KR101064236B1 - Cylindrical Secondary Battery Containing Center Pin of Improved Safety to External Impact - Google Patents

Abstract

The present invention is a secondary battery in which an electrode assembly (jelly-roll) manufactured by winding a cathode / separator / cathode is embedded in a cylindrical battery case, and includes a hollow body that provides strength on a horizontal cross section, and an outer surface of the hollow body. The center pin, which consists of an outer layer enclosing and exerting shock absorption, provides a secondary battery inserted in the core of the jelly-roll, which is subjected to a strong external shock or subjected to an impact test. As a result, when deformation occurs in the center pin, the internal short circuit is prevented or minimized by the action of the shock absorbing outer layer, thereby only generating heat without generating ignition of the battery, thereby greatly improving the safety of the battery.

Description

Cylindrical Secondary Battery Containing Center Pin of Improved Safety to External Impact}

1 is a vertical cross-sectional perspective view of a cylindrical battery of the prior art incorporating a jelly-roll electrode assembly;

2 is a horizontal cross-sectional view of the center pin along straight line A-A in the cell of FIG. 1;

3 is a perspective view of a center pin of a cylindrical secondary battery according to one embodiment of the present invention;

4 is a horizontal cross-sectional view taken along the straight line B-B at the center pin of FIG. 3.

The present invention relates to a cylindrical secondary battery including a center pin with improved safety against external impact, and more particularly, an electrode assembly (jelly-roll) manufactured by winding a cathode / separator / cathode is embedded in a cylindrical battery case. A secondary battery comprising: a center pin comprising a hollow structure for providing strength on a horizontal cross section ('hollow body') and an outer layer surrounding the outer surface of the hollow body and exerting shock absorption. To provide a secondary battery is inserted into the core of the jelly-roll.

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

According to the shape of the battery case, secondary batteries are classified into cylindrical batteries and rectangular batteries in which the electrode assembly is embedded in a cylindrical or rectangular metal can, and pouch-type batteries in which the electrode assembly is embedded in a pouch type case of an aluminum laminate sheet. .

In addition, the electrode assembly embedded in the battery case is a power generator capable of charging and discharging composed of a laminated structure of the anode / separator / cathode, a jelly-roll type wound through a separator between the long sheet-type anode and cathode coated with the active material And a plurality of positive and negative electrodes of a predetermined size are classified into a stack type in which a plurality of positive and negative electrodes are sequentially stacked in a state where a separator is interposed therebetween. Among them, the jelly-roll type electrode assembly has advantages of easy manufacturing and high energy density per weight.

The jelly-roll type electrode assembly is mainly used for cylindrical cells and rectangular cells, and FIG. 1 schematically shows a vertical cross-sectional perspective view of a cylindrical cell including a jelly-roll type electrode assembly.

Referring to FIG. 1, the cylindrical secondary battery 10 accommodates a jelly-roll type (wound) electrode assembly 20 in a cylindrical case 30 and injects an electrolyte solution into the cylindrical case 30, followed by a case 30. ) Is manufactured by combining a top cap 40 having an electrode terminal (for example, a positive electrode terminal; not shown) formed at an open upper end thereof.

The electrode assembly 20 has a structure in which a cathode 21, a cathode 22, and a separator 23 are sequentially stacked and wound in a round shape, and a cylindrical center pin 50 is formed at its core (center of jelly-roll). Is inserted. The center pin 50 is generally made of a metal material to impart a predetermined strength, and has a structure in which the plate is rounded, and as shown in FIG. 2, a hollow cylindrical shape in which the end 51 is not in contact with the horizontal cross section. It consists of a structure. The center pin 50 serves as a passage for fixing and supporting the electrode assembly and for releasing gas generated by internal reaction during charging and discharging and during operation.

However, when the center pin 50 is subjected to an external shock such as dropping or crimping of the battery, deformation is likely to occur in the hollow internal structure, and the end portion 51 of the center pin that is not in contact with the center pin penetrates the separation membrane. Contact with the electrode may cause an internal short circuit.

In particular, when a cylindrical lithium secondary battery is used in, for example, a notebook PC, most of them undergo a safety test such as an impact test. As a result of performing such an impact test, the center pin is deformed to ignite the battery. The phenomenon has been a serious problem. Moreover, the importance of the safety of the battery has been further emphasized as recent ignition events of the notebook PC occur.

Therefore, there is a high need for a technology that can effectively prevent the internal short circuit caused by the deformation of the center pin and thereby ignite the battery, thereby improving the safety of the battery.

In this regard, Japanese Patent Application Laid-Open No. 2005-259567 has a pressurizing means having an operating temperature of 70 to 150 ° C. in the core to prevent buckling that may occur when the thickness of the separator is 20 μm or less. The pressurizing means discloses a cylindrical secondary battery having a structure including a pressurizing means for arranging a center pin made of a shape memory alloy or a thermoplastic resin and a spring-shaped metal, or for arranging a foaming agent and a microcapsule, which expand in volume at a predetermined temperature. . However, the above technique is a technique applied only to a cylindrical secondary battery using a separator having a thickness of 20 μm or less, and has a structure in which a center pin is filled with a predetermined material when a predetermined condition is satisfied. As described above, the present invention is remarkably distinguished from the present invention including an outer layer exhibiting shock absorbing properties in the hollow body.

Japanese Patent Application Publication Nos. 1999-204130, 1997-270251 and 2003-092148, Japanese Patent No. 3613407, and Korean Patent Application Publication Nos. 2003-043745, 2006-037843, etc. Some variations of the center pins are shown.

However, these center pins have their advantages, but they do not solve all of the problems described above.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art and the technical problems required from the past.

After extensive research and various experiments, the inventors of the present application wrap a hollow body ('hollow body') that gives strength on a horizontal cross section, and surround the outer surface of the hollow body and exhibit shock absorption. When the center pin composed of the outer layer is inserted into the core of the jelly-roll, even when the center pin is deformed by an external impact, the shock absorbing outer layer may be used to alleviate the impact and thus prevent or minimize the internal short circuit. In addition, since it is possible to effectively discharge the gas generated during charging and discharging or operation, it has been confirmed that the safety of the battery can be greatly improved, and the present invention has been completed.

A secondary battery according to the present invention for achieving this object is a secondary battery in which an electrode assembly (jelly-roll) manufactured by winding a cathode / separation membrane / cathode is embedded in a cylindrical battery case, which provides strength on a horizontal cross section. A center pin composed of a hollow structure body ('hollow body') and an outer layer surrounding the outer surface of the hollow body and exhibiting shock absorbing properties is inserted into the core of the jelly-roll. .

As described above, in the secondary battery according to the present invention, since the center pin includes a hollow body and a shock absorbing outer layer surrounding the outer surface of the hollow body, external shock, for example, for a notebook PC When the center pin is deformed by a strong impact applied during an impact test on the cylindrical battery, the short circuit and the resulting fire of the battery can be prevented by the shock absorbing outer layer. In addition, the hollow part formed by the hollow body serves as a gas ejection passage generated during charging and discharging and operation, thereby preventing the electrode assembly from igniting under particularly harsh conditions such as high temperature to high pressure. This can improve battery safety.

The hollow body material may be, for example, one or two or more polymer materials selected from the group consisting of polypropylene, polyimide, polyamide, polycarbonate, and polymethyl methacrylate, or the polymer and filler It may be a composite material and the like, but is not limited thereto, and particularly preferably may be made of a metal material to impart a predetermined mechanical rigidity to the jelly-roll.

The material of the shock absorbing outer layer is not particularly limited as long as it is a material capable of exhibiting shock absorbing property, and preferably may be made of a porous structure having a high porosity. In the case of using a material having such a porous structure, since the impact is properly absorbed from the pores inside the porous structure when the external impact is applied, the deformation of the center pin hardly occurs or only a very fine deformation occurs. Short circuit by the deformation of the center pin can be prevented.

The shock absorbing outer layer of the porous material is not particularly limited, and may be, for example, various forms such as a porous body, a foam, or a nonwoven fabric, and preferably an open type foam or a closed type of a polymer resin. It may be made of foam. Representative examples of the polymer resin for forming the outer layer may include, but are not limited to, polyurethane, polystyrene, and the like, and the foam may be foamed by adding a chemical or physical blowing agent to an organic or inorganic material, for example. It may be manufactured by, in this case, may be manufactured in the form of foam sheet to surround the outer surface of the hollow body.

The outer layer of the open foam structure may be more desirable so that the gas generated in the jelly-roll can more easily move through the impact absorbing outer layer of the porous structure to the hollow body.

The center pin is preferably an outer diameter of 2 to 5 mm. Since the outer diameter itself means the total size of the center pin, it is not preferable because the capacity of the battery is small when the outer diameter is too large, whereas the mechanical rigidity of the center pin is small when the outer diameter is too small.

The inner diameter of the hollow body can be adjusted in a range that can properly discharge the gas generated during charging and discharging and operation while maintaining a predetermined mechanical strength, the size of 30 to 80% based on the total radius of the center pin It is preferable. When the size of the inner diameter is too large, as a result, the outer diameter of the center pin is increased, so that the above-described problems may occur and the predetermined mechanical strength may not be exerted, and conversely, when the size of the inner diameter is too small, It is not preferable because the gas cannot be discharged effectively.

The thickness of the shock absorbing outer layer may be appropriately adjusted in a range capable of alleviating the shock in response to the shock or external shock applied to the center pin as the charge and discharge of the battery is repeated, and may vary according to the material of the shock absorbing outer layer. Although not particularly limited, it may preferably be 20 to 50% in size based on the total radius of the center pin. However, when the thickness of the shock absorbing outer layer is too thick, the result is that the area of the electrode assembly is relatively reduced, and thus the battery capacity is lowered. On the contrary, when the thickness is too thin, the impact resistance of the shock absorbing outer layer may not be exhibited.

The structure of the hollow body is not particularly limited, and in one preferred example, the hollow body may be a structure in which a metal plate is bent roundly so that both ends thereof face each other, or may be a structure of a cylindrical tube.

In the former structure, both ends of the metal sheet are surrounded by the shock absorbing outer layer, and thus are not exposed even when the center pin is deformed due to a significant external impact, so that the ends penetrate the separator and come into contact with the electrode. The problem of a local short circuit can be fundamentally prevented.

An exemplary structure of a center pin according to the present invention can be easily identified below with reference to the drawings.

FIG. 3 is a perspective view schematically illustrating a center pin included in a cylindrical secondary battery according to an exemplary embodiment of the present invention, and FIG. 4 schematically illustrates a horizontal cross-sectional view along a straight line B-B of FIG. 3. Hereinafter, the present invention will be described in more detail with reference to the drawings, but the scope of the present invention is not limited thereto.

Referring to these drawings, the center pin 100 has an outer diameter R _C of 4 mm, surrounds the hollow body 220 that imparts strength on a horizontal cross section, and the outer surface of the hollow body, and has shock absorbing properties. It is comprised by including the outer layer 210 to exhibit.

The hollow body 221 may be made of a metal material to impart a predetermined mechanical strength, and has a structure bent roundly so that both ends 221 of the metal plate face each other. Through the hollow structure 230 formed by the hollow body 220, the gas generated by the short circuit inside the battery can be smoothly discharged, thereby increasing the internal pressure of the cylindrical battery to operate the safety vent and / or the CID. Therefore, it is possible to improve the safety of the battery by blocking the discharge of high-pressure gas and the energization of the current, it is possible to prevent the phenomenon that the entire jelly-roll is ejected in the harsh environment, such as high temperature to high pressure.

The outer layer 210 exhibiting shock absorption is made of an open foam, and has a thickness of 20 to 50% based on the total radius of the center pin.

By the outer layer 210 exerting the shock absorbing property, which is a structure surrounding the outer surface of the hollow body 220, the sharp end portion 221 can be fundamentally prevented from causing an internal short circuit through the separator by deformation of the conventional center pin. In addition, by absorbing an impact or an external impact applied to the center pin 200 by repetition of charging and discharging, it is possible to prevent a short circuit and consequent ignition of the battery, thereby greatly improving the safety of the battery.

The technique according to the invention can be preferably applied particularly to lithium secondary batteries of high energy density, discharge voltage, and output stability. Other components of the lithium secondary battery according to the present invention will be described in detail below.

In general, a lithium secondary battery is composed of a positive electrode, a negative electrode, a separator, a lithium salt-containing nonaqueous electrolyte, and the like.

The positive electrode is produced by, for example, applying a mixture of a positive electrode active material, a conductive material, and a binder onto a positive electrode current collector, followed by drying, and further, a filler may be further added as necessary.

The cathode current collector generally has a thickness of 3 to 500 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, the surface of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel Surface treated with carbon, nickel, titanium, silver or the like can be used. The current collector may form fine irregularities on its surface to increase the adhesion of the positive electrode active material, and may be in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The cathode active material may be a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Li _{1 + x} Mn _{2 - x} O ₄ (Where x is 0 to 0.33), lithium manganese oxides such as LiMnO ₃ , LiMn ₂ O ₃ and LiMnO ₂ ; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , Cu ₂ V ₂ O ₇ and the like; Ni-site type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ , wherein M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 to 0.3; Formula LiMn _2-x M _x O ₂ (wherein M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (wherein M = Fe, Co, Lithium manganese composite oxide represented by Ni, Cu or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with alkaline earth metal ions; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ , and the like. However, the present invention is not limited to these.

The conductive material is typically added in an amount of 1 to 50% by weight based on the total weight of the mixture including the positive electrode active material. Such a conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; Carbon blacks such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used. In some cases, since the conductive second coating layer is added to the positive electrode active material, the addition of the conductive material may be omitted.

The binder is a component that assists in bonding the active material and the conductive material to the current collector, and is generally added in an amount of 1 to 50 wt% based on the total weight of the mixture including the positive electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like.

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

The negative electrode is manufactured by applying and drying a negative electrode material on the negative electrode current collector, and if necessary, the components as described above may be further included.

The negative electrode collector is generally made to have a thickness of 3 to 500 mu m. Such an anode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery, and may be formed of a material such as copper, stainless steel, aluminum, nickel, titanium, fired carbon, surface of copper or stainless steel A surface treated with carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy, or the like can be used. In addition, like the positive electrode current collector, fine concavities and convexities may be formed on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The negative electrode material may be, for example, carbon such as hardly graphitized carbon or graphite carbon; Li _x Fe ₂ O ₃ (0≤x≤1), Li _x WO ₂ (0≤x≤1), Sn _x Me _{1 - x} Me ' _y O _z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, 2, 3 of the periodic table) Metal composite oxides such as a group element, halogen, 0 <x ≦ 1, 1 ≦ y ≦ 3, 1 ≦ z ≦ 8); Lithium metal; Lithium alloys; Silicon-based alloys; Tin-based alloys; SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ , and oxides such as Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

The separator is interposed between the cathode and the anode, and an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally from 0.01 to 10 ㎛ ㎛, thickness is generally 5 ~ 300 ㎛. As such a separator, for example, olefin polymers such as chemical resistance and hydrophobic polypropylene; Sheets or non-woven fabrics made of glass fibers or polyethylene are used. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separator.

A lithium salt containing non-aqueous electrolyte solution consists of a nonaqueous electrolyte solution and lithium. As the nonaqueous electrolyte, a liquid nonaqueous electrolyte, a solid electrolyte, an inorganic solid electrolyte, and the like are used.

Examples of the liquid nonaqueous electrolyte include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butylo lactone, and 1,2-dimethoxy. Ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolon, formamide, dimethylformamide, dioxolon, acetonitrile, nitromethane, methyl formate, acetic acid Methyl, phosphoric acid triester, trimethoxy methane, dioxorone derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, pyrionic acid Aprotic organic solvents such as methyl and ethyl propionate can be used.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, Polymers containing ionic dissociation groups, and the like can be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides, sulfates and the like of Li, such as Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ , and the like, may be used.

The lithium salt is a material that is readily soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO 4, LiBF 4, LiB 10 Cl 10, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF _{6, LiSbF 6, LiAlCl 4,} CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imide have.

In addition, the lithium salt-containing non-aqueous electrolyte contains pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, and hexa for the purpose of improving charge and discharge characteristics and flame retardancy. Phosphate triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol, aluminum trichloride, etc. This may be added. In some cases, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further added to impart nonflammability, or a carbon dioxide gas may be further added to improve high-temperature storage characteristics.

The lithium secondary battery according to the present invention can be produced by conventional methods known in the art. That is, it may be prepared by inserting a porous separator between the anode and the cathode and injecting the electrolyte therein.

The positive electrode may be manufactured by, for example, applying a slurry containing the lithium transition metal oxide active material, the conductive material, and the binder described above onto a current collector and then drying. Similarly, the negative electrode can be prepared by, for example, applying a slurry containing the above-described carbon active material, a conductive material and a binder onto a thin current collector and then drying it.

The present invention also includes a structure as described above, that is, a hollow body ('hollow body') for imparting strength on a horizontal cross section, and an outer layer surrounding the outer surface of the hollow body and exerting shock absorption. Provided is a center pin for a secondary battery configured.

The center pin according to the present invention has a novel structure which is not known in the art so far, and by this structural feature, when the deformation of the center pin occurs due to strong external impact, the internal short circuit is minimized and the ignition caused by this is minimized. It prevents and effectively releases gas generated inside without affecting battery performance.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are provided to illustrate the present invention, and the scope of the present invention is not limited thereto.

Example 1

As shown in Figure 4, both ends of the stainless steel plate is bent round to face each other to produce a hollow body having an inner diameter of 2 mm, by wrapping the outer surface of the manufactured hollow body with a 1.5 mm thick foam sheet The shock absorbing outer layer was formed to produce a center pin having an outer diameter of 3.5 mm. The center pin was inserted into the core of the electrode assembly to prepare a cylindrical secondary battery of 18650 (diameter 18 mm, length 65 mm).

Comparative Example 1

A cylindrical secondary battery was fabricated in the same manner as in Example 1, except that a center pin having a hollow circular structure was manufactured by using a stainless steel plate, and the ends were not in contact with each other in a horizontal cross section, as shown in FIG. 2. Was prepared.

Comparative Example 2

A cylindrical secondary battery was manufactured in the same manner as in Example 1, except that a cylindrical center pin having a 1.6-diameter-diameter-filled structure with end portions bonded to each other in a horizontal cross section was manufactured.

Experimental Example 1

Ten batteries prepared in Example 1 and ten batteries prepared in Comparative Examples 1 and 2 were subjected to an impact test at 4.2 V. The impact test was performed by checking whether a short circuit occurred by dropping a rod-shaped object having a diameter of 15.8 mm and a weight of 9.1 kg at a height of 610 x 25 mm based on a battery charged with 4.2 V.

As a result, all the batteries according to Example 1 did not have a short circuit, whereas short circuits were observed in three of the batteries according to Comparative Example 1. As a result of disassembling and inspecting the batteries of Comparative Example 1 in which a short circuit was induced, it was confirmed that a short circuit was caused by connecting the end of the center pin to the electrode of the jelly-roll through the separator. In addition, the battery according to Comparative Example 2 was confirmed that only the exothermic phenomenon occurs without increasing the pressure received by the jelly roll to ignite. However, the battery according to Comparative Example 2 has a structure that can not be discharged gas generated inside the jelly-roll, there is a limit to apply to the actual battery.

As described above, the secondary battery according to the present invention is equipped with a center pin having a structure surrounding the outer surface of the hollow body and including an outer layer exhibiting shock absorption, so that deformation of the center pin occurs due to strong external impact. In this case, the internal short circuit can be minimized and the ignition caused by this can be prevented, and further, the gas generated therein can be effectively released without affecting the battery performance, thereby greatly improving the safety of the battery.

Those skilled in the art to which the present invention pertains will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

Claims (12)

A secondary battery in which an electrode assembly (jelly-roll) manufactured by winding an anode / separator / cathode is embedded in a cylindrical battery case, and has a hollow structure ('hollow body') that imparts strength on a horizontal cross section; A secondary battery comprising a center pin surrounding an outer surface of a hollow body and composed of a porous structure and including an outer layer exhibiting shock absorbing properties, is inserted into a core of a jelly-roll. The secondary battery of claim 1, wherein the hollow body is made of a metal material. delete The secondary battery of claim 1, wherein the impact absorbing outer layer is made of an open type foam or a closed type foam of a polymer resin. The secondary battery of claim 4, wherein the impact absorbing outer layer is made of an open foam of polymer resin. The secondary battery of claim 1, wherein the center pin has an outer diameter of 2 to 5 mm. The secondary battery of claim 1, wherein an inner diameter of the hollow body is 30 to 80% based on the total radius of the center pin. The secondary battery of claim 1, wherein the impact absorbing outer layer has a thickness of 20 to 50% based on the total radius of the center pin. The secondary battery of claim 1, wherein the hollow body has a structure in which a metal plate is rounded so that both ends thereof face each other. The secondary battery of claim 1, wherein the hollow body has a structure of a cylindrical tube. The secondary battery of claim 1, wherein the battery is a lithium secondary battery. delete

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