Patent Description:
The present invention relates to an electrode assembly having a short circuit prevention coating portion, and more particularly to an electrode assembly having a short circuit prevention coating portion configured such that a coating portion, configured to prevent the occurrence of short circuit due to contact between a positive electrode mixture layer formed on a positive electrode tab and a negative electrode sheet, is formed at a part of the negative electrode sheet, whereby safety is improved.

In recent years, a secondary battery, which is capable of being charged and discharged, has been widely used as an energy source for wireless mobile devices. In addition, the secondary battery has attracted attention as an energy source for an electric vehicle, a hybrid electric vehicle, etc. presented as alternatives to existing gasoline and diesel vehicles using fossil fuels, which cause air pollution. As a result, the kind of applications using the secondary battery has been very diversified due to advantages of the secondary battery, and it is expected that, in the future, the secondary battery will be applied to many more fields and products than now.

Depending on the construction of an electrode and an electrolytic solution, the secondary battery may be classified as a lithium ion battery, a lithium ion polymer battery, or a lithium polymer battery. Thereamong, usage of the lithium polymer battery, which has a low possibility of leakage of the electrolytic solution and is easily manufactured, has increased. Depending on the shape of a battery case, the secondary battery is generally classified as a cylindrical battery, configured such that an electrode assembly is mounted in a cylindrical metal can, a prismatic battery, configured such that an electrode assembly is mounted in a prismatic metal can, or a pouch-shaped battery, configured such that an electrode assembly is mounted in a pouch-shaped case made of an aluminum laminate sheet.

The electrode assembly mounted in the battery case is a power generating element configured to have a structure including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode so as to be charged and discharged. The electrode assembly is classified as a jelly-roll type electrode assembly, which is configured to have a structure in which a long sheet type positive electrode having an active material applied thereto and a long sheet type negative electrode having an active material applied thereto are wound in the state in which a separator is interposed therebetween, or a stacked type cell assembly including unit cells, each of which is configured to have a structure in which a plurality of positive electrodes each having a predetermined size and a plurality of negative electrodes each having a predetermined size are sequentially stacked in the state in which separators are interposed respectively therebetween. Document <CIT> discloses a nonaqueous electrolyte secondary battery.

<FIG> is a perspective view showing a conventional electrode plate.

Referring to <FIG>, the conventional electrode plate includes an electrode current collector <NUM>, an electrode active material layer <NUM>, and an electrode tab <NUM>.

The electrode tab <NUM> may include an extension area <NUM>, an inclined portion <NUM>, and a non-coating portion <NUM>, and an electrode mixture layer including an electrode active material is applied to the extension area <NUM> and the inclined portion <NUM>.

During manufacture of an electrode assembly, a separator may shrink due to heat in a lamination process in which heat is applied, whereby the non-coating portion <NUM> or the extension area <NUM> and the inclined portion <NUM> of the conventional electrode tab <NUM> may come into contact with an adjacent electrode plate, and therefore short circuit may occur.

In addition, since the extension area <NUM> and the inclined portion <NUM> are formed at the electrode tab <NUM>, an overhang reversal phenomenon in which the capacity ratio of a negative electrode to a positive electrode (N/P ratio) is reversed may occur depending on characteristics in formation of the mixture layer.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an electrode assembly having a short circuit prevention coating portion configured such that the short circuit prevention coating portion prevents contact between a positive electrode mixture layer formed at a lower side of a positive electrode tab and a negative electrode sheet located on the same vertical line as the positive electrode mixture layer.

It is another object of the present invention to provide an electrode assembly having a short circuit prevention coating portion configured such that a shoulder portion is formed so as to extend from a negative electrode sheet by a predetermined length on the same vertical line as a positive electrode mixture layer formed at a lower side of a positive electrode tab, whereby the occurrence of an overhang reversal phenomenon is inhibited, and therefore it is possible to prevent deposition of lithium.

The scope of the invention is defined by appended claim <NUM>. An electrode assembly having a short circuit prevention coating portion according to the present invention to accomplish the above objects includes a positive electrode sheet (<NUM>) having a positive electrode tab (<NUM>) protruding from an outer end of one side thereof and a positive electrode mixture layer (<NUM>) including a positive electrode active material applied to a lower part of the positive electrode tab (<NUM>) and to a current collector, a negative electrode sheet (<NUM>) having a negative electrode tab (<NUM>) protruding from an outer end of one side thereof and a negative electrode mixture layer (<NUM>) including a negative electrode active material applied to a lower part of the negative electrode tab (<NUM>) and to a current collector, and a separator (<NUM>) located between the positive electrode sheet (<NUM>) and the negative electrode sheet (<NUM>), wherein the negative electrode sheet (<NUM>) has a shoulder portion (<NUM>) extending in a horizontal direction by a predetermined length, the negative electrode active material being applied to the shoulder portion, and the shoulder portion (<NUM>) is wrapped with a coating portion (<NUM>).

Also, in the electrode assembly according to the present invention, the coating portion (<NUM>) may include a pair of horizontal portions (<NUM>) arranged side by side and a vertical portion (<NUM>) connecting corresponding edges of the pair of horizontal portions (<NUM>) to each other.

Also, in the electrode assembly according to the present invention, the coating portion (<NUM>) may be made of an insulative material.

Also, in the electrode assembly according to the present invention, the shoulder portion (<NUM>) may be formed on a vertical extension line of the positive electrode tab (<NUM>).

Also, in the electrode assembly according to the present invention, the shoulder portion (<NUM>) may have a width (W1) greater than the width (W2) of the positive electrode tab.

In addition, the present invention provides a battery cell including the electrode assembly.

In addition, the present invention provides a battery pack including at least one battery cell.

An electrode assembly manufacturing method according to the present invention includes a step of preparing a positive electrode sheet, a negative electrode sheet, and a separator, a step of notching the negative electrode sheet to form a shoulder portion, a step of applying a coating portion onto the shoulder portion, and a step of stacking the positive electrode sheet, the separator, and the negative electrode sheet.

Also, in the electrode assembly manufacturing method according to the present invention, in the step of stacking the positive electrode sheet, the separator, and the negative electrode sheet, the stacking may be performed such that the center line of the shoulder portion and the center line of the positive electrode tab are located on the same line.

Also, in the electrode assembly manufacturing method according to the present invention, the electrode assembly may have a stacked type structure, a zigzag type structure, or a stacked and folded type structure.

Also, in the electrode assembly manufacturing method according to the present invention, the electrode assembly may be constituted by unit cells that are either bi-cells each having a single pole plate and opposite outer pole plates having a same polarity or full-cells each having opposite outer pole plates having different polarities.

As is apparent from the above description, an electrode assembly having a short circuit prevention coating portion according to the present invention has an advantage in that the coating portion is provided between a positive electrode mixture layer formed at a positive electrode tab and a shoulder portion of a negative electrode sheet in order to prevent contact therebetween, and therefore safety is improved.

In addition, the electrode assembly having the short circuit prevention coating portion according to the present invention has an advantage in that the shoulder portion is formed so as to extend by a predetermined length on a vertical line of the positive electrode mixture layer formed at the positive electrode tab, whereby the occurrence of an overhang reversal phenomenon is inhibited, and therefore it is possible to prevent deposition of lithium.

Hereinafter, an electrode assembly having a short circuit prevention coating portion according to the present invention will be described with reference to the accompanying drawings.

<FIG> is a perspective view of an electrode assembly according to a preferred embodiment of the present invention, <FIG> is a sectional view of the electrode assembly taken along line A-A' of <FIG>, and <FIG> is a plan view of a positive electrode sheet and a negative electrode sheet of the electrode assembly according to the preferred embodiment of the present invention excluding a separator when viewed from above.

Referring to <FIG>, the electrode assembly according to the preferred embodiment of the present invention includes a positive electrode sheet <NUM>, a negative electrode sheet <NUM>, a separator <NUM>, and a coating portion <NUM>.

A positive electrode tab <NUM> protrudes from an outer circumferential end of one side of the positive electrode sheet <NUM> by a predetermined length, and a positive electrode mixture layer <NUM> including a positive electrode active material is applied to a lower part of the positive electrode tab <NUM> protruding by the predetermined length and to a current collector.

Although the positive electrode mixture layer <NUM> applied to the lower part of the positive electrode tab <NUM> is shown as having a right-angled shape in <FIG>, the positive electrode mixture layer <NUM> applied to the lower part of the positive electrode tab <NUM> may be a sliding shape having a predetermined curvature or a slope having a predetermined angle.

A negative electrode tab <NUM> protrudes from an outer circumferential end of one side of the negative electrode sheet <NUM> by a predetermined length, and a negative electrode mixture layer <NUM> including a negative electrode active material is applied to a lower part of the negative electrode tab <NUM> protruding by the predetermined length and to a current collector.

Here, the negative electrode sheet <NUM> has a larger area than the positive electrode sheet <NUM> in order to inhibit the occurrence of an overhang reversal phenomenon.

In addition, a shoulder portion <NUM> extending by a predetermined length is formed at the part of the negative electrode sheet <NUM> that overlaps the part of the positive electrode sheet <NUM> at which the positive electrode tab <NUM> is formed when the electrode assembly is formed.

That is, the shoulder portion <NUM> may be formed at the negative electrode sheet <NUM> located on a vertical extension line of the positive electrode tab <NUM>, and may be formed at the portion of the negative electrode sheet <NUM> corresponding to the lower part of the positive electrode tab <NUM> to which the positive electrode mixture layer <NUM> is applied so as to extend by the predetermined length in the state in which the negative electrode mixture layer <NUM> is applied thereto. In this structure, it is possible to inhibit the occurrence of an overhang reversal phenomenon.

The negative electrode mixture layer <NUM> including the negative electrode active material is applied to the shoulder portion <NUM> when the negative electrode sheet <NUM> is formed.

In addition, the shoulder portion <NUM> is formed such that the width W1 of the shoulder portion is greater than the width W2 of the positive electrode tab <NUM>. In this case, it is possible to inhibit the occurrence of an overhang reversal phenomenon due to the positive electrode mixture layer <NUM> formed at the lower part of the positive electrode tab <NUM>, whereby it is possible to prevent the occurrence of a lithium deposition phenomenon, and therefore it is possible to improve safety.

In addition, the shoulder portion <NUM> may have a planar rectangular shape, and the protruding length of the shoulder portion <NUM> may be greater than the length of the positive electrode mixture layer <NUM> applied to the lower part of the positive electrode tab <NUM>.

The separator <NUM> is located between the positive electrode sheet <NUM> and the negative electrode sheet <NUM> and serves to prevent short circuit between the positive electrode sheet <NUM> and the negative electrode sheet <NUM> and to allow only movement of lithium ions therethrough. It is preferable for the separator to be made of any one selected from among polyethylene, polypropylene, a dual polyethylene/polypropylene layer, a triple polyethylene/polypropylene/polyethylene layer, a triple polypropylene/polyethylene/polypropylene layer, and organic fiber filter paper; however, the present invention is not limited thereto.

The coating portion <NUM> includes a pair of horizontal portions <NUM> arranged side by side in a state of being spaced apart from each other by a predetermined distance and a vertical portion <NUM> configured to connect corresponding edges of the pair of horizontal portions <NUM> to each other.

The coating portion <NUM> is located in a shape wrapping the shoulder portion <NUM> to prevent short circuit.

As an example, during manufacture of the electrode assembly, the separator may shrink due to heat after a lamination process in which heat is applied, whereby the positive electrode tab <NUM> and the shoulder portion <NUM> may come into contact with each other, and therefore short circuit may occur.

Since the coating portion <NUM> is located in a shape wrapping the shoulder portion <NUM>, however, it is possible to prevent the occurrence of short circuit due to contact between the positive electrode tab <NUM> and the shoulder portion <NUM>.

The coating portion <NUM> may be made of an insulative material, such as rubber or silicone, and the material for the coating portion is not restricted as long as the coating portion is located in a shape wrapping the shoulder portion <NUM> to maintain an insulation state.

The present invention may provide a battery cell including the electrode assembly having at least one of the above features.

The present invention may provide a battery pack including at least one battery cell.

An electrode assembly manufacturing method according to a preferred embodiment of the present invention includes a step of preparing a positive electrode sheet <NUM>, a negative electrode sheet <NUM>, and a separator <NUM>, a step of notching the negative electrode sheet <NUM> to form a shoulder portion <NUM>, a step of forming a coating portion <NUM> at the shoulder portion <NUM>, and a step of stacking the positive electrode sheet <NUM>, the separator <NUM>, and the negative electrode sheet <NUM>.

The step of preparing a positive electrode sheet, a negative electrode sheet, and a separator is a step of applying a mixture layer including an electrode active material to a current collector to form a positive electrode sheet and a negative electrode sheet and preparing a separator configured to prevent short circuit between the positive electrode sheet and the negative electrode sheet.

The step of notching the negative electrode sheet <NUM> to form a shoulder portion <NUM> is a step of notching the negative electrode sheet <NUM> having the mixture layer including the electrode active material applied to the current collector to form a negative electrode tab <NUM> and a shoulder portion <NUM> located spaced apart from the negative electrode tab <NUM> by a predetermined distance.

At this time, the positive electrode sheet <NUM> may be notched to form a positive electrode tab <NUM>, and a positive electrode mixture layer <NUM> may be applied to a lower end of the positive electrode tab <NUM>.

In the step of forming a coating portion <NUM> at the shoulder portion <NUM>, the shoulder portion <NUM> formed by notching may be wrapped with a coating portion <NUM> made of an insulative material to prevent the occurrence of short circuit due to contact with the positive electrode tab <NUM>.

The step of stacking the positive electrode sheet <NUM>, the separator <NUM>, and the negative electrode sheet <NUM> is a step of stacking the positive electrode sheet <NUM>, the separator <NUM>, and the negative electrode sheet <NUM> to form an electrode assembly.

Here, stacking may be performed such that the center line of the shoulder portion <NUM> formed at the negative electrode sheet <NUM> and the center line of the positive electrode tab <NUM> are located on the same line. The reason for this is that, if stacking is performed such that the shoulder portion <NUM> and the positive electrode tab <NUM> are misaligned with each other, an overhang reversal phenomenon may occur.

The electrode assembly manufactured by the electrode assembly manufacturing method according to the present invention may be configured to have a stacked type structure, a zigzag type structure, or a stacked and folded type structure.

Here, the electrode assembly according to the present invention may be a jelly-roll type cell assembly, which is configured to have a structure in which a long sheet type positive electrode and a long sheet type negative electrode are wound in the state in which a separator is interposed therebetween, a stacked type cell assembly including unit cells, each of which is configured to have a structure in which a rectangular positive electrode and a rectangular negative electrode are stacked in the state in which a separator is interposed therebetween, a stacked and folded type cell assembly, which is configured to have a structure in which unit cells are wound using a long separation film, or a laminated and stacked type cell assembly, which is configured to have a structure in which unit cells are stacked and attached to each other in the state in which a separator is interposed therebetween; however, the present invention in not limited thereto.

A sheet type separation film forms a stacked and folded type cell assembly having a structure in which a plurality of unit cells is wound, and the outermost part of the separation film located on a vertical extension line of a sliding portion of an electrode at the outermost side of the separation film is bent at the same curvature as the sliding portion so as to be brought into tight contact therewith, whereby it is possible to prevent the occurrence of a deposition phenomenon due to diffusion resistance in a space between a sliding portion of the outermost electrode and a separation film in a conventional electrode assembly.

In addition, the electrode assembly manufactured by the electrode assembly manufacturing method according to the present invention may be constituted by unit cells, such as bi-cells, each of which has a single pole plate and opposite outer pole plates having the same polarity, or full-cells, each of which has opposite outer pole plates having different polarities.

Claim 1:
An electrode assembly comprising:
a positive electrode sheet (<NUM>) having a positive electrode tab (<NUM>) protruding from an outer end of one side thereof and a positive electrode mixture layer (<NUM>) comprising a positive electrode active material applied to a lower part of the positive electrode tab (<NUM>) and to a positive electrode current collector, the lower part being a positive electrode tab end close to a coated area of the positive electrode current collector;
a negative electrode sheet (<NUM>) having a negative electrode tab (<NUM>) protruding from an outer end of one side thereof and a negative electrode mixture layer (<NUM>) comprising a negative electrode active material applied to a lower part of the negative electrode tab (<NUM>) and to a negative electrode current collector, the lower part being a negative electrode tab end close to a coated area of the negative electrode current collector; and
a separator (<NUM>) located between the positive electrode sheet (<NUM>) and the negative electrode sheet (<NUM>),
wherein the negative electrode sheet (<NUM>) has a shoulder portion (<NUM>) extending in a horizontal direction (A-A') by a predetermined length and formed at a part of the negative electrode sheet (<NUM>) that overlaps the part of the positive electrode sheet (<NUM>) at which the positive electrode tab (<NUM>) is formed, the negative electrode active material being applied to the shoulder portion (<NUM>), and the shoulder portion (<NUM>) is wrapped with a coating portion (<NUM>) configured to prevent contact between the positive electrode mixture (<NUM>) layer formed at the positive electrode tab (<NUM>) and the shoulder portion (<NUM>) of the negative electrode sheet (<NUM>).