Separator for electrochemical device, method for manufacturing the same, and electrochemical device comprising the same

Abstract

The present invention relates to separators for electrochemical devices, a method for manufacturing the same, and electrochemical devices including the same. More particularly, the present invention relates to separators facing dry electrodes, a method for manufacturing the same, and electrochemical devices including the same, in which the separators are formed with a coating layer including a polymer binder and inorganic particles and do not include a polyolefin substrate.

Description

Technical Field

[0001] This disclosure claims priority and benefit to Korean Patent Application Nos. 10-2024-0032161 and 10-2025-0027553, filed with the Korean Intellectual Property Office on March 6, 2024 and March 4, 2025, respectively, the entire contents of which are incorporated herein by reference.

[0002] This disclosure relates to a separator for an electrochemical device, a method for manufacturing the same, and an electrochemical device including the separator. In particular, this disclosure relates to a separator for an electrochemical device, a method for manufacturing the same, and an electrochemical device including the separator, the separator facing a dry electrode, wherein the separator is formed with a coating comprising a polymer binder and inorganic particles, and the separator does not contain a polyolefin substrate. Background Technology

[0003] Electrochemical devices use electrochemical reactions to convert chemical energy into electrical energy, and recently, lithium secondary batteries, which have high energy density and voltage, long cycle life, and are suitable for various fields, have been widely used.

[0004] A lithium-ion secondary battery may include an electrode assembly made of a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes, and may be manufactured by housing the electrode assembly together with an electrolyte liquid in a casing. The positive electrode provides lithium ions, which can migrate to the negative electrode after passing through the separator formed of a porous material.

[0005] The manufacturing process of lithium-ion batteries is mainly divided into three stages: electrode process, assembly process, and formation process. The electrode process is further divided into active material mixing process, electrode coating process, drying process, rolling process, cutting process, and winding process. Among them, the active material mixing process is the process of mixing coating materials used to form the electrode active layer. In this process, the actual electrochemical reaction in the electrode occurs in the electrode active layer, and the composition used to form the electrode active layer is also broadly referred to as an electrode mixture.

[0006] When the solvent included in the electrode mixture evaporates during the drying process, it can cause defects such as pinholes or cracks in the previously formed electrode active layer. In addition, due to uneven drying between the inside and outside of the active layer, particle floating occurs due to the difference in solvent evaporation rate (i.e., particles float in the areas that dry first), forming gaps with the relatively later-dried areas, which may degrade the electrode quality.

[0007] Therefore, research has recently been conducted on the fabrication of dry electrodes without the use of solvents.

[0008] In addition, the thinner separator offers advantages in terms of output or battery resistance.

[0009] Therefore, research is needed to achieve thin separators while introducing dry electrodes. Summary of the Invention

[0010] Technical issues

[0011] This disclosure relates to a dry electrode-oriented separator that provides improved battery performance even when in thin film form.

[0012] However, the problems to be addressed by this disclosure are not limited to those described above, and those skilled in the art will clearly understand from the following description other problems not mentioned.

[0013] Technical solution

[0014] One embodiment of this disclosure provides a separator for an electrochemical device, the separator facing a dry positive electrode, wherein the separator is formed with a coating comprising a polymer binder and inorganic particles, and the separator is a self-standing porous separator excluding a polyolefin substrate.

[0015] According to one embodiment of this disclosure, the polymeric adhesive may be an acrylic-based adhesive.

[0016] According to one embodiment of this disclosure, the content of the polymer adhesive may be 6 parts by weight or less relative to 100 parts by weight of the separator.

[0017] According to one embodiment of this disclosure, the inorganic particles may be selected from SiO2, Al2O3, AlOOH, TiO2, ZrO2, BaSO4, BaTiO3, ZnO, MgO, Mg(OH)2, Al(OH)3, Pb(Zr,Ti)O3, Pb(Mg 1 / 3 Nb 2 / 3 At least one of the group consisting of O3-PbTiO3 (PMN-PT), HfO2, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, Y2O3, SiC, ZnSn(OH)6, Zn2SnO4, ZnSnO3, Sb2O3, Sb2O4 and Sb2O5.

[0018] According to one embodiment of this disclosure, the content of inorganic particles may be 95 parts by weight or more relative to 100 parts by weight of the separator.

[0019] According to one embodiment of this disclosure, the partition may have a thickness of less than 15 μm.

[0020] According to one embodiment of this disclosure, a dry cathode may include a cathode active material, and the cathode active material may include an LFP (lithium iron phosphate) based active material.

[0021] One embodiment of this disclosure provides a method for manufacturing a separator for an electrochemical device including a dry positive electrode, the method comprising coating the dry positive electrode with a slurry comprising an inorganic particle and a polymer binder to form a self-supporting porous separator.

[0022] According to one embodiment of this disclosure, the coating can be applied using a bar coater.

[0023] One embodiment of this disclosure provides an electrochemical device including a dry positive electrode; a negative electrode; and a separator for the electrochemical device located between the dry positive electrode and the negative electrode.

[0024] Beneficial effects

[0025] By introducing a separator that does not include a polyolefin substrate, a separator for an electrochemical device according to one embodiment of the present disclosure can improve battery performance even when the separator is made thinner.

[0026] By introducing a separator that does not include a polyolefin substrate, a method for manufacturing a separator for an electrochemical device according to one embodiment of the present disclosure can improve battery performance while minimizing the thickness of the separator.

[0027] By introducing a separator excluding the polyolefin substrate into the dry electrode, an electrochemical device according to one embodiment of the present disclosure is able to improve battery performance even when the separator is made thinner. Attached Figure Description

[0028] Figure 1 This is a schematic diagram illustrating a dry positive electrode and separator according to one embodiment of the present disclosure. Detailed Implementation

[0029] In this specification, the description of certain parts as "including" certain components means that it may further include other components and does not exclude other components unless otherwise specifically stated.

[0030] In this specification, "A and / or B" means "A and B, or A or B".

[0031] In this specification, the description of being "on" a component means that another component may be further disposed therein, and does not exclude another component disposed therebetween, unless otherwise specifically stated.

[0032] In this specification, “about” and “substantially” are used to refer to, taking into account unique manufacturing and material tolerances, a range of figures or degrees or as a measure of approximation thereof, and are used to prevent unjustified use by infringers of the precise or absolute figures provided in this disclosure to aid in understanding the contents of this disclosure.

[0033] In this specification, "electrochemical device" may refer to a primary battery, a secondary battery, a supercapacitor, etc.

[0034] The contents of this disclosure will be described in more detail below.

[0035] Figure 1 This is a schematic diagram showing a dry positive electrode 200 and a separator 100 according to one embodiment of the present disclosure.

[0036] One embodiment of this disclosure includes a separator 100 for an electrochemical device, the separator 100 facing a dry positive electrode 200, wherein the separator 100 is formed with a coating including a polymer binder and inorganic particles, and the separator is a self-standing porous separator 100 excluding a polyolefin substrate.

[0037] According to one embodiment of the present disclosure, a separator 100 for an electrochemical device can improve battery performance even when the separator is thinned by introducing a separator that does not include a polyolefin substrate.

[0038] In conventional separators used in electrochemical devices, a coating comprising inorganic particles and a binder polymer is formed on at least one surface of a porous polymer substrate, and polyolefin substrates or nonwoven fabrics manufactured by dry or wet processes have been used as such porous polymer substrates.

[0039] The self-supporting porous partition 100 refers to a partition 100 having a porous structure with a coating including inorganic particles and adhesive polymer, but without the aforementioned porous polymer substrate.

[0040] According to one embodiment of this disclosure, the coating comprises a polymer binder and inorganic particles. Because the coating comprises the polymer binder and inorganic particles as described above, the heat resistance and mechanical properties of the separator are improved, short circuits in the electrodes caused by separator shrinkage at high temperatures are prevented, and pores can be formed within the coating.

[0041] According to one embodiment of this disclosure, the coating can be formed of inorganic particles, which are bonded together and integrated within the layer by polymer binder particles. Pores within the coating can be created by interstitial volumes, the empty spaces between the inorganic particles.

[0042] Meanwhile, the self-supporting porous partition 100, which does not include a polyolefin substrate, may be susceptible to external forces and has low compressibility because its external shape is formed only by inorganic particles and adhesive polymers.

[0043] According to one embodiment of this disclosure, a self-supporting porous partition with excellent compression resistance is provided by increasing the content of inorganic particles to a higher level than that of the adhesive without using a polyolefin substrate.

[0044] According to one embodiment of this disclosure, the polymer adhesive may include acrylic copolymers, styrene-butadiene copolymers, poly(acrylic acid), poly(methyl methacrylate), poly(butyl acrylate), poly(acrylonitrile), poly(vinyl pyrrolidone), poly(vinyl alcohol), poly(vinyl acetate), poly(ethylene-co-vinyl acetate), poly(ethylene oxide), poly(arylate), cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, and cyanoethyl cellulose. cellulose), cyanoethyl sucrose, pullulan, carboxyl methyl cellulose, or two or more thereof.

[0045] According to one embodiment of this disclosure, the polymeric adhesive may be an acrylic-based adhesive. Specifically, the polymeric adhesive may be an acrylic-based copolymer. By including an acrylic-based copolymer, the porosity of the separator can be maintained, and the readiness of battery manufacturing can be improved. The acrylic-based copolymer may include, but is not limited to, ethyl acrylate-N,N-dimethylacrylamide copolymer, ethyl acrylate-2-(dimethylamino)ethyl acrylate copolymer, ethyl acrylate-N,N-diethylacrylamide copolymer, ethyl acrylate-2-(diethylamino)ethyl acrylate copolymer, or two or more thereof.

[0046] According to one embodiment of this disclosure, the content of the polymer binder relative to 100 parts by weight of the separator can be 6 parts by weight or less. Specifically, the content of the polymer binder relative to 100 parts by weight can be 0.5 parts by weight or more and 6 parts by weight or less, 1 part by weight or more and 6 parts by weight or less, 0.5 parts by weight or more and 5 parts by weight or less, 1 part by weight or more and 5 parts by weight or less, 0.5 parts by weight or more and 4.5 parts by weight or less, 1 part by weight or more and 4.5 parts by weight or less, 1 part by weight or more and 4 parts by weight or less, 1 part by weight or more and 3.5 parts by weight or less, 1 part by weight or more and 3 parts by weight or less, 1 part by weight or more and 2.5 parts by weight or less, 1 part by weight or more and 2 parts by weight or less, or 1.5 parts by weight or more and 2 parts by weight or less. When the content is greater than the above ranges, the content of inorganic particles is relatively reduced, which reduces heat resistance. In addition, the battery resistance and capacity performance may be poor. When the content is below the above range, it may be difficult to form pores within the coating resulting from the combination of inorganic materials and polymer binders, which may lead to increased permeability and electrical resistance. By minimizing the content of polymer binders within the above range, a self-supporting separator superior to that in the prior art can be obtained.

[0047] According to one embodiment of this disclosure, the polymeric adhesive may have a D50 particle size of 100 nm or larger and 500 nm or smaller. Specifically, the polymeric adhesive may have a D50 particle size of 100 nm or larger and 500 nm or smaller, 100 nm or larger and 450 nm or smaller, 100 nm or larger and 400 nm or smaller, 100 nm or larger and 350 nm or smaller, 100 nm or larger and 300 nm or smaller, 100 nm or larger and 250 nm or smaller, 100 nm or larger and 200 nm or smaller, or 150 nm or larger and 450 nm or smaller. Preferably, the polymeric adhesive may have a D50 particle size of 150 nm. When the D50 particle size is larger than the above ranges, it may be difficult to form pores when bonded with inorganic materials, and when the D50 particle size is smaller than the above ranges, it is difficult to bond with the inorganic material itself, thereby reducing coatability. By adjusting the D50 particle size of the polymer binder within the above range, the bonding force with inorganic particles can be increased, thereby improving battery performance.

[0048] According to one embodiment of this disclosure, the inorganic particles may be selected from SiO2, Al2O3, AlOOH, TiO2, ZrO2, BaSO4, BaTiO3, ZnO, MgO, Mg(OH)2, Al(OH)3, Pb(Zr,Ti)O3, Pb(Mg 1 / 3 Nb 2 / 3 At least one of the group consisting of PbTiO3 (PMN-PT), HfO2, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, Y2O3, SiC, ZnSn(OH)6, Zn2SnO4, ZnSnO3, Sb2O3, Sb2O4, and Sb2O5. Preferably, the inorganic particles may be Al2O3.

[0049] According to one embodiment of this disclosure, the content of inorganic particles relative to 100 parts by weight of the separator can be 95 parts by weight or more. Specifically, the content of inorganic particles relative to 100 parts by weight of the separator can be 95 parts by weight or more and 100 parts by weight or less, 95 parts by weight or more and 99.5 parts by weight or less, 95 parts by weight or more and 99 parts by weight or less, 95 parts by weight or more and 98.5 parts by weight or less, 95 parts by weight or more and 98 parts by weight or less, 95 parts by weight or more and 97.5 parts by weight or less, 95 parts by weight or more and 97 parts by weight or less, or 95 parts by weight or more and 96.5 parts by weight or less. When the content is greater than the above ranges, the content of the polymer binder is significantly reduced, and it may be difficult to form pores in the coating resulting from the combination of inorganic materials and polymer binders, thereby leading to increased permeability and resistance. Conversely, when the content is less than the above ranges, the battery resistance and capacity performance may be poor. Furthermore, by setting a high content of inorganic particles, heat resistance can be ensured even when the partition is made thinner.

[0050] According to one embodiment of this disclosure, the D50 particle size of the inorganic particles is not particularly limited, but is preferably in the range of 0.3 μm or larger and 1 μm or smaller to form a coating with uniform thickness and appropriate porosity. Specifically, when the D50 particle size is less than 0.3 μm, the dispersibility of the inorganic particles may be reduced in the slurry used to prepare the coating, and when the D50 particle size is greater than 1 μm, the thickness of the resulting coating may increase.

[0051] In this specification, "D50 particle size" refers to the particle size at the 50% point of the cumulative distribution of particle size. Particle size can be measured using a laser diffraction method. Specifically, the powder to be measured is dispersed in a dispersion medium and then introduced into a commercially available laser diffraction particle size measurement device (e.g., Microtrac S3500). The measurement depends on the difference in the diffraction pattern of the particle size as the particles pass through the laser beam to calculate the particle size distribution. The D50 particle size can be measured by calculating the particle size at the 50% point of the cumulative distribution of particle size in the measurement device.

[0052] In one embodiment of this disclosure, the separator may have a thickness of less than 15 μm. Specifically, the separator may have a thickness greater than 8 μm and less than 15 μm, greater than 8 μm and 14 μm or less, 8.5 μm or greater and 13.5 μm or less, 9 μm or greater and 13 μm or less, 9 μm or greater and 12.5 μm or less, 9 μm or greater and 12 μm or less, 9 μm or greater and 11.5 μm or less, 9 μm or greater and 11 μm or less, or 9.5 μm or greater and 10.5 μm or less. When the thickness is greater than the above ranges, the resistance increases due to the excessively thick separator, resulting in a decrease in capacity performance and capacity loss rate. When the thickness is less than the above ranges, the coatability may decrease due to the excessively thin separator. By adjusting the separator thickness within the above ranges, the separator thickness can be reduced while ensuring heat resistance and improving battery performance. Furthermore, a thinner separator than that manufactured from a porous polymer substrate can be obtained. By setting the content of inorganic particles in the coating to a higher level, the problem of decreased heat resistance caused by separator thinning can be overcome by ensuring heat resistance performance.

[0053] In one embodiment of this disclosure, a contact thickness measuring device can be used to measure the thickness of partitions, coatings, etc. As an example of a contact thickness measuring device, the VL-50S-B manufactured by Mitutoyo Corporation can be used.

[0054] According to one embodiment of this disclosure, the coating may have a porosity of 30% by volume or greater. Specifically, the coating may have a porosity of 30% by volume or greater and 70% by volume or less, 32% by volume or greater and 68% by volume or less, 34% by volume or greater and 66% by volume or less, 36% by volume or greater and 64% by volume or less, 38% by volume or greater and 62% by volume or less, 40% by volume or greater and 60% by volume or less, 42% by volume or greater and 58% by volume or less, 44% by volume or greater and 56% by volume or less, 46% by volume or greater and 54% by volume or less, or 48% by volume or greater and 52% by volume or less. By adjusting the porosity of the coating within the above ranges, ion migration within the separator is maintained, and an increase in the resistivity of the separator can be prevented.

[0055] In this specification, porosity refers to the ratio of the volume occupied by pores to the total volume, and volume% is used as the unit.

[0056] In this specification, porosity corresponds to the value obtained by subtracting the volume converted from the weight and density of each component of the coating from the volume calculated from the thickness, width, and length of the coating.

[0057] In one embodiment of this disclosure, the porosity and pore size of the coating can be measured using the BET 6-point method via nitrogen adsorption flow using scanning electron microscopy (SEM) images, a mercury porosimeter, a capillary flow porometer, or a porosimetry analyzer (Bell Japan Inc, Belosorp-II mini). In this context, the use of a capillary flow porometer may be advantageous.

[0058] According to one embodiment of this disclosure, the separator 100 faces the dry positive electrode 200. Existing separators facing the wet positive electrode have problems; when a water dispersion process is performed during the manufacture of the wet positive electrode and then an aqueous slurry for coating is applied thereon, the coating shrinks at high temperatures, potentially leading to an increase in separator thickness and consequently poor battery performance. In contrast, the dry positive electrode is an electrode that can be coated without solvents, and even when a separator is coated on the dry positive electrode, coating shrinkage does not occur at high temperatures, resulting in superior coatability compared to the wet positive electrode.

[0059] According to one embodiment of this disclosure, the partition 100 may further include a surfactant. The surfactant may be added to further facilitate the casting of the coating composition. As a surfactant, a polyether-modified siloxane surfactant may be used, and when a surfactant is included, the coating composition can be coated with a more uniform thickness.

[0060] Polyether-modified siloxane surfactants are surfactants that contain polyether chains at the ends and / or on the side chains of a polysiloxane backbone. For example, polyether-modified siloxane surfactants may include polyoxyethylene groups and / or polyoxypropylene groups.

[0061] Commercially available materials can be used as such polyether-modified siloxane surfactants, and for example, one or more of the group consisting of BYK-345, BYK-346, BYK-347, BYK-348, BYK-349, BYK-3450, BYK-3455, BYK-3456, BYK-3560, BYK-3565 and BYK-3760 can be used.

[0062] Relative to 100 parts by weight of the coating composition, the content of the polyether-modified siloxane surfactant can be from 0.05 parts by weight to 1.0 parts by weight, or more preferably 0.1 parts by weight or more, 0.15 parts by weight or more, or 0.2 parts by weight or more, and 0.8 parts by weight or less, 0.7 parts by weight or less, or 0.6 parts by weight or less. By adjusting the part by weight of the surfactant within the above range, the effect of improving the coatability of the coating can be ensured.

[0063] According to one embodiment of this disclosure, the solvent can be used in the composition without limitation, as long as it can dissolve the above-described components, and can be combined and used in combination with one or more of the group consisting of water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl pentyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethyl ether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate, and N,N-dimethylacetamide. Preferably, water can be used as the solvent.

[0064] One embodiment of this disclosure includes a method for manufacturing a separator 100 for an electrochemical device including a dry positive electrode 200, the method comprising coating the dry positive electrode with a slurry for coating comprising inorganic particles and a polymer binder to form a self-supporting porous separator 100.

[0065] By introducing a separator that does not include a polyolefin substrate, a method for manufacturing a separator for an electrochemical device according to one embodiment of the present disclosure can improve battery performance while minimizing the thickness of the separator.

[0066] According to one embodiment of this disclosure, a method for manufacturing a separator for an electrochemical device includes mixing a slurry comprising polymer binder particles and inorganic particles for coating. Because the method includes mixing a slurry comprising polymer binder particles and inorganic particles for coating as described above, a coating can be readily formed on the separator.

[0067] According to one embodiment of this disclosure, inorganic particles can be added to and dispersed in a polymer binder. The content ratio between the inorganic particles and the polymer binder particles is as described above, and is appropriately adjusted to take into account the thickness, pore size, and porosity of the final coating prepared according to one embodiment of this disclosure.

[0068] According to one embodiment of this disclosure, polymer binder particles and inorganic particles can be dispersed in water to prepare a slurry.

[0069] According to one embodiment of this disclosure, the method of coating a slurry for coating onto a dry positive electrode can be at least one and a combination thereof selected from the group consisting of bar coating, dip coating, die coating, roll coating, and comma coating. Preferably, bar coating can be used.

[0070] According to one embodiment of this disclosure, a method for manufacturing a separator for an electrochemical device includes drying a slurry for coating to provide a coating. By including the step of drying the slurry for coating as described above to provide a coating, damage to the coating can be minimized, and solvents contained in the slurry can be easily removed.

[0071] According to one embodiment of this disclosure, the drying process is appropriately timed to minimize the occurrence of surface defects in the coating. Drying aids such as drying ovens or hot air can be used to a suitable extent.

[0072] One embodiment of this disclosure includes an electrochemical device comprising: a dry positive electrode 200; a negative electrode; and a separator 100 for use in the electrochemical device located between the dry positive electrode 200 and the negative electrode.

[0073] An electrochemical device according to one embodiment of the present disclosure is able to suppress rebound and ensure battery performance and insulation by introducing a separator 100 excluding a polyolefin substrate into a dry positive electrode 200.

[0074] In this disclosure, an electrochemical device is a device that converts chemical energy into electrical energy using an electrochemical reaction, and includes the concepts of primary batteries and secondary batteries. In this specification, a secondary battery is a battery capable of being charged and discharged, and refers to lithium-ion batteries, nickel-cadmium batteries, nickel-metal hydride batteries, etc. Lithium-ion batteries use lithium ions as ion conductors, and examples may include non-aqueous electrolyte secondary batteries including liquid electrolytes, all-solid-state batteries including solid electrolytes, lithium polymer batteries including gel polymer electrolytes, lithium metal batteries using lithium metal as the negative electrode, etc. However, lithium-ion batteries are not limited to these.

[0075] According to one embodiment of the present disclosure, a positive electrode is provided with a positive electrode current collector and a positive electrode active material layer. The positive electrode active material layer includes a positive electrode active material, a conductor, and an adhesive resin located on at least one side surface of the current collector. The positive electrode active material may include, for example, a lithium transition metal oxide; a lithium metal iron phosphate; a lithium nickel manganese cobalt oxide; an oxide in which some of the lithium nickel manganese cobalt oxides are replaced by other transition metals; or two or more thereof, but not limited thereto. Specifically, examples of the positive electrode active material may include layered compounds such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or compounds substituted by one or more transition metals; lithium manganese oxides such as the chemical formula Li 1+x Mn 2-x O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3 or LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5 or Cu2V2O7; Ni-site type lithium nickel oxides represented by the chemical formula LiNi 1-x M x O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3); lithium manganese composite oxides represented by the chemical formula LiMn 2-x M x O2 (where M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); lithium metal phosphate LiMPO4 (where M = Fe, Co, Ni or Mn); lithium nickel manganese cobalt oxide Li 1+x (NiaCobMnc) 1-x O2 (x = 0 to 0.03, a = 0.3 to 0.95, b = 0.01 to 0.35, c = 0.01 to 0.5, and a + b + c = 1); an oxide in which part of the lithium nickel manganese cobalt oxide is replaced by aluminum, Li a [Ni b Co c Mn d Al e 1-f M1 f O2 (M1 is at least one selected from the group consisting of Zr, B, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, F, P and S, 0.8 ≤ a ≤ 1.2, 0.5 ≤ b ≤ 0.99, 0 < c < 0.5, 0 < d < 0.5, 0.01 ≤ e ≤ 0.1, and 0 ≤ f ≤ 0.1); an oxide in which part of the lithium nickel manganese cobalt oxide is replaced by other transition metals, Li 1+x (Ni a Co​b Mn c M d ) 1-x O2 (where x = 0 to 0.03, a = 0.3 to 0.95, b = 0.01 to 0.35, c = 0.01 to 0.5, d = 0.001 to 0.03, and a + b + c + d = 1, and M is any one selected from the group consisting of Fe, V, Cr, Ti, W, Ta, Mg, and Mo); disulfide compounds; Fe2(MoO4)3, etc., but not limited thereto.

[0076] According to one embodiment of the present disclosure, the positive electrode active material may include an LFP (lithium iron phosphate) - based active material. With the positive electrode active material including the LFP (lithium iron phosphate) - based active material as described above, dry manufacturing is possible, and battery insulation and battery performance can be ensured without including a polyolefin substrate.

[0077] According to one embodiment of the present disclosure, the negative electrode is provided with a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer includes a negative electrode active material, a conductor, and an adhesive resin located on at least one side surface of the current collector. The negative electrode may include one selected from the following as the negative electrode active material: lithium metal oxides; carbon, such as non - graphitizable carbon or graphite - based carbon; metal composite oxides, such as Li x Fe2O3 (0 ≤ x ≤ 1), Li x WO2 (0 ≤ x ≤ 1), and 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, halogens; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8); lithium metal; lithium alloys; silicon - based alloys; tin - based alloys; metal oxides, such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5; conductive polymers, such as polyacetylene; Li - Co - Ni - based materials; and titanium oxide, or a mixture of two or more thereof.

[0078] According to one embodiment of this disclosure, the conductor may be, for example, any one selected from the group consisting of graphite, carbon black, carbon fiber or metal fiber, metal powder, conductive whiskers, conductive metal oxides, activated carbon, and polyphenylene derivatives, or a mixture of two or more of these conductive materials. More specifically, the conductor may be one selected from the group consisting of natural graphite, artificial graphite, super-p, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermally cracked carbon black, Denka black, aluminum powder, nickel powder, zinc oxide, potassium titanate, and titanium oxide, or a mixture of two or more of these conductive materials.

[0079] According to one embodiment of this disclosure, the current collector is not particularly limited, as long as it has high conductivity without causing chemical changes to the corresponding battery. For example, stainless steel, copper, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel with a surface treated with carbon, nickel, titanium, silver, etc., can be used.

[0080] According to one embodiment of this disclosure, polymers commonly used in electrodes in the art can be used as adhesive resins. Non-limiting examples of such adhesive resins may include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetatebutyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, and cyanoethyl sucrose. Examples of polysaccharides include sucrose, pullulan, and carboxyl methyl cellulose, but these are not limited to.

[0081] In one embodiment of the dry positive electrode 200 according to this disclosure, the adhesive is not particularly limited to a specific adhesive, as long as it is capable of fibrillation during the preparation of the mixture block. Fibrillation refers to the process in which the polymer is divided into fine blocks and can be performed using, for example, mechanical shear force. The surface of such fibrillated polymer fibers is unraveled, resulting in a large number of fine fibers (fibrils).

[0082] Non-limiting examples of such adhesive polymers may include polytetrafluoroethylene (PTFE), polyolefins, or mixtures thereof, specifically including polytetrafluoroethylene (PTFE), and more specifically, polytetrafluoroethylene (PTFE). Specifically, polytetrafluoroethylene (PTFE) may be included in an amount of 60% by weight or greater based on the total weight of the entire adhesive polymer. Additionally, the adhesive materials described herein may also include at least one of PEO (polyethylene oxide), PVdF (polyvinylidene fluoride), PVdF-HFP (polyvinylidene fluoride-co-hexafluoropropylene), and polyolefin-based polymers.

[0083] In the preparation of a dry positive electrode 200 according to one embodiment of this disclosure, mixing is performed to mix the electrode materials such that the electrode active material, binder polymer, and optionally conductors are uniformly distributed. Since the components are mixed in powder form, the mixing method is not limited, as long as it allows for simple mixing, and various methods can be used for mixing. However, this method is used to prepare a dry electrode without the use of solvents, and therefore, mixing can be performed as dry mixing and can be performed by introducing the materials into a device such as a mixer or supermixer.

[0084] According to one embodiment of this disclosure, when mixing is performed in a mixer, mixing can be performed in the mixer at 5,000 rpm to 20,000 rpm for 30 seconds to 20 minutes, and specifically at 10,000 rpm to 15,000 rpm for 30 seconds to 5 minutes to ensure homogeneity.

[0085] Then, a step of kneading the mixture of electrode materials at high temperature and low shear rate can be performed to obtain a mixture block.

[0086] This is a step used to fiberize the binder in the mixture prepared as described above, and is also known as the kneading process.

[0087] In one embodiment of this disclosure, low-shear kneading can be performed to fiberize the adhesive, micronize the active material, and address the problem of fiber formation from cutting; however, the steps are not limited thereto.

[0088] In this article, kneading can be performed using, for example, a kneading machine, but is not limited to this.

[0089] This kneading is a step of forming a 100% solid mixture block by combining or connecting active materials or active materials and conductor powders when the adhesive is fiberized.

[0090] In one embodiment of this disclosure, kneading can be performed at a rate of 10 rpm to 100 rpm for 1 minute to 30 minutes, and specifically, at a rate of 20 rpm to 50 rpm for 3 minutes to 10 minutes.

[0091] According to one embodiment of this disclosure, the electrochemical device prepared as described above can be inserted into a suitable housing, and an electrolyte liquid can be injected therein to manufacture a battery.

[0092] According to one embodiment of this disclosure, the electrolyte liquid comprises a liquid obtained by dissolving or dissociating a salt having a structure such as A⁺B⁻ in an organic solvent, wherein A⁺ comprises ions consisting of alkali metal cations such as Li⁺, Na⁺, or K⁺ or combinations thereof, and B⁻ comprises anions such as PF₆. - BF4 - Cl - ,Br - I - ClO4 - AsF6 - CH3CO2 - CF3SO3 - N(CF3SO2)2 - Or C(CF2SO2)3 - The ions, or combinations thereof, are formed 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), γ-butyrolactone (γ-butyrolactone), or mixtures thereof; however, the electrolyte liquid is not limited to this.

[0093] In one embodiment of this disclosure, the external shape of the electrochemical device may include a cylindrical shape, a prism shape, a pouch shape, or a coin shape, similar to a can. Preferably, the electrochemical device may be a cylindrical battery. By selecting a cylindrical battery as the electrochemical device as described above, an additional adhesive layer is not required, and a thin separator can be obtained.

[0094] Furthermore, one embodiment of this disclosure provides a battery module comprising a battery containing an electrochemical device as a unit, a battery pack including the battery module, and a device including the battery pack as a power source. Specific examples of the device may include a power tool operated by receiving power from an electric motor; electric motor vehicles, including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), etc.; electric two-wheeled bicycles, including electric bicycles (E-bikes) and electric scooters (E-scooters); electric golf carts; systems for power storage, etc., but are not limited thereto.

[0095] Invention patterns

[0096] In the following description, the present disclosure will be described in detail with reference to embodiments in order to specifically describe the present disclosure. However, embodiments based on the present disclosure can be modified in various different forms, and the scope of the present disclosure is not to be construed as limited to the embodiments described below. Embodiments of this specification are provided to describe the present disclosure more fully to those skilled in the art.

[0097] <Example 1>

[0098] An aqueous slurry (35% solids content) for coating was prepared using Al2O3 with a D50 of 500 nm as the inorganic material, an acrylic copolymer with a D50 of 150 nm (Toyo Ink, Co., Ltd. CSB-140), a PAA-based dispersant (CK-702), and a surfactant (BYK-348) in a weight ratio of 95.4:2:2:0.6.

[0099] A separator was prepared by coating one side (bar coating) of an aqueous slurry for coating onto a dry LFP cathode. Here, the separator has a thickness of 10 μm.

[0100] <Example 2>

[0101] The separator was prepared in the same manner as in Example 1, except that the separator had a thickness of 9 μm.

[0102] <Example 3>

[0103] The separator was prepared in the same manner as in Example 1, except that the separator had a thickness of 12 μm.

[0104] <Example 4>

[0105] An aqueous slurry (35% solids content) for coating was prepared using Al2O3 as the inorganic material, an acrylic copolymer with a D50 of 150 nm (Toyo Ink, Co., Ltd. CSB-140) as the polymer binder, PAA-based dispersant (CK-702), and surfactant (BYK-348) in a weight ratio of 96.5:1.5:1.4:0.6.

[0106] A separator was prepared by coating one side (bar coating) of an aqueous slurry for coating onto a dry LFP cathode. Here, the separator has a thickness of 10 μm.

[0107] <Comparative Example 1>

[0108] The separator was prepared in the same manner as in Example 1, except that the separator had a thickness of 8 μm.

[0109] <Comparative Example 2>

[0110] The separator was prepared in the same manner as in Example 1, except that the separator had a thickness of 15 μm.

[0111] <Comparative Example 3>

[0112] Polyolefin (PO) resin was extruded, and a porous polymer substrate (total thickness of approximately 10 μm) was prepared using a wet process.

[0113] The slurry for coating in Example 1 was applied to both surfaces of a porous polymer substrate to a thickness of 1.5 μm for each to prepare a separator.

[0114] <Comparative Example 4>

[0115] The separator was prepared in the same manner as in Example 1, except that a one-sided coating (rod coating) was performed on a wet LFP cathode instead of a dry LFP cathode.

[0116] <Comparative Example 5>

[0117] The separator was prepared in the same manner as in Comparative Example 3, except that a one-sided coating (rod coating) was performed on a wet LFP cathode instead of a dry LFP cathode.

[0118] <Comparative Example 6>

[0119] An aqueous slurry (35% solids content) for coating was prepared using Al2O3 as the inorganic material, an acrylic copolymer with a D50 of 150 nm (Toyo Ink, Co., Ltd. CSB-140) as the polymer binder, PAA-based dispersant (CK-702), and surfactant (BYK-348) in a weight ratio of 92:5:2.4:0.6.

[0120] A separator was prepared by coating one side (bar coating) of an aqueous slurry for coating onto a dry LFP cathode. Here, the separator has a thickness of 10 μm.

[0121] <Preparation of Electrochemical Devices>

[0122] (1) Preparation of negative electrode

[0123] A slurry for the negative electrode active material layer was prepared by mixing negative electrode active material (P20T / LSN-1, graphite), binder (ADB22D, styrene-butadiene rubber, (SBR)-based polymer), CMC aqueous solution (Daicel 2200, a product of Daicel Chemical Industries, Ltd.), and conductor (Super-C65, carbon black) with water at a weight ratio of 80.3 / 19.7:2.3:1.05:0.5, wherein the components other than water had a concentration of 50% by weight. The slurry was then coated on the surface of a copper thin film (10 μm thick) and dried to prepare a negative electrode with a negative electrode active material layer (120 μm thick).

[0124] (2) Preparation of the positive electrode

[0125] 1) Preparation of wet electrodes

[0126] A slurry for the positive electrode active material layer was prepared by mixing positive electrode active material (S20, LFP), conductor (CNT (LB-CNT)), binder (KF7200), and dispersant (HPD-01) with water at a weight ratio of 95.96:0.8:3.0:0.24, wherein the components other than water had a concentration of 50% by weight. The slurry was then coated on the surface of an aluminum film (10 μm thick) and dried to prepare a positive electrode with a positive electrode active material layer (120 μm thick).

[0127] 2) Preparation of dry electrodes

[0128] The positive electrode active material (S20, LFP), conductor (Li-435) and binder (PTFE) were introduced into a mixer at a weight ratio of 94.0:1.5:4.5 and mixed at 15,000 rpm for 1 minute to obtain a mixture.

[0129] Then, the temperature of the kneader (Shinil Dispersion Machine) was stabilized at 150°C, the mixture prepared above was introduced into the kneader, and the kneader was operated at a rate of 40 rpm for 5 minutes under a pressure of 1.1 atm to obtain a mixture block.

[0130] The mixture block is introduced into a warping mixer and pulverized at 10,000 rpm for 1 minute to obtain powder for use as electrodes.

[0131] The mixture powder for the electrode was then introduced into a laboratory process (roller diameter: 200 mm, roller temperature: 100 °C, 20 rpm), and the calendering process was repeated until the porosity was 35% or less. Here, a pressure of 221 kg / cm between the rollers was used during the final calendering to prepare the electrode film. The prepared electrode film had a thickness of 82 μm, a porosity of 31% (%), and a mAh / cm³. 2 The load.

[0132] A slurry for forming a primer layer is coated onto an aluminum foil and dried to form a primer layer on the current collector. The primer layer comprises carbon black and PVDF binder in a weight ratio of 1:2. A lamination process is performed using a roller press maintained at room temperature, such that two electrode films are laminated onto the two surfaces of the aluminum foil (average thickness: 19 μm) where the primer layer is formed. The porosity of the electrode active material layer is 30% or less, to ground the electrode film onto the current collector, thereby preparing an electrode in which the electrode active material layer is formed on both surfaces of the current collector. Here, the electrode film grounded on the current collector (i.e., the electrode active material layer) has a thickness of 75 μm, a porosity of 25.9% (%), and a mAh / cm² capacity. 2 The load.

[0133] <Experimental Example>

[0134] (1) Measurement of the initial resistance of the battery

[0135] The battery was charged and discharged three times at a rate of 0.33 C at room temperature, and the battery resistance was evaluated by the value identified when a current was applied at a rate of 2.5 C for 10 seconds at SOC 50. The measurement results are shown in Table 1 below.

[0136] (2) Evaluation of initial battery capacity and capacity retention

[0137] For each lithium secondary battery manufactured as described above, 100 charge-discharge cycles were performed. Each cycle consisted of charging the battery to 4.2 V at 0.33 C in CC-CV mode at 25 °C and discharging it to 2.5 V at a constant current of 0.33 C. The initial capacity and capacity retention after 500 cycles were measured to evaluate lifetime characteristics. The measurement results are shown in Table 1 below.

[0138] (3) Measurement of dry heat shrinkage rate at 180℃

[0139] The partitions of Comparative Example 3 and Comparative Example 5 were each cut into 5 cm x 5 cm dimensions to prepare samples. The samples were placed in a convection oven at 180 °C for 30 minutes, and then removed to calculate the thermal shrinkage ratio in the MD and TD directions according to [(length of the initial sample - length after storage at 180 °C for 0.5 hours) / (length of the initial sample)] x 100 (%). The results are shown in Table 1 below.

[0140] [Table 1]

[0141]

[0142] According to Table 1, it can be determined that in Example 1, the thickness of the separator can be controlled to be small by excluding the separator substrate in the dry LPF positive electrode, and the initial resistance of the battery is low, the initial capacity of the battery is high, and the capacity loss rate is low.

[0143] In contrast, the problem with Comparative Example 1 is that when the coating is too thin, down to a thickness of 8 μm, the partition is partially coated, resulting in an internal short circuit caused by the uncoated portion.

[0144] Comparative Example 2 did not have insulation problems, but it can be seen that as the thickness of the separator increases, the resistance increases compared to the example, resulting in poorer capacity performance and capacity loss rate.

[0145] In Comparative Examples 3 and 5, it can be seen that because the separator includes a porous polymer substrate, the separator thickness increases and the resistance and capacitance performance is worse compared to the examples. Furthermore, it can be seen that because the separator includes a porous polymer substrate, thermal shrinkage occurs in the MD and TD directions at a high temperature of 180°C when the dry heat shrinkage rate of the separator is measured. In contrast, in the embodiments of this disclosure, the separator is prepared by coating on a dry positive electrode, and no coating shrinkage occurs at high temperatures.

[0146] In Comparative Example 4, due to the difference in surface properties from the wet positive electrode, the aqueous slurry used for coating was not wetted and could not be coated.

[0147] In Comparative Example 6, it can be seen that, compared with the Example, the resistance and capacitance performance are poor due to the lower content of inorganic materials.

[0148] Therefore, in a separator for an electrochemical device according to one embodiment of the present disclosure, a method for manufacturing the separator, and an electrochemical device including the separator, the separator facing the dry positive electrode is formed with a coating comprising a polymer binder and inorganic particles, and does not include a polyolefin substrate. Thus, excellent heat resistance can be obtained, and battery performance can be improved while making the separator thinner.

[0149] [Figure Labels]

[0150] 100: partition

[0151] 200: Dry positive electrode

Claims

1. A separator for an electrochemical device, the separator facing a dry positive electrode, The partition is formed with a coating comprising a polymer binder and inorganic particles, and The partition is a self-supporting porous partition that does not include a polyolefin substrate.

2. The partition according to claim 1, wherein the polymer adhesive is an acrylic adhesive.

3. The partition according to claim 1, wherein the content of the polymer adhesive is 6 parts by weight or less relative to 100 parts by weight of the partition.

4. The separator according to claim 1, wherein the inorganic particles are selected from SiO2, Al2O3, AlOOH, TiO2, ZrO2, BaSO4, BaTiO3, ZnO, MgO, Mg(OH)2, Al(OH)3, Pb(Zr,Ti)O3, Pb(Mg 1 / 3 Nb 2 / 3 At least one of the group consisting of O3-PbTiO3 (PMN-PT), HfO2, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, Y2O3, SiC, ZnSn(OH)6, Zn2SnO4, ZnSnO3, Sb2O3, Sb2O4 and Sb2O5.

5. The separator according to claim 1, wherein the content of the inorganic particles is 95 parts by weight or more relative to 100 parts by weight of the separator.

6. The partition according to claim 1, wherein the partition has a thickness of less than 15 μm.

7. The separator according to claim 1, wherein the dry positive electrode comprises a positive electrode active material, and the positive electrode active material comprises an LFP (lithium iron phosphate) based active material.

8. A method for manufacturing a separator for an electrochemical device, the electrochemical device comprising a dry positive electrode, the method comprising: The dry positive electrode is coated with a slurry comprising inorganic particles and polymer binders to form a self-supporting porous separator.

9. The method of claim 8, wherein the coating is performed using a bar coater.

10. An electrochemical device, comprising: Dry positive electrode; negative electrode; and A separator for an electrochemical device according to claim 1, located between the dry positive electrode and the negative electrode.

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