Secondary battery with movement prevention tape

A secondary battery is disclosed. In one embodiment, the battery includes i) an electrode assembly and ii) first and second electrode tabs spaced apart from each other and extending from the electrode assembly, wherein the first and second electrode tabs have first and second outer surfaces, respectively. The battery may further include i) an electrolyte, ii) a movement prevention tape attached to at least a portion of at least one of the first and second outer surfaces, wherein at least part of the movement prevention tape is configured to become adhesive upon contacting the electrolyte and iii) a can accommodating the electrode assembly, electrode tabs and movement prevention tape.

RELATED APPLICATIONS

This application claims priority to and the benefit of Provisional Patent Application No. 61/371,118 filed on Aug. 5, 2010 in the U.S. Patent and Trademark Office, the entire contents of which are incorporated herein by reference.

This application also relates to U.S. patent application Ser. Nos. 12/554,528 and 12/554,504 both filed on Sep. 4, 2009, and Ser. No. 12/626,157 filed on Nov. 25, 2009, all of which are incorporated herein by reference in their entirety.

BACKGROUND

The described technology generally relate to a secondary battery and a method of manufacturing the same.

2. Description of the Related Technology

A secondary battery is generally formed by accommodating an electrode assembly including a positive electrode plate, a negative electrode plate and a separator interposed between the positive and negative electrode plates, in a battery case with an electrolyte. The secondary battery may be classified into cylindrical, prismatic and pouch type batteries according to the shape of the case.

The positive electrode plate has a positive electrode coating portion and the negative electrode plate has a negative electrode coating portion. The electrode assembly may further include a positive electrode tab and a negative electrode tab. The positive and negative electrode tabs are welded or attached to the positive and negative electrode plates, respectively. The positive and negative electrode tabs protrude upwardly and/or downwardly a predetermined length from the electrode assembly, and end portions of each of the electrode tabs are welded or attached to other components of the secondary battery.

SUMMARY

One inventive aspect is a secondary battery which can prevent an electrode tab from moving inside a battery case due to an external impact, such as an external vibration or a drop.

Another aspect is a secondary battery including an electrode assembly having a first electrode tab and a second electrode tab drawn out therefrom; and a case accommodating the electrode assembly, wherein a movement prevention tape, which exhibits adhesiveness when it contacts an electrolyte, is attached to at least one portion of at least one of the first electrode tab and the second electrode tab.

Another aspect is a secondary battery, comprising: an electrode assembly; first and second electrode tabs spaced apart from each other and extending from the electrode assembly, wherein the first and second electrode tabs have first and second outer surfaces, respectively; an electrolyte; a movement prevention tape attached to at least a portion of at least one of the first and second outer surfaces, wherein at least part of the movement prevention tape is configured to become adhesive upon contacting the electrolyte; and a can accommodating the electrode assembly, electrode tabs and movement prevention tape.

In the above battery, the movement prevention tape comprises i) an adhesive layer at least partially surrounding at least one of the first and second outer surfaces and ii) a base layer formed on the adhesive layer, and wherein at least part of the base layer is configured to become adhesive upon contacting the electrolyte.

In the above battery, an adhesive portion of the base layer has a tensile strength of at least about 0.1 kgf/cm2. In the above battery, the base layer is formed of a polymer film. In the above battery, the electrolyte contains a carbonate-based solvent, and wherein the carbonate-based solvent is configured to melt at least a portion of the polymer film. In the above battery, the polymer film is configured to at least partially shrink and at least partially expand. In the above battery, the polymer film is formed of at least one of the following: polystyrene (PS), polyamide, polyacrylonitrile, polycarbonate, polyethylene acetate and oriented polystyrene.

In the above battery, the base layer has a thickness of about 10 μm to about 50 μm. In the above battery, the adhesive layer is formed of at least one of the following: PMMA (poly methyl methacrylate), PEMA (poly ethyl methacrylate) and PBMA (poly butyl methacrylate). In the above battery, the adhesive layer has a thickness of about 1 μm to about 30 μm. In the above battery, the first and second electrode tabs have first and second lengths, respectively, and wherein the base layer is formed between i) a portion of about ⅔ of the length of at least one of the first and second electrode tabs and ii) the electrode assembly. In the above battery, the movement prevention tape substantially completely surrounds at least one of the first and second electrode tabs.

The above battery further comprises: a cap assembly configured to substantially close the can; a sub-plate accommodated in the can and attached to the cap assembly; and an insulator formed on a surface of the electrode assembly, wherein an adhesive portion of the movement prevention tape contacts at least one of the sub-plate and insulator. The above battery further comprises an insulation tape formed between i) at least one of the first and second outer surfaces and ii) the movement prevention tape.

In the above battery, the first and second electrode tabs are attached to opposite sides of the electrode assembly. In the above battery, the first and second electrode tabs are attached to the same side of the electrode assembly. In the above battery, the movement prevention tape is attached to the first and second outer surfaces.

Another aspect is a secondary battery, comprising: an electrode assembly; first and second electrode tabs spaced apart from each other and extending from the electrode assembly, wherein the first and second electrode tabs have first and second outer surfaces, respectively; a movement prevention tape attached to at least a portion of at least one of the first and second outer surfaces; a can accommodating the electrode assembly, electrode tabs and movement prevention tape; and a cap assembly configured to substantially close the can, wherein at least part of the movement prevention tape contacts at least the cap assembly.

In the above battery, the at least part of the movement prevention tape contacts the electrode assembly. In the above battery, the movement prevention tape comprises i) an adhesive layer at least partially surrounding at least one of the first and second outer surfaces and ii) a base layer formed on the adhesive layer. In the above battery, the base layer has a tensile strength of at least about 0.1 kgf/cm2.

The above battery further comprises: a sub-plate accommodated in the can and attached to the cap assembly; and an insulator formed on a surface of the electrode assembly, wherein at least part of the base layer contacts at least one of the sub-plate and insulator. In the above battery, the base layer is formed of at least one of the following: polystyrene (PS), polyamide, polyacrylonitrile, polycarbonate, polyethylene acetate and oriented polystyrene.

DETAILED DESCRIPTION

Generally, when an external impact, such as an external vibration or a drop, is applied to a secondary battery, an electrode tab such as the positive or negative electrode tab disposed inside the battery case may move. The movement of the electrode tab may cause the electrode tab to be separated from the non-coating portion or other components of the electrode assembly. In such a case, internal resistance of the secondary battery may increase, resulting in heating of the secondary battery.

Embodiments will now be described in detail with reference to the accompanying drawings.

As shown inFIGS. 1 through 4, a cylindrical secondary battery100includes a case110, an electrode assembly120, an upper insulation member140, a lower insulation member150, a cap assembly160, and a gasket170.

The case110may be a cylindrical, prismatic or pouch type according to the shape of the secondary battery100. For the purpose of convenience, the embodiment ofFIGS. 1-4will be described with regard to a cylindrical type secondary battery. A prismatic secondary battery and a pouch type secondary battery will later be described with reference to other embodiments.

The case110is shaped of a cylinder and may be made of a light-weight, conductive material such as aluminum, or an aluminum alloy. The case110may be formed by, for example, a deep drawing process. The case110may have various shapes according to the shape of the electrode assembly120.

The case110includes a circular bottom plate112, and a cylindrical sidewall113upwardly extending from the edge of the bottom plate112. Referring toFIG. 3A, a beading part111inwardly bent along the outer circumference of the sidewall113is formed at an upper portion of the sidewall113. The beading part111prevents the upper insulation member140, the electrode assembly120and the lower insulation member150from moving inside the case110in a direction substantially perpendicular to the bottom plate112. A crimping part116is formed at a top end of the sidewall113. The crimping part116substantially seals a gap between the case110and the cap assembly160.

Referring toFIG. 1, an opening114is formed at the upper portion of the sidewall113so as to allow the lower insulation member150, the electrode assembly120, the upper insulation member140, the gasket170and the cap assembly160to be inserted into the case110in turn.

The electrode assembly120may include a first electrode plate121, a second electrode plate122and a separator123. The separator123may include a first separator123aand a second separator123b. The electrode assembly120may be formed by sequentially stacking the first electrode plate121, the first separator123a, the second electrode plate122and the second separator123band winding the stacked structure in a cylindrical configuration. A first electrode tab127is drawn out from an upper portion of the electrode assembly120and an end of the first electrode tab127is connected to a sub-plate165of the cap assembly160. A second electrode tab128is drawn out from a lower portion of the electrode assembly120and an end of the second electrode tab128is connected to the bottom plate112of the case110.

Either one of the first electrode plate121and the second electrode plate122, for example, the first electrode plate121, may be used as a positive electrode plate, and the other, for example, the second electrode plate122, may be used as a negative electrode plate. Alternatively, the second electrode plate122may be used as a positive electrode plate, and the first electrode plate121may be used as a negative electrode plate. In the disclosed embodiments, for the purpose of convenience, it is assumed that the first electrode plate121is a positive electrode plate, and the second electrode plate122is a negative electrode plate.

Although not shown in detail, the positive electrode, that is, the first electrode plate121, includes a positive electrode collector and a positive electrode coating portion coated on at least one surface of the positive electrode collector.

The positive electrode collector may be formed of a plate made of a highly conductive metal, for example, aluminum (Al) foil, which is not considered limiting.

In one embodiment, the positive electrode coating portion is formed by coating a mixture of a positive electrode active material, a conductive agent and a binder on at least one surface of the positive electrode collector. In one embodiment, the positive active material generally includes composite metal oxides such as LiCoO2, LiMn2O4, LiNiO2, LiNi1-xCoxO2(0<x<1), LiMnO2, or the like, which are not considered limiting.

A first non-coating portion that is not coated with the positive electrode coating material is formed on at least one of a portion or both ends of a winding direction of the first electrode plate121. The first electrode tab127as a positive electrode tab is coupled to the first non-coating portion by, for example, welding, to then be drawn out from the electrode assembly120. Further, an end of the drawn-out first electrode tab127is coupled to the sub-plate165of the cap assembly160by, for example, welding, to then be electrically connected thereto.

Although not shown in detail, the negative electrode, that is, the second electrode plate122, includes a negative electrode collector and a negative electrode coating portion coated on at least one surface of the negative electrode collector.

The negative electrode collector may be formed of a plate made of a highly conductive metal, for example, copper (Cu) or nickel (Ni) foil, which are not considered limiting.

The negative electrode coating portion may be formed by coating a mixture of a negative electrode active material, a conductive agent and a binder on at least one surface of the negative electrode collector. In one embodiment, the negative active material generally includes, carbon (C) based materials, Si, Sn, tin oxides, composite tin alloys, transition metal oxides, lithium metal nitrides, or lithium metal oxides, which are not considered limiting.

A second non-coating portion that is not coated with the negative electrode coating material is formed on at least one of a portion or both ends of a winding direction of the second electrode plate122. The second electrode tab128as a negative electrode tab is coupled to the second non-coating portion by, for example, welding, to then be drawn out from the electrode assembly120. Further, an end of the drawn-out second electrode tab128is coupled to the bottom plate112of the case110by, for example, welding. Accordingly, the case110may have a negative polarity. Additionally, the case110, specifically the bottom plate112of the case110, may be used as a negative electrode terminal of the cylindrical secondary battery100.

The separator123separates the first electrode plate121and the second electrode plate122from each other. The separator123may include a first separator123aand a second separator123b. Micropores may be formed in each of the first and second separators123aand123b, and lithium ions pass through the micropores. The first and second separators123aand123bmay be made of a polymer resin such as polyethylene (PE) or polypropylene (PP), which are not considered limiting.

A movement prevention tape (or a tape)130exhibiting adhesiveness when contacting an electrolyte is attached to at least one portion of at least one of the first electrode tab127and the second electrode tab128drawn out from the electrode assembly120. The movement prevention tape130may be attached to only one of the first electrode tab127and the second electrode tab128, or may be attached to both of the first electrode tab127and the second electrode tab128. The movement prevention tape130may be attached to at least one portion of the first electrode tab127. The first electrode tab127is drawn out from the electrode assembly120and has one end coupled to the sub-plate165(FIG. 3B), so that it is positioned between the sub-plate165and the upper insulation member140. In one embodiment, if the movement prevention tape130attached to the first electrode tab127comes into contact with an electrolyte, as shown inFIGS. 3B,3C and4, the tape130partially melts and exhibits adhesiveness. In another embodiment, the tape130at least partially shrinks and at least partially expands upon contacting the electrolyte. This applies to the remaining disclosed embodiments.

Accordingly, since the adhesive portion of the movement prevention tape130is positioned between the upper insulation member140and the sub-plate165, movement of the first electrode tab127can be prevented by the adhesiveness. For example, part of the adhesive portion is adhered to a top surface of the electrode assembly120and some other part of the adhesive portion is adhered to the sub-plate165as shown inFIGS. 3B and 3C. Therefore, the adherence prevents the first electrode tab127from moving.

The movement prevention tape130may include a base layer131having a portion exhibiting adhesiveness due to a contact with an electrolyte, and an adhesive layer132formed on the reverse surface of the base layer131as shown inFIG. 2.

In one embodiment, the base layer131is formed of a polymer film partially exhibiting adhesiveness when at least a portion of the polymer film contacts the electrolyte. For example, when the polymer film contacts an electrolyte, a carbonate-based solvent contained in the electrolyte permeates between molecules of the polymer, to melt at least a portion of the film, thereby imparting adhesiveness to the film. In one embodiment, when the polymer film contacts an electrolyte, a carbonate-based solvent contained in the electrolyte melts at least a portion of the film while permeating between molecules of the polymer, and the polymer film may at least partially shrink and at least partially expand, exhibiting adhesiveness.

Here, as shown inFIGS. 3B and 3C, the adhesive portion is positioned between and adheres to the upper insulation member140and the sub-plate165and securely fixes the first electrode tab127. Therefore, even if an external impact is applied to the cylindrical secondary battery100, the first electrode tab127does not readily move.

Any film may be used as the polymer film as long as it melts due to a contact with an electrolyte to exhibit adhesiveness. The polymer film may include a film made of a material allowing easy permeation of a carbonate-based solvent in the electrolyte due to a relatively large intermolecular distance between molecules of a polymer, such as polystyrene (PS), polyamide, polyacrylonitrile, polycarbonate, polyethylene acetate or an oriented PS (OPS), which are not considered limiting.

The base layer131may have a thickness in a range of approximately 10 μm to approximately 50 μm, which is not considered limiting. When the thickness of the base layer131is in the above-mentioned range, movement of the first electrode tab127can be more effectively prevented.

The adhesive layer132is coated on the reverse surface of the base layer131, and contacts an outer surface of the first electrode tab127. The adhesive layer132may be formed of a commonly used adhesive without any particular limitation. The adhesive layer132may be formed by coating an acryl-based adhesive on the base layer131. The acryl-based adhesive may include PMMA (poly methyl methacrylate), PEMA (poly ethyl methacrylate), PBMA (poly butyl methacrylate), and the like, which are not considered limiting.

The adhesive layer132may be coated on the base layer131to various thicknesses by various well-known methods. For example, the adhesive layer132may be formed by coating an adhesive on the base layer131to a thickness of about 1 μm to about 30 μm by, for example, a knife coating method.

The movement prevention tape130may be attached to some portion of the first electrode tab127drawn out from the electrode assembly120except for an end portion. Since the end portion of the first electrode tab127is a portion welded to the sub-plate165of the cap assembly160, it is not necessary to attach the movement prevention tape130to the end portion of the first electrode tab127. In one embodiment, the portion of the electrode tap on which the movement prevention tape is attached is a region from the boundary between the electrode tap and the electrode assembly120to ⅔ of the height (length) of the exposed first electrode tap. Additionally, the movement prevention tape130may be attached by wrapping around the first electrode tab127drawn out from the electrode assembly120at least one time.

The upper insulation member140is formed to have a substantially circular plate to insulate the electrode assembly120and the beading part111of the case110from each other. A hole140ais formed at the center of the upper insulation member140to allow the first electrode tab127drawn out from the electrode assembly120to pass through the same, and the first electrode tab127passes through the hole140ato then be electrically connected to the cap assembly160.

Referring toFIG. 1, the lower insulation member150is formed to have a substantially circular plate to insulate the electrode assembly120and the bottom plate112of the case110from each other. A hole150ais formed in the lower insulation member150to allow the second electrode tab128drawn out from the electrode assembly120to pass through the same, and the second electrode tab128passes through the hole150ato then be electrically connected to the bottom plate112of the case110.

Referring toFIGS. 1 and 3A, the cap assembly160includes a cap-up161, a safety vent162positioned under the cap-up161, an insulator163positioned under the safety vent162, a cap-down164positioned under the insulator163, a sub-plate165positioned on a bottom surface of the cap-down164, and a gasket170surrounding these components from the outside.

The cap-up161is shaped of a circular plate, and has a top protrusion161aupwardly protruding from the center. In addition, a plurality of throughholes161bfor exhausting internal gases generated in the secondary battery100to the outside are formed at a side portion of the top protrusion161a. The cap-up161functions as a terminal that electrically conducting the current internally generated from the cylindrical secondary battery100to the outside. In addition, the cap-up161may be made of a metal material such as stainless.

The safety vent162is shaped of a circular plate, and positioned under the cap-up161. The safety vent162has a downwardly protruding bottom protrusion162aformed at its center, and has a peripheral portion formed in a substantially “Z” shape. The safety vent162may be made of a conductive metal material. Meanwhile, the bottom protrusion162amay further include a central groove (not shown) formed at its center and a cross-shaped groove (not shown) formed crosswise based on the central groove. When gases are generated inside the case110and the internal pressure of the case110increases a predetermined critical value or higher, the bottom protrusion162aof the safety vent162is upwardly swollen. Here, the central groove of the bottom protrusion162aand the peripheral area of the cross-shaped groove are fractured, so that the safety vent162is separated from the sub-plate165installed under the safety vent162to then be electrically disconnected, thereby interrupting current flow. Additionally, the safety vent162is configured to be opened by the fracture of the bottom protrusion162ato allow the internal gas of the case110to be exhausted to the outside of the case110. That is to say, the safety vent162is one of safety devices for preventing the cylindrical secondary battery100from exploding due to an internal gas pressure.

Although not shown, a secondary protection device may further be provided between the cap-up161and the safety vent162. The secondary protection device may be a positive temperature coefficient (PTC) device that interrupts current flow when the temperature of the cylindrical secondary battery100rises. The PTC device may include a resin layer made of a resin and carbon powder, and conductive plates coupled to upper and lower surfaces of the device layer. If the temperature of the PTC device increases, the resin of the resin layer swells, cutting interconnection between carbon powder molecules, thereby interrupting current.

In one embodiment, as shown inFIG. 1, The insulator163is formed to have an annular shape, and is formed between the safety vent162and the cap-down164to insulate the safety vent162and the cap-down164from each other.

In one embodiment, the cap-down164is formed to have a circular plate, and is positioned under the insulator163. In addition, a central throughhole164ais formed at the center of the cap-down164. The bottom protrusion162aof the safety vent162is inserted into and passes through the central throughhole164aproviding a path for exposing the bottom protrusion162ato a lower portion of the cap assembly160. In addition, the cap-down164has a plurality of holes164bformed around the central throughhole164a. The holes164bfunction to release gases generated in the electrode assembly120.

Referring toFIG. 3A, the sub-plate165is fixed while shutting the central throughhole164aof the cap-down164. In addition, the sub-plate165is coupled to the bottom protrusion162aof the safety vent162. A positive electrode tab, that is, the first electrode tab127drawn out from the electrode assembly120is attached to the bottom surface of the sub-plate165to then be electrically connected to the sub-plate165. In one embodiment, the sub-plate165is made of a metal material. Here, the safety vent162and the sub-plate165are coupled to each other, while the cap-down164and the sub-plate165are coupled to each other. Therefore, the safety vent162, the cap-down164and the sub-plate165are incorporated into one body, forming a current interrupt device (CID).

The gasket170is interposed between the opening114of the cylindrical case110and the cap assembly160, thereby substantially hermetically sealing the battery. The gasket170is configured to compress the cap-up161fastened to either interior side of the gasket170, and the peripheral portion of the safety vent162coupled to a bottom portion of the cap-up161from upper and lower sides. The gasket170may be made of a resin material such as polyethyleneterephthalate or polyethylene. The gasket170prevents the cap assembly160from being separated from the case110.

The cylindrical secondary battery100includes an electrolyte. The electrolyte may include a carbonate-based solvent. The carbonate-based solvent may be exemplified by dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC) ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and so on. The carbonate-based solvent may include at least one selected from the group consisting of DMC, DEC and DPC among the exemplified carbonate-based solvents. Such a carbonate based solvent may easily permeate between molecules of a polymer such as polystyrene (PS) having a relatively large intermolecular distance. Therefore, when the carbonate-based solvent contacts the movement prevention tape130, it is easily permeated between molecules of the polymer in the base layer131, thereby melting the base layer131and exhibiting adhesiveness.

In one embodiment, the carbonate-based solvent is contained in an amount of about 10% to about 60% by weight based on the total weight of the electrolyte. The above range may provide an optimum balance between permeation characteristic and movement preventing efficiency. However, other ranges are also possible, depending on the embodiment.

The electrolyte may further include generally commercially available components in addition to the carbonate-based solvent. The electrolyte may be any electrolyte as long as it is an electrolyte containing DMC, DEC or DPC.

FIG. 5is a perspective view of an electrode assembly used in a cylindrical secondary battery according to another embodiment, andFIG. 6is a cross-sectional view of a first electrode tab shown inFIG. 5, taken along the line B-B. As shown inFIGS. 5 and 6, an electrode assembly120includes a first electrode plate121having a first electrode tab127, a second electrode plate122having a second electrode tab128, and a separator123. In addition, an insulation tape129is attached to an interface between the first and second electrode plates121and122from which the first electrode tab127and the second electrode tab128are drawn out from the electrode assembly120. Further, a movement prevention tape130is attached to an outer side of the insulation tape129while wrapping the insulation tape129.

In one embodiment, the insulation tape129is attach to both of the first electrode tab127and the second electrode tab128and the movement prevention tape130is attached to wrap around the insulation tape129attached to the first electrode tab127. Alternatively, the movement prevention tape130may also be attached to wrap around the insulation tape129of the second electrode tab128.

The other components of the electrode assembly120, except for the movement prevention tape130and the insulation tape129, are the same as those described inFIGS. 1 through 3, and a detailed description thereabout will be omitted.

The insulation tape129prevents a short circuit between the first electrode tab127and the second electrode plate122or between the second electrode tab128and the first electrode plate121, and may be made of a generally commercially available insulating material. The insulation tape129may be formed by coating an adhesive on a film made of, for example, polyethyleneterephthalate (PET), polypropylene (PP), polyethylene (PE), or polyimide (PI). Here, any adhesive may be used as long as it has an adhesive force. The adhesive used with the movement prevention tape130may be applied to the insulation tape129.

The movement prevention tape130is attached to the insulation tape129of the first electrode tab127. Since a configuration of the movement prevention tape130is substantially the same as described inFIGS. 1 through 3, a detailed description thereabout will be omitted.

As described above, when the insulation tape129is attached to the first electrode tab127and the second electrode tab128and the movement prevention tape130is applied to the insulation tape129, improved insulation characteristics can be attained, compared to a case when the movement prevention tape130without the insulation tape129attached thereto is applied.

FIG. 7is a perspective view of a prismatic secondary battery according to still another embodiment. As shown inFIG. 7, the prismatic secondary battery200includes a substantially prismatic case210, an electrode assembly220accommodated within the case210, and a cap assembly240coupled to an upper portion of the case210.

The case210may be formed of a metal can having a substantially rectangular shape, and may serve as a terminal. The electrode assembly220includes a first electrode plate, a second electrode plate, and a separator, and is formed by, for example, winding a stack of the first electrode plate, the second electrode plate, and the separator interposed between the first and second electrode plates in a substantially rectangular configuration.

The electrode assembly220includes a first electrode tab227and a second electrode tab228. A movement prevention tape230is attached to the first electrode tab227and the second electrode tab228drawn out from the electrode assembly220.

The electrode assembly220has a substantially the same configuration as that of the electrode assembly120of the previously described cylindrical secondary battery, except that i) the electrode assembly220has a substantially rectangular shape, ii) the electrode tabs227and228are drawn out in the same direction, and iii) the movement prevention tape230is attached to both of the first electrode tab227and the second electrode tab228, and a detailed description thereabout will be omitted. In addition, since the movement prevention tape230attached to electrode tabs227and228is the same as the corresponding component of the previously described cylindrical secondary battery, a detailed description thereabout will be omitted.

As described above in the cylindrical secondary battery, in order to prevent a short circuit between the first electrode plate and the second electrode plate, an insulation tape (not shown) may be formed at an interface from which the first electrode tab227and the second electrode tab228are drawn out, and the movement prevention tape230may be formed to wrap around the insulation tape.

In one embodiment, when the movement prevention tape230contacts an electrolyte, at least a portion of the movement prevention tape230exhibits adhesiveness, movement of the first electrode tab227and the second electrode tab228can be prevented due to an adhesive force of the adhesive portion.

The cap assembly240includes a cap plate241having a size and a shape corresponding to those of an opening of the case210. A terminal throughhole241ais formed at the center of the cap plate241, and an electrolyte injection hole241bfor injecting an electrolyte is formed at one side of the cap plate241. The electrolyte injection hole241bis coupled to a plug241cto be substantially hermetically sealed.

An electrode terminal242, for example, a negative electrode terminal, may be inserted into the terminal throughhole241a. A gasket243for electrically insulating the electrode terminal242from the cap plate241is provided on an outer surface of the electrode terminal242. An insulation plate244is disposed on a bottom surface of the cap plate241. A terminal plate245is installed on a bottom surface of the insulation plate244.

The electrode terminal242is inserted into the terminal throughhole241awhile the gasket243wraps around the outer surface of the electrode terminal242. A bottom surface of the electrode terminal242is electrically connected to the terminal plate245in a state in which the insulation plate244is interposed between the electrode terminal242and the terminal plate245.

In one embodiment, the first electrode tab227drawn out from the first electrode plate is welded to the bottom surface of the cap plate241, and the second electrode tab228drawn out from the second electrode plate is welded to the bottom surface of the electrode terminal242.

Meanwhile, an insulation case246is installed on a top surface of the electrode assembly220. The insulation case246electrically insulates the electrode assembly220and the cap assembly240from each other and covers a top portion of the electrode assembly220. The insulation case246includes an electrolyte injection hole246bformed at a location corresponding to the electrolyte injection hole241bof the cap plate241, and an electrolyte is injected into the insulation case246through the electrolyte injection hole246b. In one embodiment, the insulation case246is made of an insulating polymer resin, polypropylene, which are not considered limiting.

Although not shown, the prismatic secondary battery200may also include a protective circuit module and a top cover. For example, the protective circuit module controls charge/discharge operations or malfunction of the electrode assembly220. In one embodiment, when an over-current is applied from the electrode assembly220, the protective circuit module may function to interrupt the over-current. The protective circuit module is generally configured to have various protective circuits. In addition, the top cover may cover the protective circuit module. The protective circuit module and the top cover may be easily formed by a skilled person in the related technology.

In one embodiment, when the movement prevention tape230attached to the electrode tabs227and228contacts an electrolyte, at least a portion of the movement prevention tape230melts, exhibiting adhesiveness. Since the adhesive portion of the movement prevention tape230is positioned between the cap assembly240and the electrode assembly220, it is possible to prevent the electrode tabs227and228from moving. That is, since the electrode tabs227and228are securely fixed due to an adhesive force, they can be prevented from moving inside the case210.

FIG. 8is a perspective view of a pouch type secondary battery according to still another embodiment. Referring toFIG. 8, the pouch-type secondary battery400includes a pouch-type case410, an electrode assembly420accommodated in the case410and including a first electrode tab427and a second electrode tab428, and a movement prevention tape430attached at least one portion of the first electrode tab427and the second electrode tab428.

The case410may include a core portion410amade of a metal such as aluminum (Al), a heat fusion layer410bformed on a top surface of the core portion410a, and an insulation film410cformed on a bottom surface of the core portion410a. The heat fusion layer410bserves as an adhesive layer using a modified polypropylene as a polymer resin, for example, casted polypropylene (CPP), and the insulation film410cmay be made of a resin material such as nylon or polyethyleneterephthalate (PET). The configuration and material of the pouch-type case410is not limited to those illustrated herein. The case410includes a bottom surface411having a space411afor accommodating the electrode assembly420, and a top surface412covering the bottom surface411having the space411a. The space411afor accommodating the electrode assembly420may be formed by pressing, for example.

After accommodating the electrode assembly420in the space411aof the bottom surface411, the case410is coupled to the electrode assembly420by covering and substantially hermetically sealing the top surface412.

Since the electrode assembly420and the movement prevention tape430attached to the first electrode tab427and the second electrode tab428of the electrode assembly420are substantially the same as the corresponding components of the previously described prismatic secondary battery200, a detailed description thereabout will be omitted.

The electrode assembly420is accommodated in the case410. Thereafter, the first electrode tab427and the second electrode tab428are drawn out in a predetermined direction by a predetermined length. In one embodiment, the movement prevention tape430is attached to only the electrode tabs427and428disposed inside the case410, but not attached to outwardly drawn portions of the electrode tabs427and428.

Although not shown, the pouch-type secondary battery400may also include a protective circuit module. The protective circuit module controls charge/discharge operations or malfunction of the electrode assembly420. In one embodiment, when an over-current is applied from the electrode assembly420, the protective circuit module may function to interrupt the over-current. The protective circuit module is generally configured to have various protective circuits. Here, the protective circuit module is electrically to the first electrode tab427and the second electrode tab428of the electrode assembly420.

In one embodiment, when the movement prevention tape430contacts an electrolyte, at least a portion of the movement prevention tape430melts and exhibits adhesiveness. Here, the adhesive portion can effectively suppress the electrode tabs427and428from moving inside the case410due to an adhesive force.

Hereinafter, a fabricating method of a secondary battery will be described. Depending on the embodiments, additional processes may be added, others removed, or the order of the processes changes. The fabricating method includes an electrode assembly inserting process and an electrolyte injection process. In the electrode assembly inserting process, a movement prevention tape exhibiting adhesiveness on at least a portion thereof due to a contact with an electrolyte is attached to at least one portion of surfaces of first electrode tab127and/or a second electrode tab drawn out from the electrode assembly, and the electrode assembly is inserted into a case. In the electrolyte injection process, the movement prevention tape is brought into contact with an electrolyte to allow at least a portion of the movement prevention tape to exhibit adhesiveness.

The fabricating method of the secondary battery according to one embodiment will now be described with reference toFIGS. 1 through 3. In the following, the fabricating method of the secondary battery will be described with regard to a cylindrical secondary battery100. However, one skilled in the art can easily practice the fabricating method of the secondary battery applied to other types of a secondary battery such as a prismatic secondary battery and a pouch-type secondary battery.

The fabricating method of the cylindrical secondary battery100includes inserting an electrode assembly120and injecting an electrolyte.

In the inserting of the electrode assembly120, a movement prevention tape130, which exhibits adhesiveness on at least a portion thereof when it contacts an electrolyte, is attached to at least one portion of an outer surface of the first electrode tab127drawn out from the electrode assembly120, and the electrode assembly120is inserted into a case110.

Since the movement prevention tape130has previously been described in detail with regard to the cylindrical secondary battery100, a detailed description thereof will be omitted.

Before and after inserting the electrode assembly120into the case110, some of the other components of the secondary battery100may be assembled.

For example, in a state in which a lower insulation member150, the electrode assembly120and an upper insulation member140are disposed in turn from the bottom, the second electrode tab128of the electrode assembly120is coupled to the bottom plate112of the case110by, for example, welding. In this stage, a beading part111and a crimping part116are not formed in the case110.

Next, the beading part111is formed on a sidewall113of the case110, thereby preventing the lower insulation member150, the electrode assembly120and the upper insulation member140from moving inside the case110in a direction substantially perpendicular to the bottom plate112.

As described above, the electrode assembly120is accommodated in the case110and the other components are assembled, followed by the electrolyte injection process.

In the electrolyte injection process, the movement prevention tape130is brought into contact with an electrolyte, thereby allowing at least a portion of the movement prevention tape130to exhibit adhesiveness.

The electrolyte allows lithium ions generated from electrodes by an electrochemical reaction during charging and discharging operation to move. Since the electrolyte is the same as described above, a detailed description thereof will be omitted.

When the electrolyte is injected into the case110, the electrolyte comes into contact with the movement prevention tape130attached to the first electrode tab127of the electrode assembly120. Here, at least a portion of the movement prevention tape130melts, imparting an adhesive force to the movement prevention tape130. The adhesive portion of the movement prevention tape130prevents the first electrode tab127from moving inside the case110.

After the inserting of the electrolyte, the other components of the secondary battery100are assembled. For example, the gasket170is inserted into the case110through an opening formed in the case110to then be placed on the beading part111. Then, the cap assembly160is positioned within the gasket170, and the crimping part116is formed at a top end of the sidewall113of the case110, thereby fixing the gasket170and the cap assembly160.

As described above, once the secondary battery100is assembled, the general post-treatment, that is, formation and aging processes, may be performed. The formation and aging processes may be commonly applied to the prismatic secondary battery and the pouch-type secondary battery.

The formation process activates the assembled battery by repeating charging and discharging operations. During a charging operation in the formation process, lithium ions derived from lithium metal oxide used as a material of a positive electrode move to a carbon electrode as a negative electrode for intercalation. Since lithium is highly reactive, it reacts with the carbon, negative electrode to then produce a compound, such as Li2CO3, LiO, or LiOH, forming a coating called a solid electrolyte interface (SEI) on a surface of the carbon electrode.

The aging process allows the battery to stand undisturbed for a predetermined period to stabilize the SEI coating. The aging process is generally performed by placing the assembled secondary battery100under the condition of about 50° C. to about 70° C. for about 18 hours to about 36 hours. Through the aging process, at least a portion of the movement prevention tape130melts to give a sufficiently high adhesive force. Accordingly, electrode tab movement can be effectively prevented.

Hereinafter, another embodiment will be described in more detail through the following examples, which are not considered limiting.

LiCoO2as a positive electrode active material, polyvinylidene fluoride (PVdF) as a binder, and carbon as a conductive agent were mixed in a ratio of 92:4:4 by weight, and dispersed in N-methyl-2-pyrrolidone to prepare a positive electrode slurry. The positive electrode slurry was coated on a 20 μm thick aluminum foil, dried, and pressed to prepare a positive electrode plate.

Artificial graphite as a negative electrode active material, styrene-butadiene rubber as a binder, and carboxymethylcellulose as a thickening agent were mixed in a ratio of 96:2:2, and dispersed in water to prepare a negative electrode slurry. The negative electrode slurry was coated on a 15 μm thick copper foil, dried, and pressed to prepare a negative electrode plate.

A 20 μm thick polyethylene/polypropylene porous film (commercially available from Hoechst Celanese of USA) was used as a separator. The separator was disposed between the positive electrode plate and the negative electrode plate and the resultant structure was wound to prepare an electrode assembly. Here, a movement prevention tape was attached to a positive electrode tab drawn out from the electrode assembly. The movement prevention tape was formed by coating a PMMA adhesive on a 32 μm OPS film to a thickness of 15 μm. A long diameter of the electrode assembly was 17.00 mm and a short diameter thereof was 16.56 mm. The movement prevention tape was wrapped around the positive electrode tab one time to be attached by at least two third (⅔) of a boundary surface of the electrode assembly from which the first electrode tab is drawn out. The electrode assembly wound in a jellyroll configuration was put into a cylindrical battery case made of aluminum, and an electrolyte was injected into the battery case, followed by assembling and substantially hermetically sealing a cap assembly, thereby completing a secondary battery.

Here, a mixed organic solvent including ethylene carbonate (EC):dimethyl carbonate (DMC):propylene carbonate (PC):fluorobenzene (FB) mixed in a ratio of 30:55:5:10 by volume dissolved in 1.1 M LiPF6was used as the electrolyte.

Although specific types of materials (electrode materials, binder, conductive agent, separator, base layer, adhesive layer, solvent, electrolyte, etc.) or parameters (thickness, diameter, adhesive force or tensile strength, etc.) were used in the above example 1, it is expected that substantially the same or similar benefits are obtained from other type of materials or parameters discussed in connection withFIGS. 1-9.

Experimental Example

Each of five secondary batteries fabricated in the same manner as Example 1 was subjected to a formation process, followed by cutting beading part. Then, an upper end of a first electrode tab welded to a sub-plate of a cap assembly was cut. The resultant product is shown inFIG. 4.

Next, a tensile strength (adhesive force) was measured by use of a push-pull gauge connected to the upper end of the first electrode tab having a movement prevention tape attached thereto and the measurement result is listed in Table 1.

Comparative Experimental Example

Each of five secondary batteries fabricated in substantially the same manner as Example 1, except that a polyimide (PI) insulation tape, instead of the movement prevention tape, was used, was subjected to a formation process, followed by cutting beading part. Then, an upper end of a first electrode tab welded to a sub-plate of a cap assembly was cut. The resultant product is shown inFIG. 4.

Thereafter, adhesive force was measured by use of a push-pull gauge connected to the upper end of the first electrode tab having a movement prevention tape attached thereto and the measurement result is listed in Table 1.

As confirmed from Table 1, at least a portion of the movement prevention tape attached to the positive electrode tab drawn out from the electrode assembly melted, exhibiting adhesiveness. Therefore, according to at least one of the disclosed embodiments, it is possible to effectively prevent the electrode tab from moving inside the case.

According to at least one of the disclosed embodiments, the electrode tab is securely fixed to the case by an adhesive force of the adhesive portion of the movement prevention tape. Accordingly, the secondary battery can prevent the electrode tab from moving inside the case due to an external impact, such as an external vibration or a drop.

Although the disclosed embodiments have been described with reference to the accompanying drawings, the foregoing disclosure should be interpreted as illustrative only and it should be understood that various modifications and variations can be easily made by those skilled in the art without departing from the scope and spirit of the following claims.