Plasma processing method and secondary battery manufacturing method including the same

Abstract

The present invention relates to a method for manufacturing a pouch-type secondary battery, and more particularly, to a plasma processing method with improved sealing strength of a pouch, a method for manufacturing a secondary battery, and an apparatus for manufacturing a secondary battery. According to one example of the present invention, there may be provided a pouch-type secondary battery comprising: a moving stage that supports a pouch before sealing and linearly moves the pouch in a first direction; a plasma generator internally discharging gas to form plasma; a plasma head irradiating a surface of the pouch with a plasma gas generated by the plasma generator to improve pouch seal strength after sealing; and a transfer flow path that transfers the plasma gas generated by the plasma generator to the plasma head via the carrier gas.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a pouch-type secondary battery, and more specifically, to a plasma treatment method that can increase the sealing strength of the pouch and improve the insulating performance of the seal, a method for manufacturing a secondary battery, and an apparatus for manufacturing a secondary battery. Background Technology

[0002] A secondary battery is a battery that can be reused by converting chemical energy into electrical energy during the discharge process and electrical energy into chemical energy during the charging process.

[0003] Secondary batteries may include nickel-cadmium (Ni-Cd) batteries, nickel-metal hydride (Ni-MH) batteries, lithium metal batteries, lithium-ion (Li-Ion) batteries, and lithium-ion polymer batteries (hereinafter referred to as "LIPB").

[0004] Lithium-ion batteries have a cycle life of approximately 500 cycles or more and a short charging time of approximately 1 to 2 hours. They are also about 30% to 40% lighter than nickel-metal hydride batteries, which reduces weight. Furthermore, they have the highest voltage per cell (30 to 37V) and excellent energy density among existing rechargeable batteries, which allows them to have characteristics optimized for mobile devices.

[0005] Lithium-ion batteries can be manufactured as pouch-type secondary batteries by encapsulating the battery cells in a pouch, which is an aluminum encapsulation material.

[0006] A pouch-type secondary battery may include: a battery cell housed within a pouch as encapsulation material; lead contacts electrically connected to electrodes disposed within the battery cell and thus led out to the outside of the pouch; and an insulating film electrically insulating the lead contacts. Specifically, the pouch may seal the battery cell housed therein by thermally fusing the insulating film formed on the lead contacts of the battery cell to the inner surface of the pouch, or by directly thermally fusing the inner surfaces of the pouches together. The insulating film is typically a polypropylene (PP) film.

[0007] The bag seal performs the function of sealing a certain space inside the bag that contains the electrolyte. When the battery cell is repeatedly charged / discharged, gas is generated, which increases the pressure inside the bag. Therefore, the bag seal needs to be of high strength for this reason.

[0008] Additionally, during the heat-sealing process of the bag, the polypropylene (PP) film is melted and diffused to bond the bag. The PP film not only bonds the bag but also separates the bag's metal layers, such as aluminum, from the electrolyte, thus preventing corrosion of the metal layers and preventing current from flowing through the bag and thus increasing resistance.

[0009] Korean Patent Publication No. 10-2022-0154638 (hereinafter referred to as the "Prior Patent") discloses a method for manufacturing a bag-type secondary battery to make the sealing surface of the bag uniform. In particular, in order to achieve the desired effect of maintaining the uniformity of the sealing surface even over a wide temperature range or a wide pressure range, it discloses sealing the bag after plasma treatment.

[0010] However, existing patents only consider plasma surface treatment and the uniformity of the sealing surface, without addressing sealing strength. In particular, the conditions and timing of plasma surface treatment, as well as the thermal fusion conditions, are not disclosed. Therefore, there is a need to provide specific plasma surface treatment apparatus and processes that can improve the sealing strength of bags.

[0011] The manufacturing of pouch-type secondary batteries is primarily for mass production rather than small-batch production. In particular, the sequential execution of the entire process makes maximizing process efficiency (i.e., the number of good products that can be produced per unit time) crucial. Therefore, there is a need for plasma surface treatment apparatus and processes, and consequently pouch-type secondary battery manufacturing apparatus and processes, that can be organically and easily integrated into conventional pouch-type secondary battery manufacturing processes and equipment while being easily constructed and controlled. Summary of the Invention

[0012] Technical issues

[0013] The present invention aims to increase the sealing strength of the pouch in a pouch-type secondary battery.

[0014] By way of an example of the present invention, an apparatus and method for manufacturing a pouch-type secondary battery are intended to be provided that can be easily integrated into a conventional pouch-type secondary battery manufacturing apparatus and method.

[0015] Through one example of the present invention, an apparatus and method for manufacturing a pouch-type secondary battery capable of continuous and organic plasma treatment of the pouch surface are provided.

[0016] By way of one example of the present invention, it is intended to provide a pouch-type secondary battery having a seal that is thermally fused after plasma treatment. By doing so, the problem of seal rupture and thus electrolyte leakage due to internally generated gas can be significantly reduced, thereby aiming to provide a pouch-type secondary battery with improved lifespan and performance.

[0017] Technical solution

[0018] To achieve the above objectives, according to an example of the present invention, a bag-type secondary battery manufacturing apparatus may be provided, comprising: a movable stage that supports a bag before sealing and moves the bag linearly in a first direction; a plasma generator that discharges gas internally to form plasma; a plasma head that irradiates the surface of the bag with the plasma gas generated by the plasma generator to improve the sealing strength of the bag after sealing; and a delivery path that delivers the plasma gas generated by the plasma generator to the plasma head via a carrier gas.

[0019] Preferably, the plasma generator is positioned spaced apart from the plasma head, and the two are connected through the delivery path.

[0020] The moving platform can move linearly together with the bag. Alternatively, the moving platform can be in the form of a roller and can be configured to move the bag linearly as it rotates.

[0021] The plasma heads can be configured to be spaced apart in a second direction perpendicular to the first direction.

[0022] Preferably, the plasma head is fixed and configured to irradiate the surface of the bag vertically downwards using the plasma gas.

[0023] The mobile platform can be configured to move the bag at a constant speed.

[0024] The plasma head can be configured to irradiate the surface of the bag, which is supported by the moving stage, with the plasma gas. Preferably, the moving stage and the plasma head are positioned facing each other. When the moving stage is a roller that supports and transports the bag, i.e., a conveyor roller, it is preferable that the conveyor roller and the plasma head are positioned facing each other. Therefore, since the plasma head irradiates the area where the bag is supported with the plasma gas, a smooth surface treatment is possible.

[0025] Preferably, the gas for plasma discharge and the carrier gas are continuously supplied at a constant flow rate inside the plasma generator. By doing so, the flow rate of the plasma gas irradiating the bag surface can be constantly controlled.

[0026] Preferably, the gas discharged when plasma is generated in the plasma generator contains nitrogen (N2).

[0027] Preferably, the carrier gas is nitrogen. That is, only a portion of the supplied nitrogen is discharged by the plasma, and nitrogen radicals can be supplied to the bag surface through the undischarged nitrogen. For this purpose, it is preferable that nitrogen flows into the plasma generator at a sufficient flow rate.

[0028] Preferably, the flow rate of nitrogen flowing into the plasma generator is 100 LPM to 250 LPM.

[0029] Preferably, the linear movement speed of the bag before sealing is 20 mm / s to 60 mm / s.

[0030] The gas used for plasma discharge may be compressed dry air (CDA), and the carrier gas may be nitrogen.

[0031] The compressed dry air flowing into the plasma generator may have a flow rate of 0.7 LPM.

[0032] This example demonstrates how plasma treatment intensity can be altered by adjusting the supply gas flow rate range and the bag linear velocity range. Furthermore, the plasma treatment intensity can be changed by adjusting the nitrogen flow rate range, the bag linear velocity range, the presence or absence of CDA, and the CDA flow rate range. Additionally, the plasma treatment intensity can also be adjusted by increasing or decreasing the discharge power.

[0033] Preferably, the bag, which has undergone surface treatment using the plasma gas, is sealed by thermal fusion.

[0034] Preferably, the thermal fusion is performed for 1.5 seconds at 200 degrees Celsius and 0.1 MPa pressure.

[0035] To achieve the above objectives, according to an example of the present invention, a method for manufacturing a pouch-type secondary battery can be provided, comprising: a pouch supply step of continuously moving a pouch sheet on a moving stage; a plasma surface treatment step of irradiating the surface of the pouch sheet with plasma gas generated from a plasma generator via a plasma head; a casing step of forming a pouch shell together with a battery cell by molding the plasma-surface-treated pouch sheet; and a pouch sealing step of sealing the pouch shell by thermal fusion, characterized in that the plasma gas is moved from the plasma generator to the plasma head via a carrier gas, thereby irradiating the pouch sheet.

[0036] In the bag supply step, the bags can be supplied in rolls before being cut into unit bags. Therefore, the bag sheets, supplied continuously in rolls, can be continuously plasma-treated. Then, in the shelling step, the bag sheets are cut into unit bags and, if necessary, formed.

[0037] Preferably, the plasma gas flows into the plasma head through a delivery path disposed between the plasma generator and the plasma head.

[0038] Preferably, the gas for plasma discharge and the carrier gas are continuously supplied at a constant flow rate inside the plasma generator. Therefore, with regard to the plasma generator, it is preferable to simultaneously perform gas supply, plasma discharge, and plasma gas emission.

[0039] Furthermore, preferably, the plasma head irradiates the surface of the bag, which is supported by the moving stage, using the plasma gas and the carrier gas. Because the plasma head irradiates the area where the bag is supported using the plasma gas, a smooth surface treatment is possible.

[0040] The gas used for discharge when generating plasma in the plasma generator may contain nitrogen (N2). The carrier gas may be nitrogen.

[0041] Preferably, the flow rate of nitrogen flowing into the plasma generator is 100 LPM to 250 LPM.

[0042] Preferably, the linear movement speed of the bag before sealing is 20 mm / s to 60 mm / s.

[0043] Preferably, the bag sealing step is performed within 5 minutes after the plasma surface treatment step.

[0044] Preferably, after the plasma surface treatment, the water contact angle on the surface of the bag sheet is 41 to 50 degrees.

[0045] Beneficial effects

[0046] According to the present invention, the sealing strength of the bag can be substantially increased in a pouch-type secondary battery.

[0047] An example of the present invention provides an apparatus and method for manufacturing a pouch-type secondary battery that can be easily integrated into a conventional pouch-type secondary battery manufacturing apparatus and method.

[0048] According to one example of the present invention, an apparatus and method for manufacturing a pouch-type secondary battery capable of continuously and organically plasma treating the pouch surface can be provided.

[0049] By way of one example of the present invention, a pouch-type secondary battery having a seal that is thermally fused after plasma treatment can be provided. By doing so, the problem of seal rupture and thus electrolyte leakage due to internally generated gas can be significantly reduced, thereby aiming to provide a pouch-type secondary battery with improved lifespan and performance. Attached Figure Description

[0050] Figure 1 A conceptual diagram illustrating a pouch-type secondary battery manufacturing apparatus according to an example of the present invention;

[0051] Figure 2 A diagram showing the unfolded shape of the unit bag;

[0052] Figure 3 This illustrates the manufacturing process of a pouch-type secondary battery according to an example of the present invention;

[0053] Figure 4 A simplified diagram illustrating a pouch-type secondary battery manufacturing apparatus according to an example of the present invention;

[0054] Figure 5 Image showing the water contact angle of the bag surface;

[0055] Figure 6 A table showing the measured sealing strength data;

[0056] Figure 7 A graph representing the measured sealing strength data;

[0057] Figure 8 Indicates the sampling location for the seal strength of the bag; and

[0058] Figure 9 This indicates the sampling method and dimensions in the bag. Detailed Implementation

[0059] Hereinafter, an apparatus for manufacturing a pouch-type secondary battery according to an example of the present invention will be described in detail with reference to the accompanying drawings.

[0060] First, refer to Figure 1 This describes an apparatus and method for plasma surface treatment of bags.

[0061] The bag 10 can be placed on the moving platform 20, and the moving platform 20 can be configured to move the bag linearly in a first direction.

[0062] The bag 10 may move linearly together with the moving stage 20, or only the bag 10 may move linearly on the moving stage 20. Here, the bag 10 preferably moves in the horizontal direction. As an example, it is preferable that the upper surface facing the plasma head is held horizontally, and that the upper surface moves in the bag length direction (bag supply direction).

[0063] The plasma head 30 may be positioned spaced apart from the moving stage 20. The plasma head 30 may be configured to supply plasma gas 40 to the surface of the bag 10. The plasma head 30 may have a width corresponding to the width of the bag 10. Therefore, it may be provided to supply plasma gas 40 corresponding to the entire width of the bag 10.

[0064] The plasma head can be positioned and fixed in a second direction perpendicular to the first direction. Therefore, plasma gas 40 can be continuously supplied from the fixed plasma head, and the bag 10 can continuously pass through the plasma interval or region where the plasma gas 40 is supplied. In this case, plasma surface treatment is performed on the bag 10.

[0065] The pouch 10 forms an encapsulation that houses the battery cells. Specifically, the sheet-shaped pouch 10 is cut and shaped, and the facing edge surfaces of the pouch are heat-sealed to seal the battery cells inside.

[0066] According to this example, plasma surface treatment can be performed not only on the edge surfaces of the bag to achieve heat fusion and sealing, but also on the inner surfaces of the bag that are in close contact with the battery cells. That is, according to this example, the bag to which plasma surface treatment is performed can be the bag before sealing, and can also be a bag sheet for forming an encapsulation before cutting and shaping.

[0067] When bag flakes undergo plasma surface treatment, the bag flakes can be easily subjected to continuous and automated plasma surface treatment. In particular, plasma surface treatment is not limited to just a part of the bag, especially the sealing part, which simplifies subsequent processes. As an example, continuous plasma surface treatment is not easy when performing plasma surface treatment on the four edge surfaces of a square bag.

[0068] like Figure 2 As shown, the individual bag 10 forming a single bag-shaped secondary battery can be cut from the bag sheet to form a rectangular sheet.

[0069] The bag sheet can be formed by depositing polypropylene layers on the outer and inner surfaces of a thin aluminum sheet. That is, when the bag sheet is used to form the encapsulation material, the outer surface of the polypropylene forms the outer surface of the bag, and the inner surface of the polypropylene forms the outer surface of the bag, thereby preventing the thin aluminum sheet from being exposed to external air and internal electrolyte.

[0070] As shown, the edge surfaces 13, 14, 15, and 16 of a single bag 10 can form a sealing region 11. A battery cell region 12, in which the battery cells are in close contact and filled with electrolyte, can be formed in the inner region of the sealing region 12.

[0071] A fold 17 can be formed in the middle of the battery cell region 12, and after the battery cell is placed in the battery cell region 12 on either side of the fold, the left and right battery cell regions 12 and the sealing region 10 can overlap around the fold. Then, the bag is sealed by heat-fusion sealing region 11.

[0072] In the absence of folds Figure 2 The unit bag 10 shown can be the upper and lower shells of the bag housing. Since the upper and lower shells are positioned facing each other and then sealed, the sealing area 11 appears identical. However, if a fold is present, sealing is not required due to the fold, and therefore a seal can be performed on three segments; while if no fold is present, a seal can be performed on four segments.

[0073] If only Figure 2 As shown, the sealed area 11 undergoes plasma surface treatment, which reveals that the plasma surface treatment process becomes very complex. First, the left and right edge surfaces 13 and 14 must be plasma-treated intermittently. Then, after rotating the bag 10 90 degrees, the upper and lower edge surfaces 15 and 16 must be plasma-treated intermittently. Therefore, at least two plasma heads are required, and the widths of the plasma heads may also differ from each other.

[0074] Ultimately, when only the sealed area 11 undergoes plasma surface treatment, plasma control becomes difficult and the apparatus becomes complex. In particular, the plasma surface treatment must be performed uniformly across the entire sealed area 11, but uneven plasma treatment areas may occur on the edge surfaces at the corners. This is because rotation of the bag 10 is necessary when the entire sealed area 11 undergoes plasma treatment. In this case, plasma surface treatment may not be performed on some parts, and plasma surface treatment may overlap in some parts.

[0075] Furthermore, when only the sealed area 11 undergoes plasma surface treatment, it must be performed after the bag is cut into sheet shapes. This is because the bag's direction of travel relative to the plasma treatment device must be changed. Therefore, it is not easy to perform plasma surface treatment on the bag sheets while they are being transported in a roll-to-roll (RtoR) manner.

[0076] In addition, according to one example of the invention, plasma surface treatment is performed only on one side of the bag corresponding to the inner surface of the bag, and then it is sealed, and plasma surface treatment may be unnecessary for the side of the bag corresponding to the outer surface of the bag.

[0077] According to one example of the invention, it is not necessary to change the position of the bag, and in particular, the number of plasma heads can be reduced. As an example, it is possible to allow the sheet-like bag to pass continuously through a single plasma head. Specifically, as... Figure 2 As shown, plasma treatment can be performed on the entire bag without dividing the bag into a sealing area 11 and a battery cell area 12. That is, plasma surface treatment can be very easily performed on the entire polypropylene coating corresponding to the inner surface of the bag.

[0078] Ultimately, according to this example, plasma treatment is performed on the entire side of the bag sheet before it is cut into individual bags and before it is sealed, which enables a very efficient and easy device configuration and control logic.

[0079] In the following text, reference will be made to Figure 3 A method for manufacturing a secondary battery according to an example of the present invention is described in detail.

[0080] The manufacturing process of a pouch cell includes an electrode process, an assembly process, and a formation process, wherein this example can be considered to specifically involve the assembly process.

[0081] First, a bag forming the package, i.e., the casing of a pouch-type secondary battery (S10), can be provided. That is, a bag supply step can be performed. Here, it is preferable that the bag is a sheet-shaped bag. Therefore, the bag can be continuously moved on a moving table using roll-to-roll. Here, the moving table can also be a horizontal planar table or a roller table. Here, it is preferable that the bag sheet is a roll of bag sheet before cutting, rather than a bag cut for manufacturing individual pouch-type batteries.

[0082] Plasma surface treatment (S20) is performed on the supplied bag sheet. That is, a plasma surface treatment step can be performed. As described above, plasma surface treatment can be performed by continuously irradiating the surface of the bag sheet with plasma gas from a plasma head. In this case, it is preferable that the plasma head irradiates plasma gas over approximately the entire width of the bag sheet. Therefore, as the bag sheet passes through the plasma head at a constant speed, plasma treatment can be performed on approximately the entire surface of the bag sheet. Of course, the surface referred to here is the surface on which the inner surface of the bag shell will later be formed; plasma treatment on the surface on which the outer surface of the bag shell will later be formed may be meaningless.

[0083] After plasma treatment of the bag sheet, the bag sheet is shaped to form a bag housing together with the battery cell (S30). That is, the housing step can be performed. Specifically, the rolled bag sheet can be cut into cell bags. After the battery cell comes into close contact with the cut cell bag, the bag housing can be formed. At this time, in order to insert the battery cell, the bag can be shaped to form a space for inserting the battery cell. The cell bag can be in the form of an upper and lower shell of the bag housing connected by a fold, or each of the upper and lower shells that are separate from each other can also be called a cell bag.

[0084] After forming the bag housing that houses the battery cells, the bag housing can be sealed by thermal fusion (S40). That is, a bag sealing step can be performed. Here, the bag sealing can be performed except for the path through which the electrolyte can be injected into the bag housing. Then, after performing electrolyte injection, the injection port can be further sealed.

[0085] The plasma surface treatment method and configuration according to this example will be described in detail below.

[0086] Plasma treatment technology typically refers to direct plasma. In plasma, free radicals, ions, and electrons interact with the sample at high energies, readily breaking molecular bonds and forming new ones. When this corresponds to plasma surface treatment of bags, it means the bag is placed in a plasma-generating space. That is, as... Figure 1 As shown, this means that the plasma head 30 and the stage 20 perform positive and negative functions, respectively. Plasma gas is generated by applying an alternating voltage between the plasma head 30 and the stage 20 and discharging the gas, and the generated plasma gas affects the surface of the bag.

[0087] However, integrating direct plasma processing technology into bag plasma processing is not easy. This is because it is not easy to provide electrode functionality to the stage 20, especially the moving stage 20. This is because the moving stage moves or rotates linearly. Furthermore, it is not easy to continuously supply the bag to the space where plasma is directly generated.

[0088] According to this example, the bag can be treated with indirect plasma instead of direct plasma. Here, unlike direct plasma, indirect plasma refers to a plasma generation space and a sample located in separate spaces. In other words, indirect plasma means the bag and electrodes are located in separate spaces.

[0089] like Figure 4As shown, the plasma generator 50 may include a chamber 55, and within the chamber 55, a negative electrode 51 and a positive electrode 52 facing each other may be provided. The positions of the negative and positive electrodes may be changed. The positive electrode 51 and the negative electrode 52 may be connected to an AC power supply 54 to provide power for plasma generation.

[0090] A nozzle or inlet 53 is provided for injecting gas into chamber 55. Plasma discharge gas and carrier gas can be injected into chamber 55 through inlet 53. The plasma discharge gas and carrier gas can be different gases or the same gas.

[0091] When using indirect plasma, because the electrodes are in a separate space, there is no damage to the sample surface due to high power, making it easy to convert the desired gas into plasma. However, plasma generated by electricity returns to a steady state when the energy supply is cut off, requiring a large amount of carrier gas to rapidly deliver it to the sample. Among the ions, electrons, and free radicals generated by plasma discharge, only highly chemically reactive free radicals reach the sample via the carrier gas, thereby reducing damage from physical collisions.

[0092] To supply the free radicals generated in chamber 55 to plasma head 30, a delivery path 60 is preferably provided between chamber 55 and plasma head 30. Due to the high pressure and high flow rate of the carrier gas supplied to the interior of chamber 55, the plasma gas, i.e., the free radicals, is supplied to plasma head 30 along with the carrier gas via the delivery path. The plasma gas supplied to plasma head 30 can be irradiated onto the bag surface along with the carrier gas.

[0093] Ultimately, it is known that after plasma treatment, free radicals react with the surface of the bag made of polypropylene, thereby increasing the surface energy. Then, when it melts due to high temperature, cohesion occurs between different surfaces, thus placing it in a state that facilitates sealing.

[0094] To verify the effectiveness of using indirect plasma to improve the sealing strength of bags, the following examples and comparative examples were conducted.

[0095] -Example 1-

[0096] A plasma generator 50 continuously injects 250 LPM of nitrogen (N2) and 0.7 LPM of CDA (compressed-dry air), and discharges the gas at a power of 8.0 kW to form plasma. The plasma is injected through a plasma head 30 located outside the plasma generator 50 according to the gas flow rate, and the bag 10 passes through the injection zone at a linear velocity of 20 mm / s. The bag is then heat-pressed for 1.5 seconds under plasma surface treatment at 200°C and 0.1 MPa to achieve a bag seal via thermal fusion. Since the surface treatment effect of the plasma changes over time, the heat-pressing is performed within 5 minutes after the plasma surface treatment. The actual plasma discharge gas is CDA, and the actual carrier gas is nitrogen.

[0097] Example 2

[0098] Without CDA, N2 gas is supplied at 200 LPM, and the bag linear velocity is set to 60 mm / s. Otherwise, it is the same as in Example 1. Nitrogen is both the plasma discharge gas and the carrier gas. A portion of the supplied nitrogen is discharged via plasma.

[0099] Example 3

[0100] Except for the N2 gas supply at 100 LPM, the conditions are the same as in Example 2. Nitrogen is both the plasma discharge gas and the carrier gas. A portion of the supplied nitrogen is discharged by the plasma.

[0101] -Comparative Example 1

[0102] The thermal fusion sealing conditions are the same as in Example 1, and there is no plasma treatment.

[0103] Observing Examples 1 to 3, it can be seen that the plasma surface treatment is altered by changing the flow rate of the supplied gas and / or the linear velocity of the bag. It can be seen that the higher the flow rate of the supplied gas and the slower the linear velocity of the bag, the higher the intensity of the plasma surface treatment. Furthermore, it can be seen that the intensity of the plasma treatment is increased by whether or not a CDA (Concentrated Acid) is supplied, and by the amount of CDA supplied.

[0104] Figure 5 The water contact angle and water contact image are shown for each of Examples 1 to 3 and Comparative Example 1. The water contact angle was measured as a method for determining the degree of surface treatment of the bag and indirectly observing the surface energy.

[0105] As shown in the figure, it can be seen that in all examples where plasma surface treatment was performed, the water contact angle was smaller than that of Comparative Example 1. It is anticipated that by keeping the water contact angle in the range of approximately 41 to 50 degrees, the sealing strength can be improved by increasing the adhesive physical properties. That is, it is known that the polypropylene surface-modified by plasma surface treatment is polar and generates intermolecular cohesion, thereby improving the sealing strength.

[0106] Figure 6 This is a table showing the average and deviation of the sealing strength measured in each of Examples 1 to 3 and Comparative Example 1, and... Figure 7 The graph shows the sealing strength measured in each of Examples 1 to 3 and Comparative Example 1.

[0107] like Figure 6 and Figure 7 As shown, it can be seen that the average sealing strength is improved in all three examples compared to Comparative Example 1. That is, it can be seen that an improvement in average sealing strength can be expected through indirect plasma. However, in the cases of Examples 1 and 3, the deviation in sealing strength increases compared to Comparative Example 1, making it difficult to consider a statistically significant increase in strength. However, since the lower limit of the peel strength in Examples 1 and 2 is greater than 7 kgf / 15 mm, it can be seen that sufficient sealing strength can be obtained.

[0108] Then, even if CDA is removed from the gas composition, as seen in Examples 2 and 3, an increase in sealing strength can be obtained. In particular, it can be known that the highest sealing strength and small deviation can be obtained in Example 2.

[0109] Therefore, through Examples 1 to 3, it can be seen that in indirect plasma surface treatment, the sealing strength of the bag can be obtained very effectively within the range of nitrogen supply flow rate, bag linear velocity, and the presence and flow rate of CDA.

[0110] Figure 8 The sampling location in the sealed bag is shown, and Figure 9 The sampling method and sampling size for measuring seal strength are shown.

[0111] First, it can be done through, for example Figure 8 The bag is cut along the dotted line as shown, and as... Figure 9 The sample is obtained by cutting the dotted line portion shown in the diagram. Since the bags overlap, the seal strength can be measured by pulling the upper bag while the lower bag is fixed.

[0112] The seal strength of the sealed bag was measured by using the tensile strength measurement function of a universal testing machine (UTM) to measure the force from sampling to seal rupture. The UTM was operated at a constant speed of 5 mm / min to break the seal, and the average force measured up to 8 mm after the 4.5 kgf measurement point was recorded.

[0113] Industrial applicability

[0114] It is described in the detailed description of the invention.

Claims

1. A pouch-type secondary battery manufacturing apparatus, comprising: A moving platform that supports the bag before it is sealed and moves the bag linearly in a first direction; A plasma generator that discharges gas internally to form plasma; A plasma head that irradiates the surface of the bag with plasma gas generated by the plasma generator to improve the bag's seal strength after sealing; and A transport path, wherein the transport path delivers the plasma gas generated by the plasma generator to the plasma head via a carrier gas.

2. The pouch-type secondary battery manufacturing apparatus according to claim 1, characterized in that... The plasma heads are configured to be spaced apart in a second direction perpendicular to the first direction.

3. The pouch-type secondary battery manufacturing apparatus according to claim 2, characterized in that... The plasma head is fixed and configured to irradiate the surface of the bag vertically downwards using the plasma gas.

4. The pouch-type secondary battery manufacturing apparatus according to claim 3, characterized in that... The moving stage is configured to move the bag at a constant speed, and the plasma head uses the plasma gas to irradiate the surface of the bag, which is supported by the moving stage, while it is moving.

5. The pouch-type secondary battery manufacturing apparatus according to claim 1, characterized in that... The plasma generator continuously supplies the gas for plasma discharge and the carrier gas at a constant flow rate.

6. The pouch-type secondary battery manufacturing apparatus according to claim 5, characterized in that... The gas discharged when plasma is generated in the plasma generator contains nitrogen (N2).

7. The pouch-type secondary battery manufacturing apparatus according to claim 6, characterized in that... The carrier gas is nitrogen.

8. The pouch-type secondary battery manufacturing apparatus according to claim 7, characterized in that... The flow rate of nitrogen flowing into the plasma generator is 100 LPM to 250 LPM.

9. The pouch-type secondary battery manufacturing apparatus according to claim 8, characterized in that... The linear movement speed of the bag before sealing is 20 mm / s to 60 mm / s.

10. The pouch-type secondary battery manufacturing apparatus according to claim 5, characterized in that... The gas used for plasma discharge is compressed dry air (CDA), and the carrier gas is nitrogen.

11. The pouch-type secondary battery manufacturing apparatus according to claim 10, characterized in that... The compressed dry air flowing into the plasma generator has a flow rate of 0.7 LPM.

12. The pouch-type secondary battery manufacturing apparatus according to claim 5, characterized in that... The surfaces of the bags, which are surface-treated with the plasma gas, overlap each other and are then thermally fused together to seal them.

13. The pouch-type secondary battery manufacturing apparatus according to claim 12, characterized in that... Perform thermal fusion for 1.5 seconds at 200 degrees Celsius and 0.1 MPa pressure.

14. A method for manufacturing a pouch-type secondary battery, comprising: The bag supply step involves continuously moving the bag pieces on a moving table; The plasma surface treatment step involves irradiating the surface of the bag sheet with plasma gas generated from a plasma generator via a plasma head. The casing step involves forming a bag casing together with the battery cell by molding a plasma-surface-treated bag sheet; and The bag sealing step involves sealing the bag shell by heat fusion, and The characteristic feature is that the plasma gas moves from the plasma generator to the plasma head via a carrier gas, thereby irradiating the bag sheet.

15. The method for manufacturing a pouch-type secondary battery according to claim 14, characterized in that... Inside the plasma generator, the gas for plasma discharge and the carrier gas are continuously supplied at a constant flow rate, and The plasma head uses the plasma gas and the carrier gas to irradiate the surface of the bag, which is being moved while supported by the moving stage.

16. The method for manufacturing a pouch-type secondary battery according to claim 15, characterized in that... The gas discharged when plasma is generated in the plasma generator contains nitrogen (N2).

17. The method for manufacturing a pouch-type secondary battery according to claim 16, characterized in that... The carrier gas is nitrogen.

18. The method for manufacturing a pouch-type secondary battery according to claim 17, characterized in that... The flow rate of nitrogen flowing into the plasma generator is 100 LPM to 250 LPM.

19. The method for manufacturing a pouch-type secondary battery according to claim 18, characterized in that... The linear movement speed of the bag before sealing is 20 mm / s to 60 mm / s.

20. The manufacturing method according to claim 14, characterized in that... After the plasma surface treatment, the water contact angle on the surface of the bag sheet is 41 to 50 degrees.

Images