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EP-4224612-B1 - SECONDARY BATTERY

EP4224612B1EP 4224612 B1EP4224612 B1EP 4224612B1EP-4224612-B1

Inventors

  • LIM, Hun-Hee
  • KIM, SANG-HUN
  • KANG, Min-Hyeong
  • SONG, DAE-WOONG
  • YU, Hyung-Kyun
  • Hwang, Soo-Ji

Dates

Publication Date
20260506
Application Date
20220415

Claims (13)

  1. A pouch-type secondary battery (10), comprising: an electrode assembly (12); a case (13) for accommodating the electrode assembly (12); and a vent member (15), wherein the vent member (15) is configured to protrude to the outside of the case (13), and one end of the vent member (15) protruding to the outside of the case (13) is joined to an outer side (16) of the case (13), and characterized in that the case (13) includes an accommodation portion (13a) for accommodating the electrode assembly (12) and a sealing portion (13b) containing a sealant resin and formed to seal the electrode assembly (12), and one end of the vent member (15) protruding to the outside of the case (13) is joined to the outer side (16) of the case corresponding to a region inside the accommodation portion (13a) where the electrode assembly (12) is not located.
  2. The secondary battery (10) according to claim 1, wherein a part of the vent member (15) protruding to the outside of the case (13) is bent so that one end of the vent member (15) protruding to the outside of the case (13) is joined to the outer side (16) of the case (13).
  3. The secondary battery (10) according to claim 1, wherein the other end of the vent member (15) is located in the sealing portion (13b).
  4. The secondary battery (10) according to claim 3, wherein an electrode lead (11) is attached to the electrode assembly (12), and the other end of the vent member (15) is located in the sealing portion (13b) at a side where the electrode lead (11) is exposed to the outside.
  5. The secondary battery (10) according to claim 3, wherein an electrode lead (11) is attached to the electrode assembly (12), and the other end of the vent member (15) is located in the sealing portion (13b) at a corner where the electrode lead (11) is exposed to the outside.
  6. The secondary battery (10) according to claim 1, wherein the vent member (15) has a lower melting point than the sealant resin, the melting point being measured using a scanning calorimeter (DSC).
  7. The secondary battery (10) according to claim 1, wherein the vent member (15) has a maximum sealing strength of less than 6 kgf/15 mm at 100°C or above, the sealing strength being measured by conducting a tensile test at a speed of 5 mm/min, after cutting the case 13 corresponding to the part in which the vent member 15 is inserted into a width of 15 mm and a length of 5 cm and then gripping both ends thereof using a UTM jig in a state where both ends are spread to 180°.
  8. The secondary battery (10) according to claim 1, wherein the vent member (15) has an average sealing strength of less than 4.5 kgf/15 mm at 100°C or above the sealing strength being measured by conducting a tensile test at a speed of 5 mm/min, after cutting the case 13 corresponding to the part in which the vent member 15 is inserted into a width of 15 mm and a length of 5 cm and then gripping both ends thereof using a UTM jig in a state where both ends are spread to 180°.
  9. The secondary battery (10) according to claim 1, wherein the vent member (15) contains a linear low-density polyethylene having a comonomer with a carbon number of 6 or more.
  10. The secondary battery (10) according to claim 9, wherein the linear low-density polyethylene having a comonomer with a carbon number of 6 or more is polymerized in the presence of a metallocene catalyst.
  11. The secondary battery (10) according to claim 9, wherein in the linear low-density polyethylene having a comonomer with a carbon number of 6 or more, a content of the comonomer with a carbon number of 6 or more is 15 weight% or less, based on 100 weight% of the linear low-density polyethylene having a comonomer with a carbon number of 6 or more, the content of the comonomer is measured using an H-NMR.
  12. The secondary battery (10) according to claim 9, wherein the linear low-density polyethylene having a comonomer with a carbon number of 6 or more has a poly dispersity index (PDI) of 4 or less, the PDI is measured by gel permeation chromatography (GPC) under the following conditions: column: Tosoh, HLC-8321 GPC/HT; solvent: TCB (Trichlorobenzene) + 0.04% BHT (after drying with 0.1% CaCl 2 ); flow velocity: 1.0 ml/min; sample concentration: 1.5 mg/ml; dose: 300 µl; column temperature: 160°C; detector: RI detector; and standard: Polystyrene (calibrated with a third-order function).
  13. The secondary battery (10) according to claim 9, wherein the case (13) includes a sealing portion (13b) containing a sealant resin and formed to seal the electrode assembly (12), and a difference between a crystallization temperature of the sealant resin and a crystallization temperature of the linear low-density polyethylene having a comonomer with a carbon number of 6 or more is 10°C or less, the crystallization temperatures are measured using a differential scanning calorimeter (DSC).

Description

TECHNICAL FIELD The present application claims priority to Korean Patent Application No. 10-2021-0049364 filed on April 15, 2021. The present disclosure relates to a secondary battery, and more particularly, to a secondary battery having a vent member. BACKGROUND ART Secondary batteries are highly applicable to various products and exhibit superior electrical properties such as high energy density, etc. Secondary batteries are commonly used not only in portable devices but also in electric vehicles (EVs) or hybrid electric vehicles (HEVs) driven by electrical power sources. The secondary battery is drawing attention as a new energy source for enhancing environment friendliness and energy efficiency in that the use of fossil fuels can be reduced greatly and no byproduct is generated during energy consumption. Secondary batteries widely used at present include lithium ion batteries, lithium polymer batteries, nickel cadmium batteries, nickel hydrogen batteries, nickel zinc batteries and the like. The secondary battery generally has a structure in which an electrode assembly including at least one unit cell having a positive electrode/separator/negative electrode structure is accommodated in a case of a laminate sheet in which an outer layer, a metal barrier layer and a sealant layer are sequentially laminated, and a sealant resin of the sealant layer is fused to seal the electrode assembly is sealed. In the conventional secondary battery, the battery may ignite due to various causes such as a short circuit inside the secondary battery, overcharge or overdischarge, temperature control, or the like. At this time, thermal propagation where the temperature inside the secondary battery rises rapidly and simultaneously the heat is transferred to neighboring cells may be generated, which may further increase the fire. In order to minimize damage to the electrode caused by gas when thermal propagation occurs - i.e., when the internal temperature of the secondary battery rises, directional venting characteristic is required to discharge the gas in one direction. However, the conventional secondary battery has a problem in that it is difficult to induce gas discharge in a specific direction. Therefore, the present disclosure is directed to providing a secondary battery with improved safety by inducing gas discharge in a specific direction. US 2010/239895 A1 discloses a secondary battery including a one-way exhaust valve. KR 2015 0055775 A discloses a pouch-type battery cell. DISCLOSURE Technical Problem The present disclosure is directed to providing a secondary battery with improved safety by inducing gas discharge in a specific direction. Technical Solution In one aspect of the present disclosure, there are provided secondary batteries according to the following embodiments. The first embodiment provides a secondary battery as laid out in appended claim 1. In the second embodiment according to the first embodiment, a part of the vent member protruding to the outside of the case may be bent so that one end of the vent member protruding to the outside of the case is joined to the outer side of the case. In the third embodiment according to the first embodiment, the other end of the vent member may be located in the sealing portion. In the fourth embodiment according to the third embodiment, an electrode lead may be attached to the electrode assembly, and the other end of the vent member may be located in the sealing portion at a side where the electrode lead is exposed to the outside. In the fifth embodiment according to the third or fourth embodiment, an electrode lead may be attached to the electrode assembly, and the other end of the vent member may be located in the sealing portion at a corner where the electrode lead is exposed to the outside. In the sixth embodiment according to any one of the third to fifth embodiments, the vent member may have a lower melting point than the sealant resin. In the seventh embodiment according to any one of the first to sixth embodiments, the vent member may be vented at 100°C to 120°C. In the eighth embodiment according to the seventh embodiment, the vent member may be vented at a pressure of 1.5 atm or above. In the ninth embodiment according to any one of the first to eighth embodiments, the vent member may have a maximum sealing strength of less than 6 kgf/15 mm at 100°C or above. In the tenth embodiment according to any one of the first to ninth embodiments, the vent member may have an average sealing strength of less than 4.5 kgf/15 mm at 100°C or above. In the eleventh embodiment according to any one of the first to tenth embodiments, the vent member may have a maximum sealing strength of 6 kgf/15 mm or more at room temperature to 60°C. In the twelfth embodiment according to any one of the first to eleventh embodiments, the vent member may have an average sealing strength of 4.5 kgf/15 mm or more at room temperature to 60°C. In the thirteenth embodiment according to any one