KR100627397B1 - Secondary battery module - Google Patents

Abstract

The present invention is to improve the structure of the safety valve of the secondary battery to extend the life of the secondary battery module, including a safety valve which is open at a predetermined pressure and a secondary battery module including a plurality of unit cells arranged at regular intervals The safety valve installed in the unit cell provides a secondary battery module having a different breaking strength according to the position of the unit cell.

Secondary Battery, Secondary Battery Module, Safety Valve, Breaking Strength

Description

Secondary Battery Module {SECONDARY BATTERY MODULE}

1 is a side cross-sectional view showing a unit cell according to the present invention.

Figure 2 is a perspective view showing a part of the lead portion and the bent plate according to the present invention.

The present invention relates to a secondary battery module, and more particularly, to a secondary battery module having an improved structure of a safety valve of a secondary battery.

Recently, a high output secondary battery using a high energy density nonaqueous electrolyte has been developed, and a plurality of high output secondary batteries can be connected in series to be used for driving a motor such as an electric vehicle, which requires a large power. The secondary battery is configured.

As described above, one large capacity secondary battery (hereinafter, referred to as a 'battery module' for convenience of description throughout the specification) is commonly referred to as a plurality of secondary batteries (hereinafter referred to as 'unit cells' for convenience of description throughout the specification). Each unit cell includes an electrode assembly having a positive electrode plate and a negative electrode plate disposed with a separator interposed therebetween, a case having a space part in which the electrode assembly is embedded, and coupled to the case to seal the electrode plate; And a cap assembly with terminals that are electrically connected.

In addition, the cap assembly further includes a safety device that prevents explosion of the battery by releasing gas by breaking under a set pressure condition in addition to a gasket for sealing an external terminal and a case electrically connected to the electrode plate of the electrode group.

That is, when the unit battery is overcharged or exposed at high temperature, gas is generated due to the reaction between the electrolyte and the active material layer of the battery unit or the decomposition reaction of the electrolyte and the active material layer itself. The gas may cause the battery to ignite or explode. And a safety valve is installed in the cap assembly to prevent this risk.

In addition, each unit cell is usually arranged in a predetermined interval in the housing and connects the terminals of each unit cell to form a battery module.

Here, the battery module electrically connects a plurality of unit cells, and has a structure in which a plurality of unit cells are connected to one battery module for stability of the battery module.

That is, a plurality of unit cells are arranged in a row, two end plates are disposed at the outermost side of the plurality of cells, and the unit cells in which the end plates are arranged in line are closely contacted inward.

At this time, the unit cell positioned at the outermost side receives the greatest pressure by the pressing force of the end plate, and the pressure acting toward the inner side decreases.

Therefore, since the greatest pressure acts on the outermost unit cell, the internal pressure of the unit cell is easily increased relative to the inner unit cell, so that the safety valve of the outermost unit cell is broken first. .

In addition, in this case, even if the battery module has not sufficiently reached its end of life, there is a problem in that the safety valve of the unit cell located at the outermost side is broken so that the entire battery module cannot be used.

Therefore, the present invention has been made to solve the above problems, an object of the present invention is to provide a battery module with improved lifespan by improving the safety valve of the unit cells installed in the battery module.

In order to achieve the above object, the present invention is set so that the breaking strength of the safety valve is different depending on the position of each unit cell disposed in the battery module.

To this end, in the battery module of the present invention, a plurality of unit cells in which a cap plate including a safety valve is installed is arranged in a line, and the breakage strength of the safety valve installed in the outermost unit cell is greatest.

Here, the unit cell includes an electrode assembly having a positive electrode plate and a negative electrode plate interposed therebetween, a case having a space part in which the electrode assembly is embedded, and a terminal coupled to the case to seal the terminal plate and electrically connected to the electrode plate. And a cap assembly provided.

In addition, the cap assembly further includes a safety valve that prevents the battery from being exploded by releasing the gas by breaking under a set pressure condition in addition to the gasket sealing the external terminal and the case.

In addition, the unit cells have a structure in which the positive electrode terminal and the negative electrode terminal are alternately arranged between the adjacent unit cells in a structure connected in series to form a battery module.

In addition, the breaking strength of the safety valve of the unit cell may gradually increase from the center of the battery module to the outside.

Here, the breaking strength of the safety valve can be adjusted by modifying the strength of the material constituting the safety valve, the thickness of the safety valve, the thickness of the groove formed in the safety valve, and the like.

Here, the secondary battery module is a device that operates by using a motor such as a hybrid electric vehicle (HEV), an electric vehicle (EV), a wireless cleaner, an electric bicycle, an electric scooter, and the like, and is used as an energy source for driving a motor of the device. Can be used.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view of a rechargeable battery according to an exemplary embodiment of the present invention.

Hereinafter, the present invention will be described with respect to the rectangular secondary battery, but is not limited thereto and may be applied to various structures such as a cylindrical battery.

Looking at the structure of each unit cell 50 constituting a large-capacity battery module 100 with reference to the above drawings, the unit cell 50 is the positive electrode plate 11 and the negative electrode plate 12 between the separator (13) A case 14 having an electrode assembly 10 positioned at an inner side and a space in which the electrode assembly 10 is embedded, a cap assembly 30 coupled to the case 14 to seal the cap assembly 30, and the positive electrode plate 11. And a positive electrode terminal 32 and a negative electrode terminal 33 that are electrically connected to the current collector 20 of the negative electrode plate 14 and protrude out of the cap assembly 30, and are installed in the cap assembly 30. It includes a safety valve 36 that breaks as the pressure rises.

The case 14 is made of a conductive metal such as aluminum, an aluminum alloy or nickel plated steel, and the shape is made of a cube or other shape having an internal space part in which the electrode group 10 is located.

In the present embodiment, the electrode group 10 is a jelly formed by winding the vortex in the state in which the positive electrode plate 11 and the negative electrode plate 12, each of which is coated on the current collector and laminated with the separator 13 interposed therebetween. It is made of a roll type, and the plain portion 11a of the positive electrode plate and the plain portion 12a of the negative electrode plate are disposed opposite to both ends of the electrode group 10, and the case 14 is vertically raised so that the cap assembly 30 can be turned upside down. It is installed so that the uncoated portions (11a, 12a) of the electrode group 10 is located on both sides of the case 14 relative to when placed in the downward direction, and the uncoated portions of both ends of the electrode group 10 ( The positive and negative terminals 32 and 33 of the cap assembly 30 are electrically connected to each other via the tabs 20 (or current collector plates) respectively installed at 11a and 12a.

And more specifically, the cap assembly 30 is secured to the center of the cap plate 31 and the cap plate 31 are coupled to the airtight state on the top of the case 14 via a gasket. The valve 36 is provided.

In addition, an opening 38 is formed at the center of the cap plate 31, and a safety valve 36 is installed at the opening 38, and the safety valve 36 may be broken under a predetermined internal pressure condition. It is formed into a plate shape so that.

In addition, the safety valve 36 is formed in a convexly curved shape toward the outside, and can be formed in a structure that can be easily broken at a predetermined pressure by forming a thin groove 37 in the edge of the curved portion. have.

Therefore, the breaking pressure of the safety valve can be adjusted according to the thickness of the groove 37, and the thicker the groove 37 can withstand high internal pressure.

However, the structure of the safety valve 36 is only one embodiment of the present invention, the present invention is not particularly limited to the structure of the safety valve 36, the characteristics of the unit cell 50 and the unit cell accordingly It may be variously modified according to the pressure resistance condition of 50.

2 is a plan view illustrating a rechargeable battery module 100 according to an exemplary embodiment of the present invention.

Referring to the drawings, the battery module will be described. A plurality of unit cells 50 are stacked to form a battery assembly, and end plates 61 are arranged on both side ends of the battery assembly.

In addition, a connecting rod 65 connecting the end plates 61 is inserted into the end plate 61, and a nut 68 is coupled to an end of the connecting rod 65 to fasten the end plate 61. As a result, the unit cells 50 are pressurized.

The battery assembly has a structure in which a battery partition 64 is disposed between the unit cells 50 to maintain a gap between the unit cells 50 and to distribute cooling air.

Here, the safety valves installed in the unit cells are formed to have different breaking strengths.

Particularly, as shown in FIG. 2, when the outer side portion II is a predetermined length from both side ends in the longitudinal direction of the battery module 100, and the outer side portion II is the center portion I, the center portion ( The breakdown strength of the safety valve 36 of the unit cell 50 arranged in I) and the safety valve 36 of the unit cell 50 arranged in the outer part II may be different.

Here, the safety valves 36 installed on the unit cells 50 disposed on both outer side portions II are formed of a thick plate, and the safety valves 36 installed on the unit cells 50 disposed on the center portion I. ) May be formed of a relatively thin plate, so that the breaking strength is different.

Alternatively, the thickness of the plate forming the safety valve 36 may be kept constant, but the breaking strength of the safety valve 36 may be adjusted by adjusting the thickness of the recess 37 formed in the safety valve 36. By varying the kind of material constituting the safety valve 36, a breaking material of the safety valve can be adjusted by using a material having a high strength on the outside and a material having a low strength on the inside.

However, in various safety valves 36 applied to a unit cell, a method of adjusting the breaking strength is not limited, and the breaking strength of the safety valve 36 may be adjusted by a generally known method.

In the battery module of the above structure, the unit cells 50 located in the outer portion (II) is subjected to a relatively large pressing force, the unit cells 50 located in the central portion (I) is subjected to a relatively small pressing force, safety As the breaking strength of the valve 36 is different, the safety valve 36 of the unit cells 50 disposed on the outer part II withstands a relatively large pressure, so that the unit cell disposed on the central part I is not broken early. It may break at a time similar to the safety valve 36 of the 50.

In the case of the secondary battery module 100 for HEV (hybrid electric vehicle), the breaking strength of the safety valve 36 installed in each unit cell 50 is about 8 kg / cm 2 to 9 kg / cm 2 for the outer part II. In the case of the central portion (I), it is preferable to form the 5kg / ㎠ to 7kg / ㎠.

Here, if the breaking strength of the safety valve 36 of the unit cell 50 installed in the outer part (II) is 9 kg / cm 2 or more, there is a risk of excessive accumulation of gas inside the unit cell and an explosion, and the breaking strength is 8 kg. If it is / cm 2 or less, the safety valve 36 may break early due to external pressure.

In addition, when the breaking strength of the safety valve 36 of the unit cell 50 provided in the center portion I is set to 7 kg / cm 2 or more, the unit cell 50 is excessively expanded and a large stress is applied to the end plate 61. There is a risk that the end plate 61 is damaged by the action, and if formed below 5kg / ㎠, there is a risk that the safety valve 36 can be easily broken even if the unit cell 50 is slightly expanded.

The safety valve 36 may be formed to gradually increase the breaking strength of the safety valve 36 as the safety valve 36 is installed in the unit cell 50 disposed from the center to the outside in the longitudinal direction of the battery module 100.

Here, the safety valves 36 of the unit cells 50 may be formed such that the thickness of the safety valves 36 gradually increases as they are installed in the unit cells disposed from the center to the outside in the longitudinal direction of the battery module.

Accordingly, the unit cells 50 may increase the breaking strength of the safety valve 36 as the breakdown strength of the safety valve 36 gradually increases from the center to the outside in the longitudinal direction of the battery module. Can be.

In the battery module 100 having such a structure, the end plate 61 installed on the outside presses the unit cells 50 to the inside, and the pressing force acting on the unit cell 50 gradually increases from the center to the outside, and accordingly safety Breakage strength of the valve 36 is formed to gradually increase toward the outside to prevent any one of the safety valve 36 of the unit cell 50 installed in the battery module 100 is broken early, There is an advantage that can extend the life of the battery module 100 sufficiently.

In addition, if the groove 37 is formed in the safety valve 36 in addition to the method of gradually increasing the overall thickness of the safety valve 36, the breaking strength of the safety valve 36 by gradually increasing the thickness of the groove 37. May be gradually increased, and a method of gradually increasing the strength of the material constituting the safety valve 36 may also be applied.

Hereinafter, the operation of the present invention will be described.

First, the secondary battery module 100 is configured by arranging the plurality of unit cells 50 in a row and attaching end plates 61 to the outermost sides of the unit cells 50 to fix the unit cells 50 inwardly. At this time, the pressing force acting on the unit cells 50 gradually decreases from the outside to the center and the largest pressing force acts on the outermost side.

In addition, when gas is generated inside the battery using the secondary battery module 100 for a predetermined period of time, the unit cell 50 disposed at the outermost side receiving the greatest pressing force has the largest internal pressure.

At this time, as the unit cells 50 are disposed from the center to the outside in the longitudinal direction of the secondary battery module 100, the breaking strength of the safety valve 36 installed in the unit cell 50 is increased at a predetermined ratio, and disposed outside. Even when a large internal pressure is applied to the unit cell 50, the breaking strength of the safety valve 36 is set relatively large so that the safety valve 36 is not easily broken, and a plurality of secondary battery modules 100 are installed in one secondary battery module 100. The safety valve 36 can be broken at about the same time.

The secondary battery of the present invention is a device that operates by using a motor such as a hybrid electric vehicle (HEV), an electric vehicle (EV), a wireless cleaner, an electric bicycle, an electric scooter, and the like, and is used as an energy source for driving a motor of the device. Can be used.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to

As described above, according to the exemplary embodiment of the present invention, the breaking strength of the unit cell safety valve positioned outside the battery module is greater than that of the safety valve of the unit cell positioned at the center of the battery module. The safety valve does not break prematurely and can extend the life of the battery module.

Claims (9)

In the secondary battery module comprising a plurality of unit cells having a safety valve that opens at a predetermined pressure, In the longitudinal direction of the secondary battery module when a predetermined length from both side ends as the outer side and the middle portion between the outer portion, Breaking strength of the safety valve of the unit cell disposed in the outer portion of the battery module is 8kg / ㎠ to 9㎏ / ㎠, Breaking strength of the safety valve of the unit cell disposed in the center of the battery module is 5kg / ㎠ to 7㎏ / ㎠, The secondary battery module of the safety valve is gradually increased as the safety valve is installed in the unit cell disposed from the center to the outside in the longitudinal direction of the secondary battery module. delete delete delete delete The secondary battery module of claim 1, wherein the recesses of the safety valves installed in the unit cells have different thicknesses according to positions of the unit cells. The method of claim 1, wherein the safety valve is formed in a convexly curved shape toward the outside, and has a structure that can be easily broken at a predetermined pressure by forming a concave portion with a thin thickness at the edge of the curved portion, The concave portion of the secondary battery module gradually increases in thickness as it is installed in the unit cell disposed on the outside in the longitudinal direction of the secondary battery module. The secondary battery module of claim 1, wherein the safety valves installed in the unit cells have different materials forming the safety valve according to a position of the unit cell. The secondary battery module of claim 1, wherein the safety valve is formed of a material having a greater strength as it is installed in a unit cell disposed at an outer side in the longitudinal direction of the secondary battery module.

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