Specification
Title of the invention: Cylindrical secondary battery equipped with an adhesive part containing a gas generating material
Technical field
[One]
This application claims the benefit of priority based on Korean Patent Application No. 2018-0064172 filed on June 4, 2018, and all contents disclosed in the documents of the Korean patent application are incorporated as part of this specification.
[2]
The present invention relates to a cylindrical secondary battery provided with an adhesive portion including a gas generating material, and specifically, the positive electrode tab of the jelly-roll type electrode assembly is a cap assembly through an adhesive portion including an adhesive material, a conductive material and a gas generating material It is about a cylindrical secondary battery consisting of a structure that is combined with.
Background
[3]
As energy sources for portable electronic devices, power tools, electric vehicles, and power storage systems, secondary batteries that can be used repeatedly because they can be charged and discharged have been used, and the demand for high-power, high-capacity secondary batteries is increasing.
[4]
The secondary battery includes a cylindrical secondary battery and a prismatic secondary battery in which an electrode assembly is embedded in a cylindrical or rectangular metal can according to the shape of the battery case, and a pouch-type secondary battery in which the electrode assembly is embedded in a pouch-shaped case of an aluminum laminate sheet. It is classified as
[5]
The electrode assembly built into the battery case is a charge/discharge power plant consisting of a stacked structure of a positive electrode/separator/cathode, and a jelly-roll type structure wound by interposing a separator between a sheet-shaped positive electrode and a negative electrode coated with an active material, It is classified into a stacked structure in which a plurality of anodes and cathodes of a predetermined size are sequentially stacked with a separator interposed therebetween. Among them, jelly-roll type electrode assemblies are widely manufactured because they are easy to manufacture and have high energy density per weight, and jelly-roll type electrode assemblies are generally manufactured as cylindrical batteries.
[6]
In general, in a cylindrical secondary battery, the positive electrode tab of the jelly-roll type electrode assembly is combined with the cap assembly so that the top cap serves as a positive terminal. For the combination of the positive electrode tab and the cap assembly, a welding method such as laser welding is used.
[7]
However, during the welding process, residual foreign matter may be generated to damage the exterior of the electrode assembly, and a problem of distorting the top cap may occur.
[8]
As described above, there is a need for a technology capable of solving a problem occurring in the process of forming the positive terminal of a cylindrical secondary battery and preventing overcharging of the secondary battery.
[9]
In this regard, Patent Document 1 discloses a structure in which a plurality of first electrode tabs are disposed under the sub plate and the middle plate to be bonded to both the sub plate and the middle plate, and the higher the adhesion of the bonded structure, the lower the internal resistance, so that welding It is disclosed that the likelihood of failure is reduced.
[10]
That is, Patent Document 1 discloses a structure for reducing the internal resistance of a secondary battery, but does not provide a bonding method other than a welding method in which foreign matter may occur.
[11]
Patent Document 2 discloses a structure in which a terminal plate is attached to an upper surface of a conductive adhesive, and a negative terminal is electrically connected through a hollow formed in the terminal plate, and a negative electrode tab is attached to the lower surface of the conductive adhesive. The secondary battery has a structure in which the conductive adhesive is melted or deformed so that the portion connected to the negative electrode tab and the negative terminal is separated, and a gap is generated, thereby blocking electrical connection.
[12]
Patent Document 3 is a cap assembly in which an outer circumferential surface of a laminate including a top cap and a safety vent is sequentially wrapped with a main gasket, and a current blocking member surrounding the outer circumferential surface with an auxiliary gasket is bonded under the safety vent, the Disclosed is a structure capable of preventing sagging of the main gasket by using an auxiliary gasket.
[13]
In Patent Document 4, the base plate of one of the positive and negative electrodes is wound at least 1.5 turns on the innermost side of an electrode formed by winding a positive electrode, a negative electrode, and a porous separator to form an electrode winding core, and the winding of the base plate starts. A structure is disclosed in which an electrode tab is attached to a region within 1.5 turns of the part, and the end of the electrode tab is connected to the cap assembly.
[14]
However, Patent Document 3 and Patent Document 4 do not propose a method for solving the problem that occurs in the process of connecting the electrode terminal and the electrode tab.
[15]
As described above, in a cylindrical secondary battery, it is possible to easily form a connection structure between the positive electrode tab and the cap assembly of the jelly-roll type electrode assembly, and to cut off the electrical connection in a short time. There is a high need for technology that can prevent problems caused by.
[16]
(Prior technical literature)
[17]
(Patent Document 1) Korean Patent Application Publication No. 2017-0081449
[18]
(Patent Document 2) Korean Patent Application Publication No. 2003-0044512
[19]
(Patent Document 3) Korean Patent Application Publication No. 2011-0039934
[20]
(Patent Document 4) Korean Patent Application Publication No. 2001-0054738
Detailed description of the invention
Technical challenge
[21]
An object of the present invention is to solve the above problems, and an object of the present invention is to provide a cylindrical secondary battery capable of preventing foreign matter from occurring or shaking of the cap assembly in the process of electrically connecting the electrode tab and the cap assembly.
Means of solving the task
[22]
Cylindrical secondary battery according to the present invention for achieving this purpose,
[23]
A jelly-roll type electrode assembly having a structure wound with a separator interposed between a sheet-shaped positive electrode and a negative electrode, a cylindrical battery case for accommodating the jelly-roll type electrode assembly, and a cap assembly mounted on the open top of the cylindrical battery case. And a lower surface of the cap assembly is connected to the positive electrode tab of the jelly-roll type electrode assembly by an adhesive portion, and the adhesive portion may have a structure including an adhesive material, a conductive material, and a gas generating material.
[24]
The adhesive material may be made of one or more selected from the group consisting of polyester resin, epoxy resin, phenol resin, polyvinyl acetate, polyvinyl butyral, and polyacrylic acid ester.
[25]
The conductive material is graphite, carbon black, conductive fiber; And gold, silver, copper, aluminum, and one or more selected from the group consisting of alloys thereof.
[26]
The gas generating material may be lithium carbonate (Li 2 CO 3 ), CaCO 3 , K 2 CO 3 , Na 2 CO 3 or BaCO 3 .
[27]
The content of the gas generating material may be included in a range of more than 20% by weight to 100% by weight based on the content of the conductive material.
[28]
When the voltage of the cylindrical secondary battery is increased, a reaction of the gas generating material is initiated, and the adhesive portion expands to separate the conductive material, thereby blocking current.
[29]
The reaction starting temperature of the gas generating material may be lower than the melting temperature of the adhesive material.
[30]
When the voltage of the cylindrical secondary battery is increased, the bonding force of the adhesive portion is weakened due to the melting of the adhesive material, and the positive electrode tab may be separated from the cap assembly.
[31]
The cap assembly has a structure in which a venting member and a PTC element are omitted, a current blocking element is positioned at the lower end of the cap assembly, and the jelly-roll type electrode assembly corresponds to the thickness of the omitted venting member and the PTC element. The length of the degree is extended.
[32]
The venting member of the cap assembly may have a structure such that when the bonding of the joint is weakened by the reaction of the gas generating material, the shape of the venting member is reversed and separated from the positive electrode tab.
[33]
The cap assembly includes a venting member and a PTC device and a current blocking device are omitted, a venting member is located at the lower end of the cap assembly, and the jelly-roll type electrode assembly is a PTC device and a current blocking device that are omitted. It may have a structure in which a length corresponding to the thickness of the device is extended.
Brief description of the drawing
[34]
1 is a vertical cross-sectional view of a conventional general cylindrical secondary battery.
[35]
2 is a vertical cross-sectional view of a cylindrical secondary battery according to an embodiment of the present invention.
[36]
3 is a vertical cross-sectional view of the cylindrical secondary battery of FIG. 2 in a state in which current is blocked.
[37]
4 is a vertical cross-sectional view of a cylindrical secondary battery according to another embodiment of the present invention.
[38]
5 is a vertical cross-sectional view for comparing heights of electrode assemblies included in the cylindrical secondary batteries of FIGS. 1 and 2.
[39]
6 is an enlarged view showing before and after deformation of the adhesive portion of FIG. 2.
[40]
7 is a graph showing the results of the experimental example.
Mode for carrying out the invention
[41]
The cylindrical secondary battery of the present application is a jelly-roll type electrode assembly of a structure wound with a separator interposed between a sheet-shaped positive electrode and a negative electrode, a cylindrical battery case for accommodating the jelly-roll type electrode assembly, and the open top of the cylindrical battery case And a cap assembly mounted on the cap assembly, and the lower surface of the cap assembly is connected to the anode tab of the jelly-roll type electrode assembly by an adhesive portion, and the adhesive portion includes an adhesive material, a conductive material, and a gas generating material. Can be done.
[42]
That is, in the present invention, an adhesive portion is used for bonding the lower surface of the cap assembly to the positive electrode tab of the jelly-roll type electrode assembly, and the adhesive portion includes an adhesive material, a conductive material, and a gas generating material.
[43]
Specifically, the adhesive portion of the present application is an adhesive material capable of increasing the bonding force between the positive electrode tab and the cap assembly while maintaining the shape of the adhesive portion in a normal state, a conductive material serving as an electrical connection path between the positive electrode tab and the cap assembly, and a secondary battery. When the voltage is increased, a reaction is initiated to release a gas.
[44]
As described above, the cylindrical secondary battery of the present application does not use a welding method such as laser welding used in the prior art for electrical connection between the positive electrode tab and the cap assembly serving as the positive terminal. An adhesive portion containing an adhesive substance is added to the lower surface.
[45]
Therefore, by using laser welding for a cylindrical secondary battery in the related art, it is possible to prevent problems such as damage to the separator or reaction with the electrolyte due to foreign substances falling on the electrode assembly.
[46]
The adhesive material is not particularly limited as long as it is a material capable of improving the bonding strength between the positive electrode tab and the cap assembly. For example, polyester resin, epoxy resin, phenol resin, polyvinyl acetate, polyvinyl butyral and polyacrylic acid ester It may be one or more selected from the group consisting of.
[47]
The conductive material serves as an electrical connection path between the positive electrode tab and the cap assembly, and is not particularly limited as long as it is made of a material having high electrical conductivity. For example, conductive fibers such as graphite, carbon black, carbon fiber or metal fiber ; And, it may be made of one or more selected from the group consisting of gold, silver, copper, aluminum, and alloys thereof.
[48]
The gas-generating material is not particularly limited as long as the reaction starts when the voltage of the battery is increased to release gas, and for example, lithium carbonate (Li 2 CO 3 ), CaCO 3 , K 2 CO 3 , Na 2 CO 3 Or it may consist of BaCO 3 .
[49]
The content of the gas generating material may be included in a range of more than 20% by weight to 100% by weight based on the content of the conductive material.
[50]
When the gas generating material is contained in less than 20% by weight based on the content of the conductive material, the amount of the generated gas is small, so that it is difficult to obtain a desired voltage increase effect. In addition, when the content of the gas generating material is higher than the content of the conductive material, the electrical conductivity of the anode terminal may be problematic, and thus it is not preferable.
[51]
In one specific example, the cylindrical secondary battery of the present application has a structure in which an adhesive part including a gas-generating material is added, and when the voltage of the cylindrical secondary battery is increased, a reaction of the gas-generating material is initiated and gas is generated in the adhesive part. do. Due to the generation of the gas, the adhesive portion expands, and the conductive materials that were arranged in close contact with each other in a normal state are filled with gas bubbles so that the conductive materials are separated from each other.
[52]
Accordingly, as the resistance increases, the voltage increases in proportion to the increase in the resistance, and the current is cut off when the charging end voltage is reached. That is, in a state in which the positive electrode tab and the cap assembly are connected to each other by welding, venting is performed due to an increase in the internal pressure of the battery, and unlike the conventional technology in which the positive electrode tab and the cap assembly are physically separated, the present invention includes a gas generating material. The adhesive portion expands and the particles of the conductive material are separated from each other, thereby blocking the current.
[53]
For example, when lithium carbonate is used as the gas generating material, when the voltage of the battery reaches 4.8V, the lithium carbonate is decomposed into carbon monoxide and carbon dioxide to form a gas. As a gap is created, the particles of the conductive material are separated from each other.
[54]
The reaction starting temperature of the gas generating material may be lower than the melting temperature of the adhesive material. Accordingly, in a specific temperature range, the adhesive material may not be melted, but the gas-generating material may initiate a reaction to generate gas. In such a state, the physical coupling between the positive electrode tab and the cap assembly is maintained, but resistance increases as the distance between particles of the conductive material increases due to gas generation. However, when the temperature further increases, the amount of gas generated by the gas generating material increases, and the adhesive material melts along with the adhesiveness decreases, the physical connection between the positive electrode tab and the cap assembly may be broken.
[55]
That is, when the voltage of the cylindrical secondary battery increases, the voltage increases to the charging end voltage due to an increase in resistance due to the generation of gas in the adhesive portion, and the current may be blocked. When the charging end voltage is reached, the general temperature of the battery is about 60°C. In consideration of the following points, melting of the adhesive material of the adhesive portion may not be achieved.
[56]
However, when the temperature of the battery momentarily rises before reaching the charging end voltage such as an external shock, the bonding force of the adhesive portion is weakened by the melting of the adhesive material, and the positive electrode tab may be separated from the cap assembly.
[57]
Therefore, compared to the case in which the positive electrode tab and the cap assembly are coupled by welding in the related art, since the bonding force of the adhesive portion is relatively weak, the force required to separate the positive electrode tab and the cap assembly is relatively reduced, so that rapid separation can be achieved.
[58]
In one specific example, the cap assembly may have a structure in which a venting member is included but the PTC element is omitted, and a venting member or a current blocking member is positioned at the lower end of the cap assembly, and the jelly-roll type electrode assembly May have a structure in which a length corresponding to the thickness of the omitted PTC element is extended.
[59]
A cylindrical secondary battery having such a structure can provide a cylindrical secondary battery having a high capacity as compared with a conventional cylindrical secondary battery of the same standard, since the length of the jelly-roll type electrode assembly is relatively long.
[60]
In addition, since the cylindrical secondary battery of the present application includes an adhesive portion including a gas generating material when the voltage is increased, resistance increase is induced by the gas generating material to block the current, so the PTC provided in the conventional cylindrical secondary battery Even if the element is omitted, the same effect can be obtained.
[61]
Meanwhile, the venting member may have a downwardly concave structure, and the venting member has a structure that is separated from the anode tab while inverting the shape when the bonding of the joint is weakened by the reaction of the gas generating material. . Accordingly, the positive electrode tab and the cap assembly may be physically separated.
[62]
In another specific example, considering that the cylindrical secondary battery of the present application has a structure in which the adhesive portion expands by the gas generating material and thus the resistance increases and current is blocked, the cap assembly includes a venting member, and a PTC element and a current A structure in which the blocking element is omitted, a venting member is located at the lower end of the cap assembly, and the jelly-roll type electrode assembly is a structure in which a length corresponding to the thickness of the omitted PTC element and the current blocking element is extended Can be made of.
[63]
That is, as described above, in the case of including the structure in which the PTC element and the current blocking element are omitted, the thickness of the cap assembly is relatively reduced, and the height of the jelly-roll type electrode assembly is as much as the length corresponding to the reduced thickness of the cap assembly. Since can be extended, the effect of increasing the capacity of the battery can be obtained.
[64]
In addition, the cylindrical secondary battery having the structure as described above, when compared to the cylindrical secondary battery having the structure including the venting member and the PTC element is omitted, the current blocking element is further omitted, the thickness of the omitted current blocking element , The thickness of the cap assembly is reduced.
[65]
Accordingly, when compared with a cylindrical secondary battery of the same standard, the length of the jelly-roll type electrode assembly is relatively long, and thus a cylindrical secondary battery having a high capacity can be provided.
[66]
In the case of a cylindrical secondary battery having a structure in which the PTC element and the current blocking element are omitted as described above, a venting member is located under the top cap, and an adhesive portion is added to the lower surface of the venting member, so that electrical connection with the positive electrode tab is achieved. Can be done.
[67]
[68]
Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment in which one of ordinary skill in the art can easily implement the present invention. However, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted.
[69]
In addition, the same reference numerals are used for parts having similar functions and functions throughout the drawings. Throughout the specification, when a part is said to be connected to another part, this includes not only a case in which it is directly connected, but also a case in which it is connected indirectly with another element interposed therebetween. In addition, the inclusion of a certain component does not exclude other components unless specifically stated to the contrary, but means that other components may be further included.
[70]
The present invention will be described as a detailed embodiment according to the drawings.
[71]
[72]
1 is a vertical cross-sectional view of a conventional general cylindrical secondary battery.
[73]
Referring to FIG. 1, the cylindrical secondary battery 100 includes a battery case 130 for accommodating a jelly-roll type electrode assembly 120 and a cap assembly 110 positioned above the battery case 130. A top cap 101 is located at the top of the cap assembly 110, a PTC element 102 that blocks current at high temperatures, a venting member 103 for discharging high-pressure gas, and the internal pressure of the battery. Current blocking devices 104 that block the current when rising are sequentially stacked.
[74]
A gasket 106 for securing the sealing force of the secondary battery is interposed at the contact portion between the cap assembly 110 and the battery case 130, and the positive electrode tab 121 of the jelly-roll type electrode assembly is a current blocking device 104 It is joined by welding on the lower surface of ).
[75]
An insulating member 111 is positioned on the jelly-roll type electrode assembly 120 to prevent contact between the positive electrode tab 121 and the battery case 130.
[76]
2 is a vertical cross-sectional view of a cylindrical secondary battery according to an embodiment of the present invention, and FIG. 3 is a vertical cross-sectional view of the venting member of FIG. 2 in a broken state.
[77]
Referring to FIG. 2, the cylindrical secondary battery 200 includes a battery case 230 for accommodating a jelly-roll type electrode assembly 220 and a cap assembly 210 positioned above the battery case 230. A top cap 201 is located at an upper end of the cap assembly 210 and a venting member 203 is located at a lower portion of the top cap 201.
[78]
That is, in the cap assembly 210 of the cylindrical secondary battery 200, the PTC element 102 and the current blocking element 104 are omitted from the structure of the cylindrical secondary battery 100, and the top cap 201 and the venting member 203 The gasket 206 is interposed at the contact portion between the cap assembly 210 and the battery case 230 to secure a sealing force.
[79]
The anode tab 221 of the jelly-roll type electrode assembly 220 is coupled to the lower surface of the venting member 203 through the adhesive part 205.
[80]
On the other hand, unlike FIG. 2, the cylindrical secondary battery 200 has a structure in which a current blocking member is added to the lower surface of the venting member 203, and the positive electrode tab of the electrode assembly is coupled to the current blocking member. Thus, electrical connection with the top cap can be made through the venting member.
[81]
3 is a vertical cross-sectional view of the cylindrical secondary battery of FIG. 2 in a state in which current is blocked.
[82]
Referring to FIG. 3, when the pressure inside the battery case increases due to repeated charging and discharging of the battery, the cylindrical secondary battery is a notch having a relatively thin thickness as the venting member 203, which cannot withstand the pressure, is reversed into an upwardly concave structure. It shows the state where the part is broken.
[83]
Since the adhesive part 205 contains a gas generating material, when the pressure of the battery increases, gas is generated and the adhesive part expands and the bonding force is weakened. The adhesive portion 205, which maintained the bonding of the bar, is also separated, some of which are attached to the lower surface of the venting member 203, and the remaining part of them are attached to the positive electrode tab 221.
[84]
4 is a vertical cross-sectional view of a cylindrical secondary battery according to another embodiment of the present invention.
[85]
4, the cylindrical secondary battery 300 is between the battery case 330, the cap assembly 310 and the cap assembly 310 and the battery case 330 in which the jelly-roll type electrode assembly 320 is accommodated. It is located and includes a gasket 306 for securing the sealing force of the battery case.
[86]
In the cap assembly 310, a top cap 301 is positioned at an upper portion and a venting member 303 is positioned at a lower portion of the top cap 301. That is, the cap assembly 310 of the cylindrical secondary battery 300 has a structure in which the PTC element 102 and the current blocking element 104 are omitted from the structure of the cylindrical secondary battery 100.
[87]
The positive electrode tab 321 of the jelly-roll type electrode assembly 320 is coupled to the lower surface of the venting member 303 through the adhesive part 305, and the venting member 303 is connected to the top cap 301 to provide the top cap 301. This can serve as a positive terminal.
[88]
An insulating member 311 is positioned on the jelly-roll type electrode assembly 320 to prevent contact between the positive electrode tab 321 and the battery case 330.
[89]
In the present invention, the current is blocked before the venting member is broken due to the increase in the internal pressure of the battery because the voltage increases due to the gas generation of the adhesive part, so that the current is cut off, as shown in the venting member 203 of FIG. The venting member 203 having a concave structure may not be used.
[90]
However, it goes without saying that if necessary, the venting member 203 having a downward concave shape such as the venting member 203 of FIG. 2 may be used.
[91]
5 is a vertical cross-sectional view for comparing heights of electrode assemblies included in the cylindrical secondary batteries of FIGS. 1 and 2.
[92]
Referring to FIG. 5, the cylindrical secondary battery 200 has a structure in which the PTC element 102 and the current blocking element 104 are omitted from the cylindrical secondary battery 100.
[93]
Accordingly, the thickness h2 of the cap assembly of the cylindrical secondary battery 200 becomes thinner than the thickness h1 of the cap assembly of the cylindrical secondary battery 100.
[94]
When the overall height of the cylindrical secondary battery is constant as the thickness of the cap assembly becomes thin as described above, the height (h4) of the electrode assembly of the cylindrical secondary battery 200 is the height (h3) of the electrode assembly of the cylindrical secondary battery 100 Will increase more. Accordingly, the cylindrical secondary battery 200 may be a secondary battery having a higher capacity than the cylindrical secondary battery 100.
[95]
6 is an enlarged view showing before and after deformation of the adhesive portion of FIG. 2.
[96]
Referring to FIG. 6, the upper surface of the adhesive portion is coupled to the venting member 203 and the lower surface of the adhesive portion is coupled to the positive electrode tab 221.
[97]
The adhesive part 505 includes an adhesive material 501, a conductive material 502, and a gas generating material 503.
[98]
In the normal state, the venting member 203 and the positive electrode tab 221 are coupled through the adhesive part 505, and an electrical connection is made through the conductive material 502 arranged in close contact, but gas is generated due to an increase in the voltage of the battery. When the reaction of the material 503 starts, the volume of the adhesive part 505 expands and the distance between the conductive materials 502 increases. Accordingly, an effect of increasing the resistance occurs, and the current is cut off when the charging end voltage is reached while the voltage is accelerated. In this case, the current can be cut off even if there is no physical short circuit.
[99]
Alternatively, the amount of gas is increased 503' by the reaction of the gas generating material 503 (shown in an expanded state of the gas generating material), and the adhesive portion 505 is If the bonding force is weakened, the physical bond between the positive tab and the cap assembly may be separated.
[100]
[101]
Hereinafter, it will be described with reference to the embodiments according to the present invention, but this is for an easier understanding of the present invention, and the scope of the present invention is not limited thereto.
[102]
[103]

[104]
Based on the total weight of the adhesive part, 40% by weight of epoxy resin as an adhesive material, 30% by weight of silver as a conductive material, and 30% by weight of lithium carbonate (Li 2 CO 3 ) as a gas generating material are mixed with NMP and dried to form a paste. Prepare the adhesive part.
[105]
The manufactured adhesive part was added to the lower end of the positive electrode tab and the cap assembly of the cylindrical secondary battery having the structure shown in FIG. 4 to complete the electrical connection between the positive electrode tab and the current blocking device. For the accuracy of the experiment, five secondary batteries of the same conditions were prepared.
[106]
[107]

[108]
Except that 40% by weight of silver, which is a conductive material, and 20% by weight of lithium carbonate were used in Example 1, a paste-like adhesive was manufactured by the same method as in Example 1, and the cylindrical secondary to which the adhesive was added. Five cells were prepared.
[109]
[110]

[111]
A cylindrical secondary battery having the structure shown in FIG. 1 was prepared, and five cylindrical secondary batteries having a structure in which a positive electrode tab and a cap assembly were joined by welding were manufactured.
[112]
[113]

[114]
Except that 50% by weight of silver as a conductive material and 10% by weight of lithium carbonate were used in Example 1, a paste-like adhesive was prepared by the same method as in Example 1, and the cylindrical secondary to which the adhesive was added. Five cells were prepared.
[115]
[116]

[117]
Except that 60% by weight of silver as a conductive material in Example 1 was used and no gas-generating material was used, a paste-like adhesive portion was prepared by the same method as in Example 1, and the cylindrical secondary to which the adhesive portion was added. Five cells were prepared.
[118]
[119]

[120]
Measurement of resistance of adhesive
[121]
Using the cylindrical secondary batteries prepared in Examples 1 to 2 and Comparative Examples 1 and 3, the amount of change in the previous term according to the temperature of the secondary battery was measured, and the results are shown in FIG. 7.
[122]
Resistance measurement was performed by measuring voltage using a 1 kHz AC resistor, and FIG. 7 shows an average of voltage according to SOC (%) of five samples used in each condition.
[123]
[124]
Referring to FIG. 7, in the case of Comparative Example 1 in which welding was used for bonding of the positive electrode tab, Comparative Example 2 in which a gas generating material was not added, and Comparative Example 3 in which 20% by weight of a gas generating material was added, as charging proceeds, It can be seen that there is a point where the voltage rises (as SOC increases) and the voltage increases relatively significantly in some sections, but it can be seen that the charging end voltage (8.4V) is not reached.
[125]
Therefore, the effect of blocking the current cannot be obtained by reaching the charging end voltage.
[126]
However, in the case of Example 1 to which 30% by weight of the gas-generating material was added and Example 2 to which 20% by weight was added, the voltage increased from about 140% of SOC to a rapid increase of 8.4V or more.
[127]
Accordingly, it is possible to prevent the occurrence of an explosion or the like due to overheating by blocking the flow of current.
[128]
[129]
Those of ordinary skill in the field to which the present invention belongs will be able to perform various applications and modifications within the scope of the present invention based on the above contents.
[130]
(Explanation of code)
[131]
100, 200, 300: Cylindrical secondary battery
[132]
101, 201, 301: top cap
[133]
102: PTC element
[134]
103, 203, 303: venting member
[135]
104: current blocking device
[136]
106, 206, 306: gasket
[137]
110, 210, 310: cap assembly
[138]
111, 211, 311: insulating member
[139]
120, 220, 320: jelly-roll type electrode assembly
[140]
121, 221, 321: positive tab
[141]
130, 230, 330: battery case
[142]
h1, h2: thickness of the cap assembly
[143]
h3, h4: height of the jelly-roll type electrode assembly
[144]
205, 305, 505: adhesive part
[145]
501, 501': adhesive material
[146]
502: conductive material
[147]
503, 503': gas generating substances
Industrial availability
[148]
As described above, in the cylindrical secondary battery according to the present invention, an electrical connection between the electrode assembly and the cap assembly is made by an adhesive portion including an adhesive material. can do.
[149]
In addition, since the adhesive portion includes a gas generating material, the bonding force of the adhesive portion is weakened due to a reaction of the gas generating material when a voltage increases according to an increase in the temperature of the battery, so that the electrode tab and the cap assembly can be quickly separated.
[150]
In addition, since the resistance rapidly increases as gas is generated in the adhesive portion, the flow of current may be blocked as the voltage increases above the charging end voltage.
Claims
[Claim 1]
A jelly-roll type electrode assembly having a structure wound with a separator interposed between a sheet-shaped positive electrode and a negative electrode; A cylindrical battery case for accommodating the jelly-roll type electrode assembly; And a cap assembly mounted on the open top of the cylindrical battery case. Including, the lower surface of the cap assembly is connected to the positive electrode tab of the jelly-roll type electrode assembly by an adhesive portion, the adhesive portion cylindrical secondary battery comprising an adhesive material, a conductive material and a gas generating material.
[Claim 2]
The cylindrical secondary battery of claim 1, wherein the adhesive material is made of at least one member selected from the group consisting of polyester resin, epoxy resin, phenol resin, polyvinyl acetate, polyvinyl butyral, and polyacrylic acid ester.
[Claim 3]
The method of claim 1, wherein the conductive material is graphite, carbon black, conductive fiber; And a cylindrical secondary battery made of at least one selected from the group consisting of gold, silver, copper, aluminum, and alloys thereof.
[Claim 4]
The cylindrical secondary battery of claim 1, wherein the gas generating material is lithium carbonate (Li 2 CO 3 ), CaCO 3 , K 2 CO 3 , Na 2 CO 3 or BaCO 3 .
[Claim 5]
The cylindrical secondary battery of claim 1, wherein the content of the gas generating material is in a range of more than 20% by weight to 100% by weight based on the content of the conductive material.
[Claim 6]
The cylindrical secondary battery of claim 1, wherein when the voltage of the cylindrical secondary battery is increased, a reaction of the gas-generating material is initiated, and the adhesive portion expands to separate the conductive material to block current.
[Claim 7]
The cylindrical secondary battery of claim 6, wherein the reaction starting temperature of the gas generating material is lower than the melting temperature of the adhesive material.
[Claim 8]
The cylindrical secondary battery of claim 1, wherein when the voltage of the cylindrical secondary battery is increased, the bonding force of the adhesive portion is weakened by melting of the adhesive material, and the positive electrode tab is separated from the cap assembly.
[Claim 9]
The method of claim 1, wherein the cap assembly includes a venting member and a PTC element is omitted, a venting member is positioned at a lower end of the cap assembly, and the jelly-roll type electrode assembly is formed of the omitted PTC element. Cylindrical secondary battery having a structure in which the length corresponding to the thickness is extended.
[Claim 10]
The cylindrical secondary battery of claim 9, wherein the venting member of the cap assembly has a structure that is separated from the positive electrode tab while inverting the shape when the bonding of the joint is weakened by the reaction of the gas generating material.
[Claim 11]
The method of claim 1, wherein the cap assembly includes a venting member and a PTC device and a current blocking device are omitted, a venting member is positioned at a lower end of the cap assembly, and the jelly-roll type electrode assembly is omitted. Cylindrical secondary battery having a structure in which the length corresponding to the thickness of the PTC element and the current blocking element is extended.