KR101473696B1 - Negative active material for rechargeabl lithium battery, method of preparing same, negative electrode for rechargeable lithium battery using same and rechargeable litihum battery - Google Patents

Abstract

The present invention relates to a negative electrode active material for a lithium secondary battery, wherein the negative electrode active material includes an active material and an organic crosslinked layer formed on the surface of the active material and having nano pores.

A lithium secondary battery, an anode active material, an organic crosslinked layer, a cinnamate,

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative electrode active material for a lithium secondary battery, a method for producing the same, a negative electrode for a lithium secondary battery, and a lithium secondary battery including the same. BACKGROUND ART [0002]

The present invention relates to a negative electrode active material for a lithium secondary battery, a method for producing the same, a negative electrode for a lithium secondary battery comprising the same, and a lithium secondary battery, and more particularly to a negative active material for a lithium secondary battery having excellent life characteristics, A negative electrode for a lithium secondary battery, and a lithium secondary battery.

[0002] Lithium secondary batteries, which are popular as power sources for portable electronic devices in recent years, exhibit high energy densities by using organic electrolytes and exhibiting discharge voltages two times higher than those using conventional alkaline aqueous solutions.

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

As the anode active material, various types of carbon-based materials including artificial graphite, natural graphite, and hard carbon capable of lithium insertion and desorption have been applied. Among the carbon-based materials, graphite has a discharge voltage as low as -0.2 V compared to lithium, and a battery using graphite as an anode active material exhibits a high discharge voltage of 3.6 V, thereby providing an advantage in terms of energy density of a lithium battery, And thus it is most widely used because it guarantees the longevity of the lithium secondary battery. However, when an electrode plate is manufactured using graphite as an active material, the density of the electrode plate is lowered, and the capacity is low in terms of energy density per unit volume of the electrode plate. Further, at a high discharge voltage, side reactions with graphite are likely to occur with the organic electrolyte, and there is a risk of ignition or explosion due to malfunction or overcharge of the battery.

In order to solve such a problem, an oxide-based negative electrode active material has been recently developed. For example, amorphous tin oxide, which has been developed by Fuji Film, exhibits a high capacity of 800 mAh / g per weight, but has a fatal problem with an initial irreversible capacity of about 50%. In addition, a minor problem such as reduction of tin oxide from oxides to tin metal by charging and discharging seriously occurs, making it more difficult to use in batteries. In addition, as an oxide cathode, Li _a Mg _b VO _c (0.05? A? 3, 0.12? B? 2, 2? 2c-a-2b? 5) negative active material is described in Japanese Patent Laid-Open No. 2002-216753. In addition, in the 2002 Japan Inventor's Bulletin, No. 3B05, the lithium secondary battery anode characteristics of Li _{1 .1} V _{0 .9} O ₂ were disclosed.

However, since the oxide cathode still does not exhibit satisfactory cell performance, researches on it are underway.

An object of the present invention is to provide a negative electrode active material for a lithium secondary battery exhibiting excellent life characteristics.

The present invention also provides a method for producing the negative electrode active material.

The present invention also provides a negative electrode comprising the negative electrode active material.

The present invention also provides a lithium secondary battery including the negative electrode including the negative active material.

According to one embodiment of the present invention, there is provided an anode active material for a lithium secondary battery comprising an active material and an organic crosslinked layer formed on a surface of the active material and having nano pores.

The organic crosslinking layer includes a polymer formed by crosslinking between polymers represented by the following formula (1).

[Chemical Formula 1]

(In the formula 1,

Wherein R &lt; _{1 &gt;} is a substituted or unsubstituted alkylene,

Wherein R ₂ is selected from the group consisting of hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heterocycle, and R ₉ OR ₁₀ ,

R &lt; ₃ &gt; is a substituted or unsubstituted alkylene,

The R &lt; ₄ & R ₅ is the same or different from each other, is selected from the group consisting of hydrogen, and substituted or unsubstituted alkyl,

R ₉ is a substituted or unsubstituted alkylene,

Wherein R &lt; ₁₀ &gt; is selected from the group consisting of substituted or unsubstituted alkyl, and substituted or unsubstituted aryl,

Wherein n is from 50 to 10,000,

And m is 0 to 5.)

The organic crosslinking layer preferably comprises a polymer having a weight average molecular weight of 1,000 to 1,000,000.

The organic crosslinked layer preferably has an average thickness of 5 to 350 nm.

The organic crosslinking layer is preferably contained in an amount of 0.1 to 3% by weight based on the total weight of the negative electrode active material.

According to another embodiment of the present invention, there is provided a method of manufacturing a lithium secondary battery including the steps of: coating a surface of an active material with a coating composition comprising a polymer of Formula 1; and irradiating the coated active material with UV to prepare an anode active material. A method for manufacturing a negative electrode active material for a battery is provided.

According to another embodiment of the present invention, there is provided an anode including the anode active material for a lithium secondary battery.

According to another embodiment of the present invention, there is provided a lithium secondary battery including a negative electrode including the negative active material for the lithium secondary battery.

In the negative electrode active material of the present invention, an organic crosslinking layer formed by crosslinking of the polymer of Formula (1) is formed on the surface of the active material, thereby suppressing volume change during charging and discharging. Thus exhibiting improved lifetime characteristics.

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

The negative electrode active material for a lithium secondary battery according to an embodiment of the present invention will now be described in detail.

Generally, the negative electrode active material of the lithium secondary battery is repeatedly charged and discharged, resulting in the insertion and desorption of lithium ions, resulting in repeated expansion and contraction of the negative electrode active material and cracks in the active material. As a result, And there is a problem that the electric conductivity is deteriorated.

Disclosed is a negative active material for a lithium secondary battery capable of inhibiting a volume change due to charging and discharging, preventing deterioration of lifetime and deterioration of electrical conductivity, and preventing a thick film from being formed on the surface of a negative electrode, do.

The negative electrode active material of the present invention includes an active material and an organic crosslinked layer formed on the surface of the active material and having nano pores.

The organic crosslinking layer includes a polymer formed by crosslinking between polymers represented by the following formula (1).

[Chemical Formula 1]

Representative examples of the polymer represented by Formula 1 include a polymer having a cinnamate group as shown in Formula 2 below.

(2)

The polymer formed by cross-linking of the polymer represented by Formula 1 may be a polymer represented by Formula 3 below.

(3)

Representative examples of the polymer represented by Formula 3 include a polymer represented by Formula 4 below.

[Chemical Formula 4]

In the above Chemical Formulas 1 to 4,

The R ₁ and R ₁ 'may be the same or different and are each independently a substituted or unsubstituted alkylene group, preferably a substituted or unsubstituted C ₂ to C ₄ alkylene group.

Wherein R ₂ and R ₂ 'are the same or different from each other and selected from the group consisting of hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, substituted or unsubstituted heterocycle, and R ₉ OR ₁₀ number, and more preferably substituted or unsubstituted C ₁ within the support C ₅ alkyl, phenyl, halogen (where halogen is F, Cl, Br, or I Im) with a phenyl, CH ₂ -O-CH ₃ substituted , CH ₂ -CH ₂ -O-CH ₃ , and CH ₂ -CH ₂ -CH ₂ -O-CH ₃ , and still more preferably selected from the group consisting of C ₁ to C ₅ substituted or unsubstituted Gt; is selected from the group consisting of hydrogen, substituted alkyl, and phenyl. The R ₃ And R &lt; ₃ &gt; Which may be the same or different from each other, may be substituted or unsubstituted alkylene.

R ₄ , R _{5 ,} R ₄ 'and R ₅ 'may be the same or different from each other and may be selected from the group consisting of hydrogen, and substituted or unsubstituted alkyl, preferably hydrogen, and substituted or unsubstituted C ₁ to C ₅ alkyl It can be selected.

Wherein R ₆ , R ₇ , R ₈ , R ₆ ', R ₇ ' and R ₈ 'are the same or different and are selected from the group consisting of hydrogen, halogen where the halogen is F, Cl, Br or I, Substituted alkyl, more preferably hydrogen, halogen, and substituted or unsubstituted alkyl of C ₁ to C ₅ .

The R ₉ may be a substituted or unsubstituted alkylene, and R ₁₀ may be a substituted or unsubstituted alkyl or a substituted or unsubstituted aryl group.

The n may be from 50 to 10,000, more preferably from 100 to 5,000.

M may be from 0 to 5;

Unless otherwise specified herein, "alkylene" refers to C ₁ to C ₁₀ alkylene, more preferably C ₂ to C ₅ alkylene, "aryl" refers to C ₆ to C ₃₀ aryl, more preferably C aryl of ₆ to C _12, "heterocycle" is a heterocycle of the C ₂ to C _30, a heterocycle of more preferably C ₅ to C _10, "alkyl" means C ₁ to C ₁₀ alkyl, more preferably a cycloalkyl of C ₂ to C is a C ₅ alkyl, "cycloalkyl" ₃ to C _30, more preferably C ₃ &Lt; / RTI &gt; to _C12 cycloalkyl.

Means a heteroaryl, a heterocycloalkyl, a heterocycloalkenyl, or a fused ring thereof containing a heteroatom, and the heteroatom means N, O, or S. The term " heteroaryl " In addition, the above-mentioned heterocyclic ring means that the heterocyclic ring contains 1 to 10 hetero atoms, preferably 1 to 5 hetero atoms.

Unless otherwise specified in the specification, "substituted" means that the hydrogen atom in the compound is selected from the group consisting of halogen, alkyl, alkenyl, alkoxy, aryl, cycloalkyl, heterocycloalkyl, Quot; means substituted by at least one substituent selected.

The polymer formed by crosslinking the polymer of Formula 1 preferably has a weight average molecular weight of 1,000 to 1,000,000. When the weight average molecular weight is less than 1,000, mechanical properties such as tensile strength and adhesive strength are lowered, which may cause a problem that the organic crosslinked layer is separated from the active material surface during repeated charge and discharge, which is not preferable. In addition, when the weight average molecular weight exceeds 1,000,000, the mobility of the polymer chain decreases, and the crosslinking reaction of the cinnamate group does not easily occur, which is not preferable.

The organic crosslinked layer preferably has an average thickness of 5 to 350 nm, more preferably an average thickness of 5 to 200 nm, even more preferably an average thickness of 5 to 100 nm, more preferably an average thickness of 10 to 30 nm Is even more preferable. In the above range, the organic crosslinking layer having an appropriate thickness can effectively suppress the volume change of the electrode during charging and discharging, prevent a problem that a coating is formed at the contact interface between the electrolyte and the active material, There is an advantage to be improved. However, when the thickness of the organic crosslinking layer exceeds 350 nm, a thick film may be formed on the surface of the active material to increase the resistance of the electrode. If the thickness is less than 5 nm, it is difficult to form a uniform coating layer on the surface of the active material, Is not preferable because it has insufficient effect.

The organic crosslinking layer is preferably contained in an amount of 0.1 to 3% by weight, and more preferably 0.5 to 1.5% by weight based on the total weight of the negative electrode active material. When the content of the organic crosslinking layer is less than 0.1% by weight, it is difficult to uniformly coat the surface of the active material particles, and when it exceeds 0.3% by weight, a too thick coating layer is formed on the active material surface, Which is undesirable.

The average particle diameter of the nano pores is preferably 1 to 10 nm, more preferably 1 to 5 nm, even more preferably 2 to 4 nm.

In the above range, solvated lithium ion (a complex formed by ion-dipole interaction of carbonate organic solvent and lithium ion with a size of about 1 nm) easily moves to the surface of the active material . If the average particle diameter of the nano pores is more than 10 nm, the organic solvent may be transferred to the surface of the active material to cause a reduction decomposition reaction, which is undesirable.

Examples of the active material include a lithium metal, a metal material capable of alloying with lithium, a material capable of doping and dedoping lithium, a material capable of reversibly reacting with lithium to form a lithium-containing compound, a transition metal oxide, And a composite material including the metal material and the carbonaceous material may be used.

As the metal capable of being alloyed with lithium, Al, Si, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Ag, Ge, K, Na, Ca, Sr, Ba, Sb, Zn, For example. Examples of the transition metal oxide, a substance capable of doping and dedoping lithium, and a substance capable of reacting reversibly with lithium to form a lithium-containing compound include tin oxide (SnO ₂ ), vanadium oxide, lithium vanadium oxide , Titanium nitrate, Si, SiO _x (0 <x <2), Sn, and composite tin alloys. Examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, fired coke, etc., and the like. Examples of the amorphous carbon include amorphous carbon, Examples of the crystalline carbon include amorphous, plate-like, flake, spherical or fibrous natural graphite or artificial graphite.

At this time, the carbon-based material is preferably a crystalline carbon having an Lc of 20 nm or more by X-ray diffraction and an exothermic peak at 700 DEG C or higher. In addition, such crystalline carbon can be obtained from a carbon material or a mesophase pitch fiber produced through a carbonizing step and a graphitizing step from mesophase spherical particles, and a carbonization step and a graphitization step from the mesophase pitch fiber The graphite fiber produced by the above process is preferable.

Preferably, the active material may be a metal or a mixture of a metal-based active material and a carbon-based active material, more preferably a lithium vanadium oxide represented by the following formula (5).

[Chemical Formula 5]

Li _x M _y V _z O _{2 + d}

0.5, 0? D? 0.5, and M is at least one selected from the group consisting of Al, Cr, Mo, Ti, W, Zr and combinations thereof. It is one kind of metal selected from the group.

In the negative electrode active material having the above-described structure, an organic crosslinked layer having nano pores is formed on the surface of the active material, so that lithium ions can be easily inserted into or removed from the active material, and the volume expansion and contraction phenomenon . Therefore, it is possible to prevent a problem that cracks are generated in the active material due to repetitive charging / discharging, deterioration of battery life and deterioration of electric conductivity. In addition, since the organic crosslinking layer surrounds the surface of the active material, formation of a SEI (solid electrolyte interface) coating on the negative electrode active material by the electrochemical decomposition reaction of the electrolyte at the interface between the active material and the electrolyte can be prevented during charging and discharging.

According to another embodiment of the present invention, there is provided a method of manufacturing the negative electrode active material for a lithium secondary battery.

The method comprises the steps of: (S1) coating a surface of an active material with a coating composition comprising a polymer formed by crosslinking a polymer represented by the general formula (1); and irradiating the coated active material with UV to form an anode active material (S2). &Lt; / RTI &gt;

S1 : Coating composition coating on the surface of active substance

The coating composition is prepared by dispersing the polymer represented by Formula 1 in a solvent.

The solvent may be selected from the group consisting of methanol, ethanol, propanol, isopropanol, and mixtures thereof.

The active material is added to the previously prepared coating composition. The active material is the same as described above.

S2 : UV  Research

The coated active material is irradiated with a light source. Preferably, UV (ultraviolet) irradiation can be performed. The ultraviolet region of the UV is preferably 200 to 400 nm, more preferably 250 to 350 nm. If it is irradiated at less than 200 nm, the crosslinking reaction of the polymer represented by the formula (1) may not occur, which is undesirable, and if it exceeds 400 nm, the polymer chain may be decomposed.

The irradiation of the light source is preferably performed at 20 to 35 캜, more preferably at 25 to 30 캜. In the above range, the coating composition present in the liquid or polymer form on the surface of the active material can be smoothly cured, and further heat treatment is not required, which is preferable. If the temperature is out of the range, the coating composition may be deteriorated by heat, which is not preferable.

When the light source is irradiated, the polymer represented by Formula (1) coated on the surface of the active material causes a photo-catalyzed reaction to form a polymer having a crosslinked structure.

According to another embodiment of the present invention, a negative electrode for a lithium secondary battery is provided.

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.

The negative electrode active material is the same as that described above, and it is preferably contained in an amount of 75 to 98% by weight, more preferably 85 to 95% by weight based on the total amount of the negative electrode active material layer. If the content is out of the above range, the capacity may be lowered or the amount of the binder may be decreased, which may result in deterioration of binding force with the current collector.

The negative electrode may be prepared by mixing the negative electrode active material, a binder, and optionally a conductive agent in a solvent to prepare a composition for forming the negative electrode active material layer, and then applying the composition to a negative electrode current collector such as copper. The method of manufacturing the electrode is well known in the art, and therefore, a detailed description thereof will be omitted herein.

Examples of the binder include polyvinyl alcohol, carboxymethylcellulose, hydroxypropylene cellulose, diacetylene cellulose, polyvinyl chloride, polyvinylpyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, But is not limited thereto.

As the conductive agent, any conductive material may be used without causing any chemical change. Examples of the conductive agent include natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, Metal powders such as aluminum and silver, or metal fibers, and conductive materials such as polyphenylene derivatives may also be mixed and used.

As the solvent, N-methylpyrrolidone or the like can be used, but it is not limited thereto.

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 negative electrode preferably has a volume expansion rate of 100 vol% or less, more preferably 50 vol% or less. In this range, the volume expansion rate is not large, and the electron conduction path in the electrode can be maintained, so that the battery performance is not deteriorated. However, when it is outside the above range, since the volume expansion rate is extremely high, it is difficult to maintain the electron conduction path in the electrode during repetitive charging and discharging, and battery performance may be deteriorated.

 According to another embodiment of the present invention, there is provided a lithium secondary battery including a negative electrode including the negative active material, a positive electrode, and an electrolyte.

The positive electrode includes a positive electrode active material, and the positive active material may be a compound capable of reversibly intercalating and deintercalating lithium (a lithiated intercalation compound). Concretely, it is possible to use at least one of complex oxides of metal and lithium selected from cobalt, manganese, nickel, and combinations thereof, more preferably compounds represented by any one of the following formulas have:

[Chemical Formula 6]

Li _{aa 1 - b} B _b D ₂

(In the above formula, 0.95? A? 1.1, and 0? B? 0.5)

(7)

Li _a E _{1 - b} B _b O _{2 - c} F _c

(In the above formula, 0.95? A? 1.1, 0? B? 0.5, 0? C? 0.05)

[Chemical Formula 8]

LiE _{2 - b} B _b O _{4 - c} F _c

(In the above formula, 0? B? 0.5, 0? C? 0.05)

[Chemical Formula 9]

Li _a Ni _{1 - b - c} Co _b B _c D _α

(Where 0.95? A? 1.1, 0? B? 0.5, 0? C? 0.05, 0 <?? 2)

[Chemical formula 10]

Li _a Ni _{1 -b- c} Co _b B _c O _{2 - ?} F _?

(Where 0.95? A? 1.1, 0? B? 0.5, 0? C? 0.05, 0 <? <2)

(11)

Li _a Ni _{1 -b- c} Co _b B _c O _{2 - ?} F ₂

(Where 0.95? A? 1.1, 0? B? 0.5, 0? C? 0.05, 0 <? <2)

[Chemical Formula 12]

Li _a Ni _{1 -b- c} Mn _b B _c D _?

(Where 0.95? A? 1.1, 0? B? 0.5, 0? C? 0.05, 0 <?? 2)

[Chemical Formula 13]

Li _a Ni _{1 - b - c} Mn _b B _c O _{2 - ?} F _?

(Where 0.95? A? 1.1, 0? B? 0.5, 0? C? 0.05, 0 <? <2)

[Chemical Formula 14]

Li _a Ni _{1 - b - c} Mn _b B _c O _{2 - ?} F ₂

(Where 0.95? A? 1.1, 0? B? 0.5, 0? C? 0.05, 0 <? <2)

[Chemical Formula 15]

Li _a Ni _b e _c G _d O ₂

(Where 0.90? A? 1.1, 0? B? 0.9, 0? C? 0.5, and 0.001? D? 0.1).

[Chemical Formula 16]

Li _a Ni _b Co _c Mn _d GeO ₂

(In the above formula, 0.90? A? 1.1, 0? B? 0.9, 0? C? 0.5, 0? D? 0.5, and 0.001? E? 0.1.

[Chemical Formula 17]

Li _a NiG _b O ₂

(In the above formula, 0.90? A? 1.1 and 0.001? B? 0.1).

[Chemical Formula 18]

Li _a CoG _b O ₂

(In the above formula, 0.90? A? 1.1 and 0.001? B? 0.1).

[Chemical Formula 19]

Li _a MnG _b O ₂

(In the above formula, 0.90? A? 1.1 and 0.001? B? 0.1).

[Chemical Formula 20]

Li _a Mn ₂ G _b O ₄

(In the above formula, 0.90? A? 1.1 and 0.001? B? 0.1).

[Chemical Formula 21]

QO ₂

[Chemical Formula 22]

QS ₂

(23)

LiQS ₂

&Lt; EMI ID =

V ₂ O ₅

(25)

LiV ₂ O ₅

(26)

LiIO ₂

(27)

LiNiVO ₄

(28)

Li _(3-f) J ₂ (PO ₄ ) ₃ (0? F? 3)

[Chemical Formula 29]

Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0? F? 2)

In the above Chemical Formulas 6 to 29, A is selected from the group consisting of Ni, Co, Mn, and combinations thereof;

B 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;

F is selected from the group consisting of F, S, P, and combinations thereof;

G is a transition metal or a lanthanide element 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;

I 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.

The positive electrode may also be formed by mixing the positive electrode active material, the binder and the conductive agent to form a composition for forming the positive electrode active material layer, and then applying the composition for forming the positive electrode active material layer to a positive current collector such as aluminum can do.

Examples of the conductive agent include any of natural graphite, artificial graphite, carbon black, acetylene black, ketjen 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.

Examples of the binder include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropylene cellulose, diacetylene cellulose, polyvinyl chloride, polyvinyl pyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene or polypropylene But is not limited thereto.

As the solvent, N-methylpyrrolidone or the like can be used, but it is not limited thereto.

In the lithium secondary battery of the present invention, 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.

The non-aqueous organic solvent may be a carbonate, ester, ether, ketone, alcohol, or aprotic solvent. 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), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC) may be used. Examples of the ester solvent include n-methyl acetate, n-ethyl acetate, n- Acetate, methyl propionate, ethyl propionate, gamma -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. Examples of the non-protonic solvents include X-CN (wherein R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and examples thereof include methyl ethyl ketone, A double bond aromatic ring or an ether bond); amines such as dimethylformamide; dioxolanes such as 1,3-dioxolane; sulfolanes; and the like.

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 1: 1 to 1: 9, the performance of the electrolyte may be excellent.

The non-aqueous organic solvent of the present invention may further comprise an 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 1: 1 to 30: 1.

The aromatic hydrocarbon-based organic solvent may be an aromatic hydrocarbon-based compound represented by the following formula (30).

(30)

(Wherein R _a to R _f are each independently selected from the group consisting of hydrogen, halogen, an alkyl group having 1 to 10 carbon atoms, a haloalkyl group, and combinations thereof).

Preferably, the aromatic hydrocarbon organic solvent is selected from the group consisting of benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-tri Fluorobenzene, 1,2,4-trifluorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1 , 2,4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, But are not limited to, 2,4-triiodobenzene, toluene, fluorotoluene, 1,2-difluorotoluene, 1,3-difluorotoluene, 1,4-difluorotoluene, 1, 2-dichlorotoluene, 1,2-dichlorotoluene, 1,2-dichlorotoluene, 1,2-dichlorotoluene, 2,4-trichlorotoluene, iodotoluene, 1,2-diiodotoluene, 1,3-diiodotoluene, 1,4- Iodo toluene, to which 1,2,3-tree-iodo toluene, 1,2,4-iodo toluene, xylene, and selected from the group consisting of.

The electrolyte may further include a life improving additive such as vinylene carbonate or fluoroethylene carbonate to improve battery life. When such a life improving additive is further used, its amount can be appropriately adjusted.

The lithium salt is dissolved in the organic solvent to act as a source of lithium ions in the cell to enable operation of the basic lithium secondary battery and to promote the movement of lithium ions between the anode and the cathode. The lithium salt Representative examples are _{LiPF 6, LiBF 4, LiSbF 6} , LiAsF 6, LiCF 3 SO 3, LiN (SO 2 C 2 F 5) 2, LiN (CF 3 SO 2) 2, LiC4F 9 SO 3, LiClO 4 , LiAlO ₄ , LiAlCl ₄ , LiN (C _x F _{2 x +1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ) wherein x and y are natural numbers, LiCl, LiI, lithium bisoxalate borate bisoxalate borate, and combinations thereof as a supporting electrolyte salt. The concentration of the lithium salt is preferably within the range of 0.1 to 2.0 M. If the concentration of the lithium salt is less than 0.1 M, the conductivity of the electrolyte is lowered to deteriorate the electrolyte performance. If the concentration exceeds 2.0 M, the viscosity of the electrolyte increases and the lithium ion mobility decreases.

When a solid electrolyte is used as the electrolyte, the solid electrolyte may be a polyethylene oxide polymer electrolyte or a polymer electrolyte containing at least one polyorganosiloxane side chain or polyoxyalkylene side chain, Li ₂ S-SiS ₂ , Li ₂ S-GeS ₂ , Li ₂ SP ₂ S ₅ , or Li ₂ SB ₂ S ₃ , an inorganic electrolyte such as Li ₂ S-SiS ₂ -Li ₃ PO ₄ , or Li ₂ S-SiS ₂ -Li ₃ SO ₄ Can be preferably used.

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.

An example of the lithium secondary battery of the present invention having the above-described configuration is shown in Fig. An example of the lithium secondary battery of the present invention having the above-described configuration is shown in Fig. 1, the lithium secondary battery 100 includes an electrode group 110 in which an anode 112 and a cathode 113 are positioned with a separator 114 interposed therebetween, and an electrode group 110 capable of accommodating the electrode group 110 together with an electrolyte And a case 120 having an opening at one end thereof. A cap assembly 140 for sealing the case 120 is installed in the opening of the case 120. Of course, the lithium secondary battery of the present invention is not limited to this shape, but may be any shape such as a square shape, a pouch shape, or the like.

Hereinafter, examples and comparative examples of the present invention 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 1)

1-1. Anode active material manufacturing

[Formula 1a]

0.1 g of the polymer of Formula 1a (n = 100) was dispersed in 10 ml of tetrahydrofuran to prepare a coating composition.

The coating composition and Li _{1 .1} V _{0 .9} O ₂ 1: 2, and UV irradiation was conducted to prepare an anode active material. On the surface of Li _{1 .1} V _{0 .9} O ₂ of the prepared negative active material, an organic crosslinked layer containing a polymer having the following formula (3a) (n is 100) was formed to a thickness of 50 nm, and the organic crosslinked layer had a diameter of 10 nm Of the pores were present in an amount of 60% or more .

[Chemical Formula 3]

1-2. Lithium secondary battery manufacturing

The negative electrode active material prepared above and polyvinylidene fluoride were mixed at a weight ratio of 90: 10 in N-methylpyrrolidone to prepare an anode slurry.

The negative electrode slurry was coated on a copper foil to a thickness of 70 탆 to form a thin electrode plate, dried at 135 캜 for 3 hours or more, and then pressed to manufacture a negative electrode.

LiCoO ₂ cathode active material, polyvinylidene fluoride, and carbon conductive agent were mixed at a weight ratio of 92: 4: 4 and dispersed in N-methyl-2-pyrrolidone solvent to prepare a cathode slurry. The positive electrode slurry was coated on an aluminum foil to a thickness of 70 mu m to form a thin electrode plate, dried at 135 DEG C for 3 hours or more, and then pressed to manufacture a positive electrode.

An electrolyte was prepared by adding 1.15 M LiPF ₆ to a mixed solvent of diethyl carbonate (DEC) and ethylene carbonate (EC) in a volume ratio of 7: 3.

The negative electrode and the positive electrode thus prepared were wound up using a separator made of a porous polypropylene film, placed in a battery can, and then an electrolyte was injected to prepare a lithium secondary battery. At this time, the amount of electrolyte used was 2.7 g.

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 invention as defined by the appended claims.

(Example 2)

Li _{1 .1} V _{0 .9} O ₂ was changed to SiO ₂ to prepare a negative electrode active material and a lithium secondary battery including the negative active material.

(Comparative Example 1)

A lithium secondary battery was manufactured in the same manner as in Example 1, except that Li _{1 .1} VO ₂ was not coated with the polymer of Formula (I).

(Comparative Example 2)

A lithium secondary battery was produced in the same manner as in Example 1 except that SiO was not coated with the polymer of Formula 1a.

Bridged  Pore data of polymer

0.1 g of the polymer of Formula 1a (n = 100) was dispersed in 10 ml of tetrahydrofuran to prepare a coating composition. The coating composition was coated on a glass substrate, and UV was irradiated to prepare a thin film formed by crosslinking the polymer. The pore size of the thin film was measured with a pore size meter, and it is shown in FIG.

Referring to FIG. 2, in the crosslinked polymer thin film, fine pores of 0 nm or more and 23 nm or less were formed, and most of the pores were found to be pores of 10 nm or less in most cases.

Measurement of volume expansion rate

Each of the lithium secondary batteries prepared in Examples 1 and 2 and Comparative Examples 1 and 2 was charged at 0.2 C and discharged once at 0.2 C (chemical process, FORMATION), charged at 0.5 C, discharged at 0.2 C (Standard process, STANDARD). Subsequently, each lithium secondary battery was charged once at a room temperature and a pressure of 0 psi at 0.1 C, and then decomposed to measure the volume expansion rate of the negative electrode at the initial stage. Further, the pressure was changed to 40 psi, and the battery was charged once at a pressure of 0.1 C under 40 psi, and then decomposed to measure the volume expansion rate of the negative electrode at the initial stage, which is shown in Table 1 below.

[Table 1]

Cathode Volume Expansion Rate (0 psi) Cathode Volume Expansion Rate (40 psi) Example 1 28% 21% Example 2 73% 45% Comparative Example 1 40% 32% Comparative Example 2 95% 67%

Referring to Table 1, it was confirmed that Examples 1 and 2 prepared from an anode active material having an organic crosslinked layer having nano pores on the surface had significantly less volume expansion than Comparative Examples 1 and 2.

Life characteristic measurement

Each of the lithium secondary batteries prepared in Examples 1 and 2 and Comparative Examples 1 and 2 was charged to 0.2 C and discharged once at 0.2 C (chemical conversion step), charged at 0.5 C, discharged at 0.2 C for 1 (Standard process). Thereafter, charging and discharging at 0.8 C and discharging at 200 C cycles were performed, and the results of the cycle life test are shown in FIG.

Referring to FIG. 3, the lithium secondary battery manufactured according to Example 1 and Example 2 of the present invention exhibited an excellent discharge capacity even after 200 cycles of charging and discharging. However, the lithium secondary battery manufactured according to Comparative Examples 1 and 2 has a 100 It was confirmed that the discharge capacity was rapidly reduced even during the charge and discharge cycles. Therefore, it was confirmed that the lithium secondary battery including the negative electrode active material of the present invention has excellent lifetime characteristics.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It is possible.

1 is a schematic view of a lithium secondary battery according to an embodiment of the present invention.

2 is pore data of a crosslinked polymer thin film prepared from the coating composition of Example 1 of the present invention.

3 is life data of lithium secondary batteries according to Examples 1 and 2 and Comparative Examples 1 and 2 of the present invention.

Claims (17)

Active substance; And An organic crosslinking layer formed on the surface of the active material and having nano pores, Wherein the organic crosslinking layer comprises a polymer formed by cross-linking between polymers represented by the following general formula (1) including a cinnamate group: [Chemical Formula 1]

In Formula 1, Wherein R &lt; _{1 &gt;} is substituted or unsubstituted ethylene, R ₂ is a substituted or unsubstituted phenyl group, Wherein R &lt; ₃ &gt; is a substituted or unsubstituted C1 to C10 alkylene, The R &lt; ₄ & R ₅ are the same or different from each other and selected from the group consisting of hydrogen and substituted or unsubstituted C 1 to C 10 alkyl, Wherein n is from 50 to 10,000, M is zero. delete delete The method according to claim 1, Wherein the polymer formed by cross-linking between the polymers represented by Formula 1 is represented by Formula 3 below. (3)

In Formula 3, Wherein R ₁ and R ₁ 'are the same or different and each independently ethylene, Wherein R &lt; ₂ &gt; and R &lt; ₂ & A substituted or unsubstituted phenyl group, Wherein R ₃ and R ₃ 'are the same or different and are each independently a substituted or unsubstituted C 1 to C 10 alkylene, R ₄ , R _5, R ₄ 'and R ₅ ' Are each independently selected from the group consisting of hydrogen, substituted or unsubstituted C1 to C10 alkyl, Wherein n is from 50 to 10,000, M is zero. The method according to claim 1, Wherein the organic crosslinking layer comprises a polymer having a weight average molecular weight of 1,000 to 1,000,000. The method according to claim 1, Wherein the organic crosslinking layer has an average thickness of 5 to 350 nm. The method according to claim 1, And the average particle diameter of the nano pores is 1 to 10 nm. The method according to claim 1, Wherein the organic crosslinking layer is contained in an amount of 0.1 to 3% by weight based on the total weight of the negative electrode active material. The method according to claim 1, The active material may be a lithium metal, a metal material capable of alloying with lithium, a material capable of doping and dedoping lithium, a material capable of reversibly reacting with lithium to form a lithium-containing compound, a transition metal oxide, Wherein the negative electrode active material is at least one selected from the group consisting of a composite material containing a metal material and a carbonaceous material. Coating a surface of the active material with a coating composition comprising a polymer represented by the following formula (2) containing a cinnamate group; And And irradiating the coated active material with a light source to produce a negative electrode active material. The negative active material for a lithium secondary battery according to claim 1, (2)

In Formula 2, The R &lt; ₄ & R ₅ is the same or different from each other, is selected from the group consisting of hydrogen, and substituted or unsubstituted C 1 to C 10 alkyl, Wherein R ₆ , R ₇ and R ₈ are the same or different and are selected from the group consisting of hydrogen, halogen, wherein the halogen is F, Cl, Br, or I, and substituted or unsubstituted C 1 to C 10 alkyl And, Wherein n is 50 to 10,000. 11. The method of claim 10, Wherein the light source is UV in an ultraviolet region of 200 to 400 nm. 12. The method of claim 11, Wherein the UV irradiation is performed at 20 to 35 占 폚. delete 11. The method of claim 10, The active material may be a lithium metal, a metal material capable of alloying with lithium, a material capable of doping and dedoping lithium, a material capable of reversibly reacting with lithium to form a lithium-containing compound, a transition metal oxide, Wherein the negative electrode active material is at least one selected from the group consisting of a composite material containing a metal material and a carbonaceous material. Current collector; And The negative active material according to any one of claims 1 to 9, which is formed on the current collector, And a negative electrode for a lithium secondary battery. 16. The method of claim 15, And the negative electrode has a volume expansion rate of 100 vol% or less. A negative electrode comprising the negative electrode active material according to any one of claims 1 to 9; A positive electrode comprising a positive electrode active material capable of reversibly intercalating and deintercalating lithium ions; And Electrolyte &Lt; / RTI &gt;

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