KR102621323B1 - A method for manufacturing an electrode assembly and an electrochemical device comprising the electrode assembly manufactured therefrom - Google Patents

Abstract

The electrode assembly manufacturing method according to the present invention is preset so that the separator substrate is deformed to the target size in terms of thickness, porosity, and pore size by the pressure and/or temperature applied during the lamination process, so that the separator substrate is converted to electricity after the lamination process. It can have a thickness, porosity, and pore size appropriate for driving a chemical device. Accordingly, in the electrode assembly obtained by the above manufacturing method, the separator has high insulation properties without lowering the breakdown voltage. In addition, even if high pressure is applied during the lamination process, there is less damage to the separator, and the process speed can be increased, improving processability.

Description

A method for manufacturing an electrode assembly and an electrochemical device comprising the electrode assembly manufactured therefrom}

The present invention relates to a method of manufacturing an electrode assembly for an electrochemical device and to an electrode assembly manufactured by the method. Additionally, the present invention relates to an electrochemical device including the electrode assembly.

Porous polymer film substrates are used as separators for electrochemical devices such as secondary batteries. Typically, electrode assemblies are manufactured through a lamination process in which a separator and an electrode are joined by heat and pressure. The higher the heat and pressure applied in this process, the higher the bonding force between the electrode and the separator. Recently, as the process speed has increased for the purpose of improving productivity, the time for which heat is applied to the separator has been shortened, and adhesion has been secured by increasing pressure to secure adhesion. However, by applying high pressure, the polymer film substrate used as the separator is Transformation occurs. For example, deformation or damage occurs, such as a decrease in the thickness of the polymer substrate, fracture, damage to pores, or a decrease in porosity. This may lead to a short circuit or a decrease in breakdown voltage. Additionally, in batteries using liquid electrolytes, electrolyte retention capacity may be reduced and ionic conductivity may be reduced. Accordingly, there is a request for the development of a new battery manufacturing method that can ensure the appropriate thickness, porosity, and pore size of the separator to demonstrate electrochemical performance in the final manufactured electrode assembly.

The present invention is a method of manufacturing an electrode assembly in which the separator substrate in the electrode assembly obtained by being modified by pressure conditions and/or temperature conditions applied during the lamination process for manufacturing an electrode assembly has the desired thickness, porosity, and pore size. The purpose is to provide. Another object of the present invention is to provide an electrode assembly obtained by the above method and the electrode assembly. It will be readily apparent that the objects and advantages of the present invention can be realized by means or methods and combinations thereof described in the claims.

A first aspect of the present invention relates to a method of manufacturing a battery, which method includes (S10) preparing a separator including a porous polymer substrate having a plurality of pores; and

(S20) a pressurizing step of placing the separator between the cathode and the anode and pressurizing it, wherein the porous polymer substrate includes a polymer resin and filler particles, and the porosity before performing the step (S20) is 60 vol% or more. The average pore size is 40nm to 70nm,

After performing the step (S20), the porosity reduction rate of the porous polymer substrate is 15% or more and the pore size reduction rate is 10% or more,

In step (S20), the pressurization is performed under conditions of 2Mpa or more.

A second aspect of the present invention is that in the first aspect, the porous polymer substrate includes a polyolefin-based polymer resin.

A third aspect of the present invention is that in the first or second aspect, the filler particles have a particle size of 0.001 μm to 100 μm.

The fourth aspect of the present invention is that in any one of the first to third aspects, the filler particles are included in a ratio of 50% to 85% by weight based on 100% by weight of the porous polymer substrate.

The fifth aspect of the present invention is that in any one of the first to fourth aspects, the maximum pore size of the porous polymer substrate in the step (S10) is 70 nm.

The sixth aspect of the present invention is that according to any one of the first to fifth aspects, the thickness of the porous polymer substrate in the step (S10) is 7㎛ to 25㎛.

The seventh aspect of the present invention is according to any one of the first to sixth aspects, wherein after performing the pressing step of (S20), the porous polymer substrate has a porosity of 45 vol% or less and an average pore size of 40 nm or less.

The eighth aspect of the present invention is according to any one of the first to seventh aspects, wherein the step (S1) involves coating an aqueous slurry mixed with an aqueous solvent, inorganic particles, and a water-dispersible binder resin on the surface of the porous polymer substrate. It is manufactured by doing so.

The electrode assembly manufacturing method according to the present invention is preset so that the separator substrate is deformed to the target size in terms of thickness, porosity, and pore size by the pressure and/or temperature applied during the lamination process, so that the separator substrate is converted to electricity after the lamination process. It can have a thickness, porosity, and pore size appropriate for driving a chemical device. Accordingly, in the electrode assembly obtained by the above manufacturing method, the separator has high insulation properties without lowering the breakdown voltage. In addition, even if high pressure is applied during the lamination process, there is less damage to the separator, and the process speed can be increased, improving processability.

Figure 1 shows a comparison of the cycle characteristics of the batteries of Example 1 and Comparative Example 4.
Figure 2 is an SEM image of the surface of the separator substrate of Example 1.
Figure 3 is an SEM image of the surface of the separator substrate of Comparative Example 1.

Hereinafter, the present invention will be described in detail. Prior to this, the terms or words used in this specification and patent claims should not be construed as limited to their usual or dictionary meanings, and the inventor should appropriately define the concept of terms in order to explain his or her invention in the best way. It must be interpreted with meaning and concept consistent with the technical idea of the present invention based on the principle that it can be done. Therefore, the embodiments described in this specification and the configurations shown in the drawings are only one of the most preferred embodiments of the present invention, and do not represent the entire technical idea of the present invention, so they can be replaced at the time of filing the present application. It should be understood that various equivalents and variations may exist.

Throughout the specification of the present application, when it is said that a part “includes” a certain component, this means that it does not exclude other components but may further include other components, unless specifically stated to the contrary.

In addition, the terms "about", "substantially", etc. used throughout the specification of the present application are used as meanings at or close to the numerical value when manufacturing and material tolerances inherent in the mentioned meaning are presented, and to aid understanding of the present application. It is used to prevent unscrupulous infringers from unfairly exploiting disclosures in which precise or absolute figures are mentioned.

Throughout this specification, the description of “A and/or B” means “A or B or both.”

In the present specification, porous properties mean that gaseous and/or liquid fluid can pass from one side of the object to the other side due to a structure in which the object includes a plurality of pores and the pores are connected to each other.

The present invention relates to a method of manufacturing an electrode assembly for an electrochemical device. Additionally, it relates to an electrode assembly obtained by the above manufacturing method and an electrochemical device including the electrode assembly. In the present invention, the electrochemical device is a device that converts chemical energy into electrical energy through an electrochemical reaction, and is a concept encompassing a primary battery and a secondary battery. In this specification, the secondary battery is capable of charging and discharging, and refers to a lithium ion secondary battery, a nickel-cadmium battery, a nickel-hydrogen battery, etc. The lithium ion secondary battery uses lithium ions as an ion conductor, and includes a non-aqueous electrolyte secondary battery containing a liquid electrolyte, an all-solid-state battery containing a solid electrolyte, a lithium polymer battery containing a gel polymer electrolyte, and lithium metal as the negative electrode. Examples include, but are not limited to, lithium metal batteries.

The manufacturing method of the electrode assembly according to one embodiment of the present invention is as follows.

The method for manufacturing an electrode assembly according to the present invention includes (S10) preparing a separator including a porous separator substrate; and (S20) a pressurizing step of placing the separator between the cathode and the anode and pressing it.

In particular, in the present invention, the porous separator substrate includes a polymer resin and filler particles, and before performing the step (S20), the separator substrate has a porosity of 60 vol% or more and an average pore size of 40 nm to 80 nm. In addition, after performing the step (S20), the porosity reduction rate of the separator substrate is 15 vol% or more and the pore size reduction rate is 10% or more.

Meanwhile, in step (S20), the pressurization may be performed under conditions of 2Mpa or more.

Next, the manufacturing method is described in more detail for each step.

First, prepare a separator including a porous separator substrate (S10). In the above separator substrate, for convenience of description of the invention, if necessary, the separator substrate in the state before the (S20) step is applied is referred to as 'separator substrate (Pre)', and the separator substrate in the state after the (S20) step is applied is referred to as 'the separator substrate (Pre)'. It is referred to as ‘separator substrate (Post)’.

In the present specification, the separator has a porous characteristic including a plurality of pores, and serves as a porous ion-conducting barrier that allows ions to pass while blocking electrical contact between the cathode and anode in an electrochemical device. .

The separator may additionally have different layers in terms of material or function on at least one surface of the separator substrate as needed. In one embodiment of the present invention, the separator may have an organic/inorganic composite coating layer including inorganic particles and/or binder material formed on at least one side or both sides of the separator substrate.

The separator substrate is a porous membrane containing a polymer material. Additionally, the separator substrate may include filler particles. The filler particles are introduced for the purpose of a pressure barrier to prevent the thickness, pore size, and porosity of the separator substrate from being excessively reduced in response to the high pressure applied in the lamination process, which will be described later. The filler particles may include organic fillers and/or inorganic fillers having a predetermined particle size, and are not limited to specific components as long as they have a strength equal to or greater than that of the polymer material.

Meanwhile, in one embodiment of the present invention, the polymer material may include a thermoplastic resin from the viewpoint of providing a shutdown function. The shutdown function refers to a function that prevents thermal runaway of the battery by blocking the movement of ions between the anode and the cathode by melting the polymer resin and closing the pores of the porous substrate when the battery temperature becomes high.

As such a thermoplastic resin, a thermoplastic resin with a melting point of less than 200° C. may be used, and in particular, it may include a polyolefin-based polymer resin. Examples of the polyolefin-based polymer resin include polyethylene, polypropylene, and polypentene. In one embodiment of the present invention, the thermoplastic resin may include two or more selected from polyethylene, polypropylene, and polypentene.

Meanwhile, in a specific embodiment of the present invention, the separator substrate may be selected from polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyether sulfone, It may further include at least one of polymer resins such as polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalene.

In one embodiment of the present invention, the separator substrate is made by melting and extruding a polymer material, forming it into a sheet shape, and then stretching it to cause micro cracks between lamellas, which are crystal parts of the polymer, to form micro voids. It may be manufactured using the prescribed method (dry method). Alternatively, the separator substrate is manufactured by a method (wet method) of mixing a polymer material with a plasticizer (diluents) at a high temperature to create a single phase, causing the polymer material and the plasticizer to phase separate during the cooling process, and then extracting the plasticizer to form pores. You can.

The size of the filler particles may be less than 0.001㎛ to 100㎛. Preferably, the filler particles may have a particle diameter of 0.01㎛ to 0.1㎛, and can be appropriately adjusted within the above range in consideration of the target thickness after the lamination process of the separator substrate.

Meanwhile, in one embodiment of the present invention, the filler particles may be included in the range of 50% to 85% by weight of the total 100% by weight of the porous polymer base. If the content of the filler particles is less than 50% by weight compared to 100% by weight of the porous polymer substrate, when a separator substrate with high initial porosity is applied to the electrode assembly, it is excessively compressed in the pressurization in the subsequent step (S20), resulting in porosity and Breathability characteristics may be reduced. Plastic engineering resins can be used as the organic filler, specifically polysulfone-based polymer resin (PSF), polyethersulfone-based polymer resin (PES), polyetherimide-based polymer resin (PEI), and polyphenylene sulfide-based polymer resin. Among polymer resins (PPS), polyether ether ketone polymer resins (PEEK), polyarylate polymer resins (PA), polyamideimide polymer resins (PAI), polyimide polymer resins (PI), and polyamide polymer resins. It may include one selected type or a mixture of two or more.

The inorganic fillers include BaTiO ₃ , Pb(Zr,Ti)O ₃ (PZT), b _1-x La _x Zr _1-y Ti _y O ₃ (PLZT, 0<x<1, 0<y<1), Pb(Mg _1/3 Nb _2/3 )O ₃ -PbTiO ₃ (PMN-PT), hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, Mg(OH) ₂ , NiO, CaO, ZnO, ZrO ₂ , SiO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC, Al(OH) ₃ , TiO ₂ , aluminum peroxide, zinc tin hydroxide (ZnSn(OH) ₆ ), tin-zinc oxide (Zn ₂ It may include one or a mixture of two or more selected from SnO ₄ , ZnSnO ₃ ), antimony trioxide (Sb ₂ O ₃ ), antimony tetroxide (Sb ₂ O ₄ ), and antimony pentoxide (Sb ₂ O ₅ ).

Meanwhile, in the present invention, in (S10), the separator substrate (pre) may have a porosity of 60 vol% or more, and the average pore size may be 40 nm to 70 nm. Meanwhile, the maximum pore size is 70 nm or less, or 60 nm or less. If the porosity of the separator substrate (pre) is less than 60 vol%, the porosity may decrease in the subsequent lamination process, which is not desirable because air permeability and resistance may increase excessively. Meanwhile, the porosity of the separator substrate (pre) is preferably 80 vol% or less. If it exceeds 80 vol%, the porosity will remain above 50 vol% even after step (S20), which may result in insulation failure. In addition, since the amount of binder resin used is small, safety may be impaired, such as increasing the possibility of a short circuit occurring.

On the other hand, if the average pore size is 40 nm or less, the average pore size may be reduced to 20 nn or less after the lamination process, resulting in a large increase in air permeability and a decrease in capacity due to by-products blocking small pores during charging and discharging of the battery. On the other hand, if the maximum pore size is 70 nm or more, the thickness of the separator substrate may not be uniform and thickness deformation may occur, and local thickness deformation may cause low compression resistance and deteriorate insulation properties.

In the present invention, the term 'porosity' refers to the ratio of the volume occupied by pores to the total volume, and vol% is used as its unit, and can be used interchangeably with terms such as porosity and porosity. . In the present invention, the measurement of the porosity is not particularly limited, and according to an embodiment of the present invention, for example, by BET (Brunauer-Emmett-Teller) measurement using nitrogen gas or mercury infiltration (Hg porosimeter). It can be measured. Or, in one embodiment of the present invention, the true density of the separator is calculated from the density of the obtained separator (apparent density), the composition ratio of the materials contained in the separator, and the density of each component, and the apparent density and true density ( The porosity of the separator can be calculated from the difference in net density.

Meanwhile, the size of the pores can be calculated from the pore size distribution measured using the Capillary flow Porometer method. For example, first, the separator substrate to be measured is wetted with a wetting agent such as galwick solution, and then the air pressure on one side of the substrate is gradually increased. At this time, when the applied air pressure becomes greater than the capillary attraction of the wetting agent present in the pore, the wetting agent blocking the pore is pushed out, and the pore size and distribution can be measured through the pressure and flow rate at the moment of being pushed out. In one embodiment, the range of air pressure can be controlled to 30-450 psi.

Meanwhile, in the present invention, the separator substrate (pre) may have a thickness of 7㎛ to 25㎛. If the thickness of the porous substrate does not fall within the above numerical range, it is difficult to secure an appropriate thickness of the separator post after the lamination process described later. On the other hand, if it exceeds the above range too much (i.e., if it is too thick), the resistance of the separator becomes difficult. This may increase excessively.

Meanwhile, in one embodiment of the present invention, the separator may further include an organic/inorganic composite coating layer formed on at least one surface of the separator substrate.

The organic/inorganic composite coating layer contains a binder resin and inorganic particles and has porous properties. In one embodiment of the present invention, the binder resin and the inorganic particles in the organic/inorganic composite coating layer may be included in a weight ratio of 1:99 to 30:70. The ratio may be appropriately adjusted within the above range. For example, the total of binder resin and inorganic particles may be 100 wt%, the binder resin may be 1 wt% or more, 5 wt% or more, or 10 wt% or more, and the inorganic particles may be 80 wt% or more. wt% or more, 85 wt% or more, 90 wt% or more, or 95 wt% or more.

The organic/inorganic composite coating layer may be formed by binding inorganic particles with a binder resin and accumulating them on one side. Pores inside the organic/inorganic composite coating layer may result from an interstitial volume, which is an empty space between the inorganic particles.

In one embodiment of the present invention, the porosity of the organic/inorganic composite coating layer and the heat-resistant layer may be 30 vol% to 70 vol%. If the porosity is 70 vol% or less, mechanical properties that can withstand the press process for bonding to the electrode can be secured, and the surface opening ratio is not too high, making it suitable for securing adhesion. On the other hand, if the porosity is 30 vol% or more, it is advantageous from the viewpoint of ion permeability.

The thickness of the organic/inorganic composite coating layer may be 1㎛ to 20㎛ on either side of the separator substrate, but is not particularly limited thereto. The thickness can be adjusted to an appropriate range by a person skilled in the art in terms of heat resistance or electrical resistance.

Non-limiting examples of binder resins that can be used in the organic/inorganic composite coating layer in the present invention include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-trichloroethylene ( polyvinylidene fluoride-co-trichloroethylene), polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene Vinyl acetate copolymer (polyethylene-co-vinyl acetate), polyethylene oxide, polyarylate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose It may be any one polymer resin selected from the group consisting of cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, or a mixture of two or more of these. However, it is not particularly limited to this.

In a specific embodiment of the present invention, the inorganic particles usable in the organic/inorganic composite coating layer 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 not particularly limited as long as they do not cause oxidation and/or reduction reactions in the operating voltage range of the applied electrochemical device (for example, 0 to 5 V based on Li/Li ⁺ ).

Non-limiting examples of the inorganic particles include BaTiO ₃ , Pb(Zr,Ti)O ₃ (PZT), b _1-x La _x Zr _1-y Ti _y O ₃ (PLZT, 0<x<1, 0<y <1), Pb(Mg _1/3 Nb _2/3 )O ₃ -PbTiO ₃ (PMN-PT), hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, Mg(OH) ₂ , NiO, CaO, ZnO, ZrO ₂ , SiO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC, Al(OH) ₃ , TiO ₂ , aluminum peroxide, zinc tin hydroxide (ZnSn(OH) ₆ ), tin-zinc Oxides (Zn ₂ SnO ₄ , ZnSnO ₃ ), antimony trioxide (Sb ₂ O ₃ ), antimony tetroxide (Sb ₂ O ₄ ), antimony pentoxide (Sb ₂ O ₅ ), etc., one or two or more of these may be used. It can be included.

In addition, the average diameter (D ₅₀ ) of the inorganic particles is not particularly limited, but is preferably in the range of 0.3 ㎛ to 1 ㎛ for the formation of a coating layer of uniform thickness and an appropriate porosity. If it is less than 0.3㎛, the dispersibility of inorganic particles in the slurry prepared for manufacturing the heat-resistant layer may decrease, and if it exceeds 1㎛, the thickness of the coating layer formed may increase.

In one embodiment of the present invention, the organic/inorganic composite coating layer may be manufactured using an aqueous slurry containing an aqueous solvent. First, an aqueous slurry is prepared by adding inorganic particles and binder resin into an aqueous solvent. The aqueous solvent contains water, and may further contain alcohol having 2 to 5 carbon atoms in addition to water. Additionally, the binder resin preferably has water dispersibility properties. In the present invention, the separator substrate has a large pore diameter and high porosity, so when using an organic slurry in which a polymer resin is dissolved using an organic solvent, the organic slurry penetrates into the pores of the separator substrate and destroys the separator substrate. Porosity may decrease. Accordingly, in the present invention, it is preferable that the organic/inorganic composite coating layer is formed using an aqueous slurry. When an aqueous slurry is applied in this way, the binder resin in the organic/inorganic composite coating layer can maintain its particle shape. In the present invention, the content ratio of the inorganic particles and the binder is as described above and is appropriately adjusted in consideration of the thickness, pore size, and porosity of the heat-resistant layer of the present invention to be finally manufactured.

Next, the inorganic particle slurry prepared above is applied to at least one side of the prepared separator substrate and dried. The method of applying the slurry to the surface of the separator substrate is not limited to any one method in particular, and conventional methods known in the art can be used. For example, various methods such as dip coating, die coating, roll coating, comma coating, or a combination thereof can be used.

In the drying process, temperature and time conditions are appropriately set to minimize the occurrence of surface defects in the organic/inorganic composite coating layer. For the drying, a drying auxiliary device such as a drying oven or hot air may be used within an appropriate range.

Next, (S20) a lamination process is performed in which the separator obtained in (S10) is placed between the cathode and the anode and pressed.

After performing the step (S20), the porosity reduction rate of the separator substrate (post) is more than 15% and the pore size reduction rate is more than 10%. In one embodiment of the present invention, the porosity of the separator substrate (post) may be 45 vol% or less, and the average pore size may be 40 nm or less.

In one embodiment of the present invention, the production of the electrode assembly can be performed by a lamination process in which the separator obtained by the above-described method is stacked between the cathode and the anode and bonded by pressing. In one embodiment of the present invention, the lamination process may be performed by a roll press or hot press device including a pair of pressure rollers. That is, interlayer adhesion can be achieved by sequentially stacking the cathode, separator, and anode and inserting them between the plates of the pressure roller or hot press device. At this time, the lamination process may be performed by hot pressing. As described above, before the lamination process for manufacturing the electrode assembly, the separator substrate is thick and has high porosity and pore size, so the target size can ultimately be reached by the pressure applied in the lamination process. Additionally, because the filler particles contained in the separator substrate have a cushioning effect, the separator is prevented from being excessively compressed during the lamination process.

Meanwhile, in the present invention, the pressurization in step (S20) may be performed under conditions of 2Mpa or more. The electrode assembly manufacturing process according to the present invention calculates the strain rate of the separator substrate after the lamination process and reflects this on the separator substrate (pre), so that the separator substrate has a target size after the lamination process. Accordingly, the final size is obtained by the manufacturing method of the present invention. The obtained electrode assembly can ensure that the separator substrate has thickness, porosity, and pore size appropriate for battery operation. Additionally, the inclusion of filler particles in the separator substrate has the effect of preventing excessive deformation of the separator substrate. Accordingly, the pressure applied during the lamination process can be controlled to 7 MPa or more, and even when such a high pressure is applied, the separator substrate is not excessively deformed. On the other hand, the process speed is increased, which has the effect of improving process efficiency.

In the present invention, the positive electrode includes a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material, a conductive material, and a binder resin on at least one surface of the current collector. The positive electrode active material is a layered compound such as lithium manganese composite oxide (LiMn ₂ O4, LiMnO ₂ , etc.), lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Lithium manganese oxide with the formula Li _1+x Mn _2-x O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO _{2 ,} etc.; lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiV ₃ O ₄ , V ₂ O ₅ , and Cu ₂ V ₂ O ₇ ; Ni site-type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and x = 0.01 to 0.3); _{Chemical formula LiMn 1 -xM _} , Cu or Zn), expressed as lithium manganese complex oxide; LiMn ₂ O ₄ in which part of Li in the chemical formula is replaced with an alkaline earth metal ion; disulfide compounds; It may include one type or a mixture of two or more types of Fe ₂ (MoO ₄ ) ₃ .

In the present invention, the negative electrode includes a negative electrode current collector and a negative electrode active material layer containing a negative electrode active material, a conductive material, and a binder resin on at least one surface of the current collector. The negative electrode includes carbon such as lithium metal oxide, non-graphitizable carbon, and graphitic carbon as a negative electrode active material; LixFe ₂ O ₃ (0≤x≤1), Li _x WO ₂ (0≤x≤1), Sn _x Me _1-x Me' _y O _z (Me: Mn, Fe, Pb, Ge; Me': Al , B, P, Si, elements of groups 1, 2, and 3 of the periodic table, halogen; metal complex oxides such as 0<x≤1;1≤y≤3;1≤z≤8); lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ , and metal oxides such as Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni based materials; It may contain one type or a mixture of two or more types selected from titanium oxide.

In a specific embodiment of the present invention, the conductive material is, for example, graphite, carbon black, carbon fiber or metal fiber, metal powder, conductive whisker, conductive metal oxide, activated carbon, and polyphenylene derivative. It may be any one selected from the group consisting of or a mixture of two or more types of conductive materials. More specifically, natural graphite, artificial graphite, super-p, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, denka black, aluminum powder, nickel powder, oxidation. It may be one type selected from the group consisting of zinc, potassium titanate, and titanium oxide, or a mixture of two or more types of conductive materials thereof.

The current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, for example, stainless steel, copper, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel. A surface treated with carbon, nickel, titanium, silver, etc. may be used.

As the binder resin, polymers commonly used in electrodes in the art can be used. Non-limiting examples of such binder resins include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, and polymethyl methacrylate ( polymethylmethacrylate, polyethylhexyl acrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene vinyl acetate copolymer (polyethylene-co-vinyl acetate), polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, Cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan and carboxyl methyl cellulose. cellulose), etc., but is not limited thereto.

The electrode assembly prepared as above can be charged into an appropriate case and an electrolyte solution can be injected to manufacture a battery.

In the present invention, the electrolyte solution is a salt with the same structure as A ⁺ B ^- , where A ⁺ contains an alkali metal cation such as Li ⁺ , Na ⁺ , K ⁺ or an ion consisting of a combination thereof, and B ^- contains 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(CF ₂ SO ₂ ) ₃ ^- Salts containing anions such as or a combination of these are propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and dipropyl carbonate (DPC). , dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC), gamma butyrolactone (g-butyrolactone) ) or a mixture thereof that is dissolved or dissociated in an organic solvent, but is not limited to this.

Additionally, the present invention provides a battery module including a battery including the electrode assembly as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source. Specific examples of the device include a power tool that is powered by an omni-electric motor and moves; Electric vehicles, including Electric Vehicle (EV), Hybrid Electric Vehicle (HEV), Plug-in Hybrid Electric Vehicle (PHEV), etc.; Electric two-wheeled vehicles, including electric bicycles (E-bikes) and electric scooters (E-scooters); electric golf cart; Examples include, but are not limited to, power storage systems.

Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention may be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described in detail below. Examples of the present invention are provided to more completely explain the present invention to those with average knowledge in the art.

[Example]

1) Preparation of separation membrane

Example 1

A separator substrate was manufactured using high-density polyethylene (weight average molecular weight (Mw): 300,000, Tg: 135°C), SiO ₂ (particle diameter: 50㎛), and diluent (liquid paraffin oil and soybean oil mixed at a weight ratio of 1:1). . At this time, the ratio of polyolefin: diluent: inorganic particles was set to 25:50:25 by weight.

The above ingredients were put into a twin-screw extruder, kneaded, passed through a die and a cooling casting roll, and molded into a sheet. Afterwards, MD stretching was performed, followed by twin-screw stretching using a tenter-type sequential stretching machine for TD stretching. Both MD stretching ratio and TD stretching ratio were set to 5.5 times. The diluent was removed from the stretched sheet, and heat-set at 127°C to obtain a separator substrate.

Figure 2 shows an SEM photograph of the surface of the separator substrate obtained in Example 1.

Next, alumina, dispersant (CMC), binder resin 1 (Acrylate polymer, Tg: -40℃), binder resin 2 (Acrylate polymer, Tg: 40℃), and wetting agent (fluorosurfactant) were mixed in a weight ratio of 80:1:2:16.5. An aqueous slurry was prepared by adding it to water at a ratio of :0.5. The aqueous slurry was coated on both sides of the separator substrate to prepare a separator with a thickness of 2 ㎛ on each side and a total thickness of 4 ㎛ on both sides.

Comparative Example 1

A separator substrate containing high-density polyethylene and diluent in the same ratio was manufactured in the same manner as in Example 1, except that inorganic particles SiO ₂ were not used. Figure 3 shows an SEM photograph of the surface of the separator substrate obtained in Comparative Example 1.

Next, alumina, dispersant (cyano resin), and binder resin (PVDF-HFP) were added to acetone at a weight ratio of 80:2:18 to prepare an oil-based slurry. The oil-based slurry was coated on both sides of the separator substrate to prepare a separator with a thickness of 2 ㎛ on each side and a total thickness of 4 ㎛ on both sides.

Comparative Example 2

A separator substrate was prepared in the same manner as in Example 1. Next, alumina, dispersant (Cyano resin), and binder resin 1 (PVdF-HFP) were added to acetone at a weight ratio of 80:2:18 to prepare an oil-based slurry. The oil-based slurry was coated on both sides of the separator substrate to prepare a separator with a thickness of 2 ㎛ on each side and a total thickness of 4 ㎛ on both sides.

Comparative Example 3

A separator substrate was manufactured in the same manner as Comparative Example 1. Next, alumina, dispersant (CMC), binder resin 1 (Acrylate polymer, Tg: -40℃), binder resin 2 (Acrylate polymer, Tg: 40℃), and wetting agent (fluorosurfactant) were mixed in a weight ratio of 80:1:2:16.5. An aqueous slurry was prepared by adding it to water at a ratio of :0.5. The aqueous slurry was coated on both sides of the separator substrate to prepare a separator with a thickness of 2 ㎛ on each side and a total thickness of 4 ㎛ on both sides.

Comparative Example 4

A separator substrate was manufactured in the same manner as Comparative Example 1. Next, alumina, dispersant (CMC), binder resin 1 (Acrylate polymer, Tg: -40℃), binder resin 2 (Acrylate polymer, Tg: 40℃), and wetting agent (fluorosurfactant) were mixed in a weight ratio of 80:1:2:16.5. An aqueous slurry was prepared by adding it to water at a ratio of :0.5. The aqueous slurry was coated on both sides of the separator substrate to prepare a separator with a thickness of 2 ㎛ on each side and a total thickness of 4 ㎛ on both sides.

The separator substrate (pre) obtained in each of the above examples and comparative examples is as follows.

thickness
(㎛) Porosity
(vol%) average pore size maximum pore size presence or absence of filler
Coating layer composition Example 1 9㎛ 62vol% 45nm 70㎛ you water system Comparative Example 1 9㎛ 40vol% 38nm 60㎛ radish bounded Comparative Example 2 9㎛ 62vol% 45nm 70㎛ you bounded Comparative Example 3 9㎛ 40vol% 45nm 70㎛ radish water system Comparative Example 4 9㎛ 65vol% 25nm 60㎛ radish water system

Separator base (pre) separator Ventilation
(sec/100cc) resistance
(Ω) ventilation
(sec/100cc) resistance
(Ω) Example 1 45 0.28 75 0.42 Comparative Example 1 86 0.43 147 0.77 Comparative Example 2 45 0.28 268 1.21 Comparative Example 3 72 0.39 109 0.69 Comparative Example 4 42 0.28 72 0.40

2) Manufacturing of electrode assembly

1) Manufacturing of anode

Cathode active material (LiNi _0.8 Mn _0.1 Co _0.1 O ₂ ), conductive material (carbon black), dispersant and binder resin (PVDF) are mixed with water at a weight ratio of 97.5:0.7:0.2:1.6, and the remaining components excluding water are 50 wt%. A slurry for the positive electrode active material layer with a high concentration was prepared. Next, the slurry was applied to the surface of an aluminum thin film (10㎛ thick) and dried to prepare a positive electrode having a positive electrode active material layer (120㎛ thick).

2) Preparation of cathode

Graphite (natural graphite and artificial graphite blend), conductive material (carbon black), dispersant and binder resin (SBR) are mixed with water at a weight ratio of 97.5:0.7:1.1:0.7 to create a cathode with a concentration of 50 wt% of the remaining components excluding water. A slurry for the active material layer was prepared. Next, the slurry was applied to the surface of a copper thin film (10㎛ thick) and dried to prepare a negative electrode with a negative electrode active material layer (120㎛ thick).

3) Lamination process

An electrode assembly was obtained by stacking the prepared cathode and anode with a separator interposed between them and performing a lamination process. The lamination process was performed for 10 seconds at 70°C and 5.2 MPa using a hot press.

Separator base (post) separator Porosity (vol%) Average pore size (nm) Maximum pore size (nm) Ventilation
(sec/100cc) resistance
(Ω) insulation breakdown
Voltage Ventilation
(sec/100cc) resistance
(Ω) Example 1 45 40 60 90 0.42 665 120 0.67 Comparative Example 1 37 32 55 110 0.59 447 197 1.00 Comparative Example 2 48 42 63 98 0.45 670 417 1.51 Comparative Example 3 32 45 65 115 0.62 420 165 0.92 Comparative Example 4 60 22 55 88 0.39 490 120 0.65

Porosity
Difference (vol%) Porosity
Decrease rate (%) pore size
Difference (based on average pore size, nm) pore size
Decrease rate (%) Example 1 17 27.4 5 11.1 Comparative Example 1 3 7.5 6 15.7 Comparative Example 2 14 22.6 3 6.6 Comparative Example 3 8 20.0 0 0 Comparative Example 4 5 7.7 3 12.0

As can be seen in [Table 3] and [Table 4], it was confirmed that according to the manufacturing method of Example 1 of the present invention, the resistance, air permeability, and insulation were superior to the separator of the comparative example. Meanwhile, Figure 1 shows the measured remaining capacities of Example 1 and Comparative Example 4. According to this, Comparative Example 4 had a similar porosity to Example 1, but the pore size was small, so it was confirmed that the pores were blocked during charging and discharging, resulting in a decrease in capacity retention rate.

The difference in porosity in [Table 4] represents the difference in porosity between [Table 1] and [Table 3]. Meanwhile, the porosity reduction rate was calculated based on the formula in Equation 1 below.

(Equation 1) Porosity reduction rate (%)= (A-B/A)*100

In Equation 1, A is the porosity value of the separator substrate before (S20), and B represents the porosity value of the separator substrate obtained after performing (S20).

Meanwhile, the pore size difference in Table 4 represents the difference in average pore size between Tables 1 and 3. Meanwhile, the pore size reduction rate was calculated based on the formula in Equation 2 below.

(Equation 2) Pore size reduction rate (%)= (C-D/C)*100

In Equation 2, C is the average pore size of the separator substrate before (S20), and D represents the average pore size of the separator substrate obtained after (S20).

4. Physical property evaluation

1) Obtaining the separator substrate (post)

The cathode and anode were peeled and removed from the electrode assemblies obtained in each Example and Comparative Example, the separator was taken out, and the organic/inorganic composite coating layer of the separator was removed using acetone to obtain a separator substrate.

2) Measurement of breathability

The air permeability was measured using Asahi Seico's EG01-55-1MR equipment.

3) Pore size measurement

It was measured according to pore size distribution using a capillary flow posometer (CFP method).

4) Porosity measurement

The thickness (um) and weight (g/m ² ) of the separator were measured, and porosity was calculated according to Equation 1 below.

(Formula 1) Porosity = {(Binder resin density of separator - (Weight of separator/Thickness of separator))/Binder resin density of separator} x 100

5) Resistance measurement

For the resistance, a coin cell was manufactured by interposing each separator substrate between SUS and injecting electrolyte, and the resistance (ER) was measured using the EIS method. At this time, the frequency was in the range of 100000~10000Hz. The electrolyte solution is a mixture of LiPF ₆ at a concentration of 1M in a non-aqueous solvent in which ethylene carbonate and ethylmethyl carbonate are mixed at a ratio of 3:7.

6) Insulation breakdown voltage

After hot pressing the Sus mesh and the separator substrate at 90°C, 4Mpa, 1s, the voltage was increased at a rate of 100V/s to determine the voltage reaching the fail condition (>0.5mA, 3s). For each example and comparative example, the breakdown voltage of 30 samples was measured and the lowest 1% voltage was derived through Weibull distribution analysis.

7) Capacity maintenance rate

For the batteries manufactured in Example 1 and Comparative Example 4, charging and discharging were repeated in the range of 2.5V to 4.25V at a rate of 1C each, and the ratio of the discharge capacity after each cycle to the initial discharge capacity was calculated. did. The capacity retention rate evaluation was performed at room temperature conditions.

Claims (8)

(S10) preparing a separator including a porous polymer substrate with multiple pores; and
(S20) a pressurizing step of placing the separator between the cathode and the anode and pressing it,
The separation membrane in step (S10) is manufactured by coating the surface of the porous polymer substrate with an aqueous slurry mixed with an aqueous solvent, inorganic particles, and water-dispersible binder resin,
The porous polymer substrate includes a polymer resin and filler particles, and has a porosity of 60 vol% or more and an average pore size of 40 nm to 70 nm before performing the step (S20),
After performing the step (S20), the porosity reduction rate of the porous polymer substrate is 15% or more and the pore size reduction rate is 10% or more,
In the step (S20), the pressurization is performed under conditions of 2Mpa or more.
According to paragraph 1,
A battery manufacturing method wherein the porous polymer substrate includes a polyolefin-based polymer resin.
According to paragraph 1,
A battery manufacturing method wherein the filler particles have a particle diameter of 0.001㎛ to 100㎛.
According to paragraph 1,
A battery manufacturing method wherein the filler particles are included in a ratio of 50% to 85% by weight based on 100% by weight of the porous polymer substrate.
According to paragraph 1,
A battery manufacturing method wherein the maximum pore size of the porous polymer substrate in the step (S10) is 70 nm.
According to paragraph 1,
The battery manufacturing method wherein the thickness of the porous polymer substrate in the step (S10) is 7㎛ to 25㎛.
According to paragraph 1,
A method of manufacturing a battery, wherein after performing the pressing step of (S20), the porous polymer substrate has a porosity of 45 vol% or less and an average pore size of 40 nm or less.
delete