Battery welding condition inspection method

Abstract

The present invention relates to a method for inspecting the welding condition of a battery, and provides a method for inspecting the welding condition of a battery that can quickly inspect the condition of battery electrodes in a non-destructive manner.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0091698, filed on Jul. 13, 2021, and all the contents disclosed in the document of the Korean Patent Application are incorporated herein by reference.

[0002] The present invention relates to a method for inspecting a welding state of a battery, and more particularly, to a method for inspecting a welding state of a battery capable of nondestructively and rapidly inspecting a state of an electrode of the battery.

Background Art

[0003] Generally, a battery is formed by welding a current collector coated with an active material and an electrode tab for electrical connection to an external electrical device, thereby physically and electrically connecting the current collector and the electrode tab. At this time, if the welding state is poor, the operating efficiency of the battery decreases, and in some cases, the battery may be damaged depending on the situation. Therefore, it is important to accurately determine the welding state.

[0004] In the case of a cylindrical battery, there are welds between the current collector and the electrode tab and between the electrode tab and the can, and in order to inspect the welding state thereof, a destructive inspection method of sampling the welding part through manual work has been performed.

[0005] Therefore, in the conventional method, when a problem occurs in the welding state, there is a problem such as a lot being held.

[0006] To solve this, a new inspection method capable of in-line 100% inspection is required.

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention relates to a method for inspecting a welding state of a battery, and an object thereof is to provide a method for inspecting a welding state of a battery capable of nondestructively and rapidly inspecting a state of an electrode of the battery.

[0008] The technical problems that this invention aims to solve are not limited to those described above, and any other technical problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0009] The present invention provides a method for inspecting the welding state of a battery, comprising: a first impedance measurement step of applying an alternating current or alternating voltage in a set frequency band to measure a first impedance before the electrolyte is injected into the battery; a first cole-cole plot creation step of creating a first cole-cole plot based on the first impedance; and a first welding state determination step of determining the welding state of the battery based on the x-intercept value in the first cole-cole plot. [Effects of the Invention]

[0010] The battery welding condition inspection method of the present invention is a method that allows for in-line 100% inspection during the battery production process, thereby improving the production quality of batteries and removing defective batteries in advance.

[0011] The battery welding condition inspection method of the present invention allows for confirmation of welding quality in a short amount of time.

[0012] The present invention provides a battery welding condition inspection method that allows for the determination of the battery's welding condition simply by measuring the impedance between the positive and negative electrodes in a short time without destroying the battery during the manufacturing process. This method can be applied to a battery manufacturing line and enables 100% inspection of all batteries produced.

[0013] The battery welding condition inspection method of the present invention allows for inspection of the welding condition before the electrolyte is injected, and can inspect the welding condition of the battery regardless of the electrolyte injection state. [Brief explanation of the drawing]

[0014] [Figure 1] This is a block diagram showing the method for inspecting the welding condition of a battery according to the present invention. [Figure 2] This is an equivalent circuit showing the battery during the first impedance measurement stage. [Figure 3] This graph shows the first call-call plot. [Figure 4] This is a block diagram showing another embodiment of the battery welding condition inspection method of the present invention. [Figure 5] This is an equivalent circuit showing the battery during the second impedance measurement stage. [Figure 6] This graph shows the second call-call plot. [Figure 7] This is a conceptual diagram illustrating 4-wire AC impedance measurement. [Figure 8] This is a block diagram showing yet another embodiment of the battery welding condition inspection method of the present invention. [Figure 9] This is a block diagram showing the method for manufacturing the battery of the present invention. [Modes for carrying out the invention]

[0015] The present invention provides a method for inspecting the welding state of a battery, comprising: a first impedance measurement step of applying an alternating current or alternating voltage in a set frequency band to measure a first impedance before the electrolyte is injected into the battery; a first Cole-Cole plot creation step of creating a first Cole-Cole plot based on the first impedance; and a first welding state determination step of determining the welding state of the battery based on the x-intercept value in the first Cole-Cole plot.

[0016] In the primary welding condition determination step of the battery welding condition inspection method of the present invention, if the x-intercept value in the first call-call plot is greater than or equal to a first set value, the welding condition of the battery is determined to be poor.

[0017] The welding state inspection method of the battery of the present invention further includes, after the primary welding state determination step, after electrolyte is injected into the battery, a second impedance measurement step of applying an alternating current or an alternating voltage in a set frequency band to measure a second impedance; a second Cole-Cole plot creation step of creating a second Cole-Cole plot based on the second impedance; and a secondary welding state determination step of determining the welding state of the battery based on the minimum value in the second Cole-Cole plot.

[0018] In the secondary welding state determination step of the welding state inspection method of the battery of the present invention, when the value obtained by subtracting the x-intercept value from the real part value of the minimum value in the second Cole-Cole plot is greater than or equal to a second set value, the welding state of the battery is determined to be defective.

[0019] In the first impedance measurement step and the second impedance measurement step of the welding state inspection method of the battery of the present invention, the first impedance and the second impedance are measured for each of a plurality of frequency values within the set frequency band.

[0020] In the first impedance measurement step and the second impedance measurement step of the welding state inspection method of the battery of the present invention, the measurement of the first impedance and the second impedance are measured by a four-wire AC impedance measuring instrument.

[0021] In the welding state inspection method of the battery of the present invention, a plurality of the batteries are provided, and in the first impedance measurement step or the second impedance measurement step, an alternating current or an alternating voltage is applied to the plurality of batteries connected in parallel in a set frequency band to measure the first impedance or the second impedance.

[0022] The present invention provides a method for inspecting the welding condition of a battery, comprising: a normal state impedance measurement step, in which an alternating current or alternating voltage is applied in a set frequency band to a battery with a good welding condition before electrolyte is injected into it, and the normal state impedance is measured; a normal state call-call plot creation step, in which a normal state call-call plot is created based on the normal state impedance; a test frequency extraction step, in which a frequency corresponding to the normal state x-intercept value in the normal state call-call plot is extracted as a test frequency; a battery to be inspected measurement step, in which an alternating current or alternating voltage is applied at the test frequency before electrolyte is injected into the battery to be inspected, and the welding condition determination step, in which the welding condition of the battery to be inspected is determined based on the impedance value of the battery to be inspected.

[0023] The present invention provides a method for manufacturing a battery, comprising: an electrode assembly preparation step of preparing an electrode assembly by winding or stacking current collectors and separator membranes after lamination; a first welding step of first welding tabs or current collector plates to the current collectors of the electrode assembly; a second welding step of second welding a can housing or electrode leads to the tabs or current collector plates; a primary determination step of determining the welding state of the first and second welds by applying an alternating current or alternating voltage in a set frequency band to the can housing or electrode leads; an electrolyte injection step of pouring electrolyte into the electrode assembly while it is housed in a can housing or pouch case; and a secondary determination step of determining the welding state of the first and second welds by applying an alternating current or alternating voltage in a set frequency band to the can housing or electrode leads.

[0024] The first determination step of the battery manufacturing method of the present invention includes the steps of: applying an alternating current or alternating voltage in a set frequency band to measure a first impedance; creating a first Cole-Cole plot based on the first impedance; and determining that the welding state of the battery is poor if the x-intercept value in the first Cole-Cole plot is greater than or equal to a first set value.

[0025] The secondary determination step of the battery manufacturing method of the present invention includes the steps of: applying an AC current or AC voltage in a set frequency band to measure a second impedance; creating a second Cole-Cole plot based on the second impedance; and determining that the welding condition of the battery is poor if the value obtained by subtracting the x-intercept value from the real part of the minimum value in the second Cole-Cole plot is greater than or equal to a second set value.

[0026] The embodiments of the present invention will be described in detail below with reference to the attached drawings. In this process, the size and shape of the components shown in the drawings may be exaggerated for clarity and convenience of explanation. Furthermore, terms specifically defined in consideration of the configuration and operation of the present invention may change depending on the intent or convention of the user or operator. The definitions of such terms should be based on the overall content of this specification.

[0027] Figure 1 is a block diagram illustrating the battery welding condition inspection method of the present invention. Figure 2 is an equivalent circuit showing the battery in the first impedance measurement step (step S10). Figure 3 is a graph showing the first Cole-Cole plot. Figure 4 is a block diagram illustrating another embodiment of the battery welding condition inspection method of the present invention. Figure 5 is an equivalent circuit showing the battery in the second impedance measurement step (step S40). Figure 6 is a graph showing the second Cole-Cole plot. Figure 7 is a conceptual diagram illustrating a four-wire AC impedance measurement. Figure 8 is a block diagram illustrating yet another embodiment of the battery welding condition inspection method of the present invention. Figure 9 is a block diagram illustrating the battery manufacturing method of the present invention.

[0028] The welding condition inspection method for batteries according to the present invention will be described in detail below with reference to Figures 1 to 8.

[0029] The present invention provides a battery welding condition inspection method that allows for the determination of the battery's welding condition simply by measuring the impedance between the positive and negative electrodes in a short time without destroying the battery during the manufacturing process. This method can be applied to a battery manufacturing line and enables 100% inspection of all batteries produced.

[0030] The battery welding condition inspection method of the present invention allows for inspection of the welding condition before the electrolyte is injected, and can inspect the welding condition of the battery regardless of the electrolyte injection state.

[0031] The battery welding condition inspection method of the present invention is applicable to all battery types, including cylindrical batteries, prismatic batteries, and pouch-type batteries, and is part of the battery manufacturing process that includes a welding step.

[0032] The battery to which the welding condition inspection method of the present invention is applied is one in which a tab or current collector plate is welded to the current collector of an electrode assembly in which a current collector and a separator membrane are wound or stacked, and a can housing or electrode leads are welded to the tab or current collector plate.

[0033] The current collector consists of a pair, specifically a negative electrode current collector and a positive electrode current collector. The negative electrode current collector is coated with a negative electrode active material, and the positive electrode current collector is coated with a positive electrode active material. Depending on the battery type, one or more negative electrode and positive electrode current collectors may be provided. A separator film is laminated between the negative electrode current collector and the positive electrode current collector.

[0034] The negative electrode current collector, positive electrode current collector, and separator membrane are wound or stacked in a stacked state to form an electrode assembly. For example, in cylindrical or prismatic batteries, the negative electrode current collector, positive electrode current collector, and separator membrane are wound together to form an electrode assembly, while in pouch-type batteries, they are tucked together to form an electrode assembly.

[0035] Tabs or current collector plates can function as intermediate legs made of conductive material, electrically connecting the can housing or electrode leads to the positive or negative current collector. The tabs or current collector plates also come in pairs and are welded to the negative and positive current collectors, respectively.

[0036] The can housing or electrode leads are connected to the electrode terminals of an external electrical device. In cylindrical or prismatic batteries, tabs or current collectors corresponding to the negative and positive electrodes are welded to the can housing and the electrode leads fixed to the can housing, respectively. In pouch-type batteries, electrode leads may be provided for the negative and positive electrodes, respectively.

[0037] Welding of the current collector to the tab or current collector plate, and welding of the tab or current collector plate to the can housing or electrode lead, can be done using laser welding, ultrasonic welding, resistance welding, etc.

[0038] As shown in Figure 1, the battery welding condition inspection method of the present invention includes a first impedance measurement step (step S10) in which an AC current or AC voltage is applied in a set frequency band to measure a first impedance before electrolyte is injected into the battery; a first Cole-Cole plot creation step (step S20) in which a first Cole-Cole plot is created based on the first impedance; and a primary welding condition determination step (step S30) in which the welding condition of the battery is determined based on the x-intercept value in the first Cole-Cole plot.

[0039] In the first impedance measurement step (step S10), the first impedance can be measured by electrically connecting to the can housing or electrode leads corresponding to the negative and positive electrodes. That is, the impedance value of the battery itself before electrolyte is injected is the first impedance value.

[0040] In the first impedance measurement step (step S10), the first impedance is measured for each of a plurality of frequency values ​​within the set frequency band. The set of impedance values ​​measured for a plurality of consecutive frequency values ​​constitutes the first impedance. That is, the first impedance may include a plurality of impedance values.

[0041] In the first call-call plot creation stage (step S20), the first call-call plot is a graph that displays the first impedance values ​​on the complex number plane. The first call-call plot is created on a two-dimensional graph where the x-axis represents the real part and the y-axis represents the imaginary part. The call-call plot displays multiple impedance values ​​measured for multiple frequency values ​​on the complex number plane.

[0042] When the welding of the electrode assembly's current collector to the tab or current collector plate is considered the first weld, and the welding of the tab or current collector plate to the can housing or electrode lead is considered the second weld, as shown in Figure 2, the equivalent circuit of the battery before the electrolyte is injected is a circuit in which the positive electrode equivalent circuit 11 and the negative electrode equivalent circuit 12 of the electrode assembly, the positive electrode resistance (Rp1) and negative electrode resistance (Rn1) from the first weld, and the positive electrode resistance (Rp2) and negative electrode resistance (Rn2) from the second weld are connected in series. In this case, the equivalent circuit of the battery before the electrolyte is injected is a circuit in which a capacitor (Cc) is connected in series between the positive electrode equivalent circuit 11 and the negative electrode equivalent circuit 12 of the electrode assembly.

[0043] Therefore, as shown in Figure 3, on the first Cole-Cole plot, which is a Cole-Cole plot for the battery before the electrolyte is injected, the positive electrode resistance (Rp1) and negative electrode resistance (Rn1) due to the first weld, and the positive electrode resistance (Rp2) and negative electrode resistance (Rn2) due to the second weld can correspond to the x-intercept value a.

[0044] In the positive electrode equivalent circuit 11 of the electrode assembly, Rpct is the positive electrode current collector resistance, Zpw is the positive electrode Warburg impedance, and Cpdl is the capacitance between the positive electrode current collector and the positive electrode active material. In the negative electrode equivalent circuit 12 of the electrode assembly, Rnct is the negative electrode current collector resistance, Znw is the negative electrode Warburg impedance, and Cndl is the capacitance between the negative electrode current collector and the negative electrode active material.

[0045] In the first welding condition determination stage (step S30), if the x-intercept value a in the first Cole-Cole plot is greater than or equal to a first set value, the welding condition of the battery is determined to be poor. The first set value can be calculated as a theoretical value considering the materials contained in the battery, or it can be set by considering the x-intercept value of the Cole-Cole plot obtained by measuring a battery in a normal state with good welding and no electrolyte injected. For example, the first set value is the x-intercept value of the Cole-Cole plot for a battery in a normal state, and if the welding is poor, the x-intercept value will increase, so a value greater than or equal to the first set value can be determined to be a welding defect.

[0046] As shown in Figure 4, the welding condition inspection method for a battery according to the present invention further includes, after the primary welding condition determination step (step S30), a second impedance measurement step (step S40) in which an alternating current or alternating voltage is applied in a set frequency band to measure a second impedance after electrolyte has been injected into the battery; a second Cole-Cole plot creation step (S50) in which a second Cole-Cole plot is created based on the second impedance; and a secondary welding condition determination step (step S60) in which the welding condition of the battery is determined based on the minimum value in the second Cole-Cole plot.

[0047] The present invention provides a method for inspecting the welding condition of a battery, which allows for more precise detection of defective welding by independently inspecting the welding condition before and after the injection of the electrolyte.

[0048] In the second impedance measurement step (step S40), the second impedance can be measured by electrically connecting to the can housing or electrode leads corresponding to the negative and positive electrodes. That is, the impedance value of the battery itself into which the electrolyte has been injected is the second impedance value.

[0049] In the second impedance measurement step (step S40), the second impedance is measured for each of a plurality of frequency values ​​within the set frequency band. The set of impedance values ​​measured for a plurality of consecutive frequency values ​​constitutes the second impedance. That is, the second impedance may include a plurality of impedance values.

[0050] As shown in Figure 5, the equivalent circuit of a battery into which electrolyte has been injected is a circuit in which the positive electrode equivalent circuit 11 and the negative electrode equivalent circuit 12 of the electrode assembly, the positive electrode resistance (Rp1) and negative electrode resistance (Rn1) from the first welding, and the positive electrode resistance (Rp2) and negative electrode resistance (Rn2) from the second welding are connected in series. In this case, the equivalent circuit of a battery into which electrolyte has been injected is a circuit in which a resistor (Rel) is connected in series between the positive electrode equivalent circuit 11 and the negative electrode equivalent circuit 12 of the electrode assembly.

[0051] Therefore, as shown in Figure 6, in the second Cole-Cole plot, which is a Cole-Cole plot for the battery after the electrolyte has been injected, the positive electrode resistance (Rp1) and negative electrode resistance (Rn1) due to the first weld, and the positive electrode resistance (Rp2) and negative electrode resistance (Rn2) due to the second weld can correspond to the value b obtained by subtracting the x-intercept value from the real part of the minimum value in the second Cole-Cole plot.

[0052] Therefore, in the secondary welding condition determination step (step S60), if the value b obtained by subtracting the x-intercept value from the real part of the minimum value in the second Cole-Cole plot is greater than or equal to the second set value, the welding condition of the battery can be determined to be poor. The second set value can be calculated as a theoretical value considering the materials contained in the battery, or it can be set by considering the x-intercept value of the Cole-Cole plot obtained by measuring a battery in which electrolyte in a normal state with good welding condition has been injected. For example, the second set value is the value obtained by subtracting the x-intercept value from the real part of the minimum value in the Cole-Cole plot for a battery in a normal state, and if the welding is poor, the value obtained by subtracting the x-intercept value from the real part of the minimum value in the Cole-Cole plot will increase, so a value greater than or equal to the second set value can be determined to be a welding defect.

[0053] As shown in Figure 7, in the first impedance measurement step (step S10) and the second impedance measurement step (step S40), the first impedance and the second impedance are measured using a four-wire AC impedance meter 15. The four-wire AC impedance meter 15 can precisely measure impedance values ​​of 1Ω or less while minimizing the influence of hazardous wiring resistance or contact resistance.

[0054] In the 4-wire AC impedance measuring instrument 15, the positive probe and the negative probe may each independently include terminals connected to an ammeter and terminals connected to a voltmeter, respectively.

[0055] In the first impedance measurement step (step S10) or the second impedance measurement step (step S40), an AC current or AC voltage is applied to the multiple batteries connected in parallel within a set frequency band to measure the first or second impedance. Multiple batteries can be grouped by the number of batteries required for one inspection unit, and the impedance can be measured in parallel for each group of batteries. The welding condition is judged on a group basis, and batteries in a group judged to be defective are remeasured individually.

[0056] As shown in Figure 8, as another embodiment, the battery welding condition inspection method of the present invention includes: a normal state impedance measurement step (step S110) in which an alternating current or alternating voltage is applied in a set frequency band to a battery with a good welding condition before electrolyte is injected into it to measure the normal state impedance; a normal state call-call plot creation step (step S120) in which a normal state call-call plot is created based on the normal state impedance; an inspection frequency extraction step (step S130) in which a frequency corresponding to the normal state x-intercept value in the normal state call-call plot is extracted as an inspection frequency; a battery to be inspected measurement step (step S140) in which an alternating current or alternating voltage is applied in the inspection frequency to the battery to be inspected before electrolyte is injected into it to measure the impedance; and a welding condition determination step (step S150) in which the welding condition of the battery to be inspected is determined based on the impedance value of the battery to be inspected.

[0057] In the normal state impedance measurement stage (step S110), a good battery is one whose welding condition has been verified to be normal. For example, the normal state impedance value can be determined by measuring the impedance values ​​of multiple unknown batteries, then determining the welding condition using other welding condition inspection methods such as destructive testing that samples the weld area, and selecting the impedance value measured from a battery with a normal welding condition as the normal state impedance value.

[0058] In the normal state impedance measurement step (step S110), the impedance is measured for a series of consecutive frequency values ​​to obtain the normal state impedance.

[0059] In the aforementioned test frequency extraction step (step S130), the measured frequency value when the imaginary part is 0 can be extracted as the test frequency.

[0060] In the battery measurement step (step S140), the impedance of the battery can be measured at the test frequency, which is a fixed frequency value. By testing the battery with a single frequency value that is not a frequency band, the impedance measurement time can be minimized, and even when applied to a mass production line of batteries, the delay in battery manufacturing time can be minimized.

[0061] In the welding condition determination step (step S150), if the impedance value of the battery under inspection is greater than the reference value, it can be determined that the welding is defective. The reference value can be set by considering the x-intercept value of the normal state call-call plot created in the normal state call-call plot creation step (step S120).

[0062] As shown in Figure 9, the battery manufacturing method of the present invention includes: an electrode assembly preparation step (step S100) in which a current collector and a separator membrane are laminated and then wound or stacked to prepare an electrode assembly; a first welding step (step S200) in which a tab or current collector plate is first welded to the current collector of the electrode assembly; a second welding step (step S300) in which a can housing or electrode leads are second welded to the tab or current collector plate; a primary determination step (step S400) in which an alternating current or alternating voltage is applied to the can housing or electrode leads in a set frequency band to determine the welding state of the first and second welds; an electrolyte injection step (step S500) in which electrolyte is injected while the electrode assembly is housed in a can housing or pouch case; and a secondary determination step (step S600) in which an alternating current or alternating voltage is applied to the can housing or electrode leads in a set frequency band to determine the welding state of the first and second welds.

[0063] The first judgment step (step S400) includes the steps of: applying an AC current or AC voltage in a set frequency band to measure a first impedance; creating a first Cole-Cole plot based on the first impedance; and determining that the welding condition of the battery is poor if the x-intercept value in the first Cole-Cole plot is greater than or equal to a first set value.

[0064] In another embodiment, the primary determination step (step S400) includes the steps of applying an alternating current or alternating voltage at a test frequency to measure the impedance, and determining that the welding condition of the battery is poor if the real part of the measured impedance is equal to or greater than a reference value.

[0065] The aforementioned secondary judgment step (step S600) includes the steps of: applying an AC current or AC voltage in a set frequency band to measure a second impedance; creating a second Cole-Cole plot based on the second impedance; and determining that the welding condition of the battery is poor if the value obtained by subtracting the x-intercept value from the real part of the minimum value in the second Cole-Cole plot is greater than or equal to a second set value.

[0066] Although embodiments of the present invention have been described above, these are merely illustrative examples, and those skilled in the art will understand that a wide variety of modifications and equivalent embodiments are possible. Therefore, the scope of technical protection of the present invention must be determined by the claims. [Industrial applicability]

[0067] The battery welding condition inspection method of the present invention is a method that allows for in-line 100% inspection during the battery production process, thereby improving the production quality of batteries and removing defective batteries in advance.

[0068] The battery welding condition inspection method of the present invention allows for confirmation of welding quality in a short amount of time.

[0069] The present invention provides a battery welding condition inspection method that allows for the determination of the battery's welding condition simply by measuring the impedance between the positive and negative electrodes in a short time without destroying the battery during the manufacturing process. This method can be applied to a battery manufacturing line and enables 100% inspection of all batteries produced.

[0070] The battery welding condition inspection method of the present invention allows for inspection of the welding condition before the electrolyte is injected, and can inspect the welding condition of the battery regardless of the electrolyte injection state. [Explanation of Symbols]

[0071] 11. Positive Equivalent Circuit 12 Negative Equivalent Circuit 15-wire AC impedance meter

Claims

1. A battery welding condition inspection method for inspecting the welding condition of a battery in which a tab or current collector plate is welded to the current collector of an electrode assembly in which a current collector and a separator membrane are wound or stacked, and a can housing or electrode leads are welded to the tab or current collector plate, Before the electrolyte is injected into the battery, a first impedance measurement step is performed to measure the value of the first impedance, which is the impedance value of the battery itself before the electrolyte is injected, by applying an alternating current or alternating voltage to the battery in a set frequency band via the electrode terminals included in the battery and electrode leads connected to the electrode terminals by welding, in order to inspect the welding condition. A first call-call plot creation step in which a first call-call plot is created based on the value of the first impedance, If the x-intercept value in the first call-call plot is greater than or equal to a first set value, the welding condition of the battery is judged to be poor in the first welding condition determination stage, After the electrolyte is injected into the battery, an alternating current or alternating voltage is applied to the battery via the electrode terminals and electrode leads in a set frequency band to measure the value of the second impedance, which is the impedance value of the battery itself into which the electrolyte has been injected, in order to inspect the welding condition. A second call-call plot creation step in which a second call-call plot is created based on the value of the second impedance, If the value obtained by subtracting the x-intercept value from the real part of the minimum value in the second call-call plot is greater than or equal to the second set value, the welding condition of the battery is judged to be poor in the secondary welding condition judgment stage, A method for inspecting the welding condition of batteries, including the welding condition of batteries.

2. In the first impedance measurement step and the second impedance measurement step, The method for inspecting the welding condition of a battery according to claim 1, wherein the value of the first impedance and the value of the second impedance are measured for each of a plurality of frequency values ​​within a set frequency band.

3. In the first impedance measurement step and the second impedance measurement step, The method for inspecting the welding condition of a battery according to claim 1, wherein the value of the first impedance and the value of the second impedance are measured with a four-wire AC impedance measuring instrument.

4. Multiple batteries are provided, In the first impedance measurement step or the second impedance measurement step, A method for inspecting the welding condition of a battery according to claim 1, wherein an alternating current or alternating voltage is applied to a plurality of batteries connected in parallel in a set frequency band, and the value of the first impedance or the value of the second impedance is measured.

5. The welding condition is good, and before electrolyte is injected into the battery, which includes electrode terminals and electrode leads connected to the electrode terminals by welding, an alternating current or alternating voltage is applied to the battery via the electrode terminals and electrode leads in a set frequency band to measure the normal state impedance, which is the impedance value of the battery itself before the electrolyte is injected, in order to inspect the welding condition. A normal state call-call plot creation step, which creates a normal state call-call plot based on the value of the normal state impedance, The inspection frequency extraction step involves extracting the frequencies corresponding to the normal state x intercept value in the normal state call plot as the inspection frequencies, Before the electrolyte is injected into the battery to be inspected, an alternating current or alternating voltage is applied to the battery via the electrode terminals and electrode leads at the inspection frequency to measure the impedance value in order to inspect the welding condition. A welding condition determination step in which the welding condition of the battery to be inspected is determined based on the impedance value of the battery to be inspected and a reference value set considering the x-intercept value, A method for inspecting the welding condition of batteries, including the welding condition of batteries.

6. In the manufacture of a battery including a negative electrode, a positive electrode, and a can housing or electrode leads, After laminating the current collector and separator membrane, the electrode assembly is prepared by winding or stacking them in an electrode assembly preparation step, A first welding step involves welding a tab or current collector plate to the current collector of the electrode assembly, A second welding step in which a can housing or electrode lead is second welded to the tab or the current collector plate, Before the electrolyte is injected into the battery, a first impedance measurement step is performed in which an alternating current or alternating voltage is applied to the battery in a set frequency band via the electrode terminals contained in the battery and the electrode leads connected to the electrode terminals by welding, and the value of the first impedance, which is the impedance value of the battery itself before the electrolyte is injected, is measured in order to inspect the state of the first and second welds. A first call-call plot creation step in which a first call-call plot is created based on the value of the first impedance, A primary determination step in which the welding status of the first and second welds is determined based on the x-intercept value in the first call-call plot, In response to determining the welding state of the first and second welds, an electrolyte injection step is performed in which the electrode assembly is housed in a can housing or pouch case and an electrolyte is injected; In response to the injection of the electrolyte, a secondary determination step is performed in which an alternating current or alternating voltage is applied to the electrode terminals and electrode leads in a set frequency band to determine the welding state of the first and second welds. Includes, The aforementioned second stage of judgment is, After the electrolyte has been injected into the battery, an alternating current or alternating voltage is applied to the battery via the electrode terminals and electrode leads in a set frequency band to measure the value of the second impedance, which is the impedance value of the battery itself into which the electrolyte has been injected, in order to inspect the state of the first and second welds. The steps include creating a second call-call plot based on the value of the second impedance, The process includes the step of determining that the welding condition of the battery is poor if the value obtained by subtracting the x-intercept value from the real part of the local minimum in the second call-call plot is greater than or equal to the second set value. Battery manufacturing method.

7. The aforementioned first stage of judgment is, A method for manufacturing a battery according to claim 6, comprising the step of determining that the welding state of the battery is poor if the x-intercept value in the first call-call plot is greater than or equal to a first set value.

8. The aforementioned second stage of judgment is, A method for manufacturing a battery according to claim 6, comprising the step of determining that the welding condition of the battery is poor if the value obtained by subtracting the x-intercept value from the real part value of the minimum value in the second Cole-Cole plot is greater than or equal to a second set value.

Images