WO2015099233A1

WO2015099233A1 - Anode active material, secondary battery comprising same and method for manufacturing anode active material

Info

Publication number: WO2015099233A1
Application number: PCT/KR2013/012391
Authority: WO
Inventors: 조종수; 안형기
Original assignee: 엠케이전자 주식회사
Priority date: 2013-12-27
Filing date: 2013-12-30
Publication date: 2015-07-02
Also published as: KR20150077053A

Abstract

The present invention relates to an anode active material, a secondary battery comprising the same and a method for manufacturing the anode active material and, more particularly, to: an anode active material for a secondary battery, including a ceramic coating layer having a thickness of about 1 nm to about 50 nm on the surface of a core comprising a silicon single phase and an alloy phase; the secondary battery comprising the same; and a method for manufacturing the anode active material. The anode active material for the secondary battery, according to the present invention, has excellent lifespan and electrochemical characteristics.

Description

Anode active material, secondary battery comprising same and method for manufacturing anode active material

The present invention relates to a negative electrode active material, a secondary battery including the same, and a method of manufacturing the negative electrode active material, and more particularly, to a negative electrode active material having excellent lifespan characteristics and electrochemical properties, and a secondary battery and a method of manufacturing the negative electrode active material. will be.

Recently, lithium secondary batteries are not only used as a power source for portable electronic products such as mobile phones and laptop computers, but also used as medium-large power sources such as hybrid electric vehicles (HEVs) and plug-in HEVs. The field of application is expanding rapidly. As the application field expands and the demand increases, the appearance and size of the battery are also changed in various ways, and more excellent capacity, life, and safety than the characteristics required in the existing small battery are required.

A lithium secondary battery is generally manufactured by using a material capable of intercalation and deintercalation of lithium ions as a cathode and an anode, and installing a porous separator between the electrodes and then injecting an electrolyte solution. And electricity is generated or consumed by a redox reaction by insertion and desorption of lithium ions at the positive electrode.

Graphite, which is a negative electrode active material widely used in a conventional lithium secondary battery, has a layered structure and thus has very useful characteristics for insertion and desorption of lithium ions. Graphite theoretically has a capacity of 372 mAh / g, but as the demand for high capacity lithium batteries increases recently, a new electrode that can replace graphite is required. Accordingly, active research for commercialization of electrode active materials forming an electrochemical alloy with lithium ions such as silicon (Si), tin (Sn), antimony (Sb), and aluminum (Al) as a high capacity negative electrode active material is actively conducted. It is becoming. However, silicon, tin, antimony, aluminum, etc. have the characteristics of increasing / decreasing the volume during charging / discharging through the formation of an electrochemical alloy with lithium. The electrode which introduce | transduced active materials, such as aluminum, has the problem of degrading electrode cycle characteristics. In addition, such a volume change causes cracks on the surface of the electrode active material, and continuous crack formation leads to micronization of the electrode surface, thereby degrading cycle characteristics.

The first object of the present invention is to provide a negative active material for a secondary battery having excellent life characteristics and electrochemical characteristics.

The second object of the present invention is to provide a secondary battery having excellent life characteristics and electrochemical characteristics.

The third object of the present invention is to provide a method for producing a negative active material for a secondary battery having excellent life characteristics and electrochemical characteristics.

The present invention to achieve the first object, a silicon single phase; And it has a core comprising an alloy phase, to provide a negative electrode active material for a secondary battery comprising a ceramic coating layer of about 1 nm to about 50 nm thick on the surface of the core. In this case, the alloy phase may be an alloy phase of silicon with one or more metal elements selected from the group consisting of titanium, nickel, copper, iron, manganese, aluminum, zirconium, chromium, lanthanum, tin, cerium, cobalt, and zinc.

In addition, in example embodiments, the ceramic coating layer may include aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), silicon oxide (SiO ₂ ), or boron oxide (B ₂ O ₃ ). In addition, the thickness of the ceramic coating layer may be about 3 nm to about 25 nm.

In addition, in the exemplary embodiments, the ceramic coating layer may be formed conformally on the surface of the core. In particular, the ceramic coating layer may be formed by atomic layer deposition (ALD). In addition, the ratio of the thinnest thickness to the thickest thickness of the ceramic coating layer may be about 0.75 or more.

In the above exemplary embodiments, the fraction of the silicon single phase is about 10 wt% to about 60 wt%, and the fraction of the alloy phase is about 40 wt% to the relative content of the silicon single phase and the alloy phase. About 90% by weight.

The present invention provides a secondary battery including a positive electrode including a positive electrode active material, a separator, a negative electrode including a negative electrode active material and an electrolyte to achieve the second object. In particular, the negative active material may include a ceramic coating layer having a thickness of about 1 nm to about 50 nm on the surface of the core including the silicon single phase and the alloy phase. In addition, the alloy phase may be an alloy phase of silicon with one or more metal elements selected from the group consisting of titanium, nickel, copper, iron, manganese, aluminum, zirconium, chromium, lanthanum, tin, cerium, cobalt, and zinc.

In order to achieve the third object of the present invention, silicon is mixed with at least one metal element selected from the group consisting of titanium, nickel, copper, iron, manganese, aluminum, zirconium, chromium, lanthanum, tin, cerium, cobalt and zinc. Doing; Grinding the mixture to form a core; And it provides a method for producing a negative electrode active material for a secondary battery comprising the step of forming a ceramic coating layer on the surface of the core by atomic layer deposition (ALD).

The forming of the ceramic coating layer may include supplying a metal precursor into an ALD reaction chamber in which the core is located to chemisorb the metal precursor to the surface of the core; Purging the ALD reaction chamber to remove excess metal precursor chemisorbed on the surface of the core from the ALD reaction chamber; Supplying an oxidant into the ALD reaction chamber to form a monolayer of metal oxide on the surface of the core; And purging the ALD reaction chamber as one cycle to remove the remaining unreacted oxidant remaining with the metal precursor from the ALD reaction chamber.

In this case, the forming of the ceramic coating layer may include one to ten cycles of the deposition cycle.

The method may further include heat treating the negative active material for the secondary battery after forming the ceramic coating layer. The heat treatment may be performed for about 30 minutes to about 120 minutes at a temperature of about 200 ℃ to about 500 ℃.

In the exemplary embodiments, in the step of mixing the metal element and silicon, the content of the metal element is about 10% to about 70% by weight, the content of the silicon is about 30% to about 90% by weight May be%.

The negative electrode active material for a secondary battery according to the present invention has an effect having excellent life characteristics and electrochemical characteristics.

1 is a schematic view showing a cross section of a negative electrode active material for a secondary battery according to an embodiment of the present invention.

2 is a flowchart illustrating a method of manufacturing a negative electrode active material for a secondary battery according to an embodiment of the present invention.

3 is a conceptual view for explaining the rapid cooling solidification using a melt spinner.

4 is a timing diagram illustrating a cycle of forming a ceramic coating layer according to an embodiment of the present invention.

5 is an exploded perspective view illustrating a rechargeable battery including a negative active material according to an embodiment of the present invention.

6 is a side cross-sectional view conceptually illustrating a negative electrode included in the rechargeable battery of FIG. 5.

FIG. 7 is a side cross-sectional view conceptually illustrating a positive electrode included in the rechargeable battery of FIG. 5.

8 is an image of the surface of the negative electrode active material obtained in Example 6 using a transmission electron microscope (TEM).

Hereinafter, exemplary embodiments of the inventive concept will be described in detail with reference to the accompanying drawings. However, embodiments of the inventive concept may be modified in many different forms and should not be construed as limiting the scope of the inventive concept to the embodiments described below. Embodiments of the inventive concept are preferably interpreted as being provided to those skilled in the art to more fully describe the inventive concept. Like numbers refer to like elements all the time. Furthermore, various elements and regions in the drawings are schematically drawn. Accordingly, the inventive concept is not limited by the relative size or spacing drawn in the accompanying drawings.

Terms such as first and second may be used to describe various components, but the components are not limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the inventive concept, the first component may be referred to as the second component, and vice versa, the second component may be referred to as the first component.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the inventive concepts. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the expression “comprises” or “having” is intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and that one or more other features It should be understood that it does not exclude in advance the possibility of the presence or addition of numbers, operations, components, parts or combinations thereof.

Unless defined otherwise, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art, including technical terms and scientific terms. Also, as used in the prior art, terms as defined in advance should be construed to have a meaning consistent with what they mean in the context of the technology concerned, and in an overly formal sense unless explicitly defined herein. It will be understood that it should not be interpreted.

The present invention is a negative electrode active material for a secondary battery including a silicon single phase and an alloy phase, the secondary coating having a ceramic coating layer of about 1 nm to about 50 nm thick on the surface of the core including the silicon single phase and the alloy phase Provided is a battery negative electrode active material.

1 is a schematic view showing a cross-section of a negative electrode active material 100 for a secondary battery according to an embodiment of the present invention. Referring to FIG. 1, a core 130 including a silicon single phase 110 and an alloy phase 120 is provided, and a ceramic coating layer 140 is provided on a surface of the core 130.

The silicon single phase 110 may be particles made of pure silicon (Si), may be single crystalline, may be polycrystalline, or may be amorphous.

The alloy phase 120 may be an alloy having a formula of Si-M, and the alloy may form an intermetallic compound and / or a solid solution. Wherein M may be an alkali metal, an alkaline earth metal, a group 13-16 element, a transition metal, a rare earth element, or a combination thereof (excluding Si). More specifically, M is magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr) , Hafnium (Hf), Rutherperdium (Rf), vanadium (V), niobium (Nb), tantalum (Ta), dubnium (Db), chromium (Cr), molybdenum (Mo), tungsten (W), Chevor (Sg), manganese (Mn), technetium (Tc), rhenium (Re), borium (Bh), iron (Fe), lead (Pb), ruthenium (Ru), osmium (Os), hassium (Hs) , Rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), nickel (Ni) , Lanthanum (La), cerium (Ce), cobalt (Co), boron (B), aluminum (Al), gallium (Ga), tin (Sn), indium (In), titanium (Ti), germanium (Ge) ), Phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S), selenium (Se), tellurium (Te), polonium (Po) or a combination thereof. More preferably, M may be titanium, nickel, copper, iron, manganese, aluminum, zirconium, chromium, lanthanum, tin, cerium, cobalt, zinc, or a combination thereof.

The alloy phase 120 may be configured to surround the silicon single phase 110, but there may also be a silicon single phase 110a that is not completely surrounded by the alloy phase 120.

The ceramic coating layer 140 surrounding the outer surface of the core 130 including the silicon single phase 110 and the alloy phase 120 may have a thickness of about 1 nm to about 50 nm. For example, aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), silicon oxide (SiO ₂ ) or boron oxide (B ₂ O ₃ ) may be included. In particular, the ceramic coating layer 140 may be aluminum oxide, and may have a thickness of about 3 nm to about 25 nm.

As will be described in detail later, the ceramic coating layer 140 is formed by atomic layer deposition (ALD), so that hydrothermal synthesis, physical vapor deposition (PVD), or chemical vapor deposition ( higher thickness uniformity than that formed by chemical vapor deposition (CVD). In other words, the ceramic coating layer 140 may be formed on the surface of the core 130 substantially conformally.

More specifically, the thickness uniformity of the ceramic coating layer 140 may be characterized as the ratio of the thinnest thickness to the thickest thickness, the thickness uniformity being less than or equal to 1 in consideration of its definition. It can be seen that it has a value. The ceramic coating layer 140 of the anode active material 100 for secondary batteries of the present invention may have a thickness uniformity of about 0.75 or more.

In addition, looking at the relative content ratio of the silicon single phase 110 and the alloy phase 120, the fraction of the silicon single phase 110 is about 10% to about 60% by weight, the alloy phase 120 The fraction of can be from about 40% to about 90% by weight.

2, silicon and a metal element are mixed (S10). Since the metal element has been described in detail above, a detailed description thereof will be omitted.

Mixing the silicon and the metal element may be to melt them together to form a melt. The melting step, for example, may be implemented through induction heat generation of silicon and metal elements according to high frequency induction using a high frequency induction furnace. In addition, the melt may be formed using an arc melting process or the like. The melt may include, for example, about 30 wt% to about 90 wt% silicon and about 10 wt% to about 70 wt% metal element. In addition, other unavoidable impurities may be further included.

Then, the molten mixture may be ground to form a core (S20).

In order to pulverize the mixture, first, the melt may be quenched and solidified to form a quenched solidified body. The quench solidification can be performed using a melt spinner apparatus and will be described in detail with reference to FIG. 3.

Referring to FIG. 3, the melt spinner 70 includes a cooling roll 72, a high frequency induction coil 74, and a tube 76. The cooling roll 72 may be formed of a metal having high thermal conductivity and thermal shock, and may be formed of, for example, copper or a copper alloy. The cooling roll 72 can be rotated at high speed by a rotating means 71 such as a motor, and can rotate at a speed in the range of 1000 to 5000 rpm (revolution per minute), for example. The high frequency induction coil 74 flows high frequency power by a high frequency induction means (not shown), thereby inducing high frequency to the material charged in the tube 76. In the high frequency induction coil 74, a cooling medium flows for cooling. The tube 76 may be formed using a material having low reactivity and high heat resistance with the loaded material, such as quartz or refractory glass. In the tube 76, high frequency is induced by the high frequency induction coil 74 and materials (eg, silicon and metal materials) to be melted are charged. The high frequency induction coil 74 is wound around the tube 76 and may melt the material charged in the tube 76 by high frequency induction to form a melt 77 having liquid or fluidity. The tube 76 may then prevent unwanted oxidation of the melt 77 in a vacuum or inert atmosphere. Once the melt 77 is formed, a compressed gas (such as an inert gas such as argon or nitrogen) is drawn into the tube 76 (indicated by an arrow) from one side of the tube 76 and by the compressed gas The melt 77 is discharged through the nozzle formed on the other side of the tube 76. The melt 77 discharged from the tube 76 contacts the rotating cooling roll 72 and is rapidly cooled by the cooling roll 72 to form a quench solidified body 78. The quench coagulation body 78 may have a shape of a ribbon, flake, powder, or the like. By quench solidification by such a cooling roll, the melt 77 can be cooled at a high rate, for example, at a cooling rate of 10 ³ ° C / sec to 10 ⁷ ° C / sec. The cooling rate may vary depending on the rotational speed, material, temperature, and the like of the cooling roll 72.

Therefore, when the quench solidified body is formed using a melt spinner, since the silicon single phase is rapidly precipitated in the melt, the silicon single phase forms an interface with the silicon-metal alloy phase and the silicon-metal alloy phase in the quenched solidified body. It can be uniformly dispersed inside. However, the present invention is not limited thereto. In other words, it will be understood by those skilled in the art that the quench solidification can be carried out via a method other than the melt spinner, for example, an atomizer or the like.

Subsequently, the quench coagulation body may optionally be heat treated. By the heat treatment, crystals or phases included in the quench solidified body may be recrystallized and / or grain grown. The heat treatment may be performed in a vacuum atmosphere or in an inert atmosphere including nitrogen, argon, helium, or mixtures thereof, or in a reducing atmosphere including hydrogen and the like. In addition, the heat treatment may be implemented by using an inert gas such as vacuum or nitrogen, argon, helium in a circulating manner. The heat treatment may be performed at a temperature in the range of 400 ° C. to 800 ° C. for a period of 1 minute to 60 minutes. In addition, the cooling rate after performing the heat treatment step may be in the range of 4 ℃ / min to 20 ℃ / min. In addition, the heat treatment temperature may be heat treated at a temperature lower than about 200 ℃ compared to the melting temperature of the quench solidified body. By the heat treatment, the microstructure of the quench solidified body may change.

Subsequently, the quench solidified body is pulverized to form a core. The negative electrode active material pulverized may be a powder having a diameter of several hundreds of micrometers. The powder may have a diameter in the range of 1 μm to 10 μm, for example a diameter in the range of 2 μm to 4 μm. The grinding process may be performed using known methods for grinding the alloy into powder alloy, such as milling process, ball milling process, jet milling process. For example, the size of the ground powder may be adjusted by adjusting the ball milling process time. According to exemplary embodiments, the core of the negative electrode active material may be formed into a powder having a particle diameter of several micrometers by ball milling the quenched solidified body for about 20 hours to about 50 hours.

Then, a ceramic coating layer may be formed on the surface of the core by atomic layer deposition (S30).

Referring to FIG. 4, supplying a metal precursor for a first time t ₁ in a reaction chamber in which a frying core is positioned to chemisorb the metal precursor to the surface of the core, followed by remaining chemisorbed on the surface of the core. Purging the reaction chamber for a second time t ₂ to remove excess metal precursor from the reaction chamber, and an oxidant in the reaction chamber to form a monolayer of metal oxide on the surface of the core. For a third time t ₃ , and purging the reaction chamber for a fourth time t ₄ to remove residual unreacted oxidant remaining with the metal precursor from the reaction chamber. The deposition cycle (s) comprising the steps may be performed.

The deposition cycle may be performed one or more times, and may be performed until a ceramic coating layer having a desired thickness is obtained. For example, the deposition cycle may be performed from 1 cycle to 10 cycles. The thickness of the ceramic coating layer may be about 1 nm to about 50 nm, and more preferably about 3 nm to about 25 nm, as described above.

The metal precursor may be, for example, an aluminum precursor, a silicon precursor, a zirconium precursor, or a boron precursor.

The aluminum precursor is, for example, trimethylaluminum (Al (CH ₃ ) ₃ ), triethylaluminum (Al (C ₂ H ₅ ) ₃ ), hexakis (dimethylamino) aluminum (Al ₂ (N (CH ₃ ) ₂ ) ₆ ), aluminum trichloride (AlCl ₃ ), tritertarybutyl aluminum (TTBA), triisobutyl aluminum, or tris (dimethylamido) aluminum.

The silicon precursor is, for example, silane (SiH ₄ ), disilane (Si ₂ H ₆ ), trisilane (Si ₃ H ₈ ), tetrasilane (Si ₄ H ₁₀ ), methylsilane ((CH ₃ ) SiH ₃ ), dimethylsilane ((CH ₃ ) ₂ SiH ₂ ), ethylsilane ((C ₂ H ₅ ) SiH ₃ ), methyldisilane ((CH ₃ ) Si ₂ H ₅ ), dimethyldisilane ((CH ₃ ) ₂ Si ₂ H ₄ ), hexamethylsilane ((CH ₃ ) ₆ Si ₂ ), tris (dimethylamino) silane (TDMAS), tris (tertiary-butoxy) silanol ((C ₄ H ₉ O) ₃ Si -OH), tris (tertiary-pentoxy) silanol ((C ₅ H ₁₁ O) ₃ Si-OH), di (tertiary-butoxy) silanediol ((C ₄ H ₉ O) ₂ Si (OH ) ₂ ), methyl di (tertiary-butoxy) silanediol (CH ₃ (C ₄ H ₉ O) ₂ Si-OH), bis (diethylamino) silane (SiH ₂ (NC ₂ H ₅ ) ₂ ), Monosilylamine (H ₂ N (SiH ₃ )), disilylamine (HN (SiH ₃ ) ₂ ), trisilylamine (N (SiH ₃ ) ₃ ), dimethoxysilane, diethoxysilane, trimethoxysilane, Triethoxysilane, tetramethoxysilane, tetraethoxysilane, or diethoxymethylsilane.

Examples of the zirconium precursor include tetrakisethyl methyl amido zirconium (Zr (NEtMe) ₄ , TEMAZ), tetrakis (dimethyl amido) zirconium (TDMAZ), tetrakis (diethyl amido) zirconium (TDEAZ). , Zr (O- t Bu) ₄ , ZrCl ₄ , ZrCp ₂ Me ₂ , Zr (t-BuCp) ₂ Me ₂ , tetrakis (1-methoxy-2-methyl-2-propoxy) zirconium (Zr (mmp ) ₄ ), tetrakis (2-methyl-3-butene-2-oxy) zirconium (ZMBO), Zr (DMAMP) ₄ , Zr (dmae) ₄ , Zr (dmae) ₂ (iPrO) ₂ , or bis (cyclo Pentadienyl) zirconium.

The boron precursor may be, for example, diborane (B ₂ H ₆ ), triborane (B ₃ H ₈ ), tetraborane (B ₄ H ₁₀ ), trimethylboraine ((CH ₃ ) ₃ B), Triethylborane ((C ₂ H ₅ ) ₃ B), borazine (B ₃ N ₃ H ₆ ), alkyl-substituted derivatives of borazine, or BCl ₃ .

However, the aluminum, silicon, zirconium and boron precursors are not limited thereto.

An inert gas such as helium (He), neon (Ne), argon (Ar), or a low active gas such as nitrogen (N ₂ ) may be used to purge the reaction chamber. However, it is not limited to these gases.

Water vapor (H ₂ O (g)), O ₂ , O ₃ , N ₂ O, NO, CO, CO ₂ , CH ₃ OH, or C ₂ H ₅ OH may be used as an oxidizing agent for oxidizing the metal precursor. . However, it is not limited to this.

Referring back to FIG. 2, as described above, heat treatment may be performed on the negative electrode active material having the ceramic coating layer formed on the core surface (S40).

The heat treatment may be performed for about 30 minutes to about 120 minutes at a temperature of about 200 ℃ to about 500 ℃. If the temperature of the heat treatment is too low or the time is too short, the initial efficiency of the prepared negative electrode active material may deteriorate. On the contrary, if the temperature of the heat treatment is too high or the time is too long, the material of the Si alloy core may be recrystallized to reduce the life during charging and discharging, which may cause a problem of a sharp decrease in capacity.

The heat treatment may be performed in an atmosphere, or may be performed in an inert atmosphere in which nitrogen gas, argon gas, helium gas, krypton gas, or xenon gas is present.

The negative electrode active material for the secondary battery obtained by the above method is not only excellent in initial capacity and initial efficiency as compared with the conventional negative electrode active material, it can also greatly improve the life.

5 is an exploded perspective view illustrating the rechargeable battery 1 including the negative active material according to the exemplary embodiment. 6 and 7 are side cross-sectional views conceptually illustrating a negative electrode 10 and a positive electrode 20 included in the secondary battery 1 of FIG. 5, respectively.

Referring to FIG. 5, the secondary battery 1 includes a negative electrode 10, a positive electrode 20, and a separator 30, a battery container 40, and a sealing member 50 interposed between the negative electrode 10 and the positive electrode 20. ) May be included. In addition, the secondary battery 1 may further include an electrolyte impregnated in the negative electrode 10, the positive electrode 20, and the separator 30. In addition, the negative electrode 10, the positive electrode 20, and the separator 30 may be sequentially stacked and accommodated in the battery container 40 in a spirally wound state. The battery container 40 may be sealed by the sealing member 50.

The secondary battery 1 may be a lithium secondary battery using lithium as a medium, and may be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery according to the separator 30 and the type of electrolyte. In addition, the secondary battery 1 may be classified into a coin, a button, a sheet, a cylinder, a flat, a square, and the like according to a shape, and may be classified into a bulk type and a thin film type according to the size. The secondary battery 1 illustrated in FIG. 5 exemplarily shows a cylindrical secondary battery, and the technical spirit of the present invention is not limited thereto.

Referring to FIG. 6, the negative electrode 10 includes a negative electrode current collector 11 and a negative electrode active material layer 12 positioned on the negative electrode current collector 11. The negative electrode active material layer 12 includes a negative electrode binder 14 for attaching the negative electrode active material 13 and the negative electrode active material 13 to each other. In addition, the negative electrode active material layer 12 may further include a negative electrode conductor 15 selectively. In addition, although not shown, the negative electrode active material layer 12 may further include an additive such as a filler or a dispersant. In the negative electrode 10, a negative electrode active material 13, a negative electrode binder 14, and / or a negative electrode conductor 15 may be mixed in a solvent to prepare a negative electrode active material composition, and the negative electrode active material composition may be disposed on the negative electrode current collector 11. It can be formed as an inclusion in the.

The negative electrode current collector 11 may include a conductive material and may be a thin conductive foil. The negative electrode current collector 11 may include, for example, copper, gold, nickel, stainless steel, titanium, or an alloy thereof. Alternatively, the negative electrode current collector 11 may be made of a polymer including a conductive metal. Alternatively, the negative electrode current collector 11 may be formed by compressing the negative electrode active material.

The negative electrode active material 13 may use, for example, a negative electrode active material for a lithium secondary battery, and may include a material capable of reversibly intercalating / deintercalating lithium ions. As described in detail above, the negative electrode active material 13 may be a negative electrode active material having a ceramic coating layer formed on a surface of a core made of a single silicon phase and an alloy phase.

The negative electrode binder 14 attaches the particles of the negative electrode active material 13 to each other, and also serves to attach the negative electrode active material 13 to the negative electrode current collector 11. The negative electrode binder 14 may be, for example, a polymer, for example polyimide, polyamideimide, polybenzimidazole, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, polyvinylchloride, carboxylation Polyvinylchloride, polyvinylfluoride, ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene, acrylated styrene-butadiene, Epoxy resins and the like.

The negative electrode conductor 15 may further provide conductivity to the negative electrode 10 and may be a conductive material that does not cause chemical change in the secondary battery 1, and may be, for example, graphite, carbon black, acetylene black, carbon fiber, or the like. It may include a conductive material containing a carbon-based material, a metal-based material such as copper, nickel, aluminum, silver, conductive polymer materials such as polyphenylene derivatives or mixtures thereof.

Referring to FIG. 7, the positive electrode 20 includes a positive electrode current collector 21 and a positive electrode active material layer 22 positioned on the positive electrode current collector 21. The positive electrode active material layer 22 includes a positive electrode active material 23 and a positive electrode binder 24 for adhering the positive electrode active material 23. In addition, the positive electrode active material layer 22 may further include a positive electrode conductor 25 selectively. In addition, although not shown, the positive electrode active material layer 22 may further include an additive such as a filler or a dispersant. The positive electrode 20 is prepared by mixing a positive electrode active material 23, a positive electrode binder 24, and / or a positive electrode conductor 25 in a solvent to prepare a positive electrode active material composition, the positive electrode active material composition on the positive electrode current collector 21 It can be formed by applying to.

The positive electrode current collector 21 may be a thin conductive foil, and may include, for example, a conductive material. The positive electrode current collector 21 may include, for example, aluminum, nickel, or an alloy thereof. Alternatively, the positive electrode current collector 21 may be made of a polymer including a conductive metal. Alternatively, the positive electrode current collector 21 may be formed by compressing the negative electrode active material.

The positive electrode active material 23 may use, for example, a positive electrode active material for a lithium secondary battery, and may include a material capable of reversibly inserting / desorbing lithium ions. The positive electrode active material 23 may include a lithium-containing transition metal oxide, a lithium-containing transition metal sulfide, and the like, and for example, LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li (Ni _a Co _b Mn _c ) O ₂ (0 <a <1, 0 <b <1, 0 <c <1, a + b + c = 1), LiNi _1-y Co _y O ₂ , LiCo _1-y Mn _y O ₂ , LiNi _{1 -y} Mn _y O ₂ (where 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), LiMn _2-z Ni _z O ₄ , LiMn _2-z Co _z O ₄ (where 0 <z <2), LiCoPO ₄ , and LiFePO ₄ .

The positive electrode binder 24 attaches the particles of the positive electrode active material 23 to each other, and also serves to attach the positive electrode active material 23 to the positive electrode current collector 21. The positive electrode binder 24 may be, for example, a polymer, for example polyimide, polyamideimide, polybenzimidazole, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, polyvinylchloride, carboxylation Polyvinylchloride, polyvinylfluoride, ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene, acrylated styrene-butadiene, Epoxy resins and the like.

The positive electrode conductor 25 may further provide conductivity to the positive electrode 20, and may be a conductive material that does not cause chemical change in the secondary battery 1, and may be, for example, graphite, carbon black, acetylene black, carbon fiber, or the like. It may include a conductive material containing a carbon-based material, a metal-based material such as copper, nickel, aluminum, silver, conductive polymer materials such as polyphenylene derivatives or mixtures thereof.

Referring back to FIG. 5, the separator 30 may have a porosity, and may consist of a single membrane or multiple layers of two or more layers. The separator 30 may include a polymer material, and may include, for example, at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyolefin, and the like.

The electrolyte (not shown) impregnated in the cathode 10, the anode 20, and the separator 30 may include a non-aqueous solvent and an electrolyte salt. The non-aqueous solvent is not particularly limited as long as it is used as a conventional non-aqueous solvent for non-aqueous electrolyte, and for example, carbonate solvent, ester solvent, ether solvent, ketone solvent, alcohol solvent or aprotic It may include a solvent. The non-aqueous solvent may be used alone or in mixture of one or more, and the mixing ratio in the case of mixing one or more may be appropriately adjusted according to the desired battery performance.

The electrolyte salt is not particularly limited as long as it is used as a conventional electrolyte salt for a nonaqueous electrolyte, and may be, for example, a salt having a structural formula of A ⁺ B ⁻ . Here, A ⁺ may be an ion including an alkali metal cation such as Li ⁺ , Na ⁺ , K ⁺ or a combination thereof. Also. 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 -, Or an ion such as C (CF ₂ SO ₂ ) ₃ ⁻ , or a combination thereof. For example, the electrolyte salt may be a lithium salt, for example LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiN (SO ₂ C ₂ F ₅ ) ₂ , Li (CF ₃ SO ₂ ) ₂ N, LiN (SO ₃ C ₂ F ₅ ) ₂ , LiC ₄ F ₉ SO ₃ , LiClO ₄ , LiAlO ₂ , LiAlCl ₄ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ), where , x and y may be a natural number), LiCl, LiI and LiB (C ₂ O ₄ ) ₂ It may include one or two or more selected from the group consisting of. These electrolyte salts may be used alone or in combination of two or more thereof.

Hereinafter, the structure and effects of the present invention will be described in more detail with specific examples and comparative examples, but these examples are only intended to more clearly understand the present invention and are not intended to limit the scope of the present invention.

The melt was first formed by melting using an arc melting process and a high frequency induction heating process to have 70% by weight of silicon and 15% by weight of nickel and titanium. The melt solidified rapidly to form a rapid solidified body. At this time, the rapid solidification process was performed using the melt spinner equipment. The rapid solidified body was crushed again using a ball milling process, and the cores obtained therein were charged into an ALD reactor and a ceramic coating layer was formed on the surface using ALD.

Trimethylaluminum (Al (CH ₃ ) ₃ ) was used as a precursor to form a ceramic coating layer on the surface of the core, and water vapor was used as the oxidant. The negative electrode active material was obtained by repeating ALD deposition cycle 2 cycles.

An anode active material was prepared in the same manner as in Example 1 except that the ALD deposition cycle was repeated 4 cycles instead of 2 cycles.

An anode active material was prepared in the same manner as in Example 1 except that the ALD deposition cycle was repeated 8 cycles instead of 2 cycles.

A negative electrode active material was prepared in the same manner as in Example 1 except that the heat treatment was performed at 350 ° C. for 60 minutes after the ceramic coating layer was formed.

Example 5

A negative electrode active material was prepared in the same manner as in Example 2 except that the heat treatment was performed at 350 ° C. for 60 minutes after the ceramic coating layer was formed.

A negative electrode active material was prepared in the same manner as in Example 3 except that the heat treatment was performed at 350 ° C. for 60 minutes after the ceramic coating layer was formed.

Comparative Example 1

It was used as a negative electrode active material without forming a ceramic coating layer on the surface of the core obtained in Example 1.

Comparative Example 2

Aluminum oxide was coated on the surface of the core obtained in Example 1 by using hydrothermal synthesis.

Comparative Example 3

LiPON was coated on the surface of the core obtained in Example 1 by hydrothermal synthesis.

Confirmation of Ceramic Coating Layer

In order to confirm that the ceramic coating layer was well formed on the surface of the negative electrode active material obtained in Example 6, a negative electrode active material was photographed using a transmission electron microscope (TEM). As a result, as shown in FIG. 8, it was found that the ceramic coating layer was formed on the surface of the particles with a uniform thickness of about 8 nm.

Half cell production

In order to evaluate the electrochemical properties of the negative electrode active material obtained above, a half-cell was manufactured using these. A coin cell was prepared using a metal lithium as a reference electrode and a negative electrode formed by adding a binder and a conductive material to the negative electrode active materials obtained in Examples 1 to 6 and Comparative Examples 1 to 3 as measurement electrodes. .

Evaluation of charge and discharge characteristics

Initial capacity, initial efficiency, coulombic efficiency, and capacity retention after 50 cycles were measured for the half cells prepared as described above. At this time, the first and second charge and discharge were performed at current densities of 0.1 C and 0.2 C, respectively, and the charge and discharge from the third time was charged and discharged at a current density of 1.0 C.

As a result, the same result as in Table 1 was obtained.

Table 1

	Initial capacity (mAh / g)	Initial Efficiency (%)	Coulomb Efficiency (%)	Capacity retention rate after 50 cycles (%)
Example 1	813	84.2	99.4	92.2
Example 2	812	84.3	99.4	92.7
Example 3	812	84.9	99.5	92.9
Example 4	813	87.2	99.8	94.6
Example 5	813	87.6	99.8	94.8
Example 6	813	88.3	99.9	95.2
Comparative Example 1	813	82.3	99	87.1
Comparative Example 2	757	83.5	99.2	88.5
Comparative Example 3	763	82.8	99.1	88.3

As shown in Table 1, the negative electrode active materials of Examples 1 to 6 can be seen that the initial capacity is further improved compared to when the surface layer is formed on the surface by using hydrothermal synthesis. Furthermore, it was found that the initial capacity was more disadvantageous than when the surface layer was formed on the surface of the negative electrode active material by the hydrothermal synthesis method (Comparative Example 2, Comparative Example 3) rather than when the surface layer was not formed (Comparative Example 1).

In addition, the negative electrode active materials prepared in Examples 1 to 6 not only improved initial efficiency and coulombic efficiency than the negative electrode active materials prepared in Comparative Examples 1 to 3, but also the negative electrode active materials of Examples 4 to 6, which were subjected to heat treatment, to Example 1 It was found that the initial efficiency and the coulombic efficiency were significantly improved than the negative electrode active material of the third to third.

Also in the capacity retention rate after 50 cycles, the negative electrode active materials prepared in Examples 1 to 6 showed remarkably superior characteristics compared to the negative electrode active materials prepared in Comparative Examples 1 to 3, and particularly in the negative electrode active materials of Examples 4 to 6 subjected to heat treatment. It was confirmed to have a better capacity retention rate.

Although described in detail with respect to embodiments of the present invention as described above, those of ordinary skill in the art, without departing from the spirit and scope of the invention as defined in the appended claims Various modifications may be made to the invention. Therefore, changes in the future embodiments of the present invention will not be able to escape the technology of the present invention.

The present invention can be usefully used in the secondary battery industry.

Claims

Silicon single phase; And

An alloy phase of silicon with one or more metal elements selected from the group consisting of titanium, nickel, copper, iron, manganese, aluminum, zirconium, chromium, lanthanum, tin, cerium, cobalt and zinc;

As a negative electrode active material for a secondary battery comprising:

A negative active material for a secondary battery comprising a ceramic coating layer having a thickness of about 1 nm to about 50 nm on a surface of the core including the silicon single phase and the alloy phase.
The method of claim 1,

The ceramic coating layer is an anode active material for secondary batteries, characterized in that the aluminum oxide (Al 2 O 3 ), zirconium oxide (ZrO 2 ), silicon oxide (SiO 2 ) or boron oxide (B 2 O 3 ).
The method of claim 1,

The thickness of the ceramic coating layer is a negative electrode active material for a secondary battery, characterized in that about 3 nm to about 25 nm.
The method of claim 1,

The negative electrode active material of claim 2, wherein the ceramic coating layer is formed on the surface of the core conformally.
The method of claim 4, wherein

The ceramic coating layer is a secondary battery negative electrode active material, characterized in that formed by atomic layer deposition (ALD).
The method of claim 4, wherein

The negative active material for a secondary battery, characterized in that the ratio of the thinnest thickness to the thickest thickness of the ceramic coating layer is about 0.75 or more.
The method of claim 1,

In the relative content of the silicon single phase and the alloy phase,

The fraction of the silicon single phase is from about 10% to about 60% by weight,

A fraction of the alloy phase is about 40% by weight to about 90% by weight of a negative electrode active material for a secondary battery.
A positive electrode including a positive electrode active material;

Separator;

A negative electrode including a negative electrode active material; And

Electrolyte;

As a secondary battery comprising:

The anode active material includes a ceramic coating layer having a thickness of about 1 nm to about 50 nm on a surface of a core including a silicon single phase and an alloy phase, and the alloy phase includes titanium, nickel, copper, iron, manganese, aluminum, zirconium, and chromium. A secondary battery characterized in that the alloy phase of at least one metal element selected from the group consisting of lanthanum, tin, cerium, cobalt and zinc and silicon.
Mixing silicon with at least one metal element selected from the group consisting of titanium, nickel, copper, iron, manganese, aluminum, zirconium, chromium, lanthanum, tin, cerium, cobalt and zinc;

Grinding the mixture to form a core; And

Forming a ceramic coating layer on the surface of the core by atomic layer deposition (ALD);

Method for producing a negative active material for a secondary battery comprising a.
The method of claim 9,

Forming the ceramic coating layer,

Supplying a metal precursor into an ALD reaction chamber in which the core is located to chemisorb the metal precursor to a surface of the core;

Purging the ALD reaction chamber to remove excess metal precursor chemisorbed on the surface of the core from the ALD reaction chamber;

Supplying an oxidant into the ALD reaction chamber to form a monolayer of metal oxide on the surface of the core; And

Purging the ALD reaction chamber to remove residual unreacted oxidant remaining from the ALD reaction chamber after reacting with the metal precursor;

Method for producing a negative electrode active material for a secondary battery comprising a deposition cycle comprising a cycle.
The method of claim 10,

Forming the ceramic coating layer is a manufacturing method of a negative electrode active material for a secondary battery, characterized in that it comprises one to 10 cycles of the deposition cycle.
The method of claim 9,

Heat treating the negative active material for the secondary battery after the forming of the ceramic coating layer;

Method for producing a negative electrode active material for a secondary battery, characterized in that it further comprises.
The method of claim 12,

The heat treatment is a method of manufacturing a negative electrode active material for a secondary battery, characterized in that performed at a temperature of about 200 ℃ to about 500 ℃.
The method of claim 13,

And the heat treatment is performed for about 30 minutes to about 120 minutes.
The method of claim 9,

In the step of mixing the metal element and silicon, the content of the metal element is about 10% to about 70% by weight, the content of the silicon is about 30% to about 90% by weight of the negative electrode for secondary batteries Method for producing an active material.