Separator, electrode assembly comprising same, and battery cell comprising same

Abstract

A separator according to an embodiment of the present invention comprises: a porous polymer substrate; and a porous coating layer formed on both surfaces of the porous polymer substrate, wherein: the separator has one end (A), the other end (A'), and one point (B) between the one end (A) and the other end (A') in the machine direction; the thickness of the separator is constantly maintained from the one end (A) to the other end (A'); the thicknesses of the porous polymer substrate and the porous coating layer are constantly maintained in a region (AB) between the one end (A) and the one point (B); and the thickness of the porous polymer substrate decreases and the thickness of the porous coating layer increases in a region (BA') between the one point (B) and the other end (A').

Description

Separator, electrode assembly including same, and battery cell including same

[0001] The present invention relates to a separator, an electrode assembly including the same, and a battery cell including the same.

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0012500, filed January 26, 2024, the entire contents of which are incorporated herein by reference.

[0003] As technological developments and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. Secondary batteries are attracting significant attention not only as a power source for mobile devices such as cell phones, digital cameras, laptops, and wearable devices, but also as a power source for powertrains such as electric bicycles, electric cars, and hybrid electric vehicles.

[0004] Secondary batteries are classified into cylindrical batteries, in which the electrode assembly is housed in a cylindrical metal can, square batteries, in which the electrode assembly is housed in a square metal can, and pouch batteries, in which the electrode assembly is housed in a pouch-shaped case made of aluminum laminate sheet, depending on the shape of the battery case. Among these, cylindrical batteries have the advantages of relatively large capacity and structural stability.

[0005] The present invention provides a separator capable of improving stability by preventing damage (impingement) caused by pressing the separator in a battery cell in which an electrode assembly is wound with a separator interposed between electrodes and is built into a cylindrical battery housing, an electrode assembly including the same, and a battery cell including the same.

[0006] According to one aspect of the present invention, a separator of the following embodiment, an electrode assembly including the same, and a battery cell including the same are provided.

[0007] According to a first embodiment, a separator is provided, comprising: a porous polymer substrate; and a porous coating layer formed on both sides of the porous polymer substrate and including inorganic particles and a binder polymer; wherein the separator has one end (A), another end (A') and a point (B) between the one end (A) and the other end (A') in the longitudinal direction, and the thickness of the separator is maintained constant from the one end (A) to the other end (A'), and the thicknesses of the porous polymer substrate and the porous coating layer are maintained constant in a region (AB) between the one end (A) and the point (B), and the thickness of the porous polymer substrate decreases and the thickness of the porous coating layer increases in a region (BA') between the one point (B) and the other end (A').

[0008] According to a second embodiment, in the first embodiment, the shape of the interface between the porous polymer substrate and the porous coating layer may be asymmetrical with respect to a vertical line of the center of the longitudinal direction of the separation membrane.

[0009] According to a third embodiment, in any one of the first to second embodiments, the shape of the interface between the porous polymer substrate and the porous coating layer may be symmetrical with respect to a vertical line at the center of the thickness direction of the separation membrane.

[0010] According to a fourth embodiment, in any one of the first to third embodiments, the thickness of the porous polymer substrate may linearly decrease and the thickness of the porous coating layer may linearly increase in a region (BA') between the point (B) and the other end (A').

[0011] According to the fifth embodiment, in any one of the first to fourth embodiments, the length from the one end (A) to the one point (B) may be about 10% to 70% of the length in the longitudinal direction of the separation membrane.

[0012] According to a sixth embodiment, in any one of the first to fifth embodiments, the thickness at the other end (A') of the porous polymer substrate may be about 75% to 95% of the thickness at one end (A) of the porous polymer substrate by 100%.

[0013] According to the seventh embodiment, in any one of the first to sixth embodiments, the content of the porous coating layer in the region (BA') may be about 40 parts by weight to 1300 parts by weight based on 100 parts by weight of the porous coating layer in the region (AB).

[0014] According to the eighth embodiment, in any one of the first to seventh embodiments, the content of the porous coating layer may be about 40 parts by weight to 60 parts by weight relative to 100 parts by weight of the porous polymer substrate.

[0015] According to the ninth embodiment, in any one of the first to eighth embodiments, the total length of the separation membrane in the longitudinal direction may be about 1.5 m to 5 m.

[0016] According to a tenth embodiment, an electrode assembly is provided, which includes a separator according to any one of the first to ninth embodiments; a first electrode in contact with one surface of the separator; and a second electrode in contact with the other surface of the separator, wherein the first electrode, the separator, and the second electrode are wound around the other end (A') of the separator as a winding axis.

[0017] According to the eleventh embodiment, in the tenth embodiment, the winding length of the electrode assembly may be about 1.5 m to 5 m.

[0018] According to the 12th embodiment, in any one of the 10th to 11th embodiments, the electrode assembly may be one in which the first electrode, the separator, and the second electrode are laminated in this order.

[0019] According to a thirteenth embodiment, a battery cell is provided in which an electrode assembly according to any one of the tenth to twelfth embodiments is loaded into a cylindrical battery housing together with an electrolyte.

[0020] According to the 14th embodiment, in the 13th embodiment, the form factor of the cylindrical battery housing may be 46110, 46800, 46950, 48110, 48750 or 48800.

[0021] A separator according to one embodiment of the present invention may have excellent mechanical properties, and when wound together with an electrode and loaded into a cylindrical battery housing, it may prevent or suppress damage (impingement) that occurs when the separator is pressed due to volume expansion during charging and discharging of the electrode at the center.

[0022] A battery cell including an electrode assembly according to one embodiment of the present invention has excellent mechanical properties of a separator at the center, thereby preventing or suppressing internal short circuits of the battery.

[0023] Figure 1 schematically illustrates the structure of a separation membrane according to one embodiment of the present invention.

[0024] FIG. 2 is a schematic diagram illustrating a structure of a separation membrane according to one embodiment of the present invention, with an imaginary vertical line drawn at the center of the length direction of the separation membrane.

[0025] FIG. 3 is a schematic diagram illustrating a structure of a membrane according to one embodiment of the present invention, in which an imaginary vertical line is drawn at the center of the thickness direction of the membrane.

[0026] FIG. 4 is a drawing for explaining a battery pack including a battery cell according to one embodiment of the present invention.

[0027] FIG. 5 is a drawing for explaining a vehicle including a battery pack according to one embodiment of the present invention.

[0028] In some of the accompanying drawings, corresponding components are designated by the same reference numerals. Those skilled in the art will appreciate that the drawings illustrate elements simply and clearly and are not necessarily drawn to scale. For example, to facilitate understanding of various embodiments, the dimensions of some elements depicted in the drawings may be exaggerated relative to other elements. Furthermore, elements of known technology that are useful or essential in commercially feasible embodiments may often not be depicted so as not to obscure the spirit of various embodiments of the present invention.

[0029] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0030] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0031] Justice

[0032] Throughout this specification, when it is said that a part "includes" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0033] In addition, the term "substantially" used throughout this specification is used in a sense of or near to the numerical value when manufacturing and material tolerances inherent to the meaning stated are presented, and is used to prevent unscrupulous infringers from unfairly exploiting disclosures that mention exact or absolute figures to aid understanding of this specification.

[0034] D in the original specification 50 refers to the particle size at the 50% point of the cumulative distribution of particle numbers according to particle size. In addition, D 10 D means the particle size at the 10% point of the cumulative distribution of particle numbers according to particle size. 90 It means the particle size at the 90% point of the cumulative distribution of the number of particles according to the particle size. The particle size can be measured using the laser diffraction method. For example, after the powder to be measured is dispersed in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500) and the particle size distribution is calculated by measuring the difference in the diffraction pattern according to the particle size when the particles pass through the laser beam. By calculating the particle diameters at the points where the particle number is 10%, 50% and 90% of the cumulative distribution of the number of particles according to the particle size in the measuring device, D is calculated, respectively. 10 , D 50 and D 90 can be measured.

[0035] Certain terminology used in the following detailed description of the invention is for convenience only and is not intended to limit the invention. Furthermore, directional words such as "up," "down," "left," "right," "front," "back," "inside," and "outside" indicate directions within the drawings to which reference is made, or indicate directions toward or away from the geometric center of the designated device, system, or its components, respectively.

[0036] Throughout the present specification, the "mechanical direction MD" of the separator refers to the direction of the longer length among the width and height of the separator. For example, the separator is a strip-shaped separator having an aspect ratio of 1 or more, or an aspect ratio exceeding 1, and two or more unit electrodes are arranged on the separator. At this time, the mechanical direction refers to the direction in which the unit electrodes are arranged. In general, the "mechanical direction" of the separator may coincide with the running direction of the separator or the electrode assembly in the manufacturing process of the separator or the manufacturing process of the electrode assembly using the same, and is also referred to as the "winding direction" because it is the same as the winding direction during the manufacturing process of the electrode assembly. In addition, the "thickness direction" (transverse direction TD) refers to a direction perpendicular to the longitudinal direction.

[0037] Throughout this specification, unless otherwise defined, the "thickness" of each component may refer to a value measured using a known thickness measuring device capable of measuring the thickness of a battery separator. For example, the thickness measuring device may be a VL-50S manufactured by Mitutoyo, but is not limited thereto.

[0038] As used herein, the terms "about," "approximately," and "substantially" are used to mean a range of or near that number or degree, taking into account inherent manufacturing and material tolerances.

[0039]

[0040] The electrode assembly built into the battery case is a charge-discharge power plant having a stacked structure of a positive electrode, a separator, and a negative electrode, and is classified into a jelly-roll type electrode assembly, a stack type electrode assembly, and a stack / folding type electrode assembly. The jelly-roll type electrode assembly is a form in which a separator is interposed between long sheet-shaped positive and negative electrodes coated with an active material and rolled up, and the stack type electrode assembly is a form in which a plurality of positive and negative electrodes of a predetermined size are sequentially stacked with a separator interposed therebetween, and the stack / folding type electrode assembly is a composite structure of the jelly-roll type and the stack type. Among them, the jelly-roll type electrode assembly has the advantages of being easy to manufacture and having a high energy density per weight.

[0041] In the case of cylindrical batteries, a long electrode with a fixed width is rolled into a jelly-roll-shaped electrode assembly. Cylindrical batteries manufactured by inserting this jelly-roll-shaped electrode assembly into a battery case undergo repeated contraction and expansion of the electrode during charging and discharging. Meanwhile, the electrode undergoes a cutting process during the manufacturing process, and a rough portion, a burr, may exist on the surface of the terminal portion of the electrode due to the cutting process. If the burr exists, the separator of the cylindrical battery may be damaged (impinged) by the contraction and expansion of the electrode during charging and discharging, which may cause an internal short circuit. For example, if a burr exists at the terminal portion of the electrode, the contraction and expansion of the electrode during charging and discharging of the cylindrical battery may cause the burr to rub against the inorganic particles and binder polymer in the porous coating layer of the separator, causing the inorganic particles and binder polymer to detach, thereby damaging the separator.

[0042] In addition, in the case of cylindrical batteries, unlike square batteries and pouch-type batteries that use stack-type electrode assemblies, jelly-roll-type electrode assemblies are used as electrode assemblies, and metals such as aluminum cans are used as battery housings. Therefore, when charging and discharging the battery, the direction of contraction and expansion of the electrodes is concentrated only in the centripetal direction of the jelly-roll-type electrode assembly, so the problem of damage to the separator at the center of the winding axis of the cylindrical battery cell may be more severe.

[0043] Meanwhile, in the separator of the present invention, in the porous polymer substrate and the porous coating layer formed on both sides of the porous polymer substrate and including inorganic particles and a binder polymer, the loading amount of the porous coating layer on the same area of ​​the porous polymer, for example, as the thickness of the porous coating layer increases, the content of the inorganic particles and the binder polymer increases, thereby increasing the resistance of the separator to burrs of the electrode due to shrinkage and expansion of the battery, thereby improving impingement of the separator, and an electrode assembly including the same and a battery cell including the same are provided.

[0044]

[0045] <Separator>

[0046] One embodiment of the present invention provides the following separation membrane.

[0047] According to one embodiment of the present invention, as illustrated in FIG. 1, the separator (10) comprises a porous polymer substrate (11); and a porous coating layer (12) formed on both sides of the porous polymer substrate and including inorganic particles and a binder polymer, wherein the separator (10) has one end (A), another end (A') and a point (B) between the one end (A) and the other end (A') in the longitudinal direction, and the thickness of the separator is maintained constant from the one end (A) to the other end (A'), and the thicknesses of the porous polymer substrate and the porous coating layer are maintained constant in a region (AB) between the one end (A) and the point (B), and the thickness of the porous polymer substrate decreases and the thickness of the porous coating layer increases in a region (BA') between the one point (B) and the other end (A'). For example, according to the separator of the present embodiment, the thickness of the porous polymer substrate in a region (BA') between one point (B) of the separator and the other end (A') may decrease toward the other end (A'), and the thickness of the porous coating layer may increase toward the other end (A').

[0048] In one embodiment of the present invention, the region (AB) means a part of the membrane corresponding to a section from one end (A) to one point (B) in the longitudinal direction of the membrane as illustrated in Fig. 1. In addition, in one embodiment of the present invention, the 'porous polymer substrate of the region (AB)' means a porous polymer substrate corresponding to a section from one end (A) to one point (B) in the longitudinal direction of the membrane.

[0049] As described above, when the thickness of the porous polymer substrate decreases and the thickness of the porous coating layer increases in the area (BA') between the point (B) and the other end (A'), the content of the binder polymer and the inorganic particles in the direction of the other end (A') of the separator is high, so that the bonding force between the inorganic particles is excellent, and thus the mechanical strength of the separator can be excellent.

[0050] In one embodiment of the present invention, the separator may have an interface between the porous polymer substrate and the porous coating layer that is asymmetrical in shape with respect to a vertical line at the center of the longitudinal direction (MD). The vertical line at the center of the longitudinal direction (MD) may be an imaginary line drawn perpendicular to the longitudinal direction of the separator at its center in the longitudinal direction of the separator, as illustrated in FIG. 2.

[0051] Meanwhile, in one embodiment of the present invention, the shape of the interface between the porous polymer substrate and the porous coating layer may be approximately symmetrical with respect to a vertical line at the center of the thickness direction (TD) of the separator. The vertical line at the center of the thickness direction (TD) of the separator may be an imaginary line drawn perpendicular to the thickness direction of the separator at the center in the thickness direction of the separator, as illustrated in FIG. 3.

[0052] In a separation membrane according to one embodiment of the present invention, the thickness of the porous polymer substrate in a region (BA') between the point (B) and the other end (A') may, for example, decrease toward the other end (A'), and the thickness of the porous coating layer may, for example, increase toward the other end (A'). The decrease in the thickness of the porous polymer substrate may be a linear decrease or a non-linear decrease, and the increase in the thickness of the porous coating layer may be a linear increase or a non-linear increase.

[0053] In one embodiment, the thickness of the porous polymer substrate may linearly decrease and the thickness of the porous coating layer may linearly increase in a region (BA') between the point (B) and the other end (A'). In such a case, the manufacturing process may be facilitated in preparation for a nonlinear decrease in the thickness of the porous polymer substrate during the membrane forming process.

[0054] In this specification, the term "the thickness of the membrane is maintained constant" means that when the thickness is measured at any position within a specific area using the same method, the measured thickness value exists within an error range of about 5% or less. For example, if the deviation of the thickness values ​​at any two positions within the specific area is within about 5%, 4%, 3%, 2%, 1%, or 0% (i.e., no difference), it can be said that the thickness is maintained constant.

[0055] As used herein, the term "thickness increases" means that when thickness is measured using the same method in a certain direction within a specific area, the thickness value increases continuously or discontinuously. The rate at which the thickness value increases may be maintained constant within an error range of about 5% or may change discontinuously. However, the term "thickness increases continuously" may mean that the thickness value increases continuously at a constant rate.

[0056] As used herein, the term "thickness decreases" means that when thickness is measured using the same method in a certain direction within a specific area, the thickness value decreases continuously or discontinuously. The rate at which the thickness value decreases may be maintained constant within an error range of about 5% or may change discontinuously. However, the continuous decrease in thickness may mean that the thickness value decreases continuously at a constant rate.

[0057] In one embodiment of the present invention, the thickness of the porous polymer substrate may be measured by removing the porous coating layer from the separator. For example, the thickness of the remaining porous polymer substrate may be measured after removing the porous coating layer included in the separator using a solvent capable of dissolving the porous coating layer.

[0058] In one embodiment of the present invention, the thickness of the porous coating layer can be measured by measuring the thickness of the separator and then determining the difference between the thickness of the porous polymer substrate measured according to the above with respect to the thickness of the separator, but the measurement method is not limited thereto.

[0059] In one embodiment of the present invention, the length from the one end (A) to the one point (B) may be about 10% to 70%, or about 20% to 60%, or about 30% to 50%, or about 40% to 45% of the length of the membrane in the longitudinal direction, based on 100%. When the length from the one end (A) to the one point (B) satisfies the above-described range, the heat resistance and mechanical strength of the membrane may be excellent, and the resistance of the membrane may be low. In this case, the length of the membrane may mean the length from the one end (A) to the other end (A').

[0060] In one embodiment of the present invention, the thickness at the other end (A') of the porous polymer substrate may be about 75% to 95%, or about 80% to 90%, of the thickness at one end (A) of the porous polymer substrate. For example, when the thickness at one end (A) of the porous polymer substrate is about 10 μm, the thickness at the other end (A) may be within a range of about 7.5 μm to 9.5 μm.

[0061] In one embodiment of the present invention, the porous coating layer is formed on a porous polymer substrate at a density of about 4.0 g / m 2 6.5 g / m 2 , about 4.5 g / m 2 6.3 g / m 2 or about 5.0 g / m 2 6.0 g / m 2 It can be formed with the content (loading amount).

[0062] In one embodiment of the present invention, the content of the porous coating layer in the region (BA') may be about 40 parts by weight to 1300 parts by weight, about 100 parts by weight to 1200 parts by weight, or about 200 parts by weight to 1000 parts by weight based on 100 parts by weight of the porous coating layer in the region (AB). By satisfying the above-described range of the content of the porous coating layer in the region (BA'), the mechanical properties of the separator in the region (BA') may be excellent, and the degree of damage to the separator due to shrinkage and expansion of the electrode in the center of the cylindrical battery cell including the separator according to one embodiment of the present invention may be reduced.

[0063] In one embodiment of the present invention, the content of the porous coating layer may be about 40 parts by weight to 60 parts by weight, or about 45 parts by weight to 55 parts by weight, relative to 100 parts by weight of the porous polymer substrate. The content of the porous coating layer may refer to a relative content relative to the weight of the porous polymer substrate in the region (AA'), i.e., the entire range of the separation membrane.

[0064] In one embodiment of the present invention, the total length of the membrane in the longitudinal direction may be about 1.5 m to 5 m, or about 2 m to 4.5 m.

[0065] According to one embodiment of the present invention, the porous polymer substrate has a structure having pores, for example, it may be a porous polymer film substrate or a porous polymer nonwoven fabric substrate.

[0066] The porous polymer film substrate may be a porous polymer film made of an olefin polymer such as polyethylene or polypropylene, and such an olefin polymer porous polymer film substrate exhibits a shutdown function at a temperature of, for example, about 80°C to 130°C.

[0067] At this time, the porous polymer film may be formed of an olefin polymer such as polyethylene, polypropylene, polybutylene, polypentene, etc., such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, ultra-high molecular weight polyethylene, or a polymer or a derivative thereof, either alone or in combination of two or more thereof.

[0068] Representative commercially available examples of olefin polymer porous polymer films that can be applied as such porous polymer substrates include, but are not limited to, wet polyethylene series (Asahi-Kasei E-Materials, Toray, SK IE Technology, Shanghai Energy, Sinoma, Entek), dry polypropylene series (Shenzhen Senior, Cangzhou Mingzhu), and dry polypropylene / polyethylene multilayer structure series (Polypore, Ube).

[0069] In addition, the porous polymer film substrate may be manufactured by forming 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-mentioned olefin polymer, polyester, etc. alone, or a polymer obtained by mixing two or more types thereof.

[0070] In addition, the porous polymer film substrate and the porous nonwoven fabric substrate may be formed of polymers such as polyethyleneterephthalate, polybutyleneterephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfide, polyethylenenaphthalene, etc., either singly or as a mixture thereof, in addition to the above olefin polymers.

[0071] In one embodiment of the present invention, the weight average molecular weight of the porous polymer substrate may be about 10,000 g / mol to 1,000,000 g / mol or about 100,000 g / mol to 800,000 g / mol. When the weight average molecular weight of the porous polymer substrate satisfies the above-described range, the strength of the porous polymer substrate may be excellent.

[0072] At this time, the weight average molecular weight may be measured by gel permeation chromatography (GPC: gel permeation chromatography, PL GPC220, Agilent Technologies) under the following conditions.

[0073] - Column: PL Olexis (Polymer Laboratories)

[0074] - Solvent: TCB (Trichlorobenzene)

[0075] - Flow rate: 1.0 ml / min

[0076] - Sample concentration: 1.0 mg / ml

[0077] - Injection volume: 200 ㎕

[0078] - Column temperature: 160℃

[0079] - Detector: Agilent High Temperature RI detector

[0080] - Standard: Polystyrene (corrected with a cubic function)

[0081] The thickness of the porous polymer substrate is not particularly limited as long as it satisfies the above-described ratio range relative to the total thickness of the separator, but may be, for example, about 1 ㎛ or more, 10 ㎛ or more, about 30 ㎛ or less, or about 50 ㎛ or less. When the thickness satisfies the above-described range, the positive and negative electrodes can be electrically insulated while maintaining mechanical properties.

[0082] There are no particular limitations on the pore size and porosity of the porous polymer substrate. However, for example, the porosity may be in the range of about 10% to 70%, and the pore size (diameter) may be in the range of about 0.01 μm to 5 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 a fiber or membrane.

[0083] The above porosity or pore size can be measured using BELSORP (BET equipment) of BEL JAPAN using an adsorbed gas such as nitrogen, or can be measured using a method such as mercury intrusion porosimetry or capillary flow porosimetry.

[0084] The above porous coating layer is located on both sides of the porous polymer substrate and includes a binder polymer and inorganic particles.

[0085] The above inorganic particles have the function of forming micropores by enabling the formation of empty spaces between the inorganic particles and also serve as a kind of spacer that can maintain the physical shape, and since they generally have the property of not changing physical properties even at high temperatures of 200°C or higher, the formed organic / inorganic composite porous film has excellent heat resistance.

[0086] Accordingly, in a lithium secondary battery including the separator, even if the porous polymer substrate inside the battery is ruptured due to excessive conditions caused by internal or external factors such as high temperature, overcharge, or external impact, it is difficult for the two electrodes to be completely short-circuited due to the porous coating layer, and even if a short-circuit occurs, the short-circuited area is prevented from expanding significantly, thereby improving the safety of the battery.

[0087] These inorganic particles are not particularly limited as long as they are electrochemically stable, and for example, the inorganic particles that can be used in one embodiment of the present invention can be used in the operating voltage range of the battery to which they are applied (e.g., Li / Li). + There is no particular limitation as long as no oxidation and / or reduction reaction occurs at 0 to 5 V as a reference. In addition, when using inorganic particles with ion transfer capability, by using inorganic particles with as high an ion conductivity as possible, the ion conductivity within the electrochemical device can be increased, thereby improving performance. In addition, when the inorganic particles have a high density, by using inorganic particles with as low a density as possible, the difficulty in dispersing during coating can be prevented, and the problem of weight increase during battery manufacturing can also be solved. In addition, when using an inorganic material with a high dielectric constant, it can contribute to increasing the dissociation of an electrolyte salt, such as a lithium salt, in a liquid electrolyte, thereby improving the ion conductivity of the electrolyte.

[0088] For the reasons described above, the inorganic particles may be high-k inorganic particles having a dielectric constant of 5 or more, or 10 or more, inorganic particles having piezoelectricity, inorganic particles having lithium ion transport capability, or a mixture thereof.

[0089] Examples of the inorganic particles having a dielectric constant of 5 or more include, but are not limited to, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiC, AlO(OH), Mg(OH)2, Al(OH)3, AlN, or mixtures thereof.

[0090] The above inorganic particles having piezoelectricity are non-conductive at normal pressure, but when a certain pressure is applied, they are materials that have the property of conducting electricity due to a change in their internal structure. In addition, when a certain pressure is applied and they are stretched or compressed, charges are generated, so that one side is charged positively and the other side is charged negatively, and a potential difference is generated between the two sides.

[0091] When using inorganic particles having the above characteristics, when an internal short circuit occurs between the positive and negative electrodes due to external impacts such as local crush or nail, not only does the positive and negative electrodes not come into direct contact due to the inorganic particles coated on the separator, but also an electric potential difference occurs within the particles due to the piezoelectricity of the inorganic particles, which causes electron movement between the positive and negative electrodes, i.e., a flow of microscopic current, thereby achieving a gradual decrease in the voltage of the battery and thereby improving safety.

[0092] Examples of the above piezoelectric inorganic particles include BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1- xLa x Zr 1-y Ti y O3(PLZT), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT) hafnia (HfO2) or mixtures thereof, but are not limited thereto.

[0093] The above-mentioned inorganic particles having lithium ion transfer capability refer to inorganic particles that contain lithium elements but do not store lithium and have the function of transferring lithium ions. Since the inorganic particles having lithium ion transfer capability can transfer and move lithium ions due to a type of defect existing within the particle structure, lithium ion conductivity within the battery is improved, thereby promoting improvement in battery performance.

[0094] Examples of inorganic particles having the above lithium ion transfer capability include lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 <x<2, 0<y<3), 리튬알루미늄티타늄포스페이트(Li x Al y Ti z (PO4)3, 0 <x<2, 0<y<1, 0<z<3), 14Li2O-9Al2O3-38TiO2-39P2O5등과 같은 (LiAlTiP) x O y Series glass (0 <x<4, 0<y<13), 리튬란탄티타네이트(Li x La y TiO3, 0 <x<2, 0<y<3), Li 3.25 Ge 0.25 P 0.75 Lithium germanium thiophosphate (Li) such as S4 x Ge y P z S w , 0 <x<4, 0<y<1, 0<z<1, 0<w<5), Li3N 등과 같은 리튬나이트라이드(Li x N y , 0 <x<4, 0<y<2), Li3PO4-Li2S-SiS2등과 같은 SiS2계열 glass(Li x Si y S z , 0 <x<3, 0<y<2, 0<z<4), LiI-Li2S-P2S5등과 같은 P2S5계열 glass (Li x P y Sz , 0 <x<3, 0<y<3, 0<z<7), 또는 이들의 혼합물 등이 있으나, 이에 한정되는 것은 아니다.

[0095] When the aforementioned high-k inorganic particles, piezoelectric inorganic particles, and lithium ion transferring inorganic particles are mixed, their synergistic effect can be doubled.

[0096] The separation membrane according to the present invention can form a pore structure of a porous coating layer together with pores included in a separation membrane substrate by controlling the size of inorganic particles constituting the porous coating layer, the content of the inorganic particles, and the composition of the inorganic particles and the binder polymer, and can also control the pore size and porosity together.

[0097] The average particle diameter of the above inorganic particles (D 50 ) may be, for example, about 1 ㎛ or less, or about 500 nm or less, or about 300 nm or less, for the formation of a porous coating layer of uniform thickness and its appropriate porosity. The average particle diameter (D) of the inorganic particles 50 ) satisfies this range, the dispersibility of the slurry for the porous coating layer is maintained, making it easy to control the properties of the separator, and the problem of excessive increase in the thickness of the separator, resulting in a decrease in the mechanical properties, or an internal short circuit occurring during battery charging and discharging due to an excessively large pore size can be prevented or suppressed.

[0098] The porosity of the above porous coating layer may range from about 5% to 95%, but is not limited thereto.

[0099] The content of the inorganic particles is not particularly limited, but may be, for example, about 50 wt% or more, about 60 wt% or more, about 95 wt% or less, about 97 wt% or less, or about 99 wt% or less, based on 100 wt% of the total weight of the porous coating layer. The weight ratio of the inorganic particles to the binder polymer may be, for example, about 50:50 or more, about 60:40 or more, about 70:30 or more, about 95:5 or less, about 97:3 or less, or about 99:1 or less, and may be from about 50:50 to 99:1, or from about 60:40 to 97:3, or from about 70:30 to 95:5. When the content of the above-mentioned inorganic particles satisfies this range, the problem of a decrease in 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 or suppressed, and the problem of a weakening of the peeling resistance of the porous coating layer due to a decrease in the adhesive force between inorganic particles due to a low content of the binder polymer can also be resolved.

[0100] The above binder polymer has a glass transition temperature (T g ) can be used as low as possible, for example, in the range of -200℃ to 200℃.

[0101] As an example, the binder polymer may include, but is not limited to, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trichloroethylene, polyvinylidene fluoride-chlorotrifluoroethylene, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxylmethyl cellulose, styrene butadiene copolymer, polyimide, or two or more thereof.

[0102] In the porous coating layer, the inorganic particles are filled and in contact with each other and are bound to each other by the binder polymer, thereby forming an interstitial volume between the inorganic particles, and the interstitial volume between the inorganic particles becomes an empty space to form pores.

[0103] In this embodiment, the binder polymer attaches the inorganic particles to each other so that they can remain bound to each other, for example, the binder polymer connects and fixes the inorganic particles together. In addition, the pores of the porous coating layer are pores formed by the interstitial volume between the inorganic particles becoming empty spaces, and these are spaces defined by the inorganic particles that are substantially in contact in a closed packed or densely packed structure by the inorganic particles.

[0104] In addition to the inorganic particles and binder polymers described above as components of the porous coating layer, other additives such as a conductive agent may be further included.

[0105] In one embodiment of the present invention, the thickness of the porous coating layer is not particularly limited as long as it satisfies the above-described ratio range relative to the total thickness of the separator, and may be, for example, about 0.5 ㎛ to 10 ㎛, about 0.5 ㎛ to 5 ㎛, or about 1.5 ㎛ to 3 ㎛.

[0106]

[0107] <Method for manufacturing a separation membrane>

[0108] A method for manufacturing a separation membrane according to one embodiment of the present invention may include a step of manufacturing a porous polymer substrate (S100) and a step of forming a porous coating layer (S200).

[0109] In one embodiment of the present invention, the porous polymer substrate can be manufactured by a conventional dry manufacturing method or a wet manufacturing method.

[0110] In one embodiment of the present invention, the dry manufacturing method can be manufactured by kneading a mixture containing a polymer resin, melt-extruding the mixture to prepare an unstretched sheet, and then stretching the unstretched sheet to obtain a stretched sheet.

[0111] In one embodiment of the present invention, the wet manufacturing method may include the steps of kneading a mixture including a polymer resin and a plasticizer, extruding the mixture to obtain an extrudate, cooling the extrudate on a casting roll to obtain a sheet, stretching the obtained sheet in the machine direction (MD) and the thickness direction (TD), and extracting the plasticizer from the stretched sheet with an organic solvent.

[0112] In one embodiment of the present invention, the polymer resin may include polyethylene such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, ultra-high molecular weight polyethylene, polypropylene, polybutylene, polypentene, polyester, polyethyleneterephthalate, polybutyleneterephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfide, polyethylenenaphthalene, or a mixture of two or more thereof.

[0113] In one embodiment of the present invention, a porous polymer substrate can be manufactured such that a portion between one end of the porous polymer substrate and a point (any point between the two ends) (hereinafter also referred to as a first portion) has a constant first thickness, and a portion between the one end and the other end (hereinafter also referred to as a second portion) has a thickness that decreases toward the other end, so that the thickness at the other end becomes a second thickness that is thinner than the first thickness.

[0114] In one embodiment of the present invention, the thickness of the porous polymer substrate can be controlled in the extrusion step or the stretching step. For example, the extrusion step may use a single-screw extruder or a twin-screw extruder, and a T-die is provided as a discharge unit. By controlling the T-die as a discharge unit, the thickness of the porous polymer can be controlled. In addition, the stretching step may be performed by roll method, tenter method sequential, or simultaneous stretching, and the thickness of the porous polymer can be controlled in the stretching step.

[0115]

[0116] Next, the step of forming the porous coating layer (S200) may include applying and drying a slurry for forming a porous coating layer on at least one surface of the porous polymer substrate manufactured in the step of manufacturing the porous polymer substrate (S100).

[0117] In one embodiment of the present invention, the slurry for forming the porous coating layer may be prepared by mixing inorganic particles and a binder polymer into a dispersion medium. In this case, the inorganic particles and the binder polymer may be substituted for those described above.

[0118] In one embodiment of the present invention, the dispersion medium may be a dispersion medium having a solubility index similar to that of the binder polymer to be used and a low boiling point. This is to facilitate uniform mixing and subsequent removal of the dispersion medium. Non-limiting examples of dispersion mediums that can be used include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (NMP), cyclohexane, water, or mixtures thereof.

[0119] In one embodiment of the present invention, after adding inorganic particles to a dispersion liquid in which the binder polymer is dispersed in a dispersion medium, a step of crushing the inorganic particles may be further included. At this time, the crushing time may be, for example, about 1 to 20 hours, and the particle size of the crushed inorganic particles may be about 0.001 μm to 10 μm as described above. A conventional method may be used for the crushing method, and for example, a ball mill method may be used.

[0120] In one embodiment of the present invention, the step of applying the slurry for forming the porous coating layer may use a conventional coating method known in the art as a method of coating on a porous polymer substrate, and various methods such as dip coating, die coating, roll coating, comma coating, or a mixed method thereof may be used.

[0121] In one embodiment of the present invention, the step of drying the slurry for forming the porous coating layer may be performed under a humidity condition of 10% to 80%, and may be dried by a method such as natural drying or hot air drying.

[0122] In one embodiment of the present invention, when applying the slurry for forming the porous coating layer, according to one embodiment, the thickness of the porous coating layer coated on both sides of the first portion of the porous polymer substrate having the first thickness is each constant to a third thickness, and the thickness of the porous coating layer coated on both sides of the second portion of the porous polymer substrate, which has a thickness that decreases toward the other end such that the thickness at the other end becomes the second thickness, is each increased toward the other end such that the thickness at the other end becomes the second thickness that is thicker than that of the first portion, can be formed. Through such a manufacturing process, the manufactured separator can have a constant thickness throughout.

[0123]

[0124] Electrode assembly and battery cell

[0125] An embodiment of the present invention provides an electrode assembly.

[0126] According to one aspect of the present invention, an electrode assembly is provided, comprising: a separator; a first electrode; and a second electrode, wherein the first electrode, the separator, and the second electrode are wound with the other end (A') of the separator as a winding axis.

[0127] As described above, the separation membrane has one end (A), another end (A') and a point (B) between the one end (A) and the other end (A') in the longitudinal direction, and the thickness of the separation membrane is maintained constant from the one end (A) to the other end (A'), and the thicknesses of the porous polymer substrate and the porous coating layer are maintained constant in the region (AB) between the one end (A) and the point (B), and the thickness of the porous polymer substrate decreases and the thickness of the porous coating layer increases in the region (BA') between the one point (B) and the other end (A').

[0128] The first electrode may be an anode and the second electrode may be a cathode, or the first electrode may be a cathode and the second electrode may be an anode.

[0129] In one embodiment of the present invention, the first electrode and the second electrode may be in the shape of rectangular sheets. In addition, the first electrode and the second electrode may be in the shape of sheets having an aspect ratio exceeding 1. Therefore, in the present specification, the first electrode may also be referred to as a first electrode plate, and the second electrode may also be referred to as a second electrode plate. In addition, the positive electrode may also be referred to as a positive electrode plate, and the negative electrode may also be referred to as a negative electrode plate.

[0130] In one embodiment of the present invention, the electrode assembly may be a jelly-roll type electrode assembly. For example, the electrode assembly may be a jelly-roll type electrode assembly having a structure in which a positive electrode plate as a first electrode, a negative electrode plate as a second electrode, and a separator interposed between the positive and negative electrode plates are wound in one direction, and the separator is a separator according to one embodiment of the present invention described above.

[0131] In one embodiment of the present invention, the electrode assembly may be laminated in the order of the first electrode, the separator, and the second electrode, or may be laminated in the order of the separator (i.e., the first separator), the first electrode, the separator (i.e., the second separator), and the second electrode.

[0132] In one embodiment of the present invention, the winding length of the electrode assembly may be about 1.5 m to 5 m, or about 2 m to 4.5 m.

[0133] In one embodiment of the present invention, the positive electrode active material coated on the positive electrode plate and the negative electrode active material coated on the negative electrode plate can be used without limitation as long as they are active materials known in the art.

[0134] The above positive electrode active material is a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxide (LiMnO2) such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxide such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-x M xLithiated nickel oxide, represented by the formula O2 (wherein M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3); chemical formula LiMn 2-x M x Lithium manganese composite oxides expressed as O2 (wherein M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (wherein M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which a portion of the lithium in the chemical formula is substituted with an alkaline earth metal ion; disulfide compounds; Fe2(MoO4)3 or composite oxides formed by combinations thereof, etc., which mainly contain lithium intercalation materials, and there are such types as the above, but are not limited to them.

[0135] In the present invention, the positive electrode active material is in the form of a single particle composed of one primary particle or a quasi-single particle that is an aggregate of 10 or fewer primary particles.

[0136] Previously, it was common to use spherical secondary particles composed of tens to hundreds of primary particles aggregated into positive electrode active materials. However, these secondary particles, which are composed of numerous primary particles aggregated into positive electrode active materials, are prone to particle breakage during the rolling process during the positive electrode manufacturing process, causing the primary particles to fall out, and cracks to form within the particles during the charge and discharge process. When the positive electrode active material particles break or cracks occur within the particles, the contact area with the electrolyte increases, which increases gas generation due to side reactions with the electrolyte. Increased gas generation within a cylindrical battery cell increases the pressure within the cell, posing a risk of battery explosion. For example, when the volume of a cylindrical battery cell is increased, the amount of active material within the cell increases accordingly, significantly increasing the amount of gas generated, thereby increasing the risk of battery ignition and / or explosion.

[0137] In comparison, the positive electrode active material in the form of a single particle or a pseudo-single particle in which 10 or fewer primary particles are aggregated has higher particle strength than the existing secondary particle type positive electrode active material in which tens to hundreds of primary particles are aggregated, so that particle breakage hardly occurs during rolling. In addition, in the case of the positive electrode active material in the form of a single particle or a pseudo-single particle, since the number of primary particles constituting the particle is small, the change due to volume expansion and contraction of the primary particles during charge and discharge is small, and accordingly, the occurrence of cracks inside the particle is also significantly reduced.

[0138] Therefore, when a cathode active material composed of single particles or pseudo-single particles is used as in the embodiment of the present invention, the amount of gas generated due to particle breakage and internal cracking can be significantly reduced, and thus, excellent safety can be achieved even in a large cylindrical battery cell. In the embodiment of the present invention, only a cathode active material in the form of single particles or pseudo-single particles is used as the cathode active material, and a cathode active material in the form of secondary particles is not used. This is because when a cathode active material in the form of secondary particles is included, the gas generation suppression effect is reduced, and sufficient safety cannot be obtained when applied to a large cylindrical battery cell.

[0139] Meanwhile, the cathode active material in the form of a single particle or pseudo-single particle according to an embodiment of the present invention has an average particle diameter D 50 The average particle diameter D of the positive electrode active material may be about 5 ㎛ or less, or about 1 ㎛ to 5 ㎛, or about 2 ㎛ to 5 ㎛. 50 When this above range is satisfied, the increase in resistance can be minimized.

[0140] Single particle or pseudo-single particle type cathode active materials have lower lithium mobility than secondary particle type cathode active materials because the interface between primary particles, which serves as a path for lithium ions to move within the particles, is small, which causes an increase in resistance. This increase in resistance becomes more severe as the particle size increases, and an increase in resistance adversely affects the capacity and output characteristics. Therefore, in the embodiment of the present invention, the average particle diameter D 50 By applying a single particle or pseudo-single particle positive electrode active material of 5 ㎛ or less, the movement distance of lithium ions within the particle can be minimized, thereby suppressing the increase in resistance.

[0141] The above positive electrode active material may have a primary particle size of about 0.5 ㎛ to 5 ㎛, or about 1 ㎛ to 5 ㎛, or 2 ㎛ to 5 ㎛. When the average particle size of the primary particles satisfies the above range, a positive electrode active material in the form of a single particle or a pseudo-single particle having excellent electrochemical characteristics can be formed. When the average particle size of the primary particles is too small, the number of agglomerates of the primary particles forming the positive electrode active material increases, which reduces the effect of suppressing particle breakage during rolling, and when the average particle size of the primary particles is too large, the lithium diffusion path within the primary particles becomes long, which may increase resistance and deteriorate output characteristics.

[0142] In one embodiment of the present invention, for example, the positive electrode active material may have a unimodal particle size distribution. Conventionally, bimodal positive electrode active materials have been widely used in which a large-particle positive electrode active material with a large average particle size and a small-particle positive electrode active material with a small average particle size are mixed to improve the electrode density of the positive electrode active material layer. However, as described above, in the case of positive electrode active materials in the form of single particles or pseudo-single particles, when the particle size increases, the lithium migration path becomes longer, significantly increasing the resistance. Therefore, when large-particle particles are mixed and used, a positive electrode active material having a unimodal distribution can be used to prevent the occurrence of problems in which capacity and output characteristics are deteriorated.

[0143] Meanwhile, the positive electrode active material may include a lithium nickel-based oxide, and for example, may include a lithium nickel-based oxide represented by the following chemical formula 1.

[0144] [Chemical Formula 1]

[0145] Li a Ni b Co c M 1 d M 2 e O2

[0146] In the above chemical formula 1, M 1may be Mn, Al or a combination thereof, and in one embodiment may be Mn or Mn and Al.

[0147] Above M 2 is at least one selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta and Nb, or may be at least one selected from the group consisting of Zr, Y, Mg and Ti, or may be Zr, Y or a combination thereof. M 2 Although elements are not essential, when included in appropriate amounts, they can promote grain growth during firing or play a role in improving crystal structure stability.

[0148] The above a represents the molar ratio of lithium in the lithium nickel-based oxide, and may be, for example, 0.8≤a≤1.2, 0.85≤a≤1.15, or 0.9≤a≤1.2. When the molar ratio of lithium satisfies the above range, the crystal structure of the lithium nickel-based oxide can be stably formed.

[0149] The above b represents the molar ratio of nickel among the total metals excluding lithium in the lithium nickel-based oxide, and may be, for example, 0.8≤b<1, 0.82≤b<1, or 0.83≤b<1. When the molar ratio of nickel satisfies the above range, a high energy density is exhibited, enabling high capacity implementation.

[0150] The above c represents the molar ratio of cobalt among all metals excluding lithium in the lithium nickel oxide, for example, 0 <c<0.2, 0<c<0.18, 또는 0.01≤c≤0.17일 수 있다. 코발트의 몰비가 상기 범위를 만족할 때, 양호한 저항 특성 및 출력 특성을 구현할 수 있다.

[0151] The above d is M of all metals excluding lithium in lithium nickel oxide. 1 Indicates the molar ratio of elements, for example, 0 <d<0.2, 0<d<0.18, 또는 0.01≤d≤0.17일 수 있다. M1 When the molar ratio of the elements satisfies the above range, the structural stability of the positive electrode active material is excellent.

[0152] The above e is M of all metals except lithium in lithium nickel oxide. 2 It represents the molar ratio of elements, for example, 0≤e≤0.1, or 0≤e≤0.05.

[0153] Meanwhile, the cathode active material according to the present invention may further include, if necessary, a coating layer including one or more coating elements selected from Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si and S on the surface of the lithium nickel-based oxide particles. For example, the coating element may be Al, B, Co or a combination thereof.

[0154] When a coating layer exists on the surface of lithium nickel-based oxide particles, the contact between the electrolyte and the lithium composite transition metal oxide is suppressed by the coating layer, thereby reducing the elution of transition metal or gas generation due to side reactions with the electrolyte.

[0155] The positive electrode active material may be included in an amount of about 80 parts by weight to 99 parts by weight, or about 85 parts by weight to 99 parts by weight, or about 90 parts by weight to 99 parts by weight, based on 100 parts by weight of the total positive electrode active material layer.

[0156] The above-described positive electrode current collector has a thickness of, for example, about 3 ㎛ to 500 ㎛. The positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. can be used. The electrode current collector can also form fine unevenness on its surface to increase the adhesiveness of the positive electrode active material, and various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric can be used.

[0157] A conductive material may be additionally mixed into the above-described positive electrode active material particles. The conductive material is added in an amount of about 1 to 50 parts by weight, for example, based on 100 parts by weight of the total positive electrode active material layer including the positive electrode active material. The conductive material is not particularly limited as long as it has high conductivity and does not cause chemical changes in the battery, and examples thereof include graphite such as natural graphite and 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 fluorocarbon, aluminum, and nickel powder; conductive whiskey such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0158] In addition, the negative electrode is manufactured by applying and drying negative electrode active material particles on the negative electrode current collector, and, if necessary, may further include components such as the conductive material, binder, solvent, etc. described above.

[0159] The above-described negative electrode current collector has a thickness of, for example, about 3 ㎛ to 500 ㎛. The negative electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, like the positive electrode current collector, the bonding strength of the negative electrode active material can be strengthened by forming fine unevenness on the surface, and can be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc.

[0160] The above negative active material is carbon such as non-graphitizable carbon, graphite carbon, etc.; Li x Fe2O3(0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me' y O z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of group 1, 2, and 3 of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8)의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5등의 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni계 재료 등을 사용할 수 있다.

[0161] The binder polymer usable in the above electrode is a component that assists in the bonding of electrode active material particles and conductive materials and the like and in the bonding to the electrode current collector, and is added in an amount of, for example, 1 to 50 parts by weight based on 100 parts by weight of the entire electrode active material layer including the electrode active material. Examples of such binder polymers include polyvinylidene fluoride-co-hexafluoropropylene (PVdF), polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, and cyanoethylflurane. Any one binder polymer selected from (cyanoethylpullulan), cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, or a mixture of two or more thereof, may be used, but is not limited thereto.

[0162] Non-limiting examples of solvents used in the above electrode preparation include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (NMP), cyclohexane, water, or mixtures thereof. These solvents provide an appropriate level of viscosity so that a slurry coating layer can be formed on the electrode current collector surface at a desired level.

[0163] The above negative electrode comprises a current collector; and a negative electrode active material layer located on at least one surface of the current collector and including a negative electrode active material, a binder polymer, and a conductive material, wherein the negative electrode active material layer comprises a lower region that contacts the current collector and an upper region that contacts the lower region and extends to the surface of the negative electrode active material layer, and the lower region and the upper region can each independently include at least two kinds or more of graphite and silicon-based compounds as negative electrode active materials.

[0164] The lower layer region may include natural graphite as a negative electrode active material, and the upper layer region may include artificial graphite as a negative electrode active material.

[0165] The lower layer region and the upper layer region may each independently further include a silicon-based compound as a negative electrode active material.

[0166] The above silicon compound may include at least one of SiOx (0≤x≤2) and SiC.

[0167] According to one aspect of the present invention, an embodiment of the present invention provides a battery cell.

[0168] In one embodiment of the present invention, the battery cell is configured such that the electrode assembly described above is loaded into a cylindrical battery housing together with an electrolyte.

[0169] For example, a first electrode; a second electrode and a separator interposed between the first electrode and the second electrode, wherein the separator has one end (A), another end (A') and a point (B) between the one end (A) and the other end (A') in the longitudinal direction, and the thickness of the separator is maintained constant from the one end (A) to the other end (A'), and the thickness of the porous polymer substrate and the porous coating layer is maintained constant in a region (AB) between the one end (A) and the point (B), and the thickness of the porous polymer substrate decreases and the thickness of the porous coating layer increases in a region (BA') between the one point (B) and the other end (A'), and the first electrode, the separator and the second electrode are wound around the other end (A') of the separator as a winding axis; a battery can in which the electrode assembly is accommodated; an electrolyte injected into the battery can; and may include a sealing body that seals the open end of the battery can.

[0170] Meanwhile, the form factor of the cylindrical battery housing may be 46110, 46800, 46950, 48110, 48750 or 48800.

[0171] A cylindrical battery cell according to one embodiment of the present invention may be 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, for example, the diameter (T) to the height (H)) of about 0.4 or more. Here, the form factor refers to a value indicating the diameter and height of the cylindrical battery cell. For example, in a numerical value indicating the form factor, the first 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.

[0172] For example, a cylindrical battery cell according to one embodiment of the present invention may be a 46110 cell (diameter 46 mm, height 110 mm, form factor ratio 0.418), a 46800 cell (diameter 46 mm, height 80 mm, form factor ratio 0.575), a 48950 cell (diameter 48 mm, height 95 mm, form factor ratio 0.505), a 48110 cell (diameter 48 mm, height 110 mm, form factor ratio 0.418), a 48750 cell (diameter 48 mm, height 75 mm, form factor ratio 0.64), or a 48800 cell (diameter 48 mm, height 80 mm, form factor ratio 0.600).

[0173] A cylindrical battery cell according to an embodiment of the present invention significantly reduces the amount of gas generated compared to conventional batteries by applying a cathode active material in the form of a single particle or pseudo-single particle, and thus can realize excellent safety even in a large cylindrical battery cell having a form factor ratio of 0.4 or more.

[0174] Meanwhile, the cylindrical cell according to the embodiment of the present invention may be, for example, a battery having a tab-less structure that does not include electrode tabs, but is not limited thereto.

[0175] The battery of the above tab-less structure may have, for example, a structure in which the positive and negative electrode plates each include a non-conductive portion where an active material layer is not formed, the positive and negative electrode non-conductive portions are respectively positioned at the top and bottom of the electrode assembly, a current collector plate is bonded to the positive and negative electrode non-conductive portions, and the current collector plate is connected to an electrode terminal.

[0176] An electrolyte that can be used in an electrode assembly according to an embodiment of the present invention is A + B - As a salt with the same structure as A + is Li + , Na + , K +B containing an ion composed of an alkali metal cation or a combination thereof; - is PF6 - , BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3 - The salt containing an anion such as or a combination thereof is dissolved or dissociated in an organic solvent consisting of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), gamma butyrolactone (g-butyrolactone) or a mixture thereof, but is not limited thereto. The electrolyte injection may be performed at an appropriate stage during the battery manufacturing process, depending on 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.

[0177] FIG. 4 is a drawing for explaining a battery pack (300) including a cylindrical battery cell (100) according to one embodiment of the present invention. Referring to FIG. 4, the battery pack (300) according to one embodiment of the present invention includes a battery assembly in which a plurality of cylindrical batteries (301) including a separator according to one embodiment of the present invention as described above are electrically connected, and a pack housing (302) that accommodates the battery assembly. In the drawing of the present invention, for the convenience of drawing, components such as a bus bar, a cooling unit, and a power terminal for electrical connection are omitted.

[0178] In one embodiment of the present invention, the battery pack (300) may be mounted on a vehicle. The vehicle may be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. The vehicle may include a four-wheel vehicle or a two-wheel vehicle.

[0179] FIG. 5 is a drawing for explaining a vehicle including the battery pack (300) of FIG. 4.

[0180] Referring to FIG. 5, a vehicle (V) according to one embodiment of the present invention includes a battery pack (300) according to one embodiment of the present invention. The vehicle (V) operates by receiving power from the battery pack (300) according to one embodiment of the present invention.

[0181] Hereinafter, the present invention will be described in more detail through examples, but the following examples are intended to illustrate the present invention, and the scope of the present invention is not limited to these examples.

[0182] For example, in Example 1 below, a method for manufacturing a separation membrane having a thickness of about 13 μm by forming a porous coating layer on both sides of a porous polymer substrate is exemplarily described.

[0183]

[0184] Example 1

[0185] Manufacturing of porous polymer substrates

[0186] A porous polymer substrate was manufactured using a polyethylene material having a weight average molecular weight of 600,000 g / mol. The porous polymer substrate was manufactured by stretching the fabric in the longitudinal direction (MD direction) so that the total width was 500 mm, the length (winding length) was 4 m, and the thicknesses measured at both ends were 10 ㎛ and 8 ㎛, respectively. That is, the porous polymer substrate was manufactured such that the thickness was constant at 10 ㎛ in a portion (hereinafter also referred to as the first portion) between one end and a point (any point between the two ends) of the porous polymer substrate, and the thickness decreased toward the other end in a portion (hereinafter also referred to as the second portion) between the one point and the other end, so that the thickness at the other end was 8 ㎛.

[0187] Formation of a porous coating layer

[0188] Water is used as a dispersion medium and alumina (D) is used as an inorganic particle. 50 = 500 nm) 94 parts by weight, 2.5 parts by weight of polyacrylic acid dispersant, 0.5 parts by weight of wetting agent, and 3 parts by weight of acrylate binder were mixed to prepare a slurry, and the slurry was coated on both sides of the porous polymer substrate using a doctor blade method and dried to form a porous coating layer on both sides of the porous polymer substrate. At this time, the loading amount of the porous coating layer was 6.2 g / m 2Among the manufactured membranes, a porous coating layer having a thickness of 1.5 μm was coated on both sides of a porous polymer substrate having a thickness of 10 μm, and a porous coating layer having a thickness of 2.5 μm was formed on both sides of a porous polymer substrate having a thickness of 8 μm. That is, the thickness of the porous coating layer coated on both sides of the first part of the porous polymer substrate having a thickness of 10 μm was constant at 1.5 μm, and the thickness of the porous coating layer coated on both sides of the second part of the porous polymer substrate, which decreased toward the other end and had a thickness of 8 μm at the other end, was increased toward the other end and had a thickness of 2.5 μm at the other end, so that the porous coating layer was formed.

[0189] The separation membrane manufactured by Example 1 has a constant thickness of 13 μm throughout.

[0190] The membrane manufactured in this way has one end (A), another end (A'), and a point (B) between the one end (A) and the other end (A') in the longitudinal direction, and the thickness of the membrane is maintained constant from the one end (A) to the other end (A'), and the thicknesses of the porous polymer substrate and the porous coating layer are maintained constant in the region (AB) between the one end (A) and the point (B), and the thickness of the porous polymer substrate in the region (BA') between the one point (B) and the other end (A') decreases toward the other end (A'), and the thickness of the porous coating layer increases toward the other end (A'). At this time, in the region (BA') between the one point (B) and the other end (A'), the thickness of the porous polymer substrate linearly decreases, and the thickness of the porous coating layer linearly increases.

[0191] In addition, the length from one end (A) to one point (B) was 40% of 100% of the length in the longitudinal direction of the membrane, and the thickness at the other end (A') of the porous polymer substrate was 80% of 100% of the thickness at one end (A) of the porous polymer substrate.

[0192] In addition, the content of the porous coating layer in the above region (BA') was 200 parts by weight based on 100 parts by weight of the porous coating layer in the above region (AB), and the content of the porous coating layer was 50 parts by weight based on 100 parts by weight of the porous polymer substrate.

[0193] Manufacturing of electrode assemblies and cylindrical battery cells

[0194] 17 positive electrodes and 16 negative electrodes were arranged crosswise on the upper and lower surfaces of the separator and the separator. The positive and negative electrodes had a burr at one end during the slitting process. At this time, the points where the positive ends are located on one side and the points where the negative ends are located on the other side were arranged crosswise so that the horizontal interval on the plane was 3 mm, and then wound to manufacture a jelly-roll type electrode assembly. Lithium cobalt oxide LCO was used as the positive active material, and graphite was used as the negative active material (N / P ratio > 100).

[0195] A positive current collector and a negative current collector were welded to the upper and lower portions of the above-mentioned jelly-roll type electrode assembly, respectively. Then, the electrode assembly with the positive current collector and the negative current collector welded thereto was inserted into a cylindrical battery housing having a pre-installed external terminal, the positive current collector and the external terminal were welded, and the edge of the negative current collector was welded to the beading portion. Then, the battery housing was introduced into the chamber of the electrolyte injection device, and the battery housing was erected so that the opening of the battery housing faced the direction opposite to gravity. Subsequently, LiPF6 was dissolved in an organic solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) in a ratio of 1:2:1 (volume ratio) to obtain a non-aqueous electrolyte solution by dissolving it to a concentration of 1.0 M. Then, the electrolyte was injected through the opening of the battery housing, and the chamber pressure was increased to 800 kPa over 20 seconds, maintained for 150 seconds, and then the chamber pressure was reduced to -90 kPa over 20 seconds, and a virtual vacuum state was maintained for 20 seconds. After the electrolyte impregnation process was completed, the opening of the battery housing was sealed using a gasket, completing the fabrication of a cylindrical cell.

[0196]

[0197] Comparative Example 1

[0198] In the above Example 1, the porous polymer substrate was manufactured to have a constant thickness of 10 μm, and the porous coating layer was coated to have a constant thickness when coating, so that the manufactured separator had a thickness of 13 μm, except that the manufacturing process was the same as Example 1.

[0199]

[0200] Experimental example

[0201] Experimental Example 1: Friction Coefficient Experiment

[0202] The separators of Example 1 and Comparative Example 1 were measured using a friction and wear device (Heidon). In order to simulate the phenomenon of the porous coating layer being detached due to the contraction / expansion of an electrode assembly including an electrode having a burr formed on the surface, repeated friction was applied with a 5g / Dia tip to the side of the separator with the thicker porous coating layer, and the friction coefficient was checked after 5 times and is shown in Table 1.

[0203] Friction coefficient Example 11.477 Comparative example 11.001

[0204] According to Table 1 above, the friction coefficient of the separator of Example 1 was higher than that of Comparative Example 1. That is, the separator of Example 1 had higher resistance to the tip, i.e., higher resistance to burrs of the electrode of the separator, compared to the separator of Comparative Example 1, and thus, it was confirmed that the degree of detachment of the porous coating layer due to repeated shrinkage and expansion of the electrode assembly was less, and thus the durability of the separator was superior.

[0205] Although the present disclosure has been described above with reference to embodiments thereof, it will be understood by those skilled in the art or having ordinary knowledge in the art that various modifications and changes to the various embodiments of the present disclosure may be made without departing from the technical scope of the various embodiments of the present disclosure as set forth in the claims below. Accordingly, the technical scope of the various embodiments of the present disclosure should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

Claims

1. As a separator, porous polymer substrate; and A porous coating layer formed on both sides of the porous polymer substrate and including inorganic particles and a binder polymer; The above separator has one end (A), another end (A') in the longitudinal direction, and a point (B) between the one end (A) and the other end (A'). The thickness of the separator is constant from the above-mentioned first end (A) to the other end (A'), In the region (AB) between the point (A) and the point (B), the thickness of the porous polymer substrate and the thickness of the porous coating layer are each constant. A separation membrane characterized in that the thickness of the porous polymer substrate decreases and the thickness of the porous coating layer increases in a region (BA') between the above-mentioned point (B) and the other end (A').

2. In claim 1, A separation membrane characterized in that the shape of the interface between the porous polymer substrate and the porous coating layer is asymmetrical with respect to a vertical line at the center of the longitudinal direction of the separation membrane.

3. In claim 1, A separation membrane characterized in that the shape of the interface between the porous polymer substrate and the porous coating layer is symmetrical with respect to a vertical line at the center of the thickness direction of the separation membrane.

4. In claim 1, A separation membrane characterized in that the thickness of the porous polymer substrate linearly decreases in a region (BA') between the above-mentioned point (B) and the other end (A'), and the thickness of the porous coating layer linearly increases.

5. In claim 1, A separation membrane characterized in that the length between the above-mentioned point (A) and the above-mentioned point (B) is about 10% to 70% of the length in the longitudinal direction of the separation membrane based on 100%.

6. In claim 1, A separation membrane characterized in that the thickness at the other end (A') of the porous polymer substrate is about 75% to 95% of the thickness at one end (A) of the porous polymer substrate.

7. In claim 1 A separation membrane characterized in that the content of the porous coating layer in the above region (BA') is about 40 to 1300 parts by weight based on 100 parts by weight of the porous coating layer in the above region (AB).

8. In claim 1, A separation membrane characterized in that the content of the porous coating layer is about 40 to 60 parts by weight relative to 100 parts by weight of the porous polymer substrate.

9. In claim 1, A separation membrane characterized in that the total length of the separation membrane in the longitudinal direction is about 1.5 m to 5 m.

10. A separation membrane according to claim 1; A first electrode in contact with one surface of the separator; and A second electrode is included in contact with the other surface of the separator, An electrode assembly in which the first electrode, the separator, and the second electrode are wound around the other end (A') of the separator as the winding axis.

11. In claim 10, An electrode assembly characterized in that the winding length of the electrode assembly is about 1.5 m to 5 m.

12. In claim 10, The electrode assembly is characterized in that the first electrode, the separator, and the second electrode are laminated in this order.

13. A battery cell in which the electrode assembly according to claim 10 is loaded into a cylindrical battery housing together with an electrolyte.

14. In claim 13, A battery cell characterized in that the form factor of the cylindrical battery housing is 46110, 46800, 46950, 48110, 48750 or 48800.

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