Composition for coating negative electrode active material, negative electrode active material, negative electrode composition, negative electrode, and lithium secondary battery comprising same

Abstract

The present invention relates to a composition for coating a negative electrode active material, and a negative electrode, a lithium secondary battery, a battery module, and a battery pack including same, the composition comprising a polymer having the binding group -HN-C=O-, wherein the glass transition temperature (Tg) of the polymer having the binding group -HN-C=O- is -30°C to 80°C.

Description

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

[0001] This specification claims the benefit of the filing dates 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, the entire disclosure of which is incorporated herein by reference.

[0002] 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.

[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] Meanwhile, among silicon-based active materials, silicon-based oxides, specifically SiO x Silicon-based oxides, represented by (0 < x < 2), have the advantage of exhibiting a lower degree of volume expansion / contraction during charge / discharge compared to other silicon-based active materials such as silicon (Si). However, silicon-based oxides still have the disadvantage of a lower initial efficiency due to the presence of irreversible capacity.

[0007] In this regard, research has been ongoing 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 anode slurry containing metal-doped silicon-based oxides as anode active materials, there is a problem in that the metal oxide formed by doping the metal reacts with moisture to increase the pH of the anode slurry and change its viscosity, which causes the state of the manufactured anode to deteriorate and the charge / discharge efficiency of the anode to decrease.

[0008] Accordingly, 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 enhance the charge / discharge efficiency of a negative electrode manufactured therefrom.

[0009] The present invention relates to a composition for coating an anode active material capable of improving the performance of a lithium secondary battery, an anode active material, an anode composition, an anode, and a secondary battery including the same.

[0010] One embodiment of the present invention provides a composition for coating an anode active material, comprising 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 bonding group of -HN-C=O- is a polymer of alcohol and isocyanate, and the molar ratio of the -NCO group of the isocyanate to the -OH group of the alcohol is 0.5 to 4.

[0012] One embodiment of the present invention provides a negative electrode active material comprising: a silicon-based particle; and a coating layer provided on at least a portion of the surface of the silicon-based particle, the coating layer comprising a composition for coating a negative electrode active material according to the embodiment.

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

[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 embodiment on at least one surface of the negative electrode current collector.

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

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

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

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

[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 composition for coating an anode active material including a polymer having a bonding group of -HN-C=O-, there is an effect of improving extreme volume change and particle breakage during charge and discharge of the silicon-based active material. Specifically, in the case of an electrode including a silicon-based active material, compared to a graphite-based active material, it has inferior characteristics due to volume change and particle breakage during charge and discharge, but it is possible to improve the above-mentioned inferior characteristics by coating a polymer having a bonding group of -HN-C=O-, which has impact resistance and excellent shape restoring properties to return to its original shape even when deformed by applying force, on the silicon-based active material.

[0020] Therefore, the negative active material including the negative active material coating composition according to the embodiments of the present invention, the negative electrode including the negative active material, and the secondary battery including the negative electrode have the effect of improving the discharge capacity, initial efficiency, resistance performance, or life characteristics of the battery.

[0021] Hereinafter, the present invention will be described in more detail to facilitate understanding. The present invention may be embodied in various different forms and is not limited to the embodiments described herein. In this regard, terms and words used in this specification and claims should not be construed as limited to their conventional or dictionary meanings. Rather, they should be interpreted in the sense and concept that aligns with the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of a term to best explain his or her invention.

[0022] It should be understood that the terms “include,” “comprising,” or “having” used in this specification are intended to specify the presence of a feature, number, step, component, or combination 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 we say that a part of a layer or the like is "above" or "on" another part, this includes not only cases where it is "directly above" that part, but also cases where there is another part in between. Conversely, when we say that a part is "directly above" another part, it means that there is no other part in between. Furthermore, when we say that a part is "above" or "on" a reference part, it means that it is located above or below that reference part, and does not necessarily mean that it is located "above" or "on" in the direction opposite to gravity.

[0024] 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.

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

[0026] 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.

[0027]

[0028] <Composition for negative electrode active material coating>

[0029] A composition for coating a negative electrode active material according to one embodiment of the present invention includes a polymer having a bonding group of -HN-C=O-, and the polymer having the bonding group of -HN-C=O- has a glass transition temperature (Tg) of -30°C to 80°C.

[0030] In the case of electrodes containing silicon-based active materials used in the past, they have inferior characteristics due to extreme volume change and particle breakage during charge and discharge compared to graphite-based active materials.

[0031] However, according to the above embodiment, the polymer having a bonding group of -HN-C=O- has impact resistance and has shape resilience to return to its original shape even when deformed by applying force, so the above-mentioned inferior characteristics can be improved by including the polymer having a bonding group of -HN-C=O- as a coating layer of the negative electrode active material. As a result, the breakage of the negative electrode active material can be minimized and the connection to the conductive material can be maintained, so that the characteristics of a long-life battery can be implemented.

[0032] The glass transition temperature of a polymer refers to the temperature at which Brownian motion of the polymer chains becomes active. Since it refers to the transition from amorphous polymers to chain motion after absorbing a certain amount of temperature energy, the glass transition temperature can be viewed as a measure of a molecule's shock absorption and resilience.

[0033] The glass transition temperature of the composition for coating the above negative active material was measured by differential scanning calorimetry (DSC). The composition for coating the above negative active material was placed in a differential scanning calorimeter pan, and the temperature was increased from -100°C to 200°C at a rate of 5°C / min to confirm the temperature range where the heat flow changes, which is called the glass transition temperature.

[0034] For example, a polymer having the bonding group -HN-C=O- has a glass transition temperature of -30 o C to 80o 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. When the glass transition temperature is less than -30°C, there is a problem that a polymer having a bonding group of -HN-C=O- may not be coated on the surface of the active material but may be dissolved in the slurry, and when it is more than 80°C, there is a problem that the resilience of the coating layer may be reduced during charge and discharge due to high rigidity.

[0035] According to one embodiment, the polymer having the bonding group of -HN-C=O- is a polymer of alcohol and isocyanate, and the molar ratio of the -NCO group of the isocyanate to the -OH group of the alcohol is 0.5 to 4.

[0036] When the molar ratio of the -NCO group of the isocyanate to the -OH group of the alcohol is 0.5 or more, the problem of the polymer having the -HN-C=O- bonding group not being coated on the surface of the active material but being dissolved in the slurry can be minimized, and when the molar ratio of the -NCO group of the isocyanate to the -OH group of the alcohol is 4 or less, the degree of hardness of the coating layer can be controlled to appropriately provide a shape restoring effect for the volume change of the active material during charge and discharge. Therefore, by reacting so that the molar ratio of the -NCO group of the isocyanate to the -OH group of the alcohol is 0.5 to 4, the volume change and particle breakage of the negative electrode active material during charge and discharge can be suppressed, thereby effectively improving the life characteristics of the battery.

[0037] For example, the molar ratio of the -NCO group of the isocyanate to the -OH group 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.

[0038] According to one embodiment, the polymer having the bonding group of -HN-C=O- includes a urethane polymer.

[0039] According to one embodiment, the polymer having the bonding group of -HN-C=O- has a weight average molecular weight of 5,000 g / mol to 1,000,000 g / mol.

[0040] The weight average molecular weight is measured by gel permeation chromatography (GPC) and is a value obtained by conversion from a standard polystyrene calibration curve.

[0041] According to one embodiment, the composition for coating the negative active material may further include a solvent or catalyst component.

[0042] According to one embodiment, the solvent may be NMP (methylpyrrolidone), dimethylformamide (DMF), toluene, or dimethyl sulfoxide (DMSO).

[0043] According to one embodiment, the catalyst may be an organometallic catalyst.

[0044] In one embodiment, the catalyst may be dibutyltin dilaurate (DBTDL).

[0045]

[0046] <Cathode active material>

[0047] According to one embodiment of the present invention, the negative electrode active material comprises silicon particles; and a coating layer provided on at least a portion of the surface of the silicon particles and including the negative electrode active material coating composition.

[0048] In one embodiment of the present specification, the amount of the coating layer is 0.1 wt% or more and 5 wt% or less based on 100 wt% of the total negative electrode active material. For example, the amount of the coating layer may be 0.1 wt% or more and 4 wt% or less, 0.1 wt% or more and 3 wt% or less, 0.2 wt% or more and 3 wt% or less, or 0.3 wt% or more and 3 wt% or less based on 100 wt% of the total negative electrode active material. When the amount of the coating layer exceeds 5 wt%, the weight of the coating layer increases relative to the total weight of the active material, resulting in a decrease in capacity and disadvantageous for lithium charge / discharge due to the low lithium ion conductivity of polyurethane. When the amount of the coating layer is less than 0.1 wt%, the recoverability due to volume change of the active material is minimal, and there is a risk of detachment of the coating layer during slurry mixing.

[0049] In one embodiment of the present specification, the thickness of the coating layer is 1 nm to 1 μm.

[0050] The thickness of the surface coating layer can be measured using XPS (X-ray Photoelectron Spectroscopy) depth-profile.

[0051] 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 active material including the coating layer.

[0052] 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. When the thickness of the coating layer exceeds 1 μm, it is disadvantageous in that the surface resistance is large for charging and discharging lithium, resulting in low capacity, and when it is less than 1 nm, it is disadvantageous in that the recoverability due to the volume change of the negative electrode active material during charging and discharging is minimal, and there is a risk of the coating layer being detached during slurry mixing.

[0053] According to one embodiment of the present invention, the silicon-based particles are silicon carbon composites or silicon oxide particles.

[0054] According to one embodiment, the silicon-based particles may include a silicon carbon composite, silicon oxide, or both.

[0055] According to one embodiment, the silicon carbon composite may be a Si / C-based active material.

[0056] In this specification, the silicon-carbon composite is a composite of Si and C, and is distinct from silicon carbide, denoted as SiC. Since the silicon carbide does not electrochemically react with lithium, all performances, including lifespan, may be measured as 0.

[0057] The above silicon-carbon composite may include at least one of a silicon-carbon composite formed by depositing silicon into a porous carbon structure; and a silicon-carbon composite in which carbon is composited into a porous silicon structure. The silicon-carbon composite may be a composite of silicon and graphite, etc. The silicon in the silicon-carbon composite may be nano silicon.

[0058] According to one embodiment, the silicon carbon composite includes porous carbon particles and a silicon coating layer positioned on the surface or internal pores of the porous carbon particles.

[0059] According to one embodiment, the silicon carbon composite has a surface area of ​​0.5 m by the BET method. 2 / g to 10 m 2 / g, and the pore volume can be 0.005 cm 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.

[0060] According to one embodiment, the silicon carbon composite may have a D90 particle size of 11 ㎛ to 20 ㎛, a D50 particle size of 3 ㎛ to 10 ㎛, and a D10 particle size of 0.1 ㎛ to 3 ㎛.

[0061] According to one embodiment, the silicon carbon composite can be manufactured by a method including the steps of etching carbon particles containing internal pores to expand the internal pores of the carbon particles; and the steps of forming a silicon coating layer on the surface and internal pores of the carbon particles having expanded internal pores.

[0062] 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.

[0063] The step of expanding the internal pores of the above carbon particles can be performed at a temperature range of 400°C to 1200°C for 30 minutes to 4 hours.

[0064] 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.

[0065] The step of forming the above silicon coating layer can be performed using a chemical vapor deposition method. At this time, silicon nanoparticles are deposited on the surface and / or internal pores of the carbon particles with expanded internal pores, thereby forming a silicon coating layer in the form of a film, an island, or a mixture of these.

[0066] The above silicon nanoparticles may be crystalline, quasi-crystalline, amorphous, or a combination thereof.

[0067] According to one embodiment, the silicon oxide is SiO x (0≤x<2) can be included.

[0068] The active material containing the above SiOx (0≤x<2) is SiO x (0 <x<2) 및 기공을 포함하는 실리콘 산화물 입자일 수 있다.

[0069] 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.

[0070] The silicon oxide particles may further include 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.

[0071] 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.

[0072] 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.

[0073] 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 10 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 8 wt% or 0.8 wt% to 4 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.

[0074] 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.

[0075] 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.

[0076] 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 10 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 8 wt%, and more specifically, may be included in an amount of 0.5 wt% to 4 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 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.

[0077] 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 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 a standard solution prepared using a standard solution (5 mg / kg) at the wavelength unique to the Mg element or Li element to create 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.

[0078] 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. By the carbon layer, conductivity is provided to the silicon oxide particles, and the initial efficiency, life characteristics, and battery capacity characteristics of a secondary battery including a negative active material including the silicon oxide particles may be improved. The total weight of the carbon layer may be comprised in an amount of 5 wt% to 40 wt% based on 100 wt% of the total weight of the silicon oxide particles.

[0079] In one embodiment of the present specification, the carbon layer may include at least one of amorphous carbon and crystalline carbon.

[0080] The average particle diameter (D50) of the above-mentioned negative active material may be 0.1 ㎛ to 30 ㎛, specifically 1 ㎛ to 20 ㎛, and more specifically 1 ㎛ to 10 ㎛. When the above range is satisfied, the structural stability of the active material during charge and discharge can be ensured, the problem of the level of volume expansion / contraction also increasing as the particle diameter becomes excessively large can be prevented, and the problem of initial efficiency decreasing as the particle diameter becomes excessively low can be prevented.

[0081] 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 of the particles. 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 mm, and can obtain 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 may be. In this specification, the specific surface area is measured by the BET method.

[0082]

[0083] <Method for manufacturing negative active material>

[0084] According to one embodiment of the present invention, the method for manufacturing the negative electrode active material includes the steps of preparing silicon-based particles; and the steps of forming a coating layer on the silicon-based particles.

[0085] [Steps for preparing silicon particles]

[0086] In one embodiment of the present invention, the silicon-based particles may be silicon carbon composites or silicon oxide particles.

[0087] In one embodiment of the present invention, the silicon-based particles may be silicon oxide particles formed by heat-treating a powder mixed with Si powder and SiO2 powder.

[0088] For example, the silicon oxide particles can be manufactured by vaporizing a mixed powder of Si powder and SiO2 powder by heat treatment at 1000°C to 1800°C or 1200°C to 1500°C.

[0089] The above silicon oxide particles may further include at least one of a Mg element and a Li element, and the Mg element or the Li element may be distributed on the surface and / or inside the silicon oxide particles in a form doped into the silicon oxide particles.

[0090] The above silicon oxide particles may further include a carbon layer.

[0091] In one embodiment of the present invention, the silicon-based particles may be a silicon-carbon composite manufactured by flowing SiH4 / He gas into a porous carbon structure formed by heat-treating cellulose powder.

[0092] The above silicon carbon composite may further include a carbon layer.

[0093] [Step of forming a coating layer on silicon particles]

[0094] In one embodiment of the present invention, the negative active material coating composition coated on the silicon-based particles may include a polymer having a bonding group of -HN-C=O-.

[0095] The polymer having the above-described -HN-C=O- bonding group can be applied to the description of the polymer having the above-described -HN-C=O- bonding group.

[0096] According to one embodiment of the present invention, a negative electrode active material coating composition including the silicon-based particles and a polymer having a bonding group of -HN-C=O- can be stirred to produce a negative electrode active material having a coating layer formed thereon.

[0097] For example, a composition for coating an anode active material including the above-mentioned silicon-based particles and a polymer having a bonding group of -HN-C=O- can be stirred at a speed of 200 rpm to 5000 rpm to produce an anode active material having a coating layer formed thereon.

[0098] According to one embodiment of the present invention, the negative active material on which the coating layer is formed may further include a drying step of removing all solvent by placing the negative active material in a vacuum state at 20°C to 100°C.

[0099]

[0100] <Cathode composition>

[0101] According to one embodiment of the present invention, the negative electrode composition may include the above-described negative electrode active material particles.

[0102] According to one embodiment of the present invention, the cathode composition may further include a binder.

[0103] According to one embodiment of the present invention, the cathode composition may further include a conductive material.

[0104] According to one embodiment of the present invention, the cathode composition may further include a binder and a conductive material.

[0105] 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.

[0106] According to one embodiment of the present invention, the binder may include carboxymethyl cellulose.

[0107] 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, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylic acid, and materials in which hydrogens thereof are substituted with Li, Na, Ca, etc., and may also include various copolymers thereof.

[0108] According to one embodiment of the present invention, the conductive material may include at least one of carbon black and single-walled carbon nanotubes.

[0109] The conductive material described above 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.

[0110] 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; carbon black such as acetylene black, Ketjen black, channel black, paneth 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 metal powder such as fluorocarbon, aluminum, or nickel powder.

[0111] According to one embodiment of the present invention, the conductive agent may be 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 agent may be 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 agent may be 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 agent may be 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.

[0112]

[0113] <Cathode>

[0114] One embodiment of the present invention provides a cathode comprising a cathode composition according to the above-described embodiments.

[0115] 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.

[0116] The above negative electrode active material layer includes a negative electrode composition according to the above-described embodiment.

[0117] The above negative electrode active material layer can 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, drying, and rolling.

[0118] The above-described cathode slurry may 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.

[0119] 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.

[0120]

[0121] Lithium secondary battery

[0122] One embodiment of the present invention provides a lithium secondary battery including a negative electrode, a separator, and a positive electrode according to the above-described embodiment.

[0123] The above 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.

[0124] 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.

[0125] The above 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), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; or a compound having the chemical formula Li 1+c1 Mn 2-c1 Lithium manganese oxides such as O4(0≤c1≤0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented by O2 (wherein, M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies 0.01≤c2≤0.3); chemical formula LiMn 2-c3 M c3Lithium manganese composite oxide represented by O2 (wherein M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01≤c3≤0.1) or Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); LiMn2O4, etc., in which a part of Li in the chemical formula is replaced with an alkaline earth metal ion, but is not limited thereto. The positive electrode may be Li-metal.

[0126] 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.

[0127] 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.

[0128] In addition, the positive electrode binder plays a role of improving the adhesion between positive electrode active materials and the adhesiveness between the positive electrode active materials and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, 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.

[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] The above lithium secondary battery may additionally include an electrolyte. Examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in 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 with 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 haloalkylene carbonate compounds such as difluoroethylene carbonate, 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 lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0137] According to another embodiment of the present invention, a battery pack including the lithium secondary battery is provided.

[0138] According to another embodiment of the present invention, a battery pack including the battery module is provided.

[0139] The above battery module and 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 and large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles and power storage systems.

[0140] Hereinafter, examples will be provided to specifically explain the present specification. However, the embodiments described herein may be modified in various ways, and the scope of the present application is not limited to the embodiments described below. The embodiments of the present application are provided to more fully explain the present specification to those of ordinary skill in the art.

[0141]

[0142] <Examples and Comparative Examples>

[0143] Example 1

[0144] [Preparation of negative electrode active material and negative electrode active material coating composition]

[0145] [Steps for manufacturing silicon particles]

[0146] [Manufacturing of silicon oxide particles]

[0147] SiO2, 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℃ to evaporate. Metallic magnesium was separately heated to 800℃ to evaporate. All crucibles were depressurized to 0.1 torr and the raw materials were evaporated. The vaporous mixture containing Mg was reacted for 6 hours and then solidified into a solid state in a vacuum area at 800℃. The silicon-based active material manufactured by the above method was pulverized using a ball mill for 3 to 4 hours. Thereafter, a CVD device was used under an inert gas Ar atmosphere to react methane (CH4) at 0.1 torr at a rate of 1 L / min for about 5 hours to form a carbon layer on the surface of the silicon-based active material, thereby manufacturing a magnesium silicon oxide active material coated with a carbon layer. The D50 of the final active material was controlled to be 6μm.

[0148] [Manufacturing of Silicon Carbon Composites]

[0149] Put the cellulose powder into a tubular furnace, 4 o 400 at a speed of C / min o After raising to C, it was heated under a nitrogen atmosphere for 2 hours. After that, the electric furnace was heated to 4 o 900 at C / min speed o After increasing to C, it was heated under a nitrogen atmosphere for 2 hours. After mixing the powder with sulfuric acid and nitric acid in a volume ratio of 3:1, it was heated at 60 o After stirring for 2 hours at C, the precipitate was obtained by centrifugation. The obtained powder was washed 5 times with a solvent mixed with ethanol and distilled water in a volume ratio of 1:3, and then 120 oC for 12 hours. The carbon particles were placed in a KOH solvent and heated at 800°C for 2 hours in 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 more than 12 hours. The porous carbon structure was placed in a horizontal furnace, and SiH4 / He = 5 / 95 gas was flowed at a flow rate of 50 ml / min at 700°C for 1 hour to produce a silicon-carbon composite. Thereafter, the silicon-carbon composite was placed in the furnace, and methane was flowed at 700°C to react for 2 hours to produce a silicon-carbon composite negative electrode active material including a carbon layer on the surface.

[0150] [Step of forming a coating layer on silicon particles]

[0151] A composition for coating a negative electrode active material including a polymer having a bonding group of -HN-C=O- was prepared by adding polyethylene glycol (PEG) having a molecular weight of 600 g / mol and isophorone diisocyanate (IPDI) in a dimethylformamide (DMF) solvent at a molar ratio of NCO / OH of 1.8, and adding dibutyltin dilaurate (DBTDL) as a reaction catalyst at a weight ratio of 0.03 based on the total weight of the composition for coating a negative electrode active material. Afterwards, 60 o The composition for coating the negative active material was prepared by stirring for 3 hours in a nitrogen environment in a C oil bath.

[0152] The polymer having a bonding group of -HN-C=O- contained in the above-prepared composition for coating the negative electrode active material and the negative electrode active material were mixed in a weight ratio of 1.0:99.0. The mixture was stirred for 10 minutes using a disperser at a speed of 2000 rpm per minute, and then the solvent and the polymer-coated silicon carbon composite were separated through a vacuum filtration device to obtain the obtained polymer-coated silicon carbon composite. The obtained polymer-coated silicon carbon composite had a viscosity of 80 oC was placed in a vacuum oven for 12 hours to remove all remaining solvent. The weight of the silicon carbon composite coated with the dried polymer was reduced compared to the weight of the polyethylene glycol (PEG) and isophorone diisocyanate (IPDI) introduced during polymer synthesis and the total weight of the introduced silicon carbon composite, confirming that the amount of the polymer coating layer was 0.9 wt% based on 100 wt% of the total negative electrode active material.

[0153]

[0154] [Preparation of cathode composition]

[0155] A negative electrode slurry was prepared by mixing the negative electrode active material, the conductive material carbon black single-walled carbon nanotube (SWCNT), and the binders CMC (Carboxymethyl cellulose) and SBR (Styrene-Butadiene Rubber) in a weight ratio of 95.3:1:3.7.

[0156]

[0157] [Manufacturing of the cathode]

[0158] The above cathode slurry was applied to a Cu metal film with a thickness of 20 μm and dried at a circulating air temperature of 60°C. Then, after rolling, it was dried in a vacuum oven at 130°C for about a day, and then 1.4875 cm 2 The cathode was manufactured by punching out a circular shape.

[0159]

[0160] [Manufacturing of secondary batteries]

[0161] 1.7671cm 2 A Li metal thin film formed by porous polyethylene was used as the anode. A porous polyethylene separator was interposed between the anode and the cathode, and a 1 M LiPF6 electrolyte containing an additive in a mixed solution of ethylene carbonate (EC) and methyl ethyl carbonate (EMC) in a mixing ratio of 3:7 was injected to manufacture a Li coin half-cell.

[0162]

[0163] Example 2

[0164] A negative electrode active material was prepared in the same manner as in Example 1, except that the composition for coating the negative electrode active material was prepared with a molar ratio of NCO / OH of the polymer reactant of 1.3.

[0165]

[0166] Example 3

[0167] A negative electrode active material was prepared in the same manner as in Example 1, except that the composition for coating the negative electrode active material was prepared with a molar ratio of NCO / OH of 2.5 of the polymer reactant.

[0168]

[0169] Example 4

[0170] A negative active material was manufactured in the same manner as in Example 1, except that a coating layer was manufactured on the surface of the active material by mixing the weight of the polymer and the negative active material included in the composition for coating the negative active material in a weight ratio of 0.5:99.5. Through the weight of the silicon carbon composite coated with the dried polymer compared to the weight of the polyethylene glycol (PEG) and isophorone diisocyanate (IPDI) introduced during polymer synthesis and the total weight of the introduced silicon carbon composite, it was confirmed that the amount of the polymer coating layer was 0.45 wt% based on 100 wt% of the total negative active material.

[0171]

[0172] Example 5

[0173] A negative active material was manufactured in the same manner as in Example 1, except that a weight ratio of the polymer and the negative active material included in the composition for coating the negative active material was mixed at 3.0:97.0 to form a coating layer on the surface of the active material. Through the weight of the silicon carbon composite coated with the dried polymer compared to the weight of the polyethylene glycol (PEG) and isophorone diisocyanate (IPDI) introduced during polymer synthesis and the total weight of the introduced silicon carbon composite, it was confirmed that the amount of the polymer coating layer was 2.8 wt% based on 100 wt% of the total negative active material.

[0174]

[0175] Example 6

[0176] A negative electrode active material was prepared in the same manner as in Example 1, except that the reactants used to prepare the composition for coating the negative electrode active material were prepared by mixing polyethylene glycol (PEG) having a molecular weight of 400 and hexamethylene diisocyanate (HMDI).

[0177]

[0178] Comparative Example 1

[0179] In Example 1, a composition for coating a negative electrode active material was prepared with a molar ratio of NCO / OH of 0.3 of the polymer reactant, and a coating layer was prepared on the surface of the active material by mixing the weight of the polymer included in the composition for coating a negative electrode active material and the weight ratio of the negative electrode active material at 0.05:99.95, and the negative electrode active material was prepared in the same manner. Through the reduced weight of the silicon carbon composite coated with the dried polymer compared to the weight of the polyethylene glycol (PEG) and isophorone diisocyanate (IPDI) introduced during polymer synthesis and the total weight of the introduced silicon carbon composite, it was confirmed that the amount of the polymer coating layer was 0.03 wt% based on 100 wt% of the total negative electrode active material.

[0180]

[0181] Comparative Example 2

[0182] In Example 1, a composition for coating a negative electrode active material was prepared with a molar ratio of NCO / OH of 0.2 of the polymer reactant, and a weight ratio of the polymer included in the composition for coating a negative electrode active material and the weight ratio of the negative electrode active material were mixed at 10.0:90.0 to prepare a coating layer on the surface of the active material, and the negative electrode active material was prepared in the same manner. Through the reduced weight of the silicon carbon composite coated with the dried polymer compared to the weight of the polyethylene glycol (PEG) and isophorone diisocyanate (IPDI) introduced during polymer synthesis and the total weight of the introduced silicon carbon composite, it was confirmed that the amount of the polymer coating layer was 6.8 wt% based on 100 wt% of the total negative electrode active material.

[0183]

[0184] Comparative Example 3

[0185] In Example 1, a composition for coating a negative electrode active material was prepared with a molar ratio of NCO / OH of the polymer reactant of 8.0, and a coating layer was prepared on the surface of the active material by mixing the weight of the polymer included in the composition for coating a negative electrode active material and the weight ratio of the negative electrode active material at 0.05:99.95, and the negative electrode active material was prepared in the same manner. Through the reduced weight of the silicon carbon composite coated with the dried polymer compared to the weight of the polyethylene glycol (PEG) and isophorone diisocyanate (IPDI) introduced during polymer synthesis and the total weight of the introduced silicon carbon composite, it was confirmed that the amount of the polymer coating layer was 0.05 wt% based on 100 wt% of the total negative electrode active material.

[0186]

[0187] Comparative Example 4

[0188] In Example 1, a composition for coating a negative electrode active material was prepared with a molar ratio of NCO / OH of 12.0 of the polymer reactant, and a coating layer was prepared on the surface of the active material by mixing the weight of the polymer included in the composition for coating a negative electrode active material and the weight ratio of the negative electrode active material at 10.0:90.0, and the negative electrode active material was prepared in the same manner. Through the reduced weight of the silicon carbon composite coated with the dried polymer compared to the weight of the polyethylene glycol (PEG) and isophorone diisocyanate (IPDI) introduced during polymer synthesis and the total weight of the introduced silicon carbon composite, it was confirmed that the amount of the polymer coating layer was 9.9 wt% based on 100 wt% of the total negative electrode active material.

[0189]

[0190] [Reference example]

[0191] 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 in Example 1, and a coating layer was not formed on the silicon-based particles.

[0192]

[0193] The silicon-based negative electrode active materials manufactured in the above examples and comparative examples are as shown in Table 1 below.

[0194] Composition of coating composition - Glass transition temperature of polymer having HN-C=O- bonding group - Polymer having HN-C=O- bonding group NCO / OH molar ratio of reactant Thickness of coating layer D50 (μm) Example 1 PEG (MW 600), IPDI-3.5 o C1.815nm6.3Example 2PEG (MW 600), IPDI-14.7 o C1.310nm6.3Example 3PEG (MW 600), IPDI15.2 o C2.522nm6.4Example 4PEG (MW 600), IPDI-4.0 oC1.89nm6.2Example 5PEG (MW 600), IPDI-5.3 o C1.842nm6.5Example 6PEG (MW 400), HMDI1.8 o C1.818nm6.4Comparative Example 1PEG (MW 600), IPDI-35.7 o C0.32nm6.2Comparative example 2PEG (MW 600), IPDI-43.1 o C0.2350nm6.5Comparative example 3PEG (MW 600), IPDI82.5 o C8.03.5nm6.1Comparative example 4PEG (MW 600), IPDI114.7 o C12.0500nm6.9Reference example----6.2

[0195] <Experimental example: Evaluation of discharge capacity, initial efficiency, and lifespan (capacity retention rate) characteristics> Charge and discharge were performed on the manufactured battery, and the discharge capacity, initial efficiency, and capacity retention rate were evaluated, which are listed in Table 2 below.

[0196] The 1st and 2nd cycles were charged and discharged at 0.1C, and from the 3rd to the 299th cycles, the charging and discharging was performed at 0.5C. The 300th cycle was terminated in a charged state (with lithium in the negative electrode).

[0197] Charging conditions: CC (constant current) / CV (constant voltage) (5mV / 0.005C current cut-off)

[0198] Discharge conditions: CC (constant current) condition 1.5 V

[0199] Based on the results of a single charge / discharge cycle, the discharge capacity (mAh / g) and initial efficiency (%) were derived. Specifically, the initial efficiency (%) was derived using the following calculation.

[0200] Initial efficiency (%) = (1-time discharge capacity / 1-time charge capacity) × 100

[0201] The capacity retention rate was derived by the following calculations.

[0202] Capacity retention rate (%) = (49 discharge capacity / 1 discharge capacity) × 100

[0203]

[0204] Total discharge capacity (mAh / g) Initial efficiency (%) Capacity retention rate (%) Example 150491.189.5 Example 250491.088.7 Example 350491.289.1 Example 450491.188.8 Example 550490.889.0 Example 650491.089.1 Comparative example 150489.768.3 Comparative example 246289.466.5 Comparative example 350489.376.1 Comparative example 445888.973.8 Reference example 50189.981.9

[0205] Comparative Examples 1 and 2 are cases where a polymer having a bonding group of -HN-C=O- having a glass transition temperature of less than -30°C was used as a composition for coating an anode active material. Since the coating layer was not coated on the surface of the active material but dissolved in the slurry, a low capacity retention rate was exhibited.

[0206] Comparative Examples 3 and 4 show a case where a polymer having a bonding group of -HN-C=O- with a glass transition temperature exceeding 80°C was used as a composition for coating an anode active material. The composition showed a low capacity retention rate because the shape recovery of the coating layer was reduced during charge and discharge due to the high rigidity of the coating layer.

[0207] On the other hand, Examples 1 to 6 showed a higher capacity retention rate than Comparative Examples 1 to 4 by using a polymer having a bonding group of -HN-C=O- having a glass transition temperature of -30°C to 80°C as a composition for coating an anode active material.

[0208] In addition, Comparative Examples 1 and 2 were cases where a polymer having a bonding group of -HN-C=O-, synthesized as a reactant with an NCO / OH molar ratio of alcohol and isocyanate of less than 0.5, was used as a composition for coating an anode active material, and the coating layer was not coated on the surface of the active material but dissolved in the slurry, resulting in a low capacity retention rate.

[0209] Comparative Examples 3 and 4 show a case where a polymer having a bonding group of -HN-C=O-, synthesized as a reactant with an NCO / OH molar ratio of alcohol and isocyanate exceeding 4, was used as a composition for coating an anode active material. Since a hard coating layer was formed, the shape resilience to volume change of the active material during charge and discharge was reduced, resulting in a low capacity retention rate.

[0210] On the other hand, Examples 1 to 6 showed a higher capacity retention rate than Comparative Examples 1 to 4 by using a polymer having a bonding group of -HN-C=O-, synthesized as a reactant with an NCO / OH molar ratio of alcohol and isocyanate of 0.5 to 4, as a composition for coating an anode active material.

[0211] In addition, as a reference example, a battery using a binder composition including a polyurethane polymer having a glass transition temperature of 75°C and a negative electrode active material that did not form a coating layer on silicon particles exhibited a lower capacity retention rate compared to Examples 1 to 6 of the present invention.

[0212] That is, by forming a coating layer on at least a portion of the surface of the negative electrode active material using a composition for coating a negative electrode active material including a polymer having a bonding group of -HN-C=O according to an embodiment of the present invention, it was confirmed that there is an effect of improving extreme volume change and particle breakage of the negative electrode active material during charge and discharge, and that a battery including the negative electrode active material on which the coating layer is formed has improved life characteristics.

Claims

1. Contains a polymer having a bonding group of -HN-C=O-, A composition for coating a negative electrode active material, wherein the glass transition temperature (Tg) of the polymer having the above -HN-C=O- bonding group is -30°C to 80°C.

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

3. Silicon particles; and A negative electrode active material comprising a coating layer provided on at least a portion of the surface of the silicon-based particles and comprising the composition for coating the negative electrode active material of claim 1 or 2.

4. In claim 3, A negative electrode active material having an amount of the coating layer of 0.1 wt% or more and 5 wt% or less based on 100 wt% of the total negative electrode active material.

5. In claim 3, A negative electrode active material having a thickness of the coating layer of 1 nm to 1 μm.

6. In claim 3, The above silicon-based particles are a negative active material that is a silicon carbon composite or silicon oxide particle.

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

8. In claim 7, The above-mentioned conductive material is a cathode composition comprising at least one of carbon black and single-walled carbon nanotubes.

9. In claim 7, A cathode composition wherein the conductive agent is 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 cathode composition.

10. In claim 7, A negative electrode composition wherein the binder comprises carboxymethyl cellulose.

11. Negative 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 including the negative electrode composition according to claim 7.

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

13. A battery module including a lithium secondary battery according to claim 12.

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

15. A battery pack comprising the battery module of claim 13.