KR20230097903A - Separator, electrode assembly comprising the same, and cylindrical battery cell comprising the same - Google Patents

Abstract

A separation membrane having a plurality of pores, which is divided into an upper portion, a central portion, and a lower portion in the transverse direction (TD) of the separation membrane, wherein the pore size of the central portion is smaller than the pore size of the upper and lower portions. Separation membrane, An electrode assembly including the same, and a cylindrical battery cell are presented.

Description

Separator, electrode assembly comprising the same, and cylindrical battery cell {Separator, electrode assembly comprising the same, and cylindrical battery cell comprising the same}

The present invention relates to a separator, an electrode assembly including the same, and a cylindrical battery cell, and more particularly, to a separator having improved impregnability to an electrolyte solution, an electrode assembly including the separator, and a cylindrical battery cell.

Secondary batteries, which are highly applicable to each product group and have electrical characteristics such as high energy density, are used not only in portable devices but also in electric vehicles (EVs) or hybrid electric vehicles (HEVs) driven by an electrical driving source. It is universally applied.

These secondary batteries have not only the primary advantage of significantly reducing the use of fossil fuels, but also the advantage of not generating any by-products due to the use of energy, so they are attracting attention as a new energy source for eco-friendliness and energy efficiency improvement.

Currently, types of secondary batteries widely used include lithium ion batteries, lithium polymer batteries, nickel cadmium batteries, nickel hydride batteries, nickel zinc batteries, and the like. The operating voltage of such a unit secondary battery cell, that is, a unit battery cell is about 2.5V to 4.5V. Therefore, when an output voltage higher than this is required, a battery pack may be configured by connecting a plurality of battery cells in series. In addition, a battery pack may be configured by connecting a plurality of battery cells in parallel according to a charge/discharge capacity required for the battery pack. Accordingly, the number of battery cells included in the battery pack and the type of electrical connection may be variously set according to a required output voltage and/or charge/discharge capacity.

Meanwhile, as types of unit secondary battery cells, cylindrical, prismatic, and pouch-type battery cells are known. In the case of a cylindrical battery cell, a separator, which is an insulator, is interposed between a positive electrode and a negative electrode, and a jelly roll-shaped electrode assembly is formed by winding the separator, which is inserted into a battery can, and an electrolyte is injected to configure the battery. An electrode tab in the form of a strip may be connected to the non-coated portion of each of the positive and negative electrodes, and the electrode tab electrically connects the electrode assembly and an electrode terminal exposed to the outside. For reference, the positive electrode terminal is a cap plate of a sealing body sealing the opening of the battery can, and the negative electrode terminal is the battery can.

In such a cylindrical battery cell, a significant amount of the electrolyte is stored in the upper part of the battery can connected to the cap plate and the lower part (bottom part) of the battery can, and the middle part in the width direction of the electrode assembly is far from the upper and lower parts of the can. impregnation tends to be poor. In the electrode located in the middle of the electrode assembly where the electrolyte is not well impregnated, lithium plating occurs due to electrolyte depletion, which may degrade cell performance.

Therefore, attempts to improve the impregnation of the electrolyte into the electrode assembly in the cylindrical battery cell are required.

An object of the present invention is to solve the problems of the prior art and the technical problems that have been requested from the past.

Specifically, an object of the present invention is to provide a separator with improved electrolyte impregnation performance.

It is an object of the present invention to provide a cylindrical battery cell in which an electrolyte deficient region in a cylindrical battery cell is improved by employing an electrode assembly including a separator with improved electrolyte impregnation performance in a cylindrical battery cell.

In order to achieve this object, according to an aspect of the present invention, a separation membrane of the following embodiment is provided.

According to the first embodiment,

As a separator having a plurality of pores,

The separation membrane is divided into an upper part, a central part, and a lower part in the transverse direction (TD) of the separator, and the pore size of the central part is smaller than the pore size of the upper part and the lower part.

According to the second embodiment, in the first embodiment,

The separator may be a porous polymer substrate.

According to the third embodiment, in the first embodiment,

The separator is a porous polymer substrate; and a porous coating layer having a binder polymer and inorganic particles on at least one surface of the porous polymer substrate.

According to the fourth embodiment, in the first embodiment,

The separator may be formed of only a porous coating layer (freestanding type) including a binder polymer and inorganic particles.

According to the fifth embodiment,

A jelly roll-type electrode assembly having a structure in which a positive electrode plate, a negative electrode plate, and a separator interposed between the positive and negative electrode plates are wound in one direction,

An electrode assembly is provided, characterized in that the separator is the separator of any one of the first to fourth embodiments.

According to the sixth embodiment,

A jelly roll type electrode assembly having a structure in which a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate are wound in one direction;

a battery can in which the electrode assembly is accommodated;

an electrolyte solution injected into the battery can; and

A sealing body for sealing the open end of the battery can,

A cylindrical battery cell is provided, characterized in that the separator is the separator of any one of the first to fourth embodiments.

According to the seventh embodiment, in the sixth embodiment,

A separator may be further disposed and wound on at least one of the outermost and innermost sides of the jelly roll type of the electrode assembly.

According to the eighth embodiment, in the sixth or seventh embodiment,

Upper and lower ends of the separator of the electrode assembly may be disposed in the upper and lower directions of the battery can, respectively.

According to the ninth embodiment, in any one of the sixth to eighth embodiments,

The cylindrical battery cell may have a form factor ratio of 0.4 or greater.

According to the tenth embodiment, in any one of the sixth to ninth embodiments,

The cylindrical battery cells may be 46110 cells, 48750 cells, 48110 cells, 48800 cells or 46800 cells.

According to the eleventh embodiment, in any one of the sixth to tenth embodiments,

The cylindrical battery cell may have a tab-less structure that does not include electrode tabs.

According to the twelfth embodiment, in any one of the sixth to eleventh embodiments,

The positive electrode plate and the negative electrode plate each include a non-coated portion on which an active material layer is not formed,

A positive electrode uncoated portion and a negative electrode uncoated portion are located at the upper and lower ends of the electrode assembly, respectively,

A current collecting plate is coupled to the positive electrode uncoated portion and the negative electrode uncoated portion,

The current collecting plate may be connected to an electrode terminal.

As the separator according to one embodiment of the present invention has a triple pore structure in which the pore size of the central portion is smaller than the pore sizes of the upper and lower portions in the width direction, the supply of the electrolyte to the central portion of the separator can be facilitated in a manner similar to the capillary phenomenon. there is.

A cylindrical battery cell employing such a separator as an electrode assembly can improve the electrolyte impregnation performance of the middle portion of the electrode of the electrode assembly in the width direction, thereby suppressing the lithium plating phenomenon that occurs in the center portion of the cylindrical battery cell due to electrolyte exhaustion. In addition, the amount of production can be increased by significantly shortening the process time for injecting the electrolyte into the cylindrical battery cell.

The following drawings attached to this specification illustrate preferred embodiments of the present invention, and serve to further understand the technical idea of the present invention together with the contents of the above-described invention, so the present invention is limited to those described in the drawings. It should not be construed as limiting.
1 is a perspective view showing a separation membrane according to an embodiment of the present invention.
2 is a schematic view showing the surface of a separation membrane according to an embodiment of the present invention.
3 is a schematic diagram showing an electrode assembly in the form of a jelly roll including a separator according to an embodiment of the present invention.
4 is a schematic diagram showing a cross section of a conventional cylindrical battery cell.
5 is a schematic diagram showing an electrolyte excess region and a deficiency region in a conventional cylindrical battery cell.
6 is a schematic diagram showing a cross section of a cylindrical battery cell according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail. The terms or words used in this specification and claims should not be construed as being limited to ordinary or dictionary meanings, and the inventors may appropriately define the concept of terms in order to explain their invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

According to one aspect of the present invention,

As a separator having a plurality of pores,

The separation membrane is divided into an upper part, a central part, and a lower part in the transverse direction (TD) of the separator, and the pore size of the central part is smaller than the pore size of the upper part and the lower part.

1 is a perspective view showing a separation membrane according to an embodiment of the present invention, and FIG. 2 is a schematic view showing the surface of the separation membrane according to an embodiment of the present invention.

Referring to FIG. 1, the separation membrane 10 according to one embodiment of the present invention is divided into an upper portion 11, a central portion 12, and a lower portion 13 in the transverse direction (TD) of the separation membrane, and the upper portion (11), the central portion 12, and the lower portion 13 all have a plurality of pores 11a, 12a, and 13a. At this time, the pore size of the central pores 12a included in the central portion 12 of the separation membrane 10 is the upper portion pore 11a and the lower portion pore included in the upper portion 11 and lower portion 13 of the separation membrane 10 It is smaller than the pore size of (13a).

The separation membrane 10 according to one embodiment of the present invention has a triple pore structure in which the pore size of the central portion is controlled to be small compared to the upper and lower portions in the transverse direction, so that the central portion is separated from the upper and lower ends of the separation membrane in a manner similar to the capillary phenomenon. Electrolyte is supplied smoothly in the directions E1 and E2, so that the electrolyte impregnability of the separator can be greatly improved.

The separator may be of three types.

First, the separator may be a porous polymer substrate.

Second, the separator is a porous polymer substrate; and a porous coating layer having a binder polymer and inorganic particles on at least one surface of the porous polymer substrate.

Thirdly, the separator may be made of only a porous coating layer (freestanding type) including a binder polymer and inorganic particles.

At this time, in the case of the first type in which the separator is made of a porous polymer substrate, the separator is divided into upper, central, and lower portions in the transverse direction, and the pore size of the central portion of the porous polymer substrate is the pore size of the upper and lower portions of the porous polymer substrate smaller than

In the case where the separator is of the second type including a porous polymer substrate and a porous coating layer, the separator is partitioned into upper, central, and lower portions in the transverse direction, and both the porous polymer substrate and the porous coating layer have pore sizes equal to those of the porous polymer substrate. It is smaller than the pore size of the upper and lower portions of the porous coating layer.

In addition, in the case where the separator is a third type consisting of only a porous coating layer (freestanding type) having a binder polymer and inorganic particles, the separator is divided into upper, central, and lower portions in the transverse direction, and the pore size of the central portion of the porous coating layer is It is smaller than the pore size of the upper and lower portions of the porous coating layer.

According to one embodiment of the present invention, the porous polymer substrate is not limited as long as it has a structure having pores, and may be a porous polymer substrate, specifically a porous polymer film substrate or a porous polymer nonwoven fabric substrate.

The porous polymer film substrate may be a porous polymer film made of an olefin polymer such as polyethylene or polypropylene, and the porous polymer film substrate of the olefin polymer exhibits a shutdown function at a temperature of, for example, 80 to 130 °C.

At this time, the porous polymer film is a mixture of polyethylene such as high density polyethylene, linear low density polyethylene, low density polyethylene, and ultra high molecular weight polyethylene, olefin polymers such as polypropylene, polybutylene, and polypentene, respectively, or two or more thereof. It may be formed of a polymer or a derivative thereof.

Representative commercially available examples of olefin polymer porous polymer films that can be applied as such a porous polymer substrate are wet polyethylene series (Asahi-Kasei E-Materials, Toray, SK IE Technology, Shanghai Energy, Sinoma, Entek), dry polypropylene series ( Shenzhen Senior, Cangzhou Mingzhu), dry polypropylene/polyethylene multilayer structure series (Polypore, Ube), etc. may be used, but are not limited thereto.

In addition, the porous polymer film substrate may be manufactured by molding into a film shape using various polymers such as polyester in addition to olefin polymers. In addition, the porous polymer film substrate may be formed in a structure in which two or more film layers are laminated, and each film layer may be formed of a polymer such as the above-described olefin polymer or polyester alone or a mixture of two or more thereof. may be

In addition, the porous polymer film substrate and the porous non-woven fabric substrate are made of polyethyleneterephthalate, polybutyleneterephthalate, polyester, polyacetal, polyamide ( polyamide), polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfide, polyethylenenaphthalene ), etc. may be formed of a polymer alone or a mixture thereof.

The thickness of the porous polymer substrate is not particularly limited, but may be 1 μm or more, 5 μm or more, 50 μm or less, or 100 μm or less. When the thickness satisfies this range, it is possible to improve the problem of acting as a resistance layer while maintaining mechanical properties.

The pore size and porosity of the porous polymer substrate are not particularly limited, but the porosity may be in the range of 10 to 95% and the pore size (diameter) may be in the range of 0.1 to 50 μm. When the pore size and porosity satisfy these ranges, the problem of acting as a resistance layer is prevented, and mechanical properties can be maintained. In addition, the porous polymer substrate may be in the form of fibers or membranes.

The porous coating layer is located on one side of the porous polymer substrate and includes a binder polymer and inorganic particles.

이상의 고온이 되어도 물리적 특성이 변하지 않는 특성을 갖기 때문에, 형성된 유/무기 복합 다공성 필름이 탁월한 내열성을 갖는다.The inorganic particles serve as both a role of forming micropores by enabling the formation of empty spaces between inorganic particles and a role of a kind of spacer capable of maintaining a physical shape, and generally 200

Since the physical properties do not change even at high temperatures, the formed organic/inorganic composite porous film has excellent heat resistance.

Therefore, in the lithium secondary battery including the separator, even if the porous polymer substrate is ruptured inside the battery due to excessive conditions caused by internal or external factors such as high temperature, overcharging, and external shock, it is difficult for both electrodes to be completely short-circuited by the porous coating layer. , Even if a short circuit occurs, the short circuit area is suppressed from greatly expanding, so that the safety of the battery can be improved.

These inorganic particles are not particularly limited as long as they are electrochemically stable, that is, the inorganic particles that can be used in the present invention are oxidized and / Or it is not specifically limited as long as a reduction reaction does not occur. In particular, in the case of using inorganic particles having ion transport ability, since ion conductivity in an electrochemical device can be increased to improve performance, it is preferable that the ion conductivity is as high as possible. In addition, when the inorganic particles have a high density, they are difficult to disperse during coating and increase in weight during battery manufacturing, so the density is preferably as small as possible. In addition, in the case of an inorganic material having a high permittivity, the ion conductivity of the electrolyte may be improved by contributing to an increase in the degree of dissociation of an electrolyte salt, for example, a lithium salt in the liquid electrolyte.

For the reasons described above, the inorganic particles may be inorganic particles having a high dielectric constant having a dielectric constant of 5 or more or 10 or more, inorganic particles having piezoelectricity, inorganic particles having lithium ion transport ability, or mixtures thereof. .

Examples of inorganic particles having a dielectric constant of 5 or more include SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , TiO ₂ , SiC, AlO(OH), Mg(OH) ₂ , Al(OH) ₃ , AlN, or mixtures thereof, but not limited thereto.

The inorganic particles having piezoelectricity are insulators under normal pressure, but have properties that conduct electricity due to internal structural changes when a certain pressure is applied, and exhibit high permittivity characteristics with a dielectric constant of 100 or more. When a certain pressure is applied and stretched or compressed, an electric charge is generated, and one side is positively charged and the other side is negatively charged, respectively, so that a potential difference is generated between both sides.

In the case of using inorganic particles having the above characteristics, when an internal short circuit of both electrodes occurs due to an external impact such as a local crush or a nail, the inorganic particles coated on the separator cause Not only are the anode and cathode not in direct contact, but a potential difference occurs within the particle due to the piezoelectricity of the inorganic particle. And it can promote safety improvement thereby.

Examples of the inorganic particles having piezoelectricity include BaTiO ₃ , Pb(Zr,Ti)O ₃ (PZT), Pb _1- xLa _x Zr _1-y Ti _y O ₃ (PLZT), PB (Mg ₃ Nb _2/3 ) O ₃ -PbTiO ₃ (PMN-PT) hafnia (HfO ₂ ) or a mixture thereof, but is not limited thereto.

The inorganic particles having lithium ion transfer ability refer to inorganic particles that contain lithium elements but do not store lithium and have a function of moving lithium ions, and the inorganic particles having lithium ion transfer ability are present inside the particle structure Since lithium ions can be transferred and moved due to a kind of defect, lithium ion conductivity in the battery is improved, and thus battery performance can be improved.

Examples of the inorganic particles having the lithium ion transport ability include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0<x<2, 0<y<3), lithium aluminum Titanium phosphate (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0<x<2, 0<y<1, 0<z<3), 14Li ₂ O-9Al ₂ O ₃ -38TiO ₂ -39P ₂ O ₅ (LiAlTiP)xOy series glass (0<x<4, 0<y<13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0<x<2, 0<y<3), Li _3.25 Ge Lithium germanium thiophosphate (Li _x Ge _y P _z S _w , 0<x<4, 0<y<1, 0<z<1, 0<w<5), such as _0.25 P _0.75 S ₄ , Li ₃ Lithium nitride such as N (Li _x N _y , 0<x<4, 0<y<2), SiS ₂ series glass such as Li ₃ PO ₄ -Li ₂ S-SiS ₂ (Li _x Si _y S _z , 0<x<3, 0< _y <2 _{, 0<z<4), P 2 S 5 series glass} (Li _x P _y S _z , 0 _< x<3, 0 <y<3, 0<z<7), or a mixture thereof, but is not limited thereto.

When the aforementioned high dielectric constant inorganic particles, inorganic particles having piezoelectricity, and inorganic particles having lithium ion transfer ability are used together, their synergistic effect can be doubled.

The separator according to the present invention controls the size of the inorganic particles constituting the porous coating layer, the content of the inorganic particles, and the composition of the inorganic particles and the binder polymer, thereby forming a pore structure of the porous coating layer along with pores included in the separator substrate, In addition, the pore size and porosity can be controlled together.

The average particle diameter (D50) of the inorganic particles may be 1 μm or less, 500 nm or less, or 300 nm or less as much as possible in order to form a porous coating layer having a uniform thickness and an appropriate porosity thereof. When the average particle diameter (D50) of the inorganic particles satisfies this range, the dispersibility of the slurry for the porous coating layer is maintained and it is easy to control the physical properties of the separator, and the thickness of the separator is excessively increased, resulting in deterioration in mechanical properties or An excessively large pore size may prevent an internal short circuit during charging and discharging of the battery.

The porosity of the porous coating layer may be in the range of 5 to 95%, but is not limited thereto.

The content of the inorganic particles is not particularly limited, but may be 50% by weight or more, 60% by weight or more, 95% by weight or less, 97% by weight or less, or 99% by weight or less per 100% by weight based on the total weight of the porous coating layer. That is, the weight ratio of the inorganic particles to the binder polymer may be 50:50 or more, 60:40 or more, 70:30 or more, 95:5 or less, 97:3 or less, 99:1 or less, or 50:50 to 99:1. , specifically 60:40 to 97:3, more specifically 70:30 to 95:5. When the content of the inorganic particles satisfies this range, the problem of reducing the pore size and porosity of the porous coating layer formed due to an excessive increase in the content of the binder polymer can be prevented, and since the content of the binder polymer is small, the gap between the inorganic materials is reduced. The problem of weakening the peeling resistance of the porous coating layer due to the decrease in adhesive strength can also be solved.

범위이다.Specifically, the binder polymer may have a glass transition temperature (T _g ) as low as possible, preferably -200 to 200

is the range

In addition, the binder polymer may be gelled when impregnated with a liquid electrolyte and exhibit a high degree of swelling of the electrolyte. In fact, when the binder polymers are polymers with excellent electrolyte swelling degree (or impregnation rate), the electrolyte solution injected after battery assembly is permeated into the polymer, and the polymer having the absorbed electrolyte solution has electrolyte ion conduction ability. In addition, compared to conventional hydrophobic olefin polymer-based separators, not only the wetting of battery electrolytes is improved, but also the application of polar electrolytes for batteries, which was difficult to use in the prior art, has the advantage of being possible. Accordingly, the solubility index of the binder polymer, that is, the Hildebrand solubility parameter (Hildebrand solubility parameter) is 15 to 45 MPa ^1/2 , specifically 15 to 25 MPa ^1/2 , more specifically 30 to 45 MPa ^{1/2 2} range.

When the solubility index satisfies the range of 15 to 45 MPa ^1/2 , it may be easily swelled by a conventional liquid electrolyte for a battery.

Specifically, the binder polymer is polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trichloroethylene, polyvinylidene fluoride-chlorotrifluoroethylene, polymethylmethacryl Lates, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, ethylene vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butylate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl poly Vinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxylmethylcellulose, styrene butadiene copolymer, polyimide, or two or more of these may be included, but is not limited thereto.

In the porous coating layer, the inorganic particles are charged and bound to each other by the binder polymer while in contact with each other, thereby forming an interstitial volume between the inorganic particles and forming an interstitial volume between the inorganic particles. The volume (Interstitial Volume) becomes an empty space to form a pore.

That is, the binder polymer attaches the inorganic particles to each other so that the inorganic particles can remain bound to each other, for example, the binder polymer connects and fixes the inorganic particles. In addition, the pores of the porous coating layer are pores formed by interstitial volumes between inorganic particles becoming empty spaces, which are inorganic particles that substantially come into contact with each other in a closed packed or densely packed structure. It is a space bounded by particles.

In the present specification, "particle size Dn" means the particle size at the n% point of the cumulative distribution of the number of particles according to the particle size. D50 corresponding to the average particle diameter is the particle diameter at the 50% point of the particle number cumulative distribution according to the particle size, D90 is the particle size at the 90% point of the particle number cumulative distribution according to the particle size, and D10 is the particle number cumulative distribution according to the particle size is the particle diameter at the 10% point of

The Dn can be measured using a laser diffraction method. Specifically, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g. Microtrac S3500) to measure the difference in diffraction pattern according to the particle size when the particles pass through the laser beam to distribute the particle size. yields D10, D50, and D90 can be measured by calculating the particle diameter at the point where it becomes 10%, 50%, and 90% of the particle number cumulative distribution according to the particle diameter in the measuring device.

As described above, the separator according to an embodiment of the present invention is a porous polymer substrate alone, a porous coating layer including a binder polymer and inorganic particles on at least one surface of the porous polymer substrate, or a binder polymer and inorganic particles. It may be in the form of a single porous coating layer having a.

Each type of separator is divided into upper, central, and lower parts in the transverse direction (TD) of the separator, and if the pore size of the central part can be controlled to be smaller than the pore size of the upper and lower parts, in various ways can be produced by

In the case where the separator according to an embodiment of the present invention includes a porous coating layer including a binder polymer and inorganic particles on at least one surface of a porous polymer substrate, the inorganic particles, the binder polymer, and a dispersion medium (a solvent may be used for the binder polymer) preparing a slurry for a porous coating layer comprising a); and forming a porous coating layer by applying and drying the slurry for the porous coating layer on at least one surface of the porous polymer substrate.

Preparing a slurry for a porous coating layer comprising inorganic particles, a binder polymer, and a dispersion medium (which may be a solvent for the binder polymer) when the separator is in the form of a single porous coating layer comprising a binder polymer and inorganic particles; forming a porous coating layer by applying and drying a slurry for a porous coating layer on one side of the release substrate; and separating the porous coating layer from the release substrate.

Hereinafter, a manufacturing method in the case where the separator includes a porous coating layer including a binder polymer and inorganic particles on at least one surface of a porous polymer substrate will be described step by step.

First, a porous coating layer is formed by applying and drying a slurry for a porous coating layer including inorganic particles, a binder polymer, and a dispersion medium (which may be a solvent for the binder polymer) on one surface of the porous polymer substrate.

The slurry for the porous coating layer may be prepared by dissolving a binder polymer in a dispersion medium, adding inorganic particles, and dispersing them. In this case, the inorganic particles may be added after being crushed to an appropriate size, or may be added to the solution of the binder polymer and then crushed and dispersed using a ball mill method or the like.

According to one embodiment of the present invention, the porous coating layer having the above-described interstitial volume pore structure may be formed by applying the slurry for the porous coating layer using the above-described coating device and drying the applied result. .

The dispersion medium has a solubility index similar to that of the binder polymer to be used together, and a low boiling point may be applied. This is to facilitate uniform mixing and subsequent solvent removal.

Examples of such a dispersion medium are independently selected from acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone, cyclohexane, methanol, ethanol, isopropyl alcohol, and water. It may be a compound of or a mixture of two or more.

At this time, the dispersion medium may serve as a solvent for dissolving the binder polymer and a dispersion medium for dispersing the same, depending on the type of the binder polymer mixed together.

According to one embodiment of the present invention, as a method of applying the slurry to a porous polymer substrate, there are a premetering method and a postmetering method. The total metering method is a method in which the application amount is determined in advance and introduced, and there are, for example, slot die coating, gravure coating, and the like. The post-weighing method is a method in which a slurry, which is a coating liquid, is applied to a porous polymer substrate in a sufficient coating amount and then scraped off in a prescribed amount. For example, there is bar coating. In addition, there is a direct metering coating combining the pre-metering method and the post-metering method.

The coated product may be dried to form a porous coating layer having the aforementioned interstitial volume pore structure on at least one surface of the porous polymer substrate.

In addition, after the step of applying a slurry containing a binder polymer, inorganic particles, and a dispersion medium to one side of the porous polymer substrate using the above-described coating device, the non-solvent of the binder polymer is applied to the porous polymer substrate coated with the slurry An application step may be further included. By applying the non-solvent in this way, the slurry, which is a dispersion medium and dissolved in the solvent of the binder polymer, comes into contact with the non-solvent of the binder polymer, and a phase separation phenomenon occurs. As a result, the porous coating layer is formed of a plurality of nodes including the inorganic particles and a binder polymer covering at least a portion of the surface of the inorganic particles; and the binder polymer of the nodes is formed in a thread shape, and a node connection portion for extending from the node and connecting another node, wherein the node connection portion includes a plurality of filaments derived from the binder polymer crossing each other to form a three-dimensional structure. A structure constituting a network structure may be provided.

At this time, the non-solvent coating method may include a method of immersing the pre-treated porous support in a composition containing a non-solvent, or a method of spraying and applying the non-solvent to the surface of the pre-treated porous support with a spray or the like. . This method of forming the inorganic hybrid coating layer can also be applied when an additional inorganic hybrid coating layer is formed on the other surface of the porous polymer substrate, which will be described later.

According to one aspect of the present invention, a jelly roll type electrode assembly having a structure in which a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate are wound in one direction, wherein the separator is one embodiment of the present invention described above. An electrode assembly characterized in that it is a separator is provided.

Referring to FIG. 3 , the electrode assembly 20 according to one embodiment of the present invention is a jelly roll type having a rolled structure, and the separator 10 according to one embodiment of the present invention is located on the outermost side, and the separator 10 is located on the outermost side. (10) is characterized in that the separation membrane is divided into an upper part 11, a central part 12, and a lower part 13 in the transverse direction, and the pore size of the central part is smaller than the pore size of the upper and lower parts.

According to one aspect of the present invention,

A jelly roll type electrode assembly having a structure in which a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate are wound in one direction;

a battery can in which the electrode assembly is accommodated;

an electrolyte solution injected into the battery can; and

A sealing body for sealing the open end of the battery can,

A cylindrical battery cell is provided, characterized in that the separator is the separator of one embodiment of the present invention described above.

The positive and negative electrodes to be applied together with the separator of the present invention are not particularly limited, and the electrode active material may be prepared in a form bound to an electrode current collector according to a conventional method known in the art. Non-limiting examples of the cathode active material among the electrode active materials include conventional cathode active materials that can be used for cathodes of conventional electrochemical devices, and in particular, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a combination thereof. A lithium composite oxide may be used.

Non-limiting examples of the negative electrode active material include conventional negative electrode active materials that can be used for negative electrodes of conventional electrochemical devices, and in particular, lithium metal or lithium alloy, carbon, petroleum coke, activated carbon, Lithium adsorbents such as graphite or other carbons, silicon, silicon oxides, and the like are preferred.

Non-limiting examples of the anode current collector include a foil made of aluminum, nickel or a combination thereof, and non-limiting examples of the cathode current collector include copper, gold, nickel or a copper alloy or a combination thereof. There are manufactured foils and the like.

Referring to FIG. 5, a conventional cylindrical secondary battery includes a jelly-roll type electrode assembly 110, a battery can 120 accommodating the electrode assembly 110, and coupled to an upper opening of the battery can 120 to form the can. It includes a cap assembly 130 for sealing, and a gasket 160 interposed between the battery can and the cap assembly.

In addition, a center pin 150 may be inserted into the center of the electrode assembly. When the electrode assembly is wound in a jelly-roll type, the center pin is inserted into the winding core to facilitate winding, and also. It serves to fix and support the electrode assembly.

The center pin may generally be made of a steel metal material of SUS material in order to impart a predetermined strength, and for the purpose of preventing deformation of the hollow internal structure when an external impact such as a fall or compression of a battery is applied, a flexible It may be formed of a material of metal, metal oxide or polymer.

Accordingly, these center pins are made of stainless steel, copper, tantalum, titanium, aluminum, niobium, zinc, tin, tantalum oxide, titanium oxide, aluminum oxide, niobium oxide, zinc oxide, tin oxide, copper oxide, polyethylene, polypropylene. , Polyimide, polyamide, polycarbonate, and may be made of one or more selected from the group consisting of polymethyl methacrylate, but is not limited thereto.

The center pin may have a hollow structure, and in this case, it may serve as a passage through which gas generated by an internal reaction during charging and discharging and operation of the secondary battery is discharged.

At this time, a beading part 140 provided at the front end of the battery can 120 to mount the cap assembly 130 and a crimping part 141 for sealing the battery are provided.

The jelly-roll type electrode assembly 110 has a structure wound in a jelly-roll shape with a separator 113 interposed between the positive electrode 111 and the negative electrode 112, and the positive electrode 111 has a positive electrode tab ( 111a) is attached and connected to the cap assembly 130, and a negative electrode tab 112a is attached to the negative electrode 112 and connected to the lower end of the battery can 120.

In addition, the cap assembly 130 seals the open end of the battery can, the top cap 170 forms a positive electrode terminal, increases resistance when the temperature inside the battery increases, blocks current, and contacts the top cap. A PTC (Positive Temperature Coefficient) element 180 arranged so as to cut off current and exhaust gas when the pressure inside the battery rises, and is arranged so that one surface is in contact with the PTC element and a part of the other surface is in contact with the gasket, A safety vent 190 electrically connected to the electrode assembly is provided. Here, a current blocking device 200 to which the positive electrode tab 111a is connected may be further provided. The cap assembly 130 is coupled to the open end of the top of the battery can 120 and is mounted on the beading part 140 of the battery can 120 .

Inside the battery can 110, a jelly-roll type electrode assembly 110 and an electrolyte solution (not shown) are accommodated.

The electrolyte solution that can be used in the electrode assembly of the present invention is a salt having a structure such as A ⁺ B ^- , wherein A ⁺ includes an alkali metal cation such as Li ⁺ , Na ⁺ , K ⁺ or an ion composed of a combination thereof, and B ^- PF ₆ ^- , BF ₄ ^- , Cl ^- , Br ^- , I ^- , ClO ₄ ^- , AsF ₆ ^- , CH ₃ CO ₂ ^- , CF ₃ SO ₃ ^- , N(CF ₃ SO ₂ ) ₂ ^- , C( A salt containing an anion such as CF ₂ SO ₂ ) ₃ ^- or a combination thereof is propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethylsulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethylcarbonate (EMC), gamma butyrolactone (g- butyrolactone) or dissolved or dissociated in an organic solvent consisting of a mixture thereof, but is not limited thereto. The injection of the electrolyte may be performed at an appropriate stage in the battery manufacturing process according to the manufacturing process and required physical properties of the final product. That is, it may be applied before battery assembly or at the final stage of battery assembly.

Referring to FIG. 5, in the prior art cylindrical battery cell 100, the electrolyte excess regions A and C, where the electrolyte injected into the cylindrical battery can is rich, are located at the upper and lower ends of the rolled-up jelly-like electrode assembly. and a depleted region (B) in which the electrolyte is relatively insufficient. This is because when the electrolyte is injected into the battery can, the electrolyte is first placed in the empty space, then the electrolyte is impregnated through the pores of the separator of the electrode assembly, and the electrolyte impregnated into the pores of the separator is the active material layer of the positive and negative electrodes facing the separator. It can then be impregnated into the positive and negative electrodes through the pores. In the case of a conventional separator, the pore size is almost uniform across the upper, middle, and lower ends of the separator in the transverse direction, and the upper and lower ends of the separator of the electrode assembly disposed at the upper and lower ends of the battery can where the electrolyte is first injected. It took a considerable amount of time for the electrolyte to be impregnated into the center of the separator.

However, the separator 10 wound around the electrode assembly 20 embedded in the cylindrical battery cell according to one embodiment of the present invention according to FIG. 6 has an upper end 11, a central part 12, and a lower end in the transverse direction of the separator (13), and having a triple pore structure in which the pore size in the central part is controlled to be small compared to the upper and lower ends in the transverse direction of the separator, in a manner similar to the capillary phenomenon, from the upper and lower ends of the separator to the central part (E1, E2) As the electrolyte supply becomes smooth, the electrolyte impregnability of the separator can be greatly improved.

A cylindrical battery cell according to the present invention includes a jelly-roll type electrode assembly having a structure in which a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate are wound in one direction; a battery can in which the electrode assembly is accommodated; and a sealing body sealing the open end of the battery can.

Preferably, the cylindrical battery cell according to the present invention is a large cylindrical battery cell having a form factor ratio (defined as the ratio of the diameter of the cylindrical battery divided by the height, that is, the ratio of the height (H) to the diameter (Τ)) of 0.4 or more. can Here, the form factor means a value representing the diameter and height of a cylindrical battery cell.

Cylindrical battery cells according to the present invention, for example, 46110 cells (diameter 46 mm, height 110 mm, form factor ratio 0.418), 48750 cells (diameter 48 mm, height 75 mm, form factor ratio 0.640), 48110 cells (diameter 48 mm, height 110 mm, form factor ratio 0.418), 48800 cells (diameter 48 mm, height 80 mm, form factor ratio 0.600), 46800 cells (diameter 46 mm, height 80 mm, form factor ratio 0.575). The two numbers indicate the diameter of the cell, the next two numbers indicate the height of the cell, and the last number O indicates that the cross section of the cell is circular.

The cylindrical battery cell according to the present invention significantly reduces gas generation compared to the prior art by applying a single-particle or pseudo-single-particle type cathode active material, and thus has excellent safety even in a large-sized cylindrical battery cell having a form factor ratio of 0.4 or more. can be implemented.

Meanwhile, the cylindrical battery cell according to the present invention may preferably be a battery having a tab-less structure that does not include an electrode tab, but is not limited thereto.

In the battery of the tab-less structure, for example, a positive electrode plate and a negative electrode plate each include a non-coated portion on which an active material layer is not formed, a positive electrode uncoated portion and a negative electrode uncoated portion are located at the top and bottom of the electrode assembly, respectively, and the positive electrode uncoated portion and a structure in which a current collecting plate is coupled to the uncoated portion of the negative electrode plate, and the current collecting plate is connected to an electrode terminal.

An electrode assembly according to an embodiment of the present invention may be a jelly roll type electrode assembly having a structure in which a positive electrode plate and a negative electrode plate having a sheet shape and a separator interposed therebetween are wound in one direction.

Preferably, at least one of the positive electrode plate and the negative electrode plate may include a non-coated portion not coated with an active material at an end of a long side in a winding direction. At least part of the uncoated portion can be used as an electrode tab by itself. The uncoated portion may include a core-side uncoated portion adjacent to the core of the electrode assembly, an outer circumferential uncoated portion adjacent to the outer circumferential surface of the electrode assembly, and a middle uncoated portion interposed between the core-side uncoated portion and the outer circumferential uncoated portion.

Preferably, at least one of the core-side non-coated portion and the outer circumferential non-coated portion may have a relatively lower height than the middle non-coated portion.

Although the above has been described with reference to various embodiments and drawings of the present invention, those skilled in the art will be able to make various applications and modifications within the scope of the present invention based on the above information.

Claims (12)

As a separator having a plurality of pores,
Separation membrane, characterized in that divided into upper, central, and lower portions in the transverse direction (TD) of the separator, and the pore size of the central portion is smaller than the pore sizes of the upper and lower portions. According to claim 1,
Separator, characterized in that the separator is a porous polymer substrate. According to claim 1,
The separator is a porous polymer substrate; and a porous coating layer having a binder polymer and inorganic particles on at least one surface of the porous polymer substrate. According to claim 1,
The separator is characterized in that the separator is composed of only a porous coating layer having a binder polymer and inorganic particles. A jelly roll-type electrode assembly having a structure in which a positive electrode plate, a negative electrode plate, and a separator interposed between the positive and negative electrode plates are wound in one direction,
An electrode assembly, characterized in that the separator is the separator of any one of claims 1 to 4. A jelly roll type electrode assembly having a structure in which a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate are wound in one direction;
a battery can in which the electrode assembly is accommodated;
an electrolyte solution injected into the battery can; and
A sealing body for sealing the open end of the battery can,
A cylindrical battery cell, characterized in that the separator is the separator of any one of claims 1 to 4. According to claim 6,
A cylindrical battery cell, characterized in that a separator is further disposed and wound on at least one of the outermost and innermost sides of the jelly roll type of the electrode assembly. According to claim 6,
A cylindrical battery cell, characterized in that the upper and lower ends of the separator of the electrode assembly are disposed in the upper and lower directions of the battery can, respectively. According to claim 6,
The cylindrical battery cell, characterized in that the form factor ratio of the cylindrical battery cell is 0.4 or more. According to claim 9,
The cylindrical battery cell is a cylindrical battery cell, characterized in that 46110 cells, 48750 cells, 48110 cells, 48800 cells or 46800 cells. According to claim 6,
The cylindrical battery cell is a battery of a tab-less structure that does not include an electrode tab. According to claim 6,
The positive electrode plate and the negative electrode plate each include a non-coated portion on which an active material layer is not formed,
A positive electrode uncoated portion and a negative electrode uncoated portion are located at the upper and lower ends of the electrode assembly, respectively,
A current collecting plate is coupled to the positive electrode uncoated portion and the negative electrode uncoated portion,
Cylindrical battery cell, characterized in that the current collecting plate is connected to the electrode terminal.

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