This application claims the benefit of priority based on Korean Patent Application No.
10-2022-0124981 filed on September 30, 2022, and Korean Patent Application No. 10-2023-
0026246 filed on February 27, 2023, entire content disclosed in the document of the patent
applications is included as a part of this specification.
The present invention relates to sealing structure of a liquid injection port of a battery can,
a battery cell to which the same is applied, a manufacturing method of the battery cell, a battery
pack including the battery cell, and a vehicle equipped with the battery pack.
[BACKGROUND ART]
A cylindrical battery cell is a structure wherein a jelly-roll shaped electrode assembly is
accommodated in a cylindrical metal can, and is more robust to shock and temperature than a
pouch-type battery. Accordingly, the demand for using metal can-type cells as battery cells
applied to vehicle battery packs is increasing.
The process of manufacturing a battery cell using a cylindrical can includes deep drawing
a metal sheet to form a circular bottom and a circular tube-shaped sidewall member connected to
the circular bottom, accommodating the electrode assembly in the can, and covering the open
end of the sidewall member with a cap.
Crimping or seam welding may be applied to a structure wherein the open end of the
battery can is covered with a cap and the cap and the battery can are fixed.
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Referring to Figure 1, crimping is a method of fixing the cap 40 by physically pressing
the edge of the cap 40 to the open end of the can 10 with the gasket 91 interposed therebetween.
Since crimping is a physical fixing method without applying heat, crimping may be performed
with the electrolyte solution filled in the can. Therefore, the crimping method is advantageous in
that separate liquid injection port structure and sealing structure thereof are not required.
However, since crimping is structurally more complex than welding, there are limits in securing
the internal volume of the can that accommodates the electrode assembly 20.
Contrarily, as shown in FIG. 2, seam welding is a process of bringing the perimeter of the
tip of the sidewall portion 11 of the battery can 10 into contact with the perimeter of the edge of
the cap 40 and welding the same along the circumferential direction of the cap 40 such that more
volume of the electrode assembly that may be accommodated in the battery can is secured due to
the simplicity of the fixing structure of the cap 40. Therefore, the seam welding is more
advantageous in securing electric capacity with respect to the volume of battery can.
However, when welding is performed by filling the battery can with an electrolyte
solution and then covering the open end of the battery can with a cap, there is a possibility that
the electrolyte solution may deteriorate or ignite due to the high-temperature generated by
welding.
During the seam welding, for example, the surface temperature may rise up to 1400
degrees Celsius which is the melting point of SUS when the battery can and the cap are made of
SUS. Such high-temperature heat may cause ignition of the electrolyte solution.
Thus, when the cap is to be fixed by subjecting the perimeter of the open end of the
battery can and cap to seam welding, a method may be applied wherein a battery can 10
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provided with a liquid injection port at the bottom portion or a cap 40 provided with a liquid
injection port 42 are prepared; the electrolyte solution is injected through the liquid injection port
42 provided at the cap or the bottom portion of the battery can after accommodating the
electrode assembly in the battery can and seam-welding the battery can 10 and the cap; and
closing and sealing and the liquid injection port after completing the liquid injection.
A battery cell comprising:
a can (10) with one open end;
an electrode assembly (20) accommodated in the can (10);
a cap (40) covering the open end of the can (10);
a liquid injection port (42) provided at the can (10) or the cap (40);
a closing member (50) inserted in the liquid injection port (42); and
a sealing and fixing material (52) fixing the closing member (50) inserted in the liquid
injection port (42), within the liquid injection port (42), wherein
the liquid injection port (42) has a perforated section extending in a first direction
crossing outside and inside of the battery cell, and has a cross-section defined by an intersection
of an imaginary plane extending in a second direction intersecting the first direction and an inner
circumferential surface of the liquid injection port (42),
the closing member (50) extends in the first direction, and has a cross-section defined by
an intersection of the imaginary plane extending in the second direction and an outer
circumferential surface thereof,
at least a portion of the closing member (50) in the first direction is disposed within the
perforated section of the liquid injection port (42),
the sealing and fixing material (52) is interposed between the inner circumferential
surface of the liquid injection port (42) and the outer circumferential surface of the closing
member (50) in the second direction,
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the sealing and fixing material (52) seals a space between the inner circumferential
surface of the liquid injection port (42) and the outer circumferential surface of the closing
member (50) to provide a sealed section corresponding to at least a portion of the perforated
section in the first direction and fixes the closing member (50) within the injection port (42), and
the sealing and fixing material (52) has a melting point lower than that of the can (10) or
the cap (40) where the liquid injection port (42) is provided and the melting point of the closing
member (50).
[Claim 2]
The battery cell of claim 1, wherein a minimum cross-section of the liquid injection port
(42) is smaller than a maximum cross-section of the closing member (50), and is disposed further
inward the sealed section in the first direction.
[Claim 3]
The battery cell of claim 1, wherein the liquid injection port (42) is defined by an inner
circumferential surface of a circular tube (48) extending from the can (10) or the cap (40) in the
first direction.
[Claim 4]
The battery cell of claim 3, wherein an inner end of the circular tube (48) in the first
direction extends in the axial direction to be inserted in a core hollow portion (29) of the
electrode assembly (20).