Title of invention: secondary battery
Technical field
[One]
Mutual citation with related applications
[2]
This application claims the benefit of priority based on Korean Patent Application No. 10-2018-0065057 filed on June 05, 2018, and all contents disclosed in the documents of the Korean patent application are included as part of this specification.
[3]
Technical field
[4]
The present invention relates to a secondary battery, and to a secondary battery having a structure capable of solving a safety problem that may occur due to an external short circuit.
Background
[5]
As technology development and demand for electronic devices increase, the demand for secondary batteries for supplying energy to electronic devices is also increasing. In particular, many studies have been conducted on lithium ion secondary batteries having a higher energy density and discharge voltage than before.
[6]
Depending on the structural or manufacturing characteristics, the secondary battery has a structure in which an electrode assembly made of an electrode and a separator is accommodated in a cylindrical or rectangular metal can, and an electrode assembly inside a pouch-shaped case containing aluminum It can be roughly classified as a pouch-type secondary battery having a structure accommodated in. Among them, the cylindrical secondary battery has an advantage in that it has a relatively large capacity and is structurally stable.
[7]
However, secondary batteries including cylindrical secondary batteries may be exposed to various types of risks during use, and in this case, problems such as ignition or explosion of the secondary battery may occur. In order to prevent this, the secondary battery is generally provided with various members for improving the safety of the secondary battery.
[8]
A member for improving the safety of the cylindrical secondary battery is provided between, for example, a crimping portion formed on the top of the battery can constituting the body of the secondary battery and a top cap or a safety vent, and the internal space of the secondary battery A crimping gasket that seals the gas from the outside, and a CID gasket provided between the safety vent and the CID (Current Interrupt Device) filter.
[9]
On the other hand, when an external electrically conductive object is directly electrically connected to the positive electrode and the negative electrode of the cylindrical secondary battery, the electrode tab of the secondary battery needs to be cut off as quickly as possible. However, according to the prior art, when a positive electrode and a negative electrode of a secondary battery are electrically directly connected by an external electrically conductive object, there is a problem that it takes a considerable amount of time to cut off the current by breaking the electrode tab.
Detailed description of the invention
Technical challenge
[10]
The problem to be solved by the present invention is to block current quickly by breaking the electrode tab of the secondary battery as quickly as possible when an external electrically conductive object is electrically directly connected to the positive electrode and the negative electrode of a cylindrical secondary battery.
Means of solving the task
[11]
According to an aspect of the present invention for achieving the above object, a battery can having a structure that accommodates the electrode assembly and is opened upward; A top cap provided on the top of the battery can; A safety vent provided under the top cap; A CID filter provided under the safety vent; A first gasket provided on an inner surface of an upper portion of the battery can and formed in close contact with a side portion of the safety vent to insulate the safety vent from the upper portion of the battery can; And a second gasket provided between the safety vent and the CID filter and formed in close contact with the upper portion of the CID filter to surround the outer end of the CID filter and formed in close contact with the lower portion of the safety vent. Including, an insulating layer is formed in a region where the top cap and the first gasket are in close contact, and the insulating layer includes a ceramic material and a binder.
[12]
The binder may include an organic binder.
[13]
The ceramic material may include aluminum oxide or silicon oxide.
[14]
The binder may be included in an amount of 20% to 90% by weight based on the total weight of the insulating layer.
[15]
A ratio of the thickness of the insulating layer to the thickness of the top cap may be 0.015 to 0.15.
[16]
A crimping portion having a structure bent in a whole or part of an S shape on an upper portion of the battery can; Is formed, and the first gasket may be provided in close contact with the inner surface of the crimping part.
[17]
The insulating layer may be an upper surface of the top cap, and may be formed in a region between the upper end of the crimping portion and the top cap of the inner region of the first gasket.
[18]
The thickness of the insulating layer may be 0.015mm to 0.045mm.
[19]
The thickness of the top cap may be 0.3mm to 1.0mm.
Effects of the Invention
[20]
According to the present invention, when an external electrically conductive object is directly electrically connected to a positive electrode and a negative electrode of a cylindrical secondary battery, the electrode tab of the secondary battery is cut off as quickly as possible, thereby quickly blocking current.
Brief description of the drawing
[21]
1 is a cross-sectional view showing an upper structure of a secondary battery according to a first example of the present invention.
[22]
2 is a cross-sectional view showing an upper structure of a secondary battery according to a second example of the present invention.
[23]
3 is a cross-sectional view showing the structure of a first gasket of a secondary battery according to the present invention.
Mode for carrying out the invention
[24]
Hereinafter, a structure of a secondary battery according to the present invention will be described with reference to the drawings.
[25]
[26]
Secondary battery
[27]
1 is a cross-sectional view showing an upper structure of a secondary battery according to a first example of the present invention, and FIG. 2 is a cross-sectional view showing an upper structure of a secondary battery according to a second example of the present invention.
[28]
1 to 2, the secondary battery 10 according to the present invention may include a battery can 100 that accommodates an electrode assembly (not shown). The battery can 100 may have a structure in which the upper side is open. The battery can 100 may have a cylindrical shape. That is, the secondary battery according to the present invention may be a cylindrical secondary battery.
[29]
As shown in FIGS. 1 to 2, a crimping portion 110 having a structure bent in an S-shape may be formed on an upper portion of the battery can 100. In this case, "the crimping part 110 has a structure in which the crimping part 110 is bent in an S-shape" means that the crimping part 110 has at least one area protruding to the outside of the battery can and an area protruding to the inside of the battery can. Can be interpreted as. For example, as shown in FIGS. 1 to 2, the upper part of the crimping part 110 is formed to protrude to the outside of the battery can 100, and the lower part of the crimping part 110 is inside the battery can 100. It may be formed to protrude.
[30]
A top cap 200 may be provided on the battery can 100. The top cap 200 may be configured to seal the open upper portion of the battery can 100.
[31]
A safety vent 300 may be provided under the top cap 200. The safety vent 300 may be configured for discharging gas inside the secondary battery when the pressure inside the secondary battery exceeds a predetermined range. To this end, a notch 310 having a thickness thinner than that of other regions may be formed in the safety vent 300. Hereinafter, in the present specification, a notch formed in the safety vent 300 will be referred to as a'first notch 310'. When the pressure inside the secondary battery exceeds a certain range, the first notch 310 of the safety vent 300 may be broken and gas inside the secondary battery may be discharged. Accordingly, it is possible to prevent an explosion due to an increase in pressure inside the secondary battery.
[32]
As shown in FIG. 1, the safety vent 300 may be in close contact with the bottom of the top cap 200. At this time, the end of the safety vent 300 is bent upward and then bent toward the inside of the battery can again as shown in FIG. 1, so that the end of the safety vent 300 may wrap the periphery of the top cap 200. On the other hand, as shown in FIG. 2, the end portion of the safety vent 300 may be bent upward only once to have a structure surrounding the side surface of the top cap 200.
[33]
Meanwhile, a CID filter 400 may be provided under the safety vent 300. A partial region of the safety vent 300 and a partial region of the CID filter 400 may be in close contact with or attached to each other. For example, as illustrated in FIGS. 1 to 2, the central portion of the safety vent 300 and the central portion of the CID filter 400 may be in close contact with or attached to each other. The safety vent 300 and the CID filter 400 may be spaced apart from each other in an area excluding a region in which the safety vent 300 and the CID filter 400 are in close contact with or attached to each other.
[34]
The CID filter 400 may be configured to block the current of the secondary battery in an emergency. To this end, a notch 410 having a thickness thinner than that of other regions may be formed in the CID filter 400. Hereinafter, in the present specification, a notch formed in the CID filter 400 will be referred to as a'second notch 410'. When the pressure inside the secondary battery exceeds a certain range, the CID filter 400 is broken, thereby blocking the current of the secondary battery. In particular, when the second notch 410 is formed, breakage may occur in the CID filter 400 based on the second notch 410. Accordingly, it is possible to prevent an explosion due to an increase in pressure inside the secondary battery.
[35]
Meanwhile, as described above, a top cap, a safety vent, and the like may be provided on the top of the battery can. Nevertheless, the sealing property of the inner space of the battery can may still be deteriorated. If the sealing property is poor, the electrolyte inside the secondary battery may leak to the outside, and foreign substances from outside may flow into the secondary battery.
[36]
Accordingly, in order to improve the sealing property of the inner space of the battery can, a gasket 500 may be additionally provided on the top of the battery can 100. The gasket 500 may be provided on the inner surface of the upper portion of the battery can 100. When the crimping part 110 is formed on the battery can 100, the gasket 500 may be provided in close contact with the inner surface of the crimping part 110. As described above, when the safety vent 300 has a structure that is bent upward and then bent back to the inside of the battery can, the gasket 500 may be provided between the crimping unit 110 and the safety vent, and the gasket 500 ) May be provided in close contact with the outer portion of the safety vent. Hereinafter, in the present specification, the gasket 500 provided on the upper portion of the battery can 100 will be referred to as a “first gasket”. Since the first gasket 500 is provided, the sealing property of the inner space of the battery can may be further improved.
[37]
Meanwhile, as described above, some areas of the safety vent 300 and some areas of the CID filter 400 may be in close contact or attached to each other, and in the remaining areas, the safety vent 300 and the CID filter 400 may be spaced apart from each other. In this case, a gasket 600 may be provided between the safety vent 300 and the CID filter 400 so that an area in which the safety vent 300 and the CID filter 400 are spaced apart from each other may maintain the spaced state. Hereinafter, in this specification, the gasket 600 provided in the safety vent 300 and the CID filter 400 will be referred to as a “second gasket”. Since the second gasket 600 is provided, a region in which the safety vent 300 and the CID filter 400 are spaced apart from each other may maintain the spaced state.
[38]
Subsequently, referring to FIGS. 1 to 2, an insulating layer 700 may be formed in a region where the top cap 200 and the first gasket 500 are in close contact with each other in the secondary battery according to the present invention. More preferably, the insulating layer 700 may be adhesively formed on a region of the top surface of the top cap 200 in which the top cap 200 and the first gasket 500 are in close contact (refer to the dotted line in FIG. 2 ). For example, the insulating layer 700 may be formed on the top surface of the top cap 200 by spray spraying. Alternatively, the insulating layer 700 may be formed by a coating method in which a material constituting the insulating layer is applied to the upper surface of the top cap 200 and then pressurized, and the material constituting the insulating layer is used as the top cap 200 ) May be formed by spraying a nozzle on the upper surface of the.
[39]
The insulating layer 700 may include a ceramic material and a binder. The ceramic material may include aluminum oxide or silicon oxide.
[40]
When the positive electrode and the negative electrode of the secondary battery are electrically directly connected by an external electrically conductive object, heat is generated in the secondary battery as an excessive current flows. In this case, it is preferable for safety to stop the current flowing through the secondary battery while the electrode tab of the secondary battery is cut off.
[41]
In this case, when an external electrically conductive object is directly electrically connected to the positive electrode and the negative electrode of the cylindrical secondary battery, the electrode tab of the secondary battery needs to be cut off as quickly as possible. However, according to the prior art, when the positive electrode and the negative electrode of the secondary battery are directly electrically connected to each other by an external electrically conductive object, there is a problem that it takes a considerable amount of time to cut off the current by breaking the electrode tab.
[42]
The insulating layer 700 according to the present invention may be configured to solve the problem that it takes a considerable amount of time for the electrode tab to break. That is, as a result of the experiment of the inventors of the present invention, when a separate insulating layer including a ceramic material and a binder is formed on the top surface of the top cap under certain conditions, the external electrically conductive objects are the positive and negative electrodes of the cylindrical secondary battery. When this electrical connection is directly connected, the time taken to cut off the current is remarkably shortened by breaking the electrode tab.
[43]
Since the insulating layer 700 of the present invention may include not only a ceramic material but also a binder, an insulating layer having a larger thickness may be formed than that of forming the insulating layer using a ceramic material in another manner.
[44]
For example, evaporation is a method of applying a ceramic material to the top cap. However, when the insulating layer is formed by applying a ceramic material to the top cap by a vapor deposition method, the thickness of the insulating layer is inevitably limited. That is, when the insulating layer is formed by applying a ceramic material to the top cap by a vapor deposition method, if the thickness of the insulating layer increases, the insulating layer may be peeled off due to a decrease in adhesion between the ceramic materials, so the thickness of the insulating layer is limited. . In this case, when the thickness of the insulating layer is small, heat generated inside the secondary battery, particularly in the upper portion of the secondary battery in which the electrode tab is electrically connected to the CID filter, is easily escaped. In this way, when the heat generated in the upper part of the secondary battery escapes, the temperature of the electrode tab does not increase rapidly, and thus, a problem that takes a considerable time to cut off the current may occur due to the break of the electrode tab.
[45]
However, as described above, since the insulating layer according to the present invention may include not only a ceramic material but also a binder, the bonding strength between ceramic materials may be improved by the binder. Accordingly, even if an insulating layer having a large thickness is formed on the top cap, its shape can be maintained, so that heat generated in the upper portion of the secondary battery can be prevented from escaping. Accordingly, according to the present invention, when an external electrically conductive object is directly electrically connected to the positive electrode and the negative electrode of a cylindrical secondary battery, the electrode tab may be quickly disconnected.
[46]
On the other hand, when an external electrically conductive object is electrically directly connected to the positive electrode and the negative electrode of the cylindrical secondary battery, the temperature of the entire secondary battery may rise rapidly if the electrode tab is not quickly disconnected. This may cause an explosion or fire of the secondary battery.
[47]
However, when the electrode tab is quickly cut off by forming an insulating layer on the top cap according to the present invention, it is possible to prevent the temperature of the secondary battery from rapidly increasing by blocking the current of the secondary battery. That is, according to the present invention, a local temperature increase is induced in a space in which the electrode tab is formed so that the electrode tab can be quickly cut off, but a sudden temperature increase of the entire secondary battery can be prevented.
[48]
Meanwhile, the binder in the insulating layer according to the present invention may include an organic binder. As described above, the insulating layer may be formed by spray-spraying coating, but when the binder includes an organic binder, the material constituting the insulating layer in the spray-spraying coating step can maintain a liquid phase. , The coating of the spray spray method can be made smoothly.
[49]
In addition, the binder in the insulating layer according to the present invention is 20% to 90% by weight, preferably 30% to 70% by weight, more preferably 40% to 50% by weight based on the total weight of the insulating layer. Can be included. When the binder has less than 20% by weight based on the total weight of the insulating layer, it may not be smoothly bound between ceramic materials. On the other hand, if the binder exceeds 90% by weight based on the total weight of the insulating layer, the amount of ceramic material is too small, and the heat generated in the upper part of the secondary battery can quickly escape to the outside, so the electrode tab does not break quickly. May not.
[50]
On the other hand, as shown in Figure 1, the insulating layer 700 is the upper end of the crimping portion 110 of the inner region (I, see Fig. 3) of the first gasket 500 (that is, the battery can from the top of the crimping portion). It may be formed in a region between the top cap 200 and the portion bent in the inward direction). Therefore, even if the first gasket 500 melts, an effect of preventing the battery can 100 and the safety vent 300 from directly contacting may be achieved.
[51]
Meanwhile, when the insulating layer 700 is formed on the upper surface of the top cap 200, a ratio of the thickness of the insulating layer 700 to the thickness of the top cap 200 may range from 0.015 to 0.15. When the ratio of the thickness of the insulating layer 700 to the thickness of the top cap 200 is less than 0.015, the thickness of the insulating layer becomes too small, so that heat generated at the upper part of the secondary battery is smoothly escaped to the outside. When the conductive object is electrically directly connected to the positive electrode and the negative electrode of a cylindrical secondary battery, the electrode tab may not be quickly disconnected. On the other hand, when the ratio of the thickness of the insulating layer 700 to the thickness of the top cap 200 exceeds 0.15, the thickness of the insulating layer becomes too large, so the assembling property of the secondary battery, in particular, the top cap decreases, and the shape of the secondary battery This can cause deformation problems. More preferably, a ratio of the thickness of the insulating layer 700 to the thickness of the top cap 200 may have a range of 0.021 to 0.064.
[52]
Specifically, the thickness of the insulating layer 700 may be 0.015mm to 0.045mm. In addition, the thickness of the top cap 200 may be 0.3mm to 1.0mm.
[53]
[54]
Example 1
[55]
A composition for forming an insulating layer was prepared by adding silicon dioxide (SiO 2 ), an organic binder, and an inorganic binder to the solvent isopropyl alcohol and dipropyleneglycol monomethyl ether . Silicon dioxide was included as 20% by weight, organic binder was included as 10% by weight, and inorganic binder was included as 20% by weight based on the total weight of the insulating layer-forming composition.
[56]
The insulating layer-forming composition prepared as described above was coated on the edge of the top cap of the circular battery can by a coating method to form an insulating layer having a thickness of 0.020 mm.
[57]
At this time, a safety vent is provided under the top cap, a CID filter is provided under the safety vent, the central part of the safety vent and the central part of the CID filter are adhered to each other, and the periphery of the safety vent and the CID filter are removed. 2 separated from each other by gaskets. The second gasket was in close contact with the lower surface of the safety vent and the upper surface of the CID filter. The thickness of the top cap was 0.7 mm, and the thickness of the safety vent was 0.3 mm.
[58]
The top cap was disposed on the top of the battery can in which the electrode assembly was accommodated, and sealed with a first gasket to manufacture a cylindrical secondary battery.
[59]
[60]
Example 2
[61]
A cylindrical secondary battery was manufactured in the same manner as in Example 1, except that the thickness of the insulating layer formed on the upper surface of the top cap was 0.025 mm.
[62]
[63]
Example 3
[64]
A cylindrical secondary battery was manufactured in the same manner as in Example 1, except that the thickness of the insulating layer formed on the upper surface of the top cap was 0.030 mm.
[65]
[66]
Example 4
[67]
A cylindrical secondary battery was manufactured in the same manner as in Example 1 except that the thickness of the insulating layer formed on the upper surface of the top cap was 0.035 mm.
[68]
[69]
Example 5
[70]
A cylindrical secondary battery was manufactured in the same manner as in Example 1 except that the thickness of the insulating layer formed on the top surface of the top cap was 0.040 mm.
[71]
[72]
Comparative example
[73]
A cylindrical secondary battery was manufactured in the same manner as in Example 1, except that a formed insulating layer was not formed on the top surface of the top cap.
[74]
[75]
Experimental Example 1
[76]
After electrically connecting the positive electrode and the negative electrode of the secondary battery according to the Examples and Comparative Examples using a circuit having a resistance of 15.0 mΩ, the time taken to cut off the current was measured. The measurement results are as follows.
[77]
[78]
[Table 1]
Example 1 Example 2 Example 3 Example 4 Example 5 Comparative example
Insulation layer thickness (mm) 0.020 0.025 0.030 0.035 0.040 -
Time taken to cut off current (seconds) 18.9 16.3 13.1 11.5 9.6 24.6
[79]
Compared to the comparative example, in the case of the example, it was confirmed that the time taken to cut off the current of the secondary battery was significantly reduced. For example, in the case of Example 5, it was confirmed that the time taken to cut off the current of the secondary battery was significantly reduced to a level of about 40% compared to the comparative example. Especially. According to Experimental Example 1, it can be seen that the thicker the insulating layer, the shorter the time taken to cut off the current.
[80]
Experimental Example 2
[81]
After electrically connecting the positive and negative electrodes of the secondary battery according to Example 2 and Comparative Example using a circuit having a resistance of 15.0 mΩ, current is blocked by using a thermocouple attached to the body of the secondary battery. The secondary battery temperature at the time point was measured. The measurement results are as follows.
[82]
[83]
[Table 2]
Example 2 Comparative example
Insulation layer thickness (mm) 0.025 -
Secondary battery temperature at the time the current is cut off (℃) 79.8 110.3
[84]
Compared with the comparative example, in the case of Example 2, it was confirmed that the temperature of the secondary battery at the time when the current of the secondary battery was cut off was significantly reduced. That is, in the case of the secondary battery according to Example 2, it was confirmed that the temperature of the secondary battery at the time when the current was cut off was significantly reduced to a level of about 70% compared to the secondary battery according to the Comparative Example.
Claims
[Claim 1]
A battery can accommodating the electrode assembly and having an open upper structure; A top cap provided on the top of the battery can; A safety vent provided under the top cap; A CID filter provided under the safety vent; A first gasket provided on an inner surface of an upper portion of the battery can and formed in close contact with a side portion of the safety vent to insulate the safety vent from the upper portion of the battery can; And a second gasket provided between the safety vent and the CID filter and formed in close contact with the upper portion of the CID filter to surround the outer end of the CID filter and formed in close contact with the lower portion of the safety vent. And an insulating layer is formed in a region where the top cap and the first gasket are in close contact, and the insulating layer includes a ceramic material and a binder.
[Claim 2]
The secondary battery of claim 1, wherein the binder comprises an organic binder.
[Claim 3]
The secondary battery of claim 1, wherein the ceramic material includes aluminum oxide or silicon oxide.
[Claim 4]
The secondary battery of claim 1, wherein the binder is contained in an amount of 20% to 90% by weight based on the total weight of the insulating layer.
[Claim 5]
The secondary battery of claim 1, wherein a ratio of the thickness of the insulating layer to the thickness of the top cap is 0.015 to 0.15.
[Claim 6]
The method according to claim 1, wherein the upper portion of the battery can, the crimping portion having a structure bent in the whole or part of the S shape; Is formed, and the first gasket is provided in close contact with the inner surface of the crimping part.
[Claim 7]
The secondary battery of claim 1, wherein the insulating layer is an upper surface of the top cap, and is formed in a region between an upper end of the crimping portion and the top cap of an inner region of the first gasket.
[Claim 8]
The secondary battery of claim 1, wherein the insulating layer has a thickness of 0.015mm to 0.045mm.
[Claim 9]
The secondary battery of claim 1, wherein the top cap has a thickness of 0.3mm to 1.0mm.