KR101515778B1 - Secondary Battery of Novel Structure - Google Patents

Abstract

The present invention relates to a secondary battery in which an electrode assembly is housed in a storage portion of a pouch-shaped battery case, the secondary battery comprising: an electrode assembly comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; The electrode assembly may include a battery case that is deformable in a shape that attenuates the external force when applied. When the external force is a bending moment, the electrode assembly may be bent to correspond to the external force, The secondary battery includes at least one secondary battery.

Description

[0001] The present invention relates to a secondary battery of a secondary battery,

More particularly, the present invention relates to an electrode assembly comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and an electrode assembly including the electrode assembly, Wherein the electrode assembly includes at least one uncoated portion that is not coated with an electrode active material so that the electrode assembly can be bent in response to the external force when the external force is a bending moment, And a secondary battery.

As technology development and demand for mobile devices are increasing, the demand for batteries as energy sources is rapidly increasing, and accordingly, a lot of researches on batteries capable of meeting various demands have been conducted.

Typically, in terms of the shape of a battery, there is a high demand for a prismatic secondary battery and a pouch-type secondary battery which can be applied to products such as mobile phones with a small thickness, and has advantages such as high energy density, discharge voltage, There is a high demand for lithium secondary batteries such as lithium ion batteries and lithium ion polymer batteries.

In addition, the secondary battery is classified according to the structure of the anode assembly, the cathode assembly, and the electrode assembly having the separator structure sandwiched between the anode assembly and the cathode assembly. Typically, (Stacked) electrode assembly in which a plurality of positive electrodes and negative electrodes cut in a unit of a predetermined size are sequentially stacked with a separator interposed therebetween, a jelly-roll (wound type) electrode assembly having a structure A stack / folding type electrode assembly having a structure in which a bi-cell or a full cell stacked with a separator interposed between an anode and a cathode of a unit is wound with a separator or the like can be given.

Recently, a pouch-shaped battery having a structure in which a stacked or stacked / folded electrode assembly is embedded in a pouch-shaped battery case of an aluminum laminate sheet is attracting much attention due to low manufacturing cost, small weight, Its usage is also gradually increasing.

In this regard, FIG. 1 is a schematic vertical cross-sectional view illustrating a state in which an electrode assembly is inserted into a conventional battery cell.

Referring to FIG. 1, an electrode assembly of a battery cell 10 includes a plurality of electrode layers each composed of a cathode 2, an anode 1, and a separator.

A plurality of electrode tabs 4 protruding from the anode 1 and the cathode 2 are connected to the electrode leads 6 in the form of a welded portion integrally joined by welding, for example. The electrode leads 6 are sealed by the battery case 5 in such a state that the opposite end portions to which the positive electrode and the negative electrode tab weld portions are connected are exposed.

The upper end of the battery case 5 is spaced apart from the upper end surface of the electrode assembly by a certain distance and the electrode tabs 4 of the welded portion are formed in a substantially V- . An insulating film 8 is attached to a portion of the upper and lower surfaces of the electrode lead 6 in order to increase the degree of sealing with the battery case 5 and at the same time to ensure an electrically insulated state.

However, since the structure of such an electrode assembly is formed in a state in which the positive electrode, the separator, and the negative electrode are stacked in the longitudinal direction as described above, it is difficult to use the electrode assembly as a power source for a display device which can be elastically warped.

Therefore, there is a high need for a technology that can fundamentally solve these problems.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and the technical problems required from the past.

The present inventors have conducted intensive research and various experiments, and have found that, in a secondary battery in which an electrode assembly is built, the electrode assembly and the battery case are configured to be deformable into a shape attenuating an external force, It was confirmed that a battery cell can be produced, and the present invention has been accomplished.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a rechargeable battery including: an electrode assembly including a cathode, a cathode, and a separator interposed between the anode and the cathode; Wherein the electrode assembly includes at least one uncoated portion that is not coated with an electrode active material so that the electrode assembly can be bent in response to the external force when the external force is a bending moment, Structure.

The secondary battery according to the present invention has a structure in which the battery case and the electrode assembly are deformable, so that the secondary battery can be easily bent in a desired direction.

In the secondary battery according to the present invention, the battery case is not particularly limited as long as the battery case can be deformed to attenuate an external force upon application of an external force. Preferably, the battery case may include a laminate sheet including a metal layer and a resin layer.

More specifically, it may be a pouch-shaped case having a housing portion in which an electrode assembly can be mounted on a pouch-shaped case of an aluminum laminate sheet. The battery case of such a laminate sheet is sealed by, for example, thermal fusion after mounting the electrode assembly on the housing part.

In one preferred example, the uncoated portion is positioned within a range of 0 to 35%, more preferably 0 to 30% with respect to the length of the battery with respect to the center point of the electrode assembly in the electrode terminal direction (longitudinal direction of the battery) can do. In the above, the position of 0% means the center position of the electrode assembly.

Specifically, since the need for bending the battery is generally required around the center of the battery, the uncoated portion is formed at a position exceeding 35% of the length of the battery with respect to the center of the battery, that is, If so, it may be difficult to meet such a demand.

In another preferred embodiment, the width of the uncoated portion may be about 5 to about 50% of the width of the electrode terminal in the coated portion coated with the electrode active material.

Specifically, when the width of the uncoated portion is less than 5% based on the width of the electrode terminal, the desired secondary battery can not be easily bent, and if it exceeds 50%, the overall battery capacity becomes small.

In yet another example, the width of the uncoated portion may be between 1 and 5 mm.

Specifically, if the width of the uncoated portion is less than 1 mm, bending of a desired secondary battery can not be easily performed, and if the width is more than 5 mm, the overall battery capacity becomes small.

In some cases, the width of the uncoated portion may be varied depending on the number of stacked unit cells.

For example, when the number of stacked unit cells is 5, the width of the uncoated portion may be 2 mm, and as the number of stacked unit cells increases, the width of the uncoated portion increases. As the number of stacked unit cells decreases, The width of the coated portion can be reduced.

The electrode assembly may have a stack / folding structure in which unit cells such as a stack cell, a folding cell, or a pull cell or a bicell are wound in a separation film. That is, a stacked structure in which a plurality of electrode plates are laminated with a separator being formed, a folded structure in which a plurality of electrode plates are folded in a state in which a separator is formed, or a stack / folding structure may be used. .

Preferably, in the electrode stacked structure of the electrode assembly, the uncoated portion is formed in each of the stacked electrodes, and the stacked electrodes may have the same size in the stacked up and down directions.

The bending angle of the electrode assemblies in the above structure can be adjusted as needed.

As one example, the uncoated portions of the stacked electrodes are formed at the same position in the vertical direction, so that the bending angle of the electrode assembly can be increased.

As another example, the uncoated portions in the respective stacked electrodes are formed at the alternate positions in the up-and-down direction, so that the overall bending form of the electrode assembly can be made smooth. That is, the uncoated portion may be formed at a position where the electrode active material is alternated in the vertical direction of the anode or the anode current collector of the laminated electrode.

In some cases, each of the laminated electrodes is composed of two uncoated portions, so that primary bending and secondary bending can be achieved by two uncoated portions.

Meanwhile, the electrode assembly may have a structure in which two or more unit cells are wound by a separation film.

Preferably, the number of unit cells may be 3 to 15.

As a specific example, the middle- or large-sized secondary cell has a structure in which 12 to 15 unit cells are stacked, and the small secondary cell may have a structure in which 3 to 11 unit cells are stacked.

Meanwhile, the secondary battery according to the present invention can be suitably applied to a so-called lithium ion polymer battery in which a lithium-containing electrolyte is impregnated with an electrode assembly in the form of a gel.

The lithium ion polymer battery comprises an anode, a cathode, a separator, and an electrolyte in the form of a solid or a gel.

The anode may be prepared, for example, by applying a slurry prepared by mixing a cathode mixture to a solvent such as NMP, and then drying and rolling the cathode slurry.

In addition to the positive electrode active material, the positive electrode mixture may optionally include a conductive material, a binder, a filler, and the like.

The cathode active material is a material capable of causing an electrochemical reaction. Examples of the lithium transition metal oxide include lithium cobalt oxide (LiCoO ₂ ) containing two or more transition metals and substituted with one or more transition metals, lithium Layered compounds such as nickel oxide (LiNiO ₂ ); Lithium manganese oxide substituted with one or more transition metals; Formula _{LiNi 1-y M y O 2} ( where, M = Co, Mn, Al , Cu, Fe, Mg, B, Cr, Zn or Ga and Lim, 0.01≤y≤0.7 include one or more elements of the element) A lithium nickel-based oxide represented by the following formula: _{Li 1 + z Ni 1/3 Co 1/3} Mn 1/3 O 2, Li 1 + z Ni 0 .4 Mn 0 .4 Co 0 .2 O 2 Li , such as _{1 + z Ni b Mn c Co} 1 - _{(b + c + d)} M _d O _(2-e) A _e B + c &lt; = 0.8, 0.1? C? 0.8, 0? D? 0.2, 0? E? 0.2, b + c + d <1, M = Al, Mg, Cr , Ti, Si or Y and A = F, P or Cl); And the formula _{Li 1 + x M 1-y} M 'y PO 4-z X z ( wherein, M = a transition metal, preferably Fe, Mn, Co or Ni, M' = Al, Mg or Ti, X = F, S or N, and -0.5? X? +0.5, 0? Y? 0.5, and 0? Z? 0.1), but the present invention is not limited thereto.

The conductive material is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture including the cathode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The binder is a component which assists in bonding of the active material and the conductive material and bonding to the current collector, and is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture containing the cathode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, and various copolymers.

The filler is optionally used as a component for suppressing the expansion of the electrode, and is not particularly limited as long as it is a fibrous material without causing any chemical change in the battery. Examples of the filler include olefin-based polymerizers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

The cathode current collector is generally made to have a thickness of 1 to 300 mu m. Such a positive electrode collector is not particularly limited as long as it has conductivity without causing chemical change to the battery, and may be formed on the surface of stainless steel, aluminum, nickel, titanium, sintered carbon or aluminum or stainless steel Carbon, nickel, titanium, silver, or the like may be used. The current collector may have fine irregularities on the surface thereof to increase the adhesive force of the cathode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

The negative electrode is prepared, for example, by applying a negative electrode mixture containing a negative electrode active material on a negative electrode collector and then drying the same. The negative electrode mixture may contain a conductive material, a binder, a filler, May be included.

Examples of the negative electrode active material include carbon and graphite materials such as natural graphite, artificial graphite, expanded graphite, carbon fiber, non-graphitizable carbon, carbon black, carbon nanotube, fullerene and activated carbon; Metals such as Al, Si, Sn, Ag, Bi, Mg, Zn, In, Ge, Pb, Pd, Pt and Ti which can be alloyed with lithium and compounds containing these elements; Complexes of metals and their compounds and carbon and graphite materials; Lithium-containing nitrides, and the like. Among them, a carbon-based active material, a silicon-based active material, a tin-based active material, or a silicon-carbon based active material is more preferable, and these may be used singly or in combination of two or more.

The negative electrode collector is generally made to have a thickness of 1 to 300 mu m. The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery. Examples of the negative electrode current collector include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel Surface-treated with carbon, nickel, titanium, silver or the like, aluminum-cadmium alloy, or the like can be used. In addition, like the positive electrode collector, fine unevenness can be formed on the surface to enhance the bonding force of the negative electrode active material, and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams and nonwoven fabrics.

The separation membrane is interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally 0.01 to 10 mu m and the thickness is generally 1 to 200 mu m. Such separation membranes include, for example, olefinic polymers such as polypropylene, which are chemically resistant and hydrophobic; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like is used. When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane. The separation membrane may be a multilayer film produced by a polyethylene film, a polypropylene film, or a combination of these films, a polyvinylidene fluoride, a polyethylene oxide, a polyacrylonitrile, A polyvinylidene fluoride hexafluoropropylene copolymer, or a polymer film coated with a gel-type polymer electrolyte.

As described above, the secondary battery according to the present invention has a structure in which the electrode assembly includes the uncoated portion and the battery case is deformable into a shape attenuating the external force, so that it can be easily bent at a predetermined angle.

1 is a vertical sectional view showing a state in which an electrode assembly is inserted into a conventional battery cell;
2 is an exploded perspective view of a pouch type secondary battery to which an uncoated portion according to an embodiment of the present invention is applied;
3 is a partial vertical sectional view showing the inside of an electrode assembly in a secondary battery according to another embodiment of the present invention;
4 is a partial vertical cross-sectional view illustrating the inside of an electrode assembly in a secondary battery according to another embodiment of the present invention;
5 is a vertical cross-sectional view of a secondary battery according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited by the scope of the present invention.

2 is an exploded perspective view of a pouch type secondary battery to which an uncoated portion according to an embodiment of the present invention is applied.

Referring to FIG. 2, the pouch type secondary battery 100 includes an electrode assembly 30 having two uncoated portions 200 that are not coated with an electrode active material, electrode tabs 30 extending from the electrode assembly 30, The electrode leads 60 and 70 welded to the electrode tabs 40 and 50 and the electrode assembly 30 accommodating the electrode assemblies 40 and 50 and deformable into a shape attenuating the external force when external force is applied, (20).

The electrode assembly 30 is a power generation element in which an anode and a cathode are sequentially stacked with a separation membrane interposed therebetween and an uncoated portion 200 is formed in an electrode terminal direction (longitudinal direction of the battery) have. That is, when the external force of the bending moment is applied by the uncoated portion 200, the electrode assembly 30 deforms at the same time as the battery case 20 so as to attenuate it.

The electrode tabs 40 and 50 extend from each electrode plate 30 of the electrode assembly 30 and the electrode leads 60 and 70 are connected to a plurality of electrode tabs 40 and 50 extending from each electrode plate, Respectively, and a part of the battery case 20 is exposed to the outside. An insulating film 80 is attached to portions of the upper and lower surfaces of the electrode leads 60 and 70 in order to increase the degree of sealing with the battery case 20 and at the same time to secure an electrically insulated state.

The battery case 20 is made of an aluminum laminate sheet including a resin layer and a metal layer, and provides a space for accommodating the electrode assembly 30, and has a pouch shape as a whole.

In the stacked electrode assembly 30, the upper end of the battery case 20 is connected to the electrode assembly 60 (or 70) so that a plurality of the positive electrode tabs 40 and the plurality of negative electrode tabs 50 can be coupled together. 30).

FIG. 3 is a partial vertical cross-sectional view illustrating the inside of an electrode assembly in a secondary battery according to another embodiment of the present invention.

3, the secondary battery 100a includes an electrode assembly 30a including an anode, a cathode, a separator interposed between the anode and the cathode, and an electrode assembly 30a formed by stacking a plurality of layers, 30a and a battery case 20a which can be deformed to attenuate the external force when an external force is applied.

In addition, when the external force is a bending moment, two uncoated portions 200a are formed on the electrode assembly 30a so that the electrode assembly 30a can be bent corresponding to the external force.

Specifically, the electrode assembly 30a includes a cathode 110 coated with a cathode active material on the upper and lower surfaces of the cathode current collector, a cathode 120 coated with an anode active material on the upper and lower surfaces of the anode current collector, and a separator 130 A plurality of stacked electrodes are stacked.

Uncoated portions (200a) is formed at a position of about 25%, based on the center point (A) of the electrode assembly (30a) with respect to the longitudinal direction (W ₁₎ of the cell of the electrode terminal direction.

Further, the width (W ₂₎ of the non-coated portions (200a) are formed to a size of about 30%, based on the electrode tab direction in the coating unit (W ₃₎ which is coated electrode coating.

The uncoated portions 200a are formed in the stacked electrodes 110 and 120 in the structure in which the electrodes of the electrode assembly 30a are laminated and have the same size in the stacked up and down directions.

The uncoated portions 200 are formed at the same positions in the vertical direction H in the respective laminated electrodes 110 and 120 so that the secondary battery 100c in the direction of the arrow And is easily bent at a predetermined angle due to an external bending momentum.

FIG. 4 is a schematic vertical cross-sectional view of a portion of an electrode assembly in a secondary battery according to another embodiment of the present invention.

4, except that the uncoated portions 200b are formed at the alternate positions in the vertical direction H in the stacked electrodes 112 and 122, a detailed description thereof will be omitted. Is omitted.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.

Claims (13)

An electrode assembly comprising an anode, a cathode, and a separator interposed between the anode and the cathode, and a battery case containing the electrode assembly and deformable into a shape that attenuates the external force upon application of an external force,
Wherein the electrode assembly includes at least one uncoated portion that is not coated with an electrode active material so that the electrode assembly may be bent in response to the external force when the external force is a bending moment,
The electrode assembly has a stacked structure or a stack / folding structure in which unit cells of a pull cell or a bi-cell are wound in a separation film,
In the structure in which the electrodes of the electrode assembly are laminated, the uncoated portions are formed on the respective laminated electrodes, have the same size in the stacked up and down directions,
Wherein the uncoated portions of the stacked electrodes are formed at alternate positions in the vertical direction. The secondary battery according to claim 1, wherein the battery case comprises a laminate sheet including a resin layer and a metal layer. The secondary battery according to claim 1, wherein the uncoated portion is located within a range of 0 to 35% with respect to the length of the battery with respect to the center point of the electrode assembly in the electrode terminal direction (the longitudinal direction of the battery). The secondary battery according to claim 1, wherein a width of the uncoated portion is 5 to 50% of a width of the coating portion coated with the electrode active material, the width of the uncoated portion being in the direction of the electrode terminal. The secondary battery according to claim 1, wherein the uncoated portion has a width of 1 to 5 mm. delete delete The secondary battery according to claim 1, wherein the uncoated portions of the stacked electrodes are formed at the same position in the vertical direction. delete The secondary battery according to claim 1, wherein each of the laminated electrodes includes two uncoated portions. The secondary battery according to claim 1, wherein the electrode assembly has a structure in which two or more unit cells are wound by a separation film. The secondary battery according to any one of claims 1 to 11, wherein the number of the unit cells is 3 to 15. The secondary battery according to claim 1, wherein the secondary battery is a lithium ion polymer battery.

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