Lithium secondary battery

Abstract

The present invention relates to a lithium secondary battery including a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode includes a mixed positive electrode material including a single particle-type positive electrode active material and a secondary particle-type positive electrode active material, the negative electrode includes a silicon-based negative electrode active material, and a Y value defined by equation (1) below satisfies 48 to 58. Equation (1): In equation (1), TD is a tap density value of the mixed positive electrode material measured in units of g / cc, R is a positive electrode resistance at SOC 50 measured in units of Ω, and TC is a thickness of the positive electrode measured in units of μm.

Description

lithium secondary battery

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0196369 filed on December 24, 2024, and all contents disclosed in said document are incorporated herein as part of this specification.

[0002] The present invention relates to a lithium secondary battery, and more specifically, to a lithium secondary battery having excellent lifespan characteristics and rapid charging performance.

[0003] Recently, lithium secondary batteries are being used as a power source for electric vehicles. Lithium secondary batteries for electric vehicles require high energy density and fast charging performance. To improve energy density, lithium secondary batteries are being developed that use a bimodal cathode material by mixing two types of cathode active materials with different particle sizes to increase cathode density, and a silicon-based anode active material with excellent capacity characteristics mixed with a carbon-based anode active material.

[0004] However, when a combination of a bimodal cathode material and a silicon-based anode active material is used, although capacity characteristics are improved, there is a problem in that the difference in lithium mobility between the cathode and the anode increases the resistance difference at the end of discharge, which accelerates anode degradation and degrades lifespan characteristics.

[0005] In addition, conventionally, it was common to use a mixture of large particles in the form of secondary particles and small particles in the form of secondary particles as bimodal cathode materials. However, in this case, there is a problem in that small particles break during the cathode manufacturing process, generating fine particles, which increases side reactions with the electrolyte and degrades lifespan characteristics.

[0006] The present invention aims to solve the above-mentioned problems by providing a lithium secondary battery capable of suppressing lifespan degradation caused by cathode degradation through optimizing the anode design to minimize the resistance difference between the anode and cathode at the discharge end.

[0007] [1] The present invention provides a lithium secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode comprises a mixed positive electrode material comprising a single-particle positive electrode active material and a secondary-particle positive electrode active material, and the negative electrode comprises a silicon-based negative electrode active material, and the lithium secondary battery satisfies a Y value of 48 to 58 as defined by the following formula (1).

[0008] Equation (1):

[0009]

[0010] In the above equation (1), TD is the value of the tap density of the mixed cathode material measured in g / cc, R is the cathode resistance at SOC 50 measured in Ω, and TC is the thickness of the cathode measured in μm.

[0011] [2] The present invention provides a lithium secondary battery according to [1], wherein the mixed cathode material comprises a single-particle cathode active material and a secondary-particle cathode active material in a weight ratio of 4:6 to 8:2.

[0012] [3] The present invention provides a lithium secondary battery in which, in [1] or [2], the single-particle type positive electrode active material and the secondary-particle type positive electrode active material each independently comprise a lithium nickel-based transition metal oxide having a Ni content of 90 mol% to 96 mol% among the total metals excluding lithium.

[0013] [4] The present invention provides a lithium secondary battery in which, in at least one of [1] to [3], the single-particle type positive active material has an average particle size of 3.0 μm to 8.0 μm, and the secondary-particle type positive active material has an average particle size of 10.0 μm to 15.0 μm.

[0014] [5] The present invention provides a lithium secondary battery in which, in at least one of [1] to [4], the tap density (TD) of the mixed cathode material is 3 g / cc to 7 g / cc.

[0015] [6] The present invention provides a lithium secondary battery in which the positive resistance R is 10 Ω to 25 Ω in at least one of [1] to [5].

[0016] [7] The present invention provides a lithium secondary battery in which, in at least one of [1] to [6], the anode thickness TC is 120 μm to 180 μm.

[0017] [8] The present invention provides a lithium secondary battery in which, in at least one of [1] to [7], the energy retention rate measured after 100 cycles of charging and discharging the lithium secondary battery with the following <condition 1> as one cycle is 90% to 98%.

[0018] <Condition 1> After charging the lithium secondary battery to 4.25V at a constant current of 1.5C, charge it to a constant voltage under a 1C cut-off condition and rest for 10 minutes, then discharge it to 3.8V at 0.33C and rest for 90 minutes, repeating this process 4 cycles, then charge it to 4.2V at a constant current of 0.25C and charge it to a constant voltage under a 0.05C cut-off condition, rest for 10 minutes, then discharge it to 2.5V at a constant current of 0.33C and rest for 60 minutes.

[0019] [9] The present invention provides a lithium secondary battery in which, in at least one of [1] to [8], the silicon-based negative electrode active material is silicon oxide, silicon, a silicon-carbon composite, or a combination thereof.

[0020]

[0010] The present invention provides a lithium secondary battery in which, in at least one of [1] to [9], the negative electrode further comprises a carbon-based negative electrode active material.

[0021]

[0011] The present invention provides a lithium secondary battery in which, in

[0010] the silicon-based negative electrode active material is included in an amount of 1% to 20% by weight based on the total weight of the negative electrode active material.

[0022]

[0012] The present invention provides a lithium secondary battery in which, in

[0010] or

[0011] , the carbon-based negative electrode active material is natural graphite, artificial graphite, or a combination thereof.

[0023]

[0013] The present invention provides a lithium secondary battery in which, in at least one of

[0010] to

[0012] , the carbon-based negative electrode active material comprises natural graphite and artificial graphite in a weight ratio of 70:30 to 50:50.

[0024]

[0014] The present invention provides a lithium secondary battery in which, in at least one of [1] to

[0013] , the lithium secondary battery is a cylindrical battery.

[0025] The lithium secondary battery according to the present invention is designed so that the tap density, anode resistance, and anode thickness of the anode material satisfy specific conditions, thereby reducing the resistance difference between the anode and the cathode, and as a result, the degradation of the silicon-based cathode active material is suppressed, thereby enabling excellent lifespan characteristics and rapid charging performance.

[0026] In addition, the lithium secondary battery according to the present invention uses a mixed cathode material comprising a single-particle type cathode active material and a secondary-particle type cathode active material to reduce the generation of fine particles during cathode manufacturing, thereby enabling suppression of side reactions with the electrolyte.

[0027] In addition, the lithium secondary battery according to the present invention includes a silicon-based negative electrode active material, thereby enabling excellent capacity characteristics and rapid charging performance.

[0028] Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0029] In the present invention, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0030] In the present invention, "single particle type" refers to a particle composed of 30 or fewer nodules, and is a concept that includes a single particle composed of one nodule and a pseudo-single particle which is a complex of 2 to 30 nodules.

[0031] The above “nodule” is a sub-grain unit constituting a single particle and a pseudo-single particle, and may be a single crystal that does not have crystalline grain boundaries, or a polycrystalline one in which no grain boundaries appear to exist when observed at a field of view of 5,000 to 20,000 times using a scanning electron microscope.

[0032] In the present invention, "secondary particle" refers to a particle formed by the aggregation of a plurality of primary particles, for example, tens to hundreds of primary particles. Specifically, the secondary particle may be an aggregate of 31 or more primary particles.

[0033] In the present invention, the term “particle” is a concept that includes any one or all of a single particle, a pseudo-single particle, a primary particle, a nodule, and a secondary particle.

[0034] In the present invention, the average particle size (Dmean) of nodules or primary particles refers to the arithmetic mean value calculated after measuring the particle sizes of nodules or primary particles observed in scanning electron microscope or backscatter electron diffraction (EBSD) images. For example, the particle size of the nodules or primary particles can be measured by manufacturing an electrode using the positive electrode active material powder to be measured, then cutting the electrode before rolling using ion milling (HITACHI IM-500, acceleration voltage 6kV) to obtain a cross-section, and then measuring the number of primary particles on a scale of approximately 400±10 using an FE-SEM (JEOL JSM7900F) device under conditions of acceleration voltage 15kV and WD 15 mm.

[0035] In the present invention, "average particle size D50" refers to a particle size corresponding to 50% of the volume cumulative amount of the volume cumulative particle size distribution of the powder to be measured, and can be measured using a laser diffraction method. For example, the powder to be measured can be measured by dispersing it in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), irradiating it with ultrasound of about 28 kHz at an output of 60 W, obtaining a volume cumulative particle size distribution graph, and then determining the particle size corresponding to 50% of the volume cumulative amount.

[0036]

[0037] The present invention will be described in more detail below.

[0038] A lithium secondary battery according to the present invention comprises at least one of the configurations disclosed below, and may comprise any combination of technically feasible configurations among the configurations below.

[0039] A lithium secondary battery according to the present invention comprises a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode comprises a mixed positive electrode material comprising a single-particle positive electrode active material and a secondary-particle positive electrode active material, and the negative electrode comprises a silicon-based negative electrode active material.

[0040] The lithium secondary battery according to the present invention may have a Y value defined by the following formula (1) of 48 to 58, preferably 48 to 55, more preferably 50 to 55.

[0041] Equation (1):

[0042]

[0043] In the above equation (1), TD is the value of the tap density of the mixed cathode material measured in g / cc, R is the cathode resistance at SOC 50 measured in Ω, and TC is the thickness of the cathode measured in μm.

[0044] According to the inventors' research, when the Y value satisfies the above range, the resistance difference between the positive and negative electrodes at the discharge end is reduced, thereby suppressing the degradation of the silicon-based negative electrode active material and enabling excellent lifespan characteristics and rapid charging performance. When the Y value is less than 48, long-term cycle characteristics are degraded due to non-uniform degradation of the positive electrode active material, and when the Y value exceeds 58, rapid charging performance is degraded due to reduced charge transfer within the active material.

[0045] The lithium mobility between the anode and the cathode is influenced by a combination of the intrinsic resistance of the active material and the electrode resistance. Meanwhile, the anode resistance is affected by the tap density of the mixed anode material, and the intrinsic resistance of the anode active material is affected by the anode thickness. Specifically, if the tap density of the mixed anode material decreases, the anode resistance increases slightly, and as the anode thickness increases, the anode porosity decreases, thereby reducing the resistance within the active material. The above Y can be used as an indicator representing the lithium mobility between the anode and the cathode, including factors affecting the intrinsic resistance of the active material and the anode resistance. When Y satisfies the range of 48 to 58, the resistance difference between the anode and the cathode at the end of discharge decreases, thereby improving lifespan characteristics and rapid charging performance.

[0046]

[0047] Meanwhile, the tap density of the above-mentioned mixed cathode material can be controlled according to the type, composition, and / or particle size of the cathode active material included in the mixed cathode material, and the above-mentioned cathode resistance can be controlled according to the solid content, binder content, loading amount, rolling density, etc. of the cathode slurry used during cathode manufacturing. Accordingly, a cathode having a desired Y value can be manufactured by appropriately controlling the cathode thickness and the above factors.

[0048]

[0049] Hereinafter, each component of the lithium secondary battery according to the present invention will be described in more detail.

[0050]

[0051] anode

[0052] The anode according to the present invention comprises a mixed anode material comprising a single-particle type anode active material and a secondary-particle type anode active material, and may further comprise an anode conductive material and an anode binder as needed. Specifically, the anode comprises an anode current collector and an anode active material layer formed on at least one surface of the anode current collector, and the anode active material layer may comprise the mixed anode material, the anode conductive material, and the anode binder.

[0053] The above positive current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. may be used. 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 positive current collector to increase the adhesion of the positive active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0054]

[0055] The above-mentioned mixed cathode material includes a single-particle type cathode active material and a secondary-particle type cathode active material.

[0056] The above single-particle type cathode active material is a cathode active material comprising particles composed of 30 or fewer, preferably 1 to 25, more preferably 1 to 15 nodules, and includes a single particle composed of 1 nodule and a pseudo-single particle which is a composite of 2 to 30 nodules.

[0057] The above nodules may have an average particle size of 0.8㎛ to 4.0㎛, preferably 0.8㎛ to 3㎛, and more preferably 1.0㎛ to 3.0㎛. When the average particle size of the nodules satisfies the above range, small particle breakage is minimized during electrode manufacturing, and excessive resistance can be prevented.

[0058] The above single-particle type positive electrode active material has an average particle size (D 50 ) may be 3.0㎛ to 8.0㎛, preferably 3.0㎛ to 7.5㎛, more preferably 3.0㎛ to 7.0㎛. The average particle size (D) of the single-particle type cathode active material. 50 When ) satisfies the above range, appropriate tap density and anode resistance can be realized, and an anode with high electrode density can be manufactured. Average particle size (D) of the single-particle anode active material 50 If ) is too small, the electrolyte impregnation is reduced, and if it is too large, problems such as reduced tap density and increased resistance may occur.

[0059] The secondary particle type cathode active material is a cathode active material comprising aggregates of 31 or more, preferably 40 or more, and more preferably 50 or more primary particles.

[0060] The above secondary particle-type cathode active material has an average particle size (D 50 ) may be 10.0㎛ to 15.0㎛, preferably 10.0㎛ to 14.0㎛, more preferably 10.0㎛ to 12.0㎛. The average particle size (D) of the secondary particle-type cathode active material 50 When the above range is satisfied, an appropriate tap density can be achieved, and an anode with high electrode density can be manufactured.

[0061]

[0062] The above single-particle type positive active material and the secondary-particle type positive active material may each independently include a lithium nickel-based oxide. Specifically, the above single-particle type positive active material and the secondary-particle type positive active material may each independently include a lithium nickel-based transition metal oxide in which the Ni content among the total metals excluding lithium is 90 mol% to 96 mol%. When the Ni content of the single-particle type positive active material and the secondary-particle type positive active material satisfies the above range, high capacity characteristics can be achieved by combining with a negative electrode including a silicon-based negative electrode active material.

[0063] More specifically, the single-particle type positive electrode active material and the secondary-particle type positive electrode active material may each independently include a lithium nickel-based oxide represented by the following [Chemical Formula 1].

[0064] [Chemical Formula 1]

[0065] Li 1+x [Ni a Co b M 1 c M 2 d ]O2

[0066] In the above [Chemical Formula 1], M 1 It may be Mn, Al, or a combination thereof, and preferably may be Mn or a combination of Mn and Al.

[0067] The above M 2 It may include one or more elements selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo. 2 When the element is included, the structural stability of the lithium nickel-based oxide particles is improved, enabling excellent lifespan characteristics during high-voltage operation. Preferably, the above M 2 The elements may include one or more selected from the group consisting of Ti, Mg, Al, Zr, and Y, and more preferably, may include two or more selected from the group consisting of Ti, Mg, Al, Zr, and Y.

[0068] The above 1+x represents the lithium molar ratio in the lithium nickel-based oxide, and may be -0.1≤x≤0.1, 0≤x≤0.1, or 0≤x≤0.07. When 1+x satisfies the above range, a stable layered crystal structure can be formed.

[0069] The above a represents the molar ratio of nickel among the total metals excluding lithium in the lithium nickel-based oxide, and may be 0.5≤a<1, 0.80≤a≤0.99, 0.85≤a≤0.98, or 0.90≤a≤0.96.

[0070] The above b represents the molar ratio of cobalt among the total metals excluding lithium in the lithium nickel-based oxide, where 0 <b<0.5, 0.01≤b≤0.20, 0.01≤b≤0.15 또는 0.01≤b≤0.10일 수 있다.

[0071] The above c is M among the total metals excluding lithium in the lithium nickel-based oxide. 1 Representing the molar ratio of elements, 0 <c<0.5, 0.01≤c≤0.20 0.01≤c≤0.15 또는 0.01≤c≤0.10일 수 있다.

[0072] The above d is M among the total metals excluding lithium in the lithium nickel-based oxide. 2 Representing the molar ratio of elements, 0≤d≤0.2, 0≤d≤0.1, or 0 <d≤0.1일 수 있다. M 2 When the molar ratio of the elements satisfies the above range, both the structural stability and capacity of the positive active material can be excellent.

[0073] The above single-particle type positive electrode active material and the above secondary-particle type positive electrode active material are, if necessary, coated with element M on the lithium nickel-based oxide. 3 It may further include a coating layer comprising Li-M 3 It may include a solid solution of -O. The coating element M 3 It may include one or more selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, B, Ca, Sr, W, Ta, Nb, and Mo. Preferably, the coating element M 3It may include two or more elements selected from the group consisting of Ti, Mg, Al, Zr, Y, and W. When a coating layer is formed on a lithium nickel-based oxide, the surface structure of the positive electrode active material is stabilized, and side reactions with the electrolyte can be effectively suppressed.

[0074] Single-particle cathode active materials have longer lithium migration pathways within the particles and fewer interfaces between nodules serving as pathways for lithium ions compared to secondary-particle cathode active materials, resulting in lower lithium mobility and consequently higher resistance compared to secondary-particle cathode active materials. Therefore, when single-particle cathode active materials are mixed and used as in the present invention, the cathode resistance increases while the resistance difference between the cathode and the anode decreases, thereby suppressing anode degradation.

[0075]

[0076] The above single-particle type positive active material and the above secondary-particle type positive active material have different average particle sizes (D 50 It can have ). That is, the above mixed cathode material can have a bimodal particle size distribution. If the mixed cathode material has a bimodal particle size distribution, the electrode density can be increased to improve energy density.

[0077] Preferably, the average particle size (D) of the above-mentioned single-particle type positive electrode active material 50 The average particle size (D) of the secondary particulate cathode active material 50It can be smaller than ). That is, the single-particle type cathode active material may be a small particle, and the secondary-particle type cathode active material may be a large particle. Conventionally, it was common to use a mixture of large particles in the form of secondary particles and small particles in the form of secondary particles as bimodal cathode materials; however, in this case, there was a problem in that small particles broke during the cathode rolling process, generating fine particles, which increased side reactions with the electrolyte and degraded lifespan characteristics. However, since the single-particle type cathode active material undergoes under-scaling during the manufacturing process, the particle strength is higher than that of the secondary-particle type cathode active material. Therefore, when the single-particle type cathode active material is used as a small particle as in the present invention, the breaking of small particles during the rolling process can be minimized, and accordingly, side reactions with the electrolyte are reduced, thereby achieving the effect of improving lifespan characteristics.

[0078]

[0079] The above mixed cathode material may include a single-particle cathode active material and a secondary-particle cathode active material in a weight ratio of 4:6 to 8:2, 4:6 to 7:3, or 4:6 to 6:4. When the weight ratio of the single-particle cathode active material and the secondary-particle cathode active material satisfies the above range, the tap density and cathode resistance of the mixed cathode material are controlled to an appropriate range, making it advantageous to manufacture a cathode having a desired Y value and to achieve excellent rapid charging performance and lifespan characteristics. If the content of the single-particle cathode active material is too high, the Y value may be less than 48, and rapid charging performance may be degraded; if the content of the secondary-particle cathode active material is too high, the Y value may exceed 58, and the cathode resistance decreases, increasing the resistance difference with the negative electrode at the discharge end, which may degrade lifespan characteristics.

[0080]

[0081] The above mixed cathode material may have a tap density (TD) of 3 g / cc to 7 g / cc, preferably 3.5 g / cc to 6.5 g / cc, or 4.0 g / cc to 6.5 g / cc. When the tap density of the mixed cathode material satisfies the above range, an effect of increasing lifespan characteristics can be obtained.

[0082]

[0083] Meanwhile, the above-mentioned mixed cathode material may be included in an amount of 93% to 99% by weight, preferably 95% to 98% by weight, and more preferably 95% to 97% by weight, based on the total weight of the cathode active material layer (i.e., the total amount including the mixed cathode material, the cathode conductive material, and the cathode binder). When the content of the cathode active material satisfies the above range, high energy density can be achieved.

[0084]

[0085] Next, the above-mentioned positive electrode conductive material is used to impart conductivity to the positive electrode, and in the battery being constructed, any material that possesses electronic conductivity without causing chemical changes can be used without any particular limitations. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, carbon nanotube; metal powder or metal fiber such as copper, nickel, aluminum, or silver; 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 of these may be used.

[0086] The above-mentioned positive conductive material may be included in an amount of 0.1 to 10 weight%, preferably 0.5 to 8 weight%, and more preferably 1 to 5 weight% based on the total weight of the positive active material layer.

[0087] Next, the anode binder serves to improve adhesion between anode active material particles and adhesion between the anode active material and the anode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used.

[0088] The above anode binder may be included in an amount of 0.5% to 5% by weight, preferably 1% to 4% by weight, more preferably 1% to 3% by weight, based on the total weight of the anode active material layer.

[0089]

[0090] In the present invention, the resistance (R) of the anode may be 10 Ω to 25 Ω, preferably 10 Ω to 22 Ω, and more preferably 10 Ω to 21 Ω. When the anode resistance satisfies the above range, cathode degradation due to the resistance difference with the cathode can be effectively prevented.

[0091]

[0092] The anode may have an anode thickness (TC) of 120 µm to 180 µm, preferably 130 µm to 170 µm, more preferably 140 µm to 160 µm, and even more preferably 145 µm to 155 µm. When the anode thickness satisfies the above range, the stability of the anode active material particles is improved during the cycling process, thereby enabling excellent lifespan characteristics. If the anode thickness is too thin, problems may arise where the active material particles are damaged during the rolling process, and if it is too thick, the electrode porosity increases, which may lead to performance degradation due to the high specific surface area.

[0093]

[0094] The above anode may be manufactured according to a conventional anode manufacturing method. For example, the above anode may be manufactured by mixing an anode active material, an anode binder, and / or an anode conductive material in a solvent to prepare an anode slurry, applying the anode slurry onto an anode current collector, and then drying and rolling, or by casting the anode slurry onto a separate support and then laminating the film obtained by peeling it off from the support onto an anode current collector.

[0095] Meanwhile, solvents commonly used in the relevant technical field may be used as solvents for the anode slurry; for example, dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, etc., may be used individually or as a mixture of two or more. The amount of the solvent used is sufficient if it is sufficient to dissolve or disperse the anode active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that exhibits excellent thickness uniformity when coated for anode manufacturing thereafter.

[0096]

[0097] cathode

[0098] The cathode according to the present invention comprises a silicon-based cathode active material and may further comprise a cathode conductive material and a cathode binder as needed. Specifically, the cathode comprises a cathode current collector and a cathode active material layer formed on at least one surface of the cathode current collector, and the cathode active material layer may comprise a silicon-based cathode active material, a cathode conductive material, and a cathode binder.

[0099] 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 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.

[0100]

[0101] The above silicon-based negative electrode active material may be silicon oxide, silicon, a silicon-carbon composite, or a combination thereof. The above silicon-based negative electrode active material may be Si, a Si-Me alloy (wherein Me is one or more selected from the group consisting of Al, Sn, Mg, Cu, Fe, Pb, Zn, Mn, Cr, Ti, and Ni), or silicon oxide (SiOy, where 0 <y<2), Si-C 복합체 또는 이들의 조합일 수 있으며, 바람직하게는 산화 실리콘(SiOy, 여기서, 0<y<2), 실리콘(Si), 실리콘-탄소(Si-C) 복합체 또는 이들의 조합일 수 있다. 실리콘계 음극 활물질은 높은 이론 용량을 가지기 때문에 실리콘계 음극 활물질을 포함할 경우, 용량 특성을 향상시킬 수 있다. 상기 실리콘계 음극 활물질이 음극 활물질 전체 중량을 기준으로 1중량% 내지 20중량%, 바람직하게는 1중량% 내지 15중량%, 더 바람직하게는 3중량% 내지 10중량%의 양으로 포함될 수 있다. 실리콘계 음극 활물질의 함량이 상기 범위를 만족할 경우, 높은 에너지 밀도를 구현할 수 있으며, 최적 효율 및 수명 성능을 나타낼 수 있다. 예를 들면, 실리콘계 음극 활물질의 함량이 상기 범위를 만족할 경우, 19Wh 이상의 21700 원통형 셀을 구현할 수 있다.

[0102] The above silicon-based negative electrode active material is M b It may be doped with metal, and in this case, the above M b The metal may be a Group 1 metal element or a Group 2 metal element, and specifically, may be Li, Mg, etc. Specifically, the silicon negative electrode active material is M b Metal-doped Si, SiOy(where, 0 <y<2), Si-C 복합체 등일 수 있다. 금속 도핑된 실리콘계 음극 활물질의 경우, 도핑 원소로 인해 활물질 용량은 다소 저하되나 높은 효율을 갖기 때문에, 높은 에너지 밀도를 구현할 수 있다.

[0103] The silicon-based negative electrode active material may further include a carbon coating layer on the particle surface. In this case, the amount of the carbon coating may be 20% by weight or less, preferably 1% to 20% by weight, based on the total weight of the silicon-based negative electrode active material.

[0104] If necessary, a carbon-based cathode active material may be further included as the cathode active material. The carbon-based cathode active material may be, for example, artificial graphite, natural graphite, graphitized carbon fiber, amorphous carbon, soft carbon, hard carbon, etc., and preferably may be artificial graphite, natural graphite, or a combination thereof, but is not limited thereto.

[0105] The above carbon-based negative electrode active material may contain natural graphite and artificial graphite in a weight ratio of 70:30 to 50:50, preferably 65:45 to 50:50, and more preferably 60:40 to 50:50. When the ratio of natural graphite and artificial graphite satisfies the above range, excellent rapid charging performance and lithium ion storage and mobility are exhibited. As the amount of natural graphite increases, the orientation of the active material increases, which is advantageous for lithium ion storage and mobility; however, to secure rapid charging performance, artificial graphite in a low-orientation form must be included in a certain proportion or more.

[0106] When a mixture of a silicon-based negative electrode active material and a carbon-based negative electrode active material is used as the above negative electrode active material, the mixing ratio of the silicon-based negative electrode active material and the carbon-based negative electrode active material may be 1:99 to 20:80 by weight, preferably 1:99 to 15:85, and more preferably 3:97 to 10:90.

[0107]

[0108] The above-mentioned negative electrode active material may be included in an amount of 80% to 98% by weight, preferably 90% to 98% by weight, and more preferably 93% to 98% by weight, based on the total weight of the negative electrode active material layer. When the content of the negative electrode active material satisfies the above range, excellent energy density can be achieved.

[0109]

[0110] Next, the above-mentioned cathode conductive material is used to impart conductivity to the cathode, and in the battery being constructed, it can be used without special limitations as long as it has electronic conductivity without causing chemical changes. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, carbon nanotube; metal powder or metal fiber such as copper, nickel, aluminum, or silver; 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 of these may be used.

[0111] The above-mentioned cathode conductive material may typically be included in an amount of 0.1 to 10 weight%, preferably 0.5 to 8 weight%, and more preferably 1 to 5 weight% based on the total weight of the cathode active material layer.

[0112] The above-mentioned cathode binder serves to improve adhesion between cathode active material particles and adhesion between the cathode active material and the cathode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used.

[0113] The above-mentioned cathode binder may be included in an amount of 1 to 10 weight%, preferably 1 to 8 weight%, more preferably 1 to 5 weight% based on the total weight of the positive active material layer.

[0114]

[0115] Meanwhile, in the lithium secondary battery according to the present invention, the negative electrode active material layer may have a single-layer structure or a multi-layer structure of two or more layers. For example, the negative electrode may include a first negative electrode active material layer formed on at least one surface of a negative electrode current collector and comprising a first negative electrode active material; and a second negative electrode active material layer formed on the first negative electrode active material layer and comprising a second negative electrode active material.

[0116] Meanwhile, if the negative electrode active material layer is a multilayer structure composed of two or more layers, the types and / or contents of the negative electrode active material, binder and / or conductive material in each layer may differ from one another.

[0117] For example, the content of silicon-based cathode active material among the cathode active materials in the first cathode active material layer (lower layer) and the second cathode active material layer (upper layer) can be different, or the ratio of artificial graphite to natural graphite can be different.

[0118] Alternatively, the weight ratio of the conductive material to the total weight of the second cathode active material layer (upper layer) can be formed to be higher than the weight ratio of the conductive material to the total weight of the first cathode active material layer (upper layer).

[0119] In this way, by forming the negative electrode active material layer into a multilayer structure and varying the composition of each layer, the performance characteristics of the battery, such as rapid charging performance and output characteristics, can be further improved.

[0120]

[0121] The above cathode may be manufactured according to a conventional cathode manufacturing method. For example, the above cathode may be manufactured by mixing a cathode active material, a cathode binder, and / or a cathode conductive material in a solvent to prepare a cathode slurry, applying the cathode slurry onto a cathode current collector, and then drying and rolling, or by casting the cathode slurry onto a separate support and then laminating a film obtained by peeling off from the support onto a cathode current collector.

[0122] Meanwhile, solvents commonly used in the relevant technical field may be used as solvents for the cathode slurry; for example, dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, etc., may be used individually or as a mixture of two or more. The amount of the solvent used is sufficient if it has a viscosity that dissolves or disperses the cathode active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the slurry, and subsequently provides excellent thickness uniformity when coated for anode manufacturing.

[0123]

[0124] electrolytes

[0125] The above electrolyte may include an organic solvent and a lithium salt.

[0126] 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 C2 to C20 structures 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.

[0127]

[0128] The above lithium salt can be used without special limitations as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably used within the range of 0.1 to 3.0 M, preferably 0.1 to 2.0 M, and more preferably 0.5 to 1.5 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 allow lithium ions to move effectively.

[0129]

[0130] In addition to the above electrolyte components, the above electrolyte may additionally include additives for the purpose of improving the lifespan characteristics of the battery, suppressing the reduction of battery capacity, and improving the discharge capacity of the battery. For example, the above additives may include various additives used in the relevant technical field, for example, fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinylethylene carbonate (VEC), ethylene sulfate (ESa), lithium difluorophosphate (LiPO2F2), lithium bisoxalatetoborate (LiBOB), lithium tetrafluoroborate (LiBF4), lithium difluorooxalatetoborate (LiDFOB), lithium difluorobisoxalatetophosphate (LiDFBP), lithium tetrafluorooxalatetophosphate (LiTFOP), lithium methyl sulfate (LiMS), lithium ethyl sulfate (LiES), propanesulfone (PS), propensulfone (PRS), succinonitrile (SN), adiponitrile (AND), 1,3,6-hexanedricarbonitrile (HTCN), 1,4-disyano-2-butene (DCB), fluorobenzene (FB). Ethyl di(pro-2-i-1-nyl) phosphate (EDP), 5-methyl-5-propazyloxylcarbonyl-1,3-dioxane-2-one (MPOD), etc. may be used alone or in combination, but are not limited thereto. The above additives may be included in an amount of 0.1 to 10 weight%, preferably 0.1 to 5 weight%, based on the total weight of the electrolyte.

[0131]

[0132] Separator

[0133] The lithium secondary battery according to the present invention may further include a separator between the positive electrode and the negative electrode as needed. The separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. Any separator commonly used as a separator in a lithium secondary battery 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.

[0134]

[0135] The lithium secondary battery according to the present invention, configured as described above, has excellent rapid charging performance and lifespan characteristics.

[0136] Specifically, the lithium secondary battery according to the present invention has an energy retention rate of 90% to 98%, preferably 92% to 98%, and more preferably 95% to 98%, after 100 cycles of charging and discharging with the following <Condition 1> as one cycle.

[0137] <Condition 1> After charging the lithium secondary battery to 4.25V at a constant current of 1.5C, charge it to a constant voltage under a 1C cut-off condition and rest for 10 minutes, then discharge it to 3.8V at 0.33C and rest for 90 minutes, repeating this process 4 cycles, then charge it to 4.2V at a constant current of 0.25C and charge it to a constant voltage under a 0.05C cut-off condition, rest for 10 minutes, then discharge it to 2.5V at a constant current of 0.33C and rest for 60 minutes.

[0138] The above <Condition 1> is intended to measure performance immediately after repeating 4 cycles of rapid charging. It involves charging at a high rate of 1.5 C-rate to rapidly insert lithium into the cathode structure, and then repeating a low-rate discharge and resting process at 0.33 C-rate up to 3.8 V to partially de-insert the inserted lithium and maintain a certain amount of charge. Subsequently, the energy retention rate is calculated in the section where a low-rate charge at 0.25 C-rate is followed by a complete discharge at 0.33 C-rate.

[0139]

[0140] The lithium secondary battery according to the present invention may be a cylindrical battery. Specifically, the cylindrical lithium secondary battery according to the present invention may include an electrode assembly, a cylindrical battery can in which an electrolyte is housed, and a sealing body that seals the open end of the battery can.

[0141] The electrode assembly described above may have a structure in which an anode, a separator, and a cathode are sequentially stacked and wound in one direction, wherein the anode, separator, and cathode are identical to those described above. That is, the anode comprises a mixed anode material including a single-particle type anode active material and a secondary-particle type anode active material, and the cathode comprises a silicon-based cathode active material.

[0142] In addition, the cylindrical battery of the present invention satisfies a Y value defined by the above equation (1) of 50 to 55.

[0143] Meanwhile, the electrode assembly may have a positive tab electrically connected to the positive electrode and a negative tab electrically connected to the negative electrode. The positive tab is electrically connected to a cap plate to be described later, and the negative tab may be electrically connected to a battery can to be described later.

[0144] The above-described battery can may be a general cylindrical battery can known in the art. For example, the battery can is a cylindrical container with an opening formed at one end and is made of a conductive metal material such as aluminum or steel. An electrode assembly is housed in the inner space through the opening, and an electrolyte is injected. If necessary, a beading portion and a crimping portion may be provided at the top of the cylindrical can. The beading portion inhibits the movement of the electrode assembly housed inside the can and functions as a support portion on which a seal is seated; it may be formed by pressing the outer circumference of the cylindrical can to a certain depth.

[0145] The above-mentioned crimping part is intended to combine and seal a sealing body and a cylindrical can, and has an extended and folded shape to wrap around a portion of the upper surface of the sealing body.

[0146] Next, the sealing body is intended to seal the open end of a battery can and includes a cap plate and a sealing gasket that provides airtightness and insulation between the cap plate and the battery can, and, if necessary, may further include a connecting plate electrically and mechanically coupled to the cap plate. The cap plate is pressed onto a beading portion formed on the battery can and may be secured by a crimping portion.

[0147] The cap plate is a component made of a conductive metal material that covers the top opening of the battery can. The cap plate is electrically connected to the positive electrode of the electrode assembly and is electrically insulated from the battery can through a sealing gasket. Therefore, the cap plate can function as the positive terminal of a cylindrical secondary battery. The cap plate may have a formed protrusion that protrudes upward from its center, and the protrusion may come into contact with an external power source to allow current to be applied from the external power source.

[0148] Meanwhile, the cylindrical battery may further include a safety vent and / or a current interrupt device (CID) at the bottom of the cap plate as needed.

[0149] The safety vent serves to cut off the current or exhaust gas when the pressure inside the battery rises due to an abnormal current, and may be made of metal. The thickness of the safety vent may vary depending on the material and structure, and is not particularly limited as long as it can rupture and release gas, etc. when a certain high pressure is generated inside the battery, for example, it may be 0.2 to 0.6 mm.

[0150] A Current Interrupt Device (CID) is positioned below the safety vent and above the electrode assembly to electrically connect the electrode assembly and the safety vent. The Current Interrupt Device includes a CID filter that transmits current by contacting the safety vent and interrupts the current when high voltage occurs inside the battery can, and a CID gasket that spatially separates and insulates the CID filter and the safety vent, except for a portion of the area.

[0151]

[0152] A lithium secondary battery according to the present invention can be used to manufacture a battery pack. The battery pack comprises an assembly of lithium secondary batteries electrically connected according to the present invention and a pack housing that accommodates the same, wherein the pack housing may include a busbar for electrically connecting the lithium secondary batteries, a cooling unit, an external terminal, etc. The battery pack may be mounted in a vehicle. The vehicle may be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. The vehicle includes a four-wheeled vehicle or a two-wheeled vehicle. In particular, the lithium secondary battery according to the present invention has high energy density and excellent rapid charging performance, so it can be usefully used as a battery for an electric vehicle.

[0153]

[0154] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0155]

[0156] Example 1

[0157] <Anode Manufacturing>

[0158] An anode slurry was prepared by mixing the anode active material, anode conductive material, and anode binder in a weight ratio of 97.8:0.78:1.42 in N-methylpyrrolidone. At this time, LiNi was used as the anode active material. 0.94 Co 0.03 Mn 0.03 O2 composition single-particle type positive electrode active material (D 50 =3.5㎛) and LiNi 0.97 Co 0.01 Mn 0.02 Secondary particle-type cathode active material of O2 composition (D 50A mixed cathode material was used in which the (= 11㎛) and () parts were mixed in a weight ratio of 5:5, and the tap density of the mixed cathode material was 5.9 g / cc. Bundled carbon nanotubes were used as the cathode conductive material. Polyvinylidene fluoride (PVdF) was used as the cathode binder.

[0159] The above anode slurry was applied to both sides of an aluminum current collector with a thickness of 15 μm, and then dried and rolled to produce an anode with a total thickness of 150 μm.

[0160] Cathode Manufacturing

[0161] A cathode slurry was prepared by mixing the cathode active material, cathode conductive material, cathode binder, and thickener in water in a weight ratio of 97.962:0.038:1.2:0.8. At this time, natural graphite, artificial graphite, and SiO were mixed in a weight ratio of 65.45:28.05:6.5 and used as the cathode active material. Single-walled carbon nanotubes were used as the cathode conductive material. Styrene-butadiene rubber (SBR) was used as the cathode binder, and carboxymethyl cellulose (CMC) was used as the thickener.

[0162] The above cathode slurry was applied to both sides of a copper current collector with a thickness of 8 μm, and then dried and rolled to produce a cathode with a total thickness of 159 μm.

[0163] Lithium secondary battery manufacturing

[0164] An electrode assembly was manufactured by sequentially stacking the anode and separator manufactured above, and the cathode and separator manufactured above, and then winding them. A secondary battery was manufactured by placing the electrode assembly into a cylindrical battery case, injecting an electrolyte, and sealing it.

[0165]

[0166] Example 2

[0167] LiNi as the cathode active material during cathode manufacturing 0.94 Co 0.03 Mn 0.03O2 composition single-particle type positive electrode active material (D 50 =3.5㎛) and LiNi 0.97 Co 0.01 Mn 0.02 Secondary particle-type cathode active material of O2 composition (D 50 A positive electrode, a negative electrode, and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a mixed positive electrode material having a tap density of 3.5 g / cc and a positive electrode slurry was applied such that the total thickness of the positive electrode was 140 μm, and a mixed positive electrode material was used in a weight ratio of 8:2 (= 11 μm).

[0168]

[0169] Example 3

[0170] LiNi as the cathode active material during cathode manufacturing 0.94 Co 0.03 Mn 0.03 O2 composition single-particle type positive electrode active material (D 50 =3.5㎛) and LiNi 0.97 Co 0.01 Mn 0.02 Secondary particle-type cathode active material of O2 composition (D 50 A positive electrode, a negative electrode, and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a mixed positive electrode material was used in a weight ratio of 4:6 and the tap density was 6.2 g / cc.

[0171]

[0172] Comparative Example 1

[0173] LiNi as the cathode active material during cathode manufacturing 0.94 Co 0.03 Mn 0.03 O2 composition single-particle type positive electrode active material (D 50 =3.5㎛) and LiNi 0.97 Co 0.01 Mn 0.02 Secondary particle-type cathode active material of O2 composition (D 50 A positive electrode, a negative electrode, and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a mixed positive electrode material was used in a weight ratio of 2:8 and the tap density was 7.2 g / cc. (= 11 μm)

[0174]

[0175] Comparative Example 2

[0176] LiNi as the cathode active material during cathode manufacturing 0.94 Co 0.03 Mn 0.03 O2 composition single-particle type positive electrode active material (D 50 =3.5㎛) and LiNi 0.97 Co 0.01 Mn 0.02 Secondary particle-type cathode active material of O2 composition (D 50 A positive electrode, a negative electrode, and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a mixed positive electrode material was used in a weight ratio of 8:2 and the tap density was 3.5 g / cc. (= 11 μm)

[0177]

[0178] Comparative Example 3

[0179] A positive electrode, a negative electrode, and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the positive electrode slurry was applied during the manufacturing of the positive electrode so that the total thickness of the positive electrode was 140 μm.

[0180]

[0181] Comparative Example 4

[0182] A positive electrode, a negative electrode, and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the positive electrode slurry was applied during the manufacturing of the positive electrode so that the total thickness of the positive electrode was 160 μm.

[0183]

[0184] Experimental Example 1: Anode Resistance Characteristics

[0185] A coin half-cell was manufactured by assembling an electrode assembly with a polyethylene separator interposed between the respective anode and lithium metal counter electrode prepared in the examples and comparative examples, housing it in a coin cell case, injecting an electrolyte, and sealing it.

[0186] After charging the manufactured coin half-cell to SOC 100, the voltage drop was measured after applying a pulse for 10 seconds while discharging at a DOD (Depth Of Discharge) of 1%. The positive resistance (R) is specified as the value measured at SOC 50.

[0187] The measurement results are shown in [Table 1] below.

[0188]

[0189] Experimental Example 2: Evaluation of Rapid Charging Performance

[0190] The rapid charging performance was evaluated by measuring the capacity retention rate after performing 100 charge-discharge cycles, with each lithium secondary battery prepared in the examples and comparative examples being charged at a constant current of 1.5C to 4.25V, then charged at a constant voltage under a 1C cut-off condition and rested for 10 minutes, then discharged at 0.33C to 3.8V and rested for 90 minutes, repeating this process 4 cycles, then charged at a constant current of 0.25C to 4.2V, then charged at a constant voltage under a 0.05C cut-off condition and rested for 10 minutes, then discharged at a constant current of 0.33C to 2.5V and rested for 60 minutes.

[0191] The measurement results are shown in [Table 1] below.

[0192]

[0193] Experimental Example 3: Evaluation of High-Temperature Life Characteristics

[0194] High-temperature life characteristics were evaluated by measuring the capacity retention rate while performing 200 charge-discharge cycles, with each lithium secondary battery prepared in the examples and comparative examples being charged to 4.3V at 0.25C at 40℃ and discharged to 2.5V at 0.33C as one cycle. The measurement results are shown in [Table 1] below.

[0195]

[0196] Single particle : Secondary particle weight ratio mixed Cathode material Tap density (TD) [g / cc] Resistance (R) [Ω] Cathode thickness (TC) [㎛] Y Fast charging performance High temperature life characteristics Example 15 : 55.9 13.5 150 53.10 95.19 3.3 Example 28 : 23.5 20.2 140 50.5 96.7 93.9 Example 34 : 66.2 13.1 150 54.15 97.29 4.3 Comparative Example 12 : 87.2 12.2 150 58.5 69 3.08 7.1 Comparative Example 28 : 23.5 19.7 150 45.9 79 4.48 3.8 Comparative Example 35 : 55.9 14.3 140 60.26 92.88 4.5 Comparative Example 45 : 55.912.416045.7394.586.9

[0197] Through Table 1 above, it can be confirmed that the lithium secondary batteries of Examples 1 to 3, in which Y satisfies 48 to 58, have superior lifespan characteristics after rapid charging and high-temperature lifespan characteristics compared to the lithium secondary batteries of Comparative Examples 1 to 4, in which Y is less than 48 or greater than 58.

Claims

1. In a lithium secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, The above-mentioned anode comprises a mixed anode material including a single-particle type anode active material and a secondary-particle type anode active material, and The above cathode includes a silicon-based cathode active material, and A lithium secondary battery in which the Y value defined by the following equation (1) satisfies 48 to 58. Equation (1): In the above equation (1), TD is the value of the tap density of the mixed cathode material measured in g / cc, R is the cathode resistance at SOC 50 measured in Ω, and TC is the thickness of the cathode measured in μm.

2. In Paragraph 1, A lithium secondary battery comprising the above-mentioned mixed cathode material, which includes a single-particle type cathode active material and a secondary-particle type cathode active material in a weight ratio of 4:6 to 8:

2.

3. In Paragraph 1, A lithium secondary battery in which the above single-particle type positive electrode active material and the secondary-particle type positive electrode active material each independently comprise a lithium nickel-based transition metal oxide having a Ni content of 90 mol% to 96 mol% among the total metals excluding lithium.

4. In Paragraph 1, The above single-particle type cathode active material has an average particle size of 3.0㎛ to 8.0㎛, and The above secondary particulate cathode active material is a lithium secondary battery having an average particle size of 10.0 μm to 15.0 μm.

5. In Paragraph 1, A lithium secondary battery having a tap density (TD) of the above-mentioned mixed cathode material of 3 g / cc to 7 g / cc.

6. In Paragraph 1, A lithium secondary battery having a positive resistance R of 10 Ω to 25 Ω.

7. In Paragraph 1, A lithium secondary battery having a positive electrode thickness TC of 120㎛ to 180㎛.

8. In Paragraph 1, A lithium secondary battery having an energy retention rate of 90% to 98% measured after 100 charge-discharge cycles with the following <Condition 1> as one cycle. <Condition 1> After charging the lithium secondary battery to 4.25V at a constant current of 1.5C, charge it to a constant voltage under a 1C cut-off condition and rest for 10 minutes, then discharge it to 3.8V at 0.33C and rest for 90 minutes, repeating this process 4 cycles, then charge it to 4.2V at a constant current of 0.25C and charge it to a constant voltage under a 0.05C cut-off condition, rest for 10 minutes, then discharge it to 2.5V at a constant current of 0.33C and rest for 60 minutes.

9. In Paragraph 1, The above silicon-based negative electrode active material is a lithium secondary battery that is silicon oxide, silicon, a silicon-carbon composite, or a combination thereof.

10. In Paragraph 1, A lithium secondary battery in which the above-mentioned negative electrode further comprises a carbon-based negative electrode active material.

11. In Paragraph 10, A lithium secondary battery in which the silicon-based negative electrode active material is included in an amount of 1% to 20% by weight based on the total weight of the negative electrode active material.

12. In Paragraph 10, The above carbon-based negative electrode active material is a lithium secondary battery that is natural graphite, artificial graphite, or a combination thereof.

13. In Paragraph 10, A lithium secondary battery in which the carbon-based negative electrode active material comprises natural graphite and artificial graphite in a weight ratio of 70:30 to 50:

50.

14. In Paragraph 1, The above lithium secondary battery is a cylindrical lithium secondary battery.

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