WO2022108132A1 - Non-carbon nanoparticles/polymer composite nanoparticles, anode comprising same for lithium secondary battery, and manufacturing method for non-carbon nanoparticles/polymer composite nanoparticles - Google Patents

Abstract

The present invention relates to non-carbon nanoparticles/polymer composite nanoparticles, an anode comprising same for a lithium secondary battery, and a manufacturing method for non-carbon nanoparticles/polymer composite nanoparticles. More specifically, the non-carbon nanoparticles/polymer composite nanoparticles are manufactured by forming a cross-linked polymer shell layer on the surface of a core layer of the non-carbon nanoparticles, thereby preventing volume expansion due to the intercalation and deintercalation of lithium ions and attaining improved electrical conductivity. Furthermore, the nanoparticles have excellent affinity for an electrolyte, so that the application of the nanoparticles to an anode active material can significantly improve output characteristics and long-term stability of a battery.

Description

Non-carbon nanoparticles/polymer composite nanoparticles, anode for lithium secondary battery including the same, and method for manufacturing the non-carbon nanoparticles/polymer composite nanoparticles

The present invention relates to a non-carbon nanoparticle/polymer composite nanoparticle, an anode for a lithium secondary battery comprising the same, and a method for manufacturing the non-carbon nanoparticle/polymer composite nanoparticle.

Secondary batteries capable of charging and discharging have been widely used as power supplies for portable electronic devices such as notebook computers, digital cameras, and mobile phones. Recently, as a power supply for hybrid and electric vehicles, and as a power storage device to solve the intermittent power generation of solar and wind power and improve power quality, it has attracted great attention. Accordingly, market demands for cost reduction, high energy density, excellent cycling performance, etc. 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 lithium ion secondary batteries, a type of secondary battery that operates on the principle of generating electricity while lithium ions move between the positive and negative electrodes, silicon is attracting attention as a material to replace carbon, which has a theoretical capacity limit. to be. Lithium, which is in an ionic state, is inserted and desorbed from the positive and negative active materials of the lithium ion secondary battery, and is charged and discharged by a reversible reaction thereof.

However, silicon has a problem in that it is difficult to secure stable output performance due to a serious volume change due to lithium ion removal and insertion during charging and discharging, and long-term stability is deteriorated. In addition, there is a problem in that the structural characteristics change and a sudden decrease in capacity of the secondary battery occurs. In order to solve this problem, the long-term cycle stability of the electrode has been improved by trying to form a nanostructure such as a composite of silicon and carbon, a nanotube or a nanowire, etc., but it is still difficult to secure excellent output characteristics.

[Prior art literature]

[Patent Literature]

(Patent Document 1) Korea Patent Publication No. 2018-0001518

In order to solve the above problems, an object of the present invention is to provide a method for manufacturing non-carbon nanoparticles/polymer composite nanoparticles that prevent volume expansion due to lithium ion deintercalation and have improved electrical conductivity.

Another object of the present invention is to provide a non-carbon nanoparticle/polymer composite nanoparticle in which a polymer shell layer including a polymer layer and a cross-linking layer is formed on a non-carbon nanoparticle core layer.

Another object of the present invention is to provide a non-carbon nanoparticle/polymer composite nanoparticle in which a cross-linked polymer shell layer is formed on a non-carbon nanoparticle core layer.

Another object of the present invention is to provide an anode active material for a lithium secondary battery comprising the non-carbon nanoparticles/polymer composite nanoparticles.

Another object of the present invention is to provide a negative electrode for a lithium secondary battery comprising the negative electrode active material.

Another object of the present invention is to provide a lithium secondary battery including the negative electrode.

Another object of the present invention is to provide a device including the lithium secondary battery.

The present invention comprises the steps of preparing a dispersion solution by mixing a non-carbon-based nanoparticle dispersion, a polyacrylonitrile-based polymer solution, and a surfactant; removing the organic solvent contained in the dispersion solution while stirring the dispersion solution; forming a polyacrylonitrile-based polymer layer on the surface of the non-carbon-based nanoparticles by centrifuging the dispersion solution from which the organic solvent has been removed; and heat-treating the non-carbon-based nanoparticles on which the polyacrylonitrile-based polymer layer is formed to cross-link two types of polyacrylonitrile-based polymers present on the surface of the polyacrylonitrile-based polymer layer to each other to form a cross-linking layer Preparing non-carbon nanoparticles/polymer composite nanoparticles; includes, wherein the cross-linking layer is any one of the nitrile groups of the polyacrylonitrile-based polymer present on the surface of the polyacrylonitrile-based polymer layer and the other one Non-carbon nanoparticles/polymer composite nanoparticles in which the azide groups of the polyacrylonitrile-based polymer are cross-linked with each other by a nitrile azide cycloaddition reaction, and the non-carbon-based nanoparticles are silicon nanoparticles or silica nanoparticles A method for preparing particles is provided.

In addition, the present invention is a non-carbon nanoparticle core layer; and a polymer shell layer formed on the outer surface of the non-carbon nanoparticle core layer, wherein the polymer shell layer includes a polyacrylonitrile-based polymer layer and the polyacrylonitrile-based polymer layer formed on the non-carbon nanoparticle core layer. and a crosslinking layer formed by crosslinking two types of polyacrylonitrile-based polymers present on the surface of the The nitrile group of the ronitrile-based polymer and the other azide group of the polyacrylonitrile-based polymer are cross-linked with each other by a nitrile azide cycloaddition reaction, and the non-carbon nanoparticles are silicon nanoparticles or silica nanoparticles. Phosphorus non-carbon nanoparticles/polymer composite nanoparticles are provided.

In addition, the present invention is a non-carbon nanoparticle core layer; and a polymer shell layer formed on the outer surface of the non-carbon nanoparticle core layer and cross-linked, wherein the polymer shell layer is composed of one polyacrylonitrile-co-vinylidene azide nitrile group and the other polyacrylonitrile. Non-carbon nanoparticles/polymers in which the azide group of nitrile-co-vinylidene azide is crosslinked by a nitrile azide cycloaddition reaction, and the non-carbon nanoparticles are silicon nanoparticles or silica nanoparticles. Composite nanoparticles are provided.

The present invention also provides an anode active material for a lithium secondary battery comprising the non-carbon nanoparticles/polymer composite nanoparticles.

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

The present invention also provides a lithium secondary battery including the negative electrode.

Also, the present invention provides a device including the lithium secondary battery, wherein the device is any one selected from a communication device, a transportation device, and an energy storage device.

The non-carbon nanoparticles/polymer composite nanoparticles according to the present invention form a polymer shell layer cross-linked on the surface of the non-carbon nanoparticles to produce non-carbon nanoparticles/polymer composite nanoparticles, thereby preventing volume expansion due to lithium ion deintercalation. and can have improved electrical conductivity. In addition, since it has excellent affinity with the electrolyte, it is possible to significantly improve the output characteristics and long-term stability of the battery when it is applied as an anode active material.

The effects of the present invention are not limited to the above-mentioned effects. 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 for manufacturing a silicon/polymer composite nanoparticle according to Example 1 of the present invention.

Figure 2 is a view showing the structure of the silicon / polymer composite nanoparticles according to an embodiment of the present invention.

3 schematically shows electrode stability after a charge/discharge cycle depending on whether a cross-linking layer is formed for silicon/polymer composite nanoparticles according to an embodiment of the present invention.

4 shows the TEM (a, b, c) and EDS (c, d, e) analysis results of the silicon/polymer 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), C-rate value (0.2 to 100 C) of the lithium secondary battery to which the silicon/polymer composite nanoparticles prepared in Example 1 and Comparative Example 1 of the present invention are applied. The results of measuring the discharge capacity (b) and the discharge capacity (c) according to the number of cycles are shown.

Hereinafter, the present invention will be described in more detail by way of one embodiment.

The present invention relates to a non-carbon nanoparticle/polymer composite nanoparticle, an anode for a lithium secondary battery comprising the same, and a method for manufacturing the non-carbon nanoparticle/polymer composite nanoparticle.

As described above, silicon has a problem in that it is difficult to secure stable output performance due to severe volume change due to lithium ion removal and insertion during charging and discharging. In addition, the problems of poor long-term stability, changes in structural characteristics, and rapid capacity reduction were still problems to be solved.

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

Specifically, the present invention comprises the steps of preparing a dispersion solution by mixing a non-carbon-based nanoparticle dispersion, a polyacrylonitrile-based polymer solution, and a surfactant; removing the organic solvent contained in the dispersion solution while stirring the dispersion solution; forming a polyacrylonitrile-based polymer layer on the surface of the non-carbon-based nanoparticles by centrifuging the dispersion solution from which the organic solvent has been removed; and heat-treating the non-carbon-based nanoparticles on which the polyacrylonitrile-based polymer layer is formed to cross-link two types of polyacrylonitrile-based polymers present on the surface of the polyacrylonitrile-based polymer layer to each other to form a cross-linking layer Preparing non-carbon nanoparticles/polymer composite nanoparticles; includes, wherein the cross-linking layer is any one of the nitrile groups of the polyacrylonitrile-based polymer present on the surface of the polyacrylonitrile-based polymer layer and the other one Non-carbon nanoparticles/polymer composite nanoparticles in which the azide groups of the polyacrylonitrile-based polymer are cross-linked with each other by a nitrile azide cycloaddition reaction, and the non-carbon-based nanoparticles are silicon nanoparticles or silica nanoparticles A method for preparing particles is provided.

The non-carbon-based nanoparticle dispersion may be prepared by dispersing the non-carbon-based nanoparticles in a first organic solvent. In this case, the first organic solvent may be at least one selected from the group consisting of toluene, methanol, ethanol, benzene, xylene and ethylbenzene, and toluene may be preferably used.

The non-carbon-based nanoparticles may have an average particle size of 10 to 2000 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, the non-carbon-based nanoparticles aggregate together before the polymer layer is formed on the surface of the non-carbon-based nanoparticles, and the electrochemical performance may be reduced. Electrode stability may be deteriorated due to deterioration of the performance of the non-carbon-based nanoparticles.

The polyacrylonitrile-based polymer solution may be prepared by mixing the polyacrylonitrile-based polymer with the second organic solvent. In this case, the second organic solvent is N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, tetrahydrofuran, ethylene carbonate, diethyl carbonate, dimethyl It may be at least one selected from the group consisting of carbonate, tetramethylene sulfone, anisole, diphenyl ether, nitrobenzene, benzonitrile, cresol, and phenol. Preferably, it may be N,N-dimethylformamide, N,N-dimethylacetamide, or a mixture thereof, and most preferably, it may be N,N-dimethylformamide.

Since the polyacrylonitrile-based polymer has excellent bonding strength with non-carbon-based nanoparticles and at the same time good affinity with electrolytes, it is possible to significantly improve charge/discharge characteristics and long-term cycle stability of the battery. The polyacrylonitrile-based polymer may be a polyacrylonitrile-based random copolymer in which a nitrile group and an azide group are randomly present, and specific examples include polyacrylonitrile-co-vinylidene azide, polyacrylonitrile, polyacrylonitrile, and polyacrylonitrile. (acrylonitrile-co-methylmethacrylate), poly(acrylonitrile-co-methacrylic acid), poly(acrylonitrile-co-methylacrylonitrile, and poly(acrylonitrile-co-methacrylic acid lithium) ) may be at least one selected from the group consisting of. Preferably, the polyacrylonitrile-based polymer is polyacrylonitrile-co-vinylidene azide (PANVDA) represented by the following Chemical Formula 1 can be used

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

The surfactant prevents the non-carbon-based nanoparticles from aggregating with each other, and is mixed to maximize coating efficiency so that a polyacrylonitrile-based polymer layer can be formed evenly with a uniform thickness on the surface of the non-carbon-based nanoparticles. can Specific examples of the surfactant include polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, polyoxypropylene-polyoxyethylene block copolymer, propylene glycol-ethylene glycol block copolymer and polyethylene oxide-polypropylene oxide block copolymer It may be at least one selected from the group consisting of. Preferably, a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer may be used as the surfactant.

The dispersion solution may include 1 to 20% by weight of a non-carbon-based nanoparticle dispersion, 1 to 20% by weight of a polyacrylonitrile-based polymer solution, and 60 to 98% by weight of a surfactant. Preferably, it may contain 3 to 7% by weight of the non-carbon-based nanoparticle dispersion, 4 to 6% by weight of the polyacrylonitrile-based polymer solution, and 87 to 93% by weight of the surfactant.

The step of preparing the dispersion solution may be stirred at a rotation speed of 9,000 to 15,000 rpm for 30 seconds to 30 minutes, preferably at 11,000 to 13,000 rpm for 30 seconds to 2 minutes, and most preferably at 12,000 rpm for 1 minute. . In this case, when both the rotation speed and the time conditions are not satisfied, the non-carbon-based nanoparticles aggregate with each other and uniform dispersion may be difficult.

In the step of removing the organic solvent contained in the dispersion solution, in order to effectively remove the organic solvent remaining in the non-carbon-based nanoparticles contained in the dispersion solution, 60 to 90 ° C. for 24 to 48 hours, preferably 75 to 85 ° C. 18 to 26 hours, most preferably at 80 ° C. for 24 hours. At this time, if the temperature and time conditions are not satisfied at the same time, the organic solvent remains on the surface of the non-carbon-based nanoparticles, so that the polymer layer is not properly formed or a polymer layer of non-uniform thickness is formed, thereby reducing battery stability.

In the step of forming the polyacrylonitrile-based polymer layer, centrifugation is performed at 10,000 to 14,000 rpm for 20 minutes to 1 hour, preferably at 11,000 to 13,000 rpm for 20 to 40 minutes using a centrifuge to perform non-carbon-based nano A polyacrylonitrile-based polymer layer may be formed on the surface of the particles.

In the step of preparing the non-carbon nanoparticles/polymer composite nanoparticles, the heat treatment may be performed at 110 to 150° C. for 30 minutes to 6 hours. Preferably, it may be carried out at 120 to 140° C. for 60 minutes to 3 hours, and most preferably at 130° C. for 2 hours. In this case, if the heat treatment temperature is less than 110° C. or the heat treatment time is less than 30 minutes, cross-linking may not occur sufficiently, so that the cross-linking layer may not be properly formed on the surface of the polymer layer. Conversely, if the heat treatment temperature is more than 150 ° C. or the heat treatment time is more than 6 hours, crosslinking to the polyacrylonitrile-based polymer layer is excessively formed, so that the volume expansion of the non-carbon-based nanoparticles may occur due to deintercalation of lithium ions. .

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

Since the cross-linking layer contains acrylonitrile functional groups, it is possible to effectively impregnate the liquid electrolyte to maximize the electrochemical reaction on the surface of the silicon anode, and the cross-linked polymer layer secures very high mechanical strength during long-term charging and discharging. It is possible to stably reduce the volume expansion of the silicon anode material that occurs in

The non-carbon nanoparticles/polymer composite nanoparticles contain the non-carbon nanoparticles and the polyacrylonitrile-based polymer in a weight ratio of 50:50 to 95:5, preferably 60:40 to 90:10 by weight, more preferably 66.6 :33.4 to 70:30 weight ratio, most preferably 66.6:33.4 weight ratio may be mixed. In particular, if the content of the polyacrylonitrile-based polymer is less than 50 weight ratio, the polymer layer of an appropriate thickness may not be properly formed on the surface of the non-carbon-based nanoparticles, and on the contrary, if it exceeds 5 weight ratio, the polymer layer is excessively formed. The output characteristics of the silicon cathode may be deteriorated.

In particular, although not explicitly described in the following Examples or Comparative Examples, in the method for preparing non-carbon nanoparticles/polymer composite nanoparticles according to the present invention, the non-carbon nanoparticles/polymer composite prepared by changing the following conditions After applying the nanoparticles to the silicon anode, charging and discharging were performed 500 times at 300 °C.

As a result, unlike other conditions and different numerical ranges, when all of the following conditions were satisfied, the charge/discharge capacity was maintained as high as 15,000 mAh/g or more even after 500 charge/discharge cycles at high temperature, unlike the conventional silicon anode, and at high temperature It was found that the thermal stability of

① the non-carbon-based nanoparticles are silicon nanoparticles, ② the non-carbon-based nanoparticles have an average particle size of 50 to 80 nm, and ③ the polyacrylonitrile-based polymer is polyacrylonitrile-co-vinylidene azide , ④ The surfactant is a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, ⑤ the dispersion solution is a non-carbon-based nanoparticle dispersion 3 to 7% by weight, polyacrylonitrile-based polymer solution 4 to 6% by weight and 87 to 93% by weight of a surfactant, ⑥ preparing the dispersion solution is to stir at 11,000 to 13,000 rpm for 30 seconds to 2 minutes, ⑦ preparing the non-carbon nanoparticles/polymer composite nanoparticles In the heat treatment is performed at 120 to 140 ℃ for 60 minutes to 3 hours, ⑧ The non-carbon nanoparticles / polymer composite nanoparticles are non-carbon-based nanoparticles and polyacrylonitrile-based polymer in a weight ratio of 66.6:33.4 to 70:30 may be mixed.

However, if any one of the above eight conditions was not satisfied, charging and discharging could not be continued for a long time at high temperature, and after 300 charge/discharge cycles, the battery capacity rapidly decreased, and the output characteristics and stability of the battery were not good. .

1 is a process diagram schematically illustrating a method for manufacturing a silicon/polymer composite nanoparticle according to Example 1 of the present invention. In addition, Figure 2 is a view showing the structure of the silicon / polymer composite nanoparticles according to an embodiment of the present invention. 1 and 2, after preparing a dispersion solution by mixing a non-carbon-based nanoparticle dispersion, a polyacrylonitrile-based polymer solution, and a surfactant, the organic solvent in the dispersion is removed. Then, a reaction product in which a polymer layer is formed on the surface of the silicon nanoparticles is obtained by centrifugation. Next, a process of forming a cross-linking layer by cross-linking two types of polyacrylonitrile-based polymers present on the surface of the polymer layer by heat-treating the reactant is shown.

3 schematically shows electrode stability after a charge/discharge cycle depending on whether a cross-linking layer is formed for silicon/polymer composite nanoparticles according to an embodiment of the present invention. Referring to FIG. 3 , when a cross-linking layer is not formed on the polymer layer of the silicon nanoparticles, the polymer layer is separated by repeated volume expansion/contraction of the silicon particles after a charge/discharge cycle, and the silicon nanoparticles are formed on the electrode. It shows that the electrode stability is reduced as the polymer layer is separated as the physical stress is concentrated on a specific surface.

On the other hand, when a cross-linking layer is introduced on the polymer layer, the physical stress is transferred to the physical resistance of the cross-linking layer after a charge/discharge cycle and is evenly dispersed, so that the polymer layer is not separated and is stably maintained, resulting in stable battery life. Output characteristics can be secured and electrode stability can be improved.

On the other hand, the present invention is a non-carbon nanoparticle core layer; and a polymer shell layer formed on the outer surface of the non-carbon nanoparticle core layer, wherein the polymer shell layer includes a polyacrylonitrile-based polymer layer and the polyacrylonitrile-based polymer layer formed on the non-carbon nanoparticle core layer. and a crosslinking layer formed by crosslinking two types of polyacrylonitrile-based polymers present on the surface of the The nitrile group of the ronitrile-based polymer and the other azide group of the polyacrylonitrile-based polymer are cross-linked with each other by a nitrile azide cycloaddition reaction, and the non-carbon nanoparticles are silicon nanoparticles or silica nanoparticles. Phosphorus non-carbon nanoparticles/polymer composite nanoparticles are provided.

In addition, the present invention is a non-carbon nanoparticle core layer; and a polymer shell layer formed on the outer surface of the non-carbon nanoparticle core layer and cross-linked, wherein the polymer shell layer is composed of one polyacrylonitrile-co-vinylidene azide nitrile group and the other polyacrylonitrile. Non-carbon nanoparticles/polymers in which the azide group of nitrile-co-vinylidene azide is crosslinked by a nitrile azide cycloaddition reaction, and the non-carbon nanoparticles are silicon nanoparticles or silica nanoparticles. Composite nanoparticles are provided.

The non-carbon nanoparticles may be silicon nanoparticles or silica nanoparticles, preferably silicon nanoparticles.

The polymer shell layer may have a thickness of 1 to 100 nm, preferably 2 to 50 nm, more preferably 3 to 10 nm, and most preferably 5 nm. At this time, if the thickness of the polymer shell layer is less than 1 nm, the outer surface of the non-carbon nanoparticle core layer cannot be sufficiently coated, so that when applied as a silicon anode, volume expansion may occur due to deintercalation of lithium ions. Conversely, if it exceeds 100 nm, the thickness of the polymer shell layer is too thick, so lithium ions are not properly inserted and removed, so that the output characteristics of the battery may be remarkably deteriorated.

The polymer shell layer may form a crosslinking layer by crosslinking some nitrile groups and azide groups of two types of polyacrylonitrile-based polymers on the surface of the polyacrylonitrile-based polymer layer, and the polyacrylonitrile-based polymer Due to most of the nitrile groups remaining in the layer, the rate-limiting properties can be maintained.

The polyacrylonitrile-based polymer may be a polyacrylonitrile-based random copolymer in which a nitrile group and an azide group are randomly present, and specific examples include polyacrylonitrile-co-vinylidene azide, polyacrylonitrile, polyacrylonitrile, and polyacrylonitrile. (acrylonitrile-co-methylmethacrylate), poly(acrylonitrile-co-methacrylic acid), poly(acrylonitrile-co-methylacrylonitrile, and poly(acrylonitrile-co-methacrylic acid lithium) ) may be at least one selected from the group consisting of. Preferably, the polyacrylonitrile-based polymer is polyacrylonitrile-co-vinylidene azide (PANVDA) represented by the following Chemical Formula 1 can be used

[Formula 1]

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

The copolymer may be a compound represented by the following formula (2).

(In Formula 2, n, m, and z are the repeating numbers of each repeating unit, n is an integer from 60 to 110, m is an integer from 1 to 30, and z is an integer from 1 to 60.)

In Formula 2, n is preferably an integer of 70 to 100, more preferably 80 to 90, m is preferably an integer of 5 to 20, more preferably 12 to 17, and z is preferably 1 to 30, more preferably an integer from 1 to 20.)

In addition, the present invention provides an anode active material comprising the non-carbon nanoparticles/polymer composite nanoparticles.

In addition, the present invention provides an anode including the anode active material.

In addition, the present invention provides a lithium secondary battery including the negative electrode.

In addition, the present invention provides a device including the lithium secondary battery, wherein the device is any one selected from a communication device, a transportation device, and an energy storage device.

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

[Scheme 1]

(In Scheme 1, n is 85 and m is 15.)

A 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 mixed with 10 g of dimethylformamide (Dimethylformanide, DMF). ) to prepare a polyacrylonitrile-based polymer solution. Then, 5% by weight of the silicon nanoparticle dispersion, 5% by weight of the polymer solution, and 90% by weight of the surfactant solution were added, and stirred at 12,000 rpm for 1 minute to prepare a dispersion solution. In this case, the surfactant used was a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer dissolved in 200 ml of formamide.

Then, while stirring the dispersion solution at 80° C. for 24 hours, toluene and dimethylformamide in the dispersed silicon nanoparticles were removed. The dispersion solution thus obtained was carried out at 12,000 rpm for 30 minutes using a centrifuge, and then washed 3 times with ethanol at 12,000 rpm for 15 minutes to form a PANVDA polymer layer on the surface of the silicon nanoparticles. Then, the silicon nanoparticles on which the PANVDA polymer layer is formed are heat-treated at 130° C. for 2 hours to form any one of the nitrile groups of the PANVDA polymer present on the surface of the PANVDA polymer layer and the other azide group of the PANVDA polymer present on the surface of the PANVDA polymer layer as shown in Scheme 1. Non-carbon nanoparticles/polymer composite nanoparticles were obtained that were cross-linked by nitrile azide cycloaddition reaction and formed with a PANVDAC cross-linking layer.

Comparative Example 1

Silicon/polymer composite nanoparticles were prepared in the same manner as in Example 1, except that a polyacrylonitrile polymer layer was formed on the outer surface of the silicon nanoparticles without forming a cross-linking layer.

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

The shape and structure of the silicon/polymer composite nanoparticles prepared in Example 1 were analyzed using TEM and EDS, and the results are shown in FIG. 4 .

4 shows the TEM (a, b, c) and EDS (d, e, f) analysis results of the silicon/polymer composite nanoparticles prepared in Example 1 above. 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) photograph, 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 occupy most of the C element. In addition, the C element was observed due to carbon in the polyacrylonitrile-based polymer evenly coated on the surface of the silicon nanoparticles, and it was found that it was formed to a very thin thickness compared to Si.

Experimental Example 2: FT-IR analysis of PANVDAC polymer

FT-IR analysis was performed on the PANVDAC polymer, which is the polyacrylonitrile-based polymer used in Example 1, to analyze the chemical structure, and the results are shown in FIG. 5 .

5 shows the results of FT-IR analysis of the PANVDAC polymer, which is the cross-linked polyacrylonitrile-based polymer used in Example 1. FIG. The PANVDAC polymer of Example 1 synthesized PANVDA by substituting a chlorine group with an azide group in PANVDC, which is a polyacrylonitrile-based polymer containing a chlorine group, as shown in Scheme 1, and then adding two types of PANVDA to a nitrile azide ring. It is synthesized as a PANVDAC polymer by crosslinking with each other by reaction (nitrile azide cycloaddition).

5, in the PANVDC, PANVDA and PANVDAC polymers, all nitrile groups were observed at 2247 cm ^-1 , and in the case of PANVDA polymers, an azide group was confirmed at 2212 cm ^-1 , and all azide groups in PANVDAC cross-linked PANVDA polymers The zeide group disappeared, and a tetrazole structure was formed at 1181, 1097 and 1039 cm ^-1 , and it was found that PANVDA, a polyacrylonitrile-based polymer, was successfully cross-linked with PANVDAC by azide nitrile cyclic polymerization.

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

Experimental Example 3: Evaluation of charging and discharging of lithium secondary batteries

A lithium secondary battery was manufactured by a conventional method using the silicon/polymer composite nanoparticles prepared in Example 1 and Comparative Example 1 as an anode. In this case, 1 M LiPF ₆ EC/EMC (3:7 vol%) was used as the electrolyte, and fluoroethylene carbonate (FEC) and vinyl carbonate (VC) were used as electrolyte additives. The charging/discharging experiment using the lithium secondary battery was conducted under a current condition of 0.2C to 100C and a voltage condition of 0.01V to 2V, and the results are shown in FIG. 6 .

6 is a discharge according to a change in the charge/discharge voltage profile (a) and C-rate value (0.2 to 100 C) for the lithium secondary battery to which the silicon/polymer composite nanoparticles prepared in Example 1 and Comparative Example 1 are applied. The results of measuring the capacity (b) and the discharge capacity (c) according to the number of cycles are shown. 6A shows the charge/discharge voltage profile in the first and second cycles of Example 1, and it was confirmed that the battery had a high capacity of about 2000 mAh/g. In addition, in FIG. 6(b), it was found that both Example 1 and Comparative Example 1 had a similar level of discharge capacity in each C-rate range. In addition, in FIG. 6(c), the discharge capacity of Example 1 was maintained high at about 1900 mAh/g even as the number of cycles increased, whereas in Comparative Example 1, the discharge capacity was rapidly decreased as the number of cycles increased. , it was confirmed that the discharge capacity decreased to about 1000 mAh/g after 300 cycles.

Claims (17)

1. preparing a dispersion solution by mixing a non-carbon-based nanoparticle dispersion, a polyacrylonitrile-based polymer solution, and a surfactant;

   removing the organic solvent contained in the dispersion solution while stirring the dispersion solution;

   forming a polyacrylonitrile-based polymer layer on the surface of the non-carbon-based nanoparticles by centrifuging the dispersion solution from which the organic solvent has been removed; and

   The non-carbon-based nanoparticles on which the polyacrylonitrile-based polymer layer is formed are heat-treated to cross-link two types of polyacrylonitrile-based polymers present on the surface of the polyacrylonitrile-based polymer layer to each other to form a cross-linking layer preparing carbon nanoparticles/polymer composite nanoparticles;

   including,

   In the crosslinking layer, the nitrile group of the polyacrylonitrile-based polymer, which is any one present on the surface of the polyacrylonitrile-based polymer layer, and the azide group of the other polyacrylonitrile-based polymer, which are present on the surface of the polyacrylonitrile-based polymer layer, are in the nitrile azide ring addition reaction. formed by crosslinking with each other by

   The non-carbon-based nanoparticles are silicon nanoparticles or silica nanoparticles. Non-carbon nanoparticles/polymer composite nanoparticles manufacturing method.
2. The method of claim 1,

   The non-carbon-based nanoparticles have an average particle size of 10 nm to 2000 nm.
3. The method of claim 1,

   The polyacrylonitrile-based polymer is polyacrylonitrile-co-vinylidene azide, polyacrylonitrile, poly(acrylonitrile-co-methylmethacrylate), poly(acrylonitrile-co-methacrylic acid) ), poly (acrylonitrile-co-methylacrylonitrile, and poly (acrylonitrile- lithium comethacrylate) to at least one selected from the group consisting of non-carbon nanoparticles / polymer composite nanoparticles manufacturing method.
4. According to claim 1,

   The surfactant is a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, polyoxypropylene-polyoxyethylene block copolymer, propylene glycol-ethylene glycol block copolymer and polyethylene oxide-polypropylene oxide block copolymer. A method of manufacturing non-carbon nanoparticles/polymer composite nanoparticles that is at least one selected from
5. The method of claim 1,

   The dispersion solution is a non-carbon nanoparticle / polymer composite nanoparticles comprising 1 to 20% by weight of a non-carbon-based nanoparticle dispersion, 1 to 20% by weight of a polyacrylonitrile-based polymer solution, and 60 to 98% by weight of a surfactant manufacturing method.
6. The method of claim 1,

   The step of preparing the dispersion solution is a method of producing non-carbon nanoparticles / polymer composite nanoparticles by stirring for 30 seconds to 30 minutes at a rotation speed of 9,000 to 15,000 rpm.
7. The method of claim 1,

   In the step of preparing the non-carbon nanoparticles/polymer composite nanoparticles, the heat treatment is performed at 110 to 150° C. for 30 minutes to 6 hours.
8. According to claim 1,

   The non-carbon nanoparticles/polymer composite nanoparticles are non-carbon nanoparticles and polyacrylonitrile-based polymer in a weight ratio of 50:50 to 95:5 mixed in a non-carbon nanoparticle/polymer composite nanoparticle manufacturing method.
9. According to claim 1,

   The non-carbon-based nanoparticles are silicon nanoparticles,

   The non-carbon-based nanoparticles have an average particle size of 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,

   The dispersion solution contains 3 to 7% by weight of a non-carbon-based nanoparticle dispersion, 4 to 6% by weight of a polyacrylonitrile-based polymer solution, and 87 to 93% by weight of a surfactant,

   The step of preparing the dispersion solution is to stir at 11,000 to 13,000 rpm for 30 seconds to 2 minutes,

   In the step of preparing the non-carbon nanoparticles / polymer composite nanoparticles, the heat treatment is performed at 120 to 140 ° C. for 60 minutes to 3 hours,

   The non-carbon nanoparticles / polymer composite nanoparticles are non-carbon nanoparticles and polyacrylonitrile-based polymer is mixed in a weight ratio of 66.6:33.4 to 70:30 non-carbon nanoparticles / polymer composite nanoparticles manufacturing method.
10. a non-carbon nanoparticle core layer; and

    Including; a polymer shell layer formed on the outer surface of the non-carbon nanoparticle core layer,

    The polymer shell layer is formed by crosslinking the polyacrylonitrile-based polymer layer formed on the non-carbon nanoparticle core layer and two types of polyacrylonitrile-based polymers present on the surface of the polyacrylonitrile-based polymer layer. a cross-linking layer;

    In the crosslinking layer, the nitrile group of the polyacrylonitrile-based polymer, which is any one present on the surface of the polyacrylonitrile-based polymer layer, and the azide group of the other polyacrylonitrile-based polymer, which are present on the surface of the polyacrylonitrile-based polymer layer, are in the nitrile azide ring addition reaction. formed by crosslinking with each other by

    The non-carbon nanoparticles are silicon nanoparticles or silica nanoparticles. Non-carbon nanoparticles/polymer composite nanoparticles.
11. 11. The method of claim 10,

    The polymer shell layer is non-carbon nanoparticles / polymer composite nanoparticles having a thickness of 1 to 100 nm.
12. 11. The method of claim 10,

    The polyacrylonitrile-based polymer is polyacrylonitrile-co-vinylidene azide (PANVDA) represented by the following formula (1) Non-carbon nanoparticles / polymer composite nanoparticles.

    [Formula 1]

    

    (In Formula 1, n and m are the number of repeats of each repeating unit, n is an integer of 60 to 110, and m is an integer of 1 to 30.)
13. a non-carbon nanoparticle core layer; and

    A polymer shell layer formed on the outer surface of the non-carbon nanoparticle core layer and cross-linked;

    The polymer shell layer is a copolymer in which the nitrile group of one polyacrylonitrile-co-vinylidene azide and the azide group of the other polyacrylonitrile-co-vinylidene azide are crosslinked by a nitrile azide cycloaddition reaction. is made of,

    The non-carbon nanoparticles are silicon nanoparticles or silica nanoparticles. Non-carbon nanoparticles/polymer composite nanoparticles.
14. A negative active material for a lithium secondary battery comprising the non-carbon nanoparticles/polymer composite nanoparticles according to claim 10 or 13.
15. A negative electrode for a lithium secondary battery comprising the negative active material according to claim 14 .
16. A lithium secondary battery comprising the negative electrode according to claim 15.
17. A device comprising the lithium secondary battery according to claim 16,

    The device is any one selected from a communication device, a transportation device, and an energy storage device.

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