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EP-4495614-B1 - BATTERY INSPECTION METHOD

EP4495614B1EP 4495614 B1EP4495614 B1EP 4495614B1EP-4495614-B1

Inventors

  • HEO, Yeonhyuk
  • KIM, Kwanghyun
  • CHAE, BYUNG JOON
  • RAH, KYUN IL

Dates

Publication Date
20260506
Application Date
20231215

Claims (7)

  1. A battery inspection method comprising provision of a secondary battery and comprising: a data acquisition step S10 of acquiring impedance spectral data for the secondary battery; a first function acquisition step S20 of acquiring, through function fitting, a first function which uses a logarithmic scale of a measurement frequency as an independent variable and an absolute value of impedance as a dependent variable from the impedance spectral data; a second function acquisition step S30 of acquiring a second function by differentiating the first function by the logarithmic scale of the measurement frequency; and a battery state determination step S40 of determining a state of the secondary battery based on the second function.
  2. The battery inspection method of claim 1, wherein, in the data acquisition step S10, the impedance spectral data is acquired by applying alternating current power to the secondary battery for a band of the measurement frequency including a band of 10 -2 Hz to 10 5 Hz.
  3. The battery inspection method of claim 1, wherein, in the first function acquisition step S20, the first function is acquired in the form of the following Equation 1: Z abs = F 1 log f wherein Z abs is the absolute value of the impedance, F 1 (logf) is the first function, and f is the measurement frequency.
  4. The battery inspection method of claim 3, wherein the second function is acquired in the form of the following Equation 2: F 2 log f = dZ abs d log f wherein F 2 (logf) is the second function.
  5. The battery inspection method of claim 4, wherein, in the battery state determination step S40, the state of the secondary battery is determined based on the second function in a range where the logf is 0 to 1.
  6. The battery inspection method of claim 5, wherein, in the battery state determination step S40, when an inflection point exists in the second function in the range where the logf is 0 to 1, it is determined that cracks occur in electrodes of the secondary battery.
  7. The battery inspection method according to claim 4, wherein no inflection point exists in the second function in a range where the logf is 0 to 1.

Description

Technical Field The present application claims the benefit of priority based on Korean Patent Application No. 10-2022-0175754 filed on December 15, 2022. The present disclosure relates to a battery inspection method, and relates to a battery inspection method which is capable of identifying cracks in electrodes of a completed secondary battery by non-destructive testing. Background Art US 2017/219660 A1 describes a method of determining the State of Health (SoH) and/or State of Charge (SoC) of a rechargeable battery during use of said battery. The method comprises the steps of: generating a first excitation signal within a first selected frequency range, generating a second excitation signal within a second selected frequency range, applying said first and second excitation signals on said rechargeable battery, measuring the response signal for each of said two excitation signals, and then calculate the Electrochemical Impedance (EI) as the ratio between the excitation signals and respective response signals, and then determine the SoH and/or SoC of the rechargeable battery by comparing the calculated EI to a circuit model for the battery and/or determining the SoH and/or SoC of the rechargeable battery by directly evaluating characteristics of the EI. After shipment of an initial cell, one of various phenomena that occur as a secondary battery degenerates due to progress of high-temperature storage, a charge-discharge cycle, and the like, is occurrence of microcracks in electrodes. It is important to identify the microcracks that occur in the electrodes because they can affect not only the performance and lifespan of the battery, but also its durability and safety. In addition, if the microcracks can be identified in a battery in use, it is possible to predict a maintenance cycle and future performance related to the battery, so analyzing them may serve as powerful data in battery operation. Conventionally, as a technique for identifying cracks in the electrodes, it is possible to quantify the cracks in the electrodes by analyzing an electron microscope image of the electrodes. However, since analysis of the phenomenon of occurrence of cracks in the electrodes through electron microscopy is carried out by completely disassembling the battery and extracting the electrodes from the battery, there is a problem in that the battery in which the analysis has been performed should be discarded. In other words, it was not possible to monitor a state of occurrence of cracks of the electrodes of the battery during use using the electron microscopy method. In addition, since a process of preparing an analysis sample was cumbersome and measurement took a long time, the electron microscopy method had problems with its use as immediate feedback data. Therefore, there is a need for a technology that can be applied to a battery in use as non-destructive analysis and that can perform analysis in a short period of time to immediately monitor the phenomenon of occurrence of cracks in electrodes of the battery. Disclosure of the Invention Technical Goals The present disclosure relates to a battery inspection method, and an object of the present disclosure is to provide a battery inspection method which is capable of identifying cracks in electrodes of a completed secondary battery by non-destructive testing. Technical objects to be accomplished by the present disclosure are not limited to the technical objects mentioned above, and other technical objects not mentioned may be clearly understood by those skilled in the art to which the present disclosure pertains from the following description. Technical Solutions The present invention is defined according to the subject matter of the appended independent claim. Particular embodiments are given by the additional features of the appended dependent claims. A battery inspection method of the present disclosure includes: a data acquisition step S10 of acquiring impedance spectral data for a secondary battery;a first function acquisition step S20 of acquiring, through function fitting, a first function which uses a logarithmic scale of a measurement frequency as an independent variable and an absolute value of impedance as a dependent variable from the impedance spectral data;a second function acquisition step S30 of acquiring a second function by differentiating the first function by the logarithmic scale of the measurement frequency; anda battery state determination step S40 of determining a state of the secondary battery based on the second function. In the data acquisition step S10 of the battery inspection method of the present disclosure, the impedance spectral data may be acquired by applying alternating current power to the secondary battery for a band of the measurement frequency including a band of 10-2 Hz to 105 Hz. Advantageous Effects According to a battery inspection method of the present disclosure, it is possible to identify cracks in electrodes of a completed second