KR101408623B1 - Lithium ion battery in pouch type and method of preparation of the same - Google Patents

Abstract

The present invention solves various problems that occur when a battery cell is mounted in a pouch which is a packaging material in a pouch type battery, electrolyte is injected into the pouch sealing part during the process of sealing the pouch after the electrolyte is injected (electrolytic solution wetting or interlocking sealing) The present invention also relates to a method for manufacturing a lithium ion polymer battery and a lithium ion polymer battery, wherein the electrolyte injection part is minimized to form a protrusion.

According to the present invention, it is possible to prevent microcracks, breakdown of insulation resistance, electrolytic solution loss, and inflow of external air, which are caused by the electrolyte in the sealing portion of the pouch, and sealing by varying the sealing strength or width of the sealing portion It is possible to induce safe venting of excessive generated gas when the battery malfunctions.

Pouch, Battery, Electrolyte, Injection, Sealing, Packaging, Extrusion

Description

TECHNICAL FIELD [0001] The present invention relates to a pouch-type lithium ion polymer battery and a method of manufacturing the same.

The present invention relates to a pouch type lithium ion polymer battery and a manufacturing method thereof. Provided is a method for manufacturing a pouch-shaped battery which minimizes the sealing of an electrolyte and the breakdown of insulation resistance and provides a pouch-shaped battery in which the risk of explosion is prevented by inducing directional venting when a battery malfunctions.

The biggest problem in the manufacturing process of the pouch type battery is that the electrolytic solution is wetted in the sealing part during the sealing process of the pouch as a packaging material. The electrolyte solution wetted to the sealing portion not only becomes a passage through which electrolyte loss and external air flow into the battery cell but also the insulation resistance of the battery is destroyed. Further, when the aluminum, which is the material of the pouch, reacts with the cathode of the battery through the passage, the Al alloy is formed. According to this reaction, the cathode can no longer function as a cathode and is self-discharged, which is a decisive cause of the cell die.

Accordingly, each battery company focuses on minimizing or preventing wettability of the electrolyte in the pouch sealing part when inserting the battery cell and injecting the electrolyte into the pouch when manufacturing the pouch type battery.

KR 10-2003-0066576 discloses a method for preventing the phenomenon that the electrolyte is spouted and volatilized by injecting an electrolyte under a CO ₂ atmosphere, sealing the packaging material, and performing charge / discharge reaction.

KR 10-2006-0011427 discloses a method of injecting an electrolyte in an accurate amount through a device for measuring the weight of the injected electrolyte.

EP1804313 discloses a pouch including a groove, an extension, and a flange. A battery cell is inserted into the groove of the pouch, and then the extension and the flange are sealed by one sealing part of the cell. Then, And how to do it.

However, the above documents disclose a method of injecting an electrolyte in the manufacture of a pouch-type battery, and do not mention any method for reducing electrolyte wetting in a sealing part, which is the most problematic in electrolyte injection.

An object of the present invention is to minimize electrolyte wetting on the inner wall of a pouch of a sealing part when pouch-sealed in a pouch-type battery, thereby preventing electrolytic sealing.

It is possible to minimize the partial opening and subsequent resealing of the degassing process during the manufacturing process of the pouch type battery, thereby minimizing the breakdown of the insulation resistance.

In addition, the difference in pouch sealing strength between the pouch-type battery and the pouch-type battery can lead to predicted venting when the battery malfunctions.

The present invention provides a method of manufacturing a lithium ion polymer battery, wherein an electrolyte is injected through a non-sealing projection of one side of a pouch in manufacturing a pouch type lithium ion polymer battery.

The present invention also provides a packaging material for a pouch type lithium ion polymer battery, which includes a non-sealing projection which is opened for injection and degassing of an electrolyte in the manufacturing process of the battery and is sealed in the activation and final sealing process And a pouch of a lithium ion polymer battery.

In addition, the present invention provides a battery in which a battery cell including a positive electrode, a negative electrode, and a separator is packaged in a pouch as a packaging material, wherein the pouch includes a protrusion at one side, and the protrusion has a narrow width And the electrolyte membrane is sealed.

Finally, the present invention provides an electric vehicle, wherein the battery is used as a power source, and a protrusion of the battery is disposed in the same direction as an exhaust port of the exhaust gas.

According to the present invention, it is possible to minimize the possibility of wetting the electrolyte in the sealing part of the pouch, which is a packaging material of the battery cell, during the production of the lithium ion polymer battery, and to prevent microcracks or defects The insulation resistance breakdown can be minimized.

In addition, in the present invention, directional venting can be induced when the pouch is malfunctioned by manufacturing the pouch by varying the sealing width and the strength at the time of sealing.

Particularly, in the pouch type battery, the protruding portion is made to be the same as the exhaust gas outlet of the electric vehicle by making the portion with weak sealing width and strength of the pouch as the protruding portion, or the efficiency and safety Can be designed.

When manufacturing a pouch-type lithium ion polymer battery, the folding type cell which is now completed is packed in a packaging pouch, and then an electrolyte is injected. After the activation process, the pouch is partially opened to degass the gas generated at this time, Sealing. In this case, the electrolytic solution is injected in the state that the entire surface of the pouch is opened, so that the electrolyte is wetted on the inner wall of the pouch or the diffusion of the gas / liquid electrolyte by the pressure difference caused by the vacuum during the final sealing after opening the pouch portion for the degassing process An electric current passage between the inside and the outside of the cell may occur due to the electrolyte solution on the pouch sealing portion. This causes insulation breakdown and a significant reduction in the sealing strength, resulting in deterioration of the cell performance.

Therefore, in the present invention, when the battery cell is placed in the packaging pouch and the three sides of the pouch and the other side are maximally sealed when the electrolyte is sealed, the non-sealing area (non-sealing part) is minimized. Further, the non-sealing portion is formed as a protruding portion.

The non-sealing portion is preferably formed by sealing the other side of the pouch by 4/5 or more at the time of pouch packaging. Also, in the present invention, the non-sealing portion is preferably used as a packaging material for a battery in which the pouch is present in a shape protruding from 5 to 15 mm.

By thus minimizing the non-sealing portion of the pouch, the sealing of the electrolyte can be prevented in advance.

Meanwhile, since the non-sealing portion is a portion that is opened during degassing and is resealed in the final sealing process (therefore, the non-sealing portion is also referred to as a 'D / R portion'), A reduction in the sealing thickness due to the sealing and insulation breakdown can be caused. Therefore, in the present invention, the non-sealing portion is formed as a protrusion so as to minimize the occurrence of errors due to over-sealing in the manufacturing process of the battery.

In the manufacturing process of the pouch type lithium ion polymer battery of the present invention, the battery cell is placed in a packaging material pouch prepared by protruding the non-sealing part (hereinafter, referred to as 'non-sealing protrusion'), After sealing 4/5 or more, the electrolyte is injected through the non-sealing protrusion using a tube or the like. Next, after the non-sealing projection is sealed with a sealing width of about 5 mm, the activation process is performed, and only the non-sealing projection is cut off and opened to perform the D / R process. Finally, the battery manufacturing is completed by finally sealing the non-sealing projection with a sealing width narrower than the other. The final sealing width of the non-sealing projection is about 5 mm when the sealing width of the other sealing portion is about 7 mm. However, the sealing width is shown as an example, and the present invention is not limited thereto.

In the lithium ion polymer battery thus manufactured, there is no breakdown of the insulation resistance due to the electrolyte sticking at the portion excluding the non-sealing protruding portion (D / R portion), so that the defective rate of the battery as a whole can be reduced.

Further, when the battery is expanded due to the internal gas pressure when the battery malfunctions, the battery produced by the method of the present invention has a relatively low sealing strength and a relatively small sealing width, so that the internal pressure is weakened. The part is easily opened. That is, in the battery manufactured by the manufacturing method of the present invention, directional venting is induced by making a difference in the sealing strength, thereby reducing the risk of explosion and fire. Further, in the pouch-type battery manufactured as described above, since the discharge direction of the gas can be predicted from the presence of the non-sealing protrusion, it is possible to prevent the gas from being introduced into the room when the battery and the exhaust gas outlet are designed and arranged in the electric vehicle, And can be designed safely.

5 shows the electrolyte loss and moisture permeability according to the sealing width while varying the sealing width and sealing area in order to find an optimum value for the sealing width of the pouch as a packaging material in a pouch-type battery. From these results, it was confirmed that when the sealing width is about 5 mm or more, the cell life is not greatly affected in terms of electrolyte loss and moisture permeation. Therefore, in the present invention, the sealing width of the D / R portion is sealed to be smaller than the sealing width of the other sealing portion of the pouch in the range of 5 mm or more.

The present invention will now be described in detail by way of examples. However, the present invention is not limited thereto.

Example

As shown in FIG. 1, a battery cell was inserted into an aluminum pouch including a protrusion used in the method of manufacturing a battery of the present invention, and the remaining portion except for the protrusion was sealed with a width of 7 mm. At this time, the length of the protrusion was 1/5 of one side of the pouch, and the protrusion width was 10 mm.

Next, the electrolyte was injected through the non-sealing portion. Then, the non-sealing portion was sealed with a width of 5 mm, and then a charging and discharging cycle was performed once in a voltage range of 2.5 to 4.2 V to carry out the activation process of the battery cell. Then, only the projection was opened, and the unsealed portion opened while vacuuming was degassed and finally sealed with a width of 5 mm.

Comparative Example

As a comparative example, an electrolytic solution was injected through a non-sealed surface using a conventional aluminum pouch that did not include protrusions, activated and degassed in the same manner as in Example, and the non-sealed portion was finally sealed to prepare a battery .

The insulation resistance of the batteries manufactured in Examples and Comparative Examples was measured as a method of determining the presence or absence of microcracks through non-destructive inspection. (+) Terminal of the insulation resistance meter was contacted to the anode lead, and the (-) terminal was contacted with the sealing portion (aluminum) of the cell, and then a voltage of 25 V was applied. The determination of whether or not the insulation resistance is broken is based on the following Table 1.

The electrical short is whether there is a short between the anode lead and the Al layer inside the pouch. That is, if the cathode and the Al layer of the pouch are in contact, the electric short is YES. The presence or absence of micro cracks indicates whether cracks exist in the sealing part. As shown in the table, when there is no electrical short circuit after electrolyte impregnation (in an insulated state) and no microcracks, the insulation resistance was measured to be 100 MΩ or more. Isolation maintained state. However, if the electrical short is YES (that is, in the energized state) or if there is microcracks even if the short circuit is maintained, the Al layer of the pouch is energized and the insulation resistance becomes very small.

In the case where the non-sealing projection of the present invention is included, insulation resistance breakdown is prevented like the display portion, but insulation resistance breakdown occurs frequently in the battery cell for comparison manufactured by the conventional method.

Next, the cross section of the sealing portion according to the presence or absence of the electrolytic solution, and the sealing portion corresponding to the vaporization of the electrolytic solution were photographed. The results are shown in Figures 2 and 3.

2 shows a case where the insulation resistance is maintained in the battery cell manufactured in the embodiment of the present invention. FIG. 2 and FIG. 3 are photographs of a state in which the sealing portion is wetted with the electrolyte to perform the sealing sealing .

Next, the P and F elements (salt components of the electrolytic solution) were analyzed by Energy dispersive analysis (EDS) in order to confirm whether the electrolyte leaked through the sealing part in the comparative battery cell. The results are shown in Fig. It can be seen that the electrolyte salt exists between the PP layer which is the upper part of the sealing part and Al.

1 shows a process of manufacturing a battery according to the present invention.

2 is a photograph of a cross section of a sealing part according to the presence or absence of an electrolytic solution.

FIG. 3 is a photograph of a sealing portion according to vaporization of an electrolytic solution.

FIG. 4 is an energy dispersive analysis (EDS) image of the PP layer and the Al layer which are the upper portions of the sealing portion.

FIG. 5 is a graph showing the electrolyte loss and moisture permeation amount according to the sealing width.

Claims (7)

In the production of the pouch type lithium ion polymer battery, the electrolyte is injected through the non-sealing protrusions on one side of the pouch, The non-sealing projection is protruded at one side of the pouch and protrudes at a width narrower than the width of the pouch and is sealed for the activation process of the battery after the injection of the electrolyte, Sealed, finally sealed after the degassing process, Wherein the sealing width of the non-sealing protrusion during the final sealing process is narrower than the sealing width of the other sealing portion of the pouch. The method of claim 1, wherein the non-sealing protrusions are formed to have a length of 1/5 or less of one side of the pouch and a width of 5 to 20 mm. delete A packaging material for a pouch type lithium ion polymer battery, And a non-sealing projection projecting from one side of the pouch, the projection projecting at a width narrower than the width of the side of the pouch, The non-sealing protruding portion is opened for injection of an electrolyte solution, is sealed for activation of the battery after the electrolyte is injected, is cut open for a digging process after the activation process, and after the digging process Lt; / RTI > Wherein the sealing width of the non-sealing protrusion in the final sealing process is narrower than the sealing width of the other sealing portion of the pouch. 5. The pouch of a lithium ion polymer battery according to claim 4, wherein the non-sealing protrusions are formed to have a length of 1/5 or less of one side of the pouch and a width in a range of 5 to 20 mm. In a battery in which a battery cell including an anode, a cathode, and a separator is packaged in a pouch as a packaging material, the pouch includes protrusions at one side, and the protrusion is finally sealed with a narrow width as compared with other sealing portions of the pouch ≪ / RTI > The electric vehicle according to claim 6, wherein the protruding portion of the battery is disposed in the same direction as the direction of the outlet of the exhaust gas.

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