KR20070071732A - Negative electrode for lithium secondary battery and lithium secondary battery comprising same - Google Patents

Abstract

Provided are a negative electrode for a lithium secondary battery, and a lithium secondary battery containing the negative electrode of which discharge capacity, initial efficiency and lifetime characteristics are improved. The negative electrode comprises a current collector; and a negative electrode active material layer which comprises a negative electrode active material represented by Li_xM_yV_z O_(2+d), a conducting material, graphite and a binder, wherein the ratio of the negative electrode active material and the conducting material is 90:10 to 99;1 by weight; 0.1<=x<=2.5; 0<=y<=0.5; 0.5<=z<=1.5; 0<=d<=0.5; and M is at least one metal selected from the group consisting of Al, Cr, Mo, Ti, W and Z. Preferably the conducting material is at least one selected from the group consisting of a carbon-based material, a metal material, a metal oxide and an electrically conductive polymer.

Description

A negative electrode for a lithium secondary battery and a lithium secondary battery including the same TECHNICAL FIELD

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

[Industrial use]

The present invention relates to a negative electrode for a lithium secondary battery and a lithium secondary battery including the same, and more particularly, to a negative electrode for a lithium secondary battery capable of improving efficiency and lifespan characteristics of a battery, and a lithium secondary battery including the same.

[Prior art]

Lithium secondary batteries, which are in the spotlight as power sources of recent portable small electronic devices, exhibit high energy density by showing a discharge voltage that is twice as high as that of a battery using an alkaline aqueous solution using an organic electrolyte solution.

As a cathode active material of a lithium secondary battery, lithium and a transition metal having a structure capable of intercalation of lithium, such as LiCoO ₂ , LiMn ₂ O ₄ , and LiNi _{1- x} Co _x O ₂ (0 <X <1), etc. Oxides were mainly used.

As the negative electrode active material, various types of carbon-based materials including artificial graphite, natural graphite, and hard carbon capable of inserting and desorbing lithium have been applied. The graphite in the carbon series has a low discharge voltage of -0.2V compared to lithium, and the battery using graphite as a negative electrode active material exhibits a high discharge voltage of 3.6V, providing an advantage in terms of energy density of the lithium battery and providing excellent reversibility. It is the most widely used to ensure the long life of the lithium secondary battery. However, when the electrode plate is manufactured using graphite as an active material, there is a problem in that the electrode plate density is low, and thus the capacity is low in terms of energy density per unit volume of the electrode plate. Also, at high discharge voltages, side reactions with the organic electrolyte in which graphite is used easily occur, thereby causing battery malfunction. And risk of fire or explosion due to overcharging.

In order to solve this problem, an anode active material of oxide has been recently developed. For example, the amorphous tin oxide researched and developed by Fujifilm has a high capacity of 800 mAh / g per weight, but has a fatal problem of having an initial irreversible capacity of about 50%. In addition, incidental problems such as reduction of some tin oxides from oxides to tin metals due to charging and discharging are also seriously occurring, making it more difficult to use them in batteries.

In addition, Japanese Patent Laid-Open No. 2002-216753 describes Li _a Mg _b VO _c (0.05 ≦ a ≦ 3, 0.12 ≦ _b ≦ 2, 2 ≦ 2c-a-2b ≦ 5) as an oxide cathode. Further, in the Japanese Battery discussion yojijip number 3B05 2002 years been published for a lithium secondary battery negative electrode characteristics of the _{Li 1 .1 V 0 .9 O 2} .

However, the oxide negative electrode does not yet exhibit satisfactory battery performance, and research on it is ongoing.

An object of the present invention is to provide a negative electrode for a lithium secondary battery that can improve the initial efficiency and life characteristics of the battery.

Still another object of the present invention is to provide a lithium secondary battery including the negative electrode.

In order to achieve the above object, according to an embodiment of the present invention is formed on the current collector and the current collector, for a lithium secondary battery comprising a negative electrode active material layer comprising a negative electrode active material, a conductive material, graphite and a binder of the formula (1) Provide a cathode. In this case, the negative electrode active material and the conductive material are preferably included in a weight ratio of 90:10 to 99: 1.

[Formula 1]

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

(In Formula 1, 0.1 ≤ x ≤ 2.5, 0 ≤ y ≤ 0.5, 0.5 ≤ z ≤ 1.5, 0 ≤ d ≤ 0.5, M is selected from the group consisting of Al, Cr, Mo, Ti, W, and Zr Is one or more metals.)

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

Hereinafter, the present invention will be described in more detail.

The present invention relates to a negative electrode for a lithium secondary battery, wherein the negative electrode comprises a current collector; And a negative electrode active material layer formed on the current collector and including the negative electrode active material, the conductive material, the graphite, and the binder of Chemical Formula 1.

In the present invention, by optimizing the content of the negative electrode active material and the conductive material in the negative electrode active material layer, it was possible to improve the initial efficiency and life characteristics of the battery.

Accordingly, the negative electrode active material layer in the negative electrode for a lithium secondary battery according to an embodiment of the present invention includes the negative electrode active material and the conductive material in a weight ratio of 90:10 to 99: 1, more preferably 93: 7 to 97 It is included in the weight ratio of 3: 3. When the mixed weight ratio of the negative electrode active material and the conductive material is within the above range, the initial efficiency characteristic or the initial discharge capacity value is large, so that a high capacity battery can be designed in the battery design, and the lifespan characteristics are also excellent. The discharge capacity characteristics are not preferable because of the difficulty in designing a high capacity battery when designing a cell.

The negative electrode active material in the present invention is a compound having a layered structure represented by the following formula (1).

[Formula 1]

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

(In Formula 1, 0.1 ≤ x ≤ 2.5, 0 ≤ y ≤ 0.5, 0.5 ≤ z ≤ 1.5, 0 ≤ d ≤ 0.5, M is selected from the group consisting of Al, Cr, Mo, Ti, W, and Zr Is one or more metals.)

The anode active material may be synthesized by substituting Co in another LiCoO ₂ structure with another transition metal element V and another second metal element Al, Mo, W, Ti, Cr, Zr, and discharging potential similar to that of graphite. And life characteristics. In particular, when the compound represented by Formula 1 is used as the negative electrode active material, a capacity per unit volume of 1000 mAh / cc or more can be obtained. Among the metal elements represented by M in Formula 1, Mo and W are preferable.

When x, y, z and d in the above formula 1 is out of the above-described range, since the average potential is 1.0 V or more compared to lithium metal, the discharge voltage of the battery is too high when used as a negative electrode active material. There is a problem of being lowered. Specifically, the negative electrode active material (ie, x = 0) of a metal vanadium oxide that does not contain Li is Solid State Ionics, 139, 57-65, 2001 and Journal of Power Source, 81-82, 651-655, This is described in 1999. However, the active material described in the paper has a different crystal structure from the active material of the present invention, and there is a problem in that the average discharge potential is also 1.0 V or more to be used as the negative electrode.

The conductive material serves to improve conductivity of the negative electrode active material, and any material may be used as long as the conductive material has electronic conductivity without causing chemical change in the secondary battery. Representative examples thereof include carbonaceous materials, metal materials, metal oxides, electrically conductive polymers, and the like.

When the carbonaceous material is used as the conductive material, the carbonaceous material preferably has a specific surface area of 50 m ² / g to 1000 m ² / g, and more preferably 100 m ² / g to 800m ² / g. Can have If the specific surface area of the carbon-based material is out of the above range, the irreversible capacity of the carbon-based material itself is large, and thus the initial efficiency is deteriorated. Thus, even though the actual lifespan characteristics are improved, the battery capacity shows a low capacity, which is not preferable.

Preferably, the carbon-based material may be carbon black, acetylene black, Ketjen black, furnace black, carbon fiber or fullerene, and the like, and the metal material may be copper, nickel, aluminum, or silver. In addition, cobalt oxide or titanium oxide may be used as the metal oxide, and as the electrically conductive polymer, polyphenylene, polyphenylene derivative, polythiophene, polyacene, polyacetylene. Polypyrrole, polyaniline, etc. can be used preferably.

The conductive material may be dispersed and included in the negative electrode active material layer by simple mixing with the negative electrode active material layer constituent materials, or may be coated on the surface of the negative electrode active material to surround the surface of the negative electrode active material to form a conductive material layer.

The graphite serves to improve conductivity of the negative electrode active material, and may use natural graphite or artificial graphite of plate shape, spherical shape or fiber shape. The graphite may be included in 10 to 90% by weight, more preferably 20 to 80% by weight based on the entire negative electrode active material layer. If the content of graphite is less than 10% by weight, the initial efficiency is poor and there is no capacity merit, which is not preferable.

As the binder, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropylene cellulose, diacetylene cellulose, polyvinyl chloride, polyvinylpyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene or polypropylene may be used. It may be, but is not limited thereto.

The binder may be included in an amount of 10 wt% or less, more preferably 0.1 wt% to 10 wt%, based on the total weight of the negative electrode active material layer. If the content of the binder is less than 0.1% by weight, it is not preferable because the effect of using the binder is insignificant. If the content of the binder is more than 10% by weight, the capacity per volume may decrease due to the decrease in the relative content of the active material due to the increase in the content of the binder. .

The negative electrode active material layer containing the negative electrode active material, the conductive material, the graphite, and the binder is supported by the current collector.

As the current collector, it is preferable to use one selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, and a polymer substrate coated with a conductive metal, more preferably. Copper foil or nickel foil can be used.

The negative electrode for a lithium secondary battery having the above structure is prepared by mixing the negative electrode active material, the conductive material, the graphite, and the binder of Formula 1 to prepare a composition for forming the negative electrode active material layer, and applying the composition to the current collector, followed by drying and rolling. Can be prepared.

First, the negative electrode active material, the conductive material, the graphite, and the binder are dispersed in a solvent to prepare a composition for forming a negative electrode active material layer. The negative electrode active material, the conductive material, the graphite, and the binder are the same as described above.

When the conductive material is coated on the negative electrode active material, first, the conductive material is coated on the surface of the negative electrode active material, and then mixed with graphite, a binder, and a solvent to prepare a composition for forming the negative electrode active material layer.

In the negative electrode active material coating by the conductive material, the conductive material may be coated on the negative electrode active material by mixing the conductive material and the negative electrode active material in a solid or liquid state and then performing a coating process. In the case of mixing in a solid phase, a coating process may be mainly performed by a mechanical mixing method. As an example of the mechanical mixing method, a kneading method and a shear stress may occur during mixing. Or a mechanical mixing method in which the wing structure is changed, or a mechanochemical method for inducing fusion between particle surfaces by mechanically applying shear force between particles.

In the case of mixing in a liquid phase, as in the case of mixing in a solid phase, mechanical mixing, spray drying, spray pyrolysis, or freeze drying may be mixed. In the case of liquid phase mixing, water, an organic solvent, or a mixture thereof may be used as the solvent, and the organic solvent may be ethanol, isopropyl alcohol, toluene, benzene, hexane, tetrahydrofuran, or the like.

The prepared composition may be coated on a current collector by a general coating process, followed by drying and rolling to prepare a negative electrode for a lithium secondary battery. The form of such a cathode is generally a sheet-shaped cathode, but is not limited thereto, and a columnar, disk, plate or columnar cathode may also be used. Furthermore, after dipping a metal current collector in the said slurry, it can also manufacture by drying.

The negative electrode for a lithium secondary battery manufactured as described above exhibits an excellent specific surface area and mixture density by including a negative electrode active material and a conductive material in an optimal mixing weight ratio.

In addition, the negative electrode may have a mixture density of 1.7 to 3.5 g / cc, and more preferably, may have a mixture density of 2.0 to 3.0 g / cc. In general, as the density of the mixture increases, a large amount of active material can be used in the electrode plate, thereby providing a high capacity battery. However, when the mixture density is excessively increased, the pores of the electrode plate may rapidly decrease, so that the impregnation of the electrolyte becomes difficult. There is a problem that the degradation is serious. Therefore, when the mixture density is increased to more than 3.5g / cc, a problem of high rate characteristics occurs, and when the mixture density is less than 1.7g / cc, there is a problem that the capacity is reduced.

As described above, the negative electrode for a lithium secondary battery of the present invention has excellent specific surface area and mixture density, thereby improving initial efficiency and lifespan characteristics of the battery.

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

The lithium secondary battery may be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery according to the type of separator and electrolyte used, and may be classified into a cylindrical shape, a square shape, a coin type, a pouch type, and the like, Depending on the size, it can be divided into bulk type and thin film type. Since the structure and manufacturing method of these batteries are well known in the art, detailed description thereof will be omitted.

1 is a view showing the structure of a lithium secondary battery of the present invention.

Referring to Figure 1 describes the manufacturing process of the lithium secondary battery of the present invention, the lithium secondary battery 3 is present between the positive electrode 5, the negative electrode 6 and the positive electrode 5 and the negative electrode 6 The electrode assembly 4 including the separator 7 may be manufactured by placing the electrode assembly 4 into the case 8, injecting an electrolyte into the upper part of the case 8, and sealing the cap plate 11 and the gasket 12. have.

The cathode is the same as described above.

The positive electrode includes a positive electrode active material, and as the positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound) may be used. Specifically, at least one selected from cobalt, manganese, nickel and at least one of complex oxides with lithium may be used, and more preferably, a compound represented by one of the following Chemical Formulas 2 to 19 may be used:

[Formula 2]

LiNiO ₂

[Formula 3]

LiCoO ₂

[Formula 4]

LiMnO ₂

[Formula 5]

LiMn ₂ O ₄

[Formula 6]

Li _a Ni _b B _c M _d O ₂

(Wherein 0.90 = a = 1.1, 0 = b = 0.9, 0 = c = 0.5, 0.001 = d = 0.1)

[Formula 7]

Li _a Ni _b Co _c Mn _d M _e O ₂

(Wherein 0.90 = a = 1.1, 0 = b = 0.9, 0 = c = 0.5, 0 = d = 0.5, 0.001 = e = 0.1)

[Formula 8]

Li _a NiM _b O ₂

(Wherein 0.90 = a = 1.1, 0.001 = b = 0.1)

[Formula 9]

Li _a CoM _b O ₂

(Wherein 0.90 = a = 1.1, 0.001 = b = 0.1)

[Formula 10]

Li _a MnM _b O ₂

(Wherein 0.90 = a = 1.1, 0.001 = b = 0.1)

[Formula 11]

Li _a Mn ₂ M _b O ₄

(Wherein 0.90 = a = 1.1, 0.001 = b = 0.1)

[Formula 12]

DS ₂

[Formula 13]

LiDS ₂

[Formula 14]

V ₂ O ₅

[Formula 15]

LiV ₂ O ₅

[Formula 16]

LiEO ₂

[Formula 17]

LiNiVO ₄

[Formula 18]

Li _(3-x) F ₂ (PO ₄ ) ₃ (0 = x = 3)

[Formula 19]

Li _(3-x) Fe ₂ (PO ₄ ) ₃ (0 = x = 2)

In Chemical Formulas 2 to 19, B is Co or Mn; D is Ti or Mo; E is selected from the group consisting of Cr, V, Fe, Sc, and Y; F is selected from the group consisting of V, Cr, Mn, Co, Ni, and Cu; And M is at least one transition metal or lanthanide element selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, and V.

In addition, inorganic sulfur (S ₈ , elemental sulfur) and sulfur compounds may be used in addition to the above, and the sulfur compounds include Li ₂ S _n (n ≧ 1) and Li ₂ S _n (n dissolved in catholyte). ≧ 1), an organic sulfur compound or a carbon-sulfur polymer ((C ₂ S _x ) _n : x = 2.5 to 50, n ≧ 2) and the like.

Like the negative electrode, the positive electrode may also be prepared by mixing the positive electrode active material, a binder, and optionally a conductive material to prepare a composition for forming a positive electrode active material layer, and then applying the composition to a positive electrode current collector such as aluminum.

As the electrolyte charged in the lithium secondary battery, a non-aqueous electrolyte or a known solid electrolyte may be used.

As the non-aqueous electrolyte, one in which a lithium salt is dissolved in a non-aqueous organic solvent can be used. The lithium salt acts as a source of lithium ions in the battery to enable operation of the basic lithium secondary battery. Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiAlO ₄ , LiAlCl ₄ , At least one selected from the group consisting of LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ), wherein x and y are natural numbers, and LiSO ₃ CF ₃ Can be used. It is good to contain at least LiBF ₄ in the said lithium salt, Most preferably, LiPF ₆ and LiBF ₄ are mixed and used.

The concentration of the lithium salt can be used in the range of 0.6 to 2.0 M, more preferably in the range of 0.7 to 1.6 M. If the concentration of the lithium salt is less than 0.6 M, the conductivity of the electrolyte is lowered and the performance of the electrolyte is lowered. If the concentration of the lithium salt is more than 2.0 M, the viscosity of the electrolyte is increased, thereby reducing the mobility of lithium ions.

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, ester, ether or ketone solvent may be used. Examples of the carbonate solvents include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), and ethylmethyl carbonate. (EMC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. may be used. Examples of the ester solvent include n-methyl acetate, n-ethyl acetate, n-propyl acetate, and the like. Can be used.

In addition, in the case of the carbonate solvent, it is preferable to use a mixture of cyclic carbonate and chain carbonate. In this case, it is preferable to use the cyclic carbonate and the chain carbonate by mixing in a volume ratio of 1: 1 to 1: 9. The performance of the electrolytic solution is desirable when mixed in the above volume ratio.

The non-aqueous organic solvent of the present invention may further include an aromatic hydrocarbon organic solvent in the carbonate solvent. In this case, the carbonate solvent and the aromatic hydrocarbon organic solvent are preferably mixed in a volume ratio of 1: 1 to 30: 1.

As the aromatic hydrocarbon-based organic solvent, an aromatic hydrocarbon compound of Formula 20 may be used.

[Formula 20]

(In Formula 20, R is selected from halogen, an alkyl group having 1 to 10 carbon atoms, and a combination thereof, and n is an integer of 0 to 6.)

Preferably, the aromatic hydrocarbon organic solvent is at least one solvent selected from the group consisting of benzene, fluorobenzene, toluene, fluorotoluene, trifluorotoluene, and xylene.

The non-aqueous electrolyte may further include an additive such as an overcharge inhibitor.

The solid electrolyte may also be an electrolyte of polyethylene oxide polymer 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 , Sulfide electrolytes such as Li ₂ SB ₂ S ₃ and the like, inorganic electrolytes such as Li ₂ S-SiS ₂ -Li ₃ PO ₄ , Li ₂ S-SiS ₂ -Li ₃ SO _4, and the like, may be preferably used.

The separator may exist between the positive electrode and the negative electrode according to the type of the lithium secondary battery. As the separator, polyethylene, polypropylene, polyvinylidene fluoride or two or more multilayer films thereof may be used, and polyethylene / polypropylene two-layer separator, polyethylene / polypropylene / polyethylene three-layer separator, polypropylene / polyethylene / poly It goes without saying that a mixed multilayer film such as a propylene three-layer separator can be used.

Hereinafter, preferred examples and comparative examples of the present invention are described. However, the following embodiments are only preferred embodiments of the present invention, and the present invention is not limited to the following embodiments.

 (Example 1)

Li ₂ CO ₃ , V ₂ O ₃ , and MoO ₃ are mixed in a solid phase so that the ratio of Li: V: Mo is 1.08: 0.9: 0.02, heat-treated at nitrogen atmosphere for 10 hours at 1,000 ° C., and then cooled to room temperature to obtain a negative electrode active material. Was prepared.

The prepared negative active material was mixed with graphite at 50:50, and then powder mixed with denca black (specific surface area 150 m ² / g) at a weight ratio of 99: 1 as a conductive material with respect to the negative electrode active material, followed by 10% by weight of polyvinyl. A slurry was prepared by mixing a lithium denfluoride / N-methylpyrrolidone (PVdF / NMP) solution into the mixer little by little. At this time, the amount of PVdF finally used was adjusted to 10% by weight of the total mixture.

The negative electrode slurry was coated on a copper foil (Cu-foil) having a thickness of 10 μm to form a thin electrode plate, dried at 135 ° C. for at least 3 hours, and then pressed to obtain a negative electrode plate having a thickness of 40 μm. Prepared.

(Example 2)

Li ₂ CO ₃ , V ₂ O ₃ , and MoO ₃ are mixed in a solid phase so that the ratio of Li: V: Mo is 1.08: 0.9: 0.02, heat-treated at nitrogen atmosphere for 10 hours at 1,000 ° C., and then cooled to room temperature to obtain a negative electrode active material. Was prepared.

The prepared negative active material was mixed with graphite at 50:50, and then powder mixed with denca black (specific surface area 150 m ² / g) at a weight ratio of 95: 5 with respect to the negative electrode active material, followed by 10 wt% of PVdF / The slurry was prepared by mixing the NMP solution into the mixer little by little. At this time, the amount of PVdF finally used was adjusted to 10% by weight of the total mixture.

The negative electrode slurry was coated on a copper foil (Cu-foil) having a thickness of 10 μm to form a thin electrode plate, dried at 135 ° C. for at least 3 hours, and then pressed to obtain a negative electrode plate having a thickness of 40 μm. Prepared.

(Example 3)

Li ₂ CO ₃ , V ₂ O ₃ , and MoO ₃ are mixed in a solid phase so that the ratio of Li: V: Mo is 1.08: 0.9: 0.02, heat-treated at nitrogen atmosphere for 10 hours at 1,000 ° C., and then cooled to room temperature to obtain a negative electrode active material. Was prepared.

The negative electrode active material prepared above was mixed with graphite at 50:50, and then powder mixed with denca black (specific surface area 150 m ² / g) at a weight ratio of 90:10 as a conductive material for the negative electrode active material, followed by 10 wt% of PVdF / NMP. The slurry was prepared by mixing while gradually adding the solution to the mixer. At this time, the amount of PVdF finally used was adjusted to 10% by weight of the total mixture.

The negative electrode slurry was coated on a copper foil (Cu-foil) having a thickness of 10 μm to form a thin electrode plate, dried at 135 ° C. for at least 3 hours, and then pressed to obtain a negative electrode plate having a thickness of 40 μm. Prepared.

 (Comparative Example 1)

Li ₂ CO ₃ , V ₂ O ₃ , and MoO ₃ are mixed in a solid phase so that the ratio of Li: V: Mo is 1.08: 0.9: 0.02, heat-treated at nitrogen atmosphere for 10 hours at 1,000 ° C., and then cooled to room temperature to obtain a negative electrode active material. Was prepared.

The slurry was prepared by mixing the prepared negative active material with graphite at 50:50 and then mixing the mixture with a 10 wt% PVdF / NMP solution in small portions. At this time, the amount of PVdF finally used was adjusted to 10% by weight of the total mixture.

The negative electrode slurry was coated on a copper foil (Cu-foil) having a thickness of 10 μm to form a thin electrode plate, dried at 135 ° C. for at least 3 hours, and then pressed to obtain a negative electrode plate having a thickness of 40 μm. Prepared.

(Comparative Example 2)

Li ₂ CO ₃ , V ₂ O ₃ , and MoO ₃ are mixed in a solid phase so that the ratio of Li: V: Mo is 1.08: 0.9: 0.02, heat-treated at nitrogen atmosphere for 10 hours at 1,000 ° C., and then cooled to room temperature to obtain a negative electrode active material. Was prepared.

The prepared negative active material was mixed with graphite at 50:50, and then charged with denca black (specific surface area 150 m ² / g) at a mixing weight ratio of 85:15 as a conductive material for the negative electrode active material, followed by powder mixing. The slurry was prepared by mixing the PVdF / NMP solution into the mixer little by little. At this time, the amount of PVdF finally used was adjusted to be 10% by weight of the total mixture.

The negative electrode slurry was coated on a copper foil (Cu-foil) having a thickness of 10 μm to form a thin electrode plate, dried at 135 ° C. for at least 3 hours, and then pressed to obtain a negative electrode plate having a thickness of 40 μm. Prepared.

With the cathodes of Examples 1, 2 and 3 and Comparative Examples 1 and 2 as the working electrode and the metal lithium foil as the counter electrode, a separator made of a porous polypropylene film was inserted between the working electrode and the counter electrode and propylene as the electrolyte solution. Dissolve LiPF ₆ in a concentration of 1 (mol / L) in a mixed solvent of carbonate (PC), diethyl carbonate (DEC) and ethylene carbonate (EC) (PC: DEC: EC = 1: 1: 1) The half-cell (half cell) of the 2016 coin type (coin type) was used.

The electrical characteristics of the battery were evaluated between 0.2C ↔ 0.2C (single charge and discharge) between 0.01 and 2.0 V, 0.2C ↔ 0.2C (single charge and discharge) between 0.01 and 1.0 V, and 1C between 0.01 and 1.0 V. It was carried out under the condition of ↔ 1C (100 charge / discharge). Initial charge capacity, initial discharge capacity per weight and initial discharge capacity per volume, initial efficiency and cycle life characteristics (after 100 cycle charge / discharge at 1C, measured discharge capacity expressed as percentage of initial discharge capacity) The results are shown in Table 1 below.

Plate density (g / cc) Initial charge capacity (mAh / g) Initial discharge capacity (mAh / g) Initial discharge capacity (mAh / cc) Initial Efficiency (%) Cycle life (%) Example 1 2.3 352 321 738.3 91.2 91 Example 2 2.2 350 322 708.4 92.0 95 Example 3 2.1 343 316 663.6 92.1 92 Comparative Example 1 2.3 357 319 733.7 89.4 83 Comparative Example 2 1.9 320 295 560.5 92.2 92

As shown in Table 1, the negative electrodes of Examples 1 to 3 have a smaller initial discharge capacity than the negative electrodes of Comparative Example 1, but are excellent in terms of efficiency and lifetime. In addition, since the mixture density is superior to that of the negative electrode of Comparative Example 2, the discharge capacity per electrode plate volume is excellent. Accordingly, the batteries using the negative electrodes of Examples 1, 2, and 3 had better discharge capacity per weight and discharge capacity per volume than those of the negative electrode of Comparative Examples 1 and 2, and also showed excellent charge and discharge efficiency and cycle life characteristics. Able to know.

The negative electrode for a lithium secondary battery according to the present invention can improve the initial efficiency and lifespan characteristics of the battery.

Claims (12)

Current collector; And It is formed on the current collector, and comprises a negative electrode active material layer including a negative electrode active material, a conductive material, graphite, and a binder of the formula (1), The negative electrode active material and the conductive material is a lithium secondary battery negative electrode that is included in a weight ratio of 90:10 to 99: 1. [Formula 1] Li _x M _y V _z O _{2 + d} (In Formula 1, 0.1 ≤ x ≤ 2.5, 0 ≤ y ≤ 0.5, 0.5 ≤ z ≤ 1.5, 0 ≤ d ≤ 0.5, M is selected from the group consisting of Al, Cr, Mo, Ti, W, and Zr Is one or more metals.) The method of claim 1, The negative electrode active material and the conductive material is a lithium secondary battery negative electrode which is included in a weight ratio of 93: 7 to 97: 3. The method of claim 1, M is a negative electrode for a rechargeable lithium battery of Mo or W. The method of claim 1, The conductive material is a negative electrode for a lithium secondary battery of at least one selected from the group consisting of carbon-based materials, metal materials, metal oxides and electrically conductive polymers. The method of claim 4, wherein The carbonaceous material is a negative electrode for a lithium secondary battery having a specific surface area of 50m ² / g to 1000m ² / g. The method of claim 1, The conductive material is carbon black, acetylene black, Ketjen black, furnace black, carbon fiber, fullerene, copper, nickel, aluminum, silver, cobalt oxide, titanium oxide, polyphenylene derivative, polythiophene, polyacene, polyacetylene, polypyrrole And polyaniline and at least one selected from the group consisting of lithium secondary batteries.  The method of claim 1, The conductive material is a negative electrode for a lithium secondary battery that surrounds the surface of the negative electrode active material. The method of claim 1, The graphite is a negative electrode for a lithium secondary battery that is artificial graphite or natural graphite. The method of claim 1, The graphite is a lithium secondary battery negative electrode that is contained in 10 to 90% by weight based on the total weight of the negative electrode active material layer. The method of claim 1, The binder is polyvinyl alcohol, carboxymethyl cellulose, hydroxypropylene cellulose, diacetylene cellulose, polyvinyl chloride, polyvinylpyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene and polypropylene The negative electrode for lithium secondary batteries which is 1 or more types selected. The method of claim 1, The current collector is selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam (foam), copper foam and a conductive metal coated polymer substrate. A cathode according to any one of claims 1 to 11; And A positive electrode including a positive electrode active material; And Electrolyte Lithium secondary battery comprising a.

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