KR20240057600A - Anode active material, method for preparing the same, and rechargeable lithium battery comprising the same - Google Patents

Abstract

The present invention relates to a negative electrode active material for a lithium secondary battery, comprising a core containing metal particles and nanocarbon and a shell layer containing carbon, wherein the nanocarbon has a shape that surrounds the entire metal particle, and a method for manufacturing the same. , and relates to a lithium secondary battery including 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 containing the same. Specifically, the present invention relates to a negative electrode active material capable of stable behavior even during long-term charging/discharging by controlling the shape of the negative electrode active material, a manufacturing method thereof, and a lithium secondary battery comprising the same. It is about lithium secondary batteries.

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 compositing of heterogeneous materials of silicon-based anode materials. In particular, methods for surface coating or complexing carbon materials are being widely studied in the industrial world. Complex and expensive processes were required for various surface treatments using carbon materials, 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, modification of the fundamental material design concept was required.

In other words, it was difficult to achieve the stable lifespan characteristics required for LIB because the composite using conventional carbon materials was performed with carbon 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. 2019-0047367 (2019.05.08)

The present invention was developed to solve the above problems, and its purpose is to provide a negative active material for a secondary battery with high capacity and high energy density and long life characteristics that enable stable charge/discharge behavior even after long-term use.

In addition, the purpose is to provide a manufacturing method capable of manufacturing the negative electrode active material with high efficiency and low cost, and providing an electrode and a lithium secondary battery containing the negative electrode active material can also be considered to be the purpose of the present invention.

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 one embodiment of the present invention,

In the negative active material for a lithium secondary battery having a core-shell structure including a core and a shell layer formed outside the core,

The core includes metal particles and nanocarbon,

The shell layer contains carbon,

A negative electrode active material is provided, wherein the nanocarbon has a shape that surrounds the entire metal particle.

According to one embodiment of the present invention,

Grinding metal particles (S1);

Dispersing the pulverized metal particles and nanocarbon in a solvent (S2);

Preparing spherical metal precursor powder by spray drying the dispersed solution (S3);

Compounding the spherical metal precursor powder by mixing it with at least one of crystalline carbon and amorphous carbon (S4); and

Heat treatment step (S5);

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

According to one embodiment of the present invention,

In a lithium secondary battery including a negative electrode, a positive electrode, 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.

The anode active material according to an embodiment of the present invention is composed of a core portion in which silicon particles are wrapped with nanocarbon and a shell portion containing a graphite-based material surrounding the core portion. The present invention proposes a negative electrode active material in which nanocarbon in the core uniformly surrounds silicon particles, and its specific effects are as follows.

The nanocarbon present in the core of the negative electrode active material homogeneously surrounds the silicon secondary particles composed of silicon primary particles. At this time, the nanocarbon material acts as an electron transfer path to the silicon particles and prevents the pulverization of the silicon secondary particles. It plays a role. Through this, it can contribute to developing stable lifespan characteristics by enabling a stable electrochemical reaction even during charging and discharging.

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 negative electrode active material according to an embodiment of the present invention.
Figure 2 is a diagram showing the electrical conductivity of the negative electrode active material of the preparation examples carried out in 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.

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 unless explicitly defined in the present application, should not be interpreted in an ideal or excessively formal sense. 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 overlapping 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 the negative active material for a lithium secondary battery having a core-shell structure including a core and a shell layer formed outside the core,

The core includes metal particles and nanocarbon,

The shell layer contains carbon,

The nanocarbon provides a negative electrode active material, characterized in that it has a shape that surrounds the entire metal particle.

The core of the negative electrode active material includes metal particles and nanocarbon, and the metal particles include one or more selected from the group consisting of silicon, aluminum, zinc, calcium, magnesium, iron, manganese, cobalt, nickel, germanium, tin, and lead. It may contain, and in terms of improving the energy density and maximum capacity of the negative electrode active material, it may preferably be silicon (Si).

In addition, the silicon may specifically have the form of silicon nanoparticles, silicon oxide nanoparticles, silicon carbide nanoparticles, and/or silicon alloy nanoparticles, and is preferably used to suppress volume changes of silicon, etc. due to charge and discharge. , may correspond to silicon nanoparticles with a size of 1000 nm or less, and may have a flaky structure.

Previously, silicon nanoparticles with a size of 1000 nm or less were described, but more specifically, the size of the particles may be 50 nm to 1000 nm based on D ₅₀ , preferably 80 nm to 500 nm, and more preferably may be 80 nm to 130 nm.

If the average particle size (D ₅₀ ) of the silicon nanoparticles exceeds 1000 nm, the effect of suppressing volume change may decrease and the lifespan of the battery may be reduced, and if the average particle size (D ₅₀ ) is less than 50 nm In this case, manufacturing costs may increase and battery capacity and efficiency may decrease.

In addition, the nanocarbon included in the core of the negative electrode active material has a shape that surrounds the entire metal particles included in the core. For example, the metal particle is located in the center of the core, and the nanocarbon is located in the outer portion of the core. One example is a form in which nanocarbon homogeneously surrounds metal secondary particles composed of metal primary particles.

The anode active material according to an embodiment of the present invention has a shape in which nanocarbon homogeneously surrounds metal secondary particles composed of metal primary particles as described above, thereby preventing pulverization of metal secondary particles. In addition, the nanocarbon material also plays the role of an electron transfer path to metal particles, enabling a stable electrochemical reaction even during charging and discharging, contributing to improving lifespan characteristics.

In addition, the type of nanocarbon may include, as an example, one or more of graphene and reduced graphene oxide, and the thickness may be, as an example, 1 to 500 nm, and the particle size (D ₅₀ ) may be It may be 10㎛ to 150㎛.

If the thickness is less than 1 nm, the nanocarbon surrounding the metal secondary particle may be easily peeled off due to volume expansion of metal such as silicon, and if the thickness exceeds 500 nm, the thickness of the thickened nanocarbon As a result, the movement of lithium ions, etc. may be hindered, leading to a decrease in output characteristics.

In addition, the particle size of nanocarbon such as graphene is generally used as a concept of area, and when the particle size is smaller than 10㎛, it cannot completely surround the metal secondary particles, causing metal primary particles such as silicon to be exposed to the outside. There is a possibility of being exposed to, and if the particle size is larger than 500㎛, electrochemical properties such as lifespan and efficiency may be deteriorated due to agglomeration of precursor and composite particles.

Meanwhile, in the negative electrode active material according to an embodiment of the present invention, a carbon-based shell layer is formed on the outside of the core containing the metal particles and nanocarbon.

By including this carbon-based shell layer, the metal particles and nanocarbon inside the core are not exposed to the outside and can prevent direct contact with external substances, improving electrical conductivity and ensuring electrochemical stability. , As shown in the comparison of the examples and comparative examples below, there is an effect of showing excellent initial efficiency, lifespan characteristics, and output characteristics compared to the comparative examples that do not include a carbon-based shell layer.

Meanwhile, the carbon-based shell layer may include one or more of crystalline and amorphous carbon, and the type of crystalline carbon may include graphitic carbon. More specifically, it may include natural graphite, artificial graphite, expanded graphite, etc.

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.

Meanwhile, the types of amorphous carbon are not greatly limited, but 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, polyvinyl chloride. , mesophase pitch, tar, block-copolymer, polyol, and may be formed from one or more selected from the group consisting of low molecular weight heavy oil, and more specifically, from coal-based pitch, petroleum-based pitch, and acrylic resin. It may have been formed.

Furthermore, the thickness of the shell layer may be 100 nm to 3 ㎛, and if the thickness of the shell layer is less than 100 ㎚, it may be damaged due to a change in the volume of silicon, which may adversely affect the lifespan characteristics, and the thickness is 3 ㎛. If it exceeds this, not only does the capacity of the composite decrease as the carbon amount increases, but the ionic conductivity decreases and the output characteristics may deteriorate.

Meanwhile, the nanocarbon and the carbon-based shell layer can be distinguished from each other, as described above, and the nanocarbon mainly has a two-dimensional (2D) structure like graphene, and the specific surface area (BET) of nanocarbon is 20 m2/g or more, and the electrical conductivity may be 5 S/cm or more, and the electrical conductivity may be specifically calculated by the following equation.

<Equation>

σ (electrical conductivity) = 1 / [ R (measured resistance) * t (thickness) * C (correction coefficient = 4.532)]

(In the above formula, t and R refer to the pellet thickness (t) and electrical resistance (R) when the nanocarbon powder pellet is compressed at a pressure of 2400 kgf.)

On the other hand, the carbon-based shell layer mainly has a three-dimensional (3D) structure, and the specific surface area (BET) of the carbon-based shell layer may be 10 m2/g or less.

The anode active material according to an embodiment of the present invention has a structure including the core and shell layers described above, and its size may be 3㎛ to 10㎛ based on the average particle size (D ₅₀ ), more preferably 5㎛ to 8㎛. It may be ㎛.

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.

According to one aspect of the present invention,

Grinding metal particles (S1);

Dispersing the pulverized metal particles and nanocarbon in a solvent (S2);

Preparing spherical metal precursor powder by spray drying the dispersed solution (S3);

Compounding the spherical metal precursor powder by mixing it with at least one of crystalline carbon and amorphous carbon (S4); and

Heat treatment step (S5);

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

Through the pulverizing process of step S1, the metal particles are pulverized into nano-sized pieces, and the type of metal particles used and the nanocarbon in step S2 are substantially the same as the types of metal particles and nanocarbon described in detail previously. It can be seen that it is.

As an example, preferably, the metal particles may be one or more silicon-containing nanoparticles selected from the group consisting of silicon nanoparticles, silicon oxide nanoparticles, silicon carbide nanoparticles, and silicon alloy nanoparticles, and the nanocarbon is graphene. and reduced graphene oxide.

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).

In addition, through step S4, the structure of the core-shell structure composite can be manufactured, and the crystalline carbon and amorphous carbon mixed with the spherical metal precursor powder can be considered to be the same as the crystalline carbon and amorphous carbon described in detail previously. .

The complexation process of step S4 may be carried out, as an example, through a complexer manufactured by Hansol Chemical, and may be carried out under atmospheric or inert atmosphere conditions for 1 minute to 24 hours at a reaction temperature of 40°C to 250°C. , the heat treatment process of step S5 may be carried out at a temperature of 700°C to 1100°C for 5 minutes to 5 hours, and more specifically, may be carried out at a temperature of 800°C to 1000°C for 10 minutes to 3 hours. , but is not limited to this.

Meanwhile, a lithium secondary battery including a negative electrode, a positive electrode, and an electrolyte according to an embodiment of the present invention can also be provided.

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, polytetrafluoroethylene (PTFE), etc. may be additionally disposed between the positive electrode and the negative electrode and included in the lithium secondary battery.

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

Silicon (D ₅₀ = 100 nm) and reduced graphene oxide were dispersed in an IPA solution at a ratio of 9 to 1 by weight, and then spray-dried to prepare a secondary spherical precursor with a size of 5 to 10 μm based on D ₅₀ .

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

The composite product was heat treated at 950°C to prepare a negative electrode active material.

b) Example 2

A negative electrode active material was prepared in the same manner as in Example 1, except that the silicon and reduced graphene oxide were prepared in a ratio of 8 to 2 by weight.

c) Example 3

A negative electrode active material was prepared in the same manner as in Example 1, except that the silicon and reduced graphene oxide were prepared in a ratio of 95 to 5 parts by weight.

d) Comparative Example 1

Silicon (D ₅₀ = 100 nm) and reduced graphene oxide were dispersed in an IPA solution at a ratio of 45 to 55 parts by weight, and then dried to prepare a secondary spherical precursor with a size of 5 to 10 μm based on D ₅₀ .

The anode active material was prepared by heat treating the precursor at 950°C.

e) Comparative Example 2

The IPA solution in which silicon (D ₅₀ = 102 nm) was dispersed was spray dried to prepare a secondary spherical precursor with a size of 5 to 10 μm based on D ₅₀ .

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

The composite product was heat treated at 950°C to prepare a negative electrode active material.

(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 3 and Comparative Examples 1 to 2 at a weight ratio of 94:2:4. 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 composite (secondary particles) was measured using a particle size meter (Mastersizer3000, Malvern Panalytical) using an organic solution in which the negative electrode active material was dispersed.

b) Carbon measurement

The anode active material was combusted at a high temperature of about 2200°C to 3000°C and the gas generated was measured (ELEMENTRAC CS-I, ELTRA).

c) Measurement of powder electrical conductivity

The powder electrical conductivity of the negative electrode active materials prepared in Examples 1 to 3 and Comparative Examples 1 to 2 was measured.

In this measurement method, the powder was pelletized and the electrical conductivity of the powder was measured using a 4-probe measurement method. After 500 mg of each negative active material powder was charged into a powder resistance measurement container (metal container) with an inner diameter of 2.54 cm, pressure was applied to the powder through a cylindrical conductive jig at the top and bottom of the container. At this time, the pressure of the jig was 200 The electrical resistance was measured in real time by compressing the powder pellets by gradually increasing from kgf to 2400 kgf. The thickness (t) and electrical resistance (R) of the pellet were measured when the jig pressure was 2400 kgf, and the electrical conductivity was calculated using the following equation.

<Equation>

σ (powder electrical conductivity) = 1 / [ R (measured resistance) * t (thickness) * C (correction coefficient = 4.532)]

In addition, the data results summarizing the experiments of Examples 1 to 3 and Comparative Examples 1 and 2 are shown in Table 1 below:

silicone particle size
(D50) Complex particle size
(D50) carbon content
(weight%) electrical conductivity
(S/cm) Example 1 100㎚ 6.8㎛ 58.3 19.8 Example 2 100㎚ 7.2㎛ 59.6 22.1 Example 3 100㎚ 6.9㎛ 57.7 17.9 Comparative Example 1 100㎚ 6.6㎛ 58.2 24.7 Comparative Example 2 102㎚ 7.1㎛ 58.3 6.3

(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 3 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

b) Coin full cell

Coin full cells manufactured using the negative electrode active materials prepared in Examples 1 to 3 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 3 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 3 and Comparative Examples 1 and 2 are shown in Table 2 below:

charging capacity
(mAh g-1) Discharge capacity
(mAh g-1) initial efficiency
(%) life characteristics
(% @300th) output characteristics
(C _5.0 /C _0.1 ) Cell type Coin Half Cell Coin full cell Example 1 1605.2 1417.4 88.3 78.5 72.3 Example 2 1571.3 1393.7 88.7 76.8 70.9 Example 3 1602.4 1426.1 89.0 73.7 71.0 Comparative Example 1 1675.5 1322.0 78.9 33.8 68.4 Comparative Example 2 1600.2 1409.8 88.1 40.9 62.1

Through this, Examples 1 to 3 including the negative electrode active material according to an embodiment of the present invention are superior to Comparative Example 1 not including a carbon-based shell portion in terms of initial efficiency, lifespan characteristics, and output characteristics. It can be confirmed that the lifespan characteristics and output characteristics are excellent compared to Comparative Example 2, which does not contain reduced graphene oxide (nanocarbon).

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.

1: Silicon primary particle
2: nanocarbon
3: Carbon-based shell part

Claims (16)

In the negative active material for a lithium secondary battery having a core-shell structure including a core and a shell layer formed outside the core,
The core includes metal particles and nanocarbon,
The shell layer contains carbon,
The nanocarbon is a negative electrode active material, characterized in that it has a shape that surrounds the entire metal particle. According to paragraph 1,
The thickness of the nanocarbon is 1 nm to 500 nm,
The particle size (D ₅₀ ) of the nanocarbon is 10㎛ to 150㎛, a negative electrode active material. According to paragraph 1,
The specific surface area (BET) of the nanocarbon is 20 m2/g or more, the electrical conductivity is 5 S/cm or more, and the electrical conductivity is calculated by the following equation.
<Equation>
σ (electrical conductivity) = 1 / [ R (measured resistance) * t (thickness) * C (correction coefficient = 4.532)]
(In the above formula, t and R refer to the pellet thickness (t) and electrical resistance (R) when the nanocarbon powder pellet is compressed at a pressure of 2400 kgf.) According to paragraph 1,
The nanocarbon is a negative electrode active material comprising one or more of graphene and reduced graphene oxide. According to paragraph 1,
A negative electrode active material wherein the metal particles include one or more selected from the group consisting of silicon, aluminum, zinc, calcium, magnesium, iron, manganese, cobalt, nickel, germanium, tin, and lead. According to paragraph 1,
A negative electrode active material, wherein the metal particles are one or more silicon-containing nanoparticles selected from the group consisting of silicon nanoparticles, silicon oxide nanoparticles, silicon carbide nanoparticles, and silicon alloy nanoparticles. According to paragraph 1,
A negative electrode active material, wherein the shell layer includes one or more of crystalline and amorphous carbon. In clause 7,
A negative electrode active material wherein the specific surface area (BET) of the shell layer is 10 m2/g or less. In clause 7,
A negative electrode active material wherein the crystalline carbon includes graphite-based carbon. In clause 7,
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 ( A negative electrode active material manufactured from one or more selected from the group consisting of block-copolymer), polyol, and low molecular weight heavy oil. According to paragraph 1,
The average particle size (D ₅₀ ) of the core-shell structure is 3㎛ to 10㎛,
A negative electrode active material wherein the shell layer has a thickness of 100 nm to 3 μm. Grinding metal particles (S1);
Dispersing the pulverized metal particles and nanocarbon in a solvent (S2);
Preparing spherical metal precursor powder by spray drying the dispersed solution (S3);
Compounding the spherical metal precursor powder by mixing it with at least one of crystalline carbon and amorphous carbon (S4); and
Heat treatment step (S5);
Method for producing a negative electrode active material, including. According to clause 12,
The metal particles are one or more silicon-containing nanoparticles selected from the group consisting of silicon nanoparticles, silicon oxide nanoparticles, silicon carbide nanoparticles, and silicon alloy nanoparticles,
The nanocarbon is one or more of graphene and reduced graphene oxide,
A method of producing a negative electrode active material, wherein the solvent is a solvent containing at least one selected from the group consisting of methanol, ethanol, propanol, and butanol. According to clause 12,
The crystalline carbon includes graphitic carbon,
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 ( A method of producing a negative electrode active material formed from one or more selected from the group consisting of block-copolymer), polyol, and low molecular weight heavy oil. According to clause 12,
A method of producing a negative electrode active material, wherein the heat treatment is performed at a temperature of 700°C to 1100°C for 5 minutes to 5 hours. In a lithium secondary battery including a negative electrode, a positive electrode, and an electrolyte,
A lithium secondary battery, wherein the negative electrode includes the negative electrode active material of any one of claims 1 to 11.

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