KR101867650B1 - Battery Cell Employed with Battery Case Having Depressed Groove - Google Patents

Abstract

The present invention provides an electrode assembly including an electrode lead to which a plurality of electrode tabs are coupled, the electrode assembly being embedded in a receiving portion of the battery case; A sealing surplus portion in which a battery case is thermally fused is formed on an outer periphery of the storage portion; A first electrode lead (positive electrode lead or negative electrode lead) is located at a center portion of the upper end seal surplus portion with respect to a width direction of the battery case housing portion; An indentation step for inducing a deformation of the battery case during swelling of the battery cell is formed in the direction of the electrode assembly on the upper side of the upper portion of the battery case accommodating portion adjacent to the first electrode lead to provide a battery cell having excellent safety do.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a battery cell including a battery case having an indented step formed therein,

The present invention relates to a battery cell including a battery case having an indented step formed thereon and exhibiting excellent safety.

As technology development and demand for mobile devices have increased, the demand for secondary batteries as energy sources has been rapidly increasing, and a lot of research has been conducted on batteries that can meet various demands.

Typically, in terms of the shape of a battery, there is a high demand for a prismatic secondary battery and a pouch-type secondary battery which can be applied to products such as mobile phones with a small thickness, and has advantages such as high energy density, discharge voltage, There is a high demand for lithium secondary batteries such as lithium ion batteries and lithium ion polymer batteries.

Recently, an electrode assembly in which a porous separator is interposed between a positive electrode and a negative electrode each coated with an active material on an electrode collector is impregnated with a non-aqueous electrolyte containing a lithium salt, Pouch-shaped cells are attracting much attention due to their low manufacturing cost, small weight, easy shape deformation, and their usage is gradually increasing

FIG. 1 schematically shows a general structure of a typical conventional pouch-type secondary battery as an exploded perspective view.

Referring to FIG. 1, the pouch type secondary battery 10 is configured such that the electrode assembly 30 is mounted on the housing part 21 of the battery case 20, and after the electrolyte solution is injected, the electrode assembly 30 is sealed.

Specifically, the battery case 20 includes a case body 22 including a concave shaped storage portion 21 to which the electrode assembly 30 can be mounted, and a lid 23 integrally connected to the body 22 The electrode assembly 30 is housed in the accommodating portion 21, and the battery is completed by joining the upper and lower portions, which are the contact portions, with each other.

The electrode tabs 40 and 50 extend from the respective electrode plates of the electrode assembly 30, and the electrode tabs 40 and 50 extend from the electrode tabs of the electrode assembly 30, The battery case 20 and the battery case 20 are electrically connected to each other by welding, for example, with a plurality of electrode taps 40 and 50 extending from the respective electrode plates, The sealant 24 is exposed. An insulating film 80 is attached to a portion of the upper and lower surfaces of the electrode leads 60 and 70 in order to increase the degree of sealing with the battery case 20 and at the same time to secure an electrically insulated state.

However, if the swelling phenomenon of the battery is caused by the gas generated by the reaction between the electrode and the electrolyte in the charging and discharging process of the secondary battery, the electrode may be damaged. Particularly, If such a problem is intensified, as shown in FIG. 6, ignition may occur, which may cause a serious problem on the safety of the battery.

Therefore, there is a great need for a technique capable of solving the above problems.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and the technical problems required from the past.

The inventors of the present application have conducted intensive research and various experiments and have found that a first electrode lead (positive electrode lead or negative electrode lead) is formed at the center portion of the upper end sealing surplus portion with reference to the width direction of the battery case housing portion, Lt; / RTI > In the case where the indentation step is formed on one side of the upper end of the battery case accommodating portion adjacent to the first electrode lead, when the swelling of the battery cell occurs, deformation of the battery case is induced to the portion where the indented step is formed, It is possible to secure the safety of the battery cell due to the prevention of deformation and short-circuiting. Thus, the present invention has been accomplished.

According to an aspect of the present invention, there is provided an electrode assembly including an electrode assembly having a plurality of electrode tabs coupled thereto, the electrode assembly being embedded in a battery compartment of the battery case;

A sealing surplus portion in which a battery case is thermally fused is formed on an outer periphery of the storage portion;

A first electrode lead (positive electrode lead or negative electrode lead) is located at a center portion of the upper end seal surplus portion with respect to a width direction of the battery case housing portion;

Wherein an indented step for inducing deformation of the battery case during swelling of the battery cell is formed in the direction of the electrode assembly on one side of the upper end of the battery case accommodating portion adjacent to the first electrode lead do.

Generally, when swelling occurs due to abnormal operation of the battery such as overcharging, overdischarge, overcurrent, or deterioration due to long-term charge / discharge, the battery may expand and cause ignition and explosion.

In particular, when swelling of the battery cell occurs, the stress due to the expansion is concentrated at the center portion with respect to the width direction of the battery case. Therefore, when the electrode terminal is located at the center portion of the upper end of the battery case, Which can seriously affect the safety of the battery.

Therefore, in the present invention, the recessed step is formed in the direction of the electrode assembly at one side of the upper portion of the battery case accommodating portion, adjacent to the electrode lead located at the center portion of the upper end sealing surplus portion with respect to the width direction of the battery case accommodating portion Therefore, when swelling of the battery cell occurs, the stress due to the expansion can be induced by the indentation step, and damage to the electrode terminal is prevented, so that the safety of the battery cell can be secured to a desired level.

In the present invention, " the first electrode lead is located at the center portion of the upper sealing surplus portion with respect to the width direction of the battery case receiving portion " means a center line And a center line parallel to the side surface of the electrode lead coincides with a width direction of the first electrode lead. In general, a center line in the width direction reference of the battery case accommodating portion is located inside the first electrode lead And so on.

The term " sealing sealing " refers to a sealing portion having an extra space formed on one surface of the outer peripheral surfaces formed when the electrode assembly is embedded in the receiving portion of the battery case and sealed.

The electrode assembly includes a stacked electrode assembly in which at least one positive electrode plate and at least one negative electrode plate are laminated with a separator interposed therebetween, or stacked unit cells including a positive electrode plate and a negative electrode plate are stacked- Stacked unit cell including a positive electrode plate and a negative electrode plate is laminated with a separator interposed therebetween; Or one rolled electrode assembly in which one positive electrode plate and one negative electrode plate are wound with a separator interposed therebetween.

In the battery cell, the battery case may be formed of a laminate sheet including a metal layer and a resin layer, and may be a pouch case of an aluminum laminate sheet having a receiving portion to which the electrode assembly can be attached. The battery case of such a laminate sheet is sealed by, for example, thermal fusion after mounting the electrode assembly on the housing part.

In the present invention, the size of the indented step is, for example, 1% to 10% based on the width of the battery case accommodating portion, specifically 3% to 8% As shown in Fig.

If the size of the indented step is smaller than 1% based on the width of the battery case accommodating portion, it is difficult to induce the stress due to expansion of the battery cell. If it is larger than 10%, the stress due to the expansion of the battery cell is dispersed rather than the desired effect It is not desirable because it can not be obtained.

Further, the indented step is formed to a depth of 20% to 90%, in detail, to 40% to 70%, based on the distance between the lower end of the upper sealing portion and the upper end of the electrode assembly, Depth, in particular, to a depth of 0.5 mm to 2.5 mm.

When the depth of the indented step is less than 20% or 0.1 mm based on the distance between the lower end of the upper sealing portion and the upper end of the electrode assembly, it is difficult to induce stress due to the expansion of the battery cell, % Or 3.0 mm, the stress due to the expansion of the battery cell is dispersed and the desired effect can not be obtained, and the battery case may rupture when the battery case is formed to form the indented step, which is not preferable.

As described above, the stress due to the expansion of the battery cell is concentrated at the central portion of the battery cell at the time of swelling, so that the recessed step is preferably located as close as possible to the upper center portion of the accommodating portion. However, since the first electrode lead is located at the center portion of the upper sealing surplus portion, it is important to select an appropriate position.

Thus, the indented step can be formed at a position spaced apart from the first electrode lead by a distance of 5% to 20% with respect to the width of the battery case accommodating portion, and more specifically, a distance of 5% to 15% More specifically, it may be formed at a position separated by 10% to 15%.

If the indented step is less than 5% of the distance from the first electrode lead to the width of the battery case accommodating portion, the first electrode lead may be deformed due to the stress concentrated on the indentation step, and more than 20% , The indentation step is not preferable because stress can not be induced in the central portion of the battery cell.

The shape of the indented step may be, for example, a wedge shape, a semi-circular shape, a semi-elliptical shape, or a polygonal shape in plan view, but may be a wedge shape in detail.

A second electrode lead (a negative electrode lead or a positive electrode lead) may be positioned on the other side of the upper end of the battery case housing portion where the indented step is not formed with respect to the first electrode lead (positive lead or negative lead).

In this case, the first electrode lead may be a cathode lead, the second electrode lead may be a cathode lead, the first electrode lead may be a cathode lead, and the second electrode lead may be a cathode lead, The one electrode lead may be a positive electrode lead, and the second electrode lead may be a negative electrode lead.

In the present invention, the indented step may be formed by a post-treatment step after mounting of the electrode assembly to the battery case housing part or sealing of the battery case. Preferably, however, before the electrode assembly is mounted, .

In the case of forming them together in the process of forming the housing portion of the battery case, they can be formed by, for example, drawing work.

Drawing processing may be performed by any suitable method, including, for example, deep drawing, square shell drawing, reverse redrawing, asymmetric drawing, expanding forming drawing, restriking a necking drawing, an expanding drawing, a flaring drawing, and a bell mouth drawing may be used.

In one embodiment, the indentation step may be formed together in the process of forming the receiving part by performing a deep drawing process using a die and a punch having a shape corresponding to the shape of a desired step in the present invention, or a conventional die and a punch It is also possible to perform dip-drawing using a die and a punch corresponding to the shape of the stepped portion.

The post-treatment process may be performed manually or automatically by the operation of the machine. When such a post-treatment process is used, it is preferable to form a step by applying a pressure not to cause deformation or the like of the electrode assembly mounted therein. Thus, when the step is formed by the post-processing step, the electrode assembly can be easily mounted because no step is formed in the battery case when the electrode assembly is mounted.

The battery cell according to the present invention can be a lithium secondary battery in detail. The battery cell according to the present invention can be suitably applied not only to a lithium ion battery but also to a lithium ion polymer battery in which a lithium-containing electrolyte is impregnated with an electrode assembly in the form of a gel .

The present invention also provides a battery pack in which the battery cell is mounted inside a pack case, and a device including the battery pack.

In particular, the device comprises a power tool powered by an electric motor; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and the like; An electric motorcycle including an electric bike (E-bike) and an electric scooter (E-scooter); An electric golf cart, a cell phone, a notebook, and the like.

Since the general structure and manufacturing method of the battery pack are well known in the art, a detailed description thereof will be omitted in this specification.

As described above, according to the present invention, the first electrode lead (positive lead or negative lead) is positioned at the center of the upper end seal surplus portion with respect to the width direction of the battery case housing portion; Wherein a depressed step is formed in a direction of the electrode assembly on one side of an upper end of the battery case accommodating portion adjacent to the first electrode lead to form a deformation of the battery case as a portion where the indentation step is formed upon swelling due to swelling of the battery cell So that deformation and short-circuiting of the electrode are prevented, and thus safety of the battery cell can ultimately be improved.

1 is an exploded perspective view of a general structure of a conventional pouch type secondary battery;
FIG. 2 is an exploded perspective view of a structure of a pouch type secondary battery having an indented step according to an embodiment of the present invention; FIG.
FIG. 3 (a) is a front perspective view of the secondary battery according to FIG. 2 assembled; FIG.
FIG. 3 (b) is a partially enlarged sectional view of the secondary battery in which the indented step shown in FIG. 3 (a) is formed;
FIG. 4 is a photograph of the secondary battery according to FIG. 2 assembled; FIG.
5 is a photograph showing a state in which a swelling phenomenon is generated in the secondary battery according to FIG. 2; And
6 is a photograph of a state in which a swelling phenomenon is generated in the secondary battery according to FIG.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited by the scope of the present invention.

2 is an exploded perspective view of a pouch type secondary battery according to an embodiment of the present invention. FIG. 3 (a) is a front perspective view of the secondary battery in FIG. 2 And Fig. 3 (b) is an enlarged sectional view of the recessed stepped portion of the secondary battery shown in Fig. 3 (a).

Referring to these figures, in the pouch type secondary battery 100, the positive electrode tabs 350 and the negative electrode tabs 340 are welded to the positive electrode lead 370 and the negative electrode lead 360, respectively, The electrode assembly 300 having the insulating film 380 attached thereto is mounted on the housing part 210 of the battery case 200 and injected with an electrolyte solution and then sealed.

The battery case 200 includes a lower member 220 having a receiving portion 210 to which the electrode assembly 300 can be attached and an upper member 230 in the form of a lid integrally formed at a lower end thereof consist of. A surplus portion is formed along the outer circumferential surface of the battery case 200 so that the upper member 230 and the lower member 220 are in contact with each other and can be sealed by heat fusion during the assembling process of the secondary battery 100.

The positive electrode lead 370 is located at a central portion of the upper end seal inflow portion 240 with respect to the width direction of the battery case containing portion 210 and is located at an upper end side of the battery case containing portion 210 adjacent to the positive electrode lead 370 The recessed step 250 is formed in the region. The negative electrode lead 360 is located on the other side of the upper end of the battery case receiving portion 210 where the indented step 250 is not formed.

3B, the indentation step is formed in a space between the lower end of the upper sealing part and the upper end of the electrode assembly 200 in a wedge shape, and is set to 1% (W2) of 5% to 150% from the positive electrode lead (370) with respect to the width of the battery case accommodating portion and having a depth (h) of 0.1 mm to 3.0 mm, can do.

4 is a photograph of a portion where a recessed step (a red circle) is formed in a state where the secondary battery according to FIG. 2 is assembled.

Therefore, even if a swelling phenomenon of the battery cell occurs, the stress due to the expansion is induced by the indentation step 250 formed at one side of the upper part of the battery case receiving part 210, so that the width direction of the battery case receiving part 210 The anode lead 370 positioned at the center of the upper sealing rod 240 can be prevented from being damaged and the safety of the battery cell can be improved.

[Example 1]

A positive electrode mixture slurry was prepared by adding 95 wt% of lithium cobalt oxide, 2.5 wt% of a conductive agent and 2.5 wt% of a binder as a positive electrode active material to NMP (N-methyl-2-pyrrolidone) as a solvent, , 1.5% by weight of a conductive agent and 3.5% by weight of a binder were added to NMP as a solvent to prepare a negative electrode mixture slurry. The negative electrode mixture slurry was coated on aluminum foil and copper foil, respectively. The anode and cathode were stacked with a separator interposed therebetween to assemble the anode and cathode bipoles, respectively, and the batteries were sequentially wound with a long separator to form a stack-folding electrode assembly.

Then, as shown in FIG. 2, an electrode assembly was embedded in a pouch-shaped battery case having a recessed step formed in a housing part of the battery case, and then an electrolyte solution was injected and sealed to manufacture a battery cell.

[Comparative Example 1]

1, a battery cell was fabricated in the same manner as in Example 1, except that the electrode assembly was housed in a pouch-shaped battery case in which a recessed step was not formed in the housing portion of the battery case .

[Experimental Example 1]

The battery cells prepared in Example 1 and Comparative Example 1 were subjected to initial charging and discharging at 1C / 1C and left at a high temperature of 50 ° C or more to induce swelling of the battery, Are shown in Fig. 5 and Fig. 6 as photographs.

Referring to FIG. 5, the battery according to the first embodiment of the present invention is formed with an indented step, so that the expansion stress due to the swelling phenomenon is concentrated at the indented step (dotted line portion) So that the safety of the battery can be ensured.

On the other hand, referring to FIG. 6, the battery according to Comparative Example 1 of the present invention has no indentation step, and the expansion stress due to the swelling phenomenon is concentrated at the central portion of the upper end of the battery case, It can be confirmed that ignition occurs as the lead is deformed, which seriously affects the safety of the battery.

Claims (19)

An electrode assembly including an electrode lead to which a plurality of electrode tabs are coupled is embedded in a storage portion of a battery case;
A sealing surplus portion in which a battery case is thermally fused is formed on an outer periphery of the storage portion;
A first electrode lead (positive electrode lead or negative electrode lead) is positioned at a central portion of the upper end seal surplus portion with respect to a width direction of the battery case housing portion;
Wherein an indentation step for inducing deformation of the battery case during swelling of the battery cell is formed in the direction of the electrode assembly on one side of the upper portion of the battery case accommodating portion adjacent to the first electrode lead ,
The battery case is a pouch-shaped case of a laminate sheet including a metal layer and a resin layer,
Wherein the indented step is wedge-shaped in a plane,
And a second electrode lead (a negative electrode lead or a positive electrode lead) is disposed on the other side of the upper end of the battery case housing portion where the indented step is not formed with respect to the first electrode lead (positive lead or negative lead) Battery cell. 2. The separator according to claim 1, wherein the electrode assembly has stacked electrode assemblies in which at least one positive electrode plate and at least one negative electrode plate are stacked with a separator interposed therebetween, or stacked unit cells including a positive electrode plate and a negative electrode plate are wound Stacked type electrode assembly including a positive electrode plate and a negative electrode plate stacked with a separator interposed therebetween; Or one positive electrode plate and one negative electrode plate are wound with a separator interposed therebetween. delete The battery cell according to claim 1, wherein the indented step is formed to a size of 1% to 10% based on a width of the battery case housing part. The battery cell according to claim 1, wherein the indented step is formed in a space between a lower end of the upper sealing part and an upper end of the electrode assembly. The battery cell according to claim 1, wherein the indented step is formed at a depth of 20% to 90% based on a distance between a lower end of the upper sealing part and an upper end of the electrode assembly. The battery cell according to claim 1, wherein the depth of the indented step is 0.1 mm to 3.0 mm. The battery cell according to claim 1, wherein the indented step is formed at a position spaced apart from the first electrode lead by a distance of 5% to 20% with respect to a width of the battery case accommodating portion. The battery cell according to claim 8, wherein the indented step is formed at a position spaced from the first electrode lead by a distance of 5% to 15% with respect to a width of the battery case housing part. delete delete The battery cell according to claim 1, wherein the first electrode lead is a positive electrode lead and the second electrode lead is a negative electrode lead. The battery cell according to claim 1, wherein the first electrode lead is a negative electrode lead and the second electrode lead is a positive electrode lead. The battery cell according to claim 1, wherein the indented step is formed in the process of forming the housing part of the battery case. 15. The battery cell according to claim 14, wherein the indented step is formed by drawing work. The battery cell according to claim 1, wherein the indented step is formed by a post-treatment process after mounting the electrode assembly to the case housing part or sealing the case. The battery cell according to claim 1, wherein the battery cell is a lithium secondary battery. A battery pack comprising a battery cell according to claim 17. A device comprising a battery pack according to claim 18.

Images