Lithium secondary battery separator and lithium secondary battery containing the same

Abstract

To provide a separator for lithium secondary batteries that can improve the resistance increase rate when charging at high voltage or storing at high temperatures. [Solution] The present invention relates to a separator for a lithium secondary battery and a lithium secondary battery containing the same, wherein the separator for the lithium secondary battery comprises a porous substrate and a coating layer located on at least one surface of the porous substrate, and the coating layer comprises a compound of chemical formula 1.

Description

[Technical Field]

[0001] This invention relates to a separator for lithium secondary batteries and a lithium secondary battery containing the same. [Background technology]

[0002] This application claims priority and interest in Korean Patent Application No. 10-2024-0124443, filed with the Korean Intellectual Property Office on 12 September 2024, all of which are incorporated herein by reference.

[0003] In recent years, with the rapid proliferation of electronic devices that use batteries, such as mobile phones, laptops, and electric vehicles, the demand for high-energy-density, high-capacity rechargeable batteries has been rapidly increasing. As a result, research and development to improve the performance of lithium-ion rechargeable batteries is being actively pursued.

[0004] A lithium secondary battery is a battery comprising a positive electrode and a negative electrode containing an active material that allows for the insertion and deintercalation of lithium ions, and an electrolyte. It produces electrical energy through oxidation and reduction reactions that occur when lithium ions are inserted into / deintercalated from the positive and negative electrodes.

[0005] The longer a lithium secondary battery is charged and discharged, the more likely it is that a chain reaction will occur in which [structural breakdown of the positive electrode active material located on the surface of the positive electrode → elution of transition metal ions, post-transition metal ions, and / or metalloid ions from the positive electrode active material into the electrolyte → reduction of the ions eluted into the electrolyte on the surface of the negative electrode → electrodeposition of the ions reduced on the surface of the negative electrode into transition metals, post-transition metal ions, metalloids, and / or their oxide forms]. This can lead to the formation of an unstable SEI (solid-electrolyte interphase) film on the surface of the negative electrode, causing side reactions (e.g., gas generation, increased interfacial resistance, etc.) at the interface between the negative electrode and the electrolyte, which can reduce the lifespan and / or high-temperature storage characteristics of the lithium secondary battery.

[0006] Furthermore, when a lithium secondary battery is charged at a high voltage or stored at a high temperature (e.g., 60 °C or higher), the amount of elution of transition metal ions, post-transition metal ions, and / or metalloid ions in the positive electrode active material increases.

[0007] The separator is included between the positive electrode and the negative electrode and is impregnated in the electrolytic solution. Therefore, it is preferable that the separator captures transition metal ions, post-transition metal ions, and / or metalloid ions eluted in the electrolytic solution, thereby improving the resistance increase rate during charging at a high voltage or storage at a high temperature.

Summary of the Invention

Means for Solving the Problems

[0008] One embodiment is to provide a separator for a lithium secondary battery that captures transition metal ions, post-transition metal ions, and / or metalloid ions.

[0009] Another embodiment is to provide a lithium secondary battery including the separator for a lithium secondary battery.

[0010] According to one embodiment, a separator for a lithium secondary battery is provided.

[0011] The separator for a lithium secondary battery includes a porous base material and a coating layer located on at least one surface of the porous base material, and the coating layer includes a compound represented by Chemical Formula 1.

[0012]

Chemical

[0013] According to another embodiment, a lithium secondary battery is provided.

[0014] The lithium secondary battery includes a positive electrode, a negative electrode, and a lithium secondary battery separator located between the positive electrode and the negative electrode.

[0015] A lithium secondary battery separator according to one embodiment can improve the resistance increase rate when a lithium secondary battery is charged at high voltage or stored at high temperature by capturing transition metal ions, post-transition metal ions, and / or metalloid ions dissolved in the electrolyte. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is a schematic cross-sectional view showing one example of a lithium secondary battery. [Figure 2] Figure 2 is a schematic cross-sectional view showing one example of a lithium secondary battery. [Figure 3] Figure 3 is a schematic cross-sectional view showing one example of a lithium secondary battery. [Figure 4] Figure 4 is a schematic cross-sectional view showing one example of a lithium secondary battery. [Figure 5] Figure 5 shows the resistance increase rate when batteries using separators according to Example 1 and Comparative Example 1 are stored at 60°C. In Figure 5, the X axis represents the number of storage days (in days), the Y axis represents the resistance (DC-IR) increase rate (in %), the black circles represent Example 1, and the black squares represent Comparative Example 1. [Figure 6] Figure 6 is a cross-sectional view of a separation membrane according to one embodiment. [Modes for carrying out the invention]

[0017] The following describes in detail some examples of the present invention. However, these are presented as examples only and do not limit the present invention; the present invention is defined solely by the scope of the claims described below.

[0018] Unless otherwise specified in this specification, when a part such as a layer, film, region, or plate is said to be "on top of" another part, this includes not only the case where it is "directly on top of" the other part, but also the case where there are other parts in between them.

[0019] Unless otherwise specified in this specification, singular nouns may also include plural nouns. Furthermore, unless otherwise specified, "A or B" may mean "including A, including B, or including both A and B."

[0020] In this specification, “combinations thereof” may mean mixtures, laminates, composites, copolymers, alloys, blends, and reaction products of the constituents.

[0021] In this specification, "particle size D50" means particle size, which refers to the diameter of a particle whose cumulative volume in the particle size distribution is 50% by volume. The particle size distribution may be measured by methods well known to those skilled in the art. For example, the particle size distribution may be measured with a particle size analyzer, or by transmission electron microscopy or scanning electron microscopy. Alternatively, it may be measured using a measuring device that employs dynamic light scattering, and the data may be analyzed to count the number of particles for each particle size range, after which the average particle size D50 value is calculated. Alternatively, it may be measured using laser diffraction. More specifically when measuring by laser diffraction, the particles to be measured are dispersed in a dispersion medium, then introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac's MT 3000), and after irradiating with ultrasound at approximately 28 kHz at an output of 60 W, the D50 based on 50% of the particle size distribution in the measuring device can be calculated.

[0022] In this specification, "(meth)acrylic" means acrylic and / or methacrylic.

[0023] Unless otherwise specified herein, “substitution” means that at least one hydrogen atom in a compound is a halogen atom (F, Cl, Br, I), a hydroxyl group, or C1-C 20An alkoxy group, a nitro group, a cyano group, an amine group, an imino group, an azide group, an amidino group, a hydrazino group, a hydrazono group, a carbonyl group, a carbamyl group, a thiol group, an ester group, an ether group, a carboxyl group or a salt thereof, a sulfonic acid group or a salt thereof, phosphoric acid or a salt thereof, C1 to C 20 an alkyl group, C2 to C 20 an alkenyl group, C2 to C 20 an alkynyl group, C6 to C 30 an aryl group, C3 to C 20 a cycloalkyl group, C3 to C 20 a cycloalkenyl group, C3 to C 20 a cycloalkynyl group, C2 to C 20 a heterocycloalkyl group, C2 to C 20 a heterocycloalkenyl group, C2 to C 20 It means being substituted by a substituent of a heterocycloalkyl group, a heterocycloalkenyl group, a heterocycloalkynyl group or a combination thereof.

[0024] Unless otherwise specified herein, the "heterocycloalkyl group", "heterocycloalkenyl group", "heterocycloalkynyl group" and "heterocycloalkylene group" each mean that at least one heteroatom of N, O, S or P is present in the ring compounds of cycloalkyl, cycloalkenyl, cycloalkynyl and cycloalkylene, respectively.

[0025] Unless otherwise specified in the chemical formulas herein, when a chemical bond is not drawn at a position where a chemical bond should be drawn, it means that a hydrogen atom is bonded to that position.

[0026] When describing a numerical range herein, "X to Y" means "X or more and Y or less (X ≤ and ≤ Y)".

[0027] A separator for a lithium secondary battery according to one embodiment includes a porous substrate and a coating layer located on at least one surface of the porous substrate, and the coating layer contains a compound of Chemical Formula 1 below.

[0028] The compound of chemical formula 1 can capture transition metal ions, post-transition metal ions, and / or metalloid ions that can dissolve into the electrolyte when lithium secondary batteries are charged at high voltage or stored at high temperatures (e.g., above 60°C). Therefore, the separator can suppress side reactions occurring at the interface between the negative electrode and the electrolyte (e.g., gas generation, increased interfacial resistance, etc.) and improve the lifespan and / or high-temperature storage characteristics of lithium secondary batteries.

[0029] According to one example, the transition metal ions, post-transition metal ions, and / or metalloid ions may be eluted from the positive electrode active material.

[0030] According to one example, the compound of chemical formula 1 may be contained in the separator in an amount of 95% by weight or more, for example, 95-100% by weight, for example, 100% by weight, of the transition metal ion scavenger, post-transition metal ion scavenger, and / or metalloid ion scavenger contained therein.

[0031] <Compounds of chemical formula 1> The compound of chemical formula 1 can capture transition metal ions, post-transition metal ions, and / or metalloid ions present in the electrolyte.

[0032] More specifically, the compound of chemical formula 1 can capture silicon (Si) ions, titanium (Ti) ions, vanadium (V) ions, chromium (Cr) ions, manganese (Mn) ions, iron (Fe) ions, cobalt (Co) ions, nickel (Ni) ions, copper (Cu) ions, zinc (Zn) ions, scandium (Sc) ions, or combinations thereof present in the electrolyte.

[0033] For example, the compound of chemical formula 1 may be significantly advantageous for capturing cobalt (Co) ions, nickel (Ni) ions, manganese (Mn) ions, or combinations thereof.

[0034] Here, the ions or combinations thereof may originate from the positive electrode active material and / or be present in the electrolyte due to external factors. The ions or combinations thereof may, but are not limited to, dissolve into the electrolyte when the lithium secondary battery is charged at a high voltage or stored at a high temperature (e.g., above 60°C).

[0035] Therefore, the separator can improve the lifespan and / or high-temperature storage characteristics of lithium secondary batteries by reducing the phenomenon of the ions or combinations thereof being deposited on the surface of the negative electrode. Such effects are independent of the type of positive electrode active material, the operating temperature of the lithium secondary battery, and the upper limit charging voltage.

[0036] In this specification, "capture" refers to a coordinate bond between the compound represented by chemical formula 1 and the ion. More specifically, the compound represented by chemical formula 1 may be converted into a complex represented by any one of the following chemical formulas 1-1 to 1-10 through a coordinate bond between the compound represented by chemical formula 1 and the ion.

[0037] [ka]

[0038] [ka]

[0039] [ka]

[0040] [ka]

[0041] [ka]

[0042] [ka]

[0043] [ka]

[0044] [ka]

[0045] [ka]

[0046] [ka] (R 1 ~R 24 (This is the same as the one defined in chemical formula 1.)

[0047] Compared to lithium secondary batteries that contain the compound of chemical formula 1 in the electrolyte rather than in a coating layer, lithium secondary batteries that include a separator with a coating layer containing the compound of chemical formula 1 may have an even greater advantage in that they can prevent the problem of increased viscosity of the electrolyte due to the addition of the compound.

[0048] On the other hand, in chemical formula 1, R 1 ~R 24 Each of these may independently be a hydrogen atom, a halogen atom, a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C6-C20 aryl group, or a substituted or unsubstituted C6-C20 heterocycloalkyl group.

[0049] For example, R 1 ~R 24 These atoms may all be hydrogen atoms. In this case, the compound represented by chemical formula 1 is represented by the following chemical formula 1A.

[0050] [ka]

[0051] The compound of chemical formula 1 may be present in the coating layer at an amount of 0.01 to 3% by weight. Within this range, the compound of chemical formula 1 can effectively capture dissociated transition metal ions, post-transition metal ions, and / or metalloid ions in the electrolyte, thereby improving the resistance increase rate.

[0052] The compound of chemical formula 1 may be included in the coating layer. The inclusion of the compound of chemical formula 1 in the coating layer may be advantageous in ensuring the air permeability of the separator.

[0053] According to one example, the compound of chemical formula 1 may be dispersed within the coating layer or present on the outermost surface of the coating layer.

[0054] <Porous base material> Porous substrates have numerous pores and may be substrates commonly used in electrochemical devices. Porous substrates may be polymers selected from the group consisting of polyethylene, polyolefins such as polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon, and polytetrafluoroethylene, or polymer films formed from copolymers or mixtures of two or more of these polymers.

[0055] The porous substrate may be, for example, a polyolefin-based substrate containing polyolefin, and the polyolefin-based substrate has excellent shutdown function and can contribute to improving battery safety. The polyolefin-based substrate may be selected from, for example, a polyethylene single layer film, a polypropylene single layer film, a polyethylene / polypropylene double layer film, a polypropylene / polyethylene / polypropylene triple layer film, and a polyethylene / polypropylene / polyethylene triple layer film. Furthermore, the polyolefin resin may contain a non-olefin resin in addition to the olefin resin, or a copolymer of olefin and non-olefin monomer.

[0056] The porous substrate may have a thickness of 1 μm to 40 μm, for example, 1 μm to 30 μm, 1 μm to 20 μm, or 5 μm to 15 μm.

[0057] <Coating layer> The coating layer may further contain, without limitation, any binder that does not affect the aforementioned scavenging effect of the compound of chemical formula 1.

[0058] The binder may contain one or more types of binders, including aqueous binders and organic binders.

[0059] According to one example, the aqueous binder may contain carboxyalkylcellulose or a salt thereof, including carboxymethylcellulose or a salt thereof, or one or more polymers from among (meth)acrylic acid, (meth)acrylic acid esters, (meth)acrylonitrile, (meth)acryamide, or diene rubber. For example, the aqueous binder may contain carboxymethylcellulose or a salt thereof, polyvinyl alcohol, polyacrylic acid, styrene-butadiene rubber, carboxy-modified styrene-butadiene rubber, etc.

[0060] According to one example, the organic binder may contain one or more of polyvinylidene fluoride and polyvinylidene fluoride fluoride-hexafluoropropylene.

[0061] One or more of the aqueous binders and organic binders may have a weight-average molecular weight of 10,000 to 500,000 g / mol, for example, 10,000 g / mol, 50,000 g / mol, 100,000 g / mol, 150,000 g / mol, 200,000 g / mol, 250,000, 300,000 g / mol, 350,000 g / mol, 400,000 g / mol, 450,000 g / mol, 500,000 g / mol, or 70,000 to 75,000 g / mol. Within this range, it is easy to achieve the capture effect of the compound of chemical formula 1. Here, the "weight-average molecular weight" can be determined by the polystyrene equivalent value obtained by gel permeation chromatography.

[0062] The compound of chemical formula 1 may be present in the coating layer at an amount of 0.01 to 3% by weight. Within this range, the compound of chemical formula 1 effectively captures transition metal ions, post-transition metal ions, and / or metalloid ions dissociated in the electrolyte, thereby improving the DC resistance increase rate. For example, the coating layer amounts of 0.01% by weight, 0.05% by weight, 0.1% by weight, 0.15% by weight, 0.2% by weight, 0.25% by weight, 0.3% by weight, 0.35% by weight, 0.4% by weight, 0.45% by weight, 0.5% by weight, 0.55% by weight, 0.6% by weight, 0.65% by weight, 0.7% by weight, 0.75% by weight, 0.8% by weight, 0.85% by weight, 0.9% by weight, 0.95% by weight, 1% by weight, 1.05% by weight, 1.1% by weight, 1.15% by weight, 1.2% by weight, 1.25% by weight, 1.3% by weight, 1.35% by weight, 1.4% by weight, 1.45% by weight, and 1.5% by weight. It may be included in amounts of 1.55% by weight, 1.6% by weight, 1.65% by weight, 1.7% by weight, 1.75% by weight, 1.8% by weight, 1.85% by weight, 1.9% by weight, 1.95% by weight, 2% by weight, 2.05% by weight, 2.1% by weight, 2.15% by weight, 2.2% by weight, 2.25% by weight, 2.3% by weight, 2.35% by weight, 2.4% by weight, 2.45% by weight, 2.5% by weight, 2.55% by weight, 2.6% by weight, 2.65% by weight, 2.7% by weight, 2.75% by weight, 2.8% by weight, 2.85% by weight, 2.9% by weight, 2.95% by weight, 3% by weight, 1-3% by weight, and 1-2% by weight.

[0063] The coating layer may further contain one or more organic fillers and inorganic fillers known to those skilled in the art. The organic fillers and inorganic fillers may be of common types known to those skilled in the art.

[0064] Each coating layer may have a thickness of 0.01 μm to 20 μm, and within that range, it may have a thickness of 1 μm to 5 μm.

[0065] The separator may be formed by applying a coating layer-forming composition to one or both sides of a porous substrate and then drying it. The coating layer-forming composition may contain a compound of chemical formula 1 and one or more of an aqueous binder or an organic binder. Figure 6 is a cross-sectional view showing a separator for a lithium secondary battery according to one embodiment of the present invention. Referring to Figure 3, this separator for a lithium secondary battery includes a porous substrate 1 and a coating layer 2 disposed on both sides of the porous substrate 1. The coating layer 2 may contain a compound of chemical formula 1 (not shown).

[0066] Lithium-ion battery Another embodiment provides a lithium secondary battery including a separator, a positive electrode, and a negative electrode according to one embodiment. The separator for the lithium secondary battery is as described above. The separator for the lithium secondary battery may be located between the positive electrode and the negative electrode.

[0067] The positive electrode for a lithium secondary battery may include a current collector and a positive electrode active material layer formed on the current collector. The positive electrode active material layer may include a positive electrode active material and further include a binder and / or a conductive material. As an example, the positive electrode may further include an additive that can act as a sacrificial positive electrode.

[0068] As the positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (a lithium intercalation compound) may be used. Specifically, one or more composite oxides of lithium and metals selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0069] The composite oxide may be a lithium transition metal composite oxide, and specific examples include lithium nickel oxide, lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium iron phosphate compound, cobalt-free nickel-manganese oxide, or a combination thereof.

[0070] As an example, a compound represented by any of the following chemical formulas may be used: Li a A 1-b X b O 2-c D c (0.90≦a≦1.8,0≦b≦0.5,0≦c≦0.05);Li a Mn 2-b X b O 4-c D c (0.90≦a≦1.8,0≦b≦0.5,0≦c≦0.05);Li a Ni 1-b-c Co b X c O 2-α D α (0.90≦a≦1.8,0≦b≦0.5,0≦c≦0.5,0<α<2);Li a Ni 1-b-c Mn b X c O 2-α D α (0.90≦a≦1.8,0≦b≦0.5,0≦c≦0.5,0<α<2);Li a Ni b Co c L 1 d G e O2(0.90≦a≦1.8,0≦b≦0.9,0≦c≦0.5,0≦d≦0.5,0≦e≦0.1);Li aNiG b O2(0.90≦a≦1.8,0.001≦b≦0.1);Li a CoG b O2(0.90≦a≦1.8,0.001≦b≦0.1);Li a Mn 1-b G b O2(0.90≦a≦1.8,0.001≦b≦0.1);Li a Mn2G b O4(0.90≦a≦1.8,0.001≦b≦0.1);Li a Mn 1-g G g PO4(0.90≦a≦1.8,0≦g≦0.5);Li (3-f) Fe2(PO4)3(0≦f≦2);Li a FePO4 (0.90 ≤ a ≤ 1.8).

[0071] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; L 1 This is Mn, Al, or a combination thereof.

[0072] As an example, the positive electrode active material may be a high-nickel positive electrode active material in which the nickel content is 80 mol% to 99 mol%, 85 mol% to 99 mol%, 90 mol% to 99 mol%, 91 mol% to 99 mol%, or 94 mol% to 99 mol%, based on 100 mol% of the metal excluding lithium from the lithium transition metal composite oxide. High-nickel positive electrode active materials can achieve high capacity and may be applied to high-capacity, high-density lithium secondary batteries.

[0073] The content of the positive electrode active material is 90% to 99.5% by weight of 100% by weight of the positive electrode active material layer, and the content of the binder and conductive material may be 0.5% to 5% by weight, respectively, of 100% by weight of the positive electrode active material layer.

[0074] The binder plays a role in ensuring that the positive electrode active material particles adhere well to each other, and further, that the positive electrode active material adheres well to the current collector. Typical examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylate styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon.

[0075] Conductive materials are used to impart conductivity to electrodes, and any electronically conductive material that does not undergo chemical changes in the battery that makes up the battery can be used. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fiber, carbon nanofiber, and carbon nanotubes; metallic materials in the form of metal powders or metal fibers, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0076] Al can be used as the current collector, but it is not limited to this.

[0077] The negative electrode for a lithium secondary battery includes a current collector and a negative electrode active material layer located on the current collector. The negative electrode active material layer includes a negative electrode active material and may further include a binder and / or a conductive material.

[0078] For example, the negative electrode active material layer may contain 90% to 99% by weight of negative electrode active material, 0.5% to 5% by weight of binder, and 0% to 5% by weight of conductive material.

[0079] The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and undoping lithium, or a transition metal oxide.

[0080] As the material capable of reversibly intercalating / deintercalating lithium ions, for example, a carbon-based negative electrode active material which is crystalline carbon, amorphous carbon or a combination thereof may be included. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, fired coke and the like.

[0081] As the alloy of lithium metal, an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn may be used.

[0082] As the material capable of doping and undoping lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material may be used. The Si-based negative electrode active material may be silicon, a silicon-carbon composite, SiOx (0 < x < 2), a Si-Q alloy (where Q is selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements and combinations thereof), or a combination thereof. The Sn-based negative electrode active material may be Sn, SnO2, a Sn-based alloy or a combination thereof.

[0083] The silicon-carbon composite may be a composite of silicon and amorphous carbon. In one embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coating on the surface of the silicon particles. For example, it may include secondary particles (core) which are aggregates of primary silicon particles and amorphous carbon coating layers (shell) located on the surface of the secondary particles. Amorphous carbon may also be located between the primary silicon particles; for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in the amorphous carbon matrix.

[0084] The silicon-carbon composite may further contain crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles, and an amorphous carbon coating layer located on the surface of this core.

[0085] Si-based or Sn-based anode active materials may be used in combination with carbon-based anode active materials.

[0086] The binder plays a role in ensuring that the negative electrode active material particles adhere well to each other, and further, that the negative electrode active material adheres well to the current collector. The binder may be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0087] Examples of non-aqueous binders include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or combinations thereof.

[0088] The water-based binder may be selected from styrene-butadiene rubber, (meth)acrylate styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0089] When using an aqueous binder as the negative electrode binder, it may further contain a cellulosic compound that can impart viscosity. This cellulosic compound may be a mixture of one or more carboxymethylcellulose, hydroxypropylmethylcellulose, methylcellulose, or their alkali metal salts. As the alkali metal, Na, K, or Li may be used.

[0090] The dry binder is a fibrous polymeric substance, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0091] Conductive materials are used to impart conductivity to electrodes, and any electronically conductive material that does not undergo chemical changes in the battery that makes up the battery can be used. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fiber, carbon nanofiber, and carbon nanotubes; metallic materials in the form of metal powders or metal fibers, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0092] As the negative electrode current collector, copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with a conductive metal, and combinations thereof may be used.

[0093] Lithium secondary batteries may also contain an electrolyte.

[0094] The electrolyte for lithium secondary batteries may also contain a non-aqueous organic solvent and a lithium salt.

[0095] Non-aqueous organic solvents act as a medium through which ions involved in the electrochemical reactions of batteries can move.

[0096] The non-aqueous organic solvent may be a carbonate, ester, ether, ketone, or alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0097] Examples of carbonate-based solvents that may be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).

[0098] Suitable ester solvents include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, and caprolactone.

[0099] As ether-based solvents, dibutyl ether, tetraglyceride, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran may be used. As ketone-based solvents, cyclohexanone may be used. As alcohol-based solvents, ethyl alcohol and isopropyl alcohol may be used. As aprotic solvents, nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and may include a double bond, aromatic ring, or ether group), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane and 1,4-dioxolane, and sulfolanes may be used.

[0100] Non-aqueous organic solvents may be used individually or in combination of two or more.

[0101] Furthermore, when using carbonate-based solvents, cyclic carbonates and linear carbonates may be mixed and used together, and the cyclic carbonates and linear carbonates may be mixed in a volume ratio of 1:1 to 1:9.

[0102] Lithium salts dissolve in organic solvents and act as a source of lithium ions within batteries, enabling the operation of basic lithium secondary batteries and facilitating the movement of lithium ions between the positive and negative electrodes. Typical examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide, LiFSI), LiC4F9SO3, and LiN(C x F 2x+1 SO2)(C y F 2y+1SO2) (where x and y are integers from 1 to 20), may contain one or more selected from lithium trifluoromethanesulfonate, lithium tetrafluoroethersulfonate, lithium difluorobis(oxalate)phosphate (LiDFOB), and lithium bis(oxalate)borate (LiBOB). The electrolyte contains ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) as non-aqueous organic solvents, and may contain LiPF6 as a lithium salt. In the electrolyte, ethylene carbonate (EC) is present in an amount of 1-30% by volume, ethyl methyl carbonate (EMC) in an amount of 20-60% by volume, and dimethyl carbonate (DMC) in an amount of 20-60% by volume, relative to the total volume of non-aqueous organic solvents. The electrolyte contains 0.1M to 2.0M lithium salt. The electrolyte contains one or more complexes represented by any one of the following chemical formulas 1-1 to 1-10.

[0103] Lithium secondary batteries may be classified into cylindrical, rectangular, pouch-shaped, coin-shaped, etc., depending on their form. Figures 1 to 4 are schematic diagrams showing a lithium secondary battery according to one embodiment, and Figure 1 may be cylindrical, Figure 2 rectangular, and Figures 3 and 4 pouch-shaped. Referring to Figures 1 to 4, the lithium secondary battery 100 may include an electrode assembly 40 with a separator 30 between a positive electrode 10 and a negative electrode 20, and a case 50 in which the electrode assembly 40 is housed. The positive electrode 10, negative electrode 20 and separator 30 may be impregnated with an electrolyte (not shown). The lithium secondary battery 100 may include a sealing member 60 that seals the case 50, as shown in Figure 1. Also, in Figure 2, the lithium secondary battery 100 may include a positive electrode lead tab 11 and a positive electrode terminal 12, a negative electrode lead tab 21 and a negative electrode terminal 22. As shown in Figures 3 and 4, the lithium secondary battery 100 may include electrode tabs 70, namely a positive electrode tab 71 and a negative electrode tab 72, which function as electrical pathways for inducing the current formed in the electrode assembly 40 to the outside.

[0104] A lithium secondary battery according to one embodiment of the present invention may be applied to automobiles, mobile phones, and / or various forms of electrical devices, but the present invention is not limited thereto.

[0105] Examples and comparative examples of the present invention are described below. However, the following examples are merely one embodiment of the present invention, and the present invention is not limited to these examples.

[0106] Example 1 A coating layer composition containing polyvinylidene fluoride (PVDF) and a compound of chemical formula 1A was prepared as a binder.

[0107] A polyethylene film (thickness: 18 μm, SK Corporation) was used as a porous substrate. The coating layer-forming composition was applied to both sides of the film to a thickness of 1 μm using a die-coating method, and then dried in an oven at 80°C for 16 hours to form the coating layers. This resulted in a lithium secondary battery separator consisting of a first coating layer (thickness 1 μm) containing the compound of chemical formula 1A and a PVDF binder, a porous substrate (thickness 18 μm), and a second coating layer (thickness 1 μm) containing the compound of chemical formula 1A and a PVDF binder. The compound of chemical formula 1A was present in 1% by weight of the first coating layer, and the compound of chemical formula 1A was present in 1% by weight of the second coating layer.

[0108] Example 2 A separator was manufactured in the same manner as in Example 1, except that the content of the compound of chemical formula 1A in the first coating layer was changed to 1.5% by weight, and the content of the compound of chemical formula 1A in the second coating layer was changed to 1.5% by weight.

[0109] Comparative Example 1 A separator was manufactured in the same manner as in Example 1, except that the content of the compound of chemical formula 1A in the first coating layer was changed to 0% by weight, and the content of the compound of chemical formula 1A in the second coating layer was changed to 0% by weight.

[0110] Manufacturing of lithium-ion batteries (1) Manufacturing of the positive electrode A cathode active material layer slurry was prepared by mixing 97.7% by weight of cathode active material, 1.3% by weight of polyvinylidene fluoride binder, and 1.0% by weight of carbon nanotube conductive material. This slurry was then coated onto an aluminum foil current collector, dried, and rolled to produce the cathode.

[0111] (2) Manufacturing of the negative electrode A negative electrode active material slurry was prepared by mixing 97.6% by weight of graphite negative electrode active material, 1.6% by weight of carboxymethylcellulose, and 0.8% by weight of styrene-butadiene rubber in an aqueous solvent. The negative electrode active material slurry was coated onto a copper foil current collector, and the negative electrode was produced by drying and rolling.

[0112] (3) Manufacturing of electrolyte An electrolyte was prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 2:4:4 into an organic solvent, then mixing LiPF6 lithium salt at a concentration of 1.15 M, and further dissolving the transition metal salts listed in Table 1 below.

[0113] (4) Manufacturing of lithium secondary batteries An electrode assembly was manufactured by assembling the positive and negative electrodes produced as described above with the separators of the above examples and comparative examples. The electrode assembly was then placed in a rectangular case, and the electrolyte was added to manufacture a battery.

[0114] Evaluation Example 1: Increase in DC internal resistance of lithium secondary batteries due to high-temperature storage time (unit: %) The high-temperature storage characteristics of the lithium secondary batteries of Examples 1 and 2 and Comparative Example 1 were evaluated using the following method and are shown in Table 1 and Figure 5.

[0115] The initial DC-IR (DC-IR) was measured as the ΔV / ΔI (voltage change / current change) value. Then, the battery was brought to a fully charged state (SOC (state of charge) 100%), stored at a high temperature (60°C) for 90 days, and the DC-IR was measured again. The DC-IR increase rate (%) was then calculated using the following formula 1.

[0116] [Formula 1] DC-IR increase rate [%] = (DC-IR after 90 days of high-temperature storage / initial DC-IR) × 100

[0117] Evaluation Example 2: Amount of metal deposition on the surface of the negative electrode after high-temperature storage of lithium secondary batteries (unit: ppm) For the lithium secondary batteries of Examples 1 and 2 and Comparative Example 1, after 90 days of high-temperature storage using the method of Evaluation Example 1, the batteries were disassembled and the amounts of transition metals, post-transition metals, metalloids, and / or their oxides electrodeposited on the surface of the negative electrode were measured. The results are shown in Table 1 below.

[0118] Here, the amount of transition metals, post-transition metals, semimetals, and / or their oxides electrodeposited on the surface of the negative electrode was measured using an inductively coupled plasma mass spectrometer (ICP, manufacturer: Horiba Corp., instrument name: Ultima2) to obtain the electrodeposited amount from the surface of the negative electrode obtained by disassembling the cell under SOC 100% conditions.

[0119] [Table 1]

[0120] As shown in Table 1 above, the lithium secondary battery separator of the example is effective in capturing transition metal ions, post-transition metal ions, and / or metalloid ions dissolved in the electrolyte. Therefore, the separator of the example can improve the resistance increase rate when the lithium secondary battery is charged at high voltage or stored at high temperature.

[0121] However, the comparative separator showed a higher resistance increase rate compared to the example, and also exhibited a higher amount of metal deposition on the negative electrode surface after high-temperature storage of the lithium secondary battery.

[0122] While preferred embodiments of the present invention have been described above, the present invention is not limited thereto. It can be modified and implemented in various ways within the scope of the claims, the detailed description of the invention, and the accompanying drawings, and these modifications naturally also fall within the scope of the present invention.

Claims

1. A separator for a lithium secondary battery comprising a porous substrate and a coating layer located on at least one surface of the porous substrate, The aforementioned coating layer has chemical formula 1: 【Chemistry 1】 (In the formula, R 1 ~R 24 Each of these is independently a hydrogen atom, a halogen atom, a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C6-C20 aryl group, or a substituted or unsubstituted C6-C20 heterocycloalkyl group. A separator for lithium secondary batteries containing the compound represented by [formula].

2. In chemical formula 1, R 1 ~R 24 The separator for a lithium secondary battery according to claim 1, wherein all atoms are hydrogen atoms.

3. The separator for a lithium secondary battery according to claim 1, wherein the compound of chemical formula 1 is contained in the coating layer in an amount of 0.01 to 3% by weight.

4. The lithium secondary battery separator according to claim 1, wherein the compound of chemical formula 1 is included in an amount of 95% by weight or more of the scavenger for transition metal ions, post-transition metal ions, and / or semimetallic ions contained in the separator.

5. The separator for a lithium secondary battery according to claim 4, wherein the scavenging agent captures silicon (Si) ions, titanium (Ti) ions, vanadium (V) ions, chromium (Cr) ions, manganese (Mn) ions, iron (Fe) ions, cobalt (Co) ions, nickel (Ni) ions, copper (Cu) ions, zinc (Zn) ions, scandium (Sc) ions, or combinations thereof.

6. The separator for a lithium secondary battery according to claim 1, wherein the compound of chemical formula 1 is dispersed within the coating layer or present on the outermost surface of the coating layer.

7. The separator for a lithium secondary battery according to claim 1, wherein the compound of chemical formula 1 is contained in the coating layer in an amount of 0.01 to 3% by weight.

8. The lithium secondary battery separator according to claim 1, wherein the coating layer further comprises one or more binders selected from aqueous binders and organic binders.

9. The separator for lithium secondary batteries according to claim 8, wherein one or more of the aqueous binder and the organic binder have a weight-average molecular weight of 10,000 to 500,000 g / mol.

10. The separator for lithium secondary batteries according to claim 8, wherein the binder comprises one or more copolymers of carboxyalkylcellulose or a salt thereof, (meth)acrylic acid, (meth)acrylic acid ester, (meth)acrylonitrile, (meth)acryamide, diene rubber, polyvinylidene fluoride, and polyvinylidene fluoride-hexafluoropropylene.

11. A lithium secondary battery comprising a positive electrode, a negative electrode, and a lithium secondary battery separator according to any one of claims 1 to 10, positioned between the positive electrode and the negative electrode.

12. The lithium secondary battery according to claim 11, wherein the positive electrode comprises a positive electrode active material including a lithium nickel oxide, a lithium cobalt oxide, a lithium manganese oxide, a lithium nickel cobalt manganese oxide, a lithium iron phosphate compound, a cobalt-free nickel-manganese oxide, or a combination thereof.

13. The lithium secondary battery according to claim 11, wherein the lithium secondary battery further comprises an electrolyte.

14. The lithium secondary battery according to claim 13, wherein the electrolyte comprises ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) as non-aqueous organic solvents.

15. The lithium secondary battery according to claim 14, wherein the ethylene carbonate (EC) is contained in an amount of 1 to 30% by volume, the ethyl methyl carbonate (EMC) is contained in an amount of 20 to 60% by volume, and the dimethyl carbonate (DMC) is contained in an amount of 20 to 60% by volume, based on the total volume of the non-aqueous organic solvent in the electrolyte.

16. The lithium secondary battery according to claim 13, wherein the electrolyte contains 0.1 M to 2.0 M of lithium salt.

17. The aforementioned electrolyte has chemical formulas 1-1 to 1-10: 【Chemistry 2】 【Transformation 3】 【Chemistry 4】 【Transformation 5】 【Transformation 6】 【Transformation 7】 【Transformation 8】 【Chemistry 9】 【Chemistry 10】 【Chemistry 11】 (R 1 ~R 24 (This is the same as the one defined in chemical formula 1.) A lithium secondary battery according to claim 13, comprising one or more complexes represented by any one of the following.

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