Secondary Battery Pack

Abstract

The present disclosure provides a secondary battery pack including at least one pouch-type cell; and a case having an internal space for accommodating the pouch-type cell, wherein the pouch-type cell includes an electrode assembly and a pouch film for accommodating the electrode assembly, and the pouch film is composed of only a polymer or only a polymer and an adhesive.

Description

[Technical field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0172846 dated December 12, 2022, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present disclosure relates to a secondary battery pack. More particularly, the present disclosure relates to a secondary battery pack including a pouch-type cell. [Background technology]

[0003] A secondary battery can store and supply electrical energy by charging and discharging using lithium ions. The secondary battery can be used in the form of a pack including a plurality of cells. The plurality of cells change in volume as charging and discharging proceeds. For example, a secondary battery using a silicon anode, a secondary battery using lithium metal, etc., have a problem that the thickness of the anode changes by about 10% during charging and discharging. This problem occurs in most secondary batteries, including lithium ion secondary batteries, all-solid secondary batteries, semi-solid secondary batteries, and lithium-sulfur secondary batteries.

[0004] Cylindrical and prismatic cells have fixed case shapes, so it is difficult to apply a constant pressure to the cells. Also, prismatic cells, unlike circular cells, can be more vulnerable to swelling defects, in which the large surface of the battery bulges, unless a special pressure device is used. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Korean Patent Publication No. 2022-0125096 Summary of the Invention [Problem to be solved by the invention]

[0006] Since the size of the pouch-type cell case is variable, a constant pressure can be applied from the outside even if the size of the pouch-type cell changes, and the use of pouch-type cells in secondary battery packs is being considered due to their light cell weight (high energy density) in terms of weight and safety. However, pouch-type cells contain metal to prevent moisture permeation and to strengthen impact resistance, and secondary battery packs including pouch-type cells have the disadvantage that it is difficult to achieve high energy density.

[0007] Therefore, in order to achieve high energy density, technological development is underway for secondary battery packs including pouch-type cells using non-metallic materials.

[0008] The present inventors have proposed to solve the above-mentioned problems, and an object of the present disclosure is to provide a secondary battery pack that has improved energy density, impact resistance, and can prevent the penetration of moisture and oxygen. [Means for solving the problem]

[0009] To achieve the above object, according to one embodiment of the present disclosure, there is provided a secondary battery pack including at least one pouch-type cell; and a case having an internal space for accommodating the pouch-type cell, wherein the pouch-type cells each include an electrode assembly and a pouch film for accommodating the electrode assembly, and the pouch film is made of only a polymer or only a polymer and an adhesive.

[0010] In one embodiment, the pouch film has a thickness of 20 μm or more and 200 μm or less.

[0011] In one embodiment, the weight per area of ​​the pouch film is 20 g / m 2 More than 150g / m 2 The present invention provides a secondary battery pack characterized by the following:

[0012] In one embodiment, the polymer includes at least one selected from the group consisting of nylon, polyethylene, polyamide, polyamide nylon, polypropylene, polyimide, polyvinyl chloride, polyethylene terephthalate, olefin resin, polystyrene, polycarbonate, and polyvinyl alcohol.

[0013] In one embodiment, the secondary battery pack further includes a spacer disposed on a side of the pouch-type cell inside the case, the spacer being made of a polymer, metal, or elastic material.

[0014] In one embodiment, the secondary battery pack is provided, wherein the polymer includes rubber.

[0015] In one embodiment, the secondary battery pack is characterized in that the elastic body is a leaf spring.

[0016] In one embodiment, a positive electrode terminal, a negative electrode terminal, and a gas exhaust port are arranged on an upper surface of the case, and the positive electrode terminal and the negative electrode terminal are each electrically connected to the pouch-type cell.

[0017] In one embodiment, a positive electrode terminal is disposed on an upper surface of the case, a negative electrode terminal is disposed on a lower surface of the case, the positive electrode terminal and the negative electrode terminal are each electrically connected to the pouch-type cell, and a gas exhaust port is disposed on at least one of the upper surface and the lower surface of the case. Effect of the Invention

[0018] A secondary battery pack according to an embodiment of the present disclosure includes a pouch-type cell made of only a polymer, thereby achieving a higher energy density than conventional batteries. In addition, the use of an impact-resistant case can protect the pouch-type cell, which does not contain metal, from impact. The use of the case can also prevent external moisture and oxygen from approaching the pouch-type cell. In addition, since the pouch is made of only a polymer, it can have a low weight even if it is formed thick, and can still house and use the electrode assembly even if the pouch is torn during the process of forming the pouch. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 illustrates a pouch-type cell according to one embodiment of the present disclosure. [Diagram 2] FIG. 13 illustrates a pouch-type cell according to another embodiment of the present disclosure. [Diagram 3] 2A to 2C are diagrams illustrating the steps of manufacturing the pouch of the pouch-type cell of FIG. 1. [Figure 4] 2 is a diagram showing another stage in the manufacture of the pouch of the pouch-type cell of FIG. 1. FIG. [Diagram 5] FIG. 2 is a perspective view showing an embodiment of a secondary battery pack including the pouch-type cell of FIG. 1. [Figure 6] FIG. 2 is a side view showing an embodiment of a secondary battery pack including the pouch-type cell of FIG. [Figure 7] 3 is a perspective view showing another embodiment of a secondary battery pack including the pouch-type cell of FIG. 2. FIG. [Figure 8] 3 is a side view showing another embodiment of a secondary battery pack including the pouch-type cell of FIG. 2. FIG. [Figure 9] 1 is a photograph showing the measurement of the cup forming result of a pouch-type cell according to an embodiment of the present disclosure. [Figure 10] 1 is a photograph showing the measurement of the cup forming result of a pouch-type cell according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] In the following, the present disclosure will be described in further detail to facilitate understanding of the present disclosure.

[0021] The terms and words used in this specification and the claims should not be interpreted in a limited manner to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept that corresponds to the technical idea of ​​the present disclosure, based on the principle that an inventor can appropriately define the concept of a term in order to best describe his / her invention.

[0022] FIG. 1 illustrates a pouch-type cell according to one embodiment of the present disclosure.

[0023] Referring to Fig. 1, a pouch-type cell (100a) according to an embodiment of the present disclosure includes an electrode assembly (120b) in which electrodes and separators are alternately stacked and assembled, and a pouch (110) that houses the electrode assembly, and the pouch (110) may be made of a polymer. The configuration and structure of the pouch (110) will be described later. The electrode assembly (120b) is a power generating element capable of charging and discharging, and is formed by alternately stacking electrodes and separators, the electrodes including positive and negative electrodes, and the positive electrodes, the separators, and the negative electrodes may be alternately positioned.

[0024] The electrode assembly (120b) may have electrode tabs (120a, 120c) connected to one end. In one embodiment of the present disclosure, the electrode tabs (120a, 120c) may be connected to only one side of the electrode assembly (120b). One of the electrode tabs (120a, 120c) may be an electrode tab connected to the positive electrode, and the other may be an electrode tab connected to the negative electrode. Through the electrode tabs (120a, 120c), the electrode assembly (120b) may be electrically connected to an external device.

[0025] The pouch (110) can accommodate the electrode assembly (120b). The pouch (110) can have an internal space for accommodating the electrode assembly (120b). Conventional pouches include an aluminum alloy thin film, and the polymer is laminated onto the aluminum alloy thin film. As a result, the conventional pouch can ensure a certain level of mechanical strength and prevent external gas or moisture from penetrating into the electrode assembly (120b) because it includes the aluminum alloy thin film. However, the aluminum alloy thin film increases the weight of the pouch-type cell (100a), making it difficult to ensure energy density.

[0026] FIG. 2 illustrates a pouch-type cell according to another embodiment of the present disclosure.

[0027] Referring to Fig. 2, a pouch-type cell (100b) according to another embodiment of the present disclosure includes an electrode assembly (130b) in which electrodes and separators are alternately stacked and assembled, and a pouch (110) that contains the electrode assembly and an electrolyte, and the pouch (110) may be made of a polymer. The configuration and structure of the pouch (110) will be described later. The electrode assembly (130b) including the electrolyte is a power generating element that can be charged and discharged, and is formed by alternately stacking electrodes and separators, the electrodes including positive and negative electrodes, the positive electrodes, the separators and the negative electrodes are alternately positioned, and the electrolyte can be contained in the internal pores.

[0028] The electrode assembly (130b) may have electrode tabs (130a, 130c) connected to its ends. In another embodiment of the present disclosure, the electrode tabs (130a, 130c) may be connected to both ends of the electrode assembly (130b), respectively. One of the electrode tabs (130a, 130c) may be an electrode tab connected to the positive electrode, and the other may be an electrode tab connected to the negative electrode. The electrode assembly (130b) may be electrically connected to an external device through the electrode tabs (130a, 130c).

[0029] The pouch (110) can accommodate the electrode assembly (130b) and the electrolyte. The pouch (110) can have an internal space for accommodating the electrode assembly (130b) and the electrolyte. Conventional pouches include an aluminum alloy thin film, and the polymer is laminated onto the aluminum alloy thin film. As a result, the conventional pouch can ensure a certain level of mechanical strength and prevent external gas or moisture from penetrating into the electrode assembly (130b) because of the aluminum alloy thin film. However, the aluminum alloy thin film increases the weight of the pouch-type cell (100b), making it difficult to ensure energy density.

[0030] 3 and 4 are diagrams showing different stages in the manufacture of the pouch of the pouch-type cell of FIG.

[0031] 3 and 4, the pouch (110) may include an internal space (115) for accommodating the electrode assembly. The internal space (115) may be formed by applying pressure to the pouch (110) using the lower die (150) and the punch die (140). The pouch (110) according to the embodiment of the present disclosure is made of only the polymer, so that the internal space (115) may be formed more easily than when the aluminum alloy thin film is included. In addition, the conventional pouch is manufactured with a thin thickness in order to achieve a high energy density since it includes the aluminum alloy thin film. In the process of applying pressure to form the internal space, such a conventional pouch may be caught on the corners of the lower die (150) and may be torn. In this case, the pouch is not suitable for accommodating the electrode assembly. In contrast, the pouch (110) according to the embodiment of the present disclosure may not be torn even if it is manufactured to a similar thickness using the polymer since it does not include the aluminum alloy thin film. Therefore, even if the pouch (110) is neither thick nor heavy, it can be used to accommodate the electrode assembly. The thickness of the pouch (110) may be 20 μm or more and 200 μm or less, and preferably 50 μm or more and 150 μm or less.

[0032] The pouch (110) may be a single polymer layer or may be formed of multiple polymer layers. The polymer may be one or more of nylon, polyethylene, polyamide, polyamide nylon, polypropylene, polyimide, polyvinyl chloride, polyethylene terephthalate, olefin resin, polystyrene, polycarbonate, and polyvinyl alcohol. In addition, the pouch may be formed of multiple polymer layers, and an adhesive film may be formed on one side for film adhesion. The material of the adhesive film may be an adhesive film used in general pouches for secondary batteries. For example, the pouch may be formed of an adhesive layer, a polyimide layer, and a nylon layer from the bottom to the top. The polyimide layer may be made of a polyimide material, and the nylon layer may be made of a nylon material.

[0033] Thus, because the pouch 110 does not contain metal and is composed only of polymer, a pouch-type cell including the pouch 110 can achieve a high energy density. 2 A secondary battery pack including the pouch-type cell can have a pack energy density of 240 Wh / kg or more. 2 If the weight per area of ​​the pouch (110) exceeds 20 g / m, the pack energy density will decrease to less than 240 Wh / kg, and the advantage of the energy density of the secondary battery pack according to one embodiment of the present disclosure will not be obtained. 2 If it is less than this, the film will be too thin and will lack rigidity, which may cause electrolyte leakage.

[0034] 5 and 6 are diagrams showing an embodiment of a secondary battery pack including the pouch-type cell of FIG.

[0035] 5 and 6, a secondary battery pack (200) according to an embodiment of the present disclosure may include a case (210), a positive terminal (220), a negative terminal (230), a gas exhaust port (240), a spacer (250), and a plurality of pouch-type cells (260). The plurality of pouch-type cells (260) may be substantially the same as the unidirectional tab pouch-type cell (see FIG. 1) among the above-mentioned pouch-type cells. The case (210) may include a plurality of pouch-type cells (260) therein. The number of the plurality of pouch-type cells (260) is not limited, and different numbers may be selected and used as necessary. The case (210) may be made of a material having rigidity. For example, the case (210) may be made of a material such as stainless steel, an aluminum alloy containing 50% or more of aluminum, a magnesium alloy containing 50% or more of magnesium, or a titanium alloy containing 50% or more of titanium. The case 210 can protect the plurality of pouch-type cells 260 from external impact and prevent moisture from penetrating into the plurality of pouch-type cells 260. The case 210 can protect the plurality of pouch-type cells 260 from external impact and moisture even if the aluminum alloy thin film is not used.

[0036] The case 210 may have four side surfaces, and a pair of side surfaces facing each other may have a larger area than another pair of side surfaces facing each other, for example, the pair of side surfaces may be more than twice as large as the other pair of side surfaces.

[0037] The positive electrode terminal (220) and the negative electrode terminal (230) may be connected to electrode tabs of the plurality of pouch-type cells (260) by separate connecting members (215, 225), respectively. The connecting members (215, 225) may be made of any material having electrical conductivity. The gas outlet (240) may exhaust gas generated during operation of the secondary battery pack (200). A structure including the connecting members (215, 225), the positive electrode terminal (220), the negative electrode terminal (230), and the gas outlet (240) may be defined as a top assembly. The gas outlet (240) is illustrated as being disposed on the upper surface of the case (210), but this is merely an example, and the gas outlet (240) may be disposed on the lower surface of the case (210) or on both the upper and lower surfaces of the case (210).

[0038] The spacer (250) may be disposed on the outermost side of the plurality of pouch-type cells (260) and may be in the form of a porous foam of polymer (e.g., rubber) and metal, or an elastic body (e.g., a leaf spring). The spacer (250) may reduce in volume in response to a change in pressure generated in the plurality of pouch-type cells (260). The spacer (250) may reduce in thickness by 5% to 90% at a pressure of about 10 atm. Through the spacer (250) and the rigid case (210), a certain range of pressure can be applied even if a change in volume of the plurality of pouch-type cells (260) occurs inside the case (210) without external pressure. In addition, the secondary battery pack (200) reduces the area where pressure is generated by disposing the plurality of pouch-type cells (260) in the longitudinal direction of the case (210), and can withstand the internal pressure generated from the plurality of pouch-type cells (260) without deformation of the case (210).

[0039] Since the secondary battery pack (200) includes a spacer (250), it can maintain a constant pressure range even if the thickness of the pouch-type cell (260) changes within the cell without an external device, which is advantageous in terms of weight reduction as it does not require a separate external device.

[0040] Although not shown, a partition wall may be present between each of the pouch-type cells (260). For example, the partition wall may include the same material as the spacer (250) and may reduce in volume in response to a change in pressure occurring in each of the pouch-type cells (260). The partition wall may be substantially defined as a spacer. The partition wall may be disposed between all of the pouch-type cells (260) or may be disposed only between some of the pouch-type cells (260). When the partition wall is disposed between the pouch-type cells (260), the pouch-type cells (260) can be physically separated from each other, and the venting position can be controlled when venting occurs due to swelling, thereby preventing cell-to-cell propagation between the pouch-type cells (260).

[0041] 7 and 8 are diagrams showing other embodiments of a secondary battery pack including the pouch-type cell of FIG.

[0042] 7 and 8, a secondary battery pack (300) according to another embodiment of the present disclosure may include a case (310), a positive terminal (320), a negative terminal (330), a gas exhaust port (340), a spacer (350), and a plurality of pouch-type cells (360). The plurality of pouch-type cells (360) may be substantially the same as the unidirectional tab pouch-type cell (see FIG. 1) among the above-mentioned pouch-type cells. The case (310) may include a plurality of pouch-type cells (360) therein. The number of the plurality of pouch-type cells (360) is not limited, and different numbers may be selected and used as necessary. The case (310) may be made of a material having rigidity. For example, the case (310) may be made of a material such as stainless steel, an aluminum alloy containing 50% or more of aluminum, a magnesium alloy containing 50% or more of magnesium, or a titanium alloy containing 50% or more of titanium. The case 310 can protect the plurality of pouch-type cells 360 from external impact and prevent moisture from penetrating into the plurality of pouch-type cells 360. The case 310 can protect the plurality of pouch-type cells 360 from external impact and moisture even if the aluminum alloy thin film is not used.

[0043] The case 310 may have four side surfaces, and a pair of side surfaces facing each other may have a larger area than another pair of side surfaces facing each other, for example, the pair of side surfaces may be more than twice as large as the other pair of side surfaces.

[0044] The positive electrode terminal (320) and the negative electrode terminal (330) may be connected to electrode tabs of the plurality of pouch-type cells (360) by separate connecting members (315, 325), respectively. The connecting members (315, 325) may be made of any material having electrical conductivity. The gas outlet (340) may exhaust gas generated during operation of the secondary battery pack (300). A structure including the connecting members (315, 325), the positive electrode terminal (320), and the gas outlet (340) may be defined as a top assembly. The negative electrode terminal (330) is not included in the top assembly because it is disposed at the bottom of the case (310). Although the gas outlet (340) is illustrated as being disposed at the top surface of the case (310), this is merely an example, and the gas outlet (340) may be disposed at the bottom surface of the case (310) or at both the top surface and bottom surface of the case (310).

[0045] The spacer (350) may be disposed on the outermost side of the plurality of pouch-type cells (360) and may be in the form of a polymer, rubber, or metal foam, or in the form of a leaf spring. The spacer (350) may reduce in volume in response to a change in pressure generated in the plurality of pouch-type cells (360). The spacer (350) may reduce in thickness by 5% to 90% at a pressure of about 10 atm. Through the spacer (350) and the rigid case (310), a certain range of pressure can be applied even if a change in volume of the plurality of pouch-type cells (360) occurs inside the case (310) without external pressure. In addition, the secondary battery pack (300) reduces the area where pressure is generated by disposing the plurality of pouch-type cells (360) in the longitudinal direction of the case (310), and can withstand the internal pressure generated from the plurality of pouch-type cells (360) without deformation of the case (310).

[0046] Since the secondary battery pack (300) includes a spacer (350), it can maintain a constant pressure range even if the thickness of the pouch-type cell (360) changes within the cell without an external device, which is advantageous in terms of weight reduction as it does not require a separate external device.

[0047] Although not shown, a partition may be present between each of the plurality of pouch-type cells 360. For example, the partition may include the same material as the spacer 350, and may reduce in volume in response to a change in pressure occurring in each of the plurality of pouch-type cells 360. The partition may be disposed between all of the plurality of pouch-type cells 360, or may be disposed between only some of the pouch-type cells 360.

[0048] Below, examples and comparative examples applied to lithium-sulfur batteries are compared. The specifications of the examples and comparative examples are as shown in Table 1 below. Example 1 and Comparative Example 1 each used 20 pouch-type cells, and Comparative Example 2 used cylindrical cells.

[0049] Specifically, Example 1 used a nylon pouch (thickness 100 μm), a rubber foam spacer (weight 9.4 g), and a stainless steel case (thickness 0.2t, 100*600*400 mm), while Comparative Example 1 used a pouch containing an aluminum alloy thin film (thickness 150 μm, aluminum thickness 80 μm, polymer insulating layer and adhesive layer 70 μm).

[0050] [Experimental Example 1: Confirmation of energy density]

[0051] [Table 1]

[0052] It can be seen that the secondary battery pack according to the embodiment of the present disclosure has a higher cell energy density and a higher pack energy density than the secondary battery pack according to the comparative example. The secondary battery pack has a high pack energy density because it does not need to include a separate pad or pressure device. In addition, the design complexity of the secondary battery pack is reduced, and safety is improved by applying a metal case and a gas exhaust port.

[0053] The secondary battery pack according to Comparative Example 2 uses cylindrical cells, and therefore has the lowest energy density because a metal case is applied to the cylindrical cells.

[0054] [Experimental Example 2: Safety Comparison] A comparison of the safety of Example 1, Comparative Example 1 and Comparative Example 2 can be seen in Table 2 below.

[0055] [Table 2]

[0056] In Example 1, the change in cell volume can be controlled by the partition walls in the metal case and pack. In contrast, in Comparative Example 1, since there are no partition walls in the metal case and pack, it is difficult to control the change in cell volume.

[0057] [Experimental example 3: Comparison of life characteristics] The life characteristics of secondary battery packs including pouch-type cells with and without spacers were compared. Example 2 used a 2 mm thick rubber foam spacer, and Comparative Example 3 did not use a spacer. Example 2 and Comparative Example 3 were carried out using a 400 Wh / kg level lithium-sulfur battery pouch cell, and the remaining capacity was compared by running a charge and discharge cycle at 0.3 C discharge and 0.2 C charge. The comparison results are shown in Table 3 below.

[0058] [Table 3]

[0059] It was confirmed that as the number of cycles increased, the life characteristics (capacity retention rate) of Example 2 including the spacer was maintained at a high level.

[0060] [Experimental Example 4: Confirmation of improvement of tear defects] Cup molding was performed to a depth of 6 mm or more on the pouches of Example 1 and Comparative Example 1. As a result of molding, it was found that in the case of Example 1, which used nylon as in the present invention, a cup was formed without the pouch breaking (see FIG. 9). However, in the case of Comparative Example 1, which used an aluminum pouch, a problem occurred in which the pouch broke during cup molding (see FIG. 10).

[0061] Although the present disclosure has been described above using limited examples and drawings, the present disclosure is not limited thereto, and it goes without saying that various modifications and variations are possible within the technical spirit of the present disclosure and the scope of the claims set forth below, by a person having ordinary skill in the art to which the present disclosure pertains. [Explanation of symbols]

[0062] 100a, 100b: Pouch type cell 110: Pouch 120a, 120c: electrode tabs 120b: Electrode assembly 130a, 130c: electrode tabs 130b: Electrode assembly 140: Punch mold 150: Lower mold 115: Interior space 200, 300: Secondary battery pack 210, 310: Case 220, 320: Positive terminal 230, 330: Negative terminal 240, 340: Gas exhaust port 250, 350: Spacer 260, 360: Pouch type cell 215, 225: connecting member 315, 325: Connecting members

Claims

1. At least one pouch-type cell; and a case having an internal space for housing the pouch-type cell; Each of the at least one pouch-type cells includes an electrode assembly and a pouch film that houses the electrode assembly, The pouch film is made of only a polymer or only a polymer and an adhesive.

2. The secondary battery pack according to claim 1 , wherein the pouch film has a thickness of 20 μm or more and 200 μm or less.

3. The weight per area of ​​the pouch film is 20 g / m ２ 150g / m or more ２ 2. The secondary battery pack according to claim 1, wherein:

4. 2. The secondary battery pack according to claim 1, wherein the polymer includes at least one selected from the group consisting of nylon, polyethylene, polyamide, polyamide nylon, polypropylene, polyimide, polyvinyl chloride, polyethylene terephthalate, olefin resin, polystyrene, polycarbonate, and polyvinyl alcohol.

5. The pouch-type cell further includes a spacer disposed on a side of the pouch-type cell inside the case, 5. The secondary battery pack according to claim 1, wherein the spacer is made of a polymer, a metal, or an elastic material.

6. The secondary battery pack according to claim 5 , wherein the polymer includes rubber.

7. The secondary battery pack according to claim 5 , wherein the elastic body is a leaf spring.

8. A positive electrode terminal, a negative electrode terminal, and a gas exhaust port are arranged on the upper surface of the case, The secondary battery pack according to claim 1 , wherein the positive electrode terminal and the negative electrode terminal are electrically connected to the pouch-type cell, respectively.

9. A positive terminal is disposed on an upper surface of the case, and a negative terminal is disposed on a lower surface of the case; the positive electrode terminal and the negative electrode terminal are each electrically connected to the pouch-type cell; The secondary battery pack according to claim 1 , wherein a gas exhaust port is disposed on at least one of the upper surface and the lower surface of the case.

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