KR20170076228A - Negative electrode active material for rechargable lithium battery, method for manufacturing the same, and rechargable lithium battery including the same - 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 comprising the same, which is a negative electrode active material including silicon oxide and a titanium dioxide coating layer disposed on the surface of the silicon oxide, , And the content of the titanium dioxide coating layer is 2 to 10% by weight, based on the total weight of the negative electrode active material.

Description

TECHNICAL FIELD [0001] 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 lithium secondary battery. BACKGROUND ART < RTI ID = 0.0 >

A negative electrode active material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery comprising the same.

2. Description of the Related Art Recently, lithium secondary batteries have attracted attention as power sources for driving portable electronic devices and electric vehicles. This is because, by using the organic electrolyte solution, the discharge voltage is twice as high as that of the battery using the conventional alkaline aqueous solution, and as a result, high power and energy density can be exhibited.

As a negative electrode active material used in such a lithium secondary battery, a material capable of inserting / desorbing lithium can be utilized, and various types of carbon-based materials including artificial graphite, natural graphite, and amorphous carbon are widely used.

In recent years, development of a large energy storage application system has been a hot topic, but since the capacity per unit mass of the carbon-based material currently used is as low as 350 mAh / g, it is required to use a negative electrode active material to replace it.

As a result, a silicon-based negative electrode active material exhibiting a higher capacity than the carbon-based material has been proposed, and this has been recognized in terms of miniaturization and weight reduction of the battery.

However, since such a silicon-based anode active material can store a large amount of lithium, the capacity of the battery is deteriorated due to rapid volume change caused by repeated charging and discharging, and the electric conductivity is lower than that of the carbon-based material.

On the other hand, germanium-based anode active material is also attracting attention because it has a higher capacity than a carbon-based material, has a lithium diffusion rate 100 times greater than silicon, and is advantageous in high-speed charging and discharging.

However, such a germanium-based anode active material still has a problem of volume change during charging and discharging as a backside of a high capacity characteristic, and its manufacturing cost has not been commercialized because of its high cost.

And to provide an anode active material having an improved initial charging / discharging effect.

Also, it is intended to provide a method for manufacturing an anode active material improved from the conventional sol-gel method.

Generally, lithium secondary batteries can be classified into lithium ion batteries (hereinafter referred to as "lithium secondary batteries "), lithium ion polymer batteries, and lithium polymer batteries depending on the type of the separator and electrolyte used. , Coin type, pouch type, etc., and can be divided into a bulk type and a thin film type depending on the size. The structure and the manufacturing method of these cells are well known in the art, and detailed description thereof will be omitted.

More specifically, the lithium secondary battery includes a negative electrode, a positive electrode, and a separator sequentially stacked and then wound in a spiral wound state, and the negative electrode includes a current collector and a negative electrode active material layer formed on the current collector And the negative electrode active material layer includes a negative electrode active material.

At this time, as the negative electrode active material, a material capable of reversibly intercalating / deintercalating lithium ions, a lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide is widely known .

Here, as a material capable of reversibly intercalating / deintercalating lithium ions, a carbonaceous anode active material has been commercialized, but it has been pointed out that there is a limit to manifesting a high capacity by itself.

On the other hand, silicon-based anode active material and germanium-based anode active material are used as materials capable of doping and dedoping lithium, and they exhibit a higher capacity than the carbonaceous anode active material. However, on the back surface thereof, rapid volume expansion and consequent structural instability There is a problem in that there is a problem that the electric conductivity is lower than that of the carbonaceous anode active material and the manufacturing cost is high.

The anode materials using the silicon-based materials and the materials that can compensate for these disadvantages are improved electrochemical properties. Among them, the titanium dioxide has a band gap energy of 3.2 eV, which can form a stable surface film when applied to the existing silicon oxide surface, and it can be expected to improve the thermal stability and safety related characteristics that may occur when the battery is misused.

According to an embodiment of the present invention, there is provided a negative electrode active material including silicon oxide and a titanium dioxide coating layer disposed on the surface of the silicon oxide, wherein the titanium dioxide coating layer is contained in an amount of 2 to 10 wt% A negative electrode active material for a lithium secondary battery.

More specifically, the content of the titanium dioxide coating layer may be more than 8 and 10 wt% or less.

The silicon oxide may be represented by the following formula (1).

[Chemical Formula 1]

SiO _x (0 < x < 2)

The silicon oxide may include hydrogen silsesquioxane.

In another embodiment of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: preparing a silicon oxide; Dispersing the silicon oxide in an alcohol-based solvent; Introducing a titanium oxide precursor into the alcohol-based solvent in which the silicon oxide is dispersed to induce a sol-gel reaction; Vaporizing the alcoholic solvent to obtain a powder; And heat-treating the obtained powder. The present invention also provides a method for producing a negative electrode active material for a lithium secondary battery.

The negative electrode active material obtained by the above production method may be a negative electrode active material including silicon oxide and a titanium dioxide coating layer positioned on the surface of the silicon oxide.

The negative electrode active material obtained by the above production method is a negative electrode active material including silicon oxide and a titanium dioxide coating layer positioned on the surface of the silicon oxide. The content of the titanium dioxide coating layer is 2 to 10 % &Lt; / RTI &gt;

More specifically, the content of the titanium dioxide coating layer may be more than 8 and 10 wt% or less.

The step of preparing the silicon oxide comprises the steps of adding a hydrogen silsesquioxane precursor to an acid solution and then stirring the mixture; Obtaining a precipitate by the stirring step; And drying and heat-treating the precipitate to obtain silicon oxide.

In the step of dispersing the silicon oxide in the alcoholic solvent, the alcoholic solvent may include ethyl alcohol.

Wherein the titanium oxide is at least one selected from the group consisting of triethoxysilane (C ₂ H ₅ O) ₃ SiH ₄ , triethoxysilane (C ₂ H ₅ O) ₃ SiH 4, . &Lt; / RTI &gt;

The step of heat-treating the obtained powder may be performed at 450 to 550 ° C. This is not intended to limit the scope of the present invention to such a range that is suitable for reducing titanium dioxide after coating.

The step of heat-treating the obtained powder may be carried out in an Ar atmosphere.

The step of heat-treating the obtained powder can be carried out at a rate of 180-220 ° C / hr.

In another embodiment of the present invention, cathode; And an electrolyte, wherein the negative electrode comprises a negative active material for a lithium secondary battery according to one embodiment of the present invention.

This is a lithium rechargeable battery excellent in lifetime characteristics and stability, with high-capacity characteristics being stably exhibited even when charging / discharging is repeated as the negative active material is included.

The description of the negative electrode active material is as described above, and the components of the lithium secondary battery will be described in detail.

Specifically, the separator may further include a separator between the anode and the cathode.

FIG. 1 schematically illustrates a lithium secondary battery according to an embodiment of the present invention. Referring to FIG. The lithium secondary battery 1 includes a battery container 5 including a positive electrode 3, a negative electrode 2 and an electrolyte solution impregnated in the separator 4 existing between the positive electrode 3 and the negative electrode 2, And a sealing member (6) for sealing the battery container (5).

As described above, the negative electrode of the lithium secondary battery includes a current collector and a negative electrode active material layer formed on the current collector, and the negative electrode active material layer includes a negative electrode active material. The description of the anode active material is omitted since it 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. As the binder, a water-insoluble binder, a water-soluble binder, or a combination thereof may be used.

Examples of the water-insoluble binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride , Polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

Examples of the water-soluble binder include styrene-butadiene rubber, acrylated styrene-butadiene rubber, polyvinyl alcohol, sodium polyacrylate, propylene and olefin copolymers having 2 to 8 carbon atoms, (meth) acrylic acid and (meth) Copolymers or combinations thereof.

When a water-soluble binder is used as the negative electrode binder, it may further include a cellulose-based compound capable of imparting viscosity. As the cellulose-based compound, carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, alkali metal salts thereof or the like may be used in combination. As the alkali metal, Na, K or Li can be used. The content of the thickener may be 0.1 to 3 parts by weight based on 100 parts by weight of the binder.

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, Carbon-based materials such as black and carbon fiber; 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 collector may be selected from the group consisting of a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foil, a polymer substrate coated with a conductive metal, and 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, at least one of complex oxides of metal and lithium selected from cobalt, manganese, nickel, and combinations thereof may be used. As a more specific example, a compound represented by any one of the following formulas may be used.

Li _a A _{1 - b} X _b D ₂ (0.90? A? 1.8, 0? B? 0.5); Li _a A _{1 - b} X _b O _{2 - c} D _c (0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05); LiE _{1 - b} X _b O _{2 - c} D _c (0? B? 0.5, 0? C? 0.05); LiE _{2 - b} X _b O _{4 - c} D _c (0? B? 0.5, 0? C? 0.05); Li _a Ni _{1 -b- c} Co _b X _c D _? (0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <?? 2); Li _a Ni _{1 -b- c} Co _b X _c O _{2 -α} T _α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _{1 -b- c} Co _b X _c O _{2 - ?} T ₂ (0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <? <2); Li _a Ni _{1 -b- c} Mn _b X _c D _? (0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <?? 2); Li _a Ni _{1 -b- c} Mn _b X _c O _{2- α} T _α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _{1 -bc} Mn _b X _c O _2-α T ₂ (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _b E _c G _d O ₂ (0.90? A? 1.8, 0? B? 0.9, 0? C? 0.5, 0.001? D? 0.1); Li _a Ni _b Co _c Mn _d G _e O ₂ (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li _a NiG _b O ₂ (0.90? A? 1.8, 0.001? B? 0.1); Li _a CoG _b O ₂ (0.90? A? 1.8, 0.001? B? 0.1); Li _a MnG _b O ₂ (0.90? A? 1.8, 0.001? B? 0.1); Li _a Mn ₂ G _b O ₄ (0.90? A? 1.8, 0.001? B? 0.1); Li _a MnG _b PO ₄ (0.90? A? 1.8, 0.001? B? 0.1); QO _2; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiZO 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); LiFePO ₄

In the above formula, A is selected from the group consisting of Ni, Co, Mn, and combinations thereof; X is selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements and combinations thereof; D is selected from the group consisting of O, F, S, P, and combinations thereof; E is selected from the group consisting of Co, Mn, and combinations thereof; T is selected from the group consisting of F, S, P, and combinations thereof; G is selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; Q is selected from the group consisting of Ti, Mo, Mn, and combinations thereof; Z is selected from the group consisting of Cr, V, Fe, Sc, Y, and combinations thereof; J is selected from the group consisting of V, Cr, Mn, Co, Ni, Cu, and combinations 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 at least one coating element compound selected from the group consisting of oxides, hydroxides of coating elements, oxyhydroxides of coating elements, oxycarbonates of coating elements, and hydroxycarbonates of coating elements. 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 an electric 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.

In the non-aqueous liquid electrolyte secondary battery according to an embodiment of the present invention, the non-aqueous 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.

Depending on the type of the lithium secondary battery, a separator may exist between the positive electrode and the negative electrode. The separator may be a polyethylene / polypropylene double layer separator, a polyethylene / polypropylene / polyethylene triple layer separator, a polypropylene / polyethylene / poly It is needless to say that a mixed multilayer film such as a propylene three-layer separator and the like can be used.

And to provide an anode active material having an improved initial charging / discharging effect.

Also, it is intended to provide a method for manufacturing an anode active material improved from the conventional sol-gel method.

Figure 1 is an electron micrograph of a coating material to the silicon oxide surface obtained in Example 1 to Example 2 of the TiO ₂ in a weight ratio of 10%.
2 is to prepare an electrode in accordance with the coating ingredients to the silicon oxide surface obtained in Example 1, the TiO ₂ of the embodiment a weight ratio of 10% to the third embodiment is the result of the one-time charge-discharge test.
Fig. 3 shows the results of a one-time charge / discharge test in which an electrode was manufactured according to Example 3 of Comparative Example 1. Fig.
FIG. 4 is a graph showing the recovery rate of charge / discharge capacity after a battery was manufactured using the electrodes of Example 3 and Comparative Example 1 and left at a high temperature.

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.

Hereinafter, preferred embodiments of the present invention, comparative examples thereof, and evaluation examples in which these are compared and evaluated will be described. However, the following examples are only a few of preferred embodiments of the present invention, and the present invention is not limited to the following examples.

Example

Example 1:

Add 0.1 M HCl solution of triethoxysilane ((C ₂ H ₅ O) ₃ SiH, 99.8%), which is the precursor of hydrogen silsesquioxane, and stir at 800 rpm for about 10 to 30 minutes. The solution after the reaction is filtered and the filtered precipitate is washed with demineralized water several times.

The precipitate is dried at 80-110 ° C for about 10 hours to remove any remaining moisture. The dried powder is placed in an electric furnace and heat-treated at 900 ° C for 1 hour in a 4% H ₂ / Ar atmosphere. At this time, the heating rate is 20 占 폚 / min.

Example 2:

Titanium (IV) butoxide (Ti (OC ₄ H ₉ ) ₄ ), which is a precursor of titanium oxide after dispersing the silicon oxide obtained in Example 1, in ethyl alcohol (C ₂ H ₅ OH, 95.0% 5, 10 wt%).

30 minutes to 1 hour. After stirring at room temperature, ethyl alcohol is vaporized while stirring in a hot water bath at 70 ° C. The dried powder is placed in a horizontal electric furnace and heat-treated in an Ar atmosphere at 500 ° C for 5 hours. At this time, the heating rate is 200 占 폚 / hr.

Example 3:

(PAA, Sigma-Aldrich) as a binder in a weight ratio of 8: 1: 1, and the aqueous solution obtained by dissolving the titanium oxide-coated silicon oxide obtained in Example 2, carbon black (Super- Followed by application to Cu foil, followed by vacuum drying at 120 ° C to obtain an electrode. The coin cell (2032 size) was assembled by using lithium metal and polyolefin separator, and battery evaluation was carried out. The electrolyte used was 1 M LiPF ₆ , EC: EMC (1: 2, vol%) and FEC (2%).

Comparative Example 1: A silicon oxide was produced in the same process by omitting Example 2, and an electrode and a coin cell were fabricated in the same manner as in Example 3.

Experimental Example

The batteries assembled in accordance with Example 3 and Comparative Example 1 were each charged and discharged once at room temperature and recharged. The charged battery is stored at 60 ° C for 48 hours. After storage, the battery in the charged state is discharged at room temperature. Thereafter, charging and discharging are performed once.

Figure 1 is an electron micrograph of a coating material to the silicon oxide surface obtained in Example 1 to Example 2 of the TiO ₂ in a weight ratio of 10%. As shown in FIG. 1, the TiO ₂ coating layer may be present on the surface of the silicon oxide.

2 is to prepare an electrode in accordance with the coating ingredients to the silicon oxide surface obtained in Example 1, the TiO ₂ of the embodiment a weight ratio of 10% to the third embodiment is the result of the one-time charge-discharge test.

Fig. 3 shows the results of a one-time charge / discharge test in which an electrode was manufactured according to Example 3 of Comparative Example 1. Fig.

Comparing Example 3 with Comparative Example 1, it can be seen that the initial efficiency is increased by about 2% when 10% TiO ₂ is coated on the surface by weight, and the reversible capacity is the same as the material of FIG. 3 , Respectively.

FIG. 4 is a graph showing the recovery rate of charge / discharge capacity after a battery was manufactured using the electrodes of Example 3 and Comparative Example 1 and left at a high temperature. As can be seen from FIG. 4, it can be confirmed that the thermal stability of the silicon oxide cathode is improved when TiO ₂ is coated on the surface as in the case of Example 3.

This effect is considered to be due to the fact that TiO ₂ is present on the surface to form a stable surface film, thereby increasing the reversible efficiency and capacity, and improving the thermal stability.

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.

Claims (13)

Silicon oxide and
And a titanium dioxide coating layer disposed on the surface of the silicon oxide,
Wherein the content of the titanium dioxide coating layer is 2 to 10% by weight based on 100% by weight of the total negative electrode active material.
The method according to claim 1,
Wherein the silicon oxide is represented by the following formula (1).
[Chemical Formula 1]
SiO _x (0 < x < 2)
The method according to claim 1,
Wherein the silicon oxide comprises hydrogen silsesquioxane. 2. The negative electrode active material for a lithium secondary battery according to claim 1, wherein the silicon oxide comprises hydrogen silsesquioxane.
Preparing a silicon oxide;
Dispersing the silicon oxide in an alcohol-based solvent;
Introducing a titanium oxide precursor into the alcohol-based solvent in which the silicon oxide is dispersed to induce a sol-gel reaction;
Vaporizing the alcoholic solvent to obtain a powder; And
Heat treating the obtained powder;
And a negative electrode active material for lithium secondary batteries.
5. The method of claim 4,
The negative electrode active material obtained by the above-
Wherein the anode active material is a negative electrode active material including silicon oxide and a titanium dioxide coating layer disposed on the surface of the silicon oxide.
6. The method of claim 5,
The negative electrode active material obtained by the above-
Silicon oxide and a titanium dioxide coating layer disposed on the surface of the silicon oxide, wherein the content of the titanium dioxide coating layer is 2 to 10% by weight based on 100% by weight of the total negative electrode active material. Gt;
5. The method of claim 4,
Preparing the silicon oxide,
Adding a hydrogen silsesquioxane precursor to an acid solution and stirring the solution;
Obtaining a precipitate by the stirring step; And
And drying and heat-treating the precipitate to obtain silicon oxide. The method for manufacturing a negative electrode active material for a lithium secondary battery according to claim 1,
5. The method of claim 4,
Dispersing the silicon oxide in an alcohol-based solvent,
Wherein the alcohol-based solvent comprises ethyl alcohol.
5. The method of claim 4,
Introducing a titanium oxide precursor into the alcohol-based solvent in which the silicon oxide is dispersed to induce a sol-gel reaction;
Wherein the titanium oxide comprises triethoxysilane (C ₂ H ₅ O) ₃ SiH. _{2. The method of} claim 1, wherein the titanium oxide comprises triethoxysilane (C ₂ H ₅ O) ₃ SiH.
5. The method of claim 4,
Heat treating the obtained powder,
Wherein the negative electrode active material is carried out at 450 to 550 占 폚.
5. The method of claim 4,
Heat treating the obtained powder,
Wherein the negative electrode active material is carried out in an Ar atmosphere.
5. The method of claim 4,
Heat treating the obtained powder,
Wherein the negative electrode active material is carried out at a rate of 180-220 캜 / hr.
anode;
cathode; And
An electrolyte;
The negative electrode includes the negative electrode active material for a lithium secondary battery according to any one of claims 1 to 3,
Lithium secondary battery.

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