KR100731465B1 - Lithium ion secondary battery - Google Patents

Abstract

The present invention relates to a lithium ion secondary battery, and a technical problem to be solved is to form a plurality of crack lines in advance in a safety vent, so that when the battery internal pressure is above a predetermined pressure, the crack line first ruptures, and then the battery internal pressure further increases. If the safety vent is to be ruptured to improve the safety of the battery.

To this end, a summary of the solution according to the present invention, in a lithium ion secondary battery having a safety vent of relatively thin thickness, the safety vent is disclosed a lithium ion secondary battery having at least one crack line.

In this manner, in the lithium ion secondary battery according to the present invention, the crack line is first ruptured at a predetermined internal pressure to discharge gas inside the battery, and the safety vent is secondly ruptured to discharge gas inside the battery. The safety is further improved.

Lithium Ion Secondary Battery, Safety Vent, Crack, Withstand Pressure, Gas

Description

Lithium ion secondary battery

1 is a perspective view showing an example of a lithium ion secondary battery according to the present invention.

2A to 2D are partially enlarged perspective views illustrating shapes of various crack lines formed in a safety vent in a lithium ion secondary battery according to the present invention.

3A to 3C are partially enlarged cross-sectional views illustrating a cross section of a safety vent in a lithium ion secondary battery according to the present invention.

4A is a cross-sectional view illustrating a state in which a crack line is primarily broken in a lithium ion secondary battery according to the present invention, and FIG. 4B is a cross-sectional view illustrating a state in which a safety vent is secondly broken.

5 is an exploded perspective view showing an example of a lithium ion secondary battery according to the present invention.

6 is a cross-sectional view showing an example of a lithium ion secondary battery according to the present invention.

<Description of Symbols for Main Parts of Drawings>

100; Lithium ion secondary battery according to the present invention

110; Electrode plate assembly 111; Positive plate

112; Negative plate 113; Separator

120; Can 121; Front page

122; Second page 123; Page 3

124; Opening 124; if

131; Insulated case 132; Terminal plate

133; Insulation plate 140; Cap assembly

141; Cap plate 142; Through

143; Insulating gasket 144; Electrode terminals

145; Injection hole 146; plug

148; Safety vent 148a; Front page

148b; Second page 149,149a, 149b; Crack line

The present invention relates to a lithium ion secondary battery, and more particularly, to a lithium ion secondary battery in which a crack is formed in a safety vent.

In general, a lithium ion secondary battery includes a pole plate assembly wound or stacked in a jelly roll form, a can in the form of a substantially hexahedron in which the pole plate assembly is inserted and fixed, and filled in the can to move lithium ions. It is composed of an electrolyte solution, and a cap assembly for blocking the can on the electrode plate assembly and the electrolyte.

The lithium ion secondary battery is laminated with a positive electrode plate with a positive electrode active material, a negative electrode plate with a negative electrode active material and a separator, and then wound or laminated in the form of a jelly roll, and put it in a can again, and then welds a cap assembly to the top. Seal it. Thereafter, after the electrolyte is injected, charging and inspection are performed to complete a lithium ion secondary battery in the form of a bare cell. Of course, the battery pack is assembled and inspected after attaching various safety devices, protective circuit boards, and the like to the lithium ion secondary battery in the form of a bare cell, thereby completing a normal battery pack.

On the other hand, since the lithium ion secondary battery uses the constant voltage / constant current charging method, if the charging voltage is accurately controlled in the charger, there is no overcharge phenomenon. However, the charger may be damaged or malfunction, resulting in abnormal charging. In this case, the battery voltage continues to increase due to the characteristic that the potential of the positive electrode active material, for example, lithium cobalt (LiCoO ₂ ) is continuously increased, and An abnormal heating phenomenon occurs.

Safety measures against this phenomenon include a built-in positive temperature coefficient thermistor, a separator with a shutdown function, and a protective circuit board for controlling charge and discharge voltages. There is a safety vent actuated by.

Here, the safety vent generally refers to a thinner area formed in the cap assembly, which ruptures when the internal pressure of the battery rises due to gas generation, and releases the gas inside the can to the outside, such as an explosion of a lithium ion secondary battery. It prevents the situation.

The gas is generated when the electrolyte or the active material is decomposed when the charging voltage of the lithium ion secondary battery rises above the reference voltage. Such a gas usually swells the can by increasing the battery internal pressure, and the safety vent ruptures due to an increase in the internal pressure of the battery, thereby preventing an extreme explosion or fire of the lithium ion secondary battery.

As such, the safety vent is designed to operate automatically when the battery internal pressure becomes higher than a predetermined pressure. However, such a conventional safety vent is processed so that a predetermined area of the cap assembly is relatively thin, there is a problem that the operating speed is slightly different for each battery.

That is, the safety vents are processed to have the same thickness in all cells, but in actual cells both the operating pressure and the operating speed of the safety vents are different. Moreover, in some cases the safety vents do not work. Therefore, it is difficult to maximize the safety of the battery simply by a structure that makes the thickness of the safety vent relatively thin as described above.

SUMMARY OF THE INVENTION The present invention has been made to overcome the above-mentioned problems, and an object of the present invention is to form a plurality of crack lines in a safety vent in advance, so that when the battery withstand pressure is above a predetermined pressure, the crack line first ruptures, and then the battery withstand pressure is increased. Further rise is to provide a lithium ion secondary battery that maximizes the safety of the battery by rupturing the safety vent.

In order to achieve the above object, a lithium ion secondary battery according to the present invention has a separator interposed between a positive electrode plate and a negative electrode plate and wound a plurality of times, the positive electrode plate having a positive electrode lead, and the negative electrode plate having a negative electrode plate extending a predetermined length outside. An assembly, the electrode plate assembly is accommodated, the can opening is formed on one side, the can is coupled to the opening of the can, the gasket is interposed through the electrode terminal is coupled through the cathode lead is connected at one side, The anode lead may be connected, and the other side may include a cap plate having a relatively thin safety vent, and at least one crack line may be formed in the safety vent.

Here, the crack line may have a form in which a plurality of curved portions are connected and may be generally in a form close to a straight line.

In addition, a plurality of crack lines may be arranged in a radial form with respect to the central area of the safety vent.

In addition, the crack line may be formed by a plurality of predetermined intervals arranged in the horizontal direction or the vertical direction in the safety vent.

In addition, the crack line may be formed by a plurality of predetermined intervals in the transverse direction and the longitudinal direction in the safety vent.

In addition, the safety vent may have a first flat surface and a second flat surface as an opposite surface of the first surface, and the crack line may be formed on either the first surface or the second surface.

In addition, the safety vent may have a first flat surface and a second flat surface as an opposite surface of the first surface, and the crack line may be formed on the first surface and the second surface, respectively.

In addition, the crack line may be formed to a depth of 10 to 90% of the total thickness of the safety vent.

In addition, the crack line may be formed to a depth of 50% of the total thickness of the safety vent.

As described above, in the lithium ion secondary battery according to the present invention, a crack line having a thinner thickness is further formed in the safety vent having a relatively thinner thickness, so that the safety vent operates faster and more accurately when the battery pressure increases. That is, when the internal pressure of the battery rises, gas is primarily discharged through the crack line, and when the internal pressure of the battery increases further, the entire safety vent is ruptured, thereby completely releasing the gas. Therefore, the lithium ion secondary battery according to the present invention can avoid extreme situations such as explosion or fire of the battery due to overcharging.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings such that those skilled in the art may easily implement the present invention.

1 is a perspective view showing an example of a lithium ion secondary battery according to the present invention.

As shown, the lithium ion secondary battery 100 according to the present invention includes a can 120 having a substantially hexahedron shape and a cap plate 141 coupled to an upper portion of the can 120. In addition, an electrode terminal 144 is coupled to a center of the cap plate 141. Of course, an insulating gasket 143 is interposed between the electrode terminal 144 and the cap plate 141 for electrical insulation. In addition, the cap plate 141 is formed with a liquid injection hole 145 for the injection of the electrolyte.

Further, the cap plate 141 is formed with a safety vent 148 having a relatively thin thickness and a predetermined area on one side of the electrode terminal 144, and at least one crack line in the safety vent 148. 149 is further formed.

Although the planar shape of the safety vent 148 is substantially rectangular in the figure, the present invention is not limited to the planar form of the safety vent 148. That is, the planar shape of the safety vent 148 may be a variety of forms, such as circular, oval, square, pentagonal.

In addition, the planar shape of the crack line 149 is also shown in the form of a plurality of curved parts connected at the same time, as a whole close to a straight line, but does not limit the present invention in this form. That is, the planar shape of the crack line 149 may be a closed curve or an open curve such as a circle, an ellipse, a rectangle, a pentagon, or the like.

Of course, such a safety vent 148 and the crack line 149 formed therein ruptures when the internal pressure of the battery rises, thereby releasing gas inside the battery to the outside, thereby avoiding an extreme situation such as an explosion of the battery. That is, when the internal pressure of the battery increases, the crack line 149 ruptures primarily, and the safety vent 148 ruptures secondly.

2A to 2D are partially enlarged perspective views illustrating shapes of various crack lines formed in a safety vent in a lithium ion secondary battery according to the present invention.

First, as shown in FIG. 2A, in the present invention, the crack line 149 formed in the safety vent 148 may be radially arranged about an approximately central region of the safety vent 148 in plan view. Of course, six crack lines 149 are shown in the figure, but the present invention is not limited to these numbers. That is, the crack lines 149 may be smaller or larger than six.

Subsequently, as shown in FIG. 2B, in the present invention, a plurality of crack lines 149 formed in the safety vent 148 may be arranged at regular intervals in a substantially horizontal direction.

Subsequently, as shown in FIG. 2C, a plurality of crack lines 149 formed in the safety vent 148 may be arranged at regular intervals in a substantially vertical direction.

Subsequently, as shown in FIG. 2D, the present invention may be formed by arranging crack lines 149 formed in the safety vent 148 at regular intervals in a horizontal direction and a vertical direction. That is, the crack lines 149 may cross each other in the horizontal direction and the vertical direction.

Here, although the crack line 149 has been described with reference to FIGS. 2A to 2D, the present invention is not limited to the form of the crack line 149, and various planar shapes may be possible.

3A to 3C are partially enlarged cross-sectional views illustrating a cross section of a safety vent in a lithium ion secondary battery according to the present invention.

As shown in the present invention, the thickness of the safety vent 148 is smaller than the thickness of the cap plate 141, and the safety vent 148 has a substantially flat first surface 148a and the first surface ( An opposite surface of 148a includes a substantially flat second surface 148b.

First, as shown in FIG. 3A, a plurality of crack lines 149 formed in the safety vent 148 may be formed at a predetermined depth on the first surface 148a of the safety vent 148.

In addition, as shown in FIG. 3B, a plurality of crack lines 149 formed in the safety vent 148 may be formed at a predetermined depth on the second surface 148b of the safety vent 148.

Furthermore, as shown in FIG. 3C, in the present invention, a plurality of crack lines 149a and 149b formed in the safety vent 148 may be formed on the first surface 148a and the second surface 148b, respectively, to a predetermined depth. have. In this case, the crack line 149a formed on the first surface 148a and the crack line 149b formed on the second surface 148b may be formed at different positions so as not to cross each other.

Meanwhile, the crack lines 149, 149a and 149b may be formed to a depth of 10 to 90% of the total thickness of the safety vent 148. If the depth of the crack lines 149, 149a and 149b is less than or equal to 10% of the thickness of the safety vent 148, the crack lines 149, 149a and 149b are not easily broken when the internal pressure of the battery increases. If the depth of the crack lines 149, 149a, and 149b is formed to be 90% or more of the thickness of the safety vent 148, the crack lines rupture too easily at small battery breakdown voltages. Preferably, the depths of the crack lines 149, 149a, and 149b are formed to be approximately 50% of the depth of the entire thickness of the safety vent 148.

4A is a cross-sectional view illustrating a state in which a crack line is primarily broken in a lithium ion secondary battery according to the present invention, and FIG. 4B is a cross-sectional view illustrating a state in which a safety vent is secondly broken.

As shown in FIG. 4A, when the internal pressure of the lithium ion secondary battery 100 increases to some extent due to overcharging, the crack line 149 formed in the safety vent 148 starts to rupture. That is, as the crack line 149 ruptures finely, the internal pressure of the battery is reduced by releasing gas inside the battery to the outside.

In addition, as shown in FIG. 4B, in the lithium ion secondary battery 100 according to the present invention, the safety vent 148 starts to rupture when the internal pressure of the battery increases further. That is, as the safety vent 148 completely ruptures, gas inside the battery is released to the outside more quickly, thereby reducing the battery internal pressure.

As described above, in the lithium ion secondary battery 100 according to the present invention, when the internal pressure of the battery increases, the crack line 149 firstly ruptures, and the safety vent 148 secondly ruptures, thereby causing the safety vent 148 to be overall. The operation time becomes even faster. That is, the sensitivity of the safety vent 148 is further improved. Therefore, it is possible to prevent an extreme dangerous situation such as explosion or fire of the battery due to the non-operation of the safety vent 148.

5 is an exploded perspective view showing an example of a lithium ion secondary battery according to the present invention, Figure 6 is a cross-sectional view showing an example of a lithium ion secondary battery according to the present invention. Here, the lithium ion secondary battery illustrated in FIGS. 5 and 6 is only an example in which a safety vent having a crack according to the present invention is applied, and the present invention is not limited to these drawings.

As shown, the lithium ion secondary battery 100 according to the present invention includes a pole plate assembly 110, a can 120 in which the pole plate assembly 110 is accommodated, and a can be injected into the can 120 to move lithium ions. Electrolyte solution (not shown with reference numeral) and the can 120 is blocked to prevent the electrode plate assembly 110 and the electrolyte from escaping to the outside, and the safety vent 148 in the predetermined position cap assembly ( 140).

First, the electrode plate assembly 110 has a positive electrode plate 111 attached with a positive electrode active material (for example, lithium cobalt (LiCoO ₂ )) (not shown), and a negative electrode active material (for example, graphite) (not shown) attached thereto. And a separator 113 positioned between the positive electrode plate 112 and the positive electrode plate 111 and the negative electrode plate 112 to prevent a short and allow only movement of lithium ions. The positive electrode plate 111 and the negative electrode plate 112 thereon. ) And the separator 113 are wound a plurality of times in the form of a jelly roll and are accommodated in the can 120. Here, the positive electrode plate 111 may be an aluminum (Al) foil, the negative electrode plate 112 may be a copper (Cu) foil, and the separator 113 may be polyethylene (PE) or polypropylene (PP). It does not limit the material of. In addition, a positive electrode lead 114 protruding a certain length upward is welded to the positive electrode plate 111, and a negative electrode lead 115 protruding a predetermined length upwardly is welded to the negative electrode plate 112. The positive electrode lead 114 may be made of aluminum (Al) and the negative electrode lead 115 may be made of nickel (Al), but the present invention is not limited thereto.

The can 120 has at least one first surface 121 and a second surface 122 connected to the first surface 121 and having at least one area smaller than that of the first surface 121. The third surface 123 is simultaneously connected to the first surface 121 and the second surface 122. In addition, the can 120 has a shape in which an opening 124 is formed on an upper surface of the can 120 facing the third surface 123. That is, the can 120 has a substantially rectangular parallelepiped shape having an opening 124 formed thereon. The can 120 may be formed of aluminum (Al), iron (Fe), an alloy, or an equivalent thereof, but the material is not limited thereto.

The electrolyte (not shown) is injected into the can 120 to be positioned between the positive electrode plate 111 and the negative electrode plate 112 of the electrode plate assembly 110. This electrolyte serves as a moving medium of lithium ions generated by the electrochemical reaction in the positive electrode plate 111 and the negative electrode plate 112 inside the battery during charge and discharge, which is a non-aqueous organic compound which is a mixture of lithium salts and high purity organic solvents. It may be an electrolyte solution. In addition, the electrolyte may be a polymer using a polymer electrolyte.

Meanwhile, an insulating case 131, a terminal plate 132, and an insulating plate 133 may be further coupled to the opening 124 of the can 120 as an upper portion of the pole plate assembly 110, but The invention does not necessarily require such a component. Of course, the insulating case 131, the terminal plate 132, and the insulating plate 133 are formed with through holes 131a, 132a, and 133a so that the negative electrode lead 115 extends upwardly. In addition, when the electrolyte is injected into the insulating plate 133 through a cap plate 141 to be described below, an electrolyte through hole 131b is also formed to easily flow into the electrode plate assembly 110.

The cap assembly 140 is laser welded to the opening 124 of the can 120, which includes a cap plate 141 approximately on a rectangular plate. In the center of the cap plate 141, a predetermined size through-hole 142 is formed, one side of the electrolyte injection hole 145 for the injection of the electrolyte is formed. In addition, an insulating gasket 143 is coupled to the through hole 142 of the cap plate 141, and an electrode (cathode) terminal 144 is coupled to the insulating gasket 143. Of course, the electrode terminal 144 is welded to the negative electrode lead 115 to serve as a negative electrode during discharge or charging. In addition, the positive electrode lead 114 is welded between the electrolyte injection hole 145 of the cap plate 141 and the electrode terminal 144 so that the cap plate 141 and the can 120 become the positive electrode as a whole. . In addition, the plug 146 is coupled and welded to the electrolyte injection hole 145 of the cap plate 141 so that the electrolyte is not leaked to the outside after the electrolyte is injected.

Meanwhile, a safety vent 148 having a relatively thin thickness is formed in a predetermined region of the cap plate 141. Of course, the safety vent 148 is further provided with at least one crack line 149 as described above, thereby improving the safety of the battery. Here, the planar shape, the cross-sectional shape, and the like of the crack line 149 include all the features shown and described with reference to FIGS. 1 to 4B. In addition, the safety vent 148 and the crack line 149 has been described as an example formed on the cap plate 141, but the safety vent 148 and the crack line 149 can be not only the cap plate 141 but also cans. It may be formed on at least one of the first surface 121, the second surface 122, the third surface 123, or the lower surface 125 of the 120. Of course, two or more of the safety vents 148 and the crack lines 149 formed thereon may be formed, and the safety vents 148 and the crack lines 149 are not limited to the formation positions and the number of formation.

As described above, in the lithium ion secondary battery according to the present invention, a thinner crack line is formed in a safety vent having a relatively thinner thickness, so that the safety vent operates faster and more accurately when the battery pressure increases. There is.

That is, when the internal pressure of the battery rises, the gas inside the battery is primarily discharged through the crack line, and when the internal pressure of the battery increases further, the entire safety vent is ruptured, thereby rapidly discharging the gas inside the battery to the outside quickly. Will be released.

Therefore, the lithium ion secondary battery according to the present invention can avoid extreme situations such as explosion or fire of the battery during overcharging.

What has been described above is just one embodiment for carrying out the lithium ion secondary battery according to the present invention, and the present invention is not limited to the above-described embodiment, and as claimed in the following claims, the gist of the present invention Without departing from the technical spirit of the present invention to the extent that any person of ordinary skill in the art to which the present invention pertains various modifications can be made.

Claims (18)

A can of a hexahedron shape having an opening at one side thereof, a cap plate having a rectangular shape blocking the opening of the can, and a safety vent formed to have a thickness relatively smaller than a thickness of the cap plate on a surface of the cap plate. , At least one crack line is formed in the safety vent lithium ion secondary battery. The lithium ion secondary battery of claim 1, wherein the crack line has a shape in which a plurality of curved portions are connected and is generally close to a straight line. The lithium ion secondary battery of claim 1, wherein a plurality of crack lines are arranged in a radial form around a central region of the safety vent. The lithium ion secondary battery of claim 1, wherein the crack line is any one selected from a form in which the plurality of crack lines are arranged at regular intervals in a horizontal direction and at a predetermined interval in a vertical direction. The lithium ion secondary battery of claim 1, wherein a plurality of crack lines are formed at predetermined intervals in a horizontal direction and a vertical direction in the safety vent. 2. The safety vent of claim 1 wherein the safety vent has a first flat surface and a second flat surface opposite the first surface, wherein the crack line is formed on one of the first and second surfaces. Lithium ion secondary battery which uses. 2. The safety vent of claim 1, wherein the safety vent has a first flat surface and a second flat surface as an opposite surface of the first surface, wherein the crack lines are formed on the first surface and the second surface, respectively. Lithium ion secondary battery. The lithium ion secondary battery of claim 1, wherein the crack line is formed to a depth of 10 to 90% of the total thickness of the safety vent. The lithium ion secondary battery of claim 1, wherein the crack line has a depth of 50% of the total thickness of the safety vent. A separator plate interposed between the positive electrode plate and the negative electrode plate and wound a plurality of times, the positive electrode plate having a positive electrode lead, and the negative electrode plate having a negative electrode lead extending at a predetermined length outward from the negative electrode plate; The electrode plate assembly is accommodated, and one side of the can-shaped can is formed with an opening opening, It is coupled to the opening of the can, a gasket is interposed in the center of the electrode terminal is coupled through the cathode lead is connected, the positive lead is connected to one side, the other side is formed with a relatively thin safety vent A cap plate in the form of, At least one crack line is formed in the safety vent lithium ion secondary battery. The lithium ion secondary battery of claim 10, wherein the crack line has a shape in which a plurality of curved portions are connected and is generally close to a straight line. The lithium ion secondary battery of claim 10, wherein a plurality of crack lines are arranged in a radial form around a central region of the safety vent. The lithium ion secondary battery of claim 10, wherein the crack line is any one selected from a plurality of shapes arranged at regular intervals in a horizontal direction and at a predetermined interval in a vertical direction in the safety vent. The lithium ion secondary battery of claim 10, wherein a plurality of crack lines are arranged at regular intervals in a horizontal direction and a vertical direction in the safety vent. The safety vent according to claim 10, wherein the safety vent has a first flat surface and a second flat surface as an opposite surface of the first surface, and the crack line is formed on one of the first surface and the second surface. Lithium ion secondary battery which uses. The safety vent according to claim 10, wherein the safety vent has a first flat surface and a second flat surface as an opposite surface of the first surface, and the crack lines are formed on the first surface and the second surface, respectively. Lithium ion secondary battery. The lithium ion secondary battery of claim 10, wherein the crack line has a depth of about 10% to about 90% of the total thickness of the safety vent. The lithium ion secondary battery of claim 10, wherein the crack line is formed to a depth of 50% of the total thickness of the safety vent.

Images