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

Abstract

The present invention relates to a separator for an electrochemical device, a method for manufacturing same, and an electrochemical device comprising same. More specifically, the present invention relates to: a separator for an electrochemical device, wherein the separator is in contact with a dry electrode, is made up of a coating layer comprising a polymer binder and inorganic particles, and does not include a polyolefin substrate; a method for manufacturing the separator; and an electrochemical device comprising the separator.

Description

Separator for electrochemical devices, method for manufacturing the same, and electrochemical devices including the same

[0001] This invention claims the benefit of patent application No. 10-2024-0032161, filed with the Korean Intellectual Property Office on March 6, 2024, and patent application No. 10-2025-0027553, filed with the Korean Intellectual Property Office on March 4, 2025, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a separator for an electrochemical device, a method for manufacturing the same, and an electrochemical device including the same, and more particularly, to a separator facing a dry electrode, wherein the separator is formed of a coating layer including a polymer binder and inorganic particles, and the separator does not include a polyolefin substrate, a method for manufacturing the same, and an electrochemical device including the same.

[0003] Electrochemical devices convert chemical energy into electrical energy using electrochemical reactions. Recently, lithium secondary batteries have been widely used due to their high energy density and voltage, long cycle life, and wide range of applications.

[0004] A lithium secondary battery may include an electrode assembly manufactured with a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, and may be manufactured by housing the electrode assembly in a case together with an electrolyte. The positive electrode may provide lithium ions, and the lithium ions may move to the negative electrode by passing through the separator made of a porous material.

[0005] The manufacturing process of lithium secondary batteries is largely 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, slitting process, and winding process. Among these, the active material mixing process is a process of mixing coating materials for forming an electrode active layer where the actual electrochemical reaction occurs in the electrode. The composition mixed to form the electrode active layer is also referred to as an electrode mixture in a broad sense.

[0006] During the above drying process, as the solvent contained in the electrode mixture evaporates, defects such as pinholes or cracks may be induced in the already formed electrode active layer. Furthermore, since the inside and outside of the active layer are not uniformly dried, particle floating may occur due to differences in solvent evaporation rates, i.e., particles in areas that dry first may float to form gaps with areas that dry relatively later, which may deteriorate electrode quality.

[0007] Therefore, research has recently been conducted to manufacture dry electrodes that do not use solvents.

[0008] Furthermore, there are advantages in terms of output and battery resistance as the separator thickness decreases.

[0009] Accordingly, research was needed to implement thin film separator while introducing dry electrodes.

[0010] The technical problem to be achieved by the present invention is to provide a separator facing a dry electrode, which has improved battery performance even when made thin.

[0011] However, the problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the description below.

[0012] One embodiment of the present invention provides a separator for an electrochemical device, wherein the separator is formed of a coating layer including a polymer binder and inorganic particles, and the separator is a free-standing porous separator that does not include a polyolefin substrate, in a separator facing a dry cathode.

[0013] According to one embodiment of the present invention, the polymer binder may be an acrylic binder.

[0014] According to one embodiment of the present invention, the content of the polymer binder may be 6 parts by weight or less with respect to 100 parts by weight of the separator.

[0015] According to one embodiment of the present invention, the inorganic particles are 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 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, Y2O3, SiC, ZnSn(OH)6, Zn2SnO4, ZnSnO3, Sb2O3, Sb2O4 and Sb2O5.

[0016] According to one embodiment of the present invention, the content of the inorganic particles may be 95 parts by weight or more with respect to 100 parts by weight of the separation membrane.

[0017] According to one embodiment of the present invention, the thickness of the separation membrane may be less than 15 μm.

[0018] According to one embodiment of the present invention, the dry positive electrode includes a positive electrode active material, and the positive electrode active material may include an LFP (lithium iron phosphate)-based active material.

[0019] One embodiment of the present invention provides a method for manufacturing a separator for an electrochemical device including a dry anode, the method including a step of forming a free-standing porous separator by coating a slurry for a coating layer including inorganic particles and a polymer binder on the dry anode.

[0020] According to one embodiment of the present invention, the coating may use a bar coating.

[0021] One embodiment of the present invention provides an electrochemical device including a dry positive electrode; a negative electrode; and a separator for the electrochemical device positioned between the dry positive electrode and the negative electrode.

[0022] According to one embodiment of the present invention, a separator for an electrochemical device can improve battery performance even when the separator is made thin by introducing a separator that does not include a polyolefin substrate.

[0023] A method for manufacturing a separator for an electrochemical device according to one embodiment of the present invention can improve battery performance while minimizing the thickness of the separator by introducing a separator that does not include a polyolefin substrate.

[0024] An electrochemical device according to one embodiment of the present invention can improve battery performance even when the separator is made thin by introducing a separator that does not include a polyolefin substrate into a dry electrode.

[0025] Figure 1 is a schematic diagram showing a dry cathode and separator according to one embodiment of the present invention.

[0026] In this specification, when a part is said to "include" a certain component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0027] In this specification, “A and / or B” means “A and B, or A or B.”

[0028] In this specification, when it is said that a component is “on”, this does not exclude other components being placed therebetween, unless otherwise specifically stated, but rather means that other components may be placed thereon.

[0029] In this specification, the terms "about" and "substantially" are used to mean a range of or approximation to a numerical value or degree, taking into account inherent manufacturing and material tolerances, and are used to prevent infringers from unfairly using the disclosure, which mentions exact or absolute numbers provided to aid understanding of the present invention.

[0030] In this specification, “electrochemical device” may mean a primary battery, a secondary battery, a super capacitor, etc.

[0031] Hereinafter, the present invention will be described in more detail.

[0032] Figure 1 is a schematic diagram showing a dry anode (200) and a separator (100) according to one embodiment of the present invention.

[0033] One embodiment of the present invention includes a separator (100) for an electrochemical device, wherein the separator (100) facing a dry positive electrode (200) is made of a coating layer including a polymer binder and inorganic particles, and the separator is a freestanding porous separator (100) that does not include a polyolefin substrate.

[0034] A separator (100) for an electrochemical device according to one embodiment of the present invention can improve battery performance even when the separator is made thin by introducing a separator that does not include a polyolefin substrate.

[0035] In general, a separator for an electrochemical device forms a coating layer containing inorganic particles and a binder polymer on at least one surface of a porous polymer substrate, and the porous polymer substrate uses a polyolefin substrate or nonwoven fabric manufactured through a dry or wet process.

[0036] The above freestanding porous separator (100) refers to a separator having a porous structure formed by a coating layer containing inorganic particles and a binder polymer without a porous polymer substrate as described above.

[0037] According to one embodiment of the present invention, the coating layer includes a polymer binder and inorganic particles. As described above, by including the polymer binder and the inorganic particles, the coating layer improves the heat resistance of the separator, improves mechanical properties, prevents the separator from shrinking at high temperatures and causing an electrical short circuit in the electrode, and can form pores within the coating layer.

[0038] According to one embodiment of the present invention, the coating layer may be formed by inorganic particles being bound by polymer binder particles and accumulated within the side. The pores within the coating layer may be derived from interstitial volume, which is an empty space between the inorganic particles.

[0039] Meanwhile, a freestanding porous separator (100) that does not include a polyolefin substrate may be vulnerable to external force and have low compression resistance because its outer shape is formed only with inorganic particles and a binder polymer.

[0040] According to one embodiment of the present invention, a free-standing porous separator having excellent compression resistance is provided by configuring a high content of inorganic particles relative to a binder without using a polyolefin substrate.

[0041] According to one embodiment of the present invention, the polymer binder is an acrylic copolymer, a styrene-butadiene copolymer, poly(acrylic acid), poly(methylmethacrylate), poly(butylacrylate), poly(acrylonitrile), poly(vinylpyrrolidone), poly(vinylalcohol), poly(vinylacetate), poly(ethylene-co-vinyl acetate), poly(ethylene oxide), poly(arylate), cellulose acetate, cellulose acetate butyrate, cellulose acetate It may include cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, or two or more thereof.

[0042] According to one embodiment of the present invention, the polymer binder may be an acrylic binder. Specifically, the polymer binder may be an acrylic copolymer. By including the acrylic copolymer, the porosity of the separator can be maintained and the ease of battery manufacturing can be improved. The acrylic copolymer may include, but is not limited to, an ethyl acrylate-acrylic acid-N,N-dimethylacrylamide copolymer, an ethyl acrylate-acrylic acid-2-(dimethylamino)ethyl acrylate copolymer, an ethyl acrylate-acrylic acid-N,N-diethylacrylamide copolymer, an ethyl acrylate-acrylic acid-2-(diethylamino)ethyl acrylate copolymer, or two or more thereof.

[0043] According to one embodiment of the present invention, the content of the polymer binder may be 6 parts by weight or less with respect to 100 parts by weight of the separator. Specifically, the content of the polymer binder may 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 with respect to 100 parts by weight of the separator. If the content of the polymer binder exceeds the above-mentioned range, the content of the inorganic particles may be relatively reduced, resulting in lower heat resistance and, further, poor battery resistance and capacity performance. If the content of the polymer binder is less than the above-mentioned range, it may be difficult to form pores within the coating layer due to bonding of the inorganic particles and the polymer binder, which may result in increased air permeability and resistance. By minimizing the content of the polymer binder within the above-mentioned range, a free-standing separator superior to the prior art can be realized.

[0044] According to one embodiment of the present invention, the D50 particle size of the polymer binder may be 100 nm or more and 500 nm or less. Specifically, the D50 particle size of the polymer binder may be 100 nm or more and 500 nm or less, 100 nm or more and 450 nm or less, 100 nm or more and 400 nm or less, 100 nm or more and 350 nm or less, 100 nm or more and 300 nm or less, 100 nm or more and 250 nm or less, 100 nm or more and 200 nm or less, 150 nm or more and 450 nm or less, and preferably, the D50 particle size of the polymer binder may be 150 nm. If it exceeds the above-mentioned range, pore formation may be difficult when bonding with an inorganic substance, and if it falls short of the above-mentioned range, bonding itself with an inorganic substance may be difficult, resulting in reduced coatability. By controlling the D50 particle size of the polymer binder within the above-described range, the binding force with inorganic particles can be increased, thereby improving battery performance.

[0045] According to one embodiment of the present invention, the inorganic particles are 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 )O3-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 are at least one selected from the group consisting of Al2O 3- It could be.

[0046] According to one embodiment of the present invention, the content of the inorganic particles may be 95 parts by weight or more with respect to 100 parts by weight of the separator. Specifically, the content of the inorganic particles may 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 with respect to 100 parts by weight of the separator. If the content exceeds the above-mentioned range, the content of the polymer binder is greatly reduced, so that it may be difficult to form pores inside the coating layer due to the binding of the inorganic material and the polymer binder, which may cause an increase in air permeability and resistance. In contrast, even when the above-described range is not met, cell resistance and capacity performance may be inferior. Furthermore, by setting the content of the inorganic particles high, heat resistance characteristics can be secured even when the separator is thinned.

[0047] According to one embodiment of the present invention, the D50 particle size of the inorganic particles is not particularly limited, but is preferably in the range of 0.3 ㎛ to 1 ㎛ in order to form a coating layer of uniform thickness and have an appropriate porosity. Specifically, when it is less than 0.3 ㎛, the dispersibility of the inorganic particles in the slurry prepared for manufacturing the coating layer may be reduced, and when it exceeds 1 ㎛, the thickness of the formed coating layer may increase.

[0048] In this specification, "D50 particle size" means the particle size at the 50% point of the cumulative distribution of particle numbers according to particle size. The particle size can be measured using a laser diffraction method. Specifically, after the powder to be measured is dispersed in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500), and when the particles pass through the laser beam, the difference in the diffraction pattern according to the particle size is measured to calculate the particle size distribution. By calculating the particle diameter at the point where the cumulative distribution of particle numbers according to particle size in the measuring device becomes 50%, the D50 particle size can be measured.

[0049] In one embodiment of the present invention, the thickness of the separator may be less than 15 μm. Specifically, the thickness of the separator may be more than 8 μm and less than 15 μm, more than 8 μm and 14 μm or less, 8.5 μm and 13.5 μm or less, 9 μm and 13 μm or less, 9 μm and 12.5 μm or less, 9 μm and 12 μm or less, 9 μm and 11.5 μm or less, 9 μm and 11 μm or less, or 9.5 μm and 10.5 μm or less. If the thickness exceeds the above-mentioned range, the resistance may increase due to the excessively thick separator, thereby deteriorating the capacity performance and capacity loss rate, and if the thickness falls below the above-mentioned range, the coating property may deteriorate due to the excessively thin separator. By controlling the thickness of the separator within the above-described range, heat resistance can be maintained while reducing the thickness and improving battery performance. Furthermore, the separator can be made thinner than separators typically manufactured using porous polymer substrates. The problem of heat resistance degradation due to thinning of the separator can be addressed by increasing the content of inorganic particles in the coating layer.

[0050] In one embodiment of the present invention, the thickness of the separator and coating layer, etc., can be measured using a contact thickness measuring device. The contact thickness measuring device can be, for example, the VL-50S-B from Mitutoyo.

[0051] According to one embodiment of the present invention, the porosity of the coating layer may be 30% by volume or more. Specifically, the porosity of the coating layer may be 30% by volume or more and 70% by volume or less, 32% by volume or more and 68% by volume or less, 34% by volume or more and 66% by volume or less, 36% by volume or more and 64% by volume or less, 38% by volume or more and 62% by volume or less, 40% by volume or more and 60% by volume or less, 42% by volume or more and 58% by volume or less, 44% by volume or more and 56% by volume or less, 46% by volume or more and 54% by volume or 48% by volume or more and 52% by volume. By controlling the porosity of the coating layer within the above-described range, the movement of ions in the separator can be maintained, and an increase in resistance of the separator can be prevented.

[0052] In this specification, the porosity means the ratio of the volume occupied by pores to the total volume, and uses volume% as its unit, and can be used interchangeably with terms such as porosity and porosity.

[0053] In this specification, porosity corresponds to a value obtained by subtracting a volume converted to the weight and density of each component of the coating layer from the volume calculated in the thickness, width, and length of the coating layer.

[0054] In one embodiment of the present invention, the porosity and pore size of the coating layer can be measured by the BET 6-point method using a scanning electron microscope (SEM) image, a mercury porosimeter, a capillary flow porometer, or a porosimetry analyzer (Bell Japan Inc, Belsorp-II mini) using a nitrogen gas adsorption flow method. In this case, the use of a capillary flow porometer may be advantageous.

[0055] According to one embodiment of the present invention, the separator (100) faces a dry positive electrode (200). In the case of a conventional separator facing a wet positive electrode, when a water dispersion process is performed during the manufacture of the wet positive electrode and then a slurry for an aqueous coating layer is coated, shrinkage of the coating layer occurs at high temperatures, which may cause an increase in the thickness of the separator, and thus, there is a problem of inferior battery performance. In contrast, a dry positive electrode is an electrode that can be coated without a solvent, and even if a separator is coated on the dry positive electrode, shrinkage of the coating layer does not occur at high temperatures, and thus has the advantage of superior coatability compared to a wet positive electrode.

[0056] According to one embodiment of the present invention, the separator (100) may further include a surfactant. The surfactant may be added to facilitate casting of the coating layer composition. A polyether-modified siloxane-based surfactant may be used as the surfactant, and when included, the coating layer composition can be coated with a more uniform thickness.

[0057] The above polyether-modified siloxane surfactant is a surfactant that includes a polyether chain at the end and / or side chain of the polysiloxane main chain. For example, the polyether-modified siloxane surfactant may include a polyethylene oxide group and / or a polypropylene oxide group.

[0058] These polyether-modified siloxane surfactants may be commercially available materials, and for example, at least one selected from 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 may be used.

[0059] The content of the polyether-modified siloxane-based surfactant is 0.05 to 1.0 parts by weight based on 100 parts by weight of the coating layer composition, 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 weight part of the surfactant within the above-described range, the effect of improving the coatability of the coating layer can be secured.

[0060] According to one embodiment of the present invention, a solvent can be used without limitation in its composition as long as it can dissolve the above-described components, and for example, one or more selected from 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 amyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethyl ether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate, and N,N-dimethylacetamide can be used in combination. Preferably, the solvent can be water.

[0061] One embodiment of the present invention includes a method for manufacturing a separator (100) for an electrochemical device including a dry anode (200), the method including a step of forming a free-standing porous separator (100) by coating a slurry for a coating layer including inorganic particles and a polymer binder on the dry anode.

[0062] A method for manufacturing a separator for an electrochemical device according to one embodiment of the present invention can improve battery performance while minimizing the thickness of the separator by introducing a separator that does not include a polyolefin substrate.

[0063] According to one embodiment of the present invention, the method for manufacturing the separator for an electrochemical device includes a step of mixing a slurry for a coating layer comprising polymer binder particles and inorganic particles. By including the step of mixing the slurry for a coating layer comprising polymer binder particles and inorganic particles as described above, a coating layer can be easily formed on the separator.

[0064] According to one embodiment of the present invention, inorganic particles may be added and dispersed in the polymer binder. The content ratio of the inorganic particles and the polymer binder particles is as described above, and is appropriately adjusted in consideration of the thickness, pore size, and porosity of the coating layer to be finally manufactured according to one embodiment of the present invention.

[0065] According to one embodiment of the present invention, a slurry can be prepared by dispersing polymer binder particles and inorganic particles in water.

[0066] According to one embodiment of the present invention, the method of applying the slurry for the coating layer onto the dry anode may be at least one selected from the group consisting of bar coating, dip coating, die coating, roll coating, comma coating, and combinations thereof. Preferably, bar coating may be used.

[0067] According to one embodiment of the present invention, the method for manufacturing a separator for an electrochemical device includes a step of drying the slurry for the coating layer to form a coating layer. By including the step of drying the slurry for the coating layer to form a coating layer as described above, damage to the coating layer can be minimized, and the solvent contained in the slurry can be easily removed.

[0068] According to one embodiment of the present invention, the drying process appropriately sets time conditions to minimize the occurrence of surface defects in the coating layer. The drying may be performed using a drying assist device, such as a drying oven or hot air, within an appropriate range.

[0069] One embodiment of the present invention includes an electrochemical device including a dry positive electrode (200); a negative electrode; and a separator (100) for an electrochemical device positioned between the dry positive electrode (200) and the negative electrode.

[0070] An electrochemical device according to one embodiment of the present invention can suppress the springback phenomenon and secure battery performance and insulation by introducing a separator (100) that does not include a polyolefin substrate into a dry cathode (200).

[0071] 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 the present specification, the secondary battery is capable of charging and discharging, and refers to a lithium secondary battery, a nickel-cadmium battery, a nickel-hydrogen battery, etc. The lithium secondary battery uses lithium ions as an ion conductor, and examples thereof include, but are not limited to, a non-aqueous electrolyte secondary battery including a liquid electrolyte, an all-solid-state battery including a solid electrolyte, a lithium polymer battery including a gel polymer electrolyte, and a lithium metal battery using lithium metal as an anode.

[0072] According to one embodiment of the present invention, the positive electrode has a positive electrode current collector and a positive electrode active material layer including a positive electrode active material, a conductive material, and a binder resin on at least one surface of the positive electrode 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 a portion of lithium nickel-manganese-cobalt oxide is substituted with another transition metal; or two or more thereof, but is not limited thereto. Specifically, the positive electrode active material may include, for example, a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; a compound having the chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and x = 0.01 to 0.3); chemical formula LiMn 2-x M x Lithium manganese composite oxides represented by O2 (wherein M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li2Mn3MO8 (wherein M = Fe, Co, Ni, Cu or Zn); lithium metal phosphate LiMPO4 (wherein M = Fe, CO, Ni or Mn); lithium nickel-manganese-cobalt oxide Li 1+x (NiaCobMnc) 1-xO2(x = 0 ~ 0.03, a = 0.3 ~ 0.95, b = 0.01 ~ 0.35, c = 0.01 ~ 0.5, a+b+c=1); Lithium nickel-manganese-cobalt oxide partially substituted with aluminum 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, and 0.8≤a≤1.2, 0.5≤b≤0.99, 0 <c<0.5, 0<d<0.5, 0.01≤e≤0.1, 0≤f≤0.1); 리튬 니켈-망간-코발트 산화물에 일부가 다른 전이금속으로 치환된 산화물 Li 1+x (Ni a Co b Mn c M d ) 1-x O2(x = 0 ~ 0.03, a = 0.3 ~ 0.95, b = 0.01 ~ 0.35, c = 0.01 ~ 0.5, d = 0.001 ~ 0.03, a+b+c+d=1, 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 are not limited thereto.

[0073] According to one embodiment of the present invention, the positive electrode active material may include an LFP (lithium iron phosphate)-based active material. As described above, the positive electrode active material includes an LFP (lithium iron phosphate)-based active material, thereby ensuring battery insulation and battery performance without dry manufacturing or including a polyolefin substrate.

[0074] According to one embodiment of the present invention, the negative electrode has a negative electrode current collector and a negative electrode active material layer including 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 graphite carbon as the negative electrode active material; LixFe2O3(0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me' y O z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of group 1, 2, and 3 of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, 및 Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료; 티타늄 산화물 중 선택된 1종 또는 2종 이상의 혼합물을 포함할 수 있다.

[0075] According to one embodiment of the present invention, the conductive material may be, for example, one selected from the group consisting of graphite, carbon black, carbon fibers or metal fibers, metal powders, conductive whiskers, conductive metal oxides, activated carbon, and polyphenylene derivatives, or a mixture of two or more conductive materials among these. More specifically, the conductive material 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, summer black, Denka black, aluminum powder, nickel powder, zinc oxide, potassium titanate, and titanium oxide, or a mixture of two or more conductive materials among these.

[0076] According to one embodiment of the present invention, the current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, stainless steel, copper, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. can be used.

[0077] According to one embodiment of the present invention, the binder resin may be a polymer commonly used in electrodes in the art. Non-limiting examples of such binder resins include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, polymethylmethacrylate, polyethylhexyl acrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. Examples thereof include, but are not limited to, cellulose acetatepropionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose.

[0078] According to one embodiment of the present invention, in the dry cathode (200), the binder is not limited to a specific one, as long as it can be fibrillated, particularly during the process of manufacturing the mixture lump. The fibrillation refers to a process in which a polymer is divided into fine particles, and can be performed using, for example, mechanical shear force. The surface of the polymer fibers thus fibrillated is loosened, thereby generating a large number of fine fibers (fibrils).

[0079] Non-limiting examples of such binder polymers may include polytetrafluoroethylene (PTFE), polyolefin, or a mixture thereof, specifically, polytetrafluoroethylene (PTFE), and more specifically, polytetrafluoroethylene (PTFE). Specifically, the polytetrafluoroethylene (PTFE) may be included in an amount of 60 wt% or more based on the total weight of the entire binder polymer. Meanwhile, at this time, the binder material may additionally include at least one of polyethylene oxide (PEO), polyvinylidene fluoride (PVdF), polyvinylidene fluoride-cohexafluoropropylene (PVdF-HFP), and a polyolefin-based polymer.

[0080] According to one embodiment of the present invention, in manufacturing a dry positive electrode (200), mixing for mixing the electrode materials is performed so that the electrode active material and binder polymer, and optionally the conductive material, are uniformly distributed. Since these components are mixed in powder form, they are not limited as long as they enable simple mixing thereof, and can be mixed by various methods. However, since the method is for manufacturing a dry electrode that does not use a solvent, the mixing can be performed by dry mixing, and can be performed by putting the materials into a device such as a blender or a supermixer.

[0081] According to one embodiment of the present invention, when the mixing is performed in a blender, the mixture may be manufactured by mixing in the blender at 5,000 rpm to 20,000 rpm for 30 seconds to 20 minutes, specifically at 10,000 rpm to 15,000 rpm for 30 seconds to 5 minutes, to ensure uniformity.

[0082] Next, a step of kneading the mixture of the above electrode materials at a high temperature and low shear rate to obtain a mixture lump can be performed.

[0083] A step for fiberizing the binder in the mixture manufactured as described above is also called a kneading process.

[0084] In one embodiment of the present invention, low-shear kneading may be performed to fiberize the binder, to micronize the active material, and to resolve the problem of the formed fibers being cut, but the step is not limited thereto.

[0085] At this time, the mixing is not limited, but can be performed through a kneader, for example.

[0086] This mixing is a step in which the binder is fiberized and combines or connects the active material or the active material and conductive powders to form a mixture mass with a solid content of 100%.

[0087] In one embodiment of the present invention, the mixing in the above step may be performed at a speed of 10 rpm to 100 rpm for 1 to 30 minutes, and specifically, may be performed at a speed of 20 rpm to 50 rpm for 3 to 10 minutes.

[0088] According to one embodiment of the present invention, an electrochemical device prepared as described above can be placed in an appropriate case and an electrolyte solution is injected to manufacture a battery.

[0089] According to one embodiment of the present invention, the electrolyte is A + B - As a salt with the same structure, A + is Li + , Na + , K + B containing an ion composed of an alkali metal cation or a combination thereof; - is PF6 - , BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3 -Salts containing anions such as or combinations thereof are dissolved or dissociated in organic solvents such as propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), gamma butyrolactone (γ-butyrolactone) or mixtures thereof, but are not limited thereto.

[0090] In one embodiment of the present invention, the external shape of the electrochemical device may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape. Preferably, the electrochemical device may be a cylindrical battery. As described above, by selecting a cylindrical battery, the electrochemical device can realize a thin separator without requiring an additional adhesive layer.

[0091] In addition, a battery module including a battery including the electrochemical element as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source are provided. Specific examples of the device include, but are not limited to, a power tool that is powered by an electric motor; an electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), etc.; an electric two-wheeled vehicle including an electric bicycle (E-bike) and an electric scooter (E-scooter); an electric golf cart; and a power storage system.

[0092] Hereinafter, the present invention will be described in detail using examples. However, the examples according to the present invention may be modified in various ways, and the scope of the present invention is not limited to the examples described below. The examples in this specification are provided to more fully explain the present invention to those of ordinary skill in the art.

[0093]

[0094] <Example 1>

[0095] A slurry for an aqueous coating layer was prepared by mixing Al2O3 with a D50 of 500 nm as an inorganic material, an acrylic copolymer (Toyo ink, CSB-140) with a D50 of 150 nm as a polymer binder, a PAA-based dispersant (CK-702), and a surfactant (BYK-348) in a weight ratio of 95.4: 2: 2: 0.6 (solid content 35%).

[0096] A separator was manufactured by cross-section coating (bar coating) the slurry for the above-mentioned aqueous coating layer on a dry LFP anode. At this time, the thickness of the separator was 10 μm.

[0097]

[0098] <Example 2>

[0099] A separator was manufactured in the same manner as in Example 1, except that the thickness of the separator was set to 9 μm.

[0100]

[0101] <Example 3>

[0102] A separator was manufactured in the same manner as in Example 1, except that the membrane thickness was set to 12 μm.

[0103]

[0104] <Example 4>

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

[0106] A separator was manufactured by cross-section coating (bar coating) the slurry for the above-mentioned aqueous coating layer on a dry LFP anode. At this time, the thickness of the separator was 10 μm.

[0107]

[0108] <Comparative Example 1>

[0109] A separator was manufactured in the same manner as in Example 1, except that the membrane thickness was set to 8 μm.

[0110]

[0111] <Comparative Example 2>

[0112] A separator was manufactured in the same manner as in Example 1, except that the membrane thickness was set to 15 μm.

[0113]

[0114] <Comparative Example 3>

[0115] Polyolefin (PO) resin was extruded and a porous polymer substrate (total thickness of approximately 10 μm) was manufactured using a wet method.

[0116] A separation membrane was manufactured by coating the slurry for the coating layer in Example 1 on both sides of the porous polymer substrate to a thickness of 1.5 μm.

[0117]

[0118] Comparative Example 4

[0119] A separator was manufactured in the same manner as in Example 1, except that a single-sided coating (bar coating) was performed on a wet LFP anode instead of a dry LFP anode.

[0120]

[0121] Comparative Example 5

[0122] A separator was manufactured in the same manner as in Comparative Example 3, except that a single-sided coating (bar coating) was applied to a wet LFP anode instead of a dry LFP anode.

[0123]

[0124] Comparative Example 6

[0125] A slurry for an aqueous coating layer was prepared by mixing Al2O3 as an inorganic material, an acrylic copolymer (Toyo ink, CSB-140) with a D50 of 150 nm as a polymer binder, a PAA-based dispersant (CK-702), and a surfactant (BYK-348) in a weight ratio of 92: 5: 2.4: 0.6 (solid content 35%).

[0126] A separator was manufactured by cross-section coating (bar coating) the slurry for the above-mentioned aqueous coating layer on a dry LFP anode. At this time, the thickness of the separator was 10 μm.

[0127]

[0128] <Manufacturing of electrochemical devices>

[0129] (1) Manufacturing of cathode

[0130] 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, Daicel Chemical Industries, Ltd. product): conductive agent (Super-C65, carbon black) with water in a weight ratio of 80.3 / 19.7:2.3:1.05:0.5, with a concentration of 50 wt% of the remaining components excluding water. Next, the slurry was applied to the surface of a copper thin film (thickness 10 μm) and dried to manufacture a negative electrode having a negative electrode active material layer (thickness 120 μm).

[0131]

[0132] (2) Manufacturing of positive electrode

[0133] 1) Manufacturing of wet electrodes

[0134] A slurry for a positive electrode active material layer was prepared by mixing positive electrode active material (S20, LFP): conductive agent (CNT (LB-CNT)): binder (KF7200): dispersant (HPD-01) with water in a weight ratio of 95.96:0.8:3.0:0.24, with the remaining components excluding water at a concentration of 50 wt%. Next, the slurry was applied to the surface of an aluminum thin film (thickness 10 μm) and dried to manufacture a positive electrode having a positive electrode active material layer (thickness 120 μm).

[0135]

[0136] 2) Manufacturing of dry electrodes

[0137] The cathode active material (S20, LFP): conductive material (Li-435): binder (PTFE) were placed in a blender at a weight ratio of 94.0:1.5:4.5 and mixed at 15,000 rpm for 1 minute to obtain a mixture.

[0138] Next, the temperature of the kneader (Shinil Disperser) was stabilized at 150°C, the mixture prepared above was placed in the kneader, and the mixture was operated at a speed of 40 rpm under a pressure of 1.1 atm for 5 minutes to obtain a mixture lump.

[0139] The above mixture lump was placed in a blender (Waring) and ground at 10,000 rpm for 1 minute to obtain powder for electrodes.

[0140] Afterwards, the above electrode mixed powder was put into a lab calendar (roll diameter: 200 mm, roll temperature: 100 ℃, 20 rpm) and the calendaring process was repeated so that the porosity became 35% or less. At this time, the pressure between the rolls was 221 kg / cm during the last calendaring to manufacture an electrode film. At this time, the thickness of the manufactured electrode film was 82 ㎛, the porosity (%) was 31%, and the loading amount was 5.11 mAh / cm 2 It was.

[0141] A slurry for forming a primer layer was applied to aluminum foil and dried to form a primer layer on a current collector. The primer layer includes carbon black and PVDF binder in a weight ratio of 1:2. Then, a roll press maintained at room temperature was used so that two sheets of the electrode film could be laminated on both sides of the aluminum foil (average thickness: 19 ㎛) on which the primer layer was formed, and a lamination process was performed so that the porosity of the electrode active material layer became 30% or less, thereby manufacturing an electrode in which an electrode active material layer was formed on both sides of the current collector by grounding the electrode film on the current collector. At this time, the thickness of the electrode film grounded on the current collector, i.e., the electrode active material layer, was 75 ㎛, the porosity (%) was 25.9%, and the loading was 5.05 mAh / cm 2 It was.

[0142]

[0143] <Experimental Example>

[0144] (1) Measurement of initial battery resistance

[0145] The above battery was charged and discharged three times at room temperature under the condition of 0.33 C-rate, and then the battery resistance was evaluated based on the resistance value observed when current was applied for 10 seconds at 2.5 C-rate at SOC 50. The measurement results are shown in Table 1 below.

[0146]

[0147] (2) Evaluation of initial battery capacity and capacity retention rate

[0148] For each lithium secondary battery manufactured above, 100 charge-discharge cycles were performed, in which one cycle was performed by charging to 4.2 V at 0.33 C in CC-CV mode at 25°C and discharging to 2.5 V at a constant current of 0.33 C. The initial capacity and the capacity retention rate after 500 cycles were measured to evaluate the life characteristics. The measurement results are shown in Table 1 below.

[0149]

[0150] (3) 180 ℃ Dry heat shrinkage rate measurement

[0151] The membranes of Comparative Examples 3 and 5 are cut into 5 cm × 5 cm sizes to prepare samples. After leaving the samples in a convection oven at 180°C for 30 minutes, the samples are taken out and the thermal shrinkage rates (%) in the MD and TD directions are calculated according to [(length of initial specimen - length after storage at @180°C / 0.5 h) / (length of initial specimen)] × 100 (%), and are shown in Table 1 below.

[0152]

[0153] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Anode Dry LFP Dry LFP Dry LFP Dry LFP Dry LFP Dry LFP Wet LFP Wet LFP Dry LFP Presence of separator substrate XXXXXXOXOX Inorganic content (wt%) 9 5 9 5 9 5 9 6 9 5 9 5 9 5 9 5 9 5 9 2 Separator thickness (μm) 1 0 9 1 2 1 0 8 (partial coating) 1 5 1 3 1 0 1 3 1 0 Initial battery capacity (mAh) 4 0.1 4 0.3 3 8.7 4 0.2 Short-circuit occurrence Not possible to evaluate 37.7 3 8.5 Coating Not possible to evaluate 38.6 3 8.1 Initial battery Resistance (mohm) 1.21 1.20 1.25 1.20 1.27 1.25 1.25 1.26 Capacity loss rate (%) after 25℃, 1C / 1C, 500 cycles 2.7 2.23.9 2.4 5.24.3 4.0 4.7 180 ℃ Dry heat shrinkage (%, MD / TD)------ 3 / 3- 3 / 3-

[0154]

[0155] According to Table 1 above, in the case of Example 1, it can be confirmed that the thickness of the separator can be controlled thinly by not including a separator substrate in the dry LPF anode, the initial battery resistance is low, the initial battery capacity is high, and the capacity loss rate is low.

[0156] In contrast, in the case of Comparative Example 1, if the membrane thickness is too thinly coated at 8 μm, there is a problem that partial coating occurs and an internal short occurs due to the uncoated portion.

[0157] In the case of Comparative Example 2, there is no insulation problem, but as the thickness of the separator increases, the resistance increases compared to the example, and as a result, the capacity performance and capacity loss rate are inferior.

[0158] In the case of Comparative Examples 3 and 5, since the separator includes a porous polymer substrate, the thickness of the separator increases and the resistance and capacity performance are inferior to those of the Examples. In addition, since the separator includes a porous polymer substrate, it can be seen that when measuring the dry thermal shrinkage rate of the separator, thermal shrinkage occurs in the MD and TD directions at a high temperature of 180°C. In contrast, the Examples of the present invention manufacture the separator by coating it on a dry positive electrode, so that shrinkage of the coating layer does not occur at high temperatures.

[0159] In the case of Comparative Example 4, coating was not possible because the slurry for the aqueous coating layer did not wet due to differences in the surface characteristics of the wet anode.

[0160] In the case of Comparative Example 6, it can be seen that the inorganic content is lower than that of the example, resulting in inferior resistance and capacity performance.

[0161] Therefore, in accordance with one embodiment of the present invention, a separator for an electrochemical device, a method for manufacturing the same, and an electrochemical device including the same, the separator facing the dry cathode is formed of a coating layer including a polymer binder and inorganic particles, and the separator does not include a polyolefin substrate, thereby making the separator thin while having excellent heat resistance and improving battery performance.

[0162] [Explanation of symbols]

[0163] 100: Membrane

[0164] 200: Dry anode

Claims

1. In the separator facing the dry cathode, The above separator is composed of a coating layer including a polymer binder and inorganic particles, A separator for an electrochemical device, wherein the above separator is a free-standing porous separator that does not include a polyolefin substrate.

2. In claim 1, A separator for an electrochemical device, wherein the polymer binder is an acrylic binder.

3. In claim 1, A separator for an electrochemical device, wherein the content of the polymer binder is 6 parts by weight or less per 100 parts by weight of the separator.

4. In claim 1, The above inorganic particles are 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 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, Y2O3, SiC, ZnSn(OH)6, Zn2SnO4, ZnSnO3, Sb2O3, Sb2O4 and Sb2O5, a separator for an electrochemical device, wherein the separator comprises at least one selected from 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. In claim 1, A separator for an electrochemical device, wherein the content of the above-mentioned inorganic particles is 95 parts by weight or more per 100 parts by weight of the separator.

6. In claim 1, A separator for an electrochemical device, wherein the thickness of the separator is less than 15 μm.

7. In claim 1, The above dry cathode includes a cathode active material, A separator for an electrochemical device, wherein the positive electrode active material includes an LFP (lithium iron phosphate)-based active material.

8. A method for manufacturing a separator for an electrochemical device including a dry cathode, A method for manufacturing a separator for an electrochemical device, comprising a step of forming a free-standing porous separator by coating a slurry for a coating layer containing inorganic particles and a polymer binder on the above dry anode.

9. In claim 8, A method for manufacturing a separator for an electrochemical device, wherein the above coating uses bar coating.

10. Dry anode; cathode; and An electrochemical device comprising a separator for an electrochemical device according to claim 1, positioned between the dry positive electrode and the negative electrode.

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