KR20140050182A - Electrode assembly with improved safety, and battery cell, battery pack and device comprising the same - Google Patents

Abstract

The present invention, in a polymer type battery, relates to an electrode assembly which can prevent the deterioration of a battery by preventing a floating phenomenon of an electrode interface when the swelling of the electrode or a gas is generated due to an increase in the temperature of the electrode in charging and discharging the battery, a battery cell, a battery pack and a device. The present invention provides an electrode assembly which includes at least one unit cell stack body where at least two unit cells which are between separators and located in an anode and a cathode, are stacked; and a thermal contraction member which is not reacted with an electrolyte, a battery cell including the electrode assembly, a battery pack and a device. The thermal contraction member has an upper part where at least the electrode tap of the unit cell stack body is formed, and a lower part which is open, and surrounds both surfaces of the unit cell stack body.

Description

Electrode Assembly with Improved Safety, and Battery Cell, Battery Pack and Device Comprising the Same}

The present invention relates to an electrode assembly used in a lithium secondary battery, a battery cell, a battery pack, and a device including the electrode assembly. More specifically, in a polymer type battery, a battery temperature rises during charging and discharging of the battery. Therefore, the present invention relates to an electrode assembly, a battery cell, a battery pack, and a device capable of suppressing a phenomenon in which an electrode interface is lifted during swelling or gas generation, thereby preventing battery performance deterioration.

Recently, secondary batteries capable of charging and discharging have been widely used as energy sources of wireless mobile devices. In addition, the secondary battery is an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (HEV), and the like, which are proposed as solutions for air pollution of existing gasoline vehicles and diesel vehicles using fossil fuels (Plug-In HEV) and the like.

One or two or four battery cells are used for small mobile devices, whereas medium and large battery modules, which are electrically connected to a plurality of battery cells, are used in medium and large devices such as automobiles due to the necessity of high output capacity.

As mobile devices become lighter and smaller, battery cells used for them are also required to be lighter and thinner. In addition, since the medium-large battery module is preferably manufactured in as small a size and weight as possible, a battery cell that can be charged with high integration and has a small weight for capacity is required.

In this respect, the usage of square batteries, pouch-type batteries, and the like has recently increased. In particular, a pouch-type battery using an aluminum laminate sheet or the like as an exterior member has attracted much attention in recent years due to advantages such as low weight, low manufacturing cost, and easy form deformation.

The pouch type battery is manufactured in a form in which an electrode assembly in which a unit cell having a separator interposed between a positive electrode and a negative electrode is stacked is mounted on a battery case of a laminate sheet.

In addition, such a conventional lithium polymer battery is not excellent in heat dissipation characteristics, there is a problem that the usable time of the battery is shortened. That is, the pouch-shaped exterior material is basically formed with an insulating layer on the surface that degrades the heat dissipation performance, it can not actively respond to the heat generation phenomenon generated during charging and discharging of the battery, and the discharge amount increases with increasing temperature There is a problem that the usable time of the abruptly decreases.

In addition, when the temperature of the battery is higher than the reference temperature according to the heat generation phenomenon of the battery as described above, the electrode assembly or the electrolyte is decomposed, thereby generating a large amount of gas, the exterior material is too easy because the exterior material is ductile It swells, causing a short circuit at the electrode interface, thereby shortening the battery life.

In order to solve such a problem, conventionally, to maintain the shape of the battery through a structural device outside the cell, such as a battery case or a battery pack, it was intended to suppress the electrode lifting phenomenon due to swelling.

For example, Korean Patent Laid-Open Publication No. 2006-0028713 intends to suppress swelling of a battery by bringing a metal plate into close contact with both sides of an inner sheathing material and wrapping the inner and outer sheathing material and the metal plate integrally using an outer sheathing material.

However, there is a limit in suppressing the floating phenomenon of the electrode through the structural device outside the battery. That is, the battery is formed by stacking a plurality of electrode assemblies and a plurality of electrode assemblies in which a plurality of unit cells are stacked. Even if a slight lifting occurs at the electrode interface in each unit cell, the swelling phenomenon in the entire battery becomes large. It is not easy to maintain the shape of the battery as an external exterior material.

The present invention is to suppress the phenomenon that the performance of the battery is deteriorated due to the phenomenon of the interface between the electrodes due to the swelling phenomenon or gas generation during the charge and discharge cycle of the battery to reduce the life of the battery, In addition, by applying a uniform pressure in the inside to suppress the phenomenon of lifting the electrode interface to suppress the deterioration of battery performance.

The present invention relates to an electrode assembly, comprising: one or more unit cell stacks in which two or more unit cells in which an anode and a cathode are positioned with a separator interposed therebetween are stacked; And a heat shrink member that is not reactive with an electrolyte solution, wherein the heat shrink member has an upper end and a lower end formed with at least an electrode tab of the unit cell stack, and surround both surface surfaces and both sides of the unit cell stack. It provides an electrode assembly disposed so as to.

The heat-shrinkable member may have portions of both surfaces and both sides which are adjacent to the upper surface where the electrode tab is present and the lower surface opposite thereto, respectively.

In this case, the electrode assembly may be open in the range of 5 to 20% with respect to half (L / 2) of the total length (L) of the unit cell stack independently of the top and bottom surfaces.

Meanwhile, the heat shrinkable member may have a plurality of through holes formed on a surface thereof.

Further, the heat shrinkable member may be heat shrinked at a temperature in the range of 50 to 80 ° C., and the heat shrinkage member may have a heat shrinkage of 5% or more relative to the total area.

On the other hand, the heat shrink member may be a heat shrink tube.

The heat shrinkable member may be preferably polypropylene, polyethylene, polyethylene terephthalate, polyester or a mixture thereof.

At this time, the heat shrink member is preferably 10 to 40㎛ thickness.

In the present invention, the unit cell stack may be a stack type, a winding type, or a Z folding type stack.

The present invention provides a battery cell including the electrode assembly.

The battery cell may be a lithium ion secondary battery or a lithium ion polymer secondary battery, and may be a battery cell in which the electrode assembly is embedded in a battery case.

The battery case may be a pouch type case.

The present invention provides a battery pack including two or more of the battery cells.

Furthermore, the present invention provides a device including at least one battery cell, wherein the device is a mobile phone, a portable computer, a smartphone, a smart pad, a netbook, a light electronic vehicle (LEV), an electric vehicle, a hybrid electric vehicle, a plug- Phosphorus hybrid electric vehicle, or a power storage device.

According to the present invention, a unit cell stack formed by stacking a plurality of unit cells is wrapped in a heat shrink tube having a property of shrinking with heat to provide a constant pressure to the unit cell stack, thereby providing a constant pressure in the battery during the charge and discharge cycles of the battery. It is possible to suppress the phenomenon that the interface between the electrodes during the swelling or gas generation inside improves the life characteristics of the battery.

1 is a schematic diagram showing an example of a unit cell stack to which the present invention can be applied.
FIG. 2 is a view schematically illustrating an electrode assembly in which a unit cell stack is pressed by using a heat shrink tube according to an embodiment of the present invention on both sides of the unit cell stack.

The present invention is to improve the battery life by preventing the deterioration between the electrodes due to the swelling phenomenon or gas generation during the charge and discharge cycle of the battery to suppress the deterioration of the performance of the battery, the present inventors are formed by stacking unit cells By enclosing the unit cell stack to be a heat shrink member and providing a constant pressure to the unit cell stack, the electrode lifting phenomenon due to gas generation by swelling due to temperature rise inside the battery or decomposition of the electrolyte solution during the charging and discharging cycle of the battery is prevented. It was found that deterioration of the performance of the battery can be prevented by suppressing, and the present invention has been completed.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. The accompanying drawings are intended to illustrate the present invention, and the present invention is not limited thereto.

The electrode assembly of the present invention includes at least one unit cell stack in which two or more unit cells are stacked, and a heat shrink member surrounding the unit cell stack.

The unit cell includes a positive electrode and a negative electrode and a separator positioned between the positive electrode and the negative electrode. In this case, the unit cells may be different from the type of the electrode arrangement on the two sides, such as the anode / cathode, and of course, located on both sides of the unit cell, such as anode / cathode / anode or cathode / anode / cathode The types of electrodes may be the same.

The unit cell stack is formed by stacking the unit cells as described above, and unit cells of the same type may be stacked, or different types of unit cells may be stacked. In this case, it is preferable that one unit cell and an adjacent unit cell are stacked such that different types of electrodes face each other at the boundary of the separator.

The unit cell stack is not particularly limited, but is formed by stacking a plurality of unit cells including an anode, a cathode, and a separator positioned between the anode and the cathode, and a representative example thereof is as shown in FIG. 1. The unit cell stack of the present invention may be a stack type as shown in Figs. 1A and 1B. In addition, the stack and folding type as shown in (C) of FIG. 1 formed by arranging unit cells on one sheet separator film at regular intervals and then folding the sheet separator film in a predetermined direction. and folding type) or Z folding type formed by folding in the zigzag direction.

Further, in the unit cell laminate, as shown in FIG. 1A, both the electrode tabs of the positive electrode and the negative electrode may be formed at the end of the same side, and as shown in FIG. 1B or (C). Electrode tabs of different electrodes may be formed at both ends.

The material of the positive electrode, the negative electrode and the separator of each unit cell is not particularly limited, and may be used without particular limitation in the present invention as long as it is commonly used in the art.

For example, although not limited thereto, the negative electrode may be made of lithium metal, lithium alloy, carbon, petroleum coke, activated carbon, graphite and the like on both surfaces of a negative electrode current collector produced by copper, nickel, copper alloy, The anode active material coated with the same negative electrode active material may be used. The positive electrode may be formed by coating a positive electrode active material such as lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, or the like on both surfaces of a positive electrode current collector made of aluminum, nickel or a combination thereof.

On the other hand, the separator or separator is, for example, a multi-layer film produced by polyethylene, polypropylene having a microporous structure or a combination thereof, polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile or polyvinyl A polymer film for a solid polymer electrolyte or a gel polymer electrolyte, such as a lidene fluoride hexafluoropropylene copolymer, can be used.

As can be seen from FIG. 2, the electrode assembly 10 of the present invention includes a unit cell stack 20 in which two or more unit cells are stacked, and a heat shrink member 30 surrounding a surface of the unit cell stack 20. It includes. Even if the temperature inside the battery rises during the charging and discharging of the battery, the heat contraction member 30 firmly supports the unit cell stack 20 at a constant pressure. By such a pressure, the phenomenon of lifting of the electrode interface due to swelling or gas generation inside the battery can be suppressed, and further life of the battery can be improved.

Generally, during the battery manufacturing process, a high temperature aging process is performed for a long time after the pouring process or the activation process of the electrolyte to improve the wettability of the electrolyte, and the heat shrinkage of the heat shrinkable member 30 can be achieved during the high temperature aging process. This pressurizes the unit cell stack 20.

The high temperature aging process may be carried out in a temperature range of 50 to 80 ℃. Thus, for example, it is preferable that the heat shrinkage member 30 undergoes heat shrinkage at 50 to 80 ° C. When shrinking at too low a temperature may not be easy to handle during the battery manufacturing process due to excessively sensitive heat shrinkage, if the shrinkage at too high temperature will increase the heat treatment temperature for such shrinking, which can burden the battery. have.

It is preferable that the heat shrinkable member 30 shrinks at a constant rate in the temperature range. For example, as long as it has a heat shrinkage rate of 5% or more with respect to the total area of the heat shrinkable member 30, it can be suitably used in the present invention. In the case of having a heat shrinkage of less than 5%, sufficient pressure cannot be applied to the unit cell laminate 20, and it may be insufficient to suppress the electrode lift phenomenon. In the case of having too much heat shrinkage, the pressure applied to the unit cell stack 20 may be applied, which may cause deformation of the unit cell stack 20. More preferably, the heat shrinkage does not exceed 15%. It is preferable.

In consideration of the heat treatment temperature for the heat shrinkage and the heat shrinkage rate of the heat shrinkable member 30, the length of the heat shrinkable member 30 surrounding the unit cell stack 20 may be somewhat relaxed. This can induce impregnation of the electrolyte solution into the electrode.

It is preferable that the heat-shrinkable member 30 has no reactivity with the electrolyte solution. For example, a thermoplastic resin having no reactivity with the electrolyte solution may be used, and specifically, polypropylene, polyethylene, polyethylene terephthalate, polyester, or the like may be used.

The heat shrinkable member 30 is not particularly limited but preferably has a thickness in the range of 10 to 40 μm. If the thickness of the heat shrinkable member 30 outside the above range is thinner, the tensile strength may not be sufficient. On the other hand, when the thickness of the heat-shrinkable member 30 is too thick, there is a possibility that the overall thickness of the battery may be increased. Therefore, the thickness is preferably limited to the above range.

Such a heat shrinkable member 30 is not particularly limited so that the electrode assembly 10 accommodated therein can prevent the electrode from being lifted due to swelling or gas generation during battery reaction. For example, 3 MPa It is desirable to have a tensile strength value of from 20 MPa.

As shown in FIG. 2, the heat-shrinkable member 30 has four upper and lower sides and two sides of the surface of the unit cell stack 20 except for the upper end of the unit cell stack 20 to which the electrode tabs are connected and the lower end thereof. It may be formed to surround the face. By covering the four surfaces of the unit cell stack 20 in this manner, a predetermined pressure due to heat shrinkage can be applied to the unit cell stack 20, and the lifting phenomenon of the electrode interface during the charge / discharge cycle of the battery can be suppressed. .

On the other hand, the heat shrinkable member 30 may be opened without wrapping the cross section and the edge portion of the upper portion and at the opposite bottom where the at least one electrode tab is present. In this way, the electrolyte solution impregnation into the electrode assembly 10 can be smoothly achieved through the open portions at both ends. For example, the heat shrinkable member 30 surrounds the central portion in the longitudinal direction of the unit cell stack 20, and an area open at one end thereof is half of the total length L of the unit cell stack 20 ( L / 2) may be from about 5 to 20%. In this case, the open area may be open at both ends with the same length, and the open length may not be the same.

In the heat shrinkable member 30 of the present invention, a plurality of through holes may be formed on a front surface thereof. Such a through hole is formed in the heat shrinkable member 30, so that the electrolyte solution can be more easily impregnated. The size of the through hole is not particularly limited as long as it is capable of flowing the electrolyte for impregnation of the electrolyte, and does not disadvantageously provide a constant pressure to the unit cell stack 20 by thermal contraction. In this case, the heat shrinkable member 30 may cover the four surfaces of the unit cell stack 20 as a whole.

In addition, the heat shrink member 30 is preferably a heat shrink tube. More preferably, when stacking a plurality of electrode assemblies to increase the capacity of the battery cell, the heat shrink tube does not have a weld line in order to maintain equilibrium and to prevent breakage of the heat shrink member 30 due to shrinkage. It is preferable.

The electrode assembly may include a single unit cell stack 20 in which a plurality of unit cells are stacked in the heat shrink member 30, and a plurality of unit cell stacks 20 in which two or more such uncell stacks are stacked. Can be.

Compared to the case of using a structural means for preventing the deformation of the battery outside the conventional battery, as in the present invention, the inside of the battery, that is, the unit cell laminated body 20 is surrounded by the heat shrink member 30 As a result, it is possible to more effectively suppress the phenomenon of the electrode interface caused by the temperature rise and the gas generation due to the charge and discharge cycles of the battery, thereby further improving the safety of the battery, thereby preventing deterioration of the battery performance.

The battery cell can be manufactured using the electrode assembly 10 obtained by the present invention as described above. The battery cell can be obtained by embedding the electrode assembly 10 according to the present invention inside the battery case and injecting the electrolyte solution. In this case, the electrode assembly 10 embedded in the battery case may be one electrode assembly surrounding the unit cell stack 20 with the heat shrinkable member 30, and may be two or more.

A specific method of manufacturing the battery cell by embedding the electrode assembly 10 in the battery case is not particularly limited, and a method commonly used in the art may be suitably applied in the present invention.

In this case, the battery case may be a pouch type case and may have a shape corresponding to the shape of the electrode assembly 10, but is not particularly limited.

Meanwhile, the pouch-type case may be formed of a laminate sheet. The laminate sheet may include an outermost resin layer forming an outermost layer, a barrier metal layer for preventing penetration of a material, and an inner resin layer for sealing, It is not.

In addition, the battery case preferably has a structure in which an electrode lead for electrically connecting the electrical terminals of the unit cells of the electrode assembly 10 is exposed to the outside, and although not shown, electrode leads are disposed on upper and lower surfaces of the electrode lead. Insulation film to protect the can be attached.

On the other hand, the battery cell is not limited to this, for example, preferably may be a lithium ion battery or a lithium ion polymer battery.

The battery cell obtained by the method of the present invention as described above may be used alone, or may be used in the form of a battery pack including two or more battery cells. The battery cell and / or the battery pack of the present invention may be used in various devices such as a mobile phone, a portable computer, a smart phone, a smart pad, a netbook, a LEV (Light Electronic Vehicle), an electric vehicle, a hybrid electric vehicle, Electric vehicles, electric power storage devices, and the like.

10: electrode assembly
20: unit cell stack
30: heat shrinkable member

Claims (17)

One or more unit cell stacks in which two or more unit cells in which an anode and a cathode are positioned with a separator interposed therebetween are stacked; And
And a heat shrink member that is not reactive with an electrolyte solution, wherein the heat shrink member is disposed so that at least upper and lower ends of at least electrode tabs of the unit cell stack are formed and surround both surfaces and both sides of the unit cell stack. The electrode assembly.
2. The electrode assembly of claim 1, wherein the heat shrinkable member has open portions on both surfaces and portions adjacent to the upper surface on which the electrode tab is present and the lower surface on the opposite side, respectively.
The electrode assembly of claim 2, wherein the top and bottom surfaces are independently open in a range of 5 to 20% relative to half (L / 2) of the total length (L) of the unit cell stack.
The electrode assembly of claim 1, wherein the heat contraction member has a plurality of through holes formed on a surface thereof.
The electrode assembly of claim 1, wherein the heat shrink member is heat contracted at a temperature in a range of 50 to 80 ° C., and the heat shrink rate is 5% or more relative to the total area.
The electrode assembly of claim 1, wherein the heat shrink member is a heat shrink tube.
The electrode assembly of claim 1, wherein the heat shrinkable member is polypropylene, polyethylene, polyethylene terephthalate, polyester, or a mixture thereof.
The electrode assembly of claim 1, wherein the heat shrinkable member has a thickness of 10 to 40 μm.
The electrode assembly of claim 1, wherein the heat shrinkable member has a tensile strength of 3 to 20 MPa.
The electrode assembly of claim 1, wherein the unit cell stack is a stack of a stack type, a winding type, or a Z folding type.
A battery cell comprising the electrode assembly of any one of claims 1 to 10.
The battery cell of claim 11, wherein the battery cell is a lithium ion secondary battery or a lithium ion polymer secondary battery.
The battery cell of claim 11, wherein the electrode assembly is embedded in a battery case.
The battery cell of claim 13, wherein the battery case is a pouch type case.
A battery pack comprising two or more battery cells of claim 11.
A device comprising at least one battery cell of claim 11.
17. The device of claim 16, wherein the device is a mobile phone, a portable computer, a smart phone, a smart pad, a netbook, a LEV (Light Electronic Vehicle), an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or a power storage device.

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