Lithium secondary battery, and battery module and battery pack including same

Abstract

The present application relates to a lithium secondary battery comprising a positive electrode and a negative electrode, wherein: the positive electrode comprises a positive electrode current collector and a positive electrode active material layer provided on one surface or both surfaces of the positive electrode current collector; and the negative electrode comprises a negative electrode current collector and a negative electrode active material layer provided on one surface or both surfaces of the negative electrode current collector, and the negative electrode active material layer comprises a silicon-based active material. In the lithium secondary battery, by allowing the negative electrode and the positive electrode to satisfy a specific thickness ratio and the positive electrode to satisfy a specific thickness, a lithium secondary battery exhibiting high energy density and excellent rapid charging performance is provided.

Description

Lithium secondary battery, battery module including the same, and battery pack

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2024-0195126 filed with the Korean Intellectual Property Office on December 24, 2024, the entire contents of which are incorporated herein.

[0002] The present invention relates to a lithium secondary battery, a battery module including the same, and a battery pack.

[0003] The rapid increase in the use of fossil fuels has led to a growing demand for alternative and clean energy. In response to this demand, one of the most actively researched fields is power generation and energy storage utilizing electrochemical reactions. Currently, secondary batteries are a representative example of electrochemical devices that utilize such electrochemical energy, and their scope of application is steadily expanding.

[0004] As technological development and demand for mobile devices increase, the demand for secondary batteries is also rising rapidly. Among secondary batteries, lithium-ion batteries, which possess high energy density and voltage, long cycle life, and low self-discharge rates, have been commercialized and are widely used. Furthermore, active research is underway to develop high-density electrodes with higher energy density per unit volume to manufacture electrodes for high-capacity lithium-ion batteries.

[0005] Generally, a secondary battery includes a positive electrode, a negative electrode, a separator interposed between the positive and negative electrodes, and an electrolyte. Additionally, electrodes such as the positive and negative electrodes may have an electrode active material layer provided on a current collector.

[0006] Conventional lithium-ion batteries have been developed to achieve high capacity and high energy density by using active materials with high specific capacity and increasing the weight per unit area and current density of the electrode layers formed on the current collector by increasing the content of the positive and negative layers coated on the current collector. In addition, to enhance user convenience, there was a need to secure not only high energy density characteristics but also rapid charging performance.

[0007] If rapid charging performance is improved so that the battery in an electric vehicle can be charged to 80% and used smoothly in a short time, even when the remaining capacity is almost discharged to 10% and the device is difficult to use, it can be considered to have convenience comparable to an internal combustion engine, and thus attempts are being made to develop various types or combinations of materials to improve rapid charging performance.

[0008] The present specification aims to provide a lithium secondary battery, a battery module, and a battery pack capable of solving the aforementioned problems.

[0009] One embodiment of the present specification provides a lithium secondary battery comprising a positive electrode and a negative electrode, wherein the positive electrode comprises a positive current collector; and a positive active material layer provided on one or both sides of the positive current collector, and the negative electrode comprises a negative current collector; and a negative active material layer provided on one or both sides of the negative current collector, wherein the negative active material layer comprises a carbon-based active material and a silicon-based active material as the negative active material, the positive electrode thickness is 70 μm to 103 μm, the electrode thickness ratio represented by Formula 1 below is 95% to 105%, and the weight ratio represented by Formula 2 below is 30% to 51%.

[0010] [Equation 1] (Cathode thickness) / (Anode thickness) * 100%

[0011] In the above Equation 1, the anode thickness refers to the sum of the thicknesses of the anode current collector and the anode active material layer, and the cathode thickness refers to the sum of the thicknesses of the cathode current collector and the cathode active material layer, and

[0012] [Equation 2] (Cathode weight) / (Anode weight) * 100%

[0013] In the above Equation 2, the cathode weight refers to the weight of the cathode active material layer, and the anode weight refers to the weight of the anode active material layer.

[0014] Another embodiment of the present specification provides a battery module comprising the lithium secondary battery.

[0015] Another embodiment of the present specification provides a battery pack comprising the lithium secondary battery or the battery module.

[0016] According to one embodiment of the present invention, a lithium secondary battery having high energy density and excellent rapid charging performance is provided.

[0017] According to one embodiment of the present invention, a lithium secondary battery with improved safety and lifespan characteristics is provided.

[0018] FIGS. 1 and FIGS. 4 are drawings showing a stacked structure of a lithium secondary battery according to one embodiment of the present invention.

[0019] FIG. 2 is a figure showing a positive electrode of a lithium secondary battery according to one embodiment of the present invention.

[0020] FIG. 3 is a figure showing a negative electrode of a lithium secondary battery according to one embodiment of the present invention.

[0021] <Explanation of Symbols>

[0022] 10: Cathode current collector

[0023] 20: Cathode active material layer

[0024] 30: Separator

[0025] 40: Positive active material layer

[0026] 50: Positive current collector

[0027] 100: Cathode

[0028] 200: Anode

[0029] Before describing the present invention, we will first define some terms.

[0030] The present invention may be embodied in various different forms and is not limited to the embodiments described herein. In this case, terms or 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 present invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0031] In this specification, terms such as “comprising,” “comprising,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should not be understood as precluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0032] Furthermore, when it is said that a part, such as a layer, is "above" or "on" another part, this includes not only the case where it is "directly above" the other part, but also the case where there is another part in between. Conversely, when it is said that a part is "directly above" another part, it means that there is no other part in between. Also, saying that a part is "above" or "on" a reference part means that it is located above or below the reference part, and it does not necessarily mean that it is located "above" or "on" facing the opposite direction of gravity.

[0033] In the present specification, the presence or absence and content of elements within the active material of the anode or cathode can be confirmed through ICP analysis, and ICP analysis can be performed using an inductively coupled plasma emission spectrometer (ICPAES, Perkin-Elmer 7300).

[0034] In this specification, "p to q" means a range of p or more and q or less.

[0035] In this specification, "specific surface area" is measured by the BET method, specifically calculated from the amount of nitrogen gas adsorbed at a liquid nitrogen temperature (77K) using BELSORP-mini II of BEL Japan. That is, in this application, the BET specific surface area may refer to the specific surface area measured by the above measurement method. The BET specific surface area may be measured according to DIN 66131 using N2.

[0036] In this specification, "Dn" refers to the particle size distribution and represents the particle size at the n% point of the cumulative distribution of the number of particles according to particle size. That is, D50 is the particle size at the 50% point of the cumulative distribution of the number of particles according to particle size (central particle size), D90 is the particle size at the 90% point of the cumulative distribution of the number of particles according to particle size, and D10 is the particle size at the 10% point of the cumulative distribution of the number of particles according to particle size. Meanwhile, the central particle size can be measured using the laser diffraction method. Specifically, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500) and the difference in diffraction patterns according to particle size is measured as the particles pass through the laser beam to calculate the particle size distribution.

[0037] In this specification, particle size or particle diameter may refer to the average diameter or representative diameter of each individual grain constituting the particle powder.

[0038] In this specification, "particle size (or particle diameter)" may refer to the average diameter or representative diameter of a particle. The particle may be in the form of a single particle or in the form of a secondary particle formed by the aggregation of multiple primary particles. Additionally, the central particle diameter of a particle may be used interchangeably with the average particle diameter, D50, or particle diameter, and the central particle diameter may refer to the size of a particle.

[0039] In this specification, "particle" may be in the form of a single particle, a pseudo-single particle, or a secondary particle.

[0040] In this specification, "single particle" may mean one primary particle and may include pseudo-single particles formed by aggregating, combining, or assembling 30 or fewer primary particles.

[0041] The term "secondary particles" as used in this specification refers to particles formed by the aggregation of dozens to hundreds, for example, more than 30 primary particles, by combining, combining, or assembling.

[0042] In this specification, the meaning that a polymer contains a monomer in monomer units means that the monomer participates in a polymerization reaction and is included as a repeating unit within the polymer. In this specification, when it is stated that a polymer contains a monomer, this is interpreted as the same as the polymer containing the monomer in monomer units.

[0043] In this specification, the term "polymer" is understood to be used in a broad sense including copolymers unless specified as "homopolymer."

[0044] In this specification, the weight-average molecular weight (Mw) and the number-average molecular weight (Mn) are polystyrene equivalent molecular weights measured by gel permeation chromatography (GPC), using commercially available monodisperse polystyrene polymers of various degrees of polymerization (standard samples) for molecular weight measurement as standard materials. In this specification, the term "molecular weight" means weight-average molecular weight unless otherwise specified.

[0045] In this specification, "solid content" refers to the content of a component in a mixture excluding the solvent.

[0046] In this specification, “layer” includes not only a shape formed on the entire surface when viewed in a plan view, but also a shape formed on a part of the surface.

[0047] “Thickness” may refer to the “average thickness” of an object, and may be measured, for example, through a photograph of the object taken with an optical microscope such as a scanning electron microscope.

[0048] The present invention is described in detail below so that those skilled in the art can easily practice it. However, the present invention may be embodied in various different forms and is not limited to the description below.

[0049] Recently, to achieve high capacity and high energy density in lithium-ion batteries, research is being conducted on methods to increase the thickness and weight per unit area of ​​the positive and negative electrodes formed on the current collector by increasing the content of active material in the positive and negative electrodes. However, it has been confirmed that while an excessive increase in the active material content of the positive and negative electrodes may raise the cell's energy density, it leads to an increase in internal cell resistance, causing a problem where rapid charging performance deteriorates rapidly.

[0050] In other words, since it is important for lithium-ion batteries to simultaneously secure high energy density and rapid charging performance to enhance user convenience, there is a need to develop lithium-ion batteries with high energy density and excellent rapid charging performance.

[0051] Meanwhile, there have recently been continuous attempts to apply silicon-based active materials, which have a larger capacity than carbon-based materials, as negative electrode active materials to increase capacity. Silicon-based compounds, which are high-capacity materials, have the advantage of having a larger capacity compared to graphite used conventionally, but they have a problem in that they can degrade battery characteristics by reducing the structural stability of the negative electrode because they rapidly expand in volume during the charging process and interrupt the conductive path.

[0052] In addition, in a mixed negative electrode active material in which carbon-based and silicon-based active materials are mixed, the silicon-based active material exhibits an efficiency of approximately 80 to 90%, whereas the carbon-based active material (e.g., graphite) exhibits an efficiency higher than 90%. Therefore, as the amount of silicon-based active material in the negative electrode active material increases, the efficiency of the negative electrode decreases and the irreversible ratio of the negative electrode increases. In other words, while it is essential to increase the amount of silicon-based active material to increase cell capacity, applying silicon-based active material increases the irreversible ratio of the negative electrode, making it difficult to secure an appropriate NP ratio in relation to the anode.

[0053] When the irreversible ratio of the cathode increases, the cathode may become unusable after a certain point due to a sudden drop in the room temperature cycle life, or productivity may decrease because the total capacity of the cell decreases when the irreversible capacity of the cathode increases compared to when an anode of the same capacity is applied, and the unused portion of the expensive anode active material increases.

[0054] Accordingly, in order to solve the aforementioned problem, the inventors of the present invention have conducted repeated research and discovered that when a mixed negative electrode active material comprising a carbon-based active material and a silicon-based active material is applied as the negative electrode active material, it is possible to provide a lithium secondary battery having high energy density and excellent rapid charging performance by controlling the electrode thickness ratio of the positive electrode and the negative electrode to an appropriate range, while simultaneously controlling the thickness of the positive electrode and adjusting the weight ratio of the positive electrode and the negative electrode.

[0055] That is, even when a silicon-based active material is included as the negative electrode active material, the NP ratio can be stably maintained by appropriately controlling the positive electrode thickness, the electrode thickness ratio, and the positive / negative electrode thickness ratio, thereby making it possible to provide a lithium secondary battery with improved safety and lifespan.

[0056] FIG. 1 is a diagram showing a stacked structure of a lithium secondary battery according to one embodiment of the present invention.

[0057] Referring to FIG. 1, a negative electrode (100) including a negative active material layer (20) on one side of a negative electrode current collector (10) can be seen, and a positive electrode (200) for a lithium secondary battery including a positive active material layer (40) on one side of a positive electrode current collector (50) can be seen.

[0058] A lithium secondary battery according to the present invention is characterized in that it controls the electrode thickness ratio represented by Formula 1 below to 95% to 105%.

[0059] [Equation 1] (Cathode thickness) / (Anode thickness) * 100%

[0060] In the above Equation 1, the anode thickness refers to the sum of the thicknesses of the anode current collector and the anode active material layer, and the cathode thickness refers to the sum of the thicknesses of the cathode current collector and the cathode active material layer.

[0061] According to one embodiment of the present invention, Formula 1 may be 95% to 105%. For example, Formula 1 may be 95% or more or 97% or more, and 105% or less or 104% or less. When Formula 1 falls within the above range, a lithium secondary battery having high energy density and excellent rapid charging performance, while simultaneously having excellent safety and lifespan, can be provided.

[0062] If the above Equation 1 has a value below the lower limit, the cathode thickness becomes excessively thin compared to the anode thickness. Therefore, to increase the NP ratio, the cathode capacity must be lowered by applying a cathode active material with a small capacity per unit area, or the cathode capacity per unit area must be increased by increasing the content of silicon-based active material. However, if a cathode active material with a small capacity per unit area is applied, the energy density of the secondary battery decreases, and if the content of silicon-based active material is excessively increased, there is a problem that the irreversible capacity of the cathode becomes excessively large. On the other hand, if the above Equation 1 has a value above the upper limit, there is a problem that the energy density decreases because the anode thickness becomes excessively thin compared to the cathode thickness.

[0063] In one embodiment of the present invention, the anode thickness is 70㎛ to 103㎛. For example, the anode thickness may be 70㎛ or more, 80㎛ or more, or 90㎛ or more, and may be 103㎛ or less, 100㎛ or less, or 97㎛ or less.

[0064] When the anode thickness is included within the above range, a lithium secondary battery with high energy density and excellent space efficiency can be provided. Specifically, if the anode thickness is below the lower limit, the anode cannot be formed sufficiently thick, so the required battery capacity cannot be satisfied, and if the anode thickness exceeds the upper limit, the internal cell resistance increases, which can rapidly degrade rapid charging performance and also have an adverse effect on design optimization within a limited space.

[0065] That is, one feature of the present invention is that by satisfying the electrode thickness ratio represented by Equation 1 and simultaneously satisfying the anode thickness, the performance, safety, and rapid charging performance of the lithium secondary battery can be improved simultaneously.

[0066] In particular, when setting the electrode thickness ratio, consideration is given to each current collector layer as well as the active material layer of the anode or cathode. Since the current collector determines mechanical rigidity, if only the thickness of the active material layer is matched while the current collector thickness differs, internal cell stress acts asymmetrically, which can lead to wrinkling of the separator, a risk of short circuits, and cell expansion. Therefore, to ensure mechanical stability, this application sets the total electrode thickness ratio including the current collector.

[0067] Another feature of a lithium secondary battery according to one embodiment of the present invention is that the weight ratio represented by Formula 2 below is 30% to 51%. That is, the lithium secondary battery according to one embodiment of the present invention has a weight ratio represented by Formula 2 below of 30% to 51%.

[0068] [Equation 2] (Cathode weight) / (Anode weight) * 100%

[0069] In the above Equation 2, the cathode weight refers to the weight of the cathode active material layer, and the anode thickness refers to the weight of the anode active material layer.

[0070] According to one embodiment of the present invention, the above Equation 2 may be 30% to 51%. For example, the above Equation 2 may be 30% or more, 40% or more, 45% or more, or 47% or more, and 51% or less or 50% or less. When the above Equation 2 falls within the above range, a lithium secondary battery having high energy density and excellent rapid charging performance, while simultaneously having excellent safety and lifespan, can be provided.

[0071] On the other hand, if the above Equation 2 is below the lower limit, the proportion of the negative electrode active material decreases, so to increase the NP ratio, a positive electrode active material with a small capacity per unit area must be applied to lower the capacity of the positive electrode, or the content of the silicon-based active material must be increased to increase the capacity per unit area of ​​the negative electrode. However, if a positive electrode active material with a small capacity per unit area is applied, the energy density of the secondary battery decreases, and if the content of the silicon-based active material is excessively increased, there is a problem that the irreversible capacity of the negative electrode becomes excessively large. On the other hand, if the above Equation 2 has a value exceeding the upper limit, the weight of the positive electrode becomes excessively light compared to the weight of the negative electrode, and the energy density decreases.

[0072] In the present specification, the above formula 2 may mean (weight per unit area of ​​the cathode) / (weight per unit area of ​​the anode).

[0073] Another embodiment of the present invention provides a lithium secondary battery having an NP ratio represented by the following formula 3 that is 104 or higher.

[0074] [Equation 3] (Reversible capacity of the cathode) / (Reversible capacity of the anode) * 100.

[0075] According to one embodiment of the present invention, when the NP ratio is 104 or higher, problems such as lithium precipitation or dendrite formation can be prevented, thereby maintaining the safety and cycle life of the battery. When the NP ratio is less than 104, the capacity of lithium ions at the negative electrode is limited, which may reduce the available capacity of the battery and make it difficult to achieve high energy density.

[0076] FIG. 2 is a figure showing a positive electrode of a lithium secondary battery according to one embodiment of the present invention.

[0077] Referring to FIG. 2 above, a positive electrode (200) including a positive active material layer (40) on one side of a positive electrode current collector (50) can be seen, and FIG. 2 shows that the positive active material layer is formed on one side of the positive electrode current collector, but it can be included on both sides of the positive electrode current collector.

[0078] That is, the anode (200) comprises an anode current collector (50) and an anode active material layer (40) provided on one or both sides of the anode current collector.

[0079] In one embodiment of the present invention, the thickness of the anode (200) refers to the sum of the thicknesses of the anode current collector (50) and the anode active material layer (40).

[0080] In one embodiment of the present invention, the weight of the anode (200) refers to the sum of the weights of the anode current collector (50) and the anode active material layer (40).

[0081] In one embodiment of the present invention, the anode thickness is 70㎛ to 103㎛. For example, the anode thickness may be 70㎛ or more, 80㎛ or more, or 90㎛ or more, and may be 103㎛ or less, 100㎛ or less, or 97㎛ or less.

[0082] When the anode thickness is included within the above range, a lithium secondary battery with high energy density and excellent space efficiency can be provided. Specifically, if the anode thickness is below the lower limit, the anode cannot be formed sufficiently thick, so the required battery capacity cannot be satisfied, and if the anode thickness exceeds the upper limit, it may have an adverse effect on design optimization within a limited space.

[0083] According to one embodiment of the present invention, the material of the 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, and specifically, aluminum foil may be used. In addition, the positive current collector may form fine irregularities on its surface 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.

[0084] In one embodiment of the present invention, the thickness of the positive current collector may be 5 μm to 20 μm. For example, it may be 5 μm or more, 7 μm or more, or 10 μm or more, and 20 μm or less or 15 μm or less. If the thickness of the positive current collector is less than the lower limit, the coating processability of the positive active material layer is reduced, and the resistance of the current collector may increase rapidly. On the other hand, if the thickness exceeds the upper limit, the specific gravity of the current collector increases, the energy density decreases, and the spatial arrangement inside the cell may become inefficient.

[0085] According to one embodiment of the present invention, the positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; a lithium iron oxide such as LiFe3O4; or a compound with the chemical formula Li 1+c1 Mn 2-c1 Lithium manganese oxides such as O4 (0≤c1≤0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7, etc.; chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented by O2 (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, 0.01≤c2≤0.3); chemical formula LiMn 2-c3 M c3 Examples include lithium manganese composite oxides represented by O2 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn and Ta, satisfying 0.01≤c3≤0.1) or Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu and Zn); and LiMn2O4 in which a portion of the Li in the chemical formula is substituted with alkaline earth metal ions, but are not limited thereto. The anode may also be Li-metal.

[0086] In one embodiment of the present invention, the positive active material may include nickel (Ni), cobalt (Co), and manganese (Mn).

[0087] In one embodiment of the present invention, the positive electrode active material comprises nickel, cobalt, and manganese, and may further comprise aluminum.

[0088] In one embodiment of the present invention, the positive active material layer may include at least one of cobalt, manganese, and aluminum, wherein the nickel content as the positive active material is 60 mol% or more of the metal excluding lithium in 100 mol%. Alternatively, the nickel content may be 70 mol% or more, 75 mol% or more, or 80 mol% or more of the metal excluding lithium in 100 mol%.

[0089] That is, in one embodiment of the present invention, the positive electrode active material may be a lithium complex transition metal compound containing 60 mol% or more and less than 100 mol% of nickel among metals excluding lithium, and the lithium complex transition metal compound may include one or more mixtures of two or more represented by the following chemical formula 1.

[0090] In one embodiment of the present invention, the positive electrode active material layer may include at least one of cobalt, manganese, and aluminum, wherein the nickel content as the positive electrode active material is 80 mol% or more of 100 mol% of the metal excluding lithium. Alternatively, the nickel content may be 80 mol% or more, 85 mol% or more, or 90 mol% or more of 100 mol% of the metal excluding lithium. That is, in one embodiment of the present invention, the positive electrode active material may be a high-nickel positive electrode active material.

[0091] [Chemical Formula 1]

[0092] Li a Ni 1-b-c-d Co b Mn c Q d O 2+δ

[0093] In the above formula, Q is one or more elements selected from the group consisting of Na, K, Mg, Ca, Sr, Ni, Co, Ti, Al, Si, Sn, Mn, Cr, Fe, V, and Zr, and 1≤a≤1.5, 0 <b≤0.5, 0<c≤0.5, 0≤d≤0.1, 0 <b+c+d<1, -0.1≤δ≤1.0이다.

[0094] In the lithium composite transition metal compound of Chemical Formula 1 above, Li may be included in an amount corresponding to a, i.e., 1 ≤ a ≤ 1.5. If a is less than 1, there is a risk of reduced capacity, and if it exceeds 1.5, the particles may sinter during the calcination process, making it difficult to manufacture the cathode active material. Considering the balance between the effect of improving the capacity characteristics of the cathode active material by controlling the Li content and the sinterability during the manufacture of the active material, the Li may more preferably be included in an amount of 1.1 ≤ a ≤ 1.2.

[0095] In the lithium composite transition metal compound of Formula 1 above, Ni may be included in an amount corresponding to 1-(b+c+d), for example, 0.6 ≤ 1-(b+c+d) < 1. If the composition of the lithium composite transition metal compound of Formula 1 above has a Ni content of 0.6 or more, a sufficient amount of Ni is secured to contribute to charging and discharging, thereby enabling high capacity. Preferably, the Ni content 1-(b+c+d) may be 0.6 or more, 0.7 or more, 0.75 or more, 0.8 or more, 0.85 or more, and 0.99 or less, or 0.95 or less.

[0096] In the lithium complex transition metal compound of Chemical Formula 1 above, Co is in an amount corresponding to b, i.e., 0 <b≤0.5로 포함될 수 있다. 상기 화학식 1의 리튬 복합 전이금속 화합물 내 Co의 함량이 0.5를 초과할 경우 비용 증가의 우려가 있다. Co 포함에 따른 용량 특성 개선 효과의 현저함을 고려할 때, 상기 Co는 보다 구체적으로 0.03≤b≤0.2의 함량으로 포함될 수 있다.

[0097] In the lithium complex transition metal compound of Chemical Formula 1 above, Mn has an amount corresponding to c, i.e., 0 <c≤0.5의 함량으로 포함될 수 있다. 상기 화학식 1의 리튬 복합 전이금속 화합물 내 c가 0.5를 초과하면 오히려 전지의 출력 특성 및 용량 특성이 저하될 우려가 있으며, 상기 Mn은 보다 구체적으로 0.01≤c≤0.2의 함량으로 포함될 수 있다.

[0098] In the lithium complex transition metal compound of Chemical Formula 1 above, Q may be a doping element included in the crystal structure of the lithium complex transition metal compound, and Q may be included in an amount corresponding to d, i.e., 0≤d≤0.1. Q may be one or more selected from Na, K, Mg, Ca, Sr, Ni, Co, Ti, Al, Si, Sn, Mn, Cr, Fe, V, and Zr, and for example, Q may be Al.

[0099] In one embodiment of the present invention, the lithium composite transition metal compound may include a single particle.

[0100] In one embodiment of the present invention, the lithium composite transition metal compound may further include secondary particles.

[0101] The above single particle can be manufactured by mixing a transition metal precursor and a lithium raw material and calcining them. The above secondary particle can be manufactured by a different method than the above single particle, and its composition may be the same as or different from the composition of the single particle.

[0102] According to one embodiment of the present invention, the positive active material layer may include a positive conductive material and a positive binder together with the positive active material described above.

[0103] At this time, the above-mentioned positive conductive material is used to impart conductivity to the electrode, and in the battery being constructed, any material that has electronic conductivity without causing chemical changes can be used without special 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, and carbon fibers; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives; carbon nanotubes such as single-walled carbon nanotubes (SWCNT) or multi-walled carbon nanotubes (MWCNT); and among these, one type alone or a mixture of two or more types may be used.

[0104] The content of the positive conductive material in the positive active material layer may be 0.01 to 10 parts by weight, preferably 0.03 to 8 parts by weight, relative to 100 parts by weight of the positive active material layer.

[0105] The above-mentioned 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, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, hydrogenated nitrile rubber (HNBR), or various copolymers thereof, and one of these alone or a mixture of two or more may be used.

[0106] The anode binder may be included in an amount of 0.1 parts by weight or more and 10 parts by weight or less based on 100 parts by weight of the anode active material layer, for example, 0.3 parts by weight or more and 10 parts by weight or less, or 0.5 parts by weight or more and 5 parts by weight or less.

[0107] According to one embodiment of the present invention, a cathode slurry comprising the anode binder and / or the anode conductive material together with the anode active material is provided.

[0108] An anode slurry according to one embodiment of the present invention may further include a solvent for forming an anode slurry. Specifically, the solvent for forming an anode slurry may include N-methyl-2-pyrrolidone (NMP), etc., in terms of facilitating the dispersion of components.

[0109] The above positive active material layer can be formed by applying a positive slurry containing a binder and / or a conductive material together with a positive active material to at least one surface of a positive current collector, and then drying and rolling.

[0110] In one embodiment of the present invention, the loading amount of the positive active material layer per unit area of ​​the positive current collector is 200 mg / 25 cm 2 Up to 500 mg / 25cm 2 The loading amount of the above positive active material layer is, for example, 200 mg / 25 cm 2 Above, 250 mg / 25cm 2 Above, 300 mg / 25cm 2 Above or 350 mg / 25cm 2 That is all, 500 mg / 25cm 2 Below, 450 mg / 25cm 2 Below, 400 mg / 25cm 2 Less than or equal to 380 mg / 25cm 2 It may be less than.

[0111] FIG. 3 is a figure showing a negative electrode of a lithium secondary battery according to one embodiment of the present invention.

[0112] Referring to FIG. 3 above, a cathode (100) including a cathode active material layer (20) on one side of a cathode current collector (10) can be seen, and FIG. 3 shows that the cathode active material layer is formed on one side of the cathode current collector, but it can be included on both sides of the cathode current collector.

[0113] That is, the above-mentioned cathode (100) includes a cathode current collector (10) and a cathode active material layer (20) provided on one or both sides of the cathode current collector.

[0114] In one embodiment of the present invention, the thickness of the cathode (100) refers to the sum of the thicknesses of the cathode current collector (10) and the cathode active material layer (20).

[0115] In one embodiment of the present invention, the weight of the cathode (100) refers to the sum of the weights of the cathode current collector (10) and the cathode active material layer (20).

[0116] In one embodiment of the present invention, the cathode thickness is 70㎛ to 110㎛. For example, the cathode thickness may be 70㎛ or more, 80㎛ or more, or 90㎛ or more, and 110㎛ or less, 105㎛ or less, 103㎛ or less, 100㎛ or less, 97㎛ or less, or 95㎛ or less.

[0117] When the above-mentioned cathode thickness falls within the above range, sufficient reversible capacity of the cathode is secured, thereby providing a safe and space-efficient lithium secondary battery. Specifically, if the cathode thickness is below the lower limit, the lifespan and safety of the battery are degraded due to factors such as an increased possibility of lithium precipitation resulting from a decrease in reversible capacity. On the other hand, if it exceeds the upper limit, the diffusion rate of lithium ions slows down, which negatively affects performance and may have an adverse effect on design optimization within a limited space.

[0118] According to one embodiment of the present invention, the material of the negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc., may be used, and specifically, copper foil may be used. In addition, the negative electrode current collector may form fine irregularities on its surface 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.

[0119] In one embodiment of the present invention, the thickness of the negative current collector may be 1 μm to 15 μm. For example, it may be 1 μm or more, 2.5 μm or more, or 5 μm or more, and 15 μm or less or 10 μm or less. If the thickness of the negative current collector is less than the lower limit, the coating processability of the negative active material layer is reduced, and the resistance of the current collector may increase rapidly. On the other hand, if the thickness exceeds the upper limit, the specific gravity of the current collector increases, the energy density decreases, and the spatial arrangement inside the cell may become inefficient.

[0120] In another embodiment of the present invention, the thickness of the positive current collector may be relatively thick compared to the thickness of the negative current collector. That is, the thickness of the negative current collector may be relatively thin compared to the thickness of the positive current collector. If the positive current collector is thinner than the negative current collector, the current collector resistance may become excessively high, and if the negative current collector, which has a higher density, is thicker, the weight of the entire cell may become heavier.

[0121] According to one embodiment of the present invention, the negative electrode active material comprises a silicon-based active material.

[0122] In one embodiment of the present invention, the silicon-based active material comprises at least one of silicon oxide, silicon metal complex, and silicon carbon composite. Specifically, the silicon-based active material comprises at least one of SiOx (0≤x<2), SiMy (M is a metal, 1≤y≤4), and silicon carbon composite. The silicon-based active material may comprise only one type or two or more types together. When both negative electrode active material layers comprise silicon-based active materials, the silicon-based active material of the same type may be used in the two active material layers, or silicon-based active materials of different types or different combinations may be used.

[0123] The above SiOx(0 <x<2)는 상기 실리콘계 복합 입자 내에서 매트릭스(matrix)에 해당한다. 상기 SiOx(0<x<2)는 Si 및 SiO2가 포함된 형태일 수 있으며, 상기 Si는 상(phase)을 이루고 있을 수도 있다. 즉, 상기 x는 상기 SiOx(0<x<2) 내에 포함된 Si에 대한 O의 개수비에 해당한다. 상기 실리콘계 복합 입자가 상기 SiOx(0<x<2)를 포함하는 경우, 이차 전지의 방전 용량이 개선될 수 있다.

[0124] In one embodiment of the present invention, the silicon-based active material comprises a silicon carbon composite.

[0125] In this specification, “Si / C” refers to a silicon carbon composite. The silicon carbon composite may consist of Si and C that are not bonded to each other, but may include additional components as needed. For example, the silicon carbon composite may or may not include silicon carbide, denoted as SiC or Si-C. If the silicon carbon composite includes silicon carbide, its content is 3 weight percent or less. The silicon carbon composite may exist in a crystalline, amorphous, or mixed state. According to one example, C in the silicon carbon composite may exist in an amorphous state.

[0126] The above silicon-carbon composite may be a composite of silicon and carbon, etc., and may form a structure in which graphite, graphene, or amorphous carbon, etc., surrounds a core composed of silicon and carbon, etc. In the above silicon-carbon composite, the silicon may be nano-silicon.

[0127] The above silicon carbon composite may be a physically or chemically composited carbon and silicon material, and is not limited to any composition in which carbon and silicon material form a composite.

[0128] According to one embodiment of the present invention, the Si / C may comprise porous carbon and silicon deposited on the porous carbon. Specifically, the silicon-carbon composite comprises porous carbon-based particles and silicon particles located on the surface or within the internal pores of the porous carbon-based particles.

[0129] The silicon particles formed on the surface and internal pores of the carbon-based particles may be silicon nanoparticles, and these may be crystalline, semicrystalline, amorphous, or a combination thereof.

[0130] In one embodiment of the present invention, the average particle size (D50) of the silicon-based active material may be 1 μm to 20 μm. For example, the average particle size (D50) of the silicon-based active material may be 1 μm or more, greater than 1 μm, 2 μm or more, or 3 μm or more, and may be 20 μm or less, 15 μm or less, 14 μm or less, 13 μm or less, or 10 μm or less.

[0131] In one embodiment of the present invention, the silicon-based active material generally has a characteristic BET surface area. The BET surface area of ​​the silicon-based active material is preferably 0.01 m² 2 / g to 150 m 2 / g, more preferably 0.1 m 2 / g to 100 m 2 / g, particularly preferably 0.2 m 2 / g to 80 m 2 / g, most preferably 0.2 m 2 / g to 18 m 2 / g. The BET surface area is measured according to DIN 66131 (using nitrogen).

[0132] A negative electrode active material layer according to one embodiment of the present invention may further include an additional negative electrode active material in addition to the silicon-based active material. As the additional 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 βExamples include metal oxides capable of doping and dedoping lithium, such as (0 < β < 2), SnO2, vanadium oxide, lithium titanium 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. Furthermore, the carbon material may include low-crystallinity carbon and high-crystallinity carbon. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0133] One embodiment of the present invention provides a lithium secondary battery further comprising a carbon-based active material as a negative electrode active material. The carbon-based active material may include at least one of artificial graphite and natural graphite.

[0134] That is, according to one embodiment of the present invention, the additional negative electrode active material may be a carbon-based active material. The carbon-based active material may be graphite, and the graphite may include at least one type selected from the group consisting of natural graphite and artificial graphite.

[0135] Specifically, the carbon-based active material may be natural graphite, artificial graphite, or a mixture of natural graphite and artificial graphite.

[0136] The above artificial graphite is generally manufactured by carbonizing raw materials such as coal tar, coal tar pitch, and petroleum-based heavy oils at temperatures above 2,500°C, and is used as a negative electrode active material after undergoing particle size adjustments such as grinding and secondary particle formation following this graphitization. In the case of artificial graphite, crystals are randomly distributed within the particles, and compared to natural graphite, it has a lower degree of sphericity and a somewhat pointed shape.

[0137] In addition, the artificial graphite may have an average particle size (D50) of 5 to 30 μm, preferably 10 to 25 μm.

[0138] The above natural graphite generally exists as plate-like aggregates before processing, and the plate-like particles are manufactured into a spherical shape with a smooth surface through post-processing, such as particle grinding and reassembly, in order to be used as an active material for electrode manufacturing.

[0139] In addition, the natural graphite may have a particle size of 5 to 30 μm, or 10 to 25 μm.

[0140] When the above carbon-based active material is a mixture of artificial graphite and natural graphite, the weight ratio of the artificial graphite and natural graphite may be 9.99 : 0.01 to 0.01 : 9.99, or 9.7 : 0.3 to 7:3. When satisfying this weight ratio range, superior output may be exhibited.

[0141] According to one embodiment of the present invention, the carbon-based active material may be included in an amount of 70 parts by weight or more based on 100 parts by weight of the total negative electrode active material. For example, it may be included in an amount of 70 parts by weight or more, 75 parts by weight or more, 80 parts by weight or more, 90 parts by weight or more, 98 parts by weight or more, or 99 parts by weight or more, and may be included in an amount of 100 parts by weight or less, less than 100 parts by weight, 99 parts by weight or less, 98 parts by weight or less, or 97 parts by weight or less.

[0142] According to one embodiment of the present invention, the silicon-based active material may be included in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the total negative electrode active material. For example, it may be included in an amount of 0.1 parts by weight or more, 1 part by weight or more, 5 parts by weight or more, or 6 parts by weight or more, and may be included in an amount of 10 parts by weight or less, or 9 parts by weight or less. When the silicon-based active material is included within the above range, a secondary battery having high energy density and excellent rapid charging performance can be provided. However, if the silicon-based active material is included below the lower limit, rapid charging performance may be reduced, and if it exceeds the upper limit, cell capacity may be reduced and room temperature life may be reduced due to an imbalance in the irreversible ratio.

[0143] According to one embodiment of the present invention, the cathode active material layer may include a cathode conductive material and a cathode binder together with the cathode active material described above.

[0144] In one embodiment of the present invention, the conductive material may include one or more selected from the group consisting of point-type conductive materials, planar-type conductive materials, and linear-type conductive materials.

[0145] In one embodiment of the present invention, the point-shaped conductive material can be used to improve conductivity of the cathode and refers to a spherical or point-shaped conductive material that has conductivity without causing chemical changes. Specifically, the point-shaped conductive material may be at least one selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, channel black, Farnes black, lamp black, thermal black, conductive fiber, fluorocarbon, aluminum powder, nickel powder, zinc oxide, potassium titanate, titanium oxide, and polyphenylene derivatives, and preferably may include carbon black in terms of achieving high conductivity and excellent dispersibility.

[0146] In one embodiment of the present invention, the point-shaped conductive material has a BET specific surface area of ​​40 m²2 / g or more 70m 2 It may be less than / g, and 45m 2 / g or more 65m 2 / g or less, or 50m 2 / g or more 60m 2 It may be less than / g.

[0147] In one embodiment of the present invention, the conductive material may include a planar conductive material.

[0148] The above-mentioned planar conductive material can be described as a plate-shaped conductive material or a bulk-shaped conductive material, as it can improve conductivity by increasing surface contact between silicon particles within the cathode and simultaneously suppress the interruption of conductive pathways due to volume expansion.

[0149] In one embodiment of the present invention, the planar conductive material may comprise at least one selected from the group consisting of plate-shaped graphite, graphene, graphene oxide, and graphite flakes, and preferably may be plate-shaped graphite.

[0150] In one embodiment of the present invention, the average particle size (D50) of the planar conductive material may be 2 μm to 7 μm, specifically 3 μm to 6 μm, and more specifically 4 μm to 5 μm. When the above range is satisfied, dispersion is easy without causing an excessive increase in the viscosity of the cathode slurry due to the sufficient particle size. Therefore, when dispersion is performed using the same equipment and time, the dispersion effect is excellent.

[0151] In one embodiment of the present invention, the planar conductive material may be a planar conductive material with a high specific surface area having a high BET specific surface area; or a planar conductive material with a low specific surface area.

[0152] In one embodiment of the present invention, a planar conductive material with a high specific surface area or a planar conductive material with a low specific surface area may be used without limitation as the planar conductive material; however, since the planar conductive material according to the present application may be affected to some extent by dispersion in electrode performance, it may be particularly preferable to use a planar conductive material with a low specific surface area that does not cause problems with dispersion.

[0153] In one embodiment of the present invention, the planar conductive material has a BET specific surface area of ​​5 m² 2 It can be more than / g.

[0154] In another embodiment, the planar conductive material has a BET specific surface area of ​​5m² 2 / g or more than 500m 2 It may be less than / g, preferably 5m 2 / g or more than 300m 2 / g or less, more preferably 5m 2 / g or more 250m 2 It may be less than / g.

[0155] In another embodiment, the planar conductive material is a high specific surface area planar conductive material, and has a BET specific surface area of ​​50 m² 2 / g or more than 500m 2 / g or less, preferably 80m 2 / g or more than 300m 2 / g or less, more preferably 100m 2 / g or more than 300m 2 It can satisfy a range of / g or less.

[0156] In another embodiment, the planar conductive material is a low specific surface area planar conductive material, and the BET specific surface area is 5m² 2 / g or more 40m 2 / g or less, preferably 5m 2 / g or more 30m 2 / g or less, more preferably 5m 2 / g or more 25m 2 It can satisfy a range of / g or less.

[0157] Other conductive materials may include linear conductive materials such as carbon nanotubes. The carbon nanotubes may be bundled carbon nanotubes. The bundled carbon nanotubes may comprise a plurality of carbon nanotube units. Specifically, "bundle type" here refers to a secondary shape in the form of a bundle or rope in which a plurality of carbon nanotube units are arranged parallel or intertwined with the axes along the longitudinal direction of the carbon nanotube units having substantially the same orientation, unless otherwise noted. The carbon nanotube units have a graphite sheet having a cylindrical shape with a nano-sized diameter, and sp 2 It has a bonded structure. At this time, depending on the angle and structure in which the graphite plane is rolled, it may exhibit conductive or semiconductor characteristics. Compared to entangled type carbon nanotubes, the bundled carbon nanotubes can be uniformly dispersed during cathode manufacturing and smoothly form a conductive network within the cathode, thereby improving the conductivity of the cathode.

[0158] In one embodiment of the present invention, the linear conductive material may include SWCNT; or MWCNT.

[0159] The content of the cathode conductive material in the above cathode active material layer may be 0.01 to 10 parts by weight, preferably 0.03 to 8 parts by weight, relative to 100 parts by weight of the cathode active material layer.

[0160] The cathode conductive material according to the present invention has a completely separate composition from the anode conductive material applied to the anode. That is, the cathode conductive material according to the present application serves to hold the contact points between silicon-based active materials, which undergo significant volume expansion of the electrodes due to charging and discharging, whereas the anode conductive material serves as a buffer during rolling and provides partial conductivity; thus, their composition and roles are completely different from those of the cathode conductive material of the present invention.

[0161] Furthermore, the cathode conductive material according to the present invention is applied to a silicon-based active material and has a completely different composition from a conductive material applied to a cathode composition containing only a graphite-based active material. That is, a conductive material used in an electrode having a graphite-based active material simply has particles smaller than the active material, thereby providing characteristics that improve output characteristics and impart partial conductivity; thus, its composition and role are completely different from a cathode conductive material applied together with a silicon-based active material as in the present invention.

[0162] In one embodiment of the present invention, the cathode binder may comprise at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, polyacrylamide (PAM), and materials in which hydrogens thereof are substituted with Li, Na, or Ca, and may also comprise various copolymers thereof.

[0163] A cathode binder according to one embodiment of the present invention serves to hold the active material and the conductive material to prevent distortion or structural deformation of the cathode structure, and any general binder that satisfies the above role can be applied.

[0164] In one embodiment of the present invention, the cathode composition is provided such that the cathode binder comprises at least 1 part by weight and no more than 10 parts by weight based on 100 parts by weight of the cathode active material layer.

[0165] In the case of the negative electrode according to the present invention, a silicon-based active material or a modified version thereof is used to maximize capacity characteristics, and compared to a secondary battery using only a conventional carbon-based active material, the volume expansion during charging and discharging is significantly larger. Accordingly, by including the negative electrode binder in the above content portion, it has the characteristic of efficiently controlling the volume expansion of the silicon-based active material with high rigidity during charging and discharging.

[0166] According to one embodiment of the present invention, a cathode slurry comprising the cathode binder and / or the cathode conductive material together with the cathode active material is provided.

[0167] A cathode slurry according to one embodiment of the present invention may further include a solvent for forming the cathode slurry. Specifically, the solvent for forming the cathode slurry may include distilled water or N-methyl-2-pyrrolidone (NMP), etc., in terms of facilitating the dispersion of components.

[0168] In one embodiment of the present invention, the cathode may be formed by applying and drying the cathode slurry on one or both sides of a cathode current collector.

[0169] In one embodiment of the present invention, the loading amount of the negative active material layer per unit area of ​​the negative current collector is 100 mg / 25 cm 2 Up to 220 mg / 25cm 2 The loading amount of the above cathode active material layer is, for example, 100 mg / 25 cm 2 Above, 150 mg / 25cm 2 170 mg / 25cm or higher 2 That is all, 220 mg / 25cm 2 Less than or equal to 180 mg / 25cm 2 It may be less than.

[0170] FIG. 4 is a diagram showing a stacked structure of a lithium secondary battery according to one embodiment of the present invention.

[0171] Referring to FIG. 4, a negative electrode (100) including a negative active material layer (20) on one side of a negative current collector (10) can be seen, and a positive electrode (200) including a positive active material layer (40) on one side of a positive current collector (50) can be seen, and the negative electrode (100) for a lithium secondary battery and the positive electrode (200) for a lithium secondary battery are formed in a stacked structure with a separator (30) in between.

[0172] A lithium secondary battery according to one embodiment of the present specification may include the negative electrode, the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the negative electrode and the positive electrode are each identical to the negative electrode and the positive electrode described above. Since the negative electrode and the positive electrode have been described above, a detailed description thereof is omitted.

[0173] The above separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. Any separator typically used in secondary batteries can 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 from a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and 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 fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and it may optionally be used in a single-layer or multi-layer structure.

[0174] Examples of the above electrolytes that can be used in the manufacture of lithium secondary batteries include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., but are not limited to these.

[0175] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0176] As the above-mentioned non-aqueous organic solvent, for example, aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyl lactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolone, formamide, dimethylformamide, dioxolone, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolone derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, methyl propionate, ethyl propionate, etc. may be used.

[0177] In particular, among the above carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are high-viscosity organic solvents with high dielectric constants that effectively dissociate lithium salts, so they can be used preferably. Furthermore, if low-viscosity, low-dielectric constant linear carbonates such as dimethyl carbonate and diethyl carbonate are mixed with these cyclic carbonates in appropriate proportions, an electrolyte with high electrical conductivity can be produced, making it even more preferable to use.

[0178] The metal salt mentioned above may be a lithium salt, and the lithium salt is a substance that dissolves well in the non-aqueous electrolyte; for example, as the anion of the lithium salt, F - , Cl - , I - , NO3 -, N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - One or more types selected from the group consisting of can be used.

[0179] 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, aluminum trichloride, vinylene carbonate, propanesulfone, lithium tetrafluoroborate, or fluoroethylene carbonate.

[0180] One embodiment of the present invention provides a battery module including a secondary battery according to one embodiment of the present invention.

[0181] One embodiment of the present invention provides a battery pack including a secondary battery according to one embodiment of the present invention.

[0182] One embodiment of the present invention provides a battery pack including a battery module according to one embodiment of the present invention.

[0183] One embodiment of the present invention provides a battery module comprising the secondary battery as a unit cell and a battery pack comprising the secondary battery or the battery module. Since the battery module and the battery pack include the secondary battery having high capacity, high rate capability and cycle capability, they can be used as a power source for a medium-to-large device selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0184] Hereinafter, preferred embodiments are presented to aid in understanding the present invention; however, the above embodiments are merely illustrative of the description, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and spirit of the description, and that such variations and modifications fall within the scope of the appended claims.

[0185] <Preparation Example>

[0186] Example 1

[0187] 1) Manufacture of the anode

[0188] Based on 100 parts by weight of the anode composition, LiNi as the anode active material 0.92 Co 0.04 Mn 0.02 Al 0.02 O2 and LiNi 0.93 Co 0.05 Mn 0.01 Al 0.01An anode slurry was prepared by adding 97 parts by weight of O2 (mixed in a weight ratio of 6:4), 0.8 parts by weight of MWCNT (multi-walled carbon nanotubes) and 0.4 parts by weight of plate-shaped graphite as conductive materials, and 1.8 parts by weight of a mixture of polyvinylidene fluoride (PVDF), hydrogenated nitrile rubber (HNBR), and styrene-EO as binders to N-methyl-2-pyrrolidone (NMP) as a solvent.

[0189] 367.3 mg / cm² of the anode slurry prepared above was applied to one surface of an Al current collector (thickness: 12 µm). 2 A positive electrode was manufactured by applying a loading amount, rolling, and drying in a vacuum oven at 130°C for 10 hours to form a positive electrode active material layer (positive electrode thickness 91.4 μm).

[0190] 2) Preparation of the cathode

[0191] Based on 100 parts by weight of the cathode composition, a carbon-based active material (containing artificial graphite and natural graphite in an 8:2 weight ratio) and a silicon-based active material (silicon carbon composite) were mixed in a weight ratio of 92:8 as cathode active materials. A cathode slurry was prepared by adding 96.54 parts by weight of the cathode active material, 1.8 parts by weight of SBR (Styrene Butadiene Rubber) as a binder, 1.16 parts by weight of Na-CMC (Na-doped Carboxymethyl Cellulose) as a thickener, 0.04 parts by weight of SWCNT (single-walled carbon nanotube) as a conductive material, and 0.46 parts by weight of carbon black to distilled water as a solvent.

[0192] 174.8 mg / cm² of the cathode slurry prepared above on one surface of a Cu current collector (thickness: 6㎛) 2 A cathode was manufactured by applying a loading amount, rolling, and drying in a vacuum oven at 130°C for 10 hours to form a cathode active material layer (cathode thickness 94.4 μm).

[0193] 3) Manufacturing of lithium secondary batteries

[0194] A lithium secondary battery was manufactured by interposing a separator between the anode and the cathode and injecting an electrolyte.

[0195] The above separator was formed by applying and drying a coating solution containing alumina oxide (Al2O3) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co HEP) to a thickness of 6 μm on an 8 μm thick polyethylene (PE) film.

[0196] The above electrolyte was used by adding 0.8 wt% vinylene carbonate (VC), 0.5 wt% propane sulfone (PS), 0.2 wt% lithium tetrafluoroborate (LiBF4), and 3 wt% fluoroethylene carbonate (FEC) based on the total weight of the electrolyte to an organic solvent mixed in a volume ratio of 30:50:20, in which case LiPF6 was added as a lithium salt at a concentration of 1 M.

[0197] Example 2

[0198] 3) In the manufacture of a lithium secondary battery of Example 1, a lithium secondary battery was manufactured in the same manner as in Example 1, except that ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 30:70 as the electrolyte, and vinylene carbonate (VC) was added in an amount of 0.8 wt%, propane sulfone (PS) in an amount of 0.5 wt%, lithium tetrafluoroborate (LiBF4) in an amount of 0.2 wt%, and fluoroethylene carbonate (FEC) in an amount of 30:70 based on the total weight of the electrolyte, and LiPF6 was added as the lithium salt at a concentration of 1 M.

[0199] Example 3

[0200] 1) Manufacture of the anode

[0201] Based on 100 parts by weight of the anode composition, LiNi as the anode active material0.83 Co 0.08 Mn 0.08 Al 0.01 An anode slurry was prepared by adding 97 parts by weight of O2, 1.2 parts by weight of MWCNT (multi-walled carbon nanotubes) as a conductive material, and 1.8 parts by weight of a mixture of polyvinylidene fluoride (PVDF), hydrogenated nitrile rubber (HNBR), and styrene-EO as a binder to N-methyl-2-pyrrolidone (NMP) as a solvent.

[0202] 365.2 mg / cm² of the anode slurry prepared above was applied to one surface of an Al current collector (thickness: 12 µm). 2 A positive electrode was manufactured by applying a loading amount, rolling, and drying in a vacuum oven at 130°C for 10 hours to form a positive electrode active material layer (positive electrode thickness 95.5 μm).

[0203] 2) Preparation of the cathode

[0204] Based on 100 parts by weight of a cathode composition, a cathode slurry was prepared by adding 96.54 parts by weight of graphite (containing artificial graphite and natural graphite in an 8:2 weight ratio) and silicon carbon composite (mixed in a 92:8 weight ratio) as cathode active materials, 1.8 parts by weight of SBR (Styrene Butadiene Rubber) as a binder, 1.16 parts by weight of Na-CMC (Na-doped Carboxymethyl Cellulose) as a thickener, 0.04 parts by weight of SWCNT (single-walled carbon nanotubes) as a conductive material, and 0.46 parts by weight of carbon black to distilled water as a solvent.

[0205] 176.6 mg / cm² of the cathode slurry prepared above on one surface of a Cu current collector (thickness: 6㎛) 2 A cathode was manufactured by applying a loading amount, rolling, and drying in a vacuum oven at 130°C for 10 hours to form a cathode active material layer (cathode thickness 95.0 μm).

[0206] 3) Manufacturing of lithium secondary batteries

[0207] A lithium secondary battery was manufactured by interposing a separator between the anode and the cathode and injecting an electrolyte.

[0208] The above separator was formed by applying and drying a coating solution containing alumina (Al2O3) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co HEP) to a thickness of 6 μm on an 8 μm thick polyethylene (PE) film.

[0209] The above electrolyte was used by adding 0.5 wt% vinylene carbonate (VC), 0.5 wt% propane sulfone (PS), and 3 wt% fluoroethylene carbonate (FEC) based on the total weight of the electrolyte to an organic solvent mixed in a volume ratio of 20:60:20 of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and a fluorine-based solvent (dimethylsulfamoyl fluoride), and adding LiPF6 as a lithium salt at a concentration of 1 M.

[0210] Example 4

[0211] 3) In the manufacture of a lithium secondary battery of Example 3, a lithium secondary battery was manufactured in the same manner as in Example 3, except that 0.8 wt% vinylene carbonate (VC), 0.5 wt% propane sulfone (PS), and 3 wt% fluoroethylene carbonate (FEC) were added to an organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10 based on the total weight of the electrolyte, and LiPF6 was added as a lithium salt at a concentration of 1 M.

[0212] Example 5

[0213] 1) Manufacture of the anode

[0214] Based on 100 parts by weight of the anode composition, LiNi as the anode active material 0.75 Co 0.1 Mn 0.15An anode slurry was prepared by adding 97 parts by weight of O2, 0.8 parts by weight of MWCNT (multi-walled carbon nanotubes) and 0.4 parts by weight of plate-shaped graphite as conductive materials, and 1.8 parts by weight of a mixture of polyvinylidene fluoride (PVDF), hydrogenated nitrile rubber (HNBR), and styrene-EO as binders to N-methyl-2-pyrrolidone (NMP) as a solvent.

[0215] 365.2 mg / cm² of the anode slurry prepared above was applied to one surface of an Al current collector (thickness: 12 µm). 2 A positive electrode was manufactured by applying a loading amount, rolling, and drying in a vacuum oven at 130°C for 10 hours to form a positive electrode active material layer (positive electrode thickness 95.5 μm).

[0216] 2) Preparation of the cathode

[0217] Based on 100 parts by weight of a cathode composition, a cathode slurry was prepared by adding 96.54 parts by weight of graphite (containing artificial graphite and natural graphite in an 8:2 weight ratio) and a silicon carbon composite (mixed in a 92:8 weight ratio) as cathode active materials, 1.8 parts by weight of SBR (Styrene Butadiene Rubber) as a binder, 1.16 parts by weight of Li-CMC (Li-doped Carboxymethyl Cellulose) as a thickener, 0.04 parts by weight of SWCNT (single-walled carbon nanotube) as a conductive material, and 0.46 parts by weight of carbon black to distilled water as a solvent.

[0218] 174.8 mg / cm² of the cathode slurry prepared above on one surface of a Cu current collector (thickness: 6㎛) 2 A cathode was manufactured by applying a loading amount, rolling, and drying in a vacuum oven at 130°C for 10 hours to form a cathode active material layer (cathode thickness 93.9 μm).

[0219] 3) Manufacturing of lithium secondary batteries

[0220] A lithium secondary battery was manufactured by interposing a separator between the anode and the cathode and injecting an electrolyte.

[0221] The above separator was formed by applying and drying a coating solution containing alumina (Al2O3) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co HEP) to a thickness of 6 μm on an 8 μm thick polyethylene (PE) film.

[0222] The above electrolyte was used by adding 0.5 wt% vinylene carbonate (VC), 0.5 wt% propane sulfone (PS), and 3 wt% fluoroethylene carbonate (FEC) based on the total weight of the electrolyte to an organic solvent mixed in a volume ratio of 20:60:20 of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and a fluorine-based solvent (dimethylsulfamoyl fluoride), and adding LiPF6 as a lithium salt at a concentration of 1 M.

[0223] Comparative Example 1

[0224] 1) Manufacture of the anode

[0225] Based on 100 parts by weight of the anode composition, LiNi as the anode active material 0.91 Co 0.08 Mn 0.01 An anode slurry was prepared by adding 297 parts by weight of O2, 0.8 parts by weight of MWCNT (multi-walled carbon nanotubes) and 0.4 parts by weight of plate-shaped graphite as conductive materials, and 1.8 parts by weight of a mixture of polyvinylidene fluoride (PVDF), hydrogenated nitrile rubber (HNBR), and styrene-EO as binders to N-methyl-2-pyrrolidone (NMP) as a solvent.

[0226] 413.1 mg / cm² of the anode slurry prepared above was applied to one surface of an Al current collector (thickness: 12 µm). 2A positive electrode was manufactured by applying a loading amount, rolling, and drying in a vacuum oven at 130°C for 10 hours to form a positive electrode active material layer (positive electrode thickness 104.1 μm).

[0227] 2) Preparation of the cathode

[0228] Based on 100 parts by weight of a cathode composition, a cathode slurry was prepared by adding 96.54 parts by weight of graphite (containing artificial graphite and natural graphite in an 8:2 weight ratio) and a silicon carbon composite (mixed in a 95.5:4.5 weight ratio) as cathode active materials, 1.8 parts by weight of SBR (Styrene Butadiene Rubber) as a binder, 1.16 parts by weight of Na-CMC (Na-doped Carboxymethyl Cellulose) as a thickener, 0.02 parts by weight of SWCNT (single-walled carbon nanotubes) as a conductive material, and 0.48 parts by weight of carbon black to distilled water as a solvent.

[0229] 230.5 mg / cm² of the cathode slurry prepared above on one surface of a Cu current collector (thickness: 6㎛) 2 A cathode was manufactured by applying a loading amount, rolling, and drying in a vacuum oven at 130°C for 10 hours to form a cathode active material layer (cathode thickness 117.7 μm).

[0230] 3) Manufacturing of lithium secondary batteries

[0231] A lithium secondary battery was manufactured by interposing a separator between the anode and the cathode and injecting an electrolyte.

[0232] The above separator was formed by applying and drying a coating solution containing alumina (Al2O3) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co HEP) to a thickness of 6 μm on an 8 μm thick polyethylene (PE) film.

[0233] The above electrolyte was used by adding 0.8 wt% vinylene carbonate (VC), 0.5 wt% propane sulfone (PS), 0.2 wt% lithium tetrafluoroborate (LiBF4), and 3 wt% fluoroethylene carbonate (FEC) based on the total weight of the electrolyte to an organic solvent mixed with ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70, and adding LiPF6 as a lithium salt at a concentration of 1 M.

[0234] Comparative Example 2

[0235] 3) In the manufacture of a lithium secondary battery of Comparative Example 1, a lithium secondary battery was manufactured in the same manner as Comparative Example 1, except that the electrolyte was an organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and a fluorine-based solvent (Dimethylsulfamoyl Fluoride) in a volume ratio of 30:50:20, to which vinylene carbonate (VC) was added in an amount of 0.8 wt%, propane sulfone (PS) in an amount of 0.5 wt%, lithium tetrafluoroborate (LiBF4) in an amount of 0.2 wt%, and fluoroethylene carbonate (FEC) in an amount of 30:50:20 based on the total weight of the electrolyte, and LiPF6 was added as a lithium salt at a concentration of 1 M.

[0236] Comparative Example 3

[0237] 1) Manufacture of the anode

[0238] Based on 100 parts by weight of the anode composition, LiNi as the anode active material 0.62 Co 0.06 Mn 0.32 An anode slurry was prepared by adding 97 parts by weight of O2, 0.8 parts by weight of MWCNT (multi-walled carbon nanotubes) and 0.4 parts by weight of plate-shaped graphite as conductive materials, and 1.8 parts by weight of a mixture of polyvinylidene fluoride (PVDF), hydrogenated nitrile rubber (HNBR), and styrene-EO as binders to N-methyl-2-pyrrolidone (NMP) as a solvent.

[0239] 576.1 mg / cm² of the anode slurry prepared above was applied to one surface of an Al current collector (thickness: 12 µm). 2 A positive electrode was manufactured by applying a loading amount, rolling, and drying in a vacuum oven at 130°C for 10 hours to form a positive electrode active material layer (positive electrode thickness 144 μm).

[0240] 2) Preparation of the cathode

[0241] Based on 100 parts by weight of a cathode composition, a cathode slurry was prepared by adding 96.54 parts by weight of graphite (containing artificial graphite and natural graphite in an 8:2 weight ratio) and a silicon carbon composite (mixed in a 95.5:4.5 weight ratio) as cathode active materials, 1.8 parts by weight of SBR (Styrene Butadiene Rubber) as a binder, 1.16 parts by weight of Na-CMC (Na-doped Carboxymethyl Cellulose) as a thickener, 0.02 parts by weight of SWCNT (single-walled carbon nanotubes) as a conductive material, and 0.48 parts by weight of carbon black to distilled water as a solvent.

[0242] 350.3 mg / cm² of the cathode slurry prepared above was applied to one surface of a Cu current collector (thickness: 6 μm). 2 A cathode was manufactured by applying a loading amount, rolling, and drying in a vacuum oven at 130°C for 10 hours to form a cathode active material layer (cathode thickness 186.68 μm).

[0243] 3) Manufacturing of lithium secondary batteries

[0244] A lithium secondary battery was manufactured by interposing a separator between the anode and the cathode and injecting an electrolyte.

[0245] The above separator was formed by applying and drying a coating solution containing alumina (Al2O3) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co HEP) to a thickness of 6 μm on an 8 μm thick polyethylene (PE) film.

[0246] The above electrolyte was used by adding 0.8 wt% vinylene carbonate (VC), 0.5 wt% propane sulfone (PS), 0.2 wt% lithium tetrafluoroborate (LiBF4), and 3 wt% fluoroethylene carbonate (FEC) based on the total weight of the electrolyte to an organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and adding LiPF6 as a lithium salt at a concentration of 1.2 M.

[0247] Comparative Example 4

[0248] 1) Manufacture of the anode

[0249] Based on 100 parts by weight of the anode composition, LiNi as the anode active material 0.87 Co 0.04 Mn 0.07 Al 0.02 O2 and LiNi 0.86 Co 0.08 Mn 0.06 An anode slurry was prepared by adding 97 parts by weight of O2 (mixed in a weight ratio of 5:5), 0.8 parts by weight of MWCNT (multi-walled carbon nanotubes) and 0.4 parts by weight of plate-shaped graphite as conductive materials, and 1.8 parts by weight of a mixture of polyvinylidene fluoride (PVDF), hydrogenated nitrile rubber (HNBR), and styrene-EO as binders to N-methyl-2-pyrrolidone (NMP) as a solvent.

[0250] 397.1 mg / cm² of the anode slurry prepared above was applied to one surface of an Al current collector (thickness: 12 µm). 2 A positive electrode was manufactured by applying a loading amount, rolling, and drying in a vacuum oven at 130°C for 10 hours to form a positive electrode active material layer (positive electrode thickness 99.1 μm).

[0251] 2) Preparation of the cathode

[0252] Based on 100 parts by weight of a cathode composition, a cathode slurry was prepared by adding 95.57 parts by weight of graphite (containing artificial graphite and natural graphite in an 8:2 weight ratio) and SiO₂ (mixed in a 94:6 weight ratio) as cathode active materials, 2.3 parts by weight of SBR (Styrene Butadiene Rubber) as a binder, 1.13 parts by weight of Na-CMC (Na-doped Carboxymethyl Cellulose) as a thickener, 0.02 parts by weight of SWCNT (single-walled carbon nanotubes) as a conductive material, and 0.98 parts by weight of carbon black to distilled water as a solvent.

[0253] 218.2 mg / cm² of the cathode slurry prepared above on one surface of a Cu current collector (thickness: 6 μm) 2 A cathode was manufactured by applying a loading amount, rolling, and drying in a vacuum oven at 130°C for 10 hours to form a cathode active material layer (cathode thickness 110.51 μm).

[0254] 3) Manufacturing of lithium secondary batteries

[0255] A lithium secondary battery was manufactured by interposing a separator between the anode and the cathode and injecting an electrolyte.

[0256] The above separator was formed by applying and drying a coating solution containing alumina (Al2O3) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co HEP) to a thickness of 6 μm on an 8 μm thick polyethylene (PE) film.

[0257] The above electrolyte was used by adding vinylene carbonate (VC) at 0.8 wt%, propane sulfone (PS) at 0.5 wt%, and lithium tetrafluoroborate (LiBF4) at 0.2 wt% based on the total weight of the electrolyte to an organic solvent mixed with ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70, and adding LiPF6 as a lithium salt at a concentration of 1 M.

[0258] Comparative Example 5.

[0259] In the above Example 3, the above was manufactured in the same manner as Example 1, except that the anode thickness, the range of Formula 1, and the range of Formula 2 were adjusted as shown in Table 2 below.

[0260] Comparative Example 6.

[0261] In the above Example 5, the above was manufactured in the same manner as Example 1, except that the anode thickness, the range of Formula 1, and the range of Formula 2 were adjusted as shown in Table 2 below.

[0262] Experimental Example 1: Full-cell Evaluation

[0263] The following items were evaluated for the above examples and comparative examples and are listed in Table 1 below.

[0264] 1) Energy Density (ED)

[0265] The energy density of the lithium secondary batteries prepared in the above examples and comparative examples was measured using an electrochemical charge / discharge device.

[0266] For the lithium secondary batteries of the examples and comparative examples prepared above, discharge and charge were repeated three times each at 0.33C in the operating voltage range of Table 1 at room temperature (25℃), and the specific capacity of the battery was measured under the 0.33C discharge condition, and the energy density (Wh / L) of the battery was evaluated therefrom.

[0267] Specifically, the discharge was discharged in Constant-Current (CC) mode at 0.33C until the lower voltage was reached, and the charge was charged in CC mode at 0.33C until the upper voltage was reached, and after reaching the upper voltage, the charge was charged in CC / CV mode by gradually reducing the C-rate in a Constant-Voltage (CV) state while maintaining the voltage until it reached 0.05C.

[0268] Energy density (Wh / L) = {[(Discharge capacity (mAh) * Standard voltage (V)) / 1000] / (Cell volume (L))}

[0269] The above standard voltage (Nominal Voltage) was calculated by dividing the Watt Hour measured by the charger / discharger by the discharge capacity.

[0270] 2) Fast charging time evaluation

[0271] For the lithium secondary batteries of the examples and comparative examples prepared above, a rapid charging time evaluation was conducted using an electrochemical charge / discharger. The rapid charging time evaluation was conducted in the range from State of Charge (SOC) 10% to SOC 80%.

[0272] Specifically, the SOC range was first divided into 1% intervals, and the maximum C-rate at which Li-Plating does not occur was measured for each SOC interval. Subsequently, the maximum C-rate measured for each interval was applied to continuously charge from 10% SOC to 80% SOC. The time required to complete charging in this manner (min) was measured to evaluate the rapid charging time.

[0273] Experimental Example 2: Half-cell evaluation

[0274] To evaluate the NP ratio, irreversibility ratio, anode discharge capacity, and anode efficiency, coin half-cells were fabricated for the anodes and cathodes prepared in the examples and comparative examples, respectively, using the following method.

[0275] - Production of positive half-cells

[0276] A coin half-cell was fabricated by inserting a separator between the anode and the lithium metal counter electrode prepared in each example and comparative example and injecting an electrolyte.

[0277] The above separator was formed by applying and drying a coating solution containing alumina oxide (Al2O3) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co HEP) to a thickness of 6 μm on a polyethylene (PE) film with a thickness of 9 μm.

[0278] The above electrolyte was used by adding LiPF6 as a lithium salt at a concentration of 1 M to an organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 30:30:40.

[0279] - Cathode Half Cell Fabrication

[0280] A coin half-cell was fabricated by inserting a separator between the negative electrode and the lithium metal counter electrode prepared in each example and comparative example and injecting an electrolyte. The separator was used in the same way as in the positive half-cell, and for the electrolyte, an organic solvent was prepared by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70, to which vinylene carbonate (VC) was added at 1.5 wt%, propane sulfone (PS) at 0.5 wt%, and LiPF6 as a lithium salt at a concentration of 1 M, based on the total weight of the electrolyte.

[0281] For each of the positive and negative coin half cells manufactured above, the discharge capacity and charge capacity were measured using an electrochemical charge / discharger. When measuring the charge / discharge capacity, the C-rate was set to 0.1C.

[0282] For the positive electrode, for charging, the voltage was set to the upper limit voltage of the operating voltage listed in Table 1 plus 0.05V, the CC / CV condition, and the cut-off current 0.05C, and for discharging, the process was carried out with a lower limit voltage of 2.5V and a CC condition of 0.1C.

[0283] For example, in the case of Example 1, the anode charging upper limit voltage was set to 4.25V, the 0.1C CC / CV condition and the cut-off current to 0.05C, and the discharge was carried out with a lower limit voltage of 2.5V and the 0.1C CC condition, and in the case of Example 3, the anode charging upper limit voltage was set to 4.3V, the 0.1C CC / CV condition and the cut-off current to 0.05C, and the discharge was carried out with a lower limit voltage of 2.5V and the 0.1C CC condition.

[0284] For the cathode, discharge was performed under lower limit voltage of 0.005V, 0.1C CC / CV conditions and cut-off current of 0.005C, and charging was performed under upper limit voltage of 1V and 0.1C CC conditions.

[0285] 1) Evaluation of anode discharge capacity and efficiency

[0286] The discharge capacity of the anode measured above / the charge capacity of the anode was defined as the efficiency of the anode, and the measured discharge capacity and efficiency of the anode were listed in Table 1.

[0287] 2) NP ratio evaluation

[0288] The NP Ratio is defined as the reversible capacity of the cathode / the reversible capacity of the anode, and is calculated from the ratio of discharge capacity per unit area and is listed in Table 1.

[0289] 3) Irreversible ratio

[0290] The irreversible capacity of the anode is the anode charging capacity minus the anode discharging capacity, and the irreversible capacity of the cathode is the cathode charging capacity minus the cathode discharging capacity.

[0291] Irreversibility ratio = Irreversible capacity of anode / Irreversible capacity of cathode

[0292] The above evaluation items are listed in Table 1, and in Table 1 below, Equations 1 and 2 are as follows.

[0293] [Equation 1] (Cathode thickness) / (Anode thickness) * 100%

[0294] In the above Equation 1, the anode thickness refers to the sum of the thicknesses of the anode current collector and the anode active material layer, and the cathode thickness refers to the sum of the thicknesses of the cathode current collector and the cathode active material layer.

[0295] [Equation 2] (Cathode weight) / (Anode weight) * 100%

[0296] In the above Equation 2, the cathode weight refers to the weight of the cathode active material layer, and the anode weight refers to the weight of the anode active material layer.

[0297] Anode Thickness (㎛) Formula 1 (%) Formula 2 (%) Operating Voltage (V) Energy Density (Wh / L) QC (min) NP Ratio (%) Irreversible Ratio (%) Anode Discharge Capacity (mAh / g) Anode Efficiency (%) Example 1 91.4 103.3 47.6 2.5 -4.2 74 2.3 10104.0 91.5 222.5 91 Example 2 91.4 103.3 47.6 2.5 -4.2 74 4.6 10104.0 91.5 222.5 91 Example 3 95.5 99.5 48.4 2.5 -4.3 74 1.1 10104.1 88.5 220.5 91.3 Example 495.599.548.42.5-4.3739.310104.188.5220.591.3 Example 596.297.647.62.5-4.4743.210104.510121690.1 Comparative Example 1104.1113.155.82.5-4.25750.315103.883.1222.591.9 Comparative Example 2104.1113.155.82.5-4.25753.815103.883.1222.591.9 Comparative Example 3144129.660.82.5-4.4672.125108.3125.8196.490.1 Comparative Example 499.1111.554.92.8-4.269320106.1789.120889.95 Comparative Example 5100.6104.9751.062.5-4.3715.61011779.31220.591.3 Comparative Example 695.1695.6329.832.5-4.4765.11510782.821690.1

[0298] Referring to Table 1, it can be seen that Examples 1 to 5 according to one embodiment of the present invention exhibit higher energy density and rapid charging time compared to Comparative Examples 1 to 6. In the case of Comparative Examples 1 to 3, it can be seen that the rapid charging performance is inferior because the anode thickness and Equation 1 do not satisfy the scope of the present invention. In particular, in the case of Comparative Example 4, although the anode thickness satisfies the scope of the present invention, the rapid charging performance is inferior because Equation 1 is not included within the scope of the present invention.

[0299] In addition, in the case of Comparative Example 5, Equation 1 satisfies the range of the present invention, but the cathode weight is excessively higher than the anode weight, so it does not satisfy the range of Equation 2; in this case, it can be confirmed that the energy density is inferior. In the case of Comparative Example 6, similar to Comparative Example 5, the range of Equation 1 is satisfied, but the cathode weight is excessively lower than the anode weight, so it does not satisfy the range of Equation 2; in this case, it can be confirmed that while the energy density itself may be superior, the rapid charging performance is inferior.

[0300] As a result, it was confirmed that excellent rapid charging performance and energy density can be achieved by simultaneously optimizing the anode thickness and the ratio of the anode and cathode thicknesses represented by Equation 1, and optimizing the weight ratio of the anode and cathode represented by Equation 2.

[0301] Although the present invention has been described with reference to embodiments thereof, those skilled in the art will be able to make various applications and modifications within the scope of the present invention based on the above description.

Claims

It includes an anode and a cathode, The above positive electrode comprises a positive current collector; and a positive active material layer provided on one or both sides of the positive current collector, and The above cathode comprises a cathode current collector; and a cathode active material layer provided on one or both sides of the cathode current collector, and The above negative electrode active material layer comprises a carbon-based active material and a silicon-based active material as the negative electrode active material, The anode thickness is 70㎛ to 103㎛, and The electrode thickness ratio represented by the following Formula 1 is 95% to 105%, and A lithium secondary battery having a weight ratio of 30% to 51% as indicated by Formula 2 below: [Equation 1] (Cathode thickness) / (Anode thickness) * 100% In the above Equation 1, the anode thickness refers to the sum of the thicknesses of the anode current collector and the anode active material layer, and the cathode thickness refers to the sum of the thicknesses of the cathode current collector and the cathode active material layer, and [Equation 2] (Cathode weight) / (Anode weight) * 100% In the above Equation 2, the cathode weight refers to the weight of the cathode active material layer, and the anode weight refers to the weight of the anode active material layer. In claim 1, A lithium secondary battery having a negative electrode thickness of 70 μm to 110 μm. In claim 1, The loading amount of the positive active material layer per unit area of ​​the above positive current collector is 200 mg / 25 cm 2 Up to 500 mg / 25cm 2 A lithium secondary battery. In claim 1, The loading amount of the cathode active material layer per unit area of ​​the above cathode current collector is 100 mg / 25 cm 2 Up to 220 mg / 25cm 2 A lithium secondary battery. In claim 1, A lithium secondary battery in which the thickness of the positive current collector is relatively thick compared to the thickness of the negative current collector. In claim 1, A lithium secondary battery having a positive current collector thickness of 5 μm to 20 μm. In claim 1, A lithium secondary battery having a negative current collector thickness of 1 μm to 15 μm. In claim 1, A lithium secondary battery in which the above silicon-based active material includes a silicon carbon composite. In claim 1, A lithium secondary battery comprising the above silicon-based active material in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the above negative electrode active material. In claim 1, A lithium secondary battery in which the carbon-based active material comprises at least one of artificial graphite and natural graphite. In claim 1, A lithium secondary battery in which the positive active material layer is a positive active material having a nickel content of 60 mol% or more of 100 mol% of metals excluding lithium, and comprising at least one of cobalt, manganese, and aluminum. In claim 1, A lithium secondary battery in which the positive electrode active material layer comprises, as a positive electrode active material, a nickel content of 80 mol% or more of 100 mol% of metals excluding lithium, and at least one of cobalt, manganese, and aluminum. In claim 1, A lithium secondary battery having an NP ratio of 104 or greater, expressed by the following Equation 3: [Equation 3] (Reversible capacity of the cathode) / (Reversible capacity of the anode) * 100. A battery module comprising a lithium secondary battery according to any one of claims 1 to 13. A battery pack comprising a lithium secondary battery according to any one of claims 1 to 13. A battery pack comprising the battery module of claim 14.

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