JPH11297367A - Method for inspecting short circuit of battery electrode group and apparatus for inspecting short circuit - Google Patents

Abstract

An object of the present invention is to detect, with high reliability, the presence or absence and the state of a short circuit between electrodes of a secondary battery electrode group having a structure in which a positive electrode and a negative electrode are separated by a separator. SOLUTION: At the stage before injecting the electrolytic solution at the time of battery configuration,
A method for inspecting the short-circuit state of an electrode group consisting of a positive electrode and a negative electrode and a separator disposed so as to separate the two electrodes, wherein an AC impedance between the two electrodes when an AC signal is applied between the two electrodes or The admittance and the phase angle are measured, and the short-circuit state of the electrode group is determined using the measured values.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the presence or absence of a short circuit between electrodes of a secondary battery electrode group having a structure in which a positive electrode and a negative electrode are separated by a separator, such as a nickel-hydrogen storage battery and a lithium ion secondary battery. The present invention relates to an inspection method and an inspection apparatus capable of detecting a state and a state with high reliability.

[0002]

2. Description of the Related Art Sealed small secondary batteries such as nickel-hydrogen storage batteries and lithium ion secondary batteries are widely used as power supplies for portable equipment such as communication equipment and OA equipment.

In these sealed small secondary batteries, for example, a positive electrode 9 and a negative electrode 10 are separated by a separator 11, and they are spirally wound to form an electrode group. After insertion, an electrolytic solution is injected into the case 12 and the upper portion of the case 12 is sealed with a sealing plate 13. FIG. 3 shows a half sectional view of this battery.

[0004] The separator for separating the positive electrode and the negative electrode is desirably thin in order to pack as much as possible the filler of the positive electrode and the negative electrode into the inside of the battery case having a limited size, and is usually about several tens μm to several hundred μm. A nonwoven fabric made of nylon or polypropylene having a thickness is used.

[0005] Since the positive and negative electrodes are separated by a very thin separator as described above, there is rarely a defect that burrs on the cut surface of the electrode or falling off of the active material penetrate the separator and short-circuit between the electrodes. Occurs. If a battery in which a positive electrode and a negative electrode are slightly short-circuited is left for a while after charging, the discharge capacity is greatly reduced and the battery cannot withstand actual use. Therefore, it is necessary to sort and discharge such batteries by some inspection.

Conventionally, as a method for discharging such a micro short-circuit battery, after inserting an electrode group composed of a positive electrode, a negative electrode, and a separator into a battery case, and before pouring an electrolytic solution, several electrodes are inserted between the positive electrode and the negative electrode. The inspection is performed by applying a DC voltage of about tens to several hundreds of volts and reading a leakage current (insulation resistance) at this time. That is, in a non-defective battery in which a micro short circuit does not occur between the electrodes, since the insulation between the positive electrode and the negative electrode is maintained by the separator, a leak current does not flow and a large resistance value is exhibited. In the electrode group in which conduction occurs, a leak current flows and shows a small resistance value, so that it is possible to discriminate between a good product and a defective product, and it is possible to discharge only a defective product.

[0007]

However, in the above-described detection method, the leakage current value between the electrodes when a DC voltage is applied depends on the state of use of the separator and the electrodes (water absorption depending on the production lot unit, etc.). (Varies in the amount and drying conditions) and is not constant because it varies, and there are also various types of minute short circuits between the electrodes, making it difficult to accurately capture only defective products. There is always a problem of erroneous discharge (a non-defective product is discharged as a defective product or a defective product is judged as a non-defective product).

For this reason, for example, even in an electrode group which is regarded as a non-defective product by the above-mentioned short-circuit inspection, after a battery is assembled by injecting an electrolytic solution and then subjected to a post-process such as initial charge and discharge, the state between the electrodes is changed. In some cases, it was changed and a short circuit occurred, resulting in a defective product.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method which comprises the steps of:
An inspection method for inspecting a short-circuit state of an electrode group comprising a positive electrode, a negative electrode, and a separator arranged so as to separate the two electrodes from each other. The values of the AC impedance or admittance and the phase angle are measured, and the short-circuit state of the electrode group is determined using these measured values.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION
It is directed to the above contents, particularly when an AC signal is applied between the positive and negative electrodes of the electrode group, the value of the AC impedance or admittance between both electrodes, and the value of the phase angle are measured, and these measured values are measured. To determine the short-circuit state of the electrode group.

As shown in FIG. 3, the electrode group of a small sealed secondary battery has a structure in which a positive electrode and a negative electrode face each other with a thin separator interposed therebetween, so that an AC signal is applied between both electrodes. , The reactance component 1 / 2πfC caused by the capacitor component in the battery structure is measured at the same time as the electric resistance R. (F indicates a frequency.)

That is, the electrode group of the small secondary battery can be approximated on an electric circuit as a parallel circuit of a resistor R and a capacitor C as shown in FIG. 2, and the AC impedance Z of such a circuit is expressed by the following equation. 1) and the phase angle θ is (Equation 2)
It is represented by

[0013]

(Equation 1)

[0014]

(Equation 2)

Here, R can be considered to be mainly the electric resistance of the separator interposed between the positive electrode and the negative electrode, and is a component greatly affected by a minute short circuit between the electrodes. C is a capacitance generated by a capacitor component between the two electrodes, and is a component that is greatly affected by a configuration state of the electrode group such as a facing area of the two electrode plates and a distance between the two electrode plates.

The AC impedance Z corresponds to the electric resistance in the DC circuit, and indicates the difficulty of current flow in the AC circuit. When the interval between the electrodes is closer than usual due to a defect in the configuration of the electrode group, the resistance R between the electrodes increases in proportion to the distance between the electrodes, and the capacitance C increases. Since the AC impedance Z between the two electrodes tends to be inversely proportional to the distance therebetween, the AC impedance Z between the two electrodes has a small value. Therefore, an electrode group having a lower value of the AC impedance Z than usual can be determined to be a latently defective electrode group that has a high possibility of causing a leak failure in a subsequent process since the electrodes are close to each other.

The phase angle θ represents the phase difference between the AC voltage and the AC current of the applied AC signal. In the circuit as shown in FIG. It is an index indicating how much C has an influence, and indicates a value from 0 ° to −90 °. If the measurement target can be regarded as a pure capacitor, the phase angle θ is -9
0 °, and the value of θ approaches the 0 ° side as the influence of the resistance component increases (as the electrical resistance decreases).

In the small secondary battery electrode group, the value of the phase angle θ depends on factors such as battery design and battery size, and varies depending on the type of battery to be measured.
Indicates the value of the degree.

In a non-defective electrode group having no short circuit, since the insulation between the electrodes is maintained, the value of the resistance R is sufficiently large.
Although the phase angle θ shows a value close to the −90 ° side, the resistance R is smaller than normal when part of the electrodes is partially short-circuited due to falling off of the active material or burrs of the electrodes. Therefore, the phase angle θ approaches the 0 ° side.

Therefore, an electrode group in which the phase angle θ between the two electrodes is closer to 0 ° than usual can be considered as an electrode group in which the insulation between the electrodes is reduced due to a minute short circuit or the like. .

As described above, when an AC signal is applied between the positive and negative electrodes of the electrode group, the AC impedance Z and the phase angle θ
It is possible to inspect for abnormalities in the electrode group such as micro short-circuit and configuration failure, and to select and discharge the short-circuit failure or the potentially defective electrode group with high possibility of short-circuit failure. is there.

In the above description, the short circuit state of the electrode group is determined by obtaining the AC impedance Z and the phase angle θ when an AC signal is applied between the positive and negative electrodes of the electrode group. Using a similar method, the admittance Y (Y = 1 / Z), which is the reciprocal of the AC impedance, and the phase angle can be obtained instead of the AC impedance Z to determine the short-circuit state of the electrode group.

The frequency of the AC signal used for this measurement is preferably 100 Hz to 10 kHz in order to accurately measure the state of the battery. This is 10kHz
If a higher frequency is used, the influence of the inductance component generated from the wiring part and the structure of the battery increases,
Further, when a frequency lower than 100 Hz is used, the influence of the reactance component caused by the capacitor component becomes large.

According to a fourth aspect of the present invention, there is provided an apparatus for inspecting a short circuit of an electrode group including a positive electrode, a negative electrode, and a separator arranged so as to isolate the two from each other at a stage prior to injecting an electrolyte when a battery is formed. In addition, the apparatus is configured to measure a contact terminal electrically connected to each of the positive electrode and the negative electrode, and an AC impedance and a phase angle when an AC signal is applied between both electrodes via the contact terminal. A short-circuit state of the electrode group is determined from the measured values of the AC impedance and the phase angle by the measuring device.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail.

FIG. 1 is a schematic view showing a battery 1 in which an electrode group to be measured is inserted into a battery case before injecting an electrolytic solution, and a short-circuit inspection apparatus A for inspecting a short-circuit state of the battery group in an embodiment of the present invention. is there.

In FIG. 1, reference numeral 1 denotes batteries 1, 2a and 2b before the injection of the electrolyte into which the electrode group to be measured is inserted into the battery case, and a pair of contact terminals 3a which are electrically connected to the positive electrode of the electrode group to be measured.
And 3b are a pair of contact terminals electrically connected to the negative electrode of the electrode group to be measured, and a measuring device (hereinafter referred to as a measuring device) of an AC impedance Z and a phase angle θ via lead wires 4, 5, 6, and 7, respectively. 8). Measuring device 8
Are the current detection terminal LCUR and the voltage detection terminals LPOT, H
It has a POT and a drive signal output terminal HCUR, and is connected to lead wires 4, 5, 6, and 7, respectively. An AC signal having a frequency of 1 kHz is applied between the contact terminals by the measuring device 8, and R and C of the electrode group are detected by a four-terminal measurement method. The value of the AC impedance Z between the contact terminals HCUR and the value of the phase angle θ are calculated at the same time by calculating by applying the expression 2).

Next, the measurement of the short circuit inspection of the electrode group by the short circuit inspection apparatus A will be described.

As the electrode group to be measured by the above-mentioned inspection apparatus 8, a standard nickel-hydrogen storage battery electrode group having a standard capacity of 1200 mAh and a battery size of AA was used. The composition is as follows: a nickel positive electrode having a structure in which nickel hydroxide powder is filled in a foamed nickel substrate as a positive electrode, and a hydrogen storage alloy electrode having a structure in which a hydrogen storage alloy paste is applied to the surface of a metal core material as a negative electrode. As a separator for separating the positive electrode and the negative electrode, a hydrophilic non-woven fabric made of polypropylene was used. The above-mentioned electrode group has a structure in which a spirally formed positive electrode, negative electrode, and separator are inserted into a metal battery case, and a positive electrode lead welded to the positive electrode protrudes outside the case. The negative electrode is welded to the battery case, and the battery case has a structure forming a negative electrode terminal.

At the stage before the injection of the electrolytic solution in such a battery configuration, an inspection for a short circuit of the electrode group was performed by the following method.

First, the battery 1 in which the electrode group to be measured was inserted into the battery case and before the electrolyte was injected was set in a measuring jig, and the contact terminals 2a and 2b were connected to the positive electrode lead of the battery 1 in which the electrode group to be measured was inserted into the battery case. The contact terminals 3a and 3b are brought into contact with the bottom of the battery case, respectively, to form a measurement circuit. Then, the measurement device 8 measures the values of the AC impedance Z and the phase angle θ between the electrodes when an AC signal is applied between the HCUR and the LCUR of the measurement device.

An electrode group in which the value of the AC impedance Z or the phase angle θ is out of the predetermined range is regarded as defective and is discharged from the process. An electrode group in which the values of the AC impedance Z and the phase angle θ are both within the specified ranges is regarded as a non-defective product and sent to the next step.

Since the values of the AC impedance Z and the phase angle θ differ depending on the type and size of the battery, the set values as the reference for the inspection are statistically calculated values 3σ (from the measured values of the electrode group of the battery to be measured). (sigma indicates a standard deviation).

As described above, the measurement method and the measurement apparatus according to the present invention can detect in detail the abnormality of the electrode group related to the minute short circuit from the values of the AC impedance Z and the phase angle θ of the electrode group. Accuracy is greatly improved.

In the above embodiment, the short-circuit state of the electrode group is determined by obtaining the AC impedance Z and the phase angle θ when an AC signal is applied between the positive and negative electrodes of the electrode group. Using the same method as in the above, instead of the AC impedance Z, the admittance Y (Y = 1 / Z), which is the reciprocal of the AC impedance, and the phase angle are determined to determine a set value as a reference for the inspection. Then, the short-circuit state of the electrode group can be determined by using the same method and the same inspection apparatus as those in the embodiment.

In the above embodiment, the electrode group of the cylindrical nickel-hydrogen storage battery was used as the electrode group of the battery to be inspected. However, the shape is not limited to the cylindrical type, and the square type can be similarly measured. In addition, the present invention can be applied to an electrode group having a similar structure, such as a nickel-cadmium storage battery or a lithium ion secondary battery.

[0037]

As described above, according to the inspection method and the inspection apparatus according to the present invention, the electrodes between the electrodes of the electrode group including the positive electrode, the negative electrode, and the separator interposed between the two electrodes are separated from each other. In the short-circuit inspection, the AC impedance Z or admittance between the two electrodes when an AC signal is applied between the electrodes, and the value of the phase angle θ are determined, and a short circuit between the electrodes is determined using these values. Since the abnormality of the electrode group caused by the minute short circuit can be detected in detail, the inspection accuracy of the short circuit failure is greatly improved.

[Brief description of the drawings]

FIG. 1 shows a battery in which an electrode group to be measured is inserted into a battery case,
Schematic diagram showing the short-circuit inspection device

FIG. 2 is a diagram in which an electrode group is regarded as a parallel circuit of a resistor R and a capacitor C;

FIG. 3 is a half sectional view of a cylindrical small secondary battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery before electrolyte injection 2 Contact terminal 3 Contact terminal 4 Lead wire 5 Lead wire 6 Lead wire 7 Lead wire 8 Measurement device

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Fumihiko Yoshii 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (6)

[Claims] 1. A method for inspecting a short-circuit state of an electrode group consisting of a positive electrode and a negative electrode and a separator arranged so as to separate the two from each other at a stage prior to injecting an electrolytic solution at the time of battery construction. Apply an AC signal to the AC impedance and admittance between both electrodes, and measure the value of the phase angle.
A battery electrode group short-circuit inspection method for determining a short-circuit state of the electrode group using these measured values. 2. The AC signal has a frequency of 100 Hz.
The method for inspecting a short circuit of an electrode group of a battery according to claim 1, wherein the pressure is 10 to 10 kHz. 3. The method according to claim 1, wherein the battery is a nickel-metal hydride storage battery. 4. A device for inspecting a short circuit of an electrode group consisting of a positive electrode and a negative electrode and a separator arranged so as to separate them from each other at a stage before injecting an electrolytic solution at the time of forming a battery. A contact terminal that is electrically connected to each of the positive electrode and the negative electrode, and a measuring device that measures an AC impedance or admittance when an AC signal is applied between both electrodes via the contact terminal, and a phase angle. An electrode group short-circuit inspection device for determining a short-circuit state of the electrode group from a measured value of a phase angle and AC impedance or admittance measured by the measuring device. 5. The AC signal has a frequency of 100 Hz.
The apparatus for inspecting a short circuit of an electrode group of a battery according to claim 4, wherein the frequency is 10 to 10 kHz. 6. The apparatus according to claim 4, wherein the battery is a nickel-metal hydride storage battery.