Secondary battery

A secondary battery includes a battery unit that has an accommodation space for an electrode assembly, a vent housing that defines a housing space connected with the accommodation space through a first vent hole, the vent housing including a second vent hole through which the housing space is connected with an outside of the secondary battery, a revolving member that is rotatably mounted between a closing position for closing the first and second vent holes and an opening position for opening the first and second vent holes, and first and second sealing caps that are formed at opposite sides of the revolving member with respect to a rotation axis of the revolving member. The first and second sealing caps respectively close the first and second vent holes, when the revolving member is mounted at the closing position.

CLAIM OF PRIORITY

This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application earlier filed in the Korean Intellectual Property Office on the 24 Nov. 2011 and there duly assigned Serial No. 10-2011-0123660.

BACKGROUND OF THE INVENTION

1. Field of the Invention

One or more embodiments of the present invention relate to secondary batteries.

2. Description of the Related Art

Due to reaction with an active material and an electrolyte, gases, such as CO2or H2, are generated in a secondary battery. When these gases are formed in a space inside the secondary battery, the active material in certain portions of the secondary battery may undesirably lose its function or movement of lithium ions in an electrolyte may be hindered, resulting in reduction of the lifespan of the secondary battery. Moreover, if the generated gas accumulates, an internal pressure of the secondary battery may increase, which may lead to an explosion of the secondary battery.

Thus, to improve the lifespan and stability of the secondary battery, the generated gas needs to be discharged to the outside of the secondary battery to prevent loss of the function of the active material and to remove bubbles formed in the electrolyte.

SUMMARY OF THE INVENTION

One or more embodiments of the present invention include an improved secondary battery.

One or more embodiments of the present invention include secondary batteries from which a gas accumulated therein may be easily discharged.

One or more embodiments of the present invention include a secondary battery from which a gas accumulated therein may be discharged and also an inflow of external harmful materials may be blocked.

According to one or more embodiments of the present invention, a secondary battery includes a battery unit that has an accommodation space for an electrode assembly, a vent housing that defines a housing space connected with the accommodation space through a first vent hole, the vent housing including a second vent hole through which the housing space is connected with an outside of the secondary battery, a revolving member that is rotatably mounted between a closing position for closing the first and second vent holes and an opening position for opening the first and second vent holes, and first and second sealing caps that are formed at opposite sides of the revolving member with respect to a rotation axis of the revolving member. The first and second sealing caps respectively close the first and second vent holes when the revolving member is mounted at the closing position.

The revolving member may be disposed in the housing space.

The revolving member may rotate in a first rotational direction to reach the closing position where the first and second vent holes are both closed, and may rotate in a second and opposite rotational direction to reach the opening position where the first and second vent holes are both opened.

The revolving member may include first and second arms that extend in opposite directions with respect to the rotation axis. The first and second sealing caps are formed at end portions of the first and second arms, respectively.

A weight of the first arm may bias the revolving member to the closing position, and a weight of the second arm may bias the revolving member to the opening position. The first arm extends longer than the second arm.

The secondary battery may further include an elastic body that biases the revolving member to the closing position.

The elastic body may be a rotational spring having a first end and a second end connected to the revolving member and the rotation axis, respectively.

First and second filter members may be formed at open ends of the first and second vent holes, respectively.

The first and second filter members may have selective transmittivity to allow transmission of a gas and to prevent transmission of a fluid.

The first and second sealing caps may protrude from the revolving member toward the first and second vent holes, respectively.

A cross-section of each one of the first and second sealing caps may gradually decrease in size toward the corresponding one of the first and second vent holes as the first and second sealing caps respectively protrude into the first and second vent holes.

The first and second sealing caps may be formed to have a cone shape having sharp front tips toward the first and second vent holes, respectively.

Surfaces of the first and second sealing caps contacting wall portions of the first and second vent holes may be formed with elastic layers.

The vent housing may be disposed on a cap plate that defines the accommodation space.

The first vent hole may be formed in the cap plate.

A pair of electrode terminals that have opposite polarities and are respectively electrically connected to a positive electrode plate and a negative electrode plate of the electrode assembly may protrude from the cap plate.

Accordingly, a gas accumulated inside the second battery may be easily discharged outside, and an inflow of external harmful materials may be prevented.

DETAILED DESCRIPTION OF THE INVENTION

For medium-sized or large-sized batteries, in order to obtain stability and to prevent the costs of exchanging batteries, gas is removed without destroying the batteries. However, according to the related art, a breaking portion is inserted so that a portion of a case is broken with an increase of internal pressure, and this makes it difficult to reuse a secondary battery and the stability of the secondary battery is not secured due to the breaking.

FIG. 1is a disassembled perspective view of a secondary battery constructed as an embodiment according to the principles of the present invention.FIG. 2is a cross-sectional view of the secondary battery cut along a line of II-II′FIG. 1.FIG. 3is a schematic view of an electrode assembly10ofFIG. 2.

Referring toFIGS. 1 and 2, the secondary battery constructed as the embodiment according to the principles of the present invention includes a battery unit20and a gas discharge unit100that discharges a gas accumulated in the battery unit20to the outside of the secondary battery.

In detail, the secondary battery includes the battery unit20that has an accommodation space G1for an electrode assembly, a vent housing180that defines a housing space G2that is connected with the accommodation space G1via a first vent hole OP1and in which a second vent hole OP2is formed to connect the housing space G2and outside, and a revolving member110that is rotatably mounted between a closing position P1and an opening position P2of the first and second vent holes OP1and OP2. The revolving member110and the vent housing180form the gas discharge unit100.

The first and second vent holes OP1and OP2and the revolving member110operate to close or open the first and second vent holes OP1and OP2to discharge a gas that accumulates in the accommodation space G1as an internal pressure of the accommodation space G1increases, so as to prevent accidents, such as explosion or rupture of the secondary battery.

In detail, the first and second vent holes OP1and OP2provide a discharge path of the gas accumulated in the accommodation space G1. For example, the first vent hole OP1may be formed in a cap plate30that defines the accommodation space G1. The first vent hole OP1connects the accommodation space G1and the housing space G2, providing a discharge path for discharging the gas from the accommodation space G1to the housing space G2.

The gas that has flowed into the housing space G2after passing through the first vent hole OP1is discharged to the outside of the secondary battery through the second vent hole OP2. The second vent hole OP2connects the housing space G2and the outside of the secondary battery and may be formed in the vent housing180that defines the housing space G2.

Sizes and shapes of the first and second vent holes OP1and OP2may differ. For example, the first and second vent holes OP1and OP2may be circular, wherein a diameter d1of the first vent hole OP1may be designed larger than a diameter d2of the second vent hole OP2(d1of the first vent hole OP1>d2of the second vent hole OP2). Accordingly, the first vent hole OP1connected to the accommodation space G1is formed relatively large so that a gas accumulated inside the accommodation space G1is quickly discharged, whereas the second vent hole OP2connected to the outside is formed relatively small so as to block the inflow of external harmful materials. The first and second vent holes OP1and OP2are not limited to the circular form described above and may also have other forms, such as a rectangular form.

The vent housing180may be formed to have a hollow cover shape, one surface of which is opened. For example, the vent housing180may have a rectangular parallelepiped shape of which a bottom surface is opened as illustrated inFIG. 1. However, the current embodiment of the present invention is not limited thereto, and the vent housing180may also have other various forms. For example, the vent housing180may have a closed cube form in which the first and second vent holes OP1and OP2are formed.

The vent housing180may be mounted on the cap plate30to define the housing space G2thereon. For example, the housing space G2may be defined as a space between the cap plate30and the vent housing180. The housing space G2forms a discharge path of a gas between the first and second vent holes OP1and OP2.

The first and second vent holes OP1and OP2are simultaneously opened or closed according to rotation of the revolving member110. The revolving member110may be disposed inside the vent housing180and may be rotatably fixed on the cap plate30via a rotation axis150and a support130.

FIGS. 4 and 5illustrate the revolving member110at a closing position P1and an opening position P2, as an embodiment according to the principles of the present invention. Rotation of the revolving member110between the closing position P1and the opening position P2to open and close the first and second vent holes OP1and OP2is described with reference toFIGS. 4 and 5.

The revolving member110is rotatably mounted between the closing position P1and the opening position P2of the first and second vent holes OP1and OP2. When the revolving member rotates in a first rotation direction M1with respect to the rotation axis150to arrive at the closing position P1, the first and second vent holes OP1and OP2are both closed. When the revolving member rotates in an opposite, second rotation direction M2to arrive at the opening position P2, the first and second vent holes OP1and OP2are both opened.

The revolving member110may be fixed to the cap plate30via the rotation axis150and the support130, and the vent housing180may be mounted on the cap plate30so as to accommodate the revolving member110.

The revolving member110is rotated to the closing position P1or the opening position P2depending on physical force acting on the revolving member110. For example, if an internal pressure IP of the accommodation space G1increases, the increased internal pressure IP rotates a first sealing cap121of the revolving member110to the opening position P2. Accordingly, because the revolving member110is at an opening position, the first and second vent holes OP1and OP2are also opened. The opened first and second vent holes OP1and OP2provide a discharge path V for a gas accumulated in the accommodation space G1.

However, when the internal pressure IP decreases as the gas accumulated in the accommodation space G1is discharged, the revolving member110at the opening position P2rotates to the closing position P1according to a bias force toward the closing position P1(first rotation direction M1), and the first and second vent holes OP1and OP2are also both closed.

The bias three toward the closing position P1(first rotation direction M1) may be in various form. As will be described below, the bias force may be gravity or elastic force due to an imbalance of weights of first and second arms111and112of the revolving member110, an imbalance of weights of first and second sealing caps121and122, or the elastic body160mounted on the revolving member110.

The revolving member110may be a rod member that extends substantially straight. However, two end portions of the revolving member110may be curved toward the first and second vent holes OP1and OP2, so that, as will be described below, the first and second scaling caps121and122are closely adhered to wall portions of the first and second vent holes OP1and OP2.

The revolving member110has the first and second arms111and112that extend in opposite directions with respect to the rotation axis150. The first arm111and the second arm112may be designed to have different lengths. That is, the first arm111may be formed longer than the second arm112(length L1of the first arm111>length L2of the second arm112).

For example, a weight of the first arm111generates a rotational moment that rotates the revolving member110to the closing position P1(first rotation direction M1), and a weight of the second arm112generates a rotational moment that rotates the revolving member110to the opening position P2(direction M2). As the first arm111is relatively longer, the revolving member110may be biased to the closing position P1.

For example, the revolving member110at the opening position P2due to the increased internal pressure IP of the accommodation space G1may return to the closing position P1according to a bias force towards the closing position P1(first rotation direction M1) after gas is discharged. In addition, the revolving member110that is biased to the closing position P1is prevented from arbitrarily rotating to the opening position P2by external vibration or impact, and penetration of external materials such as harmful materials like water through the opened first and second vent holes OP1and OP2is prevented.

According to another embodiment of the present invention, irrespective of the lengths L1and L2of the first and second arms111and112, the revolving member110may be biased to the closing position P1through imbalance of the weights of the first and second arms111and112or the total weights of the first and second sealing caps121and122formed at end portions of the first and second arms111and112. For example, the first and second arms111and112and/or the first and second sealing caps121and122may be formed of different materials to create weight imbalance.

The elastic body160that biases the revolving member110to the closing position P1may be connected to the revolving member110. For example, a rotational spring may be installed between the revolving member110and the rotation axis150as the elastic body160, and a first end of the rotational spring may be connected to the revolving member110and a second end of the rotational spring may be connected to the rotation axis150.

For example, the revolving member110at the opening position P2due to the increased internal pressure IP of the accommodation space G1may return to the closing position P1according to a bias force towards the closing position P1(first rotation direction M1) after gas is discharged. In addition, the revolving member110that is biased to the closing position P1is prevented, from arbitrarily rotating to the opening position P2by external vibration or impact, and penetration of external harmful materials through the opened first and second vent holes OP1and OP2is prevented.

The first and second sealing caps121and122that close or open the first and second vent holes OP1and OP2are formed at the two end portions of the revolving member110. At the closing position P1of the revolving member110, the first and second sealing caps121and122close the first and second vent holes OP1and OP2, respectively.

The first and second sealing caps121and122may be formed at end portions of the first and second arms111and112of the revolving member110to protrude from the end portions of the first and second arms111and112toward the first and second vent holes OP1and OP2.

FIGS. 6A and 6Billustrate the first and second sealing caps121and122constructed as embodiments according to the principles of the present invention, respectively.

The first and second sealing caps121and122may be formed to have a cross-section that is sufficient to closely seal the first and second vent holes OP1and OP2. The cross-section A of each one of the first and second sealing caps121and122may have a shape that decreases in size as the first and second sealing caps121and122protrude into the first and second vent holes OP1and OP2. For example, the first and second sealing caps121and122may have the smallest cross-section A at a position adjacent to the first and second vent holes OP1and OP2.

Thus, by forming the first and second sealing caps121and122to have the variable cross-section A, when the revolving member110at the opening position P2rotates to the closing position P1, the first and second sealing caps121and122at the two end portions of the revolving member110may closely contact the wall portions of the first and second vent holes OP1and OP2to maintain a stable sealing state.

For example, the first and second sealing caps121and122may have a conic shape having a sharp front tip toward the first and second vent holes OP1and OP2. The front tips of the first and second sealing caps121and122may be inserted into the first and second vent holes OP1and OP2in a depth direction of the first and second vent holes OP1and OP2.

The first and second sealing caps121and122may be formed to have a shape to correspond to the first and second vent holes OP1and OP2, respectively. For example, when the first and second vent holes OP1and OP2are formed to have a circular form, the first and second sealing caps121and122may be formed to have a cone shape. However, the embodiment of the present invention is not limited thereto; for example, when the first and second vent holes OP1and OP2are formed to have a rectangular form, the first and second sealing caps121and122may be formed to have a quadrangular pyramid shape.

Surfaces of the first and second sealing caps121and122contacting the wall portions of the first and second vent holes OP1and OP2may be formed with elastic layers121aand122a. That is, because the elastic layers121aand122aare formed on the surfaces of the first and second sealing caps121and122, respectively, the first and second sealing caps121and122and the wail portions of the first and second vent holes OP1and OP2may be in a close contact, respectively, and thus, sealing characteristics therebetween may be improved.

For example, the surfaces of the first and second sealing caps121and122may be entirely formed with elastic layers or may be selectively and partially formed with the elastic layers121aand122a. For example, the elastic layers121aand122amay be formed as rubber-based coating layers.

Referring toFIGS. 4 and 5, the accommodation space G1of the electrode assembly10is not directly connected to the outside of the secondary battery via a vent structure, but indirectly through the first and second vent holes OP1and OP2and the housing space G2. Consequently, sealing characteristics of the accommodation space G1may be improved and penetration of harmful materials from the outside may be blocked.

For example, at the closing position P1of the revolving member110, the first and second sealing caps121and122may seal the accommodation space G1of the electrode assembly so as to form a double sealing structure collectively. Also, the accommodation space G1is not directly exposed to the outside at the opening position P2of the revolving member110so that penetration of external materials may be delayed or prevented.

At open ends of the first and second vent holes OP1and OP2, first and second filter members191and192may be formed in order to block external harmful materials. For example, the first and second filter members191and192may be formed at open ends of the first and second vent holes OP1and OP2opposite to the housing space G2of the first and second vent holes OP1and OP2. The first and second sealing caps121and122may be inserted into open ends of the first and second vent holes OP1and OP2adjacent to the housing space G2and thus physical interference with the first and second filter members191and192may be prevented in the above-described configuration.

The first and second filter members191and192may have selective transmittivity such that penetration of a gas component is allowed but transmission of a fluid component is blocked. Thus, when the revolving member110is at the opening position P2, a gas passing through the first and second filter members191and192may be discharged but an inflow of external harmful materials such as a fluid component like water may be prevented. For example, the first and second filter members191and192may be formed of Gore-Tex® fabric. The Gore-Tex® fabric is a porous form of polytetrafluoroethylene with a micro-structure characterized by nodes interconnected by fibrils.

Hereinafter, a configuration of the battery unit20is described with reference toFIGS. 2and3.

The battery unit20includes the electrode assembly10, a case34that accommodates the electrode assembly10, and the cap plate30attached to the case34. For example, the electrode assembly10may be set through an open upper end of the case34and the upper end of the case34is covered by the cap plate30. The cap plate30and the case34may form the accommodation space G1in which the electrode assembly10is accommodated.

Referring toFIG. 3, the electrode assembly10may include a positive electrode plate11, a negative electrode plate12, and a separator13, and may be formed by winding a stack structure of the positive electrode plate11and the negative electrode plate12insulated from each other by the separator13therebetween in a jelly-roll shape. The positive electrode plate11may include a positive electrode collector member11aand a positive electrode active material layer11bformed on at least one surface of the positive electrode collector member11a, and a positive electrode non-coated portion11cwhere the positive electrode active material layer11bis not formed on an edge of the positive electrode collector member11ain a width direction.

The negative electrode plate12may include a negative electrode collector member12aand a negative electrode active material layer12bformed on at least one surface of the negative electrode collector member12a, and a negative electrode non-coated portion12cwhere the negative electrode active material layer12bis not formed on an edge of the negative electrode collector member12ain a width direction. For example, the positive electrode non-coated portion11cand the negative electrode non-coated portion12cmay be formed on opposite edges of the electrode assembly10in a width direction.

Unlike inFIG. 3, the electrode assembly10may have a structure in which the positive electrode plate11, the negative electrode plate12, and the separator13, which are sheet types, are stacked on one another.

As illustrated inFIG. 2, collector members50and60are electrically connected to the electrode assembly10. The collector members50and60electrically connect the electrode assembly10to positive and negative electrode terminals21and22, respectively. For example, the collector members50and60may be attached to both edges of the electrode assembly10by welding. The collector members50and60may include a positive electrode collector member11aattached to the positive electrode non-coated portion11cand a negative electrode collector member12aattached to the negative electrode non-coated portion12c.

The electrode terminals21and22that are electrically connected to the electrode assembly10may be formed to protrude from the cap plate30. In detail, a pair of electrode terminals21and22of different polarities are electrically connected to the positive and negative electrode plates11and12of the electrode assembly10, respectively. That is, a positive electrode terminal21is connected to the positive electrode plate11and a negative electrode terminal22is connected to the negative electrode plate12. The positive and negative electrode terminals21and22may be inserted into terminal holes31′ of the cap plate30, respectively, to be assembled.

The positive and negative electrode terminals21and22may be assembled each with upper and lower gaskets25and27around the positive and negative electrode terminals21and22to insulate the positive and negative electrode terminals21and22from the cap plate30. For example, the upper and lower gaskets25and27may be inserted into the terminal holes31′ from above and below the cap plate30, respectively. In addition to the upper and lower gaskets25and27, an insulating sealing material26may be further formed to insulate the positive and negative electrode terminals21and22from the cap plate30or the positive and negative electrode terminals21and22from the case34.

An electrolyte inlet hole38′ for injecting an electrolyte (not shown) into the case34may be formed in the cap plate30. After injection of an electrolyte, the electrolyte inlet hole38″ may be sealed by a sealing member38.

According to the embodiment ofFIGS. 1 and 2, the gas discharging unit100, including the revolving member110and the vent housing180, may be disposed on the cap plate30. However, the embodiment of the present invention is not limited thereto, and the gas discharging unit100may also be formed on the case34that defines the accommodation space G1of the electrode assembly10.

For example, the revolving member110may be mounted on the case34, and the vent housing180may be mounted on the case34so as to accommodate the revolving member110, and the accommodation space G1and the housing space G2may be connected to each other via the first vent hole OP1formed in the case34.

As described above, according to the one or more of the above embodiments of the present invention, a gas accumulated in a secondary battery may be easily discharged to the outside without destruction of the secondary battery, and an internal gas may be discharged by sensitively reacting to a fine pressure increase inside the secondary battery. Also, the accumulated pressure inside the secondary battery may be resolved, and at the same time, an inflow of external harmful materials may be effectively prevented.