Patent Description:
The present invention relates to a secondary battery.

Rechargeable batteries are rechargeable unlike primarily batteries, and also, the possibility of compact size and high capacity is high. Thus, recently, many studies on rechargeable batteries are being carried out. As technology development and demands for mobile devices increase, the demands for rechargeable batteries as energy sources are rapidly increasing.

Rechargeable batteries are classified into coin type batteries, cylindrical type batteries, prismatic type batteries, and pouch type batteries according to a shape of a battery case. In such a secondary battery, an electrode assembly mounted in a battery case is a chargeable and dischargeable power generating device having a structure in which an electrode and a separator are stacked.

Also, the electrode assembly may be approximately classified into a jelly-roll type electrode assembly in which a separator is interposed between a positive electrode and a negative electrode, each of which is provided as the form of a sheet coated with an active material, and then, the positive electrode, the separator, and the negative electrode are wound, a stacked type electrode assembly in which a plurality of positive and negative electrodes with a separator therebetween are sequentially stacked, and a stack/folding type electrode assembly in which stacked type unit cells are wound together with a separation film having a long length.

The secondary battery may have a risk of ignition and explosion due to overcharge thereof, and thus, it is necessary to prevent the secondary battery from being overcharged. <CIT> discloses a pouch cell wall connected to the electrode lead portion.

One aspect of the present invention is to provide a secondary battery that is capable of interrupting overcharging when the secondary battery is overcharged.

A secondary battery of the present invention is defined in the appended set of claims.

According to the present invention, the separator may be provided in the form in which the positive electrode and the negative electrode are short-circuited with each other when the pouch is swelled by the generation of the gas while the secondary battery is overcharged to interrupt the power supply due to the internal short circuit, thereby interrupting the overcharging.

The objectives, specific advantages, and novel features of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. It should be noted that the reference numerals are added to the components of the drawings in the present specification with the same numerals as possible, even if they are illustrated in other drawings. Also, the present invention may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. In the following description of the present invention, the detailed descriptions of related arts which may unnecessarily obscure the gist of the present invention will be omitted.

<FIG> is a conceptual cross-sectional view illustrating a state before a pouch is swelled in a secondary battery according to an embodiment of the present invention.

Referring to <FIG>, a secondary battery <NUM> according to an embodiment of the present invention comprises an electrode assembly <NUM> in which a positive electrode <NUM>, separators <NUM> and <NUM>, and a negative electrode <NUM> are alternately combined with each other and a pouch <NUM> accommodating the electrode assembly <NUM>. Also, the separators <NUM> and <NUM> comprise a first separator <NUM> and a second separator disposed between the positive electrode <NUM> and the negative electrode <NUM>.

Hereinafter, the secondary battery according to an embodiment of the present invention will be described in more detail with reference to <FIG> and <FIG>.

Referring to <FIG>, the electrode assembly <NUM> may be a chargeable and dischargeable power generation element and have a structure in which the electrodes <NUM> and the separators <NUM> and <NUM> are combined and alternately stacked with respect to each other.

The electrodes <NUM> may comprise a positive electrode <NUM> and a negative electrode <NUM>. Here, the electrode assembly <NUM> may have a structure in which the positive electrode <NUM>/the separators <NUM> and <NUM>/the negative electrode <NUM> are alternately stacked. Here, each of the separators <NUM> and <NUM> may be disposed between the positive electrode <NUM> and the negative electrode <NUM> and disposed outside the positive electrode <NUM> and outside the negative electrode <NUM>.

The separator <NUM> and <NUM> is made of an insulation material to electrically insulate the positive electrode <NUM> from the negative electrode <NUM>. Here, the separator <NUM>,<NUM> may be made of, for example, a polyolefin-based resin film such as polyethylene or polypropylene having micropores.

<FIG> is a conceptual cross-sectional view illustrating a state after the pouch is swelled in the secondary battery according to an embodiment of the present invention.

Referring to <FIG> and <FIG>, the separators <NUM> and <NUM> comprise a first separator <NUM> and a second separator disposed between the positive electrode <NUM> and the negative electrode <NUM>.

The first separator <NUM> has a through-hole 124a that is penetrated in a direction facing the positive electrode <NUM> and the negative electrode <NUM>.

The second separator <NUM> covers the through-hole 124a of the first separator <NUM> and has an end connected to the pouch <NUM>.

Also, the second separator <NUM> has an end fixed to an inner surface of the pouch <NUM>. Thus, when the pouch <NUM> is swelled due to generation of an internal gas, the second separator <NUM> moves in a lateral direction with respect to the direction in which the positive electrode <NUM>, the separators <NUM> and <NUM>, and the negative electrode <NUM> are stacked.

Here, the first separator <NUM> is bonded to be fixed to the positive electrode <NUM> or the negative electrode <NUM>, which face each other, and the second separator <NUM> is slidably provided without being boned to the positive electrode <NUM> or the negative electrode <NUM>, which face each other.

One end of the second separator <NUM> is fixed to a portion of the pouch <NUM>, which is disposed in the lateral direction with respect to the direction in which the positive electrode <NUM>, the separators <NUM> and <NUM>, and the negative electrode <NUM> are stacked.

Also, a spaced distance a between the other end of the second separator <NUM> and the through-hole 124a of the first separator <NUM>, which is measured in a normal state, may be less than an expansion width b of the pouch when the internal gas is generated. Thus, when the pouch is expanded, the through-hole 124a may be exposed.

Particularly, the spaced distance a may be less than an allowable expansion width of the pouch <NUM>. Thus, safety of the battery may be surely ensured within an allowable range.

The first separator <NUM> may be stacked on one surface of the positive electrode <NUM>, the second separator <NUM> may be stacked on one surface of the first separator <NUM>, and the negative electrode <NUM> may be stacked on one surface of the second separator <NUM>.

The pouch <NUM> may comprise an accommodation part <NUM> accommodating the electrode assembly <NUM> and an electrolyte solution.

Furthermore, the pouch <NUM> may be made of, for example, a flexible material.

For example, the pouch may be constituted by a plurality of layers. Here, an intermediate layer may be provided as an aluminum (Al) layer, and each of both layers may be provided as a resin layer made of a synthetic resin.

For another example, the pouch <NUM> may be constituted by a plurality of layers in which a polypropylene (PP) layer, a nylon layer, an aluminum (Al) layer, and a polyethylene terephthalate (PET) layer are stacked in order from the inside to the outside of the accommodation part <NUM>.

In the above-described secondary battery <NUM> according to an embodiment of the present invention, when the pouch <NUM> is expanded by the internal gas generated due to the overcharging, the end of the second separator <NUM> may move in the expansion direction of the pouch <NUM> to allow the portion of the second separator <NUM>, which covers the through-hole 124a of the first separator <NUM>, to move so as to open the through-hole 124a. Thus, when the overcharging occurs, the through-hole 124a of the first separator <NUM> may be opened due to the expansion of the pouch <NUM> to allow the positive electrode <NUM> and the negative electrode <NUM>, which are disposed on both sides of the first separator <NUM>, to contact with each other through the through-hole 124a of the first separator <NUM>, thereby causing short circuit. Thus, the power supply may be interrupted by the internal short circuit to interrupt the overcharging. Since the short circuit is designed with the safety range of the pouch <NUM>, the ignition due to the internal short circuit may not occur.

<FIG> is a conceptual cross-sectional view of a secondary battery according to another embodiment of the present invention, and <FIG> is an enlarged cross-sectional view of a portion A of <FIG>.

Referring to <FIG> and <FIG>, a secondary battery <NUM> according to another embodiment of the present invention is different from the secondary battery <NUM> according to the foregoing embodiment in that a fixing unit <NUM> for fixing an end of a second separator <NUM> to a pouch <NUM> is provided. Thus, contents of this embodiment, which are duplicated with those according to the forgoing embodiment, will be briefly described, and also, differences therebetween will be mainly described.

The secondary battery <NUM> according to another embodiment of the present invention comprises an electrode assembly <NUM> in which a positive electrode <NUM>, separators <NUM> and <NUM>, and a negative electrode <NUM> are combined and alternately stacked with respect to each other and a pouch <NUM> accommodating the electrode assembly <NUM>. Also, the separators <NUM> and <NUM> comprise a first separator <NUM> and a second separator disposed between the positive electrode <NUM> and the negative electrode <NUM>. Furthermore, the fixing unit <NUM> for fixing the end of the second separator <NUM> to the pouch <NUM> may be further provided.

In more detail, the fixing unit <NUM> may fix the end of the second separator <NUM> to the pouch <NUM>.

Here, an insulation layer <NUM> may be applied to an outer surface of the fixing unit <NUM> to electrically insulate the pouch <NUM> from the fixing unit <NUM> when the end of the second separator <NUM> is fixed to the pouch <NUM> through the fixing unit <NUM>.

Here, the fixing unit <NUM> may comprise, for example, a rivet.

Thus, in the secondary battery <NUM> according to another embodiment of the present invention, since the end of the second separator <NUM> is fixed to the pouch <NUM> through the fixing unit <NUM>, when the pouch <NUM> is expanded due to overcharging, the end of the second separator <NUM> may easily move in an expansion direction of the pouch <NUM> without separating the end of the second separator <NUM> from the pouch <NUM>. Thus, when the pouch <NUM> is expanded, the end of the second separator <NUM> may move in the expansion direction of the pouch <NUM> to allow a portion of the second separator <NUM>, which covers a through-hole 124a of the first separator <NUM>, to move so as to easily open the through-hole 124a. As a result, when the overcharging occurs, the through-hole 124a of the first separator <NUM> may be opened due to the expansion of the pouch <NUM> to allow the positive electrode <NUM> and the negative electrode <NUM>, which are disposed on both sides of the first separator <NUM>, to contact with each other through the through-hole 124a of the first separator <NUM>, thereby causing short circuit and easily interrupting the overcharging.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the present invention is not limited to the secondary battery according to the present invention. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the scope of the invention.

Claim 1:
A secondary battery comprising:
an electrode assembly (<NUM>) in which a positive electrode (<NUM>), a separator (<NUM>, <NUM>), and a negative electrode (<NUM>) are alternately combined to be stacked; and
a pouch accommodating the electrode assembly and an electrolyte solution therein,
wherein the separator comprises:
a first separator (<NUM>) disposed between the positive electrode (<NUM>) and the negative electrode (<NUM>) and having a through-hole (124a) penetrated in a direction facing the positive electrode (<NUM>) and the negative electrode (<NUM>); and
a second separator (<NUM>) covering the through-hole (124a) of the first separator (<NUM>) and having an end connected to the pouch (<NUM>),
the first separator (<NUM>) is fixed to the positive electrode (<NUM>) or the negative electrode (<NUM>), which face each other, and the second separator (<NUM>) is slidably provided without being bonded to the positive electrode (<NUM>) or the negative electrode (<NUM>), which face each other, wherein the end of the second separator (<NUM>) is fixed to an inner surface of the pouch (<NUM>), and
when the pouch is expanded due to the generation of the internal gas, the second separator (<NUM>) moves in a lateral direction with respect to a direction in which the positive electrode (<NUM>), the separator, and the negative electrode (<NUM>) are stacked so as to open the through-hole (124a) of the first separator (<NUM>) so that a power supply is interrupted by the internal short circuit to interrupt the overcharging.