KR101753213B1 - Battery cell and Secondary battery assembly comprising the same - Google Patents

Abstract

A battery cell according to the present invention includes: an electrode assembly; An electrode lead connected to the electrode assembly; A pouch case for accommodating the electrode assembly such that the electrode lead is drawn out to the outside; And venting means installed through the pouch case and opened when the internal pressure of the pouch case reaches a critical pressure.
According to the present invention, it is possible to perform quick venting in an abnormal situation without hindering the sealing performance of the battery cell, and to ensure the venting accurately at a predetermined pressure, securing safety in use of the secondary battery.

Description

[0001] The present invention relates to a battery cell, and a battery module and a battery pack including the battery cell,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery cell, a battery module and a battery pack including the same, and more particularly, to a battery cell having a structure capable of discharging internal gas to the outside in accordance with an increase in internal pressure, A battery module, and a battery pack.

As the use of portable electric appliances such as video cameras, portable phones, and portable PCs is being activated, the importance of secondary batteries, which are mainly used as driving power sources, is increasing.

Unlike a primary battery, which can not be charged normally, a secondary battery capable of charging and discharging is active in the development of advanced fields such as a digital camera, a cellular phone, a laptop computer, a power tool, an electric bicycle, an electric vehicle, a hybrid vehicle, Research is underway.

In particular, the lithium secondary battery has a higher energy density per unit weight and can be rapidly charged as compared with other secondary batteries such as lead-acid batteries, nickel-cadmium batteries, nickel-hydrogen batteries and nickel-zinc batteries. It is progressing.

The lithium secondary battery has an operating voltage of 3.6 V or higher and can be used as a power source for portable electronic devices, or a plurality of batteries can be connected in series or in parallel to a high output electric vehicle, a hybrid vehicle, a power tool, an electric bicycle, Is used.

The lithium secondary battery has a working voltage three times higher than that of a nickel-cadmium battery or a nickel-metal hydride battery, and has an excellent energy density per unit weight, and is rapidly used.

The lithium secondary battery can be classified into a lithium ion battery using a liquid electrolyte and a lithium ion polymer battery using a polymer solid electrolyte depending on the type of electrolyte. The lithium ion polymer battery can be divided into a fully solid lithium ion polymer battery containing no electrolytic solution and a lithium ion polymer battery using a gel polymer electrolyte containing an electrolyte depending on the kind of polymer solid electrolyte.

In the case of a lithium ion battery using a liquid electrolyte, it is usually used in a form in which a cylinder or a rectangular metal can is used as a container and welded and sealed. Since the can type secondary battery using such a metal can as a container is fixed in shape, there is a disadvantage that it restricts the design of an electrical product using the metal can as a power source, and it is difficult to reduce the volume. Accordingly, a pouch type secondary battery in which an electrode assembly and an electrolyte are sealed in a film pouch packaging material has been developed and used.

However, when the lithium secondary battery is overheated, there is a danger of explosion and it is an important task to secure safety. Overheating of a lithium secondary battery occurs for various reasons, for example, a case where an overcurrent flows beyond a limit through a lithium secondary battery. When the overcurrent flows, the internal temperature of the battery rises rapidly because the lithium secondary battery generates heat by joule heat. Also, the rapid rise of the temperature causes a decomposition reaction of the electrolytic solution and causes a thermal runaway, which eventually leads to the explosion of the battery. The overcurrent is a phenomenon in which a pointed metal object penetrates a lithium secondary battery or the insulation between an anode and a cathode is destroyed by contraction of a separator interposed between an anode and a cathode or a rush current is generated due to an abnormality of an external charging circuit or a load, Is applied to the battery or the like.

Therefore, the lithium secondary battery is used in combination with a protection circuit to protect the battery from an abnormal situation such as the occurrence of an overcurrent, and the protection circuit is provided with a fuse element for irreversibly disconnecting a line through which charging or discharging current flows when an over- .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram for explaining an arrangement structure and an operation mechanism of a fuse element in a configuration of a protection circuit combined with a battery module and / or a battery pack including a lithium secondary battery. FIG.

As shown in the figure, the protection circuit includes a fuse element 1 for protecting the battery module and / or a battery pack when an overcurrent occurs, a sense resistor 2 for sensing an overcurrent, (3) for operating the fuse element (1) and a switch (4) for switching the flow of operating current into the fuse element (1).

The fuse element 1 is installed in a main line connected to the outermost terminals of the battery module and / or the battery pack. The main line refers to a wiring through which charging current or discharging current flows. In the figure, the fuse element 1 is shown mounted on a high potential line (Pack +).

The fuse element 1 is a three-terminal element part, two terminals are connected to a main line through which a charging or discharging current flows, and one terminal is connected to the switch 4. And a fuse 1a connected in series with the main line and carpetted at a specific temperature, and a resistor 1b for applying heat to the fuse 1a.

The microcontroller 3 periodically detects the voltage across the sense resistor 2 and monitors whether an overcurrent is generated. When it is determined that an overcurrent is generated, the microcontroller 3 turns the switch 4 on. Then, a current flowing in the main line is bypassed to the fuse element 1 and applied to the resistor 1b. Thus, the joule heat generated in the resistor 1b is conducted to the fuse 1a to raise the temperature of the fuse 1a. When the temperature of the fuse 1a rises to the fusing temperature, the fuse 1a is fused, The line is irreversibly disconnected. When the main line is disconnected, the overcurrent does not flow any more, so that the problem caused by the overcurrent can be solved.

However, the above-described conventional techniques have various problems. That is, if a failure occurs in the microcontroller 3, the switch 4 is not turned on even in a state where an overcurrent is generated. In this case, since the current does not flow into the resistor 1b of the fuse element 1, there is a problem that the fuse element 1 does not operate.

If the fuse element 1 malfunctions, the internal pressure of the lithium secondary battery constituting the battery module and / or the battery pack, that is, the internal pressure of the battery cell may be continuously increased, which may cause ignition or explosion.

In particular, in the case of the pouch type battery cell 1 shown in FIG. 1, the cell is swollen due to an increase in internal pressure, and when the pressure exceeds a predetermined pressure, the sealing of the pouch case 2 is released and the gas and the electrolyte are discharged to the outside It is common to be designed to be.

However, in order for the battery cell to maintain a certain level of quality or more, the sealing force of the pouch case must be higher than a certain level, which makes it difficult to ensure a quick venting effect in an accident situation.

In addition, it is not easy to adjust the sealing force of the pouch case to a certain degree in the process of manufacturing the battery cell, so that the pressure at which the venting occurs at a constant pressure may be different, There is a problem that is difficult to secure.

The present invention has been made in view of the above-described problems, and it is an object of the present invention to provide a method for securing safety in use of a secondary battery by not only hindering the sealing property of the battery cell but also enabling quick venting in abnormal situations, The purpose is to make it possible.

It is to be understood, however, that the technical subject matter of the present invention is not limited to the above-mentioned problems, and other matters not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

According to an aspect of the present invention, there is provided a battery cell including: an electrode assembly; An electrode lead connected to the electrode assembly; A pouch case for accommodating the electrode assembly such that the electrode lead is drawn out to the outside; And venting means installed through the pouch case and opened when the internal pressure of the pouch case reaches a critical pressure.

The venting means may be installed at a position corresponding to an edge region of the edge region of the pouch case in a direction in which the electrode leads are drawn out and a space formed between the electrode assemblies.

The venting means may discharge the gas generated in the battery cell in an amount proportional to the pressure inside the battery cell.

The venting means may have a funnel shape in which the inner space gradually becomes narrower along the direction from the inside to the outside of the battery cell, and the upper opposing faces may be in contact with each other.

As the pressure inside the battery cell rises, the venting means may separate the opposing surfaces from each other, thereby discharging gas generated in the battery cell.

Wherein the venting means comprises: a lower cap having at least one first flow path; An upper cap having at least one second flow path and coupled to an upper portion of the lower cap to form an inner space; And a flow path cover disposed in the inner space and elastically pressed in a direction from the upper cap toward the lower cap to cover the second flow path.

The venting means may discharge the gas generated in the battery cell by opening the first flow path as the pressure inside the battery cell rises.

The present invention also provides a battery module and / or a battery pack according to an embodiment of the present invention including the battery cell.

The battery module according to an embodiment of the present invention is implemented by connecting a plurality of battery cells according to an embodiment of the present invention.

In addition, a battery pack according to an embodiment of the present invention is implemented by connecting a plurality of battery modules according to an embodiment of the present invention.

According to an aspect of the present invention, rapid venting in abnormal conditions is possible without hindering the sealing performance of the battery cell.

Further, according to another aspect of the present invention, safety can be ensured by using the secondary battery by causing the venting to occur exactly at a predetermined pressure.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description of the invention given below, serve to further the understanding of the technical idea of the invention. And should not be construed as limiting.
1 is a circuit diagram for explaining an arrangement structure and an operation mechanism of a fuse element in the configuration of a protection circuit coupled to a battery module.
2 is a plan view showing the internal structure of a conventional pouch type battery cell.
3 and 4 are plan views illustrating the internal structure of a battery cell according to an embodiment of the present invention.
5 is a side sectional view showing a part of the battery cell shown in Fig.
6 is a perspective view showing an embodiment of the venting means shown in Figs. 3 to 5. Fig.
7 is a cross-sectional view showing the operating principle of the venting means shown in Fig.
8 is an exploded perspective view showing another form of the venting means shown in Figs. 3 to 5. Fig.
Fig. 9 is a sectional view showing the venting means shown in Fig. 8. Fig.
10 is a diagram showing the operating principle of the venting means shown in Fig.
11 is a front view showing a battery module according to an embodiment of the present invention.
12 is a front view showing a battery module according to another embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It should be interpreted in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are only some of the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

3 to 5, the overall configuration of a battery cell 10 according to an embodiment of the present invention will be described.

FIGS. 3 and 4 are plan views illustrating the internal structure of a battery cell according to an embodiment of the present invention, and FIG. 5 is a side cross-sectional view illustrating a portion of the battery cell shown in FIG.

3 to 5, a battery cell 10 according to an embodiment of the present invention includes an electrode assembly 11, a pair of electrode leads 12, a sealant 13, a pouch case 14, Means (15).

The electrode assembly 11 includes a positive electrode plate 11a, a negative electrode plate 11b, a separation membrane 11c and an electrode tab T. [ The electrode assembly 11 may be a stacked type electrode assembly formed by interposing a separation membrane 11c between the stacked positive and negative electrodes 11a and 11b. In the drawings of the present invention, the electrode assembly 11 is of a laminated type, but it is also possible to use a jelly-roll type.

The anode plate 11a may be formed, for example, by applying a cathode active material to a collector plate made of aluminum (Al). The negative electrode plate 11b may be formed by applying a negative electrode active material to a collector plate made of, for example, copper (Cu).

LiCoO ₂ , LiNiO ₂ , LiNi _{1 -y} Co _y O ₂ (0 <y <1), LiMO ₂ (M = Mn, Fe and the like), Li (Ni _a Co _b Mn _c ) a layer such as O ₂ (0 <a <1, 0 <b <1, 0 <c <1, a + b + c = 1), LiNi _{1 -y} Mn _y O ₂ Hip type cathode active material; LiMn ₂ O ₄ , LiMn _{2 -z} Co _z O ₄ (0 <z <2), LiMn _{2 -z} Ni _z O ₄ (0 <z <2), Li (Ni _a Co _b Mn _c ) O ₄ a <b <2, 0 <b <2, 0 <c <2, a + b + c = 2); LiCoPO _4, LiFePO ₄ Or an olivine-type cathode active material.

Examples of the negative electrode active material include carbonaceous materials such as petroleum coke, activated carbon, graphite, non-graphitized carbon and graphite carbon; Li _x Fe ₂ O ₃ (0? _X? 1), Li _x WO ₂ (0? _X? 1), Sn _x Me _{1 -x} Me _y O _z (Me: Mn, Fe, Pb, : Metal complex oxides of Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen, 0 &lt; x &lt; Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{SnO, SnO 2, PbO, PbO} 2, Pb 2 O 3, Pb 3 O 4, Sb 2 O 3, Sb 2 O 4, Sb 2 O 5, GeO, GeO 2, Bi 2 O 3, Bi 2 O 4, Bi ₂ O ₅ and the like; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

The electrode tab T is formed integrally with an electrode plate 11a or a cathode plate 11b and corresponds to an uncoated region of the electrode plates 11a and 11b not coated with the electrode active material. That is, the electrode tab T includes a positive electrode tab corresponding to a region where the positive electrode active material is not applied and a negative electrode tab corresponding to a region where the negative electrode active material is not applied, among the positive electrode plate 11a.

The electrode lead 12 is attached to the electrode tab T as a thin plate-like metal and extends in the outer direction of the electrode assembly 11. The electrode lead 12 includes a positive electrode lead attached to the positive electrode tab and a negative electrode lead attached to the negative electrode tab. The positive electrode lead and the negative electrode lead may extend in the same direction or in opposite directions depending on the positions of the positive electrode tab and the negative electrode tab.

The sealant 13 is attached around the width direction of the electrode lead 12 and is interposed between the electrode lead 12 and the inner surface of the pouch case 14 and is made of a film having insulation and heat sealability. The sealant 13 may be formed of one or more materials selected from polyimide (PI), polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET) Layer (a single membrane or a multi-membrane).

The sealant 13 prevents a short circuit between the electrode lead 12 and the metal layer of the pouch case 14 from occurring. In addition, the sealant 13 improves the sealing force of the pouch case 14 in a region where the electrode lead 12 is drawn out.

That is, since the electrode lead 12 made of the metal plate and the inner surface of the pouch case 14 are not well adhered, the electrode lead 12 can be sealed even when the edge region B of the pouch case 14 is thermally fused and sealed. The sealing property in the region where the film is drawn out may be deteriorated. This phenomenon of lowering the sealing property is more prominent when the surface of the electrode lead 12 is coated with nickel (Ni).

Therefore, the sealability of the battery cell 10 can be improved by interposing the sealant 13 between the inner leads of the electrode lead 12 and the pouch case 14.

The pouch case 14 is sealed by thermally welding an edge region B where the upper case 14a and the lower case 14b abut each other while holding the electrode assembly 11 such that the electrode lead 12 is drawn out .

Such a pouch case 14 may have a multi-layered structure in order to secure excellent heat-sealability, shape, and rigidity and insulation for protecting the electrode assembly 11. For example, the pouch case 14 includes a first layer located on the innermost side and facing the electrode assembly 11, a second layer positioned on the outermost side and directly exposed to the external environment, And a third layer interposed between the layers.

In this case, for example, the first layer may be made of a material such as polypropylene (PP) having corrosion resistance against an electrolytic solution, insulation, and heat-sealability, and the second layer may be made of a material such as polyethylene terephthalate And the third layer may be made of a metal material such as aluminum (Al).

The venting means 15 is provided so as to penetrate through the pouch case 14 and is opened when the internal pressure of the pouch case 14 reaches a critical pressure, The gas generated inside the cell can be discharged to the outside, thereby ensuring safety in use of the battery cell 10. [

The venting means 15 may have a structure in which the ventilation means 15 is opened when the pressure inside the battery cell 10 rises. When the pressure inside the battery cell 10 becomes equal to or higher than the critical pressure, It is possible to discharge the generated gas inside the fuel cell stack 10.

The venting means 15 is not limited in its installation position as far as it can perform the function of discharging the gas generated in the battery cell 10. [

4, the venting means 15 is arranged in a space S in which gas is intensively collected, that is, in a direction in which the electrode lead 12 is drawn out of the rim region B of the pouch case 14 It is more advantageous that the electrode assembly 11 is provided at a position corresponding to a space S and a space S formed between the electrode assembly 11.

This is because the space between the electrode assembly 11 and the opposite surface of the pouch case 14 is very close to the space between the electrode assembly 12 and the electrode lead 12, To the space S formed in the direction of drawing out.

The specific structure of the venting means 15 is not limited as long as it has a structure capable of releasing the gas inside the battery cell 10 to the outside when the internal pressure of the battery cell 10 reaches the critical pressure. An exemplary embodiment of the venting means 15 will be described with reference to Figs. 6 and 7. Fig.

Fig. 6 is a perspective view showing one embodiment of the venting means shown in Figs. 3 to 5, and Fig. 7 is a sectional view showing the operating principle of the venting means shown in Fig.

Referring to FIG. 6, the venting means 15 may be made of an elastic material such as a rubber material, and has a funnel shape in which the internal space is gradually narrowed along the direction from the inside to the outside of the pouch case 14, It may be a unidirectional valve having a structure in which the opposing faces of the upper ends are in contact with each other.

The lower end of the venting means 15 may be fixed through one side of the cell case 14 and the upper end may protrude outward from the cell case 14.

7, when the pressure inside the battery cell 10 becomes equal to or greater than a preset threshold value, the upper end of the elastic body constituting the venting means 15 is opened, The sealed state is released, and the gas inside the pouch case 14 is discharged to the outside along the arrow direction.

Next, with reference to Figs. 8 to 10, the structure and operation principle of another exemplary embodiment of the venting means 16 will be described.

8 is an exploded perspective view showing another embodiment of the venting means shown in Figs. 3 to 5, Fig. 9 is a sectional view showing the venting means shown in Fig. 8, Fig. 10 is a cross- Fig.

8, the venting means 16 includes a lower cap 161 having at least one first flow path H1, an upper cap 162 having at least one second flow path H2, It may be a unidirectional valve including a lid cover 163 and an elastic urging member 164.

9, the lower cap 161 is fixed through one surface of the pouch case 14, and the upper cap 162 is installed on the upper portion of the lower cap 161, ). The flow path cover 163 is located in the inner space S and is elastically pressed in the direction from the upper cap 162 toward the lower cap 161 by the elastic pressure member 164 such as a spring, .

Referring to Fig. 10, the operating principle of such a venting means 16 is shown. That is, when a pressure equal to or higher than a threshold value is generated in the pouch case 14, the flow path cover 163 pushes the elastic pressure member 164 to release the sealed state of the first flow path H1, The gas inside is discharged to the outside through the inner space S and the second flow path H2 (see the arrows in Fig. 10).

As described above, the battery cell 10 according to an embodiment of the present invention includes venting means 15 and 16 for opening the gas generated inside due to an increase in internal pressure, It is possible to ensure safety in use of the battery cell 10 when an abnormal situation such as a short circuit occurs.

In addition, since the battery cell 10 is provided with such venting means 15 and 16, it is not necessary to perform venting through the rim region B of the pouch case 14, so that the sealing of the pouch case 14 The strength can be further strengthened and the quality can be improved.

The ventilation means 15 and 16 may be more important in a battery module M or a battery pack P having a larger output voltage or capacity because a plurality of battery cells are connected to each other. The module and the battery pack are shown in Figs. 11 and 12. Fig.

FIG. 11 is a front view showing a battery module according to an embodiment of the present invention, and FIG. 12 is a front view showing a battery module according to another embodiment of the present invention.

11, a battery module M according to an embodiment of the present invention includes a cell cluster in which battery cells are connected in series, parallel, or a combination of serial and parallel in a mixed manner, a module A bus bar 30 connected to the battery cell and an external terminal 40 protruding outside the module case 20 and connected to the bus bar 30.

At least one of the plurality of battery cells employed in the battery module M corresponds to the battery cell 10 according to the embodiment of the present invention described above, have.

12, the battery pack P according to an embodiment of the present invention is implemented by connecting the battery modules in serial, parallel, or serial and parallel manner by the interconnecting bar 50 do.

At least one of the plurality of battery modules employed in the battery pack P corresponds to the battery module M according to the embodiment of the present invention described above, have.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not to be limited to the details thereof and that various changes and modifications will be apparent to those skilled in the art. And various modifications and variations are possible within the scope of the appended claims.

10: Battery cell
11: electrode assembly 11a: positive electrode plate
11b: cathode plate 11c: separation membrane
T: electrode tab 12: electrode lead
13: sealant 14: pouch case
14a: upper case 14b: lower case
15, 16: Venting means B: Battery module
P: Battery pack

Claims (9)

An electrode assembly;
An electrode lead connected to the electrode assembly;
A pouch case for accommodating the electrode assembly such that the electrode lead is drawn out to the outside; And
And venting means installed through the pouch case and opened when the internal pressure of the pouch case reaches a critical pressure,
Wherein the venting means is reversibly opened in an amount proportional to the pressure inside the battery cell to discharge the gas generated in the battery cell and gradually increase the internal space along the direction from the inside to the outside of the battery cell The battery cell has a funnel shape that narrows and has a shape in which opposing upper surfaces thereof are in contact with each other. As the pressure inside the battery cell rises, the opposing surfaces are separated from each other, . The method according to claim 1,
The venting means,
Wherein the battery cell is installed at a position corresponding to a rim region of the rim of the pouch case, which is located in a direction in which the electrode leads are drawn out, and a space formed between the electrode assemblies. delete delete delete delete delete A battery module in which a plurality of battery cells according to claim 1 or 2 are connected and implemented. A battery pack in which a plurality of battery modules according to claim 8 are connected and implemented.

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