WO2017209561A1 - Cathode active material, cathode comprising same, and lithium secondary battery comprising same - Google Patents

Abstract

The present invention relates to a cathode active material, a method for preparing same, an electrode comprising same, and a lithium secondary battery comprising same, the cathode active material comprising a secondary particle comprising a first particle which is a primary particle, wherein the first particle comprises a first core and a first surface layer which is disposed on the surface of the first core and comprises carbon, wherein the first core comprises silicon and/or a silicon compound and a metal compound, wherein the metal compound comprises a metal oxide and/or a metal silicate.

Description

Negative electrode active material, negative electrode including same and lithium secondary battery comprising same

Citation with Related Applications

This application is subject to Korean Patent Application No. 10-2016-0068956, filed June 2, 2016, Korean Patent Application No. 10-2016-0068940, filed June 2, 2016, and Korea, filed June 2, 2017. Claiming the benefit of priority based on patent application No. 10-2017-0068856, all contents disclosed in the literature of that Korean patent application are incorporated as part of this specification.

Technical Field

The present invention relates to a negative electrode active material, a negative electrode including the same, and a lithium secondary battery including the same.

In accordance with the recent trend toward miniaturization and lightening of electronic devices, miniaturization and lightening of batteries serving as power sources are also required. Lithium secondary batteries are currently used as batteries capable of charging and discharging with high capacity while satisfying miniaturization and light weight, and are used in portable electronic devices and communication devices such as small video cameras, mobile phones, and notebook computers.

In general, a lithium secondary battery is composed of a positive electrode, a negative electrode, a separator, and an electrolyte, and the first and second lithium electrodes reciprocate the positive electrode such that lithium ions from the positive electrode active material are inserted into the negative electrode active material, ie, carbon particles, and are detached again during discharge. While it plays a role of transferring energy, charging and discharging are possible.

Meanwhile, as high-capacity batteries continue to be required due to the development of portable electronic devices, high-capacity negative electrode materials such as tin and silicon, which have a much higher capacity per unit weight than carbon used as an existing negative electrode material, have been actively studied. Among these, the anode material using silicon has a capacity about 10 times higher than the cathode material using carbon.

Accordingly, research has been conducted on a negative electrode material using silicon, which has a high capacity and does not damage electrodes even after repeated insertion and removal of lithium.

[Preceding technical literature]

[Patent Documents]

(Patent Document 1) KR2005-0090218A

The present invention provides a negative electrode active material that can prevent the negative electrode from expanding and contracting by an electrochemical reaction of lithium discharged from the positive electrode and silicon contained in the negative electrode during charging and discharging of a lithium secondary battery.

The present invention provides a negative electrode active material having many passages through which lithium ions can move.

The present invention is to provide a lithium secondary battery having a high capacity and high output characteristics.

The present invention is to provide a lithium secondary battery that can increase the initial efficiency (initial efficiency) and improved speed characteristics.

According to an embodiment of the present invention, it comprises a secondary particle comprising a first particle that is a primary particle, the first particle is disposed on the surface of the first core and the first core and comprises a first carbon And a surface layer, wherein the first core comprises at least one of silicon and a silicon compound; And a metal compound, wherein the metal compound is provided with a negative electrode active material including at least one of a metal oxide and a metal silicate.

According to another embodiment of the present invention, a negative electrode including the negative electrode active material is provided.

According to another embodiment of the present invention, a lithium secondary battery including the negative electrode is provided.

Since the negative electrode active material according to the present invention includes secondary particles including first particles as primary particles, a passage through which lithium ions may move also increases, so that an output characteristic of a lithium secondary battery may be improved, and a lithium secondary battery The initial efficiency of is high, and the speed characteristic (charge / discharge characteristic) can be improved.

In addition, according to the present invention, due to the voids between the primary particles, even if the insertion and desorption of lithium ions is repeated, the damage of the electrode can be minimized even if the contraction and expansion of the core is repeated.

In addition, according to the present invention, since the metal compound is doped in the first core, the initial efficiency of the battery may be further improved.

Furthermore, a first particle including a first core doped with a metal compound and a second particle including a second core not doped with the metal compound may be mixed in an appropriate weight ratio to provide a battery having high initial capacity and high initial efficiency. .

1 is a schematic diagram showing a cross section of a negative electrode active material according to an embodiment of the present invention.

2 is a schematic view showing a cross section of a negative electrode active material according to another embodiment of the present invention.

3 is a schematic view showing a cross section of a negative electrode active material according to another embodiment of the present invention.

4 is a schematic view showing a cross section of a negative electrode active material according to another embodiment of the present invention.

5 is a schematic view showing a cross section of a negative electrode active material according to another embodiment of the present invention.

6 is a schematic view showing a cross section of a negative electrode active material according to another embodiment of the present invention.

7 is a graph showing normalized doses of Examples and Comparative Examples of the present invention.

The terms or words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best explain their invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.

And while the present invention has been described with reference to the embodiments shown in the drawings, which are merely exemplary, those skilled in the art will understand that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

An anode active material according to an embodiment of the present invention includes secondary particles including first particles which are primary particles, wherein the first particles are disposed on a surface of the first core and the first core and include carbon. A first surface layer, wherein the first core comprises at least one of silicon and a silicon compound; And a metal compound, wherein the metal compound may include at least one of a metal oxide and a metal silicate.

1 is a schematic diagram showing a cross section of a negative electrode active material according to an embodiment of the present invention.

Referring to FIG. 1, the anode active material includes secondary particles 200 including first particles 110 that are primary particles. Here, the expression secondary particles means particles formed by aggregation of primary particles.

The first particles 110 may include a first core 111 and a first surface layer 112.

The first core 111 is at least one of silicon and silicon compounds; And a metal compound 113.

Since the silicon has a theoretical capacity of about 3,600 mAh / g, since the silicon has a very high capacity as compared with the negative electrode active material including graphite, the capacity of the lithium secondary battery including the same may be improved.

The silicon compound refers to a compound containing silicon, which is physically or chemically complexed with silicon oxide (SiOx, 0 <x <2) and a carbon-based material in which silicon is distributed in a silicon dioxide (SiO ₂ ) matrix. It may be a silicon alloy (Si-alloy) complexed with C or a metal, specifically silicon oxide (SiOx, 0 <x <2), more specifically SiOx (0 <x≤1), For example, it may be SiO.

When the silicon oxide (SiOx, 0 <x <2) is included in the first core 111, the silicon oxide (SiOx, 0 <x <2) is lithium due to charging and discharging of a lithium secondary battery compared to silicon. Since there is little volume expansion during insertion and desorption of ions, damage of the negative electrode active material can be reduced, and high capacity and high initial efficiency, which are effects of silicon, can be realized.

Silicon in the silicon oxide (SiOx, 0 <x≤1) may be amorphous or crystalline. When silicon in the silicon oxide (SiOx, 0 <x≤1) is crystalline, the crystal size may be greater than 0 and less than 30 nm. If the above-mentioned range is satisfied, the final product of the lithium secondary battery can implement a higher capacity than the lithium secondary battery including the existing graphite, it is possible to improve the initial efficiency.

The first core 111 may be a porous core each including a plurality of pores. The porous core may increase the lithium ion diffusion by increasing the contact area between the electrolyte and the electrode.

When the first core 111 is a porous core, the internal porosity of the first core 111 may be 5% to 90% of the total volume of the first core 111, wherein the porosity is It means '(pore volume per unit mass) / (specific volume + pore volume per unit mass)' and can be measured by mercury porosimetry or Brunauer-Emmett-Teller (BET) measurement. When the above-mentioned range is satisfied, the volume expansion of the core 111 may be suppressed during charging and discharging, and the mechanical strength may be excellent, and durability may be tolerated even during a manufacturing process of a battery such as rolling.

The average particle diameter D ₅₀ of the first core 111 may be 0.5 μm to 20 μm, and specifically 0.5 μm to 5 μm. When the average particle diameter of the first core 111 is 0.5 μm to 20 μm, aggregation is easy in forming secondary particles, and sintering does not occur even when charging and discharging are repeated. This can be prevented. In addition, the volume change during charging and discharging can be effectively prevented. At the same time, the external appearance of the electrode may be smoothly formed, and thus the active material layer may be smoothly rolled during electrode production. Accordingly, the energy density per unit volume can be improved. In the present specification, the average particle diameter (D ₅₀ ) may be defined as a particle diameter based on 50% of the particle size distribution of the particles. The average particle diameter D ₅₀ may be measured using, for example, a laser diffraction method. In general, the laser diffraction method can measure the particle diameter of several mm from the submicron region, and high reproducibility and high resolution can be obtained.

The BET specific surface area of the first core 111 may be 0.5 m 2 / g to 30 m 2 / g.

The metal compound 113 may be formed by oxidizing a metal capable of reducing the silicon compound, specifically, a metal having a reducing power capable of reducing silicon dioxide (SiO ₂ ) in the silicon compound to silicon. The metal compound 113 may include at least one of a metal oxide and a metal silicate.

The metal oxide may include an oxide of at least one metal selected from the group consisting of lithium (Li), magnesium (Mg), aluminum (Al), calcium (Ca), and titanium (Ti). Specifically, the metal oxide may be at least one of MgO, MgSi ₃ and Mg ₂ SiO ₄ .

The metal silicate may include silicate of at least one metal selected from the group consisting of lithium (Li), magnesium (Mg), aluminum (Al), calcium (Ca), and titanium (Ti).

The metal compound may be formed by a metal doped in the first core. As the metal is doped into the first core, the SiO ₂ matrix in SiO may be reduced and a metal compound may be formed. Accordingly, since the content of SiO ₂ acting as the initial irreversible can be reduced, the initial efficiency of the battery can be improved.

The weight of the metal compound 113 may be 1 wt% to 50 wt%, and specifically 2 wt% to 50 wt% with respect to the total weight of the first particles. When the above range is satisfied, the initial efficiency is effectively improved, and excessive heat generation during the reduction reaction of SiO ₂ can be suppressed from excessively increasing the size of the Si crystal. In addition, most of the doped metals participate in the reaction, so that no metal impurities may occur.

The first surface layer 112 may include carbon and be disposed on the surface of the first core 111. The first surface layer 112 prevents further surface oxidation of the first core 111. The first surface layer 112 may improve the electrical conductivity of the negative electrode active material while forming a conductive passage in the negative electrode active material. Due to the first surface layer 112, a high capacity may be expressed by increasing the capacity per unit volume of the first particle 110.

The carbon may be amorphous carbon or crystalline carbon. When the amorphous carbon is included in the first surface layer 112, the strength between the first surface layers 112 may be properly maintained to suppress expansion of the first core 111. When the crystalline carbon is included in the first surface layer 112, the conductivity of the negative electrode active material may be further improved. The crystalline carbon may be florene, carbon nanotubes, or graphene.

The first surface layer 112 may include one or more carbides independently selected from the group consisting of tar, pitch, and other organic materials. Specifically, the first surface layer 112 may each independently include tar carbide, Pitch carbide, or other organic carbides. The carbide of the other organic material may be a carbide of an organic material selected from carbides of sucrose, glucose, galactose, fructose, lactose, manos, ribose, aldohexose or kedohexose, and combinations thereof.

The first surface layer 112 is each independently substituted or unsubstituted aliphatic or alicyclic hydrocarbon, substituted or unsubstituted aromatic hydrocarbons, products obtained in the distillation process of tar, vinyl-based resin, phenol-based resin, cellulose-based resin and It may include one or more pyrolysis products selected from the group consisting of a pitch-based resin. For example, pyrolysis products such as substituted or unsubstituted aliphatic or alicyclic hydrocarbons, substituted or unsubstituted aromatic hydrocarbons, and the like can be used as a carbon source for performing chemical vapor deposition.

Specific examples of the substituted or unsubstituted aliphatic or alicyclic hydrocarbons include methane, ethane, ethylene, acetylene, propane, butane, butene, pentane, isobutane or hexane.

Specific examples of the substituted or unsubstituted aromatic hydrocarbons include benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, Anthracene, phenanthrene, and the like.

The product obtained by the said tar distillation process is gas gas oil, creosote oil, anthracene oil, naphtha cracked tar oil, etc. are mentioned.

The first surface layer 112 may include a conductive polymer including carbon, and the conductive polymer may be polycellulose sulfonate, polyacetylene, polyparaphenylene, poly (p-phenylenevinylene), polypyrrole, poly Poly (1-pyrenemethyl methacrylate), which is a homopolymer of thiophene, polyaniline, polyisothianaphthene, polyparamethylene, pyrene, and poly (1-pyrenemethyl methacrylate, which is a copolymer of pyrene Late-coatriethylene oxide methyl ether methacrylate), a polymer in which the pyrene side chain of the homopolymer or copolymer of pyrene is converted to anthracene, a polymer having a carbonyl group and a methylbenzoic ester and a conjugation bond ( It may include one or more selected from the group consisting of polyacetylene having a conjugation bond).

The first surface layer 112 may be included in an amount of 2 parts by weight to 50 parts by weight based on 100 parts by weight of the first core 111. The thickness of the first surface layer 112 may be 20 nm to 100 nm, respectively. If the above range is satisfied, the electrical conductivity of the lithium secondary battery may be improved while maintaining the conductive passages of the first cores 111.

The average particle diameter D ₅₀ of the first particles 110 may be 0.502 μm to 20.2 μm, and specifically 0.502 μm to 5.2 μm. When the above-mentioned range is satisfied, aggregation is easy in forming the secondary particles, and even when charging and discharging are repeated, sintering does not occur and change in size can be prevented. In addition, high output characteristics can be expressed.

Referring to FIG. 1, the secondary particles 200 are formed by aggregation of the first particles 110, and include pores between the first particles 110. The porosity between the first particles 110 is 2% to 50% with respect to the total volume of the secondary particles 200. When the above range is satisfied, a buffer area may be provided to the volume expansion of the first core 111 during charging and discharging, and the secondary particles 200 may be prevented from being broken. . In addition, the output speed can be improved by increasing the moving speed of lithium ions.

Since the definition and measurement method of the porosity between the first particles 110 is mentioned in the description of the internal porosity of the porous particles, it is omitted.

The average particle diameter of the secondary particles 200 may be 2 μm to 50 μm, and specifically 2 μm to 42 μm. If the above-mentioned range is satisfied, there are many passages through which lithium ions can move, and thus a lithium secondary battery, which is a final product, can exhibit high capacity, high output, high initial efficiency, and excellent speed characteristics.

The negative electrode active material according to another embodiment of the present invention is the same as the negative electrode active material of the above-described embodiment except that the secondary particles further include second particles which are primary particles. Referring to FIG. 2, the secondary particles 210 may further include second particles 120 which are primary particles together with the first particles 110 described above, and the second particles 120 may include a second particle 120. And a second surface layer 122 disposed on a surface of the core 121 and the second core 121 and including carbon, wherein the second core 121 includes at least one of silicon and a silicon compound. can do. Here, since the first particles 110 are the same as the first particles described with reference to FIG. 1, description thereof is omitted.

The second particle 120 may include a second core 121 and a second surface layer 122.

The second core 121 may include at least one of silicon and a silicon compound.

Since the silicon has a theoretical capacity of about 3,600 mAh / g, since the silicon has a very high capacity as compared with the negative electrode active material including graphite, the capacity of the lithium secondary battery including the same may be improved.

The silicon compound refers to a compound containing silicon, which is physically or chemically complexed with silicon oxide (SiOx, 0 <x <2) and a carbon-based material in which silicon is distributed in a silicon dioxide (SiO ₂ ) matrix. It may be a silicon alloy (Si-alloy) complexed with C or a metal, specifically silicon oxide (SiOx, 0 <x <2), more specifically SiOx (0 <x≤1), For example, it may be SiO.

When the silicon oxide (SiOx, 0 <x <2) is included in the second core 121, the silicon oxide (SiOx, 0 <x <2) is lithium due to charging and discharging of a lithium secondary battery compared to silicon. Since there is little volume expansion during insertion and desorption of ions, damage of the negative electrode active material can be reduced, and high capacity and high initial efficiency, which are effects of silicon, can be realized.

Silicon in the silicon oxide (SiOx, 0 <x≤1) may be amorphous or crystalline. When silicon in the silicon oxide (SiOx, 0 <x≤1) is crystalline, the crystal size may be greater than 0 and less than 30 nm. If the above-mentioned range is satisfied, the final product of the lithium secondary battery can implement a higher capacity than the lithium secondary battery including the existing graphite, it is possible to improve the initial efficiency.

The second core 121 may be a porous core each including a plurality of pores. The porous core may increase the lithium ion diffusion by increasing the contact area between the electrolyte and the electrode.

When the second core 121 is a porous core, the internal porosity of the second core 121 may be 5% to 90% of the total volume of the second core 121, wherein the porosity is It means '(pore volume per unit mass) / (specific volume + pore volume per unit mass)' and can be measured by mercury porosimetry or Brunauer-Emmett-Teller (BET) measurement. When the aforementioned range is satisfied, the volume expansion of the second core 121 may be suppressed during charging and discharging, and the mechanical strength may be excellent, and durability may be withstand even during the manufacturing process of the battery such as rolling.

The average particle diameter D ₅₀ of the second core 121 may be 0.5 μm to 20 μm, and specifically 0.5 μm to 5 μm. When the average particle diameter of the first core 121 is 0.5 μm to 20 μm, aggregation is easy in forming secondary particles, and sintering does not occur even when charging and discharging are repeated, causing cracking of the negative electrode. This can be prevented. In addition, the volume change during charging and discharging can be effectively prevented. At the same time, the external appearance of the electrode may be smoothly formed, and thus the active material layer may be smoothly rolled during electrode production. Accordingly, the energy density per unit volume can be improved.

The BET specific surface area of the second core 121 may be 0.5 m 2 / g to 30 m 2 / g.

The second surface layer 122 may include carbon and be disposed on the surface of the second core 121. The second surface layer 122 prevents further surface oxidation of the second core 121. The second surface layer 122 may improve the electrical conductivity of the negative electrode active material while forming a conductive passage in the negative electrode active material. The second surface layer 122 may increase the capacity per unit volume of the second particle 120 to express a high capacity.

The carbon may be amorphous carbon or crystalline carbon. When the amorphous carbon is included in the second surface layer 122, strength between the second surface layers 122 may be properly maintained to suppress expansion of the second core 121. When the crystalline carbon is included in the second surface layer 122, the conductivity of the negative electrode active material may be further improved. The crystalline carbon may be florene, carbon nanotubes, or graphene.

The second surface layer 122 may include one or more carbides independently selected from the group consisting of tar, pitch, and other organic materials. Specifically, the second surface layer 122 may each independently include a carbide of tar, Pitch carbide, or other organic carbides. The carbide of the other organic material may be a carbide of an organic material selected from carbides of sucrose, glucose, galactose, fructose, lactose, manos, ribose, aldohexose or kedohexose, and combinations thereof.

The second surface layer 122 is each independently substituted or unsubstituted aliphatic or alicyclic hydrocarbon, substituted or unsubstituted aromatic hydrocarbons, products obtained in the distillation process of tar, vinyl resin, phenol resin, cellulose resin and It may include one or more pyrolysis products selected from the group consisting of a pitch-based resin. For example, pyrolysis products such as substituted or unsubstituted aliphatic or alicyclic hydrocarbons, substituted or unsubstituted aromatic hydrocarbons, and the like can be used as a carbon source for performing chemical vapor deposition.

Specific examples of the substituted or unsubstituted aliphatic or alicyclic hydrocarbons include methane, ethane, ethylene, acetylene, propane, butane, butene, pentane, isobutane or hexane.

Specific examples of the substituted or unsubstituted aromatic hydrocarbons include benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, Anthracene, phenanthrene, and the like.

The product obtained by the said tar distillation process is gas gas oil, creosote oil, anthracene oil, naphtha cracked tar oil, etc. are mentioned.

The second surface layer 122 may include a conductive polymer including carbon, and the conductive polymer may be polycellulose sulfonate, polyacetylene, polyparaphenylene, poly (p-phenylenevinylene), polypyrrole, poly Poly (1-pyrenemethyl methacrylate), which is a homopolymer of thiophene, polyaniline, polyisothianaphthene, polyparamethylene, pyrene, and poly (1-pyrenemethyl methacrylate, which is a copolymer of pyrene Late-coatriethylene oxide methyl ether methacrylate), a polymer in which the pyrene side chain of the homopolymer or copolymer of pyrene is converted to anthracene, a polymer having a carbonyl group and a methylbenzoic ester and a conjugation bond ( It may include one or more selected from the group consisting of polyacetylene having a conjugation bond).

The second surface layer 122 may be included in an amount of 2 parts by weight to 50 parts by weight based on 100 parts by weight of the second core 121. The thickness of the second surface layer 122 may be 20 nm to 100 nm, respectively. If the above range is satisfied, the electrical conductivity of the lithium secondary battery may be improved while maintaining the conductive passages of the second cores 121.

The average particle diameter D ₅₀ of the second particles 120 may be 0.502 μm to 20.2 μm, and specifically 0.502 μm to 5.2 μm. When the above-mentioned range is satisfied, aggregation is easy in forming the secondary particles, and even when charging and discharging are repeated, sintering does not occur and change in size can be prevented. In addition, high output characteristics can be expressed.

In the negative electrode active material of the present embodiment described with reference to FIG. 2, the first particles 110 have a larger mass than the second particles 120, but the charge and discharge characteristics of the battery may be improved while the metal is doped during manufacture. Can be. In addition, since the amount of lithium bonds of the second particles 120 is high, high capacity characteristics of the battery may be improved. Therefore, when the battery includes a negative electrode including the secondary particles 210 formed through the first particles 110 and the second particles 120, it is possible to simultaneously achieve high capacity and excellent charge and discharge characteristics of the battery. have.

The weight ratio of the first particles 110 and the second particles 120 may be 1: 0.25 to 1: 4, and specifically 1: 0.43 to 1: 1.5. When the weight ratio is satisfied, high capacity and excellent charge / discharge characteristics of the battery may be achieved at a more preferable level, and an effect of reducing expansion of the electrode thickness may be obtained.

Referring to FIG. 2, the secondary particles 210 are formed by aggregation of the first particles 110 and the second particles 120, between the first particles 110, and the second particles ( Pores between the first and second particles 120, and between the first particles 110 and the second particles 120, between the first particles 110, between the second particles 120, and the first particles. The total porosity between the first particle 110 and the second particle 120 is 2% to 50% of the total volume of the secondary particle 210. If the above range is satisfied, a buffer area may be provided for volume expansion of the first core 111 and the second core 121 during charging and discharging, and the secondary particles 210 may be provided. Can be prevented from being crushed. In addition, the output speed can be improved by increasing the moving speed of lithium ions.

The method of defining and measuring the porosity between the first particles 110, between the second particles 120, and between the first particles 110 and the second particles 120 depends on the internal porosity of the porous particles. Since it is mentioned in the description, it is omitted.

An average particle diameter of the secondary particles 210 may be 2 μm to 50 μm, specifically 2 μm to 42 μm, and more specifically 4 μm to 30 μm. If the above-mentioned range is satisfied, there are many passages through which lithium ions can move, and thus a lithium secondary battery, which is a final product, can exhibit high capacity, high output, high initial efficiency, and excellent speed characteristics.

Referring to FIG. 3, the negative active material according to another embodiment of the present invention is similar to the negative active material according to the exemplary embodiment described with reference to FIG. 1, but the secondary particles 220 include the carbon layer 130. The only difference is that. Thus, the carbon layer 130 corresponding to the difference will be described mainly.

The carbon layer 130 may be disposed on the surface of the secondary particles. Specifically, the carbon layer 130 may be disposed on the surface of the structure in which the first particles 110 are aggregated to constitute the secondary particles 220. By the carbon layer 130, expansion of secondary particles may be suppressed during charging and discharging, and conductivity of the negative electrode active material may be further improved.

The carbon layer 130 may include carbon. In detail, the carbon layer 130 may be any one of materials that may constitute the surface layer 112 described above. Further, the carbon layer 130 and the surface layer 112 may be made of the same material, or may be made of a different material. More specifically, both the surface layer and the carbon layer may be made of carbides of the other organic materials described above, or the surface layer may be carbides of other organic materials, and the carbon layer may be carbide of pitch.

The carbon layer 130 may have a thickness of 5 nm to 100 nm, and specifically 10 nm to 100 nm. If the above range is satisfied, the electrical conductivity of the lithium secondary battery may be improved while maintaining the conductive passage between the secondary particles.

The carbon layer may be 0.1% to 50% by weight, specifically 5% to 25% by weight based on the total weight of the secondary particles. When satisfying the above range, a conductive passage for the movement of lithium ions can be secured. When the carbon layer is formed at a level higher than the above range, a problem that the initial efficiency is excessively lowered may occur.

Referring to FIG. 4, the negative electrode active material according to another embodiment of the present invention is similar to the negative electrode active material according to the embodiment described with reference to FIG. 2, but the secondary particles 230 include the carbon layer 130. The only difference is that. Since the carbon layer 130 included in the negative electrode active material of the present embodiment is the same as the carbon layer included in the negative electrode active material of the embodiment described with reference to FIG. 3, description thereof is omitted.

Referring to FIG. 5, the negative electrode active material according to another embodiment of the present invention is similar to the negative electrode active material according to the exemplary embodiment described with reference to FIG. 1, but the secondary particles 240 may form the crystalline carbonaceous material 140. The only difference is the inclusion. The differences will be explained mainly.

The crystalline carbonaceous material 140 may be primary particles. Therefore, the crystalline carbonaceous material 140 may be aggregated together with the first particles 110 to form the secondary particles 240. In detail, the crystalline carbonaceous material 140 may be mixed with the first particles 110 in a solvent, and may be formed in a configuration of secondary particles through drying and firing.

Description of the first particle 110 is as described above.

The crystalline carbon material 140 may improve the capacity and cycle characteristics of the lithium secondary battery. Specific examples of the crystalline carbon-based material 140 may include graphene, carbon nanotubes, or nanofibers.

The content of the crystalline carbonaceous material 140 may be included in an amount of 75 parts by weight to 95 parts by weight based on 100 parts by weight of the first particles 110. If the above range is satisfied, the capacity and cycle characteristics of the lithium secondary battery, which is a final product, may be further improved.

Referring to FIG. 6, the negative electrode active material according to another embodiment of the present invention is similar to the negative electrode active material according to the exemplary embodiment described with reference to FIG. 1, but the secondary particles 250 may form the crystalline carbonaceous material 140. The only difference is the inclusion. Since the crystalline carbon-based material 140 included in the secondary particles 250 of the negative electrode active material of the present embodiment is the same as the crystalline carbon-based material included in the secondary particles 240 of the negative electrode active material of the embodiment described with reference to FIG. 5, Omit the description.

The negative electrode active material according to another embodiment of the present invention is similar to the negative electrode active material of the embodiments described with reference to FIGS. 1 to 6, except that the negative electrode active material further includes graphite-based active material particles. The graphite-based active material particles may be used together with the secondary particles of the above-described embodiments. Specifically, the graphite-based active material particles may be mixed with secondary particles, and the negative electrode active material may be a mixture of two kinds of active materials. Through this, charging and discharging characteristics of a battery may be improved. The graphite-based active material particles may be at least one selected from the group consisting of artificial graphite, natural graphite, graphitized carbon fiber, and graphitized mesocarbon microbeads.

The weight ratio of the secondary particles and the graphite-based active material particles in the negative electrode active material may be 1: 1 to 1:49, specifically 1: 9 to 1:19. When the above range is satisfied, the charge and discharge characteristics of the battery are further improved, and voids between the secondary particles can be secured, so that damage to the electrode can be minimized even if the secondary particles shrink and expand repeatedly. The graphite-based active material particles may be mixed in a solvent together with the prepared secondary particles and used for preparing a negative electrode.

According to another embodiment of the present invention, a method of manufacturing a negative active material includes preparing a core including at least one of silicon or a silicon compound (first step); Forming a preliminary first particle by forming a surface layer containing carbon on the surface of the core (second step); Doping metal to the preliminary first particles and performing heat treatment to form first particles (third step); And forming a secondary particle including the first particles (fourth step). Here, the core is the first core and the second core of the present embodiments described above, the surface layer is the same as the first surface layer and the second surface layer of the present embodiments described above, the first particle is the first particle of the present embodiments described above Is the same as

In the first step, the core may be prepared by grinding a silicon or silicon compound having a large average particle diameter (D ₅₀ ) to 0.5㎛ to 20㎛. Specifically, the core may be prepared by grinding silicon oxide having an average particle diameter (D ₅₀ ) of 5 μm to 50 μm by zirconia balls in a bead mill under ethanol solvent. However, it is not necessarily limited thereto. The core may be made of silicon or a silicon compound obtained by performing heat treatment of silicon oxide in an inert gas or reducing atmosphere at a temperature range of 1,100 ° C. or less. Here, silicon oxide is a generic term for amorphous silicon oxide obtained by cooling and precipitation of silicon monoxide gas generated by heating a mixture of silicon dioxide and metal silicon. In addition, specific examples of the inert gas may include Ar, He, H ₂ or N ₂ , and these may be used alone or as a mixed gas. The temperature of the precipitation plate for cooling and precipitation of the silicon monoxide gas may be 500 ° C to 1,050 ° C.

In addition, the core may be silicon obtained by heating and evaporating metal silicon in a vacuum to precipitate on a cold plate.

In the second step, when the carbon is carbon included in the carbide of the other organic materials described above, the second and first mixtures and the mixture are pulverized and dried in a solvent by milling the mixture of the core and the other organic materials. The method may include a step 2-2 of forming a surface layer including carbon on the surface of the core by carbonizing the organic material by heat treatment after spheroidization.

The solvent is not particularly limited as long as the other organic material may be evenly dispersed, but may be an alcohol such as ethanol, n-butanol, 1-propanol or 2-propanol. The content of the organic solvent may be 100 parts by weight to 300 parts by weight based on 100 parts by weight of the particles.

In the milling process, the core and the organic material are pulverized to a desired size, and the particles and the organic material are mixed well in a solvent, so that the organic material is evenly distributed on the surface of the particles. The milling process may be performed using a beads mill, a high energy ball mill, a planetary mill, a stirred ball mill, a vibration mill, or the like. . Here, the bead mill or the ball mill may be made of a chemically inert material that does not react with silicon and organic materials, and specific examples may be made of zirconia.

The drying may be performed at a temperature range in which the solvent may be evaporated to volatilized, and the temperature range may be 60 to 150 ° C.

Instead of the other organics described above, the carbon may be derived from any of the sources of the surface layer described above.

When the carbon is carbon included in the pyrolysis product, the second step may be a step of forming a surface layer containing carbon on the surface of the core by chemical vapor deposition.

Using the chemical vapor deposition method, it is possible to form the surface layer uniformly on the surface of the core.

When the chemical vapor deposition method is performed, the temperature may be 700 ° C. to 1,200 ° C., and the carbon source may be selected to pyrolyze at the temperature to generate carbon. The carbon source may be one or two or more selected from the group consisting of substituted or unsubstituted aliphatic or alicyclic hydrocarbons, substituted or unsubstituted aromatic hydrocarbons.

When the carbon is carbon contained in the conductive polymer, the core may be dip-coated in a solution containing the conductive polymer to form a surface layer on the core. Description of the conductive polymer is as described above.

On the other hand, the core may be coarsely ground in an inert atmosphere in order to obtain a desired average particle diameter. In addition, a mixture of the core and the other organic material may further include a crystalline carbonaceous material.

In the third step, the preliminary first particles may be uniformly mixed with the metal powder in a state in which the air is blocked, and then heat-treated under an argon gas atmosphere in a furnace. Thereafter, metal powder or side reaction substances remaining on the particle surface are removed by washing with a strong acid or the like. Through this, a second particle including a core including a metal compound may be prepared. Specifically, the heat treatment may be to heat up to 900 ℃ to 1100 ℃ at a temperature increase rate of 4 ℃ / min to 6 ℃ / min, and may be heated for 1 hour to 3 hours. When the metal is doped and heat-treated before the secondary particles are prepared, the metal compound formed by oxidizing the metal is the final active material particles, as compared with the case where the metal particles are included in the core by doping and heat-treating the metal after the secondary particles are prepared. It may be more uniformly distributed within.

In the fourth step, the first particles may be aggregated to form secondary particles. Specifically, when a solution including the first particles and the solvent is prepared, and the solution is spray-dried, secondary particles in which the first particles are aggregated may be formed. The solution may further include a carbon precursor to facilitate aggregation of the first particles and the second particles.

The solvent is not particularly limited as long as the first particles are well dispersed, but specific examples thereof include water, alcohol, N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), acetonitrile, acetone, Tetrahydrofuran (THF), diethyl ether, toluene or 1,2-dichlorobenzene, and the like.

The inlet temperature during the spray drying may be 100 ° C to 250 ° C.

The secondary particles may further perform a separate firing process to improve durability and conductivity. The firing temperature may be 400 ℃ to 1,000 ℃.

In the fourth step, the secondary particles may be formed by agglomeration such that the porosity between the first particles is 2% to 50%. Specifically, in the fourth step, a filler is included in the solvent together with the first particles to prepare a solution, and the solution is spray-dried to form preliminary secondary particles in which the first particles and the filler are aggregated. Can be.

The filler is included to form secondary particles such that the porosity between the first particles is 2% to 50%, and the porosity may be adjusted by adjusting the amount of the filler. The amount of the filler may be included in a volume ratio of 1: 0.01 to 1: 0.43 with respect to the first particle. Specific examples include metals, polymethyl methacrylate (PMMA), polystyrene beads (polystylene beads), sodium chloride (NaCl), calcium chloride (KCl) or sodium sulfate (Na2SO4).

When the above-described firing process is included in the fourth step, the filler may be sodium chloride, calcium chloride or sodium sulfate. When the firing process is performed at 900 ℃ to 1,000 ℃ the filler may be polymethyl methacrylate (PMMA), sodium chloride, calcium chloride or sodium sulfate.

The preliminary secondary particles may be added to water or a mixture of water and ethanol to remove the filler, and then further subjected to an ultrasonic treatment and a drying process. Through this, secondary particles having a porosity of 2% to 50% can be prepared.

The manufacturing method of the negative electrode active material according to another embodiment of the present invention is similar to the method of manufacturing the negative electrode active material according to the above-described embodiment, but in the fourth step, using the preliminary primary particles as the second particle, It may include forming a secondary particle further comprising the first particle and the second particle. Specifically, in the fourth step, not only the first particles but also the second particles may be aggregated together to form secondary particles.

In this case, too, in the fourth step, the secondary particles may be formed by aggregation so that the porosity between the first particles and the second particles is 2% to 50%. Specifically, the fourth step is to prepare a solution by including a filler in a solvent together with the first particles, the second particles, and spray-drying the solution, the first particles, the second particles And preliminary secondary particles in which the filler is agglomerated.

The filler is included to form secondary particles such that the porosity between the first particles and the second particles is 2% to 50%, and the porosity may be adjusted by adjusting the amount of the filler. The amount of the filler may be included in a volume ratio of 1: 0.01 to 1: 0.43 with respect to the primary particles (first particles and second particles). Specific examples include metals, polymethyl methacrylate (PMMA), polystyrene beads (polystylene beads), sodium chloride (NaCl), calcium chloride (KCl) or sodium sulfate (Na2SO4).

When the above-described firing process is included in the fourth step, the filler may be sodium chloride, calcium chloride or sodium sulfate. When the firing process is performed at 900 ℃ to 1,000 ℃ the filler may be polymethyl methacrylate (PMMA), sodium chloride, calcium chloride or sodium sulfate.

The preliminary secondary particles may be added to water or a mixture of water and ethanol to remove the filler, and then further subjected to an ultrasonic treatment and a drying process. Through this, secondary particles having a porosity of 2% to 50% can be prepared.

Hereinafter, a lithium secondary battery according to another embodiment of the present invention will be described.

According to another embodiment of the present invention, a lithium secondary battery includes an electrode assembly and an electrolyte including a cathode, a cathode, and a separator disposed between the cathode and the anode.

The positive electrode may include a positive electrode current collector and a mixture of a positive electrode active material, a conductive material, and a binder on the positive electrode current collector.

The positive electrode current collector must be high in conductivity, easily adherable to the mixture, and not reactive in the voltage range of the cell. Specific examples of the positive electrode current collector include aluminum, nickel or alloys thereof. The positive electrode current collector may have a thickness of 3 μm to 500 μm.

Specific examples of the positive electrode active material include lithium cobalt oxide such as Li _x1 CoO ₂ (0.5 <x1 <1.3); Lithium nickel oxides such as Li _x2 NiO ₂ (0.5 <x2 <1.3); _{Li 1 + x3 Mn 2 - x} O 4 (0≤x3≤0.33), LiMnO 3, LiMn 2 O 3, or _{Li x4 MnO 2 (0.5 <x4} <1.3) lithium manganese oxide and the like; Lithium copper oxides such as Li ₂ CuO ₂ ; Lithium iron oxides such as LiFe ₃ O ₄ ; Lithium nickel cobalt manganese oxides such as Li [Ni _xa Co _ya Mn _za ] O ₂ (xa + ya + za = 1, 0 <xa <1, 0 <ya <1, 0 <za <1); Lithium nickel cobalt aluminum oxide such as Li [Ni _xb Co _yb Al _zb ] O ₂ (xb + yb + zb = 1, 0 <xb <1, 0 <yb <1, 0 <zb <1); Lithium vanadium compounds such as LiV ₃ O ₈ ; Nickel-site lithium nickel oxides such as LiNi _{1 - x4} M _x4 O ₂ (M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, 0.01 ≦ x4 ≦ 0.3); LiMn _{2 - x5} M _x5 O ₂ (M = Co, Ni, Fe, Cr, Zn or Ta, 0.01 ≦ x5 ≦ 0.1) or Li ₂ Mn ₃ MO ₈ (M = Fe, Co, Ni, Cu or Zn), etc. Lithium manganese composite oxide; LiMn ₂ O _{4 in} which part of lithium is substituted with alkaline earth metal ions; Disulfide compounds; Vanadium oxides such as V ₂ O ₅ or Cu ₂ V ₂ O ₇ ; Fe ₂ (MoO ₄ ) ₃ , and the like, and more specifically Li [Ni _xc Co _yc Mn _zc ] O ₂ (xc + yc + zc = 1, 0.3 ≦ xc ≦ 0.4, 0.3 ≦ yc ≦ 0.4, Lithium nickel cobalt manganese oxide such as 0.3 ≦ zc ≦ 0.4) or Li [Ni _xd Co _yd Al _zd ] O ₂ (xd + yd + zd = 1, 0.3 ≦ xd ≦ 0.4, 0.3 ≦ yd ≦ 0.4, 0.3 ≦ zd ≦ 0.4) lithium nickel cobalt aluminum oxide. These may be included one or two or more kinds in the cathode active material.

The conductive material is a material having conductivity without causing chemical change in the lithium secondary battery of the present invention. Specific examples of the conductive material include graphite such as natural graphite and artificial graphite; Carbon blacks such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Or conductive materials such as polyphenylene derivatives.

The binder is a component that assists in bonding the positive electrode active material and the conductive material to the current collector. Specific examples of the binder include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, reconstituted cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene monomer (EPDM) rubber, hydrogenated nitrile butadiene rubber (HNBR), sulfonated ethylene propylene diene, styrene butadiene rubber (SBR), fluorine rubber, various copolymers, and the like. Can be.

The negative electrode includes a negative electrode current collector and a negative electrode active material positioned on the negative electrode current collector.

The negative electrode current collector should be highly conductive, easily adhereable to the negative electrode active material, and not be reactive in the voltage range of the battery. Specific examples of the negative electrode current collector include copper, gold, nickel or alloys thereof.

Description of the negative electrode active material is the same as the description of the negative electrode active material of the above embodiments.

The separator prevents a short circuit between the positive electrode and the negative electrode and provides a passage for moving lithium ions. As the separator, an insulating thin film having high ion permeability and mechanical strength may be used. Specific examples of the separator include polyolefin-based polymer membranes such as polypropylene and polyethylene, or multiple membranes thereof, microporous films, woven fabrics, and nonwoven fabrics. When a solid electrolyte such as a polymer is used as the electrolyte to be described later, the solid electrolyte may serve as a separator.

The electrolyte may be an electrolyte containing a lithium salt. Examples of the lithium salt of the anion is ^{F -, Cl -, Br -} , 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 - , and the like _{^{-, CF 3 CO 2 -,}} SCN - or _{(CF 3 CF 2 SO 2)} 2 N. These may include one or two or more kinds in the electrolyte.

The external shape of the lithium secondary battery according to another embodiment of the present invention is not particularly limited, but specific examples thereof include a cylindrical shape, a square shape, a pouch type or a coin type using a can.

Lithium secondary battery according to another embodiment of the present invention can be used not only for the battery cell used as a power source of a small device, but also preferably used as a unit battery in a medium-large battery module including a plurality of battery cells. Specific examples of the medium-to-large device include an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, a power storage system, and the like, but are not limited thereto.

Hereinafter, preferred embodiments are provided to aid in understanding the present invention, but the above embodiments are merely illustrative of the present disclosure, and it is apparent to those skilled in the art that various changes and modifications can be made within the scope and spirit of the present disclosure. It is natural that such variations and modifications fall within the scope of the appended claims.

Example  1: Preparation of Anode Active Material

<Manufacture of core>

A silicon oxide (SiOx, 0 <x≤1) having an average particle diameter (D ₅₀ ) of 10 μm was put into a specs mill 8000M and 15 sus ball media were milled for 2 hours, and the average particle diameter (D ₅₀ ) was 1 μm. The core was prepared by grinding.

<Production of Preliminary First Particles>

A solution was prepared by adding 10 g of the core and 0.5 g of cellulose to 30 g of isopropanol. Using the zirconia beads (average particle diameter: 0.3 mm), the mixture was ground for 12 hours at a beads rotation speed of 1,200 rpm. The mixture was then dried in a drying furnace at 120 ° C. for 2 hours. The dried mixture was pulverized again in a mortar and classified to form silicon particles mixed with sucrose. Heat treatment at 800 ° C. under a nitrogen atmosphere to carbonize sucrose to form a surface layer having a thickness of 2 nm to prepare preliminary first particles. The surface layer was 2.1% by weight relative to the total weight of the core.

<Production of First Particles>

8 g of the preliminary first particles and 0.9 g of magnesium powder were mixed in an argon gas atmosphere to prepare a mixed powder. The mixed powder was placed in a tube furnace, heated to 5 ° C./min to 1030 ° C. under argon gas atmosphere, and heated for 2 hours. Thereafter, the temperature of the reactor was lowered to room temperature, and the heat-treated mixed powder was taken out and washed by stirring in 1M HCl for 1 hour. The filtered mixed powder was washed with distilled water and then dried in an oven at 60 ° C. for 8 hours to prepare first particles. As a result of analyzing the prepared first particles, the content of magnesium oxide and magnesium silicate formed by oxidizing magnesium in the first particles was 15% by weight based on the total weight of the first particles, which was determined by X-ray diffraction analysis. Measured via quantitative analysis using (XRD).

<Production of Secondary Particles>

A solution containing the first particles and ethanol / water (volume ratio 1: 9) in a volume ratio of 1:10 was stirred at 10,000 rpm for 30 minutes with a mechanical homogenizer to prepare a dispersion solution for spray drying. The dispersion solution was subjected to the inlet temperature of the mini spray dryer (manufacturer: Buchi, model name: B-290 mini spray dryer), 180 ° C, aspirator 95%, feeding rate 12 conditions. Preparative secondary particles were prepared by spray drying under, and then transferred to an alumina boat. Secondary particles were prepared by raising the temperature of a tube furnace equipped with a quartz tube having a length of 80 cm and an inner diameter of 4.8 cm to 600 ° C. at a rate of 10 ° C./min and firing while maintaining the temperature for 2 hours. . The porosity of the prepared secondary particles was 1%, and the average particle diameter (D ₅₀ ) was 5 μm. The porosity was measured by a mercury porosimeter method.

Example  2: Preparation of Anode Active Material

<Production of Core and Preliminary First Particles>

Core and preliminary first particles were prepared in the same manner as in Example 1.

<Production of First Particles>

8 g of the preliminary first particles and 10 g of magnesium powder were mixed in an argon gas atmosphere to prepare a mixed powder. The mixed powder was placed in a tube furnace, heated to 5 ° C./min to 1030 ° C. under argon gas atmosphere, and heated for 2 hours. Thereafter, the temperature of the reactor was lowered to room temperature, and the heat-treated mixed powder was taken out and washed by stirring in 1M HCl for 1 hour. The filtered mixed powder was washed with distilled water and then dried in an oven at 60 ° C. for 8 hours to prepare first particles. As a result of analyzing the prepared first particles, the content of magnesium oxide and magnesium silicate formed by oxidizing magnesium in the first particles was 51% by weight based on the total weight of the first particles, which was determined by X-ray diffraction analysis. Measured via quantitative analysis using (XRD).

<Production of Secondary Particles>

Using the said 1st particle | grains, the secondary particle of Example 2 was manufactured by the same method as the secondary particle manufacturing method of Example 1. The porosity of the prepared secondary particles was 1%, and the average particle diameter (D ₅₀ ) was 4 μm. The porosity was measured by a mercury porosimeter method.

Example  3: Preparation of Anode Active Material

<Manufacture of core>

A silicon oxide (SiOx, 0 <x≤1) having an average particle diameter (D ₅₀ ) of 10 µm was milled for 4 hours by adding 15 sus ball media to a spec mill 8000M for an average particle diameter (D ₅₀ ) of 0.4 µm. The core was prepared by grinding.

<Production of Preliminary First Particles>

Using the core, preliminary first particles having a surface layer of 2 nm thickness were prepared by the same method as the preparation method of preliminary first particle of Example 1. The surface layer was 2.1% by weight relative to the total weight of the core.

<Production of First Particles>

Using the preliminary first particles, the first particles were manufactured by the same method as the method for preparing the first particles of Example 1. As a result of analyzing the prepared first particles, the content of magnesium oxide and magnesium silicate formed by oxidizing magnesium in the first particles was 15% by weight based on the total weight of the first particles, which was determined by X-ray diffraction analysis. Measured via quantitative analysis using (XRD).

<Production of Secondary Particles>

Using the said 1st particle | grains, the secondary particle of Example 3 was manufactured by the method similar to the secondary particle manufacturing method of Example 1. The porosity of the prepared secondary particles was 1%, and the average particle diameter (D ₅₀ ) was 2 μm. The porosity was measured by a mercury porosimeter method.

Example  4: Preparation of Anode Active Material

<Manufacture of core>

A silicon oxide (SiOx, 0 <x≤1) having an average particle diameter (D ₅₀ ) of 10 µm was milled for 4 hours by adding 15 sus ball media to a spec mill 8000M for an average particle diameter (D ₅₀ ) of 0.4 µm. The core was prepared by grinding.

<Production of Preliminary First Particles>

Using the core, preliminary first particles having a surface layer of 2 nm thickness were prepared by the same method as the preparation method of preliminary first particle of Example 1. The surface layer was 2.1% by weight relative to the total weight of the core.

<Production of First Particles>

8 g of the preliminary first particles and 5 g of magnesium powder were mixed in an argon gas atmosphere to prepare a mixed powder. The mixed powder was placed in a tube furnace, heated to 5 ° C./min to 1030 ° C. under argon gas atmosphere, and heated for 2 hours. Thereafter, the temperature of the reactor was lowered to room temperature, and the heat-treated mixed powder was taken out and washed by stirring in 1M HCl for 1 hour. The filtered mixed powder was washed with distilled water and then dried in an oven at 60 ° C. for 8 hours to prepare first particles. As a result of analyzing the prepared first particles, the content of magnesium oxide and magnesium silicate formed by oxidizing magnesium in the first particles was 55% by weight based on the total weight of the first particles, which was determined by X-ray diffraction analysis. Measured via quantitative analysis using (XRD).

<Production of Secondary Particles>

Using the said 1st particle | grains, the secondary particle of Example 4 was manufactured by the method similar to the secondary particle manufacturing method of Example 1. The porosity of the prepared secondary particles was 1%, and the average particle diameter (D ₅₀ ) was 3 μm. The porosity was measured by a mercury porosimeter method.

Example  5: Preparation of Anode Active Material

<Production of Core and Preliminary First Particles>

In the same manner as the method for preparing the core and preliminary first particles of Example 1, preliminary first particles having a surface layer of 2 nm thickness were prepared. The surface layer was 2.1% by weight relative to the total weight of the core.

<Production of First Particles>

Using the preliminary first particles, the first particles were prepared by the first particle production method of Example 1. As a result of analyzing the prepared first particles, the content of magnesium oxide and magnesium silicate formed by oxidizing magnesium in the first particles was 15% by weight based on the total weight of the first particles, which was determined by X-ray diffraction analysis. Measured by quantitative analysis using (XRD).

<Production of Secondary Particles>

Secondary particles were prepared through the first particles and the second particles using the preliminary first particles as the second particles. Specifically, after mixing the first particles and the second particles in a weight ratio of 6: 4, a mechanical homogenizer comprising a solution containing the mixture and ethanol / water (volume ratio 1: 9) in a volume ratio of 1:10. A dispersion solution for spray drying was prepared by stirring at 10,000 rpm for 30 minutes with a mechanical homogenizer. The dispersion solution was subjected to the inlet temperature of the mini spray dryer (manufacturer: Buchi, model name: B-290 mini spray dryer), 180 ° C, aspirator 95%, feeding rate 12 conditions. Preparative secondary particles were prepared by spray drying under, and then transferred to an alumina boat. Secondary particles were prepared by raising the temperature of a tube furnace equipped with a quartz tube having a length of 80 cm and an inner diameter of 4.8 cm to 600 ° C. at a rate of 10 ° C./min and firing while maintaining the temperature for 2 hours. . The porosity of the prepared secondary particles was 1%, and the average particle diameter (D ₅₀ ) was 5 μm. The porosity was measured by a mercury porosimeter method.

Example  6: Preparation of Anode Active Material

<Production of Core, First Particles and Second Particles>

In the same manner as in Example 5, a core, first particles, and second particles (preliminary first particles) were prepared.

<Production of Anode Active Material>

Secondary particles were prepared in the same manner as in Example 6, except that the first particles and the second particles were mixed in a weight ratio of 1.5: 8.5. The porosity of the prepared secondary particles was 1%, and the average particle diameter (D ₅₀ ) was 5 μm. The porosity was measured by a mercury porosimeter method.

Comparative example  1: Preparation of Anode Active Material

<Production of Core and Preparative Particles>

In the same manner as the method for preparing the core and preliminary first particles of Example 1, preliminary first particles having a surface layer of 2 nm thickness were prepared. The surface layer was 2.1% by weight relative to the total weight of the core.

<Production of Secondary Particles>

Secondary particles were prepared in the same manner as in the manufacturing method of the secondary particles of Example 1, except that the first particles of Example 1 were not used and the preliminary first particles were used. The porosity of the prepared secondary particles was 1%, and the average particle diameter (D ₅₀ ) was 5 μm. The porosity was measured by a mercury porosimeter method.

Comparative example  2: Preparation of Anode Active Material

8 g of the preliminary first particles prepared in Example 1 and 0.9 g of magnesium powder were mixed under an argon gas atmosphere to prepare a mixed powder. The mixed powder was placed in a tube furnace, heated to 5 ° C./min to 1030 ° C. under argon gas atmosphere, and heated for 2 hours. Thereafter, the temperature of the reactor was lowered to room temperature, and the heat-treated mixed powder was taken out and washed by stirring in 1M HCl for 1 hour. The filtered mixed powder was washed with distilled water and then dried in an oven at 60 ° C. for 8 hours to prepare a negative active material in the form of a single particle. As a result of analyzing the prepared negative active material, the content of magnesium oxide and magnesium silicate formed by oxidizing magnesium in the negative electrode active material was 15% by weight based on the total weight of the negative electrode active material, which was X-ray diffraction analysis (XRD) It was measured through quantitative analysis using.

Example  7 to 12 and Comparative example  3, 4: battery manufacturing

<Production of Cathode>

Each negative electrode active material prepared in Examples 1 to 6 and Comparative Examples 1 and 2, fine graphite as a conductive material, and polyacrylonitrile as a binder were mixed at a weight ratio of 7: 2: 1 to prepare 0.2 g of a mixture. A negative electrode mixture slurry was prepared by adding 3.1 g of solvent N-methyl-2-pyrrolidone (NMP) to the mixture. The negative electrode mixture slurry was applied and dried on a copper (Cu) metal thin film, which is a negative electrode current collector having a thickness of 20 μm. At this time, the temperature of the air circulated was 80 ℃. Subsequently, rolls were pressed and dried in a vacuum oven at 130 ° C. for 12 hours, and then punched into a circle of 1.4875 cm 2 to prepare negative electrodes of Examples 7 to 12, respectively.

<Manufacture of battery>

Each prepared negative electrode was cut into a circle of 1.4875 cm 2, which was used as a negative electrode, and a lithium (Li) metal thin film cut into 1.4875 cm 2 circular was used as a positive electrode. Dissolving vinylene carbonate dissolved in 0.5 wt% in a mixed solution having a mixing volume ratio of methyl ethyl carbonate (EMC) and ethylene carbonate (EC) at 7: 3 through a separator of porous polyethylene between the positive electrode and the negative electrode, An electrolyte solution in which LiPF ₆ was dissolved at a concentration of 1 M was injected to prepare a lithium coin half-cell.

Test Example  1: evaluation of discharge capacity, initial efficiency, capacity retention rate and electrode thickness change rate

Charging and discharging were performed on the batteries of Examples 7 to 12 and Comparative Examples 3 and 4 to evaluate discharge capacity, initial efficiency, capacity retention rate, and electrode thickness change rate, which are shown in Table 1 below.

Meanwhile, one cycle and two cycles were charged and discharged at 0.1C, and charging and discharging were performed at 0.5C from 3 cycles to 49 cycles. The 50 cycles were terminated in the state of charging (lithium in the negative electrode), the battery was disassembled, the thickness was measured, and the electrode thickness change rate was calculated.

Charging Conditions: CC (Constant Current) / CV (Constant Voltage) (5mV / 0.005C current cut-off)

Discharge condition: CC (constant current) condition 1.5 V

Discharge capacity (mAh / g) and initial efficiency (%) were derived through the result at the time of single charge / discharge. Specifically, the initial efficiency (%) was derived by the following calculation.

Initial efficiency (%) = (discharge capacity after 1 discharge / 1 charge capacity) x 100

The capacity retention rate and the electrode thickness change rate were derived by the following calculations, respectively.

Capacity retention rate (%) = (49 discharge capacity / 1 discharge capacity) × 100

% Change in electrode thickness = (final electrode thickness change / initial electrode thickness) × 100

	Active material	Discharge Capacity (mAh / g)	Initial Efficiency (%)	Capacity retention rate (%)	% Change in electrode thickness
Example 7	Example 1	1420	82.2	87.5	107
Example 8	Example 2	1400	84.2	87	108
Example 9	Example 3	1350	81.5	87.3	105
Example 10	Example 4	1300	83.5	87.2	109
Example 11	Example 5	1508	80.08	88	105
Example 12	Example 6	1520	75.5	87.0	115
Comparative Example 3	Comparative Example 1	1550	74.0	86.5	123
Comparative Example 4	Comparative Example 2	1320	80.1	80	110

Referring to Table 1, in Examples 7 to 12 using the active material according to the present invention, it can be confirmed that compared with Comparative Example 3 in terms of initial efficiency, capacity retention rate and electrode thickness change rate. It can be seen that this is an effect obtained because the core of the first particles contains a metal compound.

Further, Example 7 using the negative electrode active material in which the metal compound is suitably included in the core at 15% by weight, discharge capacity and capacity retention rate compared to Example 8 using the negative electrode active material containing the metal compound but the content is 51% by weight You can see that this is high. In the case of Example 8, the metal doping amount for forming the metal compound is too high, the size of the crystal of Si in the negative electrode active material is too large, and a part of the metal acts as an impurity, which adversely affects the battery life, resulting in low capacity retention. see. In addition, Example 7 using the negative electrode active material of Example 1 having a suitable core size of 1 μm compared with Example 9 using the negative electrode active material of Example 3 having a small core size of 0.4 μm, the discharge capacity, initial efficiency, Capacity maintenance rate is high. This is because when using a small core, the specific surface area is increased to increase the irreversible reaction.

Example  13 to 17 and Comparative example  5, 6: manufacture of batteries

<Production of Cathode>

Mixed negative electrode active material prepared by mixing the negative electrode active material and graphite (natural graphite) prepared in Examples 1 to 5 and Comparative Examples 1 and 2 in a weight ratio of 1: 9, carbon black as a conductive material, CMC (carboxylmethyl cellulose) as a binder, and 5 g of a mixture was prepared by mixing SBR (Styrene butadiene rubber) in a weight ratio of 95.8: 1: 1.7: 1.5. 28.9 g of distilled water was added to the mixture to prepare a negative electrode mixture slurry. The negative electrode mixture slurry was applied and dried on a copper (Cu) metal thin film, which is a negative electrode current collector having a thickness of 20 μm. At this time, the temperature of the air circulated was 60 ℃. Subsequently, rolls were pressed and dried in a vacuum oven at 130 ° C. for 12 hours, and then punched into a circle of 1.4875 cm 2 to prepare negative electrodes of Examples 13 to 17 and Comparative Examples 5 and 6, respectively.

<Manufacture of battery>

Each prepared negative electrode was cut into a circle of 1.4875 cm 2, which was used as a negative electrode, and a lithium (Li) metal thin film cut into 1.4875 cm 2 circular was used as a positive electrode. Dissolving vinylene carbonate dissolved in 0.5 wt% in a mixed solution having a mixing volume ratio of methyl ethyl carbonate (EMC) and ethylene carbonate (EC) at 7: 3 through a separator of porous polyethylene between the positive electrode and the negative electrode, An electrolyte solution in which LiPF ₆ was dissolved at a concentration of 1 M was injected to prepare a lithium coin half-cell.

Test Example  2: evaluation of initial efficiency, capacity retention and electrode thickness change rate

Charging and discharging were performed on the batteries of Examples 13 to 17 and Comparative Examples 5 and 6 to evaluate initial efficiency, capacity retention rate, and electrode thickness change rate, which are described in Table 2 below. 7 shows the capacity normalized for each cycle number for Examples 13 to 16 and Comparative Examples 5 and 6. FIG.

Meanwhile, one cycle and two cycles were charged and discharged at 0.1C, and charging and discharging were performed at 0.5C from 3 cycles to 49 cycles. The 50 cycles were terminated in the state of charging (lithium in the negative electrode), the battery was disassembled, the thickness was measured, and the electrode thickness change rate was calculated.

Charging Conditions: CC (Constant Current) / CV (Constant Voltage) (5mV / 0.005C current cut-off)

Discharge condition: CC (constant current) condition 1.5 V

Initial efficiency (%) was derived through the result of one time charge / discharge. Specifically, the initial efficiency (%) was derived by the following calculation.

Initial efficiency (%) = (discharge capacity after 1 discharge / 1 charge capacity) x 100

The capacity retention rate and the electrode thickness change rate were derived by the following calculations, respectively.

Capacity retention rate (%) = (49 discharge capacity / 1 discharge capacity) × 100

% Change in electrode thickness = (change in electrode thickness / initial electrode thickness) × 100

	Active material		Initial Efficiency (%)	Capacity retention rate (%)	% Change in electrode thickness
Example 13	Example 1	black smoke	89.4	90.2	53.0
Example 14	Example 2	black smoke	90.2	89.8	53.2
Example 15	Example 3	black smoke	89.3	89.5	53.2
Example 16	Example 4	black smoke	90.1	89.2	53.3
Example 17	Example 5	black smoke	89.0	89.0	52.5
Comparative Example 5	Comparative Example 1	black smoke	86.1	88.8	53.4
Comparative Example 6	Comparative Example 2	black smoke	88.9	87.5	55.0

Referring to Table 2 and FIG. 7, it was confirmed that the batteries of Examples 13 to 17 according to the present invention had superior initial efficiency and capacity retention compared to the batteries of Comparative Examples 5 and 6. In addition, in Examples 13 to 17, compared to Examples 7 to 12, it was confirmed that the performance is excellent in terms of initial efficiency, capacity retention rate and electrode thickness change rate, through which, using the active material of the present invention with graphite In this case, it can be seen that a better effect can be derived.

[Description of the code]

110: first particle 111: first core

112: first surface layer 113: metal compound

120: second particle 121: second core

122: second surface layer 130: carbon layer

140: crystalline carbonaceous material

200, 210, 220, 230, 240, 250: secondary particles

Claims (19)

Including secondary particles including first particles that are primary particles,

The first particle comprises a first core and a first surface layer disposed on the surface of the first core and comprising carbon,

The first core,

At least one of silicon and a silicon compound; And

Contains a metal compound,

The metal compound includes at least one of a metal oxide and a metal silicate.

The method according to claim 1,

The metal compound is doped with 1% to 50% by weight relative to the total weight of the first particles.

The method according to claim 1,

The secondary particles further include second particles that are primary particles,

The second particle comprises a second core and a second surface layer disposed on the surface of the second core and comprising carbon,

The second core,

A negative electrode active material comprising at least one of silicon and silicon compounds.

The method according to claim 3,

The negative electrode active material having a weight ratio of the first particles and the second particles is 1: 0.25 to 1: 4.

The method according to claim 3

An average particle diameter (D ₅₀ ) of the first core and the second core is 0.5 μm to 20 μm, respectively.

The method according to claim 3,

The silicon included in each of the first core and the second core each includes at least one of amorphous silicon and crystalline silicon having a crystal size of greater than 0 and less than 30 nm.

The method according to claim 3,

The silicon compound included in each of the first and second cores is a silicon oxide (SiO _x , 0 <x <2) in which silicon is distributed in a silicon dioxide (SiO ₂ ) matrix.

The method according to claim 3,

The first core and the second core is a porous core including a plurality of pores.

The method according to claim 8,

The internal porosity of the porous core is 5% to 90% of the total volume of the porous core.

The method according to claim 1,

The metal oxide is a negative electrode active material including an oxide of at least one metal selected from the group consisting of lithium (Li), magnesium (Mg), aluminum (Al), calcium (Ca) and titanium (Ti).

The method according to claim 1,

The metal silicate includes a silicate of at least one metal selected from the group consisting of lithium (Li), magnesium (Mg), aluminum (Al), calcium (Ca) and titanium (Ti).

The method according to claim 3,

The thickness of the first surface layer and the second surface layer is 1 nm to 100 nm negative electrode active material.

The method according to claim 1,

The average particle diameter (D ₅₀ ) of the secondary particles is a negative electrode active material 2㎛ to 50㎛.

The method according to claim 1 or 3,

The anode active material further comprises a carbon layer disposed on the surface of the secondary particles and containing carbon.

The method according to claim 14,

The carbon layer is 5nm to 100nm negative electrode active material.

The method according to claim 1 or 3,

The anode active material further comprises a crystalline carbonaceous material wherein the secondary particles are primary particles.

The method according to claim 1 or 3,

An anode active material further comprising graphite-based active material particles.

A negative electrode comprising the negative electrode active material of claim 1 or 3.

Lithium secondary battery comprising a negative electrode of claim 18.

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