KR101390527B1 - Ptc-hybrid safety vent, and secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a safety vent, and more particularly, to a PTC hybrid safety vent, the outer peripheral surface of the safety vent is formed of a PTC element, no need for a separate PTC element when forming the cap assembly. Since the safety vane of the present invention does not need to intervene with a separate PTC device, it provides an advantageous effect in terms of ensuring battery internal space, and the secured internal space contributes to an increase in battery capacity.

PTC element, safety vent, secondary battery, space clearance, battery capacity

Description

PTC hybrid safety band and secondary battery having same {PTC-HYBRID SAFETY VENT, AND SECONDARY BATTERY COMPRISING THE SAME}

The present invention relates to a safety vent, and more particularly, to a PTC hybrid safety vent that is formed of a PTC element outer peripheral surface does not require a separate PTC element.

The secondary battery is classified into a cylindrical battery in which the case is cylindrical, a prismatic battery in which the case is square, and a pouch-type battery in which the case is thin laminate sheet, depending on the shape of the battery case.

On the other hand, the battery case has a built-in electrode assembly as a power generator capable of charging and discharging composed of a laminated structure of a positive electrode / separator / negative electrode, the jelly wound between the long sheet-like positive electrode and the negative electrode coated with the active material through a separator- It is classified into a rolled structure and a stacked structure in which a plurality of positive and negative electrodes having a predetermined size are sequentially stacked in a state where a separator is interposed therebetween.

Among these, the jelly-roll type electrode assembly has advantages such as easy manufacture and high energy density per weight, and jelly-roll type electrode assembly is easily manufactured especially in a cylindrical battery case.

However, when the battery is charged and discharged, the jelly-roll type electrode assembly tends to undergo repeated expansion and contraction, and in this process, the stress is concentrated at the central portion, and the electrode contacts the metal center pin through the separator, . The organic solvent is decomposed by the heat generated due to the internal short circuit, so that gas is generated, and the battery can be ruptured by an increase in gas pressure in the cell. Such gas pressure rise inside the battery can occur even when an internal short circuit occurs due to an external impact.

In order to solve the safety problem of the battery as described above, the cap assembly of the cylindrical battery, safety vanes for discharging high-pressure gas, PTC element to cut off the current at high temperature, current interruption element to cut off the current when the battery breakdown voltage (Current Interrupt Safety elements such as a device (CID) and a top cap forming a protruding terminal for protecting the elements have a structure fixed by a gasket.

1 is a partial cross-sectional view schematically showing the upper structure of a conventional cylindrical secondary battery.

Referring to FIG. 1, a battery 100 includes an electrode assembly 300 as a power generating element, an electrolyte injected into the can 200, a cap assembly 400 at an upper opening of the can 200, .

The cap assembly 400 includes a top cap 410 and a PTC device 420 for shutting off an overcurrent inside the gasket 500 for airtightness to be mounted on the upper beading portion 210 of the can 200, The safety bolt 430 is closely attached.

The top cap 410 protrudes upward to serve as a positive terminal by connection with an external circuit, and a plurality of through holes (not shown) for discharging gas are perforated. The safety vault 430 has its lower end connected to the positive electrode of the electrode assembly 300 through the current cut-off safety element 440 and the positive electrode lead 310.

The safety vest 430 is a thin conductive plate having a center portion thereof forming a downward depression 432 and two notches 434 having depths different from each other at the upper and lower bending portions of the depression 432 , And 436 are formed.

The current cut-off safety element 440, which cuts off the current when the pressure rises above the threshold value in the battery, is provided as a conductive plate under the safety vent 430. The material of the current cut-off safety element 440 is preferably made of the same material as the safety vest 430 and the auxiliary gasket 510 prevents the current cut-off safety element 440 and the safety vest 430 from being energized It is made of polypropylene (PP) series material.

For example, when the temperature of the battery 100 rises due to internal short circuit, overcharge, or the like caused by various causes, the amount of energizing current is greatly reduced by increasing the resistance of the PTC element 420. When the gas is generated as the electrolyte is decomposed due to the continuous rise of the temperature and the internal pressure increases accordingly, the indentation part 432 of the safety vent 430 is lifted and the current blocking safety device 440 partially ruptures to block the current. To ensure safety. However, when the pressure rises continuously, the notch 436 of the safety vent 430 is ruptured, thereby discharging the high pressure gas to the battery 100 to secure the safety.

In order to solve the safety problem of the battery as described above, the cap assembly of the cylindrical battery is provided with a number of safety devices such as safety vents, PTC elements, current interrupt device (CID). These safety devices solve battery safety problems that can be caused by a variety of causes, but serve as a major cause of battery capacity reduction.

Specifically, since the charge and discharge capacity of the cylindrical battery depends on the size of the jelly-roll embedded in the can at the external size of the same standard, when the thickness of the cap assembly increases due to the mounting of a number of safety elements, The size reduction of the jelly-roll is inevitable. Therefore, there is a high need for a technology capable of increasing battery capacity while ensuring battery safety.

In this regard, Korean Patent No. 0573103 describes a thickness of a variable plate that supports a lower portion of a conventional support plate by placing a fastening portion extending from the support plate in the cutout of the cap cover and the current limiter in the cap assembly of the secondary battery. Disclosed is a method of increasing the capacity of a battery by removing it.

However, in the above technique, since the cap assembly of the cylindrical secondary battery is formed in a quadruple structure of a cap cover, a current limiter, a variable plate, and a support plate, the triple structure includes a top cap, a PTC element, and a safety band of the present invention. Compared to the base, the thickness is large, and thus there is a limit in terms of capacity increase of the battery, and the material cost is also increased.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems of the prior art and the technical problems required from the past.

The inventors of the present application, after in-depth study and various experiments, replace the conventional safety band outer surface with a PTC element, and it is not necessary to stack additional PTC elements, so that space can be saved as much as that part. Thus, the present invention has been completed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the conventional art,

An element portion formed of a PTC element as an outer circumferential surface of the safety vent; And

Bent part with notch to open under critical pressure

Provides a PTC hybrid safety van made including.

In addition, in the present invention, the thickness of the element portion provides a PTC hybrid safety vent, characterized in that at least the thickness of the vent portion.

In addition, in the present invention, the PTC device forming the device portion provides a PTC hybrid safety vent, characterized in that the polymer-based PTC device.

In addition, the present invention provides a cylindrical secondary battery including the safety vent of the present invention.

Since the safety vane of the present invention does not need to intervene with a separate PTC device, it provides an advantageous effect in terms of ensuring battery internal space, and the secured internal space contributes to an increase in battery capacity.

Hereinafter, the present invention will be described in detail.

According to the present invention,

An element portion formed of a PTC element as an outer circumferential surface of the safety vent; And

Bent part with notch to open under critical pressure

It relates to a PTC hybrid safety van made including.

The outer circumferential surface is an outer portion farther from the center than the notch formed on the circular safety band (including both the first notch and the second notch to be described later), and the portion that is energized in contact with the top cap when the cap assembly is assembled. I speak.

5 and 6 illustrate the PTC hybrid safety vent of the present invention as described above.

As shown in Figs. 5 and 6, the PTC hybrid safety vent includes an element portion formed of a PTC element and a vent portion having a notch as the outer circumferential surface of the safety vane.

As shown in FIG. 1, in the related art, a PTC device and a safety van were used separately, and a PTC device and a top cap were stacked on the safety van. In this case, by using the safety vent and the PTC element separately, the internal space is reduced by the height of the PTC element, which leads to a problem of reducing the battery capacity.

Accordingly, in the present invention, in order to solve this problem, the outer circumferential surface of the safety vane is formed of a PTC element (ie, the PTC element and the safety vane are combined), thereby providing a safety vane that does not require a separate PTC element. Since the PTC hybrid safety vent of the present invention does not require a separate PTC device, a space equal to the thickness of the PTC device can be secured, and the battery capacity is increased by a volume corresponding to the reduced thickness.

In the present invention, the thickness of the vent part may vary depending on the material of the vent part, but is not particularly limited, and may be preferably 0.15 to 0.4 mm. The thickness of the vent portion affects the mechanical stiffness, elastic force, and the like of the safety vent. As the thickness of the vent portion becomes thicker, the space of the safety vent may occupy the inside of the battery case may increase, thereby reducing the capacity of the battery. On the contrary, when the thickness of the band part is too thin, it is not preferable because it does not exhibit the desired mechanical rigidity and can be destroyed by a weak external impact. Therefore, the thicker the thickness of the material may have a higher mechanical rigidity, but may cause a problem that the capacity of the battery is reduced, in consideration of these points in combination, a person having ordinary skill in the art It can determine suitably within a range.

In addition, the thickness of the safety vent outer circumferential surface, that is, the element portion formed of the PTC element should be at least the thickness of the vent portion. If the bent part is thicker, the top cap and the bent part may contact each other, which may cause a short circuit.

In addition, an element portion formed of a PTC element on the outer circumferential surface of the PTC hybrid safety band can be formed using any PTC element conventionally used, but a polymer PTC element is a little more preferable in consideration of bonding to the band portion ( The PTC device can be broadly classified into a ceramic PTC device in which impurities such as nickel, cobalt, manganese, and copper are added to an inorganic magnetic material, and a polymer PTC device mainly used in conductive polymers).

The PTC element forming the outer circumferential surface of the invention is very obvious to those skilled in the art, and thus a detailed description thereof will be omitted.

In one preferred embodiment, the cap assembly consists of a laminated structure of a PTC hybrid safety vant and a top cap having one or more gas outlets, and a gasket is mounted on an outer circumferential surface of the laminated structure, whereby the safety vane is a battery withstand pressure. The high pressure gas is discharged while reversing upward to increase, and the PTC element portion may have a structure that greatly improves the safety of the battery by blocking current while greatly increasing resistance when the temperature of the battery increases.

Preferably, the vent portion of the PTC hybrid safety vent has a shape in which a center is indented downwardly, and a first notch and a second notch are formed at an upper bent portion and a lower bent portion, respectively, which form the indented portion. The first notch forms a closed curve, the second notch formed at the lower portion has a structure of an open curve at one side thereof, the second notch is deeper than the first notch, and a lower end of the safety vent is located inside the battery. It may be a structure that is provided with a current blocking member that bursts when the pressure rises to block the current.

Therefore, when the pressure inside the battery rises abnormally, the pressurized gas passes through the through-hole and through-hole of the current blocking member to pressurize the safety van, and the downward indentation of the safety van is lifted by such pressure. The protruding portion welded to the indentation portion is easily separated from the current blocking member above a certain pressure (hereinafter, abbreviated as 'first critical pressure') to block the energization of the current blocking member from the current blocking member. In spite of the interruption of such current, when the pressure continues to rise and reaches a certain level (hereinafter, abbreviated as 'second critical pressure'), the second notch of the safety vane is cut off and the pressurized gas inside the upper gap is cut off. It is discharged to the outside through the hole of.

The current blocking member includes one or more through holes for discharging gas, and an upwardly protruding protrusion which is welded to the bottom of the indent of the safety vane is formed at the center thereof and connected to the anode of the jelly-roll. The anode lead is electrically connected through the bottom surface of the portion excluding the protrusion, and a bridge is formed in which a notch is formed by connecting 3 to 5 through holes and the through holes concentrically about the protrusion. It may be made of a structure.

In addition, the present invention also provides a cylindrical secondary battery comprising the PTC hybrid safety vent.

In general, the positive electrode tab welded to the positive electrode foil of the jelly-roll type electrode assembly is welded to the cap assembly and connected to the protruding terminal at the top of the battery. The negative electrode tab welded to the negative electrode foil is welded to the lower end of the battery case So that the can itself constitutes the negative terminal. Electrolyte is injected in such a state that the mounting is made, and when the open top of the can is sealed, the cylindrical battery is completed. The material of the cylindrical can is not particularly limited, and preferably, it may be formed of any one of stainless steel, steel, aluminum or its equivalent.

The battery according to the present invention may preferably be a lithium secondary battery having a high energy density, a second discharge voltage, and an output stability. Such a lithium secondary battery is composed of a positive electrode, a negative electrode, a separator, a non-aqueous electrolyte containing a lithium salt, and the like.

The positive electrode is prepared, for example, by applying a mixture of a positive electrode active material, a conductive material and a binder on a positive electrode current collector, and then drying the resultant. Optionally, a filler may be further added. The negative electrode is also manufactured by applying a negative electrode material onto the negative electrode collector and drying the same, and if necessary, the above-described components may further be included.

The separation membrane is interposed between the cathode and the anode, and an insulating thin film having high ion permeability and mechanical strength is used.

The lithium salt-containing nonaqueous electrolyte solution is composed of a nonaqueous electrolyte and a lithium salt. As the nonaqueous electrolyte solution, a liquid nonaqueous electrolyte, a solid electrolyte, and an inorganic solid electrolyte are used.

The collector, the electrode active material, the conductive material, the binder, the filler, the separator, the electrolyte, and the lithium salt are well known in the art, and a detailed description thereof will be omitted herein.

The lithium secondary battery according to the present invention can be manufactured by a conventional method known in the art. That is, a porous separator may be inserted between the anode and the cathode, and an electrolyte may be injected into the separator.

The anode can be produced, for example, by applying a slurry containing a lithium transition metal oxide active material, a conductive material and a binder as a cathode active material on a collector, followed by drying and rolling, as described above. Similarly, the negative electrode can be produced, for example, by applying a slurry containing a carbon active material, a conductive material and a binder as a negative electrode active material on a thin current collector and then drying the negative current collector as described above.

Hereinafter, the contents of the present invention will be described in detail with reference to the drawings according to one embodiment of the present invention, but the scope of the present invention is not limited thereto.

2 is a partial cross-sectional view schematically showing the upper structure of the cylindrical secondary battery.

Referring to FIG. 2, the battery 100a according to the present invention inserts an electrode assembly 300 as a power generator into the can 200, injects electrolyte therein, and caps the upper opening of the can 200. Manufactured by mounting the assembly 400.

The cap assembly 400 is installed in close contact with the PTC hybrid safety vent 430a in the airtight gasket 500 mounted on the upper beading part 210 of the can 200.

The upper cap 410 protrudes upward to serve as a positive terminal by connection with an external circuit.

The PTC hybrid safety vent 430a has a lower end thereof connected to the anode of the power generator 300 through the current blocking member 440 and the anode lead 310.

5 and 6, the PTC hybrid safety vent 430a of the present invention is a conductive thin plate, and includes an element portion and a vent portion. The central portion of the bent portion forms a downward indentation portion 432, and two notches having different depths are formed at upper and lower bending portions of the indentation portion 432. As shown in FIG. 2, the first notch 434 formed on the upper portion of the notch forms a closed curve, and the second notch 436 formed on the lower portion has an open curved structure on one side thereof. In addition, since the engagement force of the second notch 436 is made smaller than the engagement force of the first notch 434, the second notch 436 is dug deeper than the first notch 434. That is, the second notch 436 is formed deeper than the first notch 434, so that the second notch 436 is cut when the pressurized gas of the second critical pressure or more presses the safety vent 430a. On the other hand, the first notch 434 works with the second notch 436 when pressurized gas below the second threshold pressure acts on the safety vent 430a so that the indentation 432 can be lifted up.

The current cut-off member 440 which cuts off the current when the battery reaches a threshold or higher is provided below the safety vent 430a as a conductive plate. Preferably, the material of the current blocking member 440 is made of the same material as the safety vent 430a, and the auxiliary gasket 510 may prevent the current blocking member 440 and the safety vent 430a from being energized. Made of polypropylene material.

In addition, the outer circumferential surface 438 of the safety vent 430a formed of the PTC element is formed to have the same thickness as the vent portion.

3A shows an example of the current blocking member 440 according to the present invention. Referring to this, the current blocking member 440 has a plurality of through holes 441 through which gas is discharged along a side surface thereof. The protrusion 442 protruding upward is formed in the center, and the three through holes 443 concentrically around the protrusion 442 and the three bridges 444 connecting the through holes 443 are symmetrical. It is formed. The protrusion 442 is welded to the lower end of the indentation 432 of the safety vent 430a. As shown in FIG. 3B, a notch 445 is formed in the bridge 444 so that the indentation 432 is lifted up when the gas pressurized above the first threshold is applied to the safety vent 430a in the battery. The protrusion 442 welded to the indentation 432 is separated from the main body of the current blocking member 440 as the notch 445 is cut out.

4a to 4c illustrate the principle of operation of the structure.

Referring to FIG. 4A, when the internal pressure of the battery rises due to the gas generated by abnormal operation of the battery, the pressurized gas is formed in the through hole 441 and the through hole 443 formed in the current blocking member 440. Exit through the pressure is applied to the safety vent (430a). When the pressure of the gas is greater than or equal to the first critical pressure, the downward indentation 432 of the safety van 430a is lifted upward by the pressure of the gas that pressurizes the safety vane 430a. At this time, the protrusion 442 of the current blocking member 440 welded to the bottom of the indentation 432 is separated from the current blocking member 440 as shown in Figure 4b while the notch 445 is cut off. It will be lifted with 432 and the electricity will be cut off.

As such, the indentation 432 of the safety vent 430a may be lifted up because of the first notch 434 and the second notch 436 formed in the safety vent 430a. As a result, the notch portions forming the upper bent and lower bent portions of the indents 432 are flexed and lifted up the indented portions 432 that are bent downward.

Accordingly, the projected portion 442 attached to the safety vane 430a is separated from the current blocking member 440 by being disconnected from the current blocking member 440 and the PTC hybrid safety vane and the upper cap 410. Current is cut off.

When there is additional gas generation even after the current is first cut off, the safety vent 430a is continuously applied by the increased gas pressure, and when the gas pressure is greater than or equal to the second threshold pressure, as shown in FIG. 4C, As the second notch 436 of the safety vent 430a is broken, gas inside the battery is discharged to the outside. That is, the second notch 436 of the lower bent portion formed in the safety vent 430a does not endure the gas pressure inside the battery and breaks, so that the indentation portion 432 of the safety vent 430a is broken from the safety vent 430a. The gas is cut off and lifted up, and the gas leaked through the breakage gap is discharged to the outside through the hole 412 formed in the upper cap 410 to lower the internal pressure of the battery. At this time, since the second notch 436 is an open curve and a part of the notch is not formed, the part where the notch is not formed is not broken, and only the part where the notch is formed is broken, and the indentation part 432 is a safety band. It is in a state of being stuck without falling completely from 430a.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

1 is a schematic cross-sectional view showing an upper structure of a conventional cylindrical secondary battery.

2 is a partial cross-sectional view showing an upper structure of a cylindrical secondary battery.

3A and 3B show an example of the current blocking member according to the present invention.

4a to 4c illustrate the operation principle of a secondary battery according to the present invention.

5 is a cross-sectional view showing a PTC hybrid safety vent of the present invention.

6 is a perspective view showing a PTC hybrid safety vent of the present invention.

Claims (4)

An element portion formed of a PTC element as an outer circumferential surface of the safety vent; And A vent that is deformed by the first notch and the second notch dug deeper than the first notch at the first threshold pressure to cut off the current, and is opened by the second notch at a second threshold pressure higher than the first threshold pressure to release the gas. PTC hybrid safety vents containing parts. 2. The PTC hybrid safety vent as claimed in claim 1, wherein the thickness of the element portion is at least equal to the thickness of the vent portion. The PTC hybrid safety vent according to claim 1, wherein the PTC element forming the element portion is a polymer PTC element. Cylindrical secondary battery provided with a safety vent according to any one of claims 1 to 3.

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