Anode active material, anode including the same, secondary battery including the same, and method for manufacturing anode active material

Abstract

The present invention relates to a negative electrode active material, a negative electrode containing the same, a secondary battery containing the same, and a method for producing the negative electrode active material.

Description

[Technical Field]

[0001] The present invention relates to an anode active material, an anode containing the same, a secondary battery containing the same, and a method for producing the anode active material.

[0002] This application claims the benefit of the filing date of Korean Patent Application No. 10-2022-0172768, filed with the Korean Intellectual Property Office on December 12, 2022, the entire contents of which are incorporated herein by reference. [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 other hand, among silicon-based active materials, silicon-based oxides, specifically SiO xIn 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, there is still a drawback that the initial efficiency decreases due to the presence of irreversible capacity in silicon-based oxides.

[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, and there is a problem that the negative electrode active materials aggregate with each other in the slurry and the dispersibility decreases, resulting in a problem that the state of the manufactured negative electrode becomes poor and the charge / discharge efficiency of the negative electrode decreases. [[ID=P6]]

[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.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] The present invention relates to a negative electrode active material, a negative electrode containing the same, a secondary battery containing the same, and a method for manufacturing the negative electrode active material.

Means for Solving the Problems

[0011] One embodiment of the present invention is SiO xSilicon-based particles containing (0 < x < 2) and a Li compound, with a carbon layer provided on at least a part of the surface; and a coating layer containing an amphiphilic polymer provided on at least a part of the silicon-based particles are provided as a negative electrode active material.

[0012] One embodiment of the present invention provides a negative electrode containing the negative electrode active material.

[0013] One embodiment of the present invention provides a secondary battery containing the negative electrode.

[0014] One embodiment of the present invention is SiO x A method for manufacturing a negative electrode active material is provided, including the step of forming silicon-based particles containing (x < 2) and a Li compound, with a carbon layer provided on at least a part of the surface; and the step of reacting the silicon-based particles with an amphiphilic polymer precursor.

Effect of the Invention

[0015] The negative electrode active material according to one embodiment of the present invention includes a coating layer containing an amphiphilic polymer provided on the outermost surface of silicon-based particles containing a Li compound, and thus has the effect of improving the water-based processability of the slurry. Specifically, since the amphiphilic polymer contains a hydrophilic group and a hydrophobic group, the hydrophobic group reduces the reactivity between the active material and water, and prevents moisture from penetrating into the negative electrode active material in the water-based slurry, so that the silicon-based particles can be efficiently passivated. In addition, it has the effect of improving the water-based processability of the slurry by preventing side reactions between the silicon-based particles or lithium by-products and water and suppressing gas generation.

[0016] At the same time, the hydrophilic group contained in the amphiphilic polymer has the effect of improving the dispersibility of the negative electrode active material in the water-based slurry.

[0017] Therefore, a negative electrode including the negative electrode active material according to an embodiment of the present invention and a secondary battery including the negative electrode have the effect of improving the discharge capacity, initial efficiency, resistance performance, and / or life characteristics of the battery. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present specification will be explained in more detail below.

[0019] In this specification, when a part is said to "comprise" a certain component, this means that it may further include other components, rather than excluding other components, unless otherwise specified.

[0020] In this specification, when a member is said to be located "on" another member, this includes not only the case where the member is in contact with the other member, but also the case where another member is present between the two members.

[0021] 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.

[0022] As used herein, the singular expression of a term includes the plural expression unless the context clearly indicates otherwise.

[0023] In this specification, the crystallinity of the structure contained in the negative electrode active material may be confirmed by X-ray diffraction analysis. The X-ray diffraction analysis may be performed using an XRD (X-ray diffraction) analysis device (product name: D4-Endeavor, manufacturer: Bruker), and in addition to the above device, any device commonly used in the art may be appropriately adopted.

[0024] In this specification, the presence or absence and the content of elements in the negative electrode active material can be confirmed by ICP analysis, and the ICP analysis can be performed using an inductively coupled plasma atomic emission spectrometer (ICPAES, Perkin-Elmer 7300).

[0025] In this specification, the average particle size (D 50 ) can be defined as the particle size corresponding to 50% of the volume cumulative amount in the particle size distribution curve (graph curve of the particle size distribution diagram). The average particle size (D 50 ) can be measured, for example, using the laser diffraction method. The laser diffraction method can generally measure particle sizes from the submicron region to about several millimeters, and results with high reproducibility and high resolution can be obtained.

[0026] Hereinafter, preferred embodiments of the present invention will be described in detail. However, the embodiments of the present invention may be modified into various forms, and the scope of the present invention is not limited to the embodiments described below.

[0027] <Negative electrode active material> One embodiment of the present invention provides a negative electrode active material including silicon-based particles containing SiO x (0 < x < 2) and a Li compound, and having a carbon layer provided on at least a part of the surface; and a coating layer containing an amphiphilic polymer provided on at least a part of the silicon-based particles.

[0028] The negative electrode active material according to one embodiment of the present invention includes silicon-based particles. The silicon-based particles contain SiO x (0 < x < 2) and a Li compound.

[0029] The SiO x (0 < x < 2) may correspond to a matrix in the silicon-based particles. The SiO x(0 < x < 2) may be in a form containing Si and / or SiO2, and the Si may form a phase. That is, the x corresponds to the number ratio of O to Si contained in the SiO x (0 < x < 2). When the silicon-based particles contain the SiO x (0 < x < 2), the discharge capacity of the secondary battery can be improved.

[0030] The Li compound may correspond to a matrix within the silicon-based particles. The Li compound may exist in at least one form of lithium atom, lithium silicate, lithium silicide, and lithium oxide within the silicon-based particles. When the silicon-based particles contain a Li compound, there is an effect that the initial efficiency is improved.

[0031] The Li compound may be in a form doped into the silicon-based particles and distributed on the surface and / or inside of the silicon-based particles. The Li compound is distributed on the surface and / or inside of the silicon-based particles, can control the expansion / contraction of the volume of the silicon-based particles to an appropriate level, and can play a role in preventing damage to the active material. Also, the Li compound may be included in that it reduces the ratio of the irreversible phase (for example, SiO2) of the silicon-based oxide particles and increases the efficiency of the active material.

[0032] In one embodiment of the present invention, the Li compound may exist in the 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-based particles, and the amorphous lithium silicate is Li a Si b O cIt may have a complex structure in the form of (2 ≦ a ≦ 4, 0 < b ≦ 2, 2 ≦ c ≦ 5), and is not limited to the above form.

[0033] In one embodiment of the present invention, based on 100 parts by weight of the total negative electrode active material, Li may be contained in an amount of 0.1 to 40 parts by weight, or 0.1 to 25 parts by weight. Specifically, it may be contained in an amount of 1 to 25 parts by weight, and more specifically, it may be contained in an amount of 2 to 20 parts by weight. As the content of Li increases, although the initial efficiency increases, there is a problem that the discharge capacity decreases. Therefore, when the above range is satisfied, appropriate discharge capacity and initial efficiency can be realized.

[0034] The content of the Li element can be confirmed by ICP analysis. Specifically, after collecting a certain amount (about 0.01 g) of the negative electrode active material, it is transferred to a platinum crucible, nitric acid, hydrofluoric acid, and sulfuric acid are added, and it is completely decomposed on a hot plate. Then, using an inductively coupled plasma atomic emission spectrometer (ICPAES, Perkin-Elmer 7300), at the wavelength specific to the element to be analyzed, the intensity of the standard solution prepared using a standard solution (5 mg / kg) is measured to create a standard calibration curve . Thereafter, the pretreated sample solution and the blank sample are introduced into the instrument, the intensity of each is measured to calculate the actual intensity, and after calculating the concentration of each component with respect to the created calibration curve, it is converted so that the total of the whole becomes the theoretical value, and the content of the elements of the manufactured negative electrode active material can be analyzed.

[0035] In one embodiment of the present invention, the silicon-based particles may contain additional metal atoms. The metal atoms may be present in at least one form of metal atoms, metal silicates, metal silicides, and metal oxides within the silicon-based particles. The metal atoms may include at least one selected from the group consisting of Mg, Li, Al, and Ca. Thereby, the initial efficiency of the negative electrode active material can be improved.

[0036] In one embodiment of the present invention, the silicon-based particles have a carbon layer formed on at least a portion of their surfaces. The carbon layer may be formed on at least a portion of the surface, i.e., on the surface of the particles, or on the entire surface of the particles. The carbon layer provides electrical conductivity to the negative electrode active material, thereby improving the initial efficiency, lifespan characteristics, and capacity characteristics of the secondary battery.

[0037] In one embodiment of the present invention, the carbon layer comprises amorphous carbon.

[0038] The carbon layer may further include crystalline carbon.

[0039] The crystalline carbon may further improve the conductivity of the negative electrode active material. The crystalline carbon may include at least one selected from the group consisting of fullerene, carbon nanotube, and graphene.

[0040] The amorphous carbon may be a carbon-based material formed by using at least one carbide or hydrocarbon selected from the group consisting of tar, pitch, and other organic substances as a source in a chemical vapor deposition process.

[0041] The carbonized organic material may be a carbonized organic material selected from carbonized sucrose, glucose, galactose, fructose, lactose, mannose, ribose, aldohexose, or ketohexose, and combinations thereof.

[0042] The hydrocarbon may be a substituted or unsubstituted aliphatic or alicyclic hydrocarbon, or a substituted or unsubstituted aromatic hydrocarbon. The aliphatic or alicyclic hydrocarbon of the substituted or unsubstituted aliphatic or alicyclic hydrocarbon may be methane, ethane, ethylene, acetylene, propane, butane, butene, pentane, isobutane, hexane, or the like. The aromatic hydrocarbon of the substituted or unsubstituted aromatic hydrocarbon may be benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene, phenanthrene, or the like.

[0043] In one embodiment of the present invention, the carbon layer may be an amorphous carbon layer.

[0044] In one embodiment of the present invention, the carbon layer may be included in an amount of 0.1 to 50 parts by weight, 0.1 to 30 parts by weight, or 0.1 to 20 parts by weight, based on 100 parts by weight of the total negative electrode active material. More specifically, the carbon layer may be included in an amount of 0.5 to 15 parts by weight, 1 to 10 parts by weight, or 1 to 5 parts by weight. When the amount is within the above range, a decrease in the capacity and efficiency of the negative electrode active material can be prevented.

[0045] In one embodiment of the present invention, the thickness of the carbon layer may be 1 nm to 500 nm, specifically 5 nm to 300 nm. When the thickness is within this range, the conductivity of the negative electrode active material is improved, volume change of the negative electrode active material is easily suppressed, and side reactions between the electrolyte and the negative electrode active material are suppressed, resulting in improved initial efficiency and / or lifespan of the battery.

[0046] Specifically, the carbon layer may be formed by chemical vapor deposition (CVD) using at least one hydrocarbon gas selected from the group consisting of methane, ethane, and acetylene.

[0047] In one embodiment of the present invention, a coating layer containing an amphiphilic polymer is provided on at least a portion of the silicon-based particles.

[0048] The amphiphilic polymer is a substance having both hydrophilic and hydrophobic groups, and may include one or more selected from the group consisting of PEG-PPO (Polyethylene glycol-Polypropylene oxide), PEG-PS (Polyethylene glycol-Polystyrene), PS-PBA (Polystyrene-Poly(butyl acrylate)), polylysine-PPO (Polylysine-Polypropylene oxide), and polylysine-PS (Polylysine-Polystyrene), and preferably includes PEG-PS.

[0049] Specifically, when preparing the negative electrode active material, silicon-based particles having a carbon layer on at least a portion of the surface thereof are formed, doped with Li, and then coated with an amphiphilic polymer, thereby introducing a coating layer containing the amphiphilic polymer onto at least a portion of the silicon-based particles.

[0050] The weight average molecular weight of the amphiphilic polymer may be 100 g / mol to 50,000 g / mol, specifically 1,000 g / mol to 30,000 g / mol, or 5,000 g / mol to 20,000 g / mol.

[0051] In the present invention, the weight-average molecular weight (Mw) of an amphiphilic polymer can be measured by gel permeation chromatography (GPC) using an Agilent 1200 series instrument with a polystyrene standard (PS standard). Specifically, a Polymer Laboratories PLgel MIX-B 300 mm column can be used with an Agilent 1200 series instrument, with the measurement temperature at 40°C, the solvent used being tetrahydrofuran (THF), and the flow rate at 1 mL / min. Samples are prepared to a concentration of 10 mg / 10 mL and then added in 10 μL. The Mw value is calculated using a calibration curve formed using the polystyrene standard. In this case, nine types of molecular weights (g / mol) of polystyrene standards are used: 2,000 / 10,000 / 30,000 / 70,000 / 200,000 / 700,000 / 2,000,000 / 4,000,000 / 10,000,000.

[0052] The amphiphilic polymer may include a unit containing a hydrophilic group and a unit containing a hydrophobic group.

[0053] The hydrophilic group-containing unit may be a unit derived from polyethylene glycol (PEG), polylysine, poly[oligo(ethylene glycol) methyl ether methacrylate] (POEGMA), polyvinyl alcohol (PVA), polyglutamic acid (PGA), polyvinyl pyrrolidone (PVP), or polyacrylamide (PAM). However, the amphiphilic polymer may be any unit known in the art that contains a hydrophilic group.

[0054] The unit containing the hydrophilic group may be disposed near the outermost surface of the negative electrode active material. By introducing the hydrophilic group into the negative electrode active material, aggregation between the negative electrode active material particles in the aqueous slurry can be effectively suppressed, thereby improving dispersibility.

[0055] The unit containing a hydrophilic group may be contained in an amount of 20 to 80 parts by weight, specifically 30 to 70 parts by weight, or 40 to 60 parts by weight, based on a total of 100 parts by weight of the amphiphilic polymer. If the amount satisfies the above range, the dispersibility in the slurry is improved, but if the amount does not satisfy the above range, aggregation between particles occurs in the slurry.

[0056] The hydrophobic group-containing unit may be derived from polystyrene (PS), polypropylene oxide (PPO), polylactic acid (PLA), polysebacic acid (PSA), polylactic-co-glycolic acid (PLGA), or polyaspartic acid (PASP). Without being limited thereto, any hydrophobic group-containing unit known in the art may be used for the amphiphilic polymer. The incorporation of the hydrophobic group into the negative electrode active material reduces the reactivity of the negative electrode active material with water, prevents water from penetrating into the negative electrode active material in an aqueous slurry, and prevents side reactions between silicon-based particles or lithium by-products and water, thereby suppressing gas generation and improving the aqueous processability of the slurry.

[0057] The unit containing a hydrophobic group may be included in an amount of 20 to 80 parts by weight, specifically 30 to 70 parts by weight, or 40 to 60 parts by weight, based on a total of 100 parts by weight of the amphiphilic polymer. When the amount is within this range, it is effective in preventing moisture from reacting with the active material, but when the amount is not within this range, moisture may penetrate into the active material, resulting in a problem of reduced processability.

[0058] That is, by coating the surface of the negative electrode active material with an amphiphilic polymer containing both hydrophilic and hydrophobic groups, hydrophobic groups that increase the water resistance of the negative electrode active material and hydrophilic groups that increase the dispersibility of the negative electrode active material can be simultaneously introduced, thereby effectively improving the aqueous processability of the slurry.

[0059] The weight ratio of the unit containing a hydrophilic group to the unit containing a hydrophobic group may be 20:80 to 80:20, specifically 30:70 to 70:30, or 40:60 to 60:40. When this range is satisfied, excellent dispersibility in the slurry is achieved and the effect of preventing moisture from penetrating into the interior of the particles is obtained, whereas when this range is not satisfied, there is a problem that dispersibility in the slurry is reduced, causing aggregation between particles, or moisture penetrates into the interior of the particles and causes a reaction.

[0060] The negative electrode active material according to one embodiment of the present invention is prepared by ultrasonically treating a mixture of 20 g of the negative electrode active material and 80 g of distilled water, and then dissolving the D of the negative electrode active material. max When the mixture is passed through a mesh having a diameter corresponding to the above, the dispersibility according to the following formula 1 may be 70% or more.

[0061]

number

[0062] In the formula 1, W t means the total weight of the negative electrode active material contained in the mixture, W r means the weight of the negative electrode active material that could not pass through the mesh when the mixture was passed through the mesh.

[0063] The dispersibility according to the formula 1 may be 70% or more, 73% or more, 75% or more, 80% or more, 85% or more, or 88% or more, or may be 100% or less.

[0064] Specifically, the ultrasonic treatment may be carried out for 1 to 10 minutes, and preferably for 5 minutes.

[0065] The dispersibility may be measured after the mixture is sonicated and left to stand for 10 minutes before being passed through a mesh.

[0066] The mesh is a D of the negative electrode active material. max The dispersibility can be measured by appropriately using a mesh made of a material commonly used in this technical field.

[0067] Generally, when a negative electrode active material is mixed with distilled water, the negative electrode active material aggregates, and the aggregated negative electrode active material cannot pass through the mesh, resulting in poor dispersibility. However, the negative electrode active material according to the present invention includes an amphiphilic polymer coating layer on its surface, which effectively suppresses aggregation of the negative electrode active material in the aqueous slurry and improves dispersibility.

[0068] In one embodiment of the present invention, the coating layer containing the amphiphilic polymer may be provided on at least a portion of the carbon layer, or may be provided on at least a portion of the area of ​​the silicon-based particle surface where no carbon layer is provided.

[0069] The coating layer containing the amphiphilic polymer may be partially or entirely coated on the surface of the silicon-based particle or carbon layer, and may have an island or thin film shape, specifically an island shape.

[0070] In the present invention, the content of the amphiphilic polymer on the surface of the negative electrode active material can be analyzed using a combustion analyzer. Specifically, the carbon content can be analyzed by burning about 0.5 g of a sample under 99.95% pure oxygen gas using a Bruker G4 ICARUS HF.

[0071] In one embodiment of the present invention, the coating layer containing the amphiphilic polymer may be included in an amount of 0.005 to 20 parts by weight, based on 100 parts by weight of the total amount of the negative electrode active material. Specifically, the coating layer may be included in an amount of 0.01 to 10 parts by weight, 0.05 to 5 parts by weight, 0.1 to 5 parts by weight, or 0.5 to 5 parts by weight. The upper limit of the coating layer content may be 20 parts by weight, 15 parts by weight, 10 parts by weight, 7 parts by weight, 5 parts by weight, 4.5 parts by weight, 4 parts by weight, 3 parts by weight, 2 parts by weight, or 1 part by weight, and the lower limit of the coating layer content may be 0.005 parts by weight, 0.01 parts by weight, 0.05 parts by weight, 0.1 parts by weight, 0.3 parts by weight, 0.5 parts by weight, 0.6 parts by weight, or 0.7 parts by weight.

[0072] When the amphiphilic polymer is incorporated within the above range, the water resistance and dispersibility of the negative electrode active material can be effectively improved. However, when the amphiphilic polymer is incorporated below the above range, the content of hydrophilic and hydrophobic groups is low, and sufficient water resistance and dispersibility cannot be ensured. When the amphiphilic polymer is incorporated above the above range, the coating layer is not uniformly distributed, the dispersibility and passivation effect are reduced, and the amphiphilic coating layer does not participate in the electrochemical reaction, resulting in reduced capacity and efficiency of the negative electrode active material.

[0073] In one embodiment of the present invention, the weight ratio of the coating layer containing the amphiphilic polymer to the carbon layer may be 1:99 to 70:30, specifically 5:95 to 60:40, or 10:90 to 50:50.

[0074] In one embodiment of the present invention, lithium by-products may be present on the silicon-based particles. Specifically, the lithium by-products may be present on the surface of the silicon-based particles or on the surface of the carbon layer. Alternatively, the lithium by-products may be present between the amphiphilic polymer-containing coating layer and the silicon-based particles.

[0075] Specifically, the lithium by-product may refer to a lithium compound remaining near the surface of the silicon-based particles or the carbon layer after the silicon-based particles are prepared. As described above, lithium by-products that have not reacted with the acid may remain even after the acid treatment process.

[0076] The lithium by-products may include one or more selected from the group consisting of Li2O, LiOH, and Li2CO3.

[0077] The presence or absence of the lithium by-product can be confirmed by X-ray diffraction (XRD) or X-ray photoelectron spectroscopy (XPS).

[0078] The lithium by-product may be included in an amount of 5 parts by weight or less, based on 100 parts by weight of the total negative electrode active material. Specifically, it may be included in an amount of 0.001 to 5 parts by weight, 0.01 to 5 parts by weight, 0.05 to 2 parts by weight, or 0.1 to 1 part by weight. More specifically, it may be included in an amount of 0.1 to 0.8 parts by weight, or 0.1 to 0.5 parts by weight. When the content of the lithium by-product satisfies the above range, side reactions in the slurry can be reduced, viscosity changes can be reduced, and aqueous processability can be improved. In contrast, when the content of the lithium by-product is higher than the above range, the slurry exhibits basicity during formation, which can cause side reactions or viscosity changes, resulting in problems with aqueous processability.

[0079] The content of the lithium by-product can be calculated by measuring the amount of the HCl solution at a specific pH range during titration of the aqueous solution containing the negative active material with the HCl solution using a titrator.

[0080] The average particle diameter (D 50 ) of the negative electrode active material may be 0.1 μm to 30 μm, specifically may be 1 μm to 20 μm, and more specifically may be 1 μm to 10 μm. When the above range is satisfied, the structural stability of the active material during charge and discharge can be achieved, and problems such as an increase in the volume expansion / contraction level due to an excessively large particle diameter can be prevented, and problems such as a decrease in the initial efficiency due to an excessively small particle diameter can be prevented.

[0081] <Method for manufacturing negative electrode active material> One embodiment of the present invention includes a step of forming silicon-based particles containing SiO x (0 < x < 2) and a Li compound, and having a carbon layer provided on at least a part of the surface; and a step of reacting the silicon-based particles with an amphiphilic polymer precursor, and provides a method for manufacturing a negative electrode active material.

[0082] The silicon-based particles may be formed by a step of heating and vaporizing Si powder and SiO2 powder in a vacuum and then depositing the vaporized mixed gas to form preliminary particles; a step of forming a carbon layer on the surface of the formed preliminary particles; and a step of heat-treating after mixing the preliminary particles having the carbon layer formed thereon with Li powder.

[0083] Specifically, the mixed powder of the Si powder and the SiO2 powder may be heat-treated at 1300°C to 1800°C, 1400°C to 1800°C, or 1400°C to 1600°C under vacuum.

[0084] The formed preliminary particles may have the form of SiO.

[0085] <00003​​​​Specifically, after the formed preliminary particles are introduced into the reactor, hydrocarbon gas may be formed by chemical vapor deposition (CVD) at 600°C to 1200°C. The hydrocarbon gas may be at least one hydrocarbon gas selected from the group consisting of methane, ethane, propane, and acetylene, and may be heat-treated at 900°C to 1000°C.

[0087] The step of heat-treating after mixing the preliminary particles with a carbon layer formed and Li powder may be carried out at 700°C to 900°C for 4 to 6 hours, and specifically, it may be carried out at 800°C for 5 hours.

[0088] The silicon-based particles may contain, as the aforementioned Li compound, Li silicate, Li silicide, or Li oxide.

[0089] The particle size of the silicon-based particles may be adjusted by methods such as a ball mill, a jet mill, or air classification, and is not limited thereto. <​​​​​​​​​​​The amphiphilic polymer precursor may be a precursor capable of forming the aforementioned PEG-PPO, PEG-PS, PS-PBA, polylysine-PPO, or polylysine-PS. For example, the amphiphilic polymer precursor may be PS-b-PEO (Polystyrene-block-Polyethylene oxide) or PS-b-PBA (Polystyrene-b-poly(butyl acrylate)).

[0093] The step of reacting the silicon-based particles with the amphiphilic polymer precursor may include activating the surfaces of the silicon-based particles; and mixing the silicon-based particles and the amphiphilic polymer in a solvent.

[0094] Specifically, the activation step may be performed by exposing the silicon-based particles to ultraviolet light. By activating the surfaces of the silicon-based particles, the amphiphilic polymer can be easily coated onto the silicon-based particles.

[0095] The weight ratio of the silicon-based particles to the amphiphilic polymer may be 99.9:0.1 to 80:20. Specifically, it may be 99.5:0.5 to 85:15 or 99:1 to 90:10. By reacting the silicon-based particles with the amphiphilic polymer within this range, the water resistance and dispersibility of the negative electrode active material can be effectively improved. However, if the amphiphilic polymer is included in excess, the coating layer may not be uniformly distributed, resulting in reduced dispersibility and passivation effect. Furthermore, the amphiphilic coating layer may not participate in the electrochemical reaction, resulting in reduced capacity and efficiency of the negative electrode active material.

[0096] The silicon-based particles and the amphiphilic polymer can be mixed in a solvent and then stirred to provide the amphiphilic polymer on the surfaces of the silicon-based particles.

[0097] The solvent may preferably be dimethyl sulfoxide (DMSO), but is not limited thereto, and any solvent used in this technical field may be appropriately adopted.

[0098] The stirring may be carried out for 30 minutes to 6 hours, preferably 1 hour to 5 hours, or 2 hours to 4 hours.

[0099] The negative electrode active material containing the amphiphilic polymer introduced by the above-described method can improve the aqueous processability of the slurry and the dispersibility of the negative electrode active material in the slurry, thereby enabling stable formation of a negative electrode. As a result, a negative electrode containing the negative electrode active material according to the present invention and a secondary battery including the negative electrode can have improved discharge capacity, initial efficiency, resistance performance, and / or life characteristics.

[0100] <Negative electrode> The negative electrode according to an embodiment of the present invention may include the negative electrode active material described above.

[0101] Specifically, the negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. The negative electrode active material layer may include the negative electrode active material. Furthermore, the negative electrode active material layer may further include a binder, a thickener, and / or a conductive material.

[0102] The negative electrode active material layer may be formed by applying a negative electrode slurry containing a negative electrode active material, a binder, a thickener, and / or a conductive material to at least one surface of a current collector, followed by drying and rolling.

[0103] The negative electrode slurry may further include an additional negative electrode active material.

[0104] The additional negative electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, and Al alloys; and SiO. β Examples of the negative electrode active material include metal oxides capable of doping and dedoping lithium, such as SnO2, vanadium oxide, lithium titanium oxide, and lithium vanadium oxide (0<β<2); or composites containing the metallic compounds and carbonaceous materials, such as Si-C composites and Sn-C composites. A mixture of two or more of these may be used. A thin film of metallic lithium may also be used as the negative electrode active material. The carbon material may be either low-crystalline carbon or high-crystalline carbon. Typical low-crystalline carbons are soft carbon and hard carbon, while typical high-crystalline carbons are amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitches, and high-temperature-calcined carbons such as petroleum or coal tar pitch-derived cokes.

[0105] The additional negative electrode active material may be a carbon-based negative electrode active material.

[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 slurry containing the negative electrode active material according to one embodiment of the present invention may have a pH of 7 to 11 at 25°C. When the pH of the negative electrode slurry satisfies this range, the rheological properties of the slurry are stabilized. On the other hand, if the pH of the negative electrode slurry is less than 7 or exceeds 11, decomposition of carboxymethyl cellulose (CMC), which is used as a thickener, occurs, resulting in a decrease in the viscosity of the slurry and a decrease in the degree of dispersion of the active material contained in the slurry.

[0108] 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.

[0109] 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, polytetrafluoroethylene, 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.

[0110] 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.

[0111] The thickener may be carboxymethyl cellulose (CMC), but is not limited thereto, and any thickener used in the technical field may be appropriately adopted.

[0112] In one embodiment of the present invention, the weight ratio of the negative electrode active material to the additional negative electrode active material contained in the negative electrode slurry may be 1:99 to 30:70, specifically 5:95 to 30:70, or 10:90 to 20:80.

[0113] In one embodiment of the present invention, the total amount of the negative electrode active material contained in the negative electrode slurry may be 60 parts by weight to 99 parts by weight, specifically 70 parts by weight to 98 parts by weight, based on 100 parts by weight of the total solid content of the negative electrode slurry.

[0114] In one embodiment of the present invention, the binder may be included in an amount of 0.5 to 30 parts by weight, specifically 1 to 20 parts by weight, based on 100 parts by weight of the total solid content of the negative electrode slurry.

[0115] In one embodiment of the present invention, the conductive material may be included in an amount of 0.5 to 25 parts by weight, specifically 1 to 20 parts by weight, based on 100 parts by weight of the total solid content of the negative electrode slurry.

[0116] In one embodiment of the present invention, the thickener may be included in an amount of 0.5 parts by weight to 25 parts by weight, specifically 0.5 parts by weight to 20 parts by weight, more specifically 1 part by weight to 20 parts by weight, based on 100 parts by weight of the total solid content of the negative electrode slurry.

[0117] The negative electrode slurry according to an embodiment of the present invention may further include a solvent for forming the negative electrode slurry. Specifically, the solvent for forming the negative electrode slurry may include at least one selected from the group consisting of distilled water, ethanol, methanol, and isopropyl alcohol, specifically distilled water, in order to facilitate dispersion of components.

[0118] In one embodiment of the present invention, the solid content weight of the negative electrode slurry may be 20 parts by weight to 75 parts by weight, specifically 30 parts by weight to 70 parts by weight, based on 100 parts by weight of the total negative electrode slurry.

[0119] <Secondary battery> A secondary battery according to an embodiment of the present invention may include the anode according to the embodiment described above. Specifically, the secondary battery may include an anode, a cathode, a separator interposed between the cathode and the anode, and an electrolyte, and the anode is the same as the anode described above. Since the anode has been described above, detailed description thereof will be omitted.

[0120] 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.

[0121] 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.

[0122] 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; or a compound having the chemical formula Li 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 Mc3 Examples of the lithium manganese composite oxide 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 satisfies 0.01≦c3≦0.1), Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); or LiMn2O4 in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion. The positive electrode may be lithium metal (Li-metal).

[0123] 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.

[0124] 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.

[0125] The positive electrode binder improves adhesion between positive electrode active material particles 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, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof. These binders may be used singly or in combination.

[0126] The separator separates the negative electrode and the 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 preferred that the separator exhibits low resistance to ion migration in the electrolyte and has excellent electrolyte humidification capacity. 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 laminate 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.

[0127] Examples of the electrolytic solution 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 manufacturing lithium secondary batteries.

[0128] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0129] 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.

[0130] In particular, among the carbonate organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are preferably used as high-viscosity organic solvents, 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 solution having high electrical conductivity can be prepared, and therefore these cyclic carbonates are even more preferably used.

[0131] 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:

[0132] In addition to the 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.

[0133] According to another embodiment of the present invention, there is provided a battery module including the secondary battery as a unit cell, and a battery pack including the same. The battery module and the battery pack include the secondary battery having high capacity, high rate characteristics, and high cycle characteristics, and can be used as a power source for medium to large devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems. [Example]

[0134] <Examples and Comparative Examples> Example 1 94 g of powders of Si and SiO2 mixed at a molar ratio of 1:1 were mixed in a reactor and then vacuum heated at a sublimation temperature of 1,400°C. The vaporized Si and SiO2 mixed gas was then reacted in a vacuum cooling zone with a cooling temperature of 800°C and condensed into a solid phase. The condensed particles were then pulverized using a ball mill for 3 hours to produce silicon-based particles of 6 μm in size. The silicon-based particles were then placed in the hot zone of a CVD device while maintaining an inert atmosphere by flowing Ar gas, and methane was blown into the hot zone at 900°C using Ar as a carrier gas for 20 minutes. -1 The silicon-based particles were reacted under torr to form a carbon layer on their surfaces. Then, 6 g of Li metal powder was added, and the mixture was further heat-treated at 800°C in an inert atmosphere, followed by exposure to UV light to activate the particle surfaces. Next, the mixture was mixed in a DMSO (dimethylsulfoxide) solvent at a weight ratio of 1:99 (PEG-b-PS:Polyethylene glycol-block-Polystyrene) to silicon-based particles, and reacted at room temperature with stirring for 2 hours to produce an anode active material with a polymer coating layer.

[0135] Example 2 A negative electrode active material was prepared in the same manner as in Example 1, except that PEG-b-PS was changed to PS-b-PBA.

[0136] Example 3 A negative electrode active material was prepared in the same manner as in Example 1, except that the weight ratio of PEG-b-PS:silicon-based particles was changed to 10:90.

[0137] Comparative Example 1 A negative electrode active material was prepared in the same manner as in Example 1, except that the polymer coating layer formation process was omitted.

[0138] Comparative Example 2 A negative electrode active material was prepared in the same manner as in Example 1, except that the solvent was changed to water, PEG-b-PS was changed to HMDS (hexamethyldisilazane), and trimethylsilyl groups were introduced onto the surface by applying heat.

[0139] <Carbon layer content analysis> The content of the carbon layer was analyzed using a CS-analyzer (CS-800, Eltra).

[0140] <Analysis of Li content in negative electrode active material> The content of the Li atoms was confirmed by ICP analysis using an inductively coupled plasma optical emission spectrometer (ICP-OES, AVIO 500, manufactured by Perkin-Elmer 7300).

[0141] <Analysis of amphiphilic polymer content> The content of the amphiphilic polymer was confirmed by analyzing the carbon content using a combustion analyzer (G4 ICARUS HF manufactured by Bruker).

[0142] <D of negative electrode active material 50 and specific surface area analysis> D of the negative electrode active material 50 was analyzed by laser diffraction particle size analysis using a Microtrac S3500 device, and the BET specific surface area of ​​the negative electrode active material was measured using a BET measurement device (BEL-SORP-MAX, Nippon Bell).

[0143] The analytical results of the negative electrode active materials prepared in the examples and comparative examples are shown in Table 1 below.

[0144] [Table 1]

[0145] <Experimental example: Evaluation of discharge capacity, initial efficiency, and life (capacity retention rate) characteristics> Negative electrodes and batteries were manufactured using the negative electrode active materials of the examples and comparative examples, respectively.

[0146] The negative electrode active material, carbon black as a conductive material, and PAA (polyacrylic acid) as a binder were mixed in a weight ratio of 80:10:10 to prepare a mixture. Then, 7.8 g of distilled water was added to 5 g of the mixture and stirred to prepare a negative electrode slurry. The negative electrode slurry was applied to a copper (Cu) metal thin film as a negative electrode current collector with a thickness of 20 μm and dried. The circulating air temperature was 60°C. The mixture was then rolled and dried in a vacuum oven at 130°C for 12 hours to prepare a negative electrode.

[0147] The manufactured negative electrode was placed in a 1.7671 cm 2 A lithium (Li) metal thin film cut into a circular shape was used as the positive electrode. A porous polyethylene separator was placed between the positive electrode and the negative electrode, and an electrolyte solution prepared by dissolving 0.5 parts by weight of vinylene carbonate in a mixed solution of ethyl methyl carbonate (EMC) and ethylene carbonate (EC) in a volume ratio of 7:3 and dissolving LiPF6 at a concentration of 1M was injected to prepare a lithium coin half-cell.

[0148] 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.

[0149] The first and second cycles were charged and discharged at 0.1 C, and the third to 49th cycles were charged and discharged at 0.5 C. The 50th cycle was completed in a charged state (with lithium in the negative electrode).

[0150] Charging conditions: CC (constant current) / CV (constant voltage) (5mV / 0.005C current cut-off) Discharge condition: CC (constant current) condition 1.5V

[0151] 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

[0152] The capacity retention rate was calculated as follows. Capacity retention rate (%) = (49 discharge capacity / 1 discharge capacity) × 100

[0153] <Experimental example: Evaluation of slurry dispersibility> The negative electrode active materials prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were mixed in a weight ratio of 20:80 with distilled water, subjected to ultrasonic treatment for 5 minutes, and then allowed to stand for 10 minutes. max The mixture was passed through a mesh having a diameter corresponding to the size of the active material remaining on the mesh. The active material remaining on the mesh was dried in an oven at 80° C. for more than half a day, and then its weight was measured.

[0154] Dispersibility was calculated as follows:

[0155]

number

[0156] W t means the total weight of the negative electrode active material contained in the mixture, W r means the weight of the negative electrode active material that could not pass through the mesh when the mixture was passed through the mesh.

[0157] <Experimental example: Evaluation of processability (gas generation) characteristics> As part of the processability evaluation, 20 g of a slurry prepared by mixing graphite, the negative electrode active material, carbon black, CMC, and PAA in a weight ratio of 77:20:1:1:1 was placed in a pouch of approximately 10 cm x 15 cm, vacuum sealed, and then placed in an oven at 40°C to measure the volume change.

[0158] The time (hour) at which gas was generated was measured based on the time when the volume of the pouch increased by 2 mL or more compared to the volume measured immediately after the pouch was vacuum-sealed, and is shown in Table 2 below.

[0159] [Table 2]

[0160] The negative electrode active material according to the present invention is characterized by a coating layer containing an amphiphilic polymer on silicon-based particles containing a Li compound. The hydrophobic groups of the amphiphilic polymer have low reactivity with water, allowing the inorganic layer to remain unreactive with water in the aqueous slurry. This prevents water from penetrating into the negative electrode active material, thereby effectively passivating the silicon-based particles. Furthermore, the coating layer prevents side reactions between the silicon-based particles or lithium by-products and water, thereby suppressing gas generation, thereby improving the aqueous processability of the slurry. At the same time, the hydrophilic groups contained in the amphiphilic polymer locate on the surface of the negative electrode active material, thereby improving the dispersibility of the negative electrode active material in the aqueous slurry.

[0161] In contrast, when a polymer coating layer was not formed as in Comparative Example 1, aqueous dispersibility was low, making it difficult to form a stable electrode. In addition, the gas generation time point of the negative electrode slurry was accelerated due to a side reaction between lithium by-products and water, which reduced slurry processability. As a result, it was confirmed that the capacity retention rate of a secondary battery using the negative electrode active material was significantly reduced.

[0162] In Comparative Example 2, instead of a polymer coating layer, a trimethylsilyl group was introduced to the surface of the negative electrode active material to impart hydrophobicity. Although the gas generation time of the negative electrode slurry was delayed to some extent, the hydrophilicity of the negative electrode active material was still reduced and the aqueous dispersibility was somewhat low. As a result, the capacity retention rate of a secondary battery using the negative electrode active material was significantly reduced.

Claims

1. SiO ｘ (0<x<2) and a Li compound, and a silicon-based particle having a carbon layer on at least a portion of the surface thereof; and a coating layer containing an amphiphilic polymer provided on at least a portion of the silicon-based particles; A negative electrode active material comprising:

2. The negative electrode active material according to claim 1 , wherein the amphiphilic polymer includes a unit containing a hydrophilic group and a unit containing a hydrophobic group.

3. 3. The negative electrode active material according to claim 2, wherein the unit containing a hydrophilic group is derived from one or more selected from the group consisting of polyethylene glycol, polylysine, and poly[oligo(ethylene glycol) methyl ether methacrylate].

4. The negative electrode active material according to claim 2 , wherein the unit containing a hydrophobic group is derived from one or more selected from the group consisting of polystyrene and polypropylene oxide.

5. 3. The negative electrode active material according to claim 2, wherein a weight ratio of the unit containing a hydrophilic group to the unit containing a hydrophobic group is 3:7 to 7:

3.

6. 10. The negative electrode active material of claim 1, wherein the coating layer containing the amphiphilic polymer is included in an amount of 0.005 to 20 parts by weight based on 100 parts by weight of the negative electrode active material.

7. 2. The negative electrode active material of claim 1, wherein the amphiphilic polymer comprises at least one selected from the group consisting of PEG-PPO, PEG-PS, PS-PBA, polylysine-PPO, and polylysine-PS.

8. A mixture of 20 g of the negative electrode active material and 80 g of distilled water was subjected to ultrasonic treatment, and then the D of the negative electrode active material was ｍａｘ 2. The negative electrode active material of claim 1, wherein when the mixture is passed through a mesh having a diameter corresponding to [Equation 1] In the formula 1, W ｔ means the total weight of the negative electrode active material contained in the mixture, W ｒ means the weight of the negative electrode active material that was unable to pass through the mesh when the mixture was passed through the mesh.

9. The negative electrode active material of claim 1 , further comprising a lithium by-product disposed on at least a portion of the silicon-based particles.

10. The negative electrode active material of claim 9 , wherein the lithium by-product is contained in an amount of 5 parts by weight or less based on a total of 100 parts by weight of the negative electrode active material.

11. The negative electrode active material of claim 1, wherein Li is contained in an amount of 0.1 to 40 parts by weight based on a total of 100 parts by weight of the negative electrode active material.

12. The negative electrode active material of claim 1, wherein the carbon layer is included in an amount of 0.1 to 50 parts by weight based on 100 parts by weight of the total amount of the negative electrode active material.

13. SiO ｘ forming silicon-based particles comprising a (0<x<2) and Li compound, the particles having a carbon layer on at least a portion of the surface thereof; and reacting the silicon-based particles with an amphiphilic polymer precursor; The method for producing the negative electrode active material according to any one of claims 1 to 12, comprising:

14. A negative electrode comprising the negative electrode active material according to any one of claims 1 to 12.

15. A secondary battery comprising the negative electrode according to claim 14.

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