KR101037042B1 - Pouch type secondary battery with enhanced stability - Google Patents

Abstract

The present invention provides a pouch type secondary battery having at least one safety vent on at least one electrode tab extending from the electrode assembly.

The pouch type secondary battery according to the present invention has a safety vent by making a fine hole in a metal plate used as an electrode tab, and provided with a safety element used in a square or a cylindrical shape, even when the battery is exposed to an abuse situation, The venting of gas generated in the gas can be predicted easily and can be easily vented to improve the safety of the battery.

Safety vent * safety device * secondary battery * pouch * electrode tab

Description

Pouch type secondary battery with enhanced stability}

The present invention relates to a pouch type secondary battery having improved safety, and more particularly, to a pouch type secondary battery capable of safely venting by predicting gas discharge inside a battery by attaching a safety vent of a minute hole to an electrode tab. .

As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing, and accordingly, a lot of researches on batteries that can meet various demands have been conducted.

Representatively, there is a high demand for square and pouch type batteries that can be applied to products such as mobile phones with a thin thickness in terms of shape of batteries, and lithium, such as lithium cobalt polymer batteries, which has excellent energy density, discharge voltage, and safety in terms of materials. The demand for secondary batteries is high.

One of the major challenges in such secondary batteries is to improve safety. In general, lithium secondary batteries are subject to high temperature and high pressure inside the battery, which may be caused by abnormal operating conditions of the battery, such as internal short circuits, charged states exceeding the allowable current or voltage, exposure to high temperatures, impact from drops, and the like. This may cause an explosion of the battery. In one such case, there is a possibility that the pouch type secondary battery may generate an internal short circuit upon impact such as a drop or an action of external force.

BACKGROUND ART [0002] In recent years, rechargeable secondary batteries have been widely used as energy sources for wireless mobile devices. In addition, the secondary battery is attracting attention as a power source of electric vehicles, hybrid electric vehicles, etc., which are proposed as a solution for air pollution of conventional gasoline vehicles and diesel vehicles using fossil fuel.

Medium and large devices such as automobiles, due to the need for a high output large capacity, a large and large battery system that is electrically connected to a plurality of battery cells are used. Pouch type lithium ion polymer secondary batteries, which are frequently used as unit cells in such medium and large battery systems, have a relatively large size compared to batteries of the same series used in small devices.

A conventional pouch type pouch type polymer secondary battery accommodates an electrode assembly, electrode tabs extending from the electrode assembly, an electrode lead welded to the electrode tabs, and the battery part, and includes a pouch type made of a polymer resin and a laminate sheet of aluminum. It consists of including a battery case.

In addition, a thin resin film is bonded to a portion where the battery case and the electrode lead are coupled to prevent leakage of an electrolyte solution, to prevent moisture in the air from penetrating into the battery, and to secure the electrical insulation of the electrode lead.

On the other hand, the lithium secondary battery can be manufactured in various forms, the typical shape is a cylindrical and square that are mainly used in lithium ion batteries. In recent years, the lithium polymer battery has been in the spotlight and is made of a flexible material and its shape is relatively free. In addition, excellent safety and light weight will be advantageous for slimming and lightening portable electronic devices.

However, when a lithium secondary battery has an increased internal pressure due to an overcharge lamp, a pouch-type case is called a swollen so-called swelling phenomenon. When this swelling phenomenon occurs, the battery unit is deformed. As a result, the battery may locally generate a short circuit.

In addition, when overcharged or exposed to high temperatures, a gas that is highly likely to ignite is generated inside the case due to the reaction between the electrolyte and the active material layer of the electrode plate or the decomposition reaction of the electrolyte and the active material layer itself. It can be triggered.

Therefore, the battery has a high need for a secondary battery including a safety device capable of preventing the swelling phenomenon by preventing the breakdown when the internal pressure is above a certain level and preventing rupture or explosion.

Therefore, in the present invention, the pouch type secondary battery is devised to solve various threats to safety caused when exposed to overcharge or high temperature.

Accordingly, an object of the present invention is to provide a pouch type secondary battery with improved safety.

Accordingly, the present invention provides a safety vent made of fine holes in a metal plate used as an electrode tab of a pouch-type secondary battery, and has a safety device used in a cylindrical shape or a square shape on the outside of the safety vent to discharge gas generated therein. It can be predicted that it is possible to improve the safety in the conventional pouch type secondary battery.

The pouch type secondary battery of the present invention may be vented in a predictable direction at a predictable internal pressure through a minute hole formed in a metal plate used as an electrode tab and a safety device formed outside the minute hole when gas is generated in the cell. It is excellent in the safety of a pouch type battery.

Pouch-type secondary battery of the present invention for achieving the above object is characterized in that provided with at least one safety vent on at least one electrode tab extending from the electrode assembly.

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

A conventional pouch type secondary battery has an electrode assembly 10 consisting of a negative electrode plate, a separator, and a positive electrode plate (not shown), and an electrode tab of a negative electrode and a positive electrode extending from the electrode assembly 10, as shown in FIG. (20, 20 '), electrode leads (30, 30') welded to the electrode tabs (20, 20 '), pouch type battery case (not shown) for accommodating the electrode assembly, battery case and electrode lead Resin film 40 is included for sealing of 30 and 30 '.

In particular, except for the electrode leads 30 and 30 'and the resin film 40 in FIG. 1, only an enlarged view of the electrode assembly 10 and the electrode tabs 20 and 20' is shown in FIGS. 2 and 3. Shown in

In the present invention, as shown in FIG. 2, fine holes 50 are formed in at least one of the electrode tabs 20 and 20 ′ and used as safety vents.

The fine hole has an average diameter of about 0.05 to 0.5mm, and any shape is not limited as long as it provides a passage for discharging the elevated pressure from the inside of the pouch case to the outside. Capillary pipes are preferred so that the pressure can be quickly discharged from the inside of the case to the outside at high temperatures.

Specifically, the positive or negative electrode tab is made of one or more metals selected from the group consisting of copper, aluminum, nickel, chromium, silver, and platinum. The electrode tab serves as an electron transfer path inside and outside the sealed battery. The formation of the fine holes in the metal plate of the electrode tab uses a method of inserting a fiber to roll the metal and then thermally decomposing or dissolving the fiber to remove the fine holes. Any method that can be formed is not limited.

In addition, a plurality of the fine holes may be disposed along the electrode tab in order to discharge the internal pressure more quickly, but a plurality of the minute holes may be provided within a range capable of maintaining the shape of the electrode tab. The fine holes may be formed in the negative electrode tab, the positive electrode tab, or all the tabs of both electrodes.

In addition, the present invention forms a fine hole 50 in the metal plate constituting the electrode tabs (20, 20 '), and then used in the usual cylindrical or square at the outer end of the fine hole, a specific pressure In this case, it is preferable to further include a safety device 60 is vented.

In general, the safety device 60 as described above may be automatically vented when the atmospheric pressure is 1.2 atm or higher, and in addition to the safety device used in a cylindrical or square type, the sealing may be broken by an internal and external pressure difference. Structures such as a high molecular adhesion layer or a metal foil whose breaking pressure is measured are all available and are not particularly limited.

In the secondary battery of the present invention, the electrode assembly embedded in the battery case may have various structures such as a stacked (laminated) structure and a jelly-roll (wound) structure. In general, secondary batteries are classified into, for example, lithium ion batteries, lithium ion polymer batteries, lithium polymer batteries, etc., depending on the structure of the electrode assembly and the composition of the electrolyte. Among them, the manufacturing cost is low and there is little possibility of leakage of the electrolyte solution. In addition, a lithium ion polymer battery having a simple battery assembly process may be preferably used in the present invention.

Such a lithium ion polymer battery is generally manufactured by applying high temperature and high pressure to a junction portion of a case by welding a pouch-type battery case of an aluminum laminate sheet in a state where an electrode assembly of an anode / separation membrane / cathode with an electrolyte is impregnated thereon.

One end of the electrode lead is positioned inside the case with the electrode tabs of the electrode assembly attached, and the opposite end is exposed to the outside of the case. Among the electrode leads, the anode lead is generally made of a metal foil made of aluminum, and the cathode lead is generally made of a metal foil made of copper. The electrode tabs are typically coupled to the electrode leads by spot welding or the like, the thickness of the electrode leads being approximately 200 to 500 μm.

The resin sheet is interposed at the bonding portion of the battery case and the electrode lead, generally made of a polymer resin such as PP, PE, and has a thickness of 100 ~ 300 ㎛.

Hereinafter, the present invention will be described in more detail with reference to the following Examples, but the present invention is not limited thereto.

Example  1: cathode On the tab  safety Vent  Of secondary battery Manufacturing example

Fine holes having a diameter of 0.1 mm were formed in the negative electrode tab of the copper plate having a thickness of 0.3 mm connected to the negative electrode plate of the electrode assembly consisting of a negative plate / separator / anode plate. In addition, an aluminum plate fractured at 1.2 atm was welded to the end of the fine hole.

Then, an aluminum foil (anode lead) and a copper foil (anode foil) were welded to each of the electrode tabs, and a resin film of PP component was attached to its upper and lower surfaces, respectively. After mounting the electrode assembly to the pouch-type case of the aluminum laminate sheet and injecting a carbonate-based lithium electrolyte containing 1M LiPF ₆ , the sheet was heat-sealed to manufacture a lithium ion polymer battery.

Example  2: anode On the tab  safety Vent  Of secondary battery Manufacturing example

Lithium ion in the same manner as in Example 1, except that fine holes having a diameter of 0.1 mm are formed in the positive electrode tab of the aluminum plate having a thickness of 0.5 mm connected to the positive electrode plate of the electrode assembly consisting of a negative electrode plate, a separator, and a positive electrode plate. A polymer cell was produced.

Example  3: cathode Tab and  anode On the tab  safety Vent  Of secondary battery Manufacturing example

In an electrode assembly consisting of a cathode plate / separator / anode plate, 0.5 mm diameter hole in the positive electrode tab of the aluminum plate 1.0 mm thick connected to the positive electrode plate and 0.5 mm in the negative electrode tab of the copper plate 1 mm thick connected to the negative electrode plate Lithium ions were formed in the same manner as in Example 1, except that fine holes having a diameter of about and formed were welded to each end of each of the fine holes by welding an aluminum plate safety device that has been verified to be broken at 1.2 atm. A polymer cell was produced.

Comparative example  One

A lithium ion polymer battery was manufactured in the same manner as in Example 1, except that no venting device using any fine holes was formed in the negative electrode or the positive electrode tab.

[Experimental Example]

The safety of the secondary battery manufactured according to the Examples and Comparative Examples was measured as follows, and the results are shown in Table 1 below.

-Overcharge test: In a chamber of 55 ℃ (Camber), the SOC 0% of the battery was charged to 200% SOC at 1 ℃ -rate, the following was measured.

Highest temperature Vent location and timing Event UECAR Hazard level Comparative example 350 ℃ irregular Explosion 5 Example 1 70 ℃ Safety element Leakage 3 Example 2 73 ℃ Safety element Leakage 3 Example 3 68 ℃ Safety element Leakage 3

As can be seen in Table 1, the secondary battery according to the embodiment having a safety vent on at least one or more electrode tabs as in the present invention is absolutely safe and can obtain predictable safety results. In EUCAR Hazard levels of Table 1, 5 means no rupture or explosion, but it causes a flame or flame, and 3 means no venting, flame or flame, and only weighs less than 50% of the electrolyte (solvent + salt). This means that there is a loss of electrolyte leakage, and specific criteria are shown in Table 2 below. As can be seen from these results, the secondary battery provided with a safety vent according to the present invention has been proved to significantly improve safety compared to the comparative example.

Hazard
level Description Classification criteria and effects 0 No effect No effect. No loss of functionality. One Passive protection activated No defect; no leakage; no venting, fire, or flame; no rupture; no explosion; no exothermic reaction or thermal runaway. Cell reversibly damaged. Repair of protection device needed. 2 Defect / Damage No leakage; no venting, fire, or flame; no rupture; no explosion; no exothermic reaction or thermal runaway. Cell irreversibly damaged. Repair needed. 3 Leakage
D mass <50% No venting, fire, or flame; no rupture; no explosion. Weight loss <50% of electrolyte weight (electrolyte = solvent + salt) 4 Venting
D mass> 50% No fire or flame; no rupture; no explosion. Weight loss> 50% of electrolyte weight
(electrolyte = solvent + salt) 5 Fire or flame No rupture; no explosion (i.e., no flying parts). 6 Rupture No explosion, but flying parts of the active mass. 7 Explosion Explosion (i.e., disintegration of the cell)

1 is a conventional pouch type secondary battery,

2 is an example provided with a safety vent on at least one electrode tab according to an embodiment of the present invention,

Figure 3 is an example provided with a safety element at the distal end of the safety vent according to an embodiment of the present invention.

&Lt; Description of reference numerals &

10: electrode assembly 20, 20 ': electrode tab

30, 30 ': electrode lead 40: resin film

50: fine hole 60: safety device

Claims (8)

A pouch type secondary battery comprising a safety vent including at least one fine hole in at least one electrode tab extending from the electrode assembly. delete The pouch type secondary battery of claim 1, wherein an average diameter of the fine holes is 0.05 to 0.5 mm. The pouch type secondary battery of claim 1, wherein the safety vent includes a safety element vented at a predetermined pressure. The pouch type secondary battery of claim 4, wherein the pressure is atmospheric pressure. The pouch type secondary battery of claim 4, wherein the safety device is selected from cylindrical or rectangular ones. The pouch type secondary battery of claim 1, wherein the electrode tab is a negative electrode tab or a positive electrode tab. The pouch type secondary battery of claim 1, wherein the electrode tab is at least one metal plate selected from the group consisting of copper, aluminum, nickel, chromium, silver, and platinum.

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