Negative electrode active material coating composition, negative electrode active material, negative electrode composition, negative electrode, and lithium secondary battery including the same

Abstract

The present invention relates to a coating composition for a negative electrode active material, which contains a polymer having a -HN-C=O- bonding group, and the polymer having the -HN-C=O- bonding group has a glass transition temperature (Tg) of -30°C to 80°C, and to a negative electrode, a lithium secondary battery, a battery module, and a battery pack each containing the same.

Description

[Technical Field]

[0001] This specification claims the benefit of Korean Patent Application No. 10-2023-0116103 filed with the Korean Intellectual Property Office on September 1, 2023, and Korean Patent Application No. 10-2024-0116316 filed with the Korean Intellectual Property Office on August 29, 2024, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a coating composition for an anode active material, an anode active material, an anode composition, an anode, and a secondary battery including the same. [Background technology]

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

[0004] Generally, a lithium secondary battery includes a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode, an electrolyte, an organic solvent, etc. The positive electrode and the negative electrode may each have an active material layer formed on a current collector, the active material layer including a positive electrode active material and a negative electrode active material. Generally, the positive electrode uses a lithium-containing metal oxide such as LiCoO2 or LiMn2O4 as the positive electrode active material, and the negative electrode uses a lithium-free carbon-based active material or a silicon-based active material as the negative electrode active material.

[0005] Silicon-based negative electrode active materials have attracted attention due to their higher capacity and superior fast charging characteristics compared to carbon-based active materials. However, silicon-based active materials have the disadvantage of low initial efficiency due to their large irreversible capacity caused by large volume expansion / contraction during charging / discharging.

[0006] On the one hand, among silicon-based active materials, silicon-based oxides, specifically SiO x In the case of silicon-based oxides represented by (0 < x < 2), there is an advantage in that the degree of volume expansion / contraction due to charge / discharge is lower than that of other silicon-based active materials such as silicon (Si). However, silicon-based oxides still have the drawback that the initial efficiency decreases due to the presence of irreversible capacity.

[0007] In connection with this, research has been continuously conducted to reduce the irreversible capacity and improve the initial efficiency by doping or inserting metals such as Li, Al, and Mg into silicon-based oxides. However, in the case of a negative electrode slurry containing a metal-doped silicon-based oxide as a negative electrode active material, there is a problem that the metal oxide formed by doping reacts with moisture to increase the pH of the negative electrode slurry and change the viscosity. For this reason, the state of the manufactured negative electrode becomes poor, and there is a problem that the charge / discharge efficiency of the negative electrode decreases.

[0008] Therefore, there is a need to develop a negative electrode active material that can improve the phase stability of a negative electrode slurry containing a silicon-based oxide and improve the charge / discharge efficiency of the negative electrode manufactured therefrom.

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention relates to a composition for coating a negative electrode active material, a negative electrode active material, a negative electrode composition, a negative electrode, and a secondary battery including the same, which can improve the performance of a lithium secondary battery.

Means for Solving the Problems

[0010] One embodiment of the present invention provides a composition for coating a negative electrode active material containing a polymer having a bonding group of -HN-C=O-, wherein the glass transition temperature (Tg) of the polymer having the bonding group of -HN-C=O- is -30°C to 80°C.

[0011] According to one embodiment of the present invention, the polymer having the -HN-C=O- bonding group is a polymer of alcohol and isocyanate, and the molar ratio of -NCO groups of the isocyanate to -OH groups of the alcohol is 0.5 to 4.

[0012] One embodiment of the present invention provides an anode active material comprising: silicon-based particles; and a coating layer provided on at least a portion of the surface of the silicon-based particles, the coating layer comprising the anode active material coating composition according to the above-described embodiment.

[0013] One embodiment of the present invention provides a negative electrode composition comprising a negative electrode active material according to the above-described embodiment, a binder, and a conductive material.

[0014] One embodiment of the present invention provides a negative electrode comprising a negative electrode current collector and a negative electrode composition according to the above-described embodiment on at least one surface of the negative electrode current collector.

[0015] One embodiment of the present invention provides a lithium secondary battery comprising a negative electrode, a separator, and a positive electrode according to the above-described embodiment.

[0016] One embodiment of the present invention provides a battery module including the lithium secondary battery according to the above-described embodiment.

[0017] One embodiment of the present invention provides a battery pack including the lithium secondary battery according to the above-described embodiment.

[0018] One embodiment of the present invention provides a battery pack including a battery module according to the above-described embodiment. [Effects of the Invention]

[0019] According to one embodiment of the present invention, by forming a coating layer on at least a portion of the surface of a silicon-based active material using a coating composition for an anode active material containing a polymer having a -HN-C=O- bonding group, the extreme volume change and particle fracture of the silicon-based active material during charge and discharge can be improved. Specifically, electrodes containing silicon-based active materials have inferior characteristics compared to graphite-based active materials due to volume change and particle fracture during charge and discharge, but these inferior characteristics can be improved by coating the silicon-based active material with a polymer having a -HN-C=O- bonding group, which has excellent impact resistance and shape recovery ability, capable of returning to its original shape even when deformed by the application of force.

[0020] Therefore, a negative electrode active material including the negative electrode active material coating composition according to an embodiment of the present invention, a negative electrode including the negative electrode active material, and a secondary battery including the negative electrode have the effect of improving the discharge capacity, initial efficiency, resistance performance, or life characteristics of the battery. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention will be described in more detail below to facilitate understanding of the present invention. The present invention may be realized in various different forms and is not limited to the embodiments described herein. In this regard, the terms and words used in the specification and claims should not be interpreted in a limited manner to their ordinary or dictionary meanings, but should be interpreted in a manner that is consistent with the technical idea of ​​the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best describe their invention.

[0022] It should be understood that in this specification, terms such as "comprises," "provides," or "has" specify the presence of embodied features, numbers, steps, components, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0023] Furthermore, when a part such as a layer exists "on" or "above" another part, it does not only mean that it is "directly above" that part, but also includes the case where there is another part between them. In contrast, when a part exists "directly above" another part, it means that there is no other part between them. Furthermore, when a part exists "on" or "above" a reference part, it does not necessarily mean that it is located above or below the reference part, and is not necessarily located "above" or "above" the direction opposite to gravity.

[0024] The terms and words used in this specification should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as meanings and concepts that are consistent with the technical idea of ​​the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best explain their inventions.

[0025] As used herein, the singular expression of a term includes the plural expression unless the context clearly indicates otherwise.

[0026] Preferred embodiments of the present invention will be described in detail below. 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.

[0027] <Negative electrode active material coating composition> A coating composition for a negative electrode active material according to one embodiment of the present invention includes a polymer having a -HN-C=O- bonding group, and the polymer having a -HN-C=O- bonding group has a glass transition temperature (Tg) of -30°C to 80°C.

[0028] Conventionally used electrodes containing silicon-based active materials have inferior properties compared to graphite-based active materials due to extreme volume changes and particle crushing during charging and discharging.

[0029] However, according to the above-described embodiment, since a polymer having a -HN-C=O- bonding group has impact resistance and shape recovery properties, i.e., it returns to its original shape even when deformed by the application of force, the above-described inferior characteristics can be improved by including the polymer having a -HN-C=O- bonding group as a coating layer of the negative electrode active material. This minimizes the fracture of the negative electrode active material and maintains the connectivity of the conductive material, thereby achieving long-life battery characteristics.

[0030] The glass transition temperature of a polymer refers to the temperature at which the Brownian motion of polymer chains becomes active. Since it indicates that an amorphous polymer receives and absorbs a certain amount of thermal energy and transitions to polymer chain motion, the glass transition temperature can be seen as indicating the shock absorption capacity and resilience of the molecules.

[0031] The glass transition temperature of the negative electrode active material coating composition was measured using a differential scanning calorimetry (DSC). The negative electrode active material coating composition was placed in a pan of a differential scanning calorimeter and heated from -100°C to 200°C at a rate of 5°C / min. The temperature range where the heat flow changed was determined, and this was called the glass transition temperature.

[0032] For example, the polymer having a -HN-C=O- bonding group has a glass transition temperature of -30°C to 80°C. Specifically, the glass transition temperature may be -30°C to 70°C, -30°C to 60°C, -30°C to 50°C, -20°C to 40°C, -20°C to 30°C, or -20°C to 20°C. If the glass transition temperature is lower than -30°C, the polymer having a -HN-C=O- bonding group may dissolve in the slurry without being coated on the surface of the active material. If the glass transition temperature is higher than 80°C, the high rigidity may reduce the restoration of the coating layer during charge and discharge.

[0033] According to one embodiment, the polymer having a bonding group of -HN-C=O- is a polymer of alcohol and isocyanate, and the molar ratio of -NCO groups of the isocyanate to -OH groups of the alcohol is 0.5 to 4.

[0034] When the molar ratio of the -NCO groups of the isocyanate to the -OH groups of the alcohol is 0.5 or more, the problem of a polymer having a -HN-C=O- bond group dissolving in the slurry without being coated on the surface of the active material can be minimized, and when the molar ratio of the -NCO groups of the isocyanate to the -OH groups of the alcohol is 4 or less, the hardness of the coating layer can be controlled and the shape recovery effect against volumetric changes of the active material during charge and discharge can be appropriately provided. Therefore, by reacting the isocyanate so that the molar ratio of the -NCO groups of the isocyanate to the -OH groups of the alcohol is 0.5 to 4, volumetric changes and particle crushing of the negative electrode active material during charge and discharge can be suppressed, thereby effectively improving the life characteristics of the battery.

[0035] For example, the molar ratio of the —NCO groups of the isocyanate to the —OH groups of the alcohol may be 0.5 to 4, 0.5 to 3.5, 0.5 to 3, 1 to 3, or 1.2 to 2.6.

[0036] According to one embodiment, the polymer having the -HN-C=O- bonding group includes a urethane-based polymer.

[0037] According to one embodiment, the polymer having a bonding group of -HN-C=O- has a weight average molecular weight of 5,000 g / mol to 1,000,000 g / mol.

[0038] The weight average molecular weight is a value measured by gel permeation chromatography (GPC) and converted from a standard polystyrene calibration curve.

[0039] According to an embodiment, the negative electrode active material coating composition may further include a solvent or a catalyst component.

[0040] According to one embodiment, the solvent may be NMP (N-methylpyrrolidone), dimethylformamide (DMF), toluene, or dimethyl sulfoxide (DMSO).

[0041] According to one embodiment, the catalyst may be an organometallic catalyst.

[0042] According to one embodiment, the catalyst may be dibutyltin dilaurate (DBTDL).

[0043] <Negative electrode active material> According to one embodiment of the present invention, the negative electrode active material comprises silicon-based particles; and a coating layer provided on at least a portion of the surface of the silicon-based particles, the coating layer comprising the above-described negative electrode active material coating composition.

[0044] In one embodiment of the present specification, the amount of the coating layer is 0.1 wt % to 5 wt % based on 100 wt % of the total negative electrode active material. For example, the amount of the coating layer may be 0.1 wt % to 4 wt %, 0.1 wt % to 3 wt %, 0.2 wt % to 3 wt %, or 0.3 wt % to 3 wt % based on 100 wt % of the total negative electrode active material. If the amount of the coating layer exceeds 5 wt %, the weight of the coating layer relative to the weight of the total negative electrode active material increases, resulting in a decrease in capacity and disadvantageous lithium charging and discharging due to the polyurethane's low lithium ion conductivity. If the amount of the coating layer is less than 0.1 wt %, the recovery due to volumetric changes in the active material is insignificant, and the coating layer may detach during slurry mixing.

[0045] In one embodiment of the present specification, the coating layer has a thickness of 1 nm to 1 μm.

[0046] The thickness of the surface coating layer can be measured by XPS (X-ray Photoelectron Spectroscopy) depth profile.

[0047] The thickness of the surface coating layer can be determined based on the disappearance of nitrogen (N) detected while etching the surface of the negative electrode active material including the coating layer.

[0048] For example, the thickness of the coating layer is 1 nm to 1 μm. Specifically, the thickness of the coating layer may be 1 nm to 800 nm, 5 nm to 500 nm, 5 nm to 300 nm, 5 nm to 100 nm, or 5 nm to 50 nm. If the thickness of the coating layer exceeds 1 μm, it is disadvantageous in that it exhibits high surface resistance and low capacity during lithium charging and discharging, while if it is less than 1 nm, it is disadvantageous in that it exhibits little recovery due to volumetric changes in the negative electrode active material during charging and discharging, and there is a risk of the coating layer detaching when the slurry is mixed.

[0049] According to one embodiment of the present invention, the silicon-based particles are silicon carbon composite or silicon oxide particles.

[0050] According to one embodiment, the silicon-based particles may comprise a silicon carbon composite, a silicon oxide, or both.

[0051] According to one embodiment, the silicon carbon composite may be a Si / C based active material.

[0052] In this specification, the silicon carbon composite is a composite of Si and C and is distinguished from silicon carbide, which is represented as SiC. Silicon carbide does not electrochemically react with lithium and all performances, including lifespan, can be measured to be zero.

[0053] The silicon carbon composite may include at least one of a silicon carbon composite formed by depositing silicon on a porous carbon structure and a silicon carbon composite formed by compositing carbon on a porous silicon structure. The silicon carbon composite may be a composite of silicon and graphite. The silicon in the silicon carbon composite may be nanosilicon.

[0054] According to one embodiment, the silicon carbon composite comprises porous carbon-based particles and a silicon coating layer located on the surface or in the internal pores of the porous carbon-based particles.

[0055] According to one embodiment, the silicon carbon composite is formed by the BET method to a surface area of ​​0.5 m 2 / g~10m 2 / g and a pore volume of 0.005 cm 3 / g~0.03cm 3 The silicon carbon composite may have a pore volume of 0.005 cm3 measured by mercury penetration method, and the pore size measured by BET method may be 10 nm to 20 nm. 3 / g~0.03cm 3 / g.

[0056] According to one embodiment, the silicon carbon composite may have a D90 particle size of 11 μm to 20 μm, a D50 particle size of 3 μm to 10 μm, and a D10 particle size of 0.1 μm to 3 μm.

[0057] According to one embodiment, the silicon carbon composite may be prepared by a method including the steps of: etching carbon-based particles having internal pores to expand the internal pores of the carbon-based particles; and forming a silicon coating layer on the surfaces and internal pores of the carbon-based particles whose internal pores have been expanded.

[0058] The step of expanding the internal pores of the carbon-based particles may be carried out 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 may be controlled to be 0.1 L / min to 10 L / min.

[0059] The step of expanding the internal pores of the carbon-based particles may be carried out for 30 minutes to 4 hours in a temperature range of 400°C to 1200°C.

[0060] Depending on the conditions for expanding the internal pores of the carbon-based particles, the pore characteristics of the obtained porous carbon-based particles may vary.

[0061] The step of forming the silicon coating layer may be carried out using a chemical vapor deposition method. At this time, silicon nanoparticles may be deposited on the surface and / or internal pores of the carbon-based particles with expanded internal pores, and a silicon coating layer in the form of a film, an island, or a mixed form of these may be formed.

[0062] The silicon nanoparticles may be crystalline, quasi-crystalline, amorphous, or a combination thereof. <000**********

[0063] According to one embodiment, the silicon oxide may include SiO x (0 ≦ x < 2).

[0064] The SiO x (0 ≦ x < 2) containing active material may be silicon oxide particles containing SiO x (0 < x < 2) and pores.

[0065] The SiO x (0 < x < 2) corresponds to the matrix in the silicon oxide particles. The SiO x (0 < x < 2) may be in a form containing Si and SiO2, and the Si may form a phase. That is, the x in the SiO xIt corresponds to the number ratio of O to Si contained in (0 < x < 2). The silicon oxide particles are the SiO x When (0 < x < 2) is included, the discharge capacity of the secondary battery can be improved.

[0066] The silicon oxide particles may further contain at least one of a Mg compound and a Li compound. The Mg compound and the Li compound may correspond to a matrix within the silicon oxide particles.

[0067] The Mg compound and / or the Li compound may be present inside and / or on the surface of the SiO x (0 < x < 2). The initial efficiency of the battery can be improved by the Mg compound and / or the Li compound.

[0068] The Mg compound may include at least any one selected from the group consisting of Mg silicate, Mg silicide, and Mg oxide. The Mg silicate may include at least any one of Mg2SiO4 and MgSiO3. The Mg silicide may include Mg2Si. The Mg oxide may include MgO.

[0069] In one embodiment of this specification, the Mg element may be contained at 0.1% to 20% by weight, or 0.1% to 10% by weight based on 100% by weight of the silicon oxide particles. Specifically, the Mg element may be contained at 0.5% to 8% by weight, or 0.8% to 4% by weight. When the above range is satisfied, the Mg compound can be contained at an appropriate content within the silicon oxide particles, so that the volume change 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.

[0070] The Li compound may contain at least any one selected from the group consisting of Li silicate, Li silicide, and Li oxide. The Li silicate may contain at least any one of Li2SiO3, Li4SiO4, and Li2Si2O5. The Li silicide may contain Li7Si2. The Li oxide may contain Li2O.

[0071] In one embodiment of the present invention, the Li compound may contain a form of lithium silicate. The lithium silicate is Li a Si b O c (2 ≤ a ≤ 4, 0 < b ≤ 2, 2 ≤ c ≤ 5), and can be classified into crystalline lithium silicate and amorphous lithium silicate. The crystalline lithium silicate may exist in the form of at least one lithium silicate selected from the group consisting of Li2SiO3, Li4SiO4, and Li2Si2O5 within the silicon oxide particles, and the amorphous lithium silicate may be in the form of Li a Si b O c (2 ≤ a ≤ 4, 0 < b ≤ 2, 2 ≤ c ≤ 5), and is not limited to this form.

[0072] In one embodiment of the present specification, the Li element may be contained at 0.1 wt% to 20 wt%, or may be contained at 0.1 wt% to 10 wt% based on 100 wt% of the silicon oxide particles. Specifically, the Li element may be contained at 0.5 wt% to 8 wt%, and more specifically, may be contained at 0.5 wt% to 4 wt%. When the above range is satisfied, the Li compound can be contained in a suitable content within the silicon oxide particles, so that the 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.

[0073] The Mg or Li element content can be confirmed by ICP analysis. For the ICP analysis, a certain amount (approximately 0.01 g) of the negative electrode active material is accurately separated and transferred to a platinum crucible. Nitric acid, hydrofluoric acid, and sulfuric acid are added and the mixture is completely decomposed on a hot plate. Then, an inductively coupled plasma optical emission spectrometer (ICPAES, Perkin-Elmer 7300) is used to measure the intensity of a standard solution (5 mg / kg) prepared at a wavelength specific to Mg or Li, creating a reference calibration curve. The pretreated sample solution and a blank sample are then introduced into the instrument, and their respective intensities are measured to calculate the actual intensities. The concentrations of each component are calculated using the created calibration curve, and the total is converted to a theoretical value. The Mg or Li element content of the silicon oxide particles can then be analyzed.

[0074] In one embodiment of the present specification, a carbon layer may be provided on the surface and / or inside the pores of the silicon oxide particles. The carbon layer imparts electrical conductivity to the silicon oxide particles, thereby improving the initial efficiency, life characteristics, and capacity characteristics of a secondary battery including a negative electrode active material containing the silicon oxide particles. The total weight of the carbon layer may be 5 wt % to 40 wt % based on 100 wt % of the silicon oxide particles.

[0075] In one embodiment of the present specification, the carbon layer may include at least one of amorphous carbon and crystalline carbon.

[0076] The average particle size (D50) of the negative electrode active material may be 0.1 μm to 30 μm, specifically 1 μm to 20 μm, and more specifically 1 μm to 10 μm. When the average particle size is within this range, the active material is structurally stable during charge and discharge, and the problem of increased volume expansion / contraction due to an excessively large particle size is prevented, and the problem of reduced initial efficiency due to an excessively small particle size is prevented.

[0077] In this specification, the average particle size (D50) can be defined as the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve of the particles. The average particle size (D50) can be measured, for example, using a laser diffraction method. The laser diffraction method is generally capable of measuring particle sizes from the submicron range to several mm, and can provide results with high reproducibility and high resolution. The specific surface area of ​​the silicon-based active material is 2 m 2 / g~10m 2 / g. In this specification, the specific surface area is measured by the BET method.

[0078] <Method of manufacturing negative electrode active material> According to one embodiment of the present invention, the method for preparing the negative electrode active material includes the steps of: preparing silicon-based particles; and forming a coating layer on the silicon-based particles.

[0079] [Preparing silicon-based particles] In one embodiment of the present invention, the silicon-based particles may be silicon carbon composite or silicon oxide particles.

[0080] In one embodiment of the present invention, the silicon-based particles may be silicon oxide particles formed by heat-treating a powder mixture of Si powder and SiO2 powder.

[0081] For example, the silicon oxide particles can be produced by heat treating the mixed powder of the Si powder and SiO2 powder at 1000°C to 1800°C or 1200°C to 1500°C to vaporize it.

[0082] The silicon oxide particles may further include one or more of Mg and Li, and the Mg or Li may be distributed on the surface and / or inside of the silicon-based oxide particles in a doped form.

[0083] The silicon oxide particles may further include a carbon layer.

[0084] In one embodiment of the present invention, the silicon-based particles may be a silicon carbon composite prepared by passing SiH4 / He gas through a porous carbon structure formed by heat-treating cellulose powder.

[0085] The silicon carbon composite may further comprise a carbon layer.

[0086] [Step of forming a coating layer on silicon-based particles] In one embodiment of the present invention, the coating composition for a negative electrode active material coated on the silicon-based particles may include a polymer having a bonding group of -HN-C=O-.

[0087] The polymer having the -HN-C=O- bonding group may be the same as the polymer having the -HN-C=O- bonding group described above.

[0088] According to one embodiment of the present invention, a coating composition for an anode active material, including the silicon-based particles and the polymer having the -HN-C=O- bonding group, can be stirred to prepare an anode active material having a coating layer.

[0089] For example, the coating composition for the negative electrode active material, which includes the silicon-based particles prepared above and the polymer having the -HN-C=O- bonding group, can be stirred at a speed of 200 rpm to 5000 rpm to prepare a negative electrode active material having a coating layer formed thereon.

[0090] According to one embodiment of the present invention, the negative electrode active material having the coating layer formed thereon may further include a drying step of placing the negative electrode active material in a vacuum state at 20° C. to 100° C. to remove all solvents.

[0091] <Negative electrode composition> According to one embodiment of the present invention, the negative electrode composition may include the negative electrode active material particles described above.

[0092] According to one embodiment of the present invention, the negative electrode composition may further include a binder.

[0093] According to one embodiment of the present invention, the negative electrode composition may further include a conductive material.

[0094] According to one embodiment of the present invention, the negative electrode composition may further include a binder and a conductive material.

[0095] According to one embodiment of the present invention, the negative electrode composition may further include a negative electrode active material, a binder, and a conductive material.

[0096] According to one embodiment of the present invention, the binder may comprise carboxymethyl cellulose.

[0097] The 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, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, and substances in which hydrogen is substituted with Li, Na, Ca, or the like, or may include various copolymers thereof.

[0098] According to one embodiment of the present invention, the conductive material may include one or more of carbon black and single-walled carbon nanotubes.

[0099] The conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive. For example, graphite such as natural graphite and 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 and metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives may be used.

[0100] According to one embodiment of the present invention, the conductive material may be carbon black, conductive fiber, carbon nanotube, or metal powder. Specifically, in one embodiment of the present invention, the conductive material may be graphite such as natural graphite or artificial graphite; or carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black. In one embodiment of the present invention, the conductive material may be conductive fiber such as carbon fiber or metal fiber. In one embodiment of the present invention, the conductive material may be conductive tube such as carbon nanotube. The conductive material may be fluorocarbon or metal powder such as aluminum or nickel powder.

[0101] According to one embodiment of the present invention, the conductive material may be present in an amount of 0.01 parts by weight or more and 20 parts by weight or less, based on 100 parts by weight of the negative electrode active material layer composition. Specifically, in one embodiment of the present invention, the conductive material may be present in an amount of 0.01 parts by weight or more and 10 parts by weight or less, based on 100 parts by weight of the negative electrode active material layer composition. In one embodiment of the present invention, the conductive material may be present in an amount of 0.01 parts by weight or more and 7 parts by weight or less, based on 100 parts by weight of the negative electrode active material layer composition. The conductive material may be present in an amount of 0.1 parts by weight or more and 3 parts by weight or less, based on 100 parts by weight of the negative electrode active material layer composition.

[0102] <Negative electrode> One embodiment of the present invention provides a negative electrode comprising a negative electrode composition according to the above-described embodiment.

[0103] Specifically, the negative electrode may include a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector.

[0104] The negative electrode active material layer includes the negative electrode composition according to the above-described embodiment.

[0105] The negative electrode active material layer may be formed by applying a negative electrode slurry containing the above-described negative electrode composition to at least one surface of a negative electrode current collector, followed by drying and rolling.

[0106] The negative electrode slurry may include a solvent for forming a negative electrode slurry. Specifically, the solvent for forming a negative electrode slurry may include at least one solvent selected from the group consisting of distilled water, ethanol, methanol, and isopropyl alcohol, specifically distilled water, in order to facilitate dispersion of components.

[0107] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. For example, the current collector may be made of copper, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, or the like. Specifically, a transition metal that easily adsorbs carbon, such as copper or nickel, may be used as the current collector. The thickness of the current collector may be 6 μm to 20 μm, but is not limited to this.

[0108] <Lithium secondary battery> One embodiment of the present invention provides a lithium secondary battery comprising a negative electrode, a separator, and a positive electrode according to the above-described embodiment.

[0109] 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.

[0110] The positive electrode current collector in the positive electrode is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, or the like may be used. The positive electrode current collector may typically have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to enhance the adhesive strength of the positive electrode active material. The positive electrode current collector may be used in various forms, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0111] The positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; a lithium iron oxide such as LiFe3O4; 1+c1 Mn 2-c1 O4 (0≦c1≦0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented by the chemical formula LiMnO2 (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and 0.01≦c2≦0.3 is satisfied); 2-c3 M c3 Examples of the lithium manganese composite oxides include, but are not limited to, lithium manganese composite oxides represented by Li2Mn3MO8 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfying 0.01≦c3≦0.1), Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); and LiMn2O4, in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion. The positive electrode may be Li metal.

[0112] The positive electrode active material layer may contain a positive electrode conductive material and a positive electrode binder in addition to the above-described positive electrode active material.

[0113] In this case, the positive electrode conductive material is used to impart conductivity to the electrode, and can be any material that has electronic conductivity without causing chemical changes in the battery that is constructed. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives. These may be used alone or in combination of two or more.

[0114] The positive electrode binder improves adhesion between positive electrode active materials and between the positive electrode active material and the positive electrode current collector. Specific examples of the positive electrode binder include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof. These may be used alone or in combination.

[0115] The separator separates the negative electrode and positive electrode and provides a path for lithium ions to move. Any separator typically used in secondary batteries can be used without particular limitation. It is particularly preferable that the separator exhibits low resistance to ion migration and has excellent electrolyte humidifying ability. Specifically, porous polymer films, such as those made from polyolefin polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminated structures of two or more layers thereof, may be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made from high-melting-point glass fibers or polyethylene terephthalate fibers, may also be used. To ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymeric material may be used, and it may be selectively used as a single-layer or multi-layer structure.

[0116] The lithium secondary battery may further include an electrolyte, which may be used in manufacturing a lithium secondary battery, such as, but not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, or a molten inorganic electrolyte.

[0117] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0118] Examples of the non-aqueous organic solvent that can be used include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0119] In particular, among the carbonate organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, can be preferably used as high-viscosity organic solvents, because they have a high dielectric constant and dissociate lithium salts well. When such cyclic carbonates are mixed with linear carbonates having low viscosity and low dielectric constants, such as dimethyl carbonate and diethyl carbonate, in an appropriate ratio, an electrolyte having high electrical conductivity can be prepared, and therefore such cyclic carbonates can be more preferably used.

[0120] The metal salt may be a lithium salt, which is a substance that is easily dissolved in the non-aqueous electrolyte solution. For example, the anion of the lithium salt may be F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3- , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , and (CF3CF2SO2)2N - One or more selected from the group consisting of:

[0121] In addition to the constituent components of the electrolyte, the electrolyte may further include one or more additives, such as a haloalkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivative, sulfur, quinoneimine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride, in order to improve the life characteristics of the battery, suppress a decrease in battery capacity, and improve the discharge capacity of the battery.

[0122] According to another embodiment of the present invention, there is provided a battery module including the lithium secondary battery as a unit cell, and a battery pack including the same.

[0123] According to yet another embodiment of the present invention, there is provided a battery pack including the lithium secondary battery.

[0124] According to yet another embodiment of the present invention, there is provided a battery pack including the battery module.

[0125] The battery module and battery pack include the secondary battery having high capacity, high rate characteristics, and high cycle characteristics, and therefore can be used as a power source for a medium- to large-sized device selected from the group consisting of an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage system. [Example]

[0126] Hereinafter, the present specification will be described in detail with reference to examples. However, the examples according to the present specification may be modified into various other forms, and the scope of the present application should not be interpreted as being limited to the examples described below. The examples of the present application are provided to more completely explain the present specification to those skilled in the art.

[0127] <Examples and Comparative Examples> Example 1 [Production of negative electrode active material and negative electrode active material coating composition] [Step of manufacturing silicon-based particles] [Production of silicon oxide particles] SiO, a mixture of Si and SiO2 in a 1:1 molar ratio, was placed in crucible 1 and heated to a sublimation temperature of 1400°C to evaporate. Metallic magnesium was evaporated separately by heating at 800°C. The crucible was then depressurized to a 0.1 torr level, and the raw materials were evaporated. The Mg-containing vapor mixture was reacted for 6 hours and then solidified in a vacuum at 800°C. The silicon-based active material produced by this method was pulverized using a ball mill for approximately 3-4 hours. Then, methane (CH4) was reacted in a CVD apparatus under an inert Ar atmosphere at 0.1 torr at a rate of 1 L / min for approximately 5 hours to form a carbon layer on the surface of the silicon-based active material, producing a carbon-coated magnesium silicon oxide active material. The final active material had a D50 controlled at the 6 μm level.

[0128] [Manufacturing of silicon carbon composites] The cellulose powder was placed in a tubular furnace, heated to 400°C at a rate of 4°C / min, and then heated under a nitrogen atmosphere for 2 hours. The furnace was then heated to 900°C at a rate of 4°C / min and then heated under a nitrogen atmosphere for 2 hours. The powder was mixed with sulfuric acid and nitric acid in a 3:1 volume ratio, stirred at 60°C for 2 hours, and centrifuged to obtain a precipitate. The resulting powder was washed five times with a 1:3 volume ratio mixture of ethanol and distilled water and then dried at 120°C for 12 hours. The carbonaceous particles were placed in a KOH solvent and heated at 800°C for 2 hours under a nitrogen atmosphere to obtain a porous carbon structure. The porous carbon structure was washed three times with distilled water and then dried at 120°C for at least 12 hours. The porous carbon structure was placed in a horizontal furnace and a SiH4 / He=5 / 95 gas mixture was passed through at a flow rate of 50 ml / min at 700°C for 1 hour to produce a silicon carbon composite.The silicon carbon composite was then placed in the furnace and reacted with methane at 700°C for 2 hours to produce a silicon carbon composite anode active material having a carbon layer on the surface.

[0129] [Step of forming a coating layer on silicon-based particles] The negative electrode active material coating composition containing a polymer having a -HN-C=O- bonding group was prepared by dissolving polyethylene glycol (PEG) with a molecular weight of 600 g / mol and isophorone diisocyanate (IPDI) in a dimethylformamide (DMF) solvent at an NCO / OH molar ratio of 1.8, and adding dibutyltin dilaurate (DBTDL) as a reaction catalyst at a weight ratio of 0.03 relative to the total weight of the negative electrode active material coating composition. The mixture was then stirred in a nitrogen atmosphere in an oil bath at 60°C for 3 hours to produce the negative electrode active material coating composition.

[0130] The negative active material was mixed with the polymer having a -HN-C=O- bonding group contained in the negative active material coating composition prepared above at a weight ratio of 1.0:99.0. The mixture was stirred for 10 minutes using a disperser at 2000 rpm, and then a polymer-coated silicon carbon composite was obtained by separating the solvent from the silicon carbon composite using a vacuum filtration device. The resulting polymer-coated silicon carbon composite was placed in a vacuum oven at 80°C for 12 hours to remove any remaining solvent. The weight of the dried polymer-coated silicon carbon composite was determined to be 0.9 wt% based on 100 wt% of the total negative active material, based on the weight of the polyethylene glycol (PEG) and isophorone diisocyanate (IPDI) added during polymer synthesis and the total weight of the silicon carbon composite.

[0131] [Production of negative electrode composition] Anode active material, carbon black single-walled carbon nanotubes (SWCNT) as a conductive material, and binders, CMC (carboxymethyl cellulose) and SBR (styrene-butadiene rubber), were mixed in a weight ratio of 95.3:1:3.7 to prepare anode slurry.

[0132] [Manufacturing of negative electrodes] The negative electrode slurry was applied to a Cu metal thin film with a thickness of 20 μm, and then dried in circulating air at 60° C. After rolling, it was dried in a vacuum oven at 130° C. for 1 day, and then cut into 1.4875 cm 2 The negative electrode was then manufactured by punching out a circular piece.

[0133] [Secondary battery manufacturing] 1.7671cm 2 A thin film of Li metal punched into a square was used as the positive electrode. A porous polyethylene separator was placed between the positive and negative electrodes, and an electrolyte solution containing 1M LiPF6 dissolved in a 3:7 mixture of EC (ethylene carbonate) and EMC (ethyl methyl carbonate) was injected to fabricate a Li coin half cell.

[0134] Example 2 A negative active material was prepared in the same manner as in Example 1, except that the coating composition for the negative active material was prepared using a polymer reactant NCO / OH molar ratio of 1.3.

[0135] Example 3 A negative active material was prepared in the same manner as in Example 1, except that the coating composition for the negative active material was prepared using a polymer reactant NCO / OH molar ratio of 2.5.

[0136] Example 4 A negative electrode active material was prepared in the same manner as in Example 1, except that a coating layer was prepared on the surface of the active material by mixing the weight of the polymer contained in the negative electrode active material coating composition and the weight of the negative electrode active material at a weight ratio of 0.5:99.5. Based on the weight of polyethylene glycol (PEG) and isophorone diisocyanate (IPDI) added during polymer synthesis and the total weight of the added silicon carbon composite, the amount of the polymer coating layer was determined to be 0.45 wt% based on 100 wt% of the total negative electrode active material.

[0137] Example 5 A negative electrode active material was prepared in the same manner as in Example 1, except that a coating layer was prepared on the surface of the active material by mixing the weight of the polymer contained in the negative electrode active material coating composition and the weight of the negative electrode active material at a weight ratio of 3.0:97.0. Based on the weight of the polyethylene glycol (PEG) and isophorone diisocyanate (IPDI) added during polymer synthesis and the total weight of the added silicon carbon composite, the weight of the polymer coating layer was determined to be 2.8 wt% based on 100 wt% of the total negative electrode active material.

[0138] Example 6 An anode active material was prepared in the same manner as in Example 1, except that the reactant used in preparing the anode active material coating composition was prepared by mixing polyethylene glycol (PEG) having a molecular weight of 400 g / mol and hexamethylene diisocyanate (HMDI).

[0139] Comparative Example 1 A negative electrode active material was prepared in the same manner as in Example 1, except that a coating composition for a negative electrode active material was prepared using a polymer reactant NCO / OH molar ratio of 0.3, and a coating layer was prepared on the surface of the active material by mixing the weight of the polymer contained in the coating composition for a negative electrode active material to the weight of the negative electrode active material in a weight ratio of 0.05:99.95. Based on the weight of polyethylene glycol (PEG) and isophorone diisocyanate (IPDI) added during polymer synthesis and the weight of the silicon carbon composite added, the weight of the dried polymer-coated silicon carbon composite was determined to be 0.03 wt% based on 100 wt% of the total negative electrode active material.

[0140] Comparative Example 2 A negative electrode active material was prepared in the same manner as in Example 1, except that a coating composition for a negative electrode active material was prepared using a polymer reactant NCO / OH molar ratio of 0.2, and a coating layer was prepared on the surface of the active material by mixing the weight of the polymer contained in the coating composition for a negative electrode active material to the weight of the negative electrode active material in a weight ratio of 10.0:90.0. The weight of the polymer coating layer was determined to be 6.8 wt% based on 100 wt% of the total negative electrode active material, based on the weight of polyethylene glycol (PEG) and isophorone diisocyanate (IPDI) added during polymer synthesis and the weight of the silicon carbon composite added, relative to the total weight of the silicon carbon composite.

[0141] Comparative Example 3 A negative electrode active material was prepared in the same manner as in Example 1, except that a coating composition for a negative electrode active material was prepared using a polymer reactant NCO / OH molar ratio of 8.0, and a coating layer was prepared on the surface of the active material by mixing the weight of the polymer contained in the coating composition for a negative electrode active material to the weight of the negative electrode active material in a weight ratio of 0.05:99.95. Based on the weight of polyethylene glycol (PEG) and isophorone diisocyanate (IPDI) added during polymer synthesis and the weight of the silicon carbon composite added, the weight of the dried polymer-coated silicon carbon composite was determined to be 0.05 wt% based on 100 wt% of the total negative electrode active material.

[0142] Comparative Example 4 A negative electrode active material was prepared in the same manner as in Example 1, except that a coating composition for a negative electrode active material was prepared using a polymer reactant NCO / OH molar ratio of 12.0, and a coating layer was prepared on the surface of the active material by mixing the weight of the polymer contained in the coating composition for a negative electrode active material to the weight of the negative electrode active material in a weight ratio of 10.0:90.0. The weight of the polymer coating layer was determined to be 9.9 wt% based on 100 wt% of the total negative electrode active material, based on the weight of polyethylene glycol (PEG) and isophorone diisocyanate (IPDI) added during polymer synthesis and the weight of the silicon carbon composite added, relative to the total weight of the silicon carbon composite.

[0143] [Reference example] A battery was manufactured in the same manner as in Example 1, except that a binder composition containing a polyurethane polymer having a glass transition temperature of 75°C was used instead of carboxymethyl cellulose (CMC) as the binder material, and no coating layer was formed on the silicon-based particles.

[0144] The silicon-based negative electrode active materials prepared in the examples and comparative examples are as shown in Table 1 below.

[0145] [Table 1]

[0146] <Experimental example: Evaluation of discharge capacity, initial efficiency, and life (capacity retention rate) characteristics> The manufactured batteries were charged and discharged to evaluate the discharge capacity, initial efficiency, and capacity retention rate, and the results are shown in Table 2 below.

[0147] The first and second cycles were charged and discharged at 0.1 C, and from the third to the 299th cycles, they were charged and discharged at 0.5 C. The 300th cycle was completed in a charged state (with lithium in the anode). Charging conditions: CC (constant current) / CV (constant voltage) (5mV / 0.005C current cut-off) Discharge condition: CC (constant current) condition 1.5V

[0148] The discharge capacity (mAh / g) and initial efficiency (%) were calculated from the results of one charge / discharge. Specifically, the initial efficiency (%) was calculated as follows: Initial efficiency (%) = (single discharge capacity / single charge capacity) x 100

[0149] The capacity retention rate was calculated as follows. Capacity retention rate (%) = (49 discharge capacity / 1 discharge capacity) × 100

[0150] [Table 2]

[0151] Comparative Examples 1 and 2 were cases in which a polymer having a -HN-C=O- bonding group with a glass transition temperature of less than -30°C was used as a coating composition for a negative electrode active material, and the coating layer was dissolved in the slurry without being coated on the surface of the active material, resulting in a low capacity retention rate.

[0152] In Comparative Examples 3 and 4, a polymer having a -HN-C=O- bonding group with a glass transition temperature exceeding 80°C was used as the coating composition for the negative electrode active material. The high rigidity of the coating layer reduced the shape recovery of the coating layer during charging and discharging, resulting in a low capacity retention rate.

[0153] In contrast, Examples 1 to 6 showed higher capacity retention rates than Comparative Examples 1 to 4 by using a polymer having a -HN-C=O- bonding group with a glass transition temperature of -30°C to 80°C as a coating composition for negative electrode active material.

[0154] In addition, Comparative Examples 1 and 2 are cases in which a polymer having a -HN-C=O- bonding group synthesized from a reaction product of an alcohol and an isocyanate with an NCO / OH molar ratio of less than 0.5 was used as a coating composition for a negative electrode active material, and the coating layer was dissolved in the slurry without being coated on the surface of the active material, resulting in a low capacity retention rate.

[0155] Comparative Examples 3 and 4 were cases in which a polymer having a -HN-C=O- bonding group synthesized from a reaction product of alcohol and isocyanate with an NCO / OH molar ratio exceeding 4 was used as a coating composition for the negative electrode active material. A hard coating layer was formed, and the shape recovery ability of the active material against volume changes during charge and discharge was reduced, resulting in a low capacity retention rate.

[0156] In contrast, Examples 1 to 6 showed higher capacity retention rates than Comparative Examples 1 to 4 by using, as a coating composition for a negative electrode active material, a polymer having a -HN-C=O- bonding group synthesized from a reaction product of an alcohol and an isocyanate with an NCO / OH molar ratio of 0.5 to 4.

[0157] Furthermore, as a reference example, a battery using a binder composition containing a polyurethane polymer with a glass transition temperature of 75°C and a negative electrode active material in which no coating layer was formed on silicon-based particles exhibited a lower capacity retention rate than Examples 1 to 6 of the present application.

[0158] That is, by forming a coating layer on at least a portion of the surface of a negative electrode active material using a coating composition for a negative electrode active material including a polymer having a -HN-C=O- bonding group according to one embodiment of the present invention, it was confirmed that there was an effect of improving the extreme volume change and particle crushing of the negative electrode active material during charge and discharge, and that a battery including the negative electrode active material with the coating layer formed thereon had improved life characteristics.

Claims

1. It includes a polymer having a bonding group of -HN-C=O-, The polymer having the -HN-C=O- bonding group has a glass transition temperature (Tg) of -30°C to 80°C.

2. The polymer having a bonding group of -HN-C=O- is a polymer of alcohol and isocyanate, 2. The coating composition for a negative electrode active material according to claim 1, wherein a molar ratio of --NCO groups of said isocyanate to --OH groups of said alcohol is 0.5 to 4.

3. Silicon-based particles; and An anode active material comprising a coating layer provided on at least a portion of the surface of the silicon-based particles, the coating layer comprising the anode active material coating composition according to claim 1 .

4. The negative electrode active material of claim 3 , wherein the amount of the coating layer is 0.1 wt % to 5 wt % based on 100 wt % of the total negative electrode active material.

5. The negative electrode active material of claim 3 , wherein the coating layer has a thickness of 1 nm to 1 μm.

6. The negative electrode active material according to claim 3 , wherein the silicon-based particles are silicon-carbon composite or silicon oxide particles.

7. A negative electrode composition comprising the negative electrode active material according to claim 3 , a binder, and a conductive material.

8. The negative electrode composition according to claim 7 , wherein the conductive material comprises at least one of carbon black and single-walled carbon nanotubes.

9. The negative electrode composition according to claim 7 , wherein the conductive material is present in an amount of 0.01 parts by weight to 20 parts by weight based on 100 parts by weight of the negative electrode composition.

10. 8. The negative electrode composition of claim 7, wherein the binder comprises carboxymethyl cellulose.

11. a negative electrode current collector; and A negative electrode comprising a negative electrode active material layer provided on at least one surface of the negative electrode current collector and comprising the negative electrode composition according to claim 7 .

12. A lithium secondary battery comprising the negative electrode according to claim 11, a separator, and a positive electrode.

13. A battery module comprising the lithium secondary battery according to claim 12.

14. A battery pack comprising the lithium secondary battery according to claim 12.

15. A battery pack comprising the battery module according to claim 13.

Images