KR101630419B1 - Method for manufacturing negative electrode active material for rechargable lithium battery - Google Patents

Abstract

The present invention relates to a negative electrode active material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery including the same. More particularly, the present invention relates to a graphite core particle containing pores therein. A first coating layer positioned on the surface of the graphite-based core particle and including metal-based fine particles; And a second coating layer distributed on all or a part of the surface of the first coating layer and including ceramic particles. The present invention provides a method for manufacturing the negative active material for a lithium secondary battery, And a lithium secondary battery including the same can be provided.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a negative active material for a lithium secondary battery,

And a method for manufacturing an anode active material for a lithium secondary battery.

2. Description of the Related Art Recently, lithium secondary batteries, which are widely regarded as a power source for portable electronic devices, are attracting attention.

This is because, by using the organic electrolytic solution, the discharge voltage is twice as high as that of the battery using the conventional alkali aqueous solution, and as a result, high energy density can be exhibited.

Examples of the positive electrode active material of such a lithium secondary battery include lithium having a structure capable of intercalating lithium ions, such as LiCoO ₂ , LiMn ₂ O ₄ , LiNi _{1 -x} Co _x O ₂ (0 <x <1) Is mainly used.

Meanwhile, as a negative electrode active material, a material capable of lithium intercalation / deintercalation can be utilized. In the past, various types of carbon-based materials including artificial graphite, natural graphite, hard carbon, and soft carbon have been applied.

In particular, the graphite active material is currently most widely used in lithium secondary batteries due to its advantage of providing low power discharge voltage to lithium and providing advantages in terms of energy density and long life by excellent reversibility.

However, recently, as the functions of portable electronic devices have been diversified, and miniaturization and weight reduction have been progressed, there is a demand for higher capacity of lithium secondary batteries. Accordingly, a cathode having a theoretical capacity higher than the theoretical capacity of 372 mAh / Interest in active material is increasing.

Particularly, silicon-based materials have a theoretical capacity ten times higher than that of graphite, and researches for utilization thereof as an anode active material are actively underway. However, the volumetric expansion of the silicon-based metal occurs during the charging process of the cell, and cracks are generated due to such volume change. As a result, various problems such as reduction of conductivity between the active materials, desorption from the electrode plate, and continuous reaction with the electrolyte are derived .

As a result, the above-described problems cause degradation of lifetime characteristics of lithium secondary batteries, and a fundamental solution thereof has not yet been proposed, so that silicon based metal active materials are not yet commercialized.

Accordingly, the present inventors intend to provide a novel silicon-based metal active material capable of overcoming the above-described problems.

Specifically, in one embodiment of the present invention, by a mechanical coating method, there is provided a method for producing a core-shell core particle, comprising the steps of: Ceramic coating layer] of the present invention.

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According to a manufacturing method provided in an embodiment of the present invention described below, graphite-based core particles containing pores therein; A first coating layer positioned on the surface of the graphite-based core particle and including metal-based fine particles; And a second coating layer distributed on all or a part of the surface of the first coating layer, the second coating layer including ceramic particles, and a negative electrode active material for a lithium secondary battery.

Here, the content of the graphite-based core particles in the negative electrode active material and the metal-based microparticles contained in the first coating layer may be 80:20 to 99: 1 in terms of weight ratio of the graphite-based core particles to the metal- .

The content of the ceramic in the negative electrode active material may be 0.1 to 10 parts by weight based on 100 parts by weight of the total weight of the graphite-based core particles and the metal-based fine particles contained in the first coating layer.

On the other hand, the metal-based fine particles are a group of compounds comprising a metal group including an alloy made of silicon, tin, aluminum, vanadium, magnesium, antimony, and an alloy consisting of at least one of these, oxides thereof, nitrides and carbides thereof, Or a combination thereof.

Specifically, it may be at least one selected from Si, SiO _x , Si-C composite, Si-Q alloy, and combinations thereof. (Wherein x is an integer in the range of 0 < x < 2, and Q is at least one selected from the group consisting of alkali metals, alkaline earth metals, Group 13 to Group 16 elements, transition metals, rare earth elements, Element.)

The average particle diameter of the metal-based fine particles may be 0.01 to 5 탆.

In addition, the thickness of the first coating layer may be 0.01 to 10 탆.

On the other hand, the ceramic _{particles, SiO 2, Al 2 O 3} , Li4Ti 5 O 12, TiO 2, CeO 2, ZrO 2, BaTiO 3, Y 2 O 3, MgO, CuO, ZnO, AlPO 4, AlF, Si ₃ N _4, it may be less than AlN, TiN, WC, SiC, TiC, MoSi _2, Fe ₂ O _3, GeO _2, Li ₂ O, MnO, NiO, zeolite, and one selected from a combination of the two.

The average particle size of the ceramic particles may be 10 to 2000 nm.

In addition, the thickness of the second coating layer may be 10 to 2000 nm.

On the other hand, the graphite-based core particles may be one comprising at least one selected from natural graphite, artificial graphite, and combinations thereof.

Independently, the graphite-based core particle may be spherical.

The average particle diameter of the graphite-based core particles may be 5 to 30 탆.

The porosity of the graphite-based core particles may be 10 to 60% by volume based on the total volume of the graphite-based core particles.

According to an embodiment of the present invention, there is provided a method for manufacturing a magnetic recording medium, comprising the steps of: preparing graphite-based core particles containing pores therein; Forming a first coating layer containing metal-based fine particles on the surface of the graphite-based core particle to obtain an intermediate; Distributing a second coating layer comprising ceramic particles on all or part of the surface of said intermediate; And obtaining a negative electrode active material according to the present invention.

Specifically, a step of forming a first coating layer containing metal-based fine particles on the surface of the graphite-based core particle to obtain an intermediate body is characterized in that a first mixed powder comprising the graphite-based core particles and the metal- Lt; / RTI &gt; And applying a shear stress to the first mixed powder to induce fusion between surfaces of the graphite-based core particles and the metal-based fine particles.

The step of applying shear stress to the first mixed powder to induce fusion between surfaces of the graphite-based core particles and the metal-based fine particles may be performed by mechanofusion milling, shaker milling milling, planetary milling, attritor milling, disk milling, shape milling, nauta milling, nobilta milling, high speed milling, high speed mixing, and a combination thereof.

Independently from each other, a step of applying a shear stress to the first mixed powder to induce fusion between surfaces of the graphite-based core particles and the metal-based microparticles, wherein the step (a) is performed at a rotating peripheral speed of 10 to 50 m / s It can be done.

On the other hand, distributing a second coating layer containing ceramic particles on all or a part of the surface of the intermediate comprises: preparing a second mixed powder including the intermediate and the ceramic particles; And applying a shear stress to the second mixed powder to induce fusion between surfaces of the intermediate and the ceramic particles.

The step of applying a shear stress to the second mixed powder to induce fusion between the surfaces of the intermediate and the ceramic particles may be performed by ball milling, mechanofusion milling, Planar milling, attritor milling, shape milling, nauta milling, nobilta milling, high-speed milling, high-speed milling, shaker milling, planetary milling, speed mixing, paddle mixing, ribbon mixing, henschel mixing, corn type mixing, thinky mixing, homomixing, agitator, And a combination of these.

Independently, the step of applying shear stress to the second mixed powder to induce fusion between the surfaces of the intermediate and the ceramic particles is performed at a rotational circumferential speed of 5 to 70 m / s .

The negative electrode active material obtained according to an embodiment of the present invention includes a positive electrode; cathode; And a lithium secondary battery including an electrolyte. Specifically, the negative electrode includes any one of the negative electrode active materials for a lithium secondary battery described above.

According to one embodiment of the present invention, a negative electrode active material for a lithium secondary battery is provided that minimizes the volume expansion upon application to an electrode by the above structure and contributes to exhibiting excellent lifetime characteristics, even though it is a silicon-based metal active material. .
According to another embodiment of the present invention, there is provided a method of manufacturing a negative electrode active material for a lithium secondary battery, which contributes to mass production of the negative electrode active material having the above advantages.
According to another embodiment of the present invention, a lithium secondary battery having excellent life characteristics can be provided.

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1 is an exploded perspective view of a lithium secondary battery according to an embodiment of the present invention.
2 schematically illustrates a cross-sectional view of a negative electrode active material according to an embodiment of the present invention.
3 is a scanning electron micrograph showing a cross section of graphite-based core particles used in Example 1. Fig.
4 is a scanning electron microscope (SEM) image of the negative electrode active material prepared according to Example 1. Fig.
FIG. 5 is a mapping photograph showing the surface state of the negative electrode active material produced according to Example 1. FIG.
6 is a graph showing the evaluation of the thickness expansion characteristics of a negative electrode in a lithium secondary battery produced according to Examples 1 and 2 and Comparative Examples 1 and 2, respectively.
FIG. 7 is a graph showing the capacity retention rate of the lithium secondary battery manufactured according to Examples 1 and 2 and Comparative Examples 1 and 2 according to charge / discharge life span. FIG.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

Further, in the present specification, the average particle diameter means the particle diameter of D50, which refers to the particle diameter when the cumulative volume of the particles becomes 50% by volume in the small particle order.

According to a manufacturing method provided in an embodiment of the present invention to be described later, a graphite-based core particle containing pores therein; A first coating layer positioned on the surface of the graphite-based core particle and including metal-based fine particles; And a second coating layer distributed on all or a part of the surface of the first coating layer, the second coating layer including ceramic particles, and a negative electrode active material for a lithium secondary battery.

FIG. 1 is an exploded perspective view of a lithium secondary battery to which the negative active material for a lithium secondary battery can be applied, and FIG. 2 is a schematic cross-sectional view of the negative active material for a lithium secondary battery.

The lithium secondary battery of FIG. 1 will be described later. Referring to FIG. 2, the negative active material for the lithium secondary battery having a differentiated structure from the conventional negative electrode active material can be visually inspected.

 Specifically, the graphite-based core particles include pores therein, and may be in a state of being closed by a double coating layer. At this time, the surface of the graphite-based core particle may be a structure in which metal-based fine particles are primarily formed as a coating layer, and a coating layer including ceramic particles is distributed on all or a part of the surface thereof.

In this structure, the inner pores of the graphite-based core particles are formed in a space in which the metal-based microparticles can expand when the battery is charged (that is, lithium is inserted) while seeking a high capacity of the battery by the metal- It is possible to prevent the occurrence of cracks by alleviating the volume expansion in the negative electrode to which the same is applied and to effectively alleviate the volume expansion due to the ceramic particles of the second coating layer.

In addition, through such a differentiated structure, ultimately, the lithium secondary battery to which the lithium secondary battery is applied can contribute to an excellent life characteristic.

Hereinafter, the negative electrode active material obtained in one embodiment of the present invention will be described in more detail based on the structure shown in FIG. Of course, the structure shown in FIG. 2 is merely an example, but is not limited thereto.

First, the content of each of the graphite-based core particles in the negative electrode active material and the metal-based fine particles contained in the first coating layer is in the range of 80:20 to 99: 1 in terms of the weight ratio of the graphite-based core particles to the metal- .

When the weight ratio expressed by the graphite particles (graphite core particles: metal-based fine particles) satisfies the above-described range, cracking due to volume expansion of the metal-based fine particles can be minimized during charging and discharging of the battery, The long life can be achieved at the same time.

However, when the ratio is more than 99: 1, the capacity increase is small and the lithium secondary battery can not attain a high capacity. If the ratio is less than 80:20, the metal particles become bulky and the life characteristics of the lithium secondary battery deteriorate So that the range is limited as described above.

The content of the ceramic in the negative electrode active material may be 0.1 to 10 parts by weight based on 100 parts by weight of the total weight of the graphite-based core particles and the metal-based fine particles contained in the first coating layer.

When the content of the ceramic in the negative electrode active material is within the above range, the second coating layer is formed in a uniform form, and the lifetime characteristics of the lithium secondary battery can be further improved by effectively alleviating the volume expansion of the metal- .

However, if it exceeds or falls below the above range, the capacity of the negative electrode active material can be reduced by the ceramic particles, and the life characteristics of the lithium secondary battery may be deteriorated due to side reactions with the electrolyte. .

On the other hand, it has been described that the metal-based fine particles contribute to the high capacity of the lithium secondary battery as a material having a higher capacity than the conventional graphite-based active material.

Specifically, it includes a group of compounds comprising a metal group comprising an alloy of silicon, tin, aluminum, vanadium, magnesium, antimony, and one or more combinations thereof, oxides, nitrides, and carbides thereof, and combinations thereof It may be more than one selected.

More specifically, the silicon-based metal active material may be at least one selected from the group consisting of Si, SiO _x , Si-C composite, Si-Q alloy, and combinations thereof. (Wherein x is an integer in the range of 0 < x < 2, and Q is at least one selected from the group consisting of alkali metals, alkaline earth metals, Group 13 to Group 16 elements, transition metals, rare earth elements, Element.)

More specifically, it may be Si or an oxide thereof SiOx (0.1? _X ? 2).

The average particle diameter of the metal-based fine particles may be 0.01 to 5 탆. If the average particle size is larger than 5 占 퐉, the coating may not be uniformly coated on the surface of the graphite-based core particle. If the average particle size is smaller than 0.01 占 퐉, The problem of having to bear the expense of the time may arise. Therefore, the range is limited as described above.

The thickness of the first coating layer may be 0.01 to 10 탆, which may be determined by the average particle size or the content of the metal-based fine particles contained in the first coating layer.

Specifically, if the thickness of the first coating layer exceeds 10 탆, the content of the metal-based fine particles contained in the first coating layer is excessively large, which may cause a problem of increased volume expansion, By weight, the content of the metal-based fine particles is too small and a problem that a high capacity of the lithium secondary battery can not be achieved may occur. Therefore, the range is limited as described above.

On the other hand, it has been described that the ceramic particles effectively maintain the volume expansion relaxation of the metal-based fine particles and contribute to further improve the lifetime characteristics of the lithium secondary battery.

Specifically, the ceramic particles may be at least one selected from a metal oxide, a non-metal oxide, a composite metal oxide, a rare earth oxide, a compound containing a halogen group, an oxide produced from a ceramic precursor, and a combination thereof. At this time, the ceramic precursor may be zirconia, aluminum, polycarbosilane, polysiloxane, polysilazane, or a combination thereof.

More _{specifically, SiO 2, Al 2 O 3} , Li 4 Ti 5 O 12, TiO 2, CeO 2, ZrO 2, BaTiO 3, Y 2 O 3, MgO, CuO, ZnO, AlPO 4, AlF, Si 3 At least one selected from the group consisting of N ₄ , AlN, TiN, WC, SiC, TiC, MoSi ₂ , Fe ₂ O ₃ , GeO ₂ , Li ₂ O, MnO, NiO, zeolite and combinations thereof.

The average particle size of the ceramic particles may be 10 to 2000 nm. If the average particle size is larger than 2000 nm, it may be difficult to uniformly coat the first coating layer. If the average particle size is smaller than 10 nm, it is difficult to produce fine particles, There is a problem that it is necessary to bear the cost, so the range is limited as described above.

In addition, the thickness of the second coating layer may be 10 to 2000 nm, which may be determined by the average particle size or the content of the ceramic particles contained in the second coating layer.

Specifically, if the thickness of the second coating layer exceeds 2000 nm, the capacity of the lithium secondary battery may decrease as the content of the ceramic particles increases. When the thickness of the second coating layer is less than 10 nm, The content is too small, and the volume expansion of the metal-based fine particles may not be effectively mitigated. Therefore, the range is limited as described above.

On the other hand, the graphite-based core particles may be one comprising at least one selected from natural graphite, artificial graphite, and combinations thereof.

Independently, the graphite-based core particles may be spherical, and the surface of the spherical graphite-based core particles is easily coated with the metal-based particles. On the other hand, in the case of the plate-like shape or the like, it is difficult to coat the metal-based fine particles on the surface thereof, and it is difficult to form pores therein.

The average particle diameter of the graphite-based core particles may be 5 to 30 탆. If it is more than 30 μm, it may cause problems in stable electrode slurry production, and if it is less than 5 μm, it is difficult to produce spherical graphite. Therefore, the range is limited as described above.

The porosity of the graphite-based core particles may be 10 to 60% by volume based on the total volume of the graphite-based core particles. In this case, the effect of using the pores included in the graphite-based core particles as the expansion space of the active material at the time of charging the battery (i.e., lithium insertion) is maximized, and the effect of preventing cracking due to volume expansion in the cathode is prevented. The effect of improving the lifetime characteristics of the battery can also be achieved at the maximum.

However, when it is more than 60% by volume, there is a problem that the coating layers are squeezed or deformed when the coating layers are formed on the surface thereof. When the volume ratio is less than 10% by volume, the effect of preventing cracking during volume expansion by the metal- And the lifetime of the lithium secondary battery may be deteriorated. Therefore, the range is limited as described above.

According to an embodiment of the present invention, there is provided a method for manufacturing a magnetic recording medium, comprising the steps of: preparing graphite-based core particles containing pores therein; Forming a first coating layer containing metal-based fine particles on the surface of the graphite-based core particle to obtain an intermediate; Distributing a second coating layer comprising ceramic particles on all or part of the surface of said intermediate; And obtaining a negative electrode active material according to the present invention.

This is a method for producing the negative electrode active material for a lithium secondary battery having the above-mentioned structure, wherein the double coating layer can be introduced onto the surface of the graphite-based core particle by a mechanical coating method.

Hereinafter, a method of manufacturing a negative electrode active material for a lithium secondary battery according to an embodiment of the present invention will be described in detail, but the description overlapping with the above description will be omitted.

Specifically, a step of forming a first coating layer containing metal-based fine particles on the surface of the graphite-based core particle to obtain an intermediate body is characterized in that a first mixed powder comprising the graphite-based core particles and the metal- Lt; / RTI &gt; And applying a shear stress to the first mixed powder to induce fusion between surfaces of the graphite-based core particles and the metal-based fine particles.

At this time, a step of applying shear stress to the first mixed powder to induce fusion between the surfaces of the graphite-based core particles and the metal-based fine particles may be performed by the mechanical coating method described above, Means a step of introducing a coating layer consisting primarily of metal-based fine particles onto the surface.

Particularly, it is possible to use an apparatus for inducing fusion between particle surfaces by applying a shearing force between the particles by rotating a rotating blade mounted on the rotor at a high speed.

More specifically, the present invention can be applied to various types of apparatuses such as mechanofusion milling, shaker milling, planetary milling, attritor milling disk milling, shape milling, But may be carried out by any one method selected from the group consisting of nauta milling, nobilta milling, high speed mixing, and combinations thereof.

Independently, the step may be performed at a rotational circumferential speed of 10 to 50 m / s. The range is an appropriate range for forming the first coating layer composed of the metal-based fine particles.

However, if it is less than 10 m / s, it is difficult to form the first coating layer. If it is more than 50 m / s, the graphite-based core particles and the metal fine particles may crack and fracture. It is limited.

On the other hand, distributing a second coating layer containing ceramic particles on all or a part of the surface of the intermediate comprises: preparing a second mixed powder including the intermediate and the ceramic particles; And applying a shear stress to the second mixed powder to induce fusion between surfaces of the intermediate and the ceramic particles.

Applying shear stress to the second mixed powder to induce fusion between surfaces of the intermediate and the ceramic particles; This also means a step of introducing the coating layer consisting of the ceramic particles in whole or in part on the surface of the first coating layer of the intermediate by the above-mentioned mechanical coating method.

Such as ball milling, mechanofusion milling, shaker milling, planetary milling, attritor milling, shape milling, Nauta milling, nauta milling, nobilta milling, high speed mixing, paddle mixing, ribbon mixing, henschel mixing, corn type mixing, And may be carried out by any one method selected from the group consisting of thinky mixing, homo mixing, stirrer, and combinations thereof.

Independently, the step of applying shear stress to the second mixed powder to induce fusion between the surfaces of the intermediate and the ceramic particles is performed at a rotational circumferential speed of 5 to 70 m / s .

An anode active material according to an embodiment of the present invention includes: a cathode; cathode; And a lithium secondary battery including an electrolyte. Specifically, the negative electrode includes any one of the negative electrode active materials for a lithium secondary battery described above.

This is because the negative electrode active material for a lithium secondary battery is minimized in volume expansion in the negative electrode compared to the conventional silicon based active material due to its structural characteristics and is prevented from cracking due to its structure, and ultimately, lithium It is a secondary battery.

The negative electrode active material for a lithium secondary battery is as described above, and the details thereof will be described in detail.

In general, a lithium secondary battery can be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery depending on the kind of a separator and an electrolyte to be used, and is classified into a cylindrical shape, a square shape, a coin shape, Depending on the size, it can be divided into bulk type and thin type. The structure and the manufacturing method of these cells are well known in the art, and detailed description thereof will be omitted.

1 is an exploded perspective view of a lithium secondary battery according to an embodiment of the present invention. 1, the lithium secondary battery 100 has a cylindrical shape and includes a cathode 112, a cathode 114, a separator 113 disposed between the cathode 112 and the anode 114, An electrolyte 114 (not shown), an electrolyte (not shown) impregnated into the separator 113, a battery container 120, and a sealing member 140 for sealing the battery container 120. The lithium secondary battery 100 is constructed by laminating a cathode 112, a separator 113 and an anode 114 in this order and then winding them in a spiral wound state in the battery container 120.

The negative electrode includes a current collector and a negative active material layer formed on the current collector, and the negative active material layer includes a negative active material.

The negative electrode active material is as described above.

The negative electrode active material layer also includes a binder, and may further include a conductive material.

The binder serves to adhere the anode active material particles to each other and to adhere the anode active material to the current collector. Typical examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, Such as polyvinyl chloride, polyvinyl fluoride, polymers comprising ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, Styrene-butadiene rubber, epoxy resin, nylon, and the like may be used, but the present invention is not limited thereto.

The conductive material is used for imparting conductivity to the electrode. Any material can be used as long as it does not cause any chemical change in the battery. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, , Carbon-based materials such as carbon fibers; Metal powders such as copper, nickel, aluminum, and silver, or metal-based materials such as metal fibers; Conductive polymers such as polyphenylene derivatives; Or a mixture thereof may be used.

The current collector may be a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foil, a copper foil, a polymer substrate coated with a conductive metal, or a combination thereof.

The anode includes a current collector and a cathode active material layer formed on the current collector.

As the cathode active material, a compound capable of reversibly intercalating and deintercalating lithium (a lithiated intercalation compound) can be used. Concretely, it is possible to use at least one of complex oxides of cobalt, manganese, nickel or a combination of metals and lithium, and specific examples thereof include compounds represented by any one of the following formulas. Li _a A _{1 - b} R _b D ₂ wherein, in the formula, 0.90? A? 1.8 and 0? B? 0.5; Li _a E _{1 - b} R _b O _{2 - c} D _c , wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, and 0 ≤ c ≤ 0.05; LiE _{2 - b} R _b O _{4 - c} D _{c where} 0? B? 0.5, 0? C? 0.05; Li _a Ni _{1 -b- c} Co _b R _c D _{α where} 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α ≦ 2; Li _a Ni _{1 - b - c} Co _b R _c O _{2 - ?} Z _{? Wherein} 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _{1 -b- c} Co _b R _c O _{2 - ?} Z ₂ wherein 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, and 0 <? Li _a Ni _1-bc Mn _b R _c D _? Wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _{1 -b- c} Mn _b R _c O _{2 - ?} Z _{? Where the} 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _{1 -b- c} Mn _b R _c O _{2 - ?} Z ₂ wherein 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _b E _c G _d O ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, and 0.001 ≤ d ≤ 0.1; Li _a Ni _b Co _c Mn _d GeO ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, and 0.001 ≤ e ≤ 0.1; Li _a NiG _b O ₂ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); Li _a CoG _b O ₂ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); Li _a MnG _b O ₂ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); Li _a Mn ₂ G _b O ₄ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); QO _2; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiTO ₂ ; LiNiVO _4; Li _(3-f) J ₂ (PO ₄ ) ₃ (0? F? 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0? F? 2); And LiFePO _4.

In the above formula, A is Ni, Co, Mn or a combination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element or a combination thereof; D is O, F, S, P or a combination thereof; E is Co, Mn or a combination thereof; Z is F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; Q is Ti, Mo, Mn or a combination thereof; T is Cr, V, Fe, Sc, Y or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu or a combination thereof.

Of course, a compound having a coating layer on the surface of the compound may be used, or a compound having a coating layer may be mixed with the compound. The coating layer may comprise, as a coating element compound, an oxide, a hydroxide of a coating element, an oxyhydroxide of a coating element, an oxycarbonate of a coating element, or a hydroxycarbonate of a coating element. The compound constituting these coating layers may be amorphous or crystalline. The coating layer may contain Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a mixture thereof. The coating layer forming step may be carried out by any of coating methods such as spray coating, dipping, and the like without adversely affecting the physical properties of the cathode active material by using these elements in the above compound. It is a content that can be well understood by people engaged in the field, so detailed explanation will be omitted.

The cathode active material layer also includes a binder and a conductive material.

The binder serves to adhere the positive electrode active material particles to each other and to adhere the positive electrode active material to the current collector. Typical examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl Polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-acrylonitrile, styrene-butadiene rubber, Butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like, but not limited thereto.

The conductive material is used for imparting conductivity to the electrode. Any conductive material can be used without causing any chemical change in the battery. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, Metal powders such as black, carbon fiber, copper, nickel, aluminum, and silver, metal fibers, and the like, and conductive materials such as polyphenylene derivatives may be used alone or in combination.

As the current collector, Al may be used, but the present invention is not limited thereto.

The negative electrode and the positive electrode are prepared by mixing an active material, a conductive material and a binder in a solvent to prepare an active material composition, and applying the composition to a current collector. The method of manufacturing the electrode is well known in the art, and therefore, a detailed description thereof will be omitted herein. As the solvent, N-methylpyrrolidone or the like can be used, but it is not limited thereto.

The electrolyte includes a non-aqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

As the non-aqueous organic solvent, a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based or aprotic solvent may be used. Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC) EC), propylene carbonate (PC), and butylene carbonate (BC) may be used. As the ester solvent, methyl acetate, ethyl acetate, n-propyl acetate, 1,1-dimethyl ethyl acetate, methyl propionate , Ethyl propionate,? -Butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone and the like can be used. Examples of the ether solvent include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran. As the ketone solvent, cyclohexanone may be used have. As the alcoholic solvent, ethyl alcohol, isopropyl alcohol and the like can be used. As the aprotic solvent, R-CN (R is a C2 to C20 linear, branched or cyclic hydrocarbon group, An amide such as nitriles such as dimethylformamide, and dioxolanes such as 1,3-dioxolane, sulfolanes, and the like can be used.

The non-aqueous organic solvent may be used alone or in admixture of one or more. If the non-aqueous organic solvent is used in combination, the mixing ratio may be appropriately adjusted according to the desired cell performance. .

In the case of the carbonate-based solvent, it is preferable to use a mixture of a cyclic carbonate and a chain carbonate. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1: 1 to about 1: 9, the performance of the electrolytic solution may be excellent.

The non-aqueous organic solvent may further include the aromatic hydrocarbon-based organic solvent in the carbonate-based solvent. In this case, the carbonate-based solvent and the aromatic hydrocarbon-based organic solvent may be mixed in a volume ratio of about 1: 1 to about 30: 1.

The aromatic hydrocarbon-based organic solvent may be an aromatic hydrocarbon-based compound represented by the following formula (1).

[Chemical Formula 1]

In Formula 1, R ₁ to R ₆ are each independently hydrogen, halogen, a C1 to C10 alkyl group, a C1 to C10 haloalkyl group, or a combination thereof.

The aromatic hydrocarbon-based organic solvent is selected from the group consisting of benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3- , 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, 1,2,4 - triiodobenzene, toluene, fluorotoluene, 1,2-difluorotoluene, 1,3-difluorotoluene, 1,4-difluorotoluene, 1,2,3-trifluorotoluene, 1,2,4-trifluorotoluene, chlorotoluene, 1,2-dichlorotoluene, 1,3-dichlorotoluene, 1,4-dichlorotoluene, 1,2,3-trichlorotoluene, 1,2,4 - trichlorotoluene, iodotoluene, 1,2-diiodotoluene, 1,3-diiodotoluene, 1,4-diiodotol Ene, 1,2,3-tree-iodo toluene, 1,2,4-iodo toluene, xylene, or may be a combination thereof.

The non-aqueous electrolyte may further include vinylene carbonate or an ethylene carbonate-based compound represented by the following formula (2) to improve battery life.

(2)

Wherein R ₇ and R ₈ are each independently hydrogen, a halogen group, a cyano group (CN), a nitro group (NO ₂ ) or a C1 to C5 fluoroalkyl group, and at least one of R ₇ and R ₈ Is a halogen group, a cyano group (CN), a nitro group (NO ₂ ) or a C1 to C5 fluoroalkyl group.

Representative examples of the ethylene carbonate-based compound include, for example, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, fluoroethylene carbonate, . When the vinylene carbonate or the ethylene carbonate compound is further used, the amount of the vinylene carbonate or the ethylene carbonate compound can be appropriately controlled to improve the life.

The lithium salt is dissolved in the non-aqueous organic solvent to act as a source of lithium ions in the battery to enable operation of a basic lithium secondary battery, and a material capable of promoting the movement of lithium ions between the positive electrode and the negative electrode to be. The lithium salt Representative examples are _{LiPF 6, LiBF 4, LiSbF 6} , LiAsF 6, 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 are natural numbers), LiCl, LiI, LiB ( C 2 O 4) 2 ( lithium bis oxalate reyito borate (lithium bis (oxalato) borate; LiBOB) , or in a combination thereof The concentration of the lithium salt is preferably within the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity Can exhibit excellent electrolyte performance, and lithium ions can effectively migrate.

The separator 113 separates the cathode 112 and the anode 114 and provides a passage for lithium ions. Any separator 113 may be used as long as it is commonly used in a lithium battery. That is, it is possible to use an electrolyte having a low resistance to ion movement and an excellent ability to impregnate an electrolyte. For example, selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and may be nonwoven fabric or woven fabric. For example, a polyolefin-based polymer separator such as polyethylene, polypropylene and the like is mainly used for a lithium ion battery, and a coated separator containing a ceramic component or a polymer substance may be used for heat resistance or mechanical strength, Structure.

Best Mode for Carrying Out the Invention Hereinafter, preferred embodiments and comparative examples of the present invention and examples in which these characteristics can be evaluated will be described. However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited to the following examples.

< Example : &Lt; / RTI &gt; In an implementation example  Preparation of negative electrode active material for lithium secondary battery and production of lithium secondary battery containing same>

Example  1: The negative electrode active material [spherical natural graphite core-nanosilicone coating layer- TiO ₂  Ceramic coating layer]

Production of negative electrode active material

(Average particle size (D50): 10 mu m) as the graphite core particles containing the internal pores, nanosilicon (average particle size (D50): 50 nm) as the metal fine particles and TiO ₂ ceramic (average particle diameter (D50): 30 nm) were prepared.

The graphite-based core particles and the metal-based fine particles were mixed in a weight ratio of 95: 5 (graphite-based core particles: metal-based fine particles), and then a blade rotating on the rotor was mounted. For 20 minutes. As a result, an intermediate in which a nanosilicone coating layer was formed on the surface of spherical natural graphite particles was obtained.

The intermediate and the ceramic particles were mixed in a weight ratio of 100: 2 (intermediate: ceramic particles), and mechanically coated at the circumferential speed of 20 m / s for 10 minutes in the high-speed stirrer to obtain a ceramic- A negative electrode active material in the form of a composite was obtained.

Cathode manufacturing

(SBR) as a binder and carboxymethyl cellulose (CMC) as a thickener were prepared and mixed in a mass ratio of 96: 2: 2 (negative electrode active material: binder: thickener) , And dispersed in distilled water from which ions have been removed to prepare an anode active material composition.

The composition was coated on a Cu-foil current collector, dried and rolled to prepare a negative electrode having an electrode density of 1.50 +/- 0.05 g / cm &lt; ^{3 &} gt ;.

Manufacture of lithium secondary battery

A coin type 2032 half cell was fabricated by using the negative electrode as the working electrode and the lithium metal as the counter electrode.

At this time, a separator made of a porous polypropylene film was inserted between the working electrode and the counter electrode. As the electrolyte, a mixture solution of ethylmethyl carbonate (EMC) and ethylene carbonate (EC) in a volume ratio of 7: ₆ was dissolved.

Example  2: The negative electrode active material [spherical natural graphite core-nanosilicone coating layer- SiO ₂  Ceramic coating layer]

Instead of the TiO ₂ ceramics, SiO ₂ A negative electrode active material and a negative electrode were prepared in the same manner as in Example 1 except that the ceramic was used, and a lithium secondary battery was produced.

< Comparative Example : Preparation of a negative electrode active material for a lithium secondary battery not including a ceramic coating layer and production of a lithium secondary battery containing the same>

Comparative Example  One

The stirring rate of the graphite-based core particles and the metal-based fine particles after mixing was 5 m / s, and the TiO ₂ Except that a ceramic coating layer was not formed. The negative electrode active material was prepared in the same manner. Thus, a negative electrode active material having a structure in which spherical natural graphite particles and nanosilicon were mixed was obtained.

Further, a negative electrode was prepared using the negative active material, and a lithium secondary battery was produced.

Comparative Example  2

In Comparative Example 1, except that the stirring speed was 25 m / s, The negative electrode active material was prepared in the same manner. Thus, a negative electrode active material having only a nanosilicon coating layer formed on the surface of the spherical natural graphite particles could be obtained.

Further, a negative electrode was prepared using the negative active material, and a lithium secondary battery was produced.

< Experimental Example : Characterization of anode active material, cathode, lithium secondary battery>

Experimental Example  1: Scanning electron microscope ( Scanning Electron Microscope , SEM Photo analysis - Observation of anode active material

SEM photographs were taken to observe the surface characteristics of the negative electrode active material prepared in Example 1.

FIG. 3 is a scanning electron microscope (SEM) image showing a cross section of the graphite-based core particle used in Example 1, and it can be seen that pores are evenly distributed in the graphite-based core particle.

Meanwhile, a scanning electron microscope photograph of the negative electrode active material prepared according to Example 1 corresponds to FIG. 4, and a mapping photograph showing the surface state thereof corresponds to FIG.

4 and 5, it can be seen that the anode active material according to Example 1 has a structure in which a double coating layer is formed on the surface of the graphite-based core particle, and a silicone-based metal coating layer and a ceramic coating layer are formed on the surface It can be confirmed that all of the coatings are uniformly coated.

Experimental Example  2: Evaluation of Thickness Expansion Characteristics of Cathode

The following experiment was conducted to confirm the effect of suppressing the thickness (volume) expansion of the negative electrode by the negative electrode active material prepared in the examples.

First, the lithium secondary battery manufactured according to each of Examples 1 and 2 and Comparative Examples 1 and 2 was charged and discharged at a rate of 0.1 C for 3 times and 60 times, and then charged again to decompose the battery in a fully charged state.

After recovering the negative electrode from each of the decomposed cells, the negative electrode was washed with diethyl carbonate (DEC) and then dried to measure the thickness after charging and discharging the negative electrode.

At this time, since the width (width * length) of the negative electrode was constant but the volume expanded due to the change in the thickness, the thickness swelling characteristics of the negative electrode were evaluated using the following equation (1).

[Equation 1] Thickness swelling (%) = (Thickness of charged cathode electrode - Thickness of foil) / (Thickness of initial cathode electrode - Thickness of foil) * 100

Negative electrode thickness expansion rate after 3.5 times (%) 60.5 Cathode Thickness Expansion Rate (%) Example 1 44.3 84.2 Example 2 49.4 85.3 Comparative Example 1 54.1 104.1 Comparative Example 2 56.3 87.4

The above evaluation is recorded in Table 1, which is illustrated in FIG. That is, FIG. 6 is a graph showing the evaluation of the thickness expansion characteristics of a negative electrode in a lithium secondary battery manufactured according to Examples 1 and 2 and Comparative Examples 1 and 2, respectively.

 Referring to Table 1 and FIG. 6, it can be seen that the change in the thickness (volume) of the negative electrode according to Examples 1 and 2 is reduced as compared with the negative electrode according to Comparative Examples 1 and 2.

Therefore, it can be deduced that the structures of the negative electrode active materials of Examples 1 and 2 confirmed in Experimental Example 1 contribute to minimizing the thickness (volume) expansion of the negative electrode.

Experimental Example  3: Lithium secondary battery Charging and discharging  Evaluation of life characteristics

With the negative electrode active material prepared in the examples, the charge / discharge life of the lithium secondary battery was In order to confirm the improved effect, the following experiment was carried out.

First, a lithium secondary battery manufactured according to each of Examples 1 and 2 and Comparative Examples 1 and 2 was set to a cut-off voltage of 0.005 V (0.01 C), and a 0.5 C rate , The capacity retention rate was measured after repeating charging and discharging at 60 cycles while discharging at 0.5C rate up to 1.5V in the CC mode.

The results are shown in Table 2, which is shown in FIG. That is, FIG. 7 is a graph showing the capacity retention rate of the lithium secondary battery manufactured according to Examples 1 and 2 and Comparative Examples 1 and 2 according to the charge-discharge life time.

60 times Charge / Discharge Capacity Retention Rate (%) Example 1 63.4 Example 2 62.5 Comparative Example 1 41.5 Comparative Example 2 57.9

Referring to Table 2 and FIG. 7, it can be seen that the cycle capacity retention rate according to the charge and discharge repetition of the lithium secondary battery according to Examples 1 and 2 is improved compared with the lithium secondary battery according to Comparative Examples 1 and 2.

Therefore, it can be deduced that the structure of the negative electrode active materials of Examples 1 and 2 confirmed in Experimental Example 1 ultimately contributes to improvement of the charge-discharge life characteristics of the lithium secondary battery.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

100: lithium secondary battery 112: cathode
113: separator 114: positive electrode
120: battery container 140: sealing member

Claims (22)

delete delete delete delete delete delete delete delete delete delete delete delete delete delete Preparing a graphite core particle containing pores therein;
Forming a first coating layer containing metal-based fine particles on the surface of the graphite-based core particle to obtain an intermediate;
Distributing a second coating layer comprising ceramic particles on all or part of the surface of said intermediate; And
Thereby obtaining a negative electrode active material,
Forming a first coating layer containing metal-based fine particles on the surface of the graphite-based core particles to obtain an intermediate body; and a step of preparing a first mixed powder comprising the graphite-based core particles and the metal- step; And applying a shear stress to the first mixed powder to induce fusion between surfaces of the graphite-based core particles and the metal-based fine particles,
Distributing a second coating layer comprising ceramic particles on all or a part of the surface of the intermediate, comprising the steps of: preparing a second mixed powder comprising the intermediate and the ceramic particles; And applying shear stress to the second mixed powder to induce fusion between the surfaces of the intermediate and the ceramic particles.
A method for producing a negative electrode active material for lithium secondary batteries.
delete 16. The method of claim 15,
Applying a shear stress to the first mixed powder to induce fusion between surfaces of the graphite-based core particles and the metal-based fine particles,
Such as mechanofusion milling, shaker milling, planetary milling, attritor milling, disk milling, shape milling, nauta milling, wherein the method is performed by any one method selected from the group consisting of milling, nobilta milling, high speed mixing, and combinations thereof.
A method for producing a negative electrode active material for lithium secondary batteries.
16. The method of claim 15,
Applying a shear stress to the first mixed powder to induce fusion between surfaces of the graphite-based core particles and the metal-based fine particles,
Lt; RTI ID = 0.0 &gt; m / s &lt; / RTI &gt;
A method for producing a negative electrode active material for lithium secondary batteries.
delete 16. The method of claim 15,
Applying shear stress to the second mixed powder to induce fusion between surfaces of the intermediate and the ceramic particles,
Such as ball milling, mechanofusion milling, shaker milling, planetary milling, attritor milling, shape milling, Nauta milling, nauta milling, nobilta milling, high speed mixing, paddle mixing, ribbon mixing, henschel mixing, corn type mixing, Wherein the mixing is carried out by any one method selected from the group consisting of thinky mixing, homo mixing, stirrer, and combinations thereof.
A method for producing a negative electrode active material for lithium secondary batteries.
16. The method of claim 15,
Applying shear stress to the second mixed powder to induce fusion between surfaces of the intermediate and the ceramic particles,
Lt; RTI ID = 0.0 &gt; m / s &lt; / RTI &gt;
A method for producing a negative electrode active material for lithium secondary batteries.
delete

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