JP2015197968A - Impregnation inspection device and impregnation inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately obtain the degree of impregnation of a battery electrode with an electrolyte.SOLUTION: An impregnation inspection device 1 for inspecting the degree of impregnation of a battery electrode with an electrolyte includes an ultrasonic output unit 11, ultrasonic reception unit 12 and an impregnation degree determination unit 13. The ultrasonic output unit 11 outputs an ultrasonic wave toward a battery electrode impregnated with an electrolyte. The ultrasonic reception unit 12 is disposed at a position opposing to the ultrasonic output unit 11 across the battery electrode and receives the ultrasonic wave output from the ultrasonic output unit 11. The impregnation degree determination unit 13 calculates an attenuation factor of the ultrasonic wave received by the ultrasonic reception unit 12 with respect to the ultrasonic wave output by the ultrasonic output unit 11 and determines the degree of impregnation of the battery electrode with the electrolyte on the basis of the calculated attenuation factor.

Description

  The present invention relates to an impregnation inspection apparatus and an impregnation inspection method for inspecting the degree of impregnation of an electrolytic solution into a battery electrode.

  A battery is manufactured by enclosing components such as electrodes and electrolyte in a case.

  For example, in the case of a lithium ion secondary battery, a power generation element is configured by sandwiching a separator between a positive electrode and a negative electrode, and after the power generation element is arranged in the case, an electrolytic solution is injected into the case. After the injected electrolytic solution has soaked into the entire positive electrode and negative electrode, and the impregnation of the electrolytic solution into the positive electrode and negative electrode is completed, the process proceeds to the next manufacturing process.

  The impregnation time for impregnating the electrolyte with the electrode is determined, for example, by performing a test in advance. In the preliminary test, first, the impregnation time is changed for each electrode, and each electrode is disassembled to determine visually whether or not the impregnation is completed. Next, a predetermined margin time is added to the impregnation time at the electrode that is determined to be disassembled and impregnation is completed, and the addition result is set as the final impregnation time.

  Here, the rate at which the electrode is impregnated with the electrolytic solution varies depending on the temperature of the electrode and the electrolytic solution during the impregnation, and also varies depending on the properties of the electrode and the electrolytic solution. For this reason, if the impregnation time is uniformly set in the preliminary test as described above, there is a possibility that the process proceeds to the next manufacturing process even though the impregnation of the electrolyte into the electrode is not completed. In this case, the battery capacity may change, and the quality of the battery may be reduced. Therefore, the above margin time is set longer.

  However, the state in which the electrode is impregnated with the electrolytic solution is equivalent to the overdischarge state. For this reason, although there is a process of performing temporary charging in the subsequent manufacturing process, if the margin time is set to be long as described above, the process proceeds to the next manufacturing process even when the electrode is completely impregnated with the electrolyte. There is a possibility that the state of overdischarge will continue and the state of overdischarge will continue. Even in this case, the quality of the battery may be deteriorated.

  Therefore, a method has been proposed for determining whether or not the impregnation of the electrolyte into the electrode is completed by measuring the impedance of the electrode (see, for example, Patent Document 1). According to this method, the degree of impregnation of the electrolyte into the electrode can be confirmed for each electrode. For this reason, it is not necessary to set the impregnation time uniformly, and the above margin time is also unnecessary. Therefore, the deterioration of the quality as a battery can be suppressed.

Japanese Patent Application Laid-Open No. 2004-313143

  However, even if the electrode is not completely impregnated with the electrolytic solution, conduction within the electrode is established when the impregnation proceeds to some extent. For this reason, there is almost no difference between the impedance of the electrode when the impregnation has progressed to some extent and the impedance of the electrode when the impregnation of the electrolyte into the electrode is completed.

  For this reason, in the method shown in Patent Document 1, it is difficult to accurately determine the degree of impregnation of the electrolyte into the electrode. There was a possibility of shifting to the manufacturing process. For this reason, since it was necessary to set the impregnation time longer as in the above-described margin time, there was still a possibility that the overdischarge state would continue, and there was still a possibility that the quality of the battery would deteriorate. .

  Accordingly, the present invention has been made in view of the above-described problems, and an object thereof is to accurately obtain the degree of impregnation of the electrolytic solution into the battery electrode.

  The present invention proposes the following items in order to solve the above-described problems. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected and demonstrated, it is not limited to this.

  (1) The present invention is an impregnation inspection apparatus (for example, equivalent to the impregnation inspection apparatus 1 in FIG. 1) for inspecting the degree of impregnation of the electrolyte into the battery electrode (for example, equivalent to the battery electrode 100 in FIG. 2). Output means for outputting an ultrasonic wave toward the battery electrode impregnated with the electrolytic solution (for example, equivalent to the ultrasonic output unit 11 in FIG. 1), and a position facing the output means with the battery electrode interposed therebetween. A receiving means (for example, equivalent to the ultrasonic receiving unit 12 in FIG. 1) that receives the ultrasonic waves output by the output means, and the receiving means for the ultrasonic waves output by the output means. And an impregnation degree determination means (for example, equivalent to the impregnation degree determination unit 13 in FIG. 1) for obtaining an attenuation rate of the ultrasonic wave and obtaining an impregnation degree of the electrolytic solution into the battery electrode according to the obtained attenuation rate. Impregnation inspection device characterized in that It is proposed.

  Here, as the impregnation of the electrolyte into the battery electrode proceeds, the amount of bubbles present in the battery electrode decreases. However, since the ultrasonic wave is reflected when it hits the bubble, the attenuation rate of the ultrasonic wave is Varies depending on the amount. Therefore, according to the present invention, the output means outputs an ultrasonic wave toward the battery electrode, the reception means receives the ultrasonic wave, and the impregnation condition determination means outputs the ultrasonic wave toward the battery electrode. The degree of impregnation was determined according to the decay rate of. For this reason, the impregnation degree of the electrolyte solution to the battery electrode can be accurately obtained from the attenuation rate of the ultrasonic wave.

  (2) The present invention relates to the impregnation inspection apparatus according to (1), wherein the impregnation condition determining means has a change amount of the attenuation rate per unit time equal to or less than a predetermined threshold (for example, equivalent to zero described later). Then, the impregnation test | inspection apparatus characterized by determining with impregnation of the electrolyte solution to the said battery electrode being completed is proposed.

  Here, as the impregnation of the battery electrode with the electrolytic solution proceeds, the amount of bubbles present in the battery electrode decreases, so that the amount of change per unit time of the attenuation factor becomes small. Therefore, according to the present invention, in the impregnation inspection apparatus of (1), when the amount of change per unit time in the attenuation rate is equal to or less than the threshold value by the impregnation condition determination means, the impregnation of the electrolyte into the battery electrode is completed. It was decided that it was. For this reason, by setting the threshold value, it is possible to accurately determine the degree of impregnation of the electrolyte into the battery electrode.

  (3) The present invention proposes an impregnation inspection apparatus according to (1) or (2), wherein the output means outputs an ultrasonic wave toward the center of the battery electrode. Yes.

  According to the present invention, in the impregnation inspection apparatus of (1) or (2), the output means outputs ultrasonic waves toward the center of the battery electrode. For this reason, since the degree of impregnation of the electrolytic solution can be obtained for the center of the battery electrode where the completion of the impregnation is assumed to be the slowest, the portion where the impregnation of the electrolytic solution is not completed does not exist in the battery electrode Can be.

  (4) In the impregnation inspection apparatus according to (1) or (2), the output unit outputs an ultrasonic wave to each of a plurality of points of the battery electrode, and the reception unit The impregnation inspection apparatus is characterized in that it receives each of the ultrasonic waves output to a plurality of points of the battery electrode by means.

  According to the present invention, in the impregnation inspection apparatus of (1) or (2), the output means outputs ultrasonic waves to each of the plurality of points of the battery electrode, and each of the ultrasonic waves is received by the receiving means. It was decided to. For this reason, the attenuation rate of the ultrasonic wave at each of a plurality of points of the battery electrode can be obtained, and from this plurality of attenuation factors, how much impregnation has progressed in which part of the battery electrode can be obtained. Therefore, it is possible to estimate how much time the impregnation is completed in the entire battery electrode.

  (5) The present invention is an impregnation inspection method for inspecting the degree of impregnation of an electrolytic solution into a battery electrode (for example, equivalent to the battery electrode 100 in FIG. 2), toward the battery electrode impregnated with the electrolytic solution. A first step of outputting an ultrasonic wave, and a first step of receiving the ultrasonic wave output by the first step at a position opposite to the position where the ultrasonic wave is output by the first step across the battery electrode. The attenuation rate of the ultrasonic wave received by the second step with respect to the ultrasonic wave output by the step 2 and the first step is obtained, and the electrolyte solution to the battery electrode is determined according to the obtained attenuation rate. And a third step for determining the degree of impregnation.

  According to the present invention, the same effects as described above can be obtained.

  (6) The present invention is a method for manufacturing a battery having in a case a power generation element configured by sandwiching a separator between a positive electrode and a negative electrode, which are battery electrodes, and an electrolytic solution, and the power generation in the case A first step of injecting an electrolytic solution after inserting an element, a second step of outputting an ultrasonic wave toward the battery electrode impregnated with the electrolytic solution, and outputting an ultrasonic wave by the second step A third step for receiving the ultrasonic wave output by the second step at a position facing the position across the battery electrode, and the third step for the ultrasonic wave output by the second step. The fourth step for obtaining the attenuation rate of the ultrasonic wave received in the step and determining the degree of impregnation of the electrolyte into the battery electrode according to the obtained attenuation rate, and the degree of impregnation obtained in the fourth step are predetermined. Threshold And a fifth step of shifting to a subsequent process including a charging process when it is determined that the threshold value is equal to or less than the threshold value. ing.

  According to the present invention, effects similar to those described above can be achieved for the battery electrode housed in the case after the injection of the electrolytic solution.

  According to the present invention, the degree of impregnation of the electrolytic solution into the battery electrode can be accurately obtained.

It is a block diagram of the impregnation test | inspection apparatus which concerns on one Embodiment of this invention. It is a schematic diagram which shows the relationship between the ultrasonic output part and ultrasonic reception part with which the impregnation test | inspection apparatus which concerns on one Embodiment of this invention is provided, and an electric power generation element. It is a schematic diagram which shows the relationship between the ultrasonic output part and ultrasonic reception part with which the impregnation test | inspection apparatus which concerns on one Embodiment of this invention is provided, and an electric power generation element. It is a schematic diagram which shows a mode that an ultrasonic wave attenuate | damps. It is a figure which shows the relationship between the attenuation factor of an ultrasonic wave, and an impregnation condition. It is a schematic diagram which shows the relationship between the ultrasonic output part and ultrasonic reception part with which the impregnation test | inspection apparatus which concerns on the modification of this invention is provided, and an electric power generation element.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the constituent elements in the following embodiments can be appropriately replaced with existing constituent elements, and various variations including combinations with other existing constituent elements are possible. Accordingly, the description of the following embodiments does not limit the contents of the invention described in the claims.

  FIG. 1 is a block diagram of an impregnation inspection apparatus 1 according to an embodiment of the present invention. The impregnation inspection apparatus 1 inspects the degree of impregnation of the electrolytic solution into the battery electrode 100 (see FIG. 2), and includes an ultrasonic output unit 11, an ultrasonic reception unit 12, and an impregnation state determination unit 13.

  FIG. 2 is a schematic diagram illustrating a relationship among the ultrasonic output unit 11, the ultrasonic reception unit 12, and the battery electrode 100. In the present embodiment, the battery electrode 100 is one positive electrode or negative electrode of a lithium ion secondary battery, and is formed in a flat plate shape.

  The ultrasonic output unit 11 is provided in a direction and a position facing the battery electrode 100. Further, the ultrasonic receiving unit 12 is provided at a position facing the ultrasonic output unit 11 with the battery electrode 100 interposed therebetween.

  Returning to FIG. 1, the ultrasonic output unit 11 outputs ultrasonic waves toward the battery electrode 100. Here, as described above, the battery electrode 100 is formed in a flat plate shape, and the ultrasonic output unit 11 is provided in a direction and a position facing the battery electrode 100. For this reason, the ultrasonic wave output from the ultrasonic wave output unit 11 strikes the battery electrode 100 from a direction orthogonal to the surface of the battery electrode 100. In addition, the upper limit of the frequency of the ultrasonic wave output from the ultrasonic output unit 11 is 4 MHz, and the lower limit is 0.5 MHz.

  The ultrasonic receiver 12 receives the ultrasonic wave output from the ultrasonic output unit 11 at a position facing the ultrasonic output unit 11 with the battery electrode 100 interposed therebetween.

  FIG. 3 is a schematic diagram showing to which position of the battery electrode 100 the ultrasonic output unit 11 outputs ultrasonic waves. The ultrasonic output unit 11 outputs ultrasonic waves toward the portion of the battery electrode 100 where the impregnation with the electrolyte solution is slowest. Here, in the battery electrode 100 formed in a flat plate shape, the part where the impregnation of the electrolyte solution is the slowest is the center of the battery electrode 100, that is, the center of gravity of the battery electrode 100.

  FIG. 4 is a schematic diagram illustrating how the ultrasonic waves are attenuated in the battery electrode 100. As the battery electrode 100 is impregnated with the electrolytic solution, the amount of bubbles present in the battery electrode 100 decreases, and the ultrasonic waves are reflected and attenuated when they hit the bubbles. For this reason, the attenuation rate of the ultrasonic wave changes according to the amount of bubbles existing in the battery electrode 100.

  FIG. 5 is a diagram showing the relationship between the attenuation rate of ultrasonic waves and the impregnation time. In FIG. 5, the vertical axis indicates the attenuation rate of ultrasonic waves, and the horizontal axis indicates the impregnation time, which is the time since the start of the impregnation of the electrolytic solution into the battery electrode 100.

  When impregnation of the battery electrode 100 with the electrolytic solution is started, the attenuation rate of the ultrasonic wave first decreases, then increases, and finally becomes level and hardly changes. That is, the amount of change per unit time of the attenuation rate of the ultrasonic wave is large immediately after the impregnation of the electrolytic solution into the battery electrode 100, but decreases as time elapses.

  Here, since the impregnation of the electrolyte into the battery electrode 100 proceeds for a while after the impregnation of the electrolyte into the battery electrode 100, the amount of bubbles present in the battery electrode 100 decreases. Keep doing. For this reason, the amount of change per unit time of the attenuation rate of the ultrasonic wave becomes large immediately after the impregnation of the electrolytic solution into the battery electrode 100 is started.

  On the other hand, when the battery electrode 100 is completely impregnated with the electrolytic solution, the amount of bubbles present in the battery electrode 100 becomes zero and does not change. For this reason, the amount of change per unit time of the attenuation rate of the ultrasonic wave is such that when the time has elapsed since the start of the impregnation of the electrolytic solution into the battery electrode 100 and the impregnation of the electrolytic solution into the battery electrode 100 is completed, It becomes zero.

  Returning to FIG. 1, the impregnation condition determination unit 13 obtains a change amount per unit time of the attenuation rate of the ultrasonic wave received by the ultrasonic wave reception unit 12 with respect to the ultrasonic wave output by the ultrasonic wave output unit 11. Then, the degree of impregnation of the electrolytic solution into the battery electrode 100 is determined according to the amount of change per unit time in the calculated ultrasonic attenuation rate. Specifically, if the amount of change per unit time in the ultrasonic attenuation rate is equal to or less than a predetermined threshold (for example, zero), it is determined that the impregnation of the electrolyte into the battery electrode 100 is complete. To do. Further, if the change rate of the change amount per unit time is 0.01% or less, it may be determined that the impregnation of the electrolytic solution into the battery electrode 100 is completed.

  When determining the amount of change in the ultrasonic attenuation rate per unit time described above, averaging processing may be performed as necessary, or the unit time may be set longer to suppress the effects of noise and the like. May be. The unit time can be set according to the time until the impregnation is completed. For example, an average value of the time until the impregnation is completed is obtained, and a value obtained by dividing the obtained average value by 50 or 100 is described above. It may be set as a unit time. As the unit time is set longer, the accuracy of the obtained change amount increases, but the time required to obtain the change amount becomes longer.

  According to the above impregnation inspection apparatus 1, the following effects can be produced.

  The impregnation inspection apparatus 1 outputs an ultrasonic wave toward the battery electrode 100 by the ultrasonic output unit 11, receives the ultrasonic wave by the ultrasonic reception unit 12, and applies the ultrasonic wave to the battery electrode 100 by the impregnation condition determination unit 13. The degree of impregnation is determined according to the amount of change per unit time in the attenuation rate of the ultrasonic wave output in the direction. For this reason, it is possible to accurately obtain the degree of impregnation of the electrolyte into the battery electrode 100 from the ultrasonic attenuation rate.

  Further, the impregnation inspection apparatus 1 determines that the impregnation of the electrolytic solution into the battery electrode 100 is completed by the impregnation condition determination unit 13 if the amount of change in the ultrasonic attenuation rate per unit time is equal to or less than the threshold value. To do. For this reason, by setting the threshold value, the degree of impregnation of the electrolyte into the battery electrode 100 can be accurately obtained.

  Further, the impregnation inspection apparatus 1 outputs ultrasonic waves toward the center of the battery electrode 100 by the ultrasonic output unit 11. For this reason, since the degree of impregnation of the electrolytic solution can be obtained for the portion of the battery electrode 100 where the completion of the impregnation is slowest, the portion where the impregnation of the electrolytic solution is not completed does not exist in the battery electrode 100. be able to.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes a design that does not depart from the gist of the present invention.

  For example, in the above-described embodiment, the impregnation degree determination unit 13 determines the degree of impregnation of the electrolytic solution into the battery electrode 100 in accordance with the amount of change per unit time in the ultrasonic attenuation rate. However, the present invention is not limited to this. For example, it may be determined according to the value of the ultrasonic impregnation rate itself.

  In the above-described embodiment, the ultrasonic output unit 11 outputs an ultrasonic wave toward one point at the center of the battery electrode 100, and the ultrasonic reception unit 12 is output from the center of the battery electrode 100 by the ultrasonic output unit 11. It is assumed that the ultrasonic wave output toward one point is received. However, the present invention is not limited thereto, and the ultrasonic output unit 11 outputs an ultrasonic wave toward each of a plurality of points of the battery electrode 100, and the ultrasonic reception unit 12 uses the ultrasonic output unit 11 to output a plurality of battery electrodes 100. Each of the ultrasonic waves output toward the point may be received. According to this, the attenuation rate of the ultrasonic wave at each of the plurality of points of the battery electrode 100 is obtained, and at any part of the battery electrode 100 from the amount of change per unit time of the attenuation rate of the plurality of ultrasonic waves. It can be determined how much impregnation has progressed. For this reason, it is possible to estimate how much time the impregnation is completed in the entire battery electrode 100.

  Further, in the above-described embodiment, the object to be inspected for the impregnation condition is the battery electrode 100 configured by one flat positive electrode or negative electrode. However, the present invention is not limited to this. For example, a flat plate-like positive electrode 201, a flat plate-like negative electrode 202, and a separator 203 may be laminated as in the power generation element 200 shown in FIG. The element 200 may be housed in a case (eg, a case formed of laminate). In this case, the ultrasonic output unit 11 transmits ultrasonic waves from the direction in which the positive electrode 201, the negative electrode 202, and the separator 203 are laminated toward the portion of the positive electrode 201 and the negative electrode 202 where the impregnation of the electrolyte solution is slowest. Shall be output. As the portion of the positive electrode 201 and the negative electrode 202 that is most slowly impregnated with the electrolytic solution, for example, the center of gravity of the positive electrode 201 and the negative electrode 202 that is sandwiched in the middle can be applied. However, in order to insulate the positive electrode 201 and the negative electrode 202 from the case, the positive electrode 201 and the negative electrode 202 are covered with a shrink film, and the electrolyte soaks into the positive electrode 201 and the negative electrode 202 by the shrink film. There are cases where places where you can go are limited. For this reason, the portion of the positive electrode 201 and the negative electrode 202 that is most slowly impregnated with the electrolyte changes as appropriate. Therefore, it is preferable to appropriately set where the ultrasonic output unit 11 outputs ultrasonic waves.

  Further, in the above-described embodiment, the object to be inspected for the impregnation condition is the battery electrode 100 configured by one flat positive electrode or negative electrode. However, the present invention is not limited to this, and for example, a power generation element in which a positive electrode, a negative electrode, and a separator are stacked may be wound. Further, the power generation element is accommodated in a case (for example, a case formed of laminate). It may be what has been done. In this case, the ultrasonic output unit 11 outputs ultrasonic waves from the direction in which the positive electrode, the negative electrode, and the separator are laminated toward the portion of the positive electrode and the negative electrode where the impregnation with the electrolyte solution is slowest. .

  Further, in the above-described embodiment, the object to be inspected for the impregnation condition is the battery electrode 100 configured by one flat plate-like positive electrode or negative electrode. However, all the battery electrodes 100 may be inspected, or all the battery electrodes 100 may be inspected. One or more of the battery electrodes 100 may be appropriately extracted and inspected. Moreover, all the power generation elements may be inspected, or one or more of all the power generation elements may be appropriately extracted and inspected.

  Further, the present invention may be applied to a battery manufacturing method. For example, after the power generation element is housed in the case from the opening of the case and the opening is closed with a lid, the electrolytic solution is injected into the case from the electrolytic solution inlet provided in the lid. Thereafter, as in the inspection method of the present invention, ultrasonic waves are output toward the battery electrode impregnated with the electrolytic solution. The ultrasonic wave output at the position opposite to the position where the ultrasonic wave is output and the battery electrode is received. Thereafter, the attenuation rate of the received ultrasonic wave with respect to the output ultrasonic wave is obtained, and the degree of impregnation of the electrolyte into the battery electrode is obtained according to the obtained attenuation rate. Whether or not the obtained impregnation condition is within a predetermined threshold is determined by a determination unit (CPU or the like) provided in the inspection apparatus. If it is determined that the determination is within the threshold, the process proceeds to the subsequent steps including the charging step. . By doing so, it is possible to automatically shift to the next step immediately after the completion of the impregnation.

DESCRIPTION OF SYMBOLS 1; Impregnation test | inspection apparatus 11; Ultrasonic wave output part 12; Ultrasonic wave receiving part 13; Impregnation condition determination part 100; Battery electrode 200; Power generation element 201; Positive electrode 202;

Claims (6)

An impregnation inspection apparatus for inspecting the degree of impregnation of the electrolyte into the battery electrode,
An output means for outputting an ultrasonic wave toward the battery electrode impregnated with an electrolytic solution;
A receiving unit that is provided at a position facing the output unit across the battery electrode, and that receives the ultrasonic waves output by the output unit;
An impregnation degree determining means for obtaining an attenuation rate of the ultrasonic wave received by the receiving means with respect to the ultrasonic wave output by the output means, and obtaining an impregnation degree of the electrolytic solution to the battery electrode according to the obtained attenuation rate; ,
An impregnation inspection apparatus comprising:   The impregnation condition determining means determines that the impregnation of the electrolytic solution into the battery electrode is completed when the amount of change per unit time of the attenuation rate is equal to or less than a predetermined threshold value. The impregnation inspection apparatus according to claim 1.   The impregnation inspection apparatus according to claim 1, wherein the output unit outputs an ultrasonic wave toward a center of the battery electrode. The output means outputs an ultrasonic wave toward each of the plurality of points of the battery electrode;
3. The impregnation inspection apparatus according to claim 1, wherein the reception unit receives each of the ultrasonic waves output to the plurality of points of the battery electrode by the output unit. An impregnation inspection method for inspecting the degree of impregnation of the electrolyte into the battery electrode,
A first step of outputting an ultrasonic wave toward the battery electrode impregnated with an electrolyte;
A second step of receiving the ultrasonic wave output by the first step at a position opposite to the position where the ultrasonic wave is output by the first step with the battery electrode interposed therebetween;
First, an attenuation rate of the ultrasonic wave received by the second step with respect to the ultrasonic wave output by the first step is obtained, and an impregnation degree of the electrolyte solution to the battery electrode is obtained according to the obtained attenuation rate. 3 steps,
An impregnation inspection method comprising: A method for producing a battery having a power generation element and an electrolytic solution, which are configured by sandwiching a separator between a positive electrode and a negative electrode, which are battery electrodes, in a case,
A first step of injecting an electrolyte after placing the power generation element in the case;
A second step of outputting an ultrasonic wave toward the battery electrode impregnated with the electrolyte;
A third step of receiving the ultrasonic wave output by the second step at a position opposite to the position where the ultrasonic wave is output by the second step and the battery electrode in between;
First, the attenuation rate of the ultrasonic wave received in the third step with respect to the ultrasonic wave output in the second step is obtained, and the impregnation degree of the electrolytic solution to the battery electrode is obtained in accordance with the obtained attenuation rate. 4 steps,
Determining whether or not the impregnation degree obtained in the fourth step is equal to or less than a predetermined threshold value; ,
An impregnation inspection method comprising:

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