KR20220170263A - Pouch type battery case inspection system and method - Google Patents

Abstract

A pouch type battery case inspection method according to an embodiment of the present invention can inspect a pouch type battery case having a cup unit with indented shape formed. The inspection method comprises: a profile measuring step in which a pair of contactless profile sensors placed to face each other with the battery case therebetween measure a first profile corresponding to an inner surface of the cup unit and a second profile corresponding to an outer surface of the cup unit; an extension unit determining step which determines a first point corresponding to an extension unit of the cup unit on the first profile and a second point corresponding to the extension unit on the second profile; and a thickness calculating step which calculates a distance between the first point and the second point as a thickness of the extension unit.

Description

Pouch type battery case inspection system and inspection method {POUCH TYPE BATTERY CASE INSPECTION SYSTEM AND METHOD}

The present invention relates to an inspection system and inspection method for a pouch-type battery case in which a cup portion is formed.

In general, a secondary battery means a battery that can be charged and discharged, unlike a primary battery that cannot be charged, and is widely used in electronic devices such as mobile phones, laptop computers, and camcorders, or electric vehicles. In particular, since the lithium secondary battery has a higher capacity than a nickel-cadmium battery or a nickel-hydrogen battery and has a high energy density per unit weight, the degree of its utilization is rapidly increasing.

These lithium secondary batteries mainly use a lithium-based oxide and a carbon material as a positive electrode active material and a negative electrode active material, respectively. A lithium secondary battery includes an electrode assembly in which a plurality of electrodes each coated with such an electrode active material are disposed with a separator interposed therebetween, and an exterior material for sealing and housing the electrode assembly together with an electrolyte solution.

Lithium secondary batteries are classified according to the structure of the electrode assembly of the cathode/separator/cathode structure. Typically, a jelly-roll electrode having a structure in which long sheet-type cathodes and anodes are wound with a separator interposed therebetween. assembly, a stacked electrode assembly in which a plurality of positive electrodes and negative electrodes cut in units of a predetermined size are sequentially stacked with a separator interposed therebetween, and a bi-cell (bi-cell) in which positive electrodes and negative electrodes of a predetermined unit are stacked with a separator interposed therebetween A stack/folding type electrode assembly having a structure in which a cell or a full-cell are wound may be mentioned.

Recently, a pouch-type battery having a structure in which a stacked or stacked/folding type electrode assembly is embedded in a pouch-type battery case of an aluminum laminate sheet has attracted a lot of attention for reasons such as low manufacturing cost, light weight, and easy shape deformation. Its usage is gradually increasing.

A method of manufacturing such a pouch-type battery case may include a forming process of forming a cup part in a pouch film, a storage process of accommodating an electrode assembly in the cup part, and a sealing process of folding and sealing the pouch film. Particularly, in the forming process, the pouch film is pressed by a punch while being seated on a die, so that a portion of the pouch film is stretched to form a cup portion.

However, if a local region of the pouch film is excessively stretched in the forming process, there is a risk of generating a pin-hole or crack in the corresponding region. Therefore, in order to manage this risk, an inspection for determining whether the cup portion of the pouch type battery case is excessively stretched is required.

One problem to be solved by the present invention is to provide an inspection system and inspection method capable of quickly and simply inspecting the thickness of an elongated part of a cup part formed in a pouch-type battery case.

Another problem to be solved by the present invention is to provide an inspection system and inspection method capable of performing a total inspection on the thickness of the stretched portion.

The pouch-type battery case inspection method according to an embodiment of the present invention may inspect a pouch-type battery case in which a cup portion having a recessed shape is formed. The inspection method includes a profile measurement step of measuring a first profile corresponding to an inner surface of the cup part and a second profile corresponding to the outer surface of the cup part by a pair of non-contact profile sensors disposed facing each other with the battery case interposed therebetween. ; an extending part determining step of determining a first point corresponding to the extending part of the cup part on the first profile and a second point corresponding to the extending part on the second profile; and a thickness calculation step of calculating a distance between the first point and the second point as the thickness of the stretching portion.

The determining of the elongated part may include correcting the first profile to a first fitting profile by curve fitting the first profile; correcting the second profile into a second fitting profile by curve fitting the second profile; determining a point having a slope of 0 in the first fitting profile as the first point; and determining a point having a slope of 0 in the second fitting profile as the second point.

The extension part may be a corner where a pair of adjacent circumferential surfaces and a bottom surface of the cup part meet each other.

Each of the first and second profiles includes a first section corresponding to the bottom surface of the cup portion; and a second section corresponding to an edge connecting a pair of adjacent circumferential surfaces of the cup portion.

Each of the first profile and the second profile may further include a third section corresponding to a side connected to the cup portion in the battery case.

In the profile measuring step, the pair of non-contact profile sensors may face each other in an oblique direction with respect to the bottom surface and each circumferential surface of the cup part.

The pouch-type battery case inspection system according to an embodiment of the present invention may inspect a pouch-type battery case in which a cup portion having a recessed shape is formed. The inspection system may include a first non-contact profile sensor measuring a first profile corresponding to an inner surface of the cup portion; a second non-contact profile sensor disposed to face the first non-contact profile sensor with the battery case interposed therebetween and measuring a second profile corresponding to an outer surface of the cup part; and a processor for calculating the thickness of the elongated part of the cup part based on the first profile and the second profile.

The first non-contact profile sensor and the second non-contact profile sensor may face each other in an oblique direction with respect to the bottom surface and each circumferential surface of the cup part.

The first non-contact profile sensor and the second non-contact profile sensor may project a laser beam focused on the battery case in a line shape.

A part of the laser beam projected from the first non-contact profile sensor or the second non-contact profile sensor may be focused on the bottom surface of the cup part, and the other part may be focused on an edge connecting a pair of adjacent circumferential surfaces of the cup part. there is.

The processor determines a first point corresponding to the elongated portion of the cup portion on the first profile and a second point corresponding to the elongated portion on the second profile, and between the first point and the second point. The distance of can be calculated as the thickness of the stretching portion.

The processor determines a point having a slope of 0 in a first fitting profile obtained by curve fitting the first profile as the first point, and a second fitting obtained by curve fitting the second profile. A point having a slope of 0 in the profile may be determined as the second point.

According to a preferred embodiment of the present invention, in the cup portion of the pouch-type battery case, there is an advantage in that the thickness of the elongated portion having a complex shape can be easily and quickly inspected.

In addition, since the thickness of the stretched portion is measured in a non-contact manner, there is an advantage in that a total number of inspections can be performed without deformation of the battery case.

In addition, there is an advantage in managing the risk of cracks or pinholes occurring in the cup portion by measuring the thickness of the elongated portion.

1 is an exploded perspective view of a general pouch type secondary battery.
2 is a view for explaining the operation of the pouch type battery case inspection system according to an embodiment of the present invention.
3 is a perspective view of a non-contact profile sensor according to an embodiment of the present invention.
FIG. 4 is an enlarged view of a corner periphery of the pouch type battery case shown in FIG. 2 .
FIG. 5 is a cross-sectional view taken along line A-A' of FIG. 4 .
6 is a flow chart of a pouch type battery case inspection method according to an embodiment of the present invention.
7 is a graph for explaining a pouch type battery case inspection method according to an embodiment of the present invention.
8 is a graph for explaining a pouch type battery case inspection method according to another embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail so that those skilled in the art can easily practice with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited or limited by the following examples.

In order to clearly describe the present invention, parts irrelevant to the description or detailed descriptions of related known technologies that may unnecessarily obscure the subject matter of the present invention have been omitted, and in this specification, reference numerals are added to the components of each drawing. In the specification, the same or similar reference numerals are used for the same or similar components throughout the specification.

In addition, the terms or words used in this specification and claims should not be construed as being limited to ordinary or dictionary meanings, and the inventor appropriately defines the concept of terms in order to best describe his/her invention. It should be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle that it can be done.

1 is an exploded perspective view of a general pouch type secondary battery.

The pouch-type secondary battery includes a pouch-type battery case 100 formed by molding a flexible pouch film, and an electrode assembly 200 in which a plurality of electrodes and a separator are alternately stacked and stored in the battery case 100. can do.

The electrode assembly 200 may include a plurality of tabs 210 extending from the plurality of electrodes and fused to each other, and electrode leads 220 bonded to the plurality of tabs 210 fused to each other. A portion of the electrode lead 220 may protrude outside the battery case 100 and may be easily electrically connected to a power supply target (eg, a motor).

The battery case 100 may include a first case 110 and a second case 120 connected by a bridge 130 or separated from each other. And, at least one of the first case 110 and the second case 120 may include a cup portion 140 having a recessed shape and a side 150 extending outward from the circumference of the cup portion 140. can That is, a single cup portion 140 or a pair of cup portions 140 communicating with each other may form a storage space in which the electrode assembly 200 is accommodated.

Hereinafter, as shown in FIG. 1, a case in which the first case 110 and the second case 120 are connected by a bridge 130 and the cup portion 140 is formed in the first case 110 will be described as an example. do.

When the bridge 130 is folded while the electrode assembly 200 is accommodated in the cup portion 140 of the first case 110, the second case 120 comes into contact with the side 150 of the first case 110. In this state, the side 150 and the second case 120 may be bonded to each other by thermal fusion.

Meanwhile, the cup portion 140 may be formed by punching a pouch film, which is a base material of the battery case 100 . The pouch film may be a lamination sheet including a metal layer and a polymer layer laminated on both sides of the metal layer.

In more detail, in a state where the pouch film is seated on a die, a punch may press a portion of the pouch film to form the cup portion 140 . That is, the cup portion 140 may be formed by stretching a portion of the pouch film.

However, if the pouch film is excessively stretched during the forming of the cup portion 140, cracks or pinholes may occur in the cup portion 140. Therefore, the pouch type battery case inspection system (hereinafter referred to as inspection system) according to an embodiment of the present invention may inspect whether the cup portion 140 is excessively stretched.

2 is a view for explaining the operation of a pouch-type battery case inspection system according to an embodiment of the present invention, FIG. 3 is a perspective view of a non-contact profile sensor according to an embodiment of the present invention, and FIG. It is an enlarged view of the periphery of the corner of the illustrated pouch-type battery case, and FIG. 5 is a cross-sectional view taken along line AA' of FIG. 4 .

The inspection system according to an embodiment of the present invention may inspect the battery case 100 in which the cup portion 140 having a recessed shape is formed. The inspection system may inspect the battery case 100 in a state where the cup portion 140 is formed but before the electrode assembly 200 is accommodated, and whether the cup portion 140 is excessively stretched.

In more detail, the inspection system may measure the thickness of a relatively large elongated portion among the cup portion 140 . The extension portion may be a corner 146 of the cup portion 140 to be described later. And, the inspection system may determine whether the thickness of the stretched part is thinner than a predetermined normal range.

If the thickness of the stretching portion is too thin, it means that excessive stretching has occurred, and thus the battery case 100 including the stretching portion may be destroyed or recovered from the production line.

In addition, the inspection system may collect thickness data of the elongated parts of the plurality of battery cases 100 to set the normal range.

The inspection system may include a pair of non-contact profile sensors 10 (hereinafter referred to as 'sensors') facing each other with the battery case 100 interposed therebetween.

The pair of sensors 10 include a first non-contact profile sensor 10a (hereinafter referred to as 'first sensor') directed toward the inner surface of the cup portion 140 and a second non-contact profile sensor directed toward the outer surface of the cup portion 140 ( 10b) (hereinafter referred to as 'second sensor').

Each sensor 10 may measure the profile (PF) of at least a portion of the battery case 100, particularly the cup portion 140, without contacting the battery case 100. In more detail, the first sensor 10a may measure the first profile PF1 (see FIG. 5 ) corresponding to the inner surface of the cup part 140, and the second sensor 10b may measure the outer surface of the cup part 140. The second profile PF2 (see FIG. 5) corresponding to can be measured.

Each sensor 10 may be a laser profile sensor that projects a laser beam to be focused in a substantially line shape on the battery case 100 .

Referring to FIG. 3 , each sensor 10 includes a housing 11 forming an exterior, an emitting unit 12 for emitting a laser beam b toward the battery case 100, and the battery case 100. It may include an incident part 13 into which the reflected laser beam (b) is incident. The emission part 12 and the incident part 13 may be provided in the housing 11 to be spaced apart from each other, and may face different angles.

In addition, inside the housing 11, a laser light source (not shown) and an optical member (for example, for focusing a cross section of a laser beam emitted from the laser light source to have a predetermined shape and emitting it to the emitting unit 12) , a lens, etc.) and a sensing member (not shown) for detecting the laser beam b incident on the incident unit 13 may be provided.

The laser beam (b) emitted from the emitting unit 12 may be focused in a line shape on the battery case 100 and then reflected and incident to the incident unit 13 . At this time, the shape of the line in which the laser beam (b) is focused and reflected may represent the profile PF of the battery case 100 . Accordingly, the sensor 10 may measure the profile PF. Since the principle of such a laser profile sensor is a well-known technology, a detailed description thereof will be omitted.

Meanwhile, the inspection system may include a processor 20 (see FIG. 5 ) communicating with a pair of sensors 10 . The processor 20 determines the elongation part of the cup part 140 based on the first profile PF1 measured by the first sensor 10a and the second profile PF2 measured by the second sensor 10b. thickness can be calculated.

In more detail, the cup portion 140 of the battery case 100 may include a bottom surface 141 and a plurality of circumferential surfaces 142 . In addition, the bottom surface 141 and each circumferential surface 142 may be connected by a punch edge 143, and each circumferential surface 142 and the side 150 may be connected by a die edge 144, adjacent to each other. The pair of circumferential surfaces 142 may be connected by a circumferential edge 145 . Also, each of the edges 143, 144, and 145 may have a predetermined radius of curvature. That is, each of the edges 143, 144, and 145 may be a region that is pushed and stretched by a rounded edge of a die or punch while the cup portion 140 is being formed.

In addition, a corner 146 may be formed in an area where the pair of adjacent circumferential surfaces 142 and the bottom surface 141 of the cup portion 140 meet. That is, the corner 146 may be an area where a pair of adjacent punch edges 143 and the circumferential edge 145 overlap each other.

In addition, a region where a pair of adjacent circumferential surfaces 142 of the cup portion 140 and the side 150 meet may form a sub corner 147 . That is, the sub corner 147 may be an area where a pair of adjacent die edges 144 and the circumferential edge 145 overlap each other.

Also, in the process of forming the cup portion 140, the portion where the pouch film is stretched the most may be the corner 146 of the cup portion. Thus, the inspection system can inspect the thickness of the corner 146 . That is, the elongated part, which is a target for measuring the thickness of the inspection system, may be the corner 146 .

In order to accurately measure the thickness of the corner 146, the pair of sensors 10, more specifically, the emission part 12 of the pair of sensors 10, the bottom surface 141 of the cup part 140 and For each circumferential surface 142, they may face each other in an oblique direction.

As a result, some of the laser beams (b) projected from the first sensor 10a and the second sensor 10b are focused on the bottom surface 141 of the cup portion 140, and the other part is focused on the circumferential edge 145. can be focused on. Additionally, when the line shape in which the laser beams (b) projected from the first sensor 10a and the second sensor 10b are focused is formed sufficiently long, another part of the laser beam (b) is formed on the side 150 can be focused on.

Accordingly, the first profile PF1 measured by the first sensor 10a may include the inner profile of the corner 146 connecting the inner profile of the bottom surface 141 and the inner profile of the circumferential edge 145. there is. In addition, the second profile PF2 measured by the second sensor 10b may include the outer profile of the corner 146 connecting the outer profile of the bottom surface 141 and the outer profile of the circumferential edge 145. there is.

Accordingly, the processor 20 may determine a point corresponding to the corner 146 in each of the profiles PF1 and PF2 and calculate the thickness of the corner 146 . This is explained in detail below.

6 is a flow chart of a method for inspecting a pouch-type battery case according to an embodiment of the present invention, and FIG. 7 is a graph for explaining a method for inspecting a pouch-type battery case according to an embodiment of the present invention.

A method for inspecting a pouch type battery case according to an embodiment of the present invention (hereinafter referred to as 'inspection method') includes a profile measuring step (S10), an elongated part determining step (S20), and a thickness calculating step (S30), which are sequentially performed. ) may be included.

In the profile measuring step (S10), the first sensor 10a measures the first profile PF1 corresponding to the inner surface of the cup part 140, and the second sensor 10b measures the outer surface of the cup part 140. This may be a step of measuring the second profile PF2.

In the profile measurement step (S10), in a state in which the pair of sensors 10 face each other in an oblique direction with respect to the bottom surface 141 and each circumferential surface 142 of the cup portion 140, the battery case 100 ), a laser beam (b) focused in a line shape can be projected, and the laser beam (b) is reflected from the battery case 100 and incident again to the pair of sensors 10, thereby forming a first profile (PF1). ) and the second profile PF2 can be measured.

In FIG. 7 , data of the first profile PF1 and the second profile PF2 measured by the pair of sensors 10 are shown as a graph. Such a graph may be displayed on a display included in or connected to the inspection system. However, it is not limited thereto.

The first profile PF1 and the second profile PF2 may mean both an actual profile of the battery case 100 or a virtual profile displayed as a graph.

Each profile PF1 and PF2 has a first section S1 corresponding to the bottom surface 141 of the cup portion 140 and a second section S2 corresponding to the thickness edge 145 of the cup portion 140. can include In addition, each of the profiles PF1 and PF2 may further include a third section S3 corresponding to the side 150 .

In the extending part determining step (S20), a first point P1 corresponding to the extending part of the cup part 140 on the first profile PF1 and a second point corresponding to the extending part on the second profile PF2 ( It may be a step of determining P2).

In more detail, the processor 20 sets the point at which the slope of the first profile PF1 is converted from negative to positive as the first point P1 and the slope of the second profile PF2 is negative. A point at which the change from negative to positive may be determined as the second point P2.

That is, the processor 20 may determine a point where the slope is 0 in the first profile PF1, that is, a point where the differential value is 0, as the first point P1, and the slope is 0 in the second profile PF2. A point at which the differential value is 0 may be determined as the second point P2.

This corresponds to the first section S1 corresponding to the bottom surface 141 of the cup portion 140, that is, the corner 146 of the cup portion 140, and the circumferential edge 145 of the cup portion 140. This is because the direction of the second section S2 is changed.

However, it is not limited thereto, and the processor 20 may determine the first point P1 and the second point P2 in a different way on the first profile PF1 and the second profile PF2.

For example, the processor 20 may determine a point having the lowest height in the first profile PF1 as the first point P1, and a point having the lowest height in the second profile PF2 as the second point. (P2) can also be determined. In particular, this method may be useful when each of the profiles PF1 and PF2 includes a plurality of non-differentiable points, that is, when each of the profiles PF1 and PF2 is not formed smoothly and has wrinkles or the like. there is.

The thickness calculation step ( S30 ) may be a step of calculating the distance between the first point P1 and the second point P2 as the thickness of the stretching portion.

In more detail, the processor 20 may calculate the distance between the first point P1 and the second point P2 determined in the elongating portion determining step (S20), and calculate the distance between the elongating portion of the cup portion 140, That is, it can be calculated as the thickness of the corner 146.

Additionally, the processor 20 may determine whether the thickness of the elongated portion of the cup portion 140 is thinner than a predetermined normal range, and if the thickness of the elongated portion is thinner than the normal range, the battery case 100 including such an elongated portion ) can be judged as defective. Alternatively, the processor 20 may collect thickness data of the elongated parts of the cup parts 140 of the plurality of battery cases 100 and set the normal range based on this.

8 is a graph for explaining a pouch type battery case inspection method according to another embodiment of the present invention.

In the case of the inspection method according to the present embodiment, since the processor 20 is the same as in the previous embodiment except for correcting the profile PF to the fitting profile PF', overlapping contents are used and differences are avoided. mainly explained.

The stretching part determining step (S20) according to the present embodiment includes the steps of correcting the first profile PF1 to a first fitting profile, correcting the second profile PF2 to a second fitting profile, and It may include determining a point having a slope of 0 in the first fitting profile as the first point P1, and determining a point having a slope of 0 in the second fitting profile as the second point P2. there is.

That is, the processor 20 may curve-fit the first profile PF1 and the second profile PF2 to define the first fitting profile and the second fitting profile, and the first fitting profile and the second fitting profile may be defined. A point at which the slope is 0 on the two-fitting profile, that is, a point at which the differential value is 0 may be determined as the first point P1 and the second point P2.

The curve fitting refers to a process of smoothly defining a curve most suitable for a series of data elements to which constraints are applied, and a person skilled in the art can easily understand the process.

The fitting profile PF' corrected by such curve fitting may be formed to be differentiable in the entire region. Therefore, even when the profiles PF1 and PF2 are not formed smoothly and have wrinkles, the first point P1 and the second point P2 can be clearly determined.

The above description is merely an example of the technical idea of the present invention, and various modifications and variations can be made to those skilled in the art without departing from the essential characteristics of the present invention.

Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but to explain, and the scope of the technical idea of the present invention is not limited by these embodiments.

The protection scope of the present invention should be construed according to the claims below, and all technical ideas within the equivalent range should be construed as being included in the scope of the present invention.

10: non-contact profile sensor 20: processor
100: pouch type battery case 140: cup part
141: bottom surface (cup part) 142: circumferential surface (cup part)
143: punch edge 144: die edge
145: circumferential edge 146: corner
150: side PF1: first profile
PF2: 2nd profile

Claims (12)

In the inspection method of a pouch-type battery case in which a cup portion having a recessed shape is formed,
A profile measuring step of measuring a first profile corresponding to an inner surface of the cup part and a second profile corresponding to an outer surface of the cup part by a pair of non-contact profile sensors disposed facing each other with the battery case interposed therebetween;
an extending part determining step of determining a first point corresponding to the extending part of the cup part on the first profile and a second point corresponding to the extending part on the second profile; and
and a thickness calculation step of calculating a distance between the first point and the second point as the thickness of the elongated portion. According to claim 1,
The elongation part determination step,
correcting the first profile into a first fitting profile by curve fitting the first profile;
correcting the second profile into a second fitting profile by curve fitting the second profile;
determining a point having a slope of 0 in the first fitting profile as the first point; and
A pouch-type battery case inspection method comprising the step of determining a point having a slope of 0 in the second fitting profile as the second point. According to claim 1,
The stretching unit,
A pouch-type battery case inspection method in which a pair of adjacent circumferential surfaces and a bottom surface of the cup portion meet each other. According to claim 3,
Each of the first profile and the second profile,
a first section corresponding to the bottom surface of the cup part; and
A pouch-type battery case inspection method comprising a second section corresponding to an edge connecting a pair of adjacent circumferential surfaces of the cup portion. According to claim 3,
Each of the first profile and the second profile,
A pouch-type battery case inspection method further comprising a third section corresponding to a side connected to the cup portion in the battery case. According to claim 1,
In the profile measurement step,
The pair of non-contact profile sensors face each other in an oblique direction with respect to the bottom surface and each circumferential surface of the cup portion. In the inspection system of a pouch-type battery case in which a cup portion having a recessed shape is formed,
a first non-contact profile sensor measuring a first profile corresponding to the inner surface of the cup;
a second non-contact profile sensor disposed to face the first non-contact profile sensor with the battery case interposed therebetween and measuring a second profile corresponding to an outer surface of the cup portion; and
A pouch-type battery case inspection system including a processor for calculating the thickness of the elongated part of the cup part based on the first profile and the second profile. According to claim 7,
The first non-contact profile sensor and the second non-contact profile sensor face each other in an oblique direction with respect to the bottom surface and each circumferential surface of the cup portion. According to claim 7,
The first non-contact profile sensor and the second non-contact profile sensor project a laser beam focused on the battery case in a line shape. According to claim 9,
A portion of the laser beam projected from the first non-contact profile sensor or the second non-contact profile sensor is focused on the bottom surface of the cup portion, and the other portion is focused on an edge connecting a pair of adjacent circumferential surfaces of the cup portion. type battery case inspection system. According to claim 7,
the processor,
Determining a first point corresponding to the elongated portion of the cup portion on the first profile and a second point corresponding to the elongated portion on the second profile;
A pouch-type battery case inspection system for calculating the distance between the first point and the second point as the thickness of the elongated portion. According to claim 11,
the processor,
In a first fitting profile obtained by curve fitting the first profile, a point having a slope of 0 is determined as the first point,
A pouch-type battery case inspection system that determines a point having a slope of 0 in a second fitting profile obtained by curve fitting the second profile as the second point.

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