KR101480216B1 - Silicon oxide anode active material, method for preparing the same, and secondary battery using the same - Google Patents

Abstract

The present invention relates to a silicon oxide-based particle; And a carbon coating layer formed on the surface of the silicon oxide-based particles. The present invention also relates to a secondary battery using the negative active material.

Description

TECHNICAL FIELD [0001] The present invention relates to a silicon oxide based anode active material, a method of manufacturing the same, and a secondary battery using the same. BACKGROUND ART [0002]

The present invention relates to a silicon oxide based negative electrode active material, a method for producing the same, and a secondary battery using the negative electrode active material and having a high capacity and excellent charge / discharge characteristics and life characteristics.

Recently, interest in energy storage technology is increasing. The research and development of electrochemical devices is becoming more and more specific as the applications are expanded to cell phones, camcorders, notebook PCs and even the energy of battery automobiles. Among the electrochemical devices, development of rechargeable secondary batteries is of particular interest. In recent years, research and development of new electrodes and batteries are underway to improve capacity and energy density.

At present, lithium secondary batteries are attracting attention as compared with secondary batteries such as Ni-MH, Ni-Cd, and sulfuric acid-lead batteries. This is because the operating voltage is high and the energy density is much larger.

Generally, a lithium secondary battery is manufactured by using a material capable of intercalation and deintercalation of lithium ions as a cathode and an anode, and filling an organic electrolyte or a polymer electrolyte between an anode and a cathode. The lithium secondary battery generates electrical energy by an oxidation reaction and a reduction reaction when lithium ions are inserted and removed from the positive electrode and the negative electrode.

BACKGROUND ART [0002] Carbon-based materials, which are advantageous in terms of lifetime and cost of a charge / discharge cycle, are mainly used as an anode active material composing a cathode of a lithium secondary battery. However, since the upper limit of the theoretical capacity of the carbonaceous anode active material is limited to about 372 mAh / g, application to a high capacity lithium secondary battery is limited.

In order to meet such a demand, the use of a metal such as silicon (Si), tin (Sn), aluminum (Al), germanium (Ge), lead (Pd), zinc (Zn) Research is underway. Such a material can absorb and release more lithium ions than the carbon-based negative electrode active material, and is suitable for manufacturing a battery having a high capacity and a high energy density. Particularly, silicon is a material having a high theoretical capacity of about 4,200 mAh / g.

However, in the case of a silicon anode active material, its volume expands by about 300% or more by charging. In addition, cracks are generated inside and on the surface of the electrode due to mechanical stress applied at this time, and when the lithium ions are discharged by discharge, the volume shrinks. If the charge / discharge cycle is repeated in this way, the active material is separated from the current collector, and electrical insulation is generated due to the space between the silicon particles, so that the life of the battery may be drastically deteriorated. It is known that the particle size change of the active material is further enhanced by the interfacial reaction with the electrolyte.

Thus, in the past, various attempts have been made to overcome the disadvantages of the silicon anode active material. For example, there are a method of producing a negative electrode material by mixing graphite particles and silicon particles or lithium powder, a method of micronizing the general-purpose silicon powder in a nitrogen atmosphere to mix silicon microparticles and graphite, a method of mixing amorphous Si- And a method of manufacturing a material.

However, these methods are not only complicated in the production process, but also the negative electrode active materials produced by these methods are not high in electrical conductivity to satisfy a high rate charge / discharge. Further, it is difficult to control the structural change due to the volume change of the active material through the continuous charge / discharge reaction, and there is still a problem that the capacity and cycle performance of the battery are decreased because of easy separation from the active material and current collector.

Disclosed is a silicon oxide-based anode active material capable of improving the capacity, charge-discharge characteristics, and life characteristics of a battery, and a method for manufacturing the same.

It is another object of the present invention to provide a secondary battery using the negative electrode active material.

In order to accomplish the above object, the present invention provides a method for forming a chelated silicon precursor by mixing a non-aqueous solvent with a silicon-containing reactant and a chelating agent under an inert gas atmosphere and reacting at a room temperature to form a chelated silicon precursor; And heat treating the precursor in a mixed gas atmosphere of a reducing gas and an inert gas. The present invention also provides a method for producing a silicon oxide based negative electrode active material.

Wherein the silicon containing reactant is selected from the group consisting of halogenated silicon and halogenated silane.

The chelating agent preferably includes a compound containing a carboxyl group, and the compound containing a carboxyl group is preferably citric acid.

The mixing ratio of the silicon-containing reactant and the chelating agent is preferably 1: 0.01 to 2 molar ratio.

It is preferable that the non-aqueous solvent is a glycol ether-based solvent.

And the heat treatment step is performed at a temperature of 600 to 1,100 ° C.

In addition, the present invention provides a silicon oxide-based anode active material produced by the above production method.

In addition, the present invention provides a negative electrode comprising the negative electrode active material; anode; Electrolyte; And a secondary battery.

The process for preparing the negative electrode active material according to the present invention is very simple in a one-step process. Since the precursor formed in the production of the negative electrode active material can be easily handled in air and easily dissolved in water, Since uniform mixing is performed, application to a secondary battery is very high. As described above, the use of a low-cost solvent that is easy to handle in air, such as water or alcohol, is inexpensive.

In addition, the anode active material produced by the production method of the present invention has nanoparticles having a diameter of several tens of nanometers and a secondary particle diameter of several hundred nanometers to several micrometers.

In addition, since the carbon coating layer is formed on the surface of the silicon particles of the negative electrode active material of the present invention, it is possible to prevent deterioration of the capacity of the battery due to the interface reaction with the electrolyte and to improve the electric conductivity, Life characteristics can also be improved.

1 is a cross-sectional view of a negative electrode active material according to the present invention.
2A is a scanning electron microscope (SEM) photograph of the negative electrode active material prepared in Example 1. FIG.
FIG. 2B is an enlarged scanning electron micrograph of the negative active material prepared in Example 1. FIG.
FIG. 3A is a transmission electron microscope (TEM) photograph of the negative electrode active material prepared in Example 1. FIG.
FIG. 3B is a photograph showing a selected area electron diffraction (SAED) pattern of the negative electrode active material prepared in Example 1. FIG.
4 is a graph showing charge and discharge of the negative electrode manufactured in Example 1. Fig.
5 is a graph showing a change in capacitance during charge and discharge of the negative electrode manufactured in Example 1. FIG.
6 is a graph showing the charge / discharge cycle performance of the negative electrode manufactured in Example 1. FIG.
7 is a graph showing the coulombic efficiency of the negative electrode prepared in Example 1. FIG.

Hereinafter, the present invention will be described in detail.

The negative active material of the present invention may be prepared by mixing a non-aqueous solvent with a silicon-containing reactant and a chelating agent in an inert gas atmosphere, and then reacting at a room temperature to form a chelated silicon precursor; And subjecting the precursor to a reduction heat treatment in an atmosphere of a mixed gas of a reducing gas and an inert gas.

First, a silicon-containing reactant and a chelating agent are added to a non-aqueous solvent under an inert gas atmosphere, and then reacted at room temperature to form a chelated silicon precursor (hereinafter, step S100).

By reacting the silicon-containing reactant and the chelating agent in the nonaqueous solvent, the reaction can be uniformly performed as a whole. The non-aqueous solvent is preferably a glycol ether solvent. Examples of the glycol ether solvent include 1,2-dimethoxy ethane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, Ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, Diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, polyethylene glycol monomethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether, Ether, triethylene glycol ethylene glycol moiety N-methyl ether acetate, ethylene glycol monoethyl ether acetate, and the like, but are not limited thereto.

The content of the glycol ether solvent is not particularly limited as long as it can easily dissolve the silicon-containing reactant and the chelating agent.

The silicon-containing reactant is not particularly limited as long as it is a compound capable of supplying silicon (Si), and examples thereof include halogenated silicon and halogenated silane. Specific examples thereof include silicon tetrachloride (SiCl ₄ ), trichlorosilane, But is not limited thereto. According to one example of the present invention, silicon tetrachloride (SiCl ₄ ) can be used as the Si-containing reactant.

The silicon-containing reactant and the chelating agent undergo a chelating reaction at room temperature to produce a chelate compound. Since the chelating reaction is performed at room temperature, there is an advantage that it can be performed very simply.

The chelating agent usable in the present invention is not particularly limited as long as it is capable of coordinating with the silicon cations of the silicon-containing reactant to form a chelate compound. The chelating agent is preferably a compound containing a carboxyl group.

Specifically, examples of the compound containing a carboxyl group include citric acid, succinic acid, tartaric acid, maleic acid, fumaric acid, ethylenediaminetetraacetic acid (ethylenediaminetetraacetic acid ), But the present invention is not limited thereto.

According to an embodiment of the present invention, in step S100, chelated silicon may be induced in a liquid phase by mixing silicon tetrachloride, which is a silicon-containing reagent, and citric acid, a chelating agent. Specifically, Si ⁴⁺ of silicon tetrachloride reacts with the carboxyl group (-COOH) of citric acid to form Si-citrate and HCl at the molecular level, which is a chelate compound.

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Here, the mixing ratio of the silicon-containing reactant and the chelating agent is not particularly limited, but a chelate compound can be formed when the molar ratio of the silicon-containing reactant: chelating agent is 1: 0.01 to 2, The carbon layer is formed, so that it is effective for the stability and lifetime of the electrode due to the effect of inhibiting the volume expansion.

The step S100 is preferably performed under an inert gas atmosphere. Examples of the inert gas include, but are not limited to, nitrogen gas, argon gas, and helium gas.

Meanwhile, the method of manufacturing an anode active material according to the present invention may include a step of removing the glycol ether solvent, the unreacted halogen ion and by-products after the step S100. For example, when the reaction product obtained in the step S100 is heated and dried, the glycol ether solvent, the unreacted halogen and the by-product are evaporated and removed, and only the precursor is obtained.

Then, the precursor formed in the step S100 is subjected to a reduction heat treatment (hereinafter, step S200) in an atmosphere of a mixed gas of a reducing gas (H ₂ ) and an inert gas.

In step S200, Si ⁴⁺ of the precursor (for example, Si-citrate) is partially reduced through the reduction heat treatment to produce silicon oxide (SiO _x ). In addition, some carbon and oxygen are oxidized to carbon dioxide or carbon monoxide and evaporated, so that only carbon remains on the surface of the produced silicon oxide particles, so that a silicon oxide based negative electrode active material coated with carbon on its surface can be obtained. The oxygen content x of the silicon oxide (SiO _x ) is preferably 0 < x? 2.

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The heat treatment temperature is not particularly limited, but it is preferable to carry out the heat treatment at a temperature in the range of 600 to 1,100 DEG C in order to form a carbon layer by decomposing the citrate and to suppress the growth of the grain size and to obtain a preferable structure.

The heat treatment time is not particularly limited, but is preferably performed within 0.5 to 12 hours.

The process for preparing the negative electrode active material of the present invention is very simple because it is a one-step process for preparing silicon oxide and coating carbon, and the precursor formed in the production of the negative electrode active material can be easily handled in the air , Since they can be easily dissolved in water, uniform mixing is performed, so that the applicability to a secondary battery is very high.

The negative electrode active material 10 thus prepared includes silicon oxide particles 11 and a carbon coating layer 12 formed on the surface of the silicon oxide particles as shown in FIG.

The thickness of the carbon coating layer 12 is not particularly limited, but is preferably 1 nm to 30 nm.

Although the diameter of the negative electrode active material 10 is not particularly limited, the diameter of the primary particles is nanoparticles having a diameter of several nanometers to several tens of nanometers. The primary particles are aggregated and have a diameter of several hundred nanometers to tens of micrometers Thereby forming secondary particles.

Since the carbon coating layer 12 is formed on the surface of the silicon oxide-based particles, it is possible to provide an improved electric conductivity, and the silicon oxide-based particles 11 can receive a change in volume that occurs when the silicon oxide- And the interfacial reaction with the electrolytic solution can be blocked, so that the charge / discharge performance of the battery can be improved. In addition, since the negative electrode active material is stable in air and has excellent dispersibility in a solvent such as water and alcohol, it is possible to produce negative electrode slurry in air using a solvent such as water or alcohol.

The negative electrode active material of the present invention as described above is crystalline or amorphous. When the amorphous negative electrode active material is applied to a secondary battery, the life of the battery can be improved because the crystal structure change strain is small during charging and discharging of the battery.

<Secondary Battery>

In the present invention, the cathode can be produced by a conventional method known in the art. For example, a slurry is prepared by mixing and stirring a binder and a solvent, and if necessary, a conductive material and a dispersant in the negative electrode active material of the present invention, applying the slurry to a current collector of a metallic material, .

Non-limiting examples of the solvent that can be used in the production of the negative electrode include dimethyl sulfoxide (DMSO), N-methyl pyrrolidone (NMP), dimethylformamide (DMF) . Of these, N-methyl pyrrolidone (NMP) or water is preferably used as a solvent.

Non-limiting examples of usable binders include polyvinylidene fluoride (PVdF), polyamide-imide (PAI), polyacrylic acid (PAA), styrene-butadiene rubber rubber, SBR, carboxymethylcellulose (CMC), polytetrafluoroethylene (PTEE), polyvinyl acetate, polyethylene oxide, polypyrrolidone, polyvinyl alcohol, and polyacrylonitrile. These may be used alone or in combination of two or more.

The content of the binder is not particularly limited, but it is preferably about 3 to 40 parts by weight relative to 100 parts by weight of the negative electrode in order to strongly bond the negative electrode active materials.

As the conductive material, carbon black may be generally used. Commercially available products such as acetylene black series (Chevron Chemical Company or Gulf Oil Company products), Ketjen Black EC series (Armak Company products, etc.), Vulcan XC-72 (Cabot Company products), and Super P (manufactured by MMM).

Such a conductive material may improve the cycle life of the battery when used, but it may lower the capacity of the battery. For this reason, the content of the conductive material is preferably about 10 to 40 parts by weight based on 100 parts by weight of the whole cathode.

The collector of the metal material is a metal having high conductivity, and any material can be used as long as the slurry of the negative electrode active material can be easily adhered, and is not reactive in the voltage range of the battery. Typical examples thereof include a mesh, a foil, and a nonwoven fabric made of copper, nickel, stainless steel or the like. Among these, a copper foil having a thickness of about 8 탆 or more is preferable.

The method of applying the slurry to the current collector is also not particularly limited. For example, it can be applied by a method such as doctor blade, dipping, and brushing. The amount to be applied is not particularly limited, but it is preferable that the thickness of the active material layer formed after removal of the solvent or the dispersion medium is in the range of usually 0.005 to 5 mm, preferably 0.01 to 2 mm.

The method of removing the solvent or the dispersion medium is not particularly limited. However, it is preferable that the solvent or the dispersion medium is dispersed in the range of the speed as fast as the stress concentration occurs and cracks are generated in the active material layer or the active material layer is not peeled from the current collector It is preferable to use a method of removing and adjusting to be volatilized. And may be dried in a vacuum oven at 50-200 [deg.] C for 0.5-3 days, without limitation.

The electrode active material of the present invention can be used in all devices that perform electrochemical reactions. For example, there are all kinds of primary batteries, secondary batteries, fuel cells, solar cells or capacitors, among which secondary batteries are preferable.

The secondary battery of the present invention can be manufactured by a conventional method known in the art including an electrode manufactured using the electrode active material of the present invention. For example, a porous separator may be interposed between the anode and the cathode, and an electrolytic solution may be added to the separator. The secondary battery includes a lithium ion secondary battery, a lithium polymer secondary battery or a lithium-air secondary battery, a lithium ion secondary battery, a sodium polymer secondary battery, a sodium-air secondary battery, and a silicon-air secondary battery.

The positive electrode to be applied to the secondary battery of the present invention is not particularly limited, and the positive electrode active material may be bonded to the positive electrode current collector according to a conventional method known in the art. As the cathode active material, a conventional cathode active material that can be used for a cathode of a conventional secondary battery can be used, and examples thereof include LiM _x O _y (M = Co, Ni, Mn, Co _a Ni _b Mn _c ) Lithium manganese composite oxides such as LiMn ₂ O ₄ , lithium nickel oxides such as LiNiO ₂ , lithium cobalt oxides such as LiCoO ₂ , and manganese, nickel, and cobalt of these oxides, (For example, LiMPO ₄ (M = Fe, Mn, Co, Ni, or a mixture thereof)) or the like. Preferably _{LiCoO 2, LiNiO 2, LiMnO 2} , LiMn 2 O 4, Li 1 + x (Ni a Co b Mn c) O 2 (0 <x <1, 0 <a <1, 0 <b <1, 0 <c <1, a + b + c = 1), LiNi 1 - Y Co Y O 2, LiCo 1-Y O 2, LiCo 1 - Y Mn Y O 2, LiNi 1 - Y Mn Y O 2 ( here _{in, 0≤Y≤1), Li (Ni a} Co b Mn c) O 4 (0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), Li 1 _{+ x Mn 2 - Z M Z} O 4 ( here, 0 <x <1, M = Fe, Mn, Co, Ni, Cr, Al, Zn, Zr, Ti, Cs, 0 <Z <2), LiM _{1 - x} N _x PO ₄ L (M = Fe, Mn, Co, Ni, N = Fe, Mn, Co, Ni etc.), or a mixture thereof. Non-limiting examples of the positive electrode current collector include foil produced by aluminum, nickel, or a combination thereof.

The electrolytic solution may include a non-aqueous solvent and an electrolyte salt.

The nonaqueous solvent is not particularly limited as long as it is used as a nonaqueous solvent for a nonaqueous electrolyte solution, and a cyclic carbonate, a linear carbonate, a lactone, an ether, an ester or a ketone may be used, and a carbonate solvent is preferably used.

Examples of the cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), fluoroethylene carbonate (FEC) and butylene carbonate (BE). Examples of the linear carbonate include diethyl carbonate (DEC) (DMC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), and methyl propyl carbonate (MPC). Examples of the lactone include gamma butyrolactone (GBL), and examples of the ether include dibutyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane . Examples of the esters include n-methyl acetate, n-ethyl acetate, methyl propionate, methyl pivalate and the like, and the ketone is polymethyl vinyl ketone. These non-aqueous solvents may be used alone or in combination of two or more.

The electrolyte salt is not particularly limited as long as it is usually used as an electrolyte salt for a nonaqueous electrolyte. Non-limiting examples of the electrolyte salt is A ⁺ B ^- A salt of the structure, such as, A ⁺ is included in the ion consisting of alkali metal cations or a combination thereof, such as Li ^+, Na ⁺ B ^- is PF ₆ ^-, BF _{^{4 -, Cl -, Br -}} , I -, ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF 3 SO 2) 2 -, C (CF 2 SO 2) 2 ^- &lt; / RTI &gt; or a combination thereof. In particular, a lithium salt is preferable. These electrolyte salts may be used alone or in combination of two or more.

The secondary battery of the present invention may include a separator. The separating membrane that can be used is not particularly limited, but a porous separating membrane is preferable, and examples thereof include a polypropylene-based, polyethylene-based, or polyolefin-based porous separating membrane.

The secondary battery of the present invention is not limited in outer shape, but may be cylindrical, square, pouch type, coin or the like using a can.

Hereinafter, the present invention will be described in more detail by way of Examples, Comparative Examples and Experimental Examples. However, the following Examples, Comparative Examples and Experimental Examples are for illustrating the present invention, and the scope of the present invention is not limited thereto.

&Lt; Example 1 >

1-1. Negative active material  Produce

Silicon tetrachloride (SiCl ₄ ) and citric acid were added to 1,2-dimethoxyethane at a molar ratio of 1: 0.1 in an argon (Ar) gas atmosphere. The mixed solution was stirred to induce the chelating reaction at room temperature.

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After completion of the reaction, the reaction product was heated in a vacuum oven at 50 DEG C for 24 hours to evaporate 1,2-dimethoxyethane and HCl and dry to obtain a Si-citrate precursor. The obtained Si-citrate precursor was heat-treated at 900 ° C for 5 hours in a mixed gas (H ₂ / Ar) atmosphere to obtain carbon-coated silicon oxide. At this time, the Si ⁴⁺ of the precursor is partially reduced through the heat treatment to generate silicon oxide (SiO _x ), and the citrate of the Si-citrate precursor is decomposed and oxidized to CO, CO ₂ and H ₂ O, Carbon-only silicon oxide was left on the surface of the resulting silicon oxide to obtain a carbon-coated silicon oxide anode active material in a one-step process.

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A scanning electron microscope (SEM) photograph and a transmission electron microscope photograph of the negative electrode active material obtained above are shown in FIGS. 2 and 3, respectively. In FIG. 2, it was found that the spherical primary particles having a diameter of 30 to 60 nm aggregated to form spherical secondary particles having a diameter of 400 to 600 nm.

In Fig. 3, spherical silicon oxide powder primary particles having a diameter of about 30 to 60 nm were observed as the negative electrode active material. As shown in the SAED (Selected Area Electron Diffraction) pattern, no diffraction due to the crystal structure was observed and only a circular pattern was observed, indicating that the prepared silicon oxide anode active material was amorphous.

1-2. Manufacture of Secondary Battery

A negative electrode active material prepared in Example 1-1, a carbon conductive material as a conductive material, and polyacrylic acid as a binder were mixed in a weight ratio of 70: 15: 15, and these were added to water as a solvent to prepare an anode slurry Respectively. The prepared negative electrode slurry was applied to a copper current collector, and then the coated negative electrode slurry was dried at 60 캜 and dried at 110 캜 for 12 hours to prepare a negative electrode.

Ethylene carbonate (EC) and diethylene carbonate (DEC) were mixed in a volume ratio of 30:70, and 1 M of LiPF ₆ and tris (2-methoxyethoxy) vinylsilane [tris (2-methoxyethoxy) vinylsilane] was added thereto to prepare a nonaqueous electrolytic solution.

The negative electrode prepared as described above was used as a working electrode, lithium metal was used as a counter electrode, a separator polypropylene was interposed between both electrodes, and the nonaqueous electrolyte solution prepared above was injected to form lithium The secondary battery was completed.

<Experimental Example 1>

The lithium secondary battery manufactured in Example 1 was charged and discharged in the range of 0.01 to 2 V, and the results are shown in FIG.

As can be seen in FIG. 4, a plateau was observed at about 0.27 to 0.01 V during the cathodic process. This is due to the process of inserting lithium into the amorphous anode active material. On the other hand, a broad peak shape of about 0.3 to 0.4 V was observed during the anodic process. This is due to the process in which lithium is desorbed from the amorphous anode active material of Li _X Si. As a result, it was found that the anode active material prepared in Example 1-1 was amorphous, which was the same as the transmission electron microscopic analysis result.

<Experimental Example 2>

The lithium secondary battery manufactured in Example 1 was charged and discharged in a constant current-constant voltage (CC-CV) manner at a current of 0.045 A / g in a range of 0.01 to 2 V, and the measurement results are shown in FIGS. .

As can be seen from FIG. 5, when the negative electrode manufactured in Example 1-1 was applied with current while keeping the voltage down to 0.01 V by a constant current-constant voltage (CC-CV) method during one charging, The irreversible capacity in which lithium oxide (Li ₂ O), lithium silicate (Li _y SiO _x ) and silicon (Si) are formed by the reaction of the active material with lithium and a solid electrolyte interphase (SEI) layer is formed by the electrolyte decomposition reaction Occurs. It has been observed that the discharge capacity increases from one cycle to two cycles. This results in an increase in the activation of the electrode for the alloying reaction with lithium during the cycle discharge of two cycles, and the lithium oxide (Li ₂ O) and lithium silicate (Li _y SiO _x ) irreversibly generated in one cycle charging And the volume change occurring during lithium interloan reaction. It can be seen that the discharge capacity is maintained well up to 20 cycles.

As can be seen from Figs. 5 to 7, the negative electrode prepared in Example 1-1 had an initial charge capacity of about 950 mAh / g, an initial discharge capacity of about 476 mAh / g, an initial coulombic efficiency of about 50.1% But the coulombic efficiency was increased to about 90.7% or more from the second cycle and maintained at 98% up to 20 cycles while maintaining the discharge capacity of about 520 to 598 mAh / g in the second to fifth cycles. As a result, It can be seen that the desorption process is reversible. Also, the capacity retention ratio was 88% higher than the maximum discharge capacity.

In the conventional negative electrode active material, the surface area of the negative electrode active material increases due to the volume change of the negative electrode active material and the particle brittle phenomenon occurring when the lithium is inserted and removed, so that the interface of the negative electrode active material with the electrolyte increases, so that the reduction decomposition reaction of the electrolyte occurs actively. Therefore, degradation of performance occurs rapidly in 10 cycles because irreversible SEI formation is intensified and additional charging capacity is generated and electrical insulation is caused by particle brittleness.

However, the retaining ratio of the negative electrode active material of the present invention after the first cycle, particularly 20 cycles, was about 88% of the initial discharge capacity, and the coulomb efficiency was maintained at about 98%. From the above, it was found that the cycle performance of the secondary battery can be improved due to the carbon coating layer formed on the surface of the silicon oxide particles even when the negative active material according to the present invention is repeatedly charged and discharged.

10: anode active material
11: Silicon oxide-based particles
12: Carbon coating layer

Claims (13)

Mixing a non-aqueous solvent with a silicon-containing reactant and a chelating agent in an inert gas atmosphere, and then reacting at a room temperature to form a chelated silicon precursor; And
The precursor is subjected to reduction heat treatment at 900 to 1100 캜 in a mixed gas atmosphere of a reducing gas and an inert gas to form silicon oxide particles (SiO _x , 0 < x? 2) Decomposing the chelating agent component to form a carbon coating layer;
Based negative electrode active material. The method according to claim 1,
Wherein the silicon-containing reactant is selected from the group consisting of halogenated silicon and halogenated silane. The method according to claim 1,
Wherein the chelating agent comprises a compound containing a carboxyl group. The method of claim 3,
Wherein the carboxyl group-containing compound comprises citric acid. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt; The method according to claim 1,
Wherein the mixing ratio of the silicon-containing reactant and the chelating agent is in a molar ratio of 1: 0.01 to 2. The method for producing a silicon oxide based anode active material according to claim 1, The method according to claim 1,
Wherein the non-aqueous solvent comprises a glycol ether-based solvent. delete A method for producing a silicon oxide-based particle (SiO _x , 0 < x? 2) and a silicon coating layer formed on the surface of the silicon oxide-based particle, which is produced by the manufacturing method according to any one of claims 1 to 6, Oxide based negative electrode active material. delete delete 9. The method of claim 8,
Wherein the silicon oxide-based particles (SiO _x , 0 < x? 2) are crystalline or amorphous. A negative electrode comprising the silicon oxide based negative electrode active material according to claim 8;
anode;
Electrolyte; And
Membrane
And a secondary battery. A negative electrode comprising the silicon oxide based negative electrode active material according to claim 11;
anode;
Electrolyte; And
Membrane
And a secondary battery.

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