WO2007097594A1

WO2007097594A1 - Middle and large-sized battery pack of excellent cooling efficiency

Info

Publication number: WO2007097594A1
Application number: PCT/KR2007/000962
Authority: WO
Inventors: Junill Yoon; Jongmoon Yoon; Jaesung Ahn
Original assignee: Lg Chem, Ltd.
Priority date: 2006-02-27
Filing date: 2007-02-24
Publication date: 2007-08-30
Also published as: KR20070088994A; CN101401228B; TW200805736A; JP5718549B2; TWI340490B; KR100948003B1; CN101401228A; JP2009528652A; JP2015111578A

Abstract

Disclosed herein is a middle- or large-sized battery pack comprising a battery module including a plurality of unit modules horizontally stacked while each unit module is vertically erected on one side, the battery module being mounted in a sealed space of a housing member, wherein the housing member is provided at the upper or lower end of one side thereof with a coolant inlet port and at the lower or upper end of the opposite side thereof with a coolant outlet port, the battery module is mounted in the housing member such that the upper or lower end surface of the battery module is tilted toward the coolant inlet port by a predetermined angle, whereby a coolant introduced through the coolant inlet port in parallel with the battery module passes perpendicularly through the unit modules and is then discharged to the opposite side, and gaps (vertical flow channels) defined between the unit modules at the tilted upper or lower end surface of the battery module are arranged in parallel with the direction in which the coolant is introduced, whereby the cooling efficiency and the cooling uniformity of the battery pack are improved while the battery pack has a compact structure.

Description

MIDDLE AND LARGE-SIZED BATTERY PACK OF EXCELLENT COOLING EFFICIENCY

Technical Field

[1] The present invention relates to a middle- or large-sized battery pack with high cooling efficiency, and, more particularly, to a middle- or large-sized battery pack comprising a battery module including a plurality of unit modules horizontally stacked while each unit module is vertically erected on one side, the battery module being mounted in a sealed space of a housing member, wherein the housing member is provided at the upper or lower end of one side thereof with a coolant inlet port and at the lower or upper end of the opposite side thereof with a coolant outlet port, the battery module is mounted in the housing member such that the upper or lower end surface of the battery module is tilted toward the coolant inlet port by a predetermined angle, whereby a coolant introduced through the coolant inlet port in parallel with the battery module passes perpendicularly through the unit modules and is then discharged to the opposite side, and gaps (vertical flow channels) defined between the unit modules at the tilted upper or lower end surface of the battery module are arranged in parallel with the direction in which the coolant is introduced, whereby the cooling efficiency and the cooling uniformity of the battery pack are improved while the battery pack has a compact structure. Background Art

[2] One of the biggest problems caused from vehicles using fossil fuel, such as gasoline and diesel oil, is creation of air pollution. A technology for using a secondary battery, which can be charged and discharged, as a power source for vehicles has attracted considerable attention as one method of solving the above-mentioned problem. As a result, electric vehicles (EV), which are operated using only a battery, and hybrid electric vehicles (HEV), which jointly use a battery and a conventional engine, have been developed. Some of the electric vehicles and the hybrid electric vehicles are now being commercially used. A nickel-metal hydride (Ni-MH) secondary battery has been mainly used as the power source for the electric vehicles (EV) and the hybrid electric vehicles (HEV). In recent years, however, the use of a lithium-ion secondary battery has been attempted.

[3] High output and large capacity are needed for such a secondary battery to be used as the power source for the electric vehicles (EV) and the hybrid electric vehicles (HEV). To this end, a plurality of small-sized secondary batteries (unit cells) are connected in series or in parallel with each other so as to constitute a battery module, and a plurality of battery modules are connected in parallel or in series with each other so as to constitute a battery pack.

[4] In such a high-output, large-capacity secondary battery, however, a large amount of heat is generated from the unit cells during the charge and the discharge of the unit cells. When the heat generated from the unit cells during the charge and the discharge of the unit cells is not effectively removed, heat is accumulated in the unit cells with the result that the unit cells are degraded. Consequently, it is necessary to provide a cooling system for cooling a vehicle battery pack, which is a high-output, large- capacity secondary battery.

[5] One of points to be duly considered when installing a cooling system is to minimize the increase in volume of a battery pack due to the cooling system. Generally, a coolant flow channel is formed such that a coolant flows along the outer surface of a battery module and also flows through the interior of the battery module to improve the cooling efficiency of the cooling system. However, the structure of the coolant flow channel is very complex and is a factor increasing the volume of the battery pack. For this reason, a tilted flow channel is formed at a portion of the battery module such that the flow of a coolant can be guided in a tilted fashion as shown in FIG. 1.

[6] Referring to FIG. 1, a battery pack cooling system 1 includes a battery module 2 comprising a plurality of batteries, a coolant inlet port 3 mounted at the lower end of the battery module 2 in a tilted fashion, and a coolant outlet port 4 mounted at the upper end of the battery module 2 in a tilted fashion. The battery module 2 comprises a plurality of unit modules 5 electrically connected with each other such that the unit modules 5 are horizontally stacked while each unit module 5 is vertically erected on one side. Each unit module 5 comprises a plurality of secondary batteries 6 electrically connected with each other. Between the respective secondary batteries 6 of each unit module 5 are formed small gaps, through which a coolant flows. Consequently, a coolant introduced through the coolant inlet port 3 flows along the flow channel to remove heat generated from the respective secondary batteries 6, and is then discharged through the coolant outlet port 4 mounted at the upper end of the battery module 2.

[7] However, the battery pack cooling system 1 constructed as shown in FIG. 1 has the following problems.

[8] First, since the coolant inlet port 3 and the coolant outlet port 4 are mounted at the lower and upper ends of the battery module 2, respectively, in the form of a duct, the height of the battery pack increases by the size of the ducts. Specifically, a lower duct whose width is gradually decreased from the coolant inlet port 3 is mounted at a rectangular lower part of the battery module 2, and an upper duct whose width is gradually increased toward the coolant outlet port 4 is mounted at a rectangular upper part of the battery module 2. For this reason, additional spaces for mounting the upper and lower ducts are needed. When the battery module 2, which comprises the unit modules 5 horizontally stacked while each unit module 5 is vertically erected on one side, is installed in a limited inner space of a vehicle, the increased height of the battery pack cooling system acts as a serious obstacle factor.

[9] Consequently, various technologies have been developed for constructing a cooling system such that a coolant flow channel is formed as shown in FIG. 1 while maximally utilizing a space used to mount the battery module and the surroundings.

[10] In this connection, Japanese Patent Application Publication No. 2004-22317 and

Korean Patent Application Publication No. 2005-35478 disclose a cooling system of a middle- or large-sized battery pack characterized in that a battery module is mounted in a pack case while the battery module itself is tilted a predetermined angle such that a coolant flow channel is formed in the battery pack without the provision of ducts for introducing and discharging a coolant. Also, Japanese Patent Application Publication No. 2004-22317 discloses a technology for mounting a plurality of unit cells in a housing of a small-sized battery module, while tilting the unit cells by a predetermined angle, to form a coolant flow channel. In the disclosed cooling systems, a desired coolant flow channel is formed maximally utilizing the inner space of the pack case in which the battery module is mounted or the housing of the battery module. Consequently, the disclosed cooling systems suggest a possibility of manufacturing a battery pack having a smaller size than the duct structure as shown in FIG. 1.

[11] However, the disclosed cooling systems have the following problems in the aspect of the operation efficiency like the structure of FIG. 1.

[12] Specifically, a coolant introduced through a coolant inlet port collides perpendicularly against the outer surfaces of the unit modules or the secondary batteries, and is then introduced into a coolant flow channel defined between the respective unit modules or a coolant flow channel defined between secondary batteries (unit cells) constituting each unit module. Since the coolant collides perpendicularly against the outer surfaces of the unit modules, and is then introduced into the coolant flow channel, it is possible to improve the cooling efficiency through the formation of whirlpools. In a battery module including a plurality of unit modules (or secondary batteries) stacked with high integration, however, the coolant, which is a fluid, runs into high flow resistance. Consequently, when the unit modules (or the secondary batteries) are arranged at further decreased intervals to reduce the total size of the battery pack with the result that the coolant flow channel narrows, it is necessary for a coolant driving source (for example, a blowing fan) to generate a higher driving force necessary to increase the flow speed of the coolant. [13] Also, the coolant inlet port is formed in the longitudinal direction of the unit modules (or the secondary batteries). In a battery module for a middle- or large-sized battery pack constructed in a structure in which a plurality of unit modules (or secondary batteries) are stacked to provide high output and large capacity with the result that the width of the battery module is greater than the length of each unit module, therefore, the cooling nonuniformity of the battery pack is very high. Specifically, the absolute amount of a coolant introduced to a unit module (or a secondary battery) the most adjacent to the coolant inlet port is less than that of a coolant introduced to a unit module (or a secondary battery) the most distant from the coolant inlet. As a result, the cooling nonuniformity of the battery pack is high, which is further serious in the above-described structure having high flow resistance.

[14] Consequently, there is high necessity for a technology of fundamentally solving the above-mentioned problems. Disclosure of Invention Technical Problem

[15] Therefore, the present invention has been made to solve the above-mentioned problems, and other technical problems that have yet to be resolved.

[16] Specifically, it is an object of the present invention to provide a battery pack constructed in a structure in which a battery module is mounted in a housing member such that the battery module is tilted by a predetermined angle, whereby a naturally tilted flow channel is formed in a gap defined between the housing member and the upper end surface of the battery module and a gap defined between the housing member and the lower end surface of the battery module, and therefore, the battery pack has a compact structure without the increase of the height thereof due to a cooling structure such as a duct.

[17] It is another object of the present invention to provide a battery pack constructed in a structure in which gaps defined between unit modules are arranged in parallel with the direction in which a coolant is introduced, whereby the supply of the coolant to the battery module is effectively accomplished, and the amount of the coolant supplied to respective sections of the battery module is uniform, whereby the cooling efficiency and the cooling uniformity of the battery pack are improved.

[18] It is a further object of the present invention to provide a battery pack constructed in a structure in which the shape of a lower end frame constituting the battery pack coincides with the internal structure of a vehicle, whereby the battery pack is more stably mounted in the vehicle. Technical Solution

[19] In accordance with the present invention, the above and other objects can be ac- complished by the provision of a middle- or large-sized battery pack comprising a battery module including a plurality of unit modules horizontally stacked while each unit module is vertically erected on one side, the battery module being mounted in a sealed space of a housing member, wherein the housing member is provided at the upper or lower end of one side thereof with a coolant inlet port and at the lower or upper end of the opposite side thereof with a coolant outlet port, the battery module is mounted in the housing member such that the upper or lower end surface of the battery module is tilted toward the coolant inlet port by a predetermined angle, whereby a coolant introduced through the coolant inlet port in parallel with the battery module passes perpendicularly through the unit modules and is then discharged to the opposite side, and gaps (vertical flow channels) defined between the unit modules at the tilted upper or lower end surface of the battery module are arranged in parallel with the direction in which the coolant is introduced.

[20] As described above, the battery pack according to the present invention is constructed in a structure in which a battery module including a plurality of unit modules electrically connected with each other or two or more battery modules are mounted in the housing member.

[21] Each unit module may be a battery cell that can be charged and discharged or a combination of two or more battery cells.

[22] In the specification, the terms "electrical connection" and "combination" mean the connection of unit modules or battery cells in series and/or in parallel with each other to provide a battery pack having desired output and capacity, preferably high output and large capacity. For example, each battery cell includes cathodes, anodes, separators, and an electrolyte, and each battery cell is mounted in a sealed container such that each battery cell can be charged and discharged. Preferably, each battery cell may be a lithium- ion battery cell, a lithium- ion polymer battery cell, or a nickel-metal hydride battery cell.

[23] In the battery pack according to the present invention, the coolant inlet port is formed at the upper or lower end of one side of the housing member in parallel with the gaps (the vertical flow channels) between the tilted unit modules as described above. Consequently, the coolant inlet port is formed in the long side of a middle- or large-sized battery module including a plurality of stacked unit modules.

[24] Generally, the length of the long side of a battery module including a plurality of unit modules is restricted by the number of the used unit modules. For example, on the assumption that rectangular unit modules are used, the length of each unit module is a, the width of each unit module is b, the thickness of each unit module is c, and the number of the used unit modules is x, a battery module constructed by stacking the unit modules to the number of x while the unit modules are in tight contact with each other is formed in the shape of a hexahedron having sides the lengths of which are a and c x x and a height of b.

[25] This relationship will be described in more detail with reference to FIG. 2, which illustrates a battery module according to a preferred embodiment of the present invention. Referring to FIG. 2, a battery module 20 includes unit modules 10 the number of which is x. On the assumption that the length of each unit module is a, the width of each unit module is b, and the thickness of each unit module is c, it is necessary to stack the unit modules such that the lengths of sides of the battery module satisfy the following inequality: a < c x x for high output and large capacity. In this case, the length of the long side of the battery module is c x x.

[26] According to the present invention, the coolant inlet port is located at one side of the housing member parallel with the gaps (the vertical flow channels) between the unit modules, and therefore, the coolant inlet port is formed at a position corresponding to the long side (c x x) of the battery module.

[27] This structure provides various effects. First, the flow resistance, caused when the coolant is introduced into the vertical flow channels between the unit modules, decreases, and therefore, the cooling efficiency of the battery module increases. Secondly, the length between the coolant inlet port and the section of each vertical flow channel the most distant from the coolant inlet port is decreased, and therefore, the cooling uniformity of the battery module increases. Thirdly, the coolant inlet port is formed in the shape of a series of through-holes corresponding to the length of the long side of the battery module, and therefore, the flow of the coolant is possible by a small driving force.

[28] In connection with the first effect, the coolant horizontally introduced through the coolant inlet port formed in one side of the housing member is naturally introduced into the vertical flow channels (the gaps between the respective unit modules) formed in parallel with the direction in which the coolant is introduced. Consequently, the flow resistance greatly decreases. From a macroscopic viewpoint, the coolant flows perpendicularly through the respective unit modules. From a microscopic viewpoint, on the other hand, a flowing gradient is exhibited in which the coolant is gradually lowered from the coolant inlet port. Consequently, the flow resistance of the coolant decreases, and therefore, the cooling efficiency is maximized even using a small driving force.

[29] In connection with the second effect, the distance between the coolant inlet port and the section of each vertical flow channel the most distant from the coolant inlet port is restricted by the length a of each unit module. As a result, the distance between the coolant inlet port and the section of each vertical flow channel the most distant from the coolant inlet port is very small when considering the fact that the distance between the coolant inlet port and a section of each vertical flow channel of a con- ventional battery module increases depending upon the length of the long side of the battery module. Consequently, it is possible to greatly decrease the cooling nonuniformity at the section of each vertical flow channel the most distant form the coolant inlet port.

[30] In connection with the third effect, the through-holes constituting the coolant inlet port increase the amount of coolant introduced per unit time, and therefore, the flow of the coolant is possible by a small driving force. At the same time, it is possible to uniformly distribute the coolant over a large area of the battery module. To this end, it may be considered to provide a structure in which the coolant inlet port is formed directly in the upper end of the housing member facing the upper end surface of the battery module. In this case, however, the total volume of the battery pack is inevitably increased to secure a space at the outside of the housing member corresponding to the coolant inlet port. Consequently, the above-mentioned structure is not preferable.

[31] Preferably, the coolant outlet port is formed in the side opposite to the coolant inlet port side such that the coolant introduced through the coolant inlet port can be discharged after the coolant passes through the unit modules. For example, the coolant inlet port may be formed in one side adjacent to the upper end edge of the housing member in the shape of a series of through-holes, and the coolant outlet port may be formed in at least one side of the lower end of the housing member. More specifically, when the coolant inlet port is formed in the upper end of the left side of the housing member, the coolant outlet port may be formed in the lower end of the right side thereof or the lower ends of the opposite sides such that the coolant outlet port is in parallel with each other. Here, the sides of the housing member in which the coolant inlet port and the coolant outlet port are formed may be changed depending upon the direction in which the battery module is tilted. For example, when both the coolant inlet port and the coolant outlet port are formed in the left side of the housing member, the battery module is mounted such that the upper end of the battery module is tilted toward the left side of the housing member.

[32] Preferably, a cooling fan (blowing fan) is mounted in the coolant outlet port for generating a driving force necessary for the flow of the coolant.

[33] Preferably, the battery module is tilted by an angle of 1 to 40 degrees. When the tilt angle of the battery module is too small, the size of the coolant inlet port decreases, and therefore, it is difficult to increase the amount of the coolant introduced per unit time. When the tilt angle of the battery module is too large, on the other hand, the tilted disposition of the battery module may be unstable when external impacts are applied to the battery module, which is not preferable. More preferably, the battery module is tilted by an angle of 1.5 to 15 degrees.

[34] In a preferred embodiment, the battery module is mounted on a frame having a pair of supporting parts which protrude upward while being spaced apart from each other to support opposite sides of the lower end of the battery module, and the housing member is coupled with the frame such that the housing member surrounds some or all of the outer surfaces of the battery module except the lower end surface of the battery module to seal the battery module.

[35] Preferably, the supporting parts protrude perpendicularly in the direction in which the coolant is introduced through the coolant inlet port such that the opposite sides of the battery module can be supported by the supporting parts, respectively. Specifically, the supporting parts continuously protrude upward along the direction in which the unit modules are horizontally stacked while each unit module is vertically erected on one side such that the supporting parts support opposite sides of the lower ends of the stacked unit modules.

[36] The frame may be formed into a shape in which the fame can be united with the internal structure of a vehicle. For example, when the internal structure of the vehicle includes ridges and valleys for alleviating external impacts applied to the vehicle, the supporting parts of the frame may be fixed to the ridges of the internal structure of the vehicle. The details thereof are disclosed in Korean Patent Application No. 2005-99871, which has been filed in the name of the applicant of the present patent application. The disclosure of the above-mentioned patent application is hereby incorporated by reference as if fully set forth herein.

[37] As an example of a method of tilting the housing member and the upper and lower end surfaces of the battery module by a predetermined angle, it is possible to change the protruding heights of the supporting parts of the frame such that the supporting parts have different heights. Brief Description of the Drawings

[38] The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[39] FIG. 1 is a perspective view illustrating a conventional cooling system;

[40] FIG. 2 is a perspective view illustrating a battery module according to a preferred embodiment of the present invention;

[41] FIG. 3 is a perspective view illustrating a battery pack according to a preferred embodiment of the present invention; and

[42] FIG. 4 is a front see-through view of FIG. 3.

[43]

[44] <Description of Main Reference Numerals of the Drawings>

[45] 100: battery pack 10: unit module [46] 20: battery module 30: frame

[47] 40: housing member

Mode for the Invention

[48] Now, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. It should be noted, however, that the scope of the present invention is not limited by the illustrated embodiment.

[49] FIG. 3 is a perspective view illustrating a battery pack according to a preferred embodiment of the present invention, and FIG. 4 is a front see-through view of FIG. 3.

[50] Referring to these drawings, a battery pack 100 includes a battery module 20 constructed in a structure in which a plurality of unit modules 10 are electrically connected with each other such that the unit modules 10 are horizontally stacked while each unit module 10 is vertically erected on one side, a frame 30 having a pair of supporting parts 33 and 34 which protrude upward while being spaced apart from each other to support opposite sides of the lower end of the battery module 20, and a housing member 40 having a coolant inlet port 45 formed in the upper end of the left side thereof and a coolant outlet port (not shown) formed in the lower end of the right side thereof in parallel with the coolant inlet port 45. The housing member 40 is coupled to the frame 30 such that the housing member 40 surrounds the battery module 20.

[51] The battery module 20 is tilted toward the coolant inlet port 45 by a predetermined angle due to the pair of supporting parts 33 and 34 protruding with different heights from the frame 30. Consequently, a gap defined between the housing member 40 and the upper end surface 21 of the battery module 20 is tilted, and a gap defined between the housing member 40 and the lower end surface 22 of the battery module 20 is tilted, whereby a coolant flow channel is naturally formed by the tilt.

[52] A coolant introduced through the coolant inlet port flows along gaps defined between the respective unit modules 10 arranged in parallel with the direction in which the coolant is introduced, i.e., along vertical flow channels 26, and is then discharged through the coolant outlet port (not shown). As a result, large flow resistance, which occurs in the structure of FIG. 1, does not occur when the coolant is introduced into the vertical flow channels 26, and therefore, the cooling efficiency of the battery pack increases. Consequently, as shown in FIG. 3, the coolant flows along the vertical flow channelswith a gentle tilt.

[53] Also, since the coolant inlet port 45 is formed in the upper end of the left side of the housing member 40 in parallel with the vertical flow channels 26, the distance between the coolant inlet port 45 and a section A of each vertical flow channel 26 the most distant from the coolant inlet port 45 is restricted by the length of each unit module 10. Consequently, it is possible to greatly decrease the cooling nonuniformity, which is caused by the increase in distance between the coolant inlet port 45 and the section of each vertical flow channel the most distant form the coolant inlet port 45. [54] Although the preferred embodiment of the present invention has been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Industrial Applicability

[55] As apparent from the above description, the battery pack according to the present invention is constructed in a structure in which the battery module is mounted in the housing member such that the battery module is tilted by a predetermined angle, whereby a naturally tilted flow channel is formed in a gap defined between the housing member and the upper end surface of the battery module and a gap defined between the housing member and the lower end surface of the battery module. Consequently, the battery pack according to the present invention has a compact structure without the increase of the height thereof due to the cooling structure. In addition, the gaps (the vertical flow channels) between the unit modules are arranged in parallel with the direction in which the coolant is introduced. Consequently, the supply of the coolant to the battery module is effectively accomplished. Furthermore, the distance between the coolant inlet port and the section of each vertical flow channel the most distant from the coolant inlet port is restricted by the length of each unit module. Consequently, the amount of the coolant supplied to the respective sections of the battery module is uniform, and therefore, the cooling uniformity of the battery pack is improved. Also, the battery pack according to the present invention may be modified such that the shape of the lower end frame constituting the battery pack coincides with the internal structure of a vehicle. Consequently, the battery pack according to the present invention is more stably mounted in the vehicle.

Claims

[1] A middle- or large-sized battery pack comprising a battery module including a plurality of unit modules horizontally stacked while each unit module is vertically erected on one side, the battery module being mounted in a sealed space of a housing member, wherein the housing member is provided at the upper or lower end of one side thereof with a coolant inlet port and at the lower or upper end of the opposite side thereof with a coolant outlet port, the battery module is mounted in the housing member such that the upper or lower end surface of the battery module is tilted toward the coolant inlet port by a predetermined angle, whereby a coolant introduced through the coolant inlet port in parallel with the battery module passes perpendicularly through the unit modules and is then discharged to the opposite side, and gaps (vertical flow channels) defined between the unit modules at the tilted upper or lower end surface of the battery module are arranged in parallel with the direction in which the coolant is introduced.

[2] The battery pack according to claim 1, wherein each unit module is a battery cell that can be charged and discharged or a combination of two or more battery cells.

[3] The battery pack according to claim 1, wherein the coolant inlet port is formed in the long side of a middle- or large-sized battery module including a plurality of stacked unit modules.

[4] The battery pack according to claim 3, wherein when the length of each unit module is a, the width of each unit module is b, the thickness of each unit module is c, the battery module is constructed by stacking unit modules to the number of x such that the lengths of the sides satisfy the following inequality: a < c x x, and the coolant inlet port is formed in the housing member at a position corresponding to the c x x side.

[5] The battery pack according to claim 1, further comprising: a cooling fan (blowing fan) mounted in the coolant outlet port for generating a driving force necessary for the flow of the coolant.

[6] The battery pack according to claim 1, wherein the battery module is tilted by an angle of 1 to 40 degrees.

[7] The battery pack according to claim 1, wherein the coolant inlet port is formed in one side adjacent to the upper end edge of the housing member in the shape of a series of through-holes, and the coolant outlet port is formed in at least one side of the lower end of the housing member.

[8] The battery pack according to claim 7, wherein the battery module is mounted on a frame having a pair of supporting parts which protrude upward while being spaced apart from each other to support opposite sides of the lower end of the battery module, the supporting parts protrude perpendicularly in the direction in which the coolant is introduced through the coolant inlet port, and the frame is coupled to the housing member to seal the battery module.

[9] The battery pack according to claim 8, wherein the frame is formed into a shape in which the frame can be united with the internal structure of a vehicle.