Lithium secondary battery, battery module, and battery pack

Abstract

The present invention includes a positive electrode containing a positive electrode active material; a negative electrode containing 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 containing nickel (Ni), cobalt (Co), and manganese (Mn). The lithium composite transition metal compound includes at least one of single particles and pseudo-single particles. The average particle size (D50) of at least one of the single particles and pseudo-single particles is 1 μm or more and 10 μm or less. The single particle is composed of one nodule, and the pseudo-single particle is a composite composed of 30 nodules or less. The negative electrode active material is SiO x contains silicon oxide represented by (0 < x < 2), and the SiO x The average particle size (D50) of the silicon oxide represented by (0 < x < 2) is 1 μm or more, and the average particle size (D50) of at least one of the single particles and pseudo-single particles is the SiO x (0

Description

[Technical Field]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2023-0117757 filed with the Korean Intellectual Property Office on September 5, 2023, and Korean Patent Application No. 2024-0120190 filed with the Korean Intellectual Property Office on September 4, 2024, the entire contents of which 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, the rapid spread of battery-powered electronic devices, such as mobile phones, laptops, and electric vehicles, as well as power tools and vacuum cleaners, has led to a rapid increase in demand for rechargeable batteries that are small and lightweight yet offer relatively large capacity and / or high output. Lithium rechargeable batteries, in particular, are lightweight and have high energy density, and are attracting attention as a power source for electronic devices. Accordingly, active research and development efforts are underway to improve the performance of lithium rechargeable batteries.

[0004] Lithium secondary batteries have an organic or polymer electrolyte solution filled between the positive and negative electrodes, which are made of active materials that allow lithium ions to be inserted and deintercalated. Electrical energy is produced through oxidation and reduction reactions that occur when lithium ions are inserted and deintercalated at the positive and negative electrodes.

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

[0006] To address this issue, nickel-cobalt-manganese lithium composite transition metal compounds (hereafter simply referred to as "NCM-based lithium composite transition metal 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 on NCM-based lithium composite transition metal compounds to increase the capacity by increasing the Ni content. 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 the electrochemical reaction, 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 with higher energy densities than graphite, such as silicon, tin, and their oxides, have been developed. However, although these non-carbon-based negative electrode materials have high capacity, they suffer from low initial efficiency, large lithium consumption during initial charge / discharge, and large irreversible capacity loss. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Korean Patent Publication No. 10-2021-0070933

Summary of the Invention

Problems to be Solved by the Invention

[0009] The inventors of the present invention have clarified that in a lithium secondary battery designed within a limited space, optimal battery performance can be achieved by a specific combination of the types, average particle sizes, and / or the contents of each component of the active materials constituting the positive electrode and the negative electrode, and thus arrived at the present invention.

Means for Solving the Problems

[0010] One embodiment of the present application is a lithium secondary battery including a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator provided between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode active material includes a lithium composite transition metal compound containing nickel (Ni), cobalt (Co), and manganese (Mn), the lithium composite transition metal compound includes at least one of single particles and pseudo-single particles, the average particle size (D50) of at least one of the single particles and pseudo-single particles is 1 μm or more and 10 μm or less, the single particle is composed of one nodule, the pseudo-single particle is a composite composed of 30 nodules or less, and the negative electrode active material includes SiO x silicon oxide represented by (0 < x < 2), and the SiO x average particle size (D50) of the silicon oxide represented by (0 < x < 2) is 1 μm or more, and the average particle size (D50) of at least one of the single particles and pseudo-single particles is smaller than the average particle size (D50) of the SiO x silicon oxide represented by (0 < x < 2), and provides a lithium secondary battery, a battery module including the same, and a battery pack.

Effects of the Invention

[0011] 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 high-power performance, and also improve battery cycle performance. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in more detail below to facilitate understanding of the present invention. The present invention can be embodied in various different forms and is not limited to the examples described herein. In this regard, the terms and words used in the specification and claims should not be interpreted in a limited manner to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept that is consistent with the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term in order to best describe his or her invention.

[0013] It should be understood that the terms "comprise," "provide," or "have" as used herein are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, but do not preclude the possible presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0014] Furthermore, when a part such as a layer is said to be "on" another part, this does not only mean that it is "directly on top" of that other part, but also includes cases where there is another part between them. Conversely, when a part is said to be "directly on top" of another part, it means that there is no other part between them. Furthermore, being "on" a reference part means being located above or below the reference part, and does not necessarily mean being located "on" in the opposite direction of gravity.

[0015] In the present specification, "and / or" indicates that any of the listed items may be selected, 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."

[0016] 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 a magnification of 5000x to 20000x using a scanning electron microscope (SEM). As used herein, a "quasi-single particle" may be an aggregate consisting of 30 or fewer nodules. As used herein, a "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.

[0017] 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.

[0018] 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.

[0019] The measurement of the average particle size (D50) can be confirmed 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 within a refractive index range of 1.5 to 1.7, and the negative electrode active material can be measured under the conditions of a refractive index of 1.97 or 2.42. For example, after dispersing the particles in a dispersion medium, they are introduced into a commercially available laser diffraction particle size analyzer, irradiated with ultrasonic waves of approximately 28 kHz at an output of 60 W, and then a volume cumulative particle size distribution graph is obtained. Subsequently, it can be measured by determining the particle size corresponding to 50% of the volume cumulative amount.

[0020] One embodiment of the present application is a lithium secondary battery including a positive electrode containing a positive electrode active material, a negative electrode containing 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 containing nickel (Ni), cobalt (Co), and manganese (Mn). The lithium composite transition metal compound includes at least one of single particles and pseudo-single particles. The average particle size (D50) of at least one of the single particles and pseudo-single particles is 1 μm or more and 10 μm or less. The single particle is composed of one nodule, and the pseudo-single particle is a composite composed of 30 or fewer nodules. The negative electrode active material contains SiO x silicon oxide represented by (0 < x < 2), and the SiO x average particle size (D50) of the silicon oxide represented by (0 < x < 2) is 1 μm or more, and the average particle size (D50) of at least one of the single particles and pseudo-single particles is smaller than the average particle size (D50) of the SiO x silicon oxide represented by (0 < x < 2), providing a lithium secondary battery.

[0021] Lithium secondary batteries have sizes required according to their applications and must be designed within limited space accordingly. Although the demands of consumers for increased energy density and improved high-power performance are increasing, when using a cathode material with high capacity, the only option is to increase the content of the anode material to match it, so there is a limit to enhancing battery efficiency within limited space. Also, depending on the type of anode material, it is necessary to design a cathode material having an efficiency that matches the efficiency of the anode material.

[0022] For example, although the energy density can be improved, when reducing the porosity of the cathode to increase the electrode density, if strong rolling is performed for that purpose, it may cause a decrease in battery performance due to cracks generated in the particles.

[0023] The single particles used in the embodiments of the present application have high rigidity of the particles themselves, so even when the electrode density is high, the decrease in battery performance is relatively excellent. Therefore, the single particles according to the average particle size range and the SiO x Silicon oxide represented by (0 < x < 2) can be combined to increase the energy density.

[0024] In particular, the lithium secondary battery according to the present application uses silicon oxide represented by SiO x (0 < x < 2). Specifically, when compared with other silicon-based active materials (for example, Si / C), when using such an active material, it has the characteristic that the electrode quality, that is, the adhesion to the electrode, is improved.

[0025] In one embodiment of the present application, the silicon oxide represented by the SiO x (0 < x < 2) may be doped with magnesium metal or lithium metal.

[0026] The SiO according to the present application xSilicon oxide represented by (0 < x < 2) may be used without doping, or may be used after doping as described above. When doping, forming a silicate in the silicon oxide in advance can reduce the irreversible capacity during initial charging and increase the energy density of the cell.

[0027] According to an additional embodiment of the present application, the positive electrode active material includes a lithium composite transition metal compound containing nickel (Ni), cobalt (Co), and manganese (Mn). The lithium composite transition metal compound includes single particles and / or pseudo-single particles, and the average particle size (D50) of the single particles and / or pseudo-single particles is characterized by being 1 μm or more and 10 μm or less.

[0028] The smaller the average particle size (D50) of the single particles, the larger the specific surface area, the more side reactions with the electrolyte increase, and the electrochemical performance such as the lifespan may decrease. When the average particle size (D50) of the single particles is less than 1 μm, this may not be within the range of commercialization and application. Even if it exists, the lifespan performance is very low due to the increase in the specific surface area, and it may be difficult to apply.

[0029] When the average particle size (D50) of the single particles is 1 μm or more, 2 μm or more, or 3 μm or more, the side reaction of the single particles with the electrolyte decreases and the lifespan performance is excellent.

[0030] At the same time, the negative electrode active material includes SiO x silicon oxide represented by (0 < x < 2), and the SiO x The average particle size (D50) of the silicon oxide represented by (0 < x < 2) is 1 μm or more, and the average particle size (D50) of the single particles and / or pseudo-single particles is smaller than the average particle size (D50) of the silicon-carbon composite.

[0031] The SiO x The smaller the average particle size (D50) of the silicon oxide represented by (0 < x < 2), the larger the specific surface area, the more side reactions with the electrolyte increase, and the electrochemical performance such as the lifespan may decrease. The SiOx When the average particle size (D50) of silicon oxide represented by (0 < x < 2) is less than 1 μm, side reactions increase due to the increase in specific surface area, the life performance becomes very low, and it may be difficult to apply.

[0032] The above SiO x When the average particle size (D50) of silicon oxide represented by (0 < x < 2) is 1 μm or more, 3 μm or more, 4 μm or more, or 5 μm or more, side reactions with the electrolyte decrease and the life performance is excellent.

[0033] The above SiO x Silicon oxide represented by (0 < x < 2) has excellent life performance within the above range, is excellent in initial capacity and efficiency compared to other silicon-based materials such as silicon-carbon composites, and also has excellent electrochemical performance. Therefore, optimal battery performance can be realized in the combination of the average particle size with the single particles.

[0034] Even if the single particles and / or pseudo-single particles are formed with a small particle size, their particle strength can be excellent. As a result, the phenomenon of an increase in fine particles in the electrode due to particle breakage is alleviated, and thereby the life characteristics of the battery can be improved.

[0035] When the average particle size (D50) of the single particles and / or pseudo-single particles is smaller than the average particle size (D50) of the silicon oxide represented by the above SiO x (0 < x < 2), the diffusion resistance of the single particles and / or pseudo-single particles decreases relatively, and the life performance can be improved. That is, based on discharge, lithium will enter the single particles and / or pseudo-single particles, but the larger the average particle size (D50) of the single particles and / or pseudo-single particles, the more the diffusion resistance can increase. When the average particle size (D50) of the single particles and / or pseudo-single particles is the above SiO xWhen it is larger than the average particle size (D50) of silicon oxide represented by (0 < x < 2), as the diffusion resistance increases relatively, lithium cannot enter into single particles and / or pseudo-single particles and is deposited, which may lead to a decrease in battery performance and life performance.

[0036] Also, when the average particle size (D50) of the single particles is smaller than the SiO x When it is smaller than the average particle size (D50) of silicon oxide represented by (0 < x < 2), the occurrence of side reactions with the electrolyte due to the increase in the specific surface area of the single particles can be prevented, and the life performance can be improved.

[0037] When the average particle size (D50) of the single particles and / or pseudo-single particles is smaller than the SiO x When it is smaller than the average particle size (D50) of silicon oxide represented by (0 < x < 2), the diffusion resistance of the single particles and / or pseudo-single particles decreases relatively, and the life performance can be improved.

[0038] The single particles and / or pseudo-single particles have a greater resistance to lithium diffusion compared to the silicon oxide represented by SiO x (0 < x < 2). Therefore, when the average particle size (D50) of the single particles and / or pseudo-single particles is larger than the SiO x (0 < x < 2), due to the increase in lithium diffusion resistance, charge and discharge may not be performed well, and the life performance may decrease. Thus, the average particle size (D50) of the single particles and / or pseudo-single particles can be smaller than the SiO x (0 < x < 2).

[0039] According to an additional embodiment of the present application, the positive electrode active material contains the nickel, cobalt and manganese, and may further contain aluminum. That is, the positive electrode active material may further contain aluminum.

[0040] 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:

[0041] The lithium transition metal composite compound may also include single particles and / or quasi-single particles and secondary particles.

[0042] [Chemical formula 1] Li a Ni 1-b-c-d Co b Mn c Q d O 2+δ In the formula, Q is at least one element 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 Chemical Formula 1, Li may be contained in a content 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 manufacture 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 active material manufacture, the Li may more preferably be contained in a content 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. When the content of Ni in the lithium composite transition metal compound of Chemical Formula 1 is 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, preferably 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 improvement effect of capacity characteristics due to the inclusion of 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, rather, there is a risk of deterioration of the output characteristics and capacity characteristics of the battery. 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 an additional embodiment of the present application, the lithium transition metal composite compound in the positive electrode active material may include single particles and / or quasi-single particles and secondary particles.

[0049] The single particles and / or quasi-single particles may be produced by mixing a transition metal precursor and a lithium source material and calcining the mixture. The secondary particles may be produced by a method different from that for the single particles and / or quasi-single particles, and their composition may be the same as or different from that of the single particles and / or quasi-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 must be performed at a temperature higher than that used for producing secondary particles. For example, when the precursor composition is the same, the calcination temperature must be 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 as 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 less than 700°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 is more than 950°C, excessive calcination may occur, preventing proper formation of a layered crystal structure and possibly deteriorating 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 is composed of one module, and the pseudo-single particle is a composite composed of 30 or fewer modules. On the other hand, the secondary particle may be in a form in which dozens to hundreds of primary particles are aggregated.

[0053] According to an additional embodiment of the present application, the average particle size (D50) of the single particle and / or pseudo-single particle is 1 μm or more and 10 μm or less, and the average particle size (D50) of the silicon oxide represented by SiO x (0 < x < 2) is 1 μm or more.

[0054] The average particle size (D50) of the single particle and / or pseudo-single particle is 1 μm or more and 10 μm or less, and the silicon oxide represented by SiO x (0 < x < 2) may have an average particle size (D50) of 1 μm or more.

[0055] According to an embodiment of the present application, the average particle size (D50) of the single particle and / or pseudo-single particle is 10 μm or less, and the average particle size (D50) of the silicon oxide represented by SiO x (0 < x < 2) is less than 15 μm.

[0056] For example, the average particle size (D50) of the single particle and / or pseudo-single particle may be 1 μm or more and 10 μm or less, 2 μm or more and 10 μm or less, 3 μm or more and 10 μm or less, more than 1 μm and 10 μm or less, more than 2 μm and 10 μm or less, or more than 2 μm and 5 μm or less.

[0057] Even if the single particle and / or pseudo-single particle is formed with a small particle size having an average particle size (D50) of about 1 μm or more and 10 μm or less, its particle strength can be excellent. For example, when the single particle and / or pseudo-single particle is rolled with a force of 650 kgf / cm 2 , it can have a particle strength of 100 MPa to 300 MPa. Thereby, even when the single particle and / or pseudo-single particle is rolled with a strong force of 650 kgf / cm 2 , the phenomenon of an increase in fine particles in the electrode due to particle breakage is alleviated, and thereby, the life characteristics of the battery are improved.

[0058] When the average particle size (D50) of the single particle satisfies the above range, the side reaction of the single particle with the electrolyte is reduced, the life performance is excellent, the charge / discharge is performed well, and the electrochemical performance is excellent.

[0059] When the average particle size (D50) of the single particle is less than 1 μm, the life performance is very low due to the increase in the specific surface area, and it may be difficult to apply.

[0060] When the average particle size (D50) of the single particle is 10 μm or less, the charge / discharge is performed well, and the electrochemical performance is excellent.

[0061] The method for forming the single particle and / or pseudo-single particle is not particularly limited, but generally can be formed by raising the firing temperature and over-firing, and can be manufactured by using additives such as grain growth promoters useful for over-firing, or by changing the starting materials.

[0062] According to an additional embodiment of the present application, the average particle size (D50) of the SiO x silicon oxide represented by (0 < x < 2) may be 1 μm or more 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] The SiO x silicon oxide represented by (0 < x < 2) can improve the life characteristics of the battery even if it is formed with a small particle size with an average particle size (D50) of about 1 μm or more and less than 15 μm. For example, when the average particle size (D50) of the SiO x silicon oxide represented by (0 < x < 2) is in the range of 1 μm or more and less than 15 μm, the volume expansion and shrinkage rate due to charge and discharge are reduced, and the life performance can be improved. In addition, it is possible to prevent the excessive increase in the specific surface area, and to prevent the side reaction with the electrolyte due to the cycle progress, and the life performance can be improved.

[0064] The SiO xWhen the average particle size (D50) of silicon oxide displayed at (0 < x < 2) is less than 1 μm, the life performance is extremely low due to the increase in specific surface area, and it may be difficult to apply.

[0065] The above-mentioned SiO x When the average particle size (D50) of silicon oxide displayed at (0 < x < 2) is less than 15 μm, since the particles are small, charge and discharge are performed well, the volume expansion and shrinkage rate of the particles due to charge and discharge decrease, and the life performance can be improved.

[0066] According to an additional embodiment of the present application, the average particle size (D50) of the single particles and / or pseudo-single particles is characterized in that it is smaller than the average particle size (D50) of silicon oxide represented by the above-mentioned SiO x (0 < x < 2). Thereby, even if the single particles and / or pseudo-single particles are formed with a small particle size, their particle strength can be excellent. Thereby, the phenomenon of an increase in fine particles in the electrode due to particle breakage is alleviated, and thereby, the life characteristics of the battery can be improved.

[0067] The average particle size (D50) of the single particles and / or pseudo-single particles is the SiO x When it is smaller than the average particle size (D50) of silicon oxide represented by (0 < x < 2), the diffusion resistance of the single particles and / or pseudo-single particles having a larger lithium diffusion resistance than the silicon oxide represented by the above-mentioned SiO x (0 < x < 2) relatively decreases, and the life performance can be improved.

[0068] According to an embodiment of the present application, the average particle size (D50) of the single particles and / or pseudo-single particles may be 1 μm to 12 μm smaller than the average particle size (D50) of silicon oxide represented by the above-mentioned SiO x (0 < x < 2).

[0069] The average particle size (D50) of the single particles and / or pseudo-single particles is the SiO xIt may be 1.5 μm to 11.5 μm, or 2 μm to 11 μm smaller than the average particle size (D50) of silicon oxide represented by (0 < x < 2).

[0070] The average particle size (D50) of the single particles and / or pseudo-single particles is the SiO x It may be 2 μm or more, or 4 μm or more smaller than the average particle size (D50) of silicon oxide represented by (0 < x < 2). The average particle size (D50) of the single particles is the SiO x It may be 11 μm or less, 8 μm or less, or 6 μm or less smaller than the average particle size (D50) of silicon oxide represented by (0 < x < 2).

[0071] When the average particle size (D50) of the single particles and / or pseudo-single particles is smaller than the average particle size (D50) of silicon oxide represented by the SiO x (0 < x < 2), for example, when the above range is satisfied, the diffusion resistance of the single particles and / or pseudo-single particles is relatively reduced, and the life performance can be improved. That is, the larger the average particle size (D50) of the single particles and / or pseudo-single particles, the more the diffusion resistance can increase. When the average particle size (D50) of the single particles and / or pseudo-single particles is larger than the average particle size (D50) of silicon oxide represented by the SiO x (0 < x < 2), as the diffusion resistance relatively increases, precipitation of lithium etc. may occur, and the battery performance may deteriorate and the life performance may deteriorate.

[0072] Also, when the average particle size (D50) of the single particles and / or pseudo-single particles is smaller than the average particle size (D50) of silicon oxide represented by the SiO x (0 < x < 2), for example, when the above range is satisfied, the occurrence of side reactions with the electrolyte due to an increase in the specific surface area can be prevented, and the life performance can be improved.

[0073] According to one embodiment of the present application, the average particle size (D50) of the single particles and / or pseudo-single particles and the SiO xThe ratio of the average particle size (D50) of silicon oxide represented by (0 < x < 2) is 1.5:2 to 1.5:20.

[0074] The average particle size (D50) of the single particle and the SiO x The ratio of the average particle size (D50) of silicon oxide represented by (0 < x < 2) is 1.5:2 to 1.5:19 or 1.5:2 to 1.5:18.

[0075] The average particle size (D50) of the single particle and the SiO x The ratio of the average particle size (D50) of silicon oxide represented by (0 < x < 2) 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 particle and 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 single particle and / or pseudo-single particle is relatively reduced, and the life performance can be improved. That is, as the average particle size (D50) of the single particle and / or pseudo-single particle increases, the diffusion resistance can increase, and when the average particle size (D50) of the single particle and / or pseudo-single particle is larger than the average particle size (D50) of the SiO x When it is larger than the average particle size (D50) of silicon oxide represented by (0 < x < 2), as the diffusion resistance relatively increases, precipitation of lithium etc. may occur, resulting in a decrease in battery performance and a decrease in life performance.

[0077] Also, when the average particle size (D50) of the single particle and / or pseudo-single particle is smaller than the average particle size (D50) of the SiO x When it is smaller than the average particle size (D50) of silicon oxide represented by (0 < x < 2), for example, when the above range is satisfied, the occurrence of side reactions with the electrolyte due to an increase in the specific surface area can be prevented, and the life performance can be improved.

[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 quasi-single particles may be smaller than the average particle size (D50) of the secondary particles.

[0079] In the present invention, a single particle is composed of one nodule, and a quasi-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 can be distinguished from the concept of a single particle consisting of one nodule or a quasi-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 an additional 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 primary particles agglomerated 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 primary particles agglomerated in the secondary particles is too small, the number of agglomerates of the 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 primary particles agglomerated 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 may have excellent particle strength even when formed with a small particle size, thereby mitigating the phenomenon of an increase in fine particles in the electrode due to particle breakage, 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 single particles and / or quasi-single 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 single particles and / or quasi-single 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 pseudo-single particles is smaller than the average particle size (D50) of the secondary particles, for example, when the above range is satisfied, even if the single particles and / or pseudo-single particles are formed with a small particle size, their particle strength can be excellent. As a result, the phenomenon of an increase in fine particles in the electrode due to particle breakage is alleviated, thereby having an effect of improving the life characteristics and energy density of the battery.

[0089] In one embodiment of the present application, the negative electrode active material further contains graphite, and the SiO x The average particle size (D50) of silicon oxide represented by (0 < x < 2) may be smaller than the average particle size (D50) of the graphite.

[0090] The SiO x When the average particle size (D50) of silicon oxide represented by (0 < x < 2) is smaller than the average particle size (D50) of the graphite, the breakage of particles is reduced due to a decrease in the volume expansion / contraction rate during charge and discharge, and there is an effect of improving the life performance of the battery.

[0091] According to one embodiment of the present application, the average particle size (D50) of silicon oxide represented by (0 < x < 2) is 1 μm to 25 μm smaller than the average particle size (D50) of the graphite. x

[0092] For example, the average particle size (D50) of silicon oxide represented by (0 < x < 2) 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. x

[0093] The SiO x The average particle size (D50) of silicon oxide represented by (0 < x < 2) 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 SiO xThe average particle size (D50) of silicon oxide represented by (0 < x < 2) 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] SiO x When the average particle size (D50) of silicon oxide represented by (0 < x < 2) is smaller than the average particle size (D50) of the graphite, for example, when the above range is satisfied, there is an effect of improving the life performance of the battery.

[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 secondary particles, the single particles and / or pseudo-single particles, the graphite and the SiO x [[ID=q12]]The average particle size (D50) of silicon oxide represented by (0 < x < 2) is represented by A, B, C, and D respectively, and B < D ≤ A < C.

[0096] The secondary particles, the single particles and / or pseudo-single particles, the graphite and the SiO x The embodiment of silicon oxide represented by (0 < x < 2) is as described above.

[0097] The secondary particles, the single particles and / or pseudo-single particles, the graphite and the SiO x When the average particle size (D50) of silicon oxide represented by (0 < x < 2) is A, B, C, and D respectively, and when B < D ≤ A < C, there is an effect of improving the life performance of the battery.

[0098] <s According to one embodiment of the present application, the negative electrode active material further includes graphite, and the single particles and / or pseudo-single particles, the graphite and the SiO x The average particle size (D50) of silicon oxide represented by (0 < x < 2) is represented by B, C, and D respectively, and B < D < C.

[0099] The secondary particles, the single particles and / or pseudo-single particles and the SiOx The average particle size (D50) of silicon oxide represented by (0 < x < 2) is represented by A, B, and D respectively, and B < D ≤ A may be satisfied.

[0100] The average particle sizes (D50) of the secondary particles, the single particles and / or pseudo-single particles, and the graphite are represented by A, B, and C respectively, and B < A < C may be satisfied.

[0101] The secondary particles, the graphite, and the SiO x The average particle size (D50) of silicon oxide represented by (0 < x < 2) is represented by A, C, and D respectively, and D ≤ A < C may be satisfied.

[0102] When the above range is satisfied, there is an effect of improving the life performance of the battery.

[0103] In one embodiment of the present application, in the lithium secondary battery according to the above-described embodiment, the single particles and / or pseudo-single particles are contained in an amount of 15 parts by weight to 100 parts by weight with respect to 100 parts by weight of the positive electrode active material, and the SiO x The silicon oxide represented by (0 < x < 2) may be contained in an amount of 3 parts by weight to 30 parts by weight with respect to 100 parts by weight of the negative electrode active material.

[0104] According to an additional embodiment of the present application, the single particles and / or pseudo-single particles may be contained in an amount of 15 parts by weight to 100 parts by weight with respect to 100 parts by weight of the positive electrode active material. The single particles and / or pseudo-single particles may be contained in an amount of 20 parts by weight to 100 parts by weight, 30 parts by weight to 100 parts by weight, 40 parts by weight to 100 parts by weight, or 50 parts by weight to 100 parts by weight with respect 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 mono- and / or quasi-mono-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 mono- and / or quasi-mono-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, and may be in the form of an aggregate 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, in 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 aforementioned 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. The positive electrode binder may be any binder known in the art, and non-limiting examples thereof include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof. These binders 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 used without particular limitation as long as it does not undergo chemical changes in the battery and has electron conductivity. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based substances such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. Among these, one kind alone or a mixture of two or more kinds can be used.

[0115] Specifically, in one embodiment, the conductive material may include one or more of single-walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT). The conductive material may be contained in an amount of 0.1 parts by weight or more and 2 parts by weight or less based on 100 parts by weight of the composition for forming the positive electrode active material layer. For example, it may preferably be contained in an amount of 0.3 parts by weight or more and 1.5 parts by weight or less, and more preferably 0.5 parts by weight or more and 1.2 parts by weight or less.

[0116] According to the foregoing embodiment of the present application, the negative electrode active material layer may contain 3 to 30 parts by weight of silicon oxide represented by SiO x (0 < x < 2) out of 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 silicon oxide represented by SiO x (0 < x < 2) out of 100 parts by weight of the total negative electrode active material.

[0117] 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 silicon oxide represented by SiO x (0 < x < 2) out of 100 parts by weight of the total negative electrode active material. The negative electrode active material layer may contain, out of 100 parts by weight of the total negative electrode active material, SiO x(0 < x < 2) may contain 30 parts by weight or less, 20 parts by weight or less, or 10 parts by weight or less of silicon oxide.

[0118] By using silicon oxide within such a range, when combined with the aforementioned positive electrode material, excellent battery characteristics can be exhibited. In particular, x By using silicon oxide represented by (0 < x < 2), when combined with the aforementioned positive electrode material, excellent battery characteristics can be exhibited. In particular, x When containing 3 parts by weight or more of silicon oxide represented by (0 < x < 2), the effects of using the silicon oxide can be fully achieved. Also, x By using silicon oxide represented by (0 < x < 2), the effects can be fully achieved. Also, x Silicon oxide represented by (0 < x < 2) has a lower capacity compared to the SiC active material and can be used in excess compared to SiC. In particular, x When containing 30 parts by weight or less of silicon oxide represented by (0 < x < 2), expansion during charge and discharge can be prevented, and cycle characteristics can be improved.

[0119] According to an additional embodiment of the present application, in the lithium secondary battery according to the aforementioned embodiment, the negative electrode active material may further contain 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. Based on 100 parts by weight of the total negative electrode active material contained in the negative electrode active material layer, the graphite may be contained in an amount of 70 parts by weight or more and 97 parts by weight or less.

[0120] Based on 100 parts by weight of the total negative electrode active material, the graphite may be contained 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 contained in an amount of 95 parts by weight or less, 93 parts by weight or less, or 90 parts by weight or less. When the graphite is a mixture of artificial graphite and natural graphite, based on 100 parts by weight of the graphite, the artificial graphite and natural graphite may be contained 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.

[0121] In one embodiment of the present application, the negative electrode active material in 100 parts by weight of the aforementioned negative electrode active material layer 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.

[0122] According to an additional embodiment of the present application, in the lithium secondary battery according to the aforementioned embodiment, the negative electrode active material layer may further contain a negative electrode binder in addition to silicon oxide represented by SiO x (0 < x < 2) and graphite.

[0123] The negative electrode binder can play a role in improving the adhesion between negative electrode active material particles and the adhesion between negative electrode active material particles and the negative electrode current collector. As the negative electrode binder, those known in the art can be used. Non-limiting examples include polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluorine rubber, polyacrylic acid, and at least one selected from the group consisting of substances obtained by substituting hydrogen thereof with Li, Na, Ca, etc., and various copolymers thereof may also be included.

[0124] The negative electrode binder may be contained in an amount of 0.1 part by weight or more and 50 parts by weight or less based on 100 parts by weight of the negative electrode active material layer. For example, it may be preferably contained in an amount of 0.3 part by weight or more and 35 parts by weight or less, and more preferably 0.5 part by weight or more and 10 parts by weight or less.

[0125] 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 fiber or metal fiber; 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.

[0126] 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.

[0127] 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, etc. may be used. The positive electrode current collector may typically have a thickness of 1 to 500 μm, and fine irregularities may be formed on the surface of the positive electrode current collector to enhance adhesion of the positive electrode active material. The positive electrode current collector may be used in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0128] 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.

[0129] 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 effectively adsorbs carbon, such as copper or nickel, can 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.

[0130] 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 the 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.

[0131] 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 cm2 ~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.

[0132] The positive and negative electrodes can be fabricated according to conventional methods for fabricating positive and negative electrodes, except for using the positive and negative electrode active materials. Specifically, they can be fabricated by coating a composition for forming an active material layer containing the active material and, optionally, a binder and a conductive material, 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, and to provide a viscosity that allows excellent thickness uniformity during subsequent coating for fabricating positive and negative electrodes, taking into account the coating thickness and manufacturing yield of the slurry. 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.

[0133] The separator separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator commonly used in secondary batteries can be used without particular limitations. In particular, a separator that exhibits low resistance to ion migration in the electrolyte and excellent electrolyte humidification is preferred. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof, may be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made of 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 polymer material may be used, and may be used in a single-layer or multi-layer structure.

[0134] Examples of the electrolytic solution include 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, but are not limited to these.

[0135] Specifically, the electrolyte may contain a non-aqueous organic solvent and a metal salt.

[0136] Examples of the non-aqueous organic solvent that may be used include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-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.

[0137] In particular, among the carbonate-based organic solvents, cyclic carbonates such as ethylene carbonate and propylene carbonate are preferred because they are high-viscosity organic solvents with high dielectric constants that allow them to dissociate lithium salts well. Mixing such cyclic carbonates with linear carbonates having low viscosity and low dielectric constants, such as dimethyl carbonate and diethyl carbonate, in an appropriate ratio can produce an electrolyte with high electrical conductivity, making them more preferred.

[0138] 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:

[0139] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the battery's life characteristics, suppressing a decrease in battery capacity, and improving the battery's discharge capacity.

[0140] 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 this range is satisfied, the energy density of a lithium secondary battery designed in a limited space can be increased, and high-power performance and battery cycle performance can also be improved.

[0141] 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 cathode, an anode, a separator, and an electrolyte. Specifically, the battery may be comprised 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-shaped battery.

[0142] Additional embodiments of the present invention provide a battery module including the aforementioned cylindrical battery as a unit cell, a battery pack including the same, and a battery pack including the cylindrical battery.

[0143] Additional embodiments of the present invention provide a battery module including the aforementioned lithium secondary battery, a battery pack including the same, and a battery pack including the aforementioned lithium secondary battery.

[0144] The battery module and the battery pack include the secondary battery having high capacity and excellent rate-limiting and cycle characteristics, and therefore can be used as a power source for a medium- to large-sized device selected from the group consisting of an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage system.

[0145] The lithium secondary battery according to the present invention exhibits excellent discharge capacity, output characteristics, and stable 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 of the following medium- to large-sized devices: 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 shown to help understand the present invention, but these examples are merely illustrative of the present description, and it will be apparent to those skilled in the art that various changes and modifications are possible within the category 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 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 (a 50:50 weight ratio of single particles and / or pseudo-single particles to secondary particles), 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 pseudo-single particles were milled to a size D50 of 3 μm, and the secondary particles were milled to a size D50 of 7 μm, using an airflow milling method. The composition for forming a positive electrode active material layer was coated on an aluminum foil having a thickness of 30 μm so as to have a dry thickness of 103 μm, and then dried to prepare a positive electrode including a positive electrode active material layer.

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

[0149] The positive electrode and negative electrode were stacked with a separator sandwiched between them, and an electrolyte (1.0 M LiPF6, EC (ethylene carbonate) / EMC (ethylmethyl carbonate) = 30 / 70 (Vol%), VC (vinylene carbonate) 1.5%) was injected 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 lithium transition metal composite compound in the form of single particles and / or pseudo-single particles and secondary particles was 80:20 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 fabricated in the same manner as in Example 3, except that the monoparticles and / or quasi-monoparticles contained in the positive electrode active material layer were fabricated to a size of D50 = 7 μm, and the SiO contained in the negative electrode active material layer had a size of D50 = 10 μm.

[0153] <Example 5> A negative electrode was produced in the same manner as in Example 3, except that the SiO contained in the negative electrode active material layer had a D50 of 10 μm.

[0154] Example 6 A negative electrode was prepared in the same manner as in Example 3, except that the amount of SiO was 5 parts by weight based on 100 parts by weight of the negative electrode active material.

[0155] Example 7 A negative electrode was manufactured in the same manner as in Example 1, except that the monoparticles and / or quasi-monoparticles contained in the positive electrode active material layer had a D50 of 4.5 μm.

[0156] Example 8 A negative electrode was manufactured in the same manner as in Example 2, except that the monoparticles and / or quasi-monoparticles contained in the positive electrode active material layer had a D50 of 4.5 μm.

[0157] Example 9 A negative electrode was produced in the same manner as in Example 2, except that the monoparticles and / or quasi-monoparticles contained in the positive electrode active material layer had a D50 of 1 μm, the lithium transition metal composite compound in the form of secondary particles had a D50 of 14 μm, and the SiO contained in the negative electrode active material layer had a D50 of 13.5 μm.

[0158] <Comparative Example 1> A positive electrode was prepared in the same manner as in Example 1, except that the amount of the lithium transition metal composite compound in the form of secondary particles was 100 parts by weight based on 100 parts by weight of the positive electrode active material.

[0159] <Comparative Example 2> A positive electrode was produced in the same manner as in Example 3, except that the monoparticles and / or quasi-monoparticles contained in the positive electrode active material layer had a D50 of 0.5 μm.

[0160] <Comparative Example 3> A positive electrode was produced in the same manner as in Example 3, except that the monoparticles and / or quasi-monoparticles contained in the positive electrode active material layer had a D50 of 15 μm.

[0161] <Comparative Example 4> A negative electrode was produced in the same manner as in Example 3, except that the SiO contained in the negative electrode active material layer had a D50 of 0.7 μm.

[0162] <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.

[0163] <Experimental Example 1>Energy density characteristic evaluation The energy densities of the fabricated batteries were evaluated and are listed in Table 1 below.

[0164] The energy density of Example 1 was derived by the following calculation.

[0165] 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 <Experimental Example 2> Evaluation of life (capacity retention) characteristics The produced batteries were charged and discharged to evaluate the capacity retention rate, which is shown in Table 1 below.

[0166] The first and second cycles were charged and discharged at 0.1 C, and from the third cycle onwards, the charge and discharge was carried out at 0.5 C. The 100 cycles were completed in a charged state (with lithium in the anode).

[0167] 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:

[0168] Capacity retention rate (%) = (100 discharge capacity / 1 discharge capacity) x 100 (%) Table 1 below lists the energy density (based on Example 1, %) and capacity retention rate (100 cycles, %) of the examples and comparative examples.

[0169] [Table 1]

[0170] The present application can increase the energy density of a lithium secondary battery, improve high-output performance, and also improve battery cycle performance, and when Examples 1 to 9 are compared with Comparative Examples 1 to 5, it was confirmed that they are superior in energy density and / or capacity retention. Specifically, Examples 1 to 3 show a performance comparison based on the content of monoparticles and / or quasi-monoparticles in the positive electrode, and it was confirmed that as the content of monoparticles and / or quasi-monoparticles increases, the energy density increases and the life performance is equivalent to or superior to that of the monoparticles and / or quasi-monoparticles.

[0171] In the case of Example 4, the D50 particle size of the positive electrode monoparticles and / or quasi-monoparticles was increased, and in this case too, the energy density and capacity retention were excellent as described above. In Examples 5 and 6, the energy density and capacity retention were excellent even when the D50 of SiO applied to the negative electrode was increased or the content was reduced.

[0172] In Examples 7 to 9, the positive electrode monoparticles and / or pseudo-monoparticles and the D50 of SiO are within the range of the present application, and the difference therebetween is less than 1 μm or more than 12 μm. It was confirmed that the energy density and capacity retention are excellent, but are lower than those of Example 1 or Example 2.

[0173] That is, in Examples 7 and 8, the D50 particle size of the positive electrode monoparticle and / or quasi-monoparticle is larger than in Examples 1 and 2, respectively, which increases the relative diffusion resistance and may cause lithium deposition or the like, resulting in a decrease in battery performance. In Example 9, the difference in D50 particle size between the positive electrode monoparticle and / or quasi-monoparticle and SiO is larger, which may cause a decrease in life performance due to the occurrence of side reactions.

[0174] In Comparative Example 1, monoparticles and / or pseudo-monoparticles were not applied to the positive electrode, and in Comparative Examples 2 and 3, the D50 of the monoparticles and / or pseudo-monoparticles of the positive electrode was below or exceeded the range of the present application. In Comparative Example 4, the D50 range of SiO was below the range of the present application, and in Comparative Example 5, SiO was not applied to the negative electrode.

[0175] In this case, it was confirmed that the energy density and capacity retention rate were lower than those in the previous examples.

[0176] Specifically, as in Comparative Example 2, when the D50 of the positive electrode monoparticles and / or quasi-monoparticles is smaller than the range of the present application, even if the D50 of the silicon oxide contained in the negative electrode is larger, the increase in the specific surface area of ​​the monoparticles and / or quasi-monoparticles increases their reactivity with the electrolyte, increasing side reactions and resulting in a decrease in lifespan. Furthermore, when the particle size of the monoparticles and / or quasi-monoparticles is small, the particle strength decreases, making it difficult to manufacture an electrode to the desired thickness during the rolling process during electrode manufacturing, and the energy density also decreases.

[0177] In Comparative Example 3, the D50 of the positive electrode monoparticles and / or pseudo-monoparticles exceeds the range of the present invention, and in this case, the particle size increases, making charge / discharge difficult, which shortens the lifespan and reduces the energy density due to a decrease in capacity.

[0178] In the case of Comparative Example 4, the D50 of SiO contained in the negative electrode active material was formed to be smaller than the range of the present invention. In this case, too, it was confirmed that the increase in the specific surface area of ​​SiO increased the reactivity with the electrolyte, and the increase in side reactions led to a decrease in life performance.

[0179] In Comparative Examples 1 and 5, the positive electrode did not contain monoparticles and / or pseudo-monoparticles, and the negative electrode did not contain SiO, respectively. In these cases, it was confirmed that the desired energy density could not be achieved compared to the Examples.

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 and a quasi-single particle, and the average particle size (D50) of at least one of the single particle and the quasi-single particle is 1 μm or more and 10 μm or less; The single particle is composed of one nodule, and the quasi-single particle is a complex consisting of 30 or less nodules; The negative electrode active material is SiO ｘ (0<x<2), and the SiO ｘ The average particle size (D50) of silicon oxide expressed by (0<x<2) is 1 μm or more, The average particle size (D50) of at least one of the single particles and the quasi-single particles is ｘ The lithium secondary battery has an average particle size (D50) of silicon oxide expressed as (0<x<2).

2. At least one of the single particles and pseudo-single particles has an average particle size (D50) of 10 μm or less; The SiO ｘ 2. The lithium secondary battery according to claim 1, wherein the silicon oxide has an average particle size (D50) expressed as (0<x<2) of less than 15 μm.

3. The average particle size (D50) of at least one of the single particles and the quasi-single particles is ｘ 2. The lithium secondary battery according to claim 1, wherein the average particle size (D50) of silicon oxide expressed by (0<x<2) is 1 μm to 12 μm smaller.

4. The SiO ｘ 2. The lithium secondary battery according to claim 1, wherein the silicon oxide represented by (0<x<2) is doped with magnesium metal or lithium metal.

5. The lithium composite transition metal compound further includes secondary particles, 2. The lithium secondary battery according to claim 1, wherein the average particle size (D50) of at least one of the single particles and the quasi-single particles is smaller than the average particle size (D50) of the secondary particles.

6. The lithium secondary battery according to claim 5, wherein the average particle size (D50) of at least one of the single particles and the quasi-single particles is 1 μm to 18 μm smaller than the average particle size (D50) of the secondary particles.

7. The negative electrode active material further includes graphite, The SiO ｘ 2. The lithium secondary battery according to claim 1, wherein the average particle size (D50) of silicon oxide expressed by (0<x<2) is smaller than the average particle size (D50) of said graphite.

8. The SiO ｘ 8. The lithium secondary battery according to claim 7, wherein the average particle size (D50) of silicon oxide expressed by (0<x<2) is 1 μm to 25 μm smaller than the average particle size (D50) of the graphite.

9. The lithium composite transition metal compound further includes secondary particles, The negative electrode active material further includes graphite, the secondary particles, at least one of the single particles and quasi-single particles, the graphite, and the SiO ｘ 2. The lithium secondary battery according to claim 1, wherein the average particle diameters (D50) of silicon oxide particles represented by (0<x<2) are represented by A, B, C and D, respectively, and B<D≦A<C.

10. The negative electrode active material further includes graphite, At least one of the monoparticles and quasi-monoparticles, the graphite, and the SiO ｘ 2. The lithium secondary battery according to claim 1, wherein the average particle diameters (D50) of silicon oxide particles represented by (0<x<2) are represented by B, C, and D, respectively, and B<D<C.

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

12. the at least one of the single particles and the quasi-single particles is 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; The SiO ｘ 2. The lithium secondary battery according to claim 1, wherein the silicon oxide represented by (0<x<2) is contained in an amount of 3 to 30 parts by weight per 100 parts by weight of the negative electrode active material.

13. 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.

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

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

16. The average particle size (D50) of at least one of the single particles and the pseudo-single particles, and the SiO ｘ 2. The lithium secondary battery according to claim 1, wherein the ratio of the average particle diameters (D50) of silicon oxide particles expressed by (0<x<2) is 1.5:2 to 1.5:

20.

17. 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.

18. 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

19. 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.

20. A battery module comprising the lithium secondary battery according to any one of claims 1 to 19.

21. A battery pack comprising the battery module of claim 20.

22. A battery pack comprising the lithium secondary battery according to any one of claims 1 to 19.

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