KR101553551B1 - Electrode Assembly of Excellent Productivity and Battery Cell Comprising the Same - Google Patents

Abstract

The present invention is characterized in that an electrode assembly wound with a separator interposed between a positive electrode and a negative electrode coated with an electrode active material is mounted inside a battery case, and a binder layer or a binder- Wherein the separator winding part is wound around the winding center of the electrode assembly and the binder layer or the binder-inorganic compound mixed layer is not coated on the winding center of the electrode assembly. to provide.

Description

[0001] The present invention relates to an electrode assembly having improved productivity and a secondary battery including the electrode assembly.

The present invention relates to an electrode assembly having improved productivity and a secondary battery including the electrode assembly. More particularly, the present invention relates to an electrode assembly in which an electrode assembly is wound with a separator interposed between a positive electrode and a negative electrode coated with an electrode active material, And a binder layer or a binder-inorganic mixed layer is discontinuously formed on one side or both sides of the separator, and a binder layer or a binder-inorganic mixed layer is not coated on the winding center of the electrode assembly. The separator winding portion is wound around the battery cell.

2. Description of the Related Art As technology development and demand for mobile devices have increased, there has been a rapid increase in the demand for secondary batteries capable of charging and discharging as energy sources, and accordingly, a great deal of research has been conducted on secondary batteries that can meet various demands. 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.

Accordingly, the types of applications using secondary batteries are diversifying due to the advantages of secondary batteries, and it is expected that secondary batteries will be applied to more fields and products in the future.

The rechargeable battery includes a jelly-roll (wound type) electrode assembly having a structure in which an anode assembly having a positive electrode / separator / cathode structure is wound, a long sheet type anode and a cathode are wound with a separator interposed therebetween, Stacked type electrode assembly in which a plurality of positive electrodes and negative electrodes cut in size are sequentially stacked with a separator interposed therebetween, and a stack / folding type electrode assembly that is a mixed type of the jelly-roll type and stack type do. Among them, the jelly-roll type (wound type) electrode assembly has an advantage of being easy to manufacture and having a high energy density per weight.

The jelly-roll type electrode assembly is manufactured by winding a separator between a cathode sheet coated with a positive electrode active material on an aluminum foil and a negative electrode sheet coated with a negative electrode active material on a copper foil, and wound round. The winding is performed by winding the separator first on a mandrel, and winding the positive electrode sheet and the negative electrode sheet together.

In general, the jelly-roll type electrode assembly has a single-sided coating portion having different application starting points of an electrode mixture containing an electrode active material for attaching an electrode tab for electrical connection to an electrode terminal of a battery case. In this case, due to the expansion and contraction of the electrode active material generated in the course of charging / discharging of the battery, unevenness of stress caused in the one-side coating portion of the electrode occurs depending on whether the electrode active material is applied or not, If the limit is exceeded, cracks are generated in the foil, the performance of the battery is rapidly deteriorated, and in some cases, the safety of the battery such as a short circuit or an internal short circuit is threatened.

Particularly, this phenomenon frequently occurs in a relatively large portion of the bending rate in the winding process of the jelly-roll type electrode assembly.

Further, in the process of taking out the jelly-roll wound up after the end of the winding process from the winding core, the jelly-roll core portion may be detached or the jelly-roll and the winding core may be fixed.

Therefore, there is a high need for a technique capable of fundamentally solving such 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.

That is, an object of the present invention is to provide a separator, in which coating layers coated on one side or both sides of a separator with a binder layer or a binder-inorganic mixed layer are formed, and a binder layer or a binder- It is possible to prevent not only the crack of the electrode due to the unevenness of the stress frequently occurring during charging and discharging but also the internal short circuit and the reduction of the capacity of the battery, The present invention also provides a battery cell that can further improve the performance of the battery cell.

It is still another object of the present invention to provide a structure capable of reducing the material cost and reducing the occurrence of defects during the winding-out process for manufacturing an electrode assembly by applying the electrode assembly having a specific structure to the battery cell, Of the battery cell.

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 battery cell comprising: a battery case having an electrode assembly wound with a separator interposed between a positive electrode and a negative electrode coated with an electrode active material,

Coating layers on which a binder layer or a binder-inorganic mixed layer is discontinuously coated are formed on one side or both sides of the separator,

And the separator winding portion on which only the separator, which is not coated with the binder layer or the binder-inorganic material mixed layer, is wound around the winding center of the electrode assembly.

Therefore, the battery cell according to the present invention is characterized in that the coating layer is formed by coating a binder layer or a binder-inorganic mixed layer on one side or both sides of the separator discontinuously, and a binder layer or a binder- By applying the structure in which only the separator not coated with the inorganic mixed layer is wound to the battery cell, it is possible to prevent cracking of the electrode due to stress imbalance frequently occurred during charging and discharging and to reduce the coating area of the binder layer or the binder- (Jelly-roll) can be safely taken out of the core without occurrence of defects, thereby achieving improved production efficiency.

As a specific example, the electrode assembly has a horizontal cross-section and a major axis length of 1.5 to 30 times the minor axis length, and a portion of the separation membrane on which the coating portions are not formed is shortened Lt; / RTI >

Specific examples of the battery case for housing the electrode assembly having such a structure include a pouch-shaped case of a rectangular metal can or a laminate sheet. As a more specific example, the prismatic metal can can be a structure including a cylindrical or rectangular can and a cap mounted on the open upper end of the can. Among them, a battery case based on a square can having a large bending rate at a shortened portion may be more preferable.

As a further specific example, the coating portions may be arranged in a pattern at regular intervals on the separation membrane, and the portion of the separation membrane on which the coating portions are not formed may have a relatively higher flexion ratio than the other portions in the winding process of the electrode assembly As shown in FIG.

Therefore, the electrode assembly having such a structure can prevent not only cracking of the electrode due to unevenness of stress frequently occurring during charging and discharging, but also prevention of short-circuit, internal short-circuit, capacity reduction of the battery, and the like.

As another specific example, the total coating length of the coating portions may be 100 to 150% of the coating length of the electrode active material applied to the cathode.

As described above, the binder portion or the binder-inorganic material mixed layer is discontinuously coated on the coating portion on one side or both sides of the separation membrane.

The coating portion of such a separation membrane is prepared, for example, by coating inorganic particles or inorganic particles and a binder polymer on a polyolefin-based separation membrane base material. In addition to the pore structure contained in the separation membrane base material itself, an interstitial volume ) Having a uniform pore structure.

The use of a separation membrane containing such a coating can suppress an increase in thickness of the cell due to swelling at the time of chemical conversion as compared with the case where a conventional separation membrane is used, The polymer can be used as an electrolyte when a polymer capable of gelation is used as a binder polymer component when a liquid electrolyte is impregnated.

In addition, a large number of uniform pore structures are formed in both the coating part and the polyolefin-based separator film substrate. Since the lithium ions are smoothly transferred through these pores and a large amount of electrolytic solution is filled to exhibit a high impregnation rate, Improvement can be achieved.

Furthermore, since the separation membrane including the coated portion does not cause high temperature thermal shrinkage due to the heat resistance of the inorganic particles, even if the separator ruptures in the battery due to an excessive condition due to internal or external factors such as high temperature, , It is difficult for both electrodes to be short-circuited completely, and even if a short circuit occurs, the short-circuited region is prevented from being greatly enlarged, thereby improving the safety of the battery.

The inorganic particles are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles usable in the present invention are not particularly limited as long as the oxidation and / or reduction reaction does not occur in the operating voltage range of the applied battery (for example, 0 to 5 V based on Li / Li +). Particularly, when inorganic particles having an ion-transporting ability are used, the ion conductivity in the electrochemical device can be increased and the performance can be improved. Therefore, it is preferable that the ionic conductivity is as high as possible. In addition, when the inorganic particles have a high density, it is difficult to disperse the particles at the time of coating, and there is a problem of an increase in weight during the production of the battery. In the case of an inorganic substance having a high dielectric constant, dissociation of an electrolyte salt, for example, a lithium salt, in the liquid electrolyte also contributes to increase ionic conductivity of the electrolyte.

For these reasons, the inorganic particles are preferably high-permittivity inorganic particles having a dielectric constant of 5 or more, preferably 10 or more, inorganic particles having piezoelectricity, inorganic particles having lithium ion transferring ability, or a mixture thereof .

The binder may be a conventional polymer, and in particular, may have a glass transition temperature (Tg) as low as possible, and specifically may be in the range of -200 to 200 ° C. This is because the mechanical properties such as flexibility and elasticity of the final film can be improved. The polymer faithfully fulfills the role of a binder to connect and stably fix inorganic particles and particles, inorganic particles and the surface of the separator substrate, and a portion of the separator, and thereby prevents the deterioration of the mechanical properties of the finally prepared separator.

In addition, although the binder polymer does not necessarily have ion conductivity, the performance of the electrochemical device can be further improved by using a polymer having ion conductivity. Therefore, it is preferable that the binder polymer has a high permittivity constant.

Examples of usable binder polymers include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-cotylchlorethylene, polymethylmethacrylate, Polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate (cellulose acetate), cellulose acetate Cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxypropylmethylcellulose, hydroxypropylmethylcellulose, Cyanoethyl Acrylonitrile-styrene-butadiene copolymer, polyimide, or a mixture thereof, and the like may be used in combination. The term " thermosetting resin " However, it is not limited thereto, and any material including the above-mentioned characteristics may be used alone or in combination.

In one specific example, the binder layer or the binder-inorganic mixed layer may further include a dye or pigment to develop hue in a visible light, an infrared light, or an ultraviolet wavelength region.

Therefore, the coating part made of the binder layer or the binder-inorganic mixed layer is identifiable by the uncoated part and the naked eye or the camera reading device.

The coating portion having such a characteristic can be controlled to be located at a specific site by a control device equipped with a camera reading device in the course of winding the electrode assembly. Specifically, the portion where the coating portions are not formed can be controlled so that the bending rate of the electrode assembly is located at a relatively larger portion than the other portions.

Therefore, the electrode assembly according to the present invention can be manufactured by precisely controlling the non-continuously coated portions to be positioned at certain portions of the electrode assembly, thereby reducing the occurrence of defective products and improving the production efficiency.

The amount of the dye or pigment to be added is not particularly limited as long as the color can be expressed. For example, it may be 0.01 to 10%, more specifically 0.02 to 5%, based on the total weight of the coating portion.

Materials capable of expressing color in the wavelength range of the above conditions are easily selected or available to those skilled in the art, and a detailed description thereof will be omitted in this specification.

The separator winding portion located at the winding center of the electrode assembly may be, for example, a structure in which only the separator is wound 1 to 10 times. As described above, the separation membrane wind-up portion is a winding portion of the separation membrane that is not coated with the binder layer or the binder-inorganic mixed layer. Therefore, the possibility that the jelly-roll that has been wound is finished is remarkably reduced, and the incidence of defects such as the deviation of the center of the electrode assembly in the process of taking out the jelly-roll from the core is remarkably reduced.

The battery cell according to the present invention may be manufactured by housing the jelly-roll type electrode assembly as described above in a cylindrical case, or by forming the elliptical jelly-roll type electrode assembly into a rectangular case or a pouch- And the like.

As described above, the type of the battery cell of the present invention is not particularly limited as long as the jelly-roll type electrode assembly as described above is mounted on the battery case, but it is preferable that the battery cell has a high energy density, a discharge voltage, It may be a secondary battery.

The configuration, structure, manufacturing method, and the like of the secondary battery including the lithium secondary battery are obvious to those skilled in the art, so a detailed description thereof will be omitted.

The present invention also provides a device comprising one or more of the battery cells, wherein the device is in particular a mobile phone, a tablet computer, a notebook computer, a power tool, an electric vehicle, a hybrid electric vehicle, a plug- And a power storage device, but is not limited thereto.

Such devices or devices are well known in the art, so a detailed description thereof will be omitted herein.

As described above, according to the battery cell of the present invention, the coating portions coated on the one surface or both surfaces of the separator are formed and the structure in which only the separator is wound around the winding center of the electrode assembly is applied to the battery cell, The electrode assembly (jelly-roll) can be safely taken out from the core without causing defects, thereby achieving an improved production efficiency. There is an effect.

1 is a schematic view showing a winding structure of a jelly-roll type electrode assembly according to the present invention;
2 and 3 are schematic side views of the separator according to the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings according to the embodiments of the present invention, but the scope of the present invention is not limited thereto.

FIG. 1 is a schematic view showing a winding structure of a jelly-roll type electrode assembly according to the present invention, and FIGS. 2 and 3 are schematic side views of a separation membrane according to the present invention.

Referring to these drawings, a jelly-roll type electrode assembly according to the present invention includes a positive electrode 30 coated with a positive electrode active material on both surfaces of a current collector, a negative electrode 10 coated with a negative electrode active material on both surfaces of the current collector, And a separator 20 interposed between the anode 10 and the cathode 10 are wound.

The separator 20 is composed of a coating portion 22a coated with a binder layer or a binder-inorganic mixed layer 22 and an uncoated portion 21a with no such binder layer or a binder-inorganic mixed layer 22 coated thereon . The uncoated portion 21a is located at the portions 42 and 43 where the bending rate of the electrode assembly is relatively larger than the other portions and the coating portion 22a is located at the remaining portion relatively smaller than the portion where the bending rate is different.

Therefore, since the electrode assembly having such a structure is capable of buffering unevenness of stress frequently occurring during charging and discharging, it is possible to prevent the electrode from being cracked due to the unbalanced stress generated during charging and discharging.

In addition, since the binder layer or the binder-inorganic mixed layer 22 includes a dye that can be visually recognized, the coating portion 22a and the non-coated portion 21a can be accurately positioned at a desired position of the electrode assembly. It is needless to say that the position of the coating portion 22a and the non-coating portion 21a can be more accurately controlled through a control device equipped with a camera device capable of color discrimination or shading identification.

On the other hand, only the uncoated portion 21a on which the binder layer or the binder-inorganic mixed layer is not coated is wound 2 to 3 times on the winding center 41 of the electrode assembly.

Therefore, since the jelly-roll can be easily taken out from the core after the end of winding, it is possible to prevent the occurrence of defects such as the removal of the winding center 41 of the electrode assembly in the taking-out process.

On the other hand, as shown in FIG. 2, the separation membrane is discontinuously coated with a binder layer or a binder-inorganic mixed layer 22 on both side surfaces of the separation membrane sheet 21. In addition, the non-continuous coating portions 22a are spaced apart from each other and form a pattern as a whole.

As described above, this pattern is a pattern structure previously set so that the coating portion 22a and the non-coating portion 21a can be positioned at an intended position in the electrode assembly winding process.

3 is a side schematic view of a separation membrane according to another embodiment of the present invention. 3, the binder layer or the binder-inorganic mixed layer 22 is discontinuously coated only on one surface of the separator sheet 21, unlike the separator shown in Fig. The separation membrane shown in Fig. 3 is the same as the separation membrane shown in Fig. 2, except that a binder layer or a binder-inorganic mixed layer 22 is formed only on one surface of the separation membrane sheet 21. Fig.

As described above, the separation membrane according to the present invention has a pattern structure including a coating portion 22a and a non-coating portion 21a, as shown in FIGS. Accordingly, the amount of binder required for the separation membrane coating portion can be reduced as compared with the conventional separation membrane structure. In addition, since the jelly-roll that has been wound can be safely taken out from the core without causing defects, it is possible to achieve improved production efficiency.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (10)

An electrode assembly wound in a state in which a separator is interposed between a positive electrode and a negative electrode coated with an electrode active material is mounted inside the battery case,
Coating layers on which a binder layer or a binder-inorganic mixed layer is discontinuously coated are formed on one side or both sides of the separator,
The separator winding portion on which only a separator film not coated with a binder layer or a binder-inorganic material mixed layer is wound is located at the winding center of the electrode assembly,
Wherein the coating portions are arranged in a pattern at regular intervals on a separation membrane. The battery cell according to claim 1, wherein the battery case is a pouch-shaped case of a rectangular metal can or a laminated sheet. delete The battery cell according to claim 1, wherein a portion of the separation membrane on which the coating portions are not formed is located at a relatively larger portion than a portion where the bending rate is different during the winding of the electrode assembly. The battery cell according to claim 1, wherein the total coating length of the coating portions is 100 to 150% of the coating length of the electrode active material coated on the negative electrode. The electrode assembly according to claim 1, wherein the electrode assembly has a horizontal cross-section and a major axis length of 1.5 to 30 times the minor axis length, and a portion of the separation membrane on which the coating portions are not formed, Wherein the battery cell is located at a predetermined position. The method of claim 1, wherein the inorganic material is selected from the group consisting of (a) inorganic particles having a dielectric constant of 5 or more, (b) inorganic particles having piezoelectricity, and (c) inorganic particles having lithium ion- Or more. The method of claim 1, wherein the binder is selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-cotichloroethylene, polymethyl methacrylate polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, and the like. The cellulose acylate is preferably selected from the group consisting of cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, ), Cyanoethylsucc At least one selected from the group consisting of cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer and polyimide, Wherein the battery cell is a battery cell. The battery cell according to claim 1, wherein the binder layer or the binder-inorganic mixed layer further comprises a dye or pigment to develop hue in a visible light, infrared, or ultraviolet wavelength range. The battery cell according to claim 1, wherein the separation membrane wind-up unit located at the winding center of the electrode assembly has only one separation membrane wound one to ten times.

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