CN116724417A

CN116724417A - Silicon-containing anode active material, anode comprising same, and secondary battery comprising same

Info

Publication number: CN116724417A
Application number: CN202280012355.5A
Authority: CN
Inventors: 崔静贤; 李秀民; 申善英; 李龙珠
Original assignee: LG Energy Solution Ltd
Current assignee: LG Energy Solution Ltd
Priority date: 2021-08-13
Filing date: 2022-08-09
Publication date: 2023-09-08

Abstract

A silicon-containing anode active material, an anode including the same, and a secondary battery including the same, the silicon-containing anode active material including a core and a carbon layer disposed on the core, wherein the core includes SiO _x And at least one metal atom, wherein 0<x<2, the at least one metal atom comprises at least one selected from the group consisting of Mg, li, al and Ca, D ₅ /D ₅₀ Is more than 0.5, D ₅ Is above 3 μm and D ₅₀ 4 μm or more and 11 μm or less.

Description

Silicon-containing anode active material, anode comprising same, and secondary battery comprising same

Technical Field

The present application claims priority and benefit from korean patent application No. 10-2021-0107512 filed on the korean intellectual property office at day 2021, 8 and 13 and korean patent application No. 10-2022-0008544 filed on the korean intellectual property office at day 2022, 1 and 20, the entire contents of which are incorporated herein by reference.

The present application relates to a silicon-containing anode active material having a specific particle size distribution, an anode including the same, and a secondary battery including the same.

Background

Due to the rapid increase in the use of fossil fuels, the demand for using alternative energy or clean energy increases, and as part of this trend, the most actively studied fields are the power generation and storage fields using electrochemical reactions.

At present, representative examples of electrochemical devices using such electrochemical energy include secondary batteries, and the fields of use thereof are increasing. In recent years, as the technological development and demand for portable devices such as portable computers, portable telephones, cameras have increased, the demand for secondary batteries as energy sources has sharply increased, a great deal of research has been conducted on lithium secondary batteries having high energy density, i.e., high capacity, among such secondary batteries, and lithium secondary batteries having high capacity have been commercialized and widely used.

In general, a secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode contains a negative electrode active material for inserting and extracting lithium ions from a positive electrode, and a silicon-containing active material having a high discharge capacity can be used as the negative electrode active material.

However, silicon-containing active materials are accompanied by excessive volume changes during driving of the battery. Therefore, there is a problem in that the service life of the battery is reduced. In order to solve these problems in the related art, the following method is used: reducing the proportion of the silicon-containing active material used or using a binder capable of exhibiting high negative electrode adhesion, however, has a limitation in solving the problem since the silicon-containing active material itself is not improved. Further, although a technique capable of accommodating volume expansion inside by making the silicon-containing active material porous has been used, this technique has the following problems: since the capacity per unit weight of the negative electrode is reduced and particles are destroyed when rolling is performed after the electrode is prepared, the effect is reduced.

Therefore, there is an urgent need to develop a silicon-containing anode active material capable of effectively improving the service life characteristics of a battery.

[ related art literature ]

[ patent literature ]

(patent document 1) Korean patent No. 10-1586816

Disclosure of Invention

Technical problem

The present application has been made in an effort to provide a silicon-containing anode active material capable of improving capacity, efficiency and/or service life characteristics of a battery, an anode including the same, and a secondary battery including the same.

Technical proposal

Exemplary embodiments of the present application provide a silicon-containing anode active material comprising a core and a carbon layer on the core, wherein the core comprises SiO _x (0<x<2) And at least one metal atom containing at least one selected from the group consisting of Mg, li, al, and Ca, D ₅ /D ₅₀ Is more than 0.5, D ₅ Is more than 3 mu m, D ₅₀ 4 μm or more and 11 μm or less.

Another exemplary embodiment of the present application provides an anode including an anode active material, wherein the anode active material includes the above-described silicon-containing anode active material.

Still another exemplary embodiment of the present application provides a secondary battery including the negative electrode.

Advantageous effects of the application

The silicon-containing anode active material according to the exemplary embodiment of the present application has D of 0.5 or more ₅ /D ₅₀ D of 3 μm or more ₅ And D of 4 μm or more and 11 μm or less ₅₀ So that lithium ions are easily intercalated and deintercalated during charge and discharge without causing excessive side reactions with the electrolyte, and without causing excessive expansion, thus enabling improvement in capacity, efficiency, and/or life characteristics of the battery. In addition, since the silicon-containing anode active material contains at least one metal atom, which exists in the form of a metal compound such as a metal silicate, the initial efficiency of the battery can be improved.

Detailed Description

Hereinafter, the present application will be described in more detail to aid understanding of the present application.

The terms or words used in the present specification and claims should not be construed as limited to normal meanings or meanings in dictionaries, but should be construed as meaning and concept according to the technical spirit of the present application on the basis of the principle that the inventor can properly define the concept of terms to best explain his/her own application.

The terminology used in the description presented herein is for the purpose of describing exemplary embodiments only and is not intended to be limiting of the application. Singular expressions include plural expressions unless the context clearly indicates otherwise.

In the present application, the terms "comprises," "comprising," or "having" are intended to indicate the presence of implemented features, amounts, steps, components, or any combination thereof, and are to be understood to mean that the possibility of one or more other features or amounts, steps, components, or any combination thereof being present or added is not precluded.

In the present specification, D ₅ And D ₅₀ Can be defined as particle sizes corresponding to 5% and 50% of the cumulative volume in the particle size distribution curve (curve of the particle size distribution curve), respectively, of the particles. In addition, in the present specification, D _{Maximum value} And D _{Minimum of} May correspond to the maximum particle size and the minimum particle size, respectively, in the particle size distribution curve of the particles. D (D) ₅ 、D ₅₀ 、D _{Maximum value} And D _{Minimum of} Can be respectively used by, for example, laser diffraction methodAnd (5) measuring. The laser diffraction method is generally capable of measuring particle sizes ranging from a submicron region to about several millimeters, and can obtain results of high reproducibility and high resolution. D (D) ₅ And D ₅₀ The measurement of (c) can be confirmed using a Microtrac apparatus (manufacturer: microtrac company, model name: S3500) using water and Triton-X100 dispersant at a refractive index of 1.97.

In the present specification, the BET specific surface area can be measured by degassing a measurement object at 130℃for 2 hours using a BET measuring apparatus (BEL-SORP-MAX, bell corporation, japan), and N at 77K ₂ Adsorption/desorption.

In this specification, the presence or absence of a metal element and the content of the element in the anode active material can be confirmed by ICP analysis, and the ICP analysis can be performed using an inductively coupled plasma atomic emission spectrometer (ICP-OES AVIO 500 of Perkin-Elmer 7300).

<Silicon-containing negative electrode active material>

An exemplary embodiment of the present application provides a silicon-containing anode active material layer including a core and a carbon layer disposed on the core, wherein the core includes SiO _x (0<x<2) And at least one metal atom comprising at least one selected from the group consisting of Mg, li, al and Ca, D ₅ /D ₅₀ Is more than 0.5, D ₅ Is more than 3 mu m, D ₅₀ 4 μm or more and 11 μm or less.

In an exemplary embodiment of the present application, the silicon-containing anode active material includes a core.

In an exemplary embodiment of the application, the core comprises SiO _x (0<x<2)。

The SiO is _x (0<x<2) May correspond to a matrix in the silicon-containing anode active material. The SiO is _x (0<x<2) Can be Si and SiO containing ₂ And the Si may also form a phase. That is, x corresponds to that contained in SiO _x (0<x<2) The ratio of O to Si in the mixture. When the silicon-containing anode active material contains SiO _x (0<x<2) When this is done, the discharge capacity of the secondary battery can be improved.

In an exemplary embodiment of the present application, the core may include a metal atom. The at least one metal atom may be present in the silicon-containing anode active material in the form of at least one of a metal atom, a metal silicate, a metal silicide, and a metal oxide.

The at least one metal atom may include at least one selected from the group consisting of Mg, li, al, and Ca. Thus, the initial efficiency of the silicon-containing anode active material can be improved.

Specifically, the metal atom may contain one or more of Mg, li, or Al. The silicon-containing anode active material of the present application may be in a form in which relatively small-sized particles are removed, but when the metal atom is one or more of Mg, li, or Al, since even the inside of the core may be uniformly doped, the silicon-containing anode active material having the above-described characteristics may be smoothly prepared. In addition, in the silicon-containing anode active material having the particle size distribution of the present application, since metal atoms having a low atomic number are small, they can be doped more uniformly up to the inside of the core, and thus the metal atoms are most preferably Mg or Li.

The metal atoms (Li, mg, etc.) are in a form in which silicon-containing particles are doped with the atoms, and thus may be distributed on the surface and/or inside of the silicon-containing particles. The metal atoms are distributed on the surface and/or inside of the silicon-containing particles, so that the volume expansion/contraction of the silicon-containing particles can be controlled to a proper level and can be used to prevent damage to the active material. In addition, from SiO reduction _x (0<x<2) Irreversible phases in particles (e.g. SiO ₂ ) In terms of improving the efficiency of the active material, the metal atom may be contained.

The metal atoms may be present in the form of metal silicates. The metal silicate may be classified into crystalline metal silicate and amorphous metal silicate.

When the metal atom is Li, li may be selected from Li ₂ SiO ₃ 、Li ₄ SiO ₄ And Li (lithium) ₂ Si ₂ O ₅ At least one form of lithium silicate from the group consisting is present in the core.

When the metal atom is Mg, mg may be as Mg ₂ SiO ₄ And MgSiO ₃ The morphology of at least one magnesium silicate is present in the core.

In an exemplary embodiment of the present application, the content of the metal atoms may be 0.1 parts by weight or more and 40 parts by weight or less, specifically 1 part by weight or more and 25 parts by weight or less, more specifically 2 parts by weight or more and 20 parts by weight or 2 parts by weight or more and 10 parts by weight or less, based on 100 parts by weight of the silicon-containing anode active material in total. When the content of the metal atoms exceeds the above range of 0.1 parts by weight or more and 40 parts by weight or less, the following problems may exist: as the content of metal atoms increases, the initial efficiency increases, but the discharge capacity decreases, so that when the content satisfies the above range, an appropriate discharge capacity and initial efficiency can be achieved.

In an exemplary embodiment of the present application, the content of the metal atoms may be 1 part by weight or more and 25 parts by weight or less, more specifically 2 parts by weight or more and 20 parts by weight or less or 2 parts by weight or more and 10 parts by weight or less, based on 100 parts by weight of the core in total. When the content of the metal atoms exceeds the above range of 1 part by weight or more and 25 parts by weight or less, the following problems may occur: as the content of metal atoms increases, the initial efficiency increases, but the discharge capacity decreases, so that when the content satisfies the above range, an appropriate discharge capacity and initial efficiency can be achieved.

In an exemplary embodiment of the present application, the silicon-containing anode active material may include a carbon layer. The carbon layer is disposed on the core and may cover at least a portion of a surface of the core. That is, the carbon layer may be in a form of partially covering the surface of the core or covering the entire surface of the core. By the carbon layer, conductivity can be imparted to the silicon-containing anode active material, and initial efficiency, service life characteristics, and battery capacity characteristics of the secondary battery can be improved.

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

The crystalline carbon may further improve the conductivity of the silicon-containing anode active material. The crystalline carbon may contain at least one selected from the group consisting of fullerenes, carbon nanotubes, and graphene.

The amorphous carbon can suppress expansion of the silicon-containing composite particles by properly maintaining the strength of the carbon layer. The amorphous carbon may be a carbide of at least one selected from the group consisting of tar, pitch, and other organic materials, or a carbonaceous material formed using hydrocarbon as a source of a chemical vapor deposition method.

The carbide of the other organic material may be a carbide of sucrose, glucose, galactose, fructose, lactose, mannose, ribose, aldohexose or ketohexose and a carbide of an organic material selected from a combination thereof.

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. Examples of the aromatic hydrocarbon of the substituted or unsubstituted aromatic hydrocarbon include benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, benzofuran, pyridine, anthracene, phenanthrene, and the like.

In an exemplary embodiment of the present application, the content of the carbon layer may be 0.1 part by weight or more and 50 parts by weight or less, 0.1 part by weight or more and 30 parts by weight or less, or 0.1 part by weight or more and 20 parts by weight or less, based on 100 parts by weight of the total of the silicon-containing anode active material. More specifically, the content of the carbon layer may be 0.5 parts by weight or more and 15 parts by weight or less. When the above-described range of 0.1 part by weight or more and 50 parts by weight or less is satisfied, the capacity and efficiency of the anode active material can be prevented from being lowered.

In an exemplary embodiment of the present application, the thickness of the carbon layer may be 1nm to 500nm, and particularly, 5nm to 300nm. When the above-mentioned range of 1nm to 500nm is satisfied, the conductivity of the silicon-containing anode active material may be improved, so that there is an effect of improving the initial efficiency and the service life of the battery.

In an exemplary embodiment of the present application, the silicon-containing anode active material may have D of 4 μm or more and 11 μm or less ₅₀ . When the silicon-containing anode active material has a D of less than 4 μm ₅₀ At this time, the particle size may be so small that the specific surface area of the material increases, and there may be a problem in that the service life is seriously deteriorated due to many side reactions with the electrolyte. D when the silicon-containing anode active material ₅₀ Above 11 μm, the particle size may be too large so that the battery is not easily charged and discharged, and thus there may be a problem in that it is difficult to achieve capacity/efficiency during charge and discharge. Thus, when D of the silicon-containing anode active material ₅₀ When it is 4 μm or more and 11 μm or less, the battery can be easily charged and discharged, so that there can be an effect that capacity and efficiency are sufficiently achieved and service life characteristics are stable. In particular, the silicon-containing anode active material may have a D of 4.2 μm or more and 10 μm or less, specifically 4.5 μm or more and 9 μm or less, more specifically 5 μm or more and 7 μm or less ₅₀ . In this case, there may be an effect that the electrode can be easily prepared in addition to the above-described effects.

In an exemplary embodiment of the present application, the silicon-containing anode active material may have a D of 3 μm or more ₅ . D when the silicon-containing anode active material ₅ When it is smaller than 3. Mu.m, oxidation may frequently occur due to small particle size, and thus there may be a problem that capacity and efficiency become relatively small. Further, since the particle size is small, side reactions with the electrolyte during charge/discharge may increase, and thus there may be a problem in that the life characteristics are deteriorated. Therefore, when the above-mentioned range of 3 μm or more is satisfied, the content of the silicon-containing anode active material having too small a particle size in the anode can be reduced, so that the service life and stability of the battery can be improved by reducing side reactions with the electrolyte. In particular, the silicon-containing anode active material may have a thickness of 3 μm or more and 5.5 μm or less, specifically 3 μm or more andd of 5 μm or less, more specifically 3 μm or more and 4 μm or less or 3 μm or more and 3.6 μm or less ₅ 。

The silicon-containing anode active material may have a D of 0.5 or more, specifically 0.6 or more ₅ /D ₅₀ . When D is ₅ /D ₅₀ Below 0.5, the volume occupied by the undersized silicon-containing anode active material in the anode may increase, and there may be a problem in that the service life of the battery decreases, since side reactions with the electrolyte may increase with an increase in the specific surface area of the material. Thus, let D ₅ /D ₅₀ And satisfies 0.5 or more, thereby improving the service life characteristics of the battery. D of the silicon-containing anode active material ₅ /D ₅₀ The upper limit may be 1.

In this case, when D ₅ /D ₅₀ Less than 0.5, even if D of the silicon-containing anode active material ₅ And D ₅₀ Satisfying the above range, since the size in the anode is smaller than D ₅₀ The volume occupied by the active material of (c) may increase and side reactions with the electrolyte may increase, thereby possibly decreasing the service life of the battery. In contrast, when D ₅ /D ₅₀ Satisfy 0.5 or more but D ₅ Or D ₅₀ When the above range is not satisfied, the average particle size may be too small or too large, thereby posing a problem that it is difficult to achieve the service life and/or efficiency. When D is ₅ Or D ₅₀ In the hour, there are problems in that capacity and efficiency are reduced due to oxidation of a large amount of silicon-containing anode active material particles, and service life characteristics are deteriorated due to excessive electrolyte side reactions. When D is ₅₀ At high levels, the granularity is too large to allow the battery to be easily charged and discharged, so that there is a problem in that it is difficult to achieve capacity/efficiency during charging and discharging.

Thus, as in the present application, when D of the silicon-containing anode active material ₅ 、D ₅₀ And D ₅ /D ₅₀ When the above range is satisfied, the capacity, efficiency, and/or service life and/or efficiency of the battery can be improved.

In an exemplary embodiment of the present application, the silicon-containing anode active material may have a thickness of 1m ² Above/g and20m ² per gram of less than 1m ² Above/g and 15m ² Less than/g and greater than 2m ² /g and less than 10m ² /g, or 2.5m ² Above/g and 8m ² BET specific surface area of not more than/g.

The BET specific surface area may have an upper limit of 20m ² /g、18m ² /g、15m ² /g、10m ² /g、8m ² /g、5m ² /g or 4m ² /g, the lower limit of which may be 1m ² /g、1.5m ² /g、2m ² /g or 2.5m ² /g。

In an exemplary embodiment of the present application, the silicon-containing anode active material may have D of 35 μm or less, specifically 30 μm or less, more specifically 25 μm or less, or 20 μm or less _{Maximum value} . When the above-mentioned range of 35 μm or less is not satisfied, there is a problem in that the electrode may be not easily produced due to excessively large particles, and the electrode may be unevenly produced during rolling.

The silicon-containing anode active material may have a D of 1.3 μm or more, specifically 1.5 μm or more, more specifically 1.7 μm or more, or 2 μm or more _{Minimum of} . When the above range of 1.3 μm or more is satisfied, the specific surface area of the material does not become excessively large, so that there can be an effect that side reactions with the electrolyte can be reduced.

In an exemplary embodiment of the present application, the silicon-containing anode active material may be formed by: preparing a silicon-containing anode active material; adjusting the particle size of the prepared silicon-containing anode active material; and forming a carbon layer on the prepared silicon-containing negative electrode active material having a controlled particle size.

Specifically, in the preparation of the preliminary silicon-containing anode active material, the preliminary silicon-containing anode active material may be formed by: si powder, siO ₂ Mixing the powder and the metal powder, and then gasifying the mixture; condensing the vaporized mixed gas into a solid phase; the solid phase is heat treated in an inert atmosphere.

Alternatively, the preliminary silicon-containing anode active material may be formed by: si powder and SiO under vacuum ₂ The powder is heated and gasified, howeverThe vaporized mixed gas is then deposited to form silicon-containing particles, the formed silicon-containing particles and metal powder are mixed, and the resulting mixture is then heat treated.

The heat treatment step may be carried out at 700 to 900 ℃ for 4 to 6 hours, in particular at 800 ℃ for 5 hours.

The metal powder may be Mg powder or Li powder.

When Mg powder is used as the metal powder, the anode active material may be prepared by vaporizing Mg powder.

When Li powder is used as the metal powder, the anode active material may be prepared by mixing silicon-containing particles and Li powder, and then heat-treating the resultant mixture.

The silicon-containing particles may be SiOx (x=1).

In the preliminary silicon-containing anode active material, the Mg compound phase may include the Mg silicate, mg silicide, mg oxide, and the like described above.

In the preliminary silicon-containing anode active material, the Li compound phase may include the above-described Li silicate, li silicide, li oxide, or the like.

In adjusting the particle size of the preliminary silicon-containing anode active material, the particle size may be adjusted by a ball mill, a jet mill, or air classification, etc., the method is not limited thereto. For example, when the particle size of the preliminary silicon-containing anode active material is adjusted using a ball mill, 5 to 20 stainless steel ball media may be added, and specifically 10 to 15 stainless steel ball media may be added, but the number of stainless steel ball media is not limited thereto.

The milling time of the preliminary silicon-containing anode active material may be 2 hours to 5 hours, specifically 2 hours to 4 hours, more specifically 3 hours, while adjusting the particle size, but is not limited thereto.

In the formation of the carbon layer, the carbon layer may be prepared by using a Chemical Vapor Deposition (CVD) method using a hydrocarbon gas or by carbonizing a material used as a carbon source.

Specifically, the carbon layer may be formed by: the preliminary silicon-containing anode active material is introduced into a reaction furnace, and then a hydrocarbon gas is subjected to Chemical Vapor Deposition (CVD) at 600 ℃ to 1,200 ℃. 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 to 1,000 ℃.

The anode according to an exemplary embodiment of the present application may include an anode active material, and herein, the anode active material may include the above-described silicon-containing anode active material.

In an exemplary embodiment of the present application, the anode active material may further include a carbonaceous anode active material. The carbonaceous anode active material may be at least one selected from natural graphite, artificial graphite, and the like.

In an exemplary embodiment of the present application, the weight ratio of the silicon-containing anode active material to the carbon-containing anode active material in the anode active material may be 10:90 to 90:10, specifically 10:90 to 50:50.

Specifically, the anode may include an anode current collector and an anode active material layer on the anode current collector. The anode active material layer may contain the anode active material. In addition, the anode active material layer may further include a binder and/or a conductive material.

The negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical changes to the battery. For example, as the current collector, copper, stainless steel, aluminum, nickel, titanium, sintered carbon, or a material in which the surface of aluminum or stainless steel is surface-treated with carbon, nickel, titanium, silver, or the like may be used. In particular, a transition metal such as copper or nickel, which well adsorbs carbon, may be used as the current collector. Although the current collector may have a thickness of 6 μm to 20 μm, the thickness of the current collector is not limited thereto.

The adhesive may comprise at least one selected from the group consisting of: polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, 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 a material whose hydrogen is substituted with Li, na, ca, or the like, and may further contain various copolymers thereof.

The conductive material is not particularly limited as long as the conductive material has conductivity without causing chemical changes to the battery, for example, graphite such as natural graphite or artificial graphite may be used; carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers or metal fibers; conductive tubes, such as carbon nanotubes; fluorocarbon powder; metal powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives and the like.

In an exemplary embodiment of the present application, the negative electrode may be prepared by: preparing a negative electrode slurry containing a negative electrode active material, a binder, a conductive material, and a solvent; forming a negative electrode active material layer by applying the negative electrode slurry to at least one surface of a current collector, drying and rolling the current collector; and drying the current collector in which the anode active material layer is formed.

The secondary battery according to the exemplary embodiment of the present application may include the above-described negative electrode according to the exemplary embodiment. 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, the negative electrode being identical to the above-described negative electrode. Since the negative electrode has been described in detail, a detailed description thereof will be omitted.

The positive electrode may include a positive electrode current collector and a positive electrode active material layer on at least one side of the positive electrode current collector and including a positive electrode active material.

In the positive electrode, the positive electrode current collector is not particularly limited as long as the positive electrode current collector has conductivity without causing chemical changes to the battery, and for example, stainless steel, aluminum, nickel, titanium, sintered carbon, or a material in which the surface of aluminum or stainless steel is surface-treated with carbon, nickel, titanium, silver, or the like may be used. Further, the positive electrode current collector may generally have a thickness of 3 μm to 500 μm, and the adhesion of the positive electrode active material may also be enhanced by forming fine irregularities on the surface of the current collector. For example, the positive electrode current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric body.

The positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material includes: layered compounds, such as lithium cobalt oxide (LiCoO) ₂ ) And lithium nickel oxide (LiNiO) ₂ ) Or a compound substituted with more than one transition metal; lithium iron oxides, e.g. LiFe ₃ O ₄ The method comprises the steps of carrying out a first treatment on the surface of the Lithium manganese oxides, e.g. of formula Li _1+c1 Mn _2-c1 O ₄ (0≤c1≤0.33)、LiMnO ₃ 、LiMn ₂ O ₃ And LiMnO ₂ The method comprises the steps of carrying out a first treatment on the surface of the Lithium copper oxide (Li) ₂ CuO ₂ ) The method comprises the steps of carrying out a first treatment on the surface of the Vanadium oxides, e.g. LiV ₃ O ₈ 、V ₂ O ₅ And Cu ₂ V ₂ O ₇ The method comprises the steps of carrying out a first treatment on the surface of the Ni-site lithium nickel oxide, expressed as chemical formula LiNi _1-c2 M _c2 O ₂ (here, M is at least one selected from the group consisting of Co, mn, al, cu, fe, mg, B and Ga, and c2 satisfies 0.01.ltoreq.c2.ltoreq.0.3); lithium manganese composite oxide, expressed as chemical formula LiMn _2-c3 M _c3 O ₂ (where M is at least one selected from the group consisting of Co, ni, fe, cr, zn and Ta, and c3 satisfies 0.01.ltoreq.c3.ltoreq.0.1) or Li ₂ Mn ₃ MO ₈ (here, M is at least one selected from the group consisting of Fe, co, ni, cu and Zn); liMn ₂ O ₄ LiMn in which Li in the chemical formula is partially replaced with alkaline earth metal ions ₂ O ₄ Etc., but is not limited thereto. The positive electrode may be Li metal.

The positive electrode active material layer may include a positive electrode conductive material and a positive electrode binder together with the positive electrode active material.

In this case, the positive electrode conductive material is used to impart conductivity to the electrode, and may be used without particular limitation as long as the positive electrode conductive material has electron conductivity without causing chemical changes in the battery to be constituted. Specific examples thereof include: graphite, such as natural graphite or artificial graphite; carbonaceous materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fibers; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or a conductive polymer such as a polyphenylene derivative, any one or a mixture of two or more thereof may be used.

In addition, the positive electrode binder is used to improve adhesion between positive electrode active material particles and adhesion between a positive electrode active material and a positive electrode current collector. Specific examples thereof may include: polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene Propylene Diene Monomer (EPDM), sulfonated EPDM, styrene Butadiene Rubber (SBR), fluororubber, or various copolymers thereof, any one or a mixture of two or more thereof may be used.

The separator separates the anode and the cathode and provides a channel for lithium ion movement, and may be used without particular limitation as long as the separator is generally used as a separator in a secondary battery, and particularly, a separator having excellent electrolyte moisturizing ability and low resistance to ion movement in an electrolyte is preferable. Specifically, a porous polymer film, such as a porous polymer film formed of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, and an ethylene/methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a general porous nonwoven fabric, for example, a nonwoven fabric made of glass fiber, polyethylene terephthalate fiber, or the like having a high melting point may also be used. In addition, a coated separator including a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may be selectively used as a single-layer or multi-layer structure.

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, molten inorganic electrolytes, and the like, which can be used to prepare lithium secondary batteries.

In particular, the electrolyte may comprise a non-aqueous organic solvent and a metal salt.

As the nonaqueous organic solvent, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidone, 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, phosphotriester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1, 3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl propionate, and ethyl propionate can be used.

In particular, among the carbonate-based organic solvents, ethylene carbonate and propylene carbonate as cyclic carbonates may be preferably used because cyclic carbonates have a high dielectric constant as a high-viscosity organic solvent, and thus the lithium salt is well dissociated, and since the cyclic carbonates may be mixed with linear carbonates having a low viscosity and a low dielectric constant such as dimethyl carbonate and diethyl carbonate in a suitable ratio and used for preparing an electrolyte having a high conductivity, such cyclic carbonates may be more preferably used.

As the metal salt, a lithium salt, which is a material that is easily dissolved in a nonaqueous electrolyte,for example, as the anion of the lithium salt, one or more selected from the group consisting of: f (F) ^- 、Cl ^- 、I ^- 、NO ₃ ^- 、N(CN) ₂ ^- 、BF ₄ ^- 、ClO ₄ ^- 、PF ₆ ^- 、(CF ₃ ) ₂ PF ₄ ^- 、(CF ₃ ) ₃ PF ₃ ^- 、(CF ₃ ) ₄ PF ₂ ^- 、(CF ₃ ) ₅ PF ^- 、(CF ₃ ) ₆ P ^- 、CF ₃ SO ₃ ^- 、CF ₃ CF ₂ SO ₃ ^- 、(CF ₃ SO ₂ ) ₂ N ^- 、(FSO ₂ ) ₂ N ^- 、CF ₃ CF ₂ (CF ₃ ) ₂ CO ^- 、(CF ₃ SO ₂ ) ₂ CH ^- 、(SF ₅ ) ₃ C ^- 、(CF ₃ SO ₂ ) ₃ C ^- 、CF ₃ (CF ₂ ) ₇ SO ₃ ^- 、CF ₃ CO ₂ ^- 、CH ₃ CO ₂ ^- 、SCN ^- Sum (CF) ₃ CF ₂ SO ₂ ) ₂ N ^- 。

In the electrolyte, in order to improve the service life characteristics of the battery, suppress the decrease in the battery capacity, improve the discharge capacity of the battery, one or more additives, for example, halogenated alkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, N-glyme, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substitutedOxazolidinone, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol or aluminum trichloride.

According to still another exemplary embodiment of the present application, there are 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 secondary batteries having high capacity, high rate characteristics, and cycle characteristics, and thus 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 electric power storage systems.

Mode for the application

Hereinafter, preferred embodiments will be set forth to facilitate understanding of the present application, but the embodiments are merely for illustrating the present application, and it will be apparent to those skilled in the art that various changes and modifications may be made within the scope and technical spirit of the present application, and such changes and modifications are, of course, also within the appended claims.

< examples and comparative examples >

Example 1-1

Si and SiO therein are reacted in a reaction furnace ₂ After mixing 94g of powder and 6g of Mg in a molar ratio of 1:1, the resulting mixture was heated under vacuum at a sublimation temperature of 1,400 ℃. Thereafter, the vaporized Si, siO ₂ The mixed gas with Mg was reacted in a cooling zone in a vacuum state at a cooling temperature of 800 ℃ and condensed into a solid phase. Thereafter, a preliminary silicon-containing anode active material was prepared by performing heat treatment at a temperature of 800 ℃. Thereafter, after 15 stainless steel ball media were introduced into the preliminary silicon-containing anode active material using a ball mill, a battery having D was prepared by pulverizing the preliminary silicon-containing anode active material for 3 hours ₅₀ Prepared silicon-containing anode active material of size=6μm. Thereafter, while maintaining an inert atmosphere by flowing Ar gas, the preliminary silicon-containing anode active material was placed in a hot zone of a CVD apparatus, and methane was blown into the hot zone at 900 ℃ using Ar as a carrier gas, and at 10 ^-1 The reaction was carried out under the support for 20 minutes to prepare a silicon-containing anode active material having a carbon layer formed on the surface.

Examples 1 to 2

A silicon-containing anode active material was prepared in the same manner as in example 1-1 except that 10 stainless steel ball media were added thereto.

Example 2-1

In the method of example 1-1, after 94g of SiO particles were synthesized without using Mg, 6g of Li metal powder was added thereto, and heat treatment was performed at a temperature of 800 ℃ in an inert atmosphere to prepare a preliminary silicon-containing anode active material. Thereafter, after 15 stainless steel ball media were introduced into the preliminary silicon-containing anode active material using a ball mill, a battery having D was prepared by pulverizing the preliminary silicon-containing anode active material for 3 hours ₅₀ Prepared silicon-containing anode active material of size=6μm. Thereafter, while maintaining an inert atmosphere by flowing Ar gas, the preliminary silicon-containing anode active material was placed in a hot zone of a CVD apparatus, and methane was blown into the hot zone at 900 ℃ using Ar as a carrier gas, and at 10 ^-1 The reaction was carried out under the support for 20 minutes to prepare a silicon-containing anode active material having a carbon layer formed on the surface.

Example 2-2

A silicon-containing anode active material was prepared in the same manner as in example 2-1 except that 10 stainless steel ball media were added thereto.

Comparative example 1-1

A silicon-containing anode active material was prepared in the same manner as in example 1-1 except that the pulverizing time was modified to 8 hours.

Comparative examples 1 to 2

A silicon-containing anode active material was prepared in the same manner as in example 1-1 except that the pulverizing time was modified to 1 hour.

Comparative examples 1 to 3

A silicon-containing anode active material was prepared in the same manner as in example 1-1 except that the pulverizing time was modified to 5 hours.

Comparative examples 1 to 4

A silicon-containing anode active material was prepared in the same manner as in example 1-1 except that 10 stainless steel ball media were added thereto, and the pulverizing time was modified to 5 hours.

Comparative examples 1 to 5

A silicon-containing anode active material was prepared in the same manner as in example 1-1 except that 30 stainless steel ball media were added thereto, and the pulverizing time was modified to 8 hours.

Comparative examples 1 to 6

A silicon-containing anode active material was prepared in the same manner as in example 1-1 except that 30 stainless steel ball media were added thereto, and the pulverizing time was modified to 1 hour.

Comparative examples 1 to 7

A silicon-containing anode active material was prepared in the same manner as in example 1-1 except that 30 stainless steel ball media were added thereto.

Comparative example 2-1

A silicon-containing anode active material was prepared in the same manner as in example 2-1 except that the pulverizing time was modified to 8 hours.

Comparative example 2-2

A silicon-containing anode active material was prepared in the same manner as in example 2-1 except that the pulverizing time was modified to 1 hour.

Comparative examples 2 to 3

A silicon-containing anode active material was prepared in the same manner as in example 2-1 except that the pulverizing time was modified to 5 hours.

Comparative examples 2 to 4

A silicon-containing anode active material was prepared in the same manner as in example 2-1 except that 10 stainless steel ball media were added thereto, and the pulverizing time was modified to 5 hours.

Comparative examples 2 to 5

A silicon-containing anode active material was prepared in the same manner as in example 2-1 except that 30 stainless steel ball media were added thereto, and the pulverizing time was modified to 8 hours.

Comparative examples 2 to 6

A silicon-containing anode active material was prepared in the same manner as in example 2-1 except that 30 stainless steel ball media were added thereto, and the pulverizing time was modified to 1 hour.

Comparative examples 2 to 7

A silicon-containing anode active material was prepared in the same manner as in example 2-1 except that 30 stainless steel ball media were added thereto.

The silicon-containing anode active materials prepared in examples and comparative examples are shown in table 1 below.

TABLE 1

Particle size analysis of the silicon-containing anode active material was confirmed using Microtrac equipment (manufacturer: microtrac company, model name: S3500) using water and Triton-X100 dispersant at a refractive index of 1.97.

The specific surface area was degassed at 130℃for 2 hours by using a BET measuring apparatus (BEL-SORP-MAX, bell, japan) and N was carried out at 77K ₂ Adsorption/desorption.

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

< experimental example: evaluation of discharge capacity, initial efficiency and service life (Capacity Retention Rate) characteristics ]

The negative electrode active materials in examples and comparative examples were used to prepare a negative electrode and a battery, respectively.

The mixture was prepared by mixing the negative active material, carbon black as a conductive material, and polyacrylic acid (PAA) as a binder at a weight ratio of 80:10:10. Then, 7.8g of distilled water was added to 5g of the mixture, and the resultant mixture was stirred to prepare a negative electrode slurry. The negative electrode slurry was applied to a copper (Cu) metal thin film having a thickness of 20 μm as a negative electrode current collector and dried. In this case, the temperature of the circulated air was 60 ℃. Subsequently, a negative electrode was prepared by rolling the negative electrode current collector and drying the negative electrode current collector in a vacuum oven at 130 ℃ for 12 hours.

Cutting lithium (Li) metal sheet into 1.7671cm ² A lithium (Li) metal thin film obtained by rounding is used as the positive electrode. A porous polyethylene separator was interposed between the positive electrode and the negative electrode, and an electrolyte prepared as follows was injected thereto to prepare a lithium coin half cell: vinylene carbonate was dissolved in 0.5 parts by weight in a mixed solution of Ethylene Methyl Carbonate (EMC) and Ethylene Carbonate (EC) in a mixed volume ratio of 7:3, and LiPF was then added thereto ₆ Dissolved therein at a concentration of 1M.

The discharge capacity, initial efficiency and capacity retention were evaluated by charging and discharging the prepared battery, and are shown in table 2 below.

For cycle 1 and cycle 2, the battery was charged and discharged at 0.1C, and from cycle 3, the battery was charged and discharged at 0.5C. The 300 th cycle was completed in the charged state (lithium was contained in the negative electrode).

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

Discharge conditions: CC (constant current) Condition 1.5V

The discharge capacity (mAh/g) and initial efficiency (%) were obtained from the results during the 1 st charge/discharge period. Specifically, the initial efficiency (%) is calculated as follows.

Initial efficiency (%) = (discharge capacity after 1 st discharge/1 st charge capacity) ×100 charge retention rates were each calculated as follows.

Capacity retention (%) = (300 th discharge capacity/1 st discharge capacity) ×100

TABLE 2

Battery cell	Discharge capacity (mAh/g)	Initial efficiency (%)	Capacity retention (%)
				Example 1-1	1430	80	50
Examples 1 to 2	1450	80	52
				Example 2-1	1350	85	50
Example 2-2	1360	85	52
				Comparative example 1-1	1420	79	35
Comparative examples 1 to 2	1380	78	25
				Comparative examples 1 to 3	1420	78	25
Comparative examples 1 to 4	1420	78	25
				Comparative examples 1 to 5	1390	78	25
Comparative examples 1 to 6	1370	78	15
				Comparative examples 1 to 7	1420	79	45
Comparative example 2-1	1320	84	35
				Comparative example 2-2	1300	80	25
Comparative examples 2 to 3	1320	83	25
				Comparative examples 2 to 4	1320	83	25
Comparative examples 2 to 5	1320	83	25
				Comparative examples 2 to 6	1300	80	15
Comparative examples 2 to 7	1330	84	42

The silicon-containing anode active material according to the present application contains a metal atom, wherein D ₅ /D ₅₀ Is more than 0.5, D ₅ Is more than 3 mu m, D ₅₀ Is 4 μm or more and 11 μm or less, and is suitably D ₅₀ 、D ₅₀ And D ₅ /D ₅₀ The particle size distribution of (3) suppresses side reactions with the electrolyte and promotes charging and discharging, and thus has the effect that capacity/efficiency is fully achieved and service life characteristics are stabilized.

In the table 2 of the description of the present application,it was confirmed that examples 1-1 and 1-2 are negative electrode active materials containing Mg, and do not satisfy D ₅ /D ₅₀ Value or not satisfy D ₅ Value sum D ₅₀ The comparative examples 1-1 and 1-7 are excellent in all of the discharge capacity, initial efficiency and capacity retention. Further, it was confirmed that examples 2-1 and 2-2 were negative electrode active materials containing Li, and were excellent in discharge capacity, initial efficiency, and capacity retention ratio, as compared with comparative examples 2-1 to 2-7.

In contrast, comparative examples 1 and 5 satisfy the D of the present application ₅ /D ₅₀ 、D ₅ And D ₅₀ ，

Comparative examples 1-1 and 1-4 satisfy the D of the present application ₅ /D ₅₀ But does not satisfy D ₅ Or D ₅₀ It was confirmed that capacity, efficiency and service life were reduced as compared with the examples.

In particular, even D ₅ /D ₅₀ Is above 0.5, when D ₅ Less than 3 μm or D ₅₀ Below 4 μm, the overall particle size is so small that the specific surface area of the material becomes large and oxidation often occurs. Therefore, it was confirmed that the capacity, efficiency and service life were lower than those of the examples because side reactions with the electrolyte frequently occur during charge/discharge.

In addition, even D ₅ /D ₅₀ Is above 0.5, when D ₅₀ Above 11 μm, the overall particle size is so large that it can be confirmed that the capacity, efficiency and service life are reduced compared to the examples because the battery is not easily charged and discharged.

In addition, when D ₅ /D ₅₀ When the ratio is less than 0.5, the negative electrode is formed by the dimensional ratio D ₅₀ The volume occupied by the much smaller anode active material increases, so that it can be confirmed that the capacity, efficiency and service life are reduced compared to the examples due to the increase of side reactions with the electrolyte.

Therefore, the negative electrode active material of the present application can satisfy D of 0.5 or more ₅ /D ₅₀ D of 3 μm or more ₅ And D of 4 μm or more and 11 μm or less ₅₀ A value whereby oxidation of the particles is minimized and side reactions with the electrolyte are reduced, therebyIt is easy to improve the capacity, efficiency and/or service life of the battery.

Claims

1. A silicon-containing anode active material comprising:

a core and a carbon layer on the core,

wherein the core comprises SiO _x And at least one metal atom, wherein 0<x<2，

The at least one metal atom contains at least one selected from the group consisting of Mg, li, al and Ca,

wherein the silicon-containing anode active material has D of 0.5 or more ₅ /D ₅₀ And (2) and

the silicon-containing anode active material has D of 3 μm or more ₅ And D of 4 μm or more and 11 μm or less ₅₀ 。

2. The silicon-containing anode active material according to claim 1, wherein D ₅ /D ₅₀ Is 0.6 or more.

3. The silicon-containing anode active material according to claim 1, wherein the silicon-containing anode active material has D of 0.5 or more and 1 or less ₅ /D ₅₀ 。

4. The silicon-containing anode active material according to claim 1, wherein D ₅₀ 4.2 μm or more and 10 μm or less.

5. The silicon-containing anode active material according to claim 1, wherein D ₅ Is 3 μm or more and 5.5 μm or less.

6. The silicon-containing anode active material according to claim 1, wherein the silicon-containing anode active material has D of 35 μm or less _{Maximum value} 。

7. The silicon-containing anode active material according to claim 1, wherein the content of the at least one metal atom is 0.1 parts by weight or more and 40 parts by weight or less based on 100 parts by weight of the total of the silicon-containing anode active material.

8. The silicon-containing anode active material according to claim 1, wherein the at least one metal atom comprises Mg or Li.

9. The silicon-containing anode active material according to claim 1, wherein the content of the carbon layer is 0.1 parts by weight or more and 50 parts by weight or less based on 100 parts by weight of the total silicon-containing anode active material.

10. The silicon-containing anode active material of claim 1, wherein the silicon-containing anode active material has a thickness of greater than 2m ² /g and less than 10m ² BET specific surface area per gram.

11. A negative electrode, comprising:

a negative electrode active material, wherein the negative electrode active material comprises the silicon-containing negative electrode active material of claim 1.

12. The anode of claim 11, wherein the anode active material further comprises a carbon-containing anode active material.

13. The negative electrode according to claim 11, further comprising:

a negative electrode current collector; and

a negative electrode active material layer on at least one surface of the current collector,

wherein the anode active material layer contains an anode active material.

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