KR20240041584A - Anode active material, method for preparing the same, and rechargeable lithium battery comprising the same - Google Patents

Abstract

The present invention relates to a lithium secondary battery having a core-shell structure of a specific shape, wherein the core is a porous metal particle core containing metal particles, the porosity is 20% or more, and the shell contains carbon. It relates to a negative electrode active material, a method for manufacturing the same, and a lithium secondary battery containing the same.

Description

Anode active material, method for manufacturing the same, and lithium secondary battery comprising the same {Anode active material, method for preparing the same, and rechargeable lithium battery comprising the same}

The present invention relates to a negative electrode active material, a manufacturing method thereof, and a lithium secondary battery comprising the same.

Lithium Ion Battery (LIB) has high energy density and is easy to design, so it has been adopted and used as a main power source for mobile electronic devices. In the future, it will be applied to electric vehicles or renewable energy power storage devices. The scope is becoming wider.

In order to apply it to new application fields, research on LIB materials with characteristics such as higher energy density and longer lifespan is continuously required. In particular, in the case of cathode materials, research has been conducted on various materials such as carbon, silicon, tin, and germanium.

Among these, silicon-based anode materials have received much attention because they have a much higher theoretical capacity compared to currently commercialized graphite anode materials. However, in silicon-based anode materials, electrochemical properties deteriorate due to the formation of an unstable SEI (Solid Electrolyte Interphase) layer due to a side reaction between the silicon surface and the electrolyte, or the electrode material is pulverized due to internal stress due to rapid volume expansion that occurs during charging and discharging. There are problems that arise.

To solve this problem, research has been conducted on nanostructuring, surface modification, and heterogeneous material compositing of silicon-based anode materials. In particular, methods for surface coating or complexing carbon materials are being widely studied in the industrial world. Various surface treatments using carbon materials required complex and expensive processes, and although some lifespan characteristics of silicon-based anode materials were improved through surface treatment using carbon materials, there was a large volume change that occurred during charging and discharging of silicon-based anode materials. In order to respond, a revision of the fundamental material design concept was required.

In other words, it was difficult to achieve the stable lifespan characteristics required for lithium-ion batteries because the composite using conventional carbon materials was performed without improving the physical shape of the silicon-based anode material. Therefore, there is a need to develop technology for structural modification of high-capacity silicon-based negative electrode active materials in order to suppress the volume expansion of the silicon-based negative electrode material and at the same time improve the unstable lifespan characteristics of the silicon-based negative electrode material.

Public Patent Publication No. 10-2022-0067246 (2022.05.24.)

The present invention was developed to solve the above problems, and provides a negative electrode active material for a secondary battery with high capacity and high energy density and long-life characteristics capable of stable charging/discharging behavior even after long-term use, and a lithium secondary battery containing the same. The purpose is to

However, the problem to be solved by the present invention is not limited to the problems mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the description below.

According to an embodiment of the present invention, in a negative electrode active material for a lithium secondary battery having a core-shell structure,

The core-shell structure has a cross-sectional shape shown in the drawings below,

(R is the distance from the center to the outermost core,

The above r corresponds to the distance from the center to the outermost part of the core.)

The core is a porous metal particle core containing metal particles,

The shell contains carbon,

A negative electrode active material for a lithium secondary battery that satisfies 0.2≤r/R≤0.9 is provided.

According to one embodiment of the present invention, it includes a cathode, an anode, and an electrolyte,

A lithium secondary battery is provided, wherein the negative electrode includes a negative electrode active material according to an embodiment of the present invention.

According to one embodiment of the present invention, a) dispersing metal particles and amorphous carbon in a solvent;

b) adjusting the viscosity of the dispersed solution to a range of 100 cP or less;

c) preparing a spherical precursor by spray drying the solution;

d) compounding the spherical precursor by mixing at least one of crystalline carbon and amorphous carbon; and

e) heat treatment at a temperature of 700°C to 1100°C for 5 minutes to 5 hours;

A method for producing a negative electrode active material is provided, including.

The anode active material according to an embodiment of the present invention accommodates the volume expansion of secondary particles composed of silicon primary particles through macro pores secured in the core portion containing silicon particles, and thereby destroys the graphite shell portion. By preventing this, it is possible to develop stable lifespan characteristics through stable volume changes only in the core part.

The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the configuration of the invention described in the detailed description or claims of the present invention.

1 is a schematic diagram of a change in the shape of a core portion depending on the physical conditions of a negative electrode active material according to an embodiment of the present invention.
FIG. 2 is a diagram showing a Focused Ion Beam (FIB) image of a negative electrode active material according to an embodiment of the present invention.
Figure 3 is a graph showing the results of full cell life characteristics of manufacturing examples conducted in the present invention.
Figure 4 is a graph showing the results of full-cell output characteristics of manufacturing examples carried out in the present invention.
Figure 5 is a graph showing half-cell AC resistance results of manufacturing examples conducted in the present invention.

Hereinafter, embodiments will be described in detail with reference to the attached drawings. However, various changes can be made to the embodiments, so the scope of the patent application is not limited or limited by these embodiments. It should be understood that all changes, equivalents, or substitutes for the embodiments are included in the scope of rights.

The terms used in the examples are for descriptive purposes only and should not be construed as limiting. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by a person of ordinary skill in the technical field to which the embodiments belong. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and should not be interpreted in an ideal or excessively formal sense unless explicitly defined in the present application. No.

In addition, when describing with reference to the accompanying drawings, identical components will be assigned the same reference numerals regardless of the reference numerals, and duplicate descriptions thereof will be omitted. In describing the embodiments, if it is determined that detailed descriptions of related known technologies may unnecessarily obscure the gist of the embodiments, the detailed descriptions are omitted.

According to one aspect of the present invention, in a negative electrode active material for a lithium secondary battery having a core-shell structure,

The core-shell structure has a cross-sectional shape shown in the drawings below,

(R is the distance from the center to the outermost core,

The above r corresponds to the distance from the center to the outermost part of the core.)

The core is a porous metal particle core containing metal particles,

The shell contains carbon,

Provided is a negative electrode active material for a lithium secondary battery that satisfies 0.2≤r/R≤0.9.

The cross-sectional shape shown in the figure shows a cross-section of a negative electrode active material having a core-shell structure, and has a donut structure (or torus structure) with concave tops and bottoms about an arbitrary axis passing through the center of the porous silicon core. It shows the same form.

At this time, when R is the distance from the center position of the core to the furthest point of the core (longest radius) and r is the distance from the center position of the core to the point of the concave area (shortest radius), r/ Depending on the ratio of R, the core-shell shape of the negative electrode active material changes little by little, and the present inventor suggests that when the ratio of r/R falls within a certain range, there is a stable volume change of only the core portion even during continuous charging/discharging. Through this, it was found that structural destruction of the composite was prevented and stable lifespan characteristics were possible.

Specific examples of this r/R ratio range may be 0.2 or more and 0.9 or less, and preferably 0.3 to 0.7 or less.

Depending on the ratio of r/R, the fraction of macro voids formed between the core portion and the shell portion of the core-shell structure may vary. If the ratio of r/R is less than the above lower limit, the ratio between internal silicon particles may vary. The contact is weakened and acts as a resistance to the electrochemical reaction, which lowers electrical conductivity and can lead to a decrease in capacity, efficiency, etc., and deterioration of life characteristics. Conversely, if the ratio of r/R exceeds the upper limit, lifespan characteristics may be deteriorated due to destruction of the composite due to volume expansion.

Meanwhile, the metal particles included in the porous metal particle core portion of the negative electrode active material may include one or more selected from the group consisting of Si, Al, Zn, Ca, Mg, Fe, Mn, Co, Ni, and Ge, In terms of improving the energy density and maximum capacity of the negative electrode active material, Si particles are preferable. In addition, in order to suppress the volume change of the silicon, etc., it is more preferable to use Si-containing nanoparticles with a size of 1000 nm or less.

In addition, the Si-containing nanoparticles may include one or more of silicon nanoparticles, silicon oxide nanoparticles, silicon carbide nanoparticles, and silicon alloy nanoparticles, preferably containing silicon nanoparticles. .

The average particle size (D ₅₀ ) of Si-containing nanoparticles may be 50 nm to 1000 nm, preferably 80 nm to 500 nm, and more preferably 80 nm to 130 nm.

If the average particle size (D ₅₀ ) of the Si-containing nanoparticles exceeds 1000 nm, the effect of suppressing volume change may decrease, resulting in a reduced battery life, and the average particle size (D ₅₀ ) may be 50 nm. If it is less than that, manufacturing costs may increase and battery capacity and efficiency may decrease.

Meanwhile, the average particle size of the core-shell structure composite of the negative electrode active material according to an embodiment of the present invention may be 3㎛ to 10㎛, more preferably 5㎛ to 8㎛ based on D ₅₀ .

If the average particle size (D ₅₀ ) of the core-shell structure composite is less than 3㎛, a problem of lowered dispersibility in the electrode manufacturing process may occur due to fine powder, and if it exceeds 10㎛, volume expansion of the composite may occur. This may cause problems with lifespan and safety due to worsening electrode expansion.

Additionally, the thickness of the shell layer of the core-shell structural composite may be 200 nm to 3 μm. If the thickness of the shell layer is less than 200㎚, it may be damaged due to changes in the volume of silicon, which may adversely affect the lifespan characteristics. If the thickness exceeds 3㎛, the capacity of the composite not only decreases as the amount of carbon increases. In addition, ionic conductivity may decrease and output characteristics may deteriorate.

Meanwhile, the carbon included in the shell portion of the negative electrode active material may include one or more of crystalline carbon and amorphous carbon, and the crystalline carbon may include graphitic carbon as an example. More specifically, it may be natural graphite, artificial graphite, expanded graphite, etc., and among these, flaky graphite, natural graphite, etc. are preferable.

The natural graphite is graphite that is produced naturally, and examples include flake graphite and high crystalline graphite. The artificial graphite is artificially synthesized graphite that is produced by heating amorphous carbon to a high temperature. It is manufactured and examples include primary, electrographite, secondary graphite, and graphite fiber.

In addition, expanded graphite may be formed by intercalating chemicals such as acids or alkalis between layers of graphite and heating them to expand the vertical layers of the molecular structure.

In addition, the type of amorphous carbon is not greatly limited, but specific examples include sucrose, phenol resin, naphthalene resin, polyvinyl alcohol resin, and furfuryl alcohol. ) Resin, furan resin, cellulose resin, styrene resin, polyimide resin, epoxy resin or vinyl chloride resin, coal-based pitch, petroleum-based pitch, poly It may include vinyl chloride, mesophase pitch, tar, block-copolymer, polyol, low molecular weight heavy oil, etc., and more specifically, it may correspond to coal-based pitch, petroleum-based pitch, and acrylic resin.

Meanwhile, the porosity of the porous metal particle core may correspond to 20% or more, and the porosity value can be specifically derived through the following equation (1).

(In equation (1), the true density is 2.33 g·cc ^-1 .)

Additionally, the porosity of the core of the porous metal particle may be 20% or more and 50% or less, and more preferably, may be 25% or more and 50% or less. If the porosity is less than 20%, destruction of the composite may occur due to expansion of the silicon particles, causing deterioration of lifespan characteristics, and if the porosity exceeds 50%, the contact interface with the electrolyte increases, reducing the initial efficiency. This may cause deterioration of lifespan characteristics or increase irreversible capacity and reduce output characteristics.

Furthermore, the negative electrode active material according to an embodiment of the present invention has an r/R in the range of 0.2 to 0.9 and a porosity of 20% or more, or more preferably, r/R in the range of 0.3 to 0.7. In the range of , the case where the porosity corresponds to 25% or more can exhibit better life characteristics compared to the case where this is not satisfied, and this point can be seen through the examples and comparative examples described below. Describe in detail.

Meanwhile, according to one aspect of the present invention, it includes a cathode, an anode, and an electrolyte,

Provided is a lithium secondary battery, wherein the negative electrode includes the negative electrode active material described in detail above.

In addition to the negative electrode active material described above, the negative electrode may additionally include a negative electrode active material commonly used as a negative electrode active material for lithium batteries in the art. Materials of the commonly used anode active material may include, for example, one or more selected from the group consisting of lithium metal, metal alloyable with lithium, transition metal oxide, non-transition metal oxide, and carbon-based material.

In addition, the positive electrode may include a positive electrode active material, and the type of the positive electrode active material may be a lithium-containing metal oxide, and any type commonly used in the technical field can be applied to the lithium secondary battery of the present invention. .

Furthermore, the electrolyte may include a lithium salt-containing non-aqueous electrolyte, and specifically, a non-aqueous electrolyte solution, a solid electrolyte, an inorganic solid electrolyte, etc. may be used.

In addition, a separator such as glass fiber, polyester, Teflon, polyethylene, polypropylene, or polytetrafluoroethylene (PTFE) may be additionally disposed between the positive and negative electrodes and included in the lithium secondary battery.

Meanwhile, according to one aspect of the present invention, a) dispersing metal particles and amorphous carbon in a solvent;

b) adjusting the viscosity of the dispersed solution to a range of 100 cP or less;

c) preparing a spherical precursor by spray drying the solution;

d) compounding the spherical precursor by mixing at least one of crystalline carbon and amorphous carbon; and

e) heat treatment at a temperature of 700°C to 1100°C for 5 minutes to 5 hours;

It provides a method for manufacturing a negative electrode active material, including.

The metal particles and amorphous carbon defined in step a) can be considered to be substantially the same as the types of metal particles and amorphous carbon described in detail above. Preferably, the metal particles may be Si-containing nanoparticles, Preferred types of amorphous carbon include coal-based pitch, petroleum-based pitch, and acrylic resin. Additionally, the solvent may be a solvent containing one or more selected from the group consisting of methanol, ethanol, propanol, and butanol, and is preferably a solvent containing isopropyl alcohol (IPA).

Thereafter, a step (step b)) of adjusting the viscosity of the solution obtained through step a) to a range of 100 cP or less is included. Through step b), r/R and porosity within the range of an embodiment of the present invention can be obtained in a desired range, and the viscosity range is specifically 5 cP to 90 cP, more specifically 10 cP. It can be from 50 cP.

Specifically, the viscosity can be adjusted by raising the pH of a slurry in which metal particles and amorphous carbon are dispersed in a solvent to 7 or more, or by controlling the content and molecular weight of the polymer in the slurry.

In addition, through step c), a spherical precursor of a core-shell structure composite can be manufactured, and the drying temperature may be, as an example, 90°C to 130°C.

The complexing process of step d) may be carried out, for example, through a complexing machine manufactured by Hansol Chemical, and may be carried out at a reaction temperature of 40°C to 250°C for 1 minute to 24 hours under atmospheric or inert atmosphere conditions.

In addition, the heat treatment step of step e) may be performed at a temperature of 700°C to 1100°C for 5 minutes to 5 hours, and more specifically, may be performed at a temperature of 800°C to 1000°C for 10 minutes to 3 hours. However, it is not limited to this.

Hereinafter, the configuration of the present invention and its effects will be described in more detail through examples and comparative examples. However, these examples are for illustrating the present invention in more detail, and the scope of the present invention is not limited to these examples.

- Example

(1) Manufacturing of negative electrode active material

a) Example 1

Silicone (D ₅₀ = 107 nm) and acrylic polymer (Mw = 15,000) were dispersed in an isopropyl alcohol (IPA) solution at a ratio of 65 to 35 parts by weight, and the viscosity of the mixed solution was titrated to 10 cP. By spray drying, a secondary spherical precursor with a size of 5 to 10㎛ based on D ₅₀ was prepared.

The above precursor, pitch-based carbon, and flaky graphite were mixed in a weight ratio of 30:35:35, respectively, and put into a compositeizer (manufactured by Hansol Chemical), and composited for 10 minutes.

After manufacturing the composite product, it was heat treated at 930°C to prepare a negative electrode active material.

b) Example 2

A negative electrode active material was manufactured in the same manner as in Example 1, except that the silicon was manufactured using a size of 125 nm.

c) Example 3

A negative electrode active material was manufactured in the same manner as in Example 1, except that the size of silicon was 83 nm.

d) Example 4

A negative electrode active material was prepared in the same manner as in Example 1, except that the viscosity of the mixed solution was adjusted to 90 cP.

e) Comparative Example 1

A negative electrode active material was prepared in the same manner as in Example 1, except that the acrylic polymer had a molecular weight (Mw) of 70,000.

e) Comparative Example 2

A negative electrode active material was prepared in the same manner as in Example 1, except that in the composite process, the precursor, pitch-based carbon, and flaky graphite were mixed in weight parts of 30:55:15, respectively.

(2) Manufacturing of coin cells

a) Fabrication of coin half shell

A negative electrode slurry was prepared by uniformly mixing the negative electrode active material, conductive material (Super P), and binder (SBR-CMC) prepared in Examples 1 to 4 and Comparative Examples 1 to 2 at a weight ratio of 94:2:4. Thereafter, the negative electrode slurry was coated on a copper thin film current collector with a thickness of 10㎛, and the coated electrode was dried at 120°C for 20 minutes and then pressed to produce a negative electrode.

Metal lithium is used as the cathode and counter electrode, polyethylene (PE) separator is used as the separator, and ethylene carbonate (EC): Diethyl carbonate is used as the electrolyte. A CR2032 type coin half cell was manufactured using 1.0M LiPF ₆ dissolved in a solvent mixed at a volume ratio of DEC):Dimethyl carbonate (DMC) = 3:5:2.

b) Fabrication of coin pool cell

The same cathode used in the coin half cell was used, and the anode was prepared as follows:

As a positive electrode active material, prepare a positive electrode slurry by mixing LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , a conductive material (Super P), and a binder (PVDF) at a weight ratio of 95:2:3, and then mix the positive electrode slurry with a thickness of 12㎛. It was coated on an aluminum foil current collector, and the coated electrode plate was dried at 120°C for 15 minutes and pressed to produce a positive electrode.

The anode and cathode prepared above were used, a PE separator was used as the separator, and the electrolyte was EC:DEC:DMC = 2:1:7 volume ratio + fluoroethylene carbonate (FEC) 5 A CR2032 type coin full cell was manufactured using 1.5M LiPF ₆ dissolved in a % mixed solvent.

(3) Physical property evaluation method (Table 1)

a) Particle size measurement

The average particle size of the silicon particles and precursor was measured using a particle size meter (Mastersizer3000, Malvern Panalytical) using an organic solution in which the anode active material was dispersed.

b) Viscosity measurement

200 ml of slurry in which silicone and acrylic polymers were dispersed in an IPA solution was measured using a viscosity meter (DV2T, Brookfield).

c) Molecular weight determination

After dissolving the measurement sample in an organic solvent, 50 to 100 μl was measured using a molecular weight measuring device (Gel permeation chromatography, Waters).

d) Porosity measurement

The porosity of the core portion was calculated according to the following formula. In the formula below, the true density was 2.33 g/cc. In addition, the total pore volume of the formula below was measured using TriStarⅡ 3020 equipment from Micromeritics. The total pore volume was measured through the adsorption amount of nitrogen gas according to the relative pressure change at the liquid nitrogen temperature (77K).

* True density = 2.33 g·cc ^-1

d) Raman spectroscopy

The precursors of the negative electrode active materials prepared in Examples 1 to 4 and Comparative Examples 1 and 2 were analyzed using a LabRam HR Evolution Raman spectrometer (Horiba Jbin-Yvon, France).

In this Raman spectroscopy, an Ar ion laser operating at a power of 10 mW with an excitation wavelength of 514 nm was used. As shown, peaks corresponding to silicon (around 500 cm ^-1 ) and peaks corresponding to the D band (around 1320 cm ^-1 ) and G bands (around 1600 cm ^-1 ) of carbon were confirmed, respectively.

e) Measurement of major/minor diameter ratio

The major/minor diameter ratios of the negative electrode active materials prepared in Examples 1 to 4 and Comparative Examples 1 to 2 were measured as follows. Specifically, the cross section of the powder was processed using a focused-ion beam (FIB), and FESEM was performed. The major and minor diameters of the cross section were observed/measured. At this time, the ratio of the measured major diameter and minor diameter is shown in Table 1 below.

In addition, the data results summarizing the experiments of Examples 1 to 4 and Comparative Examples 1 and 2 are shown in Table 1 below.

Silicone Size (D ₅₀ ,㎚) Polymer molecular weight (Mw) Mixed solution viscosity (cP) Secondary particle size (D ₅₀ ,㎛) Porosity (%) r/R Id/Ig Example 1 107 15000 10 7.3 25.2 0.61 1.09 Example 2 125 15000 10 6.5 25.4 0.73 1.07 Example 3 83 15000 10 5.9 26.8 0.32 1.08 Example 4 107 15000 90 8.3 20.7 0.88 1.08 Example 5 107 70000 10 7.9 29.4 0.19 1.05 Example 6 107 15000 10 6.7 6.3 0.94 1.13

(4) Electrochemical evaluation method (Table 2)

Coin full cells were used to evaluate lifespan characteristics and high rate characteristics, and coin half cells were used to evaluate other battery characteristics.

a) Coin Half Cell

Coin half-cells manufactured using the negative electrode active materials prepared in Examples 1 to 4 and Comparative Examples 1 to 2 according to the present invention were operated at a current of 0.1 C at 25°C and a voltage of 0.01 V (vs. Li). It was charged at a constant current until this point, and while maintaining 0.01V, it was charged at a constant voltage until the current reached 0.05C. After the fully charged cell was rested for 10 minutes, it was discharged at a constant current of 0.1C until the voltage reached 1.5V (vs. Li) (performed twice, initial formation).

Meanwhile, “C” refers to the discharge rate of the cell, which is a value obtained by dividing the total capacity of the cell by the total discharge time.

The initial charge capacity and initial discharge capacity are the charge and discharge capacities in the first cycle, which were calculated from the following equation.

Initial efficiency [%] = (1st cycle discharge capacity/1st cycle charge capacity) × 100

In addition, the coin half cell manufactured using the negative electrode active material prepared in Examples 1 to 4 and Comparative Examples 1 to 2 was charged at 0.1 C rate and 0.01 V at room temperature (25°C) and cut-off at 0.01 V. , AC resistance was measured under the conditions of a very small excitation amplitude of 5 to 10 mV and a frequency of 1 mHz to 1 MHz, and the results are shown in Figure 5.

b) Coin full cell

Coin full cells manufactured using the negative electrode active materials prepared in Examples 1 to 4 and Comparative Examples 1 to 2 were charged at a constant current of 0.1C rate at 25°C until the voltage reached 4.2V, respectively. was charged at a constant voltage until the current reached 0.05C. After the fully charged cell was rested for 10 minutes, it was discharged at a constant current of 0.1C until the voltage reached 2.7V (performed twice, initial formation).

Afterwards, the cell was charged at a constant current of 1.0C at 25°C until the voltage reached 4.2V, and then charged at a constant voltage while maintaining 4.2V until the current reached 0.05C. After the fully charged coin cell was left to rest for 10 minutes, the discharging cycle was repeated with a constant current of 1.0C until the voltage reached 2.7V (1st to 300th cycle).

The lifespan characteristics were calculated from the following equation, and the results are shown in Table 2 and Figure 3.

Life characteristics [%] = (300th cycle discharge capacity/1st cycle discharge capacity) × 100

The measured output characteristics of cells using the negative electrode active materials prepared in Examples 1 to 4 and Comparative Examples 1 to 2 were calculated from the following equation, and the results are shown in Table 2 and Figure 4.

Output characteristics [%] = (discharge capacity of 5.0C/discharge capacity of 0.1C)×100

In addition, the data results summarizing the electrochemical evaluation experiments of Examples 1 to 4 and Comparative Examples 1 and 2 are shown in Table 2 below.

Initial charge capacity (mAh g) ^-One ) Initial discharge capacity (mAh g) ^-One ) Initial efficiency (%) AC resistance (Ω) Lifetime characteristics (% @ 300 ^th ) cell type Coin Half Cell Coin full cell Example 1 1500.4 1352.4 90.1 58.6 80.7 Example 2 1373.8 1191.1 86.7 66.1 76.1 Example 3 1621.5 1479.6 91.2 63.1 80.2 Example 4 1398.2 1224.8 87.6 61.2 75.6 Comparative Example 1 1484.5 1345.0 90.6 62.9 73.7 Comparative Example 2 1556.5 1380.6 88.7 78.3 70.8

Through this, in the case of Examples 1 to 4 containing the negative electrode active material according to an embodiment of the present invention, the r/R value was outside the range of 0.2 to 0.9 (Comparative Examples 1 and 2) or the size of the porosity was Compared to the case where it does not exceed 20% (Comparative Example 2), it can be seen that the output characteristics after 300 cycles are excellent, showing excellent life characteristics.

As described above, although the embodiments have been described with limited drawings, those skilled in the art can apply various technical modifications and variations based on the above. For example, even if the described techniques are performed in a different order than the described method, and/or the described components are combined or combined in a different form than the described method, or are replaced or substituted by other components or equivalents. Adequate results can be achieved.

Therefore, other implementations, other embodiments, and equivalents of the claims also fall within the scope of the following claims.

Claims (14)

In the anode active material for lithium secondary batteries having a core-shell structure,
The core-shell structure has a cross-sectional shape shown in the drawings below,

(R is the distance from the center to the outermost core,
The above r corresponds to the distance from the center to the outermost part of the core.)
The core is a porous metal particle core containing metal particles,
The shell contains carbon,
A negative electrode active material for a lithium secondary battery that satisfies 0.2≤r/R≤0.9. According to paragraph 1,
A negative electrode active material for a lithium secondary battery, wherein the porosity of the core is 20% or more and 50% or less, derived from the following equation (1).

(In equation (1), the true density is 2.33 g·cc ^-1 .) According to paragraph 1,
The metal particles of the core include one or more selected from the group consisting of Si, Al, Zn, Ca, Mg, Fe, Mn, Co, Ni, and Ge. According to paragraph 3,
The metal particles are Si-containing particles,
A negative electrode active material wherein the Si-containing particles include one or more selected from the group consisting of silicon nanoparticles, silicon oxide nanoparticles, silicon carbide nanoparticles, and silicon alloy nanoparticles. According to paragraph 4,
An anode active material wherein the average particle size of the Si-containing particles is 80 nm to 130 nm based on D ₅₀ . According to paragraph 1,
A negative electrode active material wherein the carbon included in the shell includes at least one of crystalline carbon and amorphous carbon. According to clause 6,
A negative electrode active material, characterized in that the crystalline carbon is graphitic carbon containing at least one of flaky graphite and natural graphite. According to clause 6,
The amorphous carbon includes sucrose, phenol resin, naphthalene resin, polyvinyl alcohol resin, furfuryl alcohol resin, furan resin, and cellulose resin. , styrene resin, polyimide resin, epoxy resin or vinyl chloride resin, coal-based pitch, petroleum-based pitch, polyvinyl chloride, mesophase pitch, tar, block copolymer (block) -copolymer), a negative electrode active material containing at least one selected from the group consisting of polyol and low molecular weight heavy oil. According to paragraph 1,
The average particle size of the core-shell structure is 3㎛ to 10㎛ based on D ₅₀ , a negative electrode active material. According to paragraph 1,
A negative electrode active material wherein the shell layer has a thickness of 200 nm to 3 μm. Includes cathode, anode and electrolyte,
A lithium secondary battery, wherein the negative electrode includes the negative electrode active material of any one of claims 1 to 10. a) dispersing metal particles and amorphous carbon in a solvent;
b) adjusting the viscosity of the dispersed solution to a range of 100 cP or less;
c) preparing a spherical precursor by spray drying the solution;
d) compounding the spherical precursor by mixing at least one of crystalline carbon and amorphous carbon; and
e) heat treatment at a temperature of 700°C to 1100°C for 5 minutes to 5 hours;
Method for producing a negative electrode active material, including. According to clause 12,
The metal particles are Si-containing nanoparticles,
A method of producing a negative electrode active material, wherein the solvent includes one or more selected from the group consisting of methanol, ethanol, propanol, and butanol. According to clause 12,
The amorphous carbon includes sucrose, phenol resin, naphthalene resin, polyvinyl alcohol resin, furfuryl alcohol resin, furan resin, and cellulose resin. , styrene resin, polyimide resin, epoxy resin or vinyl chloride resin, coal-based pitch, petroleum-based pitch, polyvinyl chloride, mesophase pitch, tar, block copolymer (block) -copolymer), polyol, and low molecular weight heavy oil,
A method of producing a negative electrode active material, wherein the crystalline carbon is graphite-based carbon.