Battery pack

Abstract

Battery pack, including: a pack housing with an interior in which a large number of battery modules or a large number of battery cells are directly installed without being modulated; and a venting element that is installed in the pack housing and configured to vent gas generated inside to the outside, wherein the ventilation element is configured such that a cross-sectional area of ​​an outlet side of the ventilation element, which is connected to an external space of the pack housing, is smaller than a cross-sectional area of ​​an inlet side of the ventilation element, which is connected to the internal space, characterized in that a cross-sectional area of ​​the outlet side is designed such that it is 0.2-0.8 times the cross-sectional area of ​​the inlet side.

Description

BACKGROUND1. AREA

[0001] Example embodiments of the present disclosure relate to a battery pack including a plurality of battery cells and a vent member for discharging gas generated in a pack casing. 2. DESCRIPTION OF THE STATE OF THE ART

[0002] Unlike a primary battery, a secondary battery can be charged and discharged, allowing it to be used in a variety of applications, including digital cameras, mobile phones, laptops, hybrid vehicles, and electric vehicles. Examples of secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-hydrogen batteries, and lithium secondary batteries.

[0003] Among these secondary batteries, many studies have been conducted on lithium secondary batteries with high energy density and discharge voltage. Recently, lithium secondary batteries have been manufactured and used in the form of flexible pouch-shaped battery cells or in the form of prismatic or cylindrical can-shaped battery cells with high rigidity.

[0004] In addition, a secondary battery is widely used in small devices such as portable electronic devices, as well as in medium- and large-sized devices such as vehicles and energy storage systems. When a secondary battery is used in such a medium- or large-sized device, a large number of secondary batteries can be electrically connected to increase the capacity and power of the entire battery. For this purpose, a large number of battery modules, in which a large number of battery cells are modularized, can be installed into a battery pack (or accumulator pack) in a medium- and large-sized device.

[0005] Such a battery pack may require various standards, and a representative standard may be safety. The safety of a battery pack in a vehicle can be particularly important, as the safety of the battery pack may be directly related to passenger safety.

[0006] One of the most important aspects of battery pack safety may be preventing ignition within the battery pack. Even if ignition or fire (flame) occurs, it may be necessary to sufficiently delay the spread of the flame generated within the battery pack. For example, if ignition occurs within the battery pack, it may be necessary to delay the spread of the flame outside the battery pack by allowing a certain amount of time (e.g., 5 minutes or more) to pass before the flame outside the battery pack is observed.

[0007] A battery pack may contain a plurality of battery cells, including a lithium secondary battery and the like. When various events occur, such as when the battery cell reaches the end of its service life, when the battery cell swells, when the battery cell is overcharged, when the battery cell is exposed to heat, when a sharp object such as a nail penetrates the battery cell casing, or when an external impact is applied to the battery cell, an electrolyte gas may leak from the battery cell. Particularly in the case of a large-capacity lithium secondary battery, when the above problems occur, a large amount of electrolyte gas may leak through a sealing portion of a bag (casing), which can be problematic.In order to discharge the electrolyte gas generated inside the battery pack from the battery pack, a vent (a vent element, a gas outlet port, a gas passage port) can be installed in the wall surface of a pack case.

[0008] The vent can also be used to vent the gas generated inside the battery to the outside, so that the vent can be used to delay the spread of flame.

[0009] Since the vent hole has an open structure, the gas in the pack case can be discharged through the vent hole, and the vent hole can also serve as a path through which air can flow from the outside of the pack case into the pack case.

[0010] Therefore, if a fire (flame) occurs inside the battery pack, the gas generated inside the battery pack can be discharged through the open vent. However, while the gas is being discharged, turbulent flow or vortex may occur, allowing air from outside the battery pack to flow into the interior of the battery pack through the vent. If outside air flows into the battery pack, an explosion may occur inside the battery pack due to the oxygen contained in the outside air.

[0011] To prevent the inflow of outside air, the size of the vent hole can be reduced. However, in this case, the air in the battery pack cannot be discharged smoothly to the outside, so the pressure inside the battery pack may increase, which may lead to deformation or damage to the battery pack. In this case, the flame inside the battery pack may directly penetrate the deformed or damaged part of the battery pack to the outside of the battery pack, which may cause a major fire outside the battery pack. SUMMARY

[0012] An exemplary embodiment of the present disclosure is to provide a battery pack that can sufficiently delay the spread of the flames to the outside even when a flame occurs inside the battery pack.

[0013] An exemplary embodiment of the present disclosure is to provide a battery pack that can prevent outside air from flowing into the battery pack through a vent member and can also reduce the pressure increase in the battery pack.

[0014] An exemplary embodiment of the present disclosure is to provide a battery pack that can reduce the possibility of ignition and flame by the discharged electrolyte gas even when a large amount of electrolyte gas in the battery pack is discharged to the outside.

[0015] According to an embodiment of the present disclosure, a battery pack includes a pack case having an interior space in which a plurality of battery modules are installed or a plurality of battery cells are directly installed without being modulated; and a vent member installed in the pack case and configured to discharge gas generated in the interior space to the outside, wherein the vent member is configured such that a cross-sectional area of ​​an outlet side of the vent member connected to an exterior space of the pack case is smaller than a cross-sectional area of ​​an inlet side of the vent member connected to the interior space.

[0016] The battery cell may comprise a bag-type secondary battery in which an electrode assembly and an electrolyte are housed in a bag-like casing, and at least a portion of the casing is sealed. The vent member may be configured to have a first region connected to the inlet side and a second region connected to the outlet side. The first region may have a constant cross-sectional area along its entire extent, and a cross-sectional area of ​​the second region may be reduced in a direction from the first region toward the outlet side.

[0017] The first region and the second region may have a circular cross-section. The first region may have a hollow cylindrical shape, and the second region may have a hollow frustoconical shape.

[0018] A length of the second region may be configured to be 0.2-0.8 times a distance from the inlet side to the outlet side, and a cross-sectional area of ​​the outlet side may be configured to be 0.2-0.8 times a cross-sectional area of ​​the inlet side, preferably 0.4-0.7 times a cross-sectional area of ​​the inlet side.

[0019] The first region may have a shape in which its cross-sectional area decreases with a first inclination angle in a direction from the inlet side to the outlet side, and the second region may have a shape in which its cross-sectional area decreases with a second inclination angle that is greater than the first inclination angle in the direction from the inlet side to the outlet side.

[0020] The inlet side of the venting element may be arranged on the same surface as an inner surface of an outer wall of the packing housing.

[0021] The venting element may be formed in the form of a hole in an outer wall of the pack housing. Alternatively, the venting element may have a shape in which at least a portion of the venting element protrudes from an outer side of an outer wall of the pack housing. At least a portion of the venting element may comprise a vent guide element attached to the outer wall of the pack housing.

[0022] At least one or more additional venting elements identical to the venting element may be provided, and wherein the plurality of venting elements are spaced apart from one another on an outer wall on one side of the pack housing. The plurality of venting elements may be arranged on the outer wall on one side of the pack housing and on another outer wall that is different from the outer wall on one side of the pack housing.

[0023] The vent element can maintain an open state without being closed, so that air flows through the vent element.

[0024] According to one embodiment of the present disclosure, a battery case includes a pack housing having a partition member that creates a plurality of interior spaces configured to accommodate at least one battery module; and at least one vent member for discharging gas generated in the interior space outside the pack housing, wherein the vent member has an inlet opening with a first cross-sectional area and an outlet opening with a second cross-sectional area smaller than the first cross-sectional area. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and other aspects, features and advantages of the present disclosure can be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings: Fig. 1A and Fig. 1B are perspective views of a battery pack according to an embodiment of the present disclosure; Fig. 1C is a perspective view of a battery cell according to one embodiment; Fig. 2A to 2D are diagrams illustrating examples of a vent member in a battery pack according to an embodiment of the present disclosure, wherein Fig. 2A is a cross-sectional diagram illustrating a vent element in a longitudinal direction, Fig. 2B is a diagram showing the venting element in Fig. 2A, seen from “A”, and Fig. 2C and Fig. 2D each represent a diagram showing a modified example of the venting element in Fig. 2A illustrates; Fig. 3A and Fig. 3B are cross-sectional diagrams showing a modified example of a vent member provided in a battery pack according to an embodiment of the present disclosure; Fig. 4 is a cross-sectional diagram showing another modified example of a vent member provided in a battery pack according to an embodiment of the present disclosure; Fig. 5 is a perspective view of a prior art battery pack; Fig. 6A and Fig. 6B are analysis diagrams illustrating a flow velocity of a fluid when ignition occurs in the Fig. 5 shown battery pack of the prior art, where Fig. 6A illustrates a fluid velocity when a diameter of the vent element is 50 mm, and Fig. 6B illustrates a fluid velocity when a diameter of the vent element is 40 mm; Fig. 7A and Fig. 7B are analysis diagrams showing a fluid velocity in a vent element with respect to the Fig. 6A illustrate the prior art battery pack, wherein Fig. 7A a fluid velocity with respect to the section V1 in Fig. 6A and Fig. 7B a fluid velocity with respect to the section V2 in Fig. 6A illustrates; Fig. 8A is an analysis diagram showing a speed and a direction of the Fig. 7A, and Fig. 8B is an analysis diagram showing a speed and a direction of the Fig. 7B; Fig. 9A to 9C are analysis diagrams illustrating the comparison of a fluid velocity in a venting element between a battery pack of an exemplary embodiment and a battery pack according to the prior art, wherein Fig. 9A illustrates a fluid velocity in a venting element according to an exemplary embodiment of the present disclosure, Fig. 9B refers to the Fig. 6A is a prior art battery pack showing a speed (the same as in Fig. 7B) of the fluid in a venting element with a diameter of 50 mm and a length of 48 mm, and Fig. 9C refers to the Fig. 6B shows a prior art battery pack showing a fluid velocity in a vent element having a diameter of 40 mm and a length of 48 mm; Fig. 10A to 10C are analysis diagrams showing the comparison of a velocity and a direction of a fluid between a battery pack of an embodiment and a battery pack according to the prior art shown in Fig. 9A to 9C, wherein Fig. 10A, Fig. 10B (as in Fig. 8B) and Fig. 10C the velocities and directions of the fluid with respect to Fig. 9A, Fig. 9B and 9C respectively; Fig. 11A to 11C are analysis diagrams showing the distribution of the internal pressure of the battery pack of one embodiment and that in Fig. 9A to 9C illustrate the prior art battery pack, wherein Fig. 11A, Fig. 11B and Fig. 11C the internal pressure of the battery pack in relation to Fig. 9A, Fig. 9B and 9C respectively; Fig. 12 is a diagram illustrating an overall structure used in analyzing the state in which electrolyte gas is discharged from the battery pack, with respect to an embodiment and the prior art; Fig. 13 is an analysis diagram showing the distribution of the velocity of the electrolyte gas and the distribution of the mixing variance of the electrolyte gas discharged from a vent member with respect to an embodiment and the prior art; Fig. 14 is an analysis diagram showing the distribution of the H2O mass fraction and the temperature distribution of the electrolyte gas escaping from a vent element with respect to an embodiment and the prior art; and Fig. 15A to 15C are diagrams showing a comparison between a battery pack of an exemplary embodiment and the prior art with respect to the analysis structure in Fig. 12 illustrate, where Fig. 15A illustrates a flame length of the electrolyte gas released from a vent element and an average pressure in the battery packs, Fig. Figure 15B is a graph illustrating a comparison of an average pressure in the battery packs, and Fig. Figure 15C is a graph illustrating a comparison of average pressure in the battery packs. DETAILED DESCRIPTION

[0026] The terms or words used in this specification and the following claims should not be interpreted to have generic or dictionary meanings. Considering that an inventor can best define the concepts of the terms or words to explain his invention, the terms or words must be understood to have meanings or concepts consistent with the technical spirit of the present disclosure. Since the embodiments set forth herein and the configurations illustrated in the drawings are merely exemplary and not representative of all the technical spirits of the present disclosure, the embodiments and configurations may be replaced with various equivalents and changes at the time of the present application.

[0027] In the drawings, like elements are designated by like reference numerals. Redundant descriptions and detailed descriptions of well-known functions and elements that may unnecessarily obscure the essence of the present disclosure are also omitted. In the accompanying drawings, some elements may be exaggerated, omitted, or briefly depicted, and the sizes of the elements do not necessarily reflect the actual sizes of these elements.

[0028] With reference to the Fig. 1A to 4, a battery pack 100 according to an embodiment is described.

[0029] Fig. 1A and Fig. 1B are perspective views of a battery pack 100 according to one embodiment. Fig. 1C is a perspective view of a battery cell according to one embodiment. Fig. 2A to 2D are diagrams illustrating examples of a venting member 130 provided in a battery pack 100 according to an embodiment of the present disclosure, wherein Fig. 2A is a cross-sectional diagram illustrating a vent element 130 in a longitudinal direction, Fig. 2B is a diagram illustrating the venting element in Fig. 2A, seen from “A”, is and Fig. 2C and Fig. 2d is a diagram illustrating a modified example of the venting element in Fig. 2A are. Fig. 3A and Fig. 3B are cross-sectional diagrams showing a modified example of a vent member 130 provided in a battery pack 100 according to an embodiment. Fig. 4 is a cross-sectional diagram showing another modified example of a vent member 130 provided in a battery pack 100 according to an embodiment.

[0030] As in Fig. 1A, the battery pack 100 according to one embodiment may include a pack housing 110 having an interior space 115 and a venting element 130.

[0031] An interior space 115 of a predetermined size may be formed in the pack housing 110, in which a plurality of battery modules 120 can be installed. Each battery module 120 may have a modular structure in which a plurality of battery cells 121 are electrically connected to one another, and the pack housing 110 may have a structure in which the plurality of battery modules 120 are electrically connected to one another. Furthermore, a separator 113 may be incorporated into the pack housing 110 to support the battery module 120.

[0032] Fig. 1A shows the example in which the plurality of battery cells 121 are modularized by the battery module 120 and installed in the interior space 115 of the pack case 110. As in Fig. 1B, however, the majority of battery cells 121 may have a cell-to-pack (CTP) structure in which the majority of battery cells 121 may be directly installed without using the battery module (ie, without being modulated).

[0033] As in Fig. 1C, the battery cell 121 provided in the battery pack 100 may be configured as a bag-type secondary battery. The bag-type secondary battery cell 121 may be formed by a bag-type casing 122. The bag-type casing 122 may be divided into an accommodating portion 123 and a sealing portion 124. The accommodating portion 123 may accommodate an electrode assembly 127 and an electrolyte (not shown). The sealing portion 124 may be divided into a first sealing portion 124a in which an electrode lead 125 and an insulating film 126 are disposed, and a second sealing portion 124b in which the electrode lead 125 is not disposed. In one embodiment, the bag-type battery cell 121 may include a lithium-ion (Li-ion) battery or a nickel-metal hydride (Ni-MH) battery that can be charged and discharged.However, in the embodiment, the battery cell provided in the battery pack 100 is not limited to a bag-type secondary battery.

[0034] A battery management system (BMS) (not shown) for controlling the battery cells or the battery module 120 may also be provided in the pack housing 110.

[0035] The vent member 130 may be installed in the packaging case 110 and may have an open shape for discharging gas generated in the internal space 115 to the outside. In other words, the vent member 130 may be installed in a through-structure on an outer wall portion 111 of the packaging case 110 and allows air to flow into and out of the packaging case 110. However, in the embodiment, the vent member 130 is not limited to a completely open structure, and a filter device such as a filter membrane may be installed in the opening portion forming the vent member 130 and may have a cover (a membrane or a flap).

[0036] The battery cell may have a structure in which an electrode assembly (not shown) formed by stacking a positive electrode plate, a negative electrode plate, and a separator can be housed within the case, and an electrolyte solution can be accommodated. In other words, the battery cell can be configured as a secondary battery that can be charged and discharged. The electrolyte contained in the case may become gaseous due to external influences, internal defects, or the like, and the gaseous electrolyte may be discharged outside the battery cell.

[0037] The vent element 130 can discharge the electrolyte gas to the outside when the electrolyte gas is generated in the interior space 115 of the pack case 110. In this case, the vent element 130 can maintain an open state without being closed to facilitate airflow through the vent element 130.

[0038] In addition, a plurality of venting elements 130 may be arranged on the outer wall 111 on one side of the pack case 110 and spaced apart from each other so that the gas generated in the interior space 115 of the battery pack 100 can be smoothly discharged to the outside. As shown in Fig. 1A and Fig. 1B, the venting element 130 may, for example, be provided on both sides of the outer wall 111 on one side relative to a center. Alternatively, at least one venting element 130 may be attached to the outer wall 111 on one side of the pack housing 110, and at least one venting element 130 may be attached to an outer wall that is different from the outer wall on one side. For example, at least one venting element 130 may be attached to the outer wall 111 shown in the Fig. 1A and Fig. 1B, at least one venting element 130 may also be mounted on the opposite outer wall opposite the outer wall on one side and / or on the other outer wall connected to the outer wall on one side. However, the arrangement position and the number of venting elements 130 are not limited thereto and can be varied.

[0039] With reference to the Fig. 2A to 4, in the venting element 130, a cross-sectional area A2 of an outlet side 132 of the venting element 130, which is connected to an exterior of the packing housing 110, can be configured to be smaller than a cross-sectional area A1 of an inlet side 131 of the venting element 130, which is connected to the interior space 115. Furthermore, the venting element 130 can have an inlet opening with a first cross-sectional area A1 and an outlet opening with a second cross-sectional area A2 that is smaller than the first cross-sectional area A1.

[0040] In other words, when the cross-sectional area A1 of the inlet side 131 is larger than the cross-sectional area A2 of the outlet side 132, the electrolyte gas generated in the internal space 115 can be easily discharged to the outside through the vent member 130, unlike the example where the cross-sectional areas of the inlet side 131 and the outlet side 132 remain the same. Accordingly, a pressure increase in the battery 100 when a flame is generated in the battery 100 and the gas is discharged can be limited. Since the cross-sectional area A2 of the outlet side 132 is smaller than the cross-sectional area A1 of the inlet side 131, the air outside the battery case 110 cannot easily flow into the internal space 115 through the vent member 130. Accordingly, the pressure in the battery pack 100 cannot increase excessively, and the inflow of outside air (oxygen) can be effectively blocked.

[0041] Referring to the Fig. 2A to 4, the venting element 130 may include a first region 133 connected to the inlet side 131 and having a relatively large cross-sectional shape, and a second region 134 connected to the outlet side 132 and having a relatively small cross-sectional shape. When calculating an average cross-sectional area for a predetermined length of the venting element 130 based on a cut-out surface according to the longitudinal direction of the venting element 130, the average cross-sectional area of ​​the second region 134 may have a lower value than the average cross-sectional area of ​​the first region 133.

[0042] For example, in the Fig. 2A, 2C to 3B, the first region 133 may extend from the inlet side 131 to the outlet side 132 in the same cross-sectional shape, and the second region 134 may extend toward the outlet side 132 in a shape in which its cross-sectional area may further decrease than that of the first region 133. That is, the first region 133 has a constant cross-sectional area along its entire extension, and a cross-sectional area of ​​the second region 134 is decreased in a direction from the first region 133 to the outlet side 132.

[0043] In addition, the first region 133 and the second region 134 may each have a circular cross-sectional shape, as shown in Fig. 2B. In this case, a diameter D1 of the inlet side 131 may have a larger shape than a diameter D2 of the outlet side 132.

[0044] Even if both the first region 133 and the second region 134 have a circular cross-sectional shape, the first region 133 of the venting element 130 may have a hollow cylindrical shape with a constant diameter D1, and the second region 134 may have the shape of a truncated hollow cone whose diameter decreases towards the outlet side 132.

[0045] Between the first region 133 and the second region 134, a boundary region BA can be formed in which a cross-sectional structure can change. In this case, the boundary region BA between the first region 133 and the second region 134 can have a structure in which linear lines can meet on the cross-sectional surface, so that an inclination can be formed, as shown in the Fig. 2A and Fig. 3B. Alternatively, the boundary region BA between the first region 133 and the second region 134 may have a structure in which the first region 133 and the second region 134 may be connected to each other in a smooth, curved surface (the curved portion is shown as a region between two vertical lines in the Fig. 2C and Fig. 3A).

[0046] In addition, the second region 134 may be inclined at a single inclination angle θ, as shown in the Fig. 2A, Fig. 2C, Fig. 3A and Fig. 3B, but as shown in Fig. 2D, the second region 134 may have a structure in which the second region 134 may be divided into two or more regions 134a and 134b, and the inclination angles θa and θb in the regions may vary. In this case, the inclination angle θb in the region 134b adjacent to the outlet side 132 may be configured to be larger than the inclination angle θa in the region 134a spaced from the outlet side 132, so that the diameter D2 of the outlet side 132 may be smaller than the diameter D2a of the portion located in the central portion of the second region 134.

[0047] As described above, when the vent element 130 has a circular cross-sectional area, the possibility of eddies or turbulence occurring in the air flowing in the vent element 130 can be reduced compared to a rectangular cross-sectional area, so that a smooth flow can be formed from the inlet side 131 to the outlet side 132. However, in the exemplary embodiment, the cross-sectional shape of the vent element 130 can be varied, such as an elliptical cross-section, and a prismatic cross-sectional structure cannot be ruled out.

[0048] In addition, the venting element 130 may have a structure in which an inclination angle is formed in both the first region 133 and the second region 134. For example, as shown in Fig. 4, the first region 133 may have a shape in which its cross-sectional area decreases by a first inclination angle θ1 in a longitudinal direction from the inlet side 133 to the outlet side 134, and the second region 134 may have a shape in which its cross-sectional area decreases by a second inclination angle θ2 that is greater than the first inclination angle θ1 in the direction from the inlet side 133 to the outlet side 134.

[0049] The length L2 of the second region 134 may be 0.2-0.8 times the distance between the inlet side 131 and the outlet side 132, that is, 0.2-0.8 times the total length L of the ventilation element 130. If the length L2 of the second region 134 is less than 0.2 times the total length L, the length of the second region 134 may be excessively shortened. Since outside air is likely to flow through the shortened second region 134, the installation effect of the second region 134 may be correspondingly reduced. If the length L2 of the second region 134 exceeds 0.8 times the total length L, the length L1 of the first region 133 may be excessively shortened. In this case, the second region 134, which has a small cross-sectional area, may be elongated, so that the gas in the interior space 115 cannot be discharged evenly through the second region 134, and accordingly, the pressure in the interior space 115 of the battery pack 100 may increase.

[0050] The cross-sectional area A2 of the outlet side 132 can be designed to be 0.2-0.8 times the cross-sectional area A1 of the inlet side 131. If the cross-sectional area A2 of the outlet side 132 is less than 0.2 times the cross-sectional area A1 of the inlet side 131, the cross-sectional area A2 of the outlet side 132 may be excessively reduced, so that the gas in the interior 115 of the battery pack 100 cannot be smoothly discharged to the outside, and the pressure in the battery pack 100 may increase. If the cross-sectional area A2 of the outlet side 132 exceeds 0.8 times the cross-sectional area A1 of the inlet side 131, the difference in diameter (cross-sectional area) between the two sides may significantly decrease, so that the effect of smoothly discharging the inside air and reducing the inflow of outside air due to the difference in cross-sectional areas may decrease.

[0051] The cross-sectional area A2 of the outlet side 132 may be designed to be 0.4-0.7 times the cross-sectional area A1 of the inlet side 131. In this case, by securing the cross-sectional area A2 of the outlet side 132, the effect of uniformly discharging the gas in the interior space 115 of the battery pack 100 to the outside and the effect of reducing the inflow of outside air can be achieved by utilizing the difference between the cross-sectional areas of the inlet side 131 and the outlet side.

[0052] Specific values ​​of the cross-sectional area A1 of the inlet side 131 of the vent element 130, the cross-sectional area A2 of the outlet side 132, the length L1 of the first region 133, the length L2 of the second region 134 can be determined depending on the volume of the interior space 115 of the battery pack 100 and the position and shape of the vent hole.

[0053] In the Fig. 1 to 4, only the example in which the venting member 130 has the first region 133 and the second region 134 is shown, but a third region whose cross-sectional shape in the longitudinal direction of the venting member 130 differs from that of the first region 133 and the second region 134 may be provided between the first region 133 and the second region 134. In other words, a third region having a value between the average cross-sectional area of ​​the first region 133 and the average cross-sectional area of ​​the second region 134 may be provided between the first region 133 and the second region 134.

[0054] The venting element 130 may be formed in the form of a hole in the outer wall 111 of the packaging housing 110 if the outer wall of the packaging housing 110 has a sufficient thickness. In other words, as in Fig. 2, the venting element 130 can be formed by incorporating a hole whose diameter D1 on the inlet side 131 is larger than the diameter D2 on the outlet side 132 in the outer wall portion 111 of the packaging housing 110.

[0055] If the thickness of the outer wall 111 of the packing housing 110 is not sufficient, as described in the Fig. 3A and Fig. 3B, the vent member 130 may have a shape in which at least a portion of the vent member 130 protrudes toward an outer side of the outer wall 111 of the pack case 110. For example, if the length of the vent member 130 is 48 mm and the thickness of the outer wall 111 is 20 mm, the vent member 130 may have a structure that protrudes 28 mm from the pack case 110.

[0056] The venting element 130 may also consist of a venting guide element 136 that is attached to the outer wall 111 of the packing housing 110. The venting guide element 136 may have a shape in which a first region 133 and a second region 134 are formed, as shown in Fig. 3A. In this case, the vent guide member 136 may be attached to an inner surface of the hole formed in the pack case 110 while being aligned with the inner side surface of the outer wall 111. Alternatively, the vent guide member 136 may have a shape in which only a portion of the vent member 130 is formed, as shown in Fig. 3B. In this case, the vent guide member 136 may have a shape in which the vent guide member 136 is fixed to the outer side surface of the outer wall 111.

[0057] With reference to the Fig. 2A to 4, the inlet side 131 of the venting element 130 can be arranged on the same surface as the inner surface of the outer wall 111 of the packing housing 110. If the inlet side 131 of the venting element 130 has the shape of a tube that projects inward toward the inner surface of the outer wall of the packing housing 110, vortices or turbulence can occur at the periphery of the inlet side 131, which projects in the shape of a tube into the interior space 115. For example, if it is assumed that the venting guide element 136 is in Fig. 3A extends to the left, the phenomenon (e.g., swirl) may occur in which the air flowing along the inner surface of the outer wall of the pack case 110 does not directly flow into the inlet of the vent guide member and does not flow smoothly. However, as in one embodiment, if the inlet side 131 of the vent member 130 is arranged on the same surface as the inner surface of the outer wall of the pack case 110, the gas in the internal space 115 can flow along the inner surface of the outer wall 115 and easily flow to the inlet side 131 of the vent member 130 and be discharged to the outside, so that the flow of the gas discharged from the pack case 110 can be improved.

[0058] The effect of the battery pack 100 according to an embodiment will be described with reference to the Fig. 1, 2A and 5 to 11C.

[0059] Fig. Figure 5 is a perspective view of a battery pack 10 according to the prior art. Fig. The prior art battery pack 10 shown in Figure 5 may include a pack case 11 and a vent member 30, and a partition wall 13 and a plurality of battery modules 20 may be arranged in the interior space 15 of the pack case 11. Furthermore, the vent member 30 may be configured to have a shape in which a space having a predetermined diameter D' extends by a predetermined length L'.

[0060] The flow analysis was carried out under the assumption that a flame at the ignition point IP of the central part of the pack housing 11 with respect to the battery pack 10 in the Fig. 5. In this case, only the flow patterns in the interior space 15 and the vent element 30 were analyzed, without taking into account the heat transfer in the pack housing 10.

[0061] The analysis was performed using a compression fluid model with a Mach number of about 0.4, and it was assumed that the fluid was generated at a constant flow velocity (21 m / s or less) in an upward direction from the ignition point IP (see Fig. The turbulence model was analyzed using Spalart-Allmaras.

[0062] Fig. Figure 6 is an analysis diagram illustrating the flow velocity of a fluid when ignition occurs in the Fig. 5 shown battery pack 10 of the prior art. Fig. Figure 6A illustrates the flow velocity when the diameter D' of the vent element is 50 mm and the length L' is 48 mm, and Fig. Figure 6B illustrates the flow velocity when the diameter of the vent element is 40 mm and the length L' is 48 mm.

[0063] Referring to Fig. 6A and Fig. 6B, most of the liquid generated at the ignition point IP had a flow pattern in which the liquid flowed along the upper space of the pack case 11, which has a relatively large space, and flowed toward the front end (-x direction) and the rear end (+x direction) of the pack case 11. Furthermore, most of the liquid flowing sideways (±y direction) at the ignition point IP had a tendency to spread into the central passage. The liquid flowing toward the rear end (+x direction) of the pack case 11 also had a flow pattern in which the liquid flowed along the inner wall surface of the outer wall and was discharged at high speed through the vent member 30.

[0064] With reference to the Fig. A flow pattern in the venting element 30 of the prior art is described.

[0065] Fig. Figure 7A shows the velocity of the fluid with respect to the section V1 in Fig. 6A. Fig. Figure 7B shows the velocity of the fluid with respect to the section V2 in Fig. 6A. Fig. 8A is an analysis diagram showing the Fig. 7A shows the velocity and direction of the fluid. Fig. 8B is an analysis diagram showing the Fig. 7B illustrates the velocity and direction of the fluid.

[0066] With reference to the Fig. 7A and Fig. 8A, in the first ventilation element V1, the area (the dark black section in Fig. 7A and the section in Fig. 8A, in which the arrow is directed in the -x direction), in which the speed has been reduced, is formed in the lower side portion of the ventilation element 30 in the drawing, and as in the enlarged section in Fig. 8A, the speed range toward the interior space 15 was formed sequentially from the outer side area of ​​the ventilation member 30 to the interior space 15 in the lower side portion of the ventilation member 30 in the drawing.

[0067] With reference to the Fig. 7B and Fig. 8B, in the second venting element V2, the area (the dark black section in Fig. 7B and the section in Fig. 8A, in which the arrow is directed in the -x direction), in which the speed has been reduced, is formed in the upper side portion of the venting element 30 in the drawing, and as in the enlarged section in Fig. 8B, the velocity region toward the interior space 15 was formed sequentially from the outer side region of the ventilation member 30 to the interior space 15 in the upper side portion of the ventilation member 30 in the drawing.

[0068] As described above, the expansion of the velocity range from the outer region of the venting element 30 into the interior space 15 may indicate that the outside air flows through a portion of the venting element 30 (the inner wall surface of the venting element 130) into the interior space 15 when the gas generated at the ignition point IP is discharged to the outside through the venting element 30. In other words, the Fig. The prior art vent member 30 shown in FIGS. 6A and 7A to 8B had a shape in which the diameter was maintained at 50 mm, and in this case, it was confirmed that the outside air and the oxygen contained therein flowed into the interior space 15 of the pack case 11. The oxygen flowing therein may be transferred to the flame and cause an explosion of the battery pack 10 or rapid spread of the flame within the battery pack 10. Accordingly, the flame within the battery pack 10 may easily spread outside the battery pack 10, which may be problematic.

[0069] If the diameter of the vent element 30 has been reduced from 50 mm to 40 mm, as in Fig. 6B, since the cross-sectional area of ​​the venting element 30 is increased by 36% compared to Fig. 6A was reduced, as in Fig. 9C and Fig. As shown in Figure 10C, the flow of gas generated at the ignition point IP and discharged to the outside through the vent member 30 was strong, so that the gas discharge rate increased rapidly. Accordingly, it was confirmed that the velocity range toward the interior 15 of the pack case 11 in the vent member 30 was extremely low, and the outside air did not flow into the interior 15. However, when the diameter was reduced, the gas generated at the ignition point IP was not sufficiently discharged through the vent member 30, so that the average pressure in the battery pack 10 quickly dropped to 2.9 × 10 4 Pa fell off, as it is in Fig. 11C. If the pressure in the battery pack 10 increases while a fire (flame) occurs in the battery pack 10, the battery pack 10 may be deformed or damaged, and the flame in the battery pack 10 may be directly exposed outside the battery pack 10, which may result in a large fire outside the battery pack 100.

[0070] In the following description, the possibility of preventing an explosion (flame explosion) or preventing the flame from spreading to the outside in the event of a fire (flame) in the battery pack 100 is described with reference to an embodiment and the prior art with reference to Fig. described.

[0071] Fig. 9A to 9C are analysis charts showing a comparison of the fluid velocity in the vent elements 30 and 130 between a battery pack of an exemplary embodiment and the prior art. Fig. 9A illustrates the flow velocity in a vent element 130 according to an embodiment, Fig. 9B refers to the Fig. 6A and illustrates the flow velocity (the same as in Fig. 7B) of the fluid in a venting element 30 with a diameter D' of 50 mm and a length L' of 48 mm, and Fig. 9C refers to the state of the art described in Fig. 6B and illustrates a velocity of the fluid in a venting element 30 having a diameter D' of 40 mm and a length L' of 48 mm.

[0072] What the venting element 130 in Fig. 9A, the diameter D1 of the inlet side 131 was 66 mm, the diameter D2 of the outlet side 132 was 50 mm, the total length L of the venting element 130 was 48 mm, the length L1 of the first region 133 was 24 mm, and the length L2 of the second region 134 was 24 mm, and to be compared with the prior art, the packing case 110 had the same structure and the same shape as those of the packing case 11 of the prior art shown in Fig. 5, Fig. 6A and Fig. 6B is shown.

[0073] Fig. 10A to 10C are analysis diagrams showing a velocity and a direction of the fluid with respect to an embodiment and the Fig. 9A to 9C show the state of the art.

[0074] Fig. 11A to 11C are analysis diagrams showing the distribution of the internal pressure of the battery packs 10 and 100 in comparison with an embodiment and the Fig. 9A to 9C show the prior art. The average internal pressure of battery packs 10 and 100 was 6.6×10 3 Pa in Fig. 11A, Fig. 1.0×10 4 Pa in Fig. 11B and Fig. 2.9×10 4 Pa in Fig. 11C.

[0075] Referring to the Fig. 9B and Fig. 10B was, as in the prior art, in which the diameter of the venting element was 30 50 mm, as described with reference to the Fig. 7B and Fig. 8B, the velocity range toward the internal space 15 is formed sequentially from the outer side portion of the vent member 30 to the internal space 15. Accordingly, in the prior art in which the diameter of the vent member 30 was 50 mm, when the gas generated at the ignition point IP was discharged to the outside through the vent member 30, the outside air flowed into the internal space 15 through a partial portion (inner wall surface) of the vent member 30. Therefore, the oxygen in the outside air flowed into the internal space 15 of the pack case 11 and was transferred to the flame, so that an explosion of the battery pack 10 may occur or an enlargement of the flame may occur, and accordingly, the fire may easily spread outside the battery pack 10.

[0076] Even in the prior art, where the diameter of the venting element 30 was reduced from 50 mm to 40 mm, as in the Fig. 9C and Fig. 10C, it was confirmed that the flow of gas generated at the ignition point IP and discharged through the venting element 30 was strong, so that the outside air rarely flowed into the interior space 15. However, it was confirmed that the gas generated at the ignition point IP was not sufficiently discharged through the venting element 30, so that the average pressure in the battery pack 10 quickly fell to 2.9×10 4 Pa increased, as in Fig. 11C. In other words, the state of the art in Fig. 11C, the average pressure has increased compared to the average pressure (1.0×10 4 Pa) of the state of the art in Fig. 11B tripled. As described above, if the pressure in the battery pack 10 increases while a fire (flame) has occurred in the battery pack 10, the battery pack 10 may be deformed or damaged, so that the flame in the battery pack 10 is directly exposed outside the battery pack 10 and may lead to a large fire outside the battery pack 10.

[0077] However, as in the exemplary embodiment for the venting element 130, in which a diameter D1 of the inlet side 131 was 66 mm and a diameter D2 of the outlet side 132 was 50 mm, as in Fig. 9A and Fig. 10A, a velocity region toward the interior space 115 was formed in the venting element 130. However, this reversed velocity region was partially formed in the boundary region BA between the first region 133 and the second region 134 and did not connect the interior space 115 to the exterior space, which are both sides of the venting element 130. In other words, since the velocity region toward the interior space 115 was not connected to the exterior space in the boundary region BA, the outside air did not flow in. Furthermore, in the embodiment, as shown in Fig. 11A, the average pressure in the battery pack 100 6.6×10 3 Pa, which was slightly lower than the average pressure (1.0× 10 4 Pa) of the state of the art in Fig. 11B, which had the same diameter D2 (50 mm) of the exhaust side.

[0078] Therefore, as in the embodiment, when the cross-sectional area A1 of the first region 133 or the diameter D1 of the inlet side 131 is configured to be larger than the cross-sectional area A2 of the second region 134 or the diameter D2 of the outlet side 132, even if the flame is generated in the battery pack 100 and the gas is discharged to the outside through the vent member 130, the oxygen in the outside air cannot flow into the internal space 115, so that the increase of the flame or explosion in the battery pack 100 can be reduced. Furthermore, even if the flame occurs in the battery pack 100, the internal average pressure cannot rise rapidly, so that rapid outward outbreak of the flame due to deformation or damage to the battery pack 100 can be prevented.Therefore, according to the embodiment, the spread of the flame in the battery pack 100 to the outside can be delayed for a considerable time, so that the safety of the battery pack 100 against fire can be ensured.

[0079] In the following description, the possibility of the occurrence of a flame in the open air due to the leakage of electrolyte gas when the electrolyte gas is quickly discharged from the battery pack 10 and 100 will be discussed with regard to an embodiment and the prior art with reference to Fig. 12 to 15C described.

[0080] Fig. 12 is a diagram illustrating an overall structure used in analyzing the state in which electrolyte gas is discharged from the battery packs 10 and 100 with respect to an embodiment and the prior art. In Fig. 12, an inlet IN for injecting the electrolyte gas was arranged on one side of the battery packs 10 and 100, and the electrolyte gas was discharged through the vent elements 30 and 130 according to the exemplary embodiment and the prior art. For the analysis area, the diameter DA was set to 1000 mm and the length LA to 4000 mm.

[0081] In addition, the composition of the electrolyte gas was determined as follows: H2 at 10%, CH4 at 5%, C2H4 at 10%, CO at 15%, CO2 at 60% by volume. The velocity of the electrolyte gas flowing through the inlet IN was set to 21 m / s and the temperature to 723 K.

[0082] In the embodiment, in the vent element 130, the diameter D1 of the inlet side 131 was 40 mm, the diameter D2 of the outlet side 132 was 20 mm, and the length L was 48 mm, and in the prior art vent element 30, the example (Comparative Example 1) in which a diameter D' was determined to be 50 mm and the length L' was 48 mm, and the example (Comparative Example 2) in which the diameter D' was determined to be 20 mm and the length L' was 48 mm were used as comparative analysis targets.

[0083] Fig. 13 is an analysis diagram illustrating the electrolyte gas velocity distribution and the mixing variance distribution of the electrolyte gas discharged from the venting elements 30 and 130 with respect to an embodiment and the prior art. Fig. 14 is an analytical diagram illustrating the H2O mass fraction distribution and the temperature distribution of the electrolyte gas discharged from the venting elements 30 and 130 with respect to an embodiment and the prior art. Fig. 15A to 15C are graphs illustrating the comparison of a flame length of the electrolyte gas escaping from the vent elements 30 and 130 and an average pressure in the battery packs 10 and 100.

[0084] The distribution of the mixing variance of the electrolyte gas in Fig. 13 shows a distribution in which the composition has changed by reaction with oxygen in the atmosphere after the electrolyte gas was released from the venting elements 30 and 130, the H2O mass fraction distribution shows the distribution of the amount of H2O generated by reaction with oxygen in the atmosphere after the electrolyte gas was released from the venting elements 30 and 130, and the temperature distribution in FIG. The temperature distribution in Fig. Figure 14 shows the temperature change distribution in the analysis space due to the flame. The larger the size and area of ​​the electrolyte gas mixture variance, the larger the size and area of ​​the H2O mass fraction, and the higher the temperature and the larger the area of ​​the area, the more the flame outside the battery pack 100 increased due to the electrolyte gas released from the vent elements 30 and 130.

[0085] Regarding the comparison between the embodiment and the prior art (Comparative Example 1) in which the diameter of the vent member 130 was 50 mm, and the prior art (Comparative Example 2) in which the diameter of the vent member 130 was 20 mm, according to a result of the analysis of combustion (possibility of external flame) outside the battery packs 10 and 100 due to the leakage of electrolyte gas when the electrolyte gas was rapidly discharged through the vent members 30 and 130, the smaller the diameters of the shaded portions 30 and 130 are, the more the mixing variance of the electrolyte gas in Fig. 13 and the distribution range of the H2O mass fraction and the temperature in Fig. 14, and the values ​​thereof increased. The smaller the diameter of the vent elements 30 and 130, the smaller the flame length, as shown in Fig. 15A. This is because, as the diameter of the vent members 30 and 130 decreases, as in the embodiment (the diameter of the outlet side was 20 mm) or Comparative Example 2 (the diameter was 20 mm), the possibility of a flame outside the battery packs 10 and 100 due to electrolyte gas leakage may decrease.

[0086] If the diameter of the vent elements 30 and 130 decreases, the discharge rate of the electrolyte gas may increase, as shown in Fig. 13, and the average pressure in battery packs 10 and 100 can increase sharply, as shown in Fig. 13 and Fig.15B. The increase in the average pressure in the battery packs 10 and 100 can lead to deformation or damage of the battery packs 10 and 100 and be accompanied by rapid discharge of the electrolyte gas. The working example (the inlet side diameter was 40 mm and the outlet side diameter was 20 mm) had the same outlet side diameter as Comparative Example 2 (20 mm diameter) but a larger inlet side diameter D1, so the pressure decreased by 12% compared to Comparative Example 2. Thus, the battery pack 100 was less likely to be broken or damaged compared to Comparative Example 2.

[0087] As described above, as in the embodiment, when the cross-sectional area A1 of the first region 133 or the diameter D1 of the inlet side 131 is configured to be larger than the cross-sectional area A2 of the second region 134 or the diameter D2 of the outlet side 132, the possibility of a flame outside the battery pack 100 due to electrolyte gas leakage when the electrolyte gas is quickly discharged through the vent member 130 can be reduced, and rapid occurrence of the flame to the outside due to deformation or breakage can be prevented. Specifically, by adjusting the cross-sectional area A1 of the first region 133 or the diameter D1 of the inlet side 131 and the cross-sectional area A2 of the second region 134 or the diameter D2 of the outlet side 132, the stable battery pack 100 can be realized.

[0088] According to the above embodiment, the propagation of the flame to the outside can be sufficiently delayed even if a flame occurs in the battery pack.

[0089] In addition, the venting element prevents outside air from entering the battery pack while the flame is generated inside the battery pack, and the gas is vented to the outside through the venting element. Accordingly, the possibility of a battery pack explosion or flame enlargement caused by the inflow of oxygen during flame generation inside the battery pack can be reduced. Furthermore, the pressure increase inside the battery pack can be reduced, thus preventing damage to the battery pack and flame leakage to the outside.

[0090] Even if a large amount of electrolyte gas in the battery pack is discharged to the outside, the possibility of ignition and flame due to the discharged electrolyte gas can be reduced.

[0091] Although the embodiments have been illustrated and described above, it will be apparent to those skilled in the art that modifications and variations may be made without departing from the scope of the present disclosure as defined by the appended claims.

Claims

[1] Battery pack comprising: a pack housing having an interior in which a plurality of battery modules or a plurality of battery cells are directly installed without being modulated; and a vent element installed in the pack housing and configured to vent gas generated in the interior to the outside, wherein the ventilation element is configured such that a cross-sectional area of ​​an outlet side of the ventilation element, which is connected to an exterior space of the package housing, is smaller than a cross-sectional area of ​​an inlet side of the ventilation element, which is connected to the interior space, characterized by that a cross-sectional area of ​​the outlet side is designed such that it is 0.2-0.8 times a cross-sectional area of ​​the inlet side. [2] The battery pack of claim 1, wherein the vent member is configured to include a first portion connected to the inlet side and a second portion connected to the outlet side. [3] Battery pack according to claim 2, wherein the first region has a constant cross-sectional area over its entire extent, and wherein a cross-sectional area of ​​the second region is reduced in a direction from the first region toward the outlet side. [4] The battery pack according to claim 2 or 3, wherein the first region and the second region have a circular cross-sectional shape. [5] Battery pack according to claim 2 or 3, wherein the first region has a hollow cylindrical shape, and wherein the second region has a hollow, frustoconical shape. [6] The battery pack according to claim 2 or 3, wherein a length of the second region is configured to be 0.2-0.8 times a distance from the inlet side to the outlet side. [7] The battery pack according to any one of claims 1 to 6, wherein a cross-sectional area of ​​the outlet side is configured to be 0.4-0.7 times a cross-sectional area of ​​the inlet side. [8] Battery pack according to claim 2, wherein the first region has a shape in which its cross-sectional area decreases with a first inclination angle in a direction from the inlet side to the outlet side, and wherein the second region has a shape in which its cross-sectional area decreases at a second inclination angle which is greater than the first inclination angle in the direction from the inlet side to the outlet side. [9] A battery pack according to any one of claims 1 to 8, wherein the inlet side of the vent member is arranged on the same surface as an inner surface of an outer wall of the pack case. [10] A battery pack according to any one of claims 1 to 9, wherein the venting member is formed in the form of a hole in an outer wall of the pack casing. [11] The battery pack according to any one of claims 1 to 9, wherein the vent member has a shape in which at least a part of the vent member protrudes to an outside of an outer wall of the pack case. [12] The battery pack of claim 11, wherein at least a portion of the vent member comprises a vent guide member mounted on the outer wall of the pack casing. [13] A battery pack according to any one of claims 1 to 12, wherein at least one or more additional venting elements are provided which are identical to the venting element, and wherein the plurality of venting elements are spaced apart from one another on an outer wall on one side of the pack housing. [14] The battery pack according to any one of claims 1 to 13, wherein the vent member maintains an open state without being closed so that air flows through the vent member. [15] Battery pack comprising: a pack housing having a partition member forming a plurality of interior spaces configured to receive at least one battery module; and at least one venting element for discharging gas generated in the interior outside the packing housing, wherein the venting element has an inlet opening with a first cross-sectional area and an outlet opening with a second cross-sectional area which is smaller than the first cross-sectional area, characterized by that a cross-sectional area of ​​the outlet side is designed to be 0.2-0.8 times a cross-sectional area of ​​the inlet side.

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