1]The present invention relates to a cylindrical secondary battery, the insulating member, and more particularly, can enhance the mechanical properties of the insulating member between tapkaep assembly and the electrode assembly of a cylindrical secondary battery exert a sufficient buffering effect against an external impact, and the battery within the volume change so to relate to avoid the risk of shorting and increase stability.
BACKGROUND
[2]
In general, secondary batteries, unlike primary batteries that can not be charged, means for charging and discharging the battery is possible, has been widely used in power supply, such as mobile phones, notebook computers, camcorders, etc. of the electronic apparatus or electric vehicle. In particular, lithium secondary batteries have an operating voltage as 3.6V, nickel is commonly used as a power source of the electronic equipment-cadmium batteries or nickel - that utilized has a capacity of about three times the hydrogen battery, has high energy density per unit weight of approximately there is a trend that is growing rapidly.
[3]
The lithium secondary battery mainly uses a lithium-based oxide and carbon materials as an anode active material and the negative active material. In addition, lithium secondary batteries may be classified into a prismatic battery, a circular cell, a pouch-shaped battery.
[4]
The lithium ion secondary battery having an electrode assembly, and a casing for accommodating the electrode assembly is sealed together with an electrolyte disposed in a cathode / separator / anode sequentially. In particular, the casing of the rectangular or circular a secondary battery is provided with a sealing coupling cap assembly in the can and a circular open end of the can having a circular open end.
[5]
Electrode assemblies are each active material by interposing a separator between the positive electrode of the applied sheet form and a negative electrode wound jelly-by interposing a separator between a roll-type and a plurality of the positive electrode of a predetermined size and a cathode divided into a stack type laminated sequentially do. Here, a jelly-electrode assembly of the roll-type and a high-production, the energy density per easily and weight advantages, especially because the housing is easy to round cans of a circular or a prismatic battery jelly-has been widely used an electrode assembly of a roll type. On the other hand, a stack type electrode assembly is widely used a pouch-shaped battery.
[6]
However, during the charge and discharge of the secondary battery, the electrode assembly is in, this process tends to be deformed while undergoing repeated expansion and contraction, jelly - for the roll-type electrode assembly, the stress is concentrated to the center of the membrane electrode through this there is a tendency that the internal short circuit caused by being in contact with the metal center pin. The internal short-circuit is connected to the heat generation of the battery may be an organic solvent is decomposed and thereby generates a gas, the casing ruptures to elevate the pressure in the battery. Of course, the gas pressure rising in the battery may be caused by the internal short circuit due to external impact.
[7]
To solve this safety issue of such batteries, the secondary battery basically includes a safety element. In particular, the circular cells, current blocking current when the internal pressure rise of the safety vent, the battery to discharge a high-pressure gas shut-off member (Current Interrupt Device: CID) that forms a protruding terminal to protect the security devices and the devices such as having a cap assembly that includes the top cap (top-cap), and a cap assembly is coupled to the can circular and sealed by a gasket.
[8]
So that the upper end face of the electrode assembly, a positive electrode tab of the plate-shaped structural bars, can be gas is discharged, and the electrode assembly is an insulating member is mounted in can be coupled to the cap plate of the cap assembly, through the center pin into the central sphere and formed with an opening communicating It is.
[9]
In general, the insulating member used for round cells, but consists of a non-woven fabric, in the case of the non-woven fabric yeoseo material that can be burned at high temperatures, when the when the external shock short occurs and the short is enlarged as an insulating member of the non-woven material combustion battery to explode this risk can be increased. In addition, the case of the possibility to get the case of such a nonwoven fabric damage at a high temperature, deformation larger, the mechanical properties by increasing the internal pressure of the battery to a low boiling solvent vaporization during expansion to low electrolyte battery circular cans leakage of the electrolyte solution itself and. Bring an increase in the internal resistance due to the inflow of air and moisture from the outside, can result in a deterioration of the battery characteristics as a result.
[10]
To solve this problem, the development of organic electroluminescent material of the insulating member with high heat resistance and mechanical properties, which can be melted to flow even at a high temperature beyond the melting point of unburned to prevent the expansion of the short circuit is required.
Detailed Description of the Invention
SUMMARY
[11]
Object of the present invention, to enhance the mechanical properties of the insulating member between tapkaep assembly and the electrode assembly of a cylindrical secondary battery, and to exert a sufficient buffering effect against an external impact, and the battery within a volume change to prevent risk of short and to increase the stability.
Problem solving means
[12]
According to a preferred embodiment of the present invention, the insulating member of the invention is a positive electrode, a negative electrode and a jelly with a membrane structure disposed between the anode and the cathode from a secondary battery that is equipped with a roll in a cylindrical battery case, the jelly-in roll as being mounted on top of the will of polypropylene, the polypropylene is in the 100 ℃ tensile strength of 20 to 30 MPa, a flexural modulus of 1500 to 1650 MPa.
[13]
According to another preferred embodiment of the present invention, the polypropylene is of 0.6 to 1.2dl / g in the intrinsic viscosity, Mw / Mn value of 1.5 to 2.5.
[14]
According to another preferred embodiment of the present invention, the insulating member is one having a fine pattern (pattern).
[15]
According to another preferred embodiment of the present invention, the shape of the pattern, mesh (mesh), the lamella (lamellar), embossing (embo), which is one of the shapes of linear, circular, elliptical, polygonal, wave.
[16]
According to another preferred embodiment of the invention, the pattern is formed by printing a pattern using a silicon master mold.
[17]
According to another preferred embodiment of the invention, a cylindrical secondary battery having the insulating member.
Effects of the Invention
[18]
According to a preferred embodiment of the present invention, an insulating member having excellent mechanical properties with a sufficient buffering effect on an impact, and the battery within the volume change is provided, it is also provided a cylindrical secondary battery including the insulating member.
Brief Description of the Drawings
[19]
1 is an illustration showing a compression test of a secondary battery employing an insulating member according to a comparative example of the present invention.
Best Mode for Carrying Out the Invention
[20]
It will be described in detail below, the preferred embodiment of the present invention. In this embodiment, not intended to limit the scope of the present invention, will presented to be illustrative only, it may be variously modified within the scope not departing from the technical gist.
[21]
[22]
An insulating member according to an embodiment of the present invention is a positive electrode, a negative electrode and a jelly with a membrane structure disposed between the anode and the cathode - in the secondary battery with the roll is mounted in a cylindrical battery case, the jelly-mounted on top of a roll as to the polypropylene.
[23]
[24]
Polypropylene, for example, by in a saturated hydrocarbon solvent such as heptane using a complex catalyst of triethyl aluminum and titanium chloride (Ⅲ) 1 ~ 40 atm, the liquid phase polymerization of propylene at 20 ~ 120 ℃ (especially 50 ~ 100 ℃) It was removed, and then by decomposing the catalyst with water to extract the solvent to obtain a polymer.
[25]
Crystal portion, the composition ratio of the non-crystalline portion of the polypropylene obtained according to the catalyst system and other reaction conditions under which it is used becomes different from the side shown by the catalyst Ziegler than that obtained from the catalyst generally obtained by high isotactic polymer content. Polypropylene produces a cross-linked by the action of radiation in the absence of air. The structure of the polypropylene fiber obtained by melt spinning is heat-treated, and varies depending on the stretching conditions, and usually is in the monoclinic crystal system with a three helix a 20.95, b 6.56, c 6.50Å (fiber cycle) having a unit of the fabric have. A specific gravity of 0.91, light intensity will not be reduced in strength among the wet and dry strength of 5 ~ 7g / d.
[26]
Figure 15 wet and dry elongation and 25%, Young's modulus of 50 ~ 65g / d, instantaneous elastic recovery at a 5% elongation is 35%. If at 130 ℃ held during 30 minutes and air shrinkage of 2.5% (equal to te discussion), resistance to strong acids, weak alkali, and solvent is usually insoluble. Decalin, tetralin, etc. melts at high temperatures. Not good castle in sunlight, dyeing is also still not enough. The stock solution or modified colored fibers acidic mordant, acid, also muldeulinda a metallic dye.
[27]
[28]
With electrical insulation and flexibility for the polymeric resin to form an insulating member in the secondary battery, the normal heat resistance and capable of maintaining the air-tightness in the harsh conditions in the battery a high temperature and high humidity, the mechanical properties of impact resistance and durability, and for the electrolyte the chemical resistance is required. For the insulating member in a conventional one polymeric resin material around the non-woven material, but the advantage, etc. of mass productivity and low cost, the mechanical properties of impact resistance and durability lowered easily release the external impact was a risk of short circuit, short-circuit during non-woven fabric the combustion is the short portion being extended was the risk of the cell further increases the pressure.
[29]
The cylindrical secondary battery according to an embodiment of the present invention for the physical properties required as an insulating member by employing a polypropylene mechanical properties of impact resistance and durability required strengthening to the insulating member of a material, specifically, a unique set forth in claim viscosity , the molecular weight can, by satisfying the tensile strength, flexural modulus at a high temperature to reduce the stability of the cylindrical battery degradation caused by the inner volume change of the cell a strong external impact.
[30]
[31]
Specifically, the polypropylene of the insulating member according to an embodiment of the present invention is characterized at 100 ℃ that the tensile strength of 20 to 30 MPa, a flexural modulus of 1500 to 1650 MPa.
[32]
Less than the tensile strength at 100 ℃ 20, but the flexural modulus is not ensured when the external impact is less than 1500 safety, not preferred that the tensile strength at 100 ℃ is 30 greater than, when the flexural modulus is 1650 more than the poly difficult to implement as a propylene-value not.
[33]
In the present invention, the tensile strength in accordance with ASTM-D638 also the flexural modulus may be measured according to ASTM D790.
[34]
[35]
In addition, the polypropylene of the insulating member according to an embodiment of the present invention is characterized in that 0.6 to 1.2dl / g in the intrinsic viscosity, Mw / Mn value of 1.5 to 2.5.
[36]
If the inherent viscosity is less than, Mw / Mn values ​​less than 1.5 0.6 not ensure the strength of the insulating member, when the intrinsic viscosity of 1.2 excess, Mw / Mn value of 2.5 or greater than preferably there is worse in formability the process difficult as the insulating member problem it is not.
[37]
[38]
Polypropylene satisfying the above properties can be obtained by stretching and heat treatment. When the stretching is a unit of molecular orientation like, when this heat treatment is to improve the heat resistance and strength. Accordingly, the inherent viscosity, Mw / Mn value, which will satisfy the tensile strength, flexural modulus. The stretch ratio is from 0 to 4%, the heat treatment is preferably 50 to 90 seconds at 100 ℃. Elongation exceeding 4%, or, when heat-treated to greater than 90 seconds, dropping the workability, heat treatment for less than 50 seconds is not preferable because not enough heat resistance and strength.
[39]
[40]
An insulating member according to the present invention can have fine patterns. A fine pattern is to widen the surface area of ​​the insulating member and a jelly-may serve to increase the degree of adhesion between the roll and tapkaep assembly improves the insulation of the insulating member.
[41]
At this time, the shape of the pattern Although there is no particular limitation, it is preferable to have a mesh (mesh), the lamella (lamellar), embossing (embo), linear, circular, elliptical, polygonal, one of the shape of the waveform.
[42]
Polypropylene is a when the fiber to be produced is possible by stacking them to create a sheet, the above arrangement of the silicon master mold of a solid rigid than, and exert pressure on the silicon master mold, is etched in the form of a silicon master mold laminated polypropylene It is directly transferred onto the sheet surface. This will become possible to form a fine pattern on a polypropylene sheet by the same transfer mechanism.
[43]
When the polypropylene sheet produced a fine pattern formed with an insulating member to the outer surface may be the surface area of ​​the insulation manufacturing a wide polypropylene sheet.
[44]
In the present invention, the silicon master mold which is used for pattern formation of polypropylene sheets may be used, prepared according to any known technique. For example, by placing the image of the desired photomask to a silicon wafer coated with a photoresist is exposed by ultraviolet rays thereby transfer the shape to the original photoresist. Then the silicon master mold can be produced by etching the silicon, depending on the desired shape.
[45]
[46]
According to one embodiment of the present invention, a secondary battery is provided having an insulating member comprising a polypropylene.
[47]
Circular secondary battery according to an embodiment of the present invention, a cap assembly to seal the can, and round for accommodating the electrode assembly along with electrolyte, the open end of the round can.
[48]
In the above secondary battery, a circular, said circular cans is made up of a lightweight conductive metal, such as aluminum or an aluminum alloy, and has a ground cylindrical structure having an enclosed top is open the opening portion and facing therewith. The inner space of the can there is accommodated a circular electrode assembly and the electrolyte.
[49]
In addition, to be filled in the circular-can the electrolyte is for moving the lithium ions generated by electrochemical reaction during charging and discharging of the secondary battery electrode plate, a mixture of lithium salts and high purity organic solvent flow non water-based organic electrolyte; Or it may include a polymer using a polymer electrolyte.
[50]
The electrode assembly is housed in the circular cans is either interposed between two electrode plates and the electrode plate in order to mutually insulate the electrode plate having a large plate shape of a roll are different in polarity from each other one of the electrode plate in may be a laminated structure comprising a separator disposed on the left or right. In addition the laminated structure may be wound "jelly roll (Jelly Roll)" form. Of course, it may be the positive electrode plate and the negative electrode plate yi of a given size with a laminated between the membrane type. Two electrode plates are among the active material slurry is applied on the current collector of a metal foil or a metal mesh comprising aluminum and copper for each structure. The slurry is typically formed of particulate active material, an auxiliary conductor, a binder and a plasticizer are stirred in a solvent is added to the state. The solvent is removed in a subsequent process. The electrode plate is wound may be present in an additional solid that is not coated with the slurry, the start end and the end of the current collector direction. Uncoated portion, the lead of the pair corresponding to each of the electrode plate is attached. A first lead attached to the top of the electrode assembly is electrically connected to the cap assembly, the second lead is attached to the lower end of the electrode assembly is connected to the bottom of the round can. Of course, the first lead and a second lead may both be drawn out in a direction of the cap assembly. The electrode assembly is preferably the second insulating plate is disposed is disposed on the first insulating plate installed in the bottom part of the circular can, the top of the electrode assembly. A first insulating plate and the insulation between the electrode assembly and the can bottom portion of the circular, the second insulating plate has an insulation between the electrode assembly and the cap assembly.
[51]
[52]
On the other hand, the center of the circles in the can, it may be prevented from loosening the electrode assembly wound in a jelly-roll form and inserted into the center pin serving as the flow channel of the gas inside the rechargeable battery. An upper that is, the top of the top of the electrode assembly in the can may be provided a circular beading portion formed bent inward pressure from the outside to prevent the electrode assembly, and the direction of flow.
[53]
Further, in the circular secondary battery, the cap assembly as assembled to the opening of round cans in a closed state by interposing a gasket, positioned on the open end of the round can sealing a circular can, and forming a positive terminal top cap; Current blocking member electrically connected with the electrode assembly; And it is connected via the current cut-off member and the connection part, but electrically connected to the current-shielding member and the top cap, due to the non-steady-state current to break the connection when the gas generated inside the ring-can to block the flow of current a safety vent.
[54]
In the cap assembly, the top cap has an electrode terminal formed so as to be connected to external devices electrically.
[55]
Also, in the cap assembly, the safety vent is bent and made in a form surrounding the outer peripheral surface of the top cap, the safety vent is protruded convexly in the middle current blocking member: is welded to (CID current InterruptDevice).
[56]
The safety vent may serve to cut off the current when the pressure rise in the battery or the exhaust gas, and may be a metallic material. May vary depending on the thickness of the safety vent is the material and the structure, and as rupture of the internal battery in case of a predetermined high pressure is not particularly limited if capable of discharging the gas, such as, for example, may be 0.2 to 0.6 mm.
[57]
The thickness of the top cap portion in contact with the safety vent is, if the range of pressure from being applied from the outside to protect the various components of the cap assembly is not particularly limited, for example, be from 0.3 to 0.5mm have. Tower is too thin thickness of the cap portion if it is difficult to achieve the desired mechanical strength, if it is too thick, there is a fear the other hand to reduce the capacity of the same size compared to the battery by the size and weight increase.
[58]
[59]
Also, in the cap assembly, the current blocking member may be separated by as that can be deformed with a safety vent by the internal pressure of the secondary battery, a current cut-off member ((Current Interrupt Device, CID) gasket and the CID filter .
[60]
Further, in the circular secondary battery, the cap assembly may include a PTC (positive temperature coefficient) element between the safety vent and the top cap. Specifically, the cap assembly is in the PTC element, and one surface is the PTC element arranged to be brought into contact with the top cap the top cap (top cap), arranged to be sealed to the open end of the round the can in contact with the projecting portion of the gasket some of the contact and the other surface is disposed to contact the uneven portion of the gasket, it may be provided with a safety vent electrically connected to the electrode assembly.
[61]
[62]
The PTC device and the internal battery when the battery temperature increases the resistance greatly increases, and functions to cut off the current, and may vary depending on the thickness and also the material structure of the PTC element, for example may be 0.2mm to 0.4mm .
[63]
If the thickness of the PTC element is thicker than 0.4mm increase in the internal resistance and to increase the size of the cell may reduce the capacity of the same size compared to cells. On the other hand, if the thickness of the PTC element, the thickness is less than 0.2mm, it can be difficult to achieve the current blocking effect at a desired temperature by the destruction of a weak external impact. Therefore, the thickness of the PTC device may be considered as a combination of these points appropriately determined within the above thickness range. The thickness of the top cap portion in contact with the PTC device, if the range that can protect the various components of the cap assembly from a pressure applied from outside is not particularly limited, and may be, for example, 0.3 to 0.5mm. If the thickness of the top cap portion is too thin, by the mechanical strength it is difficult to exert, if too thick, the size and weight increases contrary there is a possibility to reduce the capacity of the same size compared to cells.
[64]
[65]
This top cap, PTC element, and a circular secondary battery including a cap assembly including a safety vent may be used as a power source for mobile phones, laptop to provide a constant output with stability. However, the top cap, PTC element, and a lithium secondary battery of a structure having a safety vent may be difficult to provide a momentary high output, to provide a uniform output resistance of an impact. When the contact surface is changed, such as vibration rather there may be difficulties. Specifically, looking to, PTC element is typically indicate an electric resistance of about 7 to 32 mΩ at room temperature In addition, lead to rapid resistance increase with increase in temperature and, as a result, can act as a big hindrance to provide a momentarily higher output because. Furthermore, an impact upon top cap, PTC element, the contact surface of the safety vent, such as vibration, because they can not provide a uniform output, because the change in the resistance very larger.
[66]
[67]
The present invention will be described in more detail through the following examples. However, the following Examples and Experimental Examples are not intended the scope of the present invention is intended to illustrate the present invention limited by these examples and experimental examples.
[68]
[69]

[70]
Use SPCE (cold-rolled steel sheet) plated with Ni produce a round top cap and casing, which was equipped with an insulating member made of a polymer resin as set forth in one case equipped with a circular electrode assembly, and then, the following Table 1. Performing a beading process Klim form a ping part in case of the circular portions corresponding to the upper end of the electrode assembly, which was later mounted the current blocking member here equipped with a gasket to the edge portions of the current blocking element. It was then coupled to the current cut-off member and the safety vent through laser welding. Then, equipped with a PTC element and a top cap and bending the upper end of the can inwardly and then subjected to the crimping process and the pressure was produced in the previous round of cell 18650 standard (diameter 18 mm, length 65mm).
[71]
[72]

[73]
, Except that an insulating member having a fine pattern on the surface was produced in the circular secondary battery as in Example 1.
[74]
[75]

[76]
To, except that an insulating member of a polymeric resin having the characteristics as in Table 1 was produced in the circular secondary battery as in Example 1.
[77]
[78]

[79]
By compressing the secondary battery fabricated as 675kgf to whether a short circuit are shown in Table 1 below. In addition, it compressed to 1350kgf to whether a short circuit are shown in Table 1 below.
[80]
[81]
TABLE 1
Insulating members material The pattern shape Whether paragraph
675kgf 1350kgf
Example 1 PP - X X
Example 2 PP - X X
Example 3 PP - X X
Example 4 PP - X X
Example 5 PP Mesh X X
Example 6 PP Mesh X X
Example 7 PP Embo X X
Example 8 PP Embo X X
Comparative Example 1 Non-woven fabric (PE) - O O
Comparative Example 2 Non-woven fabric (PE) - O O
Comparative Example 3 Non-woven fabric (PE) - X O
Comparative Example 4 Non-woven fabric (PE) - X O

[82]
[83]
The physical properties of the polymer resin used in the above Examples and Comparative Examples insulating member made are shown in Table 2 below.
[84]
[85]
TABLE 2
The intrinsic viscosity Mw / Mn Tensile Strength (MPa, 100 ℃) Flexural modulus (MPa, 100 ℃)
Example 1 0.81 1.97 26 1577
Example 2 0.87 2.05 25 1569
Example 3 0.93 2.04 27 1599
Example 4 0.90 1.98 25 1611
Example 5 0.83 1.91 24 1593
Example 6 0.92 2.03 26 1587
Example 7 0.88 2.01 26 1609
Example 8 0.95 1.99 25 1614
Comparative Example 1 0.33 4.11 17 1261
Comparative Example 2 0.42 4.23 16 1272
Comparative Example 3 0.37 4.18 17 1313
Comparative Example 4 0.41 4.27 18 1307

[86]
[87]
The experimental results, the secondary battery of Examples 1 to 8, comprising an insulating member that meets the requirements of a grade water proposed in this invention did not cause a short circuit in the compression test results 1350 kgf.
[88]
However, in the case of the comparison does not meet the above-described water grade requirements Examples 1 to 2 675, in case of Comparative Examples 3 to 4 all occurred a short circuit, in the 1350 kgf in the 675 kgf Although short circuit has not occurred in the 1350 kgf short circuit occurs, It was.
[89]
[90]
In the above, the present invention has been been described by exemplary embodiments and drawings, the invention is not limited thereto under the technical scope of the present invention by one of ordinary skill in the art various modifications and variations within the equivalent scope of the claims to be described are possible, of course.

Claims

[Claim 1]In the secondary battery that is the roll is mounted in a cylindrical battery case, the jelly-positive electrode, a negative electrode and a separator structure of a jelly is interposed between the positive electrode and the negative electrode as an insulating member of a plate-like structure mounted on the top of the roll, wherein the insulating member is will as a polypropylene, the polypropylene is an insulating member, characterized in that the tensile strength at 100 ℃ from 20 to 30 MPa, a flexural modulus of 1500 to 1650 MPa.
[Claim 2]
The method of claim 1 wherein the polypropylene is 0.6 to 1.2dl / g in the intrinsic viscosity, the insulating member, characterized in that the Mw / Mn value of 1.5 to 2.5.
[Claim 3]
The method of claim 1, wherein the insulating member is an insulating member, characterized in that it has a fine pattern (pattern).
[Claim 4]
The method of claim 3 wherein the shape of the pattern, mesh (mesh), the lamella (lamellar), embossing (embo), linear, circular, oval, polygon, an insulating member, characterized in that, having any shape of waveform.
[Claim 5]
The method of claim 3, wherein the pattern is characterized in that the insulating member is formed by printing a pattern using a silicon master mold.
[Claim 6]
Any one of claims 1 to 5, a cylindrical secondary battery having an insulation member according to any one of items.