Pouch-type battery

Abstract

One embodiment of the present disclosure is directed to providing a pouch-type battery having improved life performance, the pouch-type battery being a pouch-type battery in which an electrode assembly is housed and sealed in a pouch-shaped case, the pouch-shaped case including a housing portion that houses the electrode assembly including a positive electrode and a negative electrode, and a cover portion that covers the housing portion, the pouch-type battery includes a main chamber portion in which the electrode assembly is located, and a sealing portion that seals the accommodating portion and the lid portion, at least a part of the sealing portion including a gas storage portion and a separation portion that separates the gas storage portion and the main chamber portion.

Description

Technical Field

[0001] The present disclosure relates to a pouch-type battery. Background Art

[0002] In recent years, the demand for high-capacity and high-energy-density lithium-ion batteries has increased. As a result, the use of silicon-based negative electrode active materials as negative electrode active materials for lithium-ion secondary batteries has increased.

[0003] However, this silicon-based negative electrode active material has a serious volume expansion, resulting in a decrease in cycle performance. In addition, the pouch-type battery using a pouch-shaped battery shell cannot prevent the volume expansion caused by the increase in internal pressure, making the volume expansion of the silicon-based negative electrode active material more susceptible to external influences.

[0004] Therefore, when using a negative electrode containing a silicon-based negative electrode active material, when designing a pouch-type battery, the volume expansion of the battery caused by the volume expansion of the silicon-based negative electrode active material is taken into consideration. Compared with the case of using a graphite negative electrode active material, the swelling ratio of the bag-shaped shell is usually set larger, and the forming depth is designed during bag molding.

[0005] Therefore, the pouch-shaped shell surface of the pouch-type batteries initially shipped has wrinkles, and is therefore likely to be judged as defective during appearance inspection. In addition, due to the uneven battery surface as described above, measurement errors occur during battery production, thereby increasing the defect rate.

[0006] On the other hand, in order to reduce problems such as wrinkle formation and thickness error on the surface of the pouch-type battery as described above, if the molding depth is designed to be the same level as when using graphite negative electrode active material during bag molding, the increase in the volume of the electrode due to the volume expansion of the silicon-based negative electrode active material may generate high pressure inside the pouch-type battery, thereby causing problems such as insulation breakdown. Summary of the invention

[0007] 1. Technical issues to be resolved

[0008] According to one embodiment, it is intended to reduce the defective judgment rate during appearance inspection of pouch-type batteries, especially pouch-type batteries containing silicon-based negative electrode active materials, and prevent problems such as electrode insulation breakdown that may be caused by battery expansion during charging and discharging.

[0009] According to another embodiment, it is intended to improve the problems that may occur in batteries containing silicon-based negative active materials due to volume expansion, and further improve the problems caused by the error between the initial design value of the molding depth of the bag-shaped shell and the value caused by volume expansion during charging and discharging.

[0010] According to yet another embodiment, the life performance of a pouch-type battery, in particular a pouch-type battery including a silicon-based negative electrode active material, is improved.

[0011] (II) Technical solution

[0012] According to one embodiment of the present disclosure, there is provided a pouch-type battery, which is a pouch-type battery that accommodates and seals an electrode assembly in a pouch-shaped shell, the pouch-shaped shell comprising a accommodating portion and a cover portion, the accommodating portion accommodating an electrode assembly comprising a positive electrode and a negative electrode, the cover portion covering the accommodating portion, the pouch-type battery comprising a main chamber portion in which the electrode assembly is located and a sealing portion that seals the accommodating portion and the cover portion, at least a portion of the sealing portion comprising a gas storage portion and an isolation portion that isolates the gas storage portion from the main chamber portion.

[0013] The gas storage portion and the separator may form a sealing portion from which electrode tabs are led out on four sides.

[0014] The gas storage portion and the separator portion may form a sealed portion from which electrode tabs are not led out on four sides.

[0015] The gas storage portion and the partition portion may be formed at a sealed portion facing each other with the main chamber portion as a center.

[0016] The sealing strength of the partition portion may be weaker than the sealing strength of the sealing portion.

[0017] The sealing portion may be formed on three or four sides of the edge of the main chamber portion.

[0018] The gas contained in the gas storage unit may be CO 2 .

[0019] The negative electrode may include a silicon-based active material.

[0020] The pouch type battery may include an electrolyte, and the electrolyte may contain CO 2 .

[0021] In addition, the pouch type battery may further include an air chamber.

[0022] (III) Beneficial effects

[0023] According to one embodiment, in a pouch-type battery, especially a pouch-type battery containing a silicon-based negative electrode active material, the volume expansion of the additional electrode is not considered during the bag forming process, but the bag is formed according to the shape of the electrode assembly, thereby preventing the bag-shaped outer packaging material from forming wrinkles and thus preventing it from being judged as defective.

[0024] According to another embodiment, a margin space is ensured by the separator and the gas storage portion, so even if the volume of the electrode increases due to the volume expansion of the negative electrode active material during the charge and discharge process of the electrode, the pressure of the battery can be prevented from increasing, thereby preventing problems such as electrode insulation breakdown from occurring.

[0025] According to another embodiment, in a pouch-type battery, especially a pouch-type battery containing a silicon-based negative electrode active material, the sealing of the isolation portion is released due to the volume expansion of the silicon-based negative electrode active material, so that the gas stored in the gas storage portion can flow into the main chamber portion, inducing the formation of a stable SEI layer on the negative electrode, thereby improving the life performance of the pouch-type battery.

[0026] In addition, a margin space is ensured by the gas storage section, so that insulation breakdown caused by the pressure exerted on the electrode assembly or electrode due to the volume expansion of the silicon negative electrode material during the charging and discharging process of the battery can be eliminated through the margin space of the gas storage section, and the problem of mismatch with the initial design value during bag molding can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 FIG. 1 is an exploded perspective view schematically showing a general pouch-type battery, and is a diagram showing an example in which an electrode assembly is accommodated in a pouch.

[0028] Figures 2 to 4 This is an example of a pouch-type battery with electrode tabs extending in one direction. Figure 2 An example is shown in which a gas storage portion is formed on the surface opposite to the surface from which the electrode tab is drawn. Figure 3 An example is shown in which a gas storage portion is formed on the surface of the lead-out electrode tab. Figure 4 An example is shown in which a gas storage portion is formed on a surface from which an electrode tab is extracted and a surface opposite to the surface from which the electrode tab is extracted.

[0029] Figure 5 and Figure 6 It is another example of a pouch-type battery with electrode tabs extending in one direction. Figure 5 and Figure 6 Examples are shown in which the gas storage portion is formed on one or both of the two side surfaces of the surface from which the electrode tab is led out.

[0030] Figure 7 and Figure 8 This is an example of a pouch-type battery with electrode tabs extending in two directions. Figure 7 An example is shown in which gas storage portions are formed on both sides of the surface from which the electrode tabs are drawn. Figure 8 An example is shown in which the gas storage portions are formed on both side surfaces of the surface from which the electrode tab is led out. Best Mode for Carrying Out the Invention

[0031] One embodiment of the present disclosure is to solve the problem of bag molding design caused by volume expansion of the negative electrode active material during the charging and discharging process of the battery including a negative electrode, especially a negative electrode containing a negative electrode active material as a negative electrode material. Specifically, if the bag molding depth is designed without considering the volume expansion of the silicon-based negative electrode active material, problems such as electrode insulation breakdown due to volume expansion may occur.

[0032] On the other hand, if the molding depth of the bag is designed to be deeper to have a margin space in consideration of the volume expansion of the silicon-based negative electrode active material as described above, then due to such a margin space, there is a high possibility that defects may occur due to bag folding, etc. during the process of inserting the electrode assembly into the bag-shaped shell, storage or transportation, etc.

[0033] Therefore, in one embodiment, in order to solve the above problems, during the manufacturing process of the battery, the bag is appropriately formed according to the size of the electrode assembly to avoid the problem caused by the margin space, and considering the volume expansion of the pouch type battery during the charging and discharging process of the battery, the margin space is formed in the pouch type battery. In addition, the pouch type battery according to one embodiment can improve the life performance of the battery.

[0034] The present disclosure provides a pouch-type battery including a gas storage portion in a sealing portion of the pouch-type battery. Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0035] like Figure 1 As shown, in a pouch-type battery according to one embodiment, an electrode assembly 11 including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode is contained in a pouch-shaped shell 20, and is filled with an electrolyte and sealed, and the structure of the electrode assembly 11 is not particularly limited.

[0036] For example, the electrode assembly 11 may be a stacked electrode stack formed by alternately stacking the positive electrode and the negative electrode in a state where each separator sheet is inserted between the positive electrode and the negative electrode, or a stacked-folded electrode stack in which the positive electrode and the negative electrode are alternately stacked while a long rectangular separator is folded in a zigzag shape, or a wound electrode stack formed by winding a rectangular separator in one direction and alternately stacking the negative electrode and the positive electrode with the separator as the boundary, or a jelly roll electrode stack formed by winding the long rectangular positive electrode and the negative electrode together in one direction with the separator inserted between the positive electrode and the negative electrode. In addition, the electrode assembly 11 may be formed by combining two or more of the above-mentioned various forms of electrode assemblies 11.

[0037] The pouch-type battery 100 may be provided by sealing the pouch-shaped case 20 in a state where the electrode assembly 11 is inserted into the pouch-shaped case 20. Figure 1 As shown, the pouch-shaped shell 20 includes: a accommodating portion 21 having a main chamber portion 31 for accommodating an electrode assembly, the main chamber portion 31 being formed with a predetermined depth so as to accommodate the electrode assembly 11; and a cover portion 23 covering the accommodating portion 21. The pouch-type battery 100 is manufactured by accommodating the electrode assembly 11 in the main chamber portion 31 of the accommodating portion 21, and then folding the accommodating portion 21 and the cover portion 23, and then sealing the edges by heating and pressurizing them.

[0038] At this time, the electrode assembly 11 inserted into the bag-shaped shell 20 is electrically connected to the outside of the shell through the electrode tabs that are a collection of the positive electrode uncoated portion and the negative electrode uncoated portion. In the pouch-type battery 100, the accommodating space portion where the electrode assembly 11 is located is called the main chamber portion 31, and the portion sealed between the accommodating portion 21 and the cover portion 23 is called the sealing portion 33.

[0039] Although not shown in the drawings, the receiving portion 21 and the cover portion 23 may be each formed at a predetermined depth to have a main chamber portion 31 in order to receive the electrode assembly 11 .

[0040] Therefore, the pouch-type battery 100 provided in one embodiment is Figure 1 The conventional pouch-type battery 100 shown in FIG. 1 is the same as the hexahedral shape of each electrode stack having a rectangular plane shape. Hereinafter, for convenience, the surface with a longer length based on the electrode is referred to as the "long axis surface", the direction horizontal to the long axis surface is referred to as the "long axis direction", the surface with a shorter length is referred to as the "short axis surface", and the direction horizontal to the short axis surface is referred to as the "short axis direction". At this time, the following description is based on the case where the electrode tab is led out from the short axis surface, but it is not limited to this, and the electrode tab can also be led out from the long axis surface.

[0041] In the pouch type battery 100, the Figure 1 The pouch-type battery shown in the figure can form the sealing parts 33 on three sides, while when a pouch in which the receiving part 21 and the cover part 23 are separated is used, the sealing parts 33 can be formed on four sides.

[0042] In addition, in the pouch type battery 100, as Figure 1 and Figure 2 As shown, the electrode tabs 13 and 15 of two polarities can be led out from one side of the bag-shaped housing 20, such as the short axis side, along the long axis direction in the same direction, and as shown in FIG. Figure 7 As shown, the electrode tabs 13 and 15 of two polarities can be led out in two directions, for example, the long axis directions on both sides of the short axis surface are led out in opposite directions.

[0043] The pouch-type battery 100 according to one embodiment has a gas storage portion 35 in at least one of the sealing portions 33. The gas storage portion 35 is formed in a portion of the sealing portion 33, and a predetermined space is formed between the receiving portion 21 and the cover portion 23 of the pouch-shaped case 20, and gas is stored inside the space, for example, the gas may be CO2, and if CO2 is filled and stored, it may be called a CO2 storage.

[0044] The gas storage part 35 is isolated from the main chamber part 31 of the bag-shaped housing 20 that accommodates the electrode assembly 11. If it is not isolated from the main chamber part 31, in the past, when the bag is formed, the volume expansion of the pouch-shaped battery 100 is considered, and the shape is formed deeper than the shape of the electrode assembly 11, which is essentially the same as giving a margin space, and may cause surface defects such as bag folding that occurs when the bag is formed in the conventional way to consider the volume expansion.

[0045] As described above, in order to isolate the main chamber part 31 and the gas storage part 35, the isolation part 37 is included between the main chamber part 31 and the gas storage part 35. The isolation part 37 can be formed by heating and pressurizing the receiving part 21 and the cover part 23 of the bag to seal, which can be performed by the same method as the conventional method of sealing a bag.

[0046] During the charging and discharging process of the pouch-type battery, when the battery shrinks or expands, the pressure generated by the shrinkage or expansion is applied to the pouch-shaped shell 20, and the seal of the isolation portion 37 is released. At this time, the gas stored in the gas storage portion 35, for example, CO2, is supplied to the interior of the battery to induce the formation of a stable solid electrolyte interphase (SEI) on the surface of the negative electrode, thereby improving the battery life performance.

[0047] The sealing area of ​​the isolation part 37 to the gas storage part 35 is smaller than the sealing area of ​​the other sealing parts 33, so when the volume of the inside of the bag-shaped shell 20 expands, the pressure generated by the volume expansion inside the battery causes the seal of the isolation part 37 to be more easily released. In addition, the sealing strength of the isolation part 37 can be weaker than the sealing strength of the sealing part 33, so as to more reliably ensure that the seal of the isolation part 37 is released due to the volume expansion inside the bag-shaped shell 20.

[0048] The sealing strength of the isolation portion 37 can be set by factors such as the content of the silicon active material contained in the negative electrode mixture layer and the electrode density, but is not particularly limited. For example, when the sealing strength of the sealing portion 33 is 100%, the sealing strength of the isolation portion 37 can be more than 30%, for example, 30% to 70%, or 30% to 50%.

[0049] More specifically, in a conventional pouch type battery, the sealing portion 33 is designed and manufactured to have a pressure of about 3 to 5 kgf / cm 2 The sealing strength of the isolating portion 37 may vary depending on the sealing strength of the sealing portion 33, but may be 1 to 3.5 kgf / cm2 on the premise that the sealing strength is weaker than that of the sealing portion 33. 2 range.

[0050] When the sealing strength of the isolation portion 37 is less than 30% of the sealing strength of the sealing portion 33, the seal can be released simply by applying pressure to the gas storage portion 35 even when there is no pressure change inside the battery. This release of the seal can provide a residual space in the bag-like shell 20, resulting in wrinkles forming in the bag-like shell 20.

[0051] When designing a battery containing a silicon-based negative electrode material, various additives such as fluoroethylene carbonate (FEC) and vinylene carbonate (VC) are added to the electrolyte in order to improve the life performance of the battery, and when a negative electrode containing a silicon-based negative electrode active material is used, CO2 can form a stable SEI layer on the surface of the negative electrode, thereby improving the cycle performance of the battery. More specifically, CO2 helps to form a stable SEI layer on the surface of graphite particles contained as the negative electrode active material.

[0052] Therefore, CO2 is filled in the gas storage portion 35 separated from the main chamber portion 31, so that during the manufacturing process of the pouch-type battery 100, the pouch-shaped shell 20 can be formed according to the size of the electrode assembly 11, thereby eliminating surface defects caused by folding of the pouch-type battery, etc. When pressure is applied due to the volume expansion of the battery inside the pouch-shaped shell 20, the gas storage portion 35 can be provided as a surplus space, thereby eliminating the increase in pressure applied to the internal electrode due to the volume expansion, thereby preventing the problem of electrode insulation breakdown.

[0053] The gas storage section 35 can be formed in various forms and at various positions. For example, it can be formed in the sealing section 33 of the lead-out electrode ear or the sealing section 33 without the lead-out electrode ear, it can be formed in any sealing section 33 centered on the main chamber section 31, and it can be formed in the sealing sections 33 facing each other centered on the main chamber section 31, which will be described in more detail below with reference to the accompanying drawings.

[0054] like Figures 2 to 6 As shown, the pouch-type battery 100 according to one embodiment of the present disclosure may be a pouch-type battery 100 in which both the negative electrode tab 15 and the positive electrode tab 13 are drawn from one side of the pouch-type battery 100, that is, any short axis surface, such as Figure 7 and Figure 8 As shown, the pouch-type battery 100 may also have the negative electrode tab 15 and the positive electrode tab 13 led out from two side surfaces of the pouch-type battery 100 , that is, the short axis surfaces on both sides.

[0055] As an embodiment of a pouch-type battery 100 in which both the negative electrode tab 15 and the positive electrode tab 13 are led out from any short-axis surface, Figure 2 and Figure 3 As shown, the electrode tab can be led out from any short-axis surface, and the gas storage portion 35 and the isolation portion 37 can be formed in the sealing portion 33 of the short-axis surface opposite thereto, and the gas storage portion 35 and the isolation portion 37 can also be formed in the sealing portion 33 of the short-axis surface from which the electrode tab is led out. According to another embodiment, as Figure 4 As shown, the gas storage portion 35 and the isolation portion 37 may be formed on the sealing portion 33 on both sides of the short axis surface.

[0056] In addition, in another embodiment, the gas storage portion 35 and the accommodating portion 37 may be formed on the sealing portion 33 of the long axis surface, such as Figure 5 As shown, the sealing portion 33 can be formed on any long axis surface, or, as shown in Figure 6 As shown, sealing portions 33 may be formed on the long axis surfaces on both sides.

[0057] In addition, although not shown in the figures, the gas storage portion 35 and the isolation portion 37 can be formed together as sealing portions 33 on the major axis surface and the minor axis surface, can be formed as a sealing portion 33 on any one minor axis surface and one or more sealing portions 33 on the major axis surface, can be formed as a sealing portion 33 on any one major axis surface and one or more sealing portions 33 on the minor axis surfaces, or can be formed as sealing portions 33 on the minor axis surfaces on both sides and sealing portions 33 on the major axis surfaces on both sides.

[0058] Figure 7 1 is an embodiment of a pouch-type battery 100 in which the negative electrode tab 15 and the positive electrode tab 13 are respectively led out from the short axis surfaces on both sides. Figure 7 As shown, the gas storage portion 35 and the isolation portion 37 can be formed in the sealing portion 33 of the short axis surface. Specifically, the gas storage portion 35 and the isolation portion 37 can be formed in the sealing portion 33 of the short axis surface on both sides, or, although not shown in the figure, can be formed in the sealing portion 33 of any short axis surface.

[0059] As another example, Figure 8 FIG. 1 shows an embodiment of a pouch-type battery 100 in which the negative electrode tab 15 and the positive electrode tab 13 are respectively led out from the short axis surfaces on both sides. Figure 8As shown, the gas storage portion 35 and the isolation portion 37 can be formed in the sealing portion 33 of the long axis surface. Specifically, the gas storage portion 35 and the isolation portion 37 can be formed in the sealing portion 33 of the long axis surface on both sides, or, although not shown in the figure, can be formed in the sealing portion 33 of any long axis surface.

[0060] In addition, although not shown in the figures, the gas storage portion 35 and the isolation portion 37 can be formed together in a sealing portion 33 on the major axis surface and a sealing portion 33 on the minor axis surface, and can be formed in a sealing portion 33 on any minor axis surface and more than one sealing portion 33 on the major axis surface, can be formed in a sealing portion 33 on a major axis surface and more than one sealing portion 33 on minor axis surfaces, or can be formed in sealing portions 33 on minor axis surfaces on both sides and sealing portions 33 on major axis surfaces on both sides.

[0061] On the other hand, the thickness of the gas storage part may be about 5 to 10 mm, but is not limited thereto.

[0062] Although not shown in the drawings, the pouch-type battery 100 according to one embodiment of the present disclosure may include a gas chamber provided as a space for collecting a large amount of gas generated inside the pouch-type battery 100 during the formation of the pouch-type battery 100 .

[0063] The air chamber may be formed in a redundant bag outside the main chamber portion 31 and may include a gas exhaust flow channel through which the gas generated in the main chamber portion 31 may move to the main chamber portion 31 and the air chamber may be removed after the gas exhaust flow channel is closed by sealing after the activation is completed.

[0064] The gas chamber may be formed outside the sealing portion 33 where the gas storage portion 35 and the partition portion 37 are not formed, and may be formed outside the gas storage portion 35 and the partition portion 37 .

[0065] According to an embodiment of the above-mentioned pouch-type battery of the present disclosure, the volume expansion of the battery can be reduced, especially in the pouch-type battery containing silicon-based negative electrode active materials, the problem of poor appearance caused by the folding of the pouch can be reduced, and the problem of electrode insulation breakdown and error with the initial design value caused by the volume expansion of the silicon-based negative electrode active material during charging and discharging can be improved.

[0066] Description of reference numerals:

[0067] 100: Pouch cell

[0068] 11: Electrode assembly

[0069] 13: Positive electrode tab

[0070] 15: Negative electrode tab

[0071] 20: Bag-shaped shell

[0072] 21: Accommodation

[0073] 23: Cover

[0074] 31: Main room

[0075] 33: Sealing part

[0076] 35: Gas storage

[0077] 37: Isolation Department

Claims

1. A pouch-type battery, wherein an electrode assembly is contained in a pouch-shaped case and sealed, the pouch-shaped case comprising a containing portion and a cover portion, the containing portion containing the electrode assembly including a positive electrode and a negative electrode, the cover portion covering the containing portion, The pouch type battery includes a main chamber portion where the electrode assembly is located and a sealing portion that seals the receiving portion and the cover portion. At least a portion of the sealing portion includes a gas storage portion and a partition portion that separates the gas storage portion from the main chamber portion.

2. The pouch-type battery according to claim 1, wherein: The gas storage portion and the separator portion form a sealing portion from which electrode tabs are drawn out on four sides.

3. The pouch-type battery according to claim 1, wherein: The gas storage portion and the separator portion form a sealed portion from which electrode tabs are not led out on four sides.

4. The pouch-type battery according to claim 1, wherein: The gas storage portion and the partition portion are formed in a sealed portion facing each other with the main chamber portion as the center.

5. The pouch-type battery according to claim 1, wherein: The sealing strength of the partition portion is weaker than the sealing strength of the sealing portion.

6. The pouch-type battery according to claim 5, wherein: The sealing strength of the separator is 1 to 3.5 kgf / cm 2 .

7. The pouch-type battery according to claim 1, wherein: The sealing portion is formed on three or four sides of the edge of the main chamber portion.

8. The pouch-type battery according to claim 1, wherein: The gas contained in the gas storage section is CO 2 .

9. The pouch-type battery according to claim 1, wherein: The negative electrode includes a silicon-based active material.

10. The pouch-type battery according to claim 1, wherein: The pouch-type battery includes an electrolyte containing CO 2 . 11 . The pouch type battery according to any one of claims 1 to 10 , further comprising an air chamber.

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