KR101927414B1 - Electro active material for secondary battery, conductive composition for secondary battery, cathode material, cathode structure and secondary battery comprising the same, and fabricating methods thereof - Google Patents

Abstract

The present invention relates to a negative electrode active material for a secondary battery, a conductive composition for a secondary battery, a negative electrode material containing the same, a negative electrode structure and a secondary battery comprising the same, and a method of manufacturing the same. The present invention relates to silicon particles; And an amorphous surface layer formed on the surface of the silicon particles. According to the present invention, since the negative electrode structure is formed of a composite of silicon particles and a carbon or lithium ion solid electrolyte, and since the oxygen content of the silicon particles is low and aggregation of the silicon particles is suppressed, A power storage device such as a lithium secondary battery can have a high energy density, a high output density, and a long charge / discharge cycle life performance.

Description

TECHNICAL FIELD [0001] The present invention relates to a negative electrode active material for a secondary battery, a conductive composition for a secondary battery, a negative electrode material containing the same, a negative electrode structure and a secondary battery containing the same, and a method for manufacturing the same. secondary battery comprising the same, and fabricating methods thereof}

The present invention relates to a negative electrode active material for a secondary battery, a conductive composition for a secondary battery, a negative electrode material containing the same, a negative electrode structure and a secondary battery comprising the same, and a method of manufacturing the same. More particularly, Carbon composite, a conductive composition for a secondary battery comprising carbon, a negative electrode material containing the same, a negative electrode structure including the negative electrode structure and a secondary battery, and a method of manufacturing the same.

Recently, it is pointed out that the global climate change may be caused by the greenhouse effect, which is mainly caused by the increase of CO ₂ gas in the atmosphere. It is pointed out that air pollution such as CO ₂ , NO _x , and hydrocarbons emitted from automobiles that are used as a means of transportation has a health effect. From the perspective of rising energy such as crude oil and environmental conservation, we have recently managed the electric power network in hybrid cars, electric vehicles, and power generation facilities, which combine an electric motor and an engine, There is great expectation for the Smart Grid, an optimizing system.

In the field of information and communications, information terminals such as smart phones are rapidly penetrating into the society because of the easy exchange of information and transmission. In this circumstance, it is expected to develop capacitive devices such as capacitors or secondary batteries with high power density, high energy density and long lifetime in order to increase the performance of smart phones, hybrid cars, electric vehicles, .

Among the above-mentioned power storage devices, lithium-ion secondary batteries which use carbon such as graphite as the negative electrode and compounds of lithium and transition metal as the positive electrode among the products that are currently commercialized have the highest energy density. However, in this "lithium ion battery ", the negative electrode is composed of a carbon material, so that theoretically it is possible to intercalate only up to 1/6 lithium atoms per carbon atom. For this reason, it is difficult to increase the capacity to a new capacity, and a new cathode material for high capacity is required. In addition, the above-mentioned "lithium ion battery" is expected to be a power source for a hybrid car or an electric vehicle because of its high energy density. However, the problem that the internal resistance of the battery is large during rapid discharge, There is also. Therefore, development of a power storage device having high output density and high energy density is required.

To meet this demand, tin, silicon and alloys capable of storing and discharging more lithium ions than graphite are being studied. Although tin or silicon can store more lithium ions electrochemically, it causes a volume expansion of about 4 times, resulting in undifferentiation when the battery is repeatedly expanded and contracted by charging and discharging, thereby deteriorating the performance of the battery.

In order to prevent the above undifferentiation, attempts have been made to extend the life of the negative electrode of a battery by pulverizing silicon or a silicon alloy into fine particles.

There is a method of pulverizing mechanically by a method of making a silicon material into fine particles, and a wet bead mill which is a kind of media mill is a device capable of pulverizing into a submicron particle size. The pulverization in the wet bead mill is carried out by (1) lowering the oxygen content of the raw material silicon powder, (2) inhibiting oxidation upon pulverization, (3) inhibiting re-agglomeration of pulverized particles, It is a problem to suppress agglomeration of particles upon drying after drying.

Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4 and Patent Document 5 disclose a method of using a bead mill for pulverizing silicon or a silicon alloy.

Patent Document 1 discloses that (i) Si particles having an average particle diameter (D ₅₀ ) of 0.05 to 5 μm are prepared by wet grinding using a bead mill, (ii) solvents used are toluene, xylene, Mesylenes, methylnaphthalenes, creosote oils and the like are used. (Iii) It is disclosed that the pulverized Si particles and the carbon material or their precursors are further subjected to a wet mixing heat treatment. However, when mixed with the carbon material or the precursor thereof before the heat treatment, the Si particles are oxidized because the oxygen source can not be completely removed, and the Si particles in the range of 0.05 to 5 탆 coagulate in the heat treatment process, There are problems such as points.

In Patent Document 2, a bead mill is disclosed as a wet grinding apparatus for forming a mixture of a Si powder and a transition metal powder by a mechanical alloying method and pulverizing the powder into particles having an average particle diameter (D ₅₀ ) of 0.50 to 20 μm. As the dispersion medium used for the wet pulverization, it is preferable to use a nonprotonic solvent such as nucleic acid, acetone, n-butyl acetate and the like, and water, methyl alcohol, ethyl alcohol, 1-propyl alcohol, 2-propyl alcohol, And the like can also be used. However, a method of pulverizing into particles having an average particle diameter (D ₅₀ ) of less than 0.5 탆 is not disclosed.

Patent Documents 3, 4, and 5 disclose that Si-Sn-Cu alloy powder is pulverized to an average particle diameter of 0.28 mu m using isopropyl alcohol as a medium and bead milling using beads zirconia beads. However, due to the undifferentiation, there is a problem that the contact resistance between the particles is increased and the charging / discharging efficiency is lowered, and the characteristics expected by using the fine particles are not expressed at present. In addition, attempts have been made to increase conductivity by increasing the conductivity even at the negative electrode and adding a small amount of carbon nanotubes and carbon nanofibers in an attempt to increase the electrochemical reaction efficiency. However, carbon nanotubes and carbon nanofibers aggregate efficiently, And it is difficult to increase the content in the negative electrode.

1. Japanese Unexamined Patent Application Publication No. 2008-112710 2. International Patent Publication No. WO2006 / 129415 3. US Patent No. 7141187 4. U.S. Patent No. 7316792 5. US Patent No. 7803290

The present invention provides a method of manufacturing a silicon material capable of storing and releasing a large amount of lithium electrochemically as a negative electrode active material for a storage device having a high energy density.

Particularly, the present invention relates to a method for producing an electrode structure for a negative electrode of a power storage device such as a lithium secondary battery (secondary battery using a redox reaction of lithium ions) having an active material layer composed of a composite of silicon particles and carbon, To provide a method for producing a slurry in which silicon particles for dispersing silicon particles for producing an electrode layer-forming slurry in which the formation of a film is inhibited and aggregation of silicon particles is suppressed. The power storage device herein includes a capacitor, a secondary battery, a device in which a capacitor and a secondary battery are combined, and a device provided with a power generation function.

A first embodiment of the present invention relates to a method for producing a slurry containing silicon particles, which comprises silicon particles and an amorphous surface layer formed on the surface of silicon particles, by dry grinding and wet grinding, The negative electrode active material for a secondary battery according to the present invention may be prepared by mixing and dispersing.

The second embodiment of the present invention includes a silicon-carbon composite including silicon particles, graphene structure carbon particles, fibrous carbon and carbon black, wherein the silicon particles are graphene structure carbon particles, fibrous carbon, and carbon black And a negative electrode active material for a secondary battery.

A third embodiment of the present invention is a method for producing a slurry, comprising: a dry milling step of dry milling a starting material under an inert atmosphere to prepare a dry milled material; and a wet milling and dispersing step of wet milling and dispersing the dry milled material to produce a slurry May be a method for producing an active material.

The fourth embodiment of the present invention may be a conductive composition for a secondary battery in which carbon is dispersed in an aprotic solvent free of proton donor.

A fifth embodiment of the present invention may be a method for producing a conductive composition for a secondary battery, which comprises a step of mixing an additive into an aprotic solvent to prepare a solution, and a dispersion step of dispersing a carbon material in the solution. The dispersion process can be performed by a bead mill.

The sixth embodiment of the present invention includes a solvent, a negative electrode active material, a conductive composition of the third embodiment, and a binder, and the negative electrode active material is selected from the group consisting of the negative active material of the first embodiment and the negative active material of the first embodiment Or more of the negative electrode material for a secondary battery.

According to a seventh aspect of the present invention, there is provided a method of manufacturing a negative active material, comprising the steps of: preparing a negative electrode active material according to the third embodiment; Comprising the steps of: providing a conductive composition according to the fifth embodiment; and mixing the negative active material and the conductive composition together with a binder in a solvent to prepare a slurry, wherein the negative active material comprises the negative active material of claim 1 and the negative active material of claim 7 A negative electrode active material, a negative electrode active material, and a negative electrode active material.

The eighth embodiment of the present invention may include a negative electrode material layer formed on a conductive metal or a conductive metal and the negative electrode material layer may be a negative electrode structure including the negative electrode material of the sixth embodiment, And the like.

A ninth embodiment of the present invention is a method for manufacturing a negative electrode structure, comprising the steps of: providing a negative electrode material according to the seventh embodiment; applying the prepared negative electrode material onto a conductive metal; and heat treating the applied negative electrode material Lt; / RTI >

A tenth embodiment of the present invention is a cathode structure according to the eighth embodiment; Separation membrane; Anode structure; And a secondary battery including a current collector.

An eleventh embodiment of the present invention may be a method of manufacturing a secondary battery including the step of providing the negative electrode structure according to the ninth embodiment, and the step of laminating the negative electrode structure, the separation membrane and the positive electrode structure provided.

According to the present invention, the negative electrode active material prepared by using the slurry in which the silicon particles are dispersed is formed of a composite of silicon particles and carbon or lithium ion solid electrolyte, and since the oxygen content of the silicon particles is low, aggregation of the silicon particles is suppressed By using the negative electrode active material in the negative electrode, a battery device such as a lithium secondary battery can have a high energy density, a high output density, and a longer charge / discharge cycle life performance.

In addition, the method for producing the negative electrode active material according to the present invention is excellent in mass productivity and can be produced at low cost.

Further, by adding the conductive composition according to the present invention to the negative electrode during the preparation of the negative electrode, the electronic conductivity of the negative electrode of the secondary battery can be improved, so that the performance of the battery can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view (a), (b), SEM photograph (c) and TEM photograph (d) of a silicon particle contained in an anode active material according to an embodiment of the present invention.
2 is a schematic view of a silicon-carbon composite included in an anode active material according to an embodiment of the present invention.
3 is a process diagram showing a process for producing the negative electrode active material according to one embodiment of the present invention.
4 is a schematic diagram showing a device system used for manufacturing the negative electrode active material according to one embodiment of the present invention.
5 is a schematic view of a conductive composition for a secondary battery according to an embodiment of the present invention.
6 is a cross-sectional view of a cathode structure manufactured according to an embodiment of the present invention.
7 is a process diagram showing a process of manufacturing a negative electrode structure manufactured according to an embodiment of the present invention.
8 is a cross-sectional schematic diagram of a power storage device manufactured according to an embodiment of the present invention.
9 to 11 are schematic views of a coin type cell, a laminate cell and a cylindrical cell, which are an example of a power storage device manufactured according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. Furthermore, embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art. Accordingly, the shapes and sizes of the elements in the drawings may be exaggerated for clarity of description, and the elements denoted by the same reference numerals in the drawings are the same elements.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view (a), (b), (c) and (c) of a silicon particle included in an anode active material according to an embodiment of the present invention. 2 is a schematic view of a silicon-carbon composite included in an anode active material according to an embodiment of the present invention. 3 is a process diagram showing a process for producing the negative electrode active material according to one embodiment of the present invention. 4 is a schematic view showing a device system used in a negative electrode active material manufacturing process according to an embodiment of the present invention. 5 is a schematic view of a conductive composition for a secondary battery according to an embodiment of the present invention. 6 is a cross-sectional view of a cathode structure manufactured according to an embodiment of the present invention. 7 is a process diagram showing a process of manufacturing a negative electrode structure manufactured according to an embodiment of the present invention. 8 is a cross-sectional schematic diagram of a power storage device manufactured according to an embodiment of the present invention. 9 to 11 are schematic views of a coin type cell, a laminate cell and a cylindrical cell, which are an example of a power storage device manufactured according to an embodiment of the present invention.

Referring to FIG. 1, the first embodiment of the present invention may be a negative electrode active material including silicon particles 100 and an amorphous surface layer 101 formed on the surface of the silicon particles 100.

The silicon particles 100 may be powders obtained by pulverizing the silicon element bulk material, and the average particle diameter of the silicon particles 100 may be 5 to 200 nm. When the average particle diameter of the silicon particles 100 is less than 5 nm, the amount of the oxidized surface area is increased and the performance of the negative electrode active material may be lower than the designed value. When the particle size is larger than 200 nm, And may be continuously generated, leading to deterioration of lifetime characteristics.

The amorphous surface layer 101 may be formed on the surface of the silicon particle 100 and the amorphous surface layer 101 may include amorphous carbon.

Since the amorphous surface layer 101 formed on the surface of the silicon particle 100 blocks the direct contact with the outside due to the silicon particle 100, surface oxidation of the silicon particle 100 can be suppressed. On the other hand, since the surface layer 101 contains carbon, it can be utilized as a carbon precursor for carbonization or graphitization which can contribute to the electron conductivity of the cathode. As a result, the oxidation of the surface of the silicon particles 100 is prevented, and the surface layer 101 containing carbon is formed thereon, whereby the electron conductivity of the cathode can be improved through carbonization or graphitization of the carbon precursor through firing.

The thickness of the amorphous surface layer 101 may be 1 to 10 nm. When the thickness of the amorphous surface layer 101 is less than 1 nm, the surface layer 101 is too thin, so it is insufficient for preventing the oxidation of the silicon particles 100. When the thickness is larger than 10 nm, the insertion of lithium ions into the active material is inhibited can do.

The primary particles may have a long diameter (a)> a short diameter (b)> a thickness (d), a long diameter of 50 to 300 nm, a short diameter of 30 to 200 nm, and a thickness of 10 to 50 nm.

In addition, FIG. 1 shows a scanning electron microscope (c) and a transmission electron microscope (d) of silicon particles coated with amorphous carbon. 1 (c) is a SEM photograph of silicon particles milled with zirconia beads having a diameter of 0.1 mm. 1 (d) is a TEM photograph of silicon particles milled with zirconia beads having a diameter of 0.2 mm, and the lower two photographs are TEM photographs of silicon particles milled with zirconia beads having a diameter of 0.03 mm . According to the photograph, it can be confirmed that the amorphous carbon layer 101 is formed on the surface of the silicon particle 100.

2 (a) and 2 (b), the second embodiment of the present invention is a method of manufacturing a carbon nanotube composite particle including silicon particles 111, graphene structure carbon particles 112, fibrous carbon 113, and carbon black 114 Carbon composite material 110 including at least one selected from the group consisting of graphene-type carbon particles 112, fibrous carbon 113, and carbon black 114. The silicon- And a negative electrode active material in contact with at least one selected from the group consisting of

It can be understood that the present embodiment is a composite of carbon in various forms to silicon particles 111, which is a main material of the negative electrode active material. That is, the silicon particles 111 are formed by combining various types of carbon, that is, carbon particles 112 of a graphene structure, a fibrous carbon 113, and a salt columnar carbon black 114. By compounding various types of carbon into silicon particles, the complexing effect can be maximized.

Referring to FIG. 2 (c), the silicon particles 100 may be powders obtained by pulverizing silicon, and the average particle size of the silicon particles 100 may be 5 to 200 nm. The amorphous surface layer 101 may be formed on the surface of the silicon particle 100. The amorphous surface layer 101 may include an amorphous carbon layer and the amorphous surface layer 101 may have a thickness of 1 to 10 nm.

The matters relating to the silicon particles 100 and the surface layer 101 thereof are the same as those described in the first embodiment.

The graphene structure carbon particles 112 may mean particles in which the carbon particles have a graphene structure. The graphene structure carbon particles 112 may include at least one selected from the group consisting of graphene and graphite. The average particle size of the graphene structure carbon particles 112 may be 300 nm to 10 mu m.

The average diameter of the fibrous carbon 113 may be 10 to 200 nm. The fibrous carbon particles 113 may include at least one selected from the group consisting of carbon nanofibers and carbon nanotubes.

The carbon black 114 has primary particles of a structure connected to the salt pillar phase, wherein the primary particles have an average particle diameter of 10 to 80 nm and the primary particles have a particle size of 2 to 5 nm.

The silicon-carbon composite 110 may have an average particle diameter of 5 to 20 mu m.

The silicon particles 111 may be in contact with at least one member selected from the group consisting of graphene structure carbon particles 112, fibrous carbon 113, and carbon black 114. Carbon such as graphene structure carbon particles 112, fibrous carbon 113 and carbon black 114 have electron conductivity, so that at least one of them is in contact with the silicon particles 111, So that the performance of the battery can be improved.

The silicon-carbon composite 110 may further include lithium ion solid electrolyte particles in addition to the various carbon atoms, and the silicon particles may be in contact with the lithium ion solid electrolyte particles. In this case, transition of lithium ions to the surface of the silicon particles may occur easily during operation of the electrical storage device.

The lithium ion inorganic solid electrolyte is a sulfur-based amorphous electrolyte represented by Li ₂ SP ₂ O ₅ , a sulfur-containing glass, lithium nitride (Li ₃ N), Li _{1 + x + y} Al _x Ti _{2 - x} Si _y P _{3 - y} O _{12 (x = 0.3, y =} 0.2) NASICON crystal structure material typified by, Li ₇ La ₃ Zr ₂ O material of garnet structure represented by _12, and germanium as represented by Li ₁₀ GeP ₂ S ₁₂ - in-sulfur compound . ≪ / RTI >

3 and 4, a third embodiment of the present invention is a method for producing a slurry by dry grinding a dry grinding process for dry grinding a starting material under an inert atmosphere, And a wet grinding and dispersing step. At least one of a dry milling process, a wet milling process and a dispersion process can be carried out by a bead mill process. It is preferable to perform all the processes by the bead mill process for the consistency of the process.

First, the starting material can be dry-pulverized under an inert atmosphere to prepare a pulverized product (dry pulverization step, first step). The starting material is not particularly limited as long as it can be used as a negative electrode material. The starting material may comprise silicon powder, and the starting material may include other materials besides silicon. Examples of additives include coal tar pitch, graphite as an example of the additive, but not limited thereto. FIG. 3 (a) shows a case where graphite as an additive material is mixed with silicon as a starting material. 3 (b) shows a case where only silicon powder is used as a starting material, and graphite as an additive material is added before wet pulverization after dry pulverization.

The silicon powder as a starting material may have an average particle diameter of several mm or less. If it is larger than this, the time required for pulverization may be prolonged, and the productivity may be lowered. The average particle diameter of the silicon particles obtained in the first step is preferably not more than several tens of micrometers, more preferably in the range of 1 to 10 micrometers. In this process, a beads mill is used as a dry grinding apparatus, but other media mills such as a jet mill and a vibrating mill may be used.

 The starting material can be dry milled under an inert atmosphere to prevent oxidation of the starting material. In the dry grinding process, high-temperature heat may be generated. Therefore, when the particles to be ground are in contact with oxygen in air, they can be easily oxidized. By performing dry grinding in an inert atmosphere, Oxidation of the material can be prevented. The inert atmosphere may be, but not limited to, a nitrogen gas atmosphere or an argon gas atmosphere.

When silicon is used as a starting material, the surface of the silicon particles can be prevented from being oxidized. When the surface of the silicon particles is oxidized, since the oxide layer has electrical insulation, the electron conductivity of the anode manufactured using the oxide layer is lowered, which may deteriorate the performance of the cathode and the power storage device.

Next, the dry pulverized pulverized material is mixed with a solvent in which the additive is dissolved, and the pulverized pulverized material is pulverized and dispersed with a wet-type bead mill to prepare a slurry (wet pulverization and dispersion step, second and third steps). If the primary particles of the starting material is less than 1 mu m, the dry milling step (first step) may be omitted and the wet milling step (second step) may be carried out. In FIG. 3, the wet grinding step is performed in two steps of the second step and the third step. However, the step may be performed in three steps or more. This is because it is preferable to gradually reduce the size of the beads and to crush the silicon particles in a multistage manner in two or more steps to crush the silicon particles to a desired size. More specifically, the silicon pulverized in the dry milling step (first step) is mixed with a solution in which the coal tar pitch, which is an additive, is dissolved in an aprotic solvent, and is pulverized for a predetermined time using the first wet bead mill in the second step Then, in the third step, the size of the beads is reduced and further pulverized with a wet bead mill to obtain a slurry in which silicon particles are dispersed.

It is necessary to transport the dry pulverized starting material in a wet pulverizing process in a state in which it is not in contact with oxygen. This is to prevent the surface of dry-milled starting material from being oxidized under an inert atmosphere.

By appropriately selecting a solvent which is a medium used in wet grinding, surface oxidation of silicon during pulverization can be suppressed and coagulation can also be suppressed. Also, it is possible to suppress the re-agglomeration of the ground silicon particles by selecting an additive and an additive material which are easily dispersed in a solvent and remain at the time of firing but do not adversely affect the performance of the electrical storage device. As the solvent used in the second and third steps, there can be used a solvent (protonic solvent) having no proton donor and a solvent (protonic solvent) having proton donor, but when an aprotic solvent is used, It is more preferable to use an aprotic solvent because the silicon surface is hardly oxidized.

The aprotic solvent may include at least one selected from the group consisting of cyclic hydrocarbons, aromatic compounds, ketones, ethers, amides, and nitrile solvents, and cyclic hydrocarbons, aromatic compounds, and ketone solvents are most preferred . The most preferable specific examples of the aprotic solvent include N-methyl-2-pyrrolidone,? -Butyrolactone, N, N-dimethylacetamide, 1,3-dimethyl-2-imidazolidine, do. The additive is not particularly limited as long as it is easily soluble or dispersible in a medium used for wet grinding and crushing and is easy to be carbonized in the firing under an inert atmosphere. In Fig. 3, the coal tar pitch as an additive is added before the second step, but it may be added before the first step, before the third step, and before the fourth step. Petroleum pitch and polycyclic aromatic hydrocarbons may be used instead of coal tar pitch. The coal tar pitch and petroleum pitch are the most desirable because they are inexpensive. Examples of the polycyclic aromatic hydrocarbons include naphthalene, anthracene, phenanthrene, naphthacene, pyrene, triphenylene, chrysene, pentacene, benzopyrylene, koranenurene, coronene and ovalene. The amount of the additive to be added is preferably 0.05 to 5 parts by weight, more preferably 0.2 to 3 parts by weight, and most preferably 0.5 to 2 parts by weight based on 100 parts by weight of silicon. The additive dissolves in an aprotic solvent to form a new crushed surface of silicon, and at the same time, it has an effect of covering the surface thereof and suppressing aggregation through electrostatic repulsion or hydrophobic repulsion.

When a protonic solvent is used as a solvent for a wet bead mill, the problem of environmental pollution and the like is small. As the protonic solvent, water and alcohol are preferable. As the additive, at least one polymer selected from the group consisting of polyvinylpyrrolidone, carboxymethylcellulose sodium salt, and polyvinyl alcohol having a ketone or ether structure is used . The amount of the additive to be added is preferably 0.05 to 5 parts by weight, more preferably 0.1 to 3 parts by weight, most preferably 0.5 to 2 parts by weight based on 100 parts by weight of the solvent. In the case where silicon is pulverized in a solvent in which the additive is dissolved, since it can more easily bond with surrounding atoms due to the dangling bonds of silicon atoms formed on the surface of the pulverized silicon particles, (1) (2) the formation of an oxide film on the surface of the silicon particles can be suppressed, (3) the dispersion of the silicon particles in the silicon particle-carbon composite is improved, The interface with the carbon material can be formed well. In addition, the additive material to be pulverized at the same time can be more stably dispersed than the solvent in which the additive is dissolved. Therefore, in the third step, a slurry uniformly dispersed in silicon and the additive material can be obtained.

The particle diameter of the silicon particles put into the wet-process bead mill in the second step is preferably several tens of 탆 or less, more preferably in the range of 1 to 10 탆. The wet grinding process may be performed until the average particle diameter of the starting material is 3 nm or more and 200 nm or less. The average particle diameter of the silicon particles obtained in the third step is preferably in the range of 3 to 200 nm, more preferably in the range of 10 to 200 nm, and most preferably in the range of 20 to 100 nm. When the average particle diameter of the starting material is less than 5 nm, aggregation may occur between the starting materials, which may result in poor dispersion in a subsequent dispersion process. When the starting material is larger than 200 nm, particles of the starting material are too large to be used as an anode active material The degree of dispersion can not be achieved.

The wet bead mill used in the present invention is preferably capable of continuous pulverization with a circulation tank. As the material of the beads used in the bead mill, zirconia, alumina, silicon nitride, and titania are preferable. Particularly, zirconia and alumina are preferable because they have high hardness and high crushing ability, so that even if they remain in the electrode or battery manufacturing process in subsequent steps, they are small in quantity and have little adverse effect. The diameter is preferably 2 mm or less in the wet- To 0.8 mm is more preferable.

The additive material may be a material that is not soluble in the medium used in the wet milling. After the dispersion process, the additive material may be branched and evenly dispersed in the slurry. The additive material may include at least one selected from the group consisting of graphite, graphene, carbon nanotube, carbon fiber, amorphous carbon, and lithium ion inorganic solid electrolyte. Preferably, it may be an inorganic solid electrolyte of graphite, graphene, carbon nanofiber, carbon nanotube, or lithium ion. As the inorganic solid electrolyte of lithium ion, a so-called "ceramic electrolyte" such as a metal, an oxide, a carbide, a boron compound, a sulfide, a phosphoric acid compound and the like is more preferable. As a concrete example, the lithium ion inorganic solid electrolyte is represented by Li ₂ SP ₂ O ₅ sulfur-based amorphous electrolyte, sulfur-containing glass, nitride, lithium _{(Li 3 N), Li 1} + x + y Al x Ti 2 - x Si y P 3 - y O 12 (x = 0.3, y = 0.2) NASICON represented by A substance having a crystal structure, a garnet structure material represented by Li ₇ La ₃ Zr ₂ O ₁₂ , and a germanium-phosphorus-sulfur compound represented by Li ₁₀ GeP ₂ S ₁₂ .

In FIG. 3, an additive material (for example, graphite) is added before or after the first step, but an additive slurry prepared by finely pulverizing and dispersing in advance in a separate step may be added between the second step and the fourth step. The additive material has a surface potential different from that of silicon, and therefore can suppress aggregation between the silicon particles. In addition, when the additive material (graphite) is added during the milling of the silicon particles, the additive material particles may be more uniformly dispersed among the silicon particles, and when the electrode structure is formed using the additive material particles, The conduction of lithium ions can be compensated.

It is possible to suppress the re-aggregation of the pulverized silicon particles by pulverizing silicon in a solvent (medium) containing a carbon source (additive or additive), suppress formation of an insulating oxide film on the surface of the silicon particles, It is possible to maintain the conductivity due to the decrease of the oxide film existing between the silicon particles and to improve the electron conductivity between the silicon particles through the carbonization or graphitization of the carbon source through the additional firing process, And as a result, the performance of the battery can be improved. Further, when silicon is pulverized in a solvent containing a solid electrolyte, insertion of lithium ions into the surface of the silicon particles may be facilitated during operation of the electrical storage device.

And irradiating ultrasonic waves during the first through third processes. The ultrasonic treatment has an effect of promoting dispersion of particles in a solvent and redispersing the aggregated particles. It is also possible to generate amorphous carbon on the surface of the silicon particles by irradiating ultrasonic energy to a slurry in which silicon particles are dispersed in a solution of coal tar pitch, petroleum pitch and polycyclic aromatic compound, and it is also possible to form carbon- .

If the concentration of the solvent in the slurry obtained in the third step is too high, the amount of the solvent can be controlled by removing the solvent by pressurization in the fourth step, centrifugation or the like to obtain a slurry having an appropriate viscosity.

In addition, the method may further include a calcining (calcining) step of drying and calcining the slurry to obtain a negative electrode active material, whereby the silicon particles having the surface layer of the amorphous carbon according to the first embodiment or the silicon particle- A negative electrode active material of the composite can be obtained (calcining step). The calcination process may be carried out under reduced pressure or an inert atmosphere. The inert atmosphere may be a nitrogen gas atmosphere or an argon gas atmosphere. When the calcination step is carried out under reduced pressure, the organic compounds present in the slurry can be more easily decomposed and volatilized. When the calcination is performed in an inert atmosphere, oxidation can be prevented and the electron conductivity of the cathode can be improved. The calcination can be carried out at such a temperature that all of the organic substances in the slurry can be volatilized and removed.

Referring to FIG. 5, the fourth embodiment of the present invention may be a conductive composition for a secondary battery in which carbon (121 to 123) is dispersed in an aprotic solvent (124) free of protons. The conductive composition for a secondary battery according to the present embodiment can be used as a conductive auxiliary agent capable of supplementing the electron conductivity of the cathode. Since the conductive auxiliary agent is present on the surface of the anode active material particles and connects the anode active material with the anode active material, the conductivity of the anode active material is increased by the conductive auxiliary agent, and consequently, the performance of the anode can be improved. Although the negative electrode has been described here, it is not necessarily limited to the negative electrode, and may be applied to the positive electrode in some cases.

The aprotic solvent may include at least one selected from the group consisting of hydrocarbons, aromatic compounds, ketones, ethers, esters, amides and nitrile solvents. The aprotic solvent means a solvent free from proton donating. When an aprotic solvent is used, it is possible to more effectively inhibit oxidation of a material to be pulverized or dispersed.

At least one additive selected from the group consisting of a coal tar pitch and a polycyclic aromatic compound may be added to the aprotic solvent. The additive is not particularly limited as long as it is a substance that can be readily carbonized under an inert atmosphere. The additive may be carbonized to contribute to the improvement of the electron conductivity of the negative electrode.

Carbon may be added to improve the electron conductivity of the cathode. However, it is not necessarily limited to carbon, and there is no particular limitation as long as it is an electron-conductive material. The carbon may include at least one selected from the group consisting of fibrous carbon (121), graphene structure carbon particles (122), and carbon black (123). Carbon can be present in various forms, and therefore is not necessarily limited to the materials listed above, but may include other types of carbon.

The fibrous carbon 121 has an average diameter of 10 to 200 nm, the graphene structure particles 122 have an average particle diameter of 10 to 200 nm, the carbon black 123 has an average particle diameter of 10 to 80 nm, And the crystal grain size may be 2 to 5 nm.

The content of carbon may be 0.05 to 1.0 g / L. When the content of carbon is less than 0.05 g / L, the effect of improving the electron conductivity of the negative electrode is insufficient because of the small contribution of the electron conductivity. When the content of carbon is more than 1.0 g / L, the content of carbon is too large, The function as the active material may be deteriorated.

A protonic solvent having a proton donor may be used instead of the aprotic solvent. In this case, the protonic solvent may include at least one member selected from the group consisting of water and an alcohol, and the protonic solvent may include one kind selected from the group consisting of polyvinylpyrrolidone, sodium carboxymethylcellulose and sodium cholate The above additives may be added.

A fifth embodiment of the present invention may be a method for producing a conductive composition for a secondary battery, which comprises a step of mixing an additive into an aprotic solvent to prepare a solution, and a dispersion step of dispersing carbon into the solution.

The dispersion process can be performed by a bead mill.

The aprotic solvent may include at least one member selected from the group consisting of hydrocarbons, aromatic compounds, ketones, ethers, esters, amides and nitrile solvents. Examples of aprotic solvents include coal tar pitches, groups of polycyclic aromatic compounds May be added.

The carbon may include at least one selected from the group consisting of fibrous carbon, graphene structure carbon particles, and carbon black. The fibrous carbon has an average diameter of 10 to 200 nm and the graphene structure particles have an average particle diameter of 10 to 200 Nm, and carbon black has an average particle diameter of 10 to 80 nm and has a structure in which a plurality of primary particles are connected in a bead shape, and the crystal grain size may be 2 to 5 nm.

The content of carbon may be 0.05 to 1.0 g / L.

A protonic solvent may be used in place of the aprotic solvent. In this case, the protonic solvent may include at least one selected from the group consisting of water and alcohol, and the protonic solvent may include polyvinylpyrrolidone, At least one additive selected from the group consisting of cellulose sodium salt and sodium cholate may be added.

In the present embodiment, the matters relating to the solvent, the additive, the carbon and the dispersion step are the same as those described in the dry milling step, the wet milling and dispersing step of the third embodiment. However, it differs in that it does not go through the calcination process.

The sixth embodiment of the present invention may be a negative electrode material comprising a negative electrode active material, a conductive agent, a binder and a solvent. The negative electrode material may be a slurry in which a negative electrode active material, a conductive agent, a binder, and a solvent are dispersed by a ball mill or the like. The negative electrode active material may include at least one of the negative electrode active material of the first embodiment and the negative electrode active material of the second embodiment. The conductive agent may include the conductive composition of the fourth embodiment. The binder may be PVDF (polyvinylidene fluoride) dissolved in NMP (N-methyl-2-pyrrolidone), styrene-butadiene rubber (SBR) dissolved in water or Carboxymethyl cellulose (CMC).

A seventh embodiment of the present invention is a negative electrode material for a secondary battery comprising a step of providing a negative electrode active material, a step of providing a conductive agent, and a step of mixing a negative electrode active material and a conductive agent together with a binder in a solvent to prepare a slurry Lt; / RTI >

First, a negative electrode active material in a slurry state can be provided according to the third embodiment. The negative electrode active material may be the negative active material of the first embodiment or the negative active material of the second embodiment. Here, the matters relating to the solvent, the additive, the carbon and the dispersion step are the same as those described in the dry milling step, the wet grinding and dispersing step of the third embodiment. However, it differs in that it does not go through the calcination process.

Next, a conductive agent (conductive composition) may be provided according to the fifth embodiment.

Next, the negative electrode active material in a slurry state can be prepared by mixing the conductive agent and the binder in the slurry state and then dispersing the conductive agent and the binder evenly through a method such as milling. The binder may be PVDF (polyvinylidene fluoride) dissolved in NMP (N-methyl-2-pyrrolidone), styrene-butadiene rubber (SBR) dissolved in water or Carboxymethyl cellulose (CMC).

In the present embodiment, matters relating to the negative electrode active material, the conductive agent, the solvent, the binder, and the like are the same as those described in the foregoing embodiment.

6, an eighth embodiment of the present invention may be a negative electrode structure 305 including a conductive metal (current collector) 300 and a negative electrode material layer 304 formed on the conductive metal 300. [ The negative electrode material layer 304 may include the negative electrode material of the sixth embodiment. The cathode structure 305 can be formed by applying a negative electrode material on the current collector 300 and then drying to remove the solvent. The negative electrode material layer 304 may be in a state where the negative electrode active material 304 and the conductive agent 303 are bonded together by the binder 302. The current collector 300 is not particularly limited as long as it has electronic conductivity and has chemical stability against an electrolytic solution. Specifically, copper or aluminum can be used.

Referring to Fig. 7, the ninth embodiment of the present invention is a method for manufacturing a negative electrode material, comprising the steps of: providing a negative electrode material according to the seventh embodiment (first to fourth steps); applying the prepared negative electrode material onto a conductive metal; (Fifth step) of heat-treating the cathode structure.

First, a negative electrode material (slurry for electrode coating) can be provided according to the seventh embodiment (first to fourth steps). That is, the negative electrode active material in a slurry state is prepared according to the third embodiment (the first to third steps, wherein the matters relating to the solvent, the additive, the carbon and the dispersion step are the same as the dry grinding step, (Conductive composition) according to the fifth embodiment, and then the conductive agent and the binder are mixed with the slurry-like negative electrode active material, followed by mixing with a bead mill or the like , The conductive agent and the binder are evenly dispersed to prepare a negative electrode material (slurry for electrode coating) in a slurry state (fourth step). In the fourth step, at least a binder may be added to the slurry of the silicon particles obtained in the third step, or a slurry for forming an electrode layer may be prepared by adding a conductive auxiliary agent or a solvent of a binder.

As the binder to be added in the fourth step, when the solvent of the slurry is an aprotic solvent, a polymer selected from polyamic acid, polyimide, polyamideimide and epoxy resin is preferable. When the solvent of the slurry is a protonic solvent, it is preferable to use at least one kind of polymer selected from carboxymethyl cellulose sodium salt, polyvinyl alcohol and chitosan, and it is more preferable to cause cross-linking reaction therebetween to cause crosslinking between polymers . In the fourth step, a conductive auxiliary agent and a viscosity controlling solvent may be added to the electrode layer-forming slurry. As the conductive auxiliary agent, at least one selected from the group consisting of graphite, graphene, carbon nanotube, carbon nanofiber and amorphous carbon Can be used. The matters relating to the negative electrode active material, the conductive agent, the solvent, the binder and the like are the same as those described in the foregoing embodiment.

Next, a negative electrode material (slurry for electrode coating) is applied on the current collector to a predetermined thickness using a doctor blade method, and the current collector coated with the negative electrode material is dried and heat treated to manufacture the negative electrode structure. The drying temperature is preferably in the range of 80 to 120 占 폚 in the case of being in the atmosphere. Organic materials such as binders can be volatilized and removed by the heat treatment process. The heat treatment temperature is determined by the boiling point of the binder and its solvent. The heat treatment at 120 ° C or higher needs to be performed under vacuum (reduced pressure) or in an inert gas atmosphere. In the case of using polyamic acid or polyamideimide as a precursor of polyimide as a binder and N-methyl-2-pyrrolidone as a solvent, the temperature is preferably in the range of 180 to 350 DEG C, Do. As the inert gas composition gas, argon, nitrogen and helium are preferable, but argon is more preferable.

8, a tenth embodiment of the present invention is a battery device comprising a negative electrode structure 402, a separation membrane 403, an anode structure 405, and current collectors 401 and 404 of an eighth embodiment have. A typical example of the electrical storage device is a lithium secondary battery, which may be a coin type, a laminate type, or a cylindrical type. Figs. 9 to 11 show cross sections of a coin type, a stacked type, and a cylindrical lithium secondary battery, respectively. The separator, the anode structure, and the current collector can be generally used widely.

An eleventh embodiment of the present invention may be a method of manufacturing an electrical storage device (secondary battery), comprising the steps of: providing a negative electrode structure according to the ninth embodiment; and laminating the provided negative electrode structure, separator, and positive electrode structure. Although the laminated structure is described in this embodiment, the laminated structure is not limited to this, and can be applied to a winding type, a coin type, and the like. Other separators, anode structures, current collectors, and the like are the same as those described in the previous embodiments.

Hereinafter, the present invention will be described in more detail with reference to Examples, Reference Examples, and Comparative Examples.

(Preparation of silicon-carbon composite)

Example M1

Silicon-carbon composites were prepared according to the process chart of FIG. 3 and the grinding system of FIG.

As a starting material, a mixed powder obtained by mixing 95 parts by weight of silicon powder and 5 parts by weight of graphite powder was used. Silicon powders having a purity of 99% and an average particle diameter of 500 mu m and graphite powders having an average particle diameter of 20 mu m were used.

The starting material was charged into the dry-type bead mill 202 using a quantitative feeder 201 and pulverized to an average particle size of about 3 μm. Zirconia beads having a particle diameter of 5 mm were used for the dry grinding and the grinding was carried out in a nitrogen gas atmosphere.

The powder obtained by the dry pulverization using the solid-liquid mixing tank 204 was mixed with a 0.07% by weight solution of a cyclohexane solution in which the coal pitch was 0.02% by weight. An artificial graphite having an average particle diameter of 5 탆 and 0.05% by weight of a multi- 0.2% by weight of Li ₂ O-Al ₂ O ₃ -SiO ₂ -P ₂ O ₅ -TiO ₂ as a lithium ion conductor (lithium ion inorganic solid electrolyte) having a tube and 0.0025% by weight of an average particle diameter of 5 μm was added to obtain a mixed solution .

The mixed solution was supplied to the first wet bead mill 209 filled with zirconia beads having a particle diameter of 0.5 mm via a first circulation tank 207 by using a pump 205. The average slurry of the starting material was pulverized for 1 hour To obtain a slurry.

The slurry was stored in a second circulation tank 210 and supplied to a second wet bead mill 212 filled with zirconia beads having a particle diameter of 0.03 mm and pulverized. The starting material was pulverized for 2 hours while circulating until the average particle diameter became 400 nm, and the obtained slurry was stored in the pulverized product dispersion slurry tank 213. Cyclo-nucleic acid was added to the obtained slurry to adjust the silicon concentration to 10% by weight. The slurry was supplied to a wet type bead mill filled with zirconia beads having a particle diameter of 0.1 mm via a third circulation tank (not shown) To a slurry obtained by adding a cyclohexane acid to a silicon concentration of 5% by weight. The slurry was supplied to a wet type bead mill filled with zirconia beads having a particle diameter of 0.05 mm via a circulation tank, and the slurry was circulated for 2 hours. Thereby obtaining a slurry in which particles and ion conductor particles were dispersed.

The pulverized dispersion slurry was dried in a vacuum dryer to remove the cyclo-nucleic acid and obtain a mixture of silicon-lithium ion inorganic solid electrolyte-graphite-coal tar pitch.

The mixture was heat-treated in a baking furnace at a temperature of 800 ° C under an argon gas atmosphere to prepare a silicon-lithium ion inorganic solid electrolyte-carbon composite.

Example  M2

As a starting raw material, metal silicon powder having a purity of 99% and a particle diameter of 300 탆 or less was added and dispersed in N-methyl-2-pyrrolidone and the first circulation tank 207 by a dispersion medium so as to be 20% (209) was pulverized for 1.5 hours while circulating in a nitrogen gas atmosphere using 0.5 mm zirconia beads and pulverized to an average particle size of about 400 nm. Subsequently, the obtained slurry was supplied to a second wet bead mill 212 filled with zirconia beads having a particle diameter of 0.3 mm via a second circulation tank 210, and pulverized for 2.5 hours while the slurry was circulated by the feed pump 211. Subsequently, N-methyl-2-pyrrolidone was added to the obtained slurry, and the mixture was fed through a third circulation tank filled with zirconia beads having a particle diameter of 0.1 mm to a third wet bead mill filled with zirconia beads having a particle diameter of 0.1 mm, , And the coal tar pitch was added so as to be 0.1 wt% with respect to silicon and pulverized for 2.5 hours to obtain a slurry of silicon particles having an average particle size of 180 nm. The obtained slurry was dried and found to have an average particle size of 50 to 200 nm by a scanning electron microscope. The scanning electron microscope was JSM-7400F from Jeol.

Example  M3

N-methyl-2-pyrrolidone was added to the slurry obtained in Example M2 to adjust the silicon concentration to 5% by weight. The slurry was supplied to a wet type bead mill filled with zirconia beads having a particle diameter of 0.05 mm via a circulation tank, But the crushing did not proceed until the average particle diameter was 110 nm or less after 1 hour. The pulverization was carried out for an additional 1 hour by adding 0.04 wt% of the coal tar pitch to the weight of silicon, and as a result, a slurry in which the average particle diameter of the silicon particles was reduced to 65 nm was obtained. The obtained slurry was dried, and a particle diameter of 30 to 100 nm observed by a scanning electron microscope and a particle of at least 5 nm were observed by a transmission electron microscope.

Example  M4

In Example 2, instead of the N-methyl-2-pyrrolidone solution in which 0.1 wt% of the coal tar pitch was dissolved, 0.1 wt% of polyvinylpyrrolidone was dissolved in ethyl alcohol as a solvent to obtain a silicone-carbon composite under the same conditions .

Reference example  M1

In Example 2, the first wet bead mill 209 was pulverized for 1.5 hours while circulating in a nitrogen atmosphere using zirconia beads having a diameter of 0.5 mm, and pulverized to a median diameter of about 400 nm to obtain a silicon slurry.

Reference example  M2

In Example M1, the coal tar pitch was not added to the cyclo-nucleic acid. A silicon-carbon composite was obtained in the same manner as in Example M1 except for the above.

Comparative Example  M1

A dry milling step of Example M1 was not carried out, and a wet grinding step using ethanol as a starting material was used as a starting material with an average particle diameter of 20 mu m of metal silicon. Thereafter, the dispersion process was carried out, followed by desolvation, followed by pulverization to prepare a dried silicon powder.

Subsequently, the dried silicon powder was dispersed in a cyclohexane solution in which 2 wt% of coal tar pitch was dissolved, dried under reduced pressure, and then heat-treated at 800 ° C in an argon gas atmosphere to prepare a silicon-carbon composite.

(Evaluation of silicon-carbon composite)

The size, distribution, and oxygen content of the silicon (Si) particles are measured by a scanning electron microscope (SEM), a transmission electron microscope (TEM), a transmission electron microscope (EDS), and electron energy loss spectrometer (EELS). The results are shown below.

The order in which the agglomeration of the silicon particles is large is as follows: Comparative Example M1> Reference Example M1> Reference Example M2> Example M2> Example M1.

The order in which SiOx is abundant is Comparative Example M1 >> Reference Example M2> Example M2> Reference Example M1> Example M1.

The order of primary particle size of silicon is Comparative Example M1> Reference Example M2> Reference Example M1> Example M2> Example M1.

According to the above results, it can be confirmed that silicon can be more finely divided according to the manufacturing method of the present invention, the silicon particles are uniformly dispersed in the obtained internal structure of the silicon-carbon composite, and the oxygen content is also small.

(Fabrication of negative electrode structure)

Example  E1, etc.

Artificial graphite having an average particle diameter of 5 占 퐉, multilayer carbon nanotubes having a diameter of 150nm, and polyamic acid according to Examples M1, M2, and M1 and Comparative Example M1 were added, and 26 parts by weight of silicone, 49 parts by weight, carbon nanotube 12 parts by weight, and polyamic acid solid component 12 parts by weight were mixed and kneaded to prepare an electrode layer forming slurry.

The slurry was coated on a 17 탆 thick copper foil using an applicator and dried at 110 캜 for 0.5 hour. The thickness and density of the slurry were adjusted with a roll press. The copper foil current collector had a thickness of 20 to 40 탆, a density of 0.9 to 1.2 g / Cm < 3 > to form a negative electrode structure.

Each of the negative electrode structures made of the silicon-carbon composite of Example M1, Example M2, Reference Example M1, Reference Example M2 and Comparative Example M1 was referred to as Example EM1, Example EM2, Reference Example EM1, Reference Example EM2, Comparative Example EM1 Was called a negative electrode structure.

(Evaluation of electrochemical lithium insertion amount of negative electrode structure)

The negative electrode structure was used as a single electrode to evaluate the amount of electrochemical lithium insertion as follows.

Each of the cathode structures of Examples EM1, EM2, Reference Example EM1, Reference Example EM2, and Comparative Example EM1 was pressed to a predetermined size to form a coin-shaped cell having metal lithium as a counter electrode, The electrochemical lithium insertion amount of the structure was evaluated. The lithium electrode was produced by pressing a metal lithium foil having a thickness of 140 탆 onto a nickel metal foil expanded metal and pressing it to a predetermined size.

A coin-shaped evaluation cell was fabricated as follows (see FIG. 9). That is, the negative electrode structure is inserted into the anode can 507 in a dry atmosphere at a dew point of -50 占 폚 or less, a polyethylene film having a thickness of 17 占 퐉 and a porosity of 40% and a microporous structure is superimposed and placed on the polypropylene gasket 508, . Subsequently, an electrolyte was dropped on the separator to form an ion conductor (separation membrane) 503. Next, the lithium negative electrode 502/501 was superimposed on the negative electrode, the cap was covered with the negative electrode cap 506, and caulked with a caulking machine to prepare an evaluation cell. As the electrolyte solution, a solution obtained by dissolving 1 M (mol / l) of lithium hexafluorophosphate (LiPF ₆ ) in a mixed solvent of ethylene carbonate and diethyl carbonate at a volume ratio of 3: 7 was used.

The electrochemical lithium insertion amount was evaluated as follows. Discharging was performed until the cell voltage became 0.01 V with the lithium electrode as the cathode and each working electrode as the anode. That is, the electricity amount used for inserting lithium into the discharged electric quantity, and the charged electricity amount were used as the electricity amount used for discharging lithium.

Charging / discharging was performed by discharging-charging once at a current of 0.05 C and 0.5 C at a current of 50 C, and the Li insertion amount (electricity amount) of the first time, the amount of Li release (electricity amount) (Li) discharge (electricity amount) of the first time, the 50th Li discharge amount (electricity amount) at the 10th time, and Li insertion (release) evaluation of the anode made of various kinds of active materials were performed. The results are shown below.

In the order of larger first Li insertion amount, Comparative Example EM1> Reference Example EM1> Reference Example EM2> Example EM2> Example EM1.

Reference Example EM1 > Reference Example EM1 > Reference Example EM2 > Reference Example EM1 is a comparative example EM1 in the order of larger ratio (%

Example 10 EM1> Reference Example EM1 Reference Example EM2 Reference Example EM2 >> Comparative Example EM1.

Considering the charging / discharging capacity and the repetition characteristics of charging / discharging repeatedly with reference to the above results, it can be confirmed that the cathode structure according to the present invention has high performance.

Table 1 shows the current characteristics of the desorption amount (capacity) of Li in Example EM2 and Reference Example EM1 in comparison. However, the desorption amount of Li at each current value was normalized to 1.0 at the current value of 0.05C.

Current value
C-rate Reference example EM1
Capacity (mAh / g) / Capacity at 0.05C (mAh / g) Example EM2
Capacity (mAh / g) / Capacity at 0.05C (mAh / g) 0.1 C 0.81 0.95 0.2C 0.69 0.87 0.5 C 0.37 0.68 1.3C - 0.51

Referring to Table 1, it can be seen that the electrode (Example EM2) produced by using the obtained silicon particles up to an average particle diameter of 180 nm pulverized by adding coal tar pitch has a good current rate characteristic of lithium desorption amount and a large amount of lithium desorption at a high current Could know.

(celebration Device  making)

A coin-type lithium secondary battery was fabricated using a battery device, and the performance was evaluated. 8 to 10 show a coin-shaped cell, a laminate, a pouch cell, and a cylindrical cell as an example of a lithium secondary battery. On each of the negative electrodes, each of the negative electrode structures of Example EM2, Reference Example EM1, Reference Example EM2, and Comparative Example EM1 was pressed at a predetermined size to produce respective coin-shaped cells. The coin-type cells were assembled in a dry atmosphere at a dew point of -50 DEG C or less.

The manufacturing process of the coin cell will be described with reference to FIG. First, a preliminarily fabricated positive electrode was inserted into the anode can 507, and a polyethylene film having a thickness of 17 mu m and a porosity of 40% micropores was stacked with the separator, and the polypropylene gasket 508 was set. To form an ion conductor (separation membrane) 503, followed by overlapping the cathode 502/501, capping with a cathode cap 506, and pre-coking with a caulking machine to prepare a coin cell.

Examples EM2, Reference Example EM1, Reference Example EM2, and Comparative Example EM1 in which a silicon-carbon composite of Example M1, Example M2, Reference Example M1, Reference Example M2, and Comparative Example M1 was used as a negative electrode active material, A coin cell manufactured by using the negative electrode structure as a negative electrode was used as a power storage device of Example DM2, Reference Example DM1, Reference Example DM2, and Comparative Example DM1.

A solution obtained by dissolving lithium hexafluorophosphate (LiPF ₆ ) 1M (mol / l) in a solvent mixed with ethylene carbonate and diethyl carbonate in a volume ratio of 3: 7 was used as the electrolytic solution.

(Fabrication of anode structure)

The positive electrode structure used as the positive electrode of the battery device of the present invention was manufactured as follows.

Lithium nickel cobalt manganese oxide _{LiNi 1/3 Co 1/3} Mn 1/3 O 2 powder to 100 parts by weight of acetylene black, 4 parts by weight were mixed and then, where the polyvinylidene fluoride containing 10% by weight on the N- methyl-2 -Pyrrolidone solution and 50 parts by weight of N-methyl-2-pyrrolidone were added and dispersed with a wet bead mill to prepare a slurry for forming the cathode active material layer.

Subsequently, the slurry was coated on an aluminum foil having a thickness of 14 탆 using a coater, dried at 110 캜 for 1 hour, and further dried at 150 캜 under reduced pressure.

Then, the thickness was adjusted by a roll press machine to prepare a positive electrode structure having a positive electrode active material layer having a thickness of 82 mu m and a density of 3.2 g / cm < 3 > By pressing the positive electrode structure to a predetermined size _{LiNi 1/3 Co 1/3} Mn 1/3 O 2 Thereby preparing a positive electrode structure.

( Charging and discharging  Test evaluation)

After charging the battery device at a constant current density of 0.2 C at a current density of 4.2 V, charging the battery device at a constant voltage of 4.2 V after 10 minutes of stopping, and when the cell voltage reached 2.7 V at a constant current density of 0.2 C The charge and discharge characteristics were evaluated by repeating charging and discharging 100 times at a current density of 1 C, and the results are shown below.

Example 100 in order of larger discharge amount Example DM1> Example DM2> Reference Example DM1> Reference Example DM2 >> Comparative Example DM1.

Considering the charge / discharge capacity and charge / discharge repetition characteristics with reference to the above results, it can be seen that the cathode according to the present invention has a high performance.

The terms used in the present invention are intended to illustrate specific embodiments and are not intended to limit the invention. The singular presentation should be understood to include plural meanings, unless the context clearly indicates otherwise. The word " comprises " or " having " means that there is a feature, a number, a step, an operation, an element, or a combination thereof described in the specification. The present invention is not limited to the above-described embodiments and the accompanying drawings, but is intended to be limited only by the appended claims. It will be apparent to those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. something to do.

100: silicon particle 101: amorphous surface layer
a: long diameter (length) b: short diameter (width)
d: thickness 110: silicon-carbon composite particle
111: silicon particles 112: graphene structure Carbon particles
113: fibrous carbon 114: carbon black
121: fibrous carbon 122: graphene structure carbon particles
123: carbon black particles 124: solvent
200: feed tank 201: constant feeder
202: Dried bead mill 203: Songbane
204: solid-liquid mixing tank 205, 208, 211, 214: liquid transfer pump
206: feed pipe 207: first circulation tank
209: first wet bead mill 210: second circulation pump
212: second wet-type bead mill 213: crushed product dispersion slurry
300: conductive metal (current collector) 301: negative active material
302: binder 303: conductive agent
304: cathode material layer 305: cathode structure
401, 501, 601, 701: negative electrode collector 402, 502, 602, 702: cathode structure
403, 503, 603, 703: ion conductors 404, 504, 604, 704: positive electrode collector
405, 505, 605, 705: anode structure 406, 608:
407, 708: negative electrode lead 408, 706: negative electrode terminal
409, 709: Positive electrode lead 410, 707: Positive electrode terminal
507, 713: Gasket 710: Safety valve
711, 712: Insulating plate

Claims (10)

A dry milling step of dry-milling the silicon material under an inert atmosphere to prepare a dry milled material; And
And a wet grinding and dispersing step of preparing a slurry by wet pulverizing and dispersing the dry pulverized material, the additive material, and the additive in a solvent so that the particle diameter of the silicon material is 5 nm or more and 200 nm or less,
Wherein lithium ion solid electrolyte particles are used as the additive material. The method according to claim 1,
Wherein at least one of the dry grinding step, the wet grinding step and the dispersing step is performed by a bead mill process. The method according to claim 1,
Wherein the additive material further comprises at least one selected from the group consisting of graphite, graphene, carbon nanotube, carbon fiber, and amorphous carbon. The method of claim 3,
The lithium ion solid electrolyte may be a sulfur-based amorphous electrolyte represented by Li ₂ SP ₂ O ₅ , a sulfur-containing glass, lithium nitride (Li ₃ N), Li _{1 + x + y} Al _x Ti _{2 - x} Si _y P _{3 - y} O _{12 (x = 0.3, y =} 0.2) NASICON crystal structure material typified by, Li ₇ La ₃ Zr ₂ O material of garnet structure represented by _12, and germanium as represented by Li ₁₀ GeP ₂ S ₁₂ - in-sulfur compound And a negative electrode active material for a secondary battery. The method according to claim 1,
Wherein the solvent is an aprotic solvent having no proton donor and at least one selected from the group consisting of cyclic hydrocarbons, aromatic compounds, ketones, ethers, esters, amides and nitrile solvents. 6. The method of claim 5,
Wherein the additive includes at least one selected from the group consisting of coal tar pitches and polycyclic aromatic compounds, which is easily carbonized in an inert atmosphere. The method according to claim 1,
Wherein the solvent is a protonic solvent having a proton donor and at least one selected from the group consisting of an alcohol and water. 8. The method of claim 7,
Wherein the additive includes at least one selected from the group consisting of polyvinylpyrrolidone, carboxymethylcellulose sodium salt, and polyvinyl alcohol, which is easily carbonized in an inert atmosphere. The method according to claim 1,
And a calcining step of drying and calcining the slurry after the dispersing step to obtain a negative electrode active material. 10. The method of claim 9,
Wherein the calcining step is performed in a reduced pressure or inert atmosphere.

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