Lithium secondary battery and urban air mobility comprising the same

Abstract

The present invention relates to a lithium secondary battery comprising: a positive current collector and a positive active material layer formed on at least one surface of the positive current collector, wherein the positive current collector has a loading amount of 2.5 mAh / cm2 to 3.8 mAh / cm2; a negative current collector and a negative active material layer formed on at least one surface of the negative current collector; and a separator interposed between the positive and negative electrodes, wherein the time required to reach 0% SOC is 10 seconds or more when discharged for 15 seconds under a constant power condition of 900 W at 35% SOC and then discharged under a constant power condition of 1,000 W, and to an urban air mobility means comprising the lithium secondary battery.

Description

Technology Field

[0001] The present invention relates to a lithium secondary battery and an urban air mobility means including the same. Specifically, it relates to a secondary battery capable of producing high output for a certain period of time or longer when the remaining capacity is low, and an urban air mobility means having improved safety in emergency situations by including the same. Background Technology

[0002] With technological advancements, the demand for lithium-ion batteries as an energy source is increasing rapidly. Recently, beyond electric vehicles and portable electronic devices, there is also a growing demand for lithium-ion batteries as a power source for Urban Air Mobility (UAM), a next-generation mode of transportation.

[0003] Since UAM must provide air services in complex urban environments, it must be designed to enable vertical take-off and landing to minimize operational space, and high safety is also required to increase social acceptance for commercialization.

[0004] In particular, since UAM operations are subject to various complex variables such as collisions with high-rise buildings and structures, lower-level turbulence, and weather changes like precipitation, the lithium-ion batteries serving as the power source must also be designed to withstand emergency situations that deviate from normal flight conditions.

[0005] However, since research on lithium-ion batteries has primarily been conducted for electric vehicles, they do not satisfy the performance requirements for UAM, specifically the output conditions considering landing in emergency situations; therefore, technological development for lithium-ion batteries for UAM is necessary. Prior art literature

[0006] (Patent Document 0001) US 2022-0102725 A1 The problem to be solved

[0007] The present invention aims to provide a lithium secondary battery capable of producing high output for a certain period of time or longer while in a state of low remaining capacity.

[0008] In addition, the present invention aims to provide an urban air transport means with improved safety in emergency situations by including the lithium secondary battery. means of solving the problem

[0009] According to one embodiment, the present invention,

[0010] It includes a positive current collector and a positive active material layer formed on at least one surface of the positive current collector, and has a loading amount of 2.5 mAh / cm² 2 Up to 3.8mAh / cm² 2 Phosphorus anode;

[0011] A cathode comprising a cathode current collector and a cathode active material layer formed on at least one surface of the cathode current collector; and

[0012] A lithium secondary battery comprising a separator interposed between the anode and the cathode, wherein

[0013] A lithium secondary battery is provided that, when discharged for 15 seconds at 900W constant output conditions at 35% SOC and then discharged at 1,000W constant output conditions, the time required to reach 0% SOC is 10 seconds or more.

[0015] In addition, an urban air mobility means including the above-mentioned lithium secondary battery is provided. Effects of the invention

[0016] The lithium secondary battery according to the present invention includes a positive electrode with a loading amount adjusted to a certain range, thereby exhibiting high output characteristics even at the lower end of the SOC. Accordingly, an urban air mobility vehicle including the lithium secondary battery has the advantage of being able to land stably even in emergency situations. Brief explanation of the drawing

[0017] Figure 1 is a figure showing the output evaluation results at the bottom of the SOC for lithium secondary batteries manufactured in the embodiments and comparative examples of the present invention. Specific details for implementing the invention

[0018] The present invention will be described in more detail below.

[0020] Urban Air Mobility (UAM) requires a high level of power output during takeoff and landing because it operates via vertical takeoff and landing. Particularly given the complex operating environment, it is essential to possess the capability to deliver high power for a certain period even at low State of Charge (SOC) levels to ensure a safe landing even if some batteries fail to function properly. However, since conventional rechargeable batteries for electric vehicles do not require this capability, applying them directly to UAM poses a problem in ensuring safety.

[0021] Accordingly, the present invention aims to provide a secondary battery that produces a high output of 1,000W or more for a certain period of time even in a low SOC range.

[0022] Specifically, the lithium secondary battery according to the present invention is,

[0023] It includes a positive current collector and a positive active material layer formed on at least one surface of the positive current collector, and has a loading amount of 2.5 mAh / cm² 2 Up to 3.8mAh / cm² 2 Phosphorus anode;

[0024] A cathode comprising a cathode current collector and a cathode active material layer formed on at least one surface of the cathode current collector; and

[0025] It includes a separator interposed between the anode and the cathode, and

[0026] When discharging for 15 seconds at 900W constant output conditions at 35% SOC, and then discharging at 1,000W constant output conditions, the time required to reach 0% SOC is 10 seconds or more.

[0028] Meanwhile, in the present invention, "primary particle" refers to a particle unit in which no grain boundaries exist externally when observed at a field of view of 5,000 to 20,000 times using a scanning electron microscope, and "secondary particle" refers to a particle formed by the aggregation of a plurality of primary particles.

[0029] In the present invention, "average particle size of primary particles" refers to the arithmetic mean value calculated after measuring the particle sizes of at least 20 primary particles observed in scanning electron microscope images. At this time, the particle size refers to the diameter of the longest axis of the primary particles.

[0030] In the present invention, "secondary particles" are particles formed by the aggregation of multiple primary particles. In order to distinguish them from conventional secondary particles formed by the aggregation of tens to hundreds of primary particles, secondary particles formed by the aggregation of 30 or fewer primary particles in the present invention are referred to as pseudo-single particles.

[0031] In the present invention, "D50" refers to the particle size corresponding to 50% of the volume cumulative particle size distribution of the corresponding particle powder, and can be measured using a laser diffraction method. For example, after dispersing the positive active material powder in a dispersion medium, it can be introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S-3500) and irradiated with ultrasound of about 28 kHz at an output of 60 W to obtain a volume cumulative particle size distribution graph, and then the particle size at the point where the volume cumulative amount is 50% can be measured from the obtained volume cumulative particle size distribution graph.

[0032] In the present invention, the “energy density of the anode” can be measured by manufacturing an electrode assembly by interposing a polyethylene-based separator with a thickness of 15 μm between the anode and a lithium metal anode, placing the assembly inside a battery case, and then injecting an electrolyte prepared by dissolving 1 M concentration of LiPF6 in a mixed organic solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7 into the case to manufacture a coin half-cell. Specifically, the value obtained by charging the coin half-cell to 4.25 V under a constant current / constant voltage condition of 0.33 C at 25°C and then discharging it until it reaches 3.0 V with a constant current of 0.33 C, multiplying the initial discharge capacity (Ah) of the secondary battery by the average discharge voltage and dividing by the weight (kg) of the coin half-cell, is described as the energy density of the anode.

[0034] Below, each component constituting the present invention will be explained in more detail.

[0036] anode

[0037] The lithium secondary battery according to the present invention has a loading amount of 2.5 mAh / cm² 2 Up to 3.8mAh / cm² 2 , preferably 3.0mAh / cm² 2 Up to 3.6mAh / cm² 2 , more preferably 3.3mAh / cm 2 Up to 3.5mAh / cm² 2 It includes a positive electrode.

[0038] When the loading amount satisfies the above range, after discharging for 15 seconds under a constant output condition of 900W at 35% SOC, it is possible to deliver an output of over 1,000W for more than 10 seconds. To achieve the minimum energy density usable in UAM, the anode loading amount must be 2.5mAh / cm² 2 It must be at least 3.8 mAh / cm² to achieve the minimum output characteristics required for application in UAM. 2 It must not exceed

[0040] The above positive active material layer comprises a positive active material having a bimodal particle size distribution composed of different alleles and sub-particles in D50, wherein the alleles and sub-particles each independently comprise a lithium nickel-based oxide; or comprises a positive active material having a monomodal particle size distribution, wherein the positive active material having a monomodal particle size distribution may comprise a lithium nickel-based oxide in the form of a quasi-single particle, which is a single particle composed of one primary particle or a secondary particle formed by aggregating 30 or fewer primary particles.

[0042] In one embodiment of the present invention, the positive electrode active material layer comprises a positive electrode active material having a bimodal particle size distribution composed of different alleles and sub-particles with a D50, wherein the alleles and sub-particles each independently comprise a lithium nickel-based oxide.

[0043] In this case, since small particles fill the voids of the opposing particles during electrode rolling, there is an advantage in that the electrode density increases and high energy density can be achieved.

[0044] The D50 of the above-mentioned allele may be 8 µm to 18 µm, preferably 8 µm to 15 µm, and more preferably 9 µm to 13 µm. In addition, the D50 of the above-mentioned subparticle may be 2 µm to 7 µm, preferably 2 µm to 6 µm, and more preferably 3 µm to 5 µm. It is advantageous for realizing high energy density when the D50 of the allele and the D50 of the subparticle satisfy the above ranges.

[0045] Meanwhile, the above-mentioned alleles and subatomic particles may each be composed independently of a single particle consisting of one primary particle; a pseudo-single particle which is a secondary particle formed by aggregating 30 or fewer primary particles; a secondary particle formed by aggregating more than 30 primary particles; or a combination thereof.

[0046] However, preferably, the above-mentioned particles may include a lithium nickel-based oxide in the form of a pseudo-single particle, which is a single particle consisting of one primary particle or a secondary particle formed by aggregating 30 or fewer primary particles.

[0047] When electrodes are constructed by mixing alleles and sub-particles, the sub-particles located between the alleles act to mitigate direct contact between the alleles, causing the sub-particles to receive relatively more physical stress, which can intensify particle breakage. Therefore, introducing sub-particles in the form of single particles or pseudo-single particles in this manner can suppress particle breakage and degradation and improve the rolling characteristics of the electrode.

[0048] Meanwhile, the anode active material with the above-mentioned bimodal particle size distribution may contain large particles and small particles in a weight ratio of 50:50 to 90:10, preferably 60:40 to 80:20. When the weight ratio of large particles to small particles is within the above range, small particles can be placed between large particles while minimizing space loss. Accordingly, the packing density is optimized, and the stress applied between the active materials during rolling can be dispersed more smoothly, which is advantageous for improving electrode rolling characteristics and realizing high energy.

[0050] In another embodiment of the present invention, the positive electrode active material layer comprises a positive electrode active material having a monomodal particle size distribution, and the positive electrode active material having a monomodal particle size distribution may comprise a lithium nickel-based oxide in the form of a quasi-mono-particle, which is a single particle consisting of one primary particle or a secondary particle formed by aggregating 30 or fewer primary particles. In this case, it is advantageous to achieve high output as a single particle rapidly participates in the reaction.

[0052] Meanwhile, in the lithium nickel-based oxide of the above single particle or quasi-single particle form, the average particle size of the primary particles may be 1 μm to 5 μm, preferably 2 μm to 4 μm.

[0053] In addition, the lithium nickel-based oxide comprises nickel, cobalt, and manganese, and specifically, the molar ratio of nickel among the transition metals may be 70 mol% or more, preferably 75 mol% or more, and more preferably 80 mol% or more. In the case of a positive electrode active material with a bimodal particle size distribution, the composition of the lithium nickel-based oxide contained in the large particles and small particles is the same or different from each other.

[0054] More specifically, the lithium nickel-based oxide can be represented by the following chemical formula 1.

[0055] [Chemical Formula 1]

[0056] Li 1+x (Ni a Co b Mn c M d )O2

[0057] In the above chemical formula 1,

[0058] M is one or more selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and

[0059] 1+x, a, b, c, and d are the atomic fractions of independent elements, respectively,

[0060] -0.2≤x≤0.2, 0.60≤a<1, 0 <b<0.40, 0<c<0.40, 0≤d≤0.10, a+b+c+d=1이다.

[0061] The above 1+x represents the molar ratio of lithium in the lithium nickel-based oxide, and may be -0.1≤x≤0.2 or 0≤x≤0.2. When the molar ratio of lithium satisfies the above range, the crystal structure of the lithium nickel-based oxide can be stably formed.

[0062] The above 'a' represents the molar ratio of nickel among all metals excluding lithium in the lithium nickel-based oxide, and may be 0.70≤a<1, 0.75≤a<1, or 0.80≤a<1. When the molar ratio of nickel satisfies the above range, high energy density is exhibited, making it possible to achieve high capacity.

[0063] The above b represents the molar ratio of cobalt among the total metals excluding lithium in the lithium nickel-based oxide, where 0 <b≤0.25, 0<b≤0.20, 또는 0<b≤0.15일 수 있다. 코발트의 몰비가 상기 범위를 만족할 때, 양호한 저항 특성 및 출력 특성을 구현할 수 있다.

[0064] The above c represents the molar ratio of manganese among the total metals excluding lithium in the lithium nickel-based oxide, where 0 <c≤0.25, 0<c≤0.20, 또는 0<c≤0.15일 수 있다. 망간의 몰비가 상기 범위를 만족할 때, 양극 활물질의 구조 안정성이 우수하게 나타난다.

[0065] The above d represents the molar ratio of element M among the total metals excluding lithium in the lithium nickel-based oxide, and the above d may be 0≤d≤0.08, 0≤d≤0.05, or 0≤d≤0.03.

[0067] Meanwhile, the lithium nickel-based oxide according to the present invention may further include a coating layer on the particle surface as needed. In this case, the coating layer may include one or more coating elements selected from the group consisting of, for example, Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mn, Sr, Sb, Bi, Si, and S. When a coating layer is present on the surface of the lithium nickel-based oxide, the contact between the electrolyte and the lithium nickel-based oxide is reduced by the coating layer, thereby providing an effect of reducing transition metal leaching or gas generation caused by side reactions with the electrolyte. Preferably, the coating layer may include B, Co, Al, or a combination thereof, and more preferably, may include Co. When Co is included in the coating layer, an effect of suppressing side reactions with the electrolyte, as well as an effect of improving output and reducing resistance, can be obtained.

[0069] The positive electrode according to the present invention comprises a positive electrode current collector and a positive electrode active material layer formed on at least one surface of the positive electrode current collector. Specifically, the positive electrode active material layer comprises the aforementioned positive electrode active material.

[0070] The above positive current collector may include a highly conductive metal, and is not particularly limited as long as it facilitates the adhesion of the positive active material layer and is non-reactive within the voltage range of the battery. The above positive current collector may be, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. Additionally, the above positive current collector may typically have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the current collector to increase the adhesion of the positive active material. It may be used in various forms, such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

[0071] The above positive active material layer may, together with the positive active material, optionally include a conductive material and a binder as needed.

[0072] At this time, the positive active material may be included in an amount of 80 to 99 weight%, more specifically 85 to 98.5 weight%, based on the total weight of the positive active material layer. Excellent capacity characteristics can be exhibited when included within the above-mentioned content range.

[0073] The above conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it possesses electronic conductivity without causing chemical changes. Specific examples include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; carbon-based materials such as carbon fibers; metal powder or metal fibers such as copper, nickel, aluminum, or silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. The above conductive material may be included in an amount of 0.1 to 15 weight% based on the total weight of the positive electrode active material layer.

[0074] The above binder serves to improve the adhesion between positive active material particles and the adhesion between the positive active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, and polymers in which hydrogens thereof are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these alone or a mixture of two or more may be used. The above binder may be included in an amount of 0.1 to 15 weight percent based on the total weight of the positive active material layer.

[0075] The above-described anode may be manufactured according to a conventional anode manufacturing method, except that the loading amount is adjusted to the above range. Specifically, it may be manufactured by dissolving or dispersing the above-described anode active material and, optionally, a binder, a conductive material, and a dispersant in a solvent to produce an anode composite, applying the mixture onto an anode current collector, and then drying and rolling it, or by casting the above-described anode composite onto a separate support and then laminating the film obtained by peeling it off from the support onto an anode current collector.

[0076] The above solvent may be a solvent generally used in the relevant technical field, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethyl formamide (DMF), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of the above solvent used is sufficient if it is sufficient to dissolve or disperse the anode active material, conductive material, binder, and dispersant, taking into account the coating thickness of the slurry and the manufacturing yield, and to have a viscosity that can exhibit excellent thickness uniformity when coated for anode manufacturing thereafter.

[0078] In one embodiment of the present invention, the energy density of the anode may be 250 Wh / kg or more, preferably 270 Wh / kg or more, and more preferably 280 Wh / kg or more. Although it is desirable for the anode to have a higher energy density as it can exhibit high energy with less weight, considering that it is difficult to meet output conditions as the anode loading increases to achieve high energy density and that there is a limit to the proportion of the aircraft's weight that the battery can occupy, the energy density may be 320 Wh / kg or less.

[0080] In one embodiment of the present invention, the porosity of the positive electrode active material layer may be 20% to 32%, preferably 21% to 28%, and more preferably 22% to 26%. It is desirable for the porosity of the positive electrode active material layer to be within the above range, as this minimizes particle breakage of the active material while increasing the packing density, thereby contributing to increasing the energy density of the battery. Here, porosity refers to a value calculated by the following [Equation 1].

[0081] [Equation 1]

[0082] Porosity (%) of the positive active material layer = ((True density of positive active material - Electrode density) / True density of positive active material) × 100

[0083] In the above Equation 1, the electrode density is a value calculated by the following Equation 2.

[0084] [Equation 2]

[0085] Electrode density = (Weight of anode - Weight of anode current collector) / (a ​​× b × c)

[0086] In the above Equation 2, a, b, and c are the width, length, and height measured after separating the positive current collector from the positive electrode, respectively.

[0088] cathode

[0089] In the above lithium secondary battery, the negative electrode comprises a negative electrode current collector and a negative electrode active material layer formed on at least one surface of the negative electrode current collector.

[0090] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative current collector may typically have a thickness of 3 μm to 500 μm, and, similar to the positive current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0091] The above-mentioned cathode active material layer optionally includes a binder and a conductive material together with the cathode active material.

[0092] As the above-mentioned negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO₂ β Examples include metal oxides capable of doping and dedoping lithium, such as (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metal compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film may be used as the negative electrode active material. The negative electrode active material may be included in an amount of 80% to 99% by weight based on the total weight of the negative electrode active material layer.

[0093] The above binder is a component that assists in the bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 0.1% to 10% by weight based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0094] The above conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0095] The above-mentioned cathode active material layer may be manufactured by applying a cathode composite material, prepared by dissolving or dispersing a cathode active material and optionally a binder and a conductive material in a solvent, onto a cathode current collector and drying it, or by casting the cathode composite material onto a separate support and then laminating the film obtained by peeling it off from the support onto a cathode current collector.

[0097] Separator

[0098] In the lithium secondary battery of the present invention, the separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. Any separator commonly used in lithium secondary batteries may be used without special limitations, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, a coated separator containing a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0100] electrolytes

[0101] The lithium secondary battery of the present invention may include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, or a molten inorganic electrolyte as an electrolyte, and preferably, as an organic liquid electrolyte, may include an electrolyte comprising an organic solvent and a lithium salt.

[0102] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.

[0103] The above lithium salt may be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, as the anion of the above lithium salt, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It may be at least one selected from the group consisting of, and the lithium salt is, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2) 2. LiCl, LiI, or LiB(C2O4)2, etc., may be used. It is preferable to use the lithium salt within the range of 0.1 to 4.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0104] In addition to the above electrolyte components, the above electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, a haloalkylene carbonate-based compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the above additives may be included in an amount of 0.1 to 5 weight% based on the total weight of the electrolyte.

[0106] lithium secondary battery

[0107] The lithium secondary battery according to the present invention may take at least 10 seconds, preferably at least 20 seconds, and more preferably at least 30 seconds to reach 0% SOC when discharged for 15 seconds at 900W constant output conditions at 35% SOC and then discharged at 1,000W constant output conditions.

[0108] Specifically, the lithium secondary battery may take at least 10 seconds, preferably at least 20 seconds, and more preferably at least 30 seconds to reach 0% SOC when discharged for 18 seconds at 900W constant output conditions at 35% SOC and then discharged at 1,100W constant output conditions.

[0109] At this time, the upper limit voltage may be 4.2V and the lower limit voltage may be 2.5V, and charging up to the upper limit voltage may be performed under constant current / constant voltage conditions, and discharging up to SOC 35% may be performed under constant output or constant current conditions, but is not limited thereto.

[0111] In addition, the above-mentioned lithium secondary battery may be used for Urban Air Mobility (UAM). As previously explained, in UAM, it is essential to have the capability to generate high output for a certain period of time even at a low State of Charge (SOC) so that a safe landing can be achieved even when some of the batteries are not functioning properly. The fact that the lithium secondary battery according to the present invention can operate for more than 10 seconds at an output of 1,000W or more at an SOC of 35% or less means that a landing time of more than 10 seconds can be secured even in a Battery Out (BO) state where one of the batteries is discharged, and thus it is suitable for application to Urban Air Mobility.

[0112] Meanwhile, discharge up to SOC 35% refers to battery operation during the cruising process before the UAM prepares for landing, that is, the period before the downward transition; discharge for 15 seconds under the above 900W constant output condition refers to the transition process of switching to landing mode after cruising; and subsequent operation at an output of 1,000W or more refers to the landing process. In other words, the present invention relates to a lithium secondary battery that satisfies the minimum output conditions required during the transition and landing processes after cruising of a UAM.

[0113] Meanwhile, the external shape of the above-mentioned lithium secondary battery is not subject to any particular restrictions, but it may be a cylindrical shape using a can, a prismatic shape, a pouch shape, or a coin shape.

[0115] According to another embodiment of the present invention, an urban air mobility means comprising the lithium secondary battery is provided. Specifically, the urban air mobility means according to the present invention may include a battery module or a battery pack comprising the lithium secondary battery as a unit cell.

[0117] The present invention will be explained in more detail below through specific embodiments.

[0119] <Manufacturing Example: Preparation of Anode>

[0120] Preparation Example 1.

[0121] Li(Ni) 0.86 Co 0.05 Mn 0.07 Al 0.02 Lithium composite transition metal oxide in the form of secondary particles having a composition of )O2 and D50=10㎛ and Li(Ni 0.86 Co 0.05 Mn 0.07 Al 0.02 A bimodal cathode material was prepared by mixing lithium composite transition metal oxides in the form of secondary particles having the composition of )O2 and D50=5㎛ in a weight ratio of 80:20.

[0122] An anode slurry having a solid content of 50 wt% was prepared by mixing the above anode material, carbon black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder in an N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 97.6:1.0:1.4. The above anode slurry was prepared at a loading amount of 2.6 mAh / cm². 2 A 15㎛ thick aluminum current collector was coated on one side and dried at 130°C, then placed between two rolling rolls and the gap between the rolling rolls was adjusted at 25°C to produce an anode with a porosity of 31% and an energy density of 256Wh / kg.

[0124] Preparation Example 2.

[0125] Li(Ni) 0.86 Co 0.05 Mn 0.07 Al 0.02 Lithium composite transition metal oxide in the form of secondary particles having a composition of )O2 and D50=10㎛ and Li(Ni 0.86 Co 0.05 Mn 0.07 Al 0.02A bimodal cathode material was prepared by mixing lithium composite transition metal oxides having the composition of )O2, D50=3.5㎛, and containing a mixture of single particles and similar single particles in a weight ratio of 80:20.

[0126] An anode slurry having a solid content of 50 wt% was prepared by mixing the above anode material, carbon black as a conductive material, and PVdF as a binder in an NMP solvent at a weight ratio of 97.6:1.0:1.4. The above anode slurry was prepared at a loading amount of 3.3 mAh / cm² 2 A 15㎛ thick aluminum current collector was coated on one side and dried at 130°C, then placed between two rolling rolls and the gap between the rolling rolls was adjusted at 25°C to produce an anode with a porosity of 26% and an energy density of 291Wh / kg.

[0128] Preparation Example 3.

[0129] Li(Ni as a cathode material 0.86 Co 0.05 Mn 0.07 Al 0.02 A cathode slurry having a solid content of 50 wt% was prepared by mixing a lithium composite transition metal oxide having the composition of O2, D50 = 3.5 μm, and containing a mixture of single particles and pseudo-single particles, carbon black as a conductive material, and PVdF as a binder in an NMP solvent at a weight ratio of 97:1.2:1.8. The above cathode slurry was prepared at a loading amount of 3.0 mAh / cm². 2 A 15㎛ thick aluminum current collector was coated on one side and dried at 130°C, then placed between two rolling rolls and the gap between the rolling rolls was adjusted at 25°C to produce an anode with a porosity of 26% and an energy density of 270Wh / kg.

[0131] Preparation Example 4.

[0132] Li(Ni as a cathode material 0.86 Co 0.05 Mn 0.07 Al 0.02A cathode slurry having a solid content of 50 wt% was prepared by mixing a lithium composite transition metal oxide having the composition of O2, D50 = 3.5 μm, and containing a mixture of single particles and pseudo-single particles, carbon black as a conductive material, and PVdF as a binder in an NMP solvent at a weight ratio of 97:1.2:1.8. The above cathode slurry was prepared at a loading amount of 3.3 mAh / cm² 2 A 15㎛ thick aluminum current collector was coated on one side and dried at 130°C, then placed between two rolling rolls and the gap between the rolling rolls was adjusted at 25°C to produce an anode with a porosity of 26% and an energy density of 280Wh / kg.

[0134] Preparation Example 5.

[0135] Li(Ni as a cathode material 0.86 Co 0.05 Mn 0.07 Al 0.02 A cathode slurry having a solid content of 50 wt% was prepared by mixing a lithium composite transition metal oxide having the composition of O2, D50 = 3.5 μm, and containing a mixture of single particles and pseudo-single particles, carbon black as a conductive material, and PVdF as a binder in an NMP solvent at a weight ratio of 97:1.2:1.8. The above cathode slurry was loaded at a rate of 3.5 mAh / cm² 2 A 15㎛ thick aluminum current collector was coated on one side and dried at 130°C, then placed between two rolling rolls and the gap between the rolling rolls was adjusted at 25°C to produce an anode with a porosity of 26% and an energy density of 280Wh / kg.

[0137] Preparation Example 6.

[0138] Li(Ni as a cathode material 0.86 Co 0.05 Mn 0.07 Al 0.02A cathode slurry having a solid content of 50 wt% was prepared by mixing a lithium composite transition metal oxide having the composition of O2, D50 = 3.5 μm, and containing a mixture of single particles and pseudo-single particles, carbon black as a conductive material, and PVdF as a binder in an NMP solvent at a weight ratio of 97:1.2:1.8. The above cathode slurry was prepared at a loading amount of 3.3 mAh / cm² 2 A 15㎛ thick aluminum current collector was coated on one side and dried at 130°C, then placed between two rolling rolls and the gap between the rolling rolls was adjusted at 25°C to produce an anode with a porosity of 21% and an energy density of 294Wh / kg.

[0140] Comparative Manufacturing Example 1.

[0141] Li(Ni) 0.86 Co 0.05 Mn 0.07 Al 0.02 Lithium composite transition metal oxide in the form of secondary particles having a composition of )O2 and D50=10㎛ and Li(Ni 0.86 Co 0.05 Mn 0.07 Al 0.02 A bimodal cathode material was prepared by mixing lithium composite transition metal oxides in the form of secondary particles having the composition of )O2 and D50=5㎛ in a weight ratio of 80:20.

[0142] An anode slurry having a solid content of 50 wt% was prepared by mixing the above anode material, carbon black as a conductive material, and PVdF as a binder in an NMP solvent at a weight ratio of 97.6:1.0:1.4. The above anode slurry was prepared at a loading amount of 4.0 mAh / cm². 2 A 15㎛ thick aluminum current collector was coated on one side and dried at 130°C, then placed between two rolling rolls and the gap between the rolling rolls was adjusted at 25°C to produce an anode with a porosity of 26% and an energy density of 282Wh / kg.

[0144] <Example: Manufacture of a Secondary Battery>

[0145] Example 1.

[0146] A cathode active material (a mixture of natural graphite and artificial graphite in a weight ratio of 70:30), an SBR binder (M37, LG Chem), and a conductive material (acetylene black) were mixed in water, a solvent, in a weight ratio of 96.0:3.0:1.0 to prepare a cathode slurry with a solid content of 60 wt%. The cathode slurry was coated onto an 8 μm thick copper thin film serving as a cathode current collector, dried, and rolled to produce a cathode.

[0147] An electrode assembly was prepared by interposing a 15 μm thick polyethylene-based separator between the anode prepared in Example 1 and the cathode, and then the assembly was inserted into a pouch-type battery case and an electrolyte was injected to manufacture a secondary battery. At this time, as the electrolyte, a solution in which 1 M LiPF6 was dissolved in an organic solvent mixed with ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 1:2 was used.

[0149] Examples 2~6.

[0150] Secondary batteries of Examples 2 to 6 were manufactured using the same process as Example 1, except that the anodes manufactured in Examples 2 to 6 were used instead of the anode manufactured in Example 1.

[0152] Comparative Example 1.

[0153] The secondary battery of Comparative Example 1 was manufactured using the same process as Example 1, except that the anode manufactured in Comparative Example 1 was used instead of the anode manufactured in Manufacturing Example 1.

[0155] <Experimental Example: Output Evaluation at Lower SOC>

[0156] The secondary batteries prepared in the above examples and comparative examples were charged to 30% SOC at 25°C with a constant current of 0.1C and activated, and then degassed.

[0157] Afterwards, charging was performed to 4.2V under 0.33C constant current / constant voltage conditions, and discharged to 35% SOC under approximately 250W constant output conditions, followed by discharging for 18 seconds under approximately 900W constant output conditions. Subsequently, the time taken to reach the lower limit voltage of 2.5V was measured while discharging under approximately 1,100W constant output conditions.

[0158] The above process was repeated in the same way for states of 30%, 25%, and 20% SOC, respectively, and the time to reach the lower limit voltage was measured. The time measured for each SOC was set as the Landing Time, and the results are shown in Fig. 1.

[0160] Based on the results of Fig. 1, the loading amount is 4.0 mAh / cm² 2 It can be confirmed that the secondary battery of Comparative Example 1 using a phosphorus anode takes less than 10 seconds to reach the lower limit voltage (SOC 0%) when discharged under the conditions of Claim 1 at SOC 35%. This means that since the time to maintain high output in the low SOC range is very short, it is difficult to secure the time required for a safe landing in an emergency situation when applied to UAM.

[0161] On the other hand, the loading amount is 2.5~3.8mAh / cm² 2 It can be confirmed that the secondary batteries of Examples 1 to 6, which use a positive electrode satisfying the range, are suitable for application to UAM because the time taken to reach the lower limit voltage (SOC 0%) when discharged from SOC 35% under the conditions of Claim 1 is 10 seconds or more.

[0162] Meanwhile, it can be confirmed that the cathodes of Preparation Examples 2 to 6, in which lithium composite transition metal oxides in the form of single particles or quasi-single particles were used for the manufacture of the cathode material, exhibit a much higher energy density—specifically an energy density of 270 Wh / kg or higher—compared to the cathode of Preparation Example 1 and Comparative Preparation Example 1, in which only lithium composite transition metal oxides in the form of secondary particles were used exclusively, while satisfying the output conditions of Claim 1 when applied to a battery. Among them, the loading amount is 3.3 to 3.5 mAh / cm² 2 In the case of Examples 2 and 4 to 6 using a positive electrode satisfying the range, it can be confirmed that an energy density of 280 Wh / kg or more is exhibited, while satisfying the output condition of Claim 1 when applied to a battery.

Claims

Claim 1 It includes a positive current collector and a positive active material layer formed on at least one surface of the positive current collector, and has a loading amount of 3.0 mAh / cm² 2 Up to 3.6mAh / cm² 2 A lithium secondary battery comprising: a positive electrode; a negative electrode including a negative current collector and a negative active material layer formed on at least one surface of the negative current collector; and a separator interposed between the positive electrode and the negative electrode, wherein the time required to reach SOC 0% is 30 seconds or more when discharged for 15 seconds under a constant power condition of 900W at SOC 35% and then discharged under a constant power condition of 1,000W. Claim 2 A lithium secondary battery according to claim 1, wherein the positive active material layer comprises a positive active material having a bimodal particle size distribution in which D50 is composed of different alleles and sub-particles, and wherein the alleles and sub-particles each independently comprise a lithium nickel-based oxide. Claim 3 A lithium secondary battery according to claim 2, wherein the D50 of the alternative is 8㎛ to 18㎛. Claim 4 A lithium secondary battery according to claim 2, wherein the D50 of the subatomic particles is 2㎛ to 7㎛. Claim 5 A lithium secondary battery according to claim 2, wherein the elementary particle comprises a lithium nickel-based oxide in the form of a pseudo-single particle, which is a single particle consisting of one primary particle or a secondary particle aggregated from 30 or fewer primary particles. Claim 6 A lithium secondary battery according to claim 1, wherein the positive active material layer comprises a positive active material having a monomodal particle size distribution, and the positive active material having a monomodal particle size distribution comprises a lithium nickel-based oxide in a pseudo-mono-particle form that is a single particle consisting of one primary particle or a secondary particle formed by aggregating 30 or fewer primary particles. Claim 7 A lithium secondary battery according to claim 5 or 6, wherein the average particle size of the primary particles is 1 μm to 5 μm. Claim 8 A lithium secondary battery according to claim 2 or 6, wherein the lithium nickel-based oxide is represented by the following chemical formula 1: [Chemical Formula 1]Li 1+x (Ni a Co b Mn c M d )O2 In the above chemical formula 1, M is one or more selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and 1+x, a, b, c, and d are each the atomic fractions of independent elements, where -0.2≤x≤0.2, 0.60≤a<1, 0 <b<0.40, 0<c<0.40, 0≤d≤0.10, a+b+c+d=1이다. Claim 9 A lithium secondary battery according to claim 1, wherein the energy density of the positive electrode is 250 Wh / kg or more. Claim 10 A lithium secondary battery according to claim 1, wherein the porosity of the positive active material layer is 20% to 32%. Claim 11 A lithium secondary battery according to claim 1, wherein the time required to reach SOC 0% is 30 seconds or more when discharged for 18 seconds under a constant power condition of 900W at SOC 35% and then discharged under a constant power condition of 1,100W. Claim 12 A lithium secondary battery according to claim 1, wherein the lithium secondary battery is for Urban Air Mobility. Claim 13 Urban air mobility means comprising the lithium secondary battery of claim 1.

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