Lithium secondary battery

Abstract

The present invention relates to a lithium secondary battery comprising: a cathode; an anode; and a separator provided between the cathode and the anode, the cathode comprising, as a cathode active material, lithium composite transition metal compound particles in a single particle form containing nickel, cobalt, and manganese, the anode comprising silicon-based particles as an anode active material, wherein the specific surface area of the silicon-based particles is at least four times that of the lithium composite transition metal compound particles.

Description

lithium secondary battery

[0001] This specification claims the benefit of the filing dates of Korean Patent Application No. 10-2023-0107196, filed with the Korean Intellectual Property Office on August 16, 2023, and Korean Patent Application No. 10-2024-0108709, filed with the Korean Intellectual Property Office on August 14, 2024, the entire disclosure of which is incorporated herein by reference.

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

[0003] The recent rapid proliferation of battery-powered electronic devices, such as mobile phones, laptops, and electric vehicles, has led to a rapid increase in demand for compact, lightweight, and relatively high-capacity secondary batteries. In particular, lithium secondary batteries, with their lightweight design and high energy density, are attracting attention as power sources for portable devices. Accordingly, active research and development efforts are underway to improve the performance of lithium secondary batteries.

[0004] Typically, a lithium secondary battery comprises a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, an electrolyte, an organic solvent, and the like. Furthermore, active material layers each containing a positive electrode active material and a negative electrode active material may be formed on a current collector. Typically, lithium-containing metal oxides such as LiCoO2 and LiMn2O4 are used as positive electrode active materials, while lithium-free carbon-based or silicon-based active materials are used as negative electrode active materials.

[0005] Among negative active materials, silicon-based materials are attracting attention for their higher capacity and superior fast-charge characteristics compared to carbon-based materials. However, silicon-based materials exhibit significant volumetric expansion and contraction during charge and discharge, and their high irreversible capacity leads to low initial efficiency.

[0006] Accordingly, the design of materials that can improve battery performance is necessary.

[0007] The present invention relates to a lithium secondary battery with improved performance.

[0008] One embodiment of the present invention provides a lithium secondary battery comprising a positive electrode; a negative electrode; and a separator provided between the positive electrode and the negative electrode, wherein the positive electrode comprises nickel, cobalt, and manganese as a positive electrode active material and comprises lithium composite transition metal compound particles in the form of single particles, and the negative electrode comprises silicon-based particles as a negative electrode active material, and the specific surface area of ​​the silicon-based particles is at least four times that of the specific surface area of ​​the lithium composite transition metal compound particles.

[0009] According to one embodiment of the present invention, the silicon-based particles include at least one of silicon carbon composite particles and silicon oxide particles.

[0010] One embodiment of the present invention provides a battery module including a lithium secondary battery according to the above-described embodiment.

[0011] One embodiment of the present invention provides a battery pack including a lithium secondary battery according to the above-described embodiment.

[0012] One embodiment of the present invention provides a battery pack including a battery module according to the above-described embodiment.

[0013] A lithium secondary battery according to one embodiment of the present invention can provide a lithium secondary battery having a high capacity compared to a case where only a carbon-based negative electrode active material is used by including silicon-based particles as a negative electrode active material, and can also improve the performance of the battery by appropriately matching a positive electrode material with a negative electrode including a silicon-based material at the battery level.

[0014] Hereinafter, the present specification will be described in more detail.

[0015] In this specification, when a part is said to "include" a certain component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0016] In this specification, when it is said that a member is located “on” another member, this includes not only cases where the member is in contact with the other member, but also cases where another member exists between the two members.

[0017] In this specification, “single particle” may mean a particle formed by a single nudole. The “nudole” may be a single crystal without a grain boundary, or may be a polycrystal in which no grain boundary appears when observed using a scanning electron microscope (SEM) at 5000x to 20000x. In this specification, “single particle” includes a pseudo-single particle. In this specification, a “pseudo-single particle” may be an aggregate formed by 30 or fewer nudules. In this specification, a “secondary particle” means a particle formed by the agglomeration of tens to hundreds of primary particles, and specifically, the secondary particle may include a particle formed by the agglomeration of 50 or more primary particles.

[0018] In this specification, “particle” may include at least one of a single particle, a quasi-single particle, a primary particle, a nodule, and a secondary particle.

[0019] The terms and words used in this specification should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0020] As used herein, the singular expression of a term includes the plural expression unless the context clearly indicates otherwise.

[0021] Hereinafter, preferred embodiments of the present invention will be described in detail. However, the embodiments of the present invention may be modified in various ways, and the scope of the present invention is not limited to the embodiments described below.

[0022]

[0023] <Specific surface area of ​​negative and positive active material particles>

[0024] According to embodiments of the present invention, the specific surface area (SSA) of the silicon-based particles included as the negative electrode active material is at least four times that of the lithium composite transition metal compound particles included as the positive electrode active material. When the lithium composite transition metal compound particles are single particles, the lithium input / output is high because the resistance is low. The above-described embodiment of the present invention designs the specific surface area in consideration of the reactivity of the single particle positive electrode active material with lithium when using silicon-based particles with a large capacity as the negative electrode active material. Specifically, by using silicon-based particles having a large specific surface area within the above-described range compared to lithium composite transition metal compound particles, the silicon-based particles can sufficiently react with lithium ions of the single particle lithium composite transition metal compound particles. Thereby, the battery life performance can be significantly improved. When using negative active material particles of silicon-based particles and positive active material particles of single particles and not satisfying the above-mentioned specific surface area range, the lithium ion reaction occurs concentratedly on the negative electrode surface, causing a large side reaction with the electrolyte, resulting in a deterioration (fading) of the life performance.

[0025] For reference, in the case of lithium composite transition metal compound particles that are not single particles, the lithium input / output performance is relatively lower than that of single particles, so it is unlikely that the life performance of the battery can be significantly improved by controlling the specific surface area relationship with the silicon-based particles of the negative electrode according to the present invention.

[0026] In one example, the specific surface area of ​​the silicon-based particles is at least 4 times the specific surface area of ​​the lithium composite transition metal compound particles included as the positive electrode active material, and may be, for example, at least 4.1 times, at least 4.2 times, or at least 4.3 times. In one example, the specific surface area of ​​the silicon-based particles is at most 20 times the specific surface area of ​​the lithium composite transition metal compound particles included as the positive electrode active material, and may be, for example, at most 15 times, or at most 10 times.

[0027] The specific surface area of ​​positive or negative active material particles can be affected by particle size, surface treatment, coating structure, coating material, or coating method.

[0028] According to one embodiment, the specific surface area of ​​the lithium composite transition metal compound particle in the form of a single particle is 0.4 m 2 / g to 0.8 m 2 / g, for example, 0.6 m 2 / g to 0.8 m 2 / g, or 0.6 m 2 / g to 0.7 m 2 / g is.

[0029] According to one embodiment, the specific surface area of ​​the silicon-based particles, such as silicon carbon composite or silicon oxide particles, is 2 m 2 / g or more, e.g. 3 m 2 / g or more.

[0030] The above specific surface area can be measured by degassing at 200°C for 8 hours and performing N2 adsorption / desorption at 77K using a BET measuring device (BEL-SORP-MAX, Nippon Bell).

[0031]

[0032] <Cathode active material>

[0033] The negative electrode of a lithium secondary battery according to one embodiment of the present invention includes silicon particles as a negative electrode active material.

[0034] The silicon-based particles may include at least one of silicon carbon composite particles and silicon oxide particles. For example, the silicon-based particles may include silicon carbon composite particles, silicon oxide particles, or both.

[0035] According to one embodiment, the silicon carbon composite may be a Si / C-based active material.

[0036] In this specification, the silicon carbon composite is a composite of Si and C, and is distinguished from silicon carbide, denoted as SiC.

[0037] The above silicon-carbon composite may be a composite of silicon and graphite, and may form a structure in which a core composed of silicon and graphite is surrounded by graphene or amorphous carbon. The silicon in the silicon-carbon composite may be nano silicon.

[0038] According to one embodiment, the silicon carbon composite includes porous carbon particles and silicon located on the surface or internal pores of the porous carbon particles.

[0039] According to one embodiment, the silicon carbon composite has a pore volume of 0.005 cm by the BET method. 3 / g to 0.03 cm 3 / g, and the pore size by the BET method may be 10 nm to 20 nm. The silicon carbon composite has a pore volume of 0.005 cm measured by the mercury penetration method. 3 / g to 0.03 cm 3 / g could be.

[0040] According to one embodiment, the silicon carbon composite can be manufactured by a method including a step of forming silicon on the surface and internal pores of porous carbon particles.

[0041] The porous carbon particles can be manufactured using methods known in the art, and for example, can be obtained by carbonizing organic materials, such as petroleum-based materials, polymers, etc., or by carbonizing naturally occurring materials, such as palm tree shells, after chemically treating them. As another example, the porous carbon particles can be obtained by a method including a step of etching carbon particles containing internal pores to expand the internal pores of the carbon particles.

[0042] The step of expanding the internal pores of the above carbon particles can be performed in a nitrogen (N2) atmosphere, an oxygen (O2) atmosphere, or an air atmosphere. Specifically, the flow rate of the oxygen (O2) or the air containing the oxygen can be controlled to 0.1 to 10 L / min.

[0043] The step of expanding the internal pores of the above carbon particles can be performed at a temperature range of 400 to 1200°C for 30 minutes to 4 hours.

[0044] Depending on the conditions for expanding the internal pores of the above carbon particles, the pore characteristics of the obtained porous carbon particles may vary.

[0045] The step of forming the above silicon can be performed using a chemical vapor deposition method. In this case, silicon nanoparticles are deposited on the surface and / or in the internal pores of the carbon particles with expanded internal pores, thereby forming silicon in the form of a film, an island, or a mixture of these.

[0046] The above silicon nanoparticles may be crystalline, quasi-crystalline, amorphous, or a combination thereof.

[0047] According to one embodiment, the silicon oxide is SiO x (0≤x<2) can be included.

[0048] The above SiO x The active material containing (0≤x<2) is SiO x (0 <x<2) 및 기공을 포함하는 실리콘 산화물 입자일 수 있다.

[0049] The above SiO x (0 <x<2)는 상기 실리콘 산화물 입자 내에서 매트릭스(matrix)에 해당한다. 상기 SiO x (0 <x<2)는 Si 및 SiO2가 포함된 형태일 수 있으며, 상기 Si는 상(phase)을 이루고 있을 수도 있다. 즉, 상기 x는 상기 SiO x (0 <x<2) 내에 포함된 Si에 대한 O의 개수비에 해당한다. 상기 실리콘 산화물 입자가 상기 SiO x (0 <x<2)를 포함하는 경우, 이차 전지의 방전 용량이 개선될 수 있다.

[0050] The silicon oxide particles may be general silicon oxide particles that do not contain additional metals or metal compounds, and may further contain at least one of a Mg compound and a Li compound, if necessary. The Mg compound and the Li compound may correspond to a matrix within the silicon oxide particles.

[0051] The above Mg compound and / or Li compound is SiO x (0 <x<2)의 내부 및 / 또는 표면에 존재할 수 있다. 상기 Mg 화합물 및 / 또는 Li 화합물에 의해 전지의 초기 효율이 개선될 수 있다.

[0052] The above Mg compound may include at least one selected from the group consisting of Mg silicate, Mg silicide, and Mg oxide. The Mg silicate may include at least one of Mg2SiO4 and MgSiO3. The Mg silicide may include Mg2Si. The Mg oxide may include MgO.

[0053] In one embodiment of the present specification, the Mg element may be included in an amount of 0.1 wt% to 20 wt%, or 0.1 wt% to 15 wt%, based on 100 wt% of the total silicon oxide particles. Specifically, the Mg element may be included in an amount of 0.5 wt% to 10 wt% or 0.8 wt% to 10 wt%. When the above range is satisfied, the Mg compound can be included in an appropriate amount in the silicon oxide particles, so that volume changes of the silicon oxide particles during charging and discharging of the battery can be easily suppressed, and the discharge capacity and initial efficiency of the battery can be improved.

[0054] The Li compound may include at least one selected from the group consisting of Li silicate, Li silicide, and Li oxide. The Li silicate may include at least one of Li2SiO3, Li4SiO4, and Li2Si2O5. The Li silicide may include Li7Si2. The Li oxide may include Li2O.

[0055] In one embodiment of the present invention, the Li compound may include a lithium silicate form. The lithium silicate may include Li a Si b O c (2≤a≤4, 0 <b≤2, 2≤c≤5)로 표시되며, 결정질 리튬 실리케이트와 비정질 리튬 실리케이트로 구분될 수 있다. 상기 결정질 리튬 실리케이트는 상기 실리콘 산화물 입자 내에서 Li2SiO3, Li4SiO4및 Li2Si2O5로 이루어진 군에서 선택된 적어도 1종의 리튬 실리케이트의 형태로 존재할 수 있으며, 비정질 리튬 실리케이트는 Li a Si b O c (2≤a≤4, 0 <b≤2, 2≤c≤5)의 형태일 수 있고, 상기 형태에 한정되지는 않는다.

[0056] In one embodiment of the present specification, the Li element may be included in an amount of 0.1 wt% to 20 wt%, or 0.1 wt% to 15 wt%, based on 100 wt% of the total silicon oxide particles. Specifically, the Li element may be included in an amount of 0.5 wt% to 10 wt%, and more specifically, may be included in an amount of 0.5 wt% to 10 wt%. When the above range is satisfied, the Li compound may be included in an appropriate amount in the silicon oxide particles, so that volume change of the negative electrode active material during charging and discharging of the battery can be easily suppressed, and the discharge capacity and initial efficiency of the battery can be improved.

[0057] The content of the above Mg element or Li element can be confirmed through ICP analysis. For the ICP analysis, a certain amount (approximately 0.01 g) of the negative electrode active material is precisely aliquoted, transferred to a platinum crucible, and completely decomposed on a hot plate by adding nitric acid, hydrofluoric acid, and sulfuric acid. Thereafter, an inductively coupled plasma electroluminescence spectrometer (ICPAES, Perkin-Elmer 7300) is used to measure the intensity of the standard solution prepared using a standard solution (5 mg / kg) at the wavelength unique to the Mg element or Li element, thereby creating a reference calibration curve. Thereafter, the pretreated sample solution and blank sample are introduced into the device, and the respective intensities are measured to calculate the actual intensity, and the concentration of each component is calculated against the created calibration curve, and then the content of the Mg element or Li element of the manufactured silicon oxide particles can be analyzed by converting so that the sum of the entire values ​​becomes the theoretical value.

[0058] In one embodiment of the present invention, the silicon-based particles may include additional metal atoms. The metal atoms may be present in the silicon-based particles in the form of at least one of a metal atom, a metal silicate, a metal silicide, and a metal oxide. The metal atoms may include at least one selected from the group consisting of Mg, Li, Al, and Ca. Accordingly, the initial efficiency of the negative electrode active material may be improved.

[0059] In one embodiment of the present invention, the silicon-based particles have a carbon layer on at least a portion of their surface. The carbon layer may be partially coated on at least a portion of the surface, i.e., the particle surface, or may be coated on the entire particle surface. The carbon layer provides conductivity to the negative electrode active material, and the initial efficiency, lifespan characteristics, and battery capacity characteristics of the secondary battery may be improved.

[0060] In one embodiment of the present invention, the carbon layer includes amorphous carbon. In addition, the carbon layer may additionally include crystalline carbon.

[0061] The above crystalline carbon can further improve the conductivity of the negative electrode active material. The above crystalline carbon can include at least one selected from the group consisting of fluorene, carbon nanotubes, and graphene.

[0062] The amorphous carbon can appropriately maintain the strength of the carbon layer, thereby suppressing expansion of the silicon-based particles. The amorphous carbon can be a carbon-based material formed using at least one carbide or hydrocarbon selected from the group consisting of tar, pitch, and other organic materials as a source for chemical vapor deposition.

[0063] The above-mentioned other organic carbonates may be carbonates of organic carbonates selected from sucrose, glucose, galactose, fructose, lactose, mannose, ribose, aldohexose or kedohexose and combinations thereof.

[0064] The hydrocarbon may be a substituted or unsubstituted aliphatic or alicyclic hydrocarbon, or a substituted or unsubstituted aromatic hydrocarbon. The aliphatic or alicyclic hydrocarbon of the substituted or unsubstituted aliphatic or alicyclic hydrocarbon may be methane, ethane, ethylene, acetylene, propane, butane, butene, pentane, isobutane, or hexane, etc. The aromatic hydrocarbon of the substituted or unsubstituted aromatic hydrocarbon may be benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene, or phenanthrene, etc.

[0065] In one embodiment of the present invention, the carbon layer may be an amorphous carbon layer.

[0066] In one embodiment of the present invention, the carbon layer may be included in an amount of 0.1 to 50 parts by weight, 0.1 to 30 parts by weight, or 0.1 to 20 parts by weight based on 100 parts by weight of the total silicon-based particles. More specifically, it may be included in an amount of 0.5 to 15 parts by weight, 1 to 10 parts by weight, or 1 to 5 parts by weight. When the above range is satisfied, a decrease in the capacity and efficiency of the negative electrode active material can be prevented.

[0067] In one embodiment of the present invention, the thickness of the carbon layer may be 1 nm to 500 nm, and specifically 5 nm to 300 nm. When the above range is satisfied, the conductivity of the negative electrode active material is improved, volume change of the negative electrode active material is easily suppressed, and side reactions between the electrolyte and the negative electrode active material are suppressed, thereby improving the initial efficiency and / or lifespan of the battery.

[0068] Specifically, the carbon layer can be formed by a chemical vapor deposition (CVD) method using at least one hydrocarbon gas selected from the group consisting of methane, ethane, and acetylene.

[0069] In the present invention, the crystallinity of the carbon layer can be confirmed by calculating the D / G band ratio according to Raman spectroscopy. Specifically, the measurement can be performed using a Renishaw 2000 Raman microscope system and a 532 nm laser excitation, and a 100x optical lens with a low laser power density and an exposure time of 30 seconds to avoid laser thermal effects. In order to reduce positional deviation, a total of 25 points are measured for a 5 μm x 5 μm area, and the calculation can be performed by calculating the average values ​​of the D band and G band after fitting using a Lorentzian function.

[0070] In this specification, the average particle diameter (D50) can be defined as the particle diameter corresponding to 50% of the volume accumulation amount in the particle diameter distribution curve. The average particle diameter (D50) can be measured using, for example, a laser diffraction method. The laser diffraction method can generally measure particle diameters from the submicron range to several millimeters, and can obtain results with high reproducibility and high resolution.

[0071] The average particle diameter (D50) of the above-described negative active material, such as silicon carbon composite particles or silicon oxide particles, may be 1 μm or more and 10 μm or less. When the above range is satisfied, the structural stability of the active material during charge and discharge can be ensured, the problem of increased volume expansion / contraction due to excessively large particle diameters can be prevented, and the problem of decreased initial efficiency due to excessively low particle diameters can be prevented.

[0072]

[0073] <Cathode>

[0074] The negative electrode of a lithium secondary battery according to one embodiment of the present invention includes the negative electrode active material described above.

[0075] Specifically, the negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. The negative electrode active material layer may include the negative electrode active material. Furthermore, the negative electrode active material layer may further include a binder, a thickener, and / or a conductive material.

[0076] The above negative electrode active material layer can be formed by applying a negative electrode slurry including a negative electrode active material, a binder, a thickener, and / or a conductive agent to at least one surface of a current collector, and drying and rolling.

[0077] The above negative electrode slurry may further include an additional negative electrode active material.

[0078] As the above additional negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO β(0 < β < 2), SnO2, vanadium oxide, lithium titanium oxide, lithium vanadium oxide, and other metal oxides capable of doping and dedoping lithium; or composites containing the above metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fiber-like forms, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes.

[0079] The above additional negative electrode active material may be a carbon-based negative electrode active material.

[0080] In one embodiment of the present invention, the silicon-based particles may be included in an amount of 3 to 30 parts by weight based on 100 parts by weight of the negative electrode active material.

[0081] When the silicon particles are included in an amount of 3 to 30 parts by weight relative to 100 parts by weight of the above-mentioned negative electrode active material, the silicon particles having a high capacity are included, making it possible to manufacture the negative electrode thinner and thereby improve the output characteristics, thereby improving the life characteristics of the secondary battery.

[0082] Specifically, when the silicon-based particles are included in an amount of 3 parts by weight or more per 100 parts by weight of the negative electrode active material, the negative electrode capacity increases compared to an anode containing only a carbon-based active material, thereby making the electrode thinner and improving the output characteristics, which is advantageous. In addition, when the content of the silicon-based active material is excessive, the problem of deterioration of the lifespan due to volume expansion occurs, but when the negative electrode active material is included in an amount of 30 parts by weight or less, this disadvantage is reduced, thereby improving the lifespan characteristics of the secondary battery. The negative electrode slurry may include a solvent for forming the negative electrode slurry. Specifically, the solvent for forming the negative electrode slurry may include at least one selected from the group consisting of distilled water, ethanol, methanol, and isopropyl alcohol, specifically, distilled water, in terms of facilitating dispersion of the components.

[0083] According to one embodiment of the present invention, the pH of the negative electrode slurry at 25°C may be 7 to 11. When the pH of the negative electrode slurry satisfies the above range, there is an effect of stabilizing the rheological properties of the slurry. On the other hand, when the pH of the negative electrode slurry is less than 7 or the pH of the negative electrode slurry exceeds 11, decomposition of carboxymethyl cellulose (CMC) used as a thickener occurs, resulting in a decrease in the viscosity of the slurry, and there is a problem of a decrease in the dispersion of the active material contained in the slurry.

[0084] The negative current collector may be any conductive material that does not cause chemical changes in the battery, and is not particularly limited thereto. For example, the current collector may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like. Specifically, a transition metal that readily absorbs carbon, such as copper or nickel, may be used as the current collector. The current collector may have a thickness of 6 μm to 20 μm, but the thickness of the current collector is not limited thereto.

[0085] The above binder may include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylic acid, and materials in which hydrogens of these are substituted with Li, Na, Ca, etc., and may also include various copolymers thereof.

[0086] The conductive material is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, paneth black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0087] The above thickener may be carboxymethyl cellulose (CMC), but is not limited thereto, and any thickener used in the present technical field may be appropriately employed.

[0088] In one embodiment of the present invention, the total negative electrode active material included in the negative electrode slurry may be included in an amount of 60 parts by weight to 99 parts by weight, specifically 70 parts by weight to 98 parts by weight, based on 100 parts by weight of the total solid content of the negative electrode slurry.

[0089] In one embodiment of the present invention, the binder may be included in an amount of 0.5 to 30 parts by weight, specifically 1 to 20 parts by weight, based on 100 parts by weight of the total solid content of the negative electrode slurry.

[0090] In one embodiment of the present invention, the conductive material may be included in an amount of 0.5 to 25 parts by weight, specifically 1 to 20 parts by weight, based on 100 parts by weight of the total solid content of the negative electrode slurry.

[0091] In one embodiment of the present invention, the thickener may be included in an amount of 0.5 to 25 parts by weight, specifically 0.5 to 20 parts by weight, and more specifically 1 to 20 parts by weight, based on 100 parts by weight of the total solid content of the negative electrode slurry.

[0092] The cathode slurry according to one embodiment of the present invention may further include a solvent for forming the cathode slurry. Specifically, the solvent for forming the cathode slurry may include at least one selected from the group consisting of distilled water, ethanol, methanol, and isopropyl alcohol, specifically distilled water, in order to facilitate dispersion of the components.

[0093] In one embodiment of the present invention, the solid content weight of the cathode slurry may be 20 parts by weight to 75 parts by weight, specifically 30 parts by weight to 70 parts by weight, based on 100 parts by weight of the total cathode slurry.

[0094]

[0095] <Cathode active material>

[0096] According to one embodiment of the present invention, a positive electrode of a lithium secondary battery includes nickel, cobalt, and manganese as positive electrode active materials, and includes lithium composite transition metal compound particles in the form of single particles. Here, the single particle form includes a pseudo-single particle form.

[0097] The above cathode active material comprises lithium composite transition metal compound particles including nickel (Ni), cobalt (Co), and manganese (Mn), wherein the lithium composite transition metal compound particles comprise single particles, the average particle diameter (D50) of the single particles is 1 μm or more, and the single particles comprise single particles composed of one nodule and quasi-single particles which are aggregates composed of 30 or fewer nodules.

[0098] The lithium composite transition metal compound particles in the form of single particles may be included in an amount of 15 to 100 parts by weight, for example, 50 to 100 parts by weight, or 85 to 100 parts by weight, based on 100 parts by weight of the positive electrode active material.

[0099] When the average particle diameter (D50) of the above single particles is 1 ㎛ or more, 3 ㎛ or more, or 5 ㎛ or more, the single particles have excellent life performance because side reactions with the electrolyte are reduced. According to one embodiment, the average particle diameter (D50) of the lithium composite transition metal compound particles in the form of single particles may be 1 ㎛ or more and 10 ㎛ or less.

[0100] According to an additional embodiment of the present application, the lithium composite transition metal compound particles include nickel, cobalt and manganese, and may further include aluminum.

[0101] In the present specification, the lithium composite transition metal compound particle contains nickel in an amount of 80 mol% or more and less than 100 mol% among metals other than lithium, and may include one or a mixture of two or more kinds represented by the following chemical formula 1.

[0102] [Chemical Formula 1]

[0103] Li aNi 1-b-c-d Co b Mn c Q d O 2+δ

[0104] In the above formula, Q is at least one element selected from the group consisting of Na, K, Mg, Ca, Sr, Ni, Co, Ti, Al, Si, Sn, Mn, Cr, Fe, V, and Zr, and 1≤a≤1.5, 0 <b≤0.5, 0<c≤0.5, 0≤d≤0.1, 0 <b+c+d≤20, -0.1≤δ≤1.0이다.

[0105] In the lithium composite transition metal compound of the above chemical formula 1, Li may be included in an amount corresponding to a, that is, 1≤a≤1.5. If a is less than 1, there is a risk of reduced capacity, and if a exceeds 1.5, the particles may be sintered during the sintering process, making it difficult to manufacture a positive electrode active material. Considering the effect of improving the capacity characteristics of the positive electrode active material according to the Li amount control and the balance of sinterability during the manufacture of the active material, the Li may be more preferably included in an amount of 1.1≤a≤1.2.

[0106] In the lithium composite transition metal compound of the above chemical formula 1, Ni may be included in a content corresponding to 1-(b+c+d), for example, 0.8≤1-(b+c+d) < 1. When the content of Ni in the lithium composite transition metal compound of the above chemical formula 1 is 0.8 or more, a sufficient amount of Ni is secured to contribute to charge / discharge, thereby promoting high capacity. Preferably, the content of Ni, 1-(b+c+d), may be 0.88, preferably 0.9 or more, and more preferably 0.93 or more. Preferably, the content of Ni, 1-(b+c+d), may be 0.99 or less, or 0.95 or less.

[0107] In the lithium complex transition metal compound of the above chemical formula 1, Co is in the content corresponding to b, i.e., 0 <b≤0.5로 포함될 수 있다. 상기 화학식 1의 리튬 복합 전이금속 화합물 내 Co의 함량이 0.5를 초과할 경우 비용 증가의 우려가 있다. Co 포함에 따른 용량 특성 개선 효과의 현저함을 고려할 때, 상기 Co는 보다 구체적으로 0.03≤b≤0.2의 함량으로 포함될 수 있다.

[0108] In the lithium complex transition metal compound of the above chemical formula 1, Mn is in the content corresponding to c, i.e., 0 <c≤0.5의 함량으로 포함될 수 있다. 상기 화학식 1의 리튬 복합 전이금속 화합물 내 c가 0.5를 초과하면 오히려 전지의 출력 특성 및 용량 특성이 저하될 우려가 있으며, 상기 Mn은 보다 구체적으로 0.01≤c≤0.2의 함량으로 포함될 수 있다.

[0109] In the lithium composite transition metal compound of the above chemical formula 1, Q may be a doping element included in the crystal structure of the lithium composite transition metal compound, and Q may be included in a content corresponding to d, that is, 0≤d≤0.1. Q may be one or two or more selected from Na, K, Mg, Ca, Sr, Ni, Co, Ti, Al, Si, Sn, Mn, Cr, Fe, V, and Zr, and for example, Q may be Al.

[0110] The lithium complex transition metal compound described above may further include secondary particles. The secondary particles refer to a form formed by the aggregation of primary particles, and can be distinguished from the concept of a single particle composed of a single nodule or a pseudo-single particle, which is an aggregate composed of 30 or fewer nodules.

[0111] According to an additional embodiment of the present application, the positive electrode active material may include single particles and secondary particles of the lithium composite transition metal compound.

[0112] The above single particles can be manufactured by mixing and calcining a transition metal precursor and a lithium source material. The secondary particles can be manufactured using a different method from the above single particles, and their composition may be the same as or different from that of the single particles.

[0113] For example, the sintering is performed at a temperature capable of forming single particles. To form these, sintering may be performed at a higher temperature than that during secondary particle production, and for example, when the precursor composition is the same, sintering may be performed at a temperature that is about 30° C. to 100° C. higher than that during secondary particle production. The sintering temperature for forming the single particles may vary depending on the metal composition in the precursor. For example, when a high-content nickel (High-Ni) NCM-based lithium composite transition metal oxide having a nickel (Ni) content of 80 mol% or more is intended to be formed into single particles, the sintering temperature may be about 700° C. to 1000° C., preferably about 800° C. to 950° C. When the sintering temperature satisfies the above range, a cathode active material including single particles having excellent electrochemical properties can be produced. When the sintering temperature is lower than 790°C, a cathode active material including a lithium complex transition metal compound in the form of secondary particles can be manufactured, and when it exceeds 950°C, excessive sintering occurs and a layered crystal structure is not properly formed, which may result in a deterioration in electrochemical properties.

[0114] The particle diameter (D50) of the secondary particles may be 1 ㎛ to 20 ㎛, 2 ㎛ to 17 ㎛, and preferably 3 ㎛ to 15 ㎛. The specific surface area (BET) of the secondary particles may be 0.05 m 2 / g to 10 m 2 / g can be, preferably 0.1 m 2 / g to 1 m 2 / g may be, more preferably 0.3 m 2 / g to 0.8 m 2 / g could be.

[0115] In a further embodiment, the secondary particles may be aggregates of primary particles, and the average particle diameter (D50) of the primary particles may be 0.5 μm to 3 μm. Specifically, the secondary particles may be aggregates of hundreds of primary particles, and the average particle diameter (D50) of the primary particles may be 0.6 μm to 2.8 μm, 0.8 μm to 2.5 μm, or 0.8 μm to 1.5 μm.

[0116]

[0117] Bipolar

[0118] According to one embodiment of the present application, the positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and including the positive electrode active material.

[0119] In the above positive electrode, the positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 to 500 ㎛, and fine unevenness may be formed on the surface of the current collector to increase the adhesive strength of the positive electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0120] The above-described positive electrode active material layer may include a positive electrode conductive material and a positive electrode binder together with the positive electrode active material described above.

[0121] At this time, the positive electrode conductive material is used to provide conductivity to the electrode, and in the battery to be constructed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like, and one of these may be used alone or a mixture of two or more may be used.

[0122] In addition, the positive electrode binder plays a role in improving the adhesion between positive electrode active material particles and the adhesiveness between the positive electrode active material and the positive electrode current collector. Specific examples thereof 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 polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof.

[0123] The positive electrode binder may be included in an amount of 0.1 to 50 parts by weight based on 100 parts by weight of the positive electrode active material layer, for example, preferably 0.3 to 35 parts by weight, more preferably 0.5 to 20 parts by weight.

[0124] The conductive material included in the above-described positive electrode active material layer is used to provide conductivity to the electrode, and can be used without special restrictions as long as it does not cause chemical changes within the battery and has electronic conductivity. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One of these may be used alone or a mixture of two or more may be used.

[0125] Specifically, in one embodiment, the conductive material may include at least one of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). The conductive material may be included in an amount of 0.1 to 2 parts by weight based on 100 parts by weight of the composition for the positive electrode active material layer, for example, preferably 0.3 to 1.5 parts by weight, more preferably 0.5 to 1.2 parts by weight.

[0126]

[0127] Secondary battery

[0128] A secondary battery according to one embodiment of the present invention includes the above-described negative electrode, positive electrode, and a separator interposed between the positive electrode and negative electrode, and may additionally include an electrolyte.

[0129] The separator separates the negative and positive electrodes and provides a passage for lithium ions to move. Any separator commonly used in secondary batteries can be used without any particular restrictions, and in particular, one that has low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, can be used. In addition, a conventional porous non-woven fabric, for example, a non-woven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. can also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength can be used, and can optionally be used in a single-layer or multi-layer structure.

[0130] Examples of the above electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0131] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0132] As the above non-aqueous organic solvent, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolan, formamide, dimethylformamide, dioxolan, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxy methane, dioxolan derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyrropionate, ethyl propionate, etc. can be used.

[0133] In particular, among the above carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are high-viscosity organic solvents with high dielectric constants and thus can be preferably used because they easily dissociate lithium salts. In addition, when low-viscosity, low-dielectric constant linear carbonates such as dimethyl carbonate and diethyl carbonate are mixed and used in an appropriate ratio with these cyclic carbonates, an electrolyte having high electrical conductivity can be produced, so that they can be used even more preferably.

[0134] The metal salt may be a lithium salt, and the lithium salt is a substance that is easily dissolved in the non-aqueous electrolyte, for example, the anion of the lithium salt is F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 -, CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - One or more selected from the group consisting of may be used.

[0135] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as, for example, difluoroethylene carbonate and other haloalkylene carbonate compounds, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery.

[0136] According to another embodiment of the present invention, a battery module including the secondary battery as a unit cell and a battery pack including the same are provided. The battery module and the battery pack include the secondary battery having high capacity, high rate characteristics, and cycle characteristics, and thus can be used as a power source for medium- to large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0137] <Examples and Comparative Examples>

[0138] Example 1

[0139] A composition for forming a positive electrode active material was prepared, which includes 98.04 parts by weight of a lithium composite transition metal compound having a content of 93.3 mol% of Ni, 4.9 mol% of Co, and 1.8 mol% of Mn among metals other than lithium, based on 100 parts by weight of a positive electrode active material, 1 part by weight of PVDF as a binder, and a CNT pre-dispersion liquid including 0.8 parts by weight of CNT as a conductive material and 0.16 parts by weight of a dispersant. At this time, the single particles were prepared to a size of D50=3 μm by an airflow grinding method. The composition for forming a positive electrode active material was coated on a 30 μm thick aluminum foil to a thickness of 103 μm in a dry state, and then dried to prepare a positive electrode.

[0140] Based on 100 parts by weight of the negative active material, a composition for forming a negative active material was prepared, which included 97.7 parts by weight of graphite (90 parts by weight based on 100 parts by weight of the negative active material) and silicon oxide active material carbon-coated by methane CVD (10 parts by weight based on 100 parts by weight of the negative active material), 1.15 parts by weight of SBR (styrene butadiene rubber) as a binder, 1 part by weight of CMC (carboxymethyl cellulose), and, in addition, 0.1 parts by weight of a dispersant and a CNT pre-dispersion liquid containing 0.05 parts by weight of single-walled CNT. At this time, the carbon-coated silicon oxide active material was prepared to have a D50=6㎛ size by an airflow grinding method, and the graphite was prepared to have a D50=17㎛ size. The composition for forming a negative active material was coated on a copper foil having a thickness of 15 ㎛ so as to have a dry thickness of 86 ㎛, and then dried to prepare a negative electrode.

[0141] The above positive and negative electrodes were laminated with a separator in between, and an electrolyte (1.0 M LiPF6, EC(ethylene carbonate) / EMC(ethylmethyl carbonate)=30 / 70 (Vol%), VC(vinylene carbonate) 1.5%) was injected to manufacture a battery.

[0142] Among the above positive electrode active material and the negative electrode active material, silicon oxide was degassed at 200°C for 8 hours using a BET measuring device (BEL-SORP-MAX, Nippon Bell), and N2 adsorption / desorption was performed at 77K to measure the specific surface area, and the values ​​were 0.6 m for each positive electrode active material. 2 / g, silicon oxide active material 3.0 m 2 / g was.

[0143]

[0144] Example 2

[0145] A battery was manufactured in the same manner as in Example 1, except that silicon oxide containing Mg, carbon-coated by methane CVD, was used as the silicon-based active material included in the negative electrode active material. The specific surface area of ​​the active material was 0.6 m for the positive electrode active material, respectively. 2 / g, Mg-silicon oxide active material 6.0 m 2 / g was.

[0146]

[0147] Example 3

[0148] A battery was manufactured in the same manner as in Example 1, except that silicon oxide containing Li, carbon-coated by methane CVD, was used as the silicon-based active material included in the negative electrode active material. The specific surface area of ​​the active material was 0.6 m for the positive electrode active material, respectively. 2 / g, Li-silicon oxide active material 3.5 m 2 / g was.

[0149]

[0150] Example 4

[0151] A battery was manufactured in the same manner as in Example 1, except that a silicon-carbon composite coated with carbon by methane CVD was used as the silicon-based active material included in the negative electrode active material. The specific surface area of ​​the active material was 0.6 m for the positive electrode active material, respectively.2 / g, silicon carbon composite active material 3.0 m 2 / g was.

[0152]

[0153] Example 5

[0154] A battery was manufactured in the same manner as in Example 1, except that the positive electrode active material was ground to D50 = 3.5 μm. The specific surface area of ​​the active material was 0.7 m for each positive electrode active material. 2 / g, silicon oxide active material 3.0 m 2 / g was.

[0155]

[0156] Example 6

[0157] A battery was manufactured in the same manner as in Example 2, except that the positive electrode active material was ground to D50 = 3.5 μm. The specific surface area of ​​the active material was 0.7 m for each positive electrode active material. 2 / g, Mg-silicon oxide active material 6.0 m 2 / g was.

[0158]

[0159] Example 7

[0160] A battery was manufactured in the same manner as in Example 3, except that the positive electrode active material was ground to D50 = 3.5 μm. The specific surface area of ​​the active material was 0.7 m for each positive electrode active material. 2 / g, Li-silicon oxide active material 3.5 m 2 / g was.

[0161]

[0162] Example 8

[0163] A battery was manufactured in the same manner as in Example 4, except that the positive electrode active material was ground to D50 = 3.5 μm. The specific surface area of ​​the active material was 0.7 m for each positive electrode active material. 2 / g, silicon carbon composite active material 3.0 m 2 / g was.

[0164]

[0165] Comparative Example 1

[0166] A battery was manufactured in the same manner as in Example 1, except that the silicon-based active material included in the negative active material was silicon oxide with a D50 of 12 μm and carbon coating by methane CVD. The specific surface area of ​​the active material was 0.6 m for the positive active material, respectively. 2 / g, Mg-silicon oxide active material 1.5 m 2 / g was.

[0167]

[0168] Comparative Example 2

[0169] A battery was manufactured in the same manner as in Example 1, except that the silicon-based active material included in the negative active material was silicon oxide containing Mg with a D50 of 12 μm and carbon-coated by methane CVD. The specific surface area of ​​the active material was 0.6 m for the positive active material, respectively. 2 / g, Mg-silicon oxide active material 2.0 m 2 / g was.

[0170]

[0171] Comparative Example 3

[0172] A battery was manufactured in the same manner as in Example 1, except that the silicon-based active material included in the negative active material was a silicon oxide containing Li with a D50 of 12 μm and carbon-coated by methane CVD. The specific surface area of ​​the active material was 0.6 m for the positive active material, respectively. 2 / g, Li-silicon oxide active material 2.0 m 2 / g was.

[0173]

[0174] Comparative Example 4

[0175] A battery was manufactured in the same manner as in Example 1, except that the silicon-based active material included in the negative electrode active material was a silicon carbon composite with a D50 of 12 μm and carbon-coated by methane CVD. The specific surface area of ​​the active material was 0.6 m for the positive electrode active material, respectively. 2 / g, silicon carbon composite active material 1.0 m 2 / g was.

[0176]

[0177] Comparative Example 5

[0178] A battery was manufactured in the same manner as in Example 1, except that the silicon-based active material included in the negative electrode active material was silicon oxide with a D50 of 6 ㎛ and a carbon coating at a pitch. The specific surface area of ​​the active material was 0.6 m for the positive electrode active material, respectively. 2 / g, silicon oxide active material 1.8 m 2 / g was.

[0179]

[0180] Comparative Example 6

[0181] A battery was manufactured in the same manner as in Example 1, except that the silicon-based active material included in the negative electrode active material was silicon oxide containing Mg with a D50 of 6 ㎛ and a carbon coating at a pitch. The specific surface area of ​​the active material was 0.6 m for the positive electrode active material, respectively. 2 / g, Mg-silicon oxide active material 2.3 m 2 / g was.

[0182]

[0183] Comparative Example 7

[0184] A battery was manufactured in the same manner as in Example 1, except that the silicon-based active material included in the negative active material was silicon oxide containing Li coated with carbon at a pitch of 6 ㎛ and having a D50 of 6 ㎛. The specific surface area of ​​the active material was 0.6 m for the positive active material, respectively. 2 / g, Li-silicon oxide active material 2.0 m 2 / g was.

[0185]

[0186] Comparative Example 8

[0187] A battery was manufactured in the same manner as in Example 1, except that the silicon-based active material included in the negative active material was a silicon carbon composite with a D50 of 6 ㎛ and a carbon coating at a pitch. The specific surface area of ​​the active material was 0.6 m for the positive active material, respectively. 2 / g, silicon carbon composite active material 1.2 m 2 / g was.

[0188]

[0189] Comparative Example 9

[0190] A battery was manufactured in the same manner as in Example 1, except that the negative active material was artificial graphite. The specific surface area of ​​the active material was 0.6 m for the positive active material, respectively. 2 / g, artificial graphite active material 0.6 m 2 / g was.

[0191]

[0192] Comparative Example 10

[0193] A battery was manufactured in the same manner as in Example 1, except that the positive electrode active material was a secondary particle. The specific surface area of ​​the active material was 0.6 m for each positive electrode active material. 2 / g, silicon carbon composite active material 3.0 m 2 / g was.

[0194]

[0195] Comparative Example 11

[0196] A battery was manufactured in the same manner as in Example 1, except that the positive electrode active material was a secondary particle. The specific surface area of ​​the active material was 0.8 m for each positive electrode active material. 2 / g, silicon carbon composite active material 3.0 m 2 / g was.

[0197]

[0198] <Experimental Example 1> Evaluation of lifespan (capacity retention rate) characteristics

[0199] The manufactured battery was charged and discharged to evaluate the capacity retention rate, which is shown in Table 1 below.

[0200] The first and second cycles were charged and discharged at 0.1 C, and from the third cycle onwards, the charging and discharging was performed at 1.0 C. The 300th cycle was terminated in a discharged state (with lithium in the positive electrode).

[0201] Charging conditions: CC (constant current) / CV (constant voltage) (4.25V / 0.05C current cut-off)

[0202] Discharge conditions: CC (constant current) condition 2.5 V

[0203] The capacity retention rate was derived by the following calculations.

[0204] Capacity retention rate (%) = (300 discharge capacity / 1 discharge capacity) × 100

[0205]

[0206] No. Anode material - Silicon-based particle Anode material Silicon-based SSA / Anode material SSA ratio 300th capacity retention Silicon-based active material Carbon coating D50 (㎛) SSA (m2 / g) Anode material SSA (m2 / g) Example 1 General silicon oxide methane CVD63 Single particle 0.65.08 1 Example 2 Mg-silicon oxide methane CVD66 Single particle 0.610.08 3 Example 3 Li-silicon oxide methane CVD63.5 Single particle 0.65.88 4 Example 4 Silicon carbon composite methane CVD63 Single particle 0.65.08 7 Example 5 General silicon oxide methane CVD63 Single particle 0.74.38 0 Example 6 Mg-silicon oxide methane CVD66 Single particle 0.78.68 3 Example 7 Li-silicon Oxide methane CVD63.5 Single particle 0.75.083 Example 8 Silicon carbon composite methane CVD63 Single particle 0.74.384 Comparative example 1 General silicon oxide methane CVD121.5 Single particle 0.62.570 Comparative example 2 Mg-silicon oxide methane CVD122 Single particle 0.63.372 Comparative example 3 Li-silicon oxide methane CVD122 Single particle 0.63.372 Comparative example 4 Silicon carbon composite methane CVD121 Single particle 0.61.775 Comparative example 5 General silicon oxide pitch 61.8 Single particle 0.63.072 Comparative example 6 Mg-silicon oxide pitch 62.3 Single particle 0.63.873 Comparative example 7 Li-silicon oxide pitch 62 Single particle 0.63.373 Comparative example 8 Silicon carbon composite pitch 61.2 Single particle 0.6 2.077 Comparative example 9 Artificial graphite pitch 150.6 Single particle 0.6 1.050 Comparative example 10 General silicon oxide methane CVD 63 Secondary particle 0.6 5.070 Comparative example 11 General silicon oxide methane CVD 63 Secondary particle 0.8 3.75 65

[0207] As described in the table above, Examples 1 to 8, in which the specific surface area of ​​the silicon-based particles was 4 times or more compared to the specific surface area of ​​the lithium composite transition metal compound particles, showed superior capacity retention after 300 cycles compared to Comparative Examples 1 to 9 and 11, in which the specific surface area of ​​the silicon-based particles was less than 4.0 compared to the specific surface area of ​​the lithium composite transition metal compound particles. Specifically, when comparing the capacity retention rates of Example 1, in which the specific surface area of ​​the silicon-based particles was 5.0 times compared to the specific surface area of ​​the lithium composite transition metal compound particles, and Comparative Example 1, in which the specific surface area of ​​the silicon-based particles was 2.5 times compared to the specific surface area of ​​the lithium composite transition metal compound particles, the capacity retention rate of Example 1 showed a result of increasing by 12.8%.

[0208] It was found that Examples 1 to 8, which included silicon particles as the negative active material, had superior capacity retention rates compared to Comparative Example 9, which did not include silicon particles as the negative active material. Specifically, when Example 4, which included a silicon carbon composite as the negative active material, and Comparative Example 9, which included only artificial graphite as the negative active material, were compared, the capacity retention rate was shown to increase by up to 74%.

[0209] In addition, it was found that Examples 1 to 8 using lithium composite transition metal compound particles in the form of single particles had superior capacity retention rates compared to Comparative Examples 10 and 11 using lithium composite transition metal compounds in the form of secondary particles. Specifically, when Example 1 including a lithium composite transition metal compound in the form of single particles was compared with Comparative Example 10 using a lithium composite transition metal compound in the form of secondary particles, the capacity retention rate was shown to increase by 12.8%.

[0210] Therefore, by using an active material in which the specific surface area of ​​the silicon-based particles of the negative active material is 4.0 times or more compared to the specific surface area of ​​the lithium composite transition metal compound particles of the positive active material, it was confirmed that the silicon-based particles can sufficiently react with the lithium ions of the lithium composite transition metal compound particles in the form of single particles, thereby significantly improving the battery life performance.

Claims

1. A lithium secondary battery comprising a positive electrode; a negative electrode; and a separator provided between the positive electrode and the negative electrode, The above positive electrode contains nickel, cobalt and manganese as positive electrode active materials, and contains lithium composite transition metal compound particles in the form of single particles, The above negative electrode contains silicon particles as a negative electrode active material, A lithium secondary battery, wherein the specific surface area of ​​the silicon particles is at least four times that of the lithium composite transition metal compound particles.

2. A lithium secondary battery according to claim 1, wherein the silicon-based particles include at least one of silicon carbon composite particles and silicon oxide particles.

3. In claim 2, the specific surface area of ​​the lithium composite transition metal compound particle is 0.4 m 2 / g to 0.8 m 2 / g, and the specific surface area of ​​the silicon carbon composite or the silicon oxide particles is 2 m 2 / Lithium secondary battery having a mass of 1000 m3 or more.

4. In claim 2, The lithium composite transition metal compound particles are contained in an amount of 15 to 100 parts by weight relative to 100 parts by weight of the positive electrode active material, A lithium secondary battery, wherein the silicon carbon composite particles or the silicon oxide particles are contained in an amount of 3 to 30 parts by weight based on 100 parts by weight of the negative active material.

5. In claim 2, The D50 of the above lithium composite transition metal compound particles is 1 μm or more and 10 μm or less, A lithium secondary battery, wherein the D50 of the silicon carbon composite particles or silicon oxide particles is 1 μm or more and 10 μm or less.

6. A battery module comprising a lithium secondary battery according to any one of claims 1 to 5.

7. A battery pack comprising a lithium secondary battery according to any one of claims 1 to 5.

8. A battery pack comprising the battery module of claim 6.