KR20230023529A - Composite nanoparticle comprising non-carbon nanoparticle and carbonaceous layer thereon, and process of preparing the same - Google Patents

Abstract

The present invention relates to composite nanoparticles containing non-carbon nanoparticles and a carbonized layer, a negative electrode for a lithium secondary battery containing the same, and a manufacturing method thereof. More specifically, according to the manufacturing method of the present invention, a composite nanoparticle material containing the non-carbon nanoparticles and carbonized layer with high residual carbon can be manufactured by coating a surface of a core layer of the non-carbon nanoparticles such as silicon with an acrylonitrile-based polymer layer in which cross-linking molecules are copolymerized through an emulsion drying method, heat-treating the same, forming a cross-linked acrylonitrile-based polymer layer, and then heat-treating the same again at high temperature. A uniform carbon layer on the surface of the non-carbon nanoparticles can suppress side reactions with the electrolyte and maximize the long-term stability of the battery when used as a negative electrode active material.

Description

Composite nanoparticle comprising non-carbon nanoparticle and carbonized layer thereon, and process of preparing the same}

The present invention relates to a non-carbon-based nanoparticle/carbonized layer composite nanoparticle, a negative electrode for a lithium secondary battery including the same, and a method for manufacturing the same.

Secondary batteries that can be charged and discharged have been widely used as power sources for portable electronic devices such as laptop computers, digital cameras, and mobile phones. Recently, it has attracted great attention as a power storage device for solving the intermittence of power supply sources of hybrid vehicles and electric vehicles, solar power generation and wind power generation, and improving power quality. Accordingly, market demands for cost reduction, high energy density, and excellent cycling performance in relation to secondary batteries are continuously increasing, and efforts and research to develop electrode materials for secondary batteries having improved electrochemical performance are being concentrated.

In particular, in a lithium ion secondary battery, which is a type of secondary battery that operates on the principle that lithium ions generate electricity while moving between the positive and negative electrodes, silicon is attracting attention as a material that can replace carbon, which has a theoretical capacity limit. am. In the cathode and anode active materials of the lithium ion secondary battery, lithium in an ionic state is intercalated and deintercalated, and charged and discharged through reversible reactions thereof.

However, silicon has a problem in that it is difficult to secure stable output performance due to serious volume change due to the insertion and removal of lithium ions during charging and discharging, and long-term stability is lowered. In addition, there is a problem in that structural characteristics change and a rapid capacity reduction phenomenon of the secondary battery occurs. In order to solve this problem, long-term cycle stability of the electrode has been improved by attempting a composite of silicon and carbon, shaping of nanostructures such as nanotubes or nanowires, but there is still a difficult problem in securing excellent output characteristics.

1. Korean Patent Publication No. 10-2018-0001518 2. Korean Patent Publication No. 10-2014-0147414 3. Korean Patent Publication No. 10-2014-0033515 4. Korean Patent Publication No. 10-2015-0141154

In order to solve the above problems, an object of the present invention is to provide non-carbon-based nanoparticles/carbonized layer composite nanoparticles that prevent volume expansion due to deintercalation of lithium ions and have improved electrical conductivity.

In addition, the present invention provides a method for preparing composite nanoparticles including non-carbonaceous nanoparticles/carbonized layers by forming a polymer shell layer including a polymer layer and a crosslinking layer on a core layer of non-carbonaceous nanoparticles and then carbonizing the polymer shell layer. The purpose.

Another object of the present invention is to provide a negative electrode active material for a lithium secondary battery including composite nanoparticles according to various embodiments of the present invention, a negative electrode including the same, and a lithium secondary battery including the same.

One aspect of the present invention is (A) a polyacrylonitrile-based polymer layer containing a nitrile group (or cyano group, -CN) in the main chain and a cross-linkable functional group capable of cross-linking with the nitrile group on the surface of non-carbon-based nanoparticles Forming to obtain non-carbon-based nanoparticles having a polyacrylonitrile-based polymer layer on the surface, (B) performing cross-linking between the nitrile group and the cross-linkable functional group to cross-link the polyacrylonitrile-based polymer layer Obtaining non-carbon-based nanoparticles having a cross-linked layer of polyacrylonitrile-based polymer on the surface by combining, (C) carbonizing the non-carbon-based nanoparticles having a cross-linked layer of polyacrylonitrile-based polymer on the surface It relates to a method for producing a composite nanomaterial comprising obtaining composite nanoparticles including non-carbonaceous nanoparticles having a carbonized layer.

Another aspect of the present invention is a non-carbon-based nanoparticle core layer; And a composite nanoparticle comprising a carbonized layer formed on an outer surface of the non-carbonaceous nanoparticle core layer, wherein the carbonized layer has a nitrile group (or cyano group, -CN) in a main chain and a crosslinkable functional group capable of crosslinking with the nitrile group Obtained by forming a polyacrylonitrile-based polymer layer containing a on the surface of the non-carbon-based nanoparticles, cross-linking the polyacrylonitrile-based polymer layer, and then carbonizing the cross-linked polyacrylonitrile-based polymer. It relates to composite nanoparticles, characterized in that.

Another aspect of the present invention relates to an anode active material, an anode, a lithium secondary battery, and a communication device, a transportation device, an energy storage device, and the like including the composite nanoparticles according to various embodiments of the present invention.

According to the present invention, by forming a cross-linked polymer shell layer on the surface of non-carbon nanoparticles and carbonizing it to prepare nanoparticle/carbonized layer composite nanoparticles, volume expansion due to intercalation and deintercalation of lithium ions can be prevented and electrical conductivity can be improved. there is. In addition, since it has excellent affinity with an electrolyte, when applied as an anode active material, the output characteristics and long-term stability of a battery can be remarkably improved.

The effects of the present invention are not limited to the effects mentioned above. It should be understood that the effects of the present invention include all effects that can be inferred from the following description.

1 is a process diagram schematically illustrating a method of manufacturing silicon/polymer composite nanoparticles used in the manufacturing process of composite nanoparticles according to Example 1 of the present invention.
Figure 2 is a view showing the structure of the silicon / polymer composite nanoparticles used in the manufacturing process of the composite nanoparticles of the present invention.
3 schematically shows electrode stability after charge/discharge cycles depending on whether a crosslinking layer is formed for the silicon/polymer composite nanoparticles used in the manufacturing process of the composite nanoparticles of the present invention.
Figure 4 shows the results of TEM (a, b, c) and EDS (c, d, e) analysis of silicon / polymer composite nanoparticles used in the manufacturing process of composite nanoparticles prepared in Example 1 of the present invention .
5 shows the results of FT-IR analysis of the PANVDA polymer used in Example 1 of the present invention.
6 is a charge/discharge voltage profile (a) and discharge according to a change in C-rate value (0.2 to 100 C) for a lithium secondary battery to which silicon/polymer composite nanoparticles prepared in Examples and Comparative Examples of the present invention are applied. It shows the result of measuring the capacity (b) and the discharge capacity (c) according to the number of cycles.

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

One aspect of the present invention is (A) a polyacrylonitrile-based polymer layer containing a nitrile group (or cyano group, -CN) in the main chain and a cross-linkable functional group capable of cross-linking with the nitrile group on the surface of non-carbon-based nanoparticles Forming to obtain non-carbon-based nanoparticles having a polyacrylonitrile-based polymer layer on the surface, (B) performing cross-linking between the nitrile group and the cross-linkable functional group to cross-link the polyacrylonitrile-based polymer layer Obtaining non-carbon-based nanoparticles having a cross-linked layer of polyacrylonitrile-based polymer on the surface by combining, (C) carbonizing the non-carbon-based nanoparticles having a cross-linked layer of polyacrylonitrile-based polymer on the surface It relates to a method for producing composite nanoparticles comprising the step of obtaining composite nanoparticles including non-carbonaceous nanoparticles having a carbonized layer.

As described above, silicon has a problem in that it is difficult to secure stable output performance due to serious volume change due to intercalation and deintercalation of lithium ions during charging and discharging. In addition, problems such as poor long-term stability, structural characteristics change, and rapid capacity reduction are still problems to be solved.

Accordingly, in the present invention, by forming a cross-linked polymer shell layer on the surface of non-carbon nanoparticles and carbonizing it to prepare composite nanoparticles including non-carbon nanoparticles and a carbonized layer, volume expansion due to deintercalation of lithium ions is prevented and improved It may have electrical conductivity. In addition, since it has excellent affinity with an electrolyte, when applied as an anode active material, the output characteristics and long-term stability of a battery can be remarkably improved. In this case, silicon nanoparticles or silica nanoparticles may be used as the non-carbon nanoparticles.

In one embodiment, the cross-linkable functional group is selected from an azide group (—N ₃ ), acrylic acid, acrylate, methacrylic acid, methacrylate, and combinations of two or more thereof.

In the present invention, 'combination' of two or more cross-linkable functional groups means that two or more cross-linkable functional groups are introduced into the main chain of a polyacrylonitrile-based polymer, and any one or both of them are polyacrylonitrile-based. This means that it can participate in cross-linking with nitrile groups present in the main chain of the polymer.

In addition, the cross-linking may be performed between one polyacrylonitrile-based polymer and another adjacent polyacrylonitrile-based polymer, and the cross-linking property with a nitrile group present in one polyacrylonitrile-based polymer at a sufficient distance. It can also occur between functional groups.

In another embodiment, the cross-linkable functional group is an azide group, and the cross-linking layer is formed by a cycloaddition reaction between the nitrile group and the azide group.

As such, preferably, the cross-linkable functional group is an azide group, and cross-linking may be achieved through a nitrile-azide cycloaddition reaction between the nitrile group and the azide group.

In another embodiment, the polyacrylonitrile-based polymer is polyacrylonitrile- co -vinylidene azide, poly(acrylonitrile- co -methylmethacrylate), poly(acrylonitrile- co -methacrylate) acrylic acid), poly(acrylonitrile- co -methylacrylonitrile), poly(acrylonitrile-comethacrylate), and combinations of two or more thereof.

In the present invention, the 'combination' of two or more types of polyacrylonitrile-based polymers may mean a mixture or blend of two or more types of these polymers, or may be a copolymer formed by two or more types of these polymers.

In the present invention, the polyacrylonitrile-based polymer has excellent bonding strength with non-carbon-based nanoparticles and at the same time has good affinity with electrolytes, so it exhibits the advantage of significantly improving the charge/discharge characteristics and long-term cycle stability of the battery.

Specific examples of the polyacrylonitrile-based polymer usable in the present invention include polyacrylonitrile- co -vinylidene azide, polyacrylonitrile, poly(acrylonitrile- co -methylmethacrylate), poly(acrylo nitrile- co -methacrylic acid), poly(acrylonitrile- co -methylacrylonitrile, poly(acrylonitrile-comethacrylate), and combinations of two or more thereof.

In another embodiment, the polyacrylonitrile-based polymer is polyacrylonitrile- co -vinylidene azide.

More preferably, the polyacrylonitrile-based polymer may be a polyacrylonitrile-based random copolymer in which a nitrile group and an azide group are randomly present in the main chain, and most preferably, polyacrylonitrile represented by the following formula (1)- co -vinylidene azide (PANVDA) can be used.

[Formula 1]

(In Formula 1, n and m are the repeating numbers of each repeating unit, where n is an integer of 60 to 110, preferably 70 to 100, more preferably 80 to 90, and m is 1 to 30, preferably It is an integer of 5 to 20, more preferably 12 to 17.)

In another embodiment, the non-carbon nanoparticles are silicon (Si) nanoparticles, silica (SiO ₂ ) nanoparticles, silicon nitride (SiN) nanoparticles, silicon oxide (SiO _x ) nanoparticles, and two or more kinds thereof. selected from mixtures.

In the present invention, the particle size of the non-carbon 'nano' particles is not limited to the nano size and can be extended to the micron size.

In another embodiment, the non-carbonaceous nanoparticles have an average particle size of 10 nm to 2,000 nm.

That is, the non-carbonaceous nanoparticles may have an average particle size of 10 to 2,000 nm, preferably 50 to 200 nm, more preferably 50 to 100 nm, and most preferably 50 to 80 nm. At this time, if the average particle size of the non-carbon-based nanoparticles is less than 10 nm, electrochemical performance may deteriorate due to aggregation of the non-carbon-based nanoparticles before a polymer layer is formed on the surface of the non-carbon-based nanoparticles. Electrode stability may deteriorate due to performance degradation of the non-carbon-based nanoparticles.

In another embodiment, the non-carbon-based nanoparticles having a cross-linked layer of a polyacrylonitrile-based polymer on the surface are prepared by mixing the cross-linked layer of the polyacrylonitrile-based polymer and the non-carbon nanoparticles in a ratio of 5:95 to 50 :50 by weight.

That is, the non-carbon nanoparticles having the cross-linked layer of polyacrylonitrile-based polymer on the surface have the non-carbon nanoparticle and the cross-linked layer of polyacrylonitrile-based polymer in a weight ratio of 50:50 to 95:5, preferably Preferably, it may be included in a weight ratio of 60:40 to 90:10, more preferably 66.6:33.4 to 70:30 weight ratio, and most preferably 66.6:33.4 weight ratio. In particular, if the content of the crosslinking layer of the polyacrylonitrile-based polymer is less than 50 weight ratio, a polymer layer having an appropriate thickness may not be properly formed on the surface of the non-carbonaceous nanoparticles, and conversely, if the content exceeds 5 weight ratio, the polymer layer is formed. As a result, output characteristics of the silicon anode may be deteriorated after the carbonization process.

In another embodiment, step (A) may be performed by preparing a dispersion solution including the non-carbonaceous nanoparticles, the polyacrylonitrile-based polymer, a surfactant, and a dispersion medium, and then removing the dispersion medium. there is.

In another embodiment, the surfactant is polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, polyoxypropylene-polyoxyethylene block copolymer, propylene glycol-ethylene glycol block copolymer, polyethylene oxide-polypropylene oxide block copolymers, and mixtures of two or more thereof.

In the present invention, the surfactant prevents the non-carbon-based nanoparticles from aggregating with each other and maximizes coating efficiency so that a polyacrylonitrile-based polymer layer can be evenly formed with a uniform thickness on the surface of the non-carbon-based nanoparticles. can be mixed for

Specific examples of the surfactant usable in the present invention include polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, polyoxypropylene-polyoxyethylene block copolymer, propylene glycol-ethylene glycol block copolymer, polyethylene oxide-polypropylene oxide block copolymers, and mixtures of two or more thereof, but are not limited thereto.

Preferably, a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer may be used as the surfactant.

In another embodiment, the preparation of the dispersion solution is performed by dissolving a solution containing the non-carbonaceous nanoparticles, the polyacrylonitrile-based polymer, the surfactant, and the dispersion medium at a speed of 9,000 to 15,000 rpm for 30 seconds to 30 minutes. stirring for a minute.

More specifically, the preparation of such a dispersion solution is stirred for 30 seconds to 30 minutes at a speed of 9,000 to 15,000 rpm, preferably for 30 seconds to 2 minutes at 11,000 to 13,000 rpm, and most preferably for 1 minute at 12,000 rpm. can do. At this time, when both the rotation speed and time conditions are not satisfied, it may be difficult to uniformly disperse the non-carbon-based nanoparticles due to aggregation with each other.

In another embodiment, step (B) may be performed by heat treatment at 110 to 150 °C for 30 minutes to 6 hours.

That is, the step (B) may be performed by heat treatment at 110 to 150 ° C. for 30 minutes to 6 hours. Preferably, it can be carried out at 120 to 140 ° C. for 60 minutes to 3 hours, and most preferably at 130 ° C. for 2 hours. At this time, if the heat treatment temperature is less than 110 °C or the heat treatment time is less than 30 minutes, crosslinking may not sufficiently occur, and thus a crosslinked layer may not be properly formed on the surface of the polymer layer. Conversely, if the heat treatment temperature exceeds 150 ° C or the heat treatment time exceeds 6 hours, excessive cross-linking occurs to the polyacrylonitrile-based polymer layer, and thus, volume expansion of the non-carbon-based nanoparticles may occur due to the deintercalation of lithium ions. .

In another embodiment, step (C) is performed by heat treatment at a temperature of 500 to 1,000 ° C for 0.5 to 6 hours.

In particular, although not explicitly described in the following Examples or Comparative Examples, in the method for producing composite nanoparticles according to the present invention, after applying the composite nanoparticles prepared under different conditions to a silicon negative electrode, 1,000 °C at 300 ° C. Ash charge/discharge was performed.

As a result, unlike the other conditions and other numerical ranges, when all of the following conditions were satisfied, the charge/discharge capacity was maintained as high as 1,500 mAh/g or more even after 500 charge/discharge cycles at high temperatures, unlike conventional silicon negative electrodes. It was found that the thermal stability of was excellent.

① The non-carbon-based nanoparticles are silicon nanoparticles,

② The average particle size of the non-carbonaceous nanoparticles is 50 to 80 nm,

③ The polyacrylonitrile-based polymer is polyacrylonitrile- co -vinylidene azide,

④ The surfactant is a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer,

⑤ Preparation of the dispersion solution is performed by stirring at 11,000 to 13,000 rpm for 30 seconds to 2 minutes,

⑥ Step (B) is performed by heat treatment at 120 to 140 ° C. for 60 minutes to 3 hours,

⑦ Non-carbon nanoparticles having a cross-linked layer of polyacrylonitrile-based polymer on the surface include the cross-linked layer of polyacrylonitrile-based polymer and the non-carbon nanoparticles in a weight ratio of 33:67 to 30:70 .

However, if any of the above conditions are not satisfied, charging and discharging cannot be continued for a long time at high temperatures, and after 700 charge/discharge cycles, the battery capacity may rapidly decrease, and the output characteristics and stability of the battery may be greatly reduced. confirmed that it could be.

Another aspect of the present invention is a non-carbon-based nanoparticle core layer; And a composite nanoparticle comprising a carbonized layer formed on an outer surface of the non-carbonaceous nanoparticle core layer, wherein the carbonized layer has a nitrile group (or cyano group, -CN) in a main chain and a crosslinkable functional group capable of crosslinking with the nitrile group Obtained by forming a polyacrylonitrile-based polymer layer containing a on the surface of the non-carbon-based nanoparticles, cross-linking the polyacrylonitrile-based polymer layer, and then carbonizing the cross-linked polyacrylonitrile-based polymer. It relates to composite nanoparticles, characterized in that.

In one embodiment, the non-carbonaceous nanoparticles have an average particle size of 10 nm to 2,000 nm, and the thickness of the carbonized layer is 1 to 100 nm.

Another aspect of the present invention relates to a negative electrode active material for a lithium secondary battery, a negative electrode for a lithium secondary battery, and a lithium secondary battery including composite nanoparticles according to various embodiments of the present invention.

Another aspect of the present invention relates to a communication device, a transportation device, an energy storage device, and the like including a lithium secondary battery according to various embodiments of the present invention.

Example

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited by the following examples.

Example 1: Preparation of carbonized composite nanoparticle material based on 600 ℃ heat treatment using Si@PANVDAC

[Scheme 1]

(m = 15, n = 85)

(1) Forming a polymer layer on the surface of silicon nanoparticles

Silicon nanoparticle dispersion was prepared by dispersing 0.2 g of silicon nanoparticles in 10 g of toluene, and 0.1 g of polyacrylonitrile- co -vinylidene azide (PANVDA) was dissolved in 10 g of dimethylformamide (DMF). A polyacrylonitrile-based polymer solution was prepared by dissolving, and a surfactant solution was prepared by dissolving the polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer in 200 mL of formamide.

After adding 5% by weight of the silicon nanoparticle dispersion, 5% by weight of the polymer solution, and 90% by weight of the surfactant solution, stirring at 12,000 rpm for 1 minute to prepare a dispersion solution, and then at 80 ° C. for 24 hours. Toluene and dimethylformamide in the dispersed silicon nanoparticles were removed by stirring.

The dispersion solution from which toluene and dimethylformamide were removed was centrifuged at 12,000 rpm for 30 minutes, and then washed three times with ethanol at 12,000 rpm for 15 minutes to form a PANVDA polymer layer on the surface of the silicon nanoparticles.

(2) Formation of PANVDAC crosslinking layer

Then, the silicon nanoparticles on which the PANVDA polymer layer is formed are heat-treated at 130 ° C. for 2 hours, so that the nitrile group present on the surface of one PANVDA polymer layer and the azide group present on the surface of the other PANVDA polymer layer as shown in Scheme 1 above Silicon/polymer composite nanoparticles having a PANVDAC crosslinking layer formed thereon were obtained by crosslinking by nitrile azide cycloaddition.

(3) Carbonization of PANVDAC crosslinking layer

The silicon/polymer composite nanoparticles having the PANVDAC crosslinking layer prepared above were carbonized by heat treatment at 600° C. in a nitrogen atmosphere to prepare a silicon/carbon composite nanoparticle material.

Example 2: Preparation of carbonized composite nanoparticle material based on 700 ° C heat treatment using Si@PANVDAC

A silica/carbon composite nanoparticle material was prepared in the same manner as in Example 1 above, except that carbonization was performed by heat treatment at 700 °C instead of 600 °C.

Comparative Example 1: Carbonized composite nanoparticle material based on 600 ℃ heat treatment using Si@PAN

Instead of forming a PANVDA polymer layer on silicon nanoparticles using polyacrylonitrile- co -vinylidene azide (PANVDA) and cross-linking it, polyacrylonitrile (PAN) was used to form a PAN polymer layer on silicon nanoparticles. Except for forming the layer, the experiment was performed in the same manner as described in (1) of Example 1 above.

Silicon/polymer nanoparticles having a PAN polymer layer thus prepared were carbonized by heat treatment at 600° C. in a nitrogen atmosphere to prepare a silicon/carbon composite nanoparticle material.

Comparative Example 2: Preparation of carbonized composite nanoparticle material based on 700 ℃ heat treatment using Si@PAN

A silica/carbon composite nanoparticle material was prepared in the same manner as in Comparative Example 1 above, except that carbonization was performed by heat treatment at 700 °C instead of 600 °C.

Comparative Example 3: Preparation of Si@PANVDAC composite nanoparticle material

In Example 1, except that the process of "(3) Carbonization of the PANVDAC crosslinking layer" was not performed, the experiment was performed in the same manner as in Example 1, and a composite with a crosslinked PANVDAC polymer layer formed on the surface of the silicon nanoparticles Nanoparticles were prepared.

Test Example 1: TEM and EDS analysis of silicon/polymer composite nanoparticles

The shape and structure of the silicon/polymer composite nanoparticles prepared in Comparative Example 3 were analyzed using TEM and EDS, and the results of TEM (a, b, c) and EDS (d, e, f) analysis are shown in FIG. 4 shown in

Referring to the TEM (a) photograph in FIG. 4, it was confirmed that silicon/polymer composite nanoparticles having a spherical shape were formed. In addition, in the case of the TEM (b, c) photographs, it was confirmed that a polymer shell layer (outermost gray border) including a PANVDA layer and a crosslinking layer was formed on the outer surface of the silicon nanoparticle core layer (dark black). .

In addition, in the case of the EDS (d, e, f), it was confirmed that Si was relatively evenly distributed to the extent that it occupied almost most of the element compared to C element. In addition, the element C is observed due to carbon in the polyacrylonitrile-based polymer evenly coated on the surface of the silicon nanoparticles, and it can be seen that it is formed in a very thin thickness compared to Si.

Test Example 2: FT-IR analysis of PANVDAC polymer

FT-IR analysis was performed on the PANVDAC polymer, which is a polyacrylonitrile-based polymer used in Comparative Example 3, to analyze the chemical structure, and the results are shown in FIG. 5.

As shown in Scheme 1 above, the PANVDAC polymer was synthesized by substituting the chlorine group with an azide group in PANVDC, a polyacrylonitrile-based polymer containing a chlorine group, and then synthesizing the two PANVDAs by nitrile azide cycloaddition reaction (nitrile azide Cycloaddition) can be cross-linked to each other to synthesize PANVDAC polymer.

Referring to FIG. 5, a nitrile group was observed at 2247 cm ⁻¹ in all of the PANVDC, PANVDA and PANVDAC polymers, and an azide group was confirmed at 2212 cm ⁻¹ in PANVDA. In addition, in the PANVDAC crosslinked PANVDA polymer, all azide peaks disappeared, and tetrazole structures were confirmed at 1181, 1097 and 1039 cm ^-1 , so that PANVDA was converted to PANVDAC by an azide nitrile ring polymerization reaction and successfully crosslinked can confirm that has been done.

The cross-linking layer thus formed may be formed by cross-linking two types of polyacrylonitrile-based polymers present on the surface of the polyacrylonitrile-based polymer layer through a 1,3-dipolar cycloaddition reaction. Specifically, in the crosslinking layer, the nitrile group of one polyacrylonitrile-based polymer present on the surface of the polyacrylonitrile-based polymer layer and the azide group of another polyacrylonitrile-based polymer are nitrile without a separate catalyst. It may be formed by crosslinking each other by an azide cycloaddition reaction.

Test Example 3: Carbon Residual Rate Analysis after Heat Treatment

For the carbonized composite nanoparticle materials prepared in Examples 1 and 2 and Comparative Examples 1 and 2, respectively, the residual rate of carbon was measured after heat treatment, and the results are shown in the table below.

The residual ratio was analyzed by measuring the weight change of inorganic substances and organic substances including polymers according to temperature change using ThermoGravimetric Analysis (TGA).

It can be seen that the carbon residual rate of Example 1 is higher than that of Comparative Example 1, and the carbon residual rate of Example 2 is higher than that of Comparative Example 2. It can be confirmed that more carbon remains after carbonization in the composite nanoparticle material coated with polymer.

In the composite nanoparticle material coated with the crosslinked PANVDAC polymer according to the present invention, it can be seen that more carbon covers the surface of the silicon particle more uniformly and stably.

In addition, it can be seen that the carbon residual rate of Example 1 is higher than that of Example 2, and the carbon residual rate of Comparative Example 1 is higher than that of Comparative Example 2. Through this, the higher the carbonization temperature, the higher the amount of carbon remaining after carbonization. decrease can be seen.

Test Example 4: Evaluation of charge and discharge of lithium secondary battery

After preparing a negative electrode as follows using the carbonized composite nanoparticle materials prepared in Examples 1 and 2 and Comparative Examples 1 to 3, respectively, a lithium secondary battery was prepared by a conventional method.

80% by weight of natural graphite, 10% by weight of silicon / carbon composite nanoparticle material prepared in the above example and comparison, 5% by weight of conductive material (Super-P), 5% by weight of SBR / CMC (5:5) binder A negative electrode was prepared.

The loading amount was 7 mg/cm ² , and the charge/discharge test was conducted at 0.5 C in the voltage range of 0.01 to 2 V, and the results are shown in the table below.

As a result, as shown in the negative half-cell performance in the table above, in Example 1 compared to Comparative Example 1 and in Example 2 compared to Comparative Example 2, the initial coulombic efficiency, initial capacity, and storage capacity were all higher. Improved results can be seen.

In addition, it was confirmed that the heat treatment at 700 ° C showed a higher performance improvement effect than the heat treatment at 600 ° C.

In addition, it was confirmed that Examples 1 and 2 showed storage capacity almost equivalent to Comparative Example 3, and showed more improved results than Comparative Example 3 in terms of initial coulombic efficiency and initial capacity.

In addition, compared to Example 1, Example 2 showed better performance in terms of initial coulombic efficiency, initial capacity, and storage capacity, which indicates that the higher the carbonization temperature, the lower the carbon residual rate after carbonization. It can be said that the result shows that the quality and performance are further improved.

Claims (20)

A method for producing composite nanoparticles comprising the following steps:
(A) A polyacrylonitrile-based polymer layer containing a nitrile group (or cyano group, -CN) in the main chain and a cross-linkable functional group capable of cross-linking with the nitrile group is formed on the surface of the non-carbon-based nanoparticles to form a polyacrylic acid on the surface Obtaining non-carbon-based nanoparticles having a ronitrile-based polymer layer,
(B) Cross-linking is performed between the nitrile group and the cross-linkable functional group to cross-link the polyacrylonitrile-based polymer layer to obtain non-carbon-based nanoparticles having a cross-linked layer of polyacrylonitrile-based polymer on the surface. steps to do,
(C) carbonizing the non-carbon-based nanoparticles having a cross-linked layer of the polyacrylonitrile-based polymer to obtain composite nanoparticles including non-carbon-based nanoparticles having a carbonized layer on the surface. The composite nanoparticle of claim 1, wherein the cross-linkable functional group is selected from an azide group (-N ₃ ), acrylic acid, acrylate, methacrylic acid, methacrylate, and a combination of two or more thereof. manufacturing method. The method of claim 1, wherein the cross-linkable functional group is an azide group,
The crosslinking layer is a method for producing composite nanoparticles, characterized in that formed by a cycloaddition reaction of the nitrile group and the azide group. The method of claim 1, wherein the polyacrylonitrile-based polymer is polyacrylonitrile- co -vinylidene azide, poly(acrylonitrile- co -methyl methacrylate), poly(acrylonitrile- co -methacrylic acid) acid), poly(acrylonitrile- co -methylacrylonitrile), poly(acrylonitrile-co-lithium methacrylate), and a method for producing composite nanoparticles, characterized in that selected from combinations of two or more thereof. The method of claim 1, wherein the polyacrylonitrile-based polymer is polyacrylonitrile- co -vinylidene azide. The method of claim 1, wherein the non-carbon nanoparticles are silicon (Si) nanoparticles, silica (SiO ₂ ) nanoparticles, silicon nitride (SiN) nanoparticles, silicon oxide (SiO _x ) nanoparticles, and mixtures of two or more of these. Method for producing composite nanoparticles, characterized in that selected from. The method of claim 1, wherein the non-carbon-based nanoparticles have an average particle size of 10 nm to 2,000 nm. The method of claim 1, wherein the non-carbon-based nanoparticles having a cross-linked layer of polyacrylonitrile-based polymer on the surface are prepared by mixing the cross-linked layer of polyacrylonitrile-based polymer and the non-carbon nanoparticles in a ratio of 5:95 to 50: Method for producing a composite nanoparticle, characterized in that it comprises a weight ratio of 50. The method of claim 1, wherein step (A) is performed by preparing a dispersion solution containing the non-carbonaceous nanoparticles, the polyacrylonitrile-based polymer, a surfactant, and a dispersion medium, and then removing the dispersion medium. Method for producing composite nanoparticles to be. 10. The method of claim 9, wherein the surfactant is polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, polyoxypropylene-polyoxyethylene block copolymer, propylene glycol-ethylene glycol block copolymer, polyethylene oxide-polypropylene oxide A method for producing a composite nanoparticle, characterized in that it is selected from a block copolymer and a mixture of two or more thereof. 10. The method of claim 9, wherein the dispersion solution is prepared by dissolving a solution containing the non-carbonaceous nanoparticles, the polyacrylonitrile-based polymer, the surfactant, and the dispersion medium at a rate of 9,000 to 15,000 rpm for 30 seconds to 30 minutes. Method for producing composite nanoparticles, characterized in that carried out by stirring during. The method of claim 1, wherein step (B) is performed by heat treatment at 110 to 150 °C for 30 minutes to 6 hours. The method of claim 1, wherein step (C) is performed by heat treatment at a temperature of 500 to 1,000 °C for 0.5 to 6 hours. The method of claim 8, wherein the non-carbon-based nanoparticles are silicon nanoparticles,
The average particle size of the non-carbon-based nanoparticles is 50 to 80 nm,
The polyacrylonitrile-based polymer is polyacrylonitrile- co -vinylidene azide,
The surfactant is a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer,
Preparation of the dispersion solution is performed by stirring at 11,000 to 13,000 rpm for 30 seconds to 2 minutes,
Step (B) is performed by heat treatment at 120 to 140 ° C. for 60 minutes to 3 hours,
The non-carbon-based nanoparticles having a cross-linked layer of polyacrylonitrile-based polymer on the surface include the cross-linked layer of polyacrylonitrile-based polymer and the non-carbon nanoparticles in a weight ratio of 33:67 to 30:70 Method for producing composite nanoparticles, characterized in that. a non-carbon-based nanoparticle core layer; And a composite nanoparticle comprising a carbonized layer formed on an outer surface of the non-carbonaceous nanoparticle core layer,
The carbonization layer forms a polyacrylonitrile-based polymer layer including a nitrile group (or cyano group, -CN) in the main chain and a cross-linkable functional group capable of cross-linking with the nitrile group on the surface of the non-carbon-based nanoparticles, Composite nanoparticles obtained by cross-linking a polyacrylonitrile-based polymer layer and then carbonizing the cross-linked polyacrylonitrile-based polymer. The method of claim 15, wherein the non-carbon-based nanoparticles have an average particle size of 10 nm to 2,000 nm,
Composite nanoparticles, characterized in that the thickness of the carbonization layer is 1 to 100 nm. An anode active material for a lithium secondary battery comprising the composite nanoparticles according to claim 16. An anode for a lithium secondary battery comprising the anode active material according to claim 17 . A lithium secondary battery comprising the negative electrode according to claim 18. A device comprising the lithium secondary battery according to claim 19,
The device is characterized in that any one selected from a communication device, a transportation device and an energy storage device.

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