Rechargeable battery including an overcharge safety device

An exemplary embodiment of the present invention provides a rechargeable battery that can block a current of a cell without causing quality scatter by removing operating scatter of the overcharge safety device upon occurrence of overcharge in the cell.An overcharge safety device according to an exemplary embodiment of the present invention includes: an electrode assembly in which a first electrode and a second electrode are disposed at opposite sides of a separator; a case in which the electrode assembly is accommodated; a cap plate that is combined to an opening of the case; a first electrode terminal and a second electrode terminal that are provided in terminal holes of the cap plate and respectively connected to the first electrode and the second electrode; and an overcharge safety device in which a first free end and a second free end of a first short-circuit member and a second short-circuit member that are respectively connected to the first electrode terminal and the second electrode terminal in the cap plane are disposed apart from each other and received in a tube.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a National Phase Patent Application of International Patent Application Number PCT/KR2017/011540, filed on Oct. 18, 2017, which claims priority of Korean Patent Application No. 10-2016-0137737, filed Oct. 21, 2016. The entire contents of both of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a rechargeable battery. More particularly, the present invention relates to a rechargeable battery in which an overcharge safety device is activated in an overcharge state in an internal space of a cell.

BACKGROUND ART

A rechargeable battery is a battery that repeatedly performs charging and discharging, differently from a primary battery. A rechargeable battery with small capacity is used in a small portable electronic device, such as a mobile phone, a notebook computer, and a camcorder, and a rechargeable battery with large capacity may be used as a motor driving power source for a hybrid vehicle and an electric vehicle.

For example, rechargeable batteries include an electrode assembly for charging and discharging, a case accommodating the electrode assembly and an electrolyte solution, a cap plate coupled to the opening of the case, and an electrode terminal that electrically connects the electrode assembly to draw out the electrode assembly to the outside of the cap plate.

In addition, the rechargeable battery includes an overcharge safety device for overcharge control. The overcharge safety device includes a short-circuit tab and a short-circuit member that is separated or short-circuited according to an internal pressure. The short-circuit tab is electrically connected to a negative electrode, and the short-circuit member is electrically connected to a positive electrode.

When a cell is overcharged, the short-circuit member is inverted and thus contacts the short-circuit tab, thereby causing discharge of a current charged in the electrode assembly. In this case, an inversion shape of the short-circuit member may not be constant. Accordingly, contact area scatter occurs from a contact surface of the short-circuit member and the short-circuit tab, thereby causing generation of resistance scatter from the contact surface. That is, the overcharge safety device cannot effectively control overcharge of the rechargeable battery, thereby generating quality scatter.

DISCLOSURE

Technical Problem

An exemplary embodiment of the present invention has been made in an effort to provide a rechargeable battery that can block a current of a cell without causing quality scatter by removing operating scatter of the overcharge safety device upon occurrence of overcharge in the cell. In addition, an exemplary embodiment of the present invention provides a rechargeable battery that includes an overcharge safety device that is not influenced by a cell manufacturing process and does not cause operating scatter.

Technical Solution

An overcharge safety device according to an exemplary embodiment of the present invention includes: an electrode assembly in which a first electrode and a second electrode are disposed at opposite sides of a separator; a case in which the electrode assembly is accommodated; a cap plate that is combined to an opening of the case; a first electrode terminal and a second electrode terminal that are provided in terminal holes of the cap plate and respectively connected to the first electrode and the second electrode; and an overcharge safety device in which a first free end and a second free end of a first short-circuit member and a second short-circuit member that are respectively connected to the first electrode terminal and the second electrode terminal in the cap plane are disposed apart from each other and received in a tube.

The overcharge safety device may further include holders that seal a first fixing portion and a second fixing portion at predetermined locations from the first free end and the second free end in the first short-circuit member and the second short-circuit member that are combined to opposite ends of the tube and extend to the inside of the tube.

The tube may be provided as a compression tube that contracts by an internal pressure increase due to a gas generated from an internal space set by the cap plate and the case upon overcharge such that the first free end and the second free end contact each other.

The tube may be provided as a heat-shrink tube that contracts by an internal heat increase generated from an internal space set by the cap plate and the case upon overcharge such that the first free end and the second free end contact each other.

The tube may be provided as a compression/heat-shrink tube that contracts by an internal pressure increase and an internal heat increase due to a gas generated from an internal space set by the cap plate and the case upon overcharge such that the first free end and the second free end contact each other.

The first short-circuit member and the second short-circuit member may extend to a predetermined length with a width and a thickness.

The first short-circuit member and the second short-circuit member may be bent between the holder and the first electrode terminal and between the holder and the second electrode terminal, and may be connected to the first electrode terminal and the second electrode terminal through a wide area of a first connection end portion and a wide area of a second connection end portion.

The first free end and the second free end may be disposed opposing each other at a distance from each other in a direction that crosses a plane of the cap plate in the case, and the first connection end portion and the second connection end portion may be connected with the first electrode terminal and the second electrode terminal in a surface-contact manner in a width direction of the cap plate in the case.

When the first free end and the second free end that are activated upon overcharge and surface-contact each other may have the same width as a fixing width of the first fixing portion and a fixing width of the second fixing portion that are fixed to the holders.

The first free end and the second free end that are activated upon overcharge and surface-contact each other may have a first width W1that is larger than a second width W2of the first fixing portion and the second fixing portion fixed to the holders.

The first free end and the second free end may surface-contact each other with an area having a predetermined length and the first width.

The first fixing portion and the second fixing portion may be fixed to the holders with the second width.

The first free end and the second free end may curve-contact each other with an area having a predetermined length and the first width.

The first fixing portion and the second fixing portion may be connected as planes to the first free end and the second free end, which are curved, and fixed to the holders with the second width.

The second electrode terminal may be connected to an uncoated region tab of the second electrode through an inner side end thereof and is connected to the second short-circuit member at an upper portion of the uncoated region tab, and the second electrode terminal may further include a fuse that is formed between the uncoated region tab and the second short-circuit member.

Advantageous Effects

As described above, according to the one embodiment of the present invention, since the overcharge safety device formed inside the tube that contacts the first short-circuit member and the second short-circuit member which are separated from each other is provided inside the cap plate, operating scatter of the overcharge safety device can be removed and a current of a cell can be blocked without quality scatter upon overcharge.

The overcharge safety device according to the exemplary embodiment can be separately manufactured from the cell and is connected with the first and second electrode terminals inside the cap plate, and thus the device is not influenced by a manufacturing process of the cell, and a current of the cell can be blocked without causing operating scatter upon overcharge.

MODE FOR INVENTION

It will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. Throughout the specification, the word “on” means positioning on or below the object portion, but does not essentially mean positioning on the upper side of the object portion based on a gravitational direction.

FIG. 1is a perspective view of a rechargeable battery according to a first exemplary embodiment of the present invention,FIG. 2is a cross-sectional view ofFIG. 1, taken along the line II-II, andFIG. 3is a cross-sectional view ofFIG. 1, taken along the line III-IIII.

Referring toFIG. 1toFIG. 3, a rechargeable battery according to the first exemplary embodiment includes an electrode assembly10that charges and discharges a current, a case30in which the electrode assembly10and an electrolyte solution are embedded, a cap plate40that is combined to an opening31of the case30to close and seal the opening31, first and second electrode terminals51and52that are electrically connected to the electrode assembly10and thus installed in the cap plate40, and an overcharge safety device20that is activated when there is an overcharge.

Although it is not illustrated, the rechargeable battery may further include a top insulator that is formed of an electric insulating material. The top insulator is disposed between an inner surface of the cap plate40and the electrode assembly10for electrical insulation therebetween.

The case30sets a space for accommodating a plate-shaped electrode assembly10and the electrolyte solution. For example, the case30is formed in a substantially rectangular parallelepiped shape, and a quadrangular-shaped opening31is provided at one side thereof through which the electrode assembly10is inserted. The case30and the cap plate40may be made of, for example, aluminum, and thus they may be combined to each other and then welded at the opening31.

The cap plate40further includes not only terminal holes H1and H2where the first and second electrode terminals51and52, are installed but also a vent hole41and an electrolyte injection opening42. The vent hole41is closed and sealed by a vent plate411such that an internal pressure that is increased due to a gas generated from the rechargeable battery due to charging and discharging of the electrode assembly10can be discharged to the outside. The vent plate411includes a notch412that induces a rupture.

The electrolyte injection opening42allows the cap plate40and the case30to be injected with the electrolyte after the cap plate40is welded to the case30. After injection of the electrolyte solution, the electrolyte injection opening42is sealed by a sealing cap421.

FIG. 4is a perspective view of the electrode assembly applied toFIG. 3. Referring toFIG. 2toFIG. 4, the electrode assembly10is formed by disposing a first electrode11(e.g., a negative electrode) and a second electrode12(e.g., a positive electrode) at opposite sides of a separator13, which is an electrical insulator.

For example, the negative electrode11, the separator13, and the positive electrode12may be spiral-wound. Although it is not illustrated, the negative electrode, the separator, and the positive electrode are stacked such that an electrode assembly can be formed.

The negative and positive electrodes11and12respectively include coated regions111and121, where an active material is coated on a current corrector made of a metal thin film (e.g., Cu, Al foil), and uncoated region tabs112and122, where the current collector is not coated with an active material and thus is exposed. The uncoated region tabs112and122are disposed at one end of the spiral-wound electrode assembly10, while having a distance D within one spiral-winding range WD of the electrode assembly10.

That is, the uncoated region tabs112of the negative electrode11are disposed at one side (i.e., the left side ofFIG. 4) in one end (i.e., an upper end ofFIG. 4) of the spiral-wound electrode assembly10, and the uncoated region tabs122of the positive electrode12are disposed at the other side (i.e., the right side ofFIG. 4) while having the distance D in the same end (i.e., the upper end ofFIG. 4) of the spiral-wound electrode assembly10.

The uncoated region tabs112and122are provided for every spiral winding of the electrode assembly10to enable a charge/discharge current to flow, and accordingly, the entire resistance of the uncoated region tabs112and122is reduced. Thus, the electrode assembly10may charge and discharge a high-capacity current through the uncoated region tabs112and122.

In the first exemplary embodiment, the electrode assembly10is formed of two assemblies. Although it is not illustrated, the electrode assembly may be formed of three or four assemblies. That is, the electrode assembly10includes a first assembly101and a second assembly102that are disposed in parallel with each other in a width direction (i.e., x-axis direction).

In addition, the first and second assemblies101and102may each be formed in the shape of a plate that forms a semicircle at opposite ends in the y-axis direction such that they can be received in the case30having the rectangular parallelepiped shape.

FIG. 5is a perspective view of a state in which the electrode terminals and the overcharge safety device are connected to the electrode assembly ofFIG. 4. Referring toFIG. 3toFIG. 5, the electrode assembly10, that is, the first and second assemblies101and102, are electrically connected in parallel by being arranged side by side.

For example, the first and second electrode terminals51and52are respectively provided in the terminal holes H1and H2of the cap plate40by using an insert molding method. Thus, the first and second electrode terminals51and52are electrically connected with the uncoated region tabs112and122while being electrically insulated from the cap plate40by molding resin members61and62(refer toFIGS. 1, 2, 3, and 5).

That is, the uncoated region tabs112and122connect the first and second assemblies101and102to the first and second electrode terminals51and52. For example, the uncoated region tabs112and122may be formed of a plurality of groups.

The uncoated region tabs112and122form areas that are set in a direction in which a plane (i.e., a y-z plane) of the electrode10extends, while disposing the first and second electrode terminals51and52therebetween in the width direction (i.e., the x-axis direction) of the cap plate40, and then bonded to side surfaces of the first and second electrode assemblies51and52.

In this case, the first and second electrode terminals51and52form areas that correspond to the areas of the uncoated region tabs112and122such that the first and second electrode terminals51and52are plane-bonded with the uncoated region tabs112and122. For example, the first and second electrode terminals51and52extend while having widths that correspond to widths of the uncoated region tabs112and122, and may be ultrasonic-welded to the uncoated region tabs112and122.

In the first exemplary embodiment, the uncoated region tabs112and122include first tab groups G11and G21and second tab groups G12and G22. The first tab groups G11and G21are respectively connected to the negative and positive electrodes11and12of the first assembly101and thus connected to the first and second electrode terminals51and52, and the second tab groups G12and G22are respectively connected to the negative and positive electrodes11and12of the second electrode assembly102and thus connected to the first and second electrode terminals51and52.

FIG. 6is a perspective view of the overcharge safety device applied toFIG. 5. Referring toFIG. 2,FIG. 3,FIG. 5, andFIG. 6, the overcharge safety device20includes a first short-circuit member21and a second short-circuit member22that are connected to the first electrode terminal51and the second electrode terminal52in the cap plate40, and a tube23that receives a first free end211and a second free end221that are respectively formed at one end of each of the first and second short-circuit members21and22.

When cells are normally operated, the first free end211and the second free end221maintain a separated state in the tube23. Upon overcharge, the internal pressure and an internal temperature are increased and thus the tube23contracts such that the first free end211and the second free end221in the separated state contact each other (i.e., are electrically short-circuited) in the tube23.

FIG. 7is an exploded perspective view of the overcharge safety device ofFIG. 6, andFIG. 8is a cross-sectional view ofFIG. 6, taken along the line VIII-VIII. Referring toFIG. 6toFIG. 8, the overcharge safety device20further includes holders24and25that are combined to opposite ends of the tube23to fix and seal the first and second short-circuit members21and22that extend toward the inside of the tube23.

The holders24and25fix and seal first and second fixing portions212and222of the first and second short-circuit members21and22at predetermined locations from the first and second free ends211and221. That is, portions of the first and second short-circuit members21and22, contacting the holders24and25, are referred to as the first and second fixing portions212and222.

The first and second short-circuit members21and22respectively have predetermined widths W, thicknesses t, and lengths L. The first and second short-circuit members21and22having the width W that is larger than the thickness t are bent between the holder24and the first electrode terminal51and between the holder25and the second electrode terminal52, and are connected to the first and second electrode terminals51and52through wide areas of first and second connection end portions213and223.

The first and second free ends211and221are disposed, while opposing each other with a gap G therebetween, in a direction (i.e., z-axis direction) that crosses a plane of the cap plate40in the case30, and the first and second connection end portions213and223are connected to the first and second electrode terminal51and52in a manner of surface-contact in a width direction (i.e., x-axis direction) of the cap plate40.

The first and second free ends211and221are activated upon overcharge and surface-contact with each other with the width W, and the width W is the same size as fixed widths of the first and second fixing portions212and222that are fixed to the holders24and25. That is, the first and second short-circuit members21and22have the same width W and the same thickness t.

FIG. 9is a cross-sectional view of the overcharge safety device ofFIG. 8, in an activated state, andFIG. 10is a cross-sectional view ofFIG. 9, taken along the line X-X. Referring toFIG. 9andFIG. 10, the tube23is formed of a chemical resistant material which is not damaged by the electrolyte solution. In addition, the tube23excludes the electrolyte solution, and maintains a low pressure that is lower than atmospheric pressure or maintains a vacuum state, to thereby allow the first and second short-circuit members21and22to be smoothly bent and enable contact operation.

For example, the tube23may be provided as a compression tube. The compression tube may contract with an internal pressure increase P due to the gas generated from the internal space formed by the cap plate40and the case30. The first free end211and the second free end221are pressed in the compression tube, which is the tube23, by contraction of the tube23and thus they may contact each other.

In this case, the tube23presses top and bottom surfaces of the first and second free ends211and221, which are formed flat and have the width W, while being bent to have a curved surface according to the internal pressure increase P such that the opposite surfaces of the first and second free ends211and221surface-contact each other at a center of the tube23.

Upon overcharging, according to the contact of the first and second free ends211and221, the first and second electrode terminals51and52connected to the first and second short-circuit members21and22and the negative and positive electrodes11and12of the electrode assembly10are short-circuited. Accordingly, a current charged in the electrode assembly10is discharged.

The second electrode terminal52further includes a fuse F formed between the uncoated region tab122and the second short-circuit member22. The second electrode terminal52is connected to the uncoated region tab122of the positive electrode12through an inner end thereof, and is connected to the second short-circuit member22at an upper portion of the uncoated region tab122. Although it is not illustrated, the fuse may be provided in the first electrode terminal, or in the first and second electrode terminals.

Thus, upon overcharging, the high-capacity current charged in the electrode assembly10is discharged while the first free end221and the second free end221contact each other, and resistance is increased and high heat is generated in a discharge line, thereby activating the fuse F. As the fuse F is activated, the positive electrode12of the electrode assembly10and the second electrode terminal52are electrically disconnected.

Since the overcharge safety device20is manufactured separately from other parts of the cell and is mounted inside the cell, the overcharge safety device20is not affected by the manufacturing process of the cell and does not have operating scatter when the cell is overcharged. Thus, the overcharge safety device20can safely block a current of the cell without causing quality scatter in the rechargeable battery.

As another example, the tube23may be provided as a heat-shrink tube. When the cell is overcharged, the heat-shrink tube may contract due to an internal heat increase generated from the internal space formed by the cap plate40and the case30. According to the contraction of the heat-shrink tube, that is, the tube23, the first free end211, and the second free end221are pressed and thus contact each other in the tube23.

As another example, the tube23may be provided as a compression/heating tube. The compression/heat-shrink tube may contract due to an internal pressure increase and an internal heat increase caused by a gas generated from an inner space set by the cap plate40and the case30upon discharge. According to the compression/heat contraction of the compress/heating tube, that is, the tube23, the first free end211and the second free end221may be pressed and thus contact each other in the tube23.

Hereinafter, various exemplary embodiments of the present invention will be described. For convenience of description, description of the same configurations will be omitted and different configurations will be described in comparison with the first and the previously described exemplary embodiments.

FIG. 11is a perspective view of an overcharge safety device applied to a rechargeable battery according to a second exemplary embodiment,FIG. 12is an exploded perspective view of the overcharge safety device ofFIG. 11, andFIG. 13is a cross-sectional view ofFIG. 11, taken along the line XIII-XIII.

Referring toFIG. 11toFIG. 13, in an overcharge safety device70applied to the rechargeable battery of the second exemplary embodiment, first and second free ends711and721of first and second short-circuit members71and72have first widths W1, which surface-contact each other when activated upon overcharge.

The first width W1is larger than a second width W2of first and second fixing portions712and722that are fixed to holders24and25. That is, the first free end711and the second free end722of the first short-circuit member71and the second short-circuit member72are formed with wider widths (i.e., W1>W2) than the first fixing portion712and the second fixing portion722.

A tube23presses top and bottom surfaces of the first and second free ends711and721having the first width W while being bent as an internal pressure P is increased, such that opposite surfaces of the first and second free ends711and721contact each other at a center of the tube23. That is, the first free end711and the second free end721surface-contact each other with an area having a predetermined length L1and the first width W1.

That is, the first and second fixing portions712and722of the first and second short-circuit members71and72are fixed to the holders24and25with the second width W2. When the second width W2is the same as the width W of the first exemplary embodiment, the first and second free ends711and721of the second exemplary embodiment form a larger contact area than the contact area of the first and second free ends211and221of the first exemplary embodiment.

That is, compared to the contact resistance of the first and second free ends221and221of the first exemplary embodiment, contact-resistance of the first and second free ends711and721of the second exemplary embodiment may be further reduced. Thus, a high-capacity current charged in the electrode assembly10may be more easily discharged compared to the first exemplary embodiment, and thus a fuse can be activated.

FIG. 14is a perspective view of an overcharge safety device applied to a rechargeable battery according to a third exemplary embodiment of the present invention,FIG. 15is an exploded perspective view of the overcharge safety device ofFIG. 14, andFIG. 16is a cross-sectional view ofFIG. 14, taken along the line XVI-XVI.

Referring toFIG. 14toFIG. 16, in an overcharge safety device80applied to a rechargeable battery of the third exemplary embodiment, first and second free ends811and821of first and second short-circuit members81and82have first widths W3, which curve-contact each other when activated upon overcharge. The first and second free ends811and821are in curved contact with an area set by a predetermined length and the first width W3. First and second fixing portions812and822are connected to the first and second curved free ends811and821in a planar manner, and are fixed to holders24and25with a second width W4.

A tube23presses top and bottom surfaces of the first and second free ends811and821formed with curves and having the first width W3while being bent as an internal pressure P is increased, such that opposite surfaces of the first and second free ends811and821contact each other at a center of the tube23.

That is, the tube23effectively presses (P2) external surfaces of the curved first and second free ends811and821. The effective pressure (P2) enables the first and second free ends811and821to surface-contact each other with an area having a predetermined length L3and the first width W3.

That is, the first and second fixing portions812and822of the first and second short-circuit members81and82are fixed to holders24and25. When the second width W4is the same as the second width W2of the second exemplary embodiment, the first and second free ends811and821of the third exemplary embodiment form a larger contact area than the contact area of the first and second free ends711and721of the second exemplary embodiment.

That is, contact resistance of the first and second free ends811and821of the third exemplary embodiment may be further reduced when compared to contact resistance of the first and second free ends711and721of the second exemplary embodiment. Accordingly, a high-capacity current charged in the electrode assembly10can be more easily discharged than in the second exemplary embodiment, and a fuse can be activated.