Patent Description:
With technological development of mobile devices, such as smartphones, laptop computers, and digital cameras, and an increase in demand therefor, research on secondary batteries, which are capable of being charged and discharged, has been actively conducted. In addition, secondary batteries, which are energy sources substituting for fossil fuels causing air pollution, have been applied to an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (P-HEV), and an energy storage system (ESS).

There are a lithium ion battery, a lithium polymer battery, a nickel cadmium battery, a nickel hydride battery, and a nickel zinc battery as secondary batteries that are widely used at present.

In general, such a secondary battery is configured such that an electrode assembly and an electrolytic solution are received in a battery case, and may be classified as a cylindrical battery having the electrode assembly mounted in a cylindrical metal can, a prismatic battery having the electrode assembly mounted in a prismatic metal can, or a pouch-shaped battery having the electrode assembly mounted in a cell case made of an aluminum laminate sheet based on the kind of the battery case.

Meanwhile, the secondary battery is repeatedly charged and discharged, and at this time heat is generated. Depending on circumstances, thermal runaway occurs due to short circuit, thermal shock, insulation breakdown, etc., which leads to a major accident, such as fire outbreak or explosion.

The reason for this is that a space in a negative electrode into which lithium ions deintercalated from a positive electrode during charging and discharging can be intercalated is insufficient, whereby the lithium ions may be deposited on a surface of the negative electrode as lithium metal, or metal impurities mixed during the manufacture of the battery are recrystallized and then come into contact with the positive electrode through a separator.

In particular, since, for the pouch-shaped battery cell, the case that encompasses the electrode assembly is thin and soft, unlike the cylindrical battery or the prismatic battery, more attention needs to be paid. Since the pouch-shaped battery cell is configured to have a structure in which the electrode assembly is merely sealed, however, there is no reliable safety means capable of securing safety.

Examples of pouch type battery cells are disclosed in documents <CIT>, <CIT>, <CIT> and <CIT>.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a pouch-shaped battery cell with improved safety capable of rupturing a case before thermal runaway occurs in the pouch-shaped battery cell, thereby preventing a secondary accident, such as fire outbreak or explosion.

It is another object of the present invention to provide a pouch-shaped battery cell with improved safety configured such that a front surface and a rear surface of the battery cell are easily identified at the time of manufacturing a battery module or a battery pack, whereby it is possible to improve speed and accuracy in manufacture.

To this end, the invention relates to a pouch-shaped battery cell according to claim <NUM>.

The pouch-shaped battery cell according to the invention may present one or more of the features of dependent claims <NUM> to <NUM>, in any technically feasible combination.

The invention also relates to a battery pack according to claim <NUM>.

A pouch-shaped battery cell with improved safety according to the present invention has an advantage in that a rupture induction portion is provided in a cell case, whereby it is possible to induce rapid rupture of the case when a swelling phenomenon occurs in the case, and therefore it is possible to prevent fire outbreak or explosion.

Also, in the pouch-shaped battery cell with improved safety according to the present invention, disposition structures of rupture induction portions provided in an upper case and a lower case are different from each other, whereby it is possible to easily distinguish between a front surface and a rear surface of the battery cell, and therefore it is possible to improve speed and accuracy of a manufacturing process at the time of manufacturing a batter module or a battery pack.

Hereinafter, a pouch-shaped battery cell with improved safety according to the present invention will be described with reference to the accompanying drawings.

<FIG> is an exploded perspective view of a pouch-shaped battery cell according to a first embodiment of the present invention, <FIG> is a plan view of the pouch-shaped battery cell shown in <FIG>, and <FIG> is a sectional view of a part of the pouch-shaped battery cell taken along line A-A' of <FIG>.

The pouch-shaped battery cell with improved safety according to the present invention includes an electrode assembly <NUM>, a cell case <NUM> configured to receive the electrode assembly <NUM>, and a rupture induction portion <NUM>.

First, the electrode assembly <NUM> received in the cell case <NUM> may be a jelly-roll type electrode assembly, which is configured to have a structure in which a long sheet type negative electrode <NUM> and a long sheet type positive electrode <NUM> are wound in the state in which a separator <NUM> is interposed therebetween, a stacked type electrode 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 electrode 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 electrode assembly, which is configured to have a structure in which unit cells are stacked in the state in which a separator is interposed therebetween and are then attached to each other. However, the present invention is not limited thereto.

Specifically, the negative electrode <NUM> is manufactured by applying a slurry mixture of a negative electrode active material and a binder to a negative electrode current collector.

Here, as the negative electrode active material, for example, there may be used carbon, such as a non-graphitizing carbon or a graphite-based carbon; a metal composite oxide, such as LixFe<NUM>O<NUM> (<NUM>≤x≤<NUM>), LixWO<NUM> (<NUM>≤x≤<NUM>), SnxMe<NUM>-xMe'yOz (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group <NUM>, <NUM>, and <NUM> elements of the periodic table, halogen; <NUM><x≤<NUM>; <NUM>≤y≤<NUM>; <NUM>≤z≤<NUM>); lithium metal; a lithium alloy; a silicon-based alloy; a tin-based alloy; a metal oxide, such as SnO, SnO<NUM>, PbO, PbO<NUM>, Pb<NUM>O<NUM>, Pb<NUM>O<NUM>, Sb<NUM>O<NUM>, Sb<NUM>O<NUM>, Sb<NUM>O<NUM>, GeO, GeO<NUM>, Bi<NUM>O<NUM>, Bi<NUM>O<NUM>, or Bi<NUM>O<NUM>; a conductive polymer, such as polyacetylene; a Li-Co-Ni-based material; or a Si-based material, such as Si, SiO, SiO<NUM>, or a mixture thereof. However, the present invention is not limited thereto.

The positive electrode <NUM> is manufactured by applying a slurry mixture of a positive electrode active material and a binder to a positive electrode current collector.

The positive electrode active material may be constituted, for example, by a layered compound, such as a lithium cobalt oxide (LiCoO<NUM>) or a lithium nickel oxide (LiNiO<NUM>), or a compound substituted with one or more transition metals; a lithium manganese oxide represented by the chemical formula Li<NUM>+xMn<NUM>-xO<NUM> (where x = <NUM> to <NUM>) or a lithium manganese oxide, such as LiMnO<NUM>, LiMn<NUM>O<NUM>, or LiMnO<NUM>; a lithium copper oxide (Li<NUM>CuO<NUM>); a vanadium oxide, such as LiV<NUM>O<NUM>, LiFe<NUM>O<NUM>, V<NUM>O<NUM>, or Cu<NUM>V<NUM>O<NUM>; a Ni-sited lithium nickel oxide represented by the chemical formula LiNi<NUM>-xMxO<NUM> (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = <NUM> to <NUM>); a lithium manganese composite oxide represented by the chemical formula LiMn<NUM>-xMxO<NUM> (where M = Co, Ni, Fe, Cr, Zn, or Ta, and x = <NUM> to <NUM>) or the chemical formula Li<NUM>Mn<NUM>MO<NUM> (where M = Fe, Co, Ni, Cu, or Zn); LiMn<NUM>O<NUM> in which a portion of Li in the chemical formula is replaced by alkaline earth metal ions; a disulfide compound; or Fe<NUM>(MoO<NUM>)<NUM>. However, the present invention is not limited thereto.

Meanwhile, each of the negative electrode current collector and the positive electrode current collector is constituted by a portion having the slurry including the active material applied thereto and a non-coated portion having no slurry applied thereto, and the non-coated portion may be cut to form an electrode tab or a separate conductive member is connected to the non-coated portion by ultrasonic welding to form the electrode tab.

An electrode lead <NUM> is connected to the electrode tab by spot welding, and an insulative film <NUM> is located around the electrode lead <NUM>.

Here, the insulative film <NUM> is located at a sealed portion at which a lower case <NUM> and an upper case <NUM> are thermally fused to each other in order to fix the electrode lead <NUM> to the cell case <NUM>.

Consequently, the flow of electricity generated by the electrode assembly <NUM> to the cell case <NUM> via the electrode lead <NUM> is prevented, and sealing of the cell case <NUM> is maintained. Meanwhile, it is preferable for the insulative film <NUM> to be made of a material having poor conduction of electricity, i.e. a nonconductive material. In general, an insulative tape that has a relatively small thickness while being easily attached to the electrode lead <NUM> is mainly used; however, the present invention is not limited thereto.

Next, the cell case <NUM> will be described.

The cell case <NUM> is constituted by a lower case <NUM> and an upper case <NUM>, and has a pocket type space portion S configured to receive the electrode assembly <NUM>.

The cell case <NUM> is made of a laminate sheet including an outer coating layer, a metal layer, and an inner coating layer, and the space portion configured to receive the electrode assembly <NUM> is formed in the cell case.

The inner coating layer is disposed in direct contact with the electrode assembly <NUM>, and therefore the inner coating layer must exhibit high insulation properties and high resistance to an electrolytic solution. In addition, the inner coating layer must exhibit high sealability in order to hermetically seal the cell case from the outside, i.e. a thermally-bonded sealed portion between inner layers must exhibit excellent thermal bonding strength.

The inner coating layer may be made of a material selected from among a polyolefin-based resin, such as polypropylene, polyethylene, polyethylene acrylate, or polybutylene, a polyurethane resin, and a polyimide resin, which exhibit excellent chemical resistance and high sealability; however, the present invention is not limited thereto, and polypropylene, which exhibits excellent mechanical properties, such as tensile strength, rigidity, surface hardness, and impact resistance, and excellent chemical resistance, may be most preferably used.

The metal layer, which is disposed so as to abut the inner coating layer, corresponds to a barrier layer configured to prevent moisture or various kinds of gas from permeating into the battery from the outside. An aluminum thin film, which is lightweight and easily shapeable, may be used as a preferred material for the metal layer.

The outer coating layer is provided on the other surface of the metal layer. The outer coating layer may be made of a heat-resistant polymer that exhibits excellent tensile strength, resistance to moisture permeation, and resistance to air transmission such that the outer coating layer exhibits high heat resistance and chemical resistance while protecting the electrode assembly. As an example, the outer coating layer may be made of nylon or polyethylene terephthalate; however, the present invention is not limited thereto.

Although the lower case <NUM> and the upper case <NUM> are shown as being completely separated from each other in the drawings, one edge of the lower case <NUM> and one edge of the upper case <NUM> may be connected to each other, or one of the lower case <NUM> and the upper case <NUM> may have a flat plate structure having no spaced portion therein.

Next, the rupture induction portion <NUM> received in the space portion S of the cell case <NUM> will be described.

The rupture induction portion <NUM> is a construction capable of inducing further swelling of the cell case <NUM> when the pressure in the cell case <NUM> increases due to swelling in order to rupture the cell case <NUM> and to interrupt connection with a corresponding lead before occurrence of thermal runaway as the result of rupturing the cell case, thereby minimizing secondary damage, such as fire outbreak or explosion.

<FIG> is a perspective view showing examples of a rupture induction portion according to a first embodiment of the present invention. Referring to <FIG>, the rupture induction portion <NUM> may have a cubic shape with a predetermined volume.

For example, the rupture induction portion may have a spherical shape, such as a round ball, a cubic shape formed by four or more flat surfaces, such as a polygonal column, a cone, a truncated cone, a truncated pyramid, or a shape formed by flat and curved surfaces, and the shape of the rupture induction portion is not particularly restricted as long as the rupture induction portion is configured to have a volume.

Here, although the size of the rupture induction portion is not particularly defined, it is preferable for the rupture induction portion to have a maximum inner diameter of <NUM> or less, since the rupture induction portion must be located between the electrode assembly <NUM> and an inner surface of the cell case <NUM>.

It is preferable for the rupture induction portion <NUM> to be provided between the electrode assembly <NUM> and an inner surface of the lower case <NUM>, between the electrode assembly <NUM> and an inner surface of the upper case <NUM>, or between the electrode assembly <NUM> and the inner surface of the lower case <NUM> and between the electrode assembly <NUM> and the inner surface of the upper case <NUM>, and it is more preferable for a plurality of rupture induction portions to be provided therebetween.

According to the invention, the rupture induction portion is provided between the electrode assembly <NUM> and the inner surface of the lower case <NUM> and between the electrode assembly <NUM> and the inner surface of the upper case <NUM> and a plurality of rupture induction portions is provided therebetween, the disposition structure of first rupture induction portions <NUM> located between the inner surface of the lower case <NUM> and the electrode assembly <NUM> and the disposition structure of second rupture induction portions <NUM> located between the inner surface of the upper case <NUM> and the electrode assembly <NUM> being different from each other.

In general, a battery module is obtained by stacking a plurality of battery cells. At this time, the battery cells must be sequentially stacked in a predetermined direction. For the pouch-shaped battery cell having the space portion provided in each of the upper case and the lower case, however, it is difficult to easily identify the pouch-shaped battery cell, since the external shapes of the upper case and the lower case are similar to each other.

When the rupture induction portions <NUM> are provided at the inner surface of the upper case <NUM> and the inner surface of the lower case <NUM>, however, outer surfaces of the lower case <NUM> and the upper case <NUM> may protrude so as to be slightly convex due to the volume of each of the rupture induction portions <NUM>. Furthermore, since the disposition structures of rupture induction portions <NUM> provided at the inner surfaces of the respective cases are different from each other, it is possible to easily distinguish between the upper case <NUM> and the lower case <NUM> with the naked eye, whereby a stacking process may be easily performed and process accuracy may be improved.

Although a total of <NUM> (<NUM> x <NUM>) first rupture induction portions <NUM> are shown as being provided at the inner surface of the lower case <NUM> such that the first rupture induction portions are disposed by twos in a horizontal direction and the first rupture induction portions are disposed by threes in a vertical direction in the state in which the first rupture induction portions are spaced apart from each other by a predetermined distance and a total of <NUM> (<NUM> x <NUM>) second rupture induction portions <NUM> are shown as being provided at the inner surface of the upper case <NUM> such that the second rupture induction portions are disposed by threes in the horizontal direction and the second rupture induction portions are disposed by twos in the vertical direction in the state in which the second rupture induction portions are spaced apart from each other by a predetermined distance in <FIG> and <FIG>, which is merely an example, it is obvious that it is possible to variously change the number of rupture induction portions and the disposition structures thereof.

Meanwhile, in <FIG>, the electrode assembly <NUM> configured in the sequence of the separator <NUM>, the negative electrode <NUM>, the separator <NUM>, and the positive electrode <NUM> in an inward direction from the outermost side is received. At this time, the rupture induction portion <NUM> may be located between the separator <NUM> located at the outermost side of the electrode assembly <NUM> and the inner surface of the cell case <NUM>.

Little space may be provided between the electrode assembly <NUM> and the inner surface of the cell case <NUM> in order to increase energy density, and therefore the fixed state of the rupture induction portion <NUM> may be maintained without a separate fixing means. However, an adhesive made of a known nonconductive material may be used in order to securely fix the rupture induction portion <NUM> at a desired position. Of course, it is obvious that the rupture induction portion <NUM> may be simultaneously formed during a process of forming the cell case <NUM>.

Here, since the rupture induction portion <NUM> is disposed in direct contact with the electrode assembly <NUM>, it is preferable for the rupture induction portion to be made of a nonconductive material not undergoing chemical reaction with an electrolytic solution, such as polypropylene, polyethylene, or polyimide resin.

<FIG> is a sectional view of the rupture induction portion according to the first embodiment of the present invention.

The first rupture induction portion <NUM> may be constituted by a core portion <NUM> and a coating portion <NUM> configured to wrap the core portion in order to minimize a reduction in volume thereof when the rupture induction portion <NUM> comes into strongly tight contact with the inner surface of the cell case <NUM> due to the pressure in the cell case <NUM>.

Here, it is preferable for the core portion <NUM> to be made of a metal material, such as aluminum, and for the coating portion <NUM> to be made of a nonconductive material, such as polypropylene, polyethylene, or polyimide resin, in order to prevent electrical conduction between the core portion <NUM> and the electrode assembly <NUM>.

Of course, it is obvious that the second rupture induction portion <NUM> may be constituted by a core portion and a coating portion, in the same manner as the first rupture induction portion <NUM>.

<FIG> is a sectional view of a part of a secondary battery according to a second embodiment of the present invention.

The second embodiment is identical in construction to the first embodiment described with reference to <FIG> except for the position of the rupture induction portion <NUM>. Hereinafter, therefore, only the different construction will be described.

In the second embodiment, an electrode assembly <NUM> configured in the sequence of a separator <NUM>, a negative electrode <NUM>, a separator <NUM>, and a positive electrode <NUM> in the inward direction from the outermost side is received. At this time, each of a first rupture induction portion <NUM> and a second rupture induction portion <NUM> may be located between a separator <NUM> located at the outermost side of the electrode assembly <NUM> and a negative electrode <NUM> located adjacent to the separator <NUM> located at the outermost side.

Each of the first rupture induction portion <NUM> and the second rupture induction portion <NUM> is inserted into the electrode assembly <NUM> during manufacture of the electrode assembly. In this case, the first rupture induction portion and the second rupture induction portion may be fixed to the electrode assembly without a separate fixing means.

Although the vicinity of each of the first rupture induction portion <NUM> and the second rupture induction portion <NUM> is shown as being empty in <FIG>, this disposition is provided to describe the place at which each of the rupture induction portions is located in more detail, and the negative electrode <NUM> and the separator <NUM> are maintained in tight contact with each other.

<FIG> is a sectional view of a part of a secondary battery according to a third embodiment of the present invention.

The third embodiment is identical in construction to the first embodiment described with reference to <FIG> except for the position of the rupture induction portion <NUM>. Hereinafter, therefore, only the different construction will be described.

In the third embodiment, an electrode assembly <NUM> configured in the sequence of an auxiliary separator <NUM>', a separator <NUM>, a negative electrode <NUM>, a separator <NUM>, and a positive electrode <NUM> in the inward direction from the outermost side is received. At this time, each of a first rupture induction portion <NUM> and a second rupture induction portion <NUM> may be located between an auxiliary separator <NUM>' of the electrode assembly <NUM> and a separator <NUM> located adjacent to the auxiliary separator <NUM>'.

The auxiliary separator <NUM>' is configured to wrap the separator <NUM> located at the outermost side once more in order to improve insulation. In the same manner as in the second embodiment, therefore, each of the first rupture induction portion <NUM> and the second rupture induction portion <NUM> is inserted into the electrode assembly <NUM> during manufacture of the electrode assembly, and the first rupture induction portion and the second rupture induction portion may be fixed to the electrode assembly without a separate fixing means.

In addition, although the vicinity of each of the first rupture induction portion <NUM> and the second rupture induction portion <NUM> is shown as being empty in <FIG>, this disposition is provided to describe the place at which each of the rupture induction portions is located in more detail, and the separator <NUM> and the auxiliary separator <NUM>' are in tight contact with each other.

A plurality of pouch-shaped battery cells may be stacked to constitute a battery module or a battery pack, and these may be used as a power supply source for various kinds of devices, such as an electric vehicle and an energy storage system.

Claim 1:
A pouch-shaped battery cell comprising:
an electrode assembly (<NUM>) comprising a negative electrode (<NUM>), a separator (<NUM>), and a positive electrode (<NUM>); and
a cell case (<NUM>) including a lower case (<NUM>) and an upper case (<NUM>) configured to define a space portion (S) configured to receive the electrode assembly (<NUM>),
a rupture induction portion (<NUM>) configured to induce rupture of the cell case (<NUM>) when pressure in the cell case (<NUM>) increases is provided in the space portion (S) of the cell case (<NUM>),
characterized in that the rupture induction portion (<NUM>) is provided in plural between the electrode assembly (<NUM>) and the inner surface of the lower case (<NUM>) and between the electrode assembly (<NUM>) and the inner surface of the upper case (<NUM>), and in that disposition structures of the rupture induction portions (<NUM>) provided at the inner surface of the lower case (<NUM>) and the inner surface of the upper case (<NUM>) are different from each other.