KR20070098163A - Negative electrode for lithium secondary battery and lithium secondary battery comprising same - Google Patents

Abstract

An anode for a lithium secondary battery is provided to improve the capacity and lifespan characteristics of a battery, and to allow a battery to exhibit high capacity particularly upon high-rate charge/discharge. An anode(6) for a lithium secondary battery comprises: a collector; and an anode active material layer formed on the collector and comprising an anode active material represented by the formula of LixVyMzO2+w (wherein x ranges from 0.1 to 2.5, y ranges from 0.5 to 1.5, z ranges from 0 to 0.5, w ranges from -0.5 to 0.5, and M is an element selected from the group consisting of Ag, Al, Cr, Mo, Ti, W, Zr and a combination thereof). The anode active material has a lattice parameter ratio c/a of 5.10-5.20, and belongs to a space group of R-3m before charge and to a space group of P-3m1 after full charge.

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.

Figure 2 is a view showing the XRD measurement results for the negative electrode active material of Example 1.

3 is a view showing the XRD pattern change of the negative electrode active material of Example 1 before and after charge and discharge.

4 is a view schematically showing the structural change of the negative electrode active material of Example 1 before and after charge and discharge.

5 is a graph showing the initial charge and discharge characteristics of the lithium secondary battery including the negative electrode active material of Example 1 and Comparative Example 1.

[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 and a lithium secondary battery including the same capable of improving capacity characteristics and lifespan characteristics of the battery.

[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.

Examples of the positive electrode active material of a lithium secondary battery include lithium and a transition metal having a structure capable of intercalating lithium, such as LiCoO ₂ , LiMn ₂ O ₄ , and LiNi _{1- x} Co _x O ₂ (0 <x <1). 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, in the case of manufacturing the electrode plate with graphite as an active material, the electrode plate density is lowered, so there is a problem in that the capacity is low in terms of energy density per unit volume of the electrode plate. Further, at high discharge voltages, side reactions easily occur with graphite and the organic electrolyte solution used, and there is a risk of ignition or explosion due to battery malfunction and overcharge.

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 shows a high capacity of 800 mAh / g per weight, but there is a fatal problem that the initial irreversible capacity is about 50%. In addition, incidental problems such as the reduction of some of the tin oxide from the oxide to the tin metal by charging and discharging are also seriously occurring, which makes the use of the battery more difficult.

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 capacity characteristics and lifespan 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, a negative electrode for a lithium secondary battery is formed on the current collector and the current collector, the negative electrode active material layer comprising a negative electrode active material, a conductive material and a binder of the formula (1) to provide. At this time, the negative electrode active material has a lattice constant ratio c / a of 5.10 to 5.20, has a space group of R-3m before charging, and a space group of P-3m1 after full charging.

[Formula 1]

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

Wherein 0.1 ≦ x ≦ 2.5, 0.5 ≦ y ≦ 1.5, 0 ≦ z ≦ 0.5, −0.5 ≦ w ≦ 0.5, and M is Ag, Al, Cr, Mo, Ti, W, Zr, and combinations thereof Is an element selected from the group consisting of

According to another embodiment of the present invention, there is provided a lithium secondary battery including the anode, a cathode including a cathode 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. In the present invention, by including a negative electrode active material in which a space group changes according to charging and discharging of a battery, capacity characteristics and lifespan characteristics of the battery can be improved.

Accordingly, the negative electrode for a rechargeable lithium battery according to one embodiment of the present invention includes a current collector; And a negative electrode active material layer formed on the current collector and including the negative electrode active material.

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, polymer substrate coated with conductive metal, and combinations thereof. More preferably, copper foil or nickel foil can be used.

A negative electrode active material layer including a negative electrode active material, a conductive agent, and a binder is positioned on the current collector.

At this time, the negative electrode active material is a compound having a layered structure (layered structure) represented by the following formula (1).

[Formula 1]

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

Wherein 0.1 ≦ x ≦ 2.5, 0.5 ≦ y ≦ 1.5, 0 ≦ z ≦ 0.5, −0.5 ≦ w ≦ 0.5, and M is Ag, Al, Cr, Mo, Ti, W, Zr, and combinations thereof It is an element selected from the group consisting of, more preferably Mo, Ti, W, and a combination thereof is preferably selected.)

The negative electrode active material of the present invention can be synthesized by substituting Co in the LiCoO ₂ structure with another transition metal element V and a second metal element Ag, Al, Cr, Mo, Ti, W, Zr, or a combination thereof. And similar discharge potential and lifetime characteristics to graphite. 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, Ti, W, and combinations thereof are preferably selected from the group.

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

The negative electrode active material has a space group of R-3m before charging and a space group of P-3m1 after charging. This is changed to the P-3m1 structure, which is a specified space group, as lithium is inserted into the active material during the charging process, and the structure is a structure in which lithium is reversibly easily removed and inserted.

In addition, X-ray diffraction analysis of CuKα X-rays (1.5418 Å, 40 kV / 30 mA) at a scanning speed of 0.02 ° / 1 sec in the 2θ range of 10 to 80 ° showed that the negative electrode active material of the present invention It has a lattice constant ratio (c / a) of 5.10 to 5.20, more preferably a lattice constant ratio of 5.13 to 5.19. When the lattice constant ratio is out of the above range, the insertion and desorption of lithium is structurally difficult, and the insertion and dissociation potential of lithium also increases to 0.6 V or more, and the difference in potential between insertion and desorption due to the contribution of the reaction of oxygen as an anion increases. The phenomenon of hysteris occurs.

In addition, the negative electrode active material of the present invention has physical properties of 2.8 kPa <lattice constant a <2.9 kPa, 14 kPa <lattice constant c <15 kPa. When the lattice constant value is out of the above-described range, the interlayer structure of the oxide is distorted, which causes a capacity reduction problem.

The negative active material of the present invention as described above is an element selected from the group consisting of vanadium raw material, lithium raw material and M raw material (M is Ag, Al, Cr, Mo, Ti, W, Zr, and combinations thereof. ) May be prepared by a manufacturing method comprising the step of solid-phase mixing and heat treatment.

More specifically, first, the vanadium raw material, the lithium raw material, and the M raw material are mixed in solid phase.

At this time, the mixing ratio of the vanadium raw material, the lithium raw material and the metal raw material can be appropriately adjusted within the range in which the desired composition of the formula (1) is obtained. The vanadium raw material is vanadium metal, VO, V ₂ O ₃ , V ₂ O ₄ , V ₂ O ₅ , V ₄ O ₇ , VOSO ₄ · nH ₂ O, NH ₄ VO ₃ And mixtures thereof.

Lithium-containing water-soluble salts may be used as the lithium raw material, and specifically, those selected from the group consisting of lithium carbonate, lithium hydroxide, lithium nitrate, lithium acetate, and mixtures thereof may be used.

In addition, the M raw material may be selected from the group consisting of oxides, hydroxides and mixtures thereof including metals selected from the group consisting of Al, Cr, Mo, Ti, W, Zr, and combinations thereof. . Examples thereof include Al (OH) ₃ , Al ₂ O ₃ , Cr ₂ O ₃ , MoO ₃ , TiO ₂ , WO ₃ or ZrO ₂ .

Subsequently, the mixture obtained after the solid phase mixing is heat-treated to prepare a negative active material for a non-aqueous electrolyte secondary battery containing the lithium-vanadium oxide of Chemical Formula 1.

The heat treatment process is preferably carried out at 500 to 1400 ℃, preferably 900 to 1200 ℃.

When the heat treatment temperature is outside the range of 500 to 1400 ° C., an impurity phase (for example, Li ₃ VO _4, etc.) may be formed, and the impurity phase may cause a decrease in capacity and life, which is not preferable.

In addition, the heat treatment step is preferably carried out in a reducing atmosphere. Specifically, it can be performed in an atmosphere such as nitrogen atmosphere, argon atmosphere, N ₂ / H ₂ mixed gas atmosphere, CO / CO ₂ mixed gas atmosphere, or helium atmosphere. At this time, the oxygen partial pressure in the reducing atmosphere is preferably adjusted to less than 2 × 10 ⁻¹ . When the oxygen partial pressure in the reducing atmosphere is 2 × 10 ^{−1 or} more, since it is an oxidizing atmosphere, the metal oxide may be synthesized in an oxidized state, that is, in another phase rich in oxygen, or in a mixed state with another impurity phase having oxygen of 2 or more. It is not desirable.

The binder serves to improve the binding force of the electrode plate of the lithium secondary battery, the binder is polyvinyl alcohol, carboxymethyl cellulose, hydroxypropylene cellulose, diacetylene cellulose, polyvinyl chloride, polyvinylpyrrolidone, poly Tetrafluoroethylene, polyvinylidene fluoride, polyethylene, or polypropylene may be used, but is not limited thereto.

The negative electrode active material and the binder of Formula 1 may be included in the negative electrode active material layer in a weight ratio of 1:99 to 99: 1, and more preferably 10:90 to 98: 2. When the mixing weight ratio of the negative electrode active material and the binder is within the above range, the energy density per volume of the electrode plate is increased, and thus the cell capacity is increased, and if it is out of the above range, the energy density per volume when compared to the existing graphite electrode is increased. It is not preferable because it is not high and there is a fear that the cell capacity is not increased.

In addition, the negative electrode active material of the present invention may further include a conductive material, and examples of the conductive material may include nickel powder, cobalt oxide, titanium oxide, carbon, and the like. As carbon, Ketjen black, acetylene black, furnace black, graphite, carbon fiber, fullerene, etc. can be illustrated.

The negative electrode for a lithium secondary battery having the above structure is prepared by mixing the negative electrode active material and the binder of Formula 1 to prepare a composition for forming a negative electrode active material layer, and then applying the composition for forming the negative electrode active material layer to a current collector, followed by drying, It can be manufactured by rolling. At this time, the type and content of the negative electrode active material and the binder included in the composition for forming the negative electrode active material layer are the same as described above.

The negative electrode active material layer-forming composition prepared above may be coated on a current collector by a general slurry coating process, followed by drying and rolling to prepare a negative electrode for a lithium secondary battery. The form of such a negative electrode is generally a sheet-shaped negative electrode, but is not limited thereto. A cylindrical, disk-shaped, plate-shaped or columnar negative electrode 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 may include a negative electrode active material in which a space group changes according to charging and discharging, thereby improving capacity characteristics and life 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.

Lithium secondary batteries may be classified into lithium ion batteries, lithium ion polymer batteries, and lithium polymer batteries according to the type of separator and electrolyte used, and may be classified into cylindrical, square, coin, or pouch types according to their type. 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, one selected from the group consisting of cobalt, manganese, nickel, and combination oxides thereof and lithium may be used. More preferably, a compound represented by one of the following Chemical Formulas 2 to 19 may be used. Can:

[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, and 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, and 0.001 ≦ e ≦ 0.1).

[Formula 8]

Li _a NiM _b O ₂

(Wherein 0.90 ≦ a ≦ 1.1 and 0.001 ≦ b ≦ 0.1)

[Formula 9]

Li _a CoM _b O ₂

(Wherein 0.90 ≦ a ≦ 1.1 and 0.001 ≦ b ≦ 0.1)

[Formula 10]

Li _a MnM _b O ₂

(Wherein 0.90 ≦ a ≦ 1.1 and 0.001 ≦ b ≦ 0.1)

[Formula 11]

Li _a Mn ₂ M _b O ₄

(Wherein 0.90 ≦ a ≦ 1.1 and 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-a) F ₂ (PO ₄ ) ₃ (0 ≤ a ≤ 3)

[Formula 19]

Li _(3-a) Fe ₂ (PO ₄ ) ₃ (0 ≤ a ≤ 2)

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

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 _f ) _n : f = 2.5 to 50, n ≧ 2) and the like.

Like the negative electrode, the positive electrode is also 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 for forming the positive electrode active material layer to a positive electrode current collector such as aluminum. can do.

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 , LiN (C _p F _{2p + 1} SO ₂ ) (C _q F _{2q + 1} SO ₂ ), wherein p and q are natural numbers, LiSO ₃ CF ₃ , and combinations thereof Can be. 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 2.0M, more preferably in the range of 0.7 to 1.6M. If the concentration of the lithium salt is less than 0.6M, the conductivity of the electrolyte is lowered, the performance of the electrolyte is lowered, and if it exceeds 2.0M, there is a problem that the mobility of lithium ions is reduced by increasing the viscosity of the electrolyte.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move. As the non-aqueous organic solvent, a carbonate-based, ester-based, ether-based or ketone-based solvent may be used. As the carbonate solvent, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), 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, γ-butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone and the like can be used. Dibutyl ether and the like may be used as the ether, but is not limited thereto. In addition, the non-aqueous organic solvent may be used alone or in combination of one or more, the mixing ratio in the case of using one or more mixing can be appropriately adjusted according to the desired battery performance, which is suitable for those skilled in the art It can be widely understood.

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 the group consisting of halogen, alkyl group having 1 to 10 carbon atoms, haloalkyl group, and combinations thereof, n is an integer of 0 to 6).

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

The non-aqueous electrolyte may further include an additive such as an overcharge inhibitor such as ethylene carbonate and fatigue carbonate.

In addition, the solid electrolyte may be a polyethylene oxide polymer electrolyte or a polymer electrolyte containing at least one polyorganosiloxane side chain or a 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. Preparation of negative electrode active material

Li ₂ CO ₃ and V ₂ O ₄ were mixed in solid phase such that the molar ratio of Li: V was 1.1: 0.90. The mixture of non-aqueous electrolyte secondary battery negative electrode active material Li _{1 .1} V _{0 .90} O ₂ was prepared by heat treatment at 1100 ℃ in a nitrogen atmosphere.

Example  2. Preparation of Anode Active Material

Li: V: Ti molar ratio of 1.1: 0.87: conducted in the same manner as in Example 1 except that a mixture of solid and 0.03 to a negative active material of _{Li 1 .1 V 0 .87 Ti 0} .03 O 2 Prepared.

Example  3. Preparation of Anode Active Material

Li: V: Ti molar ratio of 1.1: 0.85: conducted in the same manner as in Example 1 except that the solid phase and mixed with 0.05 of the negative electrode active material _{Li 1 .1 V 0 .85 Ti 0} .05 O 2 Prepared.

Comparative example  1. Preparation of negative electrode active material

The Li ₂ CO ₃ and V ₂ O ₄ under the condition that the water Li: V molar ratio of 1.1: 0.9 were mixed so that the solid phase was synthesized negative electrode active material of _{Li 1 .1 V 0 .9 O 2} .

* Structural analysis of negative active material

The X-ray diffraction pattern (Philips X 'pert X-ray Diff.) Of the negative electrode active material of Example 1 was measured.

The X-ray diffraction analysis was performed under conditions of a scanning speed of 0.02 ° / 1 sec in a 2θ range of 10 to 80 ° using X-ray (1.5418 Pa, 40 kV / 30 mA) of CuKα. Then, each measured peak value obtained by the X-ray diffraction analysis (hereinafter referred to as 'Obs.') And the theoretically calculated peak value expected when having a space group of R-3m (hereinafter referred to as 'Cal.') After verifying diffraction data of the difference between the measured peak value and the theoretical peak value (hereinafter referred to as 'Obs.-Cal.'), A quantitative analysis program based on the Rietveld refinement method ( X-ray diffraction quantitative analysis was performed by using SIEROQUANTTM). The results are shown in FIG.

Figure 2 shows the XRD measurement results for the negative electrode active material of Example 1. In Figure 2, 'Obs.' Is the measured peak value, 'Cal.' Is the theoretically calculated peak value, 'Obs.-Cal.' Is the difference between the measured peak value and the theoretically calculated peak value, Bragg position refers to the coordinates of the space group of atoms.

As shown in FIG. 2, the negative electrode active material of Example 1 exhibited a single phase diffraction pattern having a crystal structure of R-3m, and a lattice constant ratio c / a was 5.15.

Example  4 to 6. Preparation of Cathode

80% by weight of the negative electrode active material prepared in Example 1, 10% by weight of the graphite conductive material, and 10% by weight of the polytetrafluoroethylene binder were mixed in an N-methylpyrrolidone solvent to prepare a negative electrode active material slurry. The negative electrode active material slurry was applied to a copper foil current collector to prepare a negative electrode. At this time, the density of the mixture (referred to as a mixture of the active material, the conductive agent, and the binder constituting the active material layer in the current collector) in the manufactured negative electrode was 1.6 g / cc.

Example  5 and 6. Preparation of Cathode

A negative electrode was prepared in the same manner as in Example 4 except for using the negative electrode active materials prepared in Examples 2 and 3.

Comparative example  2. Preparation of Cathode

A negative electrode was prepared in the same manner as in Example 4, except that the negative active material slurry was prepared by mixing the negative electrode active material prepared in Comparative Example 1 with a ratio of 3: 7.

* Charging and discharging  Structural Changes and Battery Characteristics of Anode Material Before and After

Structural changes and electrochemical characteristics (capacity and life characteristics) of the negative electrode active material before and after charge and discharge were performed on the negative electrode including the negative electrode active materials prepared according to Examples 1 to 3 and Comparative Example 1 as follows.

With the cathode prepared in Example 4 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 carbonate (PC) and diethyl carbonate as the electrolyte solution. Coin type (2016), using LiPF6 dissolved at a concentration of 1 (mol / L) in a mixed solvent of (DEC) and ethylene carbonate (EC) (PC: DEC: EC = 1: 1: 1) Half cells of the cell were configured.

Evaluation of the electrical characteristics of the battery was carried out under the conditions of 0.1C ↔ 0.1C (single charge and discharge) between 0.01 and 2.0V.

In order to examine the structure change of the negative electrode active material before and after the charge and discharge, the change of the X-ray diffraction pattern was measured for the negative electrode including the negative electrode active material of Example 1 before and after charge and discharge. The XRD diffraction pattern was performed in the same manner as described above. The results are shown in FIG.

3 is a view showing changes in the X-ray diffraction pattern before and after the charge and discharge of the negative electrode active material of Example 1.

As shown in Figure 3, and subjected to charge-discharge test using the resulting negative electrode, a negative electrode active material of the exemplary charging all cases _{1, Li 1 .1 V 0 .9} O 2 is eoteuna indicate a single-phase diffraction pattern of a crystal structure of R-3m , fully charged negative electrode active material of example 1, after the Li ₂ V _{0 .1 .9} as O ₂ was changed to the space group P-3m1.

The negative electrodes of Examples 4, 5 and Comparative Example 2 each containing the active materials of Examples 2, 3 and Comparative Example 1 were subjected to the same method as described above to measure the X-ray diffraction pattern change.

The active materials of Examples 2 and 3 also had a space group of R-3m before charging, but the space group was changed to P-3m1 after full charge.

In contrast, the negative electrode active material of Comparative Example 1 had a space group of R-3m (c / a = 5.21), and maintained the original space group even after full charge.

4 is a view schematically showing a structure change of the negative electrode active material of Example 1 before and after charge and discharge.

Referring to FIG 4, the negative electrode active material of Example _{1, Li 1 .1 V 0 .9} O 2 is the oxygen ion-octahydro head between the oxygen ions and a hexagonal closed packed (hexagonal closed packing) before filling V metal ions are present at the ral sites, and Li ions are also present at the octahedral sites below. In other words, Li and oxygen, V and oxygen, which are transition metal elements, alternately have a space group of R-3m having a layered form. However, the anode active material of Example 1 by the insertion of full charge after lithium Li ₂ O _{.9 .1} V ₀ V when the _second metal ion sheath structure is present and the oxygen present in the ion sheath layer, and then the layer Li and Figure 1b As described above, a layer is formed in a plurality of layers, and an oxygen layer exists in the next layer, and the next layer is changed into a P-3m1 structure in which a V metal ion layer exists.

Charging and discharging were performed under the above-described charging and discharging conditions to measure initial discharge capacity and initial efficiency per weight, and the results are shown in Table 1 below.

Initial discharge capacity (mAh / g) Initial Efficiency (%) Example 1 238 77 Comparative Example 1 108 68

As shown in Table 1, the battery containing the negative electrode active material of Example 1 was significantly superior to the battery containing the negative electrode active material of Comparative Example 1 initial charge capacity and discharge efficiency.

In addition, as a result of measuring the initial reversible capacity of the battery containing the negative electrode active material of Example 1 showed a high capacity of 800mAh / cc.

In addition, charge and discharge were performed under the above-described charge and discharge conditions, and initial charge and discharge characteristics of the lithium secondary battery including the negative electrode active materials of Example 1 and Comparative Example 1 were measured. The results are shown in FIG.

As shown in FIG. 5, it can be seen that the battery including the negative electrode active material of Example 1 has a higher capacity and a significantly higher charge / discharge voltage than the battery including the negative electrode active material of Comparative Example 1.

As a result of evaluating the battery characteristics of the batteries containing the negative electrode active materials of Examples 2 and 3 in the same manner as described above, the initial charge capacity, the discharge efficiency and the initial charge and discharge at the same level as those of the battery containing the negative electrode active material of Example 1 Characteristics. From this, it was confirmed that the negative electrode active materials of Examples 2 and 3 also exhibited excellent high capacity characteristics.

The negative electrode for a lithium secondary battery according to the present invention exhibits high capacity and excellent lifespan, and in particular, can provide a lithium secondary battery having high capacity at high rate charge / discharge.

Claims (8)

Current collector; And It is formed on the current collector, and comprises a negative electrode active material layer containing a negative electrode active material and a binder of the formula (1), The negative electrode active material has a lattice constant ratio c / a of 5.10 to 5.20, and has a space group of R-3m before charging and a space group of P-3m1 after full charging. [Formula 1] Li _x V _y M _z O _{2 + w} Wherein 0.1 ≦ x ≦ 2.5, 0.5 ≦ y ≦ 1.5, 0 ≦ z ≦ 0.5, −0.5 ≦ w ≦ 0.5, and M is Ag, Al, Cr, Mo, Ti, W, Zr, and combinations thereof Is an element selected from the group consisting of The method of claim 1, The negative electrode active material is a negative electrode for a lithium secondary battery having a lattice constant ratio c / a of 5.13 to 5.19. The method of claim 1, The negative electrode active material is a lithium secondary battery negative electrode having a physical property of 2.8 kV <lattice constant a <2.9 kPa, 14 kPa <lattice constant c <15 kPa. The method of claim 1, The negative electrode active material and the binder is a lithium secondary battery negative electrode that is included in a weight ratio of 1:99 to 99: 1. The method of claim 1, The binder is polyvinyl alcohol, carboxymethyl cellulose, hydroxypropylene cellulose, diacetylene cellulose, polyvinyl chloride, polyvinylpyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, and combinations thereof A negative electrode for a lithium secondary battery that is selected from the group consisting of. The method of claim 1, The negative electrode active material layer is a negative electrode for a lithium secondary battery further comprising a conductive material. 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, a polymer substrate coated with a conductive metal, and combinations thereof. . A negative electrode according to any one of claims 1 to 7; And A positive electrode including a positive electrode active material; And Electrolyte Lithium secondary battery comprising a.

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