Lithium secondary battery, battery module, and battery pack

Abstract

The present invention relates to a lithium secondary battery. In one embodiment, the lithium secondary battery includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator provided between the positive electrode and the negative electrode, and an electrolyte, the positive electrode active material includes a lithium composite transition metal compound including nickel, cobalt, and manganese, the lithium composite transition metal compound includes at least one of single particles or similar-single particles, the average particle size of at least one of the single particles or similar-single particles is 1 μm or more, the single particle is composed of one node, and the similar-single particle is a complex consisting of 30 nodes or less, the negative electrode active material includes a silicon carbon composite, the average particle size of the silicon carbon composite is more than 1 μm, and the average particle size of at least one of the single particles or similar-single particles is smaller than the average particle size of the silicon carbon composite.

Description

[Technical Field]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2022-0097491 filed with the Korean Intellectual Property Office on August 4, 2022, and the benefit of the filing date of Korean Patent Application No. 10-2023-0091528 filed with the Korean Intellectual Property Office on July 14, 2023, and all contents disclosed in the documents of said Korean patent application are incorporated herein by reference.

[0002] The present application relates to a lithium secondary battery, a battery module, and a battery pack. [Background technology]

[0003] In recent years, with the rapid spread of battery-powered electronic devices, such as mobile phones, laptops, and electric vehicles, as well as power tools and vacuum cleaners, the demand for secondary batteries that are small and lightweight yet have relatively high capacity and / or high output has been rapidly increasing. In particular, lithium secondary batteries, which are lightweight and have high energy density, have been attracting attention as power sources for electronic devices. As a result, active research and development efforts are being made to improve the performance of lithium secondary batteries.

[0004] Lithium secondary batteries have an organic or polymer electrolyte solution filled between a positive electrode and a negative electrode, which are made of active materials that allow for the intercalation and deintercalation of lithium ions. Electrical energy is produced through oxidation and reduction reactions that occur when lithium ions are inserted into and extracted from the positive and negative electrodes.

[0005] Positive electrode active materials used in lithium secondary batteries include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMn2O4, etc.), and lithium iron phosphate compound (LiFePO4). Among these, lithium cobalt oxide (LiCoO2) is widely used as a positive electrode active material for high voltage applications due to its advantages of high operating voltage and excellent capacity characteristics. However, rising cobalt (Co) prices and unstable supply have limited its mass use as a power source in fields such as electric vehicles, creating a need for the development of alternative positive electrode active materials.

[0006] As a result, nickel-cobalt-manganese-based lithium transition metal composite compounds (hereinafter simply referred to as "NCM-based lithium transition metal composite compounds") have been developed, in which some of the cobalt (Co) is replaced with nickel (Ni) and manganese (Mn). In recent years, research has been conducted to increase the Ni content in NCM-based lithium transition metal composite compounds to increase capacity. However, high-nickel (Ni-rich) positive electrode active materials with a high nickel content have drawbacks, such as reduced thermal stability and increased side reactions during electrochemical reactions, resulting in increased resistance and gas generation.

[0007] On the other hand, graphite is commonly used as the negative electrode active material for lithium secondary batteries. However, its low capacity per unit mass (372 mAh / g) makes it difficult to increase the capacity of lithium secondary batteries. Therefore, to increase the capacity of lithium secondary batteries, non-carbon-based negative electrode materials such as silicon, tin, and their oxides have been developed as materials with higher energy densities than graphite. However, while these non-carbon-based negative electrode materials have high capacity, they suffer from low initial efficiency, high lithium consumption during initial charging and discharging, and large irreversible capacity loss. Summary of the Invention [Problem to be solved by the invention]

[0008] The present inventors have discovered that in lithium secondary batteries designed within a limited space, optimal battery performance can be achieved by a specific combination of the type, average particle size, and / or content of each component of the active materials constituting the positive and negative electrodes, and have completed the present invention. [Means for solving the problem]

[0009] One embodiment of the present application provides a lithium secondary battery including: a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; a separator disposed between the positive electrode and the negative electrode; and an electrolyte, wherein the positive electrode active material includes a lithium composite transition metal compound including nickel (Ni), cobalt (Co), and manganese (Mn), and the lithium composite transition metal compound includes at least one of single particles or similar-single particles, wherein at least one of the single particles or similar-single particles has an average particle size (D50) of 1 μm or more, the single particle consisting of one nodule, and the similar-single particles are a complex consisting of 30 nodules or less; and the negative electrode active material includes a silicon carbon composite, wherein the average particle size (D50) of the silicon carbon composite exceeds 1 μm, and the average particle size (D50) of at least one of the single particles or similar-single particles is smaller than the average particle size (D50) of the silicon carbon composite. [Effects of the Invention]

[0010] According to the embodiments described herein, it is possible to increase the energy density of a lithium secondary battery designed in a limited space, improve its high-power performance, and also improve the cycle performance of the battery. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in more detail below to facilitate understanding of the present invention. The present invention may be realized in various different forms and is not limited to the embodiments described herein. In this regard, the terms and words used in the specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as meanings and concepts that are consistent with the technical idea of ​​the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best describe their invention.

[0012] It should be understood that in this specification, the terms "comprises," "includes," or "has" are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, but do not preclude the presence or possible addition of one or more other features, numbers, steps, components, or combinations thereof.

[0013] Furthermore, when a part such as a layer is said to exist "on" or "above" another part, this includes not only the case where it exists "directly above" the other part, but also the case where there is another part between them. Conversely, when a part is said to exist "directly above" another part, it means that there is no other part between them. Furthermore, being "on" or "above" a reference part means being located above or below the reference part, and does not necessarily mean being located "above" or "above" the direction opposite to gravity.

[0014] In the present specification, "and / or" refers to selecting one of the listed items, and "and" refers to all of the listed items. For example, "A and / or B" refers to both the case of "A and B" and the case of "A or B."

[0015] As used herein, the term "single particle" may refer to a particle consisting of a single nodule. The "nodule" may be a single crystal with no grain boundaries, or a polycrystal with no grain boundaries when observed at 5,000 to 20,000 magnifications using a scanning electron microscope (SEM). As used herein, the term "quasi-single particle" may refer to an aggregate consisting of 30 or fewer nodules. As used herein, the term "secondary particle" refers to a particle formed by the aggregation of tens to hundreds of primary particles, and specifically, the secondary particle may include a particle formed by the aggregation of 50 or more primary particles.

[0016] As used herein, "particle" may include at least one of a single particle, a quasi-single particle, a primary particle, a nodule, and a secondary particle.

[0017] In this specification, the "average particle size (D50)" can be defined as the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve of the particles. The average particle size (D50) can be measured, for example, using a laser diffraction method. The laser diffraction method generally enables measurement of particle sizes from the submicron range to several mm, and can provide results with high reproducibility and high resolution.

[0018] The average particle size (D50) can be measured using a Microtrac device (manufacturer: Microtrac, model name: S3500) with water and Triton-X100 dispersant. Specifically, the average particle size (D50) of the positive electrode active material can be measured at a refractive index of 1.5 to 1.7, and that of the negative electrode active material can be measured at a refractive index of 1.97 or 2.42. For example, particles can be dispersed in a dispersion medium, introduced into a commercially available laser diffraction particle size analyzer, and irradiated with ultrasonic waves of about 28 kHz at an output of 60 W. A volume cumulative particle size distribution graph can then be obtained, and the particle size corresponding to 50% of the volume cumulative amount can be determined.

[0019] One embodiment of the present application provides a lithium secondary battery including: a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; a separator disposed between the positive electrode and the negative electrode; and an electrolyte, wherein the positive electrode active material includes a lithium composite transition metal compound including nickel (Ni), cobalt (Co), and manganese (Mn), and the lithium composite transition metal compound includes single particles and / or similar-single particles, and the single particles and / or similar-single particles have an average particle size (D50) of 1 μm or more, the single particle consists of one nodule, and the similar-single particles are a complex consisting of 30 or fewer nodules; and the negative electrode active material includes a silicon carbon composite, and the average particle size (D50) of the silicon carbon composite exceeds 1 μm, and the average particle size (D50) of the single particles and / or similar-single particles is smaller than the average particle size (D50) of the silicon carbon composite.

[0020] The silicon carbon composite may be a Si / C-based active material.

[0021] In this specification, the silicon carbon composite is a composite of Si and C and is distinguished from silicon carbide, which is represented as SiC. Since silicon carbide does not electrochemically react with lithium, all performances, including lifespan, can be measured as zero.

[0022] The silicon carbon composite may be a composite of silicon and graphite, or may have a structure in which a core of silicon and graphite is surrounded by graphene or amorphous carbon. In the silicon carbon composite, the silicon may be nanosilicon. For example, the nanosilicon may be silicon in the range of 1 nm to 999 nm.

[0023] Lithium secondary batteries have a required size depending on the application, and therefore must be designed within a limited space. While consumer demands for increased energy density and improved high-power performance are increasing, the use of high-capacity cathode materials requires an increased content of anode materials to match, limiting the ability to improve battery efficiency within a limited space. Furthermore, depending on the type of anode material, it is necessary to design a cathode material with efficiency that matches the efficiency of the anode material.

[0024] For example, energy density can be improved, but if the porosity of the positive electrode is reduced to increase electrode density, strong rolling may cause cracks in the particles, resulting in a decrease in battery performance.

[0025] The single particles used in the embodiments of the present application have high particle rigidity and relatively low degradation in battery performance even when the electrode density is high. Therefore, the energy density can be increased by combining the single particles and the silicon carbon composite according to the above average particle size range.

[0026] According to a further embodiment of the present application, the positive electrode active material includes a lithium transition metal composite compound including nickel (Ni), cobalt (Co), and manganese (Mn), the lithium transition metal composite compound including single particles and / or similar-single particles, and the single particles and / or similar-single particles have an average particle size (D50) of 1 μm or more.

[0027] As the average particle size (D50) of the single particles decreases, the specific surface area increases, which may increase side reactions with the electrolyte and reduce electrochemical performance such as lifespan. If the average particle size (D50) of the single particles is less than 1 μm, it is not within the range for commercial application, and even if it exists, it may be difficult to apply because the lifespan performance is very low due to the increase in specific surface area.

[0028] When the average particle size (D50) of the single particles is 1 μm or more, 3 μm or more, or 5 μm or more, the single particles have reduced side reactions with the electrolyte solution and have excellent life performance.

[0029] In addition, the negative electrode active material includes a silicon carbon composite, and the silicon carbon composite has an average particle size (D50) of more than 1 μm, and the average particle size (D50) of the single particles and / or quasi-single particles is smaller than the average particle size (D50) of the silicon carbon composite.

[0030] As the average particle size (D50) of the silicon carbon composite decreases, the specific surface area increases, which increases side reactions with the electrolyte and can reduce electrochemical performance such as lifespan. When the average particle size (D50) of the silicon carbon composite is less than 1 μm, the increase in specific surface area increases side reactions, which can result in very poor lifespan, making its application difficult.

[0031] When the average particle size (D50) of the silicon carbon composite is more than 1 μm, more than 3 μm, more than 5 μm, or more than 5 μm, side reactions with the electrolyte are reduced, resulting in excellent life performance.

[0032] The silicon carbon composite has excellent life performance within the above range, and the Si crystal grain size of the silicon carbon composite may be 10 nm or less. Furthermore, the silicon carbon composite has excellent initial capacity and efficiency as well as excellent electrochemical performance compared to other silicon-based materials such as SiO, and can achieve optimal battery performance by combining the average particle size with the single particles.

[0033] The single particles and / or quasi-single particles may have excellent particle strength even when formed into a small particle size, thereby mitigating the phenomenon of an increase in fine particles in the electrode due to particle cracking, thereby improving the life characteristics of the battery.

[0034] When the average particle size (D50) of the monolithic and / or quasi-monolithic particles is smaller than the average particle size (D50) of the silicon carbon composite, the diffusion resistance of the monolithic and / or quasi-monolithic particles is relatively reduced, thereby improving life performance. That is, lithium enters the monolithic and / or quasi-monolithic particles during discharge, and the larger the average particle size (D50) of the monolithic and / or quasi-monolithic particles, the greater the diffusion resistance. When the average particle size (D50) of the monolithic and / or quasi-monolithic particles is larger than the average particle size (D50) of the silicon carbon composite, the relatively increased diffusion resistance causes lithium to precipitate rather than enter the monolithic and / or quasi-monolithic particles, resulting in reduced battery performance and life performance.

[0035] In addition, when the average particle size (D50) of the single particles is smaller than the average particle size (D50) of the silicon carbon composite, the occurrence of side reactions with the electrolyte due to an increase in the specific surface area of ​​the single particles can be prevented, thereby improving the lifespan.

[0036] When the average particle size (D50) of the mono-particles and / or quasi-mono-particles is smaller than the average particle size (D50) of the silicon carbon composite, the diffusion resistance of the mono-particles and / or quasi-mono-particles is relatively reduced, thereby improving the life performance.

[0037] Since the monolithic particles and / or quasi-monolithic particles have a higher lithium diffusion resistance than the silicon carbon composite, if the average particle size (D50) of the monolithic particles and / or quasi-monolithic particles is larger than the average particle size (D50) of the silicon composite, the increased lithium diffusion resistance may result in insufficient charge / discharge and reduced life performance. Therefore, the average particle size (D50) of the monolithic particles and / or quasi-monolithic particles may be smaller than the average particle size (D50) of the silicon carbon composite.

[0038] According to a further embodiment of the present application, the positive electrode active material includes nickel, cobalt, and manganese, and may further include aluminum.

[0039] In this specification, the positive electrode active material contains 80 mol % or more and less than 100 mol % of nickel among metals excluding lithium, and the lithium composite transition metal compound containing 80 mol % or more and less than 100 mol % of nickel among metals excluding lithium may include one or a mixture of two or more types represented by the following chemical formula 1:

[0040] The lithium composite transition metal compound may also include single particles and / or similar-single particles and secondary particles.

[0041] [Chemical formula 1] Li a Ni 1-b-c-d Co b Mn c Q d O 2+δ

[0042] In the 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≦20、-0.1≦δ≦1.0である。

[0043] In the lithium transition metal composite compound of Formula 1, Li may be included in an amount corresponding to a, i.e., 1≦a≦1.5. If a is less than 1, the capacity may decrease, and if it exceeds 1.5, the particles may be sintered during the firing process, making it difficult to prepare the positive electrode active material. Considering the balance between the effect of improving the capacity characteristics of the positive electrode active material by controlling the Li content and the sinterability during the preparation of the active material, the Li may more preferably be included in an amount of 1.1≦a≦1.2.

[0044] In the lithium composite transition metal compound of Chemical Formula 1, Ni may be contained in a content corresponding to 1-(b + c + d), for example, 0.8 ≦ 1-(b + c + d) < 1. If the content of Ni in the lithium composite transition metal compound of Chemical Formula 1 is a composition of 0.8 or more, a sufficient amount of Ni for contributing to charge and discharge is ensured, and high capacity can be achieved. Preferably, 1-(b + c + d), which is the content of Ni, may be 0.88, preferably 0.9 or more, more preferably 0.93 or more. Preferably, 1-(b + c + d), which is the content of Ni, may be 0.99 or less, 0.95 or less.

[0045] In the lithium composite transition metal compound of Chemical Formula 1, Co may be contained in a content corresponding to b, that is, 0 < b ≦ 0.5. When the content of Co in the lithium composite transition metal compound of Chemical Formula 1 exceeds 0.5, there is a risk of cost increase. Considering the remarkable effect of improving the capacity characteristics by including Co, more specifically, Co may be contained in a content of 0.03 ≦ b ≦ 0.2.

[0046] In the lithium composite transition metal compound of Chemical Formula 1, Mn may be contained in a content corresponding to c, that is, a content of 0 < c ≦ 0.5. When c in the lithium composite transition metal compound of Chemical Formula 1 exceeds 0.5, on the contrary, there is a risk of deterioration of the output characteristics and capacity characteristics of the battery, and more specifically, Mn may be contained in a content of 0.01 ≦ c ≦ 0.2.

[0047] In the lithium composite transition metal compound of Chemical Formula 1, Q may be a doping element contained in the crystal structure of the lithium composite transition metal compound, and Q may be contained in a content corresponding to d, that is, 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. For example, Q may be Al.

[0048] According to a further embodiment of the present application, the lithium transition metal composite compound in the positive electrode active material may include single particles and / or similar-single particles and secondary particles.

[0049] The single particles and / or similar-single particles can be prepared by mixing a transition metal precursor and a lithium source material and calcining the mixture. The secondary particles may be prepared by a method different from that for preparing the single particles and / or similar-single particles, and their composition may be the same as or different from that of the single particles and / or similar-single particles.

[0050] For example, the calcination is performed at a temperature that allows the formation of monoparticles and / or quasi-monoparticles. To achieve this, the calcination should be performed at a temperature higher than that used for producing secondary particles. For example, if the precursor composition is the same, the calcination should be performed at a temperature about 30°C to 100°C higher than that used for producing secondary particles. The calcination temperature for forming the monoparticles and / or quasi-monoparticles may vary depending on the metal composition of the precursor. For example, when a high-nickel (Ni) NCM-based lithium transition metal composite oxide having a nickel (Ni) content of 80 mol% or more is to be formed into monoparticles and / or quasi-monoparticles, the calcination temperature may be about 700°C to 1000°C, preferably about 800°C to 950°C. When the calcination temperature satisfies the above range, a positive electrode active material containing monoparticles and / or quasi-monoparticles with excellent electrochemical properties can be produced. If the calcination temperature is lower than 790°C, a positive electrode active material containing a lithium transition metal composite compound in the form of secondary particles may be produced, whereas if the calcination temperature exceeds 950°C, excessive calcination may occur, resulting in insufficient formation of a layered crystal structure and reduced electrochemical properties.

[0051] In this specification, the terms "single particle" and / or "quasi-single particle" are used to distinguish them from conventional secondary particles formed by aggregation of tens to hundreds of primary particles.

[0052] Specifically, in the present invention, a single particle consists of one node, and a similar-single particle is a complex consisting of 30 or less nodes, whereas a secondary particle may be an agglomeration of several hundred primary particles.

[0053] According to a further embodiment of the present application, the average particle size (D50) of the monoparticles and / or quasi-monoparticles is 1 μm or more, and the average particle size (D50) of the silicon carbon composite is greater than 1 μm.

[0054] The monoparticles and / or quasi-monoparticles may have an average particle size (D50) of more than 1 μm, and the silicon carbon composite may have an average particle size (D50) of more than 1 μm.

[0055] According to an embodiment of the present application, the average particle size (D50) of the single particles and / or quasi-single particles is 12 μm or less, and the average particle size (D50) of the silicon carbon composite is less than 15 μm.

[0056] For example, the average particle size (D50) of the single particles and / or similar-single particles may be 1 μm or more and 12 μm or less, 1 μm or more and 8 μm or less, 1 μm or more and 5 μm or less, more than 1 μm and 12 μm or less, more than 1 μm and 8 μm or less, or more than 1 μm and 5 μm or less.

[0057] Even if the average particle size (D50) of the single particles and / or quasi-single particles is small, such as 1 μm to 12 μm, the particle strength can be excellent. For example, the single particles and / or quasi-single particles have a resistance of 650 kgf / cm 2 When the particle is rolled with a force of 650 kgf / cm, the particle strength is 100 MPa to 300 MPa. 2 Even if the electrode is rolled with a strong force, the phenomenon of an increase in fine particles in the electrode due to particle cracking is alleviated, thereby improving the life characteristics of the battery.

[0058] When the average particle size (D50) of the single particles satisfies the above range, the single particles have reduced side reactions with the electrolyte, excellent life performance, sufficient charge / discharge, and excellent electrochemical performance.

[0059] If the average particle size (D50) of the single particles is less than 1 μm, the life performance is very low due to the increase in specific surface area, which may make its application difficult.

[0060] When the average particle size (D50) of the single particles is 12 μm or less, charge / discharge is performed sufficiently and the electrochemical performance is excellent.

[0061] The method for forming the single particles and / or quasi-single particles is not particularly limited, but generally, they may be formed by over-firing at an elevated firing temperature, or they may be produced by using an additive such as a grain growth promoter that is useful for over-firing, or by changing the starting material.

[0062] According to a further embodiment of the present application, the silicon carbon composite may have an average particle size (D50) of more than 1 μm and less than 15 μm, 2 μm or more and 14 μm or less, or 3 μm or more and 13 μm or less.

[0063] Even if the silicon carbon composite has a small average particle size (D50) of more than 1 μm and less than 15 μm, the battery life characteristics can be improved. For example, when the silicon carbon composite has an average particle size (D50) in the range of more than 1 μm and less than 15 μm, the volume expansion and contraction rate during charge and discharge is reduced, improving the battery life. In addition, an excessive increase in specific surface area is prevented, and side reactions with the electrolyte during cycling are prevented, improving the battery life.

[0064] When the average particle size (D50) of the silicon carbon composite is 1 μm or less, the life performance is very low due to the increase in specific surface area, which may make its application difficult.

[0065] When the average particle size (D50) of the silicon carbon composite is less than 15 μm, the particles are small, charging and discharging are performed satisfactorily, and the volume expansion and contraction rate of the particles due to charging and discharging is reduced, thereby improving the life performance.

[0066] According to a further embodiment of the present application, the average particle size (D50) of the monolithic and / or quasi-monlithic particles is smaller than the average particle size (D50) of the silicon carbon composite. As a result, the monolithic and / or quasi-monlithic particles can have excellent particle strength even when formed to a small particle size, thereby mitigating the phenomenon of an increase in fine particles in the electrode due to particle cracking, thereby improving the life characteristics of the battery.

[0067] When the average particle size (D50) of the monolithic particles and / or quasi-monolithic particles is smaller than the average particle size (D50) of the silicon carbon composite, the monolithic particles and / or quasi-monolithic particles, which have a higher lithium diffusion resistance than the silicon carbon composite, have a relatively reduced diffusion resistance, thereby improving the lifespan.

[0068] According to one embodiment of the present application, the average particle size (D50) of the single particle and / or quasi-single particle may be 1 μm to 12 μm smaller than the average particle size (D50) of the silicon carbon composite.

[0069] The average particle size (D50) of the monoparticles and / or quasi-monoparticles may be 1.5 μm to 11.5 μm, or 2 μm to 11 μm smaller than the average particle size (D50) of the silicon carbon composite.

[0070] The average particle size (D50) of the monoparticles and / or quasi-monoparticles may be 2 μm or more, or 4 μm or more, smaller than the average particle size (D50) of the silicon carbon composite. The average particle size (D50) of the monoparticles may be 11 μm or less, 8 μm or less, or 6 μm or less, smaller than the average particle size (D50) of the silicon carbon composite.

[0071] When the average particle size (D50) of the monolithic particles and / or quasi-monolithic particles is smaller than the average particle size (D50) of the silicon carbon composite, for example, when the average particle size (D50) satisfies the above range, the diffusion resistance of the monolithic particles and / or quasi-monolithic particles is relatively reduced, thereby improving the lifespan. That is, as the average particle size (D50) of the monolithic particles and / or quasi-monolithic particles increases, the diffusion resistance may increase. When the average particle size (D50) of the monolithic particles and / or quasi-monolithic particles is larger than the average particle size (D50) of the silicon carbon composite, the diffusion resistance increases relatively, which may cause lithium precipitation, degrading battery performance and lifespan.

[0072] Furthermore, when the average particle size (D50) of the mono-particles and / or quasi-mono-particles is smaller than the average particle size (D50) of the silicon carbon composite, for example, when the average particle size (D50) satisfies the above range, side reactions with the electrolyte due to an increase in specific surface area can be prevented, thereby improving the lifespan.

[0073] According to one embodiment of the present application, the ratio of the average particle size (D50) of the single particles and / or quasi-single particles to the average particle size (D50) of the silicon carbon composite is 1.5:2 to 1.5:20.

[0074] The ratio of the average particle size (D50) of the single particles to the average particle size (D50) of the silicon carbon composite may be 1.5:2 to 1.5:19, or 1.5:2 to 1.5:18.

[0075] The ratio of the average particle size (D50) of the single particles to the average particle size (D50) of the silicon carbon composite may be 1.5:2 or more, 1.5:2.5 or more, 1.5:3.5 or more, or 1.5:4.5 or more. The ratio of the average particle size (D50) of the single particles to the average particle size (D50) of the silicon carbon composite may be 1.5:18 or less, 1.5:16 or less, 1.5:14 or less, 1.5:12 or less, or 1.5:10 or less.

[0076] When the above range is satisfied, the diffusion resistance of the monolithic particles and / or quasi-monolithic particles is relatively reduced, thereby improving the lifespan. That is, as the average particle size (D50) of the monolithic particles and / or quasi-monolithic particles increases, the diffusion resistance may increase. When the average particle size (D50) of the monolithic particles and / or quasi-monolithic particles is larger than the average particle size (D50) of the silicon carbon composite, the diffusion resistance increases relatively, which may cause lithium precipitation, resulting in a decrease in battery performance and lifespan.

[0077] Furthermore, when the average particle size (D50) of the mono-particles and / or quasi-mono-particles is smaller than the average particle size (D50) of the silicon carbon composite, for example, when the average particle size (D50) satisfies the above range, side reactions with the electrolyte due to an increase in specific surface area can be prevented, thereby improving the lifespan.

[0078] In one embodiment of the present application, the lithium transition metal composite compound further includes secondary particles, and the average particle size (D50) of the single particles and / or the similar-single particles may be smaller than the average particle size (D50) of the secondary particles.

[0079] In the present invention, a single particle consists of one nodule, and a similar-single particle may be in the form of a complex consisting of up to 30 nodules.

[0080] The lithium transition metal composite compound may further include secondary particles, which refer to a form formed by aggregation of primary particles and are distinguished from the concept of a single particle consisting of one nodule or a similar-single particle, which is an aggregate consisting of 30 or less nodules.

[0081] The particle diameter (D50) of the secondary particles may be 1 μm to 20 μm, 2 μm to 17 μm, and preferably 3 μm to 15 μm. The specific surface area (BET) of the secondary particles may be 0.05 m 2 / g~10m 2 / g, preferably 0.1m 2 / g~1m 2 / g, more preferably 0.3m 2 / g~0.8m 2 / g.

[0082] In a further embodiment of the present application, the secondary particles may be aggregates of primary particles, and the average particle size (D50) of the primary particles may be 0.5 μm to 3 μm. Specifically, the secondary particles may be in the form of aggregates of several hundred primary particles, and the average particle size (D50) of the primary particles may be 0.6 μm to 2.8 μm, 0.8 μm to 2.5 μm, or 0.8 μm to 1.5 μm.

[0083] When the average particle size (D50) of the agglomerated primary particles in the secondary particles satisfies the above range, a single particle and / or quasi-single particle positive electrode active material with excellent electrochemical properties can be formed. If the average particle size (D50) of the agglomerated primary particles in the secondary particles is too small, the number of agglomerated primary particles forming the lithium nickel-based oxide particles increases, reducing the effect of suppressing particle cracking during rolling. If the average particle size (D50) of the agglomerated primary particles in the secondary particles is too large, the lithium diffusion path within the primary particles becomes longer, increasing resistance and potentially reducing output characteristics.

[0084] According to a further embodiment of the present application, the average particle size (D50) of the single particles and / or quasi-single particles is smaller than the average particle size (D50) of the secondary particles. As a result, the single particles and / or quasi-single particles can have excellent particle strength even when formed to a small particle size, thereby mitigating the phenomenon of an increase in fine particles in the electrode due to particle cracking, thereby improving the life characteristics of the battery.

[0085] In one embodiment of the present application, the average particle size (D50) of the single particles and / or quasi-single particles may be smaller than the average particle size (D50) of the secondary particles by 1 μm to 18 μm.

[0086] For example, the average particle size (D50) of the single particles and / or quasi-single particles may be 1 μm to 16 μm smaller, 1.5 μm to 15 μm smaller, or 2 μm to 14 μm smaller than the average particle size (D50) of the secondary particles.

[0087] The average particle size (D50) of the mono-particles and / or quasi-mono-particles may be 1 μm or more, 2 μm or more, 4 μm or more, or 6 μm or more smaller than the average particle size (D50) of the secondary particles. The average particle size (D50) of the mono-particles and / or quasi-mono-particles may be 18 μm or less, 16 μm or less, 14 μm or less, 12 μm or less, 10 μm or less, or 8 μm or less smaller than the average particle size (D50) of the secondary particles.

[0088] When the average particle size (D50) of the single particles and / or quasi-single particles is smaller than the average particle size (D50) of the secondary particles, for example, when the above range is satisfied, the single particles and / or quasi-single particles can have excellent particle strength even when formed to a small particle size, thereby mitigating the phenomenon of an increase in fine particles in the electrode due to particle cracking, thereby improving the life characteristics and energy density of the battery.

[0089] In one embodiment of the present application, the negative electrode active material may further include graphite, and the average particle size (D50) of the silicon carbon composite may be smaller than the average particle size (D50) of the graphite.

[0090] When the average particle size (D50) of the silicon carbon composite is smaller than the average particle size (D50) of the graphite, the volume expansion / contraction rate during charge / discharge is reduced, thereby reducing particle cracking and improving the battery life.

[0091] According to one embodiment of the present application, the average particle size (D50) of the silicon carbon composite is smaller than the average particle size (D50) of the graphite by 1 μm to 25 μm.

[0092] For example, the average particle size (D50) of the silicon-carbon composite may be 2 μm to 24 μm smaller than the average particle size (D50) of the graphite, may be 3 μm to 23 μm smaller, or may be 4 μm to 22 μm smaller.

[0093] The average particle size (D50) of the silicon-carbon composite may be 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, 5 μm or more, 6 μm or more, 7 μm or more, 8 μm or more, 9 μm or more, or 10 μm or more smaller than the average particle size (D50) of the graphite. The average particle size (D50) of the silicon-carbon composite may be 25 μm or less, 23 μm or less, 22 μm or less, 20 μm or less, 18 μm or less, 16 μm or less, or 14 μm or less smaller than the average particle size (D50) of the graphite.

[0094] When the average particle size (D50) of the silicon-carbon composite is smaller than the average particle size (D50) of the graphite, for example, when the above range is satisfied, there is an effect that the life performance of the battery is improved.

[0095] In one embodiment of the present application, the lithium composite transition metal compound further includes secondary particles, the negative electrode active material further includes graphite, and the average particle sizes (D50) of the secondary particles, the single particles and / or similar-single particles, the graphite, and the silicon-carbon composite are represented by A, B, C, and D, respectively, and B < D ≤ A < C.

[0096] The embodiments of the secondary particles, the single particles and / or similar-single particles, the graphite, and the silicon-carbon composite are as described above.

[0097] When the average particle sizes (D50) of the secondary particles, the single particles and / or similar-single particles, the graphite, and the silicon-carbon composite are A, B, C, and D, respectively, when B < D ≤ A < C, there is an effect that the life performance of the battery is improved.

[0098] According to one embodiment of the present application, the negative electrode active material further comprises graphite, and the average particle diameters (D50) of the single particle and / or quasi-single particle, the graphite, and the silicon carbon composite are represented by B, C, and D, respectively; <D<Cである。

[0099] The average particle sizes (D50) of the secondary particles, the single particles and / or similar-single particles, and the silicon carbon composite are represented by A, B, and D, respectively; <D≦Aであってもよい。

[0100] The average particle diameters (D50) of the secondary particles, the single particles and / or similar-single particles, and the graphite are represented by A, B, and C, respectively; <A<Cであってもよい。

[0101] The average particle diameters (D50) of the secondary particles, the graphite, and the silicon carbon composite are represented by A, C, and D, respectively, and D≦A <Cであってもよい。

[0102] When the above range is satisfied, the battery life performance is improved.

[0103] In one embodiment of the present application, in the lithium secondary battery according to the above-described embodiment, the monoparticles and / or quasi-monoparticles may be included in an amount of 15 parts by weight to 100 parts by weight based on 100 parts by weight of the positive electrode active material, and the silicon carbon composite may be included in an amount of 3 parts by weight to 30 parts by weight based on 100 parts by weight of the negative electrode active material.

[0104] According to a further embodiment of the present application, the single particles and / or quasi-single particles may be included in an amount of 15 to 100 parts by weight relative to 100 parts by weight of the positive electrode active material, or 20 to 100 parts by weight, 30 to 100 parts by weight, 40 to 100 parts by weight, or 50 to 100 parts by weight relative to 100 parts by weight of the positive electrode active material.

[0105] For example, the monoparticles and / or quasi-monoparticles may be included in an amount of 15 parts by weight or more, 20 parts by weight or more, 25 parts by weight or more, 30 parts by weight or more, 35 parts by weight or more, 40 parts by weight or more, 45 parts by weight or more, or 50 parts by weight or more, based on 100 parts by weight of the positive electrode active material. The monoparticles and / or quasi-monoparticles may be included in an amount of 100 parts by weight or less, based on 100 parts by weight of the positive electrode active material.

[0106] When the monolayer particles and / or quasi-monolayer particles are contained in the above range, excellent battery characteristics can be exhibited in combination with the above-mentioned negative electrode material. In particular, when the monolayer particles and / or quasi-monolayer particles are contained in an amount of 15 parts by weight or more, the increase in fine particles in the electrode due to particle cracking during the rolling process after electrode fabrication can be mitigated, thereby improving the battery life characteristics.

[0107] In one embodiment of the present application, the lithium composite transition metal compound may further include secondary particles, and the secondary particles may be included in an amount of 0 to 85 parts by weight, 0 to 70 parts by weight, or 0 to 50 parts by weight relative to 100 parts by weight of the positive electrode active material.

[0108] The amount of the secondary particles may be 85 parts by weight or less, 80 parts by weight or less, 75 parts by weight or less, 70 parts by weight or less, 65 parts by weight or less, 60 parts by weight or less, 55 parts by weight or less, or 50 parts by weight or less, relative to 100 parts by weight of the positive electrode active material. The amount of the secondary particles may be 0 parts by weight or more, or 20 parts by weight or more, relative to 100 parts by weight of the positive electrode active material.

[0109] When the above range is satisfied, the above-described effects due to the presence of the single particle and / or quasi-single particle positive electrode active material can be maximized. When a secondary particle positive electrode active material is included, the components thereof may be the same as or different from those exemplified as the single particle and / or quasi-single particle positive electrode active material described above, and may refer to the form of aggregation of single particles.

[0110] In one embodiment of the present application, the positive electrode active material may be contained in an amount of 80 parts by weight or more and 99.9 parts by weight or less, preferably 90 parts by weight or more and 99.9 parts by weight or less, more preferably 95 parts by weight or more and 99.9 parts by weight or less, and even more preferably 98 parts by weight or more and 99.9 parts by weight or less, relative to 100 parts by weight of the positive electrode active material layer.

[0111] According to one embodiment of the present application, the positive electrode according to the above-described embodiment may further include a positive electrode binder and a conductive material.

[0112] The positive electrode binder may serve to improve adhesion between positive electrode active material particles and between the positive electrode active material particles and the positive electrode current collector. Any positive electrode binder known in the art may be used, and non-limiting examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof. These may be used alone or in combination.

[0113] The positive electrode binder may be included in an amount of 0.1 parts by weight to 50 parts by weight, for example, preferably 0.3 parts by weight to 35 parts by weight, more preferably 0.5 parts by weight to 20 parts by weight, based on 100 parts by weight of the positive electrode active material layer.

[0114] The conductive material contained in the positive electrode active material layer is used to impart conductivity to the electrode, and can be any material that has electronic conductivity without causing chemical changes in the battery. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives. These may be used alone or in combination.

[0115] Specifically, in one embodiment, the conductive material may include one or more of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). The conductive material may be included in an amount of 0.1 to 2 parts by weight, preferably 0.3 to 1.5 parts by weight, more preferably 0.5 to 1.2 parts by weight, based on 100 parts by weight of the composition for a positive electrode active material layer.

[0116] In this specification, the silicon carbon composite is a composite of Si and C, and peaks of Si and C (graphite) are observed in the XRD diffraction pattern, indicating that a second phase, Si / C, is not formed. The silicon carbon composite is to be distinguished from silicon carbide insulators, which are represented by SiC.

[0117] According to the above-described embodiment of the present application, the negative electrode active material layer may contain 3 to 30 parts by weight of the silicon carbon composite relative to 100 parts by weight of the total negative electrode active material. According to one example, the negative electrode active material layer may contain 3 to 20 parts by weight, or 3 to 13 parts by weight, preferably 5 to 10 parts by weight of the silicon carbon composite relative to 100 parts by weight of the total negative electrode active material.

[0118] The negative electrode active material layer may contain 3 parts by weight or more, 4 parts by weight or more, or 5 parts by weight or more of the silicon carbon composite relative to 100 parts by weight of the total negative electrode active material, and 30 parts by weight or less, 20 parts by weight or less, or 10 parts by weight or less of the silicon carbon composite relative to 100 parts by weight of the total negative electrode active material.

[0119] By using a silicon carbon composite in this range, excellent battery characteristics can be achieved in combination with the above-mentioned positive electrode material. In particular, when the silicon carbon composite is contained in an amount of 3 parts by weight or more, the effects of using the silicon carbon composite can be fully demonstrated. Furthermore, since the silicon carbon composite has a higher capacity than an SiOx-based active material, it is difficult to balance the capacity with the positive electrode active material when used in excess. In particular, when the silicon carbon composite is contained in an amount of 30 parts by weight or less, expansion during charge and discharge can be prevented and cycle characteristics can be improved.

[0120] The silicon carbon composite is a material that has higher capacity and higher efficiency than silicon-based oxides, and even when it does not contain a conductive material, it can exhibit superior resistance effects compared to anodes that contain silicon-based oxides and conductive materials. Furthermore, the silicon carbon composite exhibits higher Si crystallinity than silicon-based oxides, and therefore exhibits superior effects during high-power evaluation.

[0121] According to a further embodiment of the present application, in the lithium secondary battery according to the above embodiment, the negative electrode active material may further include a carbon-based active material. Specifically, the carbon-based active material may be graphite. The graphite may be natural graphite, artificial graphite, or a mixture thereof. The graphite may be included in an amount of 70 to 97 parts by weight based on 100 parts by weight of the total negative electrode active material included in the negative electrode active material layer.

[0122] The graphite may be included in an amount of 75 parts by weight or more, 80 parts by weight or more, or 85 parts by weight or more, based on 100 parts by weight of the total negative electrode active material. The graphite may be included in an amount of 95 parts by weight or less, 93 parts by weight or less, or 90 parts by weight or less, based on 100 parts by weight of the total negative electrode active material. When the graphite is a mixture of artificial graphite and natural graphite, the artificial graphite and natural graphite may be included in an amount of 90:10 parts by weight to 50:50 parts by weight, 85:15 parts by weight to 60:40 parts by weight, or 80:20 parts by weight to 65:35 parts by weight, based on 100 parts by weight of the graphite.

[0123] In one embodiment of the present application, the negative electrode active material may be contained in an amount of 80 parts by weight or more and 99.9 parts by weight or less, preferably 90 parts by weight or more and 99.9 parts by weight or less, more preferably 95 parts by weight or more and 99.9 parts by weight or less, and even more preferably 98 parts by weight or more and 99.9 parts by weight or less, relative to 100 parts by weight of the negative electrode active material layer.

[0124] According to a further embodiment of the present application, in the lithium secondary battery according to the above-described embodiment, the negative electrode active material layer may further include a negative electrode binder in addition to the silicon carbon composite and graphite.

[0125] The negative electrode binder may improve adhesion between negative electrode active material particles and between the negative electrode active material particles and the negative electrode current collector. Any material known in the art may be used as the negative electrode binder. Non-limiting examples of the negative electrode binder include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, and substances in which hydrogen is substituted with Li, Na, Ca, or the like, or various copolymers thereof.

[0126] The negative electrode binder may be included in an amount of 0.1 parts by weight to 50 parts by weight, for example, preferably 0.3 parts by weight to 35 parts by weight, more preferably 0.5 parts by weight to 10 parts by weight, based on 100 parts by weight of the negative electrode active material layer.

[0127] The negative electrode active material layer may not contain a conductive material, but may further contain a conductive material if necessary. The conductive material contained in the negative electrode active material layer is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. For example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fibers or metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives may be used. The content of the conductive material in the negative electrode active material layer may be 0.01 to 30 parts by weight, preferably 0.03 to 25 parts by weight, per 100 parts by weight of the negative electrode active material layer.

[0128] In one embodiment of the present application, the positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and including the positive electrode active material.

[0129] The positive electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like may be used. The positive electrode current collector may typically have a thickness of 1 μm to 500 μm, and fine irregularities may be formed on the surface of the positive electrode current collector to enhance the adhesive strength of the positive electrode active material. The positive electrode current collector may be used in various forms, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0130] In one embodiment of the present application, the negative electrode may include a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector and including the negative electrode active material.

[0131] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. For example, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, or the like. Specifically, a transition metal that easily adsorbs carbon, such as copper or nickel, may be used as the current collector. The thickness of the negative electrode current collector may be 1 μm to 500 μm, but the thickness of the current collector is not limited thereto.

[0132] In one embodiment of the present application, the positive electrode further includes a positive electrode active material layer containing the positive electrode active material, and the negative electrode further includes a negative electrode active material layer containing the negative electrode active material, and the positive electrode and negative electrode active material layers may each have a thickness of 10 μm to 500 μm. The thickness of the positive electrode active material layer may be 90% to 110%, for example, 95% to 105%, of the thickness of the negative electrode active material layer, or these thicknesses may be the same. Specifically, the thickness of the positive electrode and negative electrode active material layers may each be 15 μm to 400 μm, 20 μm to 300 μm, 25 μm to 200 μm, or 30 μm to 100 μm.

[0133] In one embodiment of the present application, the positive electrode further includes a positive electrode active material layer containing the positive electrode active material, and the loading amount per unit volume of the positive electrode active material layer is 250 mg / 25 cm 2 ~900mg / 25cm 2 The negative electrode further includes a negative electrode active material layer containing the negative electrode active material, and the loading amount per unit volume of the negative electrode active material layer is 100 mg / 25 cm 2 ~600mg / 25cm 2 Specifically, the loading amount per unit volume of the positive electrode active material layer may be 270 mg / 25 cm 2 ~800mg / 25cm 2 , 285mg / 25cm 2 ~700mg / 25cm 2 , or 300 mg / 25 cm 2~600mg / 25cm 2 The loading amount per unit volume of the negative electrode active material layer may be 120 mg / 25 cm 2 ~500mg / 25cm 2 , 135mg / 25cm 2 ~400mg / 25cm 2 , or 150 mg / 25 cm 2 ~300mg / 25cm 2 may be.

[0134] The positive and negative electrodes can be fabricated by a conventional method for fabricating positive and negative electrodes, except for the use of the positive and negative electrode active materials. Specifically, the active material layer-forming composition, including the active material and, optionally, a binder and a conductive material, can be coated on a current collector, followed by drying and rolling. The types and contents of the positive and negative electrode active materials, binder, and conductive material are as described above. The solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and may be used alone or in combination. The amount of solvent used should be sufficient to dissolve or disperse the active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the slurry, and to provide a viscosity that allows excellent thickness uniformity when applied to fabricate positive and negative electrodes. Alternatively, the positive electrode and the negative electrode can be produced by casting the active material layer-forming composition on a separate support, peeling the composition from the support, and laminating the resulting film on a current collector.

[0135] The separator separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator typically used in secondary batteries can be used without particular limitation. It is particularly preferred that the separator exhibits low resistance to electrolyte ion migration and excellent electrolyte humidification. Specifically, porous polymer films, such as those made from polyolefin polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminates of two or more layers thereof, may be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made from high-melting-point glass fibers or polyethylene terephthalate fibers, may also be used. To ensure heat resistance or mechanical strength, a separator coated with a ceramic component or a polymeric material may be used, and may be selectively used as a single-layer or multi-layer structure.

[0136] Examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in manufacturing lithium secondary batteries.

[0137] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0138] Examples of the non-aqueous organic solvent that can be used include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0139] In particular, among the carbonate organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, can be preferably used as high-viscosity organic solvents, because they have a high dielectric constant and dissociate lithium salts well. When such cyclic carbonates are mixed in an appropriate ratio with linear carbonates having low viscosity and low dielectric constants, such as dimethyl carbonate and diethyl carbonate, an electrolyte having high electrical conductivity can be prepared, and therefore such cyclic carbonates can be used more preferably.

[0140] The metal salt may be a lithium salt, which is a substance that is easily dissolved in the non-aqueous electrolyte solution. For example, the anion of the lithium salt may be 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 selected from the group consisting of:

[0141] In addition to the constituent components of the electrolyte, the electrolyte may further contain one or more additives, such as a haloalkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivative, sulfur, quinoneimine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing a decrease in battery capacity, and improving the discharge capacity of the battery.

[0142] The energy density of a lithium secondary battery according to one embodiment of the present application is 400 Wh / L to 900 Wh / L. Specifically, the energy density of the lithium secondary battery may be 425 Wh / L to 875 Wh / L, 450 Wh / L to 850 Wh / L, 475 Wh / L to 825 Wh / L, or 500 Wh / L to 800 Wh / L. When the above range is satisfied, the energy density of a lithium secondary battery designed in a limited space can be increased, and high-power performance and cycle performance of the battery can also be improved.

[0143] The lithium secondary battery according to an embodiment of the present invention may be a cylindrical battery. The cylindrical battery may refer to a battery having a cylindrical shape, including an assembly including a positive electrode, a negative electrode, a separator, and an electrolyte. Specifically, the battery may be composed of a cylindrical can, a battery assembly disposed inside the cylindrical can, and a top cap. However, the lithium secondary battery is not limited thereto and may be a prismatic battery or a pouch-type battery.

[0144] In a further embodiment of the present invention, there is provided a battery module including the cylindrical battery as a unit cell, and a battery pack including the same. The battery module and the battery pack include the secondary battery having high capacity, high rate characteristics, and high cycle characteristics, and therefore can be used as a power source for medium- to large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0145] The lithium secondary battery according to the present invention stably exhibits excellent discharge capacity, output characteristics, and cycle performance, and can be used as a power source for medium- to large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems, as well as portable devices such as mobile phones, laptops, and digital cameras. For example, the battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as power tools; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems. [Example]

[0146] Below, preferred examples are presented to help understand the present invention, but these examples are merely for the purpose of illustrating the present description, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and technical spirit of the present description, and it is natural that such changes and modifications fall within the scope of the appended claims.

[0147] Example 1 A positive electrode active material layer-forming composition was prepared using 98.04 parts by weight of a lithium composite transition metal compound containing 93.3 mol% Ni, 4.9 mol% Co, and 1.8 mol% Mn (excluding lithium) as the positive electrode active material (based on 100 parts by weight of the positive electrode active material layer), including single particles and / or quasi-single particles and secondary particles (single particles and / or quasi-single particles:secondary particles = 80:20 weight ratio), 1 part by weight of PVDF as a binder, and a CNT pre-dispersion containing 0.8 parts by weight of CNTs and 0.16 parts by weight of a dispersant as a conductive material. The single particles and / or quasi-single particles were milled to a D50 of 3 μm using an airflow milling method, and the secondary particles were milled to a D50 of 7 μm. The positive electrode active material layer-forming composition was coated onto a 30 μm-thick aluminum foil to a dry thickness of 103 μm and then dried to prepare a positive electrode.

[0148] A negative electrode active material layer-forming composition was prepared using 97.7 parts by weight of graphite (artificial graphite:natural graphite = 70:30 weight ratio, 90 parts by weight based on 100 parts by weight of negative electrode active material) and silicon carbon composite (10 parts by weight based on 100 parts by weight of negative electrode active material) as negative electrode active materials, 1.15 parts by weight of SBR (styrene-butadiene rubber) and 1 part by weight of CMC (carboxymethyl cellulose) as binders, 0.09 parts by weight of dispersant, and 0.06 parts by weight of single-walled CNTs. The silicon carbon composite was milled to a D50 of 5 μm using an airflow milling method, and the graphite was milled to a D50 of 17 μm. The negative electrode active material layer-forming composition was coated onto a 15 μm-thick copper foil to a dry thickness of 86 μm and then dried to prepare a negative electrode.

[0149] A separator was placed between the positive electrode and the negative electrode, and the electrodes were stacked. An electrolyte (1.0 M LiPF6, EC (ethylene carbonate) / EMC (ethyl methyl carbonate) = 30 / 70 (Vol%), VC (vinylene carbonate) 1.5%) was then poured into the stack to prepare a battery.

[0150] <Example 2> A positive electrode was prepared in the same manner as in Example 1, except that the weight ratio of the single particle and / or quasi-single particle and secondary particle lithium composite transition metal compound was 50:50 based on 100 parts by weight of the positive electrode active material.

[0151] Example 3 A positive electrode was prepared in the same manner as in Example 1, except that the amount of the single particles and / or quasi-single particles was 100 parts by weight based on 100 parts by weight of the positive electrode active material.

[0152] Example 4 A negative electrode was manufactured in the same manner as in Example 3, except that the D50 of the silicon carbon composite contained in the negative electrode active material layer was 9 μm.

[0153] <Example 5> A negative electrode was prepared in the same manner as in Example 3, except that the amount of the silicon carbon composite was 5 parts by weight based on 100 parts by weight of the negative electrode active material.

[0154] Example 6 A negative electrode was manufactured in the same manner as in Example 1, except that the D50 of the silicon carbon composite contained in the negative electrode active material layer was 7 μm.

[0155] Example 7 A positive electrode was manufactured in the same manner as in Example 3, except that the D50 of the single particles and / or quasi-single particles contained in the positive electrode active material layer was 1 μm.

[0156] Example 8 Positive and negative electrodes were manufactured in the same manner as in Example 2, except that the D50 of the monoparticles and / or quasi-monoparticles contained in the positive electrode active material layer was 1 μm, the D50 of the secondary particulate lithium transition metal composite compound was 5 μm, and the D50 of the silicon carbon composite contained in the negative electrode active material layer was 3 μm.

[0157] Example 9 A negative electrode was manufactured in the same manner as in Example 8, except that the D50 of the graphite contained in the negative electrode active material layer was 25 μm.

[0158] Example 10 Positive and negative electrodes were manufactured in the same manner as in Example 8, except that the D50 of the secondary particulate lithium transition metal compound contained in the positive electrode active material layer was 7 μm and the D50 of the graphite contained in the negative electrode active material layer was 13 μm.

[0159] Example 11 A negative electrode was manufactured in the same manner as in Example 10, except that the D50 of the graphite contained in the negative electrode active material layer was 17 μm.

[0160] Example 12 A negative electrode was manufactured in the same manner as in Example 10, except that the D50 of the graphite contained in the negative electrode active material layer was 25 μm.

[0161] Example 13 A positive electrode was produced in the same manner as in Example 10, except that the secondary particulate lithium transition metal compound contained in the positive electrode active material layer had a D50 of 9 μm.

[0162] Example 14 A negative electrode was manufactured in the same manner as in Example 13, except that the D50 of the graphite contained in the negative electrode active material layer was 17 μm.

[0163] Example 15 A negative electrode was manufactured in the same manner as in Example 13, except that the D50 of the graphite contained in the negative electrode active material layer was 25 μm.

[0164] Example 16 A positive electrode was produced in the same manner as in Example 8, except that the secondary particulate lithium transition metal compound contained in the positive electrode active material layer had a D50 of 15 μm.

[0165] Example 17 A negative electrode was manufactured in the same manner as in Example 10, except that the D50 of the silicon carbon composite contained in the negative electrode active material layer was 5 μm.

[0166] Example 18 A negative electrode was manufactured in the same manner as in Example 17, except that the D50 of the graphite contained in the negative electrode active material layer was 17 μm.

[0167] Example 19 A negative electrode was manufactured in the same manner as in Example 17, except that the D50 of the graphite contained in the negative electrode active material layer was 25 μm.

[0168] Example 20 A positive electrode was produced in the same manner as in Example 18, except that the secondary particulate lithium transition metal compound contained in the positive electrode active material layer had a D50 of 9 μm.

[0169] Example 21 Positive and negative electrodes were produced in the same manner as in Example 8, except that the secondary particle-like lithium transition metal compound contained in the positive electrode active material layer had a D50 of 3 μm, and the silicon carbon composite contained in the negative electrode active material layer had a D50 of 7 μm.

[0170] <Example 22> Positive and negative electrodes were produced in the same manner as in Example 21, except that the D50 of the silicon carbon composite contained in the negative electrode active material layer was 9 μm.

[0171] Example 23 Positive and negative electrodes were produced in the same manner as in Example 21, except that the D50 of the silicon carbon composite contained in the negative electrode active material layer was 12 μm.

[0172] Example 24 Positive and negative electrodes were manufactured in the same manner as in Example 10, except that the D50 of the monoparticles and / or quasi-monoparticles contained in the positive electrode active material layer was 5 μm, and the D50 of the silicon carbon composite contained in the negative electrode active material layer was 7 μm.

[0173] Example 25 A negative electrode was manufactured in the same manner as in Example 24, except that the D50 of the graphite contained in the negative electrode active material layer was 17 μm.

[0174] Example 26 A negative electrode was manufactured in the same manner as in Example 24, except that the D50 of the graphite contained in the negative electrode active material layer was 25 μm.

[0175] Example 27 A positive electrode was produced in the same manner as in Example 24, except that the secondary particulate lithium transition metal compound contained in the positive electrode active material layer had a D50 of 9 μm.

[0176] Example 28 A negative electrode was manufactured in the same manner as in Example 27, except that the D50 of the graphite contained in the negative electrode active material layer was 17 μm.

[0177] Example 29 A negative electrode was manufactured in the same manner as in Example 27, except that the D50 of the graphite contained in the negative electrode active material layer was 25 μm.

[0178] Example 30 A positive electrode was produced in the same manner as in Example 24, except that the secondary particulate lithium transition metal compound contained in the positive electrode active material layer had a D50 of 15 μm.

[0179] Example 31 A negative electrode was manufactured in the same manner as in Example 30, except that the D50 of the graphite contained in the negative electrode active material layer was 17 μm.

[0180] Example 32 A negative electrode was manufactured in the same manner as in Example 30, except that the D50 of the graphite contained in the negative electrode active material layer was 25 μm.

[0181] Example 33 Positive and negative electrodes were produced in the same manner as in Example 24, except that the D50 of the silicon carbon composite contained in the negative electrode active material layer was 9 μm.

[0182] Example 34 A negative electrode was manufactured in the same manner as in Example 33, except that the D50 of the graphite contained in the negative electrode active material layer was 17 μm.

[0183] Example 35 A negative electrode was manufactured in the same manner as in Example 33, except that the D50 of the graphite contained in the negative electrode active material layer was 25 μm.

[0184] <Comparative Example 1> A positive electrode was manufactured in the same manner as in Example 1, except that the secondary particle-like lithium composite transition metal compound was 100 parts by weight based on 100 parts by weight of the positive electrode active material.

[0185] <Comparative Example 2> A positive electrode was manufactured in the same manner as in Example 3, except that the D50 of the single particles and / or quasi-single particles contained in the positive electrode active material layer was 0.5 μm.

[0186] <Comparative Example 3> A positive electrode was manufactured in the same manner as in Example 3, except that the D50 of the single particles and / or quasi-single particles contained in the positive electrode active material layer was 15 μm.

[0187] <Comparative Example 4> A negative electrode was manufactured in the same manner as in Example 3, except that the D50 of the silicon carbon composite contained in the negative electrode active material layer was 0.5 μm.

[0188] <Comparative Example 5> A negative electrode was prepared in the same manner as in Example 3, except that the amount of graphite was 100 parts by weight based on 100 parts by weight of the negative electrode active material.

[0189] <Comparative Example 6> A negative electrode was prepared in the same manner as in Example 3, except that the amount of SiO was 10 parts by weight based on 100 parts by weight of the negative electrode active material.

[0190] <Comparative Example 7> A positive electrode was manufactured in the same manner as in Example 2, except that the D50 of the single particles and / or quasi-single particles contained in the positive electrode active material layer was 12 μm.

[0191] <Comparative Example 8> Positive and negative electrodes were manufactured in the same manner as in Example 2, except that the D50 of the monoparticles and / or quasi-monoparticles contained in the positive electrode active material layer was 5 μm, and the D50 of the silicon carbon composite contained in the negative electrode active material layer was 3 μm.

[0192] <Comparative Example 9> A positive electrode was manufactured in the same manner as in Example 2, except that the D50 of the single particles and / or quasi-single particles contained in the positive electrode active material layer was 10 μm.

[0193] <Comparative Example 10> Positive and negative electrodes were manufactured in the same manner as in Example 2, except that the D50 of the monoparticles and / or quasi-monoparticles contained in the positive electrode active material layer was 9 μm, the D50 of the secondary particles was 14 μm, and the D50 of the silicon carbon composite contained in the negative electrode active material layer was 7 μm.

[0194] <Comparative Example 11> A positive electrode was manufactured in the same manner as in Comparative Example 10, except that the D50 of the single particles and / or quasi-single particles contained in the positive electrode active material layer was 11 μm.

[0195] <Comparative Example 12> Positive and negative electrodes were manufactured in the same manner as in Comparative Example 11, except that the D50 of the monoparticles and / or quasi-monoparticles contained in the positive electrode active material layer was 10 μm, and the D50 of the silicon carbon composite contained in the negative electrode active material layer was 9 μm.

[0196] <Comparative Example 13> A positive electrode was manufactured in the same manner as in Comparative Example 12, except that the D50 of the single particles and / or quasi-single particles contained in the positive electrode active material layer was 12 μm.

[0197] <Experimental Example 1> Evaluation of energy density characteristics The energy density of the manufactured batteries was evaluated and is shown in Table 1 below.

[0198] The energy density of Example 1 was derived by the following calculation.

[0199] Cell volume measurement (unit: L): width (100 mm) x length (300 mm) x thickness (8 mm) Cell energy measurement (unit: Wh): Cell capacity (40Ah) x average voltage (3.65V) Energy density measurement (unit: Wh / L): Cell energy (Wh) / Cell volume (L) = 608 W / L

[0200] <Experimental Example 2> Evaluation of life (capacity retention) characteristics The manufactured batteries were charged and discharged to evaluate the capacity retention rate, which is shown in Table 1 below.

[0201] The first and second cycles were charged and discharged at 0.1 C, and from the third cycle onwards, the charge and discharge rate was 0.5 C. The 100th cycle ended in a charged state (with lithium in the negative electrode).

[0202] Charging conditions: CC (constant current) / CV (constant voltage) (4.25V / 0.05C current cut-off) Discharge condition: CC (constant current) condition 2.5V The capacity retention rates were calculated as follows: Capacity retention rate (%)=(100 discharge capacity / 1 discharge capacity)×100(%)

[0203] Table 1 below shows values ​​for energy density (based on Example 1, %) and capacity retention (100 cycles, %) for Examples 1 to 7 and Comparative Examples 1 to 13.

[0204] [Table 1]

[0205] Table 2 below shows the energy density (based on Example 1, %) and capacity retention (100 cycles, %) of Examples 8 to 35 based on the content of single particles and / or similar-single particles:secondary particles = 50:50 for the positive electrode and the content of silicon carbon composite:graphite = 10:90 for the negative electrode.

[0206] [Table 2]

[0207] The positive electrode active material layer according to the present invention comprises monolithic particles and / or quasi-monolithic particles having an average particle size (D50) of 1 μm or more, and the negative electrode active material layer comprises a silicon carbon composite having an average particle size (D50) of more than 1 μm, wherein the average particle size (D50) of the monolithic particles and / or quasi-monolithic particles is smaller than the average particle size (D50) of the silicon carbon composite. The monolithic particles and / or quasi-monolithic particles and the silicon carbon composite have an appropriate particle size distribution with an average particle size (D50), which suppresses side reactions with the electrolyte, facilitates charge / discharge, fully realizes capacity / efficiency, increases energy density, and provides stable life characteristics.

[0208] Examples 1 to 35 used positive and negative electrode active materials that satisfied the particle size range according to the present invention, and it was confirmed that they were excellent in energy density and capacity retention.

[0209] In contrast, Comparative Examples 1 and 5 did not contain the monoparticles and / or quasi-monoparticles contained in the positive electrode active material layer of the present invention and the silicon carbon composite contained in the negative electrode active material layer, respectively, and it was confirmed that the energy density and capacity retention rate were reduced.

[0210] Comparative Example 2 did not satisfy the D50 range of the single particles and / or quasi-single particles contained in the positive electrode active material layer of the present invention, and the overall particle size was too small, resulting in poor life performance and difficulty in charging and discharging, and it was confirmed that the capacity, efficiency, and life were reduced compared to the Examples.

[0211] Furthermore, in Comparative Examples 3 and 7 to 13, the D50 of the single particles and / or similar-single particles was larger than the D50 of the silicon carbon composite contained in the negative electrode active material layer, and it was confirmed that the capacity, efficiency, and lifespan were reduced.

[0212] Comparative Example 4 did not satisfy the D50 range of the silicon carbon composite contained in the anode active material layer used in the present invention, and the overall particle size was too small, resulting in poor life performance and difficulty in charging and discharging. As a result, it was confirmed that the capacity, efficiency, and life were reduced compared to the Examples.

[0213] That is, in Comparative Example 4, the average particle size (D50) of the silicon carbon composite was smaller than 1 μm, which increased the specific surface area, and side reactions with the electrolyte occurred as the cycle progressed, resulting in a decrease in lifespan performance. It was also confirmed that the D50 of the silicon carbon composite was smaller than the D50 of the single particles, resulting in a decrease in capacity, efficiency, and lifespan.

[0214] Comparative Example 6 did not contain the silicon carbon composite contained in the negative electrode active material layer used in the present invention, but contained an SiO composite, and it was confirmed that the energy density and capacity retention rate decreased.

Claims

1. A lithium secondary battery comprising: a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; a separator provided between the positive electrode and the negative electrode; and an electrolyte, The positive electrode active material includes a lithium composite transition metal compound including nickel (Ni), cobalt (Co), and manganese (Mn), The lithium transition metal composite compound includes at least one of a single particle or a similar-single particle, and the at least one of the single particle or the similar-single particle has an average particle size (D50) of 1 μm or more and 12 μm or less, The single particle is composed of one nodule, and the pseudo-single particle is a complex composed of 30 or fewer nodules; The negative electrode active material includes a silicon carbon composite, and the silicon carbon composite has an average particle size (D50) of more than 1 μm and less than 15 μm; an average particle size (D50) of at least one of the single particles or the quasi-single particles is smaller than an average particle size (D50) of the silicon carbon composite; The silicon carbon composite has a core in which silicon and graphite are composited, The nodule is a single crystal with no grain boundaries or a polycrystal with no grain boundaries when observed at 5,000 to 20,000 magnifications using a scanning electron microscope (SEM).

2. 2. The lithium secondary battery of claim 1, wherein the average particle size (D50) of at least one of the single particles or the quasi-single particles is 1 μm to 12 μm smaller than the average particle size (D50) of the silicon carbon composite.

3. The lithium composite transition metal compound further includes secondary particles, The lithium secondary battery according to claim 1, wherein the average particle size (D50) of at least one of the single particles or the quasi-single particles is smaller than the average particle size (D50) of the secondary particles.

4. The lithium secondary battery according to claim 3, wherein the average particle size (D50) of at least one of the single particles or the quasi-single particles is 1 μm to 18 μm smaller than the average particle size (D50) of the secondary particles.

5. The negative electrode active material further includes graphite, 2. The lithium secondary battery according to claim 1, wherein the silicon carbon composite has an average particle size (D50) smaller than the average particle size (D50) of the graphite.

6. 6. The lithium secondary battery according to claim 5, wherein the average particle size (D50) of the silicon carbon composite is 1 μm to 25 μm smaller than the average particle size (D50) of the graphite.

7. The lithium composite transition metal compound further includes secondary particles, The negative electrode active material further includes graphite, 2. The lithium secondary battery according to claim 1, wherein average particle sizes (D50) of the secondary particles, at least one of the single particles or the similar-single particles, the graphite, and the silicon carbon composite are represented by A, B, C, and D, respectively, and B<D≦A<C.

8. The negative electrode active material further includes graphite, 2. The lithium secondary battery according to claim 1, wherein the average particle sizes (D50) of at least one of the single particle or the similar-single particle, the graphite, and the silicon carbon composite are represented by B, C, and D, respectively, and B<D<C.

9. The lithium secondary battery according to claim 1 , wherein the positive electrode active material further comprises aluminum.

10. At least one of the single particles or the quasi-single particles is included in an amount of 15 to 100 parts by weight based on 100 parts by weight of the positive electrode active material; 2. The lithium secondary battery according to claim 1, wherein the silicon carbon composite is contained in an amount of 3 to 30 parts by weight based on 100 parts by weight of the negative electrode active material.

11. 2. The lithium secondary battery according to claim 1, wherein the lithium composite transition metal compound contains 80 mol % or more of nickel among metals other than lithium.

12. The lithium secondary battery according to claim 1 , wherein the positive electrode further comprises a positive electrode binder and a conductive material.

13. 2. The lithium secondary battery according to claim 1, wherein the lithium secondary battery is a cylindrical battery.

14. 2. The lithium secondary battery of claim 1, wherein a ratio of an average particle size (D50) of at least one of the single particles or the quasi-single particles to an average particle size (D50) of the silicon carbon composite is 1.5:2 to 1.5:

20.

15. the positive electrode further includes a positive electrode active material layer containing the positive electrode active material, and the negative electrode further includes a negative electrode active material layer containing the negative electrode active material, 2. The lithium secondary battery according to claim 1, wherein the thickness of the positive electrode active material layer and the negative electrode active material layer is 10 μm or more and 500 μm or less.

16. The positive electrode further includes a positive electrode active material layer containing the positive electrode active material, and the loading amount per unit volume of the positive electrode active material layer is 250 mg / 25 cm ２ ~900mg / 25cm ２ and The negative electrode further includes a negative electrode active material layer containing the negative electrode active material, and the loading amount per unit volume of the negative electrode active material layer is 100 mg / 25 cm ２ ~600mg / 25cm ２ 2. The lithium secondary battery according to claim 1, wherein

17. 2. The lithium secondary battery according to claim 1, wherein the energy density of the lithium secondary battery is 400 Wh / L to 900 Wh / L.

18. A battery module comprising the lithium secondary battery according to any one of claims 1 to 17.

19. A battery pack comprising the battery module according to claim 18.

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