Patent Description:
A secondary battery, referring to a battery that may be charged and discharged, unlike a primary battery that cannot be charged, has been applied to electric vehicles (EVs), hybrid electric vehicles (HEVs), and the like, driven by an electrical motive power source, as well as portable devices.

Lithium ion batteries, lithium polymer batteries, nickel cadmium batteries, nickel hydrogen batteries, nickel zinc batteries or the like have been widely used as secondary batteries. Such a unit secondary battery cell, i.e., a unit battery cell, has an operating voltage of about <NUM>. 5V to <NUM>. Therefore, if a higher output voltage is demanded, a plurality of secondary battery cells may be connected in series to configure a battery pack. In addition, according to a charge/discharge capacity required for the battery pack, a plurality of battery cells may also be connected in parallel to configure a battery pack. Therefore, the number of secondary battery cells included in the battery pack may be set to be various, depending on a required output voltage or charge/discharge capacity.

Types of secondary batteries currently widely used include lithium ion batteries, lithium polymer batteries, nickel cadmium batteries, nickel hydrogen batteries, nickel zinc batteries, and the like. The unit secondary battery cell, that is, the operating voltage of the unit battery cell is about <NUM>. 5V to <NUM>. Accordingly, when a higher output voltage is required, a plurality of battery cells are connected in series to form a battery pack. In addition, a plurality of battery cells may be connected in parallel to form a battery pack according to the charge/discharge capacity required for the battery pack. Accordingly, the number of battery cells included in the battery pack may be variously set according to a required output voltage or charge/discharge capacity.

When a specific battery cell or battery module malfunctions in a battery pack including a plurality of battery cells or battery modules, gas or conductive particles may be ejected into the pack, which may affect other battery cells or battery modules to cause a chain of thermal runaway. When the battery pack is mounted in a vehicle, thermal runaway of the battery pack may threaten the life of a driver or passengers, and thus, a method for preventing or delaying thermal runaway is required.

Document <CIT> discloses a battery pack assembly comprising a plurality of battery pack modules with a housing, with a smoke exhaust channel communicating the inside with the outside of the battery pack through a valve. Cell thermal insulation elements are disposed between the plurality of single cells in the battery modules, and exhaust ports are provided at the side beam of the battery pack.

Document <CIT> discloses a battery housing formed by upper and lower housings comprising a plurality of battery cells, forming a plurality of cell stack assemblies, with flow path holes for connecting the inside and outside of the battery housing.

Document <CIT> discloses a battery having a vent having a stepped (two-stage) structure; in the larger diameter part side of the vent, a valve is inserted and worn.

Exemplary embodiments provide a battery pack having a high degree of safety. In particular, exemplary embodiments provide a structure capable of discharging high-temperature flammable gas, caused by thermal runaway of a battery pack, externally as quickly as possible without ignition.

Exemplary embodiments provide a multilayer electronic component provide a multilayer electronic component including a uniform plating layer.

According to an aspect of the present disclosure, a battery pack includes: a pack housing; at least one battery module disposed inside the pack housing; and a vent hole connecting inside and outside of the pack housing, wherein the battery module includes a plurality of battery cells and a first thermal propagation (TP) blocking member disposed between the plurality of battery cells, wherein the vent hole is formed so that a cross-sectional area of an outlet side connected to an external space of the pack housing is smaller than a cross-sectional area of an inlet side connected to the internal space of the pack housing, wherein the vent hole includes:.

The battery pack may further include: an internal busbar coupled to the plurality of battery cells, wherein the first TP blocking member may be coupled to the internal busbar.

The pack housing may include a pack cover covering an upper portion of the battery module, and a second TP blocking member may be disposed between the upper portion of the battery module and the pack cover.

The second TP blocking member may be formed to surround an upper portion and a side portion of the battery module.

A total cross-sectional area of the vent hole may be greater than <NUM>,<NUM><NUM> and less than or equal to <NUM>,<NUM><NUM>.

An air layer having a thickness of <NUM> or less may be formed between the at least one battery module and the pack cover.

The at least one battery module may include a plurality of battery cells and a module case accommodating the plurality of battery cells, and the air layer may be defined as a space between the pack cover and the module case.

At least a portion of the vent hole may have a cross-sectional area decreasing from the inlet side to the outlet side.

The pack cover may include a steel material.

In an exemplary embodiment, the pack housing may include a side frame surrounding the at least one battery module, and a sealing member may be disposed between the side frame and the pack cover.

The battery pack may further include an external busbar electrically connecting at least two battery modules to each other; and a cover member surrounding a surface of the external busbar.

The cover member may include a fire resistant material or an insulating material. The first TP blocking member may include a heat resistant sheet and a pad disposed on at least one surface of the heat resistant sheet and formed of a material that is elastically deformed. The pad may have a thermal conductivity of <NUM> W/(m·K) or less. The pad may have an insulation resistance of <NUM> MΩ or more. The heat resistant sheet may include mica.

The terms used in the following description and claims are widely used common expressions selected by considering functions in various embodiments of the present disclosure. However, such terms may vary depending upon an intention of a person having ordinary skill in the art (hereinafter referred to as 'those skilled in the art'), legal/technical interpretations, or advent of new technologies. Some of the terms were selected arbitrarily by an applicant, and the terms may be interpreted as defined herein. Unless otherwise defined, the terms may be interpreted based on overall descriptions of the present disclosure and common technical knowledge in the art.

In the following description, like drawing reference numerals and symbols refer to the like elements which perform substantially the same function, even in different drawings, for convenience in explanation and for better understanding. That is, although a plurality of drawings share elements having the same reference numerals, the plurality of drawings do not relate to one embodiment.

In the following description and claims, a term including an ordinal, such as, 'first' or 'second,' may be used to distinguish elements. The ordinal is used to distinguish the same or similar elements and does not limit the meaning of the term. For instance, ordinals do not affect an order of use or an order of arrangement of elements expressed with the ordinals. Respective ordinals may be replaced with each other, if necessary.

A term in a singular form includes a plural form unless it is intentionally written that way. That is, even if a component is expressed in a singular form in this document, it should not be construed as excluding that the corresponding component is provided in plural unless otherwise specified. For example, when it is assumed that a first member is disposed on a frame in an embodiment, the embodiment is not limited to a case in which only one first member disposed on the frame but should be understood as including a case in which two or more first members are disposed on the frame.

A term, such as, 'include' or 'form,' refers to the disclosed features, numbers, steps, operations, elements, parts, or combinations thereof and is not intended to exclude any possibilities of existence or addition of one or more other features, numbers, steps, operations, elements, parts, or combinations thereof.

In this document, the X-direction, Y-direction, and Z-direction mean a direction parallel to the X-axis, a direction parallel to the Y-axis, and a direction parallel to the Z-axis illustrated in the drawings, respectively. In addition, unless otherwise specified, the X-direction is a concept including both the +X-axis direction and the -X-axis direction, which is also applied to the Y-direction and the Z-direction.

<FIG> is a perspective view of a battery pack according to an exemplary embodiment. <FIG> is an exploded perspective view of a battery pack according to an exemplary embodiment. <FIG> is an exploded perspective view of a battery module according to an exemplary embodiment.

Referring to <FIG> and <FIG>, in an exemplary embodiment, a battery pack <NUM> may include a pack housing <NUM> and a plurality of battery modules <NUM> disposed inside the pack housing <NUM>.

The pack housing <NUM> includes a pack frame <NUM> and a pack cover <NUM> coupled to an upper portion of the pack frame <NUM>. The pack frame <NUM> includes a lower plate <NUM> and a side frame <NUM> extending upwardly from the lower plate <NUM>.

At least one partition <NUM> traversing an internal space of the pack housing <NUM> vertically or horizontally may be disposed on the lower plate <NUM>. In the illustrated exemplary embodiment, a partition 113a extending in the X direction and a partition 113b extending in the Y direction are disposed to divide the inside of the pack housing <NUM> into several compartments.

At least one battery module <NUM> may be disposed in the space divided by the partition <NUM>. In the illustrated exemplary embodiment, four battery modules <NUM> are arranged in one compartment. Meanwhile, a shape of the pack housing <NUM> and the number of battery modules <NUM> are examples, and the exemplary embodiment in the present disclosure is not limited thereto. For example, the partition <NUM> may be disposed to form <NUM> or fewer or <NUM> or more compartments inside the pack. As another example, three or less or five or more battery modules <NUM> may be disposed in a single compartment.

Referring to <FIG>, in an exemplary embodiment, the battery module <NUM> includes a module case <NUM> and a plurality of battery cells accommodated in the module case <NUM>.

The module case <NUM> may be formed integrally or may be formed by coupling a plurality of cover plates. For example, <FIG> shows a structure of the battery module <NUM>, and the module case <NUM>, having a structure surrounding the lower and both side surfaces of the battery cell <NUM>, may include a lower cover plate <NUM> formed in an integral 'C' shape, an upper cover plate <NUM> covering an upper portion of the battery cell <NUM>, a front cover plate <NUM> covering a front of the battery cell <NUM>, and a rear cover plate covering a rear of the battery cell <NUM>. The shape and size of the module case <NUM> are not particularly limited and may be appropriately selected according to the purpose, the shape and number of battery cells <NUM> accommodated in the internal space.

The module case <NUM> performs a function of supporting and protecting the battery cells <NUM>, and may perform a function of supporting and protecting the battery cell <NUM>, cooling the battery cell <NUM> through water cooling or air cooling to protect the secondary battery from heat generated during charging and discharging of the battery module <NUM>, and maintaining a temperature at an appropriate level. Accordingly, the module case <NUM> is preferably formed of a material having excellent thermal conductivity, may be formed of a metal material such as aluminum, gold, pure silver, tungsten, copper, nickel, or platinum, and preferably, aluminum, but is not limited thereto.

The battery cells <NUM> accommodated in the module case <NUM> may be electrically connected to each other. Meanwhile, the number of battery cells <NUM> accommodated in the module case <NUM> may be adjusted according to purposes and is not particularly limited.

Meanwhile, the battery cell <NUM> may include an electrode assembly accommodated in a pouch-type casing, and the battery cell <NUM> according to the present disclosure may be used without limitation as long as it is commonly used. For example, the electrode assembly may include a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and a separator, and the positive electrode may be manufactured by applying a mixture of a positive electrode active material, a conductive agent, and a binder on a positive electrode current collector and drying the applied mixture. The positive electrode current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery. For example, the positive electrode current collector may be formed of stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum, or may be formed of stainless steel surface-treated with carbon, nickel, titanium, silver, etc. The current collector may have fine irregularities on a surface thereof to increase an adhesive force of the positive electrode active material, and may have various forms such as a film, sheet, foil, net, porous body, foam body, and non-woven body.

An internal busbar <NUM> electrically connected to the battery cell <NUM> may be included on a side from which an electrode lead of the battery cell <NUM> protrudes. Since the internal busbar <NUM> is formed on the side from which the electrode lead protrudes, the internal busbar may be formed on at least one of the front and rear sides of the battery cell. The internal busbar <NUM> may include a metal having excellent conductivity, for example, copper.

Referring to <FIG>, the battery modules <NUM> are electrically connected to each other through an external busbar <NUM>. The internal busbar <NUM> of the battery module <NUM> may be at least partially exposed externally of the module case <NUM> to be connected to the external busbar <NUM> connecting the battery modules <NUM> to each other.

The battery module <NUM> may include an insulating cover <NUM> covering the internal busbar <NUM> in order to protect the internal busbar <NUM> and secure insulation. The insulating cover <NUM> may be coupled to the internal busbar <NUM> with each other or by a hook. The insulating cover <NUM> may be formed of one or more selected from the group consisting of modified polypropylene oxide (MPPO), polycarbonate (PC), polyethylene (PE), and polybutylene terephthalate (PBT). As described above, the insulating cover <NUM> may be covered by the front cover plate <NUM> and the rear cover plate <NUM> constituting the module case <NUM> to configure the battery module <NUM>.

In an exemplary embodiment, the battery module <NUM> may include a first thermal propagation (TP) blocking member <NUM> disposed between cells among the plurality of battery cells <NUM>. The first TP blocking member <NUM> may be formed of a material having at least one of high heat insulation, high heat resistance, and high fire resistance. The first TP blocking member <NUM> may be configured to minimize propagation of heat generated in one battery cell to other nearby battery cells.

In an exemplary embodiment, the first TP blocking member <NUM> may be disposed between battery cell groups including two or more battery cells. For example, referring to <FIG>, the first TP blocking member <NUM> may be alternately arranged with a battery cell group including four battery cells.

The first TP blocking member <NUM> may be formed of a material including at least one of a polymer material, an inorganic material, and a ceramic material. Here, the polymer material may include, for example, a material such as a silicone-based material. Also, the inorganic material may include a material that does not contain carbon (C), for example, mica, lime, salt, silicon compounds such as glass, and some metals such as iron. The ceramic material may include a material formed of oxide, carbide, nitride, or the like formed as a metal element such as silicon (Si), aluminum (Al), titanium (Ti), zirconium (Zr) is combined with oxygen, carbon, nitrogen, and the like. These ceramic materials may be formed using natural raw materials, such as clay, kaolin, feldspar, silica, etc., or may be formed using a synthetic raw material such as silicon carbide, silicon nitride, alumina, zirconia, barium titanate, and the like.

In an exemplary embodiment, the first TP blocking member <NUM> may be coupled to the internal busbar <NUM>. For example, one end of the first TP blocking member <NUM> may be coupled to the internal busbar <NUM>. In another exemplary embodiment, the internal busbar <NUM> may be seated on an insulating plate, and the first TP blocking member <NUM> may be coupled to the insulating plate.

Meanwhile, gas inside the battery pack <NUM> may be discharged externally of the pack housing <NUM> through a vent portion <NUM> provided in the pack housing <NUM>. The vent portion <NUM> includes a vent hole <NUM> connecting the inside and the outside of the pack housing <NUM>.

If the gas generated in the battery pack <NUM> is discharged externally too slowly or if too much gas is discharged at once, flames may occur outside the battery pack <NUM>. Therefore, it is advantageous to discharge the gas occurring in the battery pack <NUM> externally of the battery pack <NUM> at an appropriate rate.

According to the exemplary embodiments described below, even if flammable gas is ejected from the battery module <NUM>, the gas may pass through the inside of the battery pack <NUM> and escape externally, without being ignited. Since the air inside the pack entirely escapes externally of the pack within a few seconds after thermal runaway, it may be difficult for a high-temperature and high-pressure gas ejected from the battery module <NUM> to mix with the air in an appropriate ratio, and accordingly, the gas may not be ignited or burnt and may be ejected externally of the pack <NUM>.

According to an exemplary embodiment, by appropriately setting a size of the vent hole <NUM>, a speed at which gas is ejected externally of the battery pack <NUM> may be relatively fast, which may prevent flames from occurring outside the battery pack <NUM>. This is because if the speed of the gas is high enough, the gas may not be sufficiently mixed with the external air, and thus, diffusion combustion may not occur. That is, the high-temperature gas inside the battery pack <NUM> may be ejected externally of the battery pack <NUM>, without being ignited.

According to an exemplary embodiment, the gas ejected after thermal runaway prevents the occurrence of flames due to a rapid increase in the gas concentration inside the battery pack <NUM>, or the discharge amount of conductive particles may be reduced due to an increase in internal pressure, thereby preventing an external short circuit or ignition.

In an exemplary embodiment, a cross-sectional area of the vent hole <NUM> may be adjusted so that the gas generated in the battery cell is not ignited. The cross-sectional area of the vent hole <NUM> refers to an area of a plane, perpendicular to a gas discharge direction. For example, when the vent hole <NUM> is provided in the form of a circular pipe having an inner radius of r, the cross-sectional area of the vent hole <NUM> is (the ratio of the circumference of a circle to its diameter)*r<NUM>. In an exemplary embodiment, when one or more vent portions <NUM> (or vent holes <NUM>) are provided, a total cross-sectional area of the vent holes <NUM> may be greater than <NUM>,<NUM><NUM> and less than or equal to <NUM>,<NUM><NUM>. In this case, the cross-sectional area may be a cross-sectional area of an outer side of the vent hole <NUM> in contact with external air. In the illustrated exemplary embodiment, two vent portions <NUM> are provided, but this is only an example, and one or three or more vent portions <NUM> may be provided.

<FIG> illustrates a vent portion according to a first exemplary embodiment. <FIG> illustrates a vent portion according to a second exemplary embodiment. <FIG> are cross-sectional views of the vent portion <NUM> taken along line II-II' in <FIG>.

Referring to <FIG>, in an exemplary embodiment, a cross-sectional area of the vent hole <NUM> of the battery pack <NUM> may be appropriately set according to the specifications of the battery pack <NUM>. The amount of gas generated inside the battery pack <NUM> per unit time depends on the quantity and chemical composition of the battery module <NUM> (or battery cells <NUM>) accommodated inside the battery pack <NUM>, and thus, in order to control a gas exhaust rate according to a design intention, it may be necessary to form the vent hole <NUM> to have different cross-sectional areas in consideration of the above factors.

In an exemplary embodiment, the vent portion <NUM> may include a gas discharge unit <NUM>. For example, when the amount of gas generated per unit time is large, the gas discharge unit <NUM> having a large vent hole <NUM> may be selected. On the contrary, when the amount of gas generated per unit time is small, the gas discharge unit <NUM> having a small vent hole <NUM> may be selected. In this case, the vent hole <NUM> includes the vent hole <NUM>.

At least one gas discharge unit <NUM> may be provided and may be coupled to one surface of the side frame <NUM> in which the vent hole <NUM> is formed. The gas discharge unit <NUM> of the present exemplary embodiment may be detachably coupled to the side frame <NUM>. Accordingly, the gas discharge unit <NUM> may be replaced by an operator as necessary.

The gas discharge unit <NUM> may be formed in a square flat plate shape and has at least one vent hole <NUM> therein.

The vent hole <NUM> is formed in the form of a through-hole and may be formed in a size smaller than the vent hole <NUM> of the side frame <NUM>. Also, the gas discharge unit <NUM> may be coupled to the side frame <NUM> such that the vent hole <NUM> overlaps the vent hole <NUM>.

Here, disposing the vent hole <NUM> to overlap the vent hole <NUM> refers to disposing the vent hole <NUM> such that at least a portion thereof is connected to the vent hole <NUM>.

The gas discharge unit <NUM> may be coupled to the side frame <NUM> through a separate fixing member such as a screw or bolt. To this end, the gas discharge unit <NUM> and the side frame <NUM> may have a fastening hole into which a fixing member is inserted. However, the present disclosure is not limited thereto, and various members may be used as long as the gas discharge unit <NUM> may be firmly coupled to one surface of the side frame <NUM>.

The operator may select the gas discharge unit <NUM> in which the vent hole <NUM> having a suitable size is formed as needed and couple the gas discharge unit <NUM> to the side frame <NUM>. For example, the gas discharge units 520a and 520b may include vent holes 530a and 530b having different sizes, respectively.

The size of the vent hole <NUM> may be defined in consideration of a type of battery cells accommodated in the battery pack <NUM> or a size of the internal space of the side frame <NUM>.

Through such a configuration, the operator may selectively couple only the gas discharge unit <NUM> to the pack housing <NUM> having the same shape, thereby completing the battery pack <NUM> including a gas outlet having a desired size.

Referring to <FIG>, in an exemplary embodiment, a plurality of gas discharge units <NUM> may be provided. For example, two or more gas discharge units 520a and 520b may be coupled to the battery pack <NUM>. A first gas discharge unit 520a is coupled to an inner surface of the side frame <NUM>, and a second gas discharge unit 520b is coupled to an outer surface of the side frame <NUM>.

When the battery pack <NUM> does not include the gas discharge unit <NUM>, pack housings in which gas outlets of various sizes are formed to correspond to the various battery cells <NUM> or the various battery modules <NUM> should be provided. In this case, the manufacturing costs may increase significantly. When the gas discharge unit <NUM> is configured to be selectively coupled as in the present exemplary embodiment, the pack housings may be manufactured collectively, which may minimize manufacturing costs.

<FIG> show a vent portion according to a third exemplary embodiment. <FIG> show a vent portion according to a fourth exemplary embodiment. <FIG> are cross-sectional views of the vent portion <NUM> taken along line II-II' in <FIG>.

Referring to <FIG>, the vent portion <NUM> has a structure in which a cross-sectional area A2 of an outlet side <NUM> connected to the external space of the pack housing <NUM> is smaller than a cross-sectional area A1 of an inlet side <NUM> connected to the internal space <NUM>.

That is, when the cross-sectional area A1 of the inlet side <NUM> is formed to be larger than the cross-sectional area A2 of the outlet side <NUM>, gas generated in the internal space may be easily discharged externally through the vent portion <NUM>, compared to a case in which the cross-sectional areas of the inlet side <NUM> and the outlet side <NUM> are maintained to be the same. Accordingly, a pressure increase inside the battery pack <NUM> is limited.

In addition, since the cross-sectional area A2 of the outlet side <NUM> is formed to be smaller than the cross-sectional area A1 of the inlet side <NUM>, the air outside the pack housing <NUM> is difficult to be introduced into the internal space <NUM> through the vent portion <NUM>.

As a result, the vent portion <NUM> according to an exemplary embodiment may effectively block inflow of external air (oxygen) without excessively increasing the pressure increase inside the battery pack <NUM>.

In an exemplary embodiment, the vent portion <NUM> may be provided in a form in which a cross-sectional area thereof decreases from the inside of the pack externally of the pack. The vent portion <NUM> may include 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 compared to the first region <NUM>. When calculating an average cross-sectional area for a predetermined length of the vent portion <NUM> based on a cut surface, perpendicular to a length direction of the vent portion <NUM>, an average cross-sectional area of the second region <NUM> may be smaller than that of the first region <NUM>.

The first region <NUM> may extend from the inlet side <NUM> to the outlet side <NUM> in the same cross-sectional shape, and the second region <NUM> extends to the outlet side <NUM> in a form in which a cross-sectional area thereof decreases, compared to the first region <NUM>.

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

In addition, when the first region <NUM> and the second region <NUM> each have a circular cross-sectional shape, the first region <NUM> of the vent portion <NUM> may have a hollow cylindrical shape with a constant diameter D1, and the second region <NUM> may have a hollow truncated cone shape having diameter decreasing toward the outlet side <NUM>.

A boundary region BA, in which a cross-sectional structure is changed, is formed between the first region <NUM> and the second region <NUM>. Whereas <FIG> and <FIG> show a boundary region BA between the first region <NUM> and the second region <NUM> in the form of a prismatic shape, <FIG> and <FIG> illustrate the embodiment in which the boundary region BA between the first region <NUM> and the second region <NUM> is connected to have a gentle curve.

In addition, the second region <NUM> may be inclined at a single inclination angle θ as illustrated in <FIG>, <FIG> or may have a structure in which the second region <NUM> is divided into two or more zones 544a and 544b in which inclination angles θa and θb in the respective regions are changed as illustrated in <FIG>. Here, the inclination angle θb in the zone 544b close to the outlet side <NUM> may be formed to be greater than the inclination angle θa in the zone 544a farther from the outlet side <NUM> so that the diameter D2 of the outlet side <NUM> is smaller than a diameter D2a of a portion located in the central portion of the second region <NUM>.

As such, when the vent portion <NUM> has a circular cross-section, the possibility of vortex or turbulence occurring in the air flowing inside the vent portion <NUM> may be reduced, compared to ab prismatic cross-section, and thus, smooth flow from the inlet side <NUM> to the outlet side <NUM> may be formed. However, in the present disclosure, the cross-sectional shape of the vent portion <NUM> may be variously modified to an oval cross-section or the like, and does not exclude a prismatic cross-sectional structure.

Also, the vent portion <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 decreases with a first inclination angle with respect to the length direction of the vent portion <NUM>, and the second region <NUM> may have a shape in which the cross-sectional area decreases with a second inclination angle greater than the first inclination angle with respect to the length direction of the vent portion <NUM>.

Meanwhile, a length L2 of the second region <NUM> may be <NUM> to <NUM> times a distance from the inlet side <NUM> to the outlet side <NUM>, that is, a total length L of the vent portion <NUM>. If the length L2 of the second region <NUM> is less than <NUM> times the total length L, the length L2 of the second region <NUM> may be excessively shortened. Accordingly, a possibility of introducing external air through the shortened second region <NUM> may be increased, and thus, an installation effect of the second region <NUM> may be reduced. Conversely, if 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 short. In this case, since the second region <NUM> having a small cross-sectional area is formed to be long, gas may not be smoothly discharged from the internal space <NUM> through the second region <NUM>, and accordingly, pressure in the internal space <NUM> of the battery pack <NUM> may be increased.

In addition, the cross-sectional area A2 of the outlet side <NUM> may be <NUM> to <NUM> times the cross-sectional area A1 of the inlet side <NUM>. If the cross-sectional area A2 of the outlet side <NUM> is less than <NUM> times the cross-sectional area A1 of the inlet side, the cross-sectional area A2 of the outlet side <NUM> may be excessively small so that gas in the internal space <NUM> of the battery pack <NUM> may not be smoothly discharged, causing a problem in that pressure inside the battery pack <NUM> increases.

Preferably, the cross-sectional area A2 of the outlet side <NUM> may be <NUM> to <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 minimizing inflow of external air using a difference between the cross-sectional areas of the inlet side <NUM> and the outlet side <NUM> may be sufficiently achieved.

Meanwhile, specific values of the cross-sectional area A1 of the inlet side <NUM> of the vent portion <NUM>, the cross-sectional area A2 of the outlet side <NUM>, the length L1 of the first region <NUM>, and the length L2 of the second region <NUM> may be determined according to a volume of the internal space <NUM> of the battery pack <NUM> and the position and shape of the vent hole.

In addition, in <FIG>, only a case in which the vent portion <NUM> has the first region <NUM> and the second region <NUM> is illustrated, but it is also possible to provide a third region having a cross-sectional shape according to the length direction of the vent portion <NUM>, different from those of the first region <NUM> and the second region <NUM>, between the first region <NUM> and the second region <NUM>. That is, 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 vent portion <NUM> may be formed in the shape of a hole in the side frame <NUM> of the pack housing <NUM> when an outer wall of the pack housing <NUM> has a sufficient thickness. That is, as illustrated in <FIG>, the vent portion <NUM> may be formed by machining a hole in which the diameter D1 of the inlet side <NUM> is greater than the diameter D2 of the outlet side <NUM> in the side frame <NUM> of the pack housing <NUM>.

Meanwhile, if the thickness of the side frame <NUM> of the pack housing <NUM> is not sufficient, at least a portion of the vent portion <NUM> may protrude outwardly of the side frame <NUM> of the pack housing <NUM> as illustrated in <FIG>. For example, when a length of the vent portion <NUM> is <NUM> and a thickness of the side frame <NUM> is <NUM>, the vent portion <NUM> may have a structure protruding outwardly of the pack housing <NUM> by <NUM>.

In addition, the vent portion <NUM> may include a venting guide member <NUM> attached to the side frame <NUM> of the pack housing <NUM>. The venting guide member <NUM> may have a shape in which the first region <NUM> and the second region <NUM> are formed, as illustrated in <FIG>. At this time, the venting guide member <NUM> may be mounted on an inner surface of a hole formed in the pack housing <NUM> and matches with the inner surface of the side frame <NUM>. Alternatively, the venting guide member <NUM> may have a shape in which only a partial region of the vent portion <NUM> is formed, as illustrated in <FIG>. At this time, the venting guide member <NUM> may have a shape attached to an outer surface of the side frame <NUM> of the venting guide member <NUM>.

In the vent portion <NUM>, the inlet side <NUM> may be positioned on the same line as the inner surface of the side frame <NUM> of the pack housing <NUM>. If the inlet side <NUM> of the vent portion <NUM> has a pipe shape protruding inwardly of the inner surface of an outer wall of the pack housing <NUM>, an eddy current or turbulence may occur in the circumference of the inlet side <NUM> protruding into the internal space <NUM> in a pipe shape. For example, assuming that the venting guide member <NUM> has a shape extending to the left in <FIG>, a phenomenon (e.g., a vortex) in which air flowing along the inner surface of the outer wall of the pack housing <NUM> does not flow directly into the inlet of the venting guide member but a flow thereof is not uniform occurs. However, when the inlet side <NUM> of the vent portion <NUM> is positioned on the same line as the inner surface of the outer wall of the pack housing <NUM> as in an exemplary embodiment in the present disclosure, gas in the internal space <NUM> may flow along the inner surface of side frame <NUM> and easily flow to the inlet side <NUM> of the vent portion <NUM> to be discharged externally, thereby effectively improving the flow of gas discharged from the pack housing <NUM>.

<FIG> is an internal cross-sectional view of a battery pack according to an exemplary embodiment. <FIG> is an internal cross-sectional view of a battery pack in which a battery module and a pack cover are coupled to an adhesive member according to an exemplary embodiment. <FIG> is an internal cross-sectional view of a battery pack in which a battery module and a pack cover are mechanically coupled according to an exemplary embodiment. <FIG> are cross-sectional views taken along line I-I' of the battery pack <NUM> in <FIG>.

Referring to <FIG>, in an exemplary embodiment, a gap between the battery module <NUM> and the pack cover <NUM> may be provided to be relatively small. In an exemplary embodiment, the gap d between the battery module <NUM> and the pack cover <NUM> may be set to <NUM> or less. That is, an air layer having a thickness of <NUM> or less may be formed between the battery module <NUM> and the pack cover <NUM>. For example, the air layer may be defined as a space between the pack cover <NUM> and the module case <NUM>.

If the gap d between the battery module <NUM> and the pack cover <NUM> is large, gas generated during thermal runaway may move to the corresponding gap d, thereby reducing a gas exhaust rate from the vent hole. According to an exemplary embodiment, as the pack cover <NUM> is positioned closer to the module case <NUM>, the volume of the empty space inside the battery pack <NUM> may be reduced, the internal pressure of the battery pack <NUM> may be quickly increased during thermal runaway, which may increase a gas ejection rate. Ignition of the gas may be prevented according to the increase of the gas ejection rate.

In addition, by maintaining the gap d between the battery module <NUM> and the pack cover <NUM> to be small, the air inside the pack may be discharged externally within a relatively short time, which may prevent the premixed combustion of gas.

When air is introduced into the battery pack <NUM>, the air may be mixed with the high-temperature and high-pressure gas discharged from the battery cell, which may lead to an occurrence of combustion and flames. Therefore, it is important to seal the inside and outside of the battery pack <NUM>. In addition, when gas leaks from a portion other than the vent portion <NUM> in a thermal runaway situation, the gas ejection rate from the vent portion <NUM> may be lowered and the gas may be ignited.

In an exemplary embodiment, a sealing member <NUM> may be disposed between the pack cover <NUM> and the pack frame <NUM>. In an exemplary embodiment, the pack frame <NUM> may include a lower plate <NUM> disposed below the plurality of battery modules <NUM> and a side frame <NUM> extending upwardly from the lower plate <NUM>, and the side frame <NUM> may be provided in the form of a side wall surrounding the plurality of battery modules <NUM>. In addition, the sealing member <NUM> may be disposed between the side frame <NUM> and the pack cover <NUM>. For example, when the edge of the pack cover <NUM> is seated on a top surface of the side frame <NUM>, the sealing member <NUM> may be applied between the edge of the pack cover <NUM> and the top surface of the side frame <NUM>. Due to the sealing member <NUM>, the entirety or most portion of the gas occurring inside the pack housing <NUM> may be discharged externally of the housing through the vent portion <NUM>, thereby ensuring a relatively high discharge rate. In addition, since air does not flow into the battery pack <NUM>, combustion of gas inside the pack may be prevented or minimized.

In an exemplary embodiment, the sealing member <NUM> may include a fire resistant material or a heat resistant material. Accordingly, even if a high-temperature gas or flame occurs inside the pack, damage to the sealing member <NUM> may be prevented or minimized, and further, sealing between the pack frame <NUM> and the pack cover <NUM> may be maintained.

Meanwhile, when the internal pressure of the battery pack <NUM> rapidly increases due to thermal runaway inside the battery pack <NUM>, the pack cover <NUM> may be deformed and the gap d between the battery module <NUM> and the pack cover <NUM> may be increased. To prevent this, in an exemplary embodiment, the pack cover <NUM> may be fixedly coupled to the battery module <NUM>. In an exemplary embodiment, the pack cover <NUM> may be fixedly coupled to some or all of the plurality of battery modules <NUM> disposed inside the pack housing <NUM>.

Referring to <FIG>, in an exemplary embodiment, an adhesive member <NUM> may be attached between the module case <NUM> and the pack cover <NUM>. The adhesive member <NUM> may include a material having excellent heat dissipation characteristics, such as thermal resin.

Referring to <FIG>, in an exemplary embodiment, the battery module <NUM> and the pack cover <NUM> may be mechanically coupled. For example, the module case <NUM> and the pack cover <NUM> may be coupled by a bolt <NUM>.

Even if an internal pressure of the battery pack <NUM> increases and the pack cover <NUM> is about to be separated from the battery module <NUM>, since the battery module <NUM> and the pack cover <NUM> are coupled to each other, the gap d between the battery module <NUM> and the pack cover may be maintained at a certain level.

Meanwhile, rigidity of the pack housing <NUM> should be improved in order to secure the gas exhaust rate. Due to the gas occurring inside the pack housing <NUM>, the internal pressure of the pack housing <NUM> may increase, and accordingly, the pack housing <NUM> may be deformed to be cracked. For example, a gap may be formed between the pack frame <NUM> and the pack cover <NUM>. In this case, the gas exhaust rate through the vent portion <NUM> may be slowed, so that the gas discharged externally of the pack may be ignited. In addition, air may be introduced from the outside of the pack housing <NUM> to the inside, which may burn the gas to accelerate heat propagation inside the battery pack <NUM>.

To solve this problem, in an exemplary embodiment, the pack cover <NUM> may be formed of a material with high rigidity. For example, the pack cover <NUM> may be formed of a steel material. As the rigidity of the pack cover <NUM> increases, deformation of the pack cover <NUM> may be suppressed, which may contribute to preventing inflow of external air into the pack housing <NUM> or quickly escaping of gas occurring inside the housing externally through the vent portion <NUM>. That is, as the rigidity of the pack cover <NUM> is improved, even if a large amount of gas occurs inside the battery pack <NUM>, the gas may be rapidly discharged through the vent portion <NUM>, and external air may be prevented from flowing into the battery pack <NUM> to delay heat propagation inside the battery pack <NUM>.

<FIG> illustrates an external busbar and a cover member according to an exemplary embodiment.

In the battery pack <NUM> including the plurality of battery modules <NUM>, when any one battery module <NUM> thermally runs, gas, flames, as well as conductive particles, may be discharged.

When the conductive particles diffuse around the external busbar <NUM>, an insulating state between the external busbar <NUM> and other members may be broken. For example, the module case <NUM> or the pack housing <NUM> may include a conductive material such as aluminum, and the external busbar <NUM> is disposed at a predetermined distance from the module case <NUM> or the pack housing <NUM>. However, if a gas containing conductive particles surrounds the periphery of the external busbar <NUM>, an insulation distance between the external busbar <NUM> and the module case <NUM> (or the pack housing <NUM>) is shortened, which may cause a short circuit between the external busbar and the module case <NUM> (or the pack housing <NUM>). Due to this, thermal runaway may spread to other battery modules inside the battery pack <NUM>. Accordingly, exposure of the external busbar <NUM> to conductive particles in a thermal runaway situation should be minimized.

In an exemplary embodiment, the external busbar <NUM> may be surrounded by the cover member <NUM> so as not to be exposed to conductive particles. The cover member <NUM> may be configured to prevent or minimize contact between the external busbar <NUM> and the conductive particles. For example, the cover member <NUM> may be provided to cover at least a portion of the surface of the external busbar <NUM>.

In an exemplary embodiment, the cover member <NUM> may be formed of a flame-retardant material or a fire-resisting insulating material. For example, the cover member <NUM> may be formed of a material that is not melted or ignited below <NUM> degrees Celsius. For example, the cover member <NUM> may include a silicon or mica material.

In an exemplary embodiment, the cover member <NUM> may be formed of a material having electrical insulating properties, such as resin. In addition, the cover member <NUM> may be formed of a material having heat resistance performance capable of maintaining a shape at a high temperature. For example, the cover member <NUM> may be formed of a resin material or a fiber composite material having heat resistance performance of <NUM> or higher.

In an exemplary embodiment, the cover member <NUM> may include a resin or a fiber composite material primarily covering the surface of the external busbar <NUM> and a flame retardant material (e.g., silicone or mica) secondarily covering the surface of the resin or fiber composite material.

<FIG> illustrates a second TP blocking member <NUM> covering the outside of the battery module <NUM> in an exemplary embodiment.

In an exemplary embodiment, the second TP blocking member <NUM> may be disposed between the battery module <NUM> and the pack cover <NUM>. When a fire occurs in the battery module <NUM>, gas, flames, dust, and conductive particles may spread to the space inside the battery pack. In an exemplary embodiment, the second TP blocking member <NUM> may be disposed in at least a portion of the outer surface of the battery module <NUM>, so that the battery module <NUM> may be protected from flames or gas ejected from the other battery module <NUM>, which may prevent a chain ignition or thermal runaway.

The second TP blocking member <NUM> may be formed of a flame-retardant material or a fire-resisting insulating material capable of blocking the propagation of flames. In the present exemplary embodiment, the second TP blocking member <NUM> may be formed of a material that does not melt or ignite below <NUM> degrees Celsius. In addition, in order to increase the heat resistance performance, the second TP blocking member <NUM> may be formed by forming a plate having a thickness of <NUM> or more. However, the configuration of the present disclosure is not limited thereto.

In an exemplary embodiment, the second TP blocking member <NUM> may be formed to cover an upper portion and a side portion of the battery module <NUM>. The second TP blocking member <NUM> may be coupled to each battery module <NUM> in the form of at least partially covering the battery module <NUM> to suppress the spread of flames or conductive particles. The second TP blocking member <NUM> may include a top cover <NUM> disposed at an upper portion of the battery module <NUM> and a side cover <NUM> extending from the top cover <NUM> to face both side surfaces of the battery module <NUM>.

<FIG> is an example of a TP blocking member disposed between battery cells according to an exemplary embodiment.

In an exemplary embodiment, the first TP blocking member <NUM> may include a heat resistant sheet <NUM> and a pad <NUM> disposed on at least one surface of the heat resistant sheet <NUM>. The heat resistant sheet <NUM> may include a material having excellent heat resistance and/or fire resistance. For example, the heat resistant sheet <NUM> may include mica. Since the heat resistant sheet <NUM> maintains its original shape relatively well even in high heat or flames, the first TP blocking member <NUM> may block or delay heat transfer more stably.

The pad <NUM> may be formed of an elastically deformable material. Since the heat resistant sheet <NUM> has relatively high rigidity, if the heat resistant sheet <NUM> directly touches the battery cells, the battery cells may be damaged. The pad <NUM> may be disposed on the battery cell together with the heat resistant sheet <NUM> and may be compressed when the battery cells are pressed against each other in a stacking direction. Accordingly, the pad <NUM> may prevent damage to the battery cells and make a pressing force applied to one surface of the battery cells uniform. For example, if a portion of a battery cell becomes convex due to swelling, stress may be concentrated in the corresponding portion, and in this case, the pad <NUM> may be compressed in response to the deformation of the battery cell and may make the pressure applied to one surface of the battery cell uniform.

In an exemplary embodiment, the pad <NUM> may include a material having a relatively lower thermal conductivity than the heat resistant sheet <NUM>. For example, the pad <NUM> may be formed of a material having a thermal conductivity of <NUM> W/(m·K) or less when measured according to the ISO <NUM> standard. In an exemplary embodiment, the pad <NUM> includes an insulating material. For example, insulation resistance of the pad <NUM>, when measured according to ASTM D257 standard, may be <NUM> megaohms (MΩ) or more.

Claim 1:
A battery pack (<NUM>) comprising:
a pack housing (<NUM>);
at least one battery module (<NUM>) disposed inside the pack housing; and
a vent hole (<NUM>) connecting inside and outside of the pack housing,
wherein the battery module includes a plurality of battery cells (<NUM>) and a first thermal propagation blocking member (<NUM>) disposed between the plurality of battery cells,
wherein the vent hole is formed so that a cross-sectional area (A2) of an outlet side (<NUM>) connected to an external space of the pack housing is smaller than a cross-sectional area (A1) of an inlet side (<NUM>) connected to an internal space (<NUM>) of the pack housing, and
wherein the vent hole includes:
a first region (<NUM>) connected to the inlet side (<NUM>) of the pack housing,
a second region (<NUM>) connected to the outlet side (<NUM>) of the pack housing and having a relatively small cross-sectional shape compared to the first region (<NUM>), wherein the second region (<NUM>) extends to the outlet side (<NUM>) in a form in which a cross-sectional area thereof decreases, and
a boundary region (BA) located between the first region and the second region, connecting the first region and the second region to have a curve.