, which is a case-negative electrode potential difference occurring between the metal case and a negative electrode potential member that is exposed to the outside of the metal case and is conductive to the negative electrode plate to be at negative electrode potential, at a first potential difference measurement time after the voltage adjustment step; a second measurement step of measuring a second potential difference, which is the case-negative electrode potential difference, at a second potential difference measurement time after a waiting period of 24 hours or more has elapsed since the first potential difference measurement time; and a case-negative electrode short-circuit determination step of determining the presence or absence of a short circuit between the metal case and the negative electrode plate, from the magnitudes of the first potential difference and the second potential difference, and from a change between the first potential difference and the second potential difference.

[0008] As described above, the potential of the metal case is a floating potential relative to the negative electrode potential, so when the potential difference between the case and the negative electrode is measured, the value is likely to vary and may be an extremely small value. However, when a micro-short circuit occurs between the metal case and the negative electrode plate, the case-negative electrode potential difference indicates approximately 0 V at the time of completion of the voltage adjustment process for adjusting the device voltage of the power storage device to the first device voltage or at the time of the first potential difference measurement. Or, it has been found that the case-negative electrode potential difference indicates a certain value, but gradually decreases toward 0 V as time passes. Even if a certain magnitude of case-negative electrode potential difference occurs at the time of completion of the voltage adjustment process, it is considered that, because a micro-short circuit occurs, the potential of the metal case gradually approaches the negative electrode potential (the potential of the negative electrode plate) as time passes, and finally becomes equal to the negative electrode potential (potential difference 0 V).

[0009] In contrast, when no short circuit occurs between the metal case and the negative plate, the case-negative electrode potential difference has an upper limit, for example, about 2.8 V in a Li-ion secondary battery with an aluminum case, and the case-negative electrode potential difference shows approximately the upper limit at the time when the voltage adjustment process is completed or at the time of measuring the first potential difference. Or, even if the case-negative electrode potential difference shows a certain value lower than the upper limit, it has been found that it gradually increases with the passage of time from the time when the voltage adjustment process is completed and settles at a value near the upper limit.

[0010] Therefore, in this method for inspecting an electric storage device, a first potential difference and a second potential difference, which are the case-negative electrode potential difference, are measured for the electric storage device at a certain first potential difference measurement time after the device voltage is adjusted to a first device voltage, and at a second potential difference measurement time after a waiting period of 24 hours or more. Then, the presence or absence of a short circuit between the metal case and the negative electrode plate is determined from the magnitude of the first potential difference and the second potential difference, and the change between the first potential difference and the second potential difference. Therefore, the influence of the variation in the case-negative electrode potential difference between the negative electrode potential and the case potential that is a floating potential with respect to the negative electrode potential is suppressed, and the presence or absence of a short circuit between the metal case and the negative electrode plate can be appropriately determined.

[0011] Examples of the "electricity storage device" include secondary batteries such as lithium ion secondary batteries, and capacitors such as lithium ion capacitors. The "metal case" is a case made of metal that houses the electrode body, and can have a rectangular parallelepiped shape, a cylindrical shape, etc. Examples of materials for the metal case include aluminum and stainless steel. The "electrode body" may be any electrode body having a configuration in which a negative electrode plate is disposed on the outer side in the thickness direction of a positive electrode plate, and examples of the electrode body include a wound type electrode body and a laminated type electrode body.

[0012] Examples of the method of "determining the presence or absence of a short circuit between the metal case and the negative electrode plate from the magnitude of the first potential difference and the second potential difference and the change between the first potential difference and the second potential difference" include the following method. First, the change between the first potential difference and the second potential difference is investigated. That is, a battery in which both the first potential difference and the second potential difference are within the lower limit range is determined to have a short circuit between the case and the negative electrode. In addition, a method is also available in which a battery in which the first potential difference is smaller than the upper limit range and the second potential difference is smaller than the first potential difference, that is, a battery in which the potential difference decreases over time, is also determined to have a short circuit between the case and the negative electrode.

[0013] (2) A method for manufacturing an electricity storage device, in the method for inspecting an electricity storage device described in (1), the voltage adjustment step is a voltage adjustment step of charging or discharging the electricity storage device that has undergone initial charging and subsequent charging and discharging to adjust it to the first device voltage, and it is preferable that the first measurement step, the second measurement step, and the case-to-negative electrode short circuit determination step are performed on each of the electricity storage devices individually.

[0014] In this method for manufacturing an electricity storage device, when manufacturing each electricity storage device, in the voltage adjustment step of the above-mentioned method for inspecting an electricity storage device, an electricity storage device that has undergone initial charging and subsequent charging and discharging is charged or discharged to adjust to a first device voltage. Then, the above-mentioned first measurement step, second measurement step, and case-negative electrode short-circuit determination step are performed, so that an electricity storage device in which the presence or absence of a short circuit between the metal case and the negative electrode plate is appropriately determined can be manufactured.

[0015] (3) The method for manufacturing an energy storage device described in (2) may further include a self-discharge inspection process for inspecting a self-discharge state of the energy storage device after the voltage adjustment process, and the self-discharge inspection process may be a method for manufacturing an energy storage device in which the first measurement process and the second measurement process are performed in parallel within the self-discharge inspection process. (4) A method for manufacturing an electricity storage device in which an electrode body having a negative electrode plate disposed outside a positive electrode plate in a thickness direction is housed in a metal case while being insulated from the metal case by an insulating film, the method including: an initial charging step of initially charging the uncharged electricity storage device; a step of charging and discharging the electricity storage device; a voltage adjustment step of charging or discharging the electricity storage device that has undergone the initial charging step and the subsequent charging and discharging steps, and adjusting the voltage to a first device voltage; a self-discharge inspection step of inspecting a self-discharge state of the electricity storage device after the voltage adjustment step; and a negative electrode potential at a time when a first potential difference is measured after the voltage adjustment step, the negative electrode plate is exposed to the outside of the metal case and is conductive to the negative electrode plate. The method for manufacturing an electricity storage device includes a first measurement step of measuring a first potential difference, which is a case-negative electrode potential difference occurring between a negative electrode potential member and the metal case; a second measurement step of measuring a second potential difference, which is the case-negative electrode potential difference, at a second potential difference measurement time after a waiting period of 24 hours or more has elapsed since the first potential difference measurement time; and a case-negative electrode short-circuit determination step of determining the presence or absence of a short circuit between the metal case and the negative electrode plate from the magnitudes of the first potential difference and the second potential difference and from a change between the first potential difference and the second potential difference, and the self-discharge inspection step may be a method for manufacturing an electricity storage device in which the first measurement step and the second measurement step are performed within the self-discharge inspection step.

[0016] In this method for manufacturing an electricity storage device, the first and second measurement steps of the above-described method for inspecting an electricity storage device are also performed in a self-discharge inspection step that is performed after the voltage adjustment step. Therefore, the time required for manufacturing the electricity storage device can be shortened compared to a case in which the first and second measurement steps are performed separately from the self-discharge inspection step.

[0017] ( 5 )Furthermore(3) Or (4)the self-discharge inspection step includes a pre-left-standing voltage measurement step of measuring a pre-left-standing device voltage of the electricity storage device after the voltage adjustment step, a leaving step of leaving the electricity storage device after the pre-left-standing device voltage measured in an open terminal state for a leaving period, a post-left-standing voltage measurement step of measuring a post-left-standing device voltage of the electricity storage device after the leaving step, a self-discharge detection step of detecting a self-discharge state of the electricity storage device using the pre-left-standing device voltage and the post-left-standing device voltage of the electricity storage device, the first measurement step being performed after the voltage adjustment step and before the leaving step in parallel or before or after the pre-left-standing voltage measurement step, and the second measurement step being performed after the leaving step and before the self-discharge detection step in parallel or before or after the post-left-standing voltage measurement step, and the waiting period may overlap the leaving period.

[0018] In this method for manufacturing an electricity storage device, the self-discharge inspection step includes a first measurement step and a second measurement step in addition to a before-leaving voltage measurement step, a leaving step, a after-leaving voltage measurement step, and a self-discharge detection step. Moreover, the first measurement step is performed in parallel with or before or after the before-leaving voltage measurement step. Moreover, the second measurement step is performed in parallel with or before or after the after-leaving voltage measurement step. And the waiting period overlaps with the leaving period. Therefore, not only can the self-discharge state of the electricity storage device be inspected by the self-discharge inspection step, but also the first potential difference and the second potential difference obtained in parallel therewith can be used to manufacture an electricity storage device in which the presence or absence of a short circuit between the metal case and the negative electrode plate can be reliably determined.

[0019] Note that the standby period overlaps with the unused period means that the standby period and the unused period at least partially overlap on the time axis.

[0020] ( 6Alternatively, a method for manufacturing a device stack in which a plurality of the power storage devices are stacked while being insulated from each other and are restrained in the stacking direction by a restraining member, and restrained devices that are the power storage devices are connected to each other, the method comprising a restraining step of stacking a plurality of the power storage devices while being insulated from each other and restraining them in the stacking direction by the restraining member to form an unconnected device stack including a plurality of the restrained devices, and in the method for inspecting a power storage device described in (1), the voltage adjustment step is a voltage adjustment step of charging or discharging a plurality of the power storage devices that have been subjected to initial charging and subsequent charging and discharging before the restraining step, to adjust the voltage to the first device voltage, and the first measurement step, the second measurement step, and the case-negative electrode short circuit determination step may be performed on each of the restrained devices that constitute the unconnected device stack after the restraining step.

[0021] In this method of manufacturing a device stack, when manufacturing the device stack, in addition to carrying out a restraint process to form an unconnected device stack, each step of the above-mentioned inspection method for an electricity storage device is carried out for each of the constrained devices that form the unconnected device stack and are more likely to develop a short circuit between the metal case and the negative plate due to restraint than in the case of a constrained device, so that a device stack can be manufactured in which the presence or absence of a short circuit between the metal case and the negative plate is appropriately determined for each of the constrained devices.

[0022] Here, a "device stack" refers to a stacked constrained body in which constrained devices, that is, power storage devices, are stacked while being insulated from each other and are constrained in the stacking direction by a constraining member, and the constrained devices are connected to each other (so as to form a circuit such as a series circuit or a parallel circuit). The method of connecting the restrained devices (electricity storage devices) may be appropriately selected according to the shape and structure of the positive and negative terminals of the electricity storage devices. For example, the bus bar may be fastened to the terminal parts of the positive and negative terminals using nuts or the like, or the terminal parts and the bus bar may be laser-welded to connect them.

[0023] When stacking and restraining the multiple power storage devices after being adjusted to the first device voltage in the voltage adjustment step to form an unconnected device stack including multiple restrained devices, the power storage devices may be quickly restrained to form device restraint bodies after being adjusted to the first device voltage. Alternatively, each power storage device may be left unconstrained or under weaker constraint than the constraint in the device stack for an appropriate period of time, and any power storage device determined to be short-circuited in this state may be removed before forming the unconnected device stack.

[0024] ( 7 )moreover( 6 ) The method for manufacturing a device stack described in the above, further comprising an intra-stack self-discharge inspection process for inspecting a self-discharge state of each of the restrained devices that constitute the unconnected device stack, wherein the intra-stack self-discharge inspection process may be a method for manufacturing a device stack that performs the first measurement process and the second measurement process within the intra-stack self-discharge inspection process. (8) Alternatively, a method for manufacturing a device stack in which a plurality of power storage devices are housed in a metal case, with an electrode body having a negative electrode plate disposed outside a positive electrode plate in a thickness direction while being insulated from the metal case by an insulating film, are stacked while being insulated from each other, and are restrained in a stacking direction by a restraining member, and restrained devices that are the power storage devices are connected to each other, the method comprising the steps of: a voltage adjustment step of charging or discharging each of the plurality of power storage devices that have gone through an initial charging step of initially charging the uncharged power storage devices and a step of charging and discharging the power storage devices, and adjusting the voltage to a first device voltage; a restraining step of stacking the plurality of power storage devices while being insulated from each other and restraining them in the stacking direction by the restraining member to form an unconnected device stack including the plurality of restrained devices; an in-stack self-discharge inspection step of inspecting a self-discharge state of each of the restrained devices; and The method includes a first measurement process of measuring a first potential difference, which is a case-negative potential difference occurring between the metal case and a negative electrode potential member that is exposed to the outside of the metal case and is conductive to the negative electrode plate to be at negative electrode potential, at a first potential difference measurement time after the voltage adjustment process; a second measurement process of measuring a second potential difference, which is the case-negative electrode potential difference, for each of the constrained devices at a second potential difference measurement time after a waiting period of 24 hours or more has been allowed from the first potential difference measurement time; and a case-negative electrode short-circuit determination process of determining the presence or absence of a short circuit between the metal case and the negative electrode plate from the magnitudes of the first potential difference and the second potential difference and the change between the first potential difference and the second potential difference, and the method for manufacturing a device stack preferably includes performing the first measurement process and the second measurement process within the stack self-discharge inspection process.

[0025] In this device stack manufacturing method, the first and second measurement steps of the above-described power storage device inspection method are also performed in the stack self-discharge inspection step, which makes it possible to shorten the time required to manufacture the device stack compared to a case in which the first and second measurement steps are performed separately from the stack self-discharge inspection step.

[0026] ( 9 )moreover( 7 ) Or (8)the method for manufacturing a device stack described in the above, wherein the in-stack self-discharge inspection step includes a pre-constrained-leave voltage measurement step of measuring a pre-constrained-leave device voltage of the constrained device after the constraining step, a constrained-leave step of leaving each of the constrained devices, whose pre-constrained-leave device voltages have been measured, in an open terminal state for a constrained-leave period, a post-constrained-leave voltage measurement step of measuring a post-constrained-leave device voltage of the constrained device after the constrained-leave step, a constrained self-discharge detection step of detecting a self-discharge state of the constrained device using the pre-constrained-leave device voltage and the post-constrained-leave device voltage of the constrained device, the first measurement step being performed after the constraining step and before the constrained-leave step in parallel or before or after the pre-constrained-leave voltage measurement step, and the second measurement step being performed after the constrained-leave step and before the constrained self-discharge detection step in parallel or before or after the post-constrained-leave voltage measurement step, and wherein the waiting period overlaps with the constrained-leave period.

[0027] In this method for manufacturing a device stack, the self-discharge inspection process within the stack includes a pre-constrained storage voltage measuring process, a constrained storage process, a post-constrained storage voltage measuring process, and a constrained self-discharge detection process, as well as a first measurement process and a second measurement process. Moreover, the first measurement process is performed in parallel with or before or after the pre-constrained storage voltage measuring process. Moreover, the second measurement process is performed in parallel with or before or after the post-constrained storage voltage measuring process. And the waiting period overlaps with the constrained storage period. Therefore, the self-discharge state of each constrained device can be inspected by the self-discharge inspection process within the stack, and the first potential difference and the second potential difference obtained in parallel therewith can be used to manufacture a device stack in which the presence or absence of a short circuit between the metal case and the negative electrode plate is reliably determined for each constrained device.

[0028] Note that the "restricted waiting period overlaps with the restricted leaving period" means that the restricted waiting period and the restricted leaving period overlap at least partially on the time axis. [Brief description of the drawings]

[0029] [Figure 1]FIG. 2 is a cross-sectional view in the cell width direction of the cells according to the first and second embodiments. [Diagram 2] FIG. 2 is a cross-sectional view in the thickness direction of the battery according to the first and second embodiments. [Diagram 3] 4 is a graph illustrating a pattern of change in the potential difference between the case and the negative electrode plate in a battery or a constrained battery according to the first and second embodiments. [Figure 4] 4 is a flowchart showing a battery manufacturing process according to the first and second embodiments. [Diagram 5] FIG. 6 is an explanatory diagram of a battery stack according to a second embodiment. [Figure 6] FIG. 11 is an explanatory diagram of an unconnected battery stack according to a second embodiment. [Figure 7] 6 is a flowchart showing a manufacturing process of a battery stack according to the second embodiment. [Figure 8] 10 is a flowchart showing the contents of a restraint short-circuit inspection step in the manufacturing process of the battery stack according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] (Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. Figures 1 and 2 show vertical cross-sectional views of a battery (electricity storage device) 10 according to the first and second embodiments in a battery width direction BH and a battery thickness direction CH. The battery 10 is a rectangular sealed lithium ion secondary battery that can be mounted in vehicles such as hybrid cars, plug-in hybrid cars, and electric cars, drones, and various devices.

[0031] The battery 10 is composed of a case 11, an electrode assembly 30 housed inside the case 11, and a positive terminal 21 and a negative terminal 25 that are supported by the case 11 and connected to the electrode assembly 30 inside the case 11 and protrude outside the case 11 (upward in Figure 1).

[0032] Of these, the case 11 is a rectangular parallelepiped box made of metal (aluminum in this embodiment 1). The case 11 has a case body 12 in the shape of a rectangular cylinder with a bottom having an opening 12P at the upper AHU in the battery height direction AH, and a rectangular plate-like lid 15 that seals the opening 12P. The battery height direction AH, battery width direction BH, and battery thickness direction CH will be described as the directions shown in Figures 1 and 2.

[0033] A positive electrode terminal 21 made of aluminum penetrating the lid body 15 is fixed to the lid body 15 in a state insulated from the lid body 15 by a positive electrode insulating member 24, forming a positive electrode terminal portion 21T exposed to the outside, and connected to a positive electrode current collector portion 35 (described later) of the electrode body 30 by a connection portion 21C. A negative electrode terminal 25 made of copper penetrating the lid body 15 is fixed to the lid body 15 in a state insulated from the lid body 15 by a negative electrode insulating member 28, forming a negative electrode terminal portion 25T exposed to the outside, and connected to a negative electrode current collector portion 36 (described later) of the electrode body 30 by a connection portion 25C.

[0034] The case 11 contains an electrolyte 40 together with the electrode body 30, a part of which is impregnated in the electrode body 30 and a part of which is pooled at the bottom of the case 11. The electrode body 30 is covered with an insulating film 50 in the form of a square bag with a bottom that is open at the upper AHU in the battery height direction AH, and insulates the negative electrode plate 32 (described below) of the electrode body 30 from the case 11.

[0035] The electrode body 30 is generally a flat rectangular parallelepiped, and is a flat wound electrode body in which a strip-shaped positive electrode plate 31 and a strip-shaped negative electrode plate 32 are wound around an axis 30X together with two strip-shaped separators 33 made of a resin porous film interposed therebetween, and then flattened by crushing, as shown in Fig. 1 and Fig. 2. However, since the negative electrode plate 32 and the separator 33 are longer than the positive electrode plate 31, the negative electrode plate 32 is disposed on the outer side THO in the thickness direction TH of the positive electrode plate 31 wound together with the negative electrode plate 32 and the separator 33, that is, on the outer periphery side, and further the separator 33 is disposed on the outer periphery side of the positive electrode plate 31 and the negative electrode plate 32. For this reason, when a short circuit occurs between the electrode body 30 and the case 11, it is only necessary to consider a short circuit between the negative electrode plate 32 and the case 11.

[0036] 1, the electrode body 30 has a positive current collecting part 35 formed by exposing the positive current collecting foil 311 of the positive plate 31 while being spirally wound on one side BH1 (the right side in FIG. 1) in the battery width direction BH along the axis 30X, and a negative current collecting part 36 formed by exposing the negative current collecting foil 321 of the negative plate 32 while being spirally wound on the other side BH2 (the left side in FIG. 1). The central part of the electrode body 30 in the battery width direction BH, sandwiched between the positive current collecting part 35 and the negative current collecting part 36, is the main body part 34.

[0037] In this embodiment, the positive electrode current collecting parts 35 of the electrode body 30 are closely attached to each other in the battery thickness direction CH at the connection part 35C, and are laser welded to the connection part 21C of the positive electrode terminal 21, so that the positive electrode terminal 21 can electrically connect to circuit members outside the battery 10. The negative electrode current collecting parts 36 of the electrode body 30 are closely attached to each other in the battery thickness direction CH at the connection part 36C, and are laser welded to the connection part 25C of the negative electrode terminal 25, so that the negative electrode terminal 25 can electrically connect to circuit members outside the battery 10. As a result, the electrode body 30 is supported by the lid body 15 (case 11) via the positive electrode terminal 21 and the negative electrode terminal 25.

[0038] As described above, the positive electrode plate 31 and the negative electrode plate 32 of the electrode body 30 are insulated from the case 11 made of aluminum by the separator 33 and the insulating film 50. However, as shown in FIG. 2, for example, a foreign object FM such as sputters generated when the cover 15 is laser-welded to the opening 12P of the case body 12 may enter the case 11 and be sandwiched between the case 11 and the main body 34 of the electrode body 30. In such a case, the foreign object FM may penetrate the insulating film 50 and the separator 33 and contact the case 11, and may also contact the negative electrode plate 32 (located on the outer side THO in the thickness direction of the positive electrode plate than the positive electrode plate 31), causing a short circuit (micro-short circuit) between the two. As can be easily understood, when the battery 10 (case 11) is compressed in the battery thickness direction CH (left-right direction in FIG. 2), the case 11 and the negative electrode plate 32 of the electrode body 30 are likely to be short-circuited through the foreign object FM.

[0039] When the case 11 and the negative electrode plate 32 of the electrode body 30 are short-circuited through the foreign object FM, the case potential PC of the case 11, which is originally insulated from the negative electrode plate 32 and should have been at a floating potential relative to the negative electrode potential PN of the negative electrode plate 32, is affected by the negative electrode potential PN. In many cases, the case potential PC becomes equal to the negative electrode potential PN, and the potential difference EF (case-negative electrode potential difference) between the case potential PC and the negative electrode potential PN (based on the negative electrode potential PN) becomes 0 (EF=PC-PN=0). If the case 11 and the negative electrode plate 32 are short-circuited in this way, the above-mentioned problems will occur, and it is therefore necessary to remove such a defective battery 10N.

[0040] Therefore, the initial charging process S1, the high-temperature aging process S2, the capacity inspection process S3, and the voltage adjustment process S4 described later were performed on a large number of batteries 10, and the battery voltage VB was set to a first voltage VB1 (VB1=3.750V) (see FIG. 4). Furthermore, at appropriate timing, a digital multimeter described later was connected to the case 11 and the negative electrode terminal 25 to measure the potential difference EF between the case potential PC and the negative electrode potential PN, and the transition of the potential difference EF was investigated. However, as described above, the potential difference EF (potential difference between the case and the negative electrode) is essentially a floating potential, so the measured value of the potential difference EF includes variations. Furthermore, for each battery 10 after the transition of the potential difference EF was investigated, the battery 10 was disassembled to check whether or not the case 11 and the negative electrode plate 32 were short-circuited. From this, it was found that in the battery 10 after completing the voltage adjustment process S4, there are four patterns PT1 to PT4 based on the magnitude and change of the potential difference EF between the case potential PC and the negative electrode potential PN, and that there is a relationship between these patterns PT1 to PT4 and the presence or absence of a short circuit between the case and the negative electrode.

[0041] These relationships will be described with reference to the graph in FIG. 3. In the graph in FIG. 3, the horizontal axis represents the elapsed time KT from the adjustment completion time Tc (described later) at which the voltage adjustment is completed in the voltage adjustment step S4, and the vertical axis represents the potential difference EF (or the constrained potential difference EP described later). First, the first pattern PT1 is a pattern taken by many of the batteries 10 in which there is no short circuit between the case and the negative electrode, and as shown by the thick solid line, is a pattern in which the potential difference EF is a value within the upper limit range regardless of the elapsed time KT. In the battery 10 of this embodiment, the upper limit range is 2.1 to 2.9 V. The reason why the upper limit range of the potential difference EF is within the above-mentioned value range is not clear, but it is thought to be related to the fact that the immersion potential of the metal (aluminum) constituting the case 11 with respect to the electrolyte 40 is approximately 2.8 V,

[0042] The second pattern PT2 is a pattern adopted by batteries 10 that are not short-circuited between the case and the negative electrode, other than the batteries of the first pattern PT1, and is a pattern in which, as shown by the arrows surrounded by solid lines, the potential difference EF is below the lower limit of the upper limit range described above (2.0 V or less) at an early stage of the elapsed time KT, but the potential difference EF increases as the elapsed time KT passes. The potential difference EF of the battery 10 showing this second pattern PT2 becomes a value within the upper limit range described above (2.1 to 2.9 V in the present embodiment 1) after the elapse of a sufficient elapsed time KT.

[0043] The third pattern PT3 is a pattern that is adopted by many of the batteries 10 in which the case and the negative electrode are short-circuited, and is a pattern in which the potential difference EF is within the lower limit range regardless of the elapsed time KT, as indicated by the thick dashed line. In the battery 10 of this embodiment, the lower limit range is 0.4 V or less (0 to 0.4 V). This third pattern PT3 is a pattern in which the potential difference EF is approximately 0 V. The reason why the potential difference EF is approximately 0 V is believed to be that the case potential PC is made approximately equal to the negative electrode potential PN due to the short circuit between the case and the negative electrode.

[0044] The fourth pattern PT4 is a pattern that is adopted by batteries 10 with a short circuit between the case and the negative electrode, other than the batteries in the third pattern, and is a pattern in which the potential difference EF is smaller than the upper limit range at an early stage of the elapsed time KT, and the potential difference EF decreases as the elapsed time KT passes, as shown by the arrow surrounded by a dashed line. Note that in the battery 10 of this embodiment, the potential difference EF at an early stage of the elapsed time KT is less than 2.1 V, and the potential difference EF decreases as the elapsed time KT passes. The reason why the potential difference EF decreases as the elapsed time KT passes is believed to be that the case potential PC gradually approaches the negative electrode potential PN due to the short circuit between the case and the negative electrode.

[0045] Therefore, by utilizing this knowledge, the presence or absence of a short circuit between the case and the negative electrode is detected as follows in the manufacture of the battery 10. Note that, in the manufacture of the battery 10, the self-discharge state of the battery 10, specifically, the presence or absence of a short circuit between the positive electrode plate 31 and the negative electrode plate 32, is usually detected. Therefore, in the first embodiment, the battery 10 is manufactured as follows.

[0046] The manufacture of the battery 10 will be described with reference to FIG. 4. First, an uncharged battery 10 is manufactured. The manufacture of a sealed battery 10 having a rectangular parallelepiped case 11 is well known, so a description thereof will be omitted. In the initial charging step S1 (see FIG. 4), the uncharged battery 10 is initially charged by CCCV charging at room temperature to an SOC of 60 to 100%. In this embodiment, for example, CCCV charging is performed in an environment of 25° C. with a constant current of 7C, a cutoff voltage of 3.75V (corresponding to SOC 60%), and a cutoff current of 0.3C. Next, in the high-temperature aging step S2, each initially charged battery 10 is left in an open state in an environment of 50 to 80° C. for 10 to 200 hours to perform high-temperature aging (for example, in this embodiment, in an environment of 70° C. for 18 hours). After the battery 10 is cooled, in a capacity inspection process S3, the battery 10 is charged to SOC 100%, and then discharged to SOC 0% to measure the capacity of the battery 10 (discharge capacity in the case of the above-mentioned method).

[0047] Next, in a voltage adjustment step S4, the battery voltage VB of each battery 10 is charged to a first voltage VB1 within the range of SOC 30 to 100% at room temperature. In this embodiment, for example, in an environment of 25°C, CCCV charging is performed with a constant current of 7C, a cutoff voltage of 3.75V (corresponding to SOC 60%), and a cutoff current of 0.3C, which are the same as in the initial charging step S1. That is, the battery voltage VB of each battery 10 is once adjusted to the same first voltage VB1 (VB1=3.75V in this embodiment). Note that the elapsed time KT is measured from the adjustment completion time Tc at which the battery voltage VB is charged to the first voltage VB1 by the voltage adjustment step S4.

[0048] Next, in an individual short circuit inspection process S5, a short circuit inspection is performed on each battery 10 after the voltage adjustment process S4. Specifically, first, in a pre-discharge voltage measurement process S51, a pre-discharge second voltage VB2a, which is the battery voltage VB of the battery 10, is measured.

[0049] In the subsequent first potential difference measuring step S52, a digital multimeter having an internal resistance of 1 MΩ or more is connected to the case 11 and the negative electrode terminal portion 25T to measure the first potential difference EF1, which is the potential difference between the case and the negative electrode. The time of this measurement is defined as a first time TF1.

[0050] In the first embodiment, the first potential difference measuring step S52 is performed following the pre-discharge voltage measuring step S51. However, as shown by the broken line in FIG. 4, the first potential difference measuring step S52 may be performed prior to the pre-discharge voltage measuring step S51. two As indicated by the dashed line, the first potential difference measuring step S52 may be performed in parallel with the pre-discharge voltage measuring step S51.

[0051] Next, in an individual storage step S53, the battery 10 with the positive electrode terminal 21 and the negative electrode terminal 25 in an open state is left unconstrained or slightly constrained in an environment of 25°C for an individual storage period IH (in this embodiment 1, IH≧5.0 days (IH≧120 hours)). Thereafter, in a post-discharge voltage measuring step S54, a post-discharge second voltage VB2b, which is the battery voltage VB of the battery 10 after being left unused, is measured.

[0052] In the subsequent second potential difference measuring step S55, a second potential difference EF2, which is the potential difference between the case and the negative electrode, is measured in the same manner as the above-described first potential difference EF1. If this measurement time is a second time TF2, the individual waiting period IWT from the first time TF1 to the second time TF2 at which the second potential difference EF2 is measured overlaps with the individual leaving period IH. Therefore, in the present embodiment 1, like the individual leaving period IH, the individual waiting period IWT is also IWT≧5.0 days (IWT≧120 hours).

[0053] In the first embodiment, the second potential difference measuring step S55 is performed following the voltage measuring step S54 after leaving the device unattended. However, as shown by the broken line in FIG. 4, the second potential difference measuring step S55 may be performed prior to the voltage measuring step S54 after leaving the device unattended. two As indicated by the dashed line, the second potential difference measuring step S55 may be performed in parallel with the post-standing voltage measuring step S54.

[0054] Then, in the individual first judgment step S56, the second voltage before leaving VB2a and the second voltage after leaving VB2b are used to judge the presence or absence of a short circuit between the positive plate 31 and the negative plate 32 of the electrode assembly 30. Specifically, the second voltage before leaving VB2a and the second voltage after leaving VB2b are used, and the difference between them is divided by the individual leaving period IH to obtain a decrease rate ((VB2a-VB2b) / IH), which is compared with a separately obtained threshold decrease rate to judge the presence or absence of a short circuit between the positive plate and the negative electrode. Then, if the individual first judgment step S56 is No, that is, if the decrease rate is smaller than the threshold decrease rate, that is, if the decrease in the battery voltage VB is gradual, it is determined that no short circuit has occurred in the battery 10, and the process proceeds to the individual second judgment step S57. Conversely, if the answer is Yes in the first individual judgment step S56, i.e., if the rate of decrease is greater than the threshold rate of decrease, i.e., if the decrease in the battery voltage VB is rapid, it is determined that there is a short circuit between the positive and negative electrodes of the tested battery 10, and the process proceeds to the battery discharge step S6.

[0055] In the subsequent individual second judgment step S57, the magnitudes of the first potential difference EF1 and the second potential difference EF2 and the change therebetween are The change in potential difference isFrom ΔF12 (=EF2-EF1), the presence or absence of a short circuit between the case 11 and the negative electrode plate 32 is determined. 。 Specifically, using the knowledge of the above-mentioned four patterns PT1 to PT4 (see FIG. 3), it is judged whether or not the case-negative electrode of the battery 10 under test is short-circuited. More specifically, in the individual second judgment step S57, the battery 10 corresponding to the above-mentioned third and fourth patterns PT3 and PT4 is selected. That is, the battery 10 in which both the first potential difference EF1 and the second potential difference EF2 are within the lower limit range (0.4 V or less in the present embodiment 1) (EF1<0.4 V, EF2<0.4 V) or the first potential difference EF1 is smaller than the upper limit range (2.1 to 2.9 V in the present embodiment 1) and the second potential difference EF2 is smaller than the first potential difference EF1 (EF1>EF2) is judged to be short-circuited between the case and the negative electrode (Yes), and is shifted to the battery discharge step S6. Conversely, in other cases, it is judged that the battery 10 under test is not short-circuited (No). Thus, the individual short circuit inspection process S5 is completed and the battery 10 is completed.

[0056] In the present embodiment 1, the individual second judgment step S57 is performed following the individual first judgment step S56. However, as shown by the dashed line in Fig. 4, the individual second judgment step S57 may be performed prior to the individual first judgment step S56, contrary to the above.

[0057] In the battery removal step S6, defective batteries 10N that are determined to have a short circuit between the positive and negative electrodes or between the case and the negative electrode are removed from the manufacturing process.

[0058] In the method for inspecting and manufacturing the battery 10 of the first embodiment, the influence of variations in the potential difference EF between the negative electrode potential PN and the case potential PC, which is a floating potential relative to the negative electrode potential PN, can be suppressed for each battery 10, and the presence or absence of a short circuit between the case 11 and the negative electrode plate 32 can be appropriately determined. Then, the battery 10 in which the presence or absence of a short circuit between the case and the negative electrode has been appropriately determined can be manufactured. Specifically, among the batteries 10 tested, defective batteries 10N in which a short circuit occurs between the case and the negative electrode are removed from the manufacturing process, and thus batteries 10 that are not short-circuited can be appropriately manufactured.

[0059] Moreover, in the above-described manufacturing method for the battery 10, the first potential difference measuring step S52 and the second potential difference measuring step S55, which are methods for inspecting the battery 10, are also performed in the individual short-circuit inspection step S5 performed after the voltage adjustment step S4. Therefore, the time required for manufacturing the battery 10 can be shortened compared to the case where the first potential difference measuring step and the second potential difference measuring step are performed separately from the individual short-circuit inspection step S5.

[0060] In the manufacturing method of the battery 10 of the first embodiment, the individual short-circuit inspection step S5 includes a first potential difference measurement step S52 and a second potential difference measurement step S55 in addition to the pre-discharge voltage measurement step S51, the individual discharge step S53, the post-discharge voltage measurement step S54, and the individual first judgment step S56. The first potential difference measurement step S52 is performed in parallel or before or after the pre-discharge voltage measurement step S51. The second potential difference measurement step S55 is performed in parallel or before or after the post-discharge voltage measurement step S54. The individual waiting period IWT overlaps with the individual discharge period IH. Therefore, the individual short-circuit inspection step S5 can inspect the self-discharge state of the battery 10, specifically, the presence or absence of a short circuit between the positive and negative electrodes, and the first potential difference EF1 and the second potential difference EF2 obtained in parallel can be used to manufacture the battery 10 in which the presence or absence of a short circuit between the case 11 and the negative electrode plate 32 is reliably judged.

[0061] (Embodiment 2) A battery stack 1 according to the second embodiment will be described below with reference to the drawings. FIG. 5 shows a battery stack (device stack) 1 according to the second embodiment. The battery stack 1 is formed by stacking a plurality of rectangular parallelepiped batteries (electricity storage devices) 10 (see FIG. 1 and FIG. 2) of the first embodiment (for example, 28 batteries in the second embodiment) and constraining them to a fixed size with a constraining member 5. In this battery stack 1, a plurality of batteries 10 are stacked in a stacking direction SH that coincides with the battery thickness direction CH (left-right direction in FIG. 2) via spacers 2, and are pressed in the stacking direction SH by the constraining member 5 to constrain them. Specifically, a plurality of constrained batteries 10P (batteries 10) and spacers 2 are stacked alternately, sandwiched between a pair of constraining plates 51, and each constrained battery 10P is pressed in the stacking direction SH and constrained using a constraining bolt 52 extending in the stacking direction SH and spanning between the constraining plates 51, a nut 53 screwed thereto, and a washer 54. The positive electrode terminal 21 and negative electrode terminal 25 of each of the constrained batteries 10P are connected to each other via a bus bar 3. In the battery stack 1 of the second embodiment, as shown in Fig. 5, each of the constrained batteries 10P is arranged in an alternately inverted manner so that the positive electrode terminals 21 and negative electrode terminals 25 are arranged alternately in a row in the stacking direction SH, and each of the constrained batteries 10P is connected in series by connecting the bus bars 3. The battery stack 1 is mounted and used in vehicles such as hybrid cars, plug-in hybrid cars, and electric cars.

[0062] In the above-mentioned embodiment 1, the relationship between the potential difference EF (case-negative electrode potential difference) between the negative electrode potential PN and the case potential PC of each individual battery 10 that has been subjected to the initial charging process S1 to the voltage adjustment process S4 and the presence or absence of a short circuit between the case and the negative electrode is explained by dividing it into four patterns PT1 to PT4. Also, by utilizing this, in the individual second judgment process S57, it was judged whether or not a short circuit occurred between the case and the negative electrode of the tested battery 10. Furthermore, it has been found that the relationship between the constrained potential difference EP (case-to-negative electrode potential difference) between the negative electrode potential PN and the case potential PC in the multiple constrained batteries 10P that constitute the battery stack 1 of this embodiment 2, and the presence or absence of a short circuit between the case and negative electrode, can also be explained by dividing it into four patterns PT1 to PT4 (see Figure 3). Therefore, in the manufacturing method of the present embodiment 2 described below, whether or not a short circuit exists between the case and the negative electrode of each tested battery 10 is determined in the same manner as in embodiment 1. In addition, whether or not a short circuit exists between the case and the negative electrode of each of the multiple constrained batteries 10P in the battery stack 1 is also determined in the same manner.

[0063] The manufacture of the battery stack 1 will be described below with reference to FIGS. 6 to 8. An uncharged battery 10 is manufactured by a known method (see FIG. 7). Then, similarly to the first embodiment, the initial charging step S1, the high-temperature aging step S2, and the capacity inspection step S3 are performed, and in the voltage adjustment step S4, each battery 10 is charged to adjust the battery voltage VB to a first voltage VB1, specifically, VB1=3.75V. Furthermore, similarly to the first embodiment, the individual short-circuit inspection step S5 (see FIG. 4) is performed, and in the individual first judgment step S56, the presence or absence of a short circuit between the positive and negative electrodes is judged, and in the individual second judgment step S57, the presence or absence of a short circuit between the case and the negative electrode is judged. A defective battery 10N judged to be short-circuited in these judgment steps S56 and S57 is discharged from the manufacturing process in the battery discharge step S6. On the other hand, a battery 10 judged not to be short-circuited in the judgment steps S56 and S57 is obtained.

[0064] In the subsequent restraining step S27 (see FIG. 7), an unconnected battery stack 1M (see FIG. 6) is formed by a known method using each battery 10 that was determined not to be short-circuited in the above-mentioned individual short-circuit inspection step S5 (individual first judgment step S56 and individual second judgment step S57), as well as the spacer 2 and the restraining member 5. In this unconnected battery stack 1M, each battery 10 is pressed and restrained in the stacking direction SH (left-right direction in the figure) to become a restrained battery 10P. Therefore, in the electrode body 30 of the restrained battery 10P, the positive electrode plate 31 and the negative electrode plate 32 are compressed in the thickness direction that coincides with the stacking direction SH via the separator 33. However, unlike the battery stack 1 (see FIG. 5), the bus bar 3 is not used, and the positive electrode terminal 21 and the negative electrode terminal 25 of each restrained battery 10P are in an open circuit state. In this unconnected battery stack 1M state, each restrained battery 10P under restraint is inspected for the presence or absence of a short circuit between the positive and negative electrodes and between the case and the negative electrode. After this restraining step S27, a plurality of (for example, 28 in this embodiment) restrained batteries 10P included in a single unconnected battery stack 1M (or battery stack 1) are treated as one group.

[0065] In the second embodiment, following the restraint step S27, in a restraint short-circuit inspection step S28 (see FIG. 8), in the unconnected battery stack 1M state, two types of short-circuit inspections are performed on each restrained battery 10P under restraint (compression) to detect whether or not a short circuit has occurred.

[0066] First, in the pre-discharge voltage measurement step S281 (see FIG. 8) of the restraint short circuit inspection step S28, the pre-discharge third voltage VB3a, which is the battery voltage VB of each restrained battery 10P constituting the unconnected battery stack 1M, is measured.

[0067] In the subsequent first potential difference measuring step S282, a first constraint potential difference EP1, which is the potential difference between the case and the negative electrode, is measured in the same manner as the first potential difference EF1. The time at which this measurement is performed is defined as a first constraint time TP1. In the second embodiment, the first potential difference measuring step S282 is performed following the voltage measuring step S281 before leaving the device unattended. However, as shown by the broken line in FIG. 8, the first potential difference measuring step S282 may be performed prior to the voltage measuring step S281 before leaving the device unattended. two As indicated by the dashed line, the first potential difference measuring step S282 may be performed in parallel with the pre-discharge voltage measuring step S281.

[0068] Next, in a constrained leaving step S283, each constrained battery 10P of the unconnected battery stack 1M is left in an open circuit state for a constrained leaving period PH (in this second embodiment, PH≧5.0 days (≧120 hours)) in an environment of 25° C. Thereafter, in a post-leaving voltage measurement step S284, a post-leaving third voltage VB3b, which is the battery voltage VB of each of the constrained batteries 10P after being left alone, is measured.

[0069] In the subsequent second potential difference measurement step S285, a second potential difference EP2, which is the potential difference between the case and the negative electrode, is measured in the same manner as the first potential difference EP1. If this measurement time is the second potential difference TP2, the locked standby period PWT from the first potential difference TP1 to the second potential difference TP2 at which the second potential difference EP2 is measured overlaps with the locked standby period PH. Therefore, in the second embodiment, the locked standby period PWT is PWT≧5.0 days (PWT≧120 hours) like the locked standby period PH.

[0070] In the second embodiment, the second potential difference measuring step S285 was performed following the voltage measuring step S284 after leaving the device unattended. However, as shown by the dashed line in Fig. 8, the second potential difference measuring step S285 may be performed prior to the voltage measuring step S284 after leaving the device unattended. Also, as shown by the dashed line in Fig. 8, the second potential difference measuring step S285 may be performed in parallel with the voltage measuring step S284 after leaving the device unattended.

[0071] Then, in the first constraint determination step S286, the pre-discarded third voltage VB3a and the post-discarded third voltage VB3b are used to determine whether or not there is a short circuit between the positive and negative electrodes of the electrode assembly 30 of the constrained battery 10P. Specifically, the decline rate ((VB3a-VB3b) / PH) obtained by dividing the difference between the pre-discarded third voltage VB3a and the post-discarded third voltage VB3b by the constrained discard period PH is compared with a threshold decline rate to determine whether or not there is a short circuit between the positive plate and the negative electrode.

[0072] Then, if the first constraint judgment step S286 is No, i.e., if the rate of decrease is smaller than the threshold rate of decrease, i.e., if the decrease in the battery voltage VB is gradual, it is determined that there is no short circuit between the positive and negative electrodes of the tested constrained battery 10P. On the other hand, if the first constraint judgment step S286 is Yes, i.e., if the rate of decrease is larger than the threshold rate of decrease, it is determined that the tested constrained battery 10P has a short circuit between the positive and negative electrodes. Note that in the first constraint judgment step S286, it is determined whether or not there is a short circuit between the positive and negative electrodes for each of the constrained batteries 10P included in the battery stack 1. However, since each of the constrained batteries 10P is constrained as an unconnected battery stack 1M, regardless of the judgment result, all of the constrained batteries 10P proceed to the second constraint judgment step S287.

[0073] In the second constraint determination step S287, the magnitudes of the first constraint potential difference EP1 and the second constraint potential difference EP2 and the change therebetween are determined. The change in the potential difference isFrom ΔP12 (=EP2-EP1), the presence or absence of a short circuit between the case 11 and the negative electrode plate 32 of the tested constrained battery 10P is judged. Specifically, using the above-mentioned knowledge (see FIG. 3), it is judged whether or not the case-negative electrode of the tested constrained battery 10P is short-circuited. More specifically, the batteries 10 corresponding to the above-mentioned third and fourth patterns PT3 and PT4 are selected. That is, the constrained battery 10P in which both the constrained first potential difference EP1 and the constrained second potential difference EP2 are within the lower limit range (0.4V or less even in the second embodiment) (EP1<0.4V, EP2<0.4V), or the constrained battery 10P in which the constrained first potential difference EP1 is smaller than the upper limit range (2.1 to 2.9V even in the second embodiment) and the constrained second potential difference EP2 is smaller than the constrained first potential difference EP1 (EP1>EP2) is judged to have a short circuit between the case and the negative electrode (Yes), and the process proceeds to the removal step S2A. Conversely, in any other case, it is determined that no short circuit has occurred in the restrained battery 10P under test (No).

[0074] Therefore, when it is determined that at least one of the constrained batteries 10P constituting the unconnected battery stack 1M has a short circuit between the case and the negative electrode (Yes), the unconnected battery stack 1M to which the constrained battery 10P belongs is transitioned to the removal step S2A. Additionally, an unconnected battery stack 1M for which it is determined in the first constraint determination step S286 that at least one constrained battery 10P has a short circuit between the positive and negative electrodes (Yes in S286) is also transitioned to the removal step S2A via the second constraint determination step S287. In short, an unconnected battery stack 1M including a constrained battery 10P (defective battery 10N) with a short circuit between the positive and negative electrodes (Yes in S286) or a short circuit between the case and the negative electrode (Yes in S287) is transitioned to the removal step S2A. On the other hand, if none of the restrained batteries 10P included in the unconnected battery stack 1M has a short circuit between the positive and negative electrodes (No in S286) and has a short circuit between the case and the negative electrode (Yes in S287), the process proceeds to the connection step S29 for each unconnected battery stack 1M.

[0075] In the second embodiment, the second restraint determination step S287 is performed following the first restraint determination step S286. However, as shown by the dashed line in Fig. 8, the second restraint determination step S287 may be performed prior to the first restraint determination step S286, contrary to the above.

[0076] In the connection process S29, the bus bar 3 is connected to the positive terminals 21 and negative terminals 25 of the group of restrained batteries 10P that make up the unconnected battery stack 1M (see FIG. 6), and the restrained batteries 10P are connected to each other to complete the battery stack 1 (see FIG. 5).

[0077] Thus, in the manufacturing method of this embodiment 2, when manufacturing the battery stack 1, in addition to performing the restraint process S27 to configure the unconnected battery stack 1M, the first potential difference measurement process S282 and the second potential difference measurement process S285 are performed for each constrained battery 10P that constitutes the unconnected battery stack 1M and is more likely to develop a short circuit between the case 11 and the negative electrode plate 32 due to restraint compared to the case where it is constrained, so that a battery stack 1 can be manufactured in which the presence or absence of a short circuit between the case 11 and the negative electrode plate 32 is appropriately determined for each constrained battery 10P. Furthermore, in the manufacturing method of the second embodiment, the first potential difference measuring step S282 and the second potential difference measuring step S285 are also performed in the constraint short-circuit inspection step S28. Therefore, the time required for manufacturing the battery stack 1 can be shortened compared to the case where the first potential difference measuring step S282 and the second potential difference measuring step S285 are performed separately from the constraint short-circuit inspection step S28.

[0078] In the manufacturing method of the battery stack 1 of the second embodiment, the restraint short circuit inspection process S28 includes a first potential difference measurement process S282 and a second potential difference measurement process S285 in addition to a before-leaving voltage measurement process S281, a restraint leaving process S283, a after-leaving voltage measurement process S284, and a restraint first determination process S286. Moreover, the first potential difference measurement process S282 is performed in parallel with or before or after the before-leaving voltage measurement process S281. Moreover, the second potential difference measurement process S285 is performed in parallel with or before or after the after-leaving voltage measurement process S284. And the restraint waiting period PWT overlaps with the restraint leaving period PH. Therefore, the constraint short circuit inspection process S28 makes it possible to inspect the self-discharge state, such as a short circuit between the positive and negative electrodes of each constrained battery 10P, and in parallel, the constraint first potential difference EP1 and the constraint second potential difference EP2 obtained can be used to manufacture a battery stack 1 in which the presence or absence of a short circuit between the case 11 and the negative electrode plate 32 for each constrained battery 10P can be reliably determined.

[0079] In the removal process S2A, the defective battery 10N is removed from the unconnected battery stack 1M that includes at least one defective battery 10N. Specifically, the fastening between the restraining bolts 52 and nuts 53 of the restraining members 5 is loosened, the defective battery 10N is removed from the unconnected battery stack 1M, and the stack is discharged from the manufacturing process.

[0080] In the subsequent re-restraint step S2B, the unconnected battery stack 1M from which the defective battery 10N has been removed is replenished with replacement batteries 10H to make up for the shortage, and the group of constrained batteries 10P is restrained again using the restraining member 5 to reconstruct the unconnected battery stack 1M (see FIG. 6). The replacement battery 10H is a battery 10 that is included in another unconnected battery stack 1M and has already been determined in the restraint short-circuit inspection step S28 to have no short circuit between the positive and negative electrodes and between the case and the negative electrode, and that has been prepared in advance for replacement. Thereafter, the restraint short-circuit inspection step S28 is performed again for the reconstructed unconnected battery stack 1M, and replacement batteries 10H are replenished until no defective batteries 10N are generated, and the reconstruction of the unconnected battery stack 1M is repeated. In the second restraint determination step S287, if the reconstructed unconnected battery stack 1M does not contain any defective batteries 10N, the reconstructed unconnected battery stack 1M is shifted to the connection step S29, as described above.

[0081] Then, in a connection step S29, the bus bar 3 is connected to the positive terminals 21 and negative terminals 25 of the group of constrained batteries 10P constituting the reconstituted unconnected battery stack 1M, and the constrained batteries 10P are connected to each other to complete the battery stack 1 (see FIG. 5 ). Thus, even if the unconnected battery stack 1M contains a battery 10 that has developed a short circuit, the unconnected battery stack 1M can be easily reconstituted to manufacture the battery stack 1.

[0082] If there is a low possibility of a defective battery 10N occurring in the unconnected battery stack 1M reconstituted by re-restraining in the re-restraint step S2B, the bus bar 3 may be connected to the positive terminals 21 and negative terminals 25 of the group of restrained batteries 10P constituting the reconstituted unconnected battery stack 1M in the second connection step S2C, as shown by the dashed lines in Fig. 7, to connect the restrained batteries 10P to each other and complete the battery stack 1 (see Fig. 7). In this way, the unconnected battery stack 1M can be reconstituted and the battery stack 1 can be manufactured even more easily.

[0083] The present invention has been described above with reference to the first and second embodiments. However, the present invention is not limited to the first and second embodiments, and can be modified as appropriate without departing from the spirit of the present invention. For example, in the battery stack 1 of the second embodiment, the restrained batteries 10P are electrically connected in series with each other via the bus bar 3. However, a battery stack in which the restrained batteries 10P are electrically connected in parallel may also be used.

[0084] In addition, in the second embodiment, in manufacturing the battery stack 1, the individual short-circuit inspection process S5 includes a first potential difference measurement process S52, a second potential difference measurement process S55, and an individual second judgment process S57 to inspect the presence or absence of a short circuit between the case and the negative electrode of each battery 10. Additionally, the constrained short-circuit inspection process S28 includes a first potential difference measurement process S282, a second potential difference measurement process S285, and a constrained second judgment process S287 to inspect the presence or absence of a short circuit between the case and the negative electrode of each constrained battery 10P in the unconnected battery stack 1M.

[0085] However, in manufacturing the battery stack 1, the inspection for case-to-negative short circuits for each battery 10 in the individual short circuit inspection process S5 may be omitted, and only the presence or absence of a case-to-negative short circuit for each constrained battery 10P in the unconnected battery stack 1M in the constrained short circuit inspection process S28 may be inspected. This is because the constraint of the batteries 10 in the stacking direction SH (battery thickness direction CH) makes case-to-negative short circuits more likely to occur in constrained batteries 10P than in unconstrained batteries 10. [Explanation of symbols]

[0086] 1 Battery stack (device stack) 1M Unconnected Battery Stack (Unconnected Device Stack) SH Stacking direction 5 Restraining member 10 Batteries (secondary batteries, power storage devices) 10N defective battery 10H refill battery 10P Restrained battery (Restrained device) 11 Case (metal case) 21 Positive terminal 25 Negative terminal (negative potential component) 30 Electrode body 31 Positive electrode plate TH Positive electrode thickness direction THO (Positive plate thickness direction) Outer side 32 Negative plate 50 Insulating film VB Battery voltage VB1 First voltage (first device voltage) VB2a Second voltage before storage (device voltage before storage) VB2b Second voltage after storage (device voltage after storage) VB3a Third voltage before storage (device voltage before storage) VB3a Third voltage after storage (device voltage after restrained storage) PP positive electrode potential PN negative electrode potential PC case potential EF potential difference (potential difference between case and negative electrode) EF1 1st potential difference (potential difference between case and negative electrode) EF2 Second potential difference (potential difference between case and negative electrode) ΔF12 Potential difference change (change between the first potential difference and the second potential difference) EP Confinement potential difference (potential difference between case and negative electrode) EP1 Confinement first potential difference (first potential difference, potential difference between case and negative electrode) EP2 Second potential difference (second potential difference, potential difference between case and negative electrode) ΔP12 Constrained potential difference change (change between the first potential difference and the second potential difference) PT1~PT4 patterns When Tc adjustment is completed KT Elapsed Time TF1 1st time (1st potential difference measurement time) TF2 2nd time (2nd potential difference measurement time) TP1 First restraint time (first potential difference measurement time) TP2 Second restraint time (second potential difference measurement time) S1 Initial charging process S4 Voltage adjustment process S5 Individual short circuit inspection process (self-discharge inspection process) S51 Voltage measurement process before storage S52,S282 1st potential difference measurement process (1st measurement process) S53 Individual leaving process (leaving process) IH Individual Standing Period (Standing Period) IWT Individual Waiting Period (Waiting Period) S54 Voltage measurement process after storage S55,S285 2nd potential difference measurement process (2nd measurement process) S56 Individual first judgment process (self-discharge detection process) S57 Individual second judgment process (case-negative electrode short circuit judgment process) S6 Battery discharge process (discharge process) S27 Restraint process S28 Restricted short circuit inspection process (stack self-discharge inspection process) S281 Voltage measurement process before leaving the device unattended (voltage measurement process before leaving the device unattended) S283 Restraint leaving process S284 Voltage measurement process after leaving (voltage measurement process after restrained leaving) PH Detention period (abandonment period) PWT Waiting Period (Waiting Period) S286 First constraint judgment process (constraint self-discharge detection process) S287 Second restraint judgment process (case-negative electrode short circuit judgment process)

Claims

1. A method for manufacturing an electricity storage device, comprising: a metal case containing an electrode assembly in which a negative electrode plate is disposed on the outer side of a positive electrode plate in a thickness direction thereof, the electrode assembly being insulated from the metal case by an insulating film, the method comprising the steps of: an initial charging step of initially charging the uncharged electricity storage device; Charging and discharging the electricity storage device; a voltage adjustment step of charging or discharging the power storage device that has been through the initial charging step and the subsequent charging / discharging step, and adjusting the voltage to a first device voltage; a self-discharge inspection step of inspecting a self-discharge state of the power storage device after the voltage adjustment step; a first measuring step of measuring a first potential difference, which is a case-negative potential difference occurring between the metal case and a negative electrode potential member that is exposed to the outside of the metal case and is conductive to the negative electrode plate to be at a negative electrode potential, at a first potential difference measurement time after the voltage adjustment step; a second measuring step of measuring a second potential difference, which is the case-to-negative electrode potential difference, at a second potential difference measuring time after a waiting period of 24 hours or more has elapsed since the first potential difference measuring time; a case-negative electrode short circuit determination step of determining whether or not there is a short circuit between the metal case and the negative electrode plate based on the magnitudes of the first potential difference and the second potential difference and a change between the first potential difference and the second potential difference, The self-discharge inspection step includes: The first measurement step and the second measurement step are performed in the self-discharge inspection step. A method for manufacturing an electricity storage device.

2. A method for manufacturing the electricity storage device according to claim 1, comprising: The self-discharge inspection step includes: a pre-discarded voltage measuring step of measuring a pre-discarded device voltage of the power storage device after the voltage adjusting step; a step of leaving the power storage device, the device voltage before being left unattended measured, for a period of time in an open terminal state; a post-standing voltage measurement step of measuring a post-standing device voltage of the power storage device after the post-standing step; a self-discharge detection step of detecting a self-discharge state of the power storage device by using the pre-discharge device voltage and the post-discharge device voltage of the power storage device; The first measurement step is performed after the voltage adjustment step and before the leaving step, in parallel with or before or after the pre-leaving voltage measurement step; The second measurement step is performed after the leaving step and before the self-discharge detection step, in parallel with or before or after the after-leaving voltage measurement step, The waiting period overlaps with the idle period. A method for manufacturing an electricity storage device.

3. A method for manufacturing a device stack in which a plurality of power storage devices are housed in a metal case, with electrode bodies each having a negative electrode plate disposed outside a positive electrode plate in the thickness direction, and insulated from the metal case by an insulating film, the device stacked while being insulated from each other and restrained in the stacking direction by a restraining member, and the restrained devices which are the power storage devices are connected to each other, comprising: a voltage adjustment step of charging or discharging each of the plurality of power storage devices that have undergone an initial charging step of initially charging the uncharged power storage devices and a step of charging and discharging the power storage devices, and adjusting the voltage to a first device voltage; a restraining step of stacking a plurality of the power storage devices while insulating them from one another and restraining them in the stacking direction with the restraining member to form an unconnected device stack including a plurality of the restrained devices; a self-discharge inspection step for inspecting a self-discharge state of each of the restrained devices; a first measurement step of measuring, for each of the restrained devices, a first potential difference which is a case-negative potential difference occurring between the metal case and a negative potential member which is exposed outside the metal case and is conductive to the negative plate and has a negative potential, at a first potential difference measurement time after the voltage adjustment step; a second measurement step of measuring a second potential difference, which is a potential difference between the case and the negative electrode, for each of the restrained devices at a second potential difference measurement time after a waiting period of 24 hours or more from the first potential difference measurement time; a case-negative electrode short circuit determination step for determining, for each of the restrained devices, the presence or absence of a short circuit between the metal case and the negative electrode plate from the magnitudes of the first potential difference and the second potential difference and a change between the first potential difference and the second potential difference; The stack self-discharge inspection step includes: The first measurement step and the second measurement step are performed in the stack self-discharge inspection step. A method for fabricating a device stack.

4. A method for manufacturing a device stack according to claim 3, comprising the steps of: The stack self-discharge inspection step includes: a pre-restraint voltage measurement step of measuring a pre-restraint voltage of the restrained device after the restraint step; a constrained storage step of leaving each of the constrained devices, the pre-constrained storage device voltage of which has been measured, in an open terminal state for a constrained storage period; a post-constraint voltage measuring step of measuring a post-constraint device voltage of the constrained device after the constrained / left-standing step; a restraint self-discharge detection step of detecting a self-discharge state of the restrained device by using the pre-restraint and post-restraint device voltage of the restrained device; The first measurement step is performed after the restraint step and before the restraint / standby step, in parallel with or before or after the pre-restraint / standby voltage measurement step; The second measurement step is performed after the restrained storage step and before the restrained self-discharge detection step, in parallel with or before or after the restrained storage voltage measurement step, The waiting period overlaps with the restrained leaving period. A method for fabricating a device stack.

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