Patent Description:
Example embodiments of the present disclosure relate to a battery pack including a plurality of battery cells and a venting member for discharging gas generated in a pack housing.

Differently from a primary battery, a secondary battery may be charged and discharged such that a secondary battery may be applied to various fields such as a digital camera, a mobile phone, a laptop, a hybrid vehicle, and an electric vehicle. Examples of a secondary battery may include a nickel-cadmium battery, a nickel-metal hydride battery, a nickel-hydrogen battery, and a lithium secondary battery.

Among such secondary batteries, many studies regarding a lithium secondary battery having high energy density and discharge voltage have been conducted. Recently, a lithium secondary battery has been manufactured and used as a pouched type battery cell having flexibility, or manufactured as a prismatic or cylindrical can type battery cell having rigidity.

Also, a secondary battery has been widely used in small-sized devices such as a portable electronic device, and also in medium-sized and large-sized devices such as vehicles and energy storage system. When a secondary battery is used in such a medium-sized or large-sized device, a large number of secondary batteries may be electrically connected to each other to increase capacity and output of the entire battery. To this end, in a medium-sized and large-sized device, a plurality of battery modules in which a plurality of battery cells are modularized may be installed in a battery pack.

Various standards may be required for such a battery pack, and a representative standard may be safety. Particularly, the safety of a battery pack provided in a vehicle may be important because the safety of the battery pack may be directly related to passenger safety.

One of the important issues related to the safety of the battery pack may be to prevent ignition in the battery pack, and even when ignition or a fire (flame) occurs, it may be necessary to sufficiently delay exposure of the flame generated in the battery pack. For example, when ignition starts in the battery pack, it may be necessary to delay the spread of the flame externally of the battery pack by allowing a predetermined time (e.g., <NUM> minutes or more) to elapse until the flame is observed outside the battery pack.

A battery pack may include a plurality of battery cells including a lithium secondary battery, and the like. When various events occurs, such as, when the lifespan of the battery cell reaches the end of 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 an casing of the battery cell, or when an external impact is applied to the battery cell, an electrolyte gas may leak out of the battery cell. In particular, in the case of a high-capacity pouch-type lithium secondary battery, when the above-mentioned issues occur, a large amount of electrolyte gas may be exposed through a sealing portion of a pouch (casing), which may be problematic. To discharge the electrolyte gas generated within the internal space of the battery pack externally of the battery pack, a venting hole (a venting member, a gas exhaust port, a gas passage port) may be installed in the wall surface of a pack housing. <CIT> describes a battery module comprising a cell stack, a module case, a pair of module covers and a ventilation unit arranged to pass through the module cover.

The venting hole may also be used to discharge the gas generated in the battery pack externally, such that the venting hole may be used to delay the spread of flame.

Since the venting hole has an open structure, the gas in the pack housing may be discharged through the venting hole, and the venting hole may also work as a path through which air from the outside of the pack housing may flow into the pack housing.

Therefore, when a fire (flame) occurs in the battery pack, the gas generated in the battery pack may be discharged through the open venting hole. However, while the gas is discharged, a turbulent flow or vortex may occur such that air outside the battery pack may flow into the internal space of the battery pack through the venting hole. When external air flows into the battery pack, an explosion may occur in the battery pack due to oxygen contained in the external air.

To prevent the inflow of external air, a size of the venting hole may be reduced to prevent the possibility of inflow of external air, but in this case, the air in the battery pack may not be smoothly discharged externally, such that the pressure in the battery pack may increase, which may cause deformation of or damage to the battery pack. In this case, the flame in the battery pack may be directly exposed externally of the battery pack through the deformed or damaged part of the battery pack, which may lead to a large fire outside the battery pack.

An example embodiment of the present disclosure is to provide a battery pack which may, even when a flame occurs in the battery pack, sufficiently delay the spread of flames externally.

An example embodiment of the present disclosure is to provide a battery pack which may prevent external air from flowing into the battery pack through a venting member and may also reduce the increase of pressure in the battery pack.

An example embodiment of the present disclosure is to provide a battery pack which may, even when a large amount of electrolyte gas in the battery pack is discharged externally, reduce the possibility of ignition and flame caused by the discharged electrolyte gas.

The present invention provides a battery pack including a pack housing having an internal space in which a plurality of battery modules are installed or a plurality of battery cells are installed directly without being modulized; and a venting member installed in the pack housing and configured to discharge gas generated in the internal space externally, wherein the venting member is configured such that a cross-sectional area of an outlet side of the venting member connected to an external space of the pack housing is smaller than a cross-sectional area of an inlet side of the venting member connected to the internal space.

The battery cell may include a pouch type secondary battery in which an electrode assembly and an electrolyte are accommodated in a pouch-type casing and at least a portion of the casing is sealed. The venting member is configured to include 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 to the outlet side.

The first region and the second region may have a circular cross-sectional shape. The first region may have a hollow cylindrical shape, and the second region may have a hollow truncated conical shape.

A length of the second region may be configured to be <NUM>-<NUM> times a distance from the inlet side to the outlet side. A cross-sectional area of the outlet side is configured to be <NUM>-<NUM> times a cross-sectional area of the inlet side, preferably <NUM>-<NUM> times a cross-sectional area of the inlet side.

The first region may have a shape in which the cross-sectional area thereof decreases at 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 the cross-sectional area thereof decreases at a second inclination angle greater than the first inclination angle in the direction from the inlet side to the outlet side.

The inlet side of the venting member may be disposed on the same surface as an internal surface of an external wall of the pack housing.

The venting member may be formed in a shape of a hole in an external wall of the pack housing. Alternatively, the venting member may have a shape in which at least a portion of the venting member protrudes to an external side of an external wall of the pack housing. At least a portion of the venting member may include a venting guide member attached to the external wall of the pack housing.

At least one or more additional venting members identical to the venting member may be provided, and wherein the plurality of the venting members are spaced apart from each other on an external wall on one side of the pack housing. The plurality of venting members may be disposed on the external wall on the one side of the pack housing and on another external wall different from the external wall on the one side of the pack housing.

The venting member may maintain an open state without being closed such that air flows through the venting member.

The present invention further provides a battery pack comprising a pack housing including a partition member creating a plurality of internal spaces configured to receive at least one battery module; and at least one venting member for discharging gas generated in the internal space externally of the pack housing, wherein the venting member has an inlet opening having a first cross-sectional area and an outlet opening having a second cross-sectional area that is smaller than the first cross-sectional area.

It is to be understood that the terms or words used in this description and the following claims must not be construed to have meanings which are general or may be found in a dictionary. Therefore, considering the notion that an inventor may most properly define the concepts of the terms or words to best explain his or her invention, the terms or words must be understood as having meanings or concepts that conform to the technical spirit of the present disclosure. Also, since the example embodiments set forth herein and the configurations illustrated in the drawings are nothing but a mere example of the present disclosure, it is to be understood that various equivalents and modifications may replace the example embodiments and configurations at the time of the present application.

In the drawings, same elements will be indicated by same reference numerals. Also, redundant descriptions and detailed descriptions of known functions and elements that may unnecessarily make the gist of the present disclosure obscure will be omitted. In the accompanying drawings, some elements may be exaggerated, omitted or briefly illustrated, and the sizes of the elements do not necessarily reflect the actual sizes of these elements.

Referring to <FIG>, a battery pack <NUM> according to an example embodiment will be described.

<FIG> and <FIG> are a perspective diagram illustrating a battery pack <NUM> according to an example embodiment. <FIG> is a perspective view of a battery cell according to an example embodiment. <FIG> are diagrams illustrating examples of a venting member <NUM> provided in a battery pack <NUM> according to an example embodiment of the present disclosure, where <FIG> is a cross-sectional diagram illustrating a venting member <NUM> taken in a length direction, <FIG> is a diagram illustrating the venting member in <FIG>, viewed from "A," and <FIG> are a diagram illustrating a modified example of the venting member in <FIG>. <FIG> are cross-sectional diagrams illustrating a modified example of a venting member <NUM> provided in a battery pack <NUM> according to an example embodiment. <FIG> is a cross-sectional diagram illustrating another modified example of a venting member <NUM> provided in a battery pack <NUM> according to an example embodiment.

As illustrated in <FIG>, the battery pack <NUM> according to an example embodiment may include a pack housing <NUM> having an internal space <NUM> and a venting member <NUM>.

An internal space <NUM> of a predetermined size may be formed in the pack housing <NUM>, and a plurality of battery modules <NUM> may be installed therein. Each battery module <NUM> may have a modular structure in which a plurality of battery cells <NUM> are electrically connected to each other, and the pack housing <NUM> may have a structure in which the plurality of battery modules <NUM> are electrically connected to each other. Also, a partition member <NUM> may be installed in the pack housing <NUM> to support the battery module <NUM>.

<FIG> illustrates the example in which the plurality of battery cells <NUM> are modularized through the battery module <NUM> and are installed in the internal space <NUM> of the pack housing <NUM>. However, as illustrated in <FIG>, the plurality of battery cells <NUM> may have a cell to pack (CTP) structure in which the plurality of battery cells <NUM> may be directly installed without using the battery module (i.e., without being modulized).

As illustrated in <FIG>, the battery cell <NUM> provided in the battery pack <NUM> may be configured as a pouch type secondary battery. The pouch-type secondary battery cell <NUM> may be formed through a pouch-type casing <NUM>. The pouch-type casing <NUM> may be divided into an receiving portion <NUM> and a sealing portion <NUM>. The receiving portion <NUM> may accommodate an electrode assembly <NUM> and an electrolyte (not illustrated). The sealing portion <NUM> may be divided into a first sealing portion 124a in which an electrode lead <NUM> and an insulation film <NUM> are disposed and a second sealing portion 124b in which the electrode lead <NUM> is not disposed. As an example, in an example embodiment, the pouch-type battery cell <NUM> may include a lithium ion (Li-ion) battery or a nickel metal hydride (Ni-MH) battery which may be charged and discharged. However, in the example embodiment, the battery cell provided in the battery pack <NUM> is not limited to a pouch type secondary battery.

Also, a battery management system (BMS) (not illustrated) for controlling the battery cells or the battery module <NUM> may be provided in the pack housing <NUM>.

The venting member <NUM> may be installed in the pack housing <NUM> and may be formed in an open shape to discharge a gas generated in the internal space <NUM> externally. In other words, the venting member <NUM> may be installed in a through structure on an external wall <NUM> portion of the pack housing <NUM> and may allow air to flow in and out of the pack housing <NUM>. However, in the example embodiment, the venting member <NUM> is not limited to a completely open structure, and a filtration device such as a filtration membrane may be installed in the opening portion forming the venting member <NUM>, and may have a cover (a membrane or a flap).

The battery cell may have a structure in which an electrode assembly (not illustrated) formed by stacking a positive electrode plate, a negative electrode plate, and a separator in the casing, and an electrolyte solution may be accommodated. In other words, the battery cell may be configured as a secondary battery which may be charged and discharged. The electrolyte contained in the casing may be gasified due to external impacts, internal defects, or the like, and the gasified electrolyte may be discharged externally of the battery cell.

The venting member <NUM> may discharge the electrolyte gas externally when the electrolyte gas is generated in the internal space <NUM> of the pack housing <NUM>. In this case, the venting member <NUM> may maintain an open state without being closed so as to facilitate the flow of air through the venting member <NUM>.

Also, a plurality of the venting members <NUM> may be disposed on the external wall <NUM> on one side of the pack housing <NUM> and may be spaced apart from each other such that the gas generated in the internal space <NUM> of the battery pack <NUM> may be smoothly discharged externally. For example, as illustrated in <FIG> and <FIG>, the venting member <NUM> may be provided on both sides of the external wall <NUM> on one side with respect to a center. Alternatively, at least one venting member <NUM> may be installed on external wall <NUM> on one side of the pack housing <NUM>, and at least one venting member <NUM> may be installed on an external wall different from the external wall on one side. For example, at least one venting member <NUM> may be installed on the external wall <NUM> on one side illustrated in <FIG> and <FIG>, and at least one venting member <NUM> may also be installed on the opposite external wall opposing the external wall on one side and/or the other external wall connected to the external wall on one side. However, the arrangement position and the number of the venting members <NUM> are not limited thereto, and may be varied.

Referring to <FIG>, in the venting member <NUM>, a cross-sectional area A2 of an outlet side <NUM> of the venting member <NUM> connected to an external space of the pack housing <NUM> is configured to be smaller than a cross-sectional area A1 of an inlet side <NUM> of the venting member <NUM> connected to the internal space <NUM>. Also, the venting member <NUM> has an inlet opening having a first cross-sectional area A1 and an outlet opening having a second cross-sectional area A2 that is smaller than the first cross-sectional area A1.

In other words, when the cross-sectional area A1 of the inlet side <NUM> is larger than the cross-sectional area A2 of the outlet side <NUM>, the electrolyte gas generated in the internal space <NUM> may be easily discharged externally through the venting member <NUM>, differently from the example in which the cross-sectional areas of the inlet side <NUM> and the outlet side <NUM> are maintained the same. Accordingly, when a flame is generated in the battery pack <NUM> and the gas is discharged, an increase in pressure in the battery pack <NUM> may be limited. Also, since the cross-sectional area A2 of the outlet side <NUM> is smaller than the cross-sectional area A1 of the inlet side <NUM>, the air outside the pack housing <NUM> may not easily flow into the internal space <NUM> through the venting member <NUM>. Accordingly, the pressure in the battery pack <NUM> may not excessively increase and the inflow of external air (oxygen) may be effectively blocked.

Referring <FIG>, the venting member <NUM> includes a first region <NUM> connected to the inlet side <NUM> and having a relatively large cross-sectional shape, and a second region <NUM> connected to the outlet side <NUM> and having a relatively small cross-sectional shape. When calculating an average cross-sectional area for a predetermined length of the venting member <NUM> based on a cut-out surface according to the length direction of the venting member <NUM>, the average cross-sectional area of the second region <NUM> has a value lower than the average cross-sectional area of the first region <NUM>.

For example, as illustrated in <FIG>, <FIG>, the first region <NUM> may extend from the inlet side <NUM> to the outlet side <NUM> in the same cross-sectional form, and the second region <NUM> may extend toward the outlet side <NUM> in a form in which a the cross-sectional area thereof may decrease further than that of the first region <NUM>. That is, the first region <NUM> has a constant cross-sectional area along its entire extent, and a cross-sectional area of the second region <NUM> is reduced in a direction from the first region <NUM> to the outlet side <NUM>.

Also, each of the first region <NUM> and the second region <NUM> may have a circular cross-sectional shape as illustrated in <FIG>. In this case, a diameter D1 of the inlet side <NUM> may have a shape larger than that of a diameter D2 of the outlet side <NUM>.

Also, when each of the first region <NUM> and the second region <NUM> has a circular cross-sectional shape, the first region <NUM> of the venting member <NUM> may have a hollow cylindrical shape with a constant diameter D1, and the second region <NUM> may have a hollow truncated conical shape of which a diameter decreases toward the outlet side <NUM>.

A boundary area BA in which a cross-sectional structure may change may be formed between the first region <NUM> and the second region <NUM>. In this case, the boundary area BA between the first region <NUM> and the second region <NUM> may have a structure in which linear lines on the cross-sectional surface may meet each other such that an inclination may be formed as illustrated in <FIG> and <FIG>. Alternatively, the boundary area BA between the first region <NUM> and the second region <NUM> may have a structure in which the first region <NUM> and the second region <NUM> may be connected to each other in a smooth curved surface (the curved portion is illustrated as a region between two vertical lines in <FIG> and <FIG>).

Also, the second region <NUM> may be inclined at a single inclination angle θ as illustrated in <FIG>, <FIG>, but as illustrated in <FIG>, the second region <NUM> may have a structure in which the second region <NUM> may be divided into two or more regions 134a, and 134b and inclination angles θa and θb in the regions may change. In this case, the inclination angle θb in the region 134b adjacent to the outlet side <NUM> may be configured to be greater than the inclination angle θa in the region 134a spaced apart from the outlet side <NUM>, such that the diameter D2 of the outlet side <NUM> may be smaller than the diameter D2a of the portion disposed in the central portion of the second region <NUM>.

As described above, when the venting member <NUM> has a circular cross-sectional surface, the possibility of vortexes or turbulence occurring in the air flowing in the venting member <NUM> may be reduced as compared to a rectangular cross-sectional surface, such that a smooth flow may be formed from the inlet side <NUM> to the outlet side <NUM>. However, in the example embodiment, the cross-sectional shape of the venting member <NUM> may be varied, such as an elliptical cross-section, and a prismatic cross-sectional structure may not be excluded.

Also, the venting member <NUM> may have a structure in which an inclination angle is formed in both the first region <NUM> and the second region <NUM>. For example, as illustrated in <FIG>, the first region <NUM> may have a shape in which the cross-sectional area thereof may decrease at a first inclination angle θ1 in a length direction from the inlet side <NUM> to the outlet side <NUM>, and the second region <NUM> may have a shape in which the cross-sectional area thereof may decrease at a second inclination angle θ2 greater than the first inclination angle θ1 in the direction from the inlet side <NUM> to the outlet side <NUM>.

A length L2 of the second region <NUM> may be <NUM>-<NUM> times a distance from the inlet side <NUM> to the outlet side <NUM>, that is, <NUM>-<NUM> times a total length L of the venting member <NUM>. When the length L2 of the second region <NUM> is less than <NUM> times the total length L, the length of the second region <NUM> may be excessively shortened. Accordingly, since it is highly likely that external air may flow into through the shortened second region <NUM>, the installation effect of the second region <NUM> may be reduced. When the length L2 of the second region <NUM> exceeds <NUM> times the total length L, the length L1 of the first region <NUM> may be excessively shortened. In this case, the second region <NUM> having a small cross-sectional area may be elongated, such that the gas in the internal space <NUM> may not be smoothly discharged through the second region <NUM>, and accordingly, the pressure in the internal space <NUM> of the battery pack <NUM> may increase.

The cross-sectional area A2 of the outlet side <NUM> is configured to be <NUM>-<NUM> times the cross-sectional area A1 of the inlet side <NUM>. When the cross-sectional area A2 of the outlet side <NUM> is less than <NUM> times the cross-sectional area A1 of the inlet side <NUM>, the cross-sectional area A2 of the outlet side <NUM> may be excessively reduced such that the gas in the internal space <NUM> of the battery pack <NUM> may not be smoothly discharged externally, and the pressure in the battery pack <NUM> may increase. When the cross-sectional area A2 of the outlet side <NUM> exceeds <NUM> times the cross-sectional area A1 of the inlet side <NUM>, a difference in diameter (cross-sectional area) between the two sides may significantly decrease, such that the effect of smoothly discharging the internal air and reducing the inflow of external air using the different in the cross-sectional areas may decrease.

The cross-sectional area A2 of the outlet side <NUM> may be configured to be <NUM>-<NUM> times the cross-sectional area A1 of the inlet side <NUM>. In this case, by securing the cross-sectional area A2 of the outlet side <NUM>, the effect of smoothly discharging the gas in the internal space <NUM> of the battery pack <NUM> externally and the effect of reducing the inflow of external air using the difference between the cross-sectional areas of the inlet side <NUM> and the outlet side may be obtained.

Specific values of the cross-sectional area A1 of the inlet side <NUM> of the venting member <NUM>, the cross-sectional area A2 of the outlet side <NUM>, the length L1 of the first region <NUM>, the length L2 of the second region <NUM> may be determined depending on the volume of the internal space <NUM> of the battery pack <NUM> and the position and shape of the venting hole.

Also, in <FIG>, only the example in which the venting member <NUM> has the first region <NUM> and the second region <NUM> is illustrated, but a third region of which a cross-sectional shape in the length direction of the venting member <NUM> is different from those of the first region <NUM> and the second region <NUM> may be provided between the first region <NUM> and the second region <NUM>. In other words, a third region having a value between the average cross-sectional area of the first region <NUM> and the average cross-sectional area of the second region <NUM> may be provided between the first region <NUM> and the second region <NUM>.

The venting member <NUM> may be formed in the shape of a hole in the external wall <NUM> of the pack housing <NUM> when the external wall of the pack housing <NUM> has a sufficient thickness. In other words, as illustrated in <FIG>, the venting member <NUM> may be formed by processing a hole of which a diameter D1 of the inlet side <NUM> is greater than a diameter D2 of the outlet side <NUM> in the external wall <NUM> portion of the pack housing <NUM>.

When the thickness of the external wall <NUM> of the pack housing <NUM> is not sufficient, as illustrated in <FIG>, the venting member <NUM> may have a shape in which at least a portion of the venting member <NUM> protrudes to an external side of the external wall <NUM> of the pack housing <NUM>. For example, when the length of the venting member <NUM> is <NUM> and the thickness of the external wall <NUM> is <NUM>, the venting member <NUM> may have a structure protruding externally of the pack housing <NUM> by <NUM>.

Also, the venting member <NUM> may be formed of a venting guide member <NUM> attached to the external wall <NUM> of the pack housing <NUM>. The venting guide member <NUM> may have a shape in which a first region <NUM> and a second region <NUM> are formed as illustrated in <FIG>. In this case, the venting guide member <NUM> may be mounted on an internal surface of the hole formed in the pack housing <NUM> while being aligned with the internal side surface of the external wall <NUM>. Alternatively, the venting guide member <NUM> may have a shape in which only a partial region of the venting member <NUM> is formed as illustrated in <FIG>. In this case, the venting guide member <NUM> may have a shape in which the venting guide member <NUM> is attached to the external side surface of the external wall <NUM>.

Referring to <FIG>, the inlet side <NUM> of the venting member <NUM> may be disposed on the same surface as the internal surface of the external wall <NUM> of the pack housing <NUM>. When the inlet side <NUM> of the venting member <NUM> has a pipe shape protruding inwardly to the internal surface of the external wall of the pack housing <NUM>, vortex or turbulence may occur on a circumference of the inlet side <NUM> protruding in the shape of a pipe to the internal space <NUM>. For example, when it is assumed that the venting guide member <NUM> in <FIG> extends to the left, the phenomenon (e.g., vortex) in which the air flowing along the internal surface of the external wall of the pack housing <NUM> may not directly flow into the inlet of the venting guide member and may not uniformly flow may occur. However, as in an example embodiment, when the inlet side <NUM> of the venting member <NUM> is disposed on the same surface as the internal surface of the external wall of the pack housing <NUM>, the gas in the internal space <NUM> may flow along the internal surface of the external wall <NUM>, and may easily flow to the inlet side <NUM> of the venting member <NUM> and discharged externally, such that the flow of gas discharged from the pack housing <NUM> may improve.

An effect of the battery pack <NUM> according to an example embodiment will be described with reference to <FIG>, <FIG>, and <FIG>.

<FIG> is a perspective diagram illustrating a battery pack <NUM> in the prior art. The battery pack <NUM> in the prior art illustrated in <FIG> may include a pack housing <NUM> and a venting member <NUM>, and a partition wall <NUM> and a plurality of battery modules <NUM> may be disposed in the internal space <NUM> of the pack housing <NUM>. Also, the venting member <NUM> may be configured to have a shape in which a space of a predetermined diameter D' extends by a predetermined length L'.

Flow analysis was performed on the assumption that a flame occurred at the ignition point IP of the central portion of the pack housing <NUM> with respect to the battery pack <NUM> in the prior art illustrated in <FIG>. In this case, only the flow patterns in the internal space <NUM> and the venting member <NUM> were analyzed without considering the heat transfer in the pack housing <NUM>.

The analysis was performed using a compressive fluid model with a Mach number of about <NUM>, and it was assumed that fluid was generated at a constant flow rate (<NUM>/s or less) in an upward direction from the ignition point IP illustrated in <FIG>. The turbulence model was analyzed by applying Spalart-Allmaras.

<FIG> is analysis diagrams illustrating a flow rate of fluid when ignition occurs in the battery pack <NUM> in the prior art illustrated in <FIG>. <FIG> illustrates a velocity of fluid when a diameter D' of the venting member is <NUM> and a length L' is <NUM>, and <FIG> illustrates a velocity of fluid when a diameter of the venting member is <NUM> and a length L' is <NUM>.

Referring to <FIG>, most of the fluid generated at the ignition point IP had a flow pattern in which the fluid flowed along the upper space of the pack housing <NUM>, which has a relatively wide space, and flowed to the front end (-x direction) and the rear end (+x direction) of the pack housing <NUM>. Also, most of the fluid flowing to the side (±y direction) at the ignition point IP had a tendency to spread to the central passage. Also, the fluid flowing to the rear end (+x direction) of the pack housing <NUM> exhibited a flow pattern in which the fluid flowed along the internal wall surface of the external wall and was discharged at high velocity through the venting member <NUM>.

A flow pattern in the venting member <NUM> of the prior art will be described with reference to <FIG>.

<FIG> illustrates a velocity of fluid with respect to portion V1 in <FIG>. <FIG> illustrates a velocity of fluid with respect to portion V2 in <FIG>. <FIG> is an analysis diagram illustrating a velocity and a direction of fluid illustrated in <FIG>. <FIG> is an analysis diagram illustrating a velocity and a direction of fluid illustrated in <FIG>.

Referring to <FIG> and <FIG>, in the first venting member V1, the area (the dark black portion in <FIG> and the portion in <FIG> in which the arrow are directed in the -x direction) in which the velocity was lowered was formed in the lower side portion of the venting member <NUM> in the drawing, and as illustrated in the enlarged portion in <FIG>, the velocity region toward the internal space <NUM> was consecutively formed from the external side region of the venting member <NUM> to the internal space <NUM> in the lower side portion of the venting member <NUM> in the drawing.

Also, referring to <FIG> and <FIG>, in the second venting member V2, the area (the dark black portion in <FIG> and the portion in <FIG> in which the arrow are directed in the -x direction) in which the velocity was lowered was formed in the upper side portion of the venting member <NUM> in the drawing, and as illustrated in the enlarged portion in <FIG>, the velocity region toward the internal space <NUM> was consecutively formed from the external side region of the venting member <NUM> to the internal space <NUM> in the upper side portion of the venting member <NUM> in the drawing.

As described above, the extension of the velocity region from the outer region of the venting member <NUM> to the internal space <NUM> may indicate that, when the gas generated at the ignition point IP is discharged through the venting member <NUM> externally, the external air flows into the internal space <NUM> through a partial region of the venting member <NUM> (the internal wall surface of the venting member <NUM>). In other words, the venting member <NUM> of the prior art illustrated in <FIG> and <FIG> had a shape in which the diameter is maintained to be <NUM>, and in this case, it was confirmed that the external air and oxygen contained therein flowed into the internal space <NUM> of the pack housing <NUM>. The oxygen flowing thereinto may be transferred to the flame and may cause an explosion of the battery pack <NUM> or rapid spread of the flame in the battery pack <NUM>. Accordingly, the flame in the battery pack <NUM> may easily spread externally of the battery pack <NUM>, which may be problematic.

When the diameter of the venting member <NUM> was reduced from <NUM> to <NUM> as illustrated in <FIG>, since the cross-sectional area of the venting member <NUM> was reduced by <NUM>% as compared to <FIG>, as illustrated in <FIG> and <FIG>, the flow of the gas generated at the ignition point IP and discharged externally through the venting member <NUM> was strongly formed, such that the gas discharge rate rapidly increased. Accordingly, it was confirmed that the velocity region toward the internal space <NUM> of the pack housing <NUM> was extremely low in the venting member <NUM>, and the external air did not flow into the internal space <NUM>. However, when the diameter was reduced, the gas generated at the ignition point IP was not sufficiently discharged through the venting member <NUM>, such that the average pressure in the battery pack <NUM> rapidly decreased to <NUM>×<NUM><NUM> Pa as illustrated in <FIG>. When the pressure in the battery pack <NUM> increases while a fire (flame) occurs in the battery pack <NUM>, the battery pack <NUM> may be deformed or damaged, and the flame in the battery pack <NUM> may be directly exposed externally of the battery pack <NUM>, which may lead to a large fire outside the battery pack <NUM>.

In the description below, the possibility of preventing an explosion (explosion of flame) or preventing spread of flame externally when a fire (flame) occurs in the battery pack <NUM> with respect to an example embodiment and the prior art will be described with reference to <FIG>.

<FIG> are analysis diagrams illustrating comparison of a velocity of fluid in venting members <NUM> and <NUM> between a battery pack of an example embodiment and the prior art. <FIG> illustrates a velocity of fluid in a venting member <NUM> according to an example embodiment, <FIG> relates to the prior art illustrated in <FIG>, illustrating a velocity (the same as in <FIG>) of fluid in a venting member <NUM> having a diameter D' of <NUM> and a length L' of <NUM>, and <FIG> relates to the prior art illustrated in <FIG>, illustrating a velocity of fluid in a venting member <NUM> having a diameter D' of <NUM> and a length L' of <NUM>.

As for the venting member <NUM> in <FIG>, a diameter D1 of the inlet side <NUM> was <NUM>, a diameter D2 of the outlet side <NUM> was <NUM>, the entire length L of the venting member <NUM> was <NUM>, the length L1 of the first region <NUM> was <NUM>, and the length L2 of the second region <NUM> was <NUM>, and to be compared with the prior art, the pack housing <NUM> had the same structure and the same shape as those of the pack housing <NUM> of the prior art illustrated in <FIG>, <FIG>.

<FIG> are analysis diagrams illustrating a velocity and a direction of fluid with respect to an example embodiment and the prior art illustrated in <FIG>.

<FIG> are analysis diagrams illustrating distribution of internal pressure of the battery packs <NUM> and <NUM> with respect to an example embodiment and the prior art illustrated in <FIG>. The internal average pressure of the battery packs <NUM> and <NUM> was <NUM>×<NUM><NUM> Pa in <FIG>, <NUM>×<NUM><NUM> Pa in <FIG>, and <NUM>×<NUM><NUM> Pa in <FIG>.

Referring to <FIG> and <FIG>, as for the prior art in which the diameter of the venting member <NUM> was <NUM>, as described with reference to <FIG> and <FIG>, the velocity region toward the internal space <NUM> was consecutively formed from the external side region of the venting member <NUM> to the internal space <NUM>. Accordingly, in the prior art in which the diameter of the venting member <NUM> was <NUM>, when the gas generated at the ignition point IP was discharged externally through the venting member <NUM>, the external air flowed into the internal space <NUM> through a partial region (internal wall surface) of the venting member <NUM>. Therefore, oxygen in the external air flowed into the internal space <NUM> of the pack housing <NUM> and was transferred to the flame, such that explosion of the battery pack <NUM> or amplification of the flame may occur, and accordingly, the fire may easily spread externally of the battery pack <NUM>.

Also, in the prior art in which the diameter of the venting member <NUM> was reduced from <NUM> to <NUM>, as illustrated in <FIG> and <FIG>, it was confirmed that the flow of the gas generated at the ignition point IP and discharged through the venting member <NUM> was strongly formed, such that the external air rarely flowed into the internal space <NUM>. However, it was confirmed that the gas generated at the ignition point IP was not sufficiently discharged through the venting member <NUM>, such that the average pressure in the battery pack <NUM> rapidly increased to <NUM>×<NUM><NUM> Pa as illustrated in <FIG>. In other words, in the prior art in <FIG>, the average pressure increased three times as compared to the average pressure (<NUM>×<NUM><NUM> Pa) of the prior art in <FIG>. As described above, when the pressure in the battery pack <NUM> increases while a fire (flame) has occurred in the battery pack <NUM>, the battery pack <NUM> may be deformed or damaged, such that the flame in the battery pack <NUM> may be directly exposed externally of the battery pack <NUM> and may lead to a large fire outside the battery pack <NUM>.

However, as in the example embodiment, as for the venting member <NUM> of which a diameter D1 of the inlet side <NUM> was <NUM>, and a diameter D2 of the outlet side <NUM> was <NUM>, as illustrated in <FIG> and <FIG>, a velocity region toward the internal space <NUM> was formed in the venting member <NUM>. However, this reverse velocity region was partially formed in the boundary region BA between the first region <NUM> and the second region <NUM>, and did not connect the internal space <NUM> to the external space, which are both sides of the venting member <NUM>. In other words, since the velocity region toward the internal space <NUM> was not connected to the external space in the boundary region BA, the external air did not flow into. Further, in the example embodiment, as illustrated in <FIG>, the average pressure in the battery pack <NUM> was <NUM>×<NUM><NUM> Pa, which was rather less than the average pressure (<NUM>×<NUM><NUM> Pa) of the prior art in <FIG> which had the same diameter D2 (<NUM>) of the outlet side.

Therefore, as in the example embodiment, when the cross-sectional area A1 of the first region <NUM> or the diameter D1 of the inlet side <NUM> is configured to be greater than the cross-sectional area A2 of the second region <NUM> or the diameter D2 of the outlet side <NUM>, even while the flame is generated in the battery pack <NUM> and the gas is discharged externally through the venting member <NUM>, oxygen in the external air may not flow into the internal space <NUM>, such that the increase of flame or explosion in the battery pack <NUM> may be reduced. Further, even when the flame occurs in the battery pack <NUM>, the internal average pressure may not rapidly increase, such that rapid exposure of the flame externally due to deformation or damage of the battery pack <NUM> may be prevented. Therefore, according to the example embodiment, the spread of the flame in the battery pack <NUM> to be outside may be delayed for a considerable time, such that the safety of the battery pack <NUM> against fire may be secured.

In the description below, the possibility of flame occurring outside due to leakage of electrolyte gas when the electrolyte gas is rapidly discharged from the battery packs <NUM> and <NUM> with respect to an example embodiment and the prior art will be described with reference to <FIG>.

<FIG> is a diagram illustrating an overall structure used in analysis of the state in which electrolyte gas is discharged from the battery packs <NUM> and <NUM> with respect to an example embodiment and the prior art. In <FIG>, an inlet IN for injecting the electrolyte gas was disposed on one side of the battery packs <NUM> and <NUM>, and the electrolyte gas was discharged through the venting members <NUM> and <NUM> according to the example embodiment and the prior art. As for the analysis area, the diameter DA was determined to be <NUM> and the length LA was determined to be <NUM>.

Also, the composition of the electrolyte gas was determined to be H<NUM> of <NUM>%, CH<NUM> of <NUM>%, C<NUM>H<NUM> of <NUM>%, CO of <NUM>%, CO<NUM> of <NUM>% based on the volume fraction. The velocity of the electrolyte gas flowing through the inlet IN was determined to be <NUM>/s, and the temperature determined to be <NUM>.

In the example embodiment, in the venting member <NUM>, a diameter D1 of the inlet side <NUM> was <NUM>, a diameter D2 of the outlet side <NUM> was <NUM>, and a length L was <NUM>, and in the venting member <NUM> in the prior art, the example (comparative example <NUM>) in which a diameter D' was determined to be <NUM> and the length L' was determined to be <NUM>, and the example (comparative example <NUM>) in which the diameter D' was determined to be <NUM>, and the length L' was determined to be <NUM> were used as comparative analysis targets.

<FIG> is an analysis diagram illustrating distribution of a velocity of electrolyte gas and distribution of mixture variance of electrolyte gas discharged from venting members <NUM> and <NUM> with respect to an example embodiment and the prior art. <FIG> is an analysis diagram illustrating distribution of H<NUM>O mass fraction and distribution of temperature of the electrolyte gas discharged from venting members <NUM> and <NUM> with respect to an example embodiment and the prior art. <FIG> are diagrams illustrating comparison of a length of flame the electrolyte gas discharged from venting members <NUM> and <NUM> and an average pressure in the battery packs <NUM> and <NUM>.

The distribution of the mixture variance of electrolyte gas in <FIG> indicates a distribution in which the composition changed by reacting with oxygen in the atmosphere after the electrolyte gas was released from the venting members <NUM> and <NUM>, the H<NUM>O mass fraction distribution indicates the distribution of the amount of H<NUM>O generated by reacting with oxygen in the atmosphere after the electrolyte gas was released from the venting members <NUM> and <NUM>, and the temperature distribution in <FIG> indicates the temperature change distribution in the analysis space due to the flame. the larger the size and area of the mixture variance of the electrolyte gas, the larger the size and area of the h<NUM>o mass fraction, and the higher the temperature and the larger the range of the area, the more the flame outside the battery pack <NUM> increased due to the electrolyte gas discharged from the venting members <NUM> and <NUM>.

As for the comparison between the example embodiment, and the prior art (comparative example <NUM>) in which the diameter of the venting member <NUM> was <NUM> and the prior art (comparative example <NUM>) in which the diameter of the venting member <NUM> was <NUM>, according to a result of analysis of combustion (possibility of external flame) outside the battery packs <NUM> and <NUM> due to leakage of electrolyte gas when the electrolyte gas was rapidly discharged through the venting members <NUM> and <NUM>, the smaller the diameters of the tinting portions <NUM> and <NUM>, the more the mixture variance of the electrolyte gas in <FIG> and the distribution region of H<NUM>O mass fraction and the temperature in <FIG> increased, and the values thereof increased. Also, as illustrated in <FIG>, the smaller the diameter of the venting members <NUM> and <NUM>, the smaller the flame length. This is because, as the diameter of the venting members <NUM> and <NUM> decreased as in the example embodiment (the diameter of the outlet side was <NUM>) or comparative example <NUM> (the diameter was <NUM>), the possibility of flame outside the battery packs <NUM> and <NUM> due to electrolyte gas leakage may decrease.

As the diameter of the venting members <NUM> and <NUM> decreased, the electrolyte gas ejection rate may increase as illustrated in <FIG> and the average pressure in the battery packs <NUM> and <NUM> may greatly increase as illustrated in <FIG> and <FIG>. The increase in the average pressure in the battery packs <NUM> and <NUM> may cause deformation or damage of the battery packs <NUM> and <NUM>, and may be accompanied by rapid discharge of the electrolyte gas. The example embodiment (the diameter of the inlet side was <NUM>, and the diameter of the outlet side was <NUM>) had the same diameter of the outlet side as that of comparative example <NUM> (diameter of <NUM>), but had the greater diameter D1 of the inlet side, such that the pressure decreased by <NUM>% as compared to comparative example <NUM>. Thus, the battery pack <NUM> was less broken or damaged as compared to comparative example <NUM>.

As described above, as in the example embodiment, when the cross-sectional area A1 of the first region <NUM> or the diameter D1 of the inlet side <NUM> is configured to be greater than the cross-sectional area A2 of the second region <NUM> or the diameter D2 of the outlet side <NUM>, the possibility of flame outside the battery pack <NUM> due to electrolyte gas leakage when the electrolyte gas is rapidly discharged through the venting member <NUM> may be lowered, and rapid exposure of the flame externally due to deformation or breakage may be prevented. In particular, by adjusting the cross-sectional area A1 of the first region <NUM> or the diameter D1 of the inlet side <NUM> and the cross-sectional area A2 of the second region <NUM> or the diameter D2 of the outlet side <NUM>, the stable battery pack <NUM> may be implemented.

According to the aforementioned example embodiment, even when a flame is generated in the battery pack, the spread of the flame externally may be sufficiently delayed.

Also, the inflow of external air into the battery pack through the venting member may be prevented while the flame is generated in the battery pack and the gas is discharged externally through the venting member. Accordingly, the possibility of explosion of the battery pack or flame amplification caused by the inflow of oxygen while the flame occurs in the battery pack may be reduced. In addition, the increase of pressure in the battery pack may be reduced such that the effect of preventing damage to the battery pack and leakage of the flame externally may be obtained.

Further, even when a large amount of the electrolyte gas in the battery pack is discharged externally, the possibility of ignition and flame due to the discharged electrolyte gas may be reduced.

Claim 1:
A battery pack, comprising:
a pack housing having an internal space in which a plurality of battery modules are installed or a plurality of battery cells are installed directly without being modulized; and
a venting member installed in the pack housing and configured to discharge gas generated in the internal space externally,
wherein the venting member is configured such that a cross-sectional area of an outlet side of the venting member connected to an external space of the pack housing is smaller than a cross-sectional area of an inlet side of the venting member connected to the internal space, wherein
the venting member is configured to include a first region connected to the inlet side and a second region connected to the outlet side,
an average cross-sectional area of the second region has a value lower than an average cross-sectional area of the first region, and
a cross-sectional area of the outlet side is configured to be <NUM>-<NUM> times a cross-sectional area of the inlet side.