[Technical Field]
This application claims priority to and the benefit of Korean Patent
Application No. 10-2020-0041436 filed in the Korean Intellectual Property Office
on April 06, 2020, and Korean Patent Application No. 10-2021-0044214 filed in
the Korean Intellectual Property Office on April 05, 2021, the entire contents of
10 which are incorporated herein by reference.
The present invention relates to a secondary battery and a device
including the same, and in particular, it relates to a secondary battery for
improving safety in a high-temperature and high-pressure environment, and a
device including the same.
15 [Background Art]
Recently, a demand for portable electronic products such as laptop
computers, video cameras, mobile phones, and the like is rapidly increasing,
and development of electric vehicles, energy storage batteries, robots, and
satellites is active, thus many researches on secondary batteries used as a
20 driving power source therefor have been performed.
The electrode assembly installed in a battery case is a generating
element that is configured with a stacked structure including a positive electrode,
a separation membrane, and a negative electrode and that may be repeatedly
2
charged and discharged, and it is classified into a jelly roll type, a stack type, and
a stack/folding type. The jelly roll type is a structure obtained by interposing a
separation membrane between long sheet type positive and negative electrodes
coated with an active material and then winding it, and the stack type is a
5 structure in which a plurality of positive and negative electrodes with a
predetermined size are sequentially stacked while a separation membrane is
interposed therebetween, while the stack/folding type is a mixed structure ofthe
jelly roll type and the stack type. Among them, the jelly roll type of electrode
assembly has high merits of easy manufacturing and high energy density per
10 unit weight.
The secondary battery is classified into a cylindrical battery in which an
electrode assembly is installed in a cylindrical metal can, a square-shaped
battery in which an electrode assembly is installed in a square-shaped metal can,
and a pouch-type battery in which an electrode assembly is installed in a
15 pouch-type case of an aluminum laminate sheet according to shapes of the
battery case. Among them, the cylindrical battery has a merit that it has
relatively high capacity and has a stable structure.
The secondary battery includes, for example, a nickel cadmium battery,
a nickel hydrogen battery, a nickel zinc battery, and a lithium secondary battery.
20 Among them, compared to the nickel-based secondary battery, the lithium
secondary battery scarcely generates a memory effect so it is freely charged and
discharged, a self-discharging rate is very low, an operation voltage is high, and
an energy density per unit weight is high, which are merits, so it is widely used in
the cutting-edge electronic device field.
3
However, when the lithium secondary battery is exposed to a high
temperature environment or when a high current flows within a short time by an
overcharge, external short-circuit, nail penetration, or local damage, there is a
risk of the battery being heated by generation of IR heat and occurrence of an
5 explosion. That is, when the pressure or temperature of the battery rises, the
decomposition reaction of the active material and the many side reactions
proceed, thereby rapidly raising the temperature of the battery, which further
accelerates the reaction between the electrolyte and the electrode. Eventually,
a thermal runaway phenomenon occurs in which the temperature of the battery
10 increases sharply, thereby resulting in ignition of the battery, and the lithium
secondary battery explodes due to the internal pressure of the battery.
Therefore, various methods for effectively controlling the lithium
secondary battery when it is in abnormal operations such as a high temperature
or a high pressure have been in discussion. A method for installing an element
15 outside a cell and a method for using a material inside the cell are used to
secure safety, and a safety vent using a change of an internal pressure of the
battery corresponds to the former case.
A conventional cylindrical secondary battery including a safety vent will
now be described with reference to FIG. 1 and FIG. 2.
20 FIG. 1 shows a partial cross-sectional view of an upper portion of a
conventional cylindrical secondary battery.
Referring to FIG. 1, a jelly roll type of electrode assembly 50 is received
into a cylindrical case 20, and a cap assembly 30 is installed to an opened upper
portion of the cylindrical case 20 thereby manufacturing a cylindrical secondary
4
battery 10.
The cap assembly 30 includes an upper cap 31 and an safety vent 32
reducing internal pressure, and the upper cap 31 may be closely attached to the
internal pressure reducing safety vent 32.
5 The safety vent 32 may be electrically connected to an electrode
assembly 50 through a current interrupt device (CID) 60. An edge of the
current interrupt device 60 may be surrounded by a CID gasket 70.
FIG. 2 shows a partial cross-sectional view when an internal pressure of
a cylindrical secondary battery of FIG. 1 increases.
10 Referring to FIG. 2, when the cylindrical secondary battery 10 is exposed
to a high temperature or heat is generated therein to increase its internal
pressure, a shape of the safety vent 32 is reversed, and the current interrupt
device 60 is separated into two portions to interrupt a current. In this instance,
the CID gasket 70 may be positioned between the safety vent 32 and the current
15 interrupt device 60 to prevent the safety vent 32 and the current interrupt device
60 separated from each other from conducting to each other.
However, the CID gasket 70 may be melted in a high-temperature and
high-pressure environment. In detail, as shown in FIG. 2, part of the CID
gasket 70 may be melted, and the current interrupt device 60 ascended by the
20 internal pressure may contact the safety vent 32, so the current may not be
interrupted and a reconnection may be generated. As the current is not
interrupted, the temperature may continue to increase, which may result in
ignition and explosion of the cylindrical secondary battery 10.
Therefore, when a melting is generated in the high-temperature and
5
high-pressure environment, there is a need to develop a CID gasket with a high
heat-deflection temperature so as to maintain an insulating characteristic.
[Detailed description of the invention]
[Technical Problem]
5 The present invention has been made in an effort to provide a secondary
battery for improving safety in a high temperature and high pressure
environment, and a device including the same.
However, the objective of the present invention is not limited to the
aforementioned one, and may be extended in various ways within the spirit and
10 scope of the present invention.
[Technical Solution]
An embodiment of the present invention provides a secondary battery
including: a current interrupt device (CID); a safety vent disposed on the current
interrupt device and electrically connected to the current interrupt device; and a
15 CID gasket for surrounding an edge of the current interrupt device, wherein the
CID gasket includes reinforcement material, and the reinforcement material
includes at least one of glass fiber, carbon fiber, aramid fiber, cellulose, ceramic
particles, and a filler.
The CID gasket may include a first portion for surrounding an edge of the
20 current interrupt device and a second portion disposed on the first portion and
extending in a center direction of the current interrupt device.
The second portion may extend between the safety vent and the current
interrupt device.
6
The CID gasket may include a polymer resin, and the polymer resin may
include at least one of polypropylene (PP), polyethylene terephthalate (PET),
polybutylene terephthalate (PBT), and perfluoroalkoxy alkane (PFA).
The CID gasket may include a polymer resin, and the polymer resin may
5 include polybutylene terephthalate (PBT).
The current interrupt device may include an exterior circumference
portion and an interrupter surrounded by the exterior circumference portion, and
when an internal pressure of the secondary battery rises, the interrupter may be
separated from the exterior circumference portion.
10 The safety vent may be electrically connected to the interrupter.
The secondary battery may further include an electrode assembly
including a positive electrode, a negative electrode, and a separation membrane,
wherein the exterior circumference portion may be electrically connected to the
positive electrode through a positive electrode tab.
15 The secondary battery may further include an upper cap disposed on the
safety vent and electrically connected to the safety vent.
The secondary battery may further include a cylindrical case.
[Advantageous effects]
The CID gasket according to the embodiments of the present invention
20 includes reinforcement material, and as thermal resistance and heat-deflection
temperature increase, the insulating characteristic may be maintained when
melting is generated in the high-temperature and high-pressure environment.
Accordingly, the safety-improved secondary battery may be manufactured.
[Description of the Drawings]
7
FIG. 1 shows a partial cross-sectional view of an upper portion of a
conventional cylindrical secondary battery.
FIG. 2 shows a partial cross-sectional view when an internal pressure of
a cylindrical secondary battery of FIG. 1 increases.
5 FIG. 3 shows a partial cross-sectional view of an upper portion of a
secondary battery according to an embodiment of the present invention.
FIG. 4 shows a partial cross-sectional view when an internal pressure of
a secondary battery of FIG. 3 increases.
FIG. 5 to FIG. 8 show graphs on estimation results of external
10 short-circuit according to an embodiment 1, an embodiment 2, a comparative
example 1, and a comparative example 2.
FIG. 9 to FIG. 12 show graphs on estimation results of external
short-circuit according to an embodiment 3, an embodiment 4, a comparative
example 3, and a comparative example 4.
15 FIG. 13 to FIG. 16 sequentially show photographs of aCT image after a
current interrupt device is separated, an upper cap, and a sealing gasket
according to an embodiment 3, an embodiment 4, a comparative example 3, and
a comparative example 4.
FIG. 17 and FIG. 18 shows graphs on estimation results of external
20 short-circuit according to an embodiment 5 and an embodiment 6.
[Mode for Invention]
The present invention will be described more fully hereinafter with
reference to the accompanying drawings, in which embodiments of the invention
are shown. As those skilled in the art would realize, the described
8
embodiments may be modified in various different ways, all without departing
from the spirit or scope of the present disclosure.
Parts that are irrelevant to the description will be omitted to clearly
describe the present invention, and the same elements will be designated by the
5 same reference numerals throughout the specification.
Parts that are irrelevant to the description are omitted to clearly describe
the present disclosure, and like reference numerals designate like elements
throughout the specification. In the drawings, the thickness of layers, films,
panels, regions, etc., are exaggerated for clarity. For ease of description, the
10 thicknesses of some layers and areas are exaggerated.
It will be understood that when an element such as a layer, film, region,
or substrate is referred to as being "on" another element, it can be directly on the
other element or intervening elements may also be present. In contrast, when
an element is referred to as being "directly on" another element, there are no
15 intervening elements present. Further, in the specification, the word "on" or
"above" means disposed on or below the object portion, and does not
necessarily mean disposed on the upper side of the object portion based on a
gravitational direction.
Unless explicitly described to the contrary, the word "comprise" and
20 variations such as "comprises" or "comprising" will be understood to imply the
inclusion of stated elements but not the exclusion of any other elements.
Further, throughout the specification, the phrase "in a plan view" means
viewing a target portion from the top, and the phrase "in a cross-sectional view"
means viewing a cross-section formed by vertically cutting a target portion from
9
the side.
FIG. 3 shows a partial cross-sectional view of an upper portion of a
secondary battery according to an embodiment of the present invention.
Referring to FIG. 3, the secondary battery 100 according to an
5 embodiment of the present invention may be manufactured by inserting the
electrode assembly 500 into the cylindrical case 200, injecting an electrolyte
solution into the same, and mounting a cap assembly 300 on the opened upper
portion of the cylindrical case.
The electrode assembly 500 is a jelly roll type of structure in which a
10 separation membrane 530 is provided between a positive electrode 510 and a
negative electrode 520 and is wound, and a center pin (not shown) may be
inserted into its center. The center pin is generally made of a metal material to
give predetermined strength, and it is configured with a hollow cylindrical
structure in which a plate is circularly bent. The center pin may fix and support
15 the electrode assembly 500 and may function as a passage for outputting gas
generated by an inner reaction at a time of charging and discharging and during
operation.
The cap assembly 300 includes an upper cap 310 and a safety vent 320,
and the upper cap 310 may be positioned on the safety vent 320 and may form a
20 mutually closely attached structure with the safety vent 320 to be thus electrically
connected to each other. The upper cap 310 has a center protruding upward,
and it may be electrically connected to the positive electrode 510 of the
electrode assembly 500 and may function as a positive electrode terminal for
access to an external circuit. In detail, the upper cap 310 may be indirectly
10
connected to the positive electrode 510 through a safety vent 320, a current
interrupt device 600, and a positive electrode tab 511.
The cylindrical case 200 may include a beading unit 210 and a crimping
unit 220.
5 The beading unit 210 indicates a portion of the cylindrical case 200
indented in a center direction of the electrode assembly 500, which is to allow
stable combination of the cap assembly 300 and prevent movement of the
electrode assembly 500.
The crimping unit 220 is positioned on an upper portion of the beading
10 unit 210 to surround the cap assembly 300, which is for stable combination of
the cap assembly 300. A sealing gasket 400 is installed inside the crimping unit
220 and the beading unit 210 to increase a sealing force between the cap
assembly 300 and the cylindrical case 200. That is, the crimping unit 220 is
formed by positioning the sealing gasket 400 between the cylindrical case 200
15 and the cap assembly 300 and bending an end of the cylindrical case 200. By
this, the installation of the cap assembly 300 and the sealing of the secondary
battery 1 00 may be performed.
Although not shown in detail, a negative electrode tab connected to the
negative electrode 520 of the electrode assembly 500 may be bonded to the
20 cylindrical case 200. Hence, the cylindrical case 200 may function as a
negative electrode terminal for access with an external circuit.
In addition, the current interrupt device (CID) 600 and the CID gasket
700 are positioned below the safety vent 320. This will now be described in
detail.
11
The secondary battery 100 according to the present embodiment
includes: a current interrupt device 600, a safety vent 320 positioned on the
current interrupt device 600 and electrically connected to the current interrupt
device 600, and a CID gasket 700 for surrounding an edge of the current
5 interrupt device 600. The CID gasket 700 may include reinforcement material,
and the reinforcement material may include at least one of glass fiber, carbon
fiber, aramid fiber, cellulose, ceramic particles, and a filler.
The safety vent 320 is a thin-film structure to which a current flows, and
in which two grooves 321 and 322 with different depths are formed.
10 The current interrupt device 600 is a member of a conductive plate, and
may include an exterior circumference portion 610 and an interrupter 620
surrounded by the exterior circumference portion 610. Further, although not
shown in detail, a plurality of via holes for discharging gas may be formed. For
separation between the exterior circumference portion 610 and the interrupter
15 620, a boundary between the exterior circumference portion 610 and the
interrupter 620 may be designed to have relatively weak strength.
The CID gasket 700 may include a first portion 710 for surrounding an
edge of the current interrupt device 600, and a second portion 720 positioned on
the first portion 710 and extending in a center direction of the current interrupt
20 device 600. In detail, the second portion 720 may extend between the safety
vent 320 and the current interrupt device 600.
FIG. 4 shows a partial cross-sectional view when an internal pressure of
a secondary battery of FIG. 3 increases. In detail, it shows that the safety vent
320 and the current interrupt device 600 interrupt the current when an internal
12
pressure of the secondary battery 100 rises.
Referring to FIG. 3 and FIG. 4, the exterior circumference portion 610
may be electrically connected to the positive electrode 510 of the electrode
assembly 500 through the positive electrode tab 511, and the interrupter 620
5 may be electrically connected to the safety vent 320. There are no limits in this
electrical connection method, and they may be connected by welding. When
the secondary battery 1 00 is normally operated, the positive electrode tab 511 ,
the current interrupt device 600, the safety vent 320, and the upper cap 310 are
electrically connected to each other, so the secondary battery 100 is connected
10 to an external circuit.
However, when pressurizing gas is applied to the safety vent 320 by the
increase of pressure inside the secondary battery 100, the shape of the safety
vent 320 is reversed. Accordingly, as shown in FIG. 4, the interrupter 620 is
separated from the exterior circumference portion 610, and an electrical
15 connection between the external circuit and the electrode assembly 500 is
blocked. According to this, when the secondary battery 100 is exposed to a
high temperature or heat is generated therein to increase the internal pressure,
explosion or ignition thereof may be prevented.
In this instance, the second portion 720 of the CID gasket 700 extends
20 between the safety vent 320 and the exterior circumference portion 610 to
prevent the safety vent 320 from contacting the exterior circumference portion
610. That is, by preventing the safety vent 320 from contacting the exterior
circumference portion 610 after the exterior circumference portion 610 is
separated from the interrupter 620, a reconnection, that is, a flowing of the
13
current, may be blocked.
As described above, there were some cases in the past that the CID
gasket was melted or changed to fail to block the contact of the safety vent 320
and the exterior circumference portion 610.
5 Differing from this, the CID gasket 700 according to an embodiment of
the present invention includes reinforcement material and may increase heat
resistance and a heat-deflection temperature. Hence, insulation may be
maintained by blocking the contact of the safety vent 320 and the exterior
circumference portion 610 in a high-temperature and high-pressure environment.
10 The reinforcement material according to the present embodiment may include at
least one of glass fiber, carbon fiber, aramid fiber, cellulose, ceramic particles,
and a filler, and particularly, it is preferable to include the glass fiber.
The CID gasket 700 includes a polymer resin, and it may be
manufactured by injection molding. The polymer resin may include at least one
15 of polypropylene (PP), polyethylene terephthalate (PET), polybutylene
terephthalate (PBT), and perfluoroalkoxy alkane (PFA). Among them, it may
include polybutylene terephthalate (PBT).
A super-engineering plastic material such as polyphenylene sulfide
(PPS) has great rigidity, so when the corresponding material is included,
20 formability is not good, and when the reinforcement material is added to the
corresponding material, a worse influence may be applied to the formability.
On the contrary, the material such as polybutylene terephthalate (PBT) or
polypropylene (PP) is an elastomer with excellent elasticity, and when the
material is included, an injecting property is improved so it is easy to form the
14
CID gasket 700. In other words, in a like way to the present embodiment, when
a polymer resin such as polypropylene (PP) or polybutylene terephthalate (PBT)
is included, the formability and flexibility of the CID gasket 700 may be obtained,
thereby easing the injection molding and increasing the contacting property to
5 the current interrupt device 600.
On the other hand, when the safety vent 320 is operable, the
temperature and the pressure inside the secondary battery 100 may be
frequently steeply increased according to a decomposition reaction of an active
material and a plurality of side reactions, and the CID gasket 700 is directly
10 exposed to the high-temperature and high-pressure gas. The CID gasket 700
needs to have heat resistance while not requiring a sealing property like the
sealing gasket 400. The CID gasket 700 according to the present embodiment
may include a polymer resin such as polypropylene (PP) or polybutylene
terephthalate (PBT) to obtain formability and flexibility, and may simultaneously
15 include reinforcement material such as glass fiber to maintain the insulating
characteristic in the high-temperature and high-pressure environment.
According to an embodiment of the present invention, a mass of the
reinforcement material vs. a mass of the CID gasket 700 may be equal to or
greater than 15% to 50%, and more preferably, 25% to 40%. For example, the
20 CID gasket 700 may include polybutylene terephthalate (PBT) and glass fiber,
and the mass of the glass fiber vs. the entire mass of the CID gasket including
the PBT and the glass fiber may be equal to or greater than 15% and equal to or
less than 50%.
When the mass of the reinforcement material vs. the mass of the CID
15
gasket 700 is less than 15%, the heat resistance and the heat-deflection
temperature of the CID gasket 700 may be not increased as much as desired.
As a result, the contacting of the safety vent 320 and the exterior circumference
portion 610 may not be intercepted and a reconnection may be generated after
5 the current interrupt device 600 is separated. In another way, a plurality of the
secondary batteries 100 may configure a battery pack, and in this instance, it
may be preferable for the mass of the reinforcement material vs. the mass of the
CID gasket 700 to be equal to or greater than 25%. When the mass of the
reinforcement material vs. the mass of the CID gasket 700 is less than 25% in
10 the battery pack unit, the CID gasket 700 may fail to endure the heat and the
pressure inside the battery pack and may be melted. A reconnection may be
generated, which may lead to a thermal runaway or an explosion of the battery
pack.
In addition, when the mass of the reinforcement material vs. the mass of
15 the CID gasket 700 is greater than 50%, formability of the CID gasket 700 may
be hindered. The CID gasket 700 may be manufactured by adding the
reinforcement material to a polymer resin such as PBT and performing injection
molding, and when the mass of the reinforcement material is greater than 50%, it
may have more rigidity than is needed, and the injection molding may not be
20 properly performed.
The CID gasket according to the present invention will now be described
with reference to a detailed embodiment and a comparative example.
Estimation Example 1: Measurement of heat-deflection temperature
(Table 1)
16
PBT+GF
Heat characteristics PBT
30%
Heat-deflection temperature (°C) at 0.45MPa 220 150
Heat-deflection temperature (°C) at 1.8MPa 200 60
Upper working temperature ("C) 120-200 120
Melting temperature ("C) 225 223
Table 1 shows an experimental group and a comparison group of the
present invention, comparing heat characteristics of aCID gasket including PBT
and glass fiber (GF) and a gasket including PBT. In the case of the CID gasket
5 including PBT and glass fiber, the mass of the glass fiber vs. the mass of the CID
gasket is 30%.
Referring to Table 1, it is found that the melting points of the respective
materials are similar to each other, but in the case of adding glass fiber, the
heat-deflection temperature is substantially increased. Particularly, in the case
10 of the heat-deflection temperature measured at 1.8MPa, values of the respective
materials have a big difference. It is found from this that heat resistance of the
CID gasket is improved by an addition of glass fiber.
Estimation Example 2: External short-circuit estimation
Embodiments 1 and 2 and comparative examples 1 and 2 are provided,
15 and an external short-circuit estimation is performed.
In detail, a CID gasket including PBT and glass fiber is applied to a
18650 cylindrical battery to provide embodiments 1 and 2, and a CID gasket
including PBT is applied to a 18650 cylindrical battery to provide comparative
17
examples 1 and 2. Regarding the embodiments 1 and 2, the mass of glass
fiber vs. the mass of the CID gasket is 30%.
In the case of the external short-circuit estimation, external lines are
connected to positive and negative terminals of a cylindrical battery with
5 predetermined resistance, and a conduct of the cylindrical battery is determined.
In the estimation example 2, external resistance of 25m0 is applied to
the cylindrical batteries according to embodiments 1 and 2 and comparative
examples 1 and 2 to determine conducts of the respective cylindrical batteries.
In detail, current values and voltage values of the cylindrical batteries, and
10 temperatures of the CID gasket, are measured with respect to time, and the
measured values are expressed in FIG. 5 to FIG. 8 and Table 2. FIG. 5 to FIG.
8 show graphs on estimation results of external short-circuit according to an
embodiment 1, an embodiment 2, a comparative example 1, and a comparative
example 2. Table 2 is a summary of results of the graphs.
15 In addition, it is measured whether a reconnection is generated after a
separation of the current interrupt device (CID) in the external short-circuit
estimation.
(Table 2)
Resistance
CID
Max. temp afterCID
separating Notes
(oC) separation
time (sec)
(mQ)
Embodiment 35.3 109 00 No reconnection
18
1
Embodiment
37.1 109 00 No reconnection
2
Comparative
40.6 120 00 No reconnection
Example 1
Comparative
40.6 117 00 No reconnection
Example 2
Referring to FIG. 5 to FIG. 8 and Table 2, a time for the current value and
the voltage value of the cylindrical battery to be steeply reduced and approach to
0 in the graph represents a time for the current interrupt device (CID) to be
5 separated as the internal pressure increases and for the current and the voltage
to be intercepted. It is found that the current interrupt device is separated in the
middle range of 30 seconds (sec) in the case of the embodiments 1 and 2, and
the current interrupt device is separated after 40 seconds (sec) in the case of the
comparative examples 1 and 2. Further, the maximum temperature (Max.
10 temp) of the cylindrical battery is measured to be high in the cases of the
comparative examples 1 and 2.
To review reasons thereof, it is found that, while the external short-circuit
estimation is progressed, the temperature and the pressure inside the cylindrical
battery are increased, and hence, the current interrupt device must be separated
15 and opened, and in the case of the comparative example 1 and 2, the CID
gasket fails to function as a supporter but is thermally deflected, so a time for
separating the current interrupt device is delayed, and the maximum
19
temperature of the cylindrical battery is increased. On the contrary, in the case
of the embodiments 1 and 2, it is found that heat resistance of the CID gasket is
improved as the glass fiber is added, thereby fluently functioning as a supporter.
Regarding the embodiments 1 and 2 and the comparative examples 1
5 and 2, the reconnection is not generated after the current interrupt device (CID)
is separated.
Estimation Example 3: External short-circuit estimation
The external short-circuit estimation is performed after the embodiments
3 and 4 and the comparative examples 3 and 4 are provided.
10 In detail, the embodiments 3 and 4 are provided by applying the CID
gasket including PBT and glass fiber to the 21700 cylindrical battery, and the
comparative examples 3 and 4 are provided by applying the CID gasket
including PBT to the 21700 cylindrical battery. Regarding the embodiments 3
and 4, the mass of the glass fiber vs. the mass of the CID gasket is 30%.
15 In the estimation example 3, external resistance of 20m0 is applied to
the cylindrical battery according to embodiments 3 and 4 and comparative
examples 3 and 4 to thus determine the conducts of the respective cylindrical
batteries. Further, it is measured whether a reconnection is generated after the
separation of the current interrupt device (CID) in the external short-circuit
20 estimation. Experimental results are shown in FIG. 9 to FIG. 12 and Table 3.
FIG. 9 to FIG. 12 show graphs on estimation results of external short-circuit
according to an embodiment 3, an embodiment 4, a comparative example 3, and
a comparative example 4. Table 3 is a summary of results of the graphs.
(Table 3)
20
Resistance
CID
Max. temp after CID
separating Notes
(oC) separation
time (sec)
(mQ)
Embodiment
40.1 101 oO No reconnection
3
Embodiment
38.2 99 oO No reconnection
4
Comparative Reconnection
38.2 94.1 7.5
Example 3 generated
Comparative Reconnection
42.2 88.7 4.9
Example4 generated
Referring to FIG. 9, FIG. 10, and Table 3, the current interrupt device is
separated around 40 seconds (sec) in the case ofthe embodiments 3 and 4, and
referring to FIG. 11, FIG. 12, and Table 3, the current interrupt device is
5 separated around 40 seconds (sec) in the case of the comparative examples 3
and 4. The embodiments 3 and 4 and the comparative examples 3 and 4 have
similar times when the current interrupt device is separated by the increase of
internal pressure. Further, the maximum temperatures (Max. temp) of the
cylindrical battery according to the embodiments 3 and 4 and the comparative
10 examples 3 and 4 are measured to be similar to each other.
However, in the case of the comparative examples 3 and 4, when a
current flow is measured after the separation of the current interrupt device (CID),
21
resistance of 7.5mn and 4.9mn are respectively measured. This signifies that
the electrical connection between the safety vent and the current interrupt device
is not completely intercepted after the separation of the current interrupt device
(CID) and a reconnection is generated. On the contrary, no reconnection is
5 generated in the case of the embodiments 3 and 4.
FIG. 13 to FIG. 16 sequentially show photographs of aCT image after a
current interrupt device is separated, an upper cap, and a sealing gasket
according to an embodiment 3, an embodiment 4, a comparative example 3, and
a comparative example 4. The CT image shows an upper portion on which a
10 cap assembly is positioned in the cylindrical battery.
Referring to FIG. 13, FIG. 14, and Table 3, as described above, no
reconnection is generated and no melting of the CID gasket or the sealing
gasket is generated in the case of the embodiments 3 and 4.
Referring to FIG. 15 and Table 3, in the case of the comparative example
15 3, the reconnection is generated and the CID gasket and the sealing gasket are
melted. Referring to FIG. 16 and Table 3, in the case of the comparative
example 4, the reconnection is generated and the sealing gasket is melted.
To sum up the experimental result, in the case of the embodiments 3 and
4 in which the glass fiber is added, heat resistance is improved and heat
20 deflection is not generated, thereby effectively intercepting the reconnection
between the safety vent and the current interrupt device. On the contrary, in
the case of the comparative examples 3 and 4 in which the glass fiber is not
added, the reconnection between the safety vent and the current interrupt device
is not intercepted because of heat deflection or melting of the CID gasket caused
22
by the increase of temperature.
Estimation Example 4: external short-circuit estimation
The external short-circuit estimation is performed when the embodiments
5 and 6 are provided.
5 In detail, the embodiments 5 and 6 are provided by allowing different
contents of glass fiber included in the CID gasket regarding the 18650 cylindrical
battery. Further, 18650 cylindrical batteries are configured in 5 (in series) • 2
(in parallel) to form a battery pack and then perform an external short-circuit
estimation.
10 In the case of the embodiment 5, the mass ofthe glass fiber vs. the mass
of the CID gasket is manufactured to be 30%, and in the case of the embodiment
6, the mass of the glass fiber vs. the mass of the CID gasket is manufactured to
be 20%.
In the estimation example 4, external resistance of 80mn is applied to
15 the battery packs including a plurality of cylindrical batteries according to the
embodiments 5 and 6 to determine the conducts of the respective battery packs.
Further, it is estimated whether a reconnection is generated after the separation
of the current interrupt device (CID) in the external short-circuit estimation.
Experimental results are shown in FIG. 17, FIG. 18, and Table 4. FIG. 17 and
20 FIG. 18 show graphs on estimation results of external short-circuit according to
an embodiment 5 and an embodiment 6. Table 4 is a summary of results of the
graphs.
(Table 4)
23
Voltage (V) I
Resistance (mO) CID Peak
Before After separating current Max. temp("C)
separation separation time (sec) (A)
ofCID ofCID
Embodiment 20.87/
Ofoa 50.6 159.2 120.1
5 41.1
Embodiment 20.87/
Explosion 49.4 159.0 -
6 41.0
Referring to FIG. 17, FIG. 18, and Table 4, in the case of the
embodiment 5, the current interrupt device is separated at 50.6 seconds (sec),
and no reconnection is generated after that. On the contrary, in the case of the
5 embodiment 6, the current interrupt device is separated at 49.4 seconds (sec),
and a reconnection is generated after that, which results in an explosion.
That is, the mass of the glass fiber vs. the mass of the CID gasket is less
than 25% in the battery pack unit, and when a less amount of the reinforcement
material is included, the CID gasket fails to endure the heat and the pressure
10 inside the battery pack but is melted to generate a reconnection, and this may
lead to a thermal runaway or an explosion of the battery pack.
In the present embodiment, terms representing directions such as before,
after, right, left, top, and bottom have been used, but they are for ease of
description, and are variable depending on a position of a target material or a
15 position of an observer.
24
One or more secondary batteries according to the above-described
present embodiment may be applied to various devices. In detail, these
devices may be applied to a transportation apparatus such as an electric bicycle,
an electric vehicle, a hybrid vehicle, and the like, but are not limited thereto, and
5 may be applied to various devices that can use the secondary battery.
While this invention has been described in connection with what is
presently considered to be practical embodiments, it is to be understood that the
invention is not limited to the disclosed embodiments, but, on the contrary, is
intended to cover various modifications and equivalent arrangements included
10 within the spirit and scope of the appended claims.

100: secondary battery
200: cylindrical case
300: cap assembly
15 310: upper cap
320: safety vent
400: sealing gasket
500: electrode assembly
600: current interrupt device
20 700: CID gasket
25
[CLAIMS]
[Claim 1]
A secondary battery comprising:
a current interrupt device (CID);
5 a safety vent disposed on the current interrupt device and electrically
connected to the current interrupt device; and
a CID gasket for surrounding an edge of the current interrupt device,
wherein the CID gasket includes reinforcement material, and
the reinforcement material includes at least one of glass fiber, carbon
10 fiber, aramid fiber, cellulose, ceramic particles, and a filler.
[Claim 2]
The secondary battery of claim 1, wherein
the CID gasket includes a first portion for surrounding an edge of the
15 current interrupt device and a second portion disposed on the first portion and
extending in a center direction of the current interrupt device.
[Claim 3]
The secondary battery of claim 2, wherein
20 the second portion extends between the safety vent and the current
interrupt device.
[Claim 4]
26
The secondary battery of claim 1, wherein
the CID gasket includes a polymer resin, and
the polymer resin includes at least one of polypropylene (PP),
polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and
5 perfluoroalkoxy alkane (PFA).
[Claim 5]
The secondary battery of claim 1, wherein
the CID gasket includes a polymer resin, and
10 the polymer resin includes polybutylene terephthalate (PBT).
[Claim 6]
The secondary battery of claim 1, wherein
the current interrupt device includes an exterior circumference portion
15 and an interrupter surrounded by the exterior circumference portion, and when
an internal pressure of the secondary battery rises, the interrupter is separated
from the exterior circumference portion.
[Claim 7]
20 The secondary battery of claim 6, wherein
the safety vent is electrically connected to the interrupter.
[Claim 8]
27
The secondary battery of claim 6, further comprising
an electrode assembly including a positive electrode, a negative
electrode, and a separation membrane,
wherein the exterior circumference portion is electrically connected to the
5 positive electrode through a positive electrode tab.
[Claim 9]
The secondary battery of claim 1, further comprising
an upper cap disposed on the safety vent and electrically connected to
10 the safety vent.
15
[Claim 10]
The secondary battery of claim 1, further comprising
a cylindrical case.
[Claim 11]
A device including a secondary battery according to claim 1.