KR20060037846A - Secondary battery - Google Patents

Abstract

The secondary battery has a first electrode active material coated on at least one surface of a first electrode current collector, a first electrode uncoated portion at both ends of the first electrode current collector, and a first protrusion formed at an end of at least one electrode active material layer. A second electrode active material coated on at least one surface of the electrode plate and the second electrode current collector, and having a second electrode uncoated portion at both ends of the second electrode current collector, and having a protrusion formed at an end of the at least one electrode active material layer. A separator interposed between the second electrode plate, the first electrode plate and the second electrode plate to insulate them, and an uneven portion where the electrode active material layer at both ends of the first electrode plate or the second electrode plate starts and ends unevenly. Since it is installed to surround the protrusion formed in the portion and the electrolyte solution includes at least one insulating member, the insulating member is formed of a heat-sealed film that can be bonded by weak heat And it does not require more than a separate adhesive layer has the effect of minimizing the volume of the electrode assembly to prevent damage of the separator and short-circuit between the electrodes.

Electrode active material layer, insulation layer, heat fusion film

Description

Secondary Battery {SECONDARY BATTERY}

1 is an exploded perspective view illustrating a secondary battery according to an embodiment of the present invention;

2 and 3 show an electrode assembly according to the invention,

4, 5 is a view showing an embodiment of a thermal fusion film according to the present invention.

<Brief Description of Major Codes in Drawings>

100: secondary battery 110: case

200: electrode assembly 210: electrode plate

211: electrode current collector 213: electrode active material layer

215: electrode tab 217: electrode uncoated portion

230: separator 240: heat-sealed film

300: Cap Assembly

The present invention relates to a secondary battery, and more particularly, to a secondary battery having an insulating member installed on an electrode plate of a secondary battery to prevent short circuit between electrodes.

Recently, compact and lightweight electric / electronic devices such as cellular phones, notebook computers, camcorders, etc. have been actively developed and produced. These portable electric / electronic devices have a battery pack that can be operated in a place where no separate power source is provided. The built-in battery pack includes at least one battery therein for outputting a predetermined level of voltage for driving the portable electric / electronic device for a certain period of time.

In consideration of economic aspects, recently, rechargeable batteries are adopting rechargeable batteries that can be recharged, small and large in capacity, and have recently been used as power sources for portable electronic devices such as camcorders, portable computers, and mobile phones. Representative examples of recent developments and uses include nickel hydride (Ni-MH) batteries, lithium ion (Li-ion) batteries, and lithium ion (Li-ion) polymer batteries.

In particular, the lithium secondary battery has an operating voltage of 3.6 V, which is three times higher than that of a nickel-cadmium (Ni-Cd) battery or a nickel-hydrogen battery, which is widely used as a power source for portable electronic equipment, and has a high energy density per unit weight. The trend is growing.

Among the secondary batteries described above, a lithium ion secondary battery accommodates an electrode assembly consisting of a positive electrode plate, a negative electrode plate, and a separator in a can made of aluminum or an aluminum alloy, closes the can with a cap assembly, and then injects and seals electrolyte into the can. It includes a bare cell formed by.

In the case of a polymer battery in which an electrode plate or a separator is formed of a polymer, the separator plays a role of an electrolyte or is used by incorporating an electrolyte component into a separator.

In lithium ion secondary batteries, the electrode plate is usually a slurry containing an electrode active material (lithium oxide in the case of positive electrode and carbon material in the case of negative electrode) on the surface of an electrode current collector made of metal foil (hereinafter, used to mean an active material layer). It is made by applying.

The slurry is formed by mixing a solvent with a plastic material, an electrode active material, a binder, and the like. As the current collector, copper is used for the negative electrode plate and aluminum for the positive electrode plate.Polyvinylidene fluoride (PVDF) and stylene butadiene rubber (SBR) are used as binders, and acetone and NMP (N-methylprolidone) are used as solvents. And the like can be used. On the other hand, water can be used as a solvent.

In the electrode assembly, a cathode electrode plate, a cathode electrode plate, and a separator are each composed of one strip, and are arranged in the order of the anode electrode plate, the separator, and the cathode electrode plate, and are wound in a jelly-roll type. .

Here, in the electrode current collector to be the positive electrode or the negative electrode plate, a slit die in which a slurry is supplied to at least one surface thereof passes through the upper surface of the electrode current collector to form an electrode active material layer having a predetermined thickness.

At this time, since the slurry supplied to the slit die is a fluid state containing a large amount of solvent, the solvent of the slurry is volatilized through a drying process, and the slurry is attached to the electrode current collector with considerable strength by the action of a binder.

When the electrode active material layer is coated on the electrode current collector, the electrode active material layer is coated by the length necessary to form one electrode, and the electrode called the `` unknown portion '' due to the necessity of welding electrode tabs between the electrode active material layers. A strip portion in which the active material layer is not coated is interposed. Thus, the electrode current collector is provided with an electrode active material layer and an electrode uncoated portion.

By the way, although there may be a difference depending on the slurry coating equipment, the coated slurry is agglomerated somewhat at the beginning of the slurry coating on the electrode current collector and the end of the slurry coating is finished compared to the portion where the electrode active material layer is continuous. Overhanging phenomena appear. The protrusions in which the slurry is aggregated and protruded appear at both ends of the electrode active material layer coated with the slurry in the positive electrode plate and the negative electrode plate.

In this case, when a pressure or other external pressure during a process such as a force during winding of the electrode assembly is received, pressure may be concentrated on the protrusion to damage the separator that electrically insulates the positive electrode plate and the negative electrode plate. The internal short circuit of the positive electrode plate and the negative electrode plate in these portions through the damaged separator is a problem because the production yield of the battery is lowered, even a safety accident may occur.

Therefore, in the related art, an insulating layer is formed on a portion including the protrusion of the electrode active material layer formed on at least one surface of the positive electrode plate or the negative electrode plate so that the positive electrode plate and the negative electrode plate are in contact with each other, or the separator that is in contact with the protrusion is damaged. To prevent them.

However, in this case, since the insulating layer covers a part of the electrode active material layer, the reaction area of the electrode active material layer is reduced. Therefore, the capacity of the battery decreases as the reaction area decreases.

That is, the capacity of the lithium ion secondary battery is proportional to the volume of the electrode active material layer reacting with each other at the positive electrode and the negative electrode. When the insulating layer is formed, the reaction area of the electrode active material layer is reduced, thereby reducing the capacity of the secondary battery.

Disclosure of Invention An object of the present invention is to solve the problems as described above, to provide a secondary battery that reduces the internal short circuit between the electrode plate by placing an insulating member that is bonded by heat to the protrusions formed on both ends of the electrode active material layer of the electrode assembly. It is.

The present invention for achieving the above object is a first electrode active material is coated on at least one surface of the first electrode current collector, having a first electrode uncoated portion at both ends of the first electrode current collector and at least one electrode active material layer A first electrode plate having a protruding portion at an end thereof, and a second electrode active material coated on at least one surface of the second electrode current collector, and having a second electrode non-coating portion at both ends of the second electrode current collector and having at least one electrode active material layer. A second electrode plate having a protrusion formed at an end of the separator, a separator interposed between the first electrode plate and the second electrode plate to insulate them, and the electrode active material layers at both ends of the first electrode plate or the second electrode plate. Provided is a secondary battery including at least one insulating member installed to surround a protrusion formed at a starting non-uniform portion and an ending non-uniform portion, wherein an electrolyte is movable.

The insulating member is provided on the upper portion of at least one of the protrusions of the both ends of the electrode active material layer of the first and second electrode plate, the width is preferably formed of about 10 ~ 20mm.

The insulating member is preferably a heat-sealed film formed of a material of PP or PE. Here, the heat-sealed film is preferably formed of a filter type, or a plurality of through holes are formed. At least five through-holes may be formed in the heat-sealed film adhered to the electrode active material layer to have an area of 30% to 90% of the area of the heat-sealed film adhered to the electrode active material layer.

At this time, the thickness of the heat-sealed film is preferably formed in 20μm or less.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is an exploded perspective view illustrating a rechargeable battery according to an exemplary embodiment of the present invention. Referring to this drawing, the secondary battery 100 includes a secondary battery case 110, a jelly-roll electrode assembly 200 accommodated in the case 110, and a cap coupled to an upper portion of the case 110. Assembly 300.

The case 110 is formed of a metal material having an open side and having a substantially rectangular box shape, and may itself serve as a terminal.

The electrode assembly 200 includes a first electrode plate 210 to which the first electrode tab 215 is attached, a second electrode plate 220 to which the second electrode tab 225 is attached, and a first and second electrode plate ( The separator 230 interposed between 210 and 220 is configured to be wound.

The cap assembly 300 is provided with a flat cap plate 310 having a size and shape corresponding to the opening of the case 110. A terminal through hole 311 is formed at the center of the cap plate 310, and an electrolyte injection hole 312 for injecting an electrolyte is formed at one side of the cap plate 310, and the electrolyte injection hole 312 is a stopper 315. It is combined with and sealed.

The terminal through hole 311 is formed at a position such that the electrode terminal 320, for example, the negative electrode terminal, can be inserted therein. The outer surface of the electrode terminal 320 is provided with a tube-shaped gasket 330 for electrical insulation with the cap plate 310.

An insulating plate 340 is disposed on the lower surface of the cap plate 310, and a terminal plate 350 is installed on the lower surface of the insulating plate 340.

The first electrode tab 215 drawn from the first electrode plate 210 is welded to the bottom surface of the cap plate 310, and the second lead drawn from the second electrode plate 220 is formed at the lower end of the electrode terminal 320. The electrode tab 225 is welded.

Meanwhile, an insulating case 360 may be installed on an upper surface of the electrode assembly 200 to electrically insulate the electrode assembly 200 from the cap assembly 300 and cover the upper end of the electrode assembly 200. The insulating case 360 may include an electrolyte injection hole 362 at a position corresponding to the electrolyte injection hole 312 of the cap plate 310 to inject the electrolyte solution.

2 is a view showing an embodiment of an electrode assembly according to the present invention, Figures 3 and 4 is a view showing an embodiment of a secondary battery electrode current collector according to the present invention. Referring to these drawings, the electrode assembly 200 includes the first electrode plate 210, the second electrode plate 220, and the separator 230 each composed of one strip. In this case, the polarities of the first electrode plate 210 and the second electrode plate 220 may be disposed as either a cathode or an anode, and the first electrode plate 210 may be a cathode.

That is, the positive electrode plate includes a positive electrode current collector made of a thin metal plate having excellent conductivity, for example, aluminum (Al) foil, and a positive electrode active material layer coated on both surfaces of the positive electrode current collector. As a cathode active material, a chalcogenide compound is used. For example, composite metal oxides such as LiCo02, LiMn204, LiNi02, LiNi1-xCox02 (0 <x <1), and LiMn02 are used. It is not limiting.

Both ends of the positive electrode plate have a positive electrode current collector region, that is, a positive electrode non-coating portion, in which a positive electrode active material layer is not formed, and a positive electrode tab is electrically connected to one of the positive electrode non-coating portions.

The negative electrode plate includes a negative electrode current collector made of a conductive metal thin plate, for example, copper (Cu) or nickel (Ni) foil, and a negative electrode active material layer coated on both surfaces of the negative electrode current collector. As the negative electrode active material, a carbon (C) -based material, Si, Sn, tin oxide, tin alloy composites, transition metal oxide, lithium metal nitride, or lithium metal oxide is used. It is not intended to limit.

Both ends of the negative electrode plate have a negative electrode current collector region, that is, a negative electrode non-coating portion, in which no negative electrode active material layer is formed, and a negative electrode tab is electrically connected to either side of the negative electrode non-coating portion.

In addition, the electrode plate 210 includes an insulating member 240 formed to cover at least one end of both ends of the electrode active material layer 213.

The insulating member is formed to surround the protrusion (a), which is a nonuniform portion of the start and end portions of the active material layer 213 formed on one surface of the electrode current collector 211 of the electrode plate 210, the width of the 10 ~ 20mm It is preferably formed to a degree. That is, when the width of the insulating member is greater than 10 to 20 mm, the movement of the electrolyte is hindered. If the insulating member is smaller than 10 to 20 mm, the insulating member is separated from the electrode current collector 211 by the force received when the electrolyte is moved.

On the other hand, since the internal temperature of the insulating member is increased to about 150 ° C. during the overcharging of the secondary battery 100, the heat fusion film 240 is preferably heat-sealed at a deformation temperature of 150 ° C. or higher so that there is no deformation such as shrinkage. The material is preferably PP or PE. Here, the thermal fusion film 240 is bonded by heat, so the adhesive layer does not have to be applied.

In addition, the heat-sealed film 240 is formed as a filter type, as shown in FIG. 4, to penetrate the electrolyte on the upper surface thereof, or as shown in FIG. 5, a plurality of penetrating up and down the base substrate 241. The through hole 245 may be formed. In FIG. 5, the through holes 245 are formed in a predetermined arrangement at regular intervals, but the through holes 245 may be alternately formed because the arrangement of the through holes 245 is not limited thereto. At least five through-holes 245 are preferably formed such that the area thereof is 30% to 90% of the area of the heat-sealed film 240 adhered to the electrode active material layers 213 and 223.

At this time, the thickness of the heat-sealed film 240 is formed to 20μm or less to minimize the volume of the electrode assembly 200.

Therefore, when the heat-sealing film 240 is installed, the volume of the electrode assembly is minimized by not using a separate adhesive layer to prevent short circuit between the electrodes.

According to the present invention, as the insulating member installed in the protrusion of the secondary battery is formed of a heat-sealed film, the heat-sealed film can be adhered by weak heat so that a separate adhesive layer is not necessary, so that a short circuit between the electrodes can be achieved while minimizing the volume of the electrode assembly. And preventing damage to the separator.

As described above, the present invention is not limited to the specific preferred embodiments described above, and those skilled in the art without departing from the gist of the present invention as claimed in the following claims. Anyone may implement various modifications, and such changes are within the scope of the claims.

Claims (11)

A first electrode plate having a first electrode active material coated on at least one surface of a first electrode current collector, having first electrode uncoated portions at both ends of the first electrode current collector, and having protrusions formed at ends of at least one electrode active material layer; A second electrode plate having a second electrode active material coated on at least one surface of a second electrode current collector, having a second electrode uncoated portion at both ends of the second electrode current collector, and a protrusion formed at an end of at least one electrode active material layer; A separator interposed between the first electrode plate and the second electrode plate to insulate them; And At least one insulating member installed to surround the protrusion formed at the nonuniform portion at which the electrode active material layer at both ends of the first electrode plate or the second electrode plate starts and the nonuniform portion at the end, and the electrolyte solution is movable; . The method of claim 1, The insulating member is a secondary battery, characterized in that installed on the upper portion of at least one of the protrusions of the both ends of the electrode active material layer of the first and second electrode plate. The method of claim 1, The insulating member is a secondary battery, characterized in that the width is formed in about 10 ~ 20mm. The method of claim 1, The insulating member is a secondary battery, characterized in that the heat sealing film. The method of claim 4, wherein The heat-sealed film is a secondary battery, characterized in that formed of a material of PP or PE. The method of claim 4, wherein The heat-sealed film is a secondary battery, characterized in that the filter type. The method of claim 4, wherein The heat-sealed film is a secondary battery, characterized in that a plurality of through holes formed. The method of claim 7, wherein The through-hole is a secondary battery, characterized in that the area is formed so that 30% to 90% of the area of the heat-sealed film bonded to the upper electrode active material layer. The method of claim 8 At least five through-holes are formed in the heat-sealed film adhered to the electrode active material layer. The method of claim 4, wherein The thickness of the heat-sealed film is a secondary battery, characterized in that 20μm or less. The method of claim 1, The first electrode plate is a secondary battery, characterized in that the negative terminal.

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