KR20210109692A - A new composite anode active material, lithium battery including the same, and method for preparing the material - Google Patents

Abstract

The present invention relates to an anode active material and a lithium battery including the same. The anode active material includes a core part comprising a crystalline carbon-based material; and a shell part including composite particles in at least one outside of the core part. The composite particles has a structure in which a filler is in a matrix composed of one component selected among at least one material selected from the group consisting of low-crystalline carbon and amorphous carbon; and a metal nitride reacting with lithium. The filler is composed of the remaining components.

Description

A novel composite anode active material, a lithium battery including the same, and a method for preparing the composite anode active material {A new composite anode active material, lithium battery including the same, and method for preparing the material}

The present invention relates to a novel composite anode active material, a secondary battery including the same, and a method for manufacturing the composite anode active material.

As part of efforts to solve the global environmental pollution problem caused by fossil fuels, many studies have been conducted in the fields of power generation and electricity storage using electrochemistry.

In particular, the demand for secondary batteries as an energy source is increasing rapidly due to the development and demand of mobile electronic devices such as PDAs, mobile phones, and notebook computers. As the demand for secondary batteries and secondary batteries for energy storage devices is rapidly increasing, research on secondary batteries is being actively conducted, and among secondary batteries, research on lithium ion batteries that are easy to design and improve capacity and lifespan is the most active.

In general, a lithium secondary battery includes a positive electrode, a negative electrode, and an electrolyte, and during the first charge, lithium ions from the positive electrode active material are inserted into the negative electrode active material such as carbon particles, and during discharging, they are desorbed from the negative electrode active material and inserted back into the positive electrode active material. As described above, since lithium ions play a role of transferring energy between the two electrodes in a reciprocating manner between the positive and negative electrodes, the lithium secondary battery can be charged and discharged.

In general, lithium transition metal oxide is used as the cathode active material of the secondary battery, and carbon-based materials such as natural graphite having excellent cycle characteristics are used as the anode active material. Recently, for high performance of mobile devices, electric vehicles, and energy storage devices, it exhibits higher energy density and operating potential than conventional anode active materials made of carbon-based materials such as natural graphite with a theoretical capacity of 372 mAh/g, has a longer cycle life, and has a self-discharge rate. There is a demand for a lithium secondary battery having a negative active material having a high capacity and a long lifespan with this low characteristic.

Research on silicon-based composite anode active materials such as carbon/silicon composites as anode active materials for such high-capacity secondary batteries is active (Patent Documents 1, 2, 3). However, Patent Document 1 uses silicon carbide (SiCx) for the anode active material composite, and forms a composite layer by firing two layers, that is, carbon precursors such as carbon-based particles, amorphous silicon particles, and pitch, and then on the composite layer again. As forming the carbon-based coating layer, it is expected that the thickness of 0.01 to 10 μm or less, which influences the performance, must be adjusted, so that manufacturing difficulties are expected. In addition, Patent Document 2 uses silicon suboxide (SiOx) as a silicon composite, but when the negative electrode contains silicon suboxide, lithium oxide is formed in the first cycle, which is the first charge/discharge, so that lithium is consumed other than electrochemistry. This has the disadvantage of shortening the life of the battery. Patent Document 3 uses a metal nitride to manufacture a high-capacity battery, but includes two layers, that is, a first layer including carbon-based negative active material particles on a current collector and silicon nitride formed on the first layer. It is made of the second layer, and since the performance of the battery depends on the thickness, manufacturing difficulties are expected to maintain the high capacity performance.

Therefore, it is necessary to develop an anode active material and lithium secondary battery technology that is easy to manufacture while exhibiting high capacity and long life by solving the above problems.

Patent Document 1: Domestic Patent Publication No. 10-2019-0010250

Patent Document 2: Domestic Patent Publication No. 10-2014-0036494

Patent Document 3: Domestic Patent Publication No. 10-2017-0110840

One aspect of the present invention is to provide a composite anode active material having improved initial discharge capacity, initial efficiency and lifespan characteristics.

Another aspect of the present invention is to provide a lithium secondary battery including the composite anode active material.

Another aspect of the present invention is to provide a method for manufacturing the composite negative electrode active material.

According to one aspect, the present invention includes a core portion comprising a crystalline carbon-based material; and a shell part including composite particles on at least one outside of the core part, wherein the composite particles include at least one material selected from the group consisting of low-crystalline carbon and amorphous carbon; and metal nitrides that react with lithium; To provide a composite anode active material having a structure in which a matrix composed of one component selected from among the other components includes a filler.

By the structure and components of the composite anode active material as described above, it is possible to solve problems such as the possibility of short circuit caused by the battery capacity, battery life, and dendrite growth of lithium on the surface of the anode active material in the prior art, and difficulties in the battery manufacturing process. .

That is, the metal nitride contained as a matrix or filler of the composite particles included in the cell part can improve the dispersibility of the solid content in the slurry with high affinity with the polar solvent of the slurry for preparing the negative electrode, and this improvement in dispersibility is used for manufacturing the negative electrode. The effect of improving the electrode characteristics by solving the problem of internal resistance due to separation of the active material layer and the current collector by minimizing the weakening of the bonding force with the current collector by connecting to the excellent distribution uniformity of the composite negative electrode active material when applied to the whole there is

According to another aspect of the present invention, a positive electrode comprising a positive electrode active material; a negative electrode including the composite active material; and an electrolyte disposed between the positive electrode and the negative electrode.

According to another aspect of the present invention, the method comprising the steps of: (i) preparing metal nitride particles; (ii) preparing composite particles by mixing the metal nitride with one or more materials selected from the group consisting of low-crystalline carbon and amorphous carbon; (iii) mixing the composite particles and a core material of a crystalline carbon-based material to obtain a mixture; and (iv) drying the mixture so that the composite particles are disposed on at least one outside of the crystalline carbon-based core part to form a cell part, or (i) preparing metal nitride particles; (ii) obtaining a mixture by mixing one or more materials selected from the group consisting of metal nitride, low crystalline carbon and amorphous carbon, and a core material of a crystalline carbon-based material; and (iii) drying the mixture so that the composite particles are disposed on at least one outside of the crystalline carbon-based core part to form a cell part;

a core part comprising a crystalline carbon-based material; and a shell part including composite particles on at least one outside of the core part, wherein the composite particles are selected from one or more materials selected from the group consisting of low-crystalline carbon and amorphous carbon and a metal nitride reacting with lithium A composite anode active material having a structure in which a filler composed of the remaining components is included in a matrix composed of components of , it is also easy to manufacture a composite negative electrode active material and a lithium secondary battery including the same.

1 is a graph showing the initial charge/discharge capacity of Examples 1 to 11 and Comparative Example 1 of the present invention.
2 is a life evaluation result.

Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used with a meaning that can be commonly understood by those of ordinary skill in the art to which the present invention belongs, and the singular form is a special sentence The plural is also included unless defined in

In the present specification, when a part such as a layer, film, region, plate, etc. is “on” or “on” another part, it includes the case where there is another part in the middle as well as directly on the other part.

In addition, in this specification, the expression "on" or "on" means located above or below the target part, and does not mean the upper side related to gravity.

Hereinafter, a composite negative electrode active material according to an embodiment of the present invention, a lithium secondary battery including the same, and a method of manufacturing the composite negative electrode active material will be described. These are presented by way of example and not by way of limitation of the present invention, which is defined by the scope of the claims set forth below.

As described above, the composite anode active material according to an aspect of the present invention includes a core part including a crystalline carbon-based material; and a filler composed of the remaining components in a matrix composed of at least one material selected from the group consisting of low-crystalline carbon and amorphous carbon and one component selected from a metal nitride reacting with lithium. and a shell portion including at least one exterior of the core portion comprising the composite particles formed therein.

The core part containing the crystalline carbon-based material serves as an electrical conduction channel due to the conductivity of the crystalline carbon-based material as the basis of the composite negative electrode active material of the present invention, and the metal nitride contained in the composite particles of the shell part reacts with lithium A group consisting of low-crystalline carbon and amorphous carbon contained in the composite particles of the shell part, etc. One or more materials selected from may be considered to serve to connect the metal nitride and the crystalline carbon-based material of the core part to each other to exhibit the above-described effect.

In general, the crystalline carbon-based material included in the core part may include a crystalline carbon-based material of artificial graphite, natural graphite, carbon fiber, or mesocarbon microbead (MCMB), and may include graphite, graphite and low crystallinity. It may be a mixture, low crystalline carbon, amorphous carbon or a mixture of low crystalline carbon and amorphous carbon. The shape of the core part may be a spherical shape in a wide range such as a perfect spherical shape or an elliptical shape. The diameter of the core including the crystalline carbon-based material may be 1 to 80 μm, and in the above range, an excellent electrically conductive channel effect may be exhibited.

The metal nitride contained in the composite particle of the shell part is capable of reacting with lithium, and the metal is silicon, tin, germanium, titanium, aluminum, etc., preferably Si (silicon), and the preferred metal nitride is silicon nitride (SiNx). )am.

In the SiNx, x is 0.01 or more and 0.5 or less, and when x is less than 0.01, Si is oxidized to SiOx, and it is difficult to increase the actual capacity due to the formation of an irreversible phase such as _{Li 4} SiO _{4 by reaction with lithium during initial charging,} When x is more than 0.5, the chance of Si reacting with lithium is reduced, so it is difficult to see the effect of increasing the initial capacity by the lithium-silicon alloy.

At least one material selected from the group consisting of low-crystalline carbon and amorphous carbon contained in the composite particles of the shell part may be pitch or coke, and the pitch is petroleum-based or coal-based coal tar pitch, petroleum pitch, condensed polycyclic aromatic It is an organic synthetic pitch obtained by polycondensation of a hydrocarbon compound or polycondensation of a hetero atom-containing condensed polycyclic aromatic hydrocarbon compound, and the like.

The structure of the composite anode active material of the present invention is, as seen above, in at least one material selected from the group consisting of low-crystalline carbon and amorphous carbon at one or more places on the core of the crystalline carbon-based material, and a metal nitride reacting with lithium. It is a structure in which composite particles are formed having a structure in which a matrix composed of one selected component contains a filler composed of the remaining components.

Such a structure may be formed by the following two methods of manufacturing a composite negative electrode active material as described above.

First, the first method comprises the steps of (i) preparing metal nitride particles; (ii) preparing composite particles by mixing the metal nitride with one or more materials selected from the group consisting of low-crystalline carbon and amorphous carbon; (iii) mixing the composite particles and a core material of a crystalline carbon-based material to obtain a mixture; and (iv) drying the mixture so that the composite particles are disposed on at least one outside of the crystalline carbon-based core part to form a cell part, and the second method is (i) preparing metal nitride particles to do; (ii) obtaining a mixture by mixing one or more materials selected from the group consisting of metal nitride, low crystalline carbon and amorphous carbon, and a core material of a crystalline carbon-based material; and (iii) drying the mixture so that the composite particles are disposed on at least one outside of the crystalline carbon-based core to form a cell part.

In the first and second methods i) preparing the metal nitride particles, a mixture of bulk metal particles having an average particle diameter of 1 μm to 10 μm and an organic solvent is pulverized by a milling process and dried to have an average particle diameter of 30 nm to 250 nm Obtaining metal particles: Partially substituting the surface of the metal particles with nitride by bubbling high-purity nitrogen gas having a purity of 99.9% or more in the mixture of the obtained metal particles and an organic solvent at 5 to 10 L/min per minute for 0.5 to 10 hours include

The metal of the thus obtained metal nitride (MNx) is silicon, tin, germanium, titanium, aluminum or the like, preferably silicon, and a preferable metal nitride is silicon nitride (SiNx).

x representing the degree of nitride substitution on the metal surface is 0.01 or more and 0.5 or less. When x is less than 0.01, Si is oxidized to SiOx, and it is difficult to increase the actual capacity due to the formation of an irreversible phase such as _{Li 4} SiO _{4 by reaction with lithium during initial charging. When x is more than 0.5, Si reacts with lithium} The opportunity is small and it is difficult to see the effect of the initial capacity increase by the lithium-silicon alloy.

(ii) preparing the composite particles by mixing the metal nitride with one or more materials selected from the group consisting of low-crystalline carbon and amorphous carbon of the first method includes the metal nitride obtained in step (i), and This is a step of obtaining composite particles by mixing low-crystalline carbon or amorphous carbon with an organic solvent and drying the mixture.

The composite particles may be obtained by dry mixing the metal nitride obtained in step (i) and low crystalline carbon or amorphous carbon without using an organic solvent.

The low-crystalline carbon or amorphous carbon may be pitch, or coke, and the pitch may be petroleum-based or coal-based.

In the first method (iii) mixing the composite particles and the core material of the crystalline carbon-based material to obtain a mixture, the composite particles and the crystalline carbon-based material obtained in step (ii) are mixed with an organic solvent. The mixture is obtained by wet mixing, or dry mixing without using an organic solvent. Both wet mixing and dry mixing can be used, but the preferred mixing method is wet mixing. In the case of dry mixing, the mixing uniformity of the composite particles of the shell part and the crystalline carbon-based material of the core part may be deteriorated, so that the effect of capacity and life may be reduced compared to wet mixing in which uniform mixing is achieved.

In addition, the organic solvent of (ii) and (iii) is methanol, ethanol, propanol, isopropanol, cyclohexanol, cyclohexanone, methyl ethyl ketone, ethylene glycol, diethyl carbonate, tetrahydrofuran (THF), dimethyl sulfoxide at least one selected from the group consisting of side (DMSO) and mixtures thereof. The amount of the organic solvent used in steps (ii) and (iii) may be 10 to 90% by weight based on 100 parts by weight of the solid content of each step.

(iv) of the first method, the step of drying the mixture to form the cell part by placing the composite particles in at least one place outside the crystalline carbon-based core part is performed by drying the wet or dry mixture of step (iii) After obtaining the composite of the step before the heat treatment, the composite of the step before the heat treatment is treated for 8 to 15 hours, including heat treatment at a temperature of 800 to 1200° C. under a nitrogen or argon atmosphere, and the treatment time is a temperature increase to the heat treatment temperature It includes time to cool the composite to room temperature after maintenance and heat treatment.

The step of (i) preparing the metal nitride particles of the second method is the same as the step (i) of the first method, and (ii) one selected from the group consisting of metal nitride, low crystalline carbon and amorphous carbon The step of obtaining a mixture by mixing the above materials, and the core part material of the crystalline carbon-based material is not separated from (ii) and (iii) of the first method, but directly metal nitride, low-crystalline carbon or amorphous carbon; and wet mixing all of the crystalline carbon-based materials in an organic solvent or dry mixing without an organic solvent to obtain a mixture, (iii) drying the mixture to form the composite particles in at least one place outside the crystalline carbon-based core part The step of forming the cell part is the same as step (iv) of the first method.

The organic solvent of step (ii) is methanol, ethanol, propanol, isopropanol, cyclohexanol, cyclohexanone, methyl ethyl ketone, ethylene glycol, diethyl carbonate, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO) and at least one selected from the group consisting of mixtures thereof. In addition, the amount of the organic solvent used in step (ii) may be 10 to 90% by weight based on 100 parts by weight of the solid content in step (ii).

The amount of the metal nitride, the amount of low crystalline carbon or amorphous carbon, and the amount of the crystalline carbon-based material used in the first method and the second method are as follows.

First, the amount of the metal nitride used is 1 to 70% by weight, preferably 1 to 50% by weight, based on 100 parts by weight of the total mixing amount of the metal nitride, low crystalline carbon or amorphous carbon, and crystalline carbon-based material.

The amount of low crystalline carbon or amorphous carbon used is 1 to 50 weight %, preferably 5 to 40 weight %, based on 100 parts by weight of the total mixture of metal nitride, low crystalline carbon or amorphous carbon, and crystalline carbon-based material. am.

The amount of the crystalline carbon-based material used is 10 to 95% by weight, preferably 20 to 90% by weight, based on 100 parts by weight of the total mixture of the metal nitride, low-crystalline carbon or amorphous carbon, and the crystalline carbon-based material.

When the amount of metal nitride used, the amount of low crystalline carbon or amorphous carbon used, and the amount of the crystalline carbon-based material used is out of the above range, the capacity and lifespan of the battery are affected.

Another aspect of the present invention is to provide a lithium secondary battery including a negative electrode including the composite negative electrode active material, a positive electrode including a positive electrode active material, and an electrolyte between the negative electrode and the positive electrode.

The negative electrode may be prepared as a negative electrode active material composition by mixing the composite negative electrode active material, binder, and solvent, and if necessary, a conductive material, a filler that suppresses the expansion of the negative electrode, a viscosity modifier, an adhesion promoter, etc. may be added. .

Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), cellulose, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxymethyl cellulose. Regenerated cellulose, polyacrylonitrile, polymethyl methacrylate, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene. Various copolymers and the like may be used, and the amount of the binder used is 0 to 20% by weight based on the total amount of the negative electrode material.

The conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and includes graphite; carbon black; conductive fiber; metal powder; conductive metal powder; A conductive material such as a polyphenylene derivative may be used.

The filler is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery, and may include olefinic polymers such as polyethylene and polypropylene; A fibrous material such as glass fiber or carbon fiber is used.

The viscosity modifier acts to adjust the viscosity for easy application of the anode active material composition on the current collector, and can be mixed up to 30% by weight of the total anode active material composition, and carboxymethyl cellulose, polyvinylidene fluoride, etc. used

The adhesion promoter is for improving adhesion to the current collector, and may be used in an amount of 10% by weight relative to the binder, and oxalic acid, adipic acid, formic acid, acrylic acid derivatives, itaconic acid derivatives, and the like are used.

The solvent may be N-methylpyrrolidone, acetone, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), isopropyl alcohol, acetone, or water, and these solvents may be used alone or as a mixture of two or more.

The amount of the composite anode active material, binder, conductive material, filler, solvent, etc. used in the production of the anode is within the above range, and a typical amount used in the field of lithium secondary batteries is used.

The negative electrode is manufactured by coating and drying the negative electrode active material composition on a current collector, and the current collector is not particularly limited as long as it has conductivity without causing a chemical reaction in the battery, copper, stainless steel, aluminum, nickel, titanium, Copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc. are used.

The positive electrode is prepared by coating and drying a positive electrode active material composition in which a positive electrode active material, a conductive material, a binder, a solvent, etc. are mixed on a current collector.

The cathode active material is not particularly limited, but lithium transition metal oxide may be used in general, Li/CO-based composite oxide such as _{LiCoO 2} , Li/Ni/Co/Mn-based such as _{LiNi x} Co _y Mn ₂ O ₂ and a Li/Ni-based composite oxide such as LiNiO2, and a Li/Mn-based composite oxide such as LiMn2O4, and these may be used alone or in combination of two or more thereof.

The conductive material, binder, solvent, etc. of the positive electrode active material composition may be used in the same manner as the conductive material, binder, and solvent of the negative electrode active material composition, and each component included in the positive electrode active material composition is used in a conventional ratio in the art. .

The electrolyte may include a non-aqueous organic solvent and a metal salt. Examples of the non-aqueous solvent include N-methylpyrrolidone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, and ethyl. Methyl carbonate, gambabutyrolactone, 1,2-dimethoxy ethane, 1,2-diethoxy ethane, tetrahydroxyfuran (THF), 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-di Oxolane, 4-methyl-1,3-dioxane, diethyl ether, formamide, dimethylformamide, dioxohan, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxy ethane, Aprotic organic compounds such as dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carboxylate derivatives, tetrahydrofuran derivatives, ethers, ethyl pyropionate, and methyl propionate Solvents may be used. The metal salt may be a lithium salt as a material easily soluble in the non-aqueous solvent, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB10Cl10, LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2 )2NLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium 4-phenyl borate, and the like can be used.

In addition, a material for improving charge/discharge characteristics, flame retardancy characteristics, nonflammability characteristics, or high temperature storage characteristics may be added to the electrolyte as needed.

The lithium secondary battery manufactured as described above can be used in small and medium-sized battery packs.

A method of manufacturing a composite negative electrode active material according to another aspect of the present invention is as described above.

Hereinafter, the present invention will be described in more detail by way of Examples, but the following Examples are provided to illustrate or specifically describe the present invention, and the scope of the present invention is not limited thereto.

In addition, since the contents not described herein can be sufficiently inferred by those skilled in the art, the description thereof will be omitted.

Examples 1 to 11 and Comparative Example 1 for the preparation of a composite negative electrode active material

<Example 1>

20% of silicon particles having an average particle size of 1 μm were processed through a bead mill together with an isopropyl alcohol solvent for 24 hours. After processing, nano-silicon particles having an average particle diameter of 100 nm were prepared through FE-SEM analysis.

The silicon surface was partially replaced with nitride by bubbling high-purity nitrogen gas to the prepared mixture of nano silicon and isopropyl alcohol at a flow rate of 10 L per minute for 1 hour.

The amount of the prepared nano silicon nitride (SiNx) substituted with nitride was analyzed through XRD analysis, and x of the silicon nitride (SiNx) was 0.1.

Rutger's petroleum pitch (softening point 250° C.) and natural graphite were mixed with the prepared mixture of silicon nitride and isopropyl alcohol, and then isopropyl alcohol was added to the mixture and wet-mixed for 1 hour.

5% by weight of silicon nitride, 20% by weight of Rutger's petroleum pitch, and 75% by weight of natural graphite based on 100 parts by weight of the total amount of the prepared silicon nitride, Rutger's petroleum pitch, and natural graphite, and the iso The total amount of propyl alcohol used was 50% based on the total solid content of the silicon nitride, Rutger's petroleum-based pitch, and natural graphite.

The mixed composite was dried in an oven for 6 hours to obtain a composite before heat treatment.

The composite was heat-treated in a nitrogen atmosphere for 10 hours, including raising the temperature to 1,000°C using a heat treatment furnace, maintaining at 1,000°C, and cooling to room temperature.

A silicon nitride-carbon composite negative active material was prepared through the above process, and coin cell manufacturing, initial discharge capacity and efficiency measurement, and lifespan characteristic evaluation were performed by the following method.

<Example 2>

The silicon surface was partially replaced with nitride by bubbling high-purity nitrogen gas to the prepared mixture of nano silicon and isopropyl alcohol having an average particle size of 100 nm at a flow rate of 5 L per minute for 1 hour. The amount of the prepared nano silicon nitride substituted with nitride was analyzed through XRD analysis, and x of the silicon nitride (SiNx) was 0.05. A silicon nitride-carbon composite anode active material was prepared in the same manner as in Example 1 except for the nano silicon nitride partial substitution method.

<Example 3>

The silicon surface was partially substituted with nitride by bubbling high-purity nitrogen gas to the prepared mixture of nano silicon and isopropyl alcohol having an average particle size of 100 nm at a flow rate of 10 L per minute for 5 hours, and the silicon nitride (SiNx) x was 0.5 . The amount of the prepared nano silicon nitride substituted with the nitride was analyzed through XRD analysis. A silicon nitride-carbon composite anode active material was prepared in the same manner as in Example 1 except for the nano silicon nitride partial substitution method.

<Example 4>

20% of silicon particles having an average particle size of 1 μm were processed for 72 hours through a bead mill together with an isopropyl alcohol solvent. After processing, nano silicon particles having an average particle diameter of 50 nm were prepared through FE-SEM analysis.

A silicon nitride-carbon composite negative active material was prepared in the same manner as in Example 1, except for the method for preparing nano silicon having an average particle size of 50 nm.

<Example 5>

20% of silicon particles having an average particle diameter of 1 μm were processed through a bead mill together with an isopropyl alcohol solvent for 8 hours. After processing, nano-silicon particles having an average particle diameter of 200 nm were prepared through FE-SEM analysis.

A silicon nitride-carbon composite negative active material was prepared in the same manner as in Example 1, except for the method for preparing nano-silicon having an average particle size of 200 nm.

<Example 6>

Silicon nitride-carbon in the same manner as in Example 1, except that silicon nitride, Rutger's petroleum pitch (softening point 250° C.), and natural graphite were used in 10 wt%, 20 wt% and 70 wt%, respectively. A composite negative electrode active material was prepared.

<Example 7>

Silicon nitride-carbon in the same manner as in Example 1, except that silicon nitride, Rutger's petroleum-based pitch (softening point 250° C.), and natural graphite were used in 20 wt%, 20 wt% and 60 wt%, respectively. A composite negative electrode active material was prepared.

<Example 8>

Silicon nitride-carbon in the same manner as in Example 1, except that silicon nitride, Rutger's petroleum-based pitch (softening point 250° C.), and natural graphite were used in 50 wt%, 20 wt% and 30 wt%, respectively. A composite negative electrode active material was prepared.

<Example 9>

Silicon nitride powder was prepared as in Example 1, and Rutger's petroleum-based pitch (softening point 250° C.) was prepared as a powder having an average particle size of 4 μm through jet mill grinding.

5% by weight of the prepared silicon nitride, 20% by weight of the petroleum-based pitch in the powder form, and 75% by weight of the natural graphite based on 100 parts by weight of a total of 100 parts by weight of the prepared silicon nitride, powdered petroleum-based pitch, and natural graphite Put in a shape mill and dry-mixed for 10 minutes to obtain a composite. The obtained composite was directly treated with the same heat treatment process as in Example 1 without a pre-treatment step of drying to obtain a composite before heat treatment to obtain a silicon nitride composite.

A silicon nitride-carbon composite negative active material was prepared in the same manner as in Example 1 using the obtained silicon nitride composite.

<Example 10>

Silicon nitride-carbon in the same manner as in Example 1, except that silicon nitride, Rutger's petroleum pitch (softening point 250° C.), and natural graphite were used in 5 wt%, 10 wt% and 85 wt%, respectively. A composite negative electrode active material was prepared.

<Example 11>

Silicon nitride-carbon in the same manner as in Example 1, except that silicon nitride, Rutger's petroleum pitch (softening point 250° C.), and natural graphite were used in 5 wt%, 30 wt%, and 65 wt%, respectively. A composite negative electrode active material was prepared.

<Comparative Example 1>

20% of silicon particles having an average particle size of 1 μm were processed through a bead mill together with an isopropyl alcohol solvent for 24 hours. After processing, nano-silicon particles having an average particle diameter of 100 nm were prepared through FE-SEM analysis.

The prepared nano-silicon was dried in a drying oven under a general air atmosphere for 1 hour. Through this, a silicon suboxide (SiOx) in which the nano-silicon surface was substituted with an oxide was prepared, and x of the silicon suboxide (SiOx) was 0.1.

A silicon suboxide-carbon composite negative active material was prepared in the same manner as in Example 1 using the silicon suboxide.

Manufacturing of coin cell (battery)

A slurry was prepared by mixing silicon nitride-carbon composite negative electrode active material: binder in ultrapure water at a ratio of 97:3. At this time, as the binder, CMC and SBR were used in a ratio of 1:1. The slurry was uniformly coated on a copper foil, dried in an oven at 80° C. for 2 hours, and further dried in a vacuum oven at 110° C. using a roll press for about 12 hours to prepare a negative electrode plate.

LiPF6 was 1.3M in a solvent in which the prepared negative electrode plate, lithium foil as a counter electrode, a porous polyethylene film as a separator, and ethylene carbonate and diethyl carbonate (DEC) were mixed in a volume ratio of 3:7 A CR2016 coin-type half cell was prepared according to a commonly known manufacturing process using a liquid electrolyte solution dissolved in concentration and containing 10% by weight of fluoro-ethylene carbonate (FEC) relative to the total electrolyte solution.

Measurement of initial discharge capacity and efficiency of coin cells

At 25°C, a constant current was applied until the battery voltage reached 0.01V (vs. Li) at a current of 0.1C rate, and when the battery voltage reached 0.01V, a constant voltage was applied until the current reached a rate of 0.01C to charge. At the time of discharging, it was discharged at a constant current of 0.1C rate until the voltage reached 1.5V (vs.Li).

Evaluation of the lifespan characteristics of coin cells

At 25°C, a constant current was applied until the battery voltage reached 0.01V (vs. Li) at a current of 0.5C rate, and when the battery voltage reached 0.01V (vs. Li), the battery was charged until the current reached 0.01C rate. It was charged by applying a constant voltage. The cycle of discharging at a constant current of 0.5C rate was repeated 50 times until the voltage reached 1.5V during discharging.

The x range of SiNx of Examples 1 to 11, the average diameter of Si particles (D50, average particle diameter), the content of SiNx, the pitch coating method, and the pitch content, and the x range of SiOx of Comparative Example 1, the average diameter of Si ( D50), SiNx content, pitch coating method, and pitch content are summarized in Table 1 below.

Table 1

Table 2 below shows the initial discharge capacity, the initial efficiency, and the capacity retention rate (battery life) after 50 cycles according to Table 1 above.

Table 2

From Table 2, Examples 1 to 11 of the composite anode active material containing a metal nitride of the present invention have capacity (initial discharge capacity), initial efficiency, and/or compared to Comparative Example 1, which is an anode active material containing silicon suboxide. It can be seen that the battery life (capacity retention rate after 50 cycles) is improved or similar, so that the anode active material of the present invention can be used as a battery anode material and exhibits excellent effects.

Claims (26)

a core part comprising a crystalline carbon-based material; and a shell part including composite particles in at least one outer part of the core part, wherein the composite particles include at least one material selected from the group consisting of low-crystalline carbon and amorphous carbon; and metal nitrides that react with lithium; A composite anode active material, characterized in that it has a structure in which a matrix consisting of one component selected from among the other components is included in the matrix. According to claim 1, wherein the crystalline carbon-based material is artificial graphite, natural graphite, carbon fiber, mesocarbon microbead (MCMB), graphite, a mixture of graphite and low crystalline, low crystalline carbon, or low crystalline carbon Composite negative active material, characterized in that it is one of a mixture of and amorphous carbon According to claim 1, wherein the at least one material selected from the group consisting of low-crystalline carbon and amorphous carbon is pitch, or coke, the pitch is petroleum-based or coal-based coal tar pitch; petroleum pitch; or an organic synthetic pitch obtained by polycondensation of a condensed polycyclic aromatic hydrocarbon compound as an organic synthetic pitch or polycondensation of a hetero atom-containing condensed polycyclic aromatic hydrocarbon compound. The composite anode active material of claim 1 , wherein the metal of the metal nitride is silicon, tin, germanium, titanium, or aluminum. The composite anode active material according to claim 4, wherein the metal is silicon and the metal nitride is silicon nitride (SiNx). The composite anode active material according to claim 5, wherein x of the silicon nitride (SiNx) is 0.01 to 0.5. The method according to claim 1, wherein the amount of the metal nitride used is 1 to 70% by weight based on 100 parts by weight of the total mixture amount of at least one material selected from the group consisting of metal nitride, low crystalline carbon and amorphous carbon, and crystalline carbon-based material. A composite negative electrode active material, characterized in that The method of claim 1, wherein the at least one material selected from the group consisting of low-crystalline carbon and amorphous carbon is at least one material selected from the group consisting of metal nitride, low-crystalline carbon and amorphous carbon, and a crystalline carbon-based material. Composite negative active material, characterized in that 1 to 50% by weight based on 100 parts by weight of the total mixing amount According to claim 1, wherein the crystalline carbon-based material is at least one material selected from the group consisting of metal nitride, low-crystalline carbon and amorphous carbon, and 10 to 95 parts by weight based on 100 parts by weight of the total mixture of the crystalline carbon-based material. %, characterized in that the composite negative electrode active material As a method of manufacturing the composite negative active material of claim 1,
(i) preparing metal nitride particles;
(ii) preparing composite particles by mixing the metal nitride with one or more materials selected from the group consisting of low-crystalline carbon and amorphous carbon;
(iii) mixing the composite particles and a core material of a crystalline carbon-based material to obtain a mixture; and
(iv) drying the mixture so that the composite particles are disposed on at least one outside of the crystalline carbon-based core part to form a cell part; The method according to claim 10, wherein the metal particles prepared in step (i) have an average particle diameter of 30 nm to 250 nm. 11. The method of claim 10, wherein the mixing of steps (ii) and (iii) uses an organic solvent, the organic solvent is methanol, ethanol, propanol, isopropanol, cyclohexanol, cyclohexanone, methyl ethyl ketone, ethylene glycol , diethyl carbonate, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), and at least one selected from the group consisting of mixtures thereof, and the amount of the organic solvent used is the solid content of each step in steps (ii) and (iii). The method of claim 1, characterized in that 10 to 90% by weight based on 100 parts by weight of the composite negative active material 11. The method of claim 10, wherein the mixing of steps (ii) and (iii) is dry mixing without using an organic solvent. As a method for producing the composite negative electrode active material of claim 1,
(i) preparing metal nitride particles;
(ii) obtaining a mixture by mixing at least one material selected from the group consisting of metal nitride, low-crystalline carbon and amorphous carbon, and a core material of a crystalline carbon-based material; and
(iii) drying the mixture so that the composite particles are disposed on at least one outside of the crystalline carbon-based core part to form a cell part; The method according to claim 14, wherein the metal particles prepared in step (i) have an average particle diameter of 30 nm to 250 nm. 15. The method of claim 14, wherein the mixing in step (ii) uses an organic solvent, the organic solvent is methanol, ethanol, propanol, isopropanol, cyclohexanol, cyclohexanone, methyl ethyl ketone, ethylene glycol, diethyl carbonate , tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), and at least one selected from the group consisting of mixtures thereof, and the amount of the organic solvent used is 10 to 90% by weight based on 100 parts by weight of the solid content in step (ii). A method for producing the composite negative active material of claim 1, characterized in that 15. The method of claim 14, wherein the mixing in step (ii) is dry mixing without using an organic solvent. A composite anode active material, characterized in that it is prepared by the method of any one of claims 10 to 17 A negative electrode assembly comprising the composite negative electrode active material according to any one of claims 1 to 9 A negative electrode assembly comprising the composite negative electrode active material according to claim 18 The negative electrode for a secondary battery, characterized in that the negative electrode assembly of claim 19 is coated on a current collector The negative electrode for a secondary battery, characterized in that the negative electrode assembly of claim 20 is coated on a current collector A secondary battery, characterized in that it contains the negative electrode for a secondary battery of claim 21 or 22 The secondary battery according to claim 23, wherein the battery is a secondary battery. A battery pack, characterized in that the secondary battery of claim 24 is used as a unit battery The battery pack according to claim 25, wherein the battery pack is for automobiles, power storage, or mobile devices.

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