KR20080047637A - Cylindrical battery of improved safety against external impact - Google Patents

Abstract

A cylindrical battery, and a middle/large sized battery module containing the battery are provided to prevent the ignition of a battery even in case of the application of strong external impact, thereby improving the safety of a battery. A cylindrical battery comprises a jelly roll type electrode assembly comprising a positive electrode, a separator and a negative electrode which is accommodated in a metal can; and a center pin which is inserted into the central hollow part of the jelly roll, wherein the center pin comprises a hollow main body(220) made of a material capable of broken in case of the application of strong external impact, and a polymer resin layer(210) coated on the outer surface of the hollow main body. If the strong external impact is applied, the electrode foil uncoated part of the jelly roll is shorted by the broken hollow main body.

Description

Cylindrical Battery of Improved Safety against 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 battery in which a wound electrode assembly ('jelly-roll') of a cathode / separator / cathode is embedded in a metal can and a center pin is inserted into a central hollow of the jelly-roll. Preferably, the center pin is composed of a hollow body of a material which is destroyed upon application of a strong external impact, and a polymer resin layer which is coated on the outer surface of the hollow body, and thus a hollow type that is destroyed upon application of a strong external impact. It provides a cylindrical battery, characterized in that the electrode foil uncoated portion of the jelly-roll is short-circuited by the main body.

As the development and demand for mobile devices increases, the demand for secondary batteries as energy sources is increasing rapidly. Among them, many researches have been conducted and commercialized and widely used for lithium secondary batteries with high energy density and discharge voltage. It is used.

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 No. 3807528 stacks a cylindrical battery can with a bottom, and a positive electrode plate and a negative electrode plate housed in the battery can, using a separator, and the hollow plate group, the electrolyte, and the hollow plate group among the wound plate groups. A cylindrical secondary battery formed by enclosing a center pin disposed inside, a safety plate mechanism on an upper portion of a center pin, and a battery can, wherein the partition wall is formed by partitioning the center pin into at least two normal spaces. Disclosed is a technology for a cylindrical secondary battery consisting of). However, the above technique has some effects in terms of giving various shapes of the center pin, which is a conductive material, to form a tip part when the impact from the outside of the electrode breaks the electrode foil, causing a short circuit. Since the protective film is not formed, there is a problem that the center pin is easily broken even in the external shock.

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

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

Accordingly, an object of the present invention is to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

The inventors of the present application, after repeated in-depth studies and various experiments, the center pin is composed of a hollow body of the material and a polymer resin layer which is coated on the outer surface of the hollow body after application of a strong external impact. In this case, the small impact prevents destruction of the hollow body by a protective film made of a polymer resin layer, and during a strong external impact, the hollow body is destroyed while inducing local short-circuits of the electrode foil non-coated portion of the jelly-roll core region. By suppressing ignition or explosion, it was confirmed that the safety of the battery can be greatly improved, and the present invention has been completed.

Accordingly, the cylindrical battery according to the present invention includes a cylindrical electrode in which a cathode / separator / cathode wound electrode assembly ('jelly roll') is embedded in a metal can and a center pin is inserted into a central hollow of the jelly roll. In the battery, the center pin is composed of a hollow body made of a material that is destroyed upon application of a strong external impact, and a polymer resin layer that is coated on the outer surface of the hollow body. It is comprised by the main body short-circuiting the electrode foil plain part of a jelly roll.

As described above, since the center pin in the cylindrical battery according to the present invention comprises a hollow body made of a material that is destroyed upon application of a strong external impact and a polymer resin layer surrounding the outer surface of the hollow body, If the center pin is deformed by an external impact, for example, a strong impact applied during an impact test on a cylindrical battery for a notebook PC, the hollow body is destroyed and the electrode foil in the jelly-roll core area is not known. The part is short-circuited locally, and the residual impact from the outside can be prevented from ignition or explosion of the battery by preventing destruction of the hollow body by the polymer resin layer applied to the outer surface of the hollow body. In addition, the hollow portion formed by the hollow body serves as a gas ejection passage generated during charging and discharging, thereby preventing the electrode assembly from igniting under particularly harsh conditions such as high temperature to high pressure, and ultimately, a battery. Can improve the safety.

The uncoated portion of the electrode foil means an end portion portion to which the electrode active material is not coated. According to the present invention, a broken center pin preferentially short-circuits such uncoated portion upon application of a strong impact. Since the positive electrode active material applied to the electrode foil is generally composed of a lithium transition metal oxide having high resistance, when such a positive electrode active material is brought into contact with the negative electrode active material, a short circuit may occur, which may cause a lot of heat generation and cause ignition or explosion of the battery. On the other hand, when the foil of the positive electrode non-coating portion of the high electrical conductivity and the foil of the negative electrode non-coating portion are brought into contact with each other, a short circuit is caused, and such large heat generation is not caused by energization based on low resistance. Therefore, the present invention improves the safety of the battery by causing a selective short circuit of such a plain part.

The material of the hollow body is not particularly limited as long as it is an electrically conductive material, and may preferably be a material having high electrical conductivity.

In addition, the material of the hollow body may be made of a glass substrate or a carbon substrate that is destroyed upon application of a strong external impact, and may be made of debris that can penetrate the electrode foil plain portion, for example, the glass substrate It may be composed of a conductive glass substrate.

The hollow body has an outer diameter of 2 to 4 mm, the thickness is preferably made of a size of 10 to 20% based on the total radius of the center pin.

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 thickness of the hollow body can be adjusted in a range capable of properly discharging the gas generated during charging and discharging and operation while maintaining a predetermined mechanical strength, the size of 20 to 40% based on the total radius of the center pin It is preferable. If the size of the thickness is too small, it may not be possible to exhibit a predetermined mechanical strength, on the contrary, if the size of the thickness is too large, it is not preferable because the hollow body may not be destroyed even under strong external impact.

The material of the polymer resin layer is not particularly limited as long as it is a material capable of exhibiting durability and shock absorbency. Preferably, polyurethane, polyacryl, ABS resin, or the like may be used. These resins may be used alone or in combination of two or more. When the hollow body is made of glass, in some cases, the polymer resin layer may be made of a porous structure to facilitate polymer coating. Such a porous structure can exhibit excellent impact resistance by appropriately absorbing the impact from the pores inside the porous structure for external impacts of a predetermined size or less, and the deformation of the center pin is hardly applied to the residual impact (various micro impacts) from the outside. By not occurring or only making a very small deformation, it is possible to prevent a short-circuit due to the deformation of the center pin for small impact or residual impact.

The thickness of the polymer resin layer can be appropriately adjusted in a range that can mitigate the impact in response to the shock or external impact applied to the center pin as the charge and discharge of the battery is repeated, and may vary depending on the material of the polymer resin layer Although not particularly limited, the size may be 5 to 10% based on the total radius of the center pin. However, when the thickness of the polymer resin layer is too thick, the area of the electrode assembly is relatively reduced, so that the fragments of the hollow body that are deteriorated by the battery capacity or the strong external impact are depleted in the electrode foil of the jelly-roll core part. It may not be possible to short-circuit parts, and on the contrary, when too thin, the desired impact resistance may not be exhibited, which is not preferable.

In one preferred embodiment, the outer surface of the hollow body may be a structure in which a plurality of notches are formed so that a predetermined sharp debris can be generated when broken, the hollow body that is destroyed when a strong impact is applied from the outside Fragments can be directed to the desired direction or location.

In the present invention, the 'notch' refers to a portion that is locally concave recessed on the outer surface of the material, and when an external force is applied thereto, stress is concentrated than other portions to cause fatigue failure. For example, a notch having a 'V' or 'U' shape formed on the outer surface of the grenade may be mentioned.

Cylindrical secondary battery according to the present invention can be preferably used as a unit cell in a high-power large-capacity battery module that can be a serious problem of safety by connecting a plurality of battery cells in series and / or parallel manner.

Accordingly, the present invention provides a medium-large battery module configured by stacking a plurality of cylindrical secondary batteries.

In general, by combining a plurality of cylindrical secondary batteries as a unit to produce a medium-large battery module having a high output capacity, in this case, since the combination method of the cylindrical secondary battery as the unit is known in the art, a detailed description thereof Omitted herein.

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, the hollow body 220 of the material that is destroyed when subjected to a strong external impact, and the outer surface of the hollow body 220 It consists of an outer layer 210 which is thinly coated with a polymer resin having a durable property for protecting the hollow body 220 from external residual impact.

The hollow body 221 is made of a crystalline material of conductive glass that can be broken and penetrate the polymer coating layer 210 when a strong impact from the outside is applied, in some cases, as shown in Figure 2, hollow A slit-shaped spacer may be further formed on the horizontal cross section so that both ends of the main body face each other. Through the hollow structure 230 formed by the hollow body 220, the gas generated during charging and discharging of the battery or a short circuit inside the battery may be smoothly discharged. Therefore, since the internal pressure of the cylindrical battery is increased to operate the safety vent and / or CID (not shown), the discharge of the high pressure gas and the energization of the current can be cut off, thereby improving the safety of the battery, and the high temperature to high pressure. It can prevent the whole jelly-roll from squirting in such harsh environment.

The outer layer 210 which protects the hollow body from the residual impact from the outside is made of a polymer resin exhibiting a predetermined durability, and has a thickness of 5 to 10% based on the thickness of the center pin, thereby applying a strong external impact. Debris of the hollow body that is destroyed during breakage easily passes through the electrode foil plain part. Specifically, the polymer resin layer 210 coated on the outer surface of the hollow body 220 protects the hollow body 220 made of a conductive glass material from external residual shocks and is destroyed by external strong impacts. By passing through the hollow body 220, a short circuit of the battery and consequent ignition can be prevented. Therefore, the safety of the battery can be greatly improved.

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 FIG. 4, the conductive glass substrate was rounded to prepare a hollow body having an outer diameter of 3.8 mm and a thickness of 0.6 mm, and the polystyrene resin was coated on the outer surface of the hollow body with a thickness of 0.2 mm to form a hollow body and a resin. A center pin having an outer diameter of 4 mm having a coating layer was prepared. 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

Using the stainless steel plate, as in Fig. 2, except that the hollow body is a hollow circular structure and a center pin was prepared without applying the polymer resin layer on the outer surface of the hollow body. A cylindrical secondary battery was produced in the same manner as in Example 1.

Experimental Example 1

Ten batteries prepared in Example 1 and ten batteries prepared in Comparative Example 1 were subjected to an impact test at a voltage of 4.2 V. The impact test was performed 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 ± 25 mm at a central portion of a battery charged with 4.2 V to determine whether fire or explosion occurred. It became.

As a result, all the batteries according to Example 1 did not ignite or explode, whereas fire or explosion was observed in three of the cells according to Comparative Example 1. As a result of disassembling and inspecting the batteries of Comparative Example 1 that caused ignition or explosion, it was confirmed that a short circuit was caused by the end of the center pin being connected to the electrode of the jelly-roll through the separator.

As described above, the secondary battery according to the present invention is equipped with a hollow main body made of a conductive glass material and a center pin coated with a durable polymer resin on the outer surface of the hollow main body. Prevents destruction of the hollow body, and in case of a strong external impact, breaks the hollow body and induces a local short circuit of the electrode foil ignorance in the jelly-roll core area, thereby suppressing ignition or explosion of the battery, thereby greatly increasing the safety of the battery. Can be improved.

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 (9)

A coiled electrode assembly ('jelly-roll') of a cathode / membrane / cathode ('jelly-roll') is embedded in a metal can and has a center pin inserted in the center hollow of the jelly-roll. The center pin has a strong external impact. It is composed of a hollow body of a material that is destroyed upon application of a polymer resin layer coated with an outer surface of the hollow body, and the electrode body of jelly-roll is solid by a hollow body that is destroyed upon application of a strong external impact. Cylindrical battery, characterized in that the short-circuit. The cylindrical battery according to claim 1, wherein the hollow body is made of a conductive material. 3. The cylindrical battery according to claim 2, wherein the hollow body is made of glass or carbon. The cylindrical battery according to claim 3, wherein the glass substrate is a conductive glass substrate. The cylindrical battery of claim 1, wherein the hollow body has an outer diameter of 2 to 4 mm and a thickness of 10 to 20% based on the total radius of the center pin. The cylindrical battery according to claim 1, wherein the polymer resin layer is one or more selected from the group consisting of polyurethane, polyacryl, and ABS resin. The cylindrical battery according to claim 1, wherein the polymer resin layer has a thickness of 5 to 10% based on the total radius of the center pin. The cylindrical battery according to claim 1, wherein a plurality of notches are formed on an outer surface of the hollow body so that a predetermined sharp debris is generated upon breakage. A high output large-capacity battery module comprising the cylindrical battery according to any one of claims 1 to 8 as a unit cell.

Images