KR20180083566A - Cylindrical Battery Cell Comprising Bottom Safety Vent - Google Patents

Abstract

The present invention relates to a cylindrical case in which an electrode assembly including an anode, a cathode, and a separator interposed between the anode and the cathode is housed therein;
A cap assembly mounted on an open upper end of the cylindrical case and having an electrode terminal formed therein;
An electrode assembly housed inside the cylindrical case; And
A lower safety vent formed at a lower portion of the cylindrical case to break the inner gas when the inner pressure of the cylindrical case reaches the breaking pressure before the other portion of the case;
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Wherein the lower safety vent is adjusted so that an angle formed between the discharge direction of the gas discharged to the outside and the ground surface is less than 90 degrees.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a cylindrical battery cell including a lower safety vent,

The present invention relates to a cylindrical battery cell including a lower safety vent.

As technology development and demand for mobile devices have increased, the demand for secondary batteries as energy sources has been rapidly increasing. Many researches have been conducted on lithium secondary batteries with high energy density and discharge voltage among such secondary batteries. .

The secondary battery is classified into a cylindrical battery and a prismatic battery in which the electrode assembly is housed in a cylindrical or rectangular metal can according to the shape of the battery case, and a pouch-shaped battery in which the electrode assembly is housed in a pouch-shaped case of an aluminum laminate sheet . Among them, the cylindrical battery has a relatively large capacity and is structurally stable.

The electrode assembly is embedded in a battery case. The electrode assembly includes a positive electrode / separator / negative electrode laminate structure. The positive electrode / separator / negative electrode has a jelly-roll type structure in which a separator is interposed between a positive electrode and a negative electrode coated with an active material. A stacked type in which a plurality of positive and negative electrodes of a predetermined size are stacked in a state in which a separator is interposed, and a stacked / folded type in which unit cells such as a pull cell or a bi-cell are wound by a separation film. Among them, the jelly-roll type electrode assembly has an advantage of being easy to manufacture and having a high energy density per weight.

In this regard, Fig. 1 schematically shows a vertical cross-sectional perspective view of a general cylindrical battery.

1, a cylindrical secondary battery 10 includes a jelly-roll type (wound type) electrode assembly 12 accommodated in a cylindrical case 13, an electrolyte is injected into the cylindrical case 13, And a cap assembly 14 having an electrode terminal formed on the open upper end of the cap assembly.

Such an electrode assembly 12 has a structure in which a positive electrode 12a and a negative electrode 12b are sandwiched between a separator 12c and a separator 12c therebetween and then wound in a round shape. The pin 15 is inserted. The center pin 15 is generally made of a metal material in order to impart a predetermined strength and has a hollow cylindrical structure in which the plate material is bent in a round shape. The center pin 15 serves as a channel for fixing and supporting the electrode assembly and a gas for discharging gas generated by an internal reaction during charging, discharging and operation.

On the other hand, the lithium secondary battery has a disadvantage of low safety. For example, when the battery is overcharged to about 4.5 V or more, decomposition reaction of the cathode active material occurs, and dendrite growth of lithium metal at the cathode and decomposition reaction of the electrolyte occur. In this process, the decomposition reaction and the many side reactions are rapidly proceeded with heat accompanied by heat, and the ignition and explosion of the battery may be caused.

Gas is generated due to the decomposition reaction of the electrolyte by heat at high temperature, and if the amount of heat generated by the battery rapidly increases within a short time, thermal runaway phenomenon may occur. Thermal runaway occurs when the battery is kept in a continuously energized state or is further accelerated, so that there is a serious problem in safety because the risk of explosion of the battery due to ignition or gas pressure becomes very large.

Accordingly, in the prior art, the cap assembly is provided with a safety vent for discharging the gas generated in the cylindrical secondary battery to the outside when the internal gas pressure becomes high. However, only the upper safety vent formed in the cap assembly has limitations in controlling or preventing the explosion of the secondary battery due to the ignition of the secondary battery or the pressure of the gas when the cylindrical secondary battery is ignited.

Furthermore, with the recent development of a secondary battery having a compact size and a large capacity, the high-density energy is exploded when the secondary battery is ignited, and the risk is further increased. Accordingly, when the secondary battery with only the upper safety vent discharges the gas through the safety vent, the explosion of the cylindrical case leads to the explosion of the metal case, which can physically damage the surrounding environment.

Accordingly, some conventional cylindrical secondary batteries further include a safety vent at the bottom of the cylindrical case for supporting the upper safety vent.

However, the safety vent formed in the lower part of the prior art is difficult to predict the discharge direction when the gas is discharged, and thus it is difficult to predict the influence due to the gas discharge. For example, when the gas is discharged in the vertical direction with respect to the ground through the safety vent formed at the bottom, the cylindrical secondary battery can be vertically pushed up like a rocket due to the reaction of the gas discharge, There was a problem.

Therefore, there is a high need for a technique that can effectively solve the problems of the prior art described above.

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

The inventors of the present application have conducted intensive research and various experiments. As will be described later, in the cylindrical battery cell of the present invention, the lower safety vent formed at the lower portion of the cylindrical case has a discharge direction The present invention has been accomplished based on the finding that it is possible to control the movement of the battery cell due to the reaction of the internal gas discharge.

According to an aspect of the present invention, there is provided a cylindrical battery cell,

A cylindrical case in which an electrode assembly including an anode, a cathode, and a separator interposed between the anode and the cathode is received;

A cap assembly mounted on an open upper end of the cylindrical case and having an electrode terminal formed therein;

An electrode assembly housed inside the cylindrical case; And

A lower safety vent formed at a lower portion of the cylindrical case to break the inner gas when the inner pressure of the cylindrical case reaches the breaking pressure before the other portion of the case;

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And the lower safety vent is adjusted so that an angle formed between the discharge direction of the gas discharged to the outside and the ground surface is less than 90 degrees.

Therefore, in the cylindrical battery cell according to the present invention, the lower safety vent formed in the lower part of the cylindrical case is adjusted so that the angle between the discharge direction of the gas discharged to the outside and the ground surface is less than 90 degrees, The energy of the gas discharge can be effectively dispersed by setting the movement of the battery cell to be rotated, for example, so that the battery cell can be prevented from blowing to the outside to prevent the secondary accident from occurring.

In one specific example, the electrode assembly may be a jelly-roll type electrode assembly having a structure in which an anode, a cathode, and a separator are laminated in order and wound in a circular shape in a cross section.

Specifically, the lower safety vent may include:

A hollow cylinder part formed by a part of a lower bottom surface of the cylindrical case being formed inside;

A bent portion formed on an upper portion of the hollow cylinder portion with respect to the ground surface, the bent portion being broken when the pressure inside the cylindrical case reaches a breaking pressure and is opened to the outside direction; And

A gas discharge port formed at a lower portion of the hollow cylinder portion and discharging the internal gas of the cylindrical case to the outside;

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In one specific example, the vent portion may be fixed to seal the upper surface of the hollow cylinder portion when the vent portion is not opened. That is, the vent portion is closed and fixed so as to block the inflow of substances to the outside until the internal pressure of the cylindrical case becomes equal to or higher than the breaking pressure.

Specifically, the bent portion may be a notch formed of a curved portion or a 'D' shaped notch formed of a straight portion and a curved portion. Here, the notch is a portion in which a groove having a constant depth is formed in a linear shape at a boundary point of the bent portion so that the thickness becomes relatively thinner than the portion other than the notch.

In addition, the bent portion that is broken when the pressure inside the cylindrical case reaches the breaking pressure or more and is opened in the outward direction may be semicircular. Specifically, the bent portion may have a semicircular circumferential shape, and the bent portion may be bent to have a semicircular shape.

In one specific example, the breaking pressure may be, for example, 10 kgf / cm 2 to 30 kgf / cm 2. In particular, when the breaking pressure is less than 10 kgf / cm 2, breakage may occur even at a low withstand pressure, resulting in a decrease in durability of the battery cell. Conversely, if the breaking pressure exceeds 30 kgf / .

In one specific example, the gas outlet may be formed with a latch extending from one side of the gas outlet to the other to adjust the angle between the open vent and the upper surface of the hollow cylinder. Specifically, the latching portion can perform an action of preventing movement of the vent portion in the outward direction, facing the one end portion of the opened vent portion.

In one specific example, the latch may be formed to have an angle between 45 degrees and 75 degrees between the upper surface of the hollow cylinder and the open vent, So that the moving energy of the battery cell can be effectively dispersed. On the contrary, when the angle is less than 45 degrees, gas discharge through the gas outlet is likely to be difficult.

In one specific example, at least a part of the upper surface and the lower surface of the hollow cylinder portion may be sealed so as not to be opened even when the pressure inside the cylindrical case reaches a breaking pressure or more. Specifically, the portion corresponding to the semicircle on the plane of the hollow cylinder portion may be a closed structure so as not to open even when the breaking pressure is exceeded.

In addition, the gas outlet may be in the form of a semicircle in a plan view. Specifically, the area of the gas outlet may be 5% to 25% based on the total area of the bottom of the cylindrical case, Gas discharge is difficult to achieve, and conversely, if it exceeds 25%, the durability of the cylindrical case may be deteriorated.

In one specific example, the cap assembly may be further provided with an upper safety vent for breaking the inner pressure of the cylindrical case when the inner pressure of the cylindrical case reaches the breaking pressure, thereby discharging the inner gas. Here, the upper safety vent may be the same as the upper safety vent applied to the cap assembly of a general cylindrical battery cell.

In one specific example, the battery cell may be a lithium secondary battery of high energy density, discharge voltage, and output stability. Other components of the lithium secondary battery according to the present invention will be described in detail below.

Generally, 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 anode may be prepared, for example, by coating a mixture of a cathode active material, a conductive material and a binder on a cathode current collector, followed by drying. If necessary, a filler may be further added to the mixture.

The cathode active material is a material capable of causing an electrochemical reaction. Examples of the lithium transition metal oxide include lithium cobalt oxide (LiCoO ₂ ) containing two or more transition metals and substituted with one or more transition metals, lithium Layered compounds such as nickel oxide (LiNiO ₂ ); Lithium manganese oxide substituted with one or more transition metals; Formula _{LiNi 1-y M y O 2} ( where, M = Co, Mn, Al , Cu, Fe, Mg, B, Cr, Zn or Ga and Lim, 0.01≤y≤0.7 include one or more elements of the element) A lithium nickel-based oxide represented by the following formula: _{Li 1 + z Ni 1/3 Co 1/3} Mn 1/3 O 2, Li 1 + z Ni 0.4 Mn 0.4 Co 0.2 O 2 , such as _{Li 1 + z Ni b Mn c} Co 1- (b + c + d _{) M d O (2-e} ) A e ( where, -0.5≤z≤0.5, 0.1≤b≤0.8, 0.1≤c≤0.8, 0≤d≤0.2 , 0≤e≤0.2, b + c + d <1, M = Al, Mg, Cr, Ti, Si or Y, and A = F, P or Cl; lithium nickel cobalt manganese composite oxide; And the formula _{Li 1 + x M 1-y} M 'y PO 4-z X z ( wherein, M = a transition metal, preferably Fe, Mn, Co or Ni, M' = Al, Mg or Ti, X = F, S or N, and -0.5? X? +0.5, 0? Y? 0.5, and 0? Z? 0.1), but the present invention is not limited thereto.

The conductive material is usually added in an amount of 1 to 20 wt% based on the total weight of the mixture including the cathode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The filler is optionally used as a component for suppressing the expansion of the anode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. Examples of the filler include olefin polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

Further, the negative electrode is prepared, for example, by coating a negative electrode current collector with a mixture of a negative electrode active material, a conductive material and a binder, and drying the mixture. Optionally, a filler may be further added to the mixture. The negative electrode active material may be at least one selected from the group consisting of graphite carbon, coke carbon, and hard carbon.

Since the configurations of the lithium secondary battery described above are well known in the art, a detailed description thereof will be omitted herein.

As described above, in the cylindrical battery cell according to the present invention, when the lower safety vent formed in the lower part of the cylindrical case is adjusted so that the angle between the discharge direction of the gas discharged downward and the ground surface is less than 90 degrees, The movement of the battery cell due to the reaction is set to rotate so that the movement energy can be effectively dispersed and the battery cell can be prevented from blowing to the outside to prevent the secondary accident from occurring.

1 is a schematic vertical cross-sectional perspective view of a conventional cylindrical battery of the prior art;
2 is a vertical sectional view showing a cylindrical battery cell according to one embodiment of the present invention;
3 is a schematic perspective view showing a bottom of a cylindrical battery cell according to one embodiment of the present invention and a schematic bottom view showing a bottom surface of a cylindrical battery cell;
FIG. 4 is a schematic perspective view illustrating a lower safety vent of a cylindrical battery cell according to an embodiment of the present invention and a ventilation part of a lower safety vent; FIG.
5 is a schematic perspective view illustrating a lower safety vent of a cylindrical battery cell according to an embodiment of the present invention.

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

2 is a vertical sectional view showing a cylindrical battery cell 100 according to one embodiment of the present invention.

2, a cylindrical battery cell 100 according to the present invention includes a cylindrical case 116 in which an electrode assembly 115 including an anode, a cathode, and a separator interposed between the anode and the cathode is received, A cap assembly 112 mounted on the open upper end of the cylindrical case 116 and having electrode terminals formed therein, an electrode assembly 115 accommodated in the cylindrical case 116, And a lower safety vent 130 formed at a lower portion of the cylindrical case 116 so as to be ruptured earlier than other portions of the case when the pressure reaches a breaking pressure to discharge the gas inside.

3 is a schematic perspective view showing a lower part of a cylindrical battery cell according to one embodiment of the present invention and a schematic bottom view showing a bottom surface 120 of a cylindrical battery cell. A schematic perspective view showing a lower safety vent of a cylindrical battery cell according to an embodiment, and a schematic plan view showing a vent portion of a lower safety vent.

Referring to FIG. 4 together with FIG. 3, the lower safety vent 130 includes a hollow cylinder portion 131 formed by a part of the lower bottom surface 120 of the cylindrical case 116 formed inside, A bent portion 132 formed on the hollow cylinder portion 131 and broken when the pressure inside the cylindrical case 116 reaches a breaking pressure and opened to the outside direction and a bent portion 132 formed on the hollow cylinder portion 131 And a gas outlet 133 formed at a lower portion of the cylindrical case 116 for discharging the inner gas of the cylindrical case 116 to the outside.

Here, the vent portion 132 is fixed to seal the upper surface 138 of the hollow cylinder portion 131 when the vent portion 132 is not opened. That is, the vent portion 132 is closed and fixed so as to block the inflow of the substance to the outside until the inner pressure of the cylindrical case 116 becomes equal to or higher than the breaking pressure.

The bent portion 132 may include a notch 135 formed of a curved portion or a D shaped notch 136 formed of a straight portion and a curved portion.

5 is a schematic perspective view illustrating a lower safety vent of a cylindrical battery cell according to an embodiment of the present invention.

Referring to FIG. 5, the bent portion 139, which is broken when the pressure inside the cylindrical case 116 reaches the breaking pressure or more, is opened in the outward direction is semicircular. The bent portion 139 has a semicircular circumferential shape, and the bent portion is bent to have a semicircular shape.

At this time, the breaking pressure is, for example, 10 kgf / cm 2 to 30 kgf / cm 2.

The gas outlet 133 is extended from one side of the gas outlet 133 to the other side to adjust the angle 140 between the open vent 132 and the upper surface 138 of the hollow cylinder 131 A latch 134 is formed. The latching portion 134 can act to prevent movement of the bent portion 132 in the outward direction, facing the one end of the opened bent portion 132. [

The lower safety vent 130 is adjusted so that the angle between the discharge direction of the gas discharged to the outside and the surface of the lower safety vent 130 is less than 90 degrees. In order to enhance safety more effectively, And the angle 140 between the upper surface and the open vent portion 132 is formed to be 45 to 75 degrees.

In addition, the portion 137 corresponding to the semicircle on the plane of the hollow cylinder portion 131 is structured to be hermetically closed so as not to be opened even when the breaking pressure is exceeded.

3 and 5, the gas outlet 133 is in the form of a semicircle in a plan view, and the area of the gas outlet 133 is 5% to 10% of the total area of the bottom surface 120 of the cylindrical case 116 25%.

As described above, in the cylindrical battery cell according to the present invention, when the lower safety vent formed at the lower part of the cylindrical case is adjusted so that the angle of the discharge direction of the gas discharged to the outside with the ground surface is less than 90 degrees, The movement of the battery cell due to the reaction of the gas discharge is set to be rotated so that the movement energy can be effectively dispersed and the battery cell can be prevented from flying out to the secondary accident.

Claims (14)

A cylindrical case in which an electrode assembly including an anode, a cathode, and a separator interposed between the anode and the cathode is received;
A cap assembly mounted on an open upper end of the cylindrical case and having an electrode terminal formed therein;
An electrode assembly housed inside the cylindrical case; And
A lower safety vent formed at a lower portion of the cylindrical case to break the inner gas when the inner pressure of the cylindrical case reaches the breaking pressure before the other portion of the case;
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Wherein the lower safety vent is adjusted such that an angle between a discharge direction of the gas discharged to the outside and the ground surface is less than 90 degrees. The cylindrical battery cell according to claim 1, wherein the electrode assembly is a jelly-roll type electrode assembly having a structure in which an anode, a cathode, and a separator are laminated in order and wound in a circular shape in a cross section. 2. The safety vent of claim 1,
A hollow cylinder part formed by a part of a lower bottom surface of the cylindrical case being formed inside;
A bent portion formed on an upper portion of the hollow cylinder portion with respect to the ground surface, the bent portion being broken when the pressure inside the cylindrical case reaches a breaking pressure and is opened to the outside direction; And
A gas discharge port formed at a lower portion of the hollow cylinder portion and discharging the internal gas of the cylindrical case to the outside;
Wherein the cylindrical battery cell comprises: The cylindrical battery cell according to claim 3, wherein the bent portion is fixed to seal the upper surface of the hollow cylinder portion when the vent portion is not opened. The cylindrical battery cell according to claim 3, wherein the bent portion comprises a notch formed of a curved portion, or a 'D' shaped notch formed of a straight portion and a curved portion. The cylindrical battery cell according to claim 3, wherein the open vent portion has a semicircular shape. The cylindrical battery cell according to claim 3, wherein the breaking pressure is 10 kgf / cm 2 to 30 kgf / cm 2. 4. The cylindrical battery cell according to claim 3, wherein the gas discharge port is formed with a latch extending from one side of the gas discharge port to the other side for adjusting the angle formed between the open vent and the upper surface of the hollow cylinder. 9. The cylindrical battery cell according to claim 8, wherein the latching portion opposes one end of the opened vent portion to prevent movement of the vent portion in the outward direction. The cylindrical battery cell according to claim 8, wherein an angle formed between an upper surface of the hollow cylinder portion and an open vent portion is 45 to 75 degrees. 4. The cylindrical battery cell according to claim 3, wherein at least a part of the upper and lower surfaces of the hollow cylinder portion is sealed so that it is not opened even when the pressure inside the cylindrical case reaches a breaking pressure or more. The cylindrical battery cell according to claim 3, wherein the gas outlet is semicircular in plan view. The cylindrical battery cell according to claim 3, wherein the area of the gas outlet is 5% to 25% based on the total area of the bottom surface of the cylindrical case. The cylindrical battery cell according to claim 1, wherein the cap assembly further comprises an upper safety vent for breaking the inner pressure of the cylindrical case when the inner pressure of the cylindrical case reaches the breaking pressure, thereby discharging the inner gas.

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