Silicon-carbon composite with yolk-shell structure, method for producing the same, and negative electrode active material containing the same

Abstract

The present invention relates to a yoke-shell silicon-carbon composite, a method for manufacturing the same, and an anode active material including the same. The yoke-shell silicon-carbon composite according to an embodiment of the present invention can be manufactured without using a strong acid, and can form uniform pores by using an inorganic layer of uniform thickness as a sacrificial layer. This allows the composite to absorb the volume expansion of silicon when used as an anode active material, thereby preventing peeling of the outermost carbon thin film. As a result, deterioration of battery performance and lifespan can be suppressed.

Description

[Technical Field]

[0001] The present invention relates to a silicon-carbon composite having a yoke-shell structure, and more particularly to a silicon-carbon composite having a yoke-shell structure, a method for producing the same, and a negative electrode active material including the same. [Background technology]

[0002] In recent years, with the development of the information and communications industry, demand for electronic devices has been increasing rapidly, and as the market for electric vehicles has become significantly more active, demand for the batteries used in these electronic devices and electric vehicles has also increased.

[0003] Secondary batteries, such as lithium secondary batteries and all-solid-state batteries, containing liquid electrolytes, are the most widely used for such applications due to their high energy density and low self-discharge when not in use. Secondary batteries are broadly composed of a positive electrode, a negative electrode, and an electrolyte (liquid or solid), and carbon materials such as graphite are widely used as the negative electrode active material for secondary batteries.

[0004] Recently, attempts to use silicon-based anode active materials have been progressing to improve the capacity of secondary batteries. Silicon has a very high theoretical energy density and is attracting attention as a next-generation battery anode active material to replace graphite. However, there are problems with silicon, such as its volume increasing by up to 300% due to a reaction with lithium during charging and discharging, and the mechanical stability of silicon as an anode active material being greatly reduced due to repeated charging and discharging, such as its fracture.

[0005] To solve this problem, a silicon-carbon composite with a yolk-shell structure was proposed, which involves using porous silicon particles with pores that can accommodate the volume expansion of silicon and forming a thin carbon film on top of them. To manufacture this composite, the surface of the silicon particles that will become the yoke must be coated with an inorganic material and then etched with a strong acid such as hydrofluoric acid.

[0006] Therefore, there is a need to develop a material that can be used as a sacrificial layer in a more environmentally friendly and convenient manner. Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a silicon-carbon composite with a yoke-shell structure that can suppress a decrease in battery performance due to volume expansion of silicon when used as a negative electrode active material by forming uniform pores by using an inorganic layer of uniform thickness as a sacrificial layer.

[0008] Another object of the present invention is to provide a method for efficiently producing the above-mentioned silicon-carbon composite having a yoke-shell structure.

[0009] A further object of the present invention is to provide a negative electrode active material containing the silicon-carbon composite with the yolk-shell structure. [Means for solving the problem]

[0010] The present invention provides a method for manufacturing a silicon-inorganic layer composite by (1) supplying silicon particles into a reactor, (2) forming an inorganic layer on the silicon particles using atomic layer deposition (ALD), and (3) forming a silicon-inorganic layer composite. and (3) removing at least a portion of the inorganic layer from the silicon-inorganic layer-carbon composite to produce a silicon-carbon composite with a yoke-shell structure.

[0011] According to one embodiment of the present invention, step (2) can be performed one or more times, with each cycle consisting of: (2-1) supplying a first precursor to a reactor and forming a first precursor multilayer in which at least a portion of the first precursor is adsorbed on the silicon particles; (2-2) purging the reactor and removing unadsorbed first precursor from the first precursor multilayer to form a first precursor monolayer; (2-3) supplying a second precursor to the reactor and reacting the first precursor monolayer with at least a portion of the second precursor to form a composite layer; and (2-4) purging the reactor and removing unreacted second precursor from the composite layer to form an inorganic layer.

[0012] Furthermore, the time for supplying the first precursor and the time for supplying the second precursor may each independently be 1 to 600 seconds.

[0013] The first precursor may also include one or more selected from the group consisting of trimethylaluminum, diethylzinc, zinc acetate, tetrakis(dimethylamino)tin(IV), butoxytris(ethylmethylamido)hafnium, titanium isopropoxide, and diisopropylaminosilane.

[0014] The second precursor may also include one or more selected from the group consisting of H2O, O3, H2O plasma, O3 plasma, and O2 plasma.

[0015] In addition, the gas used for purging in any one or more of the steps (2-2) and (2-4) may include nitrogen (N2) or argon (Ar).

[0016] The cycle can be repeated 1 to 300 times.

[0017] Furthermore, the temperature of the silicon particles can be maintained at 90 to 400°C during the cycle.

[0018] Alternatively, step (4) can be performed by etching the inorganic layer from the silicon-inorganic layer-carbon composite.

[0019] The present invention also provides a silicon-carbon composite having a yoke-shell structure, which includes silicon particles and a carbon thin film formed on the silicon particles with a predetermined pore size.

[0020] According to one embodiment of the present invention, the silicon particles may have an average particle size of 10 nm to 50 μm, and the carbon thin film may have an average thickness of 1 nm to 1 μm.

[0021] The silicon-carbon composite having the yolk-shell structure may have a porosity of 10 to 80%.

[0022] The present invention also provides a negative electrode active material comprising the silicon-carbon composite with the yolk-shell structure.

[0023] The present invention also provides an all-solid-state battery including an SEI (Solid Electrolyte Interphase) film containing the silicon-carbon composite with the yolk-shell structure. do. [Effects of the Invention]

[0024] The yoke-shell silicon-carbon composite according to an embodiment of the present invention is manufactured based on an inorganic layer formed using atomic layer deposition, which allows for precise adjustment of the thickness of the sacrificial layer. Furthermore, by using an inorganic layer of uniform thickness as the sacrificial layer, uniform pores can be formed. This allows the yoke-shell silicon-carbon composite to accommodate the volumetric expansion of silicon when used as an anode active material, thereby preventing peeling of the outermost carbon thin film. As a result, deterioration in battery performance and lifespan can be prevented. [Brief explanation of the drawings]

[0025] [Figure 1]FIG. 1 is a TEM (transmission electron microscope) image of a silicon-inorganic layer composite, which is an intermediate for a silicon-carbon composite (Example 1) according to one embodiment of the present invention. [Figure 2] FIG. 2 is a TEM-EDS (energy dispersive spectrometer) image of a silicon-inorganic layer composite, which is an intermediate of a silicon-carbon composite (Example 1) according to one embodiment of the present invention. [Figure 3] FIG. 3 is a TEM (transmission electron microscope) image of a silicon-inorganic layer-carbon composite, which is an intermediate of a silicon-carbon composite (Example 1) according to one embodiment of the present invention. [Figure 4] FIG. 4 is a TEM-EDS image of a silicon-inorganic layer-carbon composite, which is an intermediate of a silicon-carbon composite (Example 1) according to one embodiment of the present invention. [Figure 5] FIG. 5 is a TEM image of a silicon-carbon composite (Example 1) according to one embodiment of the present invention. [Figure 6] FIG. 6 is a TEM-EDS image of a silicon-carbon composite (Example 1) according to one embodiment of the present invention. [Figure 7] FIG. 7 is an image of an atomic distribution graph of a silicon-carbon composite (Example 1) according to one embodiment of the present invention. [Figure 8] FIG. 8 is a TEM image of a silicon-inorganic layer composite, which is an intermediate for a silicon-carbon composite (Example 2) according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention is not limited to the contents described below, and can be modified into various forms as long as the gist of the invention is not changed.

[0027] In this specification, the word "comprise" means that other components may be further included, unless otherwise specified.

[0028] All numbers and expressions expressing quantities of components, reaction conditions, and the like described herein should be understood to be modified in all instances by the term "about," unless otherwise specified.

[0029] As used herein, it is understood that one component may be formed above / below another component or may be attached to another component. When it is stated that something is connected or coupled, it includes all of the elements that are formed, connected, or coupled directly between these elements or indirectly through other elements.

[0030] The present invention will be described in more detail below.

[0031] Silicon-carbon composite with yolk-shell structure

[0032] The present invention provides a silicon-carbon composite having a yoke-shell structure, which includes silicon particles and a carbon thin film having a predetermined pore space formed on the silicon particles.

[0033] A silicon-carbon composite having a yoke-shell structure according to an embodiment of the present invention is obtained using, as intermediates, a silicon-inorganic layer composite including silicon particles and an inorganic layer formed on the silicon particles, and a silicon-inorganic layer-carbon composite including a carbon thin film formed on the silicon-inorganic layer composite.

[0034] Therefore, in the following, a silicon-carbon composite having a yoke-shell structure according to an embodiment of the present invention will be described while describing a silicon-inorganic layer composite and a silicon-inorganic layer-carbon composite as intermediates.

[0035] Silicon particles

[0036] In one embodiment of the present invention, the intermediate silicon-inorganic layer composite and silicon-inorganic layer-carbon composite and the final product yolk-shell structured silicon-carbon composite contain silicon particles.

[0037] The silicon particles in the yoke-shell structured silicon-carbon composite according to an embodiment of the present invention serve to charge lithium. Therefore, when the yoke-shell structured silicon-carbon composite according to an embodiment of the present invention is used as an anode active material, the silicon particles can act as a main anode active material.

[0038] The silicon particles may be crystalline or amorphous, and are preferably amorphous or a similar phase from the viewpoint of expansion / contraction during charge / discharge of the secondary battery and battery performance. When the silicon particles are crystalline, the smaller the crystal grain size, the denser the composite, which strengthens the matrix and prevents cracks. This can improve the initial efficiency and cycle life characteristics of the secondary battery. Furthermore, when the silicon particles are amorphous or a similar phase, expansion or contraction during charge / discharge of the secondary battery is small, and battery performance such as capacity characteristics can be improved.

[0039] The size of the silicon particles can be selected so that the yolk-shell structured silicon-carbon composite according to an embodiment of the present invention is suitable for use as a negative electrode active material. Specifically, the average particle size of the silicon particles can be 10 nm to 50 μm, preferably 10 nm to 25 μm. When the silicon particles satisfy this average particle size range, it can be more advantageous to achieve the object of the present invention.

[0040] The silicon particles may further include a silicon oxide compound. The silicon oxide compound may be expressed by the general formula SiOx (0.5≦x≦2). If the value of x is less than 0.5, the secondary battery may expand and contract significantly during charging and discharging, resulting in a poor service life. If the value of x is greater than 2, the amount of inactive oxides may increase, resulting in a poor initial efficiency of the secondary battery.

[0041] The content of the silicon oxide compound in the silicon particles may be 50 wt % or less based on the total weight of the silicon particles. If the content of the silicon oxide compound in the silicon particles exceeds 50 wt %, the initial efficiency of the secondary battery may decrease.

[0042] The silicon particles may further contain elements such as carbon and magnesium in addition to silicon and oxygen. The silicon content in the silicon particles can be selected so that the total silicon content in the silicon-carbon composite is 1 to 80 wt %, preferably 5 to 50 wt %. If the total silicon content in the silicon-carbon composite is less than 1 wt %, the amount of active material that absorbs and releases lithium may be insufficient, resulting in a decrease in the charge / discharge capacity of the secondary battery. If the total silicon content in the silicon-carbon composite exceeds 80 wt %, the charge / discharge capacity of the secondary battery may increase, but the electrode may expand and contract excessively during charge / discharge, further pulverizing the negative electrode active material powder and reducing the cycle characteristics of the secondary battery.

[0043] inorganic layer

[0044] In an embodiment of the present invention, the intermediate silicon-inorganic layer composite includes an inorganic layer formed on the surface of a silicon particle by atomic layer deposition (ALD), which will be described later.

[0045] The inorganic layer is formed by ALD, and there is no particular limitation on the type of material as long as it is formed as a sacrificial layer for forming a carbon thin film, and then is sufficiently removed by the etching step described below, thereby producing a silicon-carbon composite with a yoke-shell structure.

[0046] In an embodiment of the present invention, the inorganic layer may contain one or more selected from the group consisting of aluminum oxide (Al2O3), zinc oxide (ZnO), tin oxide (SnO2), hafnium oxide (HfO), zirconium oxide (ZrO2), titanium oxide (TiO2) and silicon oxide (SiO2), but is not particularly limited thereto. In a preferred embodiment of the present invention, the inorganic layer may contain aluminum oxide (Al2O3).

[0047] In a specific example of the present invention, the inorganic layer may have a thickness of 1 nm to 10 μm, preferably 1 nm to 1 μm, and more preferably 1 to 100 nm. When the inorganic layer has a thickness within this range, the inorganic layer can properly function as a sacrificial layer in the etching step described below, and can properly form pores between the silicon particles and the carbon thin film.

[0048] In an embodiment of the present invention, the inorganic layer on the surface of the silicon particle in the silicon-inorganic layer composite as an intermediate is at least partially, preferably 10 to 100 wt %, and more preferably 50 to 100 wt %, removed in the etching step described below, thereby allowing pores to be appropriately formed between the silicon particle and the carbon thin film.

[0049] Residues of the inorganic layer remaining after removal by etching may be present between the silicon particles and the carbon thin film in the yoke-shell structured silicon-carbon composite as the final product according to an embodiment of the present invention. Therefore, the yoke-shell structured silicon-carbon composite according to an embodiment of the present invention may include residues of the inorganic layer between the silicon particles and the carbon thin film. However, the present invention is not limited thereto, and if the entire inorganic layer is removed by etching, the yoke-shell structured silicon-carbon composite may not include residues of the inorganic layer between the silicon particles and the carbon thin film.

[0050] carbon thin film

[0051] A silicon-carbon composite having a yoke-shell structure according to an embodiment of the present invention includes a carbon thin film formed on the silicon particles.

[0052] The yoke-shell silicon-carbon composite according to an embodiment of the present invention includes a carbon thin film, which can ensure appropriate electrical conductivity and appropriately control the specific surface area. Therefore, when used as an anode active material for a secondary battery, the life characteristics and capacity of the secondary battery can be further improved.

[0053] The electrical conductivity of a negative electrode active material is an important factor for facilitating electron transfer during an electrochemical reaction. By including the carbon thin film in a yolk-shell silicon-carbon composite according to an embodiment of the present invention, the charge / discharge capacity, initial charge efficiency, and capacity retention of a secondary battery can be improved, and excellent electrical conductivity can be provided, thereby suppressing side reactions in the electrolyte, thereby further improving the performance of the secondary battery.

[0054] In the silicon-carbon composite having a yoke-shell structure according to an embodiment of the present invention, the carbon thin film may have a thickness of 1 nm to 1 μm, preferably 3 to 150 nm, and more preferably 5 to 100 nm. When the carbon thin film has a thickness within this range, the electrical conductivity can be improved and a decrease in the capacity of the secondary battery can be suppressed.

[0055] The carbon thin film may include at least one selected from graphene, carbon nanotubes, carbon nanofibers, and graphite. Specifically, the carbon thin film may include graphene and may further include graphite, but is not particularly limited thereto.

[0056] pore space

[0057] In the silicon-carbon composite with a yoke-shell structure according to one embodiment of the present invention, pores exist between the silicon particles and the carbon thin film.

[0058] As described above, in the silicon-inorganic layer composite serving as an intermediate for producing a silicon-carbon composite with a yolk-shell structure according to an embodiment of the present invention, the inorganic layer on the surface of the silicon particle acts as a sacrificial layer and is removed at least partially, preferably 10 to 100 wt %, and more preferably 50 to 100 wt %, in the etching step described below, thereby forming pores between the silicon particle and the carbon thin film.

[0059] In the yoke-shell silicon-carbon composite according to an embodiment of the present invention, the pores present between the silicon particles and the carbon thin film absorb the volumetric expansion of the silicon when the yoke-shell silicon-carbon composite is used as a negative electrode active material, thereby preventing the outermost carbon thin film from peeling off.

[0060] The silicon-carbon composite with a yolk-shell structure according to an embodiment of the present invention may have a porosity of 10 to 80%, preferably 10 to 50%, and more preferably 20 to 50%. Here, the porosity can be measured by the Brunauer-Emmett-Teller (BET) method, but is not particularly limited to this method. When the silicon-carbon composite with a yolk-shell structure satisfies the above porosity range, it can be more advantageous in achieving the objects of the present invention.

[0061] Manufacturing method for yolk-shell structured silicon-carbon composite

[0062] According to one embodiment of the present invention, a silicon-carbon composite having a yolk-shell structure can be produced by the steps of: (1) supplying silicon particles into a reactor; (2) forming an inorganic layer on the silicon particles using atomic layer deposition (ALD) to produce a silicon-inorganic layer composite; (3) forming a carbon thin film on the silicon-inorganic layer composite to obtain a silicon-inorganic layer-carbon composite; and (4) depositing the silicon-inorganic layer-carbon thin film on the silicon-inorganic layer composite. and removing at least a portion of the inorganic layer from the base composite to produce a silicon-carbon composite having a yolk-shell structure.

[0063] Atomic layer deposition (ALD) is a deposition method for growing thin films atomically. In conventional chemical vapor deposition (CVD), reactants are injected simultaneously, resulting in both gas-phase and surface reactions. In contrast, ALD suppresses gas-phase reactions by sequentially injecting reactants, allowing deposition to occur via surface reactions using self-limited adsorption. The thickness of the deposited film is easily controlled by the number of deposition cycles, allowing for easy control of thickness at the atomic layer level. Furthermore, ALD has been primarily used for semiconductor, dielectric, and magnetic materials due to its wide variety of thin film properties, excellent thin film characteristics, and excellent processability at relatively low temperatures. With the recent development of nanotechnology, ALD of inorganic materials has expanded beyond its traditional focus on integrated circuit devices and is now being applied to a variety of fields.

[0064] Below, we will explain step by step how to fabricate a silicon-carbon composite with a yoke-shell structure using atomic layer deposition (ALD).

[0065] Stage (1)

[0066] In the above step (1), silicon particles are fed into the reactor.

[0067] The specific content of the silicon particles used in step (1) is as explained above in the section on the silicon-carbon composite with a yolk-shell structure.

[0068] The reactor used in the method for producing a silicon-carbon composite having a yolk-shell structure according to an embodiment of the present invention is not particularly limited in structure as long as it is capable of forming an inorganic layer on the surface of silicon particles using atomic layer deposition (ALD).

[0069] Stage 2

[0070] In the step (2), atomic layer deposition (ALD) is performed on the silicon particles. The inorganic layer is formed using ALD (atomic layer deposition) to produce a silicon-inorganic layer composite.

[0071] In this case, step (2) can be performed one or more times, with each cycle consisting of the following steps: (2-1) supplying a first precursor to a reactor and forming a first precursor multilayer in which at least a portion of the first precursor is adsorbed on the silicon particles; (2-2) purging the inside of the reactor and removing unadsorbed first precursor from the first precursor multilayer to form a first precursor monolayer; (2-3) supplying a second precursor to the reactor and reacting the first precursor monolayer with at least a portion of the second precursor to form a composite layer; and (2-4) purging the inside of the reactor and removing unreacted second precursor from the composite layer to form an inorganic layer.

[0072] First, in step (2-1), a first precursor may be supplied to a reactor to form a first precursor multi-layer in which at least a portion of the first precursor is adsorbed on the silicon particles.

[0073] In an embodiment of the present invention, the first precursor may comprise one or more selected from the group consisting of trimethylaluminum, diethylzinc, zinc acetate, tetrakis(dimethylamino)tin(IV), butoxytris(ethylmethylamido)hafnium, titanium isopropoxide, and diisopropylaminosilane. The first precursor may include trimethylaluminum.

[0074] In a specific example of the present invention, the supply time of the first precursor may be 1 to 600 seconds. In a preferred example of the present invention, the supply time of the first precursor may be 1 second or more, 2 seconds or more, 5 seconds or more, 10 seconds or more, or 15 seconds or more, and 600 seconds or less, 300 seconds or less, 100 seconds or less, 50 seconds or less, or 20 seconds or less. When the supply time of the first precursor satisfies the above range, a layer of the first precursor can be properly formed on the silicon particles. However, if the supply time of the first precursor is less than 1 second, it may be difficult to form an inorganic layer of uniform thickness due to incomplete atomic layer deposition. If the supply time exceeds 600 seconds, the inorganic layer may become excessively thick, and the purging time may also increase, resulting in a longer overall process time.

[0075] Next, in step (2-2), the supply of the first precursor is stopped, the inside of the reactor is purged, and unadsorbed first precursor is removed from the first precursor multilayer, thereby forming a first precursor monolayer.

[0076] In an embodiment of the present invention, step (2-2) can be purged with an inert gas, which may include nitrogen (N2) or argon (Ar).

[0077] In an embodiment of the present invention, the purging time in step (2-2) may be 1 to 300 seconds. In a preferred embodiment of the present invention, the purging time may be 1 second or more, 2 seconds or more, 5 seconds or more, 10 seconds or more, or 15 seconds or more, and 300 seconds or less, 200 seconds or less, 100 seconds or less, 50 seconds or less, or 20 seconds or less. If the purging time is too short, residues of the first precursor may remain, resulting in the formation of an inorganic oxide thin film that is thicker than intended. If the purging time is too long, the process efficiency may decrease.

[0078] Next, in step (2-3), a second precursor is supplied to the reactor, and the first precursor monolayer and at least a portion of the second precursor are reacted to form a composite layer.

[0079] In an embodiment of the present invention, the second precursor may comprise one or more selected from the group consisting of HO, O, HO plasma, O plasma, and O plasma. In a preferred embodiment of the present invention, the second precursor may comprise HO.

[0080] The layer of the first precursor and the second precursor can react to form an inorganic layer containing, in particulate form, one or more selected from the group consisting of aluminum oxide (Al2O3), zinc oxide (ZnO), tin oxide (SnO2), hafnium oxide (HfO), zirconium oxide (ZrO2), titanium oxide (TiO2), and silicon oxide (SiO2).

[0081] In some embodiments, the supply time of the second precursor may be 1 to 600 seconds. In some preferred embodiments, the supply time of the second precursor may be 1 second or more, 2 seconds or more, 5 seconds or more, 10 seconds or more, or 15 seconds or more, and 600 seconds or less, 300 seconds or less, 100 seconds or less, 50 seconds or less, or 20 seconds or less. When the supply time of the second precursor satisfies the above range, an inorganic layer can be properly formed on the silicon particles. However, if the supply time of the second precursor is less than 1 second, it may be difficult to form an inorganic layer of uniform thickness due to incomplete atomic layer deposition. If the supply time exceeds 600 seconds, the inorganic layer may become excessively thick, and the purging time may also increase, resulting in a longer overall process time.

[0082] Next, in step (2-4), the supply of the second precursor is stopped, the inside of the reactor is purged, and unreacted second precursor is removed from the composite layer, thereby forming an inorganic layer.

[0083] In an embodiment of the present invention, steps (2-4) may be purged with an inert gas, which may include nitrogen (N2) or argon (Ar).

[0084] In an embodiment of the present invention, the purging time in step (2-4) may be 1 to 300 seconds. In a preferred embodiment of the present invention, the purging time may be 1 second or more, 2 seconds or more, 5 seconds or more, 10 seconds or more, or 15 seconds or more, and 300 seconds or less, 200 seconds or less, 100 seconds or less, 50 seconds or less, or 20 seconds or less. If the purging time is too short, residues of the second precursor may remain, resulting in the formation of an inorganic oxide thin film that is thicker than intended. If the purging time is too long, the process efficiency may decrease.

[0085] In an embodiment of the present invention, the temperature of the silicon particles may be maintained at 90 to 400°C during the cycle described above. In a preferred embodiment of the present invention, the temperature of the silicon particles may be maintained at 120 to 300°C during the cycle described above. If the temperature of the silicon particles is less than 90°C, defects may occur in the inorganic layer formed due to incomplete reaction, and if the temperature exceeds 400°C, there may be a problem of excessive formation of an inorganic thin film on the silicon particles.

[0086] In an embodiment of the present invention, the above cycle may be carried out under a pressure of 0.5 to 10 Torr. In a preferred embodiment of the present invention, the above cycle may be carried out under a pressure of 1 to 5 Torr.

[0087] In an embodiment of the present invention, the above cycle may be repeated 1 to 300 times. In a preferred embodiment of the present invention, the above cycle may be repeated 50 to 300 times. If the above cycle is repeated more than 300 times, an excessive inorganic thin film may be formed on the silicon particles, and the process time may be prolonged.

[0088] Stage (3)

[0089] In the above step (3), a carbon thin film is formed on the silicon-inorganic layer composite to obtain a silicon-inorganic layer-carbon composite.

[0090] The step of forming a carbon thin film on the silicon-inorganic layer composite particles as an intermediate may be performed using an apparatus and method known in the art to which the present invention pertains, such as, but not limited to, a chemical pyrolysis deposition method. For example, the carbon thin film may be formed by carbonizing a polymer thin film formed using an initiator-based chemical vapor deposition (iCVD) method.

[0091] In an embodiment of the present invention, the step of forming a carbon thin film on the silicon-inorganic layer composite as an intermediate may be performed by heat-treating the silicon-inorganic layer composite as an intermediate at a temperature of 400 to 1,400°C in the presence of a gaseous carbon source.

[0092] In a preferred embodiment of the present invention, the carbon source may include at least one selected from the group consisting of methane, ethane, propane, butane, methanol, ethanol, propanol, propanediol, butanediol, ethylene, propylene, butylene, butadiene, cyclopentene, acetylene, benzene, toluene, xylene, ethylbenzene, naphthalene, anthracene, and dibutylhydroxytoluene, but is not particularly limited thereto.

[0093] The step of forming a carbon thin film on the silicon-inorganic layer composite as an intermediate is In addition to the carbon source, the reaction may be carried out in the presence of at least one inert gas selected from the group consisting of hydrogen, nitrogen, helium and argon.

[0094] The reaction time (heat treatment time) for forming the carbon thin film can be appropriately adjusted depending on the heat treatment temperature, the pressure during the heat treatment, the composition of the gas mixture, and the desired carbon coating amount. For example, the reaction time may be 10 minutes to 100 hours, specifically 30 minutes to 90 hours, and more specifically 50 minutes to 40 hours, but is not particularly limited to these ranges.

[0095] In an embodiment of the present invention, the step of forming a carbon thin film on the silicon-inorganic layer composite as an intermediate may be performed by mixing the silicon-inorganic layer composite with a solution in which a carbon source is dispersed in a solvent as needed, followed by drying and heat-treating the mixture at a temperature of 400 to 1,400°C.

[0096] In a preferred embodiment of the present invention, the carbon source can be selected from the group consisting of pitch, hydrocarbon-based materials, and petroleum-based materials. More specifically, the pitch can be petroleum-based pitch, coal-based pitch, or a mixture thereof. The hydrocarbon-based material can be furfuryl alcohol or a phenolic resin. The petroleum-based material can be pyrolysis fuel oil (PFO), naphtha cracking bottom oil (NCB), ethylene cracker bottom oil (EBO), vacuum residue (VR), deasphalted oil (DAO), atmospheric residue (AR), fluid catalytic cracking decant oil (FCC-DO), residue fluid catalytic cracking decant oil (RFCC-DO), or heavy aromatic oil. The solvent can be tetrahydrofuran (THF) or alcohol.

[0097] In addition, when the carbon thin film is formed by carbonizing a polymer thin film, a volatile monomer that can be activated by an initiator to form a polymer can be activated by an initiator to polymerize the monomer, thereby forming a polymer thin film, and then the formed polymer thin film can be carbonized.

[0098] In this case, the monomer may be at least one of a vinyl or acrylate monomer containing at least one of a siloxane group, an amine group, a fluorine group, and an aromatic hydrocarbon group.

[0099] In addition, examples of the polymer thin film obtained by polymerizing the monomer include 4-vinylpyridine (4VP), 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl methacrylate, and 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl methacrylate. methacrylate, PFDMA), 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane (1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane, V4D4), 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane (1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane, V 3D3), hexavinyldisiloxane (HVDS), glycidyl methacrylate, divinylbenzene, diethylene glycol divinyl ether, diethylene glycol diacrylate (DEGDA), ethylene glycol dimethacrylate, dimethylaminoethyl methacrylate, methacrylic acid, and 1,3-diethenyl-1,1,3,3-tetramethyl-disiloxane, 1H,1H,2H,2H-perfluorodecyl acrylate, per ... Rhodecyl methacrylate, dodecafluoroheptyl acrylate, pentafluorophenyl methacrylate, 3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-pentadecafluorononyl acrylate, 2-methyl-3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-pentadecafluorononyl acrylate, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate, 2-methyl-3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate acrylate, 3,3,4,4,5,5,6,6,7,7,7-undecafluoroheptyl acrylate, 2-methyl-3,3,4,4,5,5,6,6,7,7,7-undecafluoroheptyl acrylate, 3,3,4,4,5,5,6,6,6-nonafluorohexyl acrylate, 2-methyl-3,3,4,4,5,5,6,6,6-nonafluorohexyl acrylate, 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-nonadecafluoroundecyl acrylate, 2-methyl-3,3,4,4,5,5 ,6,6,7,7,8,8,9,9,10,10,11,11,11-Nonadecafluoroundecyl acrylate, 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,12-Heneicosafluorododecyl acrylate, 2-methyl-3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,12-Heneicosafluorododecyl acrylate, 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13,13-tricosafluorotridecyl acrylate, 2-methyl-3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13,13-tricosafluorotridecyl acrylate, 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13,14,14,14-pentacosafluorotetradecyl acrylate, and 2-methyl The copolymer may be polymerized from one or more monomers selected from the group consisting of 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13,14,14,14-pentacosafluorotetradecyl acrylate, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl methacrylate, and diethylaminoethyl acrylate.

[0100] The initiator may be, for example, a peroxide, and may specifically include, but is not limited to, at least one selected from the group consisting of di-t-butyl peroxide, t-butyl peroxybenzoate, benzoyl peroxide, methyl ethyl ketone peroxide, lauryl peroxide, and benzophenone.

[0101] In this case, the flow rate of the monomer supplied to the reactor may be 0.1 sccm to 10 sccm. Specifically, the flow rate of the monomer may be 0.1 sccm or more, or 0.2 sccm or more and 10 sccm or less, 5 sccm or less, or 4 sccm or less.

[0102] The flow rate of the initiator supplied to the reactor may be 0.1 sccm to 5 sccm. Specifically, the flow rate of the initiator may be 0.1 sccm or more and 5 sccm or less, 3 sccm or less, or 2 sccm or less.

[0103] The initiator can be activated by a predetermined heat treatment, and the heat treatment can be carried out at a temperature of 135 to 350°C, preferably 140 to 340°C. Meeting the temperature conditions can be advantageous from the viewpoint of preventing changes in the properties of the reactants.

[0104] In order to increase the rate of adsorption of the monomer and free radicals, it is preferable to maintain the surface temperature of the silicon-inorganic layer composite low. Specifically, the surface temperature of the silicon-inorganic layer composite is preferably in the range of 10 to 50°C, and more preferably 13 to 45°C, but is not particularly limited to this range.

[0105] Stage (4)

[0106] In the above step (4), the inorganic layer is at least partially removed from the silicon-inorganic layer-carbon composite to produce a silicon-carbon composite with a yolk-shell structure.

[0107] In this case, step (4) can be performed by etching the inorganic layer from the silicon-inorganic layer-carbon composite, by immersing the unetched silicon-inorganic layer-carbon composite in a basic or acidic aqueous solution and treating it at room temperature to 80°C for 1 minute to 1 hour.

[0108] In a specific example of the present invention, the base may include at least one selected from the group consisting of sodium hydroxide (NaOH), potassium hydroxide (KOH), and calcium hydroxide (Ca(OH)2), but is not particularly limited thereto. Here, the concentration of the aqueous base solution may be 0.1 to 3 M, but is not particularly limited to this range.

[0109] In a specific example of the present invention, the acid may include at least one selected from the group consisting of hydrofluoric acid (HF), hydrochloric acid, sulfuric acid, and nitric acid, but is not particularly limited thereto. Here, the concentration of the acid solution may be 0.1 to 2 M, but is not particularly limited to this range.

[0110] By etching the silicon-inorganic layer-carbon composite as described above, at least a portion, preferably 10 to 100 wt %, and more preferably 50 to 100 wt %, of the inorganic layer is removed, thereby appropriately forming pores between the silicon particles and the carbon thin film. Residues of the inorganic layer remaining after removal in step (4) may be present between the silicon particles and the carbon thin film in the yolk-shell structured silicon-carbon composite as the final product according to an embodiment of the present invention.

[0111] In step (4), when pores are formed between the silicon particles and the carbon thin film, the degree of pore formation and the degree of inorganic layer remaining can be appropriately controlled by changing the size of the silicon particles, the etching time and temperature using the aqueous base solution, etc. When the silicon-carbon composite having a yolk-shell structure obtained in this manner is used as an anode active material, the electrical conductivity of the anode active material can be improved without changing the structure.

[0112] Additional Stages

[0113] In the method for manufacturing a yoke-shell structured silicon-carbon composite according to an embodiment of the present invention, the obtained yoke-shell structured silicon-carbon composite may be crushed or pulverized and classified. Classification can make the particle size distribution of the composite uniform. Here, classification can be performed by dry classification, wet classification, classification using a sieve, or the like.

[0114] negative electrode active material

[0115] According to yet another embodiment of the present invention, there is provided an anode active material comprising the silicon-carbon composite having a yolk-shell structure.

[0116] The negative electrode active material according to an embodiment of the present invention may further include a carbon-based negative electrode material, specifically, a graphite-based negative electrode material, in addition to the yoke-shell silicon-carbon composite. For example, the negative electrode active material may be obtained by mixing the yoke-shell silicon-carbon composite according to an embodiment of the present invention with a carbon-based negative electrode material, for example, a graphite-based negative electrode material.

[0117] Here, the carbon-based negative electrode material may include, for example, at least one selected from the group consisting of natural graphite, artificial graphite, soft carbon, hard carbon, mesocarbon, carbon fiber, carbon nanotube, pyrolytic carbons, cokes, fired organic polymer compounds, and carbon black, but is not particularly limited to these.

[0118] The content of the carbonaceous negative electrode material in the negative electrode active material according to an embodiment of the present invention may be 2 to 80 wt %, preferably 5 to 70 wt %, more preferably 30 to 70 wt %, based on the total weight of the negative electrode active material.

[0119] The negative electrode active material according to an embodiment of the present invention can be effectively used to manufacture a secondary battery, specifically, a negative electrode of a lithium secondary battery and a negative electrode of an all-solid-state battery.

[0120] all solid state battery

[0121] According to yet another embodiment of the present invention, there is provided an all-solid-state battery including a solid electrolyte interphase (SEI) film including the silicon-carbon composite with a yolk-shell structure.

[0122] The all-solid-state battery may be an all-solid-state battery including a positive electrode, a negative electrode, and a solid electrolyte between the positive electrode and the negative electrode, and the negative electrode may include a negative electrode active material layer, and may include an SEI (Solid Electrolyte Interphase) film including the silicon-carbon composite with the yolk-shell structure on at least a portion of the negative electrode active material particles of the negative electrode active material layer.

[0123] The negative electrode active material particles may be a carbon-based negative electrode material. In this case, the negative electrode active material is the same as that described above with respect to the negative electrode active material, and therefore, the related description will be omitted.

[0124] In addition, in addition to the negative electrode active material particles and the SEI film of the all-solid-state battery, the configuration of the negative electrode, the configuration of the positive electrode, the configuration of the solid electrolyte, and the like can be any known configuration of an all-solid-state battery, and therefore, the present invention is not particularly limited thereto. [Example]

[0125] Example

[0126] The present invention will be described in more detail below with reference to examples. The following examples are merely illustrative of the present invention and are not intended to limit the scope of the present invention.

[0127] Example 1

[0128] Manufacturing of silicon-inorganic layer composite (intermediate)

[0129] A silicon-inorganic layer composite was produced using a conventional ALD reactor. Five grams of silicon powder with average particle sizes of 20 μm and 2 μm were evenly spread on a circular silicon wafer in the reactor. An inorganic layer was formed on the surface of the silicon particles under the following conditions to produce a silicon-inorganic layer composite. The materials and process conditions used in this Example 1 are as follows:

[0130] -Silicon particles: average particle size 20μm and 2μm (REC Silicon)

[0131] -First precursor: Trimethylaluminum (EG Chem)

[0132] - Second precursor: HO (Millpore, Milli-Q)

[0133] - Precursor carrier gas: N2, 300sccm

[0134] - Average supply flow rate and time of first precursor: 2 seconds

[0135] - Purge gas and time after delivery of first precursor: N2, 60 seconds

[0136] -Average feed flow rate and time of second precursor: 2 seconds

[0137] - Purge gas and time after delivery of second precursor: N2, 60 seconds

[0138] Pressure in reactor chamber: 1.2 Torr

[0139] -Surface temperature of reactor mounting part (silicon wafer): 150℃

[0140] -Number of cycles: 100

[0141] -Formed inorganic layer: Al2O3

[0142] Test Example 1-1

[0143] (1)X-ray photoelectron spectroscopy

[0144] The silicon particles before and after the inorganic layer was formed were analyzed for elements on the particle surface using X-ray photoelectron spectroscopy (Multilab 2000, Thermo). The results are shown in Table 1.

[0145] [Table 1]

[0146] As is clear from Table 1, before the inorganic layer was formed, aluminum was present on the surface of the silicon particles. However, after forming an inorganic layer on the silicon particles by the manufacturing method of the present invention, a considerable amount of aluminum was measured. Therefore, it can be seen that a silicon-inorganic layer composite in which an inorganic layer of aluminum oxide is formed on the surface of silicon particles was manufactured by the manufacturing method of the present invention.

[0147] (2) Transmission electron microscope-energy dispersive spectrometer

[0148] Silicon particles with an average particle size of 20 μm on which the Al2O3 inorganic layer was formed were observed using a transmission electron microscope (TEM) and energy dispersive spectrometer (EDS) (Tecnai G2 F30 S-Twin, FEI company). The TEM analysis results are shown in Figure 1, and the EDS analysis results are shown in Figure 2 and Table 2.

[0149] [Table 2]

[0150] The TEM images of Figures 1a and 1b show that the silicon-inorganic layer composite obtained in Example 1 formed an inorganic layer with a uniform thickness of approximately 5 nm without problems such as severe aggregation or particle crushing, and essentially maintained its original shape. Figures 2a, 2b, and Table 2 show the results of EDS analysis of the silicon-inorganic layer composite. As is clear from Figures 2a, 2b, and Table 2, aluminum, a component of the inorganic layer, was observed on the silicon-inorganic layer composite. Therefore, it can be qualitatively confirmed that a silicon-inorganic layer composite in which an inorganic layer was formed on the surface of silicon particles was produced using the manufacturing method of the present invention.

[0151] Fabrication of silicon-inorganic layer-carbon composite

[0152] Five grams of the silicon-inorganic layer composite (intermediate) prepared above was evenly spread on a circular silicon wafer in a reactor. Vaporized monomer and initiator were supplied into the reactor chamber through an inlet to form a thin polymer film (pDVB) on the surface of the silicon-inorganic layer composite, producing a silicon-inorganic layer-polymer composite. The materials and process conditions used in this example are as follows:

[0153] Monomer: Divinylbenzene (Aldrich, 80%)

[0154] Initiator: di-t-butyl peroxide (Aldrich, 98%)

[0155] -Average initiator feed flow rate: 0.26 sccm

[0156] -Average monomer feed flow rate: 0.425sccm

[0157] - Filament temperature: 140℃

[0158] -Pressure in reactor chamber: 450mTorr

[0159] -Surface temperature of reactor mounting part (silicon wafer): 23℃

[0160] The produced silicon-inorganic layer-polymer composite was carbonized at 700° C. for 30 minutes to carbonize the polymer thin film, thereby producing a silicon-inorganic layer-carbon composite.

[0161] Test Example 1-2

[0162] (1) Transmission electron microscope-energy dispersive spectrometer

[0163] The silicon-inorganic layer-carbon composite was observed using a transmission electron microscope (TEM) and energy dispersive spectrometer (EDS) (Tecnai G2 F30 S-Twin, FEI Company). The TEM analysis results are shown in Figure 3, and the EDS analysis results are shown in Figure 4.

[0164] As a result, the TEM image of Figure 3 confirms that the silicon-inorganic layer-carbon composite obtained in the example has a uniform thin film of about 20 nm formed on the silicon particles, and the EDS analysis results of Figures 4a, 4b, and 4c confirm that aluminum and carbon are observed in uniform regions in the silicon-inorganic layer-carbon composite produced. Therefore, it can be qualitatively confirmed that a silicon-inorganic layer-carbon composite in which an inorganic layer and a carbon thin film are formed on the surface of silicon particles was produced by the production method of the present invention.

[0165] Fabrication of yolk-shell structured silicon-carbon composites

[0166] The silicon-inorganic layer-carbon composite (intermediate) prepared above was immersed in HPO (85%, Aldrich) at 50°C for 100 seconds to etch the inorganic layer, producing a silicon-carbon composite with a yolk-shell structure.

[0167] Test Example 1-3

[0168] Transmission electron microscope-energy dispersive spectroscopy

[0169] The fabricated silicon-carbon composite with a yolk-shell structure was observed using a transmission electron microscope (TEM) and energy dispersive spectrometer (EDS) (Tecnai G2 F30 S-Twin, FEI Company). The TEM analysis results are shown in Figure 5, and the EDS analysis results are shown in Figures 6 and 7. As a result, it was confirmed from the TEM photograph of FIG. 5 that the silicon-carbon composite was formed with a yolk-shell structure having uniform pores. From the results of FIGS. 6 and 7, it was confirmed that a thin carbon film was formed on the silicon particles. In particular, in FIG. 7, there was a region (near 110 nm) where no atoms were detected between the regions where carbon atoms and silicon atoms were detected, confirming the formation of predetermined pores.

[0170] <Example 2>

[0171] Manufacturing of silicon-inorganic layer composite (intermediate)

[0172] The silicon-inorganic layer composite was manufactured in the same manner as in Example 1, except for the following changes.

[0173] -Silicon particles: average particle size 20μm (REC Silicon)

[0174] -First precursor: Titanium(IV) isopropoxide (TTIP)

[0175] - Second precursor: HO (Millpore, Milli-Q)

[0176] - Precursor carrier gas: N2, 300sccm

[0177] - Average supply flow rate and time of first precursor: 15 seconds

[0178] Purge gas and time after first precursor delivery: N2, 600 seconds

[0179] -Average feed flow rate and time of second precursor: 15 seconds

[0180] - Purge gas and time after delivery of second precursor: N2, 600 seconds

[0181] Pressure in reactor chamber: 1.2 Torr

[0182] -Surface temperature of reactor mounting part (silicon wafer): 150℃

[0183] -Number of cycles: 100

[0184] -Formed inorganic layer: TiO2

[0185] Test Example 2

[0186] (1) Transmission electron microscope analysis

[0187] The silicon particles with the TiO2 inorganic layer formed thereon were analyzed using a transmission electron microscope (TEM). The TEM analysis results are shown in Figure 8.

[0188] The TEM photographs in Figures 8a and 8b show that the silicon-inorganic layer composite obtained in Example 2 formed an inorganic layer with a uniform thickness of about 6 nm without any problems such as severe aggregation or particle crushing, and that it essentially maintained its original shape.

Claims

1. (1) providing silicon particles into a reactor; (2) forming an inorganic layer on the silicon particles using atomic layer deposition (ALD) to prepare a silicon-inorganic layer composite; (3) forming a carbon thin film on the silicon-inorganic layer composite to obtain a silicon-inorganic layer-carbon composite; (4) removing at least a portion of the inorganic layer from the silicon-inorganic layer-carbon composite to produce a silicon-carbon composite having a yoke-shell structure.

2. The step (2) is (2-1) supplying a first precursor to a reactor to form a first precursor multi-layer on the silicon particles, in which at least a portion of the first precursor is adsorbed; (2-2) purging the inside of the reactor to remove unadsorbed first precursor from the first precursor multilayer, thereby forming a first precursor monolayer; (2-3) supplying a second precursor to the reactor and reacting the first precursor monolayer with at least a portion of the second precursor to form a composite layer; and (2-4) purging the inside of the reactor to remove unreacted second precursor from the composite layer and forming an inorganic layer; and (2-5) performing the above cycle one or more times.

3. 3. The method for producing a silicon-carbon composite having a yoke-shell structure according to claim 2, wherein the time for supplying the first precursor and the time for supplying the second precursor are each independently 1 to 600 seconds.

4. 3. The method for producing a silicon-carbon composite having a yoke-shell structure according to claim 2, wherein the first precursor comprises at least one selected from the group consisting of trimethylaluminum, diethylzinc, zinc acetate, tetrakis(dimethylamino)tin(IV), butoxytris(ethylmethylamido)hafnium, titanium isopropoxide, and diisopropylaminosilane.

5. The second precursor is H ２ O, O ３ , H ２ O plasma, O ３ Plasma and O ２ The method for producing a silicon-carbon composite having a yoke-shell structure according to claim 2, wherein the method comprises one or more selected from the group consisting of plasma.

6. The gas used for purging in any one or more of the steps (2-2) and (2-4) is nitrogen (N ２ 3. The method for producing a silicon-carbon composite having a yoke-shell structure according to claim 2, wherein the gas contains argon (Ar) or argon (C).

7. The method for producing a silicon-carbon composite having a yoke-shell structure according to claim 2, wherein the cycle is performed 1 to 300 times.

8. 3. The method for producing a silicon-carbon composite having a yoke-shell structure according to claim 2, wherein the temperature of the silicon particles is maintained at 90 to 400° C. during the cycle.

9. 2. The method for manufacturing a silicon-carbon composite having a yoke-shell structure according to claim 1, wherein step (4) is performed by etching the inorganic layer from the silicon-inorganic layer-carbon composite.

10. Silicon particles; a carbon thin film formed on the silicon particles with a predetermined pore space; and

11. The silicon particles have an average particle size of 10 nm to 50 μm, 11. The silicon-carbon composite of claim 10, wherein the carbon thin film has an average thickness of 1 nm to 1 μm.

12. 11. The silicon-carbon composite of claim 10, wherein the silicon-carbon composite of said yoke-shell structure has a porosity of 10 to 80%.

13. A negative electrode active material comprising the silicon-carbon composite with a yolk-shell structure according to any one of claims 10 to 12.

14. An all-solid-state battery comprising: an SEI (Solid Electrolyte Interphase) film comprising the silicon-carbon composite with a yolk-shell structure according to any one of claims 10 to 12.

Images