Silicon-containing negative electrode active material, negative electrode including the same, and secondary battery including the same

Abstract

The present invention includes a core and a carbon layer present on the core, the core comprising SiO x (0 < x < 2) and at least one metal atom, the at least one metal atom including at least one selected from the group consisting of Mg, Li, Al, and Ca, and the silicon-containing negative electrode active material having D 5 / D 50 of 0.5 or more, the silicon-containing negative electrode active material having D 5 of 3 μm or more, and the silicon-containing negative electrode active material having D 50 of 4 μm or more and 11 μm or less, a negative electrode including the same, and a secondary battery including the same.

Description

[Technical Field]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2021-0107512 filed with the Korean Intellectual Property Office on August 13, 2021, and Korean Patent Application No. 10-2022-0008544 filed with the Korean Intellectual Property Office on January 20, 2022, the contents of which are incorporated herein in their entirety.

[0002] The present invention relates to a silicon-containing negative electrode active material having a specific particle size distribution, a negative electrode containing the same, and a secondary battery containing the same. [Background technology]

[0003] The rapid increase in fossil fuel use has led to an increasing demand for alternative and clean energy, and one of the most actively researched fields in this area is the field of power generation and storage using electrochemical reactions.

[0004] Currently, secondary batteries are a typical example of electrochemical elements that use electrochemical energy, and their range of use is expanding. In recent years, with the increasing technological development and demand for portable devices such as portable computers, mobile phones, and cameras, the demand for secondary batteries as energy sources has rapidly increased. Among these secondary batteries, much research has been conducted on high-energy density, i.e., high-capacity lithium secondary batteries, which have been commercialized and are widely used.

[0005] Generally, a secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode includes a negative electrode active material that inserts and extracts lithium ions from the positive electrode. The negative electrode active material can be a silicon-containing active material with a large discharge capacity.

[0006] However, in the case of silicon-containing active materials, excessive volume changes occur during the driving process of the battery. For this reason, there is a problem that the battery life is reduced. Conventionally, in order to solve such a problem, a method of reducing the usage ratio of silicon-containing active materials or using a binder capable of exhibiting high negative electrode adhesion has been used. However, since it is not an improvement of the silicon-containing active material itself, there is a limit to solving the problem. In addition, a technique of making the silicon-containing active material porous so that volume expansion can be accommodated inside has also been used, but this has a problem that the capacity per unit weight of the negative electrode is reduced, and particles are broken during rolling after electrode manufacturing, resulting in a reduction in the effect.

[0007] Therefore, there is an urgent need to develop a silicon-containing negative electrode active material that can effectively improve the life characteristics of the battery.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] One problem to be solved by the present invention is to provide a silicon-containing negative electrode active material, a negative electrode including the same, and a secondary battery including the same, which can improve the capacity, efficiency, and / or life characteristics of the battery.

Means for Solving the Problems

[0010] One embodiment of the present invention includes a core and a carbon layer present on the core, the core includes SiO x (0 < x < 2) and at least one metal atom, the at least one metal atom includes at least one selected from the group consisting of Mg, Li, Al, and Ca, D5 / D 50 is 0.5 or more, D5 is 3 μm or more, D 50The present invention provides a silicon-containing negative electrode active material having a particle size of 4 μm or more and 11 μm or less.

[0011] One embodiment of the present invention provides a negative electrode comprising a negative electrode active material, the negative electrode active material comprising the silicon-containing negative electrode active material. One embodiment of the present invention provides a secondary battery including the negative electrode. [Effects of the Invention]

[0012] The silicon-containing negative electrode active material according to one embodiment of the present invention is D5 / D 50 is 0.5 or more, D5 is 3 μm or more, and D 50 The particle size of the silicon-containing anode active material is suitable because the particle size is between 4 μm and 11 μm, which prevents excessive side reactions with the electrolyte while facilitating lithium ion insertion / extraction during charge / discharge and prevents excessive swelling, thereby improving the capacity, efficiency, and / or life characteristics of the battery. Furthermore, the silicon-containing anode active material contains at least one metal atom, and the at least one metal atom exists in the form of a metal compound such as a metal silicate, which improves the initial efficiency of the battery. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will now be described in more detail to aid in understanding the invention. The terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best explain their inventions.

[0014] The terms used in this specification are merely used to describe exemplary embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless otherwise clearly indicated in the context.

[0015] It should be understood that in this specification, the terms "comprises," "includes," or "has" are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, but do not preclude the presence or possible addition of one or more other features, numbers, steps, components, or combinations thereof.

[0016] In this specification, D5 and D 50 can be defined as particle sizes corresponding to 5% and 50% of the cumulative volume on the particle size distribution curve (graph curve of particle size distribution diagram). max and D min may correspond to the largest particle size and the smallest particle size, respectively, in the particle size distribution curve of the particles. 50 , D max , and D min can be measured using, for example, the laser diffraction method. The laser diffraction method is generally capable of measuring particle sizes from the submicron range to several mm, and can provide results with high reproducibility and high resolution. 50 The measurement can be confirmed using a Microtrac device (manufacturer: Microtrac, model name: S3500) under the condition of a refractive index of 1.97, using water and a triton-X100 dispersant.

[0017] In this specification, the BET specific surface area can be measured by degassing the object to be measured using a BET measurement device (BEL-SORP-MAX, Nippon Bell) at 130°C for 2 hours and then performing N2 adsorption / desorption at 77K.

[0018] In this specification, the presence or absence and the content of metal 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 optical emission spectrometer (ICP-OES manufactured by Perkin-Elmer 7300, AVIO 500).

[0019] <Silicon-containing negative electrode active material> One embodiment of the present invention includes a core and a carbon layer provided on the core, and the core contains SiO x (0 < x < 2) and at least one metal atom, and the at least one metal atom includes at least one selected from the group consisting of Mg, Li, Al, and Ca, and D5 / D 50 is 0.5 or more, D5 is 3 μm or more, and D 50 is 4 μm or more and 11 μm or less, and provides a silicon-containing negative electrode active material.

[0020] In one embodiment of the present invention, the silicon-containing negative electrode active material includes a core. In one embodiment of the present invention, the core contains SiO x (0 < x < 2).

[0021] The SiO x (0 < x < 2) corresponds to a matrix in the silicon-containing negative electrode active material. The SiO x (0 < x < 2) may be in a form containing Si and SiO2, and the Si may form a phase. That is, the x corresponds to the number ratio of O to Si contained in the SiO x (0 < x < 2). When the silicon-containing negative electrode active material contains the SiO x (0 < x < 2), the discharge capacity of the secondary battery can be improved.

[0022] In one embodiment of the present invention, the core may contain a metal atom. The at least one metal atom may exist in at least one of the forms of a metal atom, a metal silicate, a metal silicide, and a metal oxide in the silicon-containing negative electrode active material.

[0023] The at least one metal atom may include at least one selected from the group consisting of Mg, Li, Al, and Ca. Thereby, the initial efficiency of the silicon-containing negative electrode active material can be improved.

[0024] Specifically, the metal atom may include one or more of Mg, Li, or Al. The silicon-containing negative electrode active material of the present invention may be in a form in which relatively small-sized particles are removed. When the metal atom is one or more of Mg, Li, or Al, doping can be uniformly performed up to the inside of the core, so that the production of the silicon-containing negative electrode active material having the above characteristics becomes smooth. Further, in the silicon-containing negative electrode active material having the particle size distribution of the present invention, since the size of the metal atom having a low atomic number is small and can be doped more uniformly up to the inside, the metal atom is most preferably Mg or Li.

[0025] The metal atom (such as Li, Mg) may be distributed on the surface and / or inside of the silicon-containing particles in a form doped into the silicon-containing particles. The metal atom is distributed on the surface and / or inside of the silicon-containing particles, can control the expansion / contraction of the volume of the silicon-containing particles to an appropriate level, and can play a role in preventing damage to the active material. Further, the metal atom may be included in terms of reducing the ratio of the irreversible phase (for example, SiO2) in SiO x (0 < x < 2) particles and increasing the efficiency of the active material.

[0026] The metal atom may exist in the form of a metal silicate. The metal silicate can be classified into a crystalline metal silicate and an amorphous metal silicate.

[0027] When the metal atom is Li, Li may exist in the form of at least one lithium silicate selected from the group consisting of Li2SiO3, Li4SiO4, and Li2Si2O5 in the core.

[0028] When the metal atom is Mg, Mg may be present in the core in the form of at least one magnesium silicate of Mg2SiO4 and MgSiO3.

[0029] In one embodiment of the present invention, the metal atoms may be included in an amount of 0.1 to 40 parts by weight, specifically 1 to 25 parts by weight, or more specifically 2 to 20 parts by weight, or 2 to 10 parts by weight, based on a total of 100 parts by weight of the silicon-containing negative electrode active material. If the content of the metal atoms exceeds the range of 0.1 to 40 parts by weight, the initial efficiency increases but the discharge capacity decreases as the content of the metal atoms increases. Therefore, when the content of the metal atoms is within the above range, suitable discharge capacity and initial efficiency can be achieved.

[0030] In one embodiment of the present invention, the metal atoms may be included in an amount of 1 to 25 parts by weight, more specifically, 2 to 20 parts by weight, or 2 to 10 parts by weight, based on a total of 100 parts by weight of the core. If the content of the metal atoms exceeds the range of 1 to 25 parts by weight, the initial efficiency increases as the content of the metal atoms increases, but the discharge capacity decreases. Therefore, when the content of the metal atoms is within the above range, suitable discharge capacity and initial efficiency can be achieved.

[0031] In one embodiment of the present invention, the silicon-containing negative electrode active material may include a carbon layer. The carbon layer may be provided on the core and cover at least a portion of the surface of the core. That is, the carbon layer may partially cover the surface of the core, or may cover the entire surface of the core. The carbon layer imparts conductivity to the silicon-containing negative electrode active material, thereby improving the initial efficiency, life characteristics, and capacity characteristics of the secondary battery.

[0032] The carbon layer may include at least one of amorphous carbon and crystalline carbon.

[0033] The crystalline carbon may further improve the conductivity of the silicon-containing negative electrode active material. The crystalline carbon may include at least one selected from the group consisting of fullerene, carbon nanotube, and graphene.

[0034] The amorphous carbon can appropriately maintain the strength of the carbon layer and suppress the expansion of the silicon-containing composite particles. The amorphous carbon may be a carbon-containing material formed by using at least one carbide selected from the group consisting of tar, pitch, and other organic substances, or a hydrocarbon as a source in a chemical vapor deposition process.

[0035] 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.

[0036] 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.

[0037] 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 a total of 100 parts by weight of the silicon-containing negative electrode active material. More specifically, the carbon layer may be included in an amount of 0.5 to 15 parts by weight. When the amount is within the range of 0.1 to 50 parts by weight, a decrease in the capacity and efficiency of the negative electrode active material can be prevented.

[0038] 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 in the range of 1 nm to 500 nm, the conductivity of the silicon-containing negative electrode active material is improved, and the initial efficiency and lifespan of the battery are improved.

[0039] In one embodiment of the present invention, D of the silicon-containing negative electrode active material 50 The D of the silicon-containing negative electrode active material may be 4 μm or more and 11 μm or less. 50 If the D of the silicon-containing negative electrode active material is less than 4 μm, the particle size is too small and the specific surface area of ​​the material is large, which causes many side reactions with the electrolyte and leads to an extreme deterioration in the lifespan. 50 If the D of the silicon-containing negative electrode active material is greater than 11 μm, the particle size is too large, making it difficult to charge and discharge, and thus making it difficult to achieve the required capacity / efficiency during charging and discharging. 50 When the D of the silicon-containing negative electrode active material is 4 μm or more and 11 μm or less, the charge / discharge is easy, the capacity / efficiency is sufficiently realized, and the life characteristics are stable. 50 The thickness may be 4.2 μm or more and 10 μm or less, specifically 4.5 μm or more and 9 μm or less, and more specifically 5 μm or more and 7 μm or less. In this case, in addition to the above-mentioned effects, the effect of facilitating the production of the electrode can be obtained.

[0040] In one embodiment of the present invention, the silicon-containing negative electrode active material may have a D5 of 3 μm or more. If the silicon-containing negative electrode active material has a D5 of less than 3 μm, the particle size is small and oxidation occurs frequently, resulting in relatively low capacity and efficiency. Furthermore, the small particle size increases side reactions with the electrolyte during charge / discharge, resulting in poor battery life characteristics. Therefore, if the D5 is within the above range of 3 μm or more, the amount of silicon-containing negative electrode active material with excessively small particle size in the negative electrode is reduced, thereby reducing side reactions with the electrolyte and improving battery life and stability. In particular, the silicon-containing negative electrode active material may have a D5 of 3 μm to 5.5 μm, specifically 3 μm to 5 μm, more specifically 3 μm to 4 μm or 3 μm to 3.6 μm.

[0041] D5 / D of the silicon-containing negative electrode active material 50 The D5 / D may be 0.5 or more, and specifically may be 0.6 or more. 50 If the D5 / D is less than 0.5, the volume occupied by the excessively small silicon-containing negative active material in the negative electrode increases, which increases the specific surface area of ​​the material and increases the side reaction with the electrolyte, resulting in a decrease in the battery life. 50 The D5 / D of the silicon-containing negative electrode active material is set to be 0.5 or more, thereby improving the life characteristics of the battery. 50 The upper limit of may be 1.

[0042] At this time, D5 and D 50 Even if D5 / D satisfies the above range, 50 If the value is less than 0.5, the negative electrode contains D 50 The volume occupied by the much smaller active material increases, which increases side reactions with the electrolyte and reduces the battery life. 50 Even if the value is 0.5 or more, D5 or D 50If D does not satisfy the above range, the average particle size will be too small or too large, resulting in problems such as difficulty in achieving the required life and / or efficiency. 50 If the value is small, the silicon-containing negative electrode active material particles are oxidized to a large extent, resulting in a decrease in capacity and efficiency, and a decrease in lifespan due to excessive side reactions with the electrolyte. 50 If the particle size is too large, it is difficult to charge and discharge the battery, which makes it difficult to achieve the required capacity and efficiency during charging and discharging.

[0043] Therefore, as in the present invention, D5 and D of the silicon-containing negative electrode active material 50 , and D5 / D 50 When these ranges are simultaneously satisfied, the capacity, efficiency, and / or life of the battery can be improved.

[0044] In one embodiment of the present invention, the BET specific surface area of ​​the silicon-containing negative electrode active material is 1 m 2 / g or more 20m 2 / g or less, and 2 / g or more 15m 2 / g or less, and 2 / g excess 10m 2 / g or less than 2.5m 2 / g or more 8m 2 / g or less.

[0045] The upper limit of the BET specific surface area is 20 m 2 / g, 18m 2 / g, 15m 2 / g, 10m 2 / g, 8m 2 / g, 5m 2 / g, or 4m 2 / g, with a lower limit of 1m 2 / g, 1.5m 2 / g, 2m 2 / g, or 2.5m 2 / g.

[0046] In one embodiment of the present invention, D of the silicon-containing negative electrode active material max The particle size may be 35 μm or less, specifically 30 μm or less, more specifically 25 μm or less, or 20 μm or less. If the particle size is not within the 35 μm or less range, the particles are too large, which can cause problems such as the electrodes not being manufactured smoothly and the electrodes being manufactured unevenly during rolling.

[0047] D of the silicon-containing negative electrode active material min may be 1.3 μm or more, specifically 1.5 μm or more, more specifically 1.7 μm or more, or 2 μm or more. If the range of 1.3 μm or more is satisfied, the specific surface area of ​​the material does not become excessively large, which has the effect of reducing side reactions with the electrolyte.

[0048] In one embodiment of the present invention, the silicon-containing negative electrode active material may be formed by the steps of: preparing a preliminary silicon-containing negative electrode active material; adjusting the particle size of the preliminary silicon-containing negative electrode active material; and forming a carbon layer on the preliminary silicon-containing negative electrode active material having the controlled particle size.

[0049] Specifically, in the step of preparing the preliminary silicon-containing negative electrode active material, the preliminary silicon-containing negative electrode active material may be formed by the steps of: mixing Si powder, SiO powder, and metal powder, followed by vaporizing the mixed gas; condensing the vaporized mixed gas into a solid phase; and heat-treating the mixed gas in an inert atmosphere.

[0050] Alternatively, the preliminary silicon-containing negative electrode active material may be formed by the steps of: heating Si powder and SiO powder in a vacuum to vaporize them, and then depositing the vaporized mixed gas to form silicon-containing particles; and mixing the formed silicon-containing particles with a metal powder, followed by heat treatment.

[0051] The heat treatment step may be performed at 700° C. to 900° C. for 4 to 6 hours, and specifically at 800° C. for 5 hours.

[0052] The metal powder may be Mg powder or Li powder. When Mg powder is used as the metal powder, it may be vaporized to produce the negative electrode active material.

[0053] When Li powder is used as the metal powder, the negative electrode active material may be prepared by mixing silicon-containing particles and Li powder and then heat-treating the mixture.

[0054] The silicon-containing particles are SiO x (x=1) is also acceptable. In the preliminary silicon-containing negative electrode active material, the Mg compound phase may include the above-mentioned Mg silicate, Mg silicide, Mg oxide, or the like.

[0055] In the preliminary silicon-containing negative electrode active material, the Li compound phase may include the above-mentioned Li silicate, Li silicide, Li oxide, etc.

[0056] The particle size of the preliminary silicon-containing negative active material may be adjusted by, but is not limited to, a ball mill, a jet mill, or air classification. For example, when adjusting the particle size of the preliminary silicon-containing negative active material using a ball mill, 5 to 20 stainless steel ball media, specifically 10 to 15 stainless steel ball media, may be added, but is not limited to, the number of stainless steel ball media.

[0057] In the step of adjusting the particle size, the grinding time of the preliminary silicon-containing negative electrode active material may be 2 hours to 5 hours, specifically 2 hours to 4 hours, and more specifically 3 hours, but is not limited thereto.

[0058] In the step of forming the carbon layer, the carbon layer may be manufactured by using a chemical vapor deposition (CVD) method using a hydrocarbon gas, or by carbonizing a material serving as a carbon source.

[0059] Specifically, the silicon-containing negative electrode active material may be charged into a reactor, and then subjected to chemical vapor deposition (CVD) of a hydrocarbon gas 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.

[0060] <Negative electrode> The negative electrode according to one embodiment of the present invention may include a negative electrode active material, and the negative electrode active material may include the silicon-containing negative electrode active material described above.

[0061] In an embodiment of the present invention, the negative electrode active material may further include a carbon-containing negative electrode active material, which may be at least one selected from natural graphite, artificial graphite, and the like.

[0062] In one embodiment of the present invention, the weight ratio of the silicon-containing negative electrode active material to the carbon-containing negative electrode active material in the negative electrode active material may be 10:90 to 90:10, specifically 10:90 to 50:50.

[0063] 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. The negative electrode active material layer may further include a binder and / or a conductive material.

[0064] The negative electrode current collector is not particularly limited as long as it does not induce 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 thereto.

[0065] The binder may include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), 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.

[0066] The conductive material is not particularly limited as long as it does not induce chemical changes in the battery and is conductive, and examples thereof include 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; fluorocarbon powder; metal powder such as 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.

[0067] In one embodiment of the present invention, the negative electrode may be manufactured by the steps of: preparing a negative electrode slurry including a negative electrode active material, a binder, a conductive material, and a solvent; applying the negative electrode slurry to at least one surface of a current collector, drying the current collector, and rolling the current collector to form a negative electrode active material layer; and drying the current collector on which the negative electrode active material layer is formed.

[0068] <Secondary battery> A secondary battery according to an embodiment of the present invention may include the negative electrode according to the embodiment described above. Specifically, the secondary battery may include a negative electrode, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, and the negative electrode is the same as the negative electrode described above. Since the negative electrode has been described above, detailed description thereof will be omitted.

[0069] The positive electrode may include a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector and containing the positive electrode active material.

[0070] The positive electrode current collector in the positive electrode is not particularly limited as long as it does not induce chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-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 the surface of the current collector may be formed with fine irregularities 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.

[0071] 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 M c3 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).

[0072] 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.

[0073] In this case, the positive electrode conductive material is used to impart conductivity to the electrode, and can be used without any particular limitation as long as it 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-containing 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, and the like, and one or more of these may be used alone or in combination.

[0074] 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. One or more of these may be used alone or in combination.

[0075] The separator separates the negative electrode and positive electrode and provides a path for lithium ion migration. Any separator typically used in secondary batteries can be used without particular limitations. It is particularly preferable that the separator exhibits low resistance to electrolyte ion migration 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.

[0076] Examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in manufacturing lithium secondary batteries. Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0077] 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.

[0078] 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 in an appropriate ratio with linear carbonates having low viscosity and low dielectric constants, such as dimethyl carbonate and diethyl carbonate, an electrolyte having high conductivity can be prepared, and therefore these cyclic carbonates are even more preferably used.

[0079] The metal salt may be a lithium salt, which is a substance that is easily dissolved in the non-aqueous electrolyte. 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:

[0080] In addition to the constituent components of the electrolyte, the electrolyte may further include one or more additives, such as a haloalkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, 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.

[0081] 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-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems. [Example]

[0082] Below, preferred examples are presented to help understand the present invention. However, the following 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, and it goes without saying that such changes and modifications fall within the scope of the appended claims.

[0083] <Examples and Comparative Examples> Example 1-1 94g of powder of Si and SiO2 mixed at a 1:1 molar ratio and 6g of Mg were mixed in a reactor and then vacuum heated at a sublimation temperature of 1,400°C. The vaporized Si, SiO2, and Mg mixed gas was then reacted in a vacuum cooling zone with a cooling temperature of 800°C and solidified. A heat treatment was then performed in an inert atmosphere at a temperature of 800°C (additional heat treatment temperature) to produce a preliminary silicon-containing negative electrode active material. The preliminary silicon-containing negative electrode active material was then milled for 3 hours using a ball mill with 15 stainless steel ball media added. 50 Then, while maintaining an inert atmosphere by flowing Ar gas, the preliminary silicon-containing negative electrode active material was placed in the hot zone of a CVD apparatus, and the methane was blown into the hot zone at 900°C using Ar as a carrier gas for 10 minutes. -1 Torr was used for the reaction for 20 minutes to prepare a silicon-containing negative electrode active material having a carbon layer formed on the surface.

[0084] Example 1-2 A silicon-containing negative active material was prepared in the same manner as in Example 1-1, except that 10 stainless steel ball media were added.

[0085] Example 2-1 In the method of Example 1-1, 94 g of SiO particles were synthesized without using Mg, and then 6 g of Li metal powder was added and heat-treated in an inert atmosphere at a temperature of 800°C to produce a pre-silicon-containing negative electrode active material. Then, the pre-silicon-containing negative electrode active material was milled for 3 hours using a ball mill with 15 stainless steel ball media. 50 Then, while maintaining an inert atmosphere by flowing Ar gas, the preliminary silicon-containing negative electrode active material was placed in the hot zone of a CVD apparatus, and the methane was blown into the hot zone at 900°C using Ar as a carrier gas for 10 minutes. -1 Torr was used for the reaction for 20 minutes to prepare a silicon-containing negative electrode active material having a carbon layer formed on the surface.

[0086] Example 2-2 A silicon-containing negative active material was prepared in the same manner as in Example 2-1, except that 10 stainless steel ball media were added.

[0087] Comparative Example 1-1 A silicon-containing negative electrode active material was prepared in the same manner as in Example 1-1, except that the grinding time was changed to 8 hours.

[0088] Comparative Example 1-2 A silicon-containing negative electrode active material was prepared in the same manner as in Example 1-1, except that the grinding time was changed to 1 hour.

[0089] Comparative Examples 1-3 A silicon-containing negative electrode active material was prepared in the same manner as in Example 1-1, except that the grinding time was changed to 5 hours.

[0090] Comparative Examples 1-4 A silicon-containing negative active material was prepared in the same manner as in Example 1-1, except that 10 stainless steel ball media were added and the grinding time was changed to 5 hours.

[0091] Comparative Examples 1-5 A silicon-containing negative active material was prepared in the same manner as in Example 1-1, except that 30 stainless steel ball media were added and the grinding time was changed to 8 hours.

[0092] Comparative Examples 1-6 A silicon-containing negative active material was prepared in the same manner as in Example 1-1, except that 30 stainless steel ball media were added and the grinding time was changed to 1 hour.

[0093] Comparative Examples 1-7 A silicon-containing negative active material was prepared in the same manner as in Example 1-1, except that 30 stainless steel ball media were added.

[0094] Comparative Example 2-1 A silicon-containing negative electrode active material was prepared in the same manner as in Example 2-1, except that the grinding time was changed to 8 hours.

[0095] Comparative Example 2-2 A silicon-containing negative electrode active material was prepared in the same manner as in Example 2-1, except that the grinding time was changed to 1 hour.

[0096] Comparative Example 2-3 A silicon-containing negative electrode active material was prepared in the same manner as in Example 2-1, except that the grinding time was changed to 5 hours.

[0097] Comparative Example 2-4 A silicon-containing negative electrode active material was prepared in the same manner as in Example 2-1, except that 10 stainless steel ball media were added and the grinding time was changed to 5 hours.

[0098] Comparative Example 2-5 A silicon-containing negative active material was prepared in the same manner as in Example 2-1, except that 30 stainless steel ball media were added and the grinding time was changed to 8 hours.

[0099] Comparative Example 2-6 A silicon-containing negative active material was prepared in the same manner as in Example 2-1, except that 30 stainless steel ball media were added and the grinding time was changed to 1 hour.

[0100] Comparative Example 2-7 A silicon-containing negative active material was prepared in the same manner as in Example 2-1, except that 30 stainless steel ball media were added.

[0101] The silicon-containing negative electrode active materials prepared in the examples and comparative examples are shown in Table 1 below.

[0102] [Table 1]

[0103] The particle size analysis of the silicon-containing negative electrode active material was performed using a Microtrac device (manufacturer: Microtrac, model name: S3500) under the condition of a refractive index of 1.97, using water and a triton-X100 dispersant.

[0104] The specific surface area was measured using a BET measuring device (BEL-SORP-MAX, Nippon Bell) by degassing at 130° C. for 2 hours and then performing N 2 adsorption / desorption at 77K.

[0105] The content of the metal atoms was confirmed by ICP analysis using an inductively coupled plasma optical emission spectrometer (ICP-OES, AVIO 500, manufactured by Perkin-Elmer 7300).

[0106] <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.

[0107] 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. 7.8 g of distilled water was then added to 5 g of the mixture and stirred to prepare a negative electrode slurry. The negative electrode slurry was applied to a 20 μm-thick copper (Cu) metal thin film as a negative electrode current collector 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.

[0108] The manufactured negative electrode was placed in a 1.7671 cm 2 Cut into circles 、 Lithium (Li) metal thin film Used as a counter electrode The above Opposite 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 1M LiPF6 was injected to prepare a lithium coin half-cell.

[0109] The produced 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.

[0110] 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 in the negative electrode).

[0111] Charging conditions: CC (constant current) / CV (constant voltage) (5mV / 0.005C current cut-off) Discharge condition: CC (constant current) condition 1.5V

[0112] 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 1 discharge / 1st charge capacity) x 100 The capacity retention rates were calculated as follows. Capacity retention rate (%) = (300th discharge capacity / 1st discharge capacity) × 100

[0113] [Table 2]

[0114] The silicon-containing negative electrode active material according to the present invention contains metal atoms and 50 is 0.5 or more, D5 is 3 μm or more, and D 50 is 4 μm or more and 11 μm or less, and suitable D5, D 50 , and D5 / D 50 By having the particle size distribution, side reactions with the electrolyte are suppressed, charge and discharge are easy, capacity / efficiency is sufficiently realized, and life characteristics are stable.

[0115] In Table 2, Examples 1-1 and 1-2 are negative electrode active materials containing Mg, and D5 / D 50 value or D5 value and D 50It can be seen that Examples 2-1 and 2-2 are negative electrode active materials containing Li, and are superior to Comparative Examples 2-1 to 2-7 in terms of discharge capacity, initial efficiency, and capacity retention rate.

[0116] In contrast, the comparative example 1-5 is the D5 / D of the present invention 50 , D5, D 50 In the case of Comparative Examples 1-1 to 1-4, the D5 / D of the present invention is not satisfied. 50 Although it satisfies the above, D5 or D 50 It was confirmed that the above conditions were not satisfied and the capacity, efficiency, and lifespan were lower than those of the examples.

[0117] Specifically, D5 / D 50 Even if D5 is 0.5 or more, if D5 is less than 3 μm or D 50 When the particle size is less than 4 μm, the overall particle size is too small, the specific surface area of ​​the material is large, and oxidation occurs frequently. Therefore, it was confirmed that side reactions with the electrolyte occur frequently during charge / discharge, resulting in lower capacity, efficiency, and lifespan than in the examples.

[0118] Also, D5 / D 50 Even if is 0.5 or more, D 50 When the particle size exceeds 11 μm, the overall particle size is too large, making charge / discharge difficult, and it was confirmed that the capacity, efficiency, and lifespan are lower than those of the examples.

[0119] Also, D5 / D 50 If the value is less than 0.5, the negative electrode contains D 50 It was confirmed that the volume occupied by the much smaller negative electrode active material increases, which increases side reactions with the electrolyte, resulting in lower capacity, efficiency, and lifespan than in the examples.

[0120] Therefore, the negative electrode active material of the present invention is D5 / D 50 is 0.5 or more, D5 is 3 μm or more, and D 50 By satisfying the value of 4 μm to 11 μm, particle oxidation can be minimized, side reactions with the electrolyte can be reduced, and the capacity, efficiency, and / or lifespan of the battery can be easily improved.

Claims

1. A silicon-containing negative electrode active material comprising a core and a carbon layer on the core, The core is made of SiO ｘ (0<x<2) and at least one metal atom; the at least one metal atom comprises Mg or Li; The silicon-containing negative electrode active material is D ５ / D ５０ is 0.6 or more, The silicon-containing negative electrode active material is D ５ is 3 μm or more, and D ５０ is 4 μm or more and 11 μm or less, The silicon-containing negative electrode active material contains the at least one metal atom in an amount of 0.1 parts by weight to 40 parts by weight, based on a total of 100 parts by weight of the silicon-containing negative electrode active material.

2. The silicon-containing negative electrode active material is D ５ / D ５０ The silicon-containing negative electrode active material according to claim 1 , wherein the σ is 0.6 or more and 1 or less.

3. The silicon-containing negative electrode active material is D ５０ The silicon-containing negative electrode active material according to claim 1 , wherein the average particle size is 4.2 μm or more and 10 μm or less.

4. The silicon-containing negative electrode active material is D ５ The silicon-containing negative electrode active material according to claim 1 , wherein the average particle size is 3 μm or more and 5.5 μm or less.

5. The silicon-containing negative electrode active material is D ｍａｘ The silicon-containing negative electrode active material according to claim 1 , wherein the average particle size is 35 μm or less.

6. The silicon-containing negative electrode active material according to claim 1 , wherein the carbon layer is contained in an amount of 0.1 parts by weight to 50 parts by weight based on a total of 100 parts by weight of the silicon-containing negative electrode active material.

7. The silicon-containing negative electrode active material has a BET specific surface area of ​​2 m ２ / g excess 10m ２ 2. The silicon-containing negative electrode active material according to claim 1, wherein the silicon content is less than 1 / g.

8. a negative electrode active material, The negative electrode, wherein the negative electrode active material comprises the silicon-containing negative electrode active material according to claim 1 .

9. The anode of claim 8 , wherein the anode active material further comprises a carbon-containing anode active material.

10. a negative electrode current collector; and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, The negative electrode according to claim 8 , wherein the negative electrode active material layer contains the negative electrode active material.

11. A secondary battery comprising the negative electrode according to claim 8.

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