Anode, method for manufacturing anode, anode slurry, and secondary battery including anode

Abstract

The present invention relates to a negative electrode, a method for producing a negative electrode, a negative electrode slurry, and a secondary battery including the negative electrode.

Description

[Technical Field]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2021-0176771, filed with the Korean Intellectual Property Office on December 10, 2021, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a negative electrode, a method for producing the negative electrode, a negative electrode slurry, and a secondary battery including the negative electrode. [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 small, lightweight, and relatively high-capacity secondary batteries has been rapidly increasing. In particular, lithium secondary batteries, which are lightweight and have high energy density, have been attracting attention as a power source for portable devices. As a result, research and development efforts to improve the performance of lithium secondary batteries have been actively pursued.

[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] Among negative electrode active materials, silicon-based active materials have attracted attention due to their high capacity and excellent high-speed 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 a silicon-based oxide represented by (0 < x < 2), there is an advantage in that the degree of volume expansion / contraction due to charge / discharge is smaller compared to other silicon-based active materials such as silicon (Si). However, there is still a disadvantage that the initial efficiency of the silicon-based oxide decreases due to the presence of an irreversible capacity.

[0007] Regarding 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 the silicon-based oxide. 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, resulting in a poor state of the manufactured negative electrode and a problem of decreased charge / discharge efficiency of the negative electrode.

[0008] Therefore, there is a current need to develop a method that can improve the phase stability of the negative electrode slurry containing the 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, a method for manufacturing a negative electrode, a negative electrode slurry, and a secondary battery including the negative electrode.

Means for Solving the Problems

[0011] One embodiment of the present invention is a negative electrode including a negative electrode current collector; and a negative electrode active material layer provided on the negative electrode current collector, wherein the negative electrode active material layer includes a silicon-based active material, and the silicon-based active material is SiOx It includes silicon-based particles containing (0 < x < 2) and Li, and the negative electrode contains 0.05 parts by weight or more and 1.5 parts by weight or less of one or more elements selected from the group consisting of aluminum, boron, zinc, and zirconium elements based on 100 parts by weight of the negative electrode active material layer in total, and has a structure in which one or more elements selected from the group consisting of aluminum, boron, zinc, and zirconium elements are bonded to oxygen, and provides a negative electrode.

[0012] One embodiment of the present invention is SiO x A method for manufacturing a negative electrode, including the steps of mixing a silicon-based active material containing silicon-based particles containing (0 < x < 2) and Li, a conductive material, a binder, and an acid to form a negative electrode slurry; and applying the negative electrode slurry to at least one surface of a negative electrode current collector to form a negative electrode active material layer, wherein the acid is an acid containing one or more elements selected from the group consisting of aluminum, boron, zinc, and zirconium elements, provides a method for manufacturing a negative electrode.

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

[0014] One embodiment of the present invention is a negative electrode slurry containing a silicon-based active material, wherein the silicon-based active material contains silicon-based particles containing (0 < x < 2) and Li, and the negative electrode slurry contains 0.05 parts by weight or more and 1.5 parts by weight or less of one or more elements selected from the group consisting of aluminum, boron, zinc, and zirconium elements based on 100 parts by weight of the total solid content of the negative electrode slurry, and has a structure in which one or more elements selected from the group consisting of aluminum, boron, zinc, and zirconium elements are bonded to oxygen, and provides a negative electrode slurry.

Advantages of the Invention

[0015] ​​In one embodiment of the present invention, an anode includes a certain amount of Al, B, Zn, or Zr in the anode slurry by adding an acid containing Al, B, Zn, or Zr during the preparation of the anode slurry, and the element is bonded to oxygen. Specifically, when the acid is added during the preparation of the anode slurry, the base (OH - ) reacts preferentially with the acid before reacting with the Si of the active material, and the OH on the Si surface reacts with the acid, thereby preventing the base from approaching the Si.

[0016] Therefore, the rheological properties and gas generation of the negative electrode slurry are suppressed, changes in the slurry viscosity are reduced, and the added acid reacts with the base, so there is no damage to other materials such as the CMC (carboxy methyl cellulose) binder due to the acid. Therefore, when the negative electrode is applied to a secondary battery, the discharge capacity, initial efficiency, resistance performance, and / or life characteristics of the battery are improved. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present specification will be explained in more detail below.

[0018] In this specification, when a part is said to "comprise" a certain component, this does not mean that it excludes other components, but that it may further include other components, unless otherwise specified.

[0019] In this specification, when a member is said to be located "on" another member, this includes not only when the member is in contact with the other member, but also when there is another member between the two members.

[0020] The terms or words used in this specification should not be construed as being limited to their ordinary or dictionary meanings, but should be construed in a meaning and concept that is consistent with the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term in order to best describe his / her invention.

[0021] As used herein, the singular expression of a term includes the plural expression unless the context clearly indicates otherwise.

[0022] In this specification, the crystallinity of the structure contained in the negative electrode or the material contained in the negative electrode can be confirmed by X-ray diffraction analysis. X-ray diffraction analysis can be performed using an X-ray diffraction (XRD) analysis device (product name: D4-Endeavor, manufacturer: Bruker), and in addition to the above device, any device commonly used in the art can be used as appropriate.

[0023] Herein, the presence or absence of elements in the negative electrode and the content of the elements can be confirmed by ICP analysis, which can be performed using an inductively coupled plasma optical emission spectrometer (ICPAES, Perkin-Elmer 7300).

[0024] In this specification, the average particle size (D 50 The average particle size (D) can be defined as the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve (graph curve of particle size distribution). 50 ) can be measured, for example, by the laser diffraction method. The laser diffraction method generally enables measurement of particle sizes from the submicron range to several mm, and can provide results with high reproducibility and high resolution.

[0025] Preferred embodiments of the present invention will be described in detail below. However, the embodiments of the present invention can be modified in various ways, and the scope of the present invention is not limited to the embodiments described below.

[0026] One embodiment of the present invention is a negative electrode comprising: a negative electrode current collector; and a negative electrode active material layer provided on the negative electrode current collector, wherein the negative electrode active material layer contains a silicon-based active material, and the silicon-based active material is SiO xIt includes silicon-based particles containing Li where (0 < x < 2), and the negative electrode contains 0.05 parts by weight or more and 1.5 parts by weight or less of one or more elements selected from the group consisting of aluminum, boron, zinc, and zirconium elements based on 100 parts by weight of the negative electrode active material layer, and has a structure in which one or more elements selected from the group consisting of aluminum, boron, zinc, and zirconium elements are bonded to oxygen, providing a negative electrode.

[0027] Generally, when manufacturing silicon-based oxides by doping silicon-based particles with Li, a method of heat-treating together with lithium powder after carbon coating the silicon-based particles for doping is used. In this case, there is an advantage of increased initial efficiency, but damage to the carbon layer occurs due to lithium doping after carbon coating, and lithium by-products that did not react with the silicon-based particles will exist. Therefore, the silicon-based particles (silicon-based oxides) and unreacted lithium by-products will become basic during the production of the aqueous slurry, and there is a problem that gas is generated by the reaction of Si of the silicon-based active material with a base (OH - ), and the rheological properties change.

[0028] To solve this, the present invention provides a negative electrode manufactured by adding an acid containing Al, B, Zn, or Zr in the process of manufacturing the negative electrode slurry. Specifically, in the slurry manufacturing process, the aforementioned acid is added to preferentially react with the acid before the base in the slurry reacts with Si of the silicon-based active material, and the OH on the Si surface is reacted with the acid to prevent the approach of the base. Therefore, the reaction between Si and the base in the slurry is suppressed, the rheological properties and gas generation of the slurry are suppressed, and the change in the slurry viscosity becomes small. Also, since the added acid reacts with the base, there is no damage to other materials such as a CMC (carboxy methyl cellulose) binder due to acidity.

[0029] Therefore, the secondary battery including the negative electrode has the effect of improving the discharge capacity, initial efficiency, resistance performance, and / or life characteristics of the battery.

[0030] In one embodiment of the present invention, the negative electrode contains 0.05 parts by weight to 1.5 parts by weight of one or more elements selected from the group consisting of aluminum, boron, zinc, and zirconium, based on a total of 100 parts by weight of the negative electrode active material layer.

[0031] Specifically, the negative electrode contains one or more elements selected from the group consisting of aluminum, boron, zinc, and zirconium in an amount of 0.05 to 1.3 parts by weight, 0.08 to 1.2 parts by weight, or more specifically 0.1 to 1 part by weight, based on 100 parts by weight of the negative electrode active material layer in total. The lower limit of the content may be 0.05 parts by weight, 0.06 parts by weight, 0.07 parts by weight, 0.08 parts by weight, 0.09 parts by weight, 0.1 parts by weight, or 0.15 parts by weight, and the upper limit may be 1.5 parts by weight, 1.3 parts by weight, 1.2 parts by weight, 1.1 parts by weight, or 1 part by weight.

[0032] When the content of each element is within the above range, the rheological properties of the negative electrode slurry and gas generation are appropriately suppressed, the negative electrode is stably formed, and a secondary battery including the negative electrode has improved discharge capacity, initial efficiency, resistance performance, and / or life characteristics. On the other hand, when the content of each element is less than the above range, sufficient acid to react with the base cannot be provided, resulting in gas generation during slurry preparation and reduced negative electrode performance. When the content of each element is greater than the above range, the capacity of the negative electrode decreases and the element acts as a resistor that hinders the diffusion of lithium ions.

[0033] The contents of aluminum, boron, zinc, and zirconium elements contained in the negative electrode can be confirmed by ICP analysis, which can be performed using an inductively coupled plasma optical emission spectrometer (ICPAES, Perkin-Elmer 7300).

[0034] The at least one element selected from the group consisting of aluminum, boron, zinc, and zirconium may be contained in the negative electrode active material layer.

[0035] In one embodiment of the present invention, the negative electrode comprises a structure in which at least one element selected from the group consisting of aluminum, boron, zinc, and zirconium is bonded to oxygen.

[0036] The structure in which one or more elements selected from the group consisting of aluminum, boron, zinc, and zirconium are bonded to oxygen may be a hydroxide containing one or more elements selected from the group consisting of aluminum, boron, zinc, and zirconium.

[0037] The structure in which at least one element selected from the group consisting of aluminum, boron, zinc, and zirconium is bonded to oxygen may be a lithium aluminum compound, a lithium boron compound, a lithium zinc compound, or a lithium zirconium compound.

[0038] In one embodiment of the present invention, the negative electrode may have a structure in which aluminum is bonded to oxygen (Al-O). Specifically, the aluminum is bonded to oxygen when an aluminum-containing acid added to a slurry is converted to a base (OH). - ) or reacts with OH groups on the silicon surface to form a compound with an Al-O bond or a compound containing Li and Al. For example, the aluminum may be present in the form of Al(OH)3 or LiAl2(OH)7·2H2O.

[0039] In one embodiment of the present invention, the negative electrode may include a structure in which boron is bonded to oxygen (BO). Specifically, the boron is bonded to oxygen when a boron-containing acid added to the slurry is converted to a base (OH - ) or reacts with OH groups on the Si surface to form a compound having a B-O bond or a compound containing B and O. For example, the boron may exist in the form of B(OH)3, B(OLi)3, or BO.

[0040] In one embodiment of the present invention, the negative electrode may have a structure in which zinc is bonded to oxygen (Zn-O). Specifically, the zinc is bonded to oxygen when the zinc-containing acid added to the slurry is converted to a base (OH). - ) or reacts with OH groups on the silicon surface to form a compound having a Zn-O bond. For example, the zinc may exist in the form of Zn(OH)2.

[0041] In one embodiment of the present invention, the negative electrode may have a structure in which zirconium is bonded to oxygen (Zr-O). Specifically, the zirconium is bonded to oxygen when the zirconium-containing acid added to the slurry is converted to a base (OH). - ) or reacts with OH groups on the Si surface to form a compound having a Zr-O bond. For example, the zirconium may exist in the form of ZrO(OH)2.

[0042] The aluminum, boron, zinc, and zirconium may be contained within the negative electrode active material layer. In one example, the aluminum, boron, zinc, and zirconium may be contained in a region outside the negative electrode active material distributed in the negative electrode active material layer.

[0043] The Al—O, BO, Zn—O, and Zr—O bonds can be confirmed by XPS (Nexsa ESCA System, Thermo Fisher Scientific (NEXSA 1)) analysis.

[0044] In one embodiment of the present invention, the negative electrode contains aluminum element, and a peak appears in the range of 74 eV to 75.5 eV (binding energy) in XPS analysis.

[0045] In one embodiment of the present invention, when the negative electrode contains boron element, a peak appears in the range of 192 eV to 194 eV (binding energy) in XPS analysis.

[0046] In one embodiment of the present invention, the negative electrode contains zinc element, and a peak appears in the range of 1022 eV to 1024 eV (binding energy) during XPS analysis.

[0047] In one embodiment of the present invention, the negative electrode contains zirconium element, and a peak appears in the range of 182 eV to 184 eV (binding energy) during XPS analysis.

[0048] The binding energy range means the binding energy range between each element and oxygen. That is, when a peak is detected within the above range, it means that the structure in which each element is combined with oxygen is included.

[0049] In one embodiment of the present invention, the negative electrode may contain a hydroxide containing at least one selected from the group consisting of the aluminum, boron, zinc, and zirconium elements. For example, the negative electrode may contain Al(OH)3, B(OH)3, Zn(OH)2, or ZrO(OH)2, etc.

[0050] In one embodiment of the present invention, the negative electrode may contain at least one selected from the group consisting of lithium aluminum compounds, lithium boron compounds, lithium zinc compounds, and lithium zirconium compounds. Specifically, the lithium aluminum compound, lithium boron compound, lithium zinc compound, and lithium zirconium compound can exist in the form of an oxide or a hydroxide, and the hydroxide containing at least one selected from the group consisting of the above-mentioned aluminum, boron, zinc, and zirconium elements reacts with OH - or a lithium by-product, etc. to form. For example, the lithium aluminum compound and the lithium boron compound may exist in the forms of LiAl2(OH)7·2H2O and B(OLi)3, respectively.

[0051] The silicon-based active material according to one embodiment of the present invention includes silicon-based particles containing SiO x (0 < x < 2) and Li.

[0052] The above-mentioned SiO x (0 < x < 2) corresponds to the matrix within the silicon-based particles. The above-mentioned SiO x (0 < x < 2) may be in a form containing Si and SiO2, and the Si may form a phase. That is, the above-mentioned x corresponds to the number ratio of O to Si contained within SiO x (0 < x < 2). When the silicon-based particles contain the above-mentioned SiO x (0 < x < 2), the discharge capacity of the secondary battery can be improved.

[0053] The silicon-based particles contain Li. The Li may exist in at least one of the forms of lithium atoms, lithium silicate, lithium silicide, and lithium oxide within the silicon-based particles, and preferably may exist in the form of lithium silicate. When the Li exists in the form of a Li compound, the Li compound can correspond to the matrix within the silicon-based particles. When the silicon-based particles contain Li, there is an effect of improving the initial efficiency.

[0054] The Li can be contained in the silicon-based particles through steps of heating and vaporizing a mixed powder of Si and SiO2, then depositing the vaporized mixed gas to form SiO, mixing the formed SiO with Li powder, and then performing heat treatment.

[0055] That is, the Li can be distributed on the surface and / or inside of the silicon-based particles in a form doped into the silicon-based particles. The Li is distributed on the surface and / or inside of the silicon-based particles, can control the volume expansion / contraction of the silicon-based particles to an appropriate level, and can play a role in preventing damage to the active material. Also, the Li may be included in terms of reducing the ratio of the irreversible phase (e.g., SiO2) of the silicon-based oxide particles to increase the efficiency of the active material.

[0056] In one embodiment of the present invention, Li may be present in the form of lithium silicate. The lithium silicate is represented by 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 can be present 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 can be composed of a complex in the form of Li a Si b O c (2 ≤ a ≤ 4, 0 < b ≤ 2, 2 ≤ c ≤ 5), and is not limited to this form.

[0057] In one embodiment of the present invention, Li contained in the silicon-based active material may be contained in an amount of 1 to 25 parts by weight based on 100 parts by weight of the silicon-based active material in total. Specifically, it may be contained in an amount of 3 to 20 parts by weight, 5 to 10 parts by weight, or 6 to 9 parts by weight, or 6 to 8 parts by weight, and more specifically, it may be contained in an amount of 7 to 8 parts by weight. As the content of Li increases, the initial efficiency increases, but there is a problem that the discharge capacity decreases. Therefore, when the above range is satisfied, an appropriate discharge capacity and initial efficiency can be realized.

[0058] The Li element content can be confirmed by ICP analysis. Specifically, a certain amount (approximately 0.01 g) of silicon-based active material is taken and transferred to a platinum crucible. Nitric acid, hydrofluoric acid, and sulfuric acid are added and the material is completely decomposed on a hot plate. Then, an inductively coupled plasma (ICPAES, Perkin-Elmer 7300) is used to measure the intensity of a standard solution (5 mg / kg) prepared at the characteristic wavelength of the element to be analyzed, and a reference calibration curve is created. The pretreated sample solution and the base sample are then introduced into the instrument, and their respective intensities are measured to calculate the actual intensities. The concentration of each component is calculated relative to the created calibration curve, and the total is converted to a theoretical value, allowing the element content of the manufactured silicon-based active material to be analyzed.

[0059] A carbon layer may be provided on at least a portion of the surface of the silicon-based particle according to one embodiment of the present invention. In this case, the carbon layer may be provided on at least a portion of the surface, i.e., the particle surface, or may be provided on the entire particle surface. The carbon layer imparts conductivity to the silicon-based active material, thereby improving the initial efficiency, life characteristics, and battery capacity characteristics of the secondary battery.

[0060] Specifically, the carbon layer may include crystalline carbon or amorphous carbon, and preferably includes amorphous carbon.

[0061] The crystalline carbon can further improve the conductivity of the silicon-based active material. The crystalline carbon may include at least one selected from the group consisting of fullerene, carbon nanotube, and graphene.

[0062] The amorphous carbon can appropriately maintain the strength of the carbon layer and suppress the expansion of the silicon-based particles. The amorphous carbon may be a carbon-based material formed by using at least one carbide selected from the group consisting of tar, pitch, and other organic substances, or hydrocarbons as a source in a chemical vapor deposition process.

[0063] The carbonized organic material may be a carbonized organic material selected from the group consisting of sucrose, glucose, galactose, fructose, lactose, mannose, ribose, aldohexose, and kedohexose, and combinations thereof.

[0064] The hydrocarbon may be a substituted or unsubstituted aliphatic or alicyclic hydrocarbon, or a substituted or unsubstituted aromatic hydrocarbon. The aliphatic or alicyclic hydrocarbon of the substituted or unsubstituted aliphatic or alicyclic hydrocarbon may be methane, ethane, ethylene, acetylene, propane, butane, butene, pentane, isobutane, 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.

[0065] Specifically, the carbon layer may be formed by disposing a carbonaceous precursor on silicon-based particles and then heat-treating the resulting material. The carbonaceous precursor may be graphene or graphite for producing crystalline carbon, or may be a carbonaceous material formed by using at least one carbide selected from the group consisting of tar, pitch, and other organic substances for producing amorphous carbon, or a hydrocarbon such as methane, ethane, or acetylene as a source in a chemical vapor deposition process.

[0066] In one embodiment of the present invention, the carbon layer may be included in an amount of 1 to 20 parts by weight, 1 to 10 parts by weight, specifically 2 to 5 parts by weight, and more specifically 3 to 4 parts by weight, based on a total of 100 parts by weight of the silicon-based active material. When the amount is within this range, a decrease in the capacity and efficiency of the silicon-based active material can be prevented.

[0067] The average particle size (D 50) may be 0.1 μm to 30 μm, specifically 1 μm to 20 μm, and more specifically 1 μm to 15 μm. When the particle size satisfies this range, the active material is structurally stable during charge and discharge, the problem of an excessively large particle size resulting in an increased level of volume expansion / contraction is prevented, and the problem of an excessively small particle size resulting in a decrease in initial efficiency is prevented.

[0068] The particle size of the silicon-based active material can be adjusted by methods such as, but not limited to, a ball mill, a jet mill, or air classification.

[0069] In one embodiment of the present invention, the negative electrode includes a negative electrode current collector; and a negative electrode active material layer provided on the negative electrode current collector, the negative electrode active material layer including a silicon-based active material.

[0070] In one embodiment of the present invention, the at least one element selected from the group consisting of aluminum, boron, zinc, and zirconium may be contained in a negative electrode active material layer formed from the negative electrode slurry, and the negative electrode active material layer may have a structure in which oxygen is bonded to one or more elements selected from the group consisting of aluminum, boron, zinc, and zirconium.

[0071] The negative electrode current collector is not particularly limited as long as it is conductive and does not induce chemical changes in the battery. 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, transition metals that adsorb carbon well, such as copper and nickel, can 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.

[0072] In one embodiment of the present invention, the negative electrode active material layer may further include a binder and a conductive material.

[0073] 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.

[0074] The conductive material is not particularly limited as long as it does not induce chemical changes 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.

[0075] In one embodiment of the present invention, the negative electrode active material layer may further include a thickener. The thickener may be, but is not limited to, carboxymethyl cellulose (CMC), and any thickener commonly used in the art may be used.

[0076] In one embodiment of the present invention, the negative electrode active material layer may contain an additional active material.

[0077] The additional 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 (0<β<2), SnO 2、 Examples of the negative electrode active material include metal oxides capable of doping and dedoping lithium, such as vanadium oxide, lithium titanium oxide, and lithium vanadium oxide; or composites containing the metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites. One or 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 examples of low-crystalline carbon include soft carbon and hard carbon, while typical examples of high-crystalline carbon include 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-fired carbon such as petroleum or coal tar pitch-derived cokes.

[0078] In an embodiment of the present invention, the negative electrode active material layer may further include a carbon-based active material. Specifically, the carbon-based active material may be graphite.

[0079] In one embodiment of the present invention, the weight ratio of the silicon-based active material to the carbon-based active material (silicon-based active material: carbon-based active material) is 1:99 to 30:70, and specifically, it may be 5:95 to 30:70 or 10:90 to 20:80.

[0080] One embodiment of the present invention is a negative electrode slurry containing a silicon-based active material, wherein the silicon-based active material contains silicon-based particles containing SiO x (0 < x < 2) and Li, and the negative electrode slurry contains 0.05 parts by weight or more and 1.5 parts by weight or less of one or more elements selected from the group consisting of aluminum, boron, zinc, and zirconium elements, based on 100 parts by weight of the total solid content of the negative electrode slurry, and has a structure in which one or more elements selected from the group consisting of aluminum, boron, zinc, and zirconium elements are bonded to oxygen. A negative electrode slurry is provided.

[0081] Regarding the silicon-based active material contained in the negative electrode slurry, the content related to the above-described silicon-based active material can be applied.

[0082] Regarding the aluminum, boron, zinc, and zirconium elements contained in the negative electrode slurry, the content related to the above-described aluminum, boron, zinc, and zirconium elements can be applied.

[0083] In one embodiment of the present invention, the negative electrode slurry may contain a hydroxide containing at least one selected from the group consisting of aluminum, boron, zinc, and zirconium elements. For example, the negative electrode slurry may contain Al(OH)3, B(OH)3, Zn(OH)2, or ZrO(OH)2, etc.

[0084] In one embodiment of the present invention, the negative electrode slurry may contain at least one selected from the group consisting of a lithium aluminum compound, a lithium boron compound, a lithium zinc compound, and a lithium zirconium compound. Specifically, the lithium aluminum compound, the lithium boron compound, the lithium zinc compound, and the lithium zirconium compound may exist in the form of an oxide or a hydroxide, and a hydroxide containing at least one selected from the group consisting of the aforementioned aluminum, boron, zinc, and zirconium elements reacts with OH - in the slurry or may be formed by reacting with lithium by-products or the like. For example, the lithium aluminum compound and the lithium boron compound may exist in the forms of LiAl2(OH)7·2H2O and B(OLi)3, respectively.

[0085] The negative electrode according to one embodiment of the present invention may be manufactured by a step of applying the negative electrode slurry to at least one surface of a negative electrode current collector to form a negative electrode active material layer.

[0086] One embodiment of the present invention is a method for manufacturing a negative electrode, including: forming a negative electrode slurry by mixing a silicon-based active material containing silicon-based particles containing SiO x (0 < x < 2) and Li, a conductive material, a binder, and an acid; and applying the negative electrode slurry to at least one surface of a negative electrode current collector to form a negative electrode active material layer, wherein the acid is an acid containing at least one element selected from the group consisting of aluminum, boron, zinc, and zirconium elements.

[0087] The method for manufacturing a negative electrode according to one embodiment of the present invention includes: forming a negative electrode slurry by mixing a silicon-based active material containing silicon-based particles containing SiO x (0 < x < 2) and Li, a conductive material, a binder, and an acid containing at least one element selected from the group consisting of aluminum, boron, zinc, and zirconium elements.

[0088] The silicon-based particles may be formed by heating and vaporizing Si powder and SiO powder, depositing the vaporized gas mixture to form preliminary particles, and mixing the resulting preliminary particles with Li powder and then heat-treating the mixture.

[0089] A carbon layer may be provided on at least a portion of the surface of the silicon-based particle, and the carbon layer may be formed by chemical vapor deposition (CVD) using a hydrocarbon gas or by carbonizing a carbon source material.

[0090] In one embodiment of the present invention, in the step of forming the negative electrode slurry, the silicon-based active material, the conductive material, and the binder may be mixed together, and then the acid may be added thereto. Alternatively, the silicon-based active material, the conductive material, the binder, and the acid may be mixed together to form the negative electrode slurry.

[0091] Generally, when doping silicon-based particles with Li, the silicon-based particles are coated with carbon and then heat-treated with lithium powder. This method has the advantage of increasing the initial efficiency, but the carbon layer is damaged by the lithium doping after the carbon coating, and lithium by-products that have not reacted with the silicon-based particles are present. Therefore, the silicon-based particles and unreacted lithium by-products become basic during the preparation of the aqueous slurry, and the Si in the negative electrode active material and the base (OH) - ) reacts to generate gas, which changes the rheological properties.

[0092] To solve this problem, in the present invention, in the process of producing the negative electrode slurry, an acid containing one or more elements selected from the group consisting of aluminum, boron, zinc, and zirconium is added to the slurry to reduce the base (OH -Before reacting with silicon, the acid reacts with the silicon surface OH, preventing the base from approaching. This suppresses the reaction between silicon and the base in the slurry, improving the rheological properties of the slurry and suppressing gas generation, while minimizing changes in slurry viscosity. Furthermore, the added acid reacts with the base, preventing damage to other materials, such as the CMC (carboxy methyl cellulose) binder, due to acidity.

[0093] Therefore, a secondary battery including a negative electrode prepared by the above method has improved discharge capacity, initial efficiency, resistance performance and / or life characteristics of the battery.

[0094] In one embodiment of the present invention, the acid containing one or more elements selected from the group consisting of aluminum, boron, zinc, and zirconium may be one or more selected from the group consisting of Al(OH)3, B(OH)3, Zn(OH)2, and ZrO(OH)2. When such an acid is used, Al(OH)3, B(OH)3, Zn(OH)2, or ZrO(OH)2 reacts with the base in the slurry or with OH groups on the silicon surface, preventing the base from approaching the silicon, thereby suppressing changes in the rheological properties of the slurry and suppressing gas generation. On the other hand, using a strong acid instead of the above-mentioned acids can cause rapid lithium dissolution from the active material, damaging the structure of the active material, and can also react with binders such as CMC, resulting in persistent viscosity changes.

[0095] In one embodiment of the present invention, the acid containing one or more elements selected from the group consisting of aluminum, boron, zinc, and zirconium may be mixed in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the total solids content of the negative electrode slurry. Specifically, the acid may be mixed in an amount of 0.1 to 4 parts by weight, more specifically, 0.1 to 3 parts by weight or 0.1 to 2 parts by weight. The lower limit of the acid content may be 0.1 parts by weight, 0.3 parts by weight, 0.5 parts by weight, 0.7 parts by weight, or 0.8 parts by weight, and the upper limit of the acid content may be 5 parts by weight, 4 parts by weight, 3 parts by weight, or 2 parts by weight.

[0096] When the acid content satisfies the above range, the rheological properties of the negative electrode slurry and gas generation are appropriately suppressed, the negative electrode is stably formed, and a secondary battery including the negative electrode has improved discharge capacity, initial efficiency, resistance performance, and / or life characteristics. On the other hand, when the acid content is less than the above range, a sufficient source for reaction with the base cannot be provided, resulting in gas generation. When the acid content is greater than the above range, the capacity of the negative electrode decreases and the acid acts as a resistor that hinders the diffusion of lithium ions.

[0097] In one embodiment of the present invention, the negative electrode slurry contains at least one element selected from the group consisting of aluminum, boron, zinc, and zirconium elements.

[0098] The above-mentioned contents can be applied to the aluminum, boron, zinc, and zirconium elements.

[0099] In one embodiment of the present specification, the process of mixing the negative electrode slurry may be carried out by a method known in the art.

[0100] In one embodiment of the present specification, the negative electrode slurry may have a pH of 10 to 13 at 25°C, specifically 11 to 12.5, and more specifically 12 to 12.5. When the pH of the negative electrode slurry satisfies the above range, it is effective in preventing the elution of Li from within the active material. On the other hand, if the pH of the negative electrode slurry is less than 10, there is a problem that Li elutes from within the active material, causing the active material structure to collapse. On the other hand, if the pH of the negative electrode slurry exceeds 13, there is a problem that Si in the active material reacts with the base due to a strong base, accelerating gas generation.

[0101] In one embodiment of the present invention, the negative electrode slurry may include an additional active material. The above-described content may be applied to the additional active material.

[0102] In an embodiment of the present invention, the negative electrode slurry may further include a carbon-based active material. Specifically, the carbon-based active material may be graphite.

[0103] In one embodiment of the present invention, the weight ratio of the silicon-based active material to the carbon-based active material (silicon-based active material:carbon-based active material) may be 1:99 to 30:70, specifically 5:95 to 30:70 or 10:90 to 20:80.

[0104] In one embodiment of the present invention, the negative electrode slurry may further include a thickener. The thickener may be, but is not limited to, carboxymethyl cellulose (CMC), and any thickener commonly used in the art may be used.

[0105] In one embodiment of the present invention, the total negative electrode active material, which is a combination of the silicon-based active material and the carbon-based active material, may be included in the negative electrode slurry in an amount of 60 parts by weight to 99 parts by weight, specifically 70 parts by weight to 98 parts by weight, based on 100 parts by weight of the total solid content of the negative electrode slurry.

[0106] In one embodiment of the present invention, the binder may be included in the negative electrode slurry in an amount of 0.5 parts by weight to 30 parts by weight, 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.

[0107] In one embodiment of the present invention, the conductive material may be contained in the negative electrode slurry in an amount of 0.5 parts by weight to 25 parts by weight, 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.

[0108] In one embodiment of the present invention, the thickener may be contained in the negative electrode slurry 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.

[0109] 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.

[0110] 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 negative electrode slurry in total.

[0111] A method for manufacturing a negative electrode according to an embodiment of the present invention includes a step of coating a negative electrode slurry on at least one surface of a negative electrode current collector to form a negative electrode active material layer.

[0112] A method for manufacturing a negative electrode according to an embodiment of the present invention includes the steps of applying the negative electrode slurry to at least one surface of a current collector, and then drying and rolling the current collector.

[0113] The negative electrode current collector is not particularly limited as long as it is conductive and does not induce chemical changes in the battery. 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, transition metals that adsorb carbon well, such as copper and nickel, can 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.

[0114] The method for applying the negative electrode slurry is not particularly limited as long as it is a method commonly used in the art, and may be, for example, a coating method using a slot die, or may be a Mayer bar coating method, a gravure coating method, a dip coating method, a spray coating method, or the like.

[0115] The drying step can be carried out by appropriately adopting a method commonly used in the art.

[0116] The rolling step can be carried out by appropriately adopting a method commonly used in the art.

[0117] 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.

[0118] The positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and including the positive electrode active material.

[0119] The positive electrode current collector in the positive electrode is not particularly limited as long as it is conductive and does not induce chemical changes in the battery. 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. The positive electrode current collector may typically have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the collector surface to enhance the adhesive strength of the positive electrode active material. It may be used in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0120] 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-c1O4 (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 Ni-site type lithium nickel oxide represented by the chemical formula LiMn 2-c3 M c3 Examples of suitable lithium manganese composite oxides include, but are not limited to, lithium manganese composite oxides represented by Li2Mn3MO8 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01≦c3≦0.1) or 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 Li metal.

[0121] The positive electrode active material layer may contain a positive electrode conductive material and a positive electrode binder in addition to the above-mentioned positive electrode active material.

[0122] The positive electrode conductive material is used to impart conductivity to the electrode, and can be any material that has electronic conductivity without undergoing chemical changes in the battery. Specific examples include graphite such as natural graphite and artificial graphite; carbonaceous 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.

[0123] 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 may be used alone or in combination.

[0124] The separator separates the negative electrode and positive electrode and provides a path for lithium ions to move. Any separator typically used in secondary batteries can be used without particular limitations. In particular, a separator that exhibits low resistance to ion migration in the electrolyte and excellent electrolyte humidification capacity is preferred. Specifically, a porous polymer film, such as a porous polymer film made from a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure 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 separator coated with a ceramic component or a polymer material may also be used, and may be used in a single-layer or multi-layer structure.

[0125] 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.

[0126] Specifically, the electrolyte may contain a non-aqueous organic solvent and a metal salt.

[0127] Examples of the non-aqueous organic solvent that may be used include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0128] In particular, among the carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are preferred because they are high-viscosity organic solvents with high dielectric constants that allow for good dissociation of lithium salts. Mixing such cyclic carbonates with linear carbonates having low viscosity and low dielectric constants, such as dimethyl carbonate and diethyl carbonate, in an appropriate ratio can produce an electrolyte solution with high electrical conductivity, making them more preferred.

[0129] 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:

[0130] In addition to the components of the electrolyte solution, the electrolyte solution may further contain 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, for the purpose of improving the life characteristics of the battery, suppressing a decrease in battery capacity, and improving the discharge capacity of the battery.

[0131] 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.

[0132] [Example] Below, preferred examples are presented to help understand the present invention. However, the above examples are merely illustrative of the present description, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and technical spirit of the present description. It is natural that such changes and modifications fall within the scope of the appended claims.

[0133] <Examples and Comparative Examples> Example 1 94 g of powders of Si and SiO2 mixed at a 1:1 molar ratio 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 to solidify. The preliminary silicon-based active material was 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 the methane was blown into the hot zone at 900°C using Ar as a carrier gas for 5 hours and 10 minutes. -1 After reacting under torr to form a carbon layer on the surface of the silicon-based particles, 8 g of Li metal powder was added, and further heat treatment was carried out in an inert atmosphere at a temperature of 800°C to produce a silicon-based active material.

[0134] The silicon-based active material prepared as above and the carbon-based active material, graphite (average particle size (D50): 20 μm), were mixed in a weight ratio of 15:85 and used as a negative electrode active material.

[0135] The negative electrode active material, styrene-butadiene rubber (SBR) as a binder, Super C65 as a conductive material, carboxymethyl cellulose (CMC) as a thickener, and Al(OH)3 as an acid were mixed in a weight ratio of 95:2:1:1:1 and added to distilled water as a solvent for forming the negative electrode slurry to prepare the negative electrode slurry. XRD analysis of the negative electrode slurry (product name: D4-Endeavor, manufacturer: Bruker) detected Al(OH)3 and LiAl2(OH)7·2H2O in the slurry.

[0136] The negative electrode slurry was applied to one surface of a copper current collector (thickness: 15 μm) as a negative electrode current collector at 3.6 mAh / cm 2 The coated film was rolled and dried in a vacuum oven at 130°C for 10 hours to form a negative electrode active material layer (thickness: 50 μm) to prepare a negative electrode (thickness: 65 μm).

[0137] Example 2 A negative electrode was fabricated in the same manner as in Example 1, except that B(OH) was used as the acid. XRD analysis of the negative electrode slurry revealed that B(OH) and B(OLi) were present in the slurry.

[0138] Example 3 A negative electrode was fabricated in the same manner as in Example 1, except that Zn(OH)2 was used as the acid. XRD analysis of the negative electrode slurry detected Zn(OH)2 and a lithium zinc compound in the slurry.

[0139] Example 4 A negative electrode was fabricated in the same manner as in Example 1, except that ZrO(OH)2 was used as the acid. XRD analysis of the negative electrode slurry detected ZrO(OH)2 and a lithium zirconium compound in the slurry.

[0140] Example 5 A negative electrode was prepared in the same manner as in Example 1, except that the negative electrode active material, styrene-butadiene rubber (SBR) as a binder, Super C65 as a conductive material, carboxymethyl cellulose (CMC) as a thickener, and Al(OH)3 as an acid were mixed in a weight ratio of 93:2:1:1:3.

[0141] Comparative Example 1 A negative electrode active material was prepared in the same manner as in Example 1, except that the negative electrode active material, styrene-butadiene rubber (SBR) as a binder, Super C65 as a conductive material, and carboxymethyl cellulose (CMC) as a thickener were mixed in a weight ratio of 96:2:1:1.

[0142] Comparative Example 2 A negative electrode was prepared in the same manner as in Example 1, except that the negative electrode active material, styrene-butadiene rubber (SBR) as a binder, Super C65 as a conductive material, carboxymethyl cellulose (CMC) as a thickener, and Al(OH)3 as an acid were mixed in a weight ratio of 95.95:2:1:1:0.05.

[0143] Comparative Example 3 A negative electrode was prepared in the same manner as in Example 1, except that the negative electrode material, styrene-butadiene rubber (SBR) as a binder, Super C65 as a conductive material, carboxymethyl cellulose (CMC) as a thickener, and Al(OH)3 as an additive were mixed in a weight ratio of 90:2:1:1:6.

[0144] The compositions of the negative electrode slurries and negative electrodes prepared in the examples and comparative examples are as shown in Table 1 below.

[0145] [Table 1]

[0146] ICP analysis (measurement of elemental content) The contents of Al, B, Zn, and Zr elements contained in the negative electrode were confirmed by ICP analysis. Specifically, the ICP analysis was measured using an inductively coupled plasma optical emission spectrometer (ICPAES, Perkin-Elmer 7300).

[0147] XPS analysis (presence or absence of oxygen bonding) The presence or absence of the B-O, Al-O, Zn-O, and Zr-O bonds was confirmed by XPS (Nexsa ESCA System, Thermo Fisher Scientific (NEXSA 1)) analysis to determine whether peaks were detected in the bond energy range of each element with oxygen.

[0148] Measurement of gas generation rate The negative electrode slurries prepared in the examples and comparative examples were each placed in a 7 mL aluminum pouch and sealed.

[0149] The difference between the weight of the aluminum pouch containing the negative electrode slurry in air and the weight of the aluminum pouch in water at 23°C was calculated and divided by the density of water at 23°C to measure the volume of gas immediately after the production of the negative electrode slurry.

[0150] Next, the aluminum pouch containing the negative electrode slurry was stored at 60°C for 3 days, and then the difference between the weight of the aluminum pouch containing the negative electrode slurry in air and the weight of the aluminum pouch in water at 60°C was calculated, and this was divided by the density of water at 60°C to measure the volume of gas after storing the negative electrode slurry for 3 days.

[0151] The difference between the gas volume measured after storing the negative electrode slurry for 3 days and the gas volume measured immediately after producing the negative electrode slurry was defined as the amount of gas generated, and is shown in Table 1 above.

[0152] <Experimental example: Discharge capacity, initial efficiency, and life (capacity retention rate) characteristic evaluation> 1.7671cm 2 The 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 containing 0.5 parts by weight of vinylene carbonate dissolved in a 7:3 volumetric mixture of ethyl methyl carbonate (EMC) and ethylene carbonate (EC) and 1M LiPF6 was injected to fabricate a lithium coin half-cell.

[0153] The produced batteries were charged and discharged, and the discharge capacity, initial efficiency, and capacity retention rate were evaluated. The results are shown in Table 2 below.

[0154] The first and second cycles were charged and discharged at 0.1 C, and from the third cycle onwards, the charge and discharge rate was 0.5 C. The 300th cycle was completed in a charged state (with lithium contained in the negative electrode).

[0155] Charging conditions: CC (constant current) / CV (constant voltage) (5mV / 0.005C current cut-off) Discharge condition: CC (constant current) condition 1.5V

[0156] 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 (%) = (discharge capacity after one discharge / one charge capacity) × 100

[0157] The capacity retention rates were calculated as follows. Capacity retention rate (%) = (299 discharge capacity / 1 discharge capacity) × 100

[0158] [Table 2]

[0159] As can be seen from Table 2, the negative electrodes of Examples 1 to 5 contain 0.05 to 1.5 parts by weight of Al, B, Zn, or Zr in the negative electrode based on the negative electrode slurry solid content (negative electrode active material layer), and have a structure in which the element is bonded to oxygen, and it can be seen that they are all excellent in discharge capacity, initial efficiency, and capacity retention rate.

[0160] On the other hand, in Comparative Examples 1 and 2, where acid was not added or only a small amount was added during negative electrode production, resulting in either no Al or a small amount of Al in the negative electrode, it was confirmed that the discharge capacity, initial efficiency, and capacity retention rate were significantly reduced. Also, in Comparative Examples 1 and 2, because acid was not added or only a small amount was added during the negative electrode production process, the base in the negative electrode slurry was not properly neutralized and reacted with Si in the negative electrode active material, resulting in a slurry gas generation rate that was 40 times higher.

[0161] Furthermore, in the case of Comparative Example 3, in which an excess amount of acid was added during the production of the negative electrode, causing the negative electrode to contain an excess amount of Al, it was confirmed that the capacity of the negative electrode was reduced due to the excess Al, and that the excess Al acted as a resistor that hindered the diffusion of lithium ions, resulting in a decrease in the discharge capacity of the battery and a decrease in the initial efficiency and capacity retention rate.

Claims

1. A negative electrode including a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector, the negative electrode active material layer contains a silicon-based active material, The silicon-based active material is SiO ｘ (0<x<2) and silicon-based particles containing Li, the negative electrode active material layer contains one or more elements selected from the group consisting of boron and zinc in an amount of 0.05 parts by weight to 1.5 parts by weight based on a total of 100 parts by weight of the negative electrode active material layer; The structure includes one or more elements selected from the group consisting of boron and zinc elements bonded to oxygen, the one or more elements selected from the group consisting of boron and zinc are added as an acid containing the one or more elements selected from the group consisting of boron and zinc during a process of preparing a negative electrode slurry for producing the negative electrode active material layer; the structure in which one or more elements selected from the group consisting of boron and zinc are bonded to oxygen is a hydroxide containing one or more elements selected from the group consisting of boron and zinc.

2. 2. The negative electrode according to claim 1, wherein the one or more elements selected from the group consisting of boron and zinc are contained in an amount of 0.1 parts by weight to 1 part by weight based on a total of 100 parts by weight of the negative electrode active material layer.

3. 2. The negative electrode according to claim 1, wherein the structure in which one or more elements selected from the group consisting of boron and zinc elements are bonded to oxygen is a lithium boron compound or a lithium zinc compound.

4. 2. The negative electrode according to claim 1, wherein the silicon-based active material contains 5 to 10 parts by weight of Li based on a total of 100 parts by weight of the silicon-based active material.

5. The negative electrode according to claim 1 , wherein the silicon-based active material further comprises a carbon layer provided on at least a portion of the silicon-based particles.

6. The negative electrode according to claim 1 , wherein the negative electrode active material layer further comprises a carbon-based active material.

7. 7. The negative electrode according to claim 6, wherein the weight ratio of the silicon-based active material to the carbon-based active material (silicon-based active material:carbon-based active material) is 1:99 to 30:

70.

8. SiO ｘ (x<2) and Li-containing silicon-based active material, a conductive material, a binder, and an acid are mixed to form a negative electrode slurry; and 10. A method for manufacturing a negative electrode, comprising: applying the negative electrode slurry to at least one surface of a negative electrode current collector to form a negative electrode active material layer, the acid is an acid containing one or more elements selected from the group consisting of aluminum, boron, zinc, and zirconium; The acid containing one or more elements selected from the group consisting of aluminum, boron, zinc, and zirconium is mixed in an amount of 0.1 parts by weight to 5 parts by weight based on 100 parts by weight of the total solid content of the negative electrode slurry, The acid containing one or more elements selected from the group consisting of aluminum, boron, zinc and zirconium elements is Al(OH) ３ , B(OH) ３ , Zn(OH) ２ and ZrO(OH) ２ The method for producing a negative electrode is one or more selected from the group consisting of:

9. 9. The method for producing a negative electrode according to claim 8, wherein the acid containing one or more elements selected from the group consisting of aluminum, boron, zinc, and zirconium is mixed in an amount of 0.1 parts by weight to 4 parts by weight based on 100 parts by weight of a total solids content of the negative electrode slurry.

10. The method of claim 8 , wherein the negative electrode slurry further comprises a carbon-based active material.

11. The method for producing a negative electrode according to claim 8 , wherein the negative electrode slurry contains one or more elements selected from the group consisting of aluminum, boron, zinc, and zirconium.

12. A secondary battery comprising the negative electrode according to any one of claims 1 to 7.

13. A negative electrode slurry containing a silicon-based active material, The silicon-based active material is SiO ｘ (0<x<2) and silicon-based particles containing Li, the negative electrode slurry contains one or more elements selected from the group consisting of boron and zinc in an amount of 0.05 parts by weight to 1.5 parts by weight based on 100 parts by weight of the total solid content of the negative electrode slurry; The structure includes one or more elements selected from the group consisting of boron and zinc elements bonded to oxygen, the structure in which the one or more elements selected from the group consisting of boron and zinc are bonded to oxygen is a hydroxide containing the one or more elements selected from the group consisting of boron and zinc.

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