KR100972187B1 - Negative active material for rechargeable lithium battery, preparation method thereof and rechargeable lithium battery comprising thereof - Google Patents

Abstract

The present invention relates to a negative electrode active material for a lithium secondary battery, a method of manufacturing the same, and a lithium secondary battery including the same, and more particularly, a negative electrode for a lithium secondary battery capable of improving life characteristics of a high capacity lithium secondary battery using a metal as a negative electrode active material. It relates to an active material, a method for preparing the same, and a lithium secondary battery including the same.

Anode Active Material, Anode, Lithium Secondary Battery, Si-C Bonding

Description

A negative active material for a lithium secondary battery, a method of manufacturing the same, and a lithium secondary battery comprising the same

The present invention relates to a negative electrode active material for a lithium secondary battery, a method of manufacturing the same, and a lithium secondary battery including the same, and more particularly, a negative electrode for a lithium secondary battery capable of improving life characteristics of a high capacity lithium secondary battery using a metal as a negative electrode active material. It relates to an active material, a method for preparing the same, and a lithium secondary battery including the same.

Li-ion batteries have a high unit cell voltage (3-4V) and energy density (200Wh / l, 100Wh / kg) and a wide range of operating temperatures, so they are portable transceivers that are said to be the so-called 3C products as well as power sources for electric vehicles. It is widely used as a power source for laptops, camcorders, camcorders, etc., and its range of use is gradually increasing.

Lithium ion batteries using repeated insertion and extraction reactions of Li ions are also called Rocking-Chair Systems. LiCoO ₂ , LiNiO ₂ , LiNi _1-y Co _y as positive electrode active materials in currently commercialized battery systems Transition metal oxides such as O ₂ and LiMn ₂ O ₄ are used as lithium intercalating carbon as a negative electrode active material. Carbon-based materials used as the anode active material may be classified into soft carbon having a uniaxial orientation at low temperature and hard carbon having a uniaxial orientation at high temperature.

Graphite, which is currently commercialized in batteries, is a material belonging to soft carbon and shows very reversible charge / discharge behavior due to the uniaxial orientation of the graphite layer, thereby showing excellent electrode life. In addition, since the electrode potential is 0 V _{Li / Li +} when the Li ion is charged, the potential is almost similar to that of pure Li metal, and thus higher energy can be obtained when forming an oxide-based anode and a cell. It has advantages However, the low theoretical capacity of graphite (372 mAh / g, 837 mAh / cm ³ ) at the present time when a high capacity battery is required, despite the above advantages of graphite as a negative electrode material, is a critical obstacle to the continuous use of graphite as a negative electrode material. It is becoming. Therefore, in order to increase the capacity of the battery, it is necessary to develop a new negative electrode material having a high capacity.

As a novel material that can replace the carbon-based negative electrode active material, metal materials such as Si, Sn, Al, and Sb have been studied. In such a metal material, charging / discharging is performed by an alloying / non-alloying reaction with Li, and it is known to exhibit a higher capacity than graphite, which is a commercial anode active material. However, metals such as Si, Sn, Al, and Sb cause large volume expansion and contraction in the process of alloying / unalloying with Li, resulting in deterioration of life characteristics due to micronization and loss of conductive paths. Have In particular, Si is known to be the most suitable material as a high-capacity cathode material in terms of discharge capacity (4200mAh / g) and discharge voltage (0.4V), but the large amount of 400% caused when Li ions are inserted (charged) into the material Due to volume expansion, pulverization of the active material occurs, which has shown a sharp drop in life characteristics.

In recent years, active researches have been made to solve these problems, and the focus of most studies is to reduce the volume expansion itself through the micronization of Si and to randomly create an electrochemically inactive matrix around the Si. It is adapted to absorb the volume expansion of Si. Among the studies, the most significant improvement in the life characteristics of Si was the use of a soft matrix suitable for mechanically absorbing the volume expansion caused by the alloying / non-metallization of Si. As the soft matrix, various kinds of carbon materials were mainly adopted, and the typical addition methods are as follows.

(1) A simple mixture of various carbon materials and Si

(2) Chemically fixed fine powder Si etc. on carbon surface using silane coupling agent

(3) A material which fixed amorphous carbon on the surface of Si-based active material through thermal decomposition of organic precursors, chemical vapor deposition (CVD), etc.

However, in (1) the material in which the Si powder is simply mixed with carbon, the carbon is released from the Si during the process of undergoing large volume expansion and contraction of several hundred percent of Si as charging and discharging proceeds, thereby causing the electrical conductivity of the material. There is a problem that the life characteristics are greatly reduced due to degradation.

In addition, the material (2) chemically fixed fine Si on the surface of carbon by using the silane coupling agent or the like remains in a state where carbon is in close contact with Si at the initial stage of charging and discharging, so that Si may function as a negative electrode active material. As the discharge cycle progresses, the residual expansion in Si due to alloying and non-alloying of Li increases significantly, and the Si is liberated from carbon by breaking the bond by the silane coupling agent, which greatly reduces the life characteristics of the lithium secondary battery. I have a problem. In addition, the silane coupling process may not be uniformly performed during the production of the negative electrode material, and there is a problem that a negative electrode material of stable quality cannot be easily produced.

The material coated with the surface of the Si-based active material with (3) pyrolysis carbon and CVD carbon has the same problems as those of the above-mentioned material of chemically fixing fine powder Si on the carbon surface using a silane coupling agent or the like. have.

An object of the present invention is to provide a negative electrode active material for a lithium secondary battery that can provide a battery having improved life characteristics.

Another object of the present invention is to provide a method for producing a negative electrode active material for a lithium secondary battery having the above physical properties.

Still another object of the present invention is to provide a lithium secondary battery including the negative electrode active material.

The present invention provides a negative electrode active material for a lithium secondary battery, including an alloy consisting of an active metal and an inactive metal and a carbon-based material bonded through an active metal and an active metal-carbon bond in the alloy. .

The present invention, in the manufacture of a negative electrode active material for a lithium secondary battery, the step of alloying an active metal and an inactive metal; The present invention provides a method of manufacturing a negative electrode active material for a rechargeable lithium battery including adding a carbon-based material to an alloy of the active metal and an inactive metal to form an active metal-carbon bond and controlling porosity in the alloy metal.

In the lithium secondary battery, a lithium secondary battery comprising an anode active material and an inert metal and an anode active material for a lithium secondary battery comprising an active metal and an carbon-based material bonded through an active metal-carbon bond in the alloy To provide

The negative electrode active material for a lithium secondary battery of the present invention can improve the life characteristics of a lithium secondary battery by solving problems such as micronization and electrical short circuit caused by volume expansion of a metal-based active material which have been examined as a negative electrode active material of a conventional high capacity lithium secondary battery.

This invention shows the negative electrode active material for lithium secondary batteries.

The present invention relates to a negative electrode active material for a lithium secondary battery, wherein the negative electrode active material includes an alloy consisting of an active metal and an inactive metal, and a carbon-based material bonded through an active metal and an active metal-carbon bond in the alloy.

As the active metal, at least one metal selected from the group consisting of Si, Sn, Al, Zn, Pb, Bi, Ag, Cd, and Sb may be used.

The active metal may be one or more metals selected from the group consisting of Si and Sn.

In the above active metal, Si may be used.

In the above-mentioned inert metal, at least one metal selected from the group consisting of Co, Ni, Mn, Fe, and Cu may be used.

In the above inert metal may be used one or more metals selected from the group consisting of Co, Cu and Ni.

As the inert metal, Cu may be used.

The carbonaceous material is at least one material selected from the group consisting of graphite, carbon nanotubes, carbon nanowires, soft carbons, and hard carbons. Can be used.

The active metal may be used in the form of a powder having an average particle diameter of 50 μm or less.

The active metal may be used in the form of a powder having an average particle diameter of 1 to 50㎛.

The inert metal may be used in the form of a powder having an average particle diameter of 50 μm or less.

In the above, the average particle diameter of the inert metal may be used in the form of a powder having a thickness of 1 to 50 μm.

The carbonaceous material may be used in the form of a powder having an average particle diameter of 50 μm or less.

The carbonaceous material may be used in the form of a powder having an average particle diameter of 1 to 50㎛.

This invention shows the manufacturing method of the negative electrode active material for lithium secondary batteries.

The present invention, in the manufacture of a negative electrode active material for a lithium secondary battery, the step of alloying an active metal and an inactive metal; Adding a carbon-based material to the alloy of the active metal and the inert metal to form an active metal-carbon bond and to adjust the porosity (porosity) in the alloy metal represents a method of manufacturing a negative electrode active material for a lithium secondary battery.

The alloying of the active metal and the inactive metal in the preparation of the negative active material for the lithium secondary battery may be any one selected from ball-milling, mechano-fusion, and arc-melting. It can carry out by a method.

When preparing the negative active material for the lithium secondary battery, the active metal and the carbon-based alloy in the alloy by adding a carbon-based material to the alloy consisting of an active metal and an inactive metal and ball-milling or mechano-fusion It may form an active metal-carbon bond of the material.

In preparing the negative active material for the lithium secondary battery, at least one metal selected from the group consisting of Si, Sn, Al, Zn, Pb, Bi, Ag, Cd, and Sb may be used.

In preparing the negative active material for the lithium secondary battery, the active metal may be one or more metals selected from the group consisting of Si and Sn.

Si may be used as an active metal in the preparation of the negative electrode active material for a lithium secondary battery.

The active metal may be used in the form of a powder having an average particle diameter of 50 μm or less in the preparation of the negative active material for a lithium secondary battery.

In preparing the negative active material for the lithium secondary battery, the active metal may be used in the form of a powder having an average particle diameter of 1 to 50 μm.

In the manufacture of the negative electrode active material for the lithium secondary battery, an inert metal may use at least one metal selected from the group consisting of Co, Ni, Mn, Fe, and Cu.

In the manufacture of the negative electrode active material for the lithium secondary battery, the inert metal may be one or more metals selected from the group consisting of Co, Cu, and Ni.

Cu may be used as an inert metal in the preparation of the negative active material for a lithium secondary battery.

An inert metal may be used in the form of a powder having an average particle diameter of 50 μm or less in the preparation of the negative active material for a lithium secondary battery.

An inert metal may be used in the form of a powder having an average particle diameter of 1 to 50 μm in the preparation of the negative active material for a lithium secondary battery.

The carbon-based material in the preparation of the negative active material for the lithium secondary battery is a group consisting of graphite, carbon nanotubes, carbon nanowires, soft carbons, and hard carbons. One or more substances selected from can be used.

In preparing the negative active material for the lithium secondary battery, the carbonaceous material may be used in the form of a powder having an average particle diameter of 50 μm or less.

In preparing the negative active material for the lithium secondary battery, the carbonaceous material may be used in the form of a powder having an average particle diameter of 1 to 50 μm.

The present invention includes a negative electrode containing a negative active material for a lithium secondary battery including an alloy made of the above-mentioned active metal and inactive metal and a carbon-based material bonded through an active metal and an active metal-carbon bond in the alloy.

The present invention includes a lithium secondary battery containing a negative electrode active material for a lithium secondary battery comprising an alloy made of the above-mentioned active metal and inactive metal and a carbon-based material bonded through an active metal and an active metal-carbon bond in the alloy. do.

The present invention is a lithium secondary battery containing a negative electrode active material for a lithium secondary battery comprising an alloy consisting of the above-mentioned active metal and inactive metal and a carbon-based material bonded through an active metal and an active metal-carbon bond in the alloy It includes.

Hereinafter, the present invention will be described in more detail.

When the metal-based active material is used as a negative electrode active material of a lithium secondary battery, lithium ions move to the negative electrode during charging and the volume expands by alloying the metal-based active material with lithium, and during discharge, the volume shrinks due to the movement of lithium ions to the positive electrode. . When this process is repeated, a crack occurs in the metal-based active material, and eventually splits into fine particles, which is called micronization. In addition, a phenomenon in which the active material is detached from the current collector or the conductive material in the negative electrode and is electrically disconnected occurs. Due to these phenomena, when the charge and discharge are repeated, the electrical conductivity in the negative electrode is gradually deteriorated, which causes the life characteristics of the secondary battery to deteriorate rapidly.

In order to solve the above problem, the negative electrode active material of the present invention is an alloy composed of a mechanical complex of an active metal and an inactive metal and a carbon-based carbon that can form a strong active metal-carbon (C) bonding to the alloy. Made of matter.

The active metal is not particularly limited as long as it forms an alloy with lithium during battery reaction and participates in electrochemical reaction, but at least one of Si, Sn, Al, Zn, Pb, Bi, Ag, Cd and Sb is It is preferred to be used, and more preferably one or more of Si and Sn, which are known to have the highest capacity.

The active metal may be used in powder form.

The inert metal is not particularly limited as long as it does not participate in the electrochemical reaction with lithium during battery reaction, but at least one of Co, Ni, Mn, Fe, and Cu is preferably used, and among them, the electrical conductivity is More preferably, at least one of Cu, Co, and Ni, which is known to be the best, is used.

The inert metal may be used in powder form.

In the negative electrode active material of the present invention, the carbon-based material bonded by the strong active metal-carbon bond to the alloy consisting of mechanical complexation of the active metal and the inactive metal absorbs the volume expansion of the alloy consisting of the active metal and the inactive metal. It serves to maintain electrical conductivity, crystalline carbon or amorphous carbon may be used as follows. The crystalline carbon may be a natural graphite or artificial graphite in the form of plate, flake, spherical or fibrous, and the like may include carbon nanotube, carbon nanowire, carbon fiber, and the like. Examples of the amorphous carbon include soft carbon, hard carbon, cokes, mesophase pitch, and the like.

In the crystalline carbon, if the X-ray diffraction intensity of the (002) plane is I (002) and the X-ray diffraction intensity of the (110) plane is I (110), I (110) / I (002) is 0.2 or less. It is preferably 0.04 or less, more preferably 0.002 to 0.2, most preferably 0.002 to 0.04.

The active metal is preferably in the form of a powder having an average particle diameter of 50 µm or less, more preferably in the form of a powder having an average particle diameter of 1-40 µm, 1-30 µm, 1-20 µm or 1-10 µm. If the average particle diameter of the active metal powder exceeds 50 μm, the total surface area of the active metal powder particles is small, which causes a problem of inferior reactivity of the active material including the active metal powder.

The inert metal is preferably in the form of a powder having an average particle diameter of 50 µm or less, and more preferably in the form of a powder having an average particle diameter of 1-40 µm, 1-30 µm, 1-20 µm or 1-10 µm. If the average particle diameter of the inert metal powder particles exceeds 50㎛, there is a problem that the electrochemical deterioration is increased by the additional volume expansion.

The carbonaceous material is preferably in the form of a powder having an average particle diameter of 50 µm or less, more preferably in the form of a powder having an average particle diameter of 1-40 µm, 1-30 µm, 1-20 µm, or 1-10 µm.

1 is a schematic cross-sectional view of a negative electrode active material according to an embodiment of the present invention.

As shown in FIG. 1, the negative electrode active material of the present invention is a Si-Cu alloy formed by mechanical synthesis of Si particles as an active metal and Cu particles as an inactive metal, and Si and carbon of a Si-Cu alloy are Si-C bonds. It is composed of carbon-based materials (C) connected. At this time, due to the presence of the Si-C bond it can prevent the electrical short circuit due to volume expansion in the charge and discharge process, the pores (pore) inside the negative electrode active material serves to absorb the volume expansion.

2 is a cross-sectional view schematically showing a state during charging of a negative electrode active material according to an embodiment of the present invention.

Referring to FIG. 2, even when an alloy made of an active metal (Si) and an inert metal (Cu) is expanded, a volume expansion can be absorbed by a large amount of pores distributed around a cathode active material, and also among the active metals of the alloy. Due to the presence of the carbon-based material in which the Si and the carbon of the carbon-based material are linked to the Si-C bond, it is possible to prevent an electrical short circuit due to expansion.

In the negative electrode active material of the present invention, an active metal-carbon bond is present at the interface between the alloy and the carbon-based material composed of the active metal and the inactive metal, and the active metal-carbon phase in the negative electrode active material is within the scope of the present invention. When crystalline carbon is used as the carbon-based material, lithiated carbon may be formed due to the insertion of lithium. Even if the negative active material includes such lithiated carbon, it is included in the scope of the present invention.

In the method of manufacturing a negative electrode active material for a secondary battery of the present invention, the step of alloying the active metal and the inactive metal mechanically by ball-milling method, mechano-fusion method or melting method using arc-melting, and alloyed particles And forming the active metal-carbon bonds between the active metal particles and the carbon and controlling the porosity in the negative electrode active material particles by ball-milling or mechano-fusion.

First, the ratio of active and inactive metals is determined and mechanically energized to the mixed powder to make an alloy containing the appropriate intermetallic compound. In this case, it is preferable to use a high energy ball-miller or mechano-fusion that can apply high energy in a short time, rather than a small planetary ball-miller for effective alloying. In order to obtain the desired alloy composition, it is possible to adjust the holding time and ball-to-powder ratio in the ball-milling method and the rotation rpm in the mechano-fusion method.

At this time, the alloy can be alloyed using 10 to 100 parts by weight of the inert metal with respect to 100 parts by weight of the active metal when preparing the alloy consisting of the active metal and the inactive metal.

The active metal may be one or more selected from the group consisting of Si, Sn, Al, Zn, Pb, Bi, Ag, Cd and Sb, which may be alloyed with lithium electrochemically, and Co, Ni, One or more types selected from the group of Mn, Fe, and Cu can be used.

Then, an alloy of the active metal and the inactive metal and the carbon-based material obtained are mixed at a desired ratio, and the resulting mixture is energized by ball-milling method or mechano-fusion method. A negative electrode active material containing (pore) can be formed.

At this time, the alloy and the carbon-based material composed of the active metal and the inactive metal are mixed with 20-120 parts by weight of the carbon-based material with respect to 100 parts by weight of the alloy consisting of the active metal and the inactive metal, and then energy is obtained by the ball-milling method or the mechano-fusion method. Finally, the negative electrode active material containing the active metal-carbon bond and a large amount of pores can be formed.

The carbonaceous material may be used at least one selected from the group consisting of graphite, carbon nanotube, carbon nanowire, soft carbon and hard carbon.

Alloys and carbonaceous materials composed of active metals and inactive metals are mixed with 20 to 120 parts by weight of carbonaceous materials with respect to 100 parts by weight of alloys consisting of active metals and inert metals, and then energy is obtained by ball-milling or mechano-fusion. Finally, the pore can be adjusted.

The reason for adjusting the porosity is that the porosity absorbs volume expansion when alloying an inert metal such as Li and an active alloy such as Si, thereby preventing deterioration of its lifetime characteristics and directly affecting electrolyte impregnation. . Carbon materials also contribute to the formation of voids, and because the size of the alloy changes in ball milling conditions, these conditions can also contribute to the formation of voids.

Meanwhile, in the negative electrode active material for a lithium secondary battery of the present invention, an active metal-carbon bond is formed by adding a carbon-based material to an alloy composed of an active metal and an inactive metal, and absorption of volume expansion through formation of pores through the addition of a carbon-based material In addition, the increase in the electrical conductivity of the active material as a whole can be expected, but due to the large volume expansion of the active metals Si and Sn, the degradation due to volume expansion cannot be prevented only through the addition of a carbon-based material. The alloying of the active metal and the inactive metal allows the inactive metal part to additionally absorb the volume expansion caused by the alloying of the inactive metal such as Li of the active metal. This is why it was used.

The present invention provides a lithium secondary battery comprising the above-mentioned negative electrode active material for a lithium secondary battery.

The present invention provides a lithium secondary battery comprising a negative electrode active material for a lithium secondary battery produced by the above-mentioned method.

The present invention provides a lithium secondary battery including the negative electrode containing the negative electrode active material for the lithium secondary battery mentioned above.

The present invention provides a lithium secondary battery comprising a negative electrode containing a negative electrode active material for a lithium secondary battery prepared by the above-mentioned method.

The present invention provides a lithium secondary battery comprising a cathode including an anode active material for the lithium secondary battery mentioned above, a cathode including an anode active material capable of reversible intercalation / de-intercalation of lithium, and an electrolyte solution. .

The present invention provides a negative electrode including a negative electrode active material for a lithium secondary battery prepared by the above-mentioned method, a positive electrode including a positive electrode active material capable of reversible intercalation / de-intercalation of lithium, and a lithium including an electrolyte solution. It provides a secondary battery.

The lithium secondary battery of the present invention exhibits improved lifetime characteristics by including the negative electrode active material of the present invention which is not micronized or easily detached from the conductive material and the current collector.

In the lithium secondary battery, the negative electrode may be prepared as a negative electrode by applying a sorbent mixture prepared by mixing the negative electrode active material according to the present invention with a binder to a current collector such as copper, and may be prepared as a negative electrode by adding a conductive material as necessary. Can be.

Examples of the conductive material include nickel powder, cobalt oxide, titanium oxide, carbon, and the like, and examples of carbon used as the conductive material include ketjen black, acetylene black, furnace black, graphite, and fullerene. Among these, graphite plays a role not only as a conductive material but also as an electrode structure skeleton.

Examples of the binder include polyvinylidene fluoride and polyvinyl fluoride.

3 is an exploded perspective view showing an example of a lithium secondary battery of the present invention. The lithium secondary battery is composed mainly of a negative electrode, a positive electrode, a separator disposed between the negative electrode and the positive electrode, an electrolyte solution impregnated in the negative electrode, the positive electrode and the separator, a battery container, and a sealing member for sealing the battery container.

The shape of the lithium secondary battery illustrated in FIG. 3 may be in various shapes such as a cylindrical shape, a coin shape, a sheet shape, or the like.

In the lithium secondary battery, the positive electrode includes a positive electrode active material, a conductive material, and a binder.

The cathode active material is a compound capable of reversibly intercalation / de-intercalation of lithium, such as LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , LiFeO ₂ , V ₂ O ₅ , TiS, MoS or LiFePO ₄ . As the separator, an olefin porous film such as polyethylene or polypropylene can be used.

In the lithium secondary battery, the electrolyte solution includes a non-aqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the cell can move. Examples of the non-aqueous organic solvent include benzene, toluene, fluorobenzene, 1,2-difluorobenzene, 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3- Dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, iodobenzene, 1,2-diiobenzene, 1,3-diiodo Benzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, 1,2,4-triiodobenzene, fluorotoluene, 1,2-difluorotoluene, 1,3- Difluorotoluene, 1,4-difluorotoluene, 1,2,3-trifluorotoluene, 1,2,4-trifluorotoluene, chlorotoluene, 1,2-dichlorotoluene, 1,3- Dichlorotoluene, 1,4-dichlorotoluene, 1,2,3-trichlorotoluene, 1,2,4-trichlorotoluene, iodotoluene, 1,2-diiodotoluene, 1,3-diiodo Toluene, 1,4-diiodotoluene, 1,2,3-triiodotoluene, 1,2,4-triiodotoluene, R-CN (where R is 2-50 carbon atoms Linear, branched or cyclic hydrocarbon groups, which may include double bonds, aromatic rings, or ether bonds), dimethylformamide, dimethylacetate, xylene, cyclohexane, tetrahydrofuran, 2-methyltetrahydro Furan, cyclohexanone, ethanol, isopropyl alcohol, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, methylpropyl carbonate, propylene carbonate, methyl propionate, ethyl propionate, methyl acetate, ethyl acetate, propyl acetate, One or two or more of dimethoxyethane, 1,3-dioxolane, diglyme, tetraglyme, ethylene carbonate, propylene carbonate, sulfolane, valerotactone, decanolide, and mevalolactone may be used in combination. The mixing ratio in the case of mixing one or more of the organic solvents can be appropriately adjusted according to the desired battery performance, which can be widely understood by those skilled in the art. The lithium salt is a substance that dissolves in an organic solvent and acts as a source of lithium ions in the battery to enable the operation of a basic lithium secondary battery and to promote the movement of lithium ions between the positive electrode and the negative electrode. Representative examples of such lithium salts are LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , LiN (C _a F _{2a + 1} SO ₂ ) (C _b F _{2b + 1} SO ₂ ) (where a and b are natural waters), LiCl, LiI and the like may be used alone or in combination of two or more thereof. .

In addition, a polymer solid electrolyte may be used instead of the electrolyte solution. In this case, it is preferable to use a polymer having high ion conductivity with respect to lithium ions, and polyethylene oxide, polypropylene oxido, polyethyleneimine, and the like may be used. A gel obtained by adding the solvent and the solute to this polymer can also be used.

Hereinafter, the present invention will be described in detail with reference to Examples and Test Examples. However, these are intended to explain the present invention in more detail, and the scope of the present invention is not limited thereto.

≪ Example 1 >

Si-Cu alloys were prepared using crystalline Si in powder form having an average particle diameter of 17 μm as the active metal, and powder having an average particle size of Cu (Japanese high purity chemical product) as 17 μm as the inactive metal.

When manufacturing Si-Cu alloy, high energy ball-milling method, which is a kind of mechanical alloying method, was used, and the ball-milling time was adjusted to adjust the proportion of intermetallic compounds that can be uniformly distributed between Si and Cu. It was carried out for 8 hours, Si and Cu were added in a weight ratio of 1: 1 to prepare a Si-Cu alloy.

During ball-milling, the powder was sealed in a stainless steel container together with stainless steel ball. At this time, the ball-to-powder ratio was 7.5: 1 and the inside of the stainless steel container was kept at argon (Ar) to show oxidation during ball-milling. The reaction was allowed to be suppressed. The ball-milling equipment used was the SPEX-8000 with a rpm of 500.

Si-Cu alloy obtained above and a carbon powder having an average particle diameter of 17 μm were weighed at a weight ratio of 1: 1, and then ball-milled for 30 minutes to produce a composite containing an active metal, an inactive metal, and carbon (Si-Cu / C composite) was prepared.

Comparative Example 1

Si and carbon were weighed at a weight ratio of 1: 1, and then Si / C composite was prepared by ball-milling for 30 minutes.

<Manufacture example 1>

A composite including an active metal, an inert metal, and carbon prepared in Example 1 was used as a negative electrode active material, and the negative active material and the carbon powder, which is a conductive material, were prepared in N-methylpyrrolidinone solvent. A vinylidene binder was added to the dissolved binder solution and mixed to prepare a negative electrode active material slurry. The negative electrode active material slurry was coated on Cu foil, dried in a vacuum oven at 110 ° C., and pressed in a press to prepare a negative electrode.

The lithium secondary battery half battery was produced using the said negative electrode and Li metal counter electrode. In this case, a mixed solution (1: 1 volume ratio) of ethylene carbonate and diethylene carbonate in which 1M LiPF ₆ was dissolved was used.

<Manufacture example 2>

A lithium secondary battery was manufactured in the same manner as in Preparation Example 1, except that Si / C composite prepared in Comparative Example 1 was used as a negative electrode active material.

<Test Example 1>

XRD pattern and scanning electron micrographs of the negative electrode active material prepared according to Example 1 are shown in FIGS. 4 and 5, respectively.

It can be seen from FIG. 4 that the intermetallic compound Cu ₃ Si is partially generated through the alloying of Si and Cu, and the carbon maintains its crystallinity well without forming a SiC phase.

In addition, it can be seen from FIG. 5 that the Si-Cu alloy powder and the carbon powder are well assembled.

<Test Example 2>

Structural excellence of the negative electrode active material prepared according to Example 1 is well illustrated in FIGS. 6, 7, and 8.

In the transmission electron micrograph of FIG. 6, it can be seen that an amorhpous carbon layer exists between the Si-Cu alloy powder and the carbon powder, and FIG. 7 shows that bonding between Si and carbon exists in this carbon layer. have. This Si-C bonding serves to prevent the electrical short that may occur during the volume expansion of Si by Li insertion. In addition, in FIG. 8, it can be seen that a large amount of nano-size pores exist in the Si-Cu / C composite, which is a function of absorbing the volume expansion of Si generated during Li insertion. Is an important factor in preventing electrochemical degradation.

<Test Example 3>

Charge and discharge and life characteristics of the lithium secondary battery manufactured in Preparation Example 1 were measured and shown in FIGS. 9 and 10, respectively. 11 is a lifespan characteristics of a battery prepared according to Preparation Example 2. FIG.

As shown in the comparison of FIGS. 10 and 11, the life characteristics of the battery employing the Si-Cu / C composite as the negative electrode active material are much improved compared to the life characteristics of the battery employing Si powder or the Si / C composite as the negative electrode active material. It was. Through this, the negative electrode active material of the lithium secondary battery of the present invention can improve the life characteristics of the lithium secondary battery by solving problems such as micronization and electrical short circuit caused by volume expansion of the metal-based active material, which have been examined as a negative electrode active material of a conventional high capacity lithium secondary battery. It could be confirmed.

In FIG. 9, the thin disconnection is the charge / discharge curve of the first cycle, and the thick line is the overlapping charge / discharge curve from 2 to 50 cycles.

As described above, although described with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and modified within the scope of the present invention without departing from the spirit and scope of the invention described in the claims below. It will be appreciated that it can be changed.

The negative electrode active material for a lithium secondary battery of the present invention can improve the life characteristics of a lithium secondary battery by solving problems such as micronization and electrical short circuit caused by volume expansion of a metal-based active material which have been examined as a negative electrode active material of a conventional high capacity lithium secondary battery.

Therefore, the lithium secondary battery including the negative electrode active material for the lithium secondary battery of the present invention can increase the capacity of the portable transceiver, the notebook, and the camcorder using a conventional lithium battery, by further increasing the capacity of the battery. It can contribute to the industrial development by increasing the applicability as the power source of electric vehicles requiring high capacity.

1 is a schematic cross-sectional view of a negative electrode active material according to an embodiment of the present invention.

2 is a cross-sectional view schematically showing a state during charging of the negative electrode active material according to an embodiment of the present invention.

3 is an exploded perspective view illustrating a lithium secondary battery according to an embodiment of the present invention.

4 is an X-ray diffraction (XRD) pattern of the anode active material according to Example 1 of the present invention.

5 is a scanning electron micrograph of a negative electrode active material according to Example 1 of the present invention.

6 is a transmission electron micrograph of a negative electrode active material according to Example 1 of the present invention.

7 is a Fourier Transform Infrared (FTIR) Spectra of the anode active material according to Example 1 of the present invention.

8 is a Pore distribution of the negative electrode active material according to Example 1 of the present invention.

9 is a graph showing charge and discharge characteristics of a lithium secondary battery manufactured according to Example 1 of the present invention.

10 is a graph showing the life characteristics of the lithium secondary battery prepared according to Example 1.

11 is a graph showing the life characteristics of the lithium secondary battery prepared according to Comparative Example 1.

Claims (17)

delete delete delete delete delete delete delete In the manufacture of the negative electrode active material for a lithium secondary battery, 1 type selected from the group consisting of Co, Ni, Mn, Fe and Cu with respect to 100 parts by weight of at least one active metal selected from the group consisting of Si, Sn, Al, Zn, Pb, Bi, Ag, Cd and Sb Alloying using 10 to 100 parts by weight of the above inert metal; 20 to 120 parts by weight of at least one carbon-based material selected from the group consisting of carbon nanotube, carbon nanowire, soft carbon and hard carbon is added to 100 parts by weight of the alloy of the active metal and the inactive metal, and ball-milling or mechano-fusion is added. Forming an active metal-carbon bond and adjusting a porosity in the alloy metal. The method of claim 8, wherein the alloying of the active metal and the inactive metal is performed by any one method selected from ball milling, mechano-fusion, and arc-melting. delete delete The method of claim 8, wherein the active metal is a powder having an average particle diameter of 1 to 50 μm. delete The method of claim 8, wherein the inert metal is a powder having an average particle diameter of 1 to 50 μm. delete The method of claim 8, wherein the carbonaceous material is a powder having an average particle diameter of 1 to 50 μm. A lithium secondary battery comprising a negative electrode active material for a lithium secondary battery produced by the method of claim 8.

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