Patent Description:
With the increase in technology development and demand for mobile devices, the demand for secondary batteries is also rapidly increasing. Among the secondary batteries, lithium secondary batteries are widely used as an energy source for various electronic products as well as various mobile devices because of their high energy density and high operating voltage and excellent storage and lifespan characteristics.

An electrode assembly that has a structure consisting of a positive electrode, a separator, and a negative electrode to form a lithium secondary battery is largely classified into a jelly-roll type (winding type), a stack type (stacked type), and a stack/folding type, which is a type in which the j elly-roll type and the stack type are combined, according to a structure thereof. A method of manufacturing the electrode assembly is slightly changed according to the above-described structure.

The electrode assembly is accommodated in a case, and the secondary battery may be classified into a prismatic type, a coin type, a cylindrical type, a pouch type, and the like according to a shape of the case. Next, a process of injecting an electrolyte into the case is performed. That is, the lithium secondary battery is manufactured by injecting the electrolyte in a state in which the electrode assembly is accommodated in the battery case and then sealing the case.

Meanwhile, the electrode assembly is subjected to a failure inspection process and then is accommodated in an exterior material by being filled with an electrolyte and sealed. As a method of inspecting failures before the electrolyte is injected, a short-circuit inspection for detecting a short-circuit state of the electrode assembly is performed. Before the electrolyte is injected, a positive electrode and a negative electrode of the electrode assembly are electrically insulated by a separator between the positive electrode and the negative electrode. However, during a manufacturing process, for some reason, the insulation may be broken and a short circuit, in which the positive electrode and the negative electrode are electrically connected, may occur. Since a failed electrode assembly in which a short circuit has occurred reduces manufacturing yield, the failed electrode assembly is detected by a short-circuit tester and excluded from a manufacturing line.

<FIG> is a schematic diagram illustrating a configuration of a conventional short-circuit tester <NUM>.

In <FIG>, an electrode assembly <NUM> is accommodated in a case <NUM>, and an electrolyte is not injected into the case <NUM>. The electrode assembly <NUM> is composed of a positive electrode <NUM>, a separator <NUM>, and a negative electrode <NUM>, and the short-circuit tester <NUM> is electrically connected to tabs (terminals) 1a and 3a of the positive electrode <NUM> and the negative electrode <NUM>. The short-circuit tester is provided with a predetermined power source, and applies a predetermined voltage from the power source to the electrode assembly <NUM> to detect a short-circuit state of the electrode assembly.

However, the conventional short-circuit tester detects a magnitude of a voltage or current of the electrode assembly <NUM>, which is detected by applying a constant voltage to the electrode assembly <NUM>, only at a specific time point, and compares a value of the magnitude and a set value to determine whether the electrode assembly <NUM> passes or fails. For example, when a current value is lower than a set value, "PASS" is displayed on a display panel <NUM> of the short-circuit tester <NUM>, and when an overcurrent higher than the set value flows, "FAIL" is displayed on the display panel <NUM> of the short-circuit tester <NUM>. However, although the conventional short-circuit tester <NUM> may find a failure, the conventional short-circuit tester <NUM> may not specifically identify the cause of the failure. In order to prevent a failure from occurring repeatedly, the cause of the failure should be identified and removed. In addition, for research and development of the electrode assembly, the type of failure needs to be specified.

In particular, it is difficult to detect false negatives, which are not actual product failures, caused by circuit disconnection, pin contact abnormalities, or the like with the conventional short-circuit tester. When a normal electrode assembly is determined to be a failure due to equipment abnormality, this becomes a factor that reduces manufacturing yield. Alternatively, when an abnormal electrode assembly is determined to be normal due to equipment abnormality, this leads to the same result as not actually inspecting the electrode assembly, resulting in reduced inspection accuracy.

Further, there are several types of intrinsic failures in which a current exceeds a measurement upper limit due to the occurrence of a short circuit and it is determined as a High Fail by the short-circuit tester. For example, it is difficult for the conventional short-circuit tester to distinguish a bridge failure, in which separation occurs in an electrode and a separated portion connects a positive electrode and a negative electrode like a bridge to generate a short circuit, or a spot failure, in which a spot-shaped hole is generated in a separator and thus insulation between a positive electrode and a negative electrode is broken.

In order to detect the above-described types of failures, changes in voltage or current of the electrode assembly need to be specifically analyzed, but the conventional short-circuit tester calculates the magnitude of the voltage or current of the electrode assembly only at a specific time point to determine only PASS/FAIL, and is difficult to measure changes in voltage or current over time.

Accordingly, there is a need for the development of a failure inspection technique capable of inspecting the cause of a short-circuit or failure of an electrode assembly before an electrolyte is injected into a secondary battery.

<CIT> discloses an inspection device for inspecting a structure body including a pair of electrodes and a separator disposed between the pair of electrodes. The inspection device includes: a measurement unit including a direct-current constant voltage generator that generates a constant inspection voltage applied to the pair of electrodes, and a detection circuit that detects a current value between the pair of electrodes resulting from the application of the inspection voltage; and a processing unit that determines whether the structure body is defective or non-defective based on the detected current value, and the processing unit has a function that, if two or more points at which a ratio (ΔI/Δt) of a current value variation amount (ΔI) to a time variation amount (Δt) varies from a value of no less than <NUM> to a negative value are observed or no point at which the ratio (ΔI/Δt) varies from a value of no less than <NUM> to a negative value is observed during a period of time immediately after the application of the inspection voltage until the current value becomes constant, determines the structure body as a defective product, and an auxiliary function that obtains a peak current value Ipeak, a peak current appearing time tpeak and a current area SI of a current waveform representing variation in current value I over passage of time t, and if any one of the peak current value Ipeak, the peak current appearing time tpeak and the current area SI deviates from a preset threshold value including an upper limit value and a lower limit value, determines the structure body as a defective product.

<CIT> discloses a method for testing a precursor of a secondary cell with high reliability and high efficiency to judge the precursor to be acceptable or defective. The current flowing when a test voltage is applied between a pair of electrodes is measured before an electrolyte is placed between the electrodes. If a current the current value of which exceeds a predetermined reference current value is detected during the time from the start of application of a voltage to a normal secondary cell precursor until the current becomes constant, the precursor is determined to be defective.

<CIT> addresses the problem of how to provide a novel inspection method for effectively and reliably inspecting a secondary battery precursor (electrode plate group), a manufacturing method for the secondary battery using the inspection method, and an inspection device for use in the inspection. As solution, it is suggested: Before filling an electrolyte liquid into between a pair of electrodes, a current flowing in along an inspection voltage being applied while applying the inspection voltage which is constant between the pair of electrodes. When a current value exceeding a reference current value that is previously set is detected in a time period from when voltage application to a normal secondary battery precursor is started to when the current becomes constant, the precursor is determined as being defective.

An object of the present invention is to provide an apparatus for inspecting failures of an electrode assembly, capable of effectively determining types of the failures of the electrode assembly before injecting an electrolyte.

Another object of the present invention is to provide a method of inspecting failures of an electrode assembly capable of detecting a false negative, a bridge failure, and a spot failure that may not be determined by a conventional short-circuit tester. The invention is defined by an apparatus according to claim <NUM> and a method according to claim <NUM>.

One aspect of the present invention provides an apparatus for inspecting a failure of an electrode assembly before injecting an electrolyte, including a short-circuit tester configured to detect a short circuit of the electrode assembly by applying a predetermined voltage to a positive electrode and a negative electrode of the electrode assembly; a multimeter electrically connected to the short-circuit tester and configured to measure a voltage and a current of the electrode assembly over a predetermined period of time; and a failure determination part connected to the multimeter and configured to monitor changes in voltage and current measured by the multimeter and determine a type of a failure of the electrode assembly from data on the changes in voltage and current over the predetermined period of time. The failure determination part detects a false negative of the electrode assembly by comparing voltage and current waveforms. When a peak of the current waveform, which is determined according to a size of the electrode assembly, is less than or equal to a predetermined magnitude when the voltage waveform is a normal waveform, the failure determination part determines the failure as the false negative.

In an example, the multimeter may be a digital multimeter.

In a preferred example, the failure determination part may be connected to the short-circuit tester and may receive information about short-circuit detection from the short-circuit tester.

In an example, when there is no peak in the current waveform when the voltage waveform is a normal waveform, the failure determination part may determine the failure as the false negative.

In another embodiment, the failure determination part may detect whether the electrode assembly has a bridge failure and a spot failure from data on changes in voltage and current of the electrode assembly with the failure, which is determined as a High Fail by the short-circuit tester, over the predetermined period of time.

In a specific example, the failure determination part may determine the electrode assembly having a maximum voltage lower than a threshold maximum voltage, which is a maximum voltage at a point at which maximum voltage statistical distribution curves of the electrode assembly with the bridge failure and the electrode assembly with the spot failure first overlap each other, as having the bridge failure.

Further, the failure determination part may determine the electrode assembly having a maximum voltage greater than a threshold maximum voltage, which is a maximum voltage at a point at which maximum voltage statistical distribution curves of the electrode assembly with the bridge failure and the electrode assembly with the spot failure first overlap each other, as having the spot failure.

Another aspect of the present invention provides a method of inspecting a failure of an electrode assembly before injecting an electrolyte, including measuring a voltage and a current of the electrode assembly over time by applying a predetermined voltage to a positive electrode and a negative electrode of the electrode assembly; and determining at least one failure type from among a false negative, a bridge failure, and a spot failure from data on changes in voltage and current over the predetermined period of time. In the failure inspection method, when a peak of a current waveform, which is determined according to a type of the electrode assembly, is less than or equal to a predetermined magnitude when a voltage waveform of the electrode assembly is a normal waveform, it is determined as the false negative.

In a specific example, in the failure inspection method, when there is no peak in a current waveform when a voltage waveform of the electrode assembly is a normal waveform, it may be determined as the false negative.

In another embodiment, in the electrode assembly failure inspection method, when a maximum current value measured from the electrode assembly exceeds a set upper limit value, the electrode assembly having the bridge failure and the spot failure may be detected from the data on the change in voltage of the electrode assembly over the predetermined period of time.

In a specific example, an electrode assembly having a maximum voltage lower than a threshold maximum voltage, which is a maximum voltage at a point at which maximum voltage statistical distribution curves of the electrode assembly with the bridge failure and the electrode assembly with the spot failure first overlap each other, may be determined as having the bridge failure, and an electrode assembly having a maximum voltage greater than the threshold maximum voltage may be determined as having the spot failure.

According to the present invention, false negatives of an electrode assembly before an electrolyte is injected can be accurately determined, thereby improving manufacturing yield.

Further, according to the present invention, causes of failures can be effectively specified by identifying types of intrinsic failures such as a bridge failure and a spot failure.

Hereinafter, the detailed configuration of the present invention will be described in detail with reference to the accompanying drawings and various embodiments. The embodiments described below are exemplarily illustrated for understanding of the invention, and the accompanying drawings are not shown as actual scale to aid in understanding the invention, and dimensions of some components may be exaggerated.

While the present invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that there is no intent to limit the present invention to the particular forms disclosed, but on the contrary, the present invention is to cover all modifications, and alternatives falling within the scope of the present invention.

An electrode assembly failure inspection apparatus of the present invention is for an electrode assembly before injecting an electrolyte. The electrode assembly before injecting an electrolyte includes all of an electrode cell assembly in which a positive electrode, a separator, and a negative electrode are laminated by a lamination process and cut in units of cells, a stacked type electrode assembly in which electrode cell assemblies are stacked, a folding type electrode assembly in which the electrode cell assembly is folded with a separator, a stack-folding type electrode assembly in which the electrode cell assembly is stacked and folded with a separator, and a packaging cell in which an electrode cell assembly is accommodated in a case but is still in a stage before an electrolyte is injected. Accordingly, the electrode assembly, which is to be inspected, of the present invention is not necessarily accommodated in a case.

<FIG> is a schematic diagram illustrating a configuration of an electrode assembly failure inspection apparatus of the present invention.

An electrode assembly failure inspection apparatus <NUM> of the present invention includes a short-circuit tester <NUM> configured to detect a short circuit of an electrode assembly <NUM> by applying a predetermined voltage to a positive electrode <NUM> and a negative electrode <NUM> of the electrode assembly <NUM>; a multimeter <NUM> electrically connected to the short-circuit tester <NUM> and configured to measure a voltage and current of the electrode assembly <NUM> over time; and a failure determination part <NUM> connected to the multimeter <NUM> and configured to monitor changes in voltage and current measured by the multimeter and determine types of failures of the electrode assembly <NUM> from data on the changes in voltage and current over a predetermined period of time.

For convenience of description, in the inspection apparatus <NUM> of <FIG>, a size of the electrode assembly <NUM> or a battery cell is exaggerated to be larger than those of the short-circuit tester <NUM>, the multimeter <NUM>, and the failure determination part <NUM>.

The present invention includes the short-circuit tester <NUM> configured to apply a predetermined voltage to the electrode assembly <NUM>, which is accommodated in the case <NUM> or not accommodated in the case <NUM>, before injecting an electrolyte. The short-circuit tester <NUM> is provided with a predetermined power source and thus detects a short-circuit state of the electrode assembly <NUM> by applying a predetermined voltage from the power source to the positive electrode <NUM> and the negative electrode <NUM> of the electrode assembly <NUM>. The short-circuit tester <NUM> determines whether the electrode assembly passes or fails by applying a predetermined voltage, which is set according to the type or size of the electrode assembly <NUM>, and measuring a current/voltage that is generated due to the application of the voltage and measured from the electrode assembly.

<FIG> is a graph illustrating a result of PASS/FAIL determination by the short-circuit tester of <FIG>.

As shown in <FIG>, an example in which <NUM> High Fails as a failure type are detected by the short-circuit tester <NUM> is illustrated. The term "High Fail" refers to a failure in a case in which a short circuit is generated in the electrode assembly <NUM> and a current value exceeds a measurement limit of the short-circuit tester <NUM> or a set current upper limit. However, the short-circuit tester <NUM> may only determine a pass/fail of the electrode assembly, and may not identify a specific type of failure. This is because the short-circuit tester <NUM> is set to determine a pass/fail with a current or voltage value measured at a specific time point, and even when current/voltage values at different time points are able to be measured, corresponding numerical data measured by the short-circuit tester <NUM> is volatilized without being preserved due to the characteristics of the device. Accordingly, it is difficult for the short-circuit tester <NUM> to determine a specific type of failure, particularly, a false negative such as a pin contact failure.

The inspection apparatus <NUM> of the present invention includes the multimeter <NUM> electrically connected to the short-circuit tester <NUM> to measure changes in voltage and current of the electrode assembly <NUM> over time. Since the multimeter <NUM> is not provided with a power source, the multimeter <NUM> may not independently apply a voltage to the electrode assembly <NUM>. However, when the multimeter <NUM> is electrically connected to terminals of the short-circuit tester <NUM>, the multimeter <NUM> is in a form of being electrically connected to the electrode assembly <NUM> through the short-circuit tester <NUM>. Thus, voltage and current values that are not preserved due to volatility in the short-circuit tester <NUM> may also be measured continuously through the multimeter <NUM>. The multimeter <NUM> may include a digital multimeter (DMM) capable of easily measuring voltage, current, resistance, and the like.

The failure inspection apparatus <NUM> of the present invention also includes the failure determination part <NUM> connected to the multimeter <NUM> and configured to monitor changes in voltage and current measured by the multimeter <NUM> and determine types of failures of the electrode assembly <NUM> from data on the changes in voltage and current over a predetermined period of time. The failure determination part <NUM> may monitor voltage and current values over time, which are measured by the multimeter <NUM> over time, and visually display changes thereof in a graph or waveform. To this end, the failure determination part <NUM> includes a storage part configured to store voltage and current data received from the multimeter, a conversion part configured to convert a change in the data over time into visual information of a graph or waveform, and a determination part configured to determine types of failures of the electrode assembly from data on changes in voltage and current over a predetermined period of time. For the data conversion or failure determination, the failure determination part <NUM> is provided with a predetermined software (LAP VIEW). In addition, the inspection apparatus <NUM> of the present invention may include a display part <NUM> configured to display the visual information of changes in the voltage and current data over time in the form of a graph or waveform.

As described above, in the present invention, voltage and current values over time, which are difficult to measure using the conventional short-circuit tester, may be measured by connecting the multimeter <NUM> to the short-circuit tester <NUM>, and changes in voltage and current of the electrode assembly <NUM> may be continuously monitored by connecting the multimeter <NUM> to the failure determination part <NUM> equipped with specially developed software. In the present invention, an inexpensive multimeter commonly used in the field of electrical engineering is provided as a part of the inspection apparatus, and the failure determination part of predetermined software determines types of failures, so that it is possible to inspect the failure of the electrode assembly <NUM> at low cost without employing an expensive tester such as an oscilloscope or an impulse tester.

The failure determination part <NUM> of the present invention may determine types of failures in consideration of not only voltage changes but also current changes over a predetermined period of time. Depending on the types of failures, the type and size of the electrode assembly <NUM> or a battery cell in which the electrode assembly is employed, or the like, the application time (e.g., hundreds to thousands of milliseconds) of the voltage and current changes, with which a failure may be determined, may vary.

An electrode assembly failure inspection method before injecting an electrolyte of the present invention includes measuring a voltage and current of an electrode assembly over time by applying a predetermined voltage to a positive electrode and a negative electrode of the electrode assembly; and determining at least one failure type of failures from among a false negative, a bridge failure, and a spot failure from data on changes in voltage and current over a predetermined period of time.

According to the inspection method of the present invention, first, a predetermined voltage is applied to the positive electrode and the negative electrode of the electrode assembly to measure the voltage and current of the electrode assembly over time. The application of the voltage may be performed by the short-circuit tester <NUM> as shown in <FIG>. In addition, the measuring of the voltage and current of the electrode assembly over time may be performed by a digital multimeter connected to the short-circuit tester. As described above, by only connecting the digital multimeter to the conventional short-circuit tester, changes in voltage and current of the electrode assembly over time may be measured without adding a separate power source or device.

Next, the inspection method of the present invention includes determining at least one type of failure from among a false negative, a bridge failure, and a spot failure from data on changes in voltage and current over a predetermined period of time. In the present invention, the type of failures are determined by considering both data of voltage and current, not data of either voltage or current.

Hereinafter, an electrode assembly failure inspection process according to the present invention will be described in more detail.

First, a case in which an electrode assembly with a false negative is detected according to the present invention will be described.

According to the present invention, an electrode assembly with a false negative may be detected by comparing voltage and current waveforms. Voltage and current waveforms of a normal electrode assembly will be described first in order to identify waveforms in a false negative.

<FIG> is a graph of voltage and current waveforms of a normal electrode assembly over a predetermined period of time (<NUM> msec). The voltage and current waveforms are prepared on the basis of data measured by DMM-<NUM> from National Instruments (hereinafter, DMM-<NUM>).

As illustrated in the drawing, when a predetermined voltage is applied, for example, by a short-circuit tester, the voltage waveform of the normal electrode assembly increases to a predetermined value determined according to the type of the electrode assembly and then decreases after a predetermined period of time. Since the electrode assembly before an electrolyte is injected is a kind of capacitor, when a voltage is applied to the electrode assembly, in each of a positive electrode and a negative electrode, charges of the corresponding polarity are collected, so that a voltage of a predetermined value (<NUM> V in <FIG>) is measured from the electrode assembly as shown in <FIG>. At this point, as shown in <FIG>, a current shows a predetermined peak value and then converges to a value close to zero. Since an electrolyte is not injected, a value of the current is close to zero because insulation resistance becomes close to infinity.

<FIG> is a set of graphs illustrating a comparison between voltage-current waveforms of each of a normal electrode assembly and a false failed electrode assembly, which are measured by the electrode assembly failure inspection apparatus <NUM> of the present invention.

In (a) of <FIG> is shown the voltage and current waveforms of the normal electrode assembly, which are similar to those of <FIG>. The voltage waveform appears to be similar to that of <FIG> except that a maximum voltage is <NUM> V. In addition, the current waveform also appears to be close to zero, except that a peak current is <NUM> mA. On the other hand, the current waveform of the electrode assembly with a false negative in (b) of <FIG> is different. The false negative is a failure due to a circuit disconnection or a pin contact failure. Thus, it can be seen that, in the case of the false negative, the voltage waveform is almost the same (a maximum voltage is <NUM> V) as the waveform (normal waveform) of the normal electrode assembly but there is no peak in the current waveform.

Accordingly, according to the inspection method of the present invention, in a case in which there is no peak in the current waveform when the voltage waveform of the electrode assembly is the normal waveform, it is determined as a false negative. The voltage and current waveforms may be extracted from data on changes in voltage and current monitored by the failure determination part <NUM> of the inspection apparatus <NUM> of the present invention (see the above-described software "LAP VIEW").

Further, in the failure determination part <NUM> of the inspection apparatus <NUM> of the present invention, in a case in which there is no peak in the current waveform when the voltage waveform of the electrode assembly is the normal waveform, it is determined as a false negative.

Meanwhile, depending on the type of electrode assembly, even when there is a peak in the current waveform, the peak may be less than the peak of the normal electrode assembly. For example, even in the case of a false negative of a pin contact failure, a small peak may be measured in the current waveform depending on the contact state, rather than not completely flowing current. Thus, it can be regarded as a false negative even when the peak is less than or equal to a predetermined magnitude in addition to the case in which there is no peak in the current waveform.

Accordingly, according to an example of the inspection method of the present invention, in the case in which the peak in the current waveform is less than or equal to a predetermined magnitude when the voltage waveform of the electrode assembly is the normal waveform, it may be determined as a false negative.

Further, in the failure determination part <NUM> of the inspection apparatus <NUM> of the present invention, in the case in which the peak in the current waveform is less than or equal to a predetermined magnitude when the voltage waveform of the electrode assembly is the normal waveform, it is determined as a false negative.

Meanwhile, in the waveforms of the voltage and current monitored by the inspection apparatus <NUM> or the like of the present invention, even when the current waveform is the same as the waveform of the false negative, when the voltage waveform is different from the normal waveform, it is not determined as a false negative.

According to the present invention, a bridge failure and a spot failure, which may not be measured with a conventional short-circuit tester, may also be detected.

The bridge failure refers to a failure in which separation occurs in an electrode and a separated portion connects a positive electrode and a negative electrode like a bridge to generate a short circuit, and the spot failure refers to a failure in which a spot-shaped hole is generated in a separator and thus insulation between a positive electrode and a negative electrode is broken.

When the insulation between the positive electrode and the negative electrode is broken, a current value measured in an electrode assembly exceeds a measurement limit of a short-circuit tester or exceeds or a set current upper limit. This is referred to as "High Fail. " The conventional short-circuit tester may measure the High Fail, but may not determine whether the High Fail is the bridge failure or the spot failure.

In a failure inspection method of the present invention, when a maximum current value measured from the electrode assembly exceeds a set upper limit value when a predetermined voltage is applied to the electrode assembly, the electrode assemblies having a bridge failure and a spot failure may be detected from data on changes in voltage of the electrode assembly over a predetermined period of time.

The upper limit value of the maximum current value may be a set value determined as a High Fail in the short-circuit tester <NUM>. In order to obtain information about the maximum current value of the electrode assembly, the failure determination part <NUM> of the inspection apparatus <NUM> of the present invention may be connected to the short-circuit tester <NUM> to receive information about the detection of a short circuit therefrom. That is, the failure inspection apparatus <NUM> of the present invention may receive information about a current from, for example, the short-circuit tester <NUM>, and detect the bridge failure and the spot failure from voltage data of the multimeter <NUM>. Alternatively, the bridge failure and the spot failure may be detected from voltage and current data measured by the multimeter <NUM>.

In the case of the bridge failure, since a voltage is not significantly increased even when a voltage is applied by the short-circuit tester, a maximum voltage is not greater than that in the spot failure. However, when the number of electrode assemblies or battery cells to be measured is increased, the maximum voltage of the spot failure is not necessarily greater than the maximum voltage of the bridge failure. This is because, in the case of the bridge failure, a variation range of the maximum voltage is large according to the resistance of a separated electrode portion. Accordingly, it is difficult to distinguish the bridge failure and the spot failure by only the magnitude of the voltage.

In the present embodiment, in consideration of this, the bridge failure and the spot failure are distinguished by a statistical approach.

That is, first, it is determined whether the maximum current value measured from the electrode assembly exceeds a set upper limit value (e.g., a current value sufficient to be determined as a High Fail in the short-circuit tester).

When the maximum current value exceeds the upper limit value, reference is made to statistical distribution curves of the maximum voltages of the bridge failure and the spot failure of the electrode assembly.

<FIG> is a set of graphs illustrating maximum voltages of a bridge failure and a spot failure according to the frequency of each failure.

The graphs of <FIG> are prepared on the basis of data on maximum voltages measured by DMM-<NUM> for <NUM> electrode assemblies, each of which is determined as having a failure of a High Fail, in a folding process when a test voltage of a short-circuit tester <NUM> (model name N2. <NUM>) is set to <NUM> V. In <FIG>, an X-axis represents the maximum voltage, and a Y-axis represents the number of electrode assemblies or battery cells having the corresponding maximum voltage.

As shown in (a) of <FIG>, although the maximum voltage of the spot failure is generally larger than the maximum voltage of the bridge failure, it can be seen that the reverse case is possible depending on the electrode assembly. However, it can be seen that, as shown in (b) of <FIG>, most bridge failures and spot failures are respectively present on left and right sides of a point (see an arrow in <FIG>) at which a maximum voltage statistical distribution curve, which connects the maximum voltages of the electrode assemblies with a bridge failure, and a maximum voltage statistical distribution curve, which connects the maximum voltages of the electrode assemblies with a spot failure, first meet. Accordingly, when the maximum voltage (<NUM> V in <FIG>) at the point at which the maximum voltage statistical distribution curves of both failures first meet is referred to as a threshold maximum voltage, the electrode assembly having a maximum voltage lower than this threshold maximum voltage may be determined as the bridge failure, and in contrast, the electrode assembly having a maximum voltage greater than the threshold maximum voltage may be determined as having the spot failure.

That is, the failure determination part <NUM> of the failure inspection apparatus <NUM> of the present invention may determine the bridge failure or the spot failure, for example, by comparing the threshold maximum voltage, which is determined from the maximum voltage statistical distribution curves of the bridge failure and the spot failure input to the storage part or another database, and the maximum voltage among the voltages of the electrode assemblies, which are measured over a predetermined period of time by a multimeter or the like, over time.

<FIG> is a graph of another embodiment illustrating maximum voltages of a bridge failure and a spot failure according to the frequency of each failure. The graph of <FIG> is prepared on the basis of data on maximum voltages measured by DMM-<NUM> for <NUM> electrode assemblies, each of which is determined as having a failure of a High Fail, in a folding process when a test voltage of a short-circuit tester <NUM> (model name E52) is set to <NUM> V.

It can be seen even in the present embodiment that bridge failures tend to be biased to a left side (lower maximum voltage) and spot failures tend to be biased to a right side (higher maximum voltage) centered on a threshold maximum voltage (<NUM> V), which is a maximum voltage at a point at which maximum voltage statistical distribution curves of both failures first meet.

Claim 1:
An apparatus (<NUM>) for inspecting a failure of an electrode assembly (<NUM>) before injecting an electrolyte, the apparatus (<NUM>) comprising:
a short-circuit tester (<NUM>) configured to detect a short circuit of the electrode assembly (<NUM>) by applying a predetermined voltage to a positive electrode (<NUM>) and a negative electrode (<NUM>) of the electrode assembly (<NUM>);
a multimeter (<NUM>) electrically connected to the short-circuit tester (<NUM>) and configured to measure a voltage and a current of the electrode assembly (<NUM>) over a predetermined period of time; and
a failure determination part (<NUM>) connected to the multimeter (<NUM>) and configured to monitor changes in voltage and current measured by the multimeter (<NUM>) and determine a type of a failure of the electrode assembly (<NUM>) from data on the changes in voltage and current over the predetermined period of time,
wherein the failure determination part (<NUM>) is configured to detect a false negative of the electrode assembly (<NUM>) by comparing voltage and current waveforms,
wherein, when a peak of the current waveform, which is determined according to a size type of the electrode assembly (<NUM>), is less than or equal to a predetermined magnitude when the voltage waveform is a normal waveform, the failure determination part (<NUM>) determines the failure as the false negative.