JP7278312B2 - SELF-DISCHARGE INSPECTION METHOD FOR ELECTRICITY STORAGE DEVICE AND METHOD FOR MANUFACTURING ELECTRICITY STORAGE DEVICE - Google Patents

Description

The present invention relates to an electricity storage device self-discharge inspection method for determining a self-discharge state of an electricity storage device, and an electricity storage device manufacturing method including the self-discharge inspection method.

In the production of electricity storage devices such as lithium ion secondary batteries, metal foreign matter such as iron and copper may be mixed inside the electrode body, etc., and the mixed metal foreign matter may cause an internal short circuit in the electricity storage device. Self-discharge may occur. Therefore, in the manufacturing process of an electricity storage device, it may be desired to determine the presence or absence of an internal short circuit in the electricity storage device, the magnitude of the self-discharge state, and the appropriateness of the self-discharge state.

For example, the following methods are known for inspecting internal short circuits in electric storage devices. That is, the pre-detection device voltage of a pre-charged electricity storage device is measured, an output voltage equal to the pre-detection device voltage is continuously applied to the electricity storage device from the external power source, and the power supply current flowing from the external power source to the electricity storage device is measured. detect. Then, based on the detected power supply current, an internal short circuit of the power storage device is determined. Incidentally, as a related prior art, there is Patent Document 1 (see the claims of Patent Document 1, etc.).

JP 2019-16558 A

However, even with the internal short-circuit inspection method described above, it takes time for the magnitude of the power supply current to stabilize, so there has been a demand to further shorten the inspection time.
The present invention has been made in view of the current situation, and provides a self-discharge inspection method for an electricity storage device that can shorten the self-discharge inspection time of an electricity storage device, and a method for manufacturing an electricity storage device including this self-discharge inspection method. intended to provide

(1) One aspect of the present invention for solving the above problems is a self-discharge inspection method for an electricity storage device for inspecting self-discharge of an electricity storage device, wherein the electricity storage device has an open circuit voltage at a first device temperature of When the device temperature of the electricity storage device, which is the first device voltage, is changed from the first device temperature to the second device temperature, the open circuit voltage of the electricity storage device changes from the first device voltage to the lower second device temperature. 2 device voltage, and a first device voltage for measuring the first device voltage of the electricity storage device when the device temperature of the precharged electricity storage device is the first device temperature. a measuring step, a continuous voltage applying step of continuously applying a power supply voltage equal to the first device voltage from an external power source to the electric storage device, and a device temperature of the electric storage device in parallel with the continuous voltage applying step, A device temperature changing step of changing the device temperature from the first device temperature to the second device temperature, a current detecting step of detecting a power current flowing from the external power source to the power storage device, and based on the detected power current, and a determination step of determining a self-discharge state of the electricity storage device.

In the self-discharge inspection method for an electric storage device described above, the first device voltage measurement step, the continuous voltage application step, the current detection step, and the judgment step for judging the self-discharge state of the electric storage device are performed. This makes it possible to determine the self-discharge state of the power storage device using the power supply current that flows from the external power source to the power storage device.

Moreover, when the device temperature of the electricity storage device, which is the object of this inspection method and whose open circuit voltage is the first device voltage under the first device temperature, is changed from the first device temperature to the second device temperature, , the open circuit voltage of the electric storage device is stepped down from the first device voltage to a lower second device voltage. This inspection method has a device temperature changing step of changing the device temperature of the electric storage device from the first device temperature toward the second device temperature in parallel with the continuous voltage application step. Therefore, in the continuous voltage application step, in addition to the device voltage drop due to the progress of self-discharge, the device temperature is changed from the first device temperature to the second device temperature, which may cause the battery voltage to drop. It is possible to hasten the drop in the device voltage in this continuous voltage application step, thereby increasing the power supply current more quickly and stabilizing the power supply current more quickly. Thus, it is possible to determine the self-discharge state of the electricity storage device in the determination step earlier.

The self-discharge inspection method of the electricity storage device described above can be performed in the manufacturing process of the electricity storage device, as will be described later. It can also be carried out for used electricity storage devices.
Examples of the "electricity storage device" include secondary batteries such as lithium ion secondary batteries, electric double layer capacitors, and capacitors such as lithium ion capacitors.
The open-circuit voltage is the voltage that occurs between the terminals of the electricity storage device when the current flowing from the outside to the electricity storage device is zero, and it is not necessary to disconnect (open) the terminals of the electricity storage device from the circuit for measurement.

The first device temperature is the device temperature at which the power storage device is held prior to the device temperature changing step. The first device temperature may be appropriately selected from within the usable temperature range of the electric storage device, and for example, normal temperature (15 to 25°C) such as 20°C may be employed.

Further, the second device temperature is a temperature that can be determined when the first device temperature is determined, and the device temperature of the electricity storage device whose open circuit voltage under the first device temperature is the first device voltage is calculated from the first device temperature. It refers to a device temperature selected from a range in which the open circuit voltage of the storage device changes to a device voltage (second device voltage) lower than the first device voltage when changed. Therefore, the second device temperature may be lower or higher than the first device temperature depending on the type of power storage device, electrode material, and the like.

The device temperature changing step is a step of changing the device temperature of the electricity storage device. The power storage device is left in a temperature-controlled room having an environmental temperature, and the device temperature of the power storage device is set to a first device temperature equal to the first environmental temperature. Thereafter, in the device temperature changing step, the room temperature of the thermostatic chamber is changed to the second environmental temperature while the electric storage device is connected to the external power supply, and the device temperature of the electric storage device is set to the second device temperature equal to the second environmental temperature. and a method of changing up to this second device temperature. In addition, a first room having an indoor temperature as a first environmental temperature and a second room having an indoor temperature as a second environmental temperature are prepared, and the power storage device is left in the first room in advance. Let the temperature be a first device temperature equal to the first ambient temperature. Thereafter, in the device temperature changing step, the electricity storage device is transferred from the first chamber into the second chamber while being connected to the external power supply, and the device temperature of the electricity storage device is changed toward the second device temperature equal to the second environmental temperature. A method and a method of changing up to this second device temperature are also available.

In the determining step, the self-discharge state is determined based on the power supply current. Specifically, there is a method of determining the self-discharge state by using a power supply current that changes with time or a stable power supply current that flows when the power supply current is stabilized. As a method for determining the self-discharge state from the change in the power supply current over time, for example, first, from the change in the power supply current over time, the estimated stable power supply current obtained when the power storage device reaches the second device temperature and the power supply current stabilizes. Estimate a value. In addition, a method of judging whether the self-discharge state is good or bad (OK/NG) from the magnitude of the estimated stable power supply current value and the threshold current value, and A/B according to the magnitude of the estimated stable power supply current A determination method such as a method of classifying into a plurality of ranks, such as /C, etc., can be used. Also, there is a determination method that directly determines whether the self-discharge state of the power storage device is good or bad or ranks it based on the amount of change in the power supply current per unit time.

On the other hand, as a method of determining the self-discharge state using the stable power supply current that flows when the power supply current stabilizes, for example, the power storage device reaches the second device temperature and the power supply current stabilizes when the power supply current stabilizes. get the value. In addition, a method for judging whether the self-discharge state is good or bad (OK/NG) from the magnitude of the stable power supply current value and the threshold current value, and A/B/C according to the magnitude of the stable power supply current .

Note that the detected change over time in the power supply current refers to a temporal change in the power supply current that occurs during the period from the start of the continuous voltage application step until the value of the power supply current flowing through the power storage device stabilizes. It can be indicated by the amount of increase in the power supply current that occurs during a specified period, the slope of the increase, and the like. In addition, when a sufficient time has passed in the continuous voltage application step, a stable power supply current corresponding to the magnitude of the self-discharge current flowing in the power storage device flows. This stable power supply current is defined as a stable power supply current.

As for the timing of starting the device temperature changing process, which is performed in parallel after the continuous voltage applying process is started, it is preferable to start the device temperature changing process immediately after the continuous voltage applying process is started. However, the device temperature change step may be started after a predetermined time such as 30 seconds, 1 minute, or 5 minutes has elapsed since the start of the continuous voltage application step.

(2) In the self-discharge inspection method for an electricity storage device of (1), prior to the first device voltage measuring step, the electricity storage device is left in a holding chamber at a first environmental temperature, and the electricity storage device The self-discharge inspection method for an electricity storage device may include a step of leaving the device temperature to the first device temperature equal to the first environmental temperature.

In this inspection method, the device temperature of the electric storage device can be reliably set to the first device temperature equal to the first environmental temperature by the standing step, and the electric storage device having the first device temperature in the subsequent first device voltage measurement step. Since the device can be provided, the first device voltage can be properly measured without being affected by temperature fluctuations.

(3) The self-discharge inspection method for an electricity storage device according to (1) or (2), wherein the device temperature changing step is preferably started after the continuous voltage application step is started. .

In this testing method, the device temperature change step is started after the continuous voltage application step is started. A difference between the output voltage of the power supply and the device voltage can be prevented.

It is preferable to start the device temperature change step immediately after the start of the continuous voltage application step, and it is desirable to start the device temperature change step immediately after the start of the continuous voltage application step. This is because the device voltage change of the electricity storage device due to the device temperature change can be caused more quickly, and the time until the power supply current increases and saturation can be shortened.

(4) Still another solution includes an initial charging step of initially charging an assembled uncharged electricity storage device to a predetermined charge state to obtain a precharged electricity storage device, and the above-mentioned (1) to (3). and an inspection step of inspecting the self-discharge state of the initially charged energy storage device by the self-discharge inspection method for an energy storage device according to any one of 1.).

In the above-described method for manufacturing an electricity storage device, after the initial charging step, the device temperature changing step is performed in parallel with the continuous voltage application step, and the inspection step is performed by the above-described self-discharge inspection method in which the voltage measurement step and the judgment step are performed. Therefore, the existence and degree of short circuit in the initial stage of the electricity storage device can be appropriately inspected in a short time to manufacture the electricity storage device.

It is more preferable to provide a high-temperature aging step in which the electric storage device is left in an open state at a high temperature and a subsequent cooling step between the initial charging step and the inspection step, since the voltage of the electric storage device is easily stabilized.

1 is a longitudinal sectional view of a battery according to an embodiment and modifications; FIG. FIG. 4 is a flow chart of a battery manufacturing process including a battery self-discharge test process according to the embodiment and a modification, and an explanatory diagram illustrating movement of the battery. FIG. 10 is a circuit diagram of a state in which an external power supply is connected to the battery, relating to the battery self-discharge inspection method according to the embodiment and the modification. Schematic time changes of environment temperature TK, battery temperature TB, output voltage VS, and power supply current IB with respect to voltage application time t and temperature change time tm for good and defective batteries according to the embodiment and the modification. is a graphical representation.

(embodiment)
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a vertical cross-sectional view of a lithium ion secondary battery (hereinafter also simply referred to as "battery") 1 according to this embodiment. The battery 1 comprises a rectangular parallelepiped box-shaped battery case 10, a flat wound electrode body 20 and an electrolytic solution 15 accommodated therein, and a positive electrode terminal member 30 and a negative electrode terminal member supported by the battery case 10. 40 and the like. In this embodiment, a lithium-transition metal composite oxide, specifically lithium-nickel-cobalt-manganese oxide, is used as the positive electrode active material, and a carbon material, specifically graphite, is used as the negative electrode active material.

Next, a method for manufacturing the battery 1 including a self-discharge inspection method for determining the insulation inside the battery 1 will be described (see FIG. 2). First, in "assembling step S1", an uncharged battery 1 (see FIG. 1) is assembled.

Next, in the "initial charging step S2", the assembled battery 1 is initially charged. Specifically, using a restraining jig (not shown), 10 batteries 1 arranged in a row in the battery thickness direction (the direction perpendicular to the paper surface in FIG. 1) are restrained while being compressed in the battery thickness direction. do. In this restrained state, each battery 1 undergoes from the initial charging step S2 to the continuation determination step S9 and the battery temperature change step S10, which will be described later. In each step, the battery temperature TB of each battery 1 is detected by a temperature detection device STS having a temperature sensor ST brought into contact with a predetermined position of the battery case 10 (see FIG. 3).

After constraining each battery 1 with a constraining jig, a charging/discharging device (not shown) is connected to both terminal members 30 and 40 of each battery 1 at an initial charging temperature FT (FT=20° C.), and a constant current is applied. Each battery 1 is initially charged by constant voltage (CCCV) charging until the battery voltage VB of each battery 1 reaches a predetermined value (VB=4.0 V in this embodiment).

Next, in the "high temperature aging step S3", each battery 1 that has been initially charged is aged at an aging temperature ET (ET = 63°C) with both terminal members 30 and 40 open for an aging period EK (EK = 20 hours). ) for high temperature aging. When this high-temperature aging is performed, the battery voltage VB of each battery 1 is lowered to a battery voltage corresponding to about 80% SOC.

Next, in the “cooling step S4”, the battery 1 is placed in the cooling chamber CR under the cooling temperature CT (CT=20° C.) for 20 minutes, and forcedly cooled by a fan, thereby reducing the battery temperature TB to approximately 20° C. ( TB≈20° C.) (see FIG. 2).

Further, in the "leaving step S5", the battery 1 is transferred into the first chamber KR1 where the environmental temperature TK is set to the first environmental temperature TK1 (TK1=20.0° C.), and is left for a standing period HP (for example, HP=30 minutes). After being left alone, the battery temperature TB of the battery 1 is set to the first battery temperature TB1 (TB1=20.0° C.) which is the same as the first environmental temperature TK1 (see FIG. 2).

In the following "first battery voltage measurement step" S6, the first battery voltage VB1, which is the open circuit voltage (OCV) of the battery 1 at the first battery temperature TB1 (TB1=20.0° C.), is measured. Specifically, as shown in FIG. 3, when the external power supply EP is connected to the battery 1 and the power supply current IB flowing from the external power supply EP to the battery 1 is set to IB=0, the first battery voltage VB1 of the battery 1 is to measure. More specifically, a pair of probes P1 and P2 of the external power supply EP are brought into contact with the positive terminal member 30 and the negative terminal member 40 of the battery 1, respectively, and the first battery voltage VB1 of the battery 1 is measured (see FIG. 3). ).

The connection state between the probe P1 and the positive terminal member 30 and the contact state between the probe P2 and the negative terminal member 40 are maintained (without reconnecting the pair of probes P1 and P2 to the terminal members 30 and 40). From the first battery voltage measurement step S6 to the continuation determination step S9, which will be described later, are performed. The contact states of the probes P1 and P2 with the terminal members 30 and 40 change each time contact occurs, and contact resistances R1 and R1, respectively generated between the probe P1 and the positive electrode terminal member 30 and between the probe P2 and the negative electrode terminal member 40, are generated. This is to avoid fluctuations in the magnitude of R2.

In FIG. 3, the wiring resistance Rw indicates the wiring resistance distributed within the external power supply EP and from the external power supply EP to the probes P1 and P2. Further, the contact resistance R1 indicates the contact resistance generated between one probe P1 of the external power supply EP and the positive electrode terminal member 30 of the battery 1, and the contact resistance R2 indicates the contact resistance between the other probe P2 of the external power supply EP and the battery 1. The contact resistance generated with the negative electrode terminal member 40 is shown.

Also shown in FIG. 3 is an equivalent circuit of battery 1 including battery component 1B, series resistance Rs and short circuit resistance Rp. Of these, the battery component 1B is the capacity component formed by the battery 1 . The series resistance Rs is a battery resistance that appears to exist in series with the battery component 1B between both terminal members 30 and 40 of the battery 1 . On the other hand, the short-circuit resistance Rp is a resistance that indicates the magnitude of self-discharge caused by an internal short-circuit of the battery 1 . A self-discharge current ID indicated by a dashed arrow indicates a self-discharge current flowing from the battery component 1B to the short-circuit resistor Rp.

The external power supply EP is a precision DC power supply that can variably and accurately control the output voltage VS generated by its own DC power supply EPE, as well as measure the power supply current IB that flows out from the DC power supply EPE with high accuracy. be. The external power supply EP has a voltmeter EPV capable of measuring the battery voltage VB and an ammeter EPI capable of precisely measuring the power supply current IB flowing from the external power supply EP to the battery 1 . The environmental temperature TK around the battery 1 is detected using a temperature detection device KTS having a temperature sensor KT consisting of a thermistor (see FIG. 3).

As described above, in the present embodiment, in the first battery voltage measurement step S6, under the first environmental temperature TK1, the first battery temperature TB1 is equal to the first environmental temperature TK1 (TB1=TK1=20. After connecting the external power supply EP to the battery 1 at 0° C.), measure the first battery voltage VB1 (open circuit voltage) of the battery 1 with the voltmeter EPV included in the external power supply EP under the condition of the power supply current IB=0. do. In the present embodiment, a value in the vicinity of approximately 3.9 V, which corresponds to an SOC of approximately 80%, is normally measured as the first battery voltage VB1.

In the "continuous voltage application step" S7, under the first environmental temperature TK1, the battery voltage VB is in the state of the first battery voltage VB1 (VB=VB1), and the DC power supply EPE of the external power supply EP is applied to the above-described first battery voltage measurement. An output voltage VS (VS=VB1) equal to the first battery voltage VB1 measured in step S6 is generated and applied to the battery 1 (voltage application time t=0), after which an output equal to the first battery voltage VB1 Application of the voltage VS (VS=VB1) is continued. In other words, the output voltage VS generated by the external power supply EP is maintained at a magnitude equal to the initially obtained first battery voltage VB1.

In the following "current detection step" S8, the power supply current IB is detected. That is, the power supply current value IB(n) (n is an integer greater than or equal to 0 indicating the order of acquisition) flowing from the external power supply EP to the battery 1 is acquired every predetermined time (every 10 seconds in this embodiment). At the beginning of the application of the output voltage VS (voltage application time t=0), VS=VB1, so the power supply current IB does not flow (IB(0)=0). However, as will be described later, the power supply current IB (power supply current value IB(n)) gradually increases and then stabilizes.

In the "continuation determination step" S9, it is determined whether or not to repeat the voltage continuation application step S7 and the current detection step S8 again. In the present embodiment, when the battery 1 is a non-defective product (a battery with a large short-circuit resistance Rp and a small self-discharge current ID), the power supply current IB obtained after starting to apply the output voltage VS to the battery 1 (specifically, Specifically, it is determined whether or not a standby duration time TTs sufficient for the power supply current value IB(n)) to reach a stable stable power supply current IBs has elapsed. Here, if No, that is, if the voltage application time t has not passed the standby continuation time TTs (voltage application time t<TTs), the process returns to the continuous voltage application step S7 to stop applying the output voltage VS to the battery 1. Continuing (S7), the power supply current IB is detected (S8). On the other hand, if Yes, that is, if the voltage application time t has passed the standby continuation time TTs (voltage application time t≧TTs), the process proceeds to the “determining step” S11.

Here, the power supply current IB when the output voltage VS (VS=VB1) equal to the first battery voltage VB1 is continuously applied to the battery 1 from the external power supply EP while the environmental temperature TK is maintained at the first environmental temperature TK1. is examined with reference to FIG.
As a premise, as shown in the middle part of FIG. 4, the output voltage VS applied to the battery 1 from the external power supply EP is the first battery voltage after the start of voltage application (t=0), regardless of the elapse of the voltage application time t. It is assumed that the voltage is maintained equal to the first battery voltage VB1 measured in the measurement step S6.
4, the environmental temperature TK is maintained at the first environmental temperature TK1, and the battery temperature TB of the battery 1 is the same as the first environmental temperature TK1, the first battery temperature TB1 (TB1=TK1 = 20.0°C).

After the output voltage VS is applied to the battery 1 from the external power supply EP, as the voltage application time t elapses, the battery voltage VB becomes the first battery voltage at the start of the continuous voltage application step S7 (voltage application time t=0). Gradually decreases from VB1. This is because the charge stored in the battery component 1B is gradually discharged by the self-discharge current ID through the short-circuit resistance Rp, so that the battery component voltage VBB generated in the battery component 1B gradually decreases. Note that the battery component voltage VBB matches the battery voltage VB, which is the open-circuit voltage of the battery 1, when the power supply current IB is zero (IB=0). Therefore, at the start of application of the output voltage VS to the battery 1 (voltage application time t=0), the battery component voltage VBB is equal to the first battery voltage VB1 (VBB=VB1=VS:t=0).

By the way, an external power supply EP is connected to the battery 1, and an output voltage VS (VS=VB1) equal to the first battery voltage VB1 is continuously applied. Therefore, when the battery component voltage VBB generated in the battery component 1B becomes smaller, a potential difference (VB1-VBB) is generated across the series resistor Rs as can be easily understood from FIG. It flows to the battery 1 along the route indicated by the dashed-dotted arrow (IB>0, VB1=VBB+Rs·IB).
As indicated by the thin solid line or thin broken line in the lower part of FIG. 4, the magnitude of this power supply current IB gradually increases as the battery component voltage VBB of the battery component 1B decreases. However, as can be understood from FIG. 3, the power supply current IB increases as the battery component voltage VBB decreases, and the power supply current IB flowing through the short-circuit resistor Rp causes a back electromotive force Vp (Vp= When Rp·IB) becomes equal to the battery component voltage VBB generated in the battery component 1B, the self-discharge current ID no longer flows from the battery component 1B. As a result, the drop in the battery component voltage VBB in the battery component 1B also stops, and the power supply current IB becomes a stable stable power supply current IBs equal to the self-discharge current ID.

Therefore, if the battery 1 to be tested is a non-defective product (battery with a large short-circuit resistance Rp and a small self-discharge current ID), the battery component voltage VBB of the battery component 1B will slowly drop, so that the power supply current IB also increases slowly (see the thin solid line at the bottom of FIG. 4). In addition, the stable power supply current value IBsg of this non-defective product is small.

On the other hand, when the battery 1 to be tested is a defective product (a battery having a smaller short-circuit resistance Rp and a relatively larger self-discharge current ID than a good battery), As a result, the battery component voltage VBB of the battery component 1B decreases relatively quickly, so the power supply current IB also increases relatively quickly (see the thin dashed line in the lower part of FIG. 4). The stable power supply current value IBsn of the defective product is also larger than the stable power supply current value IBsg of the non-defective product.

In this way, the quality of the tested battery 1 is determined by the value of the stable power supply current IBs, or by the speed of increase of the power supply current IB (change over time of the power supply current IB) and the state of change. (See Patent Document 1). For example, in the lower graph of FIG. 4, the threshold current value IBth is determined to be an intermediate value between the stable power supply current value IBsg for good products and the stable power supply current value IBsn for defective products, as shown in FIG. . As a result, the values IBsg and IBsn of the power supply current IBs obtained during stable operation are compared with the threshold current value IBth to determine whether or not the battery 1 is non-defective. In addition, since the speed of change over time of the power supply current IB (slope of change in the power supply current IB until the power supply current IB reaches the stable power supply current values IBsg and IBsn) differs between good products and defective products, the power supply current IB It is also possible to determine whether the battery 1 is good or bad based on changes in the power supply current IB over time.

However, it takes time from when the application of the first battery voltage VB1 to the battery 1 is started until the quality of the battery 1 can be determined. For example, when determining by obtaining the value of the stable power supply current IBs, it is necessary to wait until the value of the stable power supply current IBs is obtained. For example, in the above example indicated by the thin solid line and the broken line in the lower graph of FIG. It can be seen that it is necessary to set the standby duration TTs in step S9 to a value of TTs=55 minutes or longer, as indicated by the dashed arrow in the lower graph of FIG.

Determining whether the battery 1 is good or bad based on the change in the power supply current IB over time can be performed in a shorter time than when the value of the stable power supply current IBs is obtained as described above. However, even in this case, it may be difficult to make an appropriate judgment when the increase in the power supply current IB has not progressed sufficiently. It is necessary to wait, for example, about 30 minutes or more after starting the application of the one-battery voltage VB1 (set the waiting duration TTs in the continuation determination step S9 to a value of TTs=30 minutes or more).

Therefore, in the present embodiment, as shown in FIG. 3, the battery is A "battery temperature changing step" S10 is performed to change the battery temperature TB of No. 1 from the first battery temperature TB1 toward the second battery temperature TB2. Specifically, the first battery temperature TB1 (specifically, TB1 = 20.0°C) is changed to a second battery temperature TB2 (TB2 = 20.2°C) that is 0.2°C higher. . More specifically, as indicated by the thick dashed line in the upper graph of FIG. The battery 1 in the first chamber KR1 at the temperature TK1 (TK1=20.0° C.) is moved to the second chamber KR2 at the second ambient temperature TK2 (TK2=20.2° C.) (see FIG. 2). Thus, the environmental temperature TK around the battery 1 is changed from the first environmental temperature TK1 to the second environmental temperature TK2 in a step function manner with the temperature change time tm=0 as a boundary. As a result, as indicated by the thick solid line in the upper graph of FIG. 4, before the temperature change time tm=0, the first battery temperature TB1 (TK1=TB1=20.0° C.) is equal to the first environmental temperature TK1. The battery temperature TB of the battery 1 is changed toward a second battery temperature TB2 (TK2=TB2=20.2° C.) equal to the second environmental temperature TK2.

The reason for this is that the battery 1 of the present embodiment, whose open-circuit voltage under the first battery temperature TB1 is the first battery voltage, changes the battery temperature TB from the first battery temperature TB1 to the second battery temperature TB2. , the open circuit voltage of the battery 1 drops from the first battery voltage VB1 to the lower second battery voltage VB2. In this embodiment, since the battery temperature changing step S10 is started after the voltage continuous application step S7 is started, the open circuit voltage of the battery 1 changes to the first battery voltage VB1 due to the change in the battery temperature TB accompanying the conversion of the environmental temperature TK. , thereby preventing a difference between the output voltage VS of the external power supply EP and the first battery voltage VB1 at the start of the continuous voltage application step S7.

In the embodiment, the battery temperature changing step S10 is started immediately after the continuous voltage application step S7 is started, that is, the output voltage VS of the external power supply EP is started to be applied to the battery 1 (voltage application time t=0). The battery temperature TB is started to change from the first battery temperature TB1 to the second battery temperature TB2 (temperature change time tm=0). Therefore, the battery temperature TB can be quickly reached and stabilized at the second battery temperature TB2, and the battery voltage VB can be quickly raised to reach the second battery voltage VB2 and be stabilized. However, the device temperature change step is performed after a predetermined time such as 30 seconds (t=30 seconds) or 5 minutes (t=5 minutes) from the start of the continuous voltage application step S10 (voltage application time t=0). may be started.

Further, in this embodiment, the battery temperature TB of the battery 1 at the first battery temperature TB1 (TB1=20.0° C.) is raised toward the second battery temperature TB2 (TB2=20.2° C.). However, depending on the battery temperature range (range of battery temperature TB, range of battery voltage (SOC)), and the type of battery such as each material used in the battery, it is possible to lower the temperature to a second battery temperature TB2 that is lower than the first battery temperature TB1. , the first battery voltage VB1 may be stepped down to the second battery voltage VB2. As can be easily understood, in this case, in the "battery temperature changing step" S10, the battery temperature TB of the battery 1 is lowered from the first battery temperature TB1 to a lower second battery temperature TB2.

In the present embodiment, by utilizing the fact that the battery 1 has the temperature characteristic described above, in parallel with the continuous voltage application step S7, the battery temperature TB of the battery 1 is is changed (heated) from the first battery temperature TB1 toward the second battery temperature TB2. In this embodiment, as indicated by the thick solid line in the upper graph of FIG. After being moved to the second chamber with the second environmental temperature TK2, the second battery temperature TB2 (TK2=TB2=20.2° C.) is reached and stabilized within approximately 15 minutes (temperature change time tm≦15 minutes).

Then, in the continuous voltage application step S7, in the test battery 1, in addition to the decrease in the battery voltage VB due to the progress of self-discharge, the battery temperature TB is changed from the first battery temperature TB1 toward the second battery temperature TB2. A decrease in the battery voltage VB due to this can also be caused. Therefore, it is possible to hasten the drop in the battery voltage VB in the continuous voltage application step S7, increase the power supply current IB more quickly, and bring the power supply current IB to the stable power supply current IBs more quickly. Thus, the determination of the self-discharge state of the battery 1 in the determination step S11 can be made earlier.

Specifically, compared to the case where the battery temperature change step S10 is not provided in parallel, the standby duration TTs for determining whether or not the continuation determination step S9 has elapsed can be shortened. For example, when the battery temperature change step S10 is not provided in parallel (see the thin solid line and the broken line in the lower graph of FIG. 4), the standby duration TTs for obtaining the stable power supply current values IBsg and IBsn is set to TTs = 55 minutes or longer. On the other hand, in the present embodiment in which the battery temperature changing step S10 is provided in parallel, as indicated by the thick solid line and the broken line in the lower graph of FIG. , IBsn can be obtained, the standby duration TTs can be set to, for example, TTs=18 minutes, as indicated by the solid-line arrow, so that the judgment step S11 can be started earlier and the judgment can be made earlier. can be done.

In the “determining step” S11, based on the obtained power supply current IB, specifically, after the start of the continuous voltage application step S7 (voltage application time t=0), the current obtained until the standby duration time TTs elapses. The self-discharge state of the battery 1 is determined using the columns of the power supply current values IB(0), IB(1), . . . , IB(n).

Specifically, in this embodiment, among a series of power supply current values IB(0), IB(1), . , seven power supply current values IB(n−6) to IB(n) obtained at the end of the standby duration TTs (last 60 seconds in this embodiment) are averaged to obtain the average final power supply current Calculate the value IBE (IBE=(IB(n-6)+...+IB(n))/7). The average final power supply current value IBE indicates the magnitude of the stable power supply current IBs obtained at the end of the standby duration time TTs. This is compared with the threshold current value IBth, and the battery 1 whose average final power supply current value IBE is smaller than the threshold current value IBth (IBE<IBth) is determined to be non-defective. Thus, a battery 1 that has been charged and tested for self-discharge can be produced.

On the other hand, the battery 1 whose average final power source current value IBE is equal to or greater than the threshold current value IBth (IBE≧IRth) is determined to be defective. Batteries 1 determined to be defective are excluded and discarded. Alternatively, it is disassembled and reused.

In the above-described embodiment, in the determination step S11, a plurality of power supply current values IB(n) obtained at the final stage are averaged to calculate the average final power supply current value IBE corresponding to the value of the stable power supply current IBs. Then, this was compared with the threshold current value IBth to determine whether the battery 1 was good or bad.
However, at each point in time when the power supply current value IB(n) is obtained in the current detection step S8, a moving average of a plurality of (for example, seven) power supply current values IB(n−6) to IB(n) obtained most recently The self-discharge state of the battery 1 may be determined in the determination step S11 by sequentially calculating the value MIB(n) and using the finally obtained moving average value MIB(n). That is, in the determination step S11, the quality of the battery 1 may be determined by comparing the finally obtained moving average value MIB(n) corresponding to the stable power supply current IBs with the threshold current value IBth.

Further, in the above embodiment, the first chamber KR1 and the second chamber KR2 are provided, and the battery temperature TB is changed by moving the battery 1 from the first chamber KR1 to the second chamber KR2. However, without using the second chamber, the battery temperature TB is set to the first battery temperature TB1 equal to the first environmental temperature TK1, and the environmental temperature TK of the first chamber KR1 is raised to the second environmental temperature TK2, The battery temperature TB can also be changed from the first battery temperature TB1 toward the second battery temperature TB2.

(deformed form)
In the above-described embodiment, in the continuation determination step S9, the stable power supply current value IBs (IBsg, IBsn ) until the standby duration TTs (TTs=18 minutes in the embodiment) elapses, and in the determination step S11, the average of a plurality of power supply current values IB(n) obtained at the end of the standby duration TTs An example in which the final power supply current value IBE is calculated and used to determine the self-discharge state of the battery 1 is shown.

On the other hand, in the present modification, in the present modification 1, the internal short circuit of the battery 1 is determined based on the change over time of the power supply current IB flowing from the external power supply EP to the battery 1 . Specifically, in the flow of manufacturing the battery 1 shown in FIG. 2, in order to make the determination in the determination step S11 earlier than in the embodiment, the standby duration time TTt in the continuation determination step S9 is changed to the stable power supply current IBs. can be shortened to ⅓ (TTt=6 minutes in this modification) of the time (waiting duration TTs in the embodiment) for which is obtained.

On top of that, in this modification, in the determination step S11, a series of power sources acquired at predetermined time intervals (every 10 seconds in this modification) within the standby duration time TTt (6 minutes in this modification) Among the current values IB(0), IB(1), . . . , IB(n), a plurality (19 ) power supply current values IB(n) and the like are used to determine the average rate of change HA, that is, the average amount of change HA per unit time (in this modification, the average amount of change HA per minute: HA=(IB(n) )-IB(n-18))/3). The average change rate HA indicates the slope of increase in the power supply current IB obtained in the latter half of the standby duration TTt.

This average rate of change HA is compared with a threshold rate of change HAth, and batteries 1 with an average rate of change HA smaller than the threshold rate of change HAth (HA<HAth) are determined to be non-defective. Even in this manner, a battery 1 that has been charged and tested for self-discharge can be manufactured. Moreover, since the standby duration TTt in the continuation determination step S9 is set shorter than the standby duration TTs in the embodiment, the time up to the determination step S11 can be shortened, and the self-discharge of the battery 1 can be made earlier. inspection can be carried out. In addition, it is possible to manufacture the battery 1 in which the inspection of the self-discharge state has been completed earlier.

A battery 1 with an average rate of change HA greater than or equal to a threshold rate of change HAth (HA≧HAth) is determined to be defective. Batteries 1 that are determined to be defective are excluded and discarded, or disassembled and reused, as in the embodiment.

In the above, the present invention has been described in accordance with the embodiments and modifications, but the present invention is not limited to the above-described embodiments and the like, and can be appropriately modified and applied without departing from the scope of the invention. Needless to say.

For example, in the embodiment and the modification, in the manufacturing process of the battery 1, the inspection process of the self-discharge inspection of the battery 1 shown in the first battery voltage measurement process S6 to the determination process S11 is performed. On the other hand, it is also possible to conduct a self-discharge test on used batteries 1 that have already been put on the market and used. In this case, in addition to the assembly step S1, the initial charging step S2, the high-temperature aging step S3, and the cooling step S4 are not performed, and the used battery 1 charged to a predetermined state of charge is subjected to each step after the leaving step S5. I do. That is, after the used battery 1 is restrained in the same manner as in the embodiment, a charging/discharging device (not shown) is connected to the battery 1 in the same manner as in the initial charging step S2 of the first embodiment, and the environmental temperature TK=20° C. Under constant current and constant voltage (CCCV) charging, the battery is charged to a battery voltage VB of 3.9 V, which corresponds to an SOC of 80%.

In the leaving step S5, this charged and used battery 1 is left under a first environmental temperature TK1 (TK1=20.0° C.), and the battery temperature TB of the battery 1 is lowered to the first battery temperature TB1 (TB1=20.0° C.). .0°C). After that, the first battery voltage measurement step S6 to the judgment step S11 are performed as in the embodiment or the modification. Thus, the self-discharge test of the used battery 1 is completed. By doing so, the self-discharge test of the used battery 1 can be performed in a shorter time than conventionally.

Moreover, in the embodiment and the modification, the quality of the battery 1 is determined by comparison with the threshold current value IBth and the threshold change rate HAth. However, for example, three different threshold current values IBth1, IBTh2, and IBth3 are set, and compared with the value of the stable power supply current IBs of each battery 1, the battery 1 is adjusted according to the value of the stable power supply current IBs. Batteries 1 may be classified into three or more ranks using a plurality of different threshold values, such as classification into four ranks A to D.

In the embodiment, it is considered that the power supply current Ib is stable when the voltage application time t elapses up to a predetermined standby duration TTs (for example, TTs=18 minutes), and in the continuation determination step S9, the standby duration TTs is Determine if it has passed. However, in the continuation determination step S9, it may be determined whether or not the power supply current value IB(n) has stabilized, and if it has stabilized (Yes), the process may proceed to the determination step S11. Specifically, for example, in the continuation determination step S9, the moving average value of the power supply current value IB(n) (for example, the moving average value of seven power supply current values IB(n−6) to IB(n) for 60 seconds ) is sequentially calculated, and whether or not the power supply current value IB(n) has stabilized may be determined from the transition of the value (for example, the magnitude of the differential value of the moving average value).

In the embodiments and the like, the battery 1 (see FIG. 1) including the flat wound electrode body 20 was illustrated as the battery 1 to be tested, but the battery 1 is not limited to this. For example, the present technology can also be applied in the manufacture and inspection of a battery having a laminated electrode body. In the case of the laminated electrode body, when compressing the positive electrode plate, the separator and the negative electrode plate, the battery is compressed in the stacking direction of the positive electrode plate, the separator and the negative electrode plate. Cylindrical batteries in which cylindrically wound electrode bodies are housed are also applicable. In addition, the present invention can be applied to self-discharge inspection and manufacturing of power storage devices such as secondary batteries of various forms, electric double layer capacitors, and capacitors such as lithium ion capacitors.

1 (charged) battery (storage device)
30 Positive electrode terminal member 40 Negative electrode terminal member S2 Initial charging step S5 Leaving step KR1 First chamber (holding chamber)
S6 first battery voltage measurement step (first device voltage measurement step, inspection step)
S7 voltage continuous application step (inspection step)
S8 current detection step (inspection step)
S9 Continuation judgment step (inspection step)
TTs, TTt Standby duration time S10 Battery temperature change process (device temperature change process, inspection process)
S11 judgment step (inspection step)
TB Battery temperature (device temperature)
TB1 First battery temperature (first device temperature)
TB2 Second battery temperature (second device temperature)
TK Environmental temperature TK1 First environmental temperature (first environmental temperature)
TK2 Second environmental temperature (second environmental temperature)
HP Leaving period VB Battery voltage (device voltage)
VB1 First battery voltage (first device voltage)
VBS Stabilized battery voltage EP External power supply VS (External power supply) output voltage t Voltage application time tm Temperature change time IB Power supply current IB (n) (Acquired) power supply current value

Claims (4)

A self-discharge inspection method for an electricity storage device for inspecting self-discharge of an electricity storage device, comprising:
The electricity storage device
When the device temperature of the electricity storage device whose open circuit voltage at the first device temperature is the first device voltage is changed from the first device temperature to the second device temperature, the open circuit voltage of the electricity storage device It has the characteristic of stepping down from the 1st device voltage to a lower 2nd device voltage,
a first device voltage measuring step of measuring the first device voltage of the electricity storage device when the device temperature of the electricity storage device that has been charged in advance is the first device temperature;
a voltage continuous application step of continuously applying a power supply voltage equal to the first device voltage from an external power supply to the electricity storage device;
A device temperature changing step of changing the device temperature of the electricity storage device from the first device temperature toward the second device temperature in parallel with the continuous voltage application step;
a current detection step of detecting a power supply current flowing from the external power supply to the power storage device;
and a determination step of determining a self-discharge state of the storage device based on the sensed power supply current. A self-discharge inspection method for an electricity storage device according to claim 1,
Prior to the first device voltage measurement step,
A self-discharge inspection of an electricity storage device, comprising a leaving step of leaving the electricity storage device in a holding chamber having a first environmental temperature to set the device temperature of the electricity storage device to the first device temperature equal to the first environmental temperature. Method. A self-discharge inspection method for an electricity storage device according to claim 1 or 2,
A self-discharge inspection method for an electric storage device, wherein the device temperature changing step is started after the continuous voltage application step is started. an initial charging step of initially charging the assembled uncharged power storage device to a predetermined charge state to obtain a precharged power storage device;
A method for manufacturing an electricity storage device, comprising: an inspection step of inspecting the self-discharge state of the electricity storage device that has been charged for the first time by the self-discharge inspection method for an electricity storage device according to any one of claims 1 to 3.

Images