Flexible printed circuit board for measuring the internal pressure of pouch battery cells and method of measuring the internal pressure of pouch battery cells

Abstract

A flexible printed circuit board for measuring an internal pressure of a pouch battery cell according to the present application includes a sensor unit on which a pressure sensor is mounted, a board portion provided with connector pins connected to each lead wire, and an extension portion extending from the sensor unit to the board portion of the connector, wherein the extension portion can include a metal protective film surrounding an outer surface of an insulating film in a predetermined section.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an apparatus for measuring an internal pressure of a pouch battery cell and a method of measuring an internal pressure of a pouch battery cell by using the apparatus.

[0002] This application claims priority to Korean Patent Application No. 10-2020-0184945, filed on December 28, 2020 in Korea, the disclosure of which is incorporated herein by reference. BACKGROUND

[0003] Recently, interest in energy storage technology is increasing. As the field of application expands to energy for mobile phones, camcorders, and laptop computers, and even to electric vehicles, research and development of electrochemical devices are becoming active. Electrochemical devices are the most focused field in this regard, and among them, the development of rechargeable batteries that can be charged and discharged is the focus of interest.

[0004] Among current secondary batteries, lithium secondary batteries developed in the early 1990s are attracting attention compared to conventional batteries such as Ni-MH, because lithium secondary batteries have high operating voltage and high energy density.

[0005] One of the main research tasks of lithium secondary batteries is to improve the safety of lithium secondary batteries. Lithium secondary batteries have several problems that threaten the safety of secondary batteries, such as internal short circuit due to external impact, heat generation due to overcharging and overdischarging, electrolyte decomposition due to heat generation, and thermal runaway.

[0006] In particular, the explosion of a secondary battery is caused by various reasons, but the increase in gas pressure inside the secondary battery due to electrolyte decomposition is also one of the reasons. In detail, when a secondary battery is repeatedly charged and discharged, gas is generated due to an electrochemical reaction between an electrolyte and an electrode active material. The generated gas increases the internal pressure of the secondary battery, thereby causing various problems such as weakening of fastening between components, damage to the outer battery case of the secondary battery, early operation of the protection circuit, deformation of the electrode, internal short circuit, and explosion.

[0007] In order to solve such a safety problem of a secondary battery, it is necessary to manufacture an outer battery case that can obtain pressure data by accurately measuring the change in the internal pressure of a secondary battery during charging and discharging, and can design a charging and discharging algorithm of a BMS protection circuit or sufficiently withstand the maximum internal pressure by reflecting the pressure data.

[0008] To accurately measure the change in the internal pressure of a secondary battery cell, one good approach is to insert a pressure sensor into the secondary battery cell. However, particularly in the case of a pouch battery cell, it is difficult to insert a pressure sensor into the pouch outer case, and there is no other suitable method. Therefore, it is not possible to accurately grasp how the internal pressure of the pouch battery cell changes during charging and discharging. Then, the present applicant has recently attempted a method of installing a pressure sensor on one end of a flexible printed circuit board capable of three-dimensional (3D) wiring and having a very small thickness, and inserting the resulting structure into a pouch battery cell to measure the internal pressure of the pouch battery cell. However, it is difficult to insert one end of the flexible printed circuit board into the pouch battery cell and seal the pouch outer case of the pouch battery cell.

[0009] For example, the pouch outer case 1 is generally composed of two pouch sheets, and the respective edges of the two pouch sheets are heat-welded and sealed. At this time, the polyimide film is peeled off from the outer surface of the flexible printed circuit board 2 so that the flexible printed circuit board 2 can be well bonded between the two pouch sheets. However, as shown in FIG. 1, the flexible printed circuit board 2 is cut or the conductor pattern in the cut portion is damaged during heat-welding, so communication is suspended. Figure 1 SUMMARY

[0010] TECHNICAL PROBLEM

[0011] The present disclosure is designed to solve the problems of the related art, and therefore the present disclosure aims to provide a flexible printed circuit board for pouch battery cell internal pressure measurement capable of inserting a pressure sensor into a pouch battery cell without causing a functional problem and measuring the internal pressure of the pouch battery cell, and a pouch battery cell internal pressure measurement method using the same.

[0012] The technical problems to be solved in the present disclosure are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those of ordinary skill in the art according to the following description of the present disclosure.

[0013] TECHNICAL SOLUTION

[0014] In one aspect of the present disclosure, there is provided a flexible printed circuit board for pouch battery cell internal pressure measurement, the flexible printed circuit board comprising: a sensing portion on which a pressure sensor is installed; a board portion having connector pins connected to a plurality of lead wires, respectively; and an extension portion extending from the sensing portion to the board portion, wherein the extension portion includes a protective sleeve made of a metal material, the protective sleeve surrounding an outer surface of the insulating film in a predetermined section.

[0015] The protective sleeve can be a gold or copper plated film. ​

[0016] The width of the sensing portion can be equal to or less than the width of a gas pocket portion formed in a pouch battery cell that is an internal pressure measurement target, and the protective sleeve can be formed to extend with a length equal to or greater than the width of a sealing portion formed in the pouch battery cell.

[0017] The sensing portion can be coated with parylene.

[0018] Bottom filling or conformal coating is added to a portion of the sensing portion in which the pressure sensor and the plurality of lead wires are soldered.

[0019] The pressure sensor can be a waterproof micro electro mechanical system (MEMS) pressure sensor.

[0020] The sensing portion can further include a temperature sensor.

[0021] The sensing portion can be provided in a plurality, and the plate portion can be provided in one.

[0022] In one aspect of the disclosure, there is provided a method of measuring an internal pressure of a pouch battery cell by using the flexible printed circuit board for pouch battery cell internal pressure measurement described above, the pouch battery cell including a pouch outer case including an upper pouch sheet and a lower pouch sheet covering upper and lower sides of an electrode assembly, respectively, the method including: a pressure sensor installing step of sealing the pouch outer case by heat welding the protective sleeve together with the upper pouch sheet and the lower pouch sheet when the sensing portion is placed in a gas pocket portion inside the pouch battery cell; and an internal pressure measuring step of connecting a data analysis device to the plate portion and measuring the internal pressure of the pouch battery cell while repeating charging and discharging of the pouch battery cell.

[0023] In the pressure sensor installing step, the pouch battery cell is partially sealed by heat sealing edges of the upper pouch sheet and the lower pouch sheet to have a remaining unsealed section before the sensing portion is placed in the gas pocket portion, so that the sensing portion can be inserted, and, after the sensing portion is inserted into the pouch outer case through the unsealed section, the pouch outer case is sealed by heat welding the unsealed section.

[0024] When the unsealed section is heat welded, the upper pouch sheet, the protective sleeve, and the lower pouch sheet can be integrally heat welded to each other by using a heat extrusion jig having a groove corresponding to the shape of the protective sleeve of the extension portion.

[0025] By using a flexible printed circuit board comprising two sensing units and one plate, in the pressure sensor installation step, one sensing unit can be placed in the airbag portion on the side where the positive electrode lead of the pouch battery cell is located, and the other sensing unit can be placed in the airbag portion on the side where the negative electrode lead of the pouch battery cell is located.

[0026] Beneficial effects

[0027] According to this disclosure, a flexible printed circuit board for measuring the internal pressure of a pouch cell is provided, which enables the insertion of a pressure sensor into the pouch cell without causing functional problems and measures the internal pressure of the pouch cell. This disclosure also provides a method for measuring the internal pressure of a pouch cell using the flexible printed circuit board.

[0028] The effects of this disclosure are not limited to those described above, and those skilled in the art to which this disclosure pertains will clearly understand any effects not mentioned based on this specification and the accompanying drawings. Attached Figure Description

[0029] Figure 1 This is an image showing a flexible printed circuit board being cut while the outer shell of a conventional bag is being sealed.

[0030] Figure 2 This is a view of a flexible printed circuit board for measuring the internal pressure of a single cell in a pouch cell, according to an embodiment of this disclosure.

[0031] Figure 3 This is a view of an example of a flexible printed circuit board disposed in a pouch cell according to an embodiment of the present disclosure.

[0032] Figure 4 yes Figure 3 The diagram shows a flexible printed circuit board in which the pressure sensor is located inside a single pouch cell.

[0033] Figure 5 yes Figure 4 The diagram shows a pressure sensor.

[0034] Figure 6 It is along Figure 2 A schematic cross-sectional view taken by the A-A' line.

[0035] Figure 7 This is a schematic diagram of the sealed portion of the outer shell of a bag in which a protective sleeve for a flexible printed circuit board, according to an embodiment of the present disclosure, has been placed.

[0036] Figure 8 This is a reference diagram used to explain a method for measuring the internal pressure of a single cell in a pouch cell according to another embodiment of this disclosure.

[0037] Figure 9 This is a reference diagram used to explain a method for measuring the internal pressure of a single cell in a pouch cell by using a flexible printed circuit according to another embodiment of this disclosure. Detailed Implementation

[0038] Embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. The terms or words used in this specification and claims should not be construed as limited to their typical or dictionary meanings, but should be interpreted as having meanings and concepts consistent with the technical aspects of the invention, based on the principle that the inventor is able to appropriately define the concepts of the terms in order to best describe his / her own invention.

[0039] Therefore, the embodiments described in this specification and the constructions shown in the accompanying drawings are merely preferred embodiments of this disclosure and do not represent all technical aspects of this disclosure. It should be understood that various equivalent and modified examples of these constructions may be adopted when this application is filed.

[0040] Figure 2 This is a view of a flexible printed circuit board for measuring the internal pressure of a single cell in a pouch cell, according to an embodiment of this disclosure. Figure 3 This is a view of an example of a flexible printed circuit board disposed in a pouch cell according to an embodiment of the present disclosure. Figure 4 yes Figure 3 The diagram shows a flexible printed circuit board in which the pressure sensor is located inside a single pouch cell.

[0041] In the flexible printed circuit board 100 according to the embodiments of the present disclosure, insulation and coating can be achieved by placing a copper-clad laminate on a base film 102a, stacking a dry film on the resulting structure, and performing exposure, development and etching to form conductors 101 having predetermined intervals therebetween, and then bonding a cover film 102b to the conductors 101.

[0042] The conductor 101 may be formed of a metal with excellent conductivity, such as copper (Cu) or silver (Ag), and the insulating film 102 may be formed of an insulating material such as polyethylene terephthalate or polyamide, and may include the base film 102a and the cover film 102b.

[0043] Because the flexible printed circuit board 100 can handle a large number of signals and loads in a minimal volume, has insulating properties and is flexible, and is very thin, the pressure sensor 111 can be mounted on one end of the flexible printed circuit board 100 and placed inside the pouch cell 200, and can be used to measure the internal pressure of the pouch cell 200.

[0044] refer toFigure 2 According to an embodiment of the present disclosure, the flexible printed circuit board 100 for measuring the internal pressure of a pouch cell 200 includes a sensing portion 110, an extension portion 120, and a board portion 130.

[0045] refer to Figure 3 and Figure 4 The sensing unit 110 is a portion that enters the pouch cell 200, which serves as the target for internal pressure measurement, and is manufactured to have a width and length that allow it to be placed within the air bladder portion 230 formed in the pouch cell 200. Specifically, the sensing unit 110 is manufactured with a width equal to or less than the width of the air bladder portion 230. The pressure sensor 111 can be mounted on the end of the sensing unit 110. In addition to the pressure sensor 111, a temperature sensor 112 or a gas sensor (not shown) can also be mounted on the sensing unit 110 to simultaneously collect data such as the internal pressure of the pouch cell 200 and gas levels.

[0046] The entire sensing element 110 can be coated with paraffin. Paraffin coating refers to a polymer coating deposited on an object in a gaseous form under vacuum at room temperature in a shape-independent manner, with a thickness unit of nanometers (nm) or micrometers (µm). When such a paraffin coating is applied, a thin and transparent polymer film is formed on the entire surface of the sensing element 110. In this case, even when the sensing element 110 is placed inside the pouch cell 200, corrosion or damage to the sensing element 110 due to the electrolyte can be prevented.

[0047] Additionally, an underfill or conformal coating can be applied to the brazed portion of the sensing unit to enhance the resistance of the location where the pressure sensor is mounted to physical and chemical shocks, where the pressure sensor and the wires are connected to each other.

[0048] The underfill refers to the method of filling the bottom side of an encapsulation (such as a chip) with insulating resin. The conformal coating works by forming a very thin film on a printed circuit board (PCB) or various electrical boards using a coating material, thereby extending the lifespan of components and circuit devices against external environmental and physical influences.

[0049] A waterproof microelectromechanical system (MEMS) pressure sensor 111 can be used as the pressure sensor 111.

[0050] like Figure 5As shown, the waterproof MEMS pressure sensor 111 can have the following structure: a sensor chip 111c is located inside a cylindrical cap 111a filled with an adhesive gel 111b, and a PCB 111d connected to the sensor chip 111c covers the lower end of the cylindrical cap 111a. Compared to conventional MEMS pressure sensors that directly contact external fluids (non-corrosive gases) to measure pressure, the waterproof MEMS pressure sensor 111 used in this embodiment can directly measure the pressure of liquids and various types of gases because the adhesive gel 111b is filled in the cylindrical cap 111a and can withstand electrolytes and has excellent waterproof performance.

[0051] The extension 120 is the portion that extends from the sensing portion 110 to the plate portion 130, and a portion of the extension 120 can be thermally welded to the sealing portion 240 of the pouch cell 200.

[0052] The outer casing 220 of the bag may include an upper bag piece 221 and a lower bag piece 222. Both the upper bag piece 221 and the lower bag piece 222 include an outer insulating layer, a metal layer, and an inner adhesive layer, and respectively cover the upper and lower sides of the electrode assembly 210. When the outer casing 220 is sealed, the corresponding edges of the upper bag piece 221 and the lower bag piece 222 are typically heat-welded to each other. In this case, the edge portions of the upper bag piece 221 and the lower bag piece 222 produced by heat welding are referred to as sealing portions 240 or platforms.

[0053] The electrode assembly 210 is an assembly of electrode plates and a separator, and can be configured such that one or more positive electrode plates and one or more negative electrode plates are positioned such that the separator is placed therebetween. Electrode terminals can be included in each electrode plate of the electrode assembly 210 and can be connected to electrode leads. In the pouch cell 200, positive electrode leads 201 and negative electrode leads 202 can be positioned between the upper pouch sheet 221 and the lower pouch sheet 222, and a corresponding end of the positive electrode lead 201 and the negative electrode lead 202 can be exposed and thus used as electrode terminals.

[0054] In order to insert the sensing part 110 of the flexible printed circuit board 100 into the pouch battery cell 200 and prevent leakage of the internal pressure of the pouch battery cell 200, a portion of the extension 120 is placed between the upper pouch piece 221 and the lower pouch piece 222, and in this state, the outer housing 220 of the pouch is sealed.

[0055] In this case, to prevent damage caused by applied heat and pressure and to strengthen the adhesion to the internal adhesive layer of the outer casing 220 of the bag, the extension 120 of the flexible printed circuit board 100 according to this disclosure includes a protective sleeve 121 in a predetermined section. The predetermined section refers to the section of the extension 120 that will be placed in the sealing portion 240 of the bag battery cell 200.

[0056] like Figure 4 As shown, the protective layer 121 can extend in length equal to or longer than the width of the sealing portion 240 formed in the pouch cell 200.

[0057] refer to Figure 6 The protective sleeve 121 can be formed of a metal such as gold (Au) or copper (Cu) and can be configured to enclose the outer surface of a predetermined segment of the insulating film 102. Typically, although the insulating film 102 is made of polyimide, which has excellent heat resistance, it may be easily cut or cracked in the wire 101 due to the simultaneous application of heat and pressure during the heat welding of the outer casing 220 of the bag. However, in this disclosure, the protective sleeve 121, formed of a metallic material, surrounds the insulating film 102, thereby protecting both the insulating film 102 and the wire 101 from heat and pressure during heat welding. Furthermore, the protective sleeve 121, formed of a metallic material, can bond strongly to the inner adhesive layer of the bag sheet, thereby improving the sealing properties of the corresponding portion.

[0058] Come back for reference Figures 2 to 4 The plate portion 130 is the portion disposed outside the pouch cell 200 and includes connector pins 132 capable of connecting to external devices. The connector pins 132 can be individually connected to the wires 101 via soldering 131. The plate portion 130 may be formed to have a width larger than the sensing portion 110 or the extension portion 120, and the wires 101 may be extended to have a large width within the plate portion 130. Each connector pin 132 may be soldered (indicated by reference numeral 131) to each of the extended wires 101.

[0059] A rod-shaped support 133 can be provided at the end of the plate portion 130, and the connector pins 132 can all extend straight through the support 133, maintaining a certain distance from each other, and are connected to the arm connector of an external device.

[0060] A method for measuring the internal pressure of a pouch cell 200 by using a flexible printed circuit board 100 having the structure described above, according to this disclosure, for measuring the internal pressure of a pouch cell 200.

[0061] The method for measuring the internal pressure of the battery cell 200 includes a pressure sensor installation step and an internal pressure measurement step.

[0062] like Figure 4 As shown, inside the pouch battery cell 200, an airbag portion 230 exists between the area where the electrode assembly 210 is located and the heat-welded sealing portion 240 of the outer pouch casing 220. The sensing portion 110 of the flexible printed circuit board 100 is placed in the airbag portion 230.

[0063] For example, during the manufacturing of the pouch battery cell 200, when the electrode assembly 210 is placed in the outer housing 220 of the pouch, the sensing unit 110 can be placed in a position corresponding to the airbag portion 230, and the electrolyte injection / wetting process and the process of sealing the outer housing 220 of the pouch can be performed, so that the pouch battery cell 200 with the flexible printed circuit board 100 attached can be manufactured.

[0064] Alternatively, after manufacturing the pouch battery cell 200, the flexible printed circuit board 100 can be inserted into the pouch battery cell 200. In this case, the pouch battery cell 200 is manufactured with an unsealed section, so that the sensing unit 110 can be easily inserted into the pouch battery cell 200. The unsealed section refers to the section that is left unsealed when the outer pouch housing 220 is sealed by heat-welding the corresponding edges of the upper pouch piece 221 and the lower pouch piece 222, so that the sensing unit 110 can be inserted. After the sensing unit 110 of the flexible printed circuit board 100 is pushed into the pouch battery cell 200 through the unsealed section, the outer pouch housing 220 is sealed by heat-welding the unsealed section. At this time, the protective sleeve 121 of the extension 120 is heat-welded between the upper pouch piece 221 and the lower pouch piece 222.

[0065] Specifically, the unsealed section is heat-welded using a hot extrusion jig 30 having a groove 31 corresponding to the shape of the protective sleeve 121 of the extension 120. Due to the thickness of the extension 120 including the protective sleeve 121, the portion of the outer casing 220 of the bag, in which the protective sleeve 121 containing the extension 120 is inserted, may have low bonding strength compared to other sealed areas of the bag outer casing 220. This may be due to a lifting phenomenon caused by the inability to properly apply heat and pressure to the two corners of the protective sleeve 121 and between the upper bag piece 221 and the lower bag piece 222.

[0066] In this embodiment, to prevent the aforementioned lifting phenomenon, such as Figure 7As shown, the upper bag sheet 221 is extruded from the top using a hot extrusion jig 30 including a groove 31, and simultaneously, the lower bag sheet 222 is extruded from the bottom using a flat hot extrusion jig (not shown), thereby integrally heat-welding the upper bag sheet 221, the protective sleeve 121 of the extension 120, and the lower bag sheet 222. In this case, the upper, lower, left, and right sides of the protective sleeve 121 are tightly bonded to the upper bag sheet 221 and the lower bag sheet 222, thus improving the sealing properties of the outer casing 220 of the bag and the fixation properties of the flexible printed circuit board 100.

[0067] As described above, when fabricating a pouch battery cell 200 with a flexible printed circuit board 100 already mounted on it, the internal pressure of the pouch battery cell 200 is measured while repeatedly charging and discharging the pouch battery cell 200. The pouch battery cell 200 can be fabricated using, for example... Figure 8 The charging / discharging fixture 40 shown is charged / discharged.

[0068] The charging / discharging fixture 40 may include voltage holders 41 and 42, a substrate 44, and a pressure plate 45. The pouch cell 200 is placed on the substrate 44 of the surface plate, and the pressure plate 45 is placed on the pouch cell 200. To apply pressure to the pouch cell 200 during charging and discharging, the substrate 44 and the pressure plate 45 may have bolts and nuts at their corners and are configured to allow for adjustable vertical spacing.

[0069] The positive electrode lead 201 and negative electrode lead 202 of the pouch cell 200 can be connected to the voltage holders 41 and 42 respectively, and a charging / discharging supply source (not shown) for supplying voltage / current can be connected to the voltage holders 41 and 42, thereby charging and discharging the pouch cell.

[0070] The board portion 130 of the flexible printed circuit board 100 can be connected to the control device 50 via cable connector C1, and the control device 50 can be connected to a display device (not shown) that displays the value from the pressure sensor 111 via another cable C2.

[0071] According to this configuration, the internal pressure change of the pouch battery cell 200 is monitored while the charging and discharging of the pouch battery cell 200 is repeated. When gas is generated inside the pouch battery cell 200 during charging and discharging, the gas is collected in the air bladder portion 230, and the gas pressure is measured by the pressure sensor 111. The measured gas pressure value can be displayed on a display device in real time. Moreover, while the internal pressure change of the pouch battery cell 200 is monitored by the pressure sensor 111, the internal temperature change of the pouch battery cell 200 can be monitored by the temperature sensor 112.

[0072] Thus, when the flexible printed circuit board 100 for measuring the internal pressure of the pouch battery cell 200 is inserted into the air bladder portion 230 of the pouch battery cell 200 and the pouch battery cell 200 is sealed, the pressure sensor 111 can directly measure the internal pressure of the pouch battery cell 200 without any functional problems, even when the pressure sensor 111 is inserted into the pouch battery cell 200.

[0073] Figure 9 This is a reference diagram used to explain a method for measuring the internal pressure of a single cell in a pouch cell by using a flexible printed circuit board according to another embodiment of this disclosure.

[0074] Reference Figure 9 This disclosure describes a flexible printed circuit board 100 for measuring the internal pressure of a pouch cell 200 according to another embodiment of the present disclosure, and a method for measuring the internal pressure of the pouch cell 200 by using the flexible printed circuit board 100.

[0075] Figure 9 The same reference numerals as those in the embodiments described above denote the same components, and repeated descriptions of the same components will be omitted. The differences from the embodiments described above will be mainly described.

[0076] The flexible printed circuit board 100 for measuring the internal pressure of a pouch cell 200 according to this embodiment may include two sensing units 110 and a board portion 130. An extension 120 may be configured to extend from each sensing unit 110 and merge with each sensing unit 110 in the board portion 130. A pressure sensor 111 may be mounted on each of the two sensing units 110, and the board portion 130 may include a plurality of connector pins 132 necessary for signal transmission from the two sensing units 110.

[0077] When using a flexible printed circuit board 100 for measuring the internal pressure of a pouch cell 200, one sensing unit 110 can be placed in the air bladder portion 230 on the side where the positive electrode lead 201 of the pouch cell 200 is located, and another sensing unit 110 can be placed in the air bladder portion 230 on the side where the negative electrode lead 202 of the pouch cell 200 is located. In this case, the pressure distribution in each region within the pouch cell 200 can be measured.

[0078] According to this embodiment, the flexible printed circuit board 100 for measuring the internal pressure of the pouch battery cell 200 can be manufactured to have two or three sensing parts 110 or more than three sensing parts 110, and the pressure sensor 111 can be placed at several locations within the pouch battery cell 200.

[0079] This disclosure has been described in detail. However, it should be understood that the detailed description and specific examples are given by way of illustration only while indicating preferred embodiments of this disclosure, as various changes and modifications within the scope of this disclosure will become apparent to those skilled in the art based on the detailed description.

[0080] Furthermore, when terms indicating directions such as up, down, left, right, front, and back are used in this specification, these terms indicate relative positions and are merely for descriptive convenience. It will be apparent to those skilled in the art that these terms may vary depending on the position of the target object or the observer's position.

Claims

1. A flexible printed circuit board for measuring the internal pressure of a single cell in a pouch cell, the flexible printed circuit board comprising a plurality of conductive wires and an insulating film, the insulating film having insulating properties and flexibility, and surrounding the plurality of conductive wires, the flexible printed circuit board comprising: The pressure sensor is mounted on the sensing unit; The board portion has connector pins respectively connected to the plurality of wires, and the board portion is connected to a data analysis device; and An extension portion, which extends from the sensing portion to the plate portion, The extension includes a protective sleeve made of metal material, which surrounds the outer surface of the insulating film in a predetermined section. The pressure sensor is mounted on one end of the flexible printed circuit board and placed inside the pouch battery cell to measure the internal pressure of the pouch battery cell.

2. The flexible printed circuit board according to claim 1, wherein, The protective sleeve is made of gold or copper.

3. The flexible printed circuit board according to claim 1, wherein, The width of the sensing element is equal to or less than the width of the air bladder portion formed in the pouch cell, which serves as the target for internal pressure measurement. The protective sleeve is formed to extend in length equal to or greater than the width of the sealing portion formed in the pouch battery cell.

4. The flexible printed circuit board according to claim 1, wherein, The sensing element is coated with palilin.

5. The flexible printed circuit board according to claim 4, wherein, An underfill or conformal coating is additionally added to the sensing portion, where the pressure sensor and the plurality of wires are brazed.

6. The flexible printed circuit board according to claim 1, wherein, The pressure sensor is a waterproof microelectromechanical system pressure sensor.

7. The flexible printed circuit board according to claim 1, wherein, The sensing unit further includes a temperature sensor.

8. The flexible printed circuit board according to claim 1, wherein, The sensing units are configured in multiple ways, and the plate portion is configured as one.

9. A method for measuring the internal pressure of a pouch cell using a flexible printed circuit board for measuring the internal pressure of a pouch cell according to any one of claims 1-8, the pouch cell comprising a pouch outer housing, the pouch outer housing comprising an upper pouch sheet and a lower pouch sheet respectively covering an upper side and a lower side of an electrode assembly, the method comprising: Pressure sensor installation steps: When the sensing unit is placed in the air bladder portion inside the bag battery cell, the outer casing of the bag is sealed by heat welding the protective sleeve together with the upper bag piece and the lower bag piece; and Internal pressure measurement steps: Connect the data analysis device to the plate and measure the internal pressure of the pouch cell while repeatedly charging and discharging the pouch cell.

10. The method according to claim 9, wherein, In the pressure sensor installation step, before placing the sensing part into the airbag portion, the bag battery cell is partially sealed by heat-sealing the edges of the upper and lower bag pieces, leaving an unsealed section so that the sensing part can be inserted. After the sensing part is inserted into the outer casing of the bag through the unsealed section, the outer casing of the bag is sealed by heat-welding the unsealed section.

11. The method according to claim 10, wherein, When the unsealed section is heat-welded, the upper bag piece, the protective sleeve, and the lower bag piece are integrally heat-welded together using a hot extrusion jig with a groove corresponding to the shape of the protective sleeve of the extension.

12. The method according to claim 9, wherein, By using a flexible printed circuit board comprising two sensing units and one plate, in the pressure sensor installation step, one of the two sensing units is placed in the airbag portion on the side where the positive electrode lead of the pouch battery cell is located, and the other sensing unit is placed in the airbag portion on the side where the negative electrode lead of the pouch battery cell is located.

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