JP2015087372A - Secondary battery inspection method and secondary battery inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery inspection method and a secondary battery inspection device capable of promptly inspecting whether a fine short-circuit occurs to a secondary battery.SOLUTION: A secondary battery inspection method of the present invention includes: measuring a magnetic field intensity of a secondary battery 701 in a state of opening a cathode and an anode of the secondary battery 701; detecting a magnetic field 703 generated by a current flowing in the secondary battery 701 on the basis of the measured magnetic field intensity of the secondary battery 701; and determining that a short-circuit occurs in the secondary battery 701 if the magnetic field 703 generated by the current is detected. Furthermore, a secondary battery inspection device 100 of the present invention includes: a magnetic sensor 101 measuring the magnetic field intensity of the secondary battery 701; a magnetic field detection unit 102 detecting the magnetic field 703 generated by a current flowing in the secondary battery 701 on the basis of the magnetic field intensity measured by the magnetic sensor 101; and a short-circuit determination unit 103 determining that a short-circuit occurs in the secondary battery 701 if the magnetic field detection unit 102 detects the magnetic field 703 generated by the current.

Description

  The present invention relates to a secondary battery inspection method and inspection apparatus.

When a conductive foreign substance is mixed in the secondary battery, the conductive substance may penetrate through the separator inside the battery, which may cause a short circuit between the positive electrode and the negative electrode. When a short circuit occurs between the positive electrode and the negative electrode, a current having a value obtained by dividing the electromotive force of the secondary battery by the internal resistance of the short circuit part flows in the secondary battery. When such a current due to a short circuit flows, the voltage of the secondary battery decreases.
As a method of inspecting the voltage drop of the secondary battery due to the short circuit before shipping, Patent Document 1 ages the secondary battery, and compares the voltage drop amount before and after the aging of the terminal voltage with a threshold value. A secondary battery inspection method for determining the presence or absence of a short circuit is disclosed.

Japanese Patent Laid-Open No. 2004-13276

  In the secondary battery inspection method disclosed in Patent Document 1, the amount of potential drop after aging for several days is measured. The amount of potential drop of the secondary battery due to a minute short circuit is very small. In addition, even a good secondary battery without a short circuit causes a potential drop due to a chemical reaction or the like. As shown in FIG. 5, the potential drop 501 due to a short circuit falls linearly with respect to time, whereas the potential drop 502 caused by a chemical reaction or the like saturates halfway and stops at a certain value.

Since the potential drop 501 due to a short circuit and the potential drop 502 due to a chemical reaction or the like proceed very slowly, it takes several days until the difference between a non-defective product and a defective product occurs. For this reason, as shown in FIG. 6, a clear difference appears in the amount of potential drop between the non-defective product and the defective product, and it takes time to separate the potential drop 501 due to a short circuit from the potential drop 502 due to a chemical reaction or the like. .
As described above, the inspection of the minute short circuit of the secondary battery has a problem that it takes time because it needs to be aged for several days.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a secondary battery inspection method and inspection apparatus capable of quickly inspecting the presence or absence of a micro short circuit in a secondary battery.

The inspection method of the secondary battery of the present invention is as follows:
With the positive and negative electrodes of the secondary battery open, measure the magnetic field strength of the secondary battery,
Based on the measured magnetic field strength of the secondary battery, detect the magnetic field created by the current flowing in the secondary battery,
When a magnetic field generated by the current is detected, it is determined that there is a short circuit in the secondary battery.

The inspection apparatus for a secondary battery of the present invention is
A magnetic sensor for measuring the magnetic field strength of the secondary battery;
Based on the magnetic field strength of the secondary battery measured by the magnetic sensor, a magnetic field detection unit that detects a magnetic field created by a current flowing in the secondary battery;
In the magnetic field detection unit, including a pass / fail determination unit that determines that there is a short circuit when a magnetic field generated by the current is detected,
The magnetic sensor measures the magnetic field strength of the secondary battery with the positive electrode and the negative electrode of the secondary battery open.

  In the secondary battery inspection method and the secondary battery inspection apparatus according to the present invention, the presence or absence of a short circuit inside the secondary battery is inspected by measuring the magnetic field strength generated in the secondary battery. Therefore, it is possible to provide a secondary battery inspection method and inspection apparatus that can quickly inspect the presence or absence of a micro short circuit in the secondary battery.

The above secondary battery inspection method is
Measuring the first magnetic field strength of the secondary battery when the voltage of the secondary battery is the first voltage;
Changing the voltage of the secondary battery from the first voltage to the second voltage;
Measuring a second magnetic field strength at the second voltage of the secondary battery;
A magnetic field generated by a current flowing in the secondary battery may be detected based on a difference between the first magnetic field strength and the second magnetic field strength.

  The residual magnetic field of the secondary battery itself is constant even when the voltage is changed. On the other hand, when there is a short circuit, changing the voltage of the secondary battery changes the magnetic field strength of the secondary battery. In the method for inspecting a secondary battery according to the present invention, the presence or absence of a micro short circuit in the secondary battery can be determined quickly by determining whether there is a difference in the measured magnetic field strength before and after changing the voltage of the secondary battery. Inspection can be performed with high accuracy.

The above secondary battery inspection method is
Measure the magnetic field strength of the secondary battery at a plurality of voltages,
From the relationship between the plurality of voltages and the measured magnetic field strength, the inclination of the magnetic field strength with respect to the plurality of voltages is calculated,
The presence or absence of a short circuit of the secondary battery may be determined based on the inclination.

  Since the secondary battery inspection method according to the present invention can take a large amount of measurement voltage, errors due to measurement variations can be reduced. By reducing the influence of measurement variations, it is possible to improve the accuracy of the quality determination of the secondary battery.

The above secondary battery inspection method is
Measuring the magnetic field strength of a secondary battery without a short circuit, and based on the difference between the magnetic field strength of the secondary battery without the short circuit and the measured magnetic field strength of the secondary battery to be inspected, the secondary battery to be inspected It may be characterized by detecting a magnetic field generated by an electric current flowing in the inside.

  In the secondary battery inspection method according to the present invention, the difference between the magnetic field strength of the secondary battery without a short circuit and the measured magnetic field strength of the secondary battery to be inspected is calculated. Thereby, since the quality determination can be performed based on the difference between the secondary battery to be inspected and the non-defective sample, the accuracy of the quality determination of the secondary battery can be improved.

The above secondary battery inspection method is
When the magnetic field strength of the secondary battery measured using a magnetic sensor exceeds the measurable range of the magnetic sensor, the magnetic field strength of the secondary battery to be measured is within the measurable range. A magnetic field may be applied to the secondary battery.

  According to the method for inspecting a secondary battery according to the present invention, even when the magnitude of the residual magnetic field differs for each individual secondary battery, the peak of the magnetic field strength can be within the measurable range of the magnetic sensor. it can.

The above secondary battery inspection method is
Measure the magnetic field strength of the secondary battery while changing the relative positional relationship between the secondary battery and the magnetic sensor,
The position of the short circuit may be specified based on the measured magnetic field strength of the secondary battery.

  In the secondary battery inspection method according to the present invention, the magnetic field strength is measured at a plurality of positions by changing the positional relationship between the secondary battery and the magnetic sensor. Thereby, since the position where the magnetic field which the electric current which flows in a secondary battery produces is detected, the short circuit part in a secondary battery can be specified.

Furthermore, the inspection method of the secondary battery described above is
The inspection may be performed while the secondary battery is pressurized.

Some secondary batteries are short-circuited when no pressure is applied from the outside, but short-circuited when pressure is applied from the outside. In the inspection process of the secondary battery, it is necessary to appropriately remove such quasi-defective products.
In the secondary battery inspection method according to the present invention, when the secondary battery is inspected as described above, the secondary battery can be restrained and pressurized to appropriately remove the semi-defective product.

Moreover, the inspection method of the above-mentioned secondary battery is as follows.
The magnetic field strength of the secondary battery may be measured in a magnetic shield box that blocks an environmental magnetic field.

  In the inspection method of the secondary battery according to the present invention, the influence of the environmental magnetic field can be reduced by measuring the magnetic field strength in the magnetic shield box, so that the accuracy of the determination of the quality of the secondary battery is improved. Can do.

Furthermore, the inspection method of the secondary battery described above is
The magnetic field strength of the secondary battery may be measured using a plurality of magnetic sensors arranged in a two-dimensional grid.

  In the method for inspecting a secondary battery according to the present invention, the magnetic field strength of the secondary battery can be simultaneously measured for a plurality of parts, so that the magnetic field distribution on the surface of the secondary battery can be detected by a single measurement. Thereby, the short circuit site | part in a secondary battery can be identified rapidly. It is also possible to cancel the influence of the environmental magnetic field by arranging a plurality of magnetic sensors and taking the difference in the measured magnetic field of each magnetic sensor.

  ADVANTAGE OF THE INVENTION According to this invention, the inspection method and inspection apparatus of a secondary battery which can test | inspect rapidly the presence or absence of the micro short circuit of a secondary battery can be provided.

1 is a diagram illustrating a configuration of a secondary battery inspection device according to a first embodiment; It is a figure which shows an internal state when the secondary battery concerning Embodiment 1 does not have a short circuit. It is a figure which shows an internal state when the secondary battery concerning Embodiment 1 has a short circuit. 3 is a flowchart showing a flow of a secondary battery inspection method according to the first embodiment; It is a figure which shows the example of the electric potential drop in the test | inspection method of the conventional secondary battery. It is a figure which shows the difference of the electrical potential drop of the quality goods and inferior goods in the inspection method of the conventional secondary battery. FIG. 3 is a diagram illustrating a configuration of a secondary battery inspection device according to a second embodiment; 6 is a flowchart illustrating a flow of a secondary battery inspection method according to a second embodiment; It is a figure which shows an example of the result of having measured the magnetic field intensity, changing the relative position of a secondary battery and a magnetic sensor. FIG. 10 is a diagram showing a modification of the secondary battery inspection method according to the second exemplary embodiment; 6 is a flowchart showing a flow of a secondary battery inspection method according to a third embodiment; FIG. 9 is a diagram illustrating an example of a relationship between a voltage of a secondary battery and a measured magnetic field strength in the secondary battery inspection method according to the third embodiment. FIG. 6 is a diagram illustrating a configuration of a secondary battery inspection device according to a fourth embodiment; 6 is a flowchart illustrating a flow of a secondary battery inspection method according to a fourth embodiment; It is a figure which shows an example of the measurement result of a magnetic field intensity in case the residual magnetic field of a secondary battery is large.

[Embodiment 1]
Embodiments of the present invention will be described below with reference to the drawings.
As illustrated in FIG. 1, the secondary battery inspection device 100 includes a magnetic sensor 101, a magnetic field detection unit 102, and a pass / fail determination unit 103. The secondary battery 701 is an inspection target of the secondary battery inspection apparatus 100. The secondary battery inspection device 100 inspects the presence or absence of a short circuit inside the secondary battery 701. When the positive electrode and the negative electrode are short-circuited due to the inclusion of the conductive foreign matter 702 inside the secondary battery 701 or the precipitation phenomenon inside the battery, current flows through the short-circuited portion. A magnetic field 703 is generated in the secondary battery 701 without applying a voltage. The secondary battery inspection device 100 inspects the presence or absence of a short circuit inside the secondary battery 701 by measuring the strength of the magnetic field 703 (hereinafter also referred to as magnetic field strength).

  The secondary battery 701 to be inspected is, for example, a lithium ion secondary battery, a nickel hydride secondary battery, or the like. The secondary battery inspecting apparatus 100 according to the present embodiment may be any secondary battery as long as it is a secondary battery that generates a magnetic field when short-circuited.

  For example, a lithium ion secondary battery is a secondary battery that can be charged and discharged by moving lithium ions in a non-aqueous electrolyte between a positive electrode and a negative electrode that occlude and release lithium ions. A lithium ion secondary battery includes a positive electrode material carrying a positive electrode active material, a negative electrode material carrying a negative electrode active material, a separator interposed between the positive electrode material and the negative electrode material, and a non-aqueous electrolyte. Lithium ion secondary batteries include, for example, those having a wound electrode body obtained by winding a strip-shaped positive electrode material and a strip-shaped negative electrode material through a strip-shaped separator, or a plurality of positive electrode materials and a plurality of negative electrode materials. And those having a laminated electrode body laminated alternately via separators.

  The magnetic sensor 101 measures a magnetic field 703 generated by the secondary battery 701. As the magnetic sensor 101, for example, a SQUID (Superconducting Quantum Interference Device) sensor or an MI (Magneto-Impedance) sensor is used. The sensitivity of the magnetic sensor 101 depends on the distance from a location where a current is generated (in other words, a location where a magnetic field is generated). Therefore, it is preferable to dispose the magnetic sensor 101 close to the secondary battery 701. In particular, by arranging the magnetic sensor 101 so as to be in contact with the surface of the secondary battery 701, the sensitivity of the magnetic sensor 101 can be improved.

  In addition, by arranging a plurality of magnetic sensors 101 around the secondary battery 701, measurement accuracy can be improved and measurement time can be shortened. For example, a plurality of magnetic sensors 101 may be arranged in a two-dimensional lattice so that the magnetic field distribution on the upper surface of the secondary battery 701 can be measured at a time. Further, the magnetic sensor 101 may be provided on each surface around the secondary battery 701. For example, the magnetic sensor 101 may be provided on the upper and lower surfaces of the secondary battery 701. Moreover, you may provide the magnetic sensor 101 mainly in the place where a short circuit is easy to generate | occur | produce.

  Based on the magnetic field strength of the secondary battery 701 measured by the magnetic sensor 101, the magnetic field detection unit 102 detects a magnetic field generated by a current (short-circuit current) that flows through a short-circuit location inside the secondary battery 701. FIG. 2 shows a state where there is no short circuit in the secondary battery 701. FIG. 3 shows a state where a short circuit exists in the secondary battery 701. Inside the secondary battery 701, there are a positive electrode material 201, a negative electrode material 202, and a separator 203 sandwiched between the positive electrode material 201 and the negative electrode material 202. When there is no short circuit in the secondary battery 701, as shown in FIG. 2, the positive electrode material 201 and the negative electrode material 202 are insulated by the separator 203, and the positive electrode material 201 and the negative electrode material 202 are No current flows.

On the other hand, as shown in FIG. 3, when the positive electrode and the negative electrode are short-circuited because the conductive foreign material 702 is mixed between the positive electrode material 201 and the negative electrode material 202 of the secondary battery 701, Current flows. In this case, a current I represented by I = V / R flows based on Ohm's law due to the electromotive force V of the secondary battery 701 and the electrical resistance R of the short circuit part. In a lithium ion secondary battery, the amount of short-circuit current that flows varies depending on the degree of short-circuit. For example, when a short-circuit current of several hundred μA is flowing, it is about 10 ⁻¹² T even at a location several cm away from the short-circuit portion. The magnetic field will be generated. Note that the secondary battery inspection apparatus 100 according to the present embodiment can also be used to detect a short circuit other than when the conductive foreign material 702 is mixed to cause a short circuit.

  The pass / fail determination unit 103 determines that there is a short circuit when the magnetic field detection unit 102 detects the magnetic field generated by the short circuit current. On the other hand, the pass / fail determination unit 103 determines that there is no short circuit when the magnetic field detection unit 102 does not detect the magnetic field generated by the short circuit current. Since the positive electrode material 201 and the negative electrode material 202 of the secondary battery 701 are insulated by the separator 203, no current flows in the secondary battery 701 unless there is a short circuit.

  In the secondary battery inspection apparatus 100 according to the present embodiment, a magnetic shield box that blocks an environmental magnetic field may be provided, and the magnetic field strength of the secondary battery 701 may be measured in the magnetic shield box. In order to put the secondary battery 701 in the magnetic shield box, it is necessary to provide an opening in the magnetic shield box. The opening may be a structure that is always open, or may be a structure in which the opening is covered with a lid after the secondary battery 701 is placed in the magnetic shield box.

  Further, the influence of the environmental magnetic field may be canceled using the output of the magnetic sensor 101. In this case, it is not necessary to provide a magnetic shield box. For example, it is possible to cancel the influence of the environmental magnetic field by arranging a plurality of magnetic sensors 101 and taking the difference between the measured magnetic fields of the magnetic sensors 101.

  Consider a case where a plurality of magnetic sensors 101 are arranged such that the distance from the secondary battery 701 is different for each magnetic sensor 101. In this case, there are the magnetic sensor 101 close to the secondary battery 701 and the magnetic sensor 101 far from the secondary battery 701. The magnetic field created by the short-circuit current in the secondary battery 701 is strong near the secondary battery 701 and weakens when it is away from the secondary battery 701. That is, the strength of the magnetic field created by the short-circuit current detected by each magnetic sensor 101 varies depending on the distance from the secondary battery 701.

  On the other hand, the magnetic field generated by the short-circuit current is very weak compared to the environmental magnetic field. For this reason, when the influence of the environmental magnetic field is strong, a uniform environmental magnetic field is detected by each magnetic sensor 101 regardless of the distance from the secondary battery. Thus, by comparing the magnetic fields detected by the magnetic sensors 101, it is possible to determine whether or not there is an influence of the environmental magnetic field. Moreover, the influence of an environmental magnetic field can be negated by taking the difference of the magnetic field intensity which each magnetic sensor 101 measured at this time.

  In the secondary battery 701, there is an individual that can be said to be a semi-defective product, in which a short circuit does not occur when no pressure is applied from the outside, but a short circuit occurs when pressure is applied from the outside. In the inspection process of the secondary battery, it is necessary to appropriately remove such quasi-defective products.

  In this embodiment, when inspecting a secondary battery, the secondary battery 701 may be restrained and pressurized in order to cause a short circuit in the secondary battery 701 of such a semi-defective product. For example, the secondary battery 701 is pressurized with a load cell or the like while being restrained using a restraining plate. Thereby, the separator 203 sandwiched between the positive electrode material 201 and the negative electrode material 202 is compressed, and a short circuit can easily occur. A restraining plate that does not affect the magnetic field, for example, resin is used. It is also possible to embed the magnetic sensor 101 in the constraining plate so that the distance between the magnetic sensor 101 and the secondary battery 701 that is the measurement object is not separated. In addition, it is possible to reduce the distance between the magnetic sensor 101 and the secondary battery 701 by reducing the thickness of the restraint plate only in the vicinity of the measurement position of the magnetic sensor 101.

  As described above, when the secondary battery is inspected, the sub-defective product can be appropriately removed by restraining and pressurizing the secondary battery.

Next, a secondary battery inspection method according to the present embodiment will be described. FIG. 4 is a flowchart showing the flow of the inspection method for the secondary battery 701.
First, the secondary battery 701 to be inspected is placed in the secondary battery inspection apparatus 100 (S401). For example, when the secondary battery 701 to be inspected is a lithium ion secondary battery, a lithium ion secondary battery charged in a predetermined state of charge (SOC) after a predetermined conditioning process is performed. It is good also as inspection object. In order for a current to flow from the positive electrode material 201 to the negative electrode material 202 when the positive electrode material 201 and the negative electrode material 202 of the lithium ion secondary battery are short-circuited, the lithium ion secondary battery needs to be charged with a predetermined SOC. is there.

  Next, the magnetic field intensity of the secondary battery 701 is measured by the magnetic sensor 101 in a state where no voltage is applied to the secondary battery 701 (S402). Here, the state where no voltage is applied refers to a state where the positive electrode and the negative electrode of the secondary battery 701 are opened. During the measurement of the magnetic field strength, the voltage value of the secondary battery 701 is constant.

  Next, based on the difference between the magnetic field intensity of the secondary battery 701 to be inspected measured by the magnetic sensor 101 and the magnetic field intensity of a non-short secondary battery, the magnetic field detection unit 102 causes the secondary to be inspected. A magnetic field generated by a short-circuit current flowing through the short-circuited location inside the battery 701 is detected (S403). For example, when there is a short circuit inside the secondary battery 701 to be inspected, a short circuit current flows in the secondary battery 701 to be inspected, and thus a magnetic field 703 is generated. In this case, the difference between the magnetic field strength of the secondary battery 701 to be inspected and the magnetic field strength of a good secondary battery without a short circuit increases. The magnetic field detection unit 102 can detect the current flowing in the secondary battery 701 to be inspected by detecting the difference in magnetic field intensity. In addition, the magnetic field strength of a non-short secondary battery that is a comparison target is measured in advance.

  Next, when the magnetic field generated by the short-circuit current is not detected in step S403 (NO in S403), the pass / fail determination unit 103 determines that the secondary battery 701 to be inspected is a non-defective product and sends it to the next process (S404). On the other hand, when the pass / fail determination unit 103 detects a magnetic field in which a short-circuit current is generated in step S403 (YES in S403), the secondary battery 701 to be inspected is determined to be a defective product having a short circuit in the secondary battery 701 ( S405).

  In the secondary battery inspection method according to the present embodiment, a predetermined threshold value may be provided when detecting the magnetic field generated by the short-circuit current in step S403. For example, when the difference between the magnetic field strength of the secondary battery 701 to be inspected and the magnetic field strength of a non-defective secondary battery is larger than a predetermined threshold (magnetic field), the magnetic field detection unit 102 checks the secondary battery 701 to be inspected. You may determine with the short circuit current flowing internally.

  In step S403, the magnetic field detection unit 102 uses the difference between the magnetic field intensity of the secondary battery 701 to be inspected and the magnetic field intensity of a non-defective secondary battery to cause a short circuit current to flow in the secondary battery 701 to be inspected. The amount may be determined. When the current value obtained in step S403 is larger than a predetermined threshold value (current value), a current (that is, a current that can be determined to be short-circuited) flows in the secondary battery 701 to be inspected. It may be determined that

  If the inspection apparatus 100 is not easily affected by the environmental magnetic field or individual differences of the secondary batteries, such as when the secondary battery inspection apparatus 100 is provided with a magnetic shield box and the residual magnetic field of the secondary battery 701 is small, a comparison is made. The magnetic field generated by the short-circuit current flowing in the secondary battery 701 to be inspected may be detected without measuring the magnetic field strength of the non-defective secondary battery that is the target. That is, when the secondary battery inspection apparatus 100 is not easily influenced by the environmental magnetic field and the individual difference in the residual magnetic field is small, when the abnormal magnetic field is detected in the secondary battery 701 to be inspected, the inspection target 2 It can be determined that a short-circuit current is flowing in the secondary battery 701. For example, the magnetic field detection unit 102 determines that a short-circuit current is flowing in the secondary battery 701 to be inspected when the strength of the magnetic field generated in the secondary battery 701 to be inspected is equal to or greater than a predetermined threshold. May be.

  As described above, in the invention according to the present embodiment, the presence or absence of a short circuit inside the secondary battery is inspected by measuring the magnetic field strength generated in the secondary battery. Therefore, it is possible to provide a secondary battery inspection method and inspection apparatus that can quickly inspect the presence or absence of a micro short circuit in the secondary battery.

[Embodiment 2]
The secondary battery inspection apparatus 300 according to the second embodiment will be described with reference to FIG. The secondary battery to be inspected may itself generate a residual magnetic field. Since the distribution and strength of the residual magnetic field are different for each secondary battery, it is necessary to consider the influence of the residual magnetic field when inspecting the secondary battery for the presence of a micro short circuit. In the second embodiment described below, a secondary battery inspection method and inspection apparatus capable of reducing the influence of such a residual magnetic field will be described.

  As shown in FIG. 7, the secondary battery inspection device 300 includes a magnetic sensor 101, a magnetic field detection unit 102, a pass / fail determination unit 103, a storage unit 304, and a charge / discharge device 310. The secondary battery 701 is an inspection target of the secondary battery inspection device 300. The secondary battery inspection device 300 inspects the presence or absence of a short circuit inside the secondary battery 701. The secondary battery inspection device 300 according to the present embodiment includes a storage unit 304 and a charge / discharge device 310, and the secondary battery inspection device 100 according to the first embodiment (see FIG. 1). Different. Charging / discharging device 310 is connected to the positive electrode and the negative electrode of secondary battery 701. The charging / discharging device 310 can change the voltage of the secondary battery 701 by charging / discharging the secondary battery 701.

Next, a secondary battery inspection method according to the present embodiment will be described. FIG. 8 is a flowchart showing the flow of the secondary battery inspection method according to the present embodiment.
First, the secondary battery 701 to be inspected is placed in the secondary battery inspection device 300 (S601).
Next, the magnetic field intensity of the secondary battery 701 is measured by the magnetic sensor 101 with the positive electrode and the negative electrode of the secondary battery 701 open (S602). The voltage of the secondary battery 701 at this time is defined as a first voltage V1, and the magnetic field intensity measured by the magnetic sensor 101 is defined as a first magnetic field intensity B1. Note that the voltage value of the secondary battery 701 is constant during the measurement of the magnetic field strength.

  Next, the charging / discharging device 310 is connected to the positive electrode and the negative electrode of the secondary battery 701, and the voltage of the secondary battery 701 is set to the second voltage by the charging / discharging device 310 while the positional relationship between the secondary battery 701 and the magnetic sensor is fixed. The voltage V2 is changed to (S603). With the voltage of the secondary battery 701 set to the second voltage V2, the magnetic field strength of the secondary battery 701 is measured by the magnetic sensor 101 with the positive electrode and the negative electrode opened (S604). At this time, the magnetic field intensity measured by the magnetic sensor 101 is defined as a second magnetic field intensity B2. Note that the voltage value of the secondary battery 701 is constant during the measurement of the magnetic field strength.

  The second voltage V2 may be larger or smaller than the first voltage V1. In addition, the first voltage V1 can be the lower limit voltage of the secondary battery 701 and the second voltage V2 can be the upper limit voltage of the secondary battery 701. As the difference between the first voltage V1 and the second voltage V2 is increased, the difference in magnetic field intensity generated from the secondary battery 701 is increased, so that the detection sensitivity of the micro short circuit is improved. In order to improve the detection sensitivity, a voltage higher than the upper limit voltage or a voltage lower than the lower limit voltage may be used only during inspection.

  Next, the quality determination unit 103 determines whether or not the first magnetic field strength B1 measured in step S602 is equal to the second magnetic field strength B2 measured in step S604 (S605). That is, it is determined whether there is a difference in the measured magnetic field strength before and after the voltage of the secondary battery 701 is changed. The residual magnetic field of the secondary battery 701 itself is constant even when the voltage is changed. On the other hand, since the amount of current flowing through the short-circuit portion depends on the voltage of the secondary battery 701, if there is a short circuit, changing the voltage of the secondary battery 701 also changes the magnetic field strength of the secondary battery 701. .

  When the pass / fail determination unit 103 determines that the first magnetic field strength B1 and the second magnetic field strength B2 are equal (YES in S605), the secondary battery 701 to be inspected is determined to be a non-defective product and sent to the next process (S606). ). On the other hand, when the pass / fail determination unit 103 determines in step S605 that the first magnetic field strength B1 and the second magnetic field strength B2 are not equal (NO in S605), the secondary battery 701 to be inspected is stored in the secondary battery 701. (S607). The secondary battery 701 determined to be defective is not sent to the subsequent process.

  The residual magnetic field of the secondary battery 701 itself is constant even when the voltage is changed. On the other hand, when there is a short circuit, the magnetic field strength of the secondary battery 701 changes when the voltage of the secondary battery 701 is changed. The secondary battery inspection method according to the present embodiment determines whether or not there is a micro short circuit in the secondary battery by determining whether there is a difference in the measured magnetic field strength before and after the voltage of the secondary battery 701 is changed. Can be inspected quickly and accurately.

  Further, the secondary battery 701 has a residual magnetic field, and the distribution and strength of the residual magnetic field vary depending on the individual secondary battery 701. FIG. 9 is a diagram illustrating an example of a result of measuring the magnetic field strength while placing the secondary battery 701 on a transport unit such as a belt conveyor and changing the relative position between the secondary battery 701 and the magnetic sensor 101. The voltage of the secondary battery 701 is shown in FIG. 9 as a result of measuring the magnetic field strength of the secondary batteries 701 in three different lots of lot A to lot C. In this measurement, the voltage of the secondary battery 701 is the same for all of lot A to lot C. However, the measured magnetic field intensity curves are different for lot A to lot C, and the residual magnetic fields of lot A to lot C are different.

  For example, when a magnetic layer is formed on the lower surface of the inspection object carrier to cancel the residual magnetic field of the inspection object, the residual magnetic field of the secondary battery 701 has a large individual difference. It is necessary to form a magnetic layer suitable for the magnetic field, which increases the cost required for inspection. However, in the secondary battery inspection method according to the present embodiment, since the change in magnetic field strength when the voltage of one secondary battery 701 is changed is detected, the individual residual magnetic field of the secondary battery 701 is detected. It is possible to reduce the influence of variation for each. For this reason, the presence or absence of the micro short circuit of the secondary battery 701 can be inspected quickly and accurately.

(Modification)
The modification of the inspection method of the secondary battery concerning this embodiment is shown. FIG. 10 is a diagram showing a modification of the inspection method for the secondary battery. FIG. 10 shows a state in which the secondary battery 701 is placed on a conveying means such as a belt conveyor and the magnetic field strength is measured while the relative position between the secondary battery 701 and the magnetic sensor 101 is changed. As shown in FIG. 10, when the secondary battery 701 is moved in the order of (a), (b), and (c) in the horizontal direction, the secondary battery 701 is directly under the magnetic sensor 101 (with the target). Depending on the strength and direction of the magnetic field, the detection area extends in the horizontal direction, but for the sake of simplicity, the area to be detected is assumed to be the detection area only immediately below the sensor.

  By changing the positional relationship between the secondary battery 701 and the magnetic sensor 101, the first magnetic field strength B1 and the second magnetic field strength B2 are measured at a plurality of positions. Then, the position where the difference between the first magnetic field strength B1 and the second magnetic field strength B2 is maximized can be determined as the short-circuit portion of the secondary battery 701. For example, in FIG. 10, if the difference between the first magnetic field strength B1 and the second magnetic field strength B2 is maximized at the position (a), the measurement range of the magnetic sensor 101 is entered at the position (a). It can be determined that there is a short circuit at the site.

In this modification, the secondary battery 701 is moved and the secondary battery inspection method shown in FIG. 8 is performed at a plurality of positions.
On the other hand, instead of moving the secondary battery 701 and measuring the magnetic field intensity in this way, a plurality of magnetic sensors 101 are arranged around the secondary battery 701, and the presence or absence of a short circuit and the identification of the short-circuited part are performed simultaneously. By doing so, the inspection time can be shortened.

[Embodiment 3]
In the present embodiment, the same secondary battery inspection apparatus 300 as in the second embodiment is used.
A method for inspecting a secondary battery according to the present embodiment will be described. FIG. 11 is a flowchart showing the flow of the secondary battery inspection method according to the present embodiment.
First, the secondary battery 701 to be inspected is placed in the secondary battery inspection apparatus 300 (S801).

  Next, the magnetic field intensity of the secondary battery 701 is measured by the magnetic sensor 101 in a state where the positive electrode and the negative electrode of the secondary battery 701 are opened (S802). The voltage of the secondary battery 701 at this time is defined as a first voltage V1, and the magnetic field intensity measured by the magnetic sensor 101 is defined as a first magnetic field intensity B1. The measured magnetic field strength value B 1 is stored in the storage unit 304.

  Next, the charging / discharging device 310 is connected to the positive electrode and the negative electrode of the secondary battery 701, and the voltage of the secondary battery 701 is changed by the charging / discharging device 310 while the positional relationship between the secondary battery 701 and the magnetic sensor 101 is fixed. The voltage V2 is changed to 2 (S803). With the voltage of the secondary battery 701 set to the second voltage V2, the magnetic field strength of the secondary battery 701 is measured by the magnetic sensor 101 in a state where the positive electrode and the negative electrode are opened (S804). At this time, the magnetic field intensity measured by the magnetic sensor 101 is defined as a second magnetic field intensity B2. The measured magnetic field strength value B 2 is stored in the storage unit 304.

  The pass / fail determination unit 103 changes the voltage of the secondary battery 701 to the second voltage V2 and measures the magnetic field strength, and then determines whether or not the magnetic field strength of the secondary battery 701 has been measured at all desired voltages (S805). ). When the pass / fail judgment unit 103 judges that the magnetic field of the secondary battery 701 is not measured with all desired voltages (NO in S805), the voltage of the secondary battery 701 is changed (S803), and the magnetic sensor 101 The magnetic field strength of the secondary battery 701 is measured (S804).

  In this manner, the magnetic field strengths B1 to Bn corresponding to the desired voltages V1 to Vn can be measured by repeating the processes of steps S803 to S805. When changing the voltage of the secondary battery 701, for example, when the voltage of the secondary battery 701 sent from the previous process is high, the battery is discharged by the charging / discharging device 310 and the voltage is gradually lowered. Good. In addition, when the voltage of the secondary battery 701 sent from the previous process is low, charging may be performed by the charging / discharging device 310, and the voltage may be sequentially increased.

  When it is determined that the magnetic field of the secondary battery 701 has been measured at all desired voltages (YES in S805), the pass / fail determination unit 103 obtains the relationship between the voltage of the secondary battery 701 and the measured magnetic field strength (S806). . FIG. 12 shows an example of the relationship between the voltage of the secondary battery 701 and the measured magnetic field strength. In FIG. 12, a defective product with a short circuit is indicated by a solid line, and a non-defective product without a short circuit is indicated by a broken line.

  Next, the pass / fail determination unit 103 calculates the gradient of the measured magnetic field strength with respect to the voltage of the secondary battery 701, and determines whether the gradient of the magnetic field strength is smaller than the threshold (S807). For the gradient of the magnetic field strength, the gradient of the graph plotting the magnetic field strength for each measurement voltage may be obtained, or the gradient may be obtained by the least square method. As the measurement voltage is increased, an error in inclination due to measurement variation can be reduced. By reducing the tilt error, the accuracy of the quality determination of the secondary battery 701 can be improved. A threshold value that is a criterion for pass / fail determination is calculated in advance and stored in the storage unit 304.

  If the gradient of the magnetic field strength with respect to the voltage is smaller than the threshold (YES in S807), the magnetic field strength does not increase even if the voltage increases, so the secondary battery 701 to be inspected is determined to be a non-defective product and sent to the next process (S808). .

  When the gradient of the magnetic field strength with respect to the calculated voltage is larger than the threshold value (NO in S807), the magnetic field strength increases as the voltage increases, so that the secondary battery 701 to be inspected is not short-circuited in the secondary battery 701. It is determined as a non-defective product (S809). The secondary battery 701 determined to be defective is not sent to the subsequent process.

  Since the secondary battery inspection method according to this embodiment can take a large amount of measurement voltage, errors due to measurement variations can be reduced. By reducing the influence of measurement variation, the accuracy of the quality determination of the secondary battery 701 can be improved.

[Embodiment 4]
A secondary battery inspection apparatus 1000 according to the present embodiment will be described with reference to FIG. As shown in FIG. 13, the secondary battery inspection apparatus 1000 includes a magnetic sensor 101, a magnetic field detection unit 102, a pass / fail determination unit 103, a storage unit 304, a charge / discharge device 310, and a corrected magnetic field generation unit 111. The correction magnetic field control unit 112 and the magnetic shield box 120 are provided. The secondary battery inspection apparatus 1000 according to the present embodiment includes a correction magnetic field generation unit 111 and a correction magnetic field control unit 112, the secondary battery inspection apparatus 300 according to the second embodiment (FIG. 7). Different from reference).

  The correction magnetic field generation unit 111 generates a magnetic field so as to cancel the residual magnetic field of the secondary battery 701. The correction magnetic field generation unit 111 has a simple configuration in which a current is passed through a conducting wire, and may generate a magnetic field using Ampere's law, or may be an electromagnet using a coil. The intensity of the magnetic field generated by the correction magnetic field generation unit 111 can be controlled by changing the value of the current passed through the correction magnetic field generation unit 111. The correction magnetic field generation unit 111 may be any unit that can change the intensity of the generated magnetic field by changing a parameter that can be controlled from the outside of the magnetic shield box 120, and is limited to the above-described configuration. is not. For example, a single material whose magnetic field changes by changing current, voltage, or temperature may be used.

  The correction magnetic field control unit 112 controls the correction magnetic field generation unit 111. The correction magnetic field control unit 112 acquires the magnetic field strength measured by the magnetic sensor 101 from the pass / fail determination unit 103, and changes the magnetic field generated by the correction magnetic field generation unit 111 in accordance with the magnetic field strength.

  The magnetic shield box 120 blocks an external magnetic field. By performing the inspection inside the magnetic shield box 120, the influence of the external magnetic field can be reduced, so that the magnetic field can be corrected with high accuracy.

A method for inspecting a secondary battery according to the present embodiment will be described. FIG. 14 is a flowchart showing the flow of the secondary battery inspection method according to the present embodiment.
First, the secondary battery 701 to be inspected is placed in a secondary battery inspection device (S901).
Next, the magnetic field intensity of the secondary battery 701 is measured by the magnetic sensor 101 in a state where the positive electrode and the negative electrode of the secondary battery 701 are opened (S902). The measured magnetic field strength B0 is stored in the storage unit 304.

  Next, the quality determination unit 103 determines whether or not magnetic field correction is necessary in the measurement of the magnetic field strength from the measurement result of the magnetic field strength B0 (S903). FIG. 15 is a diagram illustrating an example of the measurement result of the magnetic field strength when the residual magnetic field of the secondary battery 701 is large. In FIG. 15, the secondary battery 701 is placed on a conveying means such as a belt conveyor, and the magnetic field strength is measured while changing the relative position between the secondary battery 701 and the magnetic sensor 101.

  In FIG. 15, the measurement result of the portion surrounded by the broken line has swung out the measurable range of the magnetic sensor 101, and the magnetic field strength cannot be accurately measured. In such a case, the correction magnetic field generation unit 111 is used to apply a magnetic field in a direction that cancels the residual magnetic field of the secondary battery 701, so that the magnetic field strength measurement zero point so that it is within the measurable range of the magnetic sensor 101. Can be corrected. Even when the sensitivity of the magnetic sensor 101 has not been fully affected, if the magnetic field correction is performed near the upper limit or lower limit of the measurable range, the detection capability is improved by correcting the magnetic field. Good.

When the pass / fail determination unit 103 determines that the magnetic field correction needs to be performed (YES in S903), the correction magnetic field generation unit 111 is used to correct the magnetic field (S904).
After the magnetic field correction, the corrected magnetic field strength is measured, and the quality of the secondary battery 701 is determined based on the corrected magnetic field strength measurement result (S905).

  When the pass / fail determination unit 103 determines that the magnetic field correction is not necessary (NO in S903), the measurement of the magnetic field strength is continued without performing the magnetic field correction, and the pass / fail of the secondary battery 701 is determined based on the measurement result of the magnetic field strength. Is determined (S906). The measurement of the magnetic field strength may be performed by any of the methods described in the first to third embodiments.

  According to the secondary battery inspection apparatus 1000 according to the present embodiment, the peak of the magnetic field strength is within the measurable range of the magnetic sensor 101 even when the magnitude of the residual magnetic field differs for each individual secondary battery 701. Can be.

  Further, when the voltage of the secondary battery 701 is changed, a magnetic field is generated by the current that is charged and discharged. When using a highly sensitive SQUID sensor, if a large magnetic field enters the sensor, a magnetic flux trap / jump occurs, and even if the charge / discharge current is set to 0 (even if the charge / discharge is stopped), output from the sensor The applied magnetic field strength signal may not be restored. This is because, for example, when measuring a non-defective secondary battery, the magnetic field strength does not change even if the voltage is changed, but the magnetic field strength changes before and after the voltage change due to the characteristics of the sensor. Will be measured. In particular, such a phenomenon may occur when the voltage is changed by passing a large current with the aim of shortening the inspection time.

  When the voltage is changed by flowing a large current in this way, the charging / discharging current is gradually increased from a small value, and the intensity of the magnetic field generated by the correction magnetic field generation unit 111 according to the output value of the magnetic sensor 101 is increased. By adjusting, it is possible to prevent a large magnetic field from entering the sensor unit. In addition, if high current charging / discharging is required due to the inspection time, etc., and magnetic flux trapping / jumping by this method cannot be avoided, another high-sensitivity sensor such as an MI sensor or fluxgate sensor should be used. Can also be avoided. In particular, in recent years, the sensitivity of MI sensors and fluxgate sensors has improved remarkably, and the difference in detection sensitivity from the case of using a SQUID sensor has become smaller, which is an effective measure.

  Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention. For example, the secondary battery that is a target of the secondary battery inspection method according to the present invention is not limited to a secondary battery for automobiles, but is a secondary battery for home appliances such as a mobile phone and a notebook personal computer. There may be. In addition, the secondary battery that is the target of the secondary battery inspection method according to the present invention may be any battery that generates current when a short circuit occurs, and is not limited to a lithium ion battery or a nickel metal hydride battery. Absent.

100, 300, 1000 Secondary battery inspection device 101 Magnetic sensor 102 Magnetic field detector 103 Pass / fail judgment unit 111 Corrected magnetic field generator 112 Corrected magnetic field controller 120 Magnetic shield box 201 Positive electrode material 202 Negative electrode material 203 Separator 304 Storage unit 310 Charge / Discharge Device 701 Secondary battery 702 Conductive foreign matter 703 Magnetic field

Claims (10)

With the positive and negative electrodes of the secondary battery open, measure the magnetic field strength of the secondary battery,
Based on the measured magnetic field strength of the secondary battery, detect the magnetic field created by the current flowing in the secondary battery,
A secondary battery inspection method for determining that a short circuit is present in the secondary battery when a magnetic field generated by the current is detected. A method for inspecting a secondary battery according to claim 1,
Measuring the first magnetic field strength of the secondary battery when the voltage of the secondary battery is the first voltage;
Changing the voltage of the secondary battery from the first voltage to the second voltage;
Measuring a second magnetic field strength at the second voltage of the secondary battery;
A method for inspecting a secondary battery, comprising: detecting a magnetic field generated by a current flowing in the secondary battery based on a difference between the first magnetic field intensity and the second magnetic field intensity. A method for inspecting a secondary battery according to claim 1,
Measure the magnetic field strength of the secondary battery at a plurality of voltages,
From the relationship between the plurality of voltages and the measured magnetic field strength, the inclination of the magnetic field strength with respect to the plurality of voltages is calculated,
The method for inspecting a secondary battery, wherein the presence or absence of a short circuit of the secondary battery is determined based on the inclination. A method for inspecting a secondary battery according to claim 1,
Measuring the magnetic field strength of a secondary battery without a short circuit, and based on the difference between the magnetic field strength of the secondary battery without the short circuit and the measured magnetic field strength of the secondary battery to be inspected, the secondary battery to be inspected A method for inspecting a secondary battery, characterized by detecting a magnetic field generated by a current flowing in the inside. A method for inspecting a secondary battery according to any one of claims 1 to 4,
When the magnetic field strength of the secondary battery measured using a magnetic sensor exceeds the measurable range of the magnetic sensor, the magnetic field strength of the secondary battery to be measured is within the measurable range. A method for inspecting a secondary battery, comprising applying a magnetic field to the secondary battery. A method for inspecting a secondary battery according to any one of claims 1 to 5,
Measure the magnetic field strength of the secondary battery while changing the relative positional relationship between the secondary battery and the magnetic sensor,
The method for inspecting a secondary battery, wherein the position of the short circuit is specified based on the measured magnetic field strength of the secondary battery. A method for inspecting a secondary battery according to any one of claims 1 to 6,
An inspection method for a secondary battery, wherein the inspection is performed in a state where the secondary battery is pressurized. A secondary battery inspection method according to any one of claims 1 to 7,
A method of inspecting a secondary battery, comprising: measuring a magnetic field strength of the secondary battery in a magnetic shield box that blocks an environmental magnetic field. A method for inspecting a secondary battery according to any one of claims 1 to 8,
A method for inspecting a secondary battery, wherein the magnetic field strength of the secondary battery is measured using a plurality of magnetic sensors arranged in a two-dimensional lattice pattern. A magnetic sensor for measuring the magnetic field strength of the secondary battery;
Based on the magnetic field strength of the secondary battery measured by the magnetic sensor, a magnetic field detection unit that detects a magnetic field created by a current flowing in the secondary battery;
In the magnetic field detection unit, including a pass / fail determination unit that determines that there is a short circuit when a magnetic field generated by the current is detected,
The said magnetic sensor measures the magnetic field intensity of the said secondary battery in the state which open | released the positive electrode and negative electrode of the said secondary battery. The inspection apparatus of the secondary battery characterized by the above-mentioned.

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