Weld-defect detection system and method

Abstract

A weld-defect detection system and method are disclosed. A weld-defect detection system according to the present invention may comprise: a charging unit for charging a battery pack including a plurality of battery cells and electrode tabs welded to the plurality of battery cells; a discharging unit for discharging the charged battery pack; a voltage measurement unit for measuring voltages of the plurality of battery cells included in the battery pack according to charging or discharging through the charging unit or the discharging unit; and a weld-defect detection unit for detecting whether welds between the plurality of battery cells and the electrode tabs in the battery pack are defective, on the basis of results of voltage measurements of the plurality of battery cells measured by the voltage measurement unit.

Description

Defective welding detection system and method

[0001] The present invention relates to a defective welding detection system and method, and to a defective welding detection system and method for measuring the voltage of a plurality of battery cells included in a battery pack according to charging or discharging, and detecting whether welding of a plurality of battery cells and electrode tabs within the battery pack is defective based on the voltage measurement results.

[0002]

[0003] Secondary batteries, unlike non-rechargeable primary batteries, are rechargeable and dischargeable. Low-capacity secondary batteries are used in small, portable electronic devices such as smartphones, feature phones, laptop computers, digital cameras, and camcorders, while large-capacity secondary batteries are widely used as power sources for motor drives and power storage in hybrid and electric vehicles. A secondary battery comprises an electrode assembly having a positive and negative electrode, a case housing the electrode assembly, and electrode terminals connected to the electrode assembly.

[0004] In battery packs composed of secondary batteries, multiple battery cells are interconnected to secure the necessary power system depending on the applicable device. The multiple battery cells included in the battery pack are electrically connected through electrode tabs, and resistance welding between the multiple battery cells and the electrode tabs is essential during this process. When resistance welding multiple battery cells and electrode tabs in this way, if the welding is not performed properly, the battery pack will not function properly. Therefore, a process is required to detect whether the resistance welding has been performed properly. In particular, in battery packs where multiple battery cells are connected in series and parallel, the number of resistance welds to be checked is large, and direct inspection such as pull tests, visual inspections, and X-ray inspections is required to inspect them, which has the problem of requiring a lot of time and manpower. Furthermore, there is a problem that the quality of the battery pack that has passed the inspection results varies depending on the individual skills of the inspector.

[0005] The above-described information disclosed in the background technology of this invention is only intended to enhance understanding of the background of the present invention, and therefore may include information that does not constitute prior art.

[0006]

[0007] The problem to be solved by the present invention is to provide a defective welding detection system and method that measures the voltage of a plurality of battery cells included in a battery pack according to charging or discharging in order to solve the above-mentioned problem, and detects whether the welding of a plurality of battery cells and electrode tabs within the battery pack is defective based on the voltage measurement result.

[0008] However, the technical problems to be solved by the present invention are not limited to the problems described above, and other problems not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

[0009]

[0010] A defective welding detection system according to one embodiment of the present invention may include a charging unit for charging a battery pack including a plurality of battery cells and electrode tabs welded to the plurality of battery cells; a discharging unit for discharging the charged battery pack; a voltage measuring unit for measuring voltages of the plurality of battery cells included in the battery pack according to charging or discharging through the charging unit or the discharging unit; and a defective welding detecting unit for detecting whether welding of the plurality of battery cells and the electrode tabs within the battery pack is defective based on voltage measurement results of the voltage measuring unit for the plurality of battery cells.

[0011] In one embodiment, the voltage measuring unit can measure the voltage of each battery cell of each battery bank corresponding to a group of battery cells connected in parallel among the plurality of battery cells included in the battery pack charged through the charging unit.

[0012] In one embodiment, the charging unit can charge the battery pack at a predetermined charging rate for a predetermined charging time.

[0013] In one embodiment, the voltage measuring unit can measure the voltage of the battery cells of each battery bank after a predetermined rest period has elapsed after the battery pack is charged through the charging unit.

[0014] In one embodiment, the voltage measuring unit can measure the voltage of the battery cells of each battery bank included in the battery pack charged through the charging unit and then measure the voltage of the battery cells of each battery bank included in the battery pack discharged through the discharging unit.

[0015] In one embodiment, the discharge unit can discharge the battery pack at a predetermined discharge rate for a predetermined discharge time.

[0016] In one embodiment, the voltage measuring unit can measure the voltage of the battery cell of each battery bank after a predetermined rest period after the battery pack is discharged through the discharging unit.

[0017] In one embodiment, the defective welding detection unit calculates a voltage difference between a battery bank having a maximum voltage and a battery bank having a minimum voltage, and when the voltage difference between the battery bank having the maximum voltage and the battery bank having the minimum voltage is equal to or greater than a predetermined first voltage value, it can be determined that the welding of the plurality of battery cells and the electrode tabs within the battery pack is defective.

[0018] In one embodiment, when the welding of the plurality of battery cells and the electrode tabs within the battery pack is determined to be defective, the defective welding detection unit calculates a voltage difference between a battery cell having a maximum voltage and a battery cell having a minimum voltage within each battery bank, and determines a battery bank in which the voltage difference between the battery cell having the maximum voltage and the battery cell having the minimum voltage is greater than a predetermined second voltage value as a battery bank with defective welding.

[0019] In one embodiment, the defective welding detection system may include a control unit that communicates with a battery management system (BMS) included in the battery pack to control charging of the charging unit or discharging of the discharging unit.

[0020] A method for detecting defective welding according to one embodiment of the present invention may include a charging step of charging a battery pack including a plurality of battery cells and electrode tabs welded to the plurality of battery cells through a charging unit; a discharging step of discharging the charged battery pack through a discharging unit; a voltage measuring step of measuring voltages of the plurality of battery cells included in the battery pack according to charging or discharging through the charging unit or the discharging unit through a voltage measuring unit; and a defective welding detecting step of detecting whether welding of the plurality of battery cells and the electrode tabs within the battery pack is defective based on voltage measurement results of the voltage measuring unit of the plurality of battery cells through a defective welding detecting unit.

[0021] In one embodiment, the voltage measuring step may include a step of measuring the voltage of each battery cell of each battery bank corresponding to a group of battery cells connected in parallel among the plurality of battery cells included in the battery pack charged through the charging unit.

[0022] In one embodiment, the charging step may include charging the battery pack at a predetermined charge rate for a predetermined charge time.

[0023] In one embodiment, the voltage measuring step may include a step of measuring the voltage of a battery cell of each battery bank after a predetermined rest period has elapsed after the battery pack is charged through the charging unit.

[0024] In one embodiment, the voltage measuring step may include a step of measuring the voltage of the battery cells of each battery bank included in the battery pack charged through the charging unit and then measuring the voltage of the battery cells of each battery bank included in the battery pack discharged through the discharging unit.

[0025] In one embodiment, the discharging step may include discharging the battery pack at a predetermined discharge rate for a predetermined discharge time.

[0026] In one embodiment, the voltage measuring step may include a step of measuring the voltage of a battery cell of each battery bank after a predetermined rest period has elapsed after the battery pack is discharged through the discharge unit.

[0027] In one embodiment, the defective welding detection step may include: calculating a voltage difference between a battery bank having a maximum voltage and a battery bank having a minimum voltage; and determining that the welding of the plurality of battery cells and the electrode tabs within the battery pack is defective when the voltage difference between the battery bank having the maximum voltage and the battery bank having the minimum voltage is equal to or greater than a predetermined first voltage value.

[0028] In one embodiment, the defective welding detection step may further include, when it is determined that the welding of the plurality of battery cells and the electrode tabs within the battery pack is defective, calculating a voltage difference between a battery cell having a maximum voltage and a battery cell having a minimum voltage within each battery bank; and determining a battery bank in which the voltage difference between the battery cell having the maximum voltage and the battery cell having the minimum voltage is greater than a predetermined second voltage value as a battery bank with defective welding.

[0029] In one embodiment, the defective welding detection method may include a control step of controlling charging of the charging unit or discharging of the discharging unit by communicating with a battery management system (BMS) included in the battery pack through a control unit.

[0030]

[0031] According to one embodiment of the present invention, by measuring the voltage of a plurality of battery cells included in a battery pack according to charging or discharging, and detecting whether welding of a plurality of battery cells and electrode tabs within the battery pack is defective based on the voltage measurement result, a resistance welding inspection can be automatically performed without the need to perform direct inspection through time and manpower during a resistance welding inspection.

[0032] According to one embodiment of the present invention, after automatically performing a resistance welding inspection in the first stage, a separate detailed inspection is performed in the second stage on a product that is problematic due to defective welding, thereby shortening the process lead time and efficiently performing selection of defective resistance welding.

[0033] However, the effects that can be obtained through the present invention are not limited to the effects described above, and other technical effects that are not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

[0034]

[0035] The following drawings attached to this specification illustrate preferred embodiments of the present invention, and together with the detailed description of the invention described below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0036] Figure 1a is a top perspective view of a cylindrical secondary battery.

[0037] Figure 1b is a cross-sectional view of a cylindrical secondary battery.

[0038] FIG. 2 is a drawing illustrating a battery pack to which a defective welding detection system according to one embodiment of the present invention can be applied.

[0039] FIG. 3 is a schematic diagram illustrating a defective welding detection system according to one embodiment of the present invention.

[0040] Figure 4 is a flowchart for explaining a method for detecting defective welding according to one embodiment of the present invention.

[0041]

[0042] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, terms or words used in this specification and claims should not be interpreted as limited to their typical or dictionary meanings, and should be interpreted with meanings and concepts that conform to the technical spirit of the present invention based on the principle that the inventor can appropriately define the concept of a term to best explain his or her own invention. Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are only some of the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention. Therefore, it should be understood that various equivalents and modified examples may exist as substitutes for them at the time of filing this application.

[0043] Additionally, when used herein, the terms "comprise", "include" and / or "comprising", "including" specify the presence of stated features, numbers, steps, operations, elements, elements and / or groups thereof, but do not preclude the presence or addition of one or more other features, numbers, operations, elements, elements and / or groups thereof.

[0044] Additionally, to facilitate understanding of the invention, the attached drawings may not be drawn to scale and some components may be exaggerated in size. Furthermore, identical components may be assigned the same reference numbers in different embodiments.

[0045] The statement that two compared objects are "identical" means "substantially identical." Therefore, "substantially identical" may include deviations considered low in the art, such as deviations of less than 5%. Furthermore, uniformity of a parameter over a given region may imply uniformity on average.

[0046] Although terms like "first" and "second" are used to describe various components, these components are not limited by these terms. These terms are used merely to distinguish one component from another, and unless otherwise specified, a "first" component may also be a "second" component.

[0047] Throughout the specification, unless otherwise specifically stated, each element may be singular or plural.

[0048] Any configuration being placed “on top (or bottom)” of a component or “on top (or bottom)” of a component may mean not only that any configuration is placed in contact with the top (or bottom) surface of said component, but also that other configurations may intervene between said component and any configuration placed on (or under) said component.

[0049] Additionally, when a component is described as being "on," "connected to," or "coupled to" another component, it should be understood that the components may be directly connected or coupled to one another, but that other components may also be "interposed" between the components, or that each component may be "connected," "coupled," or "connected" through other components.

[0050] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. Furthermore, the use of "may" when describing embodiments of the present invention refers to "one or more embodiments of the present invention." Expressions such as "one or more" and "one or more" preceding a list of elements modify the list as a whole and do not modify individual elements within the list.

[0051] When reference is made throughout the specification to “A and / or B,” this means A, B, or A and B, unless otherwise stated, and when reference is made to “C to D,” this means C or more and D or less, unless otherwise stated.

[0052] When phrases such as "at least one of A, B, and C," "at least one of A, B, or C," "at least one selected from the group A, B, and C," or "at least one selected from A, B, and C," are used to specify a list of elements A, B, and C, the phrases can refer to any suitable combination.

[0053] The term "use" may be considered synonymous with the term "utilize." As used herein, the terms "substantially," "about," and similar terms are used as terms of approximation rather than degrees, and are intended to take into account inherent variations in measured or calculated values ​​that would be recognized by those skilled in the art.

[0054] Although terms such as first, second, third, etc. may be used herein to describe various elements, components, regions, layers, and / or sections, these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or cross-section from another element, component, region, layer, or cross-section. Thus, a first element, component, region, layer, or section discussed below could also be termed a second element, component, region, layer, or section without departing from the teachings of the exemplary embodiments.

[0055] For ease of description, spatially relative terms such as "beneath," "below," "lower," "above," "upper," and the like may be used in the specification to describe the relationship of one element or feature to other element(s) or features as depicted in the drawings. It will be understood that spatially relative positions encompass different orientations of the device in use or operation in addition to the orientations depicted in the figures. For example, if the device in the drawings is turned over, other elements are understood to be "beneath" or "below," and the depicted elements are understood to be "above" or "above" other elements. Thus, the term "beneath" can encompass both the above and below orientations.

[0056] The terms used herein are for the purpose of describing embodiments of the invention and are not intended to limit the invention.

[0057]

[0058] The present invention will be described in detail with reference to the attached drawings below.

[0059]

[0060] Secondary batteries come in coin, cylindrical, square, and pouch shapes. Since the present invention is fundamentally applicable to cylindrical secondary batteries, a brief overview of cylindrical secondary batteries will be provided before describing embodiments of the present invention.

[0061] Figure 1a is a top perspective view of a cylindrical secondary battery, and Figure 1b is a cross-sectional view of the cylindrical secondary battery.

[0062] Referring to FIGS. 1A and 1B, a cylindrical secondary battery includes an electrode assembly (30), a case (10) that accommodates the electrode assembly (30) and an electrolyte therein, a cap assembly (50) that is coupled to an opening of the case (10) to seal the case (10), and an insulating plate (37) positioned between the electrode assembly (30) and the cap assembly (50) inside the case (10).

[0063] The electrode assembly (30) may include a separator (32), a first electrode (33) and a second electrode (31) positioned with the separator (32) between them, and may be wound in a jelly-roll shape.

[0064] The first electrode (33) includes a first substrate and a first active material layer positioned on the first substrate. A first lead tab (35) may extend outward from a first non-conductive portion of the first substrate where the first active material layer is not positioned, and the first lead tab (35) may be electrically connected to a cap assembly (50).

[0065] The second electrode (31) includes a second substrate and a second active material layer positioned on the second substrate. A second lead tab (34) may extend outward from a second non-conductive portion of the second substrate where the second active material layer is not positioned, and the second lead tab (34) may be electrically connected to the case (10). The first lead tab (35) and the second lead tab (34) may extend in opposite directions.

[0066] The first electrode (33) can function as a positive electrode. In this case, the first substrate can be composed of, for example, aluminum foil, and the first active material layer can include, for example, a transition metal oxide. The second electrode (31) can function as a negative electrode. In this case, the second substrate can be composed of, for example, copper foil or nickel foil, and the second active material layer can include, for example, graphite.

[0067] The separator (32) functions to prevent short circuiting between the first electrode (33) and the second electrode (31) while allowing the movement of lithium ions. The separator (32) may be composed of, for example, a polyethylene film, a polypropylene film, a polyethylene-polypropylene film, etc.

[0068] The case (10) accommodates the electrode assembly (30) and the electrolyte, and together with the cap assembly (50) forms the outer shape of the battery. The case (10) may include a body portion (12) having a roughly cylindrical shape, and a bottom portion (11) connected to one side of the body portion (12). A beading portion (13) deformed toward the inside may be positioned in the body portion (12), and a crimping portion (15) bent toward the inside may be positioned at an end on the opening side of the body portion (12).

[0069] The beading portion (13) can prevent the electrode assembly (30) from moving inside the case (10) and facilitate the settling of the gasket (14) and the cap assembly (50). The crimping portion (15) can firmly fix the cap assembly (50) by pressing the edge of the cap assembly (50) through the gasket (14). The case (10) can be made of, for example, nickel-plated iron.

[0070] The cap assembly (50) can be secured to the inside of the crimping portion (15) through the gasket (14) to seal the case (10). The cap assembly (50) can include a cap up, a safety vent, a cap down, an insulating member, and a sub-plate, but is not limited to these examples and can be modified in various ways.

[0071] The cap up may be positioned at the uppermost side of the cap assembly (50). The cap up may include a terminal portion that protrudes upwardly to be connected to an external circuit, and an exhaust port for discharging gas may be positioned around the terminal portion.

[0072] The safety vent may be located beneath the cap up. The safety vent may include a protrusion that protrudes downwardly and connects to the subplate, and at least one notch located around the protrusion.

[0073] If gas is generated due to overcharging or abnormal operation of the secondary battery, the protrusion may be deformed upward by pressure and separated from the subplate, while the safety vent may be cut along the notch. The cut safety vent can release the gas to the outside, preventing an explosion of the secondary battery.

[0074] The cap down may be positioned below the safety vent. The cap down may have a first opening for exposing the protrusion of the safety vent and a second opening for gas discharge. An insulating member may be positioned between the safety vent and the cap down to insulate the safety vent and the cap down.

[0075] The sub-plate may be positioned below the cap down. The sub-plate may be secured to the lower surface of the cap down to block the first opening of the cap down, and a protrusion of the safety vent may be secured to the sub-plate. A first lead tab (35) extended from the electrode assembly (30) may be secured to the sub-plate. Accordingly, the cap up, the safety vent, the cap down, and the sub-plate may be electrically connected to the first electrode (33) of the electrode assembly (30).

[0076] The insulating plate (37) may be positioned to contact the electrode assembly (30) below the beading portion (13), and a tab opening for withdrawing a first lead tab (35) may be provided in the insulating plate (37). The cap assembly (50), which is electrically connected to the first electrode (33) by the first lead tab (35), faces the electrode assembly (30) with the insulating plate (37) interposed therebetween, and may be maintained in an insulated state from the electrode assembly (30) by the insulating plate (37). Meanwhile, another insulating plate (36) may be included for insulation between the electrode assembly (30) and the bottom portion (11) of the case (10).

[0077]

[0078] FIG. 2 is a drawing illustrating a battery pack to which a defective welding detection system according to one embodiment of the present invention can be applied.

[0079] Referring to FIG. 2, a battery pack (60) to which a defective welding detection system according to one embodiment of the present invention can be applied includes a plurality of battery cells (61), a cell holder (62) that supports the plurality of battery cells (61) to maintain an array structure, an electrode tab (63) for electrically connecting the plurality of battery cells (61) in a multi-series-parallel structure, and a battery management system (BMS) that monitors current, voltage, temperature, etc. of the plurality of battery cells (61) and manages charging and discharging.

[0080] The process of manufacturing a battery pack (60) includes a process of fastening a plurality of battery cells (61) to a cell holder (62) and electrically connecting electrode tabs (63) to the electrodes of the plurality of battery cells (61) by resistance welding. Conventionally, the inspection of whether the welding between the plurality of battery cells (61) and the electrode tabs (64) was properly performed was performed by directly inspecting each battery cell (61) to find welding defects through a full inspection such as a pull test, a visual inspection, and an X-ray inspection. Accordingly, the conventional method of inspecting for defective welding took a lot of time and manpower, and there was a problem that the quality of the battery pack that had undergone the inspection results varied depending on the individual ability of the inspector.

[0081]

[0082] FIG. 3 is a schematic diagram illustrating a defective welding detection system according to one embodiment of the present invention.

[0083] Referring to FIG. 3, a defective welding detection system (100) according to one embodiment of the present invention is connected to a battery pack (60) and detects whether welding of a plurality of battery cells (61) and electrode tabs (63) within the battery pack (60) is defective. In one embodiment, the battery pack (60) may be the battery pack (60) described with reference to FIG. 2.

[0084] A defective welding detection system (100) according to one embodiment of the present invention may include a charging unit (110), a discharging unit (120), a voltage measuring unit (130), a defective welding detection unit (140), and a control unit (150).

[0085]

[0086] The charging unit (110) charges the battery pack (60) including a plurality of battery cells (61) and electrode tabs (63) welded to the plurality of battery cells (61). In one embodiment, the charging unit (110) may charge for a predetermined period of time before inspection. This is because the defective welding detection system (100) according to one embodiment of the present invention can detect defective welding for a battery pack (60) that has been charged to a predetermined amount. For example, the charging unit (110) may charge for 10 minutes with a current of 5 A. Then, the charging unit (110) may charge the battery pack (60) at a predetermined charging rate for a predetermined charging time in order to perform an inspection for detecting defective welding. Here, the predetermined charging rate and charging time may be determined according to the specifications of the charger that charges the battery pack (60). For example, the predetermined charging rate may be 0.3 C, and the predetermined charging time may be 3 seconds.

[0087]

[0088] The discharge unit (120) can discharge the charged battery pack (60). The discharge unit (120) can consume electricity by passing a current flowing from the battery pack (60) through a resistor. In one embodiment, the battery pack (60) charged by the charging unit (110) can be discharged at a predetermined discharge rate for a predetermined discharge time. Generally, the discharge current is greater than the charge current, and therefore, the predetermined discharge rate may be greater than the predetermined charge rate of the charging unit (110). For example, the predetermined discharge rate may be 0.5 C, and the predetermined discharge time may be 3 seconds.

[0089]

[0090] The voltage measuring unit (130) measures the voltage of a plurality of battery cells (61) included in the battery pack (60) according to charging or discharging through the charging unit (110) or the discharging unit (120).

[0091] In one embodiment, the voltage measuring unit (130) can measure the voltage of the battery cells (61) of each battery bank corresponding to a group of battery cells (61) connected in parallel among a plurality of battery cells (61) included in a battery pack (60) charged through the charging unit (110). At this time, the voltage measuring unit (130) can measure the voltage of the battery cells (61) of each battery bank after a predetermined rest period has elapsed after the battery pack (60) has been charged through the charging unit (110). The purpose of this predetermined rest period is to measure the voltage of the battery cells (61) of each battery bank after the voltage has stabilized. However, the voltages measured at this time do not show a significant difference for each battery bank.

[0092] In one embodiment, after measuring the voltage of the battery cell (61) of each battery bank included in the battery pack (60) charged through the charging unit (110), the voltage measuring unit (130) can measure the voltage of the battery cell (61) of each battery bank included in the battery pack (60) discharged through the discharging unit (120). At this time, the voltage measuring unit (130) can measure the voltage of the battery cell (61) of each battery bank after a predetermined rest period has elapsed after the battery pack (60) has been discharged through the discharging unit (120). The purpose of this predetermined rest period is to measure the voltage after the voltage of the battery cell (61) of each battery bank has stabilized. Unlike after charging, the measured voltage after discharging shows a significant difference for each battery bank because the discharge current is greater than the charge current. Therefore, it is possible to detect whether the welding of multiple battery cells (61) and electrode tabs (63) is poor by using the voltage difference for each battery bank.

[0093]

[0094] The defective welding detection unit (140) detects whether the welding of the plurality of battery cells (61) and the electrode tabs (63) within the battery pack (60) is defective based on the voltage measurement results of the plurality of battery cells (61) of the voltage measurement unit (130). In one embodiment, the defective welding detection unit (140) calculates the voltage difference between the battery bank having the maximum voltage and the battery bank having the minimum voltage, and when the voltage difference between the battery bank having the maximum voltage and the battery bank having the minimum voltage is equal to or greater than a predetermined first voltage value, it can be determined that the welding of the plurality of battery cells (61) and the electrode tabs (63) within the battery pack (60) is defective.

[0095] In addition, in one embodiment, when the defective welding detection unit (140) determines that the welding of a plurality of battery cells (61) and electrode tabs (63) within the battery pack (60) is defective, the unit calculates the voltage difference between the battery cell having the maximum voltage and the battery cell having the minimum voltage within each battery bank, and determines a battery bank in which the voltage difference between the battery cell having the maximum voltage and the battery cell having the minimum voltage is greater than a predetermined second voltage value as a battery bank with defective welding.

[0096] Accordingly, the defective welding detection system (100) according to one embodiment of the present invention can not only determine whether the welding of a plurality of battery cells (61) and electrode tabs (63) within a battery pack (60) is defective, but can also detect a battery bank in which an actual welding defect has occurred. Here, the predetermined first voltage value or the predetermined second voltage value may be a voltage difference value derived from a normal battery pack after deleting one electrode tab and then performing the charge / discharge and voltage measurement process as described above. This is because, if a welding defect has occurred between one electrode tab and a battery cell, a voltage difference value similar to that in which one electrode tab has been deleted will be derived.

[0097]

[0098] The control unit (150) can control the charging of the charging unit (110) or the discharging of the discharging unit (120) by communicating with the BMS (64) included in the battery pack (60). In one embodiment, the control unit (150) can include a communication module for communicating with the BMS (64). At this time, both wired and wireless communication methods can be used as the communication method.

[0099]

[0100] Figure 4 is a flowchart for explaining a method for detecting defective welding according to one embodiment of the present invention.

[0101] As illustrated in FIG. 4, a defective welding detection method according to one embodiment of the present invention may include steps S210 to S250.

[0102] Step S210 is a charging step for charging a battery pack including a plurality of battery cells and electrode tabs welded to the plurality of battery cells through a charging unit. Step S210 may include a step for charging the battery pack at a predetermined charging rate for a predetermined charging time.

[0103] Step S220 is a discharging step for discharging a charged battery pack through a discharging unit. In one embodiment, step S220 may include discharging the battery pack at a predetermined discharge rate for a predetermined discharge time.

[0104] Step S230 is a control step that controls the charging of the charging unit or the discharging of the discharging unit by communicating with the battery management system (BMS) included in the battery pack through the control unit.

[0105] Step S240 is a voltage measuring step for measuring the voltage of a plurality of battery cells included in a battery pack according to charging or discharging through a charging unit or a discharging unit through a voltage measuring unit. In one embodiment, step S240 may include a step for measuring the voltage of a battery cell of each battery bank corresponding to a group of battery cells connected in parallel among a plurality of battery cells included in a battery pack charged through the charging unit. And in one embodiment, step S240 may include a step for measuring the voltage of a battery cell of each battery bank included in a battery pack charged through the charging unit and then measuring the voltage of a battery cell of each battery bank included in a battery pack discharged through the discharging unit.

[0106] Step S250 is a defective welding detection step that detects whether the welding of a plurality of battery cells and electrode tabs within a battery pack is defective based on the voltage measurement results of a voltage measurement unit of a plurality of battery cells through a defective welding detection unit. In one embodiment, step S250 may include a step of calculating a voltage difference between a battery bank having a maximum voltage and a battery bank having a minimum voltage, and a step of determining that the welding of the plurality of battery cells and the electrode tabs within the battery pack is defective if the voltage difference between the battery bank having the maximum voltage and the battery bank having the minimum voltage is equal to or greater than a first voltage value. In another embodiment, step S250 may include a step of calculating a voltage difference between a battery cell having a maximum voltage and a battery cell having a minimum voltage within each battery bank if the welding of the plurality of battery cells and the electrode tabs within the battery pack is determined to be defective, and a step of determining that a battery bank in which the voltage difference between the battery cell having the maximum voltage and the battery cell having the minimum voltage is equal to or greater than a second voltage value is a battery bank having defective welding.

[0107]

[0108] The method for detecting defective welds according to an embodiment of the present invention, as described above, has been described with reference to the flowchart presented in the drawings. For simplicity, the method has been depicted and described as a series of blocks; however, the present invention is not limited to the order of the blocks, and some blocks may occur in a different order or simultaneously with other blocks than depicted and described herein, and various other branches, flow paths, and block orders that achieve the same or similar results may be implemented. Furthermore, not all depicted blocks may be required to implement the method described herein.

[0109]

[0110] Meanwhile, in the description referring to FIG. 4, each step may be further divided into additional steps or combined into fewer steps, depending on the implementation of the present invention. Furthermore, some steps may be omitted as needed, and the order of steps may be changed. Furthermore, even if other omitted content is present, the content of FIGS. 1A to 3 may be applied to the content of FIG. 4. Furthermore, the content of FIG. 4 may be applied to the content of FIGS. 1A to 3.

[0111]

[0112] Below, materials that can be used in a secondary battery according to the present invention are described.

[0113] A compound capable of reversible intercalation and deintercalation of lithium (a lithiated intercalation compound) can be used as a cathode active material. Specifically, one or more of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof can be used.

[0114] The above composite oxide may be a lithium transition metal composite oxide, and specific examples thereof include lithium nickel-based oxide, lithium cobalt-based oxide, lithium manganese-based oxide, lithium iron phosphate-based compound, cobalt-free nickel-manganese-based oxide, or a combination thereof.

[0115] As an example, a compound represented by any one of the following chemical formulas may be used: Li a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b-c Mn b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); Li a NiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Lia Mn2G b O4(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5); Li (3-f) Fe2(PO4)3(0≤f≤2); Li a FePO4(0.90≤a≤1.8).

[0116] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; L 1 is Mn, Al, or a combination thereof.

[0117] A positive electrode for a lithium secondary battery may include a current collector and a positive electrode active material layer formed on the current collector. The positive electrode active material layer includes a positive electrode active material and may further include a binder and / or a conductive material.

[0118] The content of the positive electrode active material may be 90 wt% to 99.5 wt% with respect to 100 wt% of the positive electrode active material layer, and the contents of the binder and conductive material may be 0.5 wt% to 5 wt%, respectively, with respect to 100 wt% of the positive electrode active material layer.

[0119] The above-mentioned collector may be made of Al, but is not limited thereto.

[0120] The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0121] The material capable of reversibly intercalating / deintercalating the lithium ions may include a carbon-based negative electrode active material, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0122] As the material capable of doping and dedoping the lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used. The Si-based negative electrode active material may be silicon, a silicon-carbon composite, SiOx (0 <x<2), Si계 합금, 또는 이들의 조합일 수 있다.

[0123] The above silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles.

[0124] The silicon-carbon composite may further comprise crystalline carbon. For example, the silicon-carbon composite may comprise a core comprising crystalline carbon and silicon particles and an amorphous carbon coating layer positioned on the surface of the core.

[0125] A negative electrode for a lithium secondary battery includes a current collector and a negative electrode active material layer positioned on the current collector. The negative electrode active material layer includes a negative electrode active material and may further include a binder and / or a conductive material.

[0126] For example, the negative electrode active material layer may include 90 to 99 wt% of the negative electrode active material, 0.5 to 5 wt% of the binder, and 0 to 5 wt% of the conductive material.

[0127] The above binder may be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof. When an aqueous binder is used as the negative electrode binder, a cellulose-based compound capable of imparting viscosity may be further included.

[0128] The negative electrode current collector may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and a combination thereof.

[0129] An electrolyte for a lithium secondary battery contains a non-aqueous organic solvent and a lithium salt.

[0130] The above non-aqueous organic solvent acts as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0131] The above non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof, and may be used alone or in combination of two or more thereof.

[0132] Additionally, when using a carbonate solvent, a mixture of cyclic carbonate and chain carbonate can be used.

[0133] Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators may be polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film comprising two or more layers of these materials.

[0134] The separator may include a porous substrate and a coating layer comprising an organic material, an inorganic material, or a combination thereof, positioned on one or both sides of the porous substrate.

[0135] The above organic material may include a polyvinylidene fluoride-based antibody or a (meth)acrylic polymer.

[0136] The above inorganic materials are Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, It may include inorganic particles selected from, but not limited to, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0137] The organic and inorganic substances may be mixed and present in one coating layer, or a coating layer including an organic substance and a coating layer including an inorganic substance may be present in a laminated form.

[0138]

[0139] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical idea of ​​the present invention and the equivalent scope of the patent claims to be described below by a person having ordinary skill in the art to which the present invention pertains.

Claims

A charging unit for charging a battery pack including a plurality of battery cells and electrode tabs welded to the plurality of battery cells; A discharge unit for discharging the charged battery pack; A voltage measuring unit that measures the voltage of the plurality of battery cells included in the battery pack according to charging or discharging through the charging unit or the discharging unit; and A defective welding detection system characterized by including a defective welding detection unit that detects whether welding of the plurality of battery cells and the electrode tabs within the battery pack is defective based on voltage measurement results of the plurality of battery cells by the voltage measurement unit. In the first paragraph, The above voltage measuring unit, A defective welding detection system characterized in that the voltage of each battery cell of each battery bank corresponding to a group of battery cells connected in parallel among the plurality of battery cells included in the battery pack charged through the charging unit is measured. In the second paragraph, The above charging part, A defective welding detection system characterized in that the battery pack is charged at a predetermined charging rate for a predetermined charging time. In the second paragraph, The above voltage measuring unit, A defective welding detection system characterized in that after the battery pack is charged through the charging unit and a predetermined rest period has elapsed, the voltage of the battery cell for each battery bank is measured. In the second paragraph, The above voltage measuring unit, A defective welding detection system characterized in that the voltage of the battery cells of each battery bank included in the battery pack charged through the charging unit is measured, and then the voltage of the battery cells of each battery bank included in the battery pack discharged through the discharging unit is measured. In paragraph 5, The above discharge unit is, A defective welding detection system characterized by discharging the above battery pack at a predetermined discharge rate for a predetermined discharge time. In paragraph 5, The above voltage measuring unit, A defective welding detection system characterized in that after the battery pack is discharged through the discharge unit and a predetermined rest period has elapsed, the voltage of the battery cell of each battery bank is measured. In paragraph 5, The above defective welding detection unit, A defective welding detection system characterized in that it calculates a voltage difference between a battery bank having a maximum voltage and a battery bank having a minimum voltage, and if the voltage difference between the battery bank having the maximum voltage and the battery bank having the minimum voltage is equal to or greater than a predetermined first voltage value, it is determined that the welding of the plurality of battery cells and the electrode tabs within the battery pack is defective. In paragraph 8, The above defective welding detection unit, A defective welding detection system characterized in that, when the welding of the plurality of battery cells and the electrode tabs within the battery pack is determined to be defective, the voltage difference between the battery cell having the maximum voltage and the battery cell having the minimum voltage within each battery bank is calculated, and a battery bank in which the voltage difference between the battery cell having the maximum voltage and the battery cell having the minimum voltage is greater than a predetermined second voltage value is determined to be a battery bank with defective welding. In the first paragraph, A defective welding detection system characterized by including a control unit that controls charging of the charging unit or discharging of the discharging unit by communicating with a battery management system (BMS) included in the battery pack. A charging step for charging a battery pack including a plurality of battery cells and electrode tabs welded to the plurality of battery cells through a charging unit; A discharging step for discharging the charged battery pack through a discharging section; A voltage measuring step for measuring the voltage of the plurality of battery cells included in the battery pack according to charging or discharging through the charging unit or the discharging unit through the voltage measuring unit; and A method for detecting defective welding, characterized in that it includes a defective welding detection step for detecting whether welding of the plurality of battery cells and the electrode tab within the battery pack is defective based on voltage measurement results of the plurality of battery cells by the voltage measurement unit through a defective welding detection unit. In Article 11, The above voltage measurement step is, A method for detecting defective welding, characterized in that it comprises a step of measuring the voltage of a battery cell of each battery bank corresponding to a group of battery cells connected in parallel among the plurality of battery cells included in the battery pack charged through the charging unit. In Article 12, The above charging step is, A method for detecting defective welding, characterized in that it comprises a step of charging the battery pack at a predetermined charging rate for a predetermined charging time. In Article 12, The above voltage measurement step is, A method for detecting defective welding, characterized in that it comprises a step of measuring the voltage of a battery cell for each battery bank after a predetermined rest period has elapsed after the battery pack is charged through the charging unit. In Article 12, The above voltage measurement step is, A method for detecting defective welding, characterized in that it comprises a step of measuring the voltage of a battery cell of each battery bank included in the battery pack charged through the charging unit and then measuring the voltage of a battery cell of each battery bank included in the battery pack discharged through the discharging unit. In Article 15, The above discharge step is, A method for detecting defective welding, characterized in that it comprises a step of discharging the battery pack at a predetermined discharge rate for a predetermined discharge time. In Article 15, The above voltage measurement step is, A method for detecting defective welding, characterized in that it comprises a step of measuring the voltage of a battery cell for each battery bank after a predetermined rest period has passed after the battery pack has been discharged through the discharge unit. In Article 15, The above defective welding detection step is: A step of calculating the voltage difference between a battery bank having a maximum voltage and a battery bank having a minimum voltage; and A method for detecting defective welding, characterized in that it includes a step of determining that the welding of the plurality of battery cells and the electrode tabs within the battery pack is defective when the voltage difference between the battery bank having the maximum voltage and the battery bank having the minimum voltage is equal to or greater than a predetermined first voltage value. In Article 18, The above defective welding detection step is: When the welding of the plurality of battery cells and the electrode tabs within the battery pack is determined to be poor, a step of calculating the voltage difference between the battery cell having the maximum voltage and the battery cell having the minimum voltage within each battery bank; and A method for detecting defective welding, characterized in that it further includes a step of determining a battery bank in which a voltage difference between a battery cell having the maximum voltage and a battery cell having the minimum voltage is greater than a predetermined second voltage value as a battery bank with defective welding. In Article 11, A method for detecting defective welding, characterized in that it includes a control step for controlling charging of the charging unit or discharging of the discharging unit by communicating with a battery management system (BMS) included in the battery pack through a control unit.

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