CN118715634A - Lithium secondary batteries, battery modules and battery packs - Google Patents

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 between the positive electrode and the negative electrode; and an electrolyte, wherein the positive electrode active material contains a lithium composite transition metal compound containing nickel (Ni), cobalt (Co), and manganese (Mn), the lithium composite transition metal compound contains at least one of single particles or quasi-single particles, the at least one of single particles or quasi-single particles has an average particle diameter (D ₅₀) of 1 μm or more, the single particles are composed of one agglomerate, the quasi-single particles are composites composed of 30 or less agglomerates, the negative electrode active material contains a silicon-carbon composite, the silicon-carbon composite has an average particle diameter (D ₅₀) of more than 1 μm, and the average particle diameter (D ₅₀) of the at least one of single particles and quasi-single particles is smaller than the average particle diameter (D ₅₀) of the silicon-carbon composite.

Description

Lithium secondary batteries, battery modules and battery packs

Technical Field

This application claims priority to and the benefit of Korean Patent Application No. 10-2022-0097491 filed in the Korean Intellectual Property Office on August 4, 2022, and Korean Patent Application No. 10-2023-0091528 filed in the Korean Intellectual Property Office on July 14, 2023, the entire contents of which are incorporated herein by reference.

The invention relates to a lithium secondary battery, a battery module and a battery pack.

Background Art

In recent years, with the rapid popularization of electronic devices using batteries, such as not only mobile phones, laptops and electric vehicles, but also power tools and cleaners, the demand for small and lightweight secondary batteries with relatively high capacity and/or high output is rapidly increasing. In particular, lithium secondary batteries are lightweight and have high energy density, thus attracting attention as driving power sources for electronic devices. Therefore, attempts to improve the performance of lithium secondary batteries have been actively studied and developed.

Lithium secondary batteries generate electric energy through oxidation and reduction reactions during insertion or extraction of lithium ions at the positive and negative electrodes in a state in which an organic electrolyte or a polymer electrolyte is filled between a positive electrode and a negative electrode composed of an active material capable of inserting and extracting lithium ions.

As positive electrode active materials for lithium secondary batteries, lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), lithium manganese oxide (LiMnO ₂ , LiMn ₂ O ₄ , etc.), lithium iron phosphate compounds (LiFePO ₄ ), etc. have been used. Among them, lithium cobalt oxide (LiCoO ₂ ) is widely used due to its advantages of high operating voltage and excellent capacity characteristics, and is used as a high-voltage positive electrode active material. However, because the price of cobalt (Co) has risen and the supply is unstable, its large-scale use as a power source in fields such as electric vehicles is limited, and there is an urgent need to develop a positive electrode active material that can replace cobalt.

Therefore, a nickel-cobalt-manganese lithium composite transition metal compound (hereinafter referred to as "NCM lithium composite transition metal compound") in which a portion of cobalt (Co) is replaced by nickel (Ni) and manganese (Mn) has been developed. In recent years, people have studied how to increase the capacity of NCM lithium-based composite transition metal compounds by increasing the content of Ni in the compound. However, Ni-rich positive active materials with high nickel content have disadvantages such as increased resistance and increased gas generation due to deterioration of thermal stability and increased side reactions during electrochemical reactions.

On the other hand, although graphite is generally used as the negative electrode active material of lithium secondary batteries, it is difficult to improve the capacity of lithium secondary batteries because graphite has a small capacity per unit mass of 372 mAh/g. Therefore, in order to improve the capacity of lithium secondary batteries, negative electrode materials such as silicon, tin and their oxides have been developed as non-carbon-based negative electrode materials with higher energy density than graphite. However, although these non-carbon-based negative electrode materials have large capacity, the problem with these materials is that the consumption of lithium is large and the irreversible loss of capacity is large during the initial charge and discharge process due to low initial efficiency.

Summary of the invention

Technical issues

The inventors have found that in a lithium secondary battery designed in 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 active materials constituting the positive and negative electrodes, thereby completing the present invention.

Technical Solution

One embodiment of the present disclosure provides a lithium secondary battery and a battery module and a battery pack including the same, the 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 contains a lithium composite transition metal compound containing nickel (Ni), cobalt (Co) and manganese (Mn), the lithium composite transition metal compound contains at least one of a single particle or a quasi-single particle, wherein each single particle is composed of one agglomerate, wherein each quasi-single particle is a composite of 30 or less agglomerates, and an average particle size (D ₅₀ ) of at least one of the single particle or the quasi-single particle is 1 μm or more, and the negative electrode active material contains a silicon-carbon composite, the silicon-carbon composite has an average particle size (D ₅₀ ) greater than 1 μm, and the average particle size (D 50 ) of at least one of the single particle or the quasi-single particle is smaller than _{the average particle size (D 50 )} of the silicon-carbon composite.

Beneficial Effects

According to the embodiments described in this specification, the energy density of a lithium secondary battery designed in a limited space can be increased, its high output performance can be improved, and the cycle performance of the battery can also be improved.

DETAILED DESCRIPTION

Hereinafter, in order to help understand the present invention, the present invention will be described in more detail. The present invention can be implemented in various different forms and is not limited to the exemplary embodiments described herein. In this case, the terms or words used in the specification and claims should not be interpreted as limited to the typical or dictionary meanings, but should be interpreted using the meanings and concepts consistent with the technical spirit of the present invention on the basis of the principle that the inventor can appropriately define the concept of the term to best describe his/her own invention.

In the present invention, the terms "comprise", "include" or "have" are intended to refer to the presence of implemented features, quantities, steps, constituent elements or any combination thereof, and should be understood to mean that the possibility of the presence or addition of one or more other features or quantities, steps, constituent elements or any combination thereof is not excluded.

The case where a part such as a layer exists "above" or "on" another part includes not only the case where the part exists "directly above" another part, but also the case where another part exists therebetween. Conversely, the case where a part exists "directly above" another part means that no other part exists therebetween. Furthermore, the case of being "above" or "on" a reference part means being located above or below the reference part, and does not necessarily mean being "above" or "on" located in the opposite direction of gravity.

In the present invention, a "single particle" is a particle composed of a single agglomerate. The "agglomerate" according to the present invention may be a single crystal lacking any grain boundaries, or may be a polycrystalline in which grain boundaries do not appear when observed in a field of view of 5000× to 20000× using a scanning electron microscope (SEM). In the present invention, a "quasi-single particle" refers to a particle of a composite formed by 30 or less agglomerates.

In the present invention, "secondary particles" refer to particles formed by the aggregation of tens to hundreds of primary particles. More specifically, secondary particles are aggregates of 50 or more primary particles.

In the present invention, when describing "particles", any one or all of single particles, quasi-single particles, primary particles, agglomerates and secondary particles may be included.

In this specification, "average particle size ( _D50 )" may be defined as a particle size corresponding to 50% of the volume cumulative amount in the particle size distribution curve of the particles. The average particle size ( _D50 ) may be measured using, for example, a laser diffraction method. The laser diffraction method is generally capable of measuring particle sizes from the submicron region to about several millimeters, and can obtain results with high reproducibility and high resolution.

The measurement of the average particle size (D ₅₀ ) can be confirmed by using a Microtrac instrument (manufacturer: Microtrac, model name: S3500) using water and Triton-X100 dispersant. Specifically, the average particle size (D ₅₀ ) of the positive electrode active material can be measured in a refractive index range of 1.5 to 1.7, and the negative electrode active material can be measured under a refractive index condition of 1.97 or 2.42. For example, after the particles are dispersed in a dispersion medium, the resulting dispersion is introduced into a commercially available laser diffraction particle size measuring device to irradiate the dispersion with an ultrasonic wave of about 28 kHz at an output of 60 W, and then a volume cumulative particle size distribution diagram is obtained, and then the average particle size can be measured by obtaining a particle size corresponding to 50% of the volume cumulative amount.

One embodiment of the present invention provides a lithium secondary battery, the lithium secondary battery comprising: a positive electrode comprising a positive electrode active material; a negative electrode comprising 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 contains a lithium composite transition metal compound containing nickel (Ni), cobalt (Co) and manganese (Mn), the lithium composite transition metal compound contains single particles and/or quasi-single particles having an average particle size ( _D50 ) of 1 μm or more, each single particle is composed of one agglomerate, and each quasi-single particle is a composite of 30 or less agglomerates, the negative electrode active material contains a silicon-carbon composite, the silicon-carbon composite has an average particle size ( _D50 ) greater than 1 μm, and the average particle size ( _D50 ) of the single particles or quasi-single particles is smaller than the average particle size ( _D50 ) of the silicon-carbon composite.

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

In this specification, the silicon carbon composite is a composite of Si and C, and is distinguished from silicon carbide represented by SiC. Since silicon carbide does not electrochemically react with lithium, all properties such as life characteristics can be measured as zero.

The silicon-carbon composite may be a composite of silicon, graphite, etc., or may form a structure in which a core made of a composite of silicon, graphite, etc. is surrounded by graphene, amorphous carbon, etc. In the silicon-carbon composite, silicon may be nano-silicon. For example, the nano-silicon may be silicon in the range of 1 nm to 999 nm.

Lithium secondary batteries have the size required for their use and need to be designed within a limited space. Although consumers' demand for increased energy density and improved high-output performance continues to increase, there is no choice but to increase the content of negative electrode materials to meet the needs when using high-capacity positive electrode materials, so there are limitations in improving battery efficiency within a limited space. In addition, depending on the type of negative electrode material, it is necessary to design a positive electrode material with an efficiency that matches the efficiency of the negative electrode material.

For example, the energy density can be improved, but when the electrode density is increased by reducing the porosity of the positive electrode, strong rolling for this purpose may cause deterioration of battery performance due to cracks generated on particles.

The single particles used in the embodiment of the present invention have high particle rigidity, and thus are relatively excellent in terms of battery performance degradation even when the electrode density is high. Therefore, the energy density can be increased by combining the single particles with the silicon-carbon composite according to the average particle size range.

According to another embodiment of the present invention, it is characterized in that the positive electrode active material contains a lithium composite transition metal compound containing nickel (Ni), cobalt (Co) and manganese (Mn), and the lithium composite transition metal compound contains single particles and/or quasi-single particles, and the average particle size ( _D50 ) of the single particles and/or quasi-single particles is greater than 1 μm.

As the average particle size (D ₅₀ ) of single particles and/or quasi-single particles becomes smaller, the specific surface area increases and the side reaction with the electrolyte increases, which may lead to a decrease in electrochemical performance such as life performance. If the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles is less than 1 μm, this may not be a commercially applicable range, and even so, the life performance may be very poor due to the increase in specific surface area, making it difficult to apply.

When the average particle size (D ₅₀ ) of the single particle and/or quasi-single particle is 1 μm or more, 3 μm or more, or 5 μm or more, the single particle and/or quasi-single particle has excellent service life performance due to reduced side reactions with the electrolyte.

In another aspect, the negative electrode active material comprises a silicon-carbon composite having an average particle size (D ₅₀ ) greater than 1 μm, and the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles is smaller than the average particle size (D ₅₀ ) of the silicon-carbon composite.

As the average particle size (D ₅₀ ) of the silicon-carbon composite becomes smaller, the specific surface area increases and the side reaction with the electrolyte increases, which may lead to a decrease in electrochemical performance such as life performance. If the average particle size (D ₅₀ ) of the silicon-carbon composite is less than 1 μm, the life performance may become very low due to the increase in side reactions caused by the increase in the specific surface area, which may be difficult to apply.

When the average particle size (D ₅₀ ) of the silicon-carbon composite is greater than 1 μm, greater than 3 μm, or greater than 5 μm, a side reaction with an electrolyte is reduced, resulting in excellent life performance.

Within the above range, the silicon-carbon composite has excellent service life performance, and the silicon grain size of the silicon-carbon composite can be less than 10 nm. In addition, the silicon-carbon composite has better initial capacity and efficiency than other silicon systems such as SiO, and has excellent electrochemical properties, thereby achieving optimal battery performance at the average value of single particles and/or quasi-single particle combinations.

Even if the single particle and/or quasi-single particle is formed of a small particle size, the single particle and/or quasi-single particle can also have excellent particle strength, and the excellent particle strength can alleviate the phenomenon of an increase in the number of particles in the electrode due to particle breakage, thereby improving the service life characteristics of the battery.

When the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles is smaller than the average particle size (D ₅₀ ) of the silicon-carbon composite, the diffusion resistance of the single particles and/or quasi-single particles can be relatively reduced to improve the service life performance. That is, lithium enters the single particles and/or quasi-single particles on the basis of discharge, and the diffusion resistance can increase with the increase of the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles. If the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles is larger than the average particle size (D ₅₀ ) of the silicon-carbon composite, lithium may not enter the single particles and/or quasi-single particles due to the relative increase in diffusion resistance, and may precipitate, resulting in a decrease in battery performance and a decrease in service life performance.

When the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles is smaller than the average particle size (D ₅₀ ) of the silicon-carbon composite, the single particles and/or quasi-single particles can be prevented from causing side reactions with the electrolyte due to an increase in specific surface area, thereby improving service life performance.

If the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles is smaller than the average particle size (D ₅₀ ) of the silicon-carbon composite, diffusion resistance of the single particles and/or quasi-single particles may be relatively reduced, thereby improving service life performance.

Because the single particles and/or quasi-single particles have a greater lithium diffusion resistance than the silicon-carbon composite, if the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles is larger than the average particle size (D ₅₀ ) of the silicon-carbon composite, the lithium diffusion resistance increases, so that the charge and discharge cannot be smoothly performed, resulting in poor service life performance. Therefore, the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles may be smaller than the average particle size (D ₅₀ ) of the silicon-carbon composite.

According to other exemplary embodiments of the present invention, the positive electrode active material includes nickel, cobalt, and manganese, and may further include aluminum.

According to an embodiment of the present invention, in the lithium composite transition metal compound, the content of nickel is 80 mol % or more relative to the metal other than lithium.

In another embodiment, in the positive electrode active material, the content of nickel is 80 mol% or more and less than 100 mol% relative to the metal other than lithium, and the lithium composite transition metal compound having a nickel content of 80 mol% or more and less than 100 mol% relative to the metal other than lithium may include one or a mixture of two or more represented by the following Chemical Formula 1.

The lithium composite transition metal compound may include secondary particles in addition to single particles and/or quasi-single particles.

[Chemical formula 1]

Li _a Ni _1-bcd Co _b Mn _c Q _d O _2+δ

In the chemical formula, Q is any one or more elements selected from Na, K, Mg, Ca, Sr, Ni, Co, Ti, Al, Si, Sn, Mn, Cr, Fe, V and Zr, 1≤a≤1.5, 0<b≤0.5, 0<c≤0.5, 0≤d≤0.1, 0<b+c+d≤20 and -0.1≤δ≤1.0.

In the lithium composite transition metal compound of Chemical Formula 1, the content of Li may correspond to a, that is, 1≤a≤1.5. There is a problem that when a is less than 1, the capacity may be reduced, and when a exceeds 1.5, the particles may be sintered during the firing process, making it difficult to prepare the positive electrode active material. Considering the effect of improving the capacity characteristics of the positive electrode active material by controlling the content of Li and the balance of sintering during the preparation of the active material, the content of Li may be more preferably 1.1≤a≤1.2.

In the lithium composite transition metal compound of Chemical Formula 1, the content of Ni may correspond 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 becomes a composition of 0.8 or more, a sufficient amount of Ni that contributes to charge and discharge can be ensured to achieve high capacity. Preferably, 1-(b+c+d) as the Ni content may be 0.88 or more, preferably 0.9 or more, and more preferably 0.93 or more. Preferably, 1-(b+c+d) as the Ni content may be 0.99 or less or 0.95 or less.

In the lithium composite transition metal compound of Chemical Formula 1, the content of Co may correspond 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 problem of increased cost. Considering the significant effect of improving capacity characteristics by including Co, the content of Co may be more specifically 0.03≤b≤0.2.

In the lithium composite transition metal compound of Chemical Formula 1, the content of Mn may correspond to c, that is, 0<c≤0.5. There is a problem that when c in the lithium composite transition metal compound of Chemical Formula 1 exceeds 0.5, the output characteristics and capacity characteristics of the battery may be deteriorated instead, and the content of Mn may be more specifically 0.01≤c≤0.2.

In the lithium composite transition metal compound of Chemical Formula 1, Q may be a doping element included in the crystal structure of the lithium composite transition metal compound, and the content of Q may correspond 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.

According to other exemplary embodiments of the present invention, the lithium composite transition metal compound in the positive electrode active material may include single particles and/or quasi-single particles and secondary particles.

The single particle and/or quasi-single particle can be prepared by mixing a transition metal precursor and a lithium raw material and sintering the resulting mixture. The secondary particle can be prepared by a method different from that of the single particle and/or quasi-single particle, and its composition can be the same as or different from that of the single particle and/or quasi-single particle.

For example, the firing is carried out at a temperature capable of forming single particles and/or quasi-single particles. In order to form single particles and/or quasi-single particles, the firing needs to be carried out at a temperature higher than that in the preparation of secondary particles. For example, when the composition of the precursor is the same, it is necessary to fire at a temperature about 30°C to 100°C higher than that when preparing secondary particles. The firing temperature for forming single particles and/or quasi-single particles may vary according to the metal composition in the precursor. For example, when it is desired to form a high Ni NCM-based lithium composite transition metal oxide with a nickel (Ni) content of 80 mol% or more in the form of single particles and/or quasi-single particles, the firing temperature may be 700°C to 1000°C, preferably about 800°C to 950°C. When the firing temperature satisfies the above range, a positive electrode active material containing single particles and/or quasi-single particles having excellent electrochemical properties can be prepared. When the firing temperature is lower than 790°C, a positive electrode active material containing a lithium composite transition metal compound in the form of secondary particles can be prepared, whereas when the firing temperature exceeds 950°C, over-firing may occur and a layered crystal structure may not be properly formed, thereby deteriorating electrochemical performance.

In the present invention, single particles and/or quasi-single particles are terms used to distinguish from secondary particles formed by aggregation of tens to hundreds of primary particles in the prior art.

Specifically, in the present invention, a single particle is composed of one agglomerate, and a quasi-single particle is an aggregate of 30 or less agglomerates. In contrast, a secondary particle may be in the form of an aggregate of several hundred primary particles.

According to other exemplary embodiments of the present invention, the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles is 1 μm or more, and the silicon-carbon composite has an average particle size (D ₅₀ ) greater than 1 μm.

According to an exemplary embodiment, the single particles and/or quasi-single particles may have an average particle size (D ₅₀ ) of 1 μm or more, and the silicon-carbon composite may have an average particle size (D ₅₀ ) greater than 1 μm.

According to other embodiments of the present invention, the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles is 12 μm or less, and the silicon-carbon composite has an average particle size (D ₅₀ ) of less than 15 μm.

For example, the single particle and/or quasi-single particle may have an average particle size (D50) of 1 μm to 12 μm, 1 μm to 8 μm, 1 μm to 5 μm, greater than 1 μm to 12 μm, greater than 1 μm to 8 μm, or greater than 1 μm to ₅ μm.

Even if the single particle and/or quasi-single particle is formed into a small particle size having an average particle size (D ₅₀ ) of 1 μm or more and 12 μm or less, the particle strength can be excellent. For example, when rolled at a force of 650 kgf/cm ² , the single particle and/or quasi-single particle can have a particle strength of 100 to 300 MPa. As a result, even if the single particle and/or quasi-single particle is rolled at a strong force of 650 kgf/cm ² , the phenomenon of an increase in the number of particles in the electrode due to particle rupture is alleviated, thereby improving the service life characteristics of the battery.

When the average particle size (D ₅₀ ) of the single particle and/or quasi-single particle satisfies the above range, the single particle and/or quasi-single particle has excellent service life performance due to reduced side reactions with electrolytes, and has excellent electrochemical performance due to good charge and discharge.

If the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles is less than 1 μm, the service life performance may be very poor due to the increase in specific surface area, making it difficult to apply.

If the average particle size (D ₅₀ ) of the single particle and/or quasi-single particle is 12 μm or less, the single particle and/or quasi-single particle has excellent electrochemical performance due to good charge and discharge.

The method for forming the single particles and/or quasi-single particles is not particularly limited, but generally, the single particles and/or quasi-single particles can be formed by increasing the firing temperature to achieve overfiring, and the single particles and/or quasi-single particles can be prepared by using additives such as grain growth promoters that facilitate overfiring or by changing the starting material.

According to other embodiments of the present invention, the silicon-carbon composite may have an average particle size (D ₅₀ ) greater than 1 μm and less than 15 μm, greater than 2 μm and less than 14 μm, or greater than 3 μm and less than 13 μm.

Even if the silicon-carbon composite is formed into a small particle size (D ₅₀ ) greater than 1 μm and less than 15 μm, the service life characteristics of the battery can be improved. For example, when the average particle size (D ₅₀ ) of the _silicon -carbon composite is greater than 1 μm and less than 15 μm, the volume expansion and contraction rate occurring with charge and discharge can be reduced to improve the service life performance. In addition, the specific surface area is prevented from being excessively increased to prevent a side reaction with the electrolyte due to the progress of the cycle, thereby improving the service life performance.

If the average particle size (D ₅₀ ) of the silicon-carbon composite is 1 μm or less, the service life performance may be very poor due to an increase in specific surface area, making it difficult to apply.

If the average particle size (D ₅₀ ) of the silicon-carbon composite is less than 15 μm, the particles are small and can easily complete charge and discharge, and the volume expansion and contraction rate of the particles due to charge and discharge can be reduced, thereby improving the service life performance.

According to other embodiments of the present invention, the average particle size (D ₅₀ ) of the single particle and/or quasi-single particle is characterized by being smaller than the average particle size (D ₅₀ ) of the silicon-carbon composite. Thus, even if the single particle and/or quasi-single particle is formed of a small particle size, the single particle and/or quasi-single particle can have excellent particle strength, and the excellent particle strength can alleviate the phenomenon of an increase in the number of particles in the electrode due to particle rupture, thereby improving the service life characteristics of the battery.

If the average particle size ( _D50 ) of the single particles and/or quasi-single particles is smaller than _that of the silicon-carbon composite, the diffusion resistance of the single particles and/or quasi-single particles having greater lithium diffusion resistance than the silicon-carbon composite may be relatively reduced, thereby improving service life performance.

According to one embodiment of the present invention, the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles is 1 μm to 12 μm smaller than the average particle size (D ₅₀ ) of the silicon-carbon composite.

The average particle size (D ₅₀ ) of the single particles and/or quasi-single particles may be smaller than the average particle size (D ₅₀ ) of the silicon-carbon composite by 1.5 μm to 11.5 μm, or 2 μm to 11 μm.

The average particle size ( _D50 ) of the single particles and/or quasi-single particles may be 2 μm or more or 4 μm smaller than the average particle size ( _D50 ) of the silicon-carbon composite. The average particle size ( _{D50) of the single particles and/or quasi-single particles may be 11 μm or less, 8 μm or less, or 6 μm or less than the average particle size (D50 )} of the silicon-carbon composite.

When the average particle size (D ₅₀ ) of the single particle and/or quasi-single particle is smaller than the average particle size (D ₅₀ ) of the silicon-carbon composite, for example, when the above range is satisfied, the diffusion resistance of the single particle can be relatively reduced to improve the service life performance. That is, as the average particle size (D ₅₀ ) of the single particle and/or quasi-single particle increases, the diffusion resistance may increase, and when the average particle size (D ₅₀ ) of the single particle and/or quasi-single particle is larger than the average particle size (D ₅₀ ) of the silicon-carbon composite, lithium precipitation may occur due to the relative increase in diffusion resistance, resulting in degradation of battery performance and degradation of service life performance.

When the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles is smaller than the average particle size (D ₅₀ ) of the silicon-carbon composite, for example, when the above range is satisfied, side reactions with the electrolyte due to an increase in specific surface area can be prevented, thereby improving service life performance.

According to one embodiment of the present invention, the ratio of the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles to the average particle size (D ₅₀ ) of the silicon-carbon composite is in the range of 1.5:2 to 1.5:20.

In some embodiments, the ratio of the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles to the average particle size (D ₅₀ ) of the silicon-carbon composite may be 1.5:2 to 1.5:19, or 1.5:2 to 1.5:18.

In some embodiments, the ratio of the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles to the average particle size (D ₅₀ ) 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. In some embodiments, the ratio of the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles to the average particle size (D ₅₀ ) 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.

When the above range is met, the diffusion resistance of the single particle and/or quasi-single particle can be relatively reduced to improve the service life performance. That is, as the average particle size (D ₅₀ ) of the single particle and/or quasi-single particle increases, the diffusion resistance may increase, and when the average particle size (D ₅₀ ) of the single particle and/or quasi-single particle is greater than the average particle size (D ₅₀ ) of the silicon-carbon composite, lithium precipitation may occur due to the relative increase in diffusion resistance, resulting in degradation of battery performance and service life performance.

When the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles is smaller than the average particle size (D ₅₀ ) of the silicon-carbon composite, for example, when the above range is satisfied, side reactions with the electrolyte due to an increase in specific surface area can be prevented, thereby improving service life performance.

In an exemplary embodiment of the present invention, the lithium composite transition metal compound further includes secondary particles, and the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles is smaller than the average particle size (D ₅₀ ) of the secondary particles.

In the present invention, the single particle is composed of one agglomerate, and the quasi-single particle is an aggregate of 30 or less agglomerates, and the secondary particle may be in the form of an aggregate of several hundred primary particles.

The lithium composite transition metal compound may further include secondary particles. The secondary particles are particles formed by aggregation of primary particles and can be distinguished from the concept of single particles consisting of one agglomerate or quasi-single particles that are aggregates of 30 or less agglomerates.

The secondary particles may have a particle size ( _D50 ) of 1 to 20 μm, 2 to 17 μm, preferably 3 to 15 μm. The secondary particles ^may have a specific surface area (BET) of 0.05 to ^{10 m2 /} g, preferably 0.1 to 1 ^m2 /g, and more preferably 0.3 to 0.8 ^m2 /g.

In other exemplary embodiments of the present invention, the secondary particles are aggregates of primary particles, and the average particle size (D ₅₀ ) 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 primary particles may have an average particle size (D ₅₀ ) of 0.6 μm to 2.8 μm, 0.8 μm to 2.5 μm, or 0.8 μm to 1.5 μm.

When the average particle size (D ₅₀ ) of the primary particles aggregated in the secondary particles satisfies the above range, a single-particle positive electrode active material with excellent electrochemical performance can be formed. When the average particle size (D ₅₀ ) of the primary particles aggregated in the secondary particles is too small, the number of aggregated primary particles forming lithium nickel-based oxide particles increases, thereby reducing the effect of suppressing particle breakage during rolling, and when the average particle size (D ₅₀ ) of the primary particles aggregated in the secondary particles is too large, the diffusion path of lithium in the primary particles becomes longer, thereby increasing resistance and the output characteristics may be deteriorated.

According to other embodiments of the present invention, the average particle size (D ₅₀ ) of the single particle and/or quasi-single particle is characterized by being smaller than the average particle size (D ₅₀ ) of the secondary particle. Thus, even if the single particle and/or quasi-single particle is formed of a small particle size, the single particle can have excellent particle strength, and the excellent particle strength can alleviate the phenomenon of an increase in the number of particles in the electrode due to particle rupture, thereby improving the service life characteristics of the battery.

In one embodiment of the present invention, the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles is 1 μm to 18 μm smaller than the average particle size (D ₅₀ ) of the secondary particles.

For example, the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles may be smaller than the average particle size (D ₅₀ ) of the secondary particles by 1 μm to 16 μm, 1.5 μm to 15 μm, or 2 μm to 14 μm.

The average particle size (D ₅₀ ) of the single particle and/or quasi-single particle may be smaller than the average particle size (D ₅₀ ) of the secondary particle by 1 μm or more, 2 μm or more, 4 μm or more, or 6 μm or more. The average particle size (D ₅₀ ) of the single particle and/or quasi-single particle may be smaller than the average particle size (D ₅₀ ) of the secondary particle by 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. When the average particle size (D ₅₀ ) of the single particle and/or quasi-single particle is smaller than the average particle size (D ₅₀ ) of the secondary particle, for example, when the above range is satisfied, the single particle and/or quasi-single particle may have excellent particle strength even when formed of a small particle size, and the excellent particle strength alleviates the phenomenon of an increase in the number of particles in the electrode due to particle rupture, thereby having the effect of improving the service life characteristics of the battery and increasing the energy density.

In the lithium secondary battery according to the exemplary embodiment described above, 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.

In one embodiment of the present invention, the negative electrode active material further comprises graphite, and the average particle size (D ₅₀ ) of the silicon-carbon composite is smaller than the average particle size (D ₅₀ ) of the graphite.

When the average particle size (D ₅₀ ) of the silicon-carbon composite is smaller than the average particle size (D ₅₀ ) of the graphite, the volume expansion/contraction rate is reduced during the charge and discharge process, resulting in reduced particle breakage, thereby improving the battery life performance. According to one embodiment of the present invention, the average particle size (D ₅₀ ) of the silicon-carbon composite is 1 μm to 25 μm smaller than the average particle size (D ₅₀ ) of the graphite.

For example, the average particle size (D ₅₀ ) of the silicon-carbon composite may be smaller than the average particle size (D ₅₀ ) of the graphite by 2 μm to 24 μm, 3 μm to 23 μm, or 4 μm to 22 μm.

The average particle size (D ₅₀ ) of the silicon-carbon composite may be smaller than the average particle size (D ₅₀ ) of the graphite by 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. The average particle size (D ₅₀ ) of the silicon-carbon composite may be smaller than the average particle size (D ₅₀ ) of the graphite by 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.

When the average particle size (D ₅₀ ) of the silicon-carbon composite is smaller than the average particle size (D ₅₀ ) of graphite, for example, when the above range is satisfied, there is an effect of improving the battery life performance.

In one embodiment of the present invention, the lithium composite transition metal compound further comprises secondary particles, the negative electrode active material further comprises graphite, and the average particle sizes (D ₅₀ ) of the secondary particles, the single particles and/or quasi-single particles, the graphite and the silicon-carbon composite are represented by A, B, C and D, respectively, wherein B＜D≤A＜C.

Exemplary embodiments of the secondary particles, the single particles and/or quasi-single particles, the graphite, and the silicon-carbon composite are as described above.

When the average particle sizes (D ₅₀ ) of the secondary particles, the single particles and/or quasi-single particles, the graphite and the silicon-carbon composite are A, B, C and D respectively, the condition of B<D≤A<C has the effect of improving the battery life performance.

According to one embodiment of the present invention, the negative electrode active material further comprises graphite, and the average particle sizes (D ₅₀ ) of the single particle and/or quasi-single particle, the graphite and the silicon-carbon composite are represented by B, C and D, respectively, wherein B<D<C.

The average particle diameters (D ₅₀ ) of the secondary particles, the single particles and/or quasi-single particles, and the silicon-carbon composite are represented by A, B, and D, respectively, and may be B<D≤A.

The average particle diameters (D ₅₀ ) of the secondary particles, the single particles and/or quasi-single particles, and the graphite are represented by A, B, and C, respectively, and may be B<A<C.

The average particle diameters (D ₅₀ ) of the secondary particles, the graphite, and the silicon-carbon composite are represented by A, C, and D, respectively, and may be D≤A<C.

When the above range is met, there is an effect of improving the battery life performance.

In one embodiment of the present invention, in the lithium secondary battery according to the above exemplary embodiment, based on 100 parts by weight of the positive electrode active material, the content of the single particles and/or quasi-single particles is 15 parts by weight to 100 parts by weight, and based on 100 parts by weight of the negative electrode active material, the content of the silicon-carbon composite is 3 parts by weight to 30 parts by weight.

According to other exemplary embodiments of the present invention, based on 100 parts by weight of the positive electrode active material, the content of the single particle and/or quasi-single particle is 15 parts by weight to 100 parts by weight. Based on 100 parts by weight of the positive electrode active material, the content of the single particle and/or quasi-single particle may be 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.

For example, based on 100 parts by weight of the positive electrode active material, the content of the single particle and/or quasi-single particle may be 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 content of the single particle and/or quasi-single particle may be less than 100 parts by weight.

When the single particles and/or quasi-single particles within the above range are included, they can exhibit excellent battery characteristics by combining with the above negative electrode materials. Specifically, when the amount of the single particles and/or quasi-single particles is 15 parts by weight or more, the phenomenon of an increase in the number of particles in the electrode due to particle rupture during the rolling process after manufacturing the electrode can be reduced, thereby improving the service life characteristics of the battery.

In an exemplary embodiment of the present invention, the lithium composite transition metal compound may further include secondary particles, wherein the content of the secondary particles may be 0 to 85 parts by weight, 0 to 70 parts by weight, or 0 to 50 parts by weight based on 100 parts by weight of the positive electrode active material.

Based on 100 parts by weight of the positive electrode active material, 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. Based on 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.

When the above range is met, the above effect due to the presence of the single particle and/or quasi-single particle positive electrode active material can be maximized. When a positive electrode active material of secondary particles is included, the component may be the same as the component exemplified as the above single particle positive electrode active material, or may be other components, and may be in the form of aggregates in the form of single particles.

In one embodiment of the present invention, the positive electrode also contains a positive electrode active material layer comprising the positive electrode active material, and in 100 parts by weight of the positive electrode active material layer, the content of the positive electrode active material can be more than 80 parts by weight and less than 99.9 parts by weight, preferably more than 90 parts by weight and less than 99.9 parts by weight, more preferably more than 95 parts by weight and less than 99.9 parts by weight, and even more preferably more than 98 parts by weight and less than 99.9 parts by weight.

According to one embodiment of the present invention, the positive electrode according to the above exemplary embodiment further includes a positive electrode binder and a conductive material.

The positive electrode binder is used to improve the bonding between the positive electrode active material particles and the adhesion between the positive electrode active material particles and the positive electrode current collector. As the positive electrode binder, a binder known in the art can be used, and its 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, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer rubber (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber or its various copolymers, and any one thereof or a mixture of two or more thereof can be used.

The content of the positive electrode binder may be 0.1 parts by weight to 50 parts by weight, for example, preferably 0.3 parts by weight to 35 parts by weight, and 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.

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 the conductive material has electronic conductivity without causing chemical changes in the battery. Specific examples thereof include: graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon 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, and any one thereof or a mixture of two or more thereof may be used.

Specifically, in an exemplary embodiment, the conductive material may include one or more of single-walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT). Based on 100 parts by weight of the composition for the positive electrode active material layer, the content of the conductive material may be 0.1 parts by weight or more and 2 parts by weight or less, for example, preferably 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.

In this specification, the silicon carbon composite is a composite of Si and C, peaks of Si and C (graphite) are observed in an XRD diffraction pattern, and a second phase Si/C does not seem to be formed. The silicon carbon composite is different from a silicon carbide insulator represented by SiC.

According to the above embodiment of the present invention, the negative electrode further contains a negative electrode active material layer containing a negative electrode active material, and based on 100 parts by weight of the total negative electrode active material, the negative electrode active material layer contains 3 parts by weight to 30 parts by weight of the silicon-carbon composite. According to one example, based on 100 parts by weight of the total negative electrode active material, the negative electrode active material layer may contain 3 parts by weight to 20 parts by weight or 3 parts by weight to 13 parts by weight, preferably 5 parts by weight to 10 parts by weight of the silicon-carbon composite.

Based on 100 parts by weight of the total negative electrode active material, 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. Based on 100 parts by weight of the total negative electrode active material, the negative electrode active material layer may contain less than 30 parts by weight, less than 20 parts by weight, or less than 10 parts by weight of the silicon-carbon composite.

By using the silicon-carbon composite within the above range, it can exhibit excellent battery characteristics by combining with the above positive electrode material. In particular, when the content of the silicon-carbon composite is 3 parts by weight or more, the effect of using the silicon-carbon composite can be fully exhibited. In addition, because the silicon-carbon composite has a higher capacity than the SiOx-based active material, when used in excess, it may be difficult to balance the capacity of the positive electrode active material, especially when the content of the silicon-carbon composite is 30 parts by weight or less, expansion during charge and discharge can be prevented to improve cycle characteristics.

The silicon-carbon composite is a material having higher capacity and higher efficiency than silicon-based oxides, and even when no conductive material is included, it is possible to exhibit superior effects in terms of resistance than a positive electrode including silicon-based oxides and conductive materials. In addition, since the silicon-carbon composite has higher Si crystallinity than silicon-based oxides, it is possible to exhibit superior effects during high output evaluation.

According to other embodiments of the present invention, in the lithium secondary battery according to the above exemplary 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. Based on 100 parts by weight of all negative electrode active materials contained in the negative electrode active material layer, the content of the graphite may be 70 parts by weight or more and 97 parts by weight or less.

Based on 100 parts by weight of all negative electrode active materials, the content of the graphite may be 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 all negative electrode active materials, the content of the graphite may be 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 content of the artificial graphite and natural graphite may be 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.

In one embodiment of the present invention, in 100 parts by weight of the negative electrode active material layer, the content of the negative electrode active material may be greater than 80 parts by weight and less than 99.9 parts by weight, preferably greater than 90 parts by weight and less than 99.9 parts by weight, more preferably greater than 95 parts by weight and less than 99.9 parts by weight, and even more preferably greater than 98 parts by weight and less than 99.9 parts by weight.

According to other embodiments of the present invention, in the lithium secondary battery according to the above exemplary embodiment, the negative electrode active material layer may further include a negative electrode binder in addition to the silicon-carbon composite and graphite.

The negative electrode binder is used to improve the bonding between the negative electrode active material particles and the adhesion between the negative electrode active material particles and the negative electrode current collector. As the negative electrode binder, a binder known in the art can be used, and its non-limiting examples may include at least one selected from the following: 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 rubber (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, and materials in which hydrogen is replaced by Li, Na, Ca, etc., and various copolymers thereof may also be included.

The content of the negative electrode binder may be 0.1 parts by weight to 50 parts by weight, for example, preferably 0.3 parts by weight to 35 parts by weight, and 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.

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 the conductive material has conductivity without causing chemical changes in the battery, and for example, substances such as the following can be used: graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black and thermal black; conductive fibers such as carbon fibers or metal fibers; conductive tubes such as carbon nanotubes; carbon fluoride; metal powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives, etc. Based on 100 parts by weight of the negative electrode active material layer, the content of the conductive material in the negative electrode active material layer may be 0.01 parts by weight to 30 parts by weight, preferably 0.03 parts by weight to 20 parts by weight.

In one embodiment of the present invention, 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 a positive electrode active material.

There is no particular limitation on the positive electrode current collector as long as the current collector has conductivity without causing chemical changes in the battery, and for example: stainless steel, aluminum, nickel, titanium, calcined carbon; or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. can be used. In addition, the positive electrode current collector can generally have a thickness of 1 μm to 500 μm, and the adhesion of the positive electrode active material can also be enhanced by forming fine concavoconvexities on the surface of the current collector. For example, the positive electrode current collector can be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and non-woven fabrics.

In one embodiment of the present invention, the negative electrode includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector and including a negative electrode active material.

As long as the negative electrode current collector has conductivity without causing chemical changes in the battery, the negative electrode current collector is sufficient and is not particularly limited. For example, as the current collector, copper, stainless steel, aluminum, nickel, titanium, fired carbon; or aluminum or stainless steel with a surface treated with carbon, nickel, titanium, silver, etc. can be used. Specifically, transition metals such as copper or nickel that can adsorb carbon well can be used as current collectors. The thickness of the current collector can be 1 μm to 500 μm, but the thickness of the current collector is not limited thereto.

In one embodiment of the present invention, the positive electrode further contains a positive electrode active material layer containing a positive electrode active material, the negative electrode further contains a negative electrode active material layer containing a negative electrode active material, and the thickness of the positive electrode active material layer and the negative electrode active material layer are respectively 10 μm or more and 500 μm or less. The thickness of the positive electrode active material layer may be 90% to 110% of the thickness of the negative electrode active material layer, for example 95% to 105%, and the thickness of the active material layer may be the same. Specifically, the positive electrode active material layer and the negative electrode active material layer may each have a thickness of 15 μm or more and 400 μm or less, 20 μm or more and 300 μm or less, 25 μm or more and 200 μm or less, or 30 μm or more and 100 μm or less.

In one embodiment of the present invention, the positive electrode further comprises a positive electrode active material layer comprising a positive electrode active material, and the positive electrode active material layer has a unit volume loading of 250 mg/ ^25cm2 to 900 mg/ ^25cm2 , and the negative electrode further comprises a negative electrode active material layer comprising a negative electrode active material, and the negative electrode active material layer has a unit volume loading of 100 mg/ ^25cm2 to 600 mg/ ^25cm2 . Specifically, the positive electrode active material layer may have a loading per unit volume of 270 ^to 800 mg/25 ^{cm2 ,} 285 to 700 mg/25 ^cm2, or 300 ^to 600 mg/25 ^cm2 , and the negative electrode active material layer may have a loading per unit volume of 120 ^to 500 mg/25 ^cm2 , 135 ^to 400 mg/25 ^cm2, or ¹⁵⁰ to 300 mg/25 ^cm2 .

The positive electrode and the negative electrode can be manufactured by the method for manufacturing the positive electrode and the negative electrode in the related art, provided that the above-mentioned positive electrode active material and the negative electrode active material are used. Specifically, after the composition for forming the active material layer containing the above-mentioned active material and the optional binder and the conductive material is applied to the collector, the positive electrode and the negative electrode can be manufactured by drying and rolling the collector. In this case, the type and content of the positive electrode active material and the negative electrode active material, the binder and the conductive material are as described above. The solvent can be a commonly used solvent in the art, examples of which include dimethyl sulfoxide (DMSO), isopropanol, N-methylpyrrolidone (NMP), acetone, water, etc., and any one or a mixture of two or more thereof can be used. As long as the coating thickness and preparation yield of the slurry are taken into account, the amount of the solvent can dissolve or disperse the active material, the conductive material and the binder, and has a viscosity that can show excellent thickness uniformity in the subsequent coating for manufacturing the positive and negative electrodes, then the amount of the solvent is sufficient. Alternatively, by another method, the positive electrode and the negative electrode may be manufactured by casting the active material layer-forming composition on a separate support and then laminating a film obtained by peeling off the support on a current collector.

The separator is used to separate the negative electrode from the positive electrode and provide a mobile channel for lithium ions, and can be used without particular restrictions, as long as the separator is generally used as a separator in a secondary battery, and in particular, a separator having excellent moisture retention ability for the electrolyte and low resistance to ion movement in the electrolyte is preferred. Specifically, it is possible to use: a porous polymer film, for example, a porous polymer film formed by a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, and an ethylene/methacrylate copolymer; or a laminated structure of two or more layers thereof. In addition, ordinary porous non-woven fabrics, such as non-woven fabrics made of high melting point glass fibers, polyethylene terephthalate fibers, etc., can also be used. In addition, in order to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer material can be used, and can be selectively used in a single-layer or multi-layer structure.

Examples of the electrolyte include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which can be used to prepare lithium secondary batteries, but are not limited thereto.

Specifically, the electrolyte may include a nonaqueous organic solvent and a metal salt.

As the nonaqueous organic solvent, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidone, 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, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate and ethyl propionate can be used.

In particular, among the carbonate-based organic solvents, ethylene carbonate and propylene carbonate as cyclic carbonates can be preferably used because the cyclic carbonates have a high dielectric constant as a high-viscosity organic solvent, thereby dissociating lithium salts well, and the cyclic carbonates can be mixed with low-viscosity and low-dielectric-constant linear carbonates such as dimethyl carbonate and diethyl carbonate in an appropriate ratio and used to prepare an electrolyte with high conductivity, so such cyclic carbonates can be more preferably used.

As the metal salt, a lithium salt can be used. ^The lithium salt is a material that is easily soluble in a non-aqueous electrolyte. For example, as an anion of the lithium salt, one or more selected from the following can be used: 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 ^- , (CF ₃ SO ₂ ) ₃ C ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- .

In the electrolyte, in order to improve the life characteristics of the battery, inhibit the reduction of the battery capacity, and increase the discharge capacity of the battery, on the basis of containing the above-mentioned electrolyte components, for example, one or more additives such as the following may be included: halogenated alkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, (condensed) glycol dimethyl ethers, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted Oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol or aluminum trichloride.

The lithium secondary battery according to an exemplary embodiment of the present invention has an energy density of 400 Wh/L to 900 Wh/L. Specifically, the lithium secondary battery may have an energy density of 425 Wh/L to 875 Wh/L, 450 Wh/L to 850 Wh/L, 475Wh/L to 825 Wh/L or 500 Wh/L to 800 Wh/L. When the above range is met, the energy density of the lithium secondary battery designed in a limited space can be improved, the high output performance of the lithium secondary battery can be improved, and the cycle performance of the battery can also be improved.

The lithium secondary battery according to an exemplary embodiment of the present invention may be a cylindrical battery. A cylindrical battery means that the battery itself containing components including a positive electrode, a negative electrode, a separator and an electrolyte is in a cylindrical form, specifically, it may be composed of a cylindrical can, a battery assembly disposed in the cylindrical can, and a top cover. However, the lithium secondary battery is not limited thereto, and may be a square battery or a pouch battery.

Other exemplary embodiments of the present invention provide a battery module including the above cylindrical battery as a unit cell and a battery pack including the battery module. Since the battery module and the battery pack include the secondary battery having high capacity, high rate performance and high cycle characteristics, they can be used as a power source for medium and large devices selected from the following: electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles and power storage systems.

Because the lithium secondary battery according to the exemplary embodiment of the present invention stably exhibits excellent discharge capacity, output characteristics and cycle performance, the lithium secondary battery can be used as a power source for the following devices: portable devices such as mobile phones, laptops and digital cameras; and medium and large devices selected from electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles and power storage systems. For example, the battery module or battery pack can be used as a power source for one or more medium and large devices in the following: power tools; electric vehicles, including electric vehicles (EV), hybrid electric vehicles and plug-in hybrid electric vehicles (PHEV); and power storage systems.

Modes for Carrying Out the Invention

Hereinafter, preferred embodiments will be proposed to help understand the present invention, but these embodiments are provided only to illustrate the present invention, and it is obvious to those skilled in the art that various substitutions and variations within the scope of the present invention and the technical spirit are possible. Naturally, such substitutions and variations also fall within the scope of the appended claims.

<Example 1>

A composition for forming a positive electrode active material layer is prepared, wherein based on 100 parts by weight of the positive electrode active material layer, the composition comprises: 98.04 parts by weight (weight ratio of single particles and/or quasi-single particles: secondary particles = 80:20) of a lithium composite transition metal compound as a positive electrode active material, which has a content of 93.3 mol% Ni, 4.9 mol% Co and 1.8 mol% Mn relative to metals other than lithium; 1 part by weight of PVDF as a binder; and a CNT pre-dispersion, which comprises 0.8 parts by weight of CNT as a conductive material and 0.16 parts by weight of a dispersant. In this case, the single particles and/or quasi-single particles are prepared to a size of D ₅₀ = 3 μm by a gas flow milling method, and the secondary particles are prepared to a size of D ₅₀ = 7 μm. The composition for forming a positive electrode active material layer is coated on an aluminum foil having a thickness of 30 μm so as to have a thickness of 103 μm in a dry state, and then dried to manufacture a positive electrode.

A composition for forming a negative electrode active material layer was prepared, wherein based on 100 parts by weight of the negative electrode active material layer, the composition included: 97.7 parts by weight of graphite as a negative electrode active material (artificial graphite: natural graphite weight ratio = 70:30, based on 100 parts by weight of the negative electrode active material is 90 parts by weight) and a silicon-carbon composite (based on 100 parts by weight of the negative electrode active material is 10 parts by weight); 1.15 parts by weight of styrene-butadiene rubber (SBR) as a binder and 1 part by weight of carboxymethyl cellulose (CMC), and also included a CNT pre-dispersion, the CNT pre-dispersion including 0.09 parts by weight of a dispersant and 0.06 parts by weight of single-walled CNTs. In this case, the silicon-carbon composite was prepared to a size of D ₅₀ = 5 μm, and the graphite was prepared to a size of D ₅₀ = 17 μm by airflow pulverization. The negative electrode active material layer-forming composition was coated on a copper foil having a thickness of 15 μm so as to have a thickness of 86 μm in a dry state, and then dried to manufacture a negative electrode.

The positive electrode and the negative electrode were stacked with a separator therebetween, and an electrolyte (1.0 M LiPF ₆ , ethylene carbonate (EC)/ethyl methyl carbonate (EMC)=30/70 (volume %), vinylene carbonate (VC) 1.5%) was injected to manufacture a battery.

<Example 2>

A positive electrode was manufactured in the same manner as in Example 1, except that the weight ratio of the single particles and/or quasi-single particles to the secondary particles in the lithium composite transition metal compound was adjusted to 50:50 based on 100 parts by weight of the positive electrode active material. Then, a battery was manufactured in the same manner as in Example 1, except that the manufactured positive electrode was used.

<Example 3>

A positive electrode was manufactured in the same manner as in Example 1 except that the content 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. Then, a battery was manufactured in the same manner as in Example 1 except that the manufactured positive electrode was used.

<Example 4>

Except that the silicon-carbon composite contained in the negative electrode active material had D ₅₀ =9 μm, a negative electrode was manufactured in the same manner as in Example 3. Then, a battery was manufactured in the same manner as in Example 3 except that the manufactured negative electrode was used.

<Example 5>

A negative electrode was manufactured in the same manner as in Example 3 except that the content of the silicon carbon composite was 5 parts by weight based on 100 parts by weight of the negative electrode active material. Then, a battery was manufactured in the same manner as in Example 3 except that the manufactured negative electrode was used.

<Example 6>

Except that the silicon-carbon composite contained in the negative electrode active material had D ₅₀ =7 μm, a negative electrode was manufactured in the same manner as in Example 1. Then, a battery was manufactured in the same manner as in Example 1, except that the manufactured negative electrode was used.

<Example 7>

Except that the single particle and/or quasi single particle contained in the positive electrode active material had D ₅₀ =1 μm, a positive electrode was manufactured in the same manner as in Example 3. Then, a battery was manufactured in the same manner as in Example 3 except that the manufactured positive electrode was used.

<Example 8>

A positive electrode and a negative electrode were manufactured in the same manner as in Example 2, except that the single particles and/or quasi-single particles and the secondary particles contained in the positive electrode active material had D ₅₀ = 1 μm and 5 μm, respectively, and the silicon-carbon composite contained in the negative electrode active material had D ₅₀ = 3 μm. Then, a battery was manufactured in the same manner as in Example 2, except that the manufactured positive electrode and negative electrode were used.

<Example 9>

Except that graphite contained in the negative electrode active material had D ₅₀ =25 μm, a negative electrode was manufactured in the same manner as in Example 8. Then, a battery was manufactured in the same manner as in Example 8, except that the manufactured negative electrode was used.

<Example 10>

A positive electrode and a negative electrode were manufactured in the same manner as in Example 8, except that the secondary particles contained in the positive electrode active material had _D50 = 7 μm and the graphite contained in the negative electrode active material had _D50 = 13 μm. Then, a battery was manufactured in the same manner as in Example 8, except that the manufactured positive electrode and negative electrode were used.

<Example 11>

Except that graphite contained in the negative electrode active material had D ₅₀ =17 μm, a negative electrode was manufactured in the same manner as in Example 10. Then, a battery was manufactured in the same manner as in Example 10 except that the manufactured negative electrode was used.

<Example 12>

Except that graphite contained in the negative electrode active material had D ₅₀ =25 μm, a negative electrode was manufactured in the same manner as in Example 10. Then, a battery was manufactured in the same manner as in Example 10 except that the manufactured negative electrode was used.

<Example 13>

Except that the secondary particles contained in the positive electrode active material had D ₅₀ =9 μm, a positive electrode was manufactured in the same manner as in Example 10. Then, a battery was manufactured in the same manner as in Example 10 except that the manufactured positive electrode was used.

<Example 14>

Except that graphite contained in the negative electrode active material had D ₅₀ =17 μm, a negative electrode was manufactured in the same manner as in Example 13. Then, a battery was manufactured in the same manner as in Example 13 except that the manufactured negative electrode was used.

<Example 15>

Except that graphite contained in the negative electrode active material had D ₅₀ =25 μm, a negative electrode was manufactured in the same manner as in Example 13. Then, a battery was manufactured in the same manner as in Example 13 except that the manufactured negative electrode was used.

<Example 16>

Except that the secondary particles contained in the positive electrode active material had D ₅₀ =15 μm, a positive electrode was manufactured in the same manner as in Example 8. Then, a battery was manufactured in the same manner as in Example 8, except that the manufactured positive electrode was used.

<Example 17>

Except that the silicon-carbon composite contained in the negative electrode active material had D ₅₀ =5 μm, a negative electrode was manufactured in the same manner as in Example 10. Then, a battery was manufactured in the same manner as in Example 10 except that the manufactured negative electrode was used.

<Example 18>

Except that graphite contained in the negative electrode active material had D ₅₀ =17 μm, a negative electrode was manufactured in the same manner as in Example 17. Then, a battery was manufactured in the same manner as in Example 17 except that the manufactured negative electrode was used.

<Example 19>

Except that graphite contained in the negative electrode active material had D ₅₀ =25 μm, a negative electrode was manufactured in the same manner as in Example 17. Then, a battery was manufactured in the same manner as in Example 17 except that the manufactured negative electrode was used.

<Example 20>

Except that the secondary particles contained in the positive electrode active material had D ₅₀ =9 μm, a positive electrode was manufactured in the same manner as in Example 18. Then, a battery was manufactured in the same manner as in Example 18, except that the manufactured positive electrode was used.

<Example 21>

A positive electrode and a negative electrode were manufactured in the same manner as in Example 8, except that the secondary particles contained in the positive electrode active material had _D50 = 3 μm, and the silicon carbon composite contained in the negative electrode active material had _D50 = 7 μm. Then, a battery was manufactured in the same manner as in Example 8, except that the manufactured positive electrode and negative electrode were used.

<Example 22>

Except that the silicon-carbon composite contained in the negative electrode active material had D ₅₀ =9 μm, a negative electrode was manufactured in the same manner as in Example 21. Then, a battery was manufactured in the same manner as in Example 21, except that the manufactured negative electrode was used.

<Example 23>

Except that the silicon-carbon composite contained in the negative electrode active material had D ₅₀ =12 μm, a negative electrode was manufactured in the same manner as in Example 21. Then, a battery was manufactured in the same manner as in Example 21 except that the manufactured negative electrode was used.

<Example 24>

Except that the single particle and/or quasi-single particle contained in the positive electrode active material had D ₅₀ =5 μm, and the silicon-carbon composite contained in the negative electrode active material had D ₅₀ =7 μm, a positive electrode and a negative electrode were manufactured in the same manner as in Example 10. Then, a battery was manufactured in the same manner as in Example 10 except that the manufactured positive electrode and negative electrode were used.

<Example 25>

Except that graphite contained in the negative electrode active material had D ₅₀ =17 μm, a negative electrode was manufactured in the same manner as in Example 24. Then, a battery was manufactured in the same manner as in Example 24, except that the manufactured negative electrode was used.

<Example 26>

Except that graphite contained in the negative electrode active material had D ₅₀ =25 μm, a negative electrode was manufactured in the same manner as in Example 24. Then, a battery was manufactured in the same manner as in Example 24, except that the manufactured negative electrode was used.

<Example 27>

Except that the secondary particles contained in the positive electrode active material had D ₅₀ =9 μm, a positive electrode was manufactured in the same manner as in Example 24. Then, a battery was manufactured in the same manner as in Example 24, except that the manufactured positive electrode was used.

<Example 28>

Except that graphite contained in the negative electrode active material had D ₅₀ =17 μm, a negative electrode was manufactured in the same manner as in Example 27. Then, a battery was manufactured in the same manner as in Example 27, except that the manufactured negative electrode was used.

<Example 29>

Except that graphite contained in the negative electrode active material had D ₅₀ =25 μm, a negative electrode was manufactured in the same manner as in Example 27. Then, a battery was manufactured in the same manner as in Example 27, except that the manufactured negative electrode was used.

<Example 30>

Except that the secondary particles contained in the positive electrode active material had D ₅₀ =15 μm, a positive electrode was manufactured in the same manner as in Example 24. Then, a battery was manufactured in the same manner as in Example 24, except that the manufactured positive electrode was used.

<Example 31>

Except that graphite contained in the negative electrode active material had D ₅₀ =17 μm, a negative electrode was manufactured in the same manner as in Example 30. Then, a battery was manufactured in the same manner as in Example 30, except that the manufactured negative electrode was used.

<Example 32>

Except that graphite contained in the negative electrode active material had D ₅₀ =25 μm, a negative electrode was manufactured in the same manner as in Example 30. Then, a battery was manufactured in the same manner as in Example 30, except that the manufactured negative electrode was used.

<Example 33>

Except that the silicon-carbon composite contained in the negative electrode active material had D ₅₀ =9 μm, a negative electrode was manufactured in the same manner as in Example 24. Then, a battery was manufactured in the same manner as in Example 24, except that the manufactured negative electrode was used.

<Example 34>

Except that graphite contained in the negative electrode active material had D ₅₀ =17 μm, a negative electrode was manufactured in the same manner as in Example 33. Then, a battery was manufactured in the same manner as in Example 33, except that the manufactured negative electrode was used.

<Example 35>

Except that graphite contained in the negative electrode active material had D ₅₀ =25 μm, a negative electrode was manufactured in the same manner as in Example 33. Then, a battery was manufactured in the same manner as in Example 33, except that the manufactured negative electrode was used.

<Comparative Example 1>

A positive electrode was manufactured in the same manner as in Example 1 except that the content of the secondary particles contained in the positive electrode active material was 100 parts by weight based on 100 parts by weight of the positive electrode active material. Then, a battery was manufactured in the same manner as in Example 1 except that the manufactured positive electrode was used.

<Comparative Example 2>

Except that the single particle and/or quasi single particle contained in the positive electrode active material had D ₅₀ =0.5 μm, a positive electrode was manufactured in the same manner as in Example 3. Then, a battery was manufactured in the same manner as in Example 3 except that the manufactured positive electrode was used.

<Comparative Example 3>

A positive electrode was manufactured in the same manner as in Example 3, except that the single particle and/or quasi single particle contained in the positive electrode active material had D ₅₀ =15 μm. Then, a battery was manufactured in the same manner as in Example 3, except that the manufactured positive electrode was used.

<Comparative Example 4>

Except that the silicon-carbon composite contained in the negative electrode active material had D ₅₀ =0.5 μm, a negative electrode was manufactured in the same manner as in Example 3. Then, a battery was manufactured in the same manner as in Example 3 except that the manufactured negative electrode was used.

<Comparative Example 5>

A negative electrode was manufactured in the same manner as in Example 3 except that the content of graphite contained in the negative electrode active material was 100 parts by weight based on 100 parts by weight of the negative electrode active material. Then, a battery was manufactured in the same manner as in Example 3 except that the manufactured negative electrode was used.

<Comparative Example 6>

A negative electrode was manufactured in the same manner as in Example 3 except that the content of SiO contained in the negative electrode active material was 10 parts by weight based on 100 parts by weight of the negative electrode active material. Then, a battery was manufactured in the same manner as in Example 3 except that the manufactured negative electrode was used.

<Comparative Example 7>

A positive electrode was manufactured in the same manner as in Example 2, except that the single particle and/or quasi single particle contained in the positive electrode active material had D ₅₀ =12 μm. Then, a battery was manufactured in the same manner as in Example 2, except that the manufactured positive electrode was used.

<Comparative Example 8>

Except that the single particle and/or quasi-single particle contained in the positive electrode active material had D ₅₀ =5 μm, and the silicon-carbon composite contained in the negative electrode active material had D ₅₀ =3 μm, a positive electrode and a negative electrode were manufactured in the same manner as in Example 2. Then, a battery was manufactured in the same manner as in Example 2 except that the manufactured positive electrode and negative electrode were used.

<Comparative Example 9>

Except that the single particle and/or quasi single particle contained in the positive electrode active material had D ₅₀ =10 μm, a positive electrode was manufactured in the same manner as in Example 2. Then, a battery was manufactured in the same manner as in Example 2 except that the manufactured positive electrode was used.

<Comparative Example 10>

A positive electrode and a negative electrode were manufactured in the same manner as in Example 2, except that the single particles and/or quasi-single particles and the secondary particles contained in the positive electrode active material had D ₅₀ = 9 μm and 14 μm, respectively, and the silicon-carbon composite contained in the negative electrode active material had D ₅₀ = 7 μm. Then, a battery was manufactured in the same manner as in Example 2, except that the manufactured positive electrode and negative electrode were used.

<Comparative Example 11>

Except that the single particle and/or quasi single particle contained in the positive electrode active material had D ₅₀ =11 μm, a positive electrode was manufactured in the same manner as in Comparative Example 10. Then, a battery was manufactured in the same manner as in Comparative Example 10 except that the manufactured positive electrode was used.

<Comparative Example 12>

A positive electrode and a negative electrode were manufactured in the same manner as in Comparative Example 11, except that the single particle and/or quasi-single particle contained in the positive electrode active material had D ₅₀ =10 μm, and the silicon-carbon composite contained in the negative electrode active material had D ₅₀ =9 μm. Then, a battery was manufactured in the same manner as in Comparative Example 11, except that the manufactured positive electrode and negative electrode were used.

<Comparative Example 13>

A positive electrode was manufactured in the same manner as in Comparative Example 12, except that the single particle and/or quasi single particle contained in the positive electrode active material had D ₅₀ =12 μm. Then, a battery was manufactured in the same manner as in Comparative Example 12, except that the manufactured positive electrode was used.

<Experimental Example 1> Evaluation of Energy Density Characteristics

The energy density of the fabricated batteries was evaluated and is shown in Table 1 below.

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

Battery volume measurement (unit: L): width (100 mm) × length (300 mm) × thickness (8 mm)

Battery energy measurement (unit: Wh): Battery capacity (40 Ah) × average voltage (3.65 V)

Energy density measurement (unit: Wh/L): battery energy (Wh)/battery volume (L) = 608 Wh/L

<Experimental Example 2> Evaluation of service life (capacity retention rate) characteristics

The capacity retention ratio was evaluated by charging and discharging the manufactured batteries and is shown in Table 1 below.

For the 1st and 2nd cycles, the battery was charged and discharged at 0.1 C, and from the 3rd cycle onwards, the battery was charged and discharged at 0.5 C. The 100th cycle was completed in the charged state (lithium was contained in the negative electrode).

Charging conditions: CC (constant current)/CV (constant voltage) (4.25 V/0.005 C current cutoff)

Discharge condition: CC (constant current) condition 2.5 V

The capacity retention ratios were each derived by the following calculation.

Capacity retention rate (%) = (100th discharge capacity/1st discharge capacity) × 100

Table 1 below shows the values of energy density (based on Example 1, %) and capacity retention rate (100 cycles, %) of Examples 1 to 7 and Comparative Examples 1 to 13.

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

It is characterized in that the lithium composite transition metal compound contained in the positive electrode active material according to the present invention comprises single particles and/or quasi-single particles having an average particle size (D ₅₀ ) of 1 μm or more, the negative electrode active material comprises a silicon-carbon composite having an average particle size (D ₅₀ ) greater than 1 μm, and the average particle size (D ₅₀ ) of the single particles and/or quasi-single particles is smaller than the average particle size (D ₅₀ ) of the silicon-carbon composite. The single particles and/or quasi-single particles and the silicon-carbon composite have a particle size distribution of an appropriate average particle size (D ₅₀ ) to suppress side reactions with the electrolyte and promote charging/discharging, so that because the capacity/efficiency is appropriately achieved, there is an effect of increasing energy density and stabilizing service life characteristics.

In Examples 1 to 35, the positive electrode active material and the negative electrode active material satisfying the particle size range according to the present invention were used, and it was confirmed that the energy density and the capacity retention rate were excellent.

In contrast, in Comparative Examples 1 and 5, the single particles included in the positive electrode active material of the present invention and the silicon-carbon composite included in the negative electrode active material were not included, and it was confirmed that the energy density and the capacity retention ratio were deteriorated.

In Comparative Example 2, the average particle size (D ₅₀ ) range of single particles and/or quasi-single particles contained in the positive electrode active material of the present invention is not satisfied, and it can be confirmed that the total particle size is too small, resulting in low life performance and difficulty in charging and discharging, thereby resulting in decreased capacity, efficiency and life compared with the examples.

Furthermore, in Comparative Examples 3 and 8 to 14, the average particle size (D ₅₀ ) of single particles and/or quasi-single particles was larger than that of the silicon-carbon composite contained in the negative electrode active material, and it was confirmed _that the capacity, efficiency and service life were deteriorated.

In Comparative Example 4, the average particle size (D ₅₀ ) of the silicon-carbon composite contained in the negative electrode active material of the present invention is not satisfied, and it can be confirmed that the total particle size is too small, resulting in low life performance and difficulty in charge and discharge, thereby resulting in decreased capacity, efficiency and life compared with the examples.

That is, in Comparative Example 4, the average particle size (D ₅₀ ) of the silicon-carbon composite is less than 1 μm, which increases the specific surface area, resulting in a decrease in service life performance due to reaction with the electrolyte as the cycle progresses, and because the D ₅₀ of the silicon-carbon composite is smaller than the D ₅₀ of the single particle and/or quasi-single particle, the capacity, efficiency and service life are reduced.

Comparative Example 6 does not contain the silicon-carbon composite contained in the negative electrode active material used in the present invention, but contains a SiO composite, and it can be confirmed that the energy density and the capacity retention ratio are deteriorated.

Claims (20)

1. A lithium secondary battery, the lithium secondary battery comprising:

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 is provided, which is a metal-containing electrolyte,

Wherein the positive electrode active material contains a lithium composite transition metal compound including nickel (Ni), cobalt (Co) and manganese (Mn),

Wherein the lithium composite transition metal compound comprises at least one of single particles or quasi-single particles having an average particle diameter (D ₅₀) of 1 μm or more, wherein each single particle is composed of one agglomerate, wherein each quasi-single particle is a composite of 30 or less agglomerates,

Wherein the anode active material comprises a silicon-carbon composite, wherein the silicon-carbon composite has an average particle diameter (D ₅₀) of greater than 1 μm, and

Wherein the average particle diameter (D ₅₀) of at least one of the single or quasi-single particles is smaller than the average particle diameter (D ₅₀) of the silicon-carbon composite.

2. The lithium secondary battery according to claim 1, wherein at least one of the single particles or quasi-single particles has an average particle diameter (D ₅₀) of 12 μm or less, and

Wherein the average particle size (D ₅₀) of the silicon-carbon composite is less than 15 μm.

3. The lithium secondary battery according to claim 1, wherein an average particle diameter (D ₅₀) of at least one of the single particles or quasi-single particles is 1 μm to 12 μm smaller than an average particle diameter (D ₅₀) of the silicon-carbon composite.

4. The lithium secondary battery according to claim 1, wherein the lithium composite transition metal compound further comprises secondary particles, and

The average particle diameter (D ₅₀) of at least one of the single particle or quasi-single particle is smaller than the average particle diameter (D ₅₀) of the secondary particle.

5. The lithium secondary battery according to claim 4, wherein an average particle diameter (D ₅₀) of at least one of the single particle or the quasi-single particle is 1 μm to 18 μm smaller than an average particle diameter (D ₅₀) of the secondary particle.

6. The lithium secondary battery according to claim 1, wherein the negative electrode active material further comprises graphite,

Wherein the average particle diameter (D ₅₀) of the silicon-carbon composite is smaller than the average particle diameter (D ₅₀) of the graphite.

7. The lithium secondary battery according to claim 6, wherein an average particle diameter (D ₅₀) of the silicon-carbon composite is 1 μm to 25 μm smaller than an average particle diameter (D ₅₀) of the graphite.

8. The lithium secondary battery according to claim 1, wherein the lithium composite transition metal compound further comprises secondary particles,

Wherein the negative electrode active material further comprises graphite,

Wherein the average particle diameters (D ₅₀) of the secondary particles, at least one of the single particles or quasi-single particles, the graphite and the silicon-carbon composite are represented by A, B, C and D, respectively, and wherein B < D.ltoreq.A < C.

9. The lithium secondary battery according to claim 1, wherein the anode active material further comprises graphite, and

Wherein the average particle diameters (D ₅₀) of at least one of the single particles or quasi-single particles, the graphite, and the silicon-carbon composite are represented by B, C and D, respectively, and B < D < C.

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

11. The lithium secondary battery according to claim 1, wherein the content of at least one of the single particles or quasi-single particles is 15 to 100 parts by weight based on 100 parts by weight of the positive electrode active material, and

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.

12. The lithium secondary battery according to claim 1, wherein the content of nickel in the lithium composite transition metal compound is 80mol% or more with respect to other metals than lithium.

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

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

15. The lithium secondary battery according to claim 1, wherein a ratio of an average particle diameter (D ₅₀) of at least one of the single particles or quasi-single particles to an average particle diameter (D ₅₀) of the silicon-carbon composite is in a range of 1.5:2 to 1.5:20.

16. The lithium secondary battery according to claim 1, wherein the positive electrode further comprises a positive electrode active material layer having the positive electrode active material,

The anode further comprises an anode active material layer having the anode active material, and

The positive electrode active material layer and the negative electrode active material layer each have a thickness of 10 μm or more and 500 μm or less.

17. The lithium secondary battery according to claim 1, wherein the positive electrode further comprises a positive electrode active material layer having the positive electrode active material, the positive electrode active material layer having a load per unit volume of 250mg/25cm ² to 900mg/25cm ², and

The anode further includes an anode active material layer having the anode active material, and a unit volume loading of the anode active material layer is 100mg/25cm ² to 600mg/25cm ².

18. The lithium secondary battery according to claim 1, wherein the lithium secondary battery has an energy density of 400Wh/L to 900 Wh/L.

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

20. A battery pack comprising the battery module of claim 19.