JP2010034001A - Inspection method of battery and separator for battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform determination on defective or non-defective product with a high degree of accuracy without causing damages to separators, and to accurately select good products with less losses. <P>SOLUTION: An inspection method for a separator used for a cell with a hydrophilic treatment applied thereto includes a current-value measuring process for applying a constant AC voltage E (V) causing no partial discharge in between a pair of electrodes 11, 12, in order to measure a current value I (mA) across metallic electrodes, under such condition that the front and back sides of the separator 10 is sandwiched by the pair of metallic electrodes 11, 12 with a surfacial area S (cm<SP>2</SP>) and a gap t (mm) between the electrodes; and a withstanding-factor measuring process for measuring a withstanding factor Z (Z=I×t/SE), based on the current value I (mA) measured at the current-value measuring process. The measured separator is screened out as defective if the measured withstanding factor Z is above a predetermined constant level. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for inspecting a battery separator that has been subjected to a hydrophilic treatment and a method for inspecting a battery that includes a separator that has been subjected to a hydrophilic treatment.

  In recent years, it has become necessary to accurately identify batteries that have a short cycle life and are likely to be short-circuited in the future (so-called latent short batteries). In particular, batteries that are used for applications such as hybrid electric vehicles (HEVs) and electric vehicles (PEVs) that require long battery life in series or have a longer lifespan are more stringent. It became necessary to sort out the short battery.

  Therefore, a voltage is applied between the electrodes in a state where the electrode group formed by winding or laminating a pair of electrodes consisting of a positive electrode and a negative electrode through a separator is not in contact with the electrolytic solution, and a dielectric breakdown occurs between the electrodes. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2000-195565) has proposed a method of detecting a current to detect and distinguishing a latent short battery from a non-defective battery.

  In the identification method proposed in Patent Document 1 described above, when the voltage applied between the electrodes is increased before the electrolyte is injected, the voltage is lower than the voltage at which arc discharge leading to dielectric breakdown occurs. Local discharge, that is, partial discharge may occur. In this partial discharge, if there are non-uniform parts (for example, defects, voids, etc.) in the separator, the electrostatic capacity of that part is small, so when a voltage is applied, it is discharged at a lower voltage than other parts. Is caused by the occurrence of

When such partial discharge occurs, ozone, nitrogen oxides, etc. are generated and the separator is deteriorated. For this reason, even if the voltage of the normal battery electrode group is lower than the dielectric breakdown, partial discharge may occur in the separator, which may damage the separator of the normal battery electrode group.
Against this background, a defective product inspection method for accurately discriminating the electrode group of the latent short battery without damaging the electrode group of the normal battery has been desired.

Therefore, a defective product inspection method for accurately discriminating the electrode group of the latent short battery has been proposed in Japanese Patent Application Laid-Open No. 2004-342476.
In the defective product inspection method proposed in Patent Document 2, a voltage is applied to an electrode group composed of a pair of electrodes facing each other via a separator to cause a current to flow through the electrode group. The quality of the electrode group is determined by comparing with a predetermined current flowing through the electrode group.
JP 2000-195565 A JP 2004-342476 A

However, in the defective product inspection method proposed in Patent Document 2 described above, since a non-defective product and a defective product are determined only by the magnitude of the energization current, the reliability is inferior and high-precision determination cannot be performed. It was.
This is because the energization current varies due to variations in the physical properties of the separator. In other words, when the current value of the latent short determination is set low, it may be determined that even the non-defective battery is defective, and the loss occurrence ratio may be large. On the other hand, when the current value of the latent short determination is set high, even a defective product is determined as a non-defective battery, and the defective product may flow out and reliability may be impaired.

For this reason, the separator is inspected for the basis weight (that is, the fiber amount) of the separator to be used and the degree of hydrophilic treatment.
However, not only variations in physical properties of separators, but also variations in hydrophilization treatment (for example, variations in functional group amounts and residual components resulting from hydrophilization treatment) and variations in separator storage conditions (for example, outside the hoop) Non-defective batteries may be judged as potential short batteries (pseudo shorts) due to variations in the dielectric constant of the separator due to the degree of contact with outside air, etc. I couldn't say it was done.

  Accordingly, the present invention has been made to solve the above-described problem, and it is possible to accurately determine whether a separator is good or bad without damaging the separator, and to reduce the occurrence of loss, and a potential short battery. It is an object of the present invention to provide a battery separator inspection method and a battery inspection method capable of accurately determining the above.

The method for inspecting a battery separator having been subjected to the hydrophilization treatment according to the present invention comprises a pair of metal electrodes arranged so that the surface area is S (cm ² ) and the distance between the electrodes is t (mm). A current value measuring step for measuring a current value I (mA) flowing between the pair of electrodes by applying an AC voltage E (V) between the pair of electrodes so that a partial discharge does not occur in a state where the electrode is sandwiched, and a current value measurement A withstand voltage index calculating step for obtaining a withstand voltage index Z (Z = I × (t / SE)) based on the current value I (mA) measured in the process, and the obtained withstand voltage index Z is equal to or greater than a preset value. If so, it is excluded as an unused separator.

When an AC voltage is applied in a state where the front and back surfaces of the separator are sandwiched between a pair of metal electrodes, the space between these electrodes can be regarded as a kind of capacitor. The current flowing between the pair of electrodes decreases as the distance between the electrodes increases, and increases as the facing area increases. Therefore, when a voltage of E (V) is applied between a pair of metal electrodes having a surface area of S (cm ² ) and a distance between electrodes of t (mm), a current of I (mA) flows between the metal electrodes. Then, the amount of current I (mA) flowing between the metal electrodes is affected by the interelectrode distance (t), the surface area (S), and the applied voltage (E). Therefore, when these values fluctuate, it is necessary to correct them. Arise.

  Therefore, if the magnitude of the amount of current flowing between the metal electrodes is defined as a withstand voltage index Z, a relational expression of Z = I × (t / SE) is obtained. If the pressure index Z is large, it means that the current flowing between the separators is large. Therefore, if a reference value (threshold value) is set in advance, a separator having a pressure index Z larger than the threshold value, that is, large variation. The separator can be eliminated in advance. For this reason, the present invention includes a withstand voltage index calculating step for obtaining a withstand voltage index Z (Z = I × (t / SE)) based on the current value I (mA) measured in the current value measuring step. If the pressure index Z is equal to or greater than a preset value, it is excluded as an unused separator. Thereby, it becomes possible to reduce the variation of the separator to be used.

On the other hand, the method for inspecting a battery having a separator subjected to the hydrophilization treatment of the present invention is a pair of metal electrodes arranged so that the surface area is S (cm ² ) and the distance between the electrodes is t (mm). A current value measuring step of measuring the current value I (mA) flowing between the pair of electrodes by applying an alternating voltage E (V) between the pair of electrodes, in which the partial discharge does not occur with the front and back surfaces of the separator sandwiched; The withstand voltage index calculating step for obtaining the withstand voltage index Z (Z = I × (t / SE)) based on the current value I (mA) measured in the current value measuring step, and the obtained withstand voltage index Z is preset. If the value is equal to or greater than the value, a separator exclusion process that eliminates the separator as an unused separator, and a positive / negative electrode group formed by winding or stacking a positive electrode plate and a negative electrode plate via a separator that is not excluded by the separator exclusion process Partial discharge occurs between the electrodes A current value measurement step of measuring a current value I (mA) flowing between the electrodes by applying a high AC voltage E (V), and a potential based on the current value I (mA) measured in the current value measurement step And a latent short determination step for determining a short.

  Thereby, since the used separator is a separator with small variations, it is possible to suppress variations in the current value in the voltage application inspection in the electrode group, and the discrimination accuracy of the potential short circuit is remarkably improved. In addition, since the current value flowing through the electrode group can be reduced and stabilized, the current specification of the measuring device can be reduced, and the measuring device can be provided at low cost.

  In the present invention, if the obtained withstand pressure index Z is equal to or greater than a preset value, it is excluded as a non-use separator. Therefore, it is possible to reduce variations in separators used. Before determining the electrode group, it is determined whether the separator is good or bad, and the electrode group is formed using only the separator determined to be good. As a result, variations in separators can be suppressed, and variations in current values can also be suppressed, so that the accuracy of determining potential short-circuits is greatly improved.

  Next, embodiments of the present invention will be described in detail below. However, the present invention is not limited to these embodiments, and can be appropriately modified and implemented without departing from the scope of the present invention. FIG. 1 is a plan view schematically showing a state in which an AC voltage is applied to the separator of the present invention to perform a voltage application test. FIG. 2 is a perspective view schematically showing a spiral electrode group formed by winding a pair of electrodes composed of a positive electrode and a negative electrode through a separator. 3 is a cross-sectional view schematically showing a state in which a voltage application inspection is performed by applying an AC voltage to a spiral electrode body formed by welding positive and negative current collectors to the spiral electrode group of FIG. It is. FIG. 4 is a cross-sectional view schematically showing a nickel-hydrogen storage battery as an example of the present invention.

1. Separator Having a liquid retention performance as a function of the separator is essential from the viewpoint of battery characteristics. In this case, as a method for retaining the liquid retention performance in the separator, there is a method of using a hydrophilic fiber such as a nylon resin in addition to a method of hydrophilizing a non-hydrophilic fiber such as a polyolefin resin. is there. Here, in separators used in batteries for applications that require high durability such as HEV and PEV, since materials such as nylon resin fibers are decomposed and deteriorated, there is a problem in durability. A method of hydrophilizing a polyolefin resin fiber is used.

Therefore, in the present invention, as the separator 10, a non-woven sheet formed by wet papermaking of a single fiber made only of polypropylene and a core-sheath fiber made of polypropylene and polyethylene is used. In this case, in order to hydrophilize the nonwoven fabric sheet, a functional group such as a sulfonic acid group is introduced into the nonwoven fabric sheet in contact with a mixed gas containing a fluorine gas and a reactive gas containing a sulfur atom. ing. The separator 10 is formed so as to have a basis weight of 50 g / m ² and a thickness of 0.13 mm.

  When the hydrophilization treatment is performed as described above, the liquid retention performance varies due to variations in functional groups and variations in the residue of the hydrophilization treatment. For this reason, using seven types of separators 10 consisting of a, b, c, d, e, f, and g, the functional group amount of each separator a, b, c, d, e, f, and g (in this case, , S (sulfur) amount) was determined by XPS (X-ray Photoelectron Spectroscopy). Then, the results shown in Table 1 below were obtained. In this case, based on the obtained functional group amount, the functional group amount of the separator a is set to 10, and the functional group amounts of the other separators b, c, d, e, f, and g are compared with the ratio (functional group amount ratio). It showed in. The separator a is a reference separator, and is picked up from the production process based on empirical rules and the like as having a stable quality.

Next, the pressure resistance index Z of each of the separators a, b, c, d, e, f, and g described above was obtained as follows. That is, as shown in FIG. 1, a separator 10 (a, b, c, d, e, f, g) formed to have a thickness of 0.13 mm has a planar size of 5 cm × 5 cm (planar It was sandwiched between a pair of nickel metal electrodes 11 and 12 having an area S (S = 25 cm ² ) so that the distance t was 0.1 mm (t = 0.1 mm). Thereafter, an AC voltage (E = 150 V) of 150 V at 60 Hz and the current detection circuit 16 were connected between the terminal portion 11 a of the electrode 11 and the terminal portion 12 a of the electrode 12.

Next, an AC voltage of 150 V at 60 Hz (E = 150 V) is applied from the AC voltage source 15 between these terminal portions 11a and 12a, and the current value I (mA) flowing between the electrodes 11 and 12 is detected by current. Measured with circuit 16. And when the pressure | voltage resistant index | exponent Z was calculated | required as Z = I * (t / SE) based on the measured electric current value I (mA), the result as shown in following Table 1 was obtained. In Table 1, the obtained pressure resistance index Z of the separator a is expressed as 10, and the pressure resistance index Z of the other separators b, c, d, e, f, and g is expressed as a ratio (pressure resistance ratio). Yes.

  As is clear from the results in Table 1, the amount of the functional group (S amount) was examined as an index for knowing the degree of variation of the separator, but the pressure resistance index Z (note that the pressure resistance index Z is t , S, and E are constant, which is proportional to the measured current value). This is to measure the amount of S (sulfur) in order to know the amount of functional groups introduced by the hydrophilization treatment, but hydrophilicity (liquid retention performance) depends only on the amount of functional groups (S amount). This is because it is considered that the functional group amount (S amount), the residual component of the hydrophilization treatment, the moisture in the air, and the like are affected.

  Then, based on the results of Table 1, the separators e and f having a pressure index ratio (Z ratio) of 200 (in this case, 200 is a threshold) or more are excluded, and the pressure index ratio (Z ratio) is 200. The separators a, b, c, d, and g that are less than (threshold value) were adopted as non-defective separators. Note that as the set value (threshold value) of the pressure resistance index ratio (Z ratio) is set lower, the variation in the separator can be reduced. As a result, in the inspection of the battery in the post process, those having a short distance between the electrodes are excluded, and the inspection becomes high in quality. However, as a separator, the probability of being rejected as a defective product increases. After all, the set value (threshold value) of the pressure index ratio (Z ratio) is about the variation of the separators and whether they become defective when they are assembled (strict inspection standards for batteries are discharged and pseudo short products are also discharged) It is desirable to set appropriately considering this.

2. Electrode body (1) Hydrogen storage alloy negative electrode First, a water storage binder comprising 0.1 mass% of CMC (carboxymethylcellulose) and water (or pure water) with respect to 100 mass parts of the hydrogen storage alloy powder. A styrene butadiene latex (SBR) and a carbon-based conductive agent were added. Thereafter, these were mixed and kneaded to prepare a hydrogen storage alloy slurry. Next, a negative electrode core 21 made of a Ni-plated mild steel porous substrate (punching metal) is prepared, and a hydrogen storage alloy slurry is added to the negative electrode core 21 so that the filling density is 5.0 g / cm ^3. After applying and drying, the active material layer 22 was formed by rolling to a predetermined thickness. Then, it cut | disconnected so that it might become a predetermined dimension, and the hydrogen storage alloy negative electrode 20 was produced.

(2) Nickel Positive Electrode On the other hand, a porous nickel sintered substrate 31 having a porosity of about 85% is immersed in a mixed aqueous solution of nickel nitrate and cobalt nitrate having a specific gravity of 1.75. Inside, nickel salt and cobalt salt were retained. Thereafter, the porous nickel sintered substrate was immersed in a 25% by mass sodium hydroxide (NaOH) aqueous solution to convert the nickel salt and the cobalt salt into nickel hydroxide and cobalt hydroxide, respectively.

Next, after thoroughly washing with water to remove the alkaline solution, drying was performed, and the pores of the porous nickel sintered substrate 31 were filled with an active material mainly composed of nickel hydroxide. Such an active material filling operation is repeated a predetermined number of times (for example, 6 times), so that the packing density of the active material 32 mainly composed of nickel hydroxide in the pores of the porous sintered substrate 31 becomes 2.5 g / cm ³ . It filled so that it might become. Then, after making it dry at room temperature, it cut | disconnected to the predetermined dimension and the nickel positive electrode 30 was produced.

(3) Electrode body Thereafter, the hydrogen storage alloy negative electrode 20 and the nickel positive electrode 30 produced as described above are used, and a separator 10 (a, b, c, d, g) is interposed therebetween. A spiral electrode group was prepared by spirally winding. The core exposed portion 23 of the hydrogen storage alloy negative electrode 20 is exposed at the lower part of the spiral electrode group thus produced, and the core exposed portion 33 of the nickel positive electrode 30 is exposed at the upper portion thereof. ing. Next, the negative electrode current collector 24 is welded to the core exposed portion 23 exposed at the lower end surface of the obtained spiral electrode group, and the core exposed portion 33 of the nickel positive electrode 30 exposed at the upper end surface of the spiral electrode group. A positive electrode current collector 34 was welded onto the electrode body A to obtain an electrode body A (A1 to A4, A7). The electrode body A1 is provided with the separator a, the electrode body A2 is provided with the separator b, the electrode body A3 is provided with the separator c, and the electrode body A4 is provided with the separator d. The electrode body A7 was provided with the separator g.

  On the other hand, a hydrogen storage alloy negative electrode 20 and a nickel positive electrode 30 are used, and a separator 10 (a, b, c, d, e, f, g) is interposed between them to form a spiral electrode. After forming the group, the negative electrode current collector 24 and the positive electrode current collector 34 were welded in the same manner as described above to obtain an electrode body X (X1 to X7). The electrode body X1 is provided with the separator a, the electrode body X2 is provided with the separator b, the electrode body X3 is provided with the separator c, and the electrode body X4 is provided with the separator d. The electrode body X5 was provided with the separator e, the electrode body X6 was provided with the separator f, and the electrode body X7 was provided with the separator g.

(4) Voltage application inspection Next, using the obtained electrode body A (A1 to A4, A7) and electrode body X (X1 to X7), the voltage application electrode 25 was connected to the negative electrode current collector 24 and the positive electrode After connecting the voltage application electrode 35 to the current collector 34, an AC voltage of 150 V at 60 Hz (E = 150 V) is applied between these electrodes 25, 35 from the AC voltage source 40 for 5 seconds. The current value I (mA) flowing between the currents 35 was measured by the current detection circuit 50. Next, based on the obtained current value I (mA), the current value I (mA) of the electrode bodies A1, X1 using the separator a is set to 10, and the other separators b, c, d, e, f, g When the current values I (mA) of the electrode bodies A2 to A4 and A7 and the electrode bodies X2 to X7 using the above were shown as a ratio (current value ratio) to the current values I, the results shown in Table 2 below were obtained.
In addition, after the voltage application inspection, the electrode bodies A1 to A4 and A7 and the electrode bodies X1 to X7 were disassembled and examined, and no potential short circuit occurred in each of the electrode bodies A1 to A4 and A7 and the electrode bodies X1 to X7. It was confirmed.

As is clear from the results of Table 2 above, it can be seen that the maximum current value ratio is 30 in the electrode body A, whereas the maximum current value ratio is 80 in the electrode body X. From this, it can be seen that the electrode body A can suppress the current value in the voltage application inspection to be lower.
That is, for example, when the increase in the current value due to the potential short is +30, the electrode body X may not be able to determine a defective product. This is because it is determined that the product is non-defective when 10 + 30 = 40 when 110 of +30 is set as the threshold for 80 at the maximum. In addition, it may be determined that even a non-defective product is a defective product. This is because it is determined that 80 (X5) and 45 (X6) which are non-defective products are defective when 10 + 30 = 40 is set as a threshold value.
On the other hand, in the electrode body A, a non-defective product is determined to be a non-defective product, and a defective product is determined to be a defective product. This is because when 10 + 30 = 40 is set as a threshold value, all can be determined as non-defective products.
Regarding the threshold value of the energization amount of the separator and the threshold value in the voltage application test of the spiral electrode body, the battery design such as the separator thickness and the electrode plate surface area, the waste loss in the separator and the waste loss in the spiral electrode body It may be set in consideration of the relationship of

3. Nickel-hydrogen storage battery Next, an example of manufacturing a nickel-hydrogen storage battery using the electrode body A (A1 to A4, A7) manufactured as described above will be described below. In this case, after the obtained electrode body A (A1 to A4, A7) is accommodated in a bottomed cylindrical outer can 60 in which nickel is plated on iron (the outer surface of the bottom surface becomes a negative electrode external terminal), the negative electrode The current collector 24 was welded to the inner bottom surface of the outer can 60. On the other hand, the current collecting lead portion 35 extending from the positive electrode current collector 34 was welded to a sealing plate 62a constituting the bottom portion of the sealing body 62 that also served as a positive electrode terminal and was fitted with an insulating gasket 61 on the outer peripheral portion. The sealing body 62 is provided with a positive electrode cap 62b, and a pressure valve including a valve body 62c and a spring 62d which are deformed when a predetermined pressure is reached is disposed in the positive electrode cap 62b.

  Next, after forming the annular groove 63 on the outer periphery of the upper portion of the outer can 60, the electrolyte was injected, and the outer peripheral portion of the sealing body 62 was mounted on the annular groove 63 formed on the upper portion of the outer can 60. An insulating gasket 61 was placed. Then, the nickel-hydrogen storage battery is produced by caulking the opening edge 64 of the outer can 60. In this case, an alkaline electrolyte composed of a 30% by mass potassium hydroxide (KOH) aqueous solution in the outer can 60 is 2.5 g (2.5 g / Ah) or 2.8 g (2.8 g) per battery capacity (Ah). / Ah).

  In the above-described embodiment, an example in which the present invention is applied to a method for manufacturing a nickel-hydrogen storage battery has been described. However, the manufacturing method of the present invention is not limited to a nickel-hydrogen storage battery, and other alkaline storage batteries can be manufactured. Of course, the method can also be applied. Moreover, the manufacturing method of this invention is not restricted only to the manufacturing method of alkaline electrical storage, It can apply to any battery as long as it is a battery provided with the separator to which the hydrophilic treatment was performed.

It is a top view which shows typically the state which applies an alternating voltage to the separator of this invention and performs a voltage application test | inspection. It is a perspective view which shows typically the spiral electrode group formed by winding a pair of electrode which consists of a positive electrode and a negative electrode through a separator. It is sectional drawing which shows typically the state which applies an alternating voltage to the spiral electrode body formed by welding a positive / negative collector to the spiral electrode group of FIG. 2, and performs a voltage application test | inspection. It is sectional drawing which shows typically the nickel-hydrogen storage battery of an example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Separator, 11, 12 ... Nickel metal electrode, 15 ... AC voltage source, 16 ... Current detection circuit, 20 ... Hydrogen storage alloy negative electrode, 21 ... Negative electrode core, 22 ... Active material layer, 23 ... Core body exposure part 24 ... negative electrode current collector, 30 ... nickel positive electrode, 31 ... nickel sintered substrate, 33 ... core exposed portion, 34 ... positive electrode current collector, 34a ... positive electrode lead, 40 ... AC voltage source, 50 ... current detection Circuit: 60 ... exterior can, 61 ... insulating gasket, 62 ... sealing body, 62a ... sealing plate, 62b ... positive electrode cap, 62c ... valve plate, 62d ... spring, 63 ... annular groove, 64 ... opening edge

Claims (2)

A method for inspecting a battery separator that has been subjected to a hydrophilic treatment,
AC voltage E (V) at which partial discharge does not occur in a state where the front and back surfaces of the separator are sandwiched between a pair of metal electrodes arranged so that the surface area is S (cm ² ) and the distance between the electrodes is t (mm) A current value measuring step of measuring a current value I (mA) applied between the pair of electrodes and flowing between the metal electrodes;
A withstand voltage index calculating step of obtaining a withstand voltage index Z (Z = I × (t / SE)) based on the current value I (mA) measured in the current value measuring step,
An inspection method for a battery separator, characterized in that if the obtained pressure resistance index Z is equal to or greater than a preset value, it is excluded as an unused separator. A method for inspecting a battery comprising a separator subjected to a hydrophilic treatment,
AC voltage E (V) at which partial discharge does not occur in a state where the front and back surfaces of the separator are sandwiched between a pair of metal electrodes arranged so that the surface area is S (cm ² ) and the distance between the electrodes is t (mm) A current value measuring step of measuring a current value I (mA) applied between the pair of electrodes and flowing between the metal electrodes;
A withstand voltage index calculating step for obtaining a withstand voltage index Z (Z = I × (t / SE)) based on the current value I (mA) measured in the current value measuring step;
If the determined pressure index Z is equal to or greater than a preset value, a separator removing step of eliminating as a non-use separator,
AC voltage E (V) at which partial discharge does not occur between the positive and negative electrodes of the electrode group formed by winding or laminating the positive electrode plate and the negative electrode plate through the separator not excluded by the separator excluding step. A current value measuring step of measuring a current value I (mA) flowing between the electrodes when applied;
A method for inspecting a battery, comprising: a potential short determination step for determining a potential short based on the current value I (mA) measured in the current value measurement step.

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