KR20140071214A - Negative active material for lithium secondary battery, method of preparing same, and lithium secondary battery comprising same - Google Patents

Abstract

The present invention relates to a negative electrode active material for a lithium secondary battery, a method for manufacturing the same, and the lithium secondary battery including the same, in which the negative electrode active material is a compound represented by the following chemical formula 1: Li_1+xAl_-x-yM_yO_2+Z (In the chemical formula 1 described above: 0.01<=x<=0.5, 0<=y<=0.3, and -0.2<=z<=0.2; and M is an element which is selected from the group consisting of B, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, W, Ag, Sn, Ge, Si, and combinations thereof). The negative electrode active material according to the present invention shows high capacity and excellent life characteristics. In particular, the lithium secondary battery which shows high capacity during high rate charge can be provided.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a negative electrode active material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery including the negative active material,

The present invention relates to a negative electrode active material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery comprising the same, more preferably a negative electrode active material for a lithium secondary battery exhibiting a high capacity and excellent lifetime characteristics, The present invention relates to a secondary battery.

[0002] Lithium secondary batteries, which have been popular as power sources for portable electronic devices in recent years, exhibit a high energy density by using an organic electrolytic solution and exhibiting discharge voltages two times higher than those of conventional batteries using an aqueous alkaline solution.

Examples of the positive electrode active material of the lithium secondary battery include lithium and a transition metal having a structure capable of intercalating lithium such as LiCoO ₂ , LiMn ₂ O ₄ , LiNi _1-x Co _x O ₂ (0 <x <1) Oxide is mainly used.

Various types of carbon-based materials including artificial graphite, natural graphite, and hard carbon capable of lithium insertion and deintercalation have been applied to the anode active material. Graphite such as artificial graphite or natural graphite among the carbon-based materials has a discharge voltage as low as -0.2 V compared to lithium, and a battery using graphite as a negative electrode active material exhibits a high discharge voltage of 3.6 V, which is advantageous in terms of energy density of a lithium battery And it is also widely used because it guarantees a long life time of a lithium secondary battery with excellent reversibility. 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. In addition, side reactions between graphite and an organic electrolyte are liable to occur at a high discharge voltage, and there is a risk of ignition or explosion due to malfunction of the battery and overcharging.

To solve this problem, an anode active material of oxide has recently been developed. For example, amorphous tin oxide that Fuji Film has developed has a high capacity of 800 mAh / g per weight. However, this tin oxide has a fatal problem in which the initial irreversible capacity is about 50%, and some of the tin oxides are reduced from tin oxide to tin metal by charging and discharging, Which makes it more difficult.

In addition, a negative electrode active material Li _a Mg _b VO _c (0.05? A? 3, 0.12? B? 2, 2? 2c-a-2b? 5) is disclosed in JP 2002-216753 as an oxide cathode . In addition, the negative electrode characteristic of lithium secondary battery Li _1.1 V _0.9 O ₂ was disclosed in the volume 3B05 of Japan Battery Discussion 2002.

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

An object of the present invention is to provide a negative electrode active material for a lithium secondary battery having a high capacity and excellent lifetime characteristics.

Another object of the present invention is to provide a method for producing the negative electrode active material.

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

The present invention provides a negative active material for a lithium secondary battery comprising a compound represented by the following formula (1).

[Chemical Formula 1]

Li _{1 + x} Al _{1-x y} M _y O _{2 + z}

Wherein M is at least one element selected from the group consisting of B, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo , W, Ag, Sn, Ge, Si, and combinations thereof.

The present invention also relates to a process for preparing a negative electrode active material for a lithium secondary battery comprising the compound of the formula (1), which comprises the step of mixing the lithium source material, the Al raw material and the M raw material to prepare a mixture and heat- &Lt; / RTI &gt;

The present invention also provides a lithium secondary battery including a negative electrode including a negative active material including the compound of Formula 1, a positive electrode containing a positive electrode active material capable of intercalating and deintercalating lithium ions, Thereby providing a battery.

The negative electrode for a lithium secondary battery according to the present invention exhibits a high capacity and excellent lifetime characteristics, and can provide a lithium secondary battery exhibiting a high capacity particularly at high rate charging and discharging.

1 is a view showing XRD measurement results of LiAlO ₂ according to an embodiment of the present invention.
2 is a schematic cross-sectional view of a lithium secondary battery according to the present invention.
3 is a graph showing the XRD measurement results of the negative electrode active material of Comparative Example 1 according to the present invention.
4 to 10 are graphs showing XRD measurement results of the negative electrode active materials of Examples 1 to 7 according to the present invention.
11 is a graph showing charge / discharge efficiency of the negative electrode active material according to Example 1 of the present invention.

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

Research has been conducted on lithium-metal oxides, particularly lithium-transition metal oxides, as a cathode active material for lithium secondary batteries. The lithium-transition metal oxide has a spinel structure and a layered network structure, so that lithium ions can be smoothly inserted and removed. Therefore, the lithium-transition metal oxide is mainly used as an effective cathode active material. However, such a lithium-transition metal oxide can not be used as an anode active material since it is a high-potential compound having a charge-discharge potential of about 4.3V.

Accordingly, the inventors of the present invention have been studying lithium-transition metal oxides. In the lithium-transition metal oxide structure such as LiCoO ₂ , which has been conventionally used as a cathode active material, Co has been replaced with another metal element Al and another second metal element M can be used as a negative electrode active material, thereby completing the present invention.

That is, the negative electrode active material of the present invention exhibits a higher density than conventional graphite active materials and can increase the energy density per volume. Also, compared with the conventional metal or alloy active material, the volume change due to lithium ion de- It is a small negative active material.

Accordingly, in one aspect, the present invention provides a negative active material for a lithium secondary battery comprising a compound represented by the following formula (1).

[Chemical Formula 1]

Li _{1 + x} Al _{1-x y} M _y O _{2 + z}

In the above formula (1), x, y, and z are preferably 0.01? X? 0.5, 0? Y? 0.3, and -0.2? Z? 0.2. Since the redox pair of Al uses +3 to +5 in the case where x, y, and z are out of the above range, or the structure is different from the present invention, the average potential relative to the lithium metal is too high, There is a problem that the discharge voltage of the battery becomes too low for use as an active material.

Wherein M is an element selected from the group consisting of B, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, W, Ag, Sn, Ge, Si, Preferably an element selected from the group consisting of B, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Si and combinations thereof.

Conventional In the case of LiCoO ₂ or LiNiO ₂ of the R-3m structure used as a cathode active material, oxygen, lithium and a transition metal have an interlayer structure, and a part of the lithium layer is intercalated into a rocking chair of a lithium secondary battery type electrode material. The R-3m structure refers to a structure in which Li, oxygen, a transition metal element and oxygen are alternately layered.

For example, the LiAlO ₂ structure is shown in FIG. In the case where 1 mol or more of lithium is inserted into the structure of LiAlO ₂ in FIG. 1, a reversible change to the structure shown in FIG. 4 is observed. Reversible insertion / desorption of lithium can be observed even when a part of aluminum (Al) in LiAlO ₂ is replaced with Li to be rich in Li, and other transition metals (such as Mn, Mo, Cr and Al) are substituted.

That is, there exist Al metal ions (in which Li and a third metal are substituted) in the octahedral site of oxygen ions between oxygen ions which are hexagonal closed packing, Is present in Octahedral, and when it becomes Li ₂ AlO ₂ structure by the insertion of lithium, an Al metal ion layer (Li and a third metal is substituted) exists, and then an oxygen ion layer exists in the layer, and Li The layer is in a multi-layered structure, the next layer is an oxygen layer, and the next layer is changed to a structure in which an Al metal ion layer (Li and a third metal is substituted) exists.

In the present invention, a portion of the Al layer is replaced with another metal and Li to improve the lattice constant, i.e., the distance between the a-axes, for smooth deintercalation of lithium at low electric fields. As a result, the lithium layer is widened, and therefore lithium insertion / removal is facilitated in a crystal structure in which lithium is inserted. As described above, since the insertion / removal of lithium is facilitated, that is, the lithium diffusion rate is increased at the time of charging and discharging, the lifetime and high-rate characteristics can be improved.

The negative electrode active material of the present invention uses the compound of Formula 1 as an anode active material for a lithium secondary battery, having an optimal composition so that lithium can be smoothly intercalated at a low electric potential, using the above-described change in lattice structure. The compound of formula (1) has an average oxidation number of metal Al in the range of +3 to +5, more preferably in the range of +3 to +4 (oxidation number of metal Al is +3) +5. Therefore, the redox potential is 1 V or less, more preferably 0.01 to 1 V, relative to lithium metal. That is, since the oxidation-reduction reaction couples of vanadium oxide are mainly +3 to +4 and +4 to +5, the initial oxidation-reduction potential is 2V or more compared with the lithium metal, This has the advantage. Therefore, when the compound of Formula 1 of the present invention is used as a negative electrode active material, it can be expected that a high battery discharge voltage is exhibited.

The negative electrode active material of the present invention has a distance ratio (c / a axial ratio) between crystal axes before insertion of lithium ions is 1.0 to 6.5, preferably 1.0 to 3.2. When the distance ratio (c / a axial ratio) between the crystal axes before lithium insertion is out of the above range, insertion and desorption of lithium ions are structurally difficult, and the insertion elimination potential of lithium ions is also increased to 0.6 V or more. The hysteresis phenomenon occurs in which the potential difference between the insertion and the desorption is increased due to the contribution of the reaction.

In the negative electrode active material of the present invention, the distance ratio between crystal axes after insertion of lithium ions is 1.0 to 6.5, preferably 1.2 to 3.2. If it is smaller than the above range, the change of the lattice due to the inserted Li is small, so that the diffusion of Li into the lattice is difficult, and on the other hand, it becomes difficult to maintain the crystal structure when it is large.

In the negative electrode active material of the present invention, the lattice volume is changed to 30% or less, preferably 27 to 0% by lithium ion deintercalation. When the crystal lattice volume is larger than 30%, cracking of the electrode plate occurs due to the volume change, resulting in a short circuit of the conduction path, detachment of the active material from the electrode plate, and agglomeration with surrounding particles There is a problem that the characteristics of a battery such as an increase in internal resistance, a capacity decrease, and a deterioration of life are remarkably deteriorated.

The negative electrode active material of the present invention is capable of constant current / constant voltage charging. That is, the conventional carbon (graphite) active material exhibited capacity by constant current and constant voltage charging. However, in the case of a metal or metal / graphite composite which is a high capacity active substance recently studied, ), The use of a constant voltage causes serious problems of reversibility and safety due to deterioration due to the collapse of the structure due to lithium insertion or precipitation on the surface without being diffused into the crystal structure. As a result, conventional metal or metal / graphite composite anode active materials can not be charged under the same conditions as those used when conventional graphite is used as a negative active material, so that it is practically impossible to use them in batteries. On the other hand, Constant current / constant voltage charging is available, so it can be useful for batteries.

In addition, the anode active material of the present invention has a theoretical energy density per unit volume of 4.2 g / cc and an electrode plate density of approximately 3.0 g / cc in the production of an actual plate, and when the capacity per unit weight is 300 mAh / g, Since the theoretical capacity per unit volume is 1200 mAh / cc or more and an energy density of 900 mAh / cc or more can be obtained, the theoretical energy density per unit volume is 2.0 g / cc and the actual energy density is 1.6 g / cc, and 360 mAh / g, respectively, compared to the actual capacity of 570 mAg / cc per unit volume.

In addition, the anode active material of the present invention is superior in safety to the organic electrolytic solution as compared with the carbon anode active material.

According to another aspect of the present invention, there is provided a process for preparing a negative electrode active material of the above formula (1), comprising the steps of mixing a lithium source material, an Al source material, and a M source material in a solid phase to prepare a mixture and heat- .

Hereinafter, the preparation method will be described in more detail. First, a mixture of a lithium raw material, an Al raw material, and a M raw material is mixed in a solid phase.

At this time, the mixing ratio of the lithium source material, the Al source material, and the M source material can be appropriately controlled within a range in which a desired composition can be obtained in the compound of the formula (1).

The lithium source material may be selected from the group consisting of lithium carbonate, lithium hydroxide, lithium nitrate, lithium acetate, and combinations thereof.

The raw material of Al may be selected from the group consisting of Al, oxides and hydroxides thereof. Specific examples thereof include Al ₂ O ₃ , Al (ClO ₄ ) .9H ₂ O But is not limited thereto.

The raw material of M may be selected from the group consisting of B, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, W, Ag, And oxides and hydroxides thereof, can be used. Specific examples thereof include B ₂ O ₃ , Ti ₂ O ₃ , TiO ₂ , Cr ₂ O ₃ , Fe ₂ O ₃ , FeOOH, CoO, MnOOH, MoO ₃ , NiO, CuO, WO ₃ , ZrO ₂ , Ag ₂ O, AgO , SnO ₂ , SnO ₂ , GeO ₂ , SiO ₂ , SiO ₂ , VO ₂ , V ₂ O ₃ , V ₂ O ₄ , V ₂ O ₅ , V ₄ O ₇ , VOSO ₄ .nH ₂ O or NH ₄ VO ₃ have.

Subsequently, the mixture obtained after solid-phase mixing is heat-treated to prepare a negative electrode active material for a lithium secondary battery comprising the compound of the formula (1).

The heat treatment is preferably performed at a temperature of 300 to 1400 ° C, more preferably 700 to 1200 ° C. If the heat treatment temperature is outside the range of 300 to 1400 ° C, an impurity phase (for example, Li ₃ AlO ₄ ) may be formed, and the capacity and life may be lowered due to the impurity phase, which is not preferable .

The heat treatment step is preferably performed in a reducing atmosphere. Specifically, this can be performed in an atmosphere of vacuum, nitrogen atmosphere, argon atmosphere, N ₂ / H ₂ mixed gas atmosphere, CO / CO ₂ mixed gas atmosphere, helium atmosphere, H ₂ gas atmosphere or a combination thereof.

The negative electrode active material for a lithium secondary battery according to the present invention includes the compound of Formula 1 having excellent capacity per unit volume, and thus has excellent capacity characteristics and can improve the initial efficiency and life characteristics of the battery.

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

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

A schematic sectional view of a lithium secondary battery according to the present invention is shown in FIG. 2. A process of manufacturing the lithium secondary battery of the present invention will be described with reference to FIG.

The lithium secondary battery 3 includes an electrode assembly 4 including a positive electrode 5, a negative electrode 6 and a separator 7 existing between the positive electrode 5 and the negative electrode 6, And then injecting an electrolytic solution into the upper part of the case 8 and sealing it with the cap plate 11 and the gasket 12 to assemble it.

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

The negative electrode active material is the same as described above, and it is preferably contained in an amount of 1 to 99% by weight, more preferably 10 to 98% by weight based on the total weight of the negative electrode active material layer. If the content is out of the above range, the capacity may be reduced and the relative amount of the binder may be reduced, which may lower the bonding force with the current collector.

The negative electrode may be prepared by mixing the negative electrode active material, a binder and optionally a conductive material 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.

The binder serves to adhere the anode active material particles to each other and to adhere the anode active material to the current collector. Examples include polyvinyl alcohol, carboxymethylcellulose, hydroxypropylene cellulose, diacetylene cellulose, polyvinyl chloride, polyvinyl pyrrolidone, carboxylated polyvinyl chloride, polyvinyl difluoride, ethylene oxide Polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon and the like can be used , But is not limited thereto.

The conductive material is used for imparting conductivity to the electrode, and any electronic conductive material that does not cause chemical change in the battery constituting the battery can be used. Examples thereof include metal powders such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, copper, nickel, aluminum and silver or metal fibers. Conductive materials may be mixed and used.

The solvent may be N-methyl pyrrolidone or the like, but is not limited thereto.

The current collector may be selected from the group consisting of a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foil, a copper foil, a polymer substrate coated with a conductive metal and a combination thereof.

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

The cathode active material may be a lithiated intercalation compound capable of reversibly intercalating and deintercalating lithium. Concretely, it is possible to use at least one compound oxide of lithium and metal selected from cobalt, manganese, nickel, molybdenum, titanium and combinations thereof, more preferably at least one compound represented by any one of the following formulas Can be used:

(2)

Li _{aa 1-b} B _b D ₂

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

(3)

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 4]

LiE _2-b B _b O _4-c F _c

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

[Chemical Formula 5]

Li _a Ni _1-bc Co _b B _c D _?

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

[Chemical Formula 6]

Li _a Ni _{1- b c} Co _b B _c O _2-α F _α

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

(7)

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 8]

Li _a Ni _1-bc Mn _b B _c D _?

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

[Chemical Formula 9]

Li _a Ni _1-bc Mn _b B _c O _2-α F _α

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

[Chemical formula 10]

Li _a Ni _1-bc Mn _b B _c O _{2 -?} F ₂

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

(11)

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 12]

Li _a Ni _b Co _c Mn _d G _e O 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 13]

Li _a AG _b O ₂

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

[Chemical Formula 14]

Li _a MnG _b O ₂

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

[Chemical Formula 15]

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 16]

QO ₂

[Chemical Formula 17]

QS ₂

[Chemical Formula 18]

LiQS ₂

[Chemical Formula 19]

V ₂ O ₅

[Chemical Formula 20]

LiV ₂ O ₅

[Chemical Formula 21]

LiIO ₂

[Chemical Formula 22]

LiNiVO ₄

(23)

Li _(3-f) J ₂ (PO ₄ ) ₃

(In the above formula, 0? F? 2).

&Lt; EMI ID =

Li _(3-f) Fe ₂ (PO ₄ ) ₃

(In the above formula, 0? F? 2).

In the above formulas 2 to 24,

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 metal or a lanthanide element selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V,

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.

In addition to the above, inorganic sulfur (S ₈ , elemental sulfur) and sulfur compound may be used, and as the sulfur compound, Li ₂ S _n (n ≥ 1), Li ₂ S _n dissolved in a catholite 1), an organic sulfur compound or a carbon-sulfur polymer ((C ₂ S _f ) _n : f = 2.5 to 50, n≥2).

Further, a compound having a coating layer on the surface of the compound may be used, or a compound having a coating layer may be mixed with the compound. The coating layer may comprise at least one coating element compound selected from the group consisting of oxides, hydroxides of coating elements, oxyhydroxides of coating elements, oxycarbonates of coating elements, and hydroxycarbonates of coating elements. The compound constituting these coating layers may be amorphous or crystalline. As the coating element included in the coating layer, Mg, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a mixture thereof may be used. The coating layer forming step may be carried out by any of coating methods such as spray coating, dipping, and the like without adversely affecting the physical properties of the cathode active material by using these elements in the above compound. It is a content that can be well understood by people engaged in the field, so detailed explanation will be omitted.

The positive electrode may also be formed by mixing the positive electrode active material, the binder and optionally the conductive material to prepare 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.

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

As the non-aqueous electrolyte, a lithium salt dissolved in a non-aqueous organic solvent may be used. The lithium salt acts as a source of lithium ions in the battery, thereby enabling operation of a basic lithium secondary battery. The lithium salt may be LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ 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 , LiCl, And a combination thereof.

The concentration of the lithium salt may be 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 to deteriorate the performance of the electrolyte. If the concentration exceeds 2.0 M, the viscosity of the electrolyte increases and the lithium ion mobility decreases.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move. As the non-aqueous organic solvent, a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based or aprotic solvent may be used. Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC) (EMC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). Examples of the ester solvents include n-methyl acetate, n-ethyl acetate, n-propyl acetate, dimethylacetate, methylpropionate, ethylpropionate,? -Butyrolactone, decanolide, valerolactone Mevalonolactone, caprolactone, and the like can be used. Examples of the ether solvent include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran and the like. As the ketone solvent, cyclohexanone and the like can be used. As the alcoholic solvent, ethyl alcohol, isopropyl alcohol, etc. may be used. Examples of the aprotic solvent include N-CN (X is a linear, branched or cyclic hydrocarbon group having 2 to 20 carbon atoms, which may include a double bond aromatic ring or an ether bond); Amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; Sulfolanes and the like can be used.

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

In the case of the carbonate-based solvent, it is preferable to use a mixture of a cyclic carbonate and a chain carbonate. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of 1: 1 to 1: 9, the performance of the electrolytic solution 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 (25).

(25)

Wherein R ₁ to R ₆ are each independently selected from the group consisting of hydrogen, halogen, an alkyl group having 1 to 10 carbon atoms, a haloalkyl group, and a combination 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 non-aqueous electrolyte may further include vinylene carbonate or an ethylene carbonate-based compound represented by the following formula (26) to improve battery life.

(26)

(Wherein R ₇ in the formula, R ₇ and R ₈ are each independently selected from hydrogen, halogen, cyano (CN), nitro group (the group consisting of alkyl groups of NO _2), and a fluorinated group having 1 to 5 carbon atoms, And R ₈ is selected from the group consisting of a halogen group, a cyano group (CN), a nitro group (NO ₂ ) and an alkyl group having 1 to 5 fluorinated carbon atoms, provided that R ₇ and R ₈ are not both hydrogen. )

Representative examples of the ethylene carbonate-based compound include difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate,

Cyanoethylene carbonate, fluoroethylene carbonate, and the like. When such a life improving additive is further used, its amount can be appropriately adjusted.

The non-aqueous electrolyte may further include additives such as an overcharge inhibitor such as ethylene carbonate, pyrocarbonate and the like.

Also, the solid electrolyte may be a polymer electrolyte containing 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 a sulfide electrolyte such as 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, and the like 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.

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

Example 1: Preparation of Li _1.1 Al _0.9 O ₂ Manufacturing

Li ₂ CO ₃ and Al ₂ O ₃ were mixed in a solid phase such that the molar ratio of Li: Al was 1.1: 0.9. The mixture was heat treated at 800 캜 in a reducing atmosphere and then cooled to room temperature to prepare Li _1.1 Al _0.9 O ₂ anode active material for lithium secondary battery.

Example 2: Li1.1Al _0.89 B _0.01 O ₂ Manufacturing

Li ₂ CO ₃ , Al ₂ O ₃ and B ₂ O ₃ were mixed in a solid phase such that the molar ratio of Li: Al: B was 1.1: 0.89: 0.01. The mixture was heat treated at 800 캜 in a reducing atmosphere and then cooled to room temperature to prepare Li _1.1 Al _0.9 B _0.01 O ₂ anode active material for a lithium secondary battery.

Example 3: Preparation of Li _1.1 Al _0.89 Cu _0.01 O ₂ Manufacturing

Li ₂ CO ₃ , Al ₂ O ₃ and CuO were mixed in a solid phase such that the molar ratio of Li: Al: Cu was 1.1: 0.89: 0.01. The mixture was heat treated at 800 캜 in a reducing atmosphere and then cooled to room temperature to prepare Li _1.1 Al _0.89 Cu _0.01 O ₂ anode active material for a lithium secondary battery.

Example 4: Preparation of Li _1.1 Al _0.89 Co _0.01 O ₂ Manufacturing

Li ₂ CO ₃ , Al ₂ O ₃ and CoO were mixed in a solid phase such that the molar ratio of Li: Al: Co was 1.1: 0.89: 0.01. The mixture was heat treated at 800 캜 in a reducing atmosphere and then cooled to room temperature to prepare Li ₁ .1 Al _0.89 Co _0.01 O ₂ anode active material for a lithium secondary battery.

Example 5: Preparation of Li _1.1 Al _0.89 Fe _0.01 O ₂ Manufacturing

Li ₂ CO ₃ , Al ₂ O ₃ and Fe ₂ O ₃ were mixed in a solid phase such that the molar ratio of Li: Al: Fe was 1.1: 0.89: 0.01. The mixture was heat treated at 800 ° C in a reducing atmosphere and then cooled to room temperature to prepare Li ₁ .1Al _0.89 Fe _0.01 O ₂ anode active material for lithium secondary batteries.

Example 6: Preparation of Li _1.1 Al _0.89 Ni _0.01 O ₂ Manufacturing

Li ₂ CO ₃ , Al ₂ O ₃ and NiO were mixed in a solid phase such that the molar ratio of Li: Al: Ni was 1.1: 0.89: 0.01. The mixture was heat treated at 800 캜 in a reducing atmosphere and then cooled to room temperature to prepare Li 1 .1 Al _0.89 Ni _0.01 O 2 anode active material for a lithium secondary battery.

Example 7: Preparation of Li _1.1 Al _0.89 Mn _0.01 O ₂ Manufacturing

Li ₂ CO ₃ , Al ₂ O ₃ and MnOOH were mixed in a solid phase such that the molar ratio of Li: Al: Mn was 1.1: 0.89: 0.01. The mixture was heat treated at 800 캜 in a reducing atmosphere and cooled to room temperature to prepare Li _1.1 Al _0.89 Mn _0.01 O ₂ anode active material for a lithium secondary battery.

Comparative Example 1:

Li ₂ CO ₃ and V ₂ O ₄ were mixed in a solid phase such that the molar ratio of Li: V was 1.1: 0.9. The mixture was heat-treated at 1050 ° C under a hydrogen atmosphere, and then cooled to room temperature to prepare Li _1.1 V _0.9 O ₂ anode active material for a lithium secondary battery.

Comparative Example 2:

Graphite was used as an anode active material.

Experimental Example 1: Analysis of Structure of Anode Active Material

An X-ray diffraction pattern (Philips X'pert MPD) was measured for the structural analysis of the negative electrode active materials prepared in Examples 1 to 7 and Comparative Example 1. [ The X-ray diffraction analysis was carried out at a scanning rate of 0.02 ㅀ / sec exposure in a 2θ range of 10 to 90 사용 using X-ray of CuKα (1.5418 Å, 40 kV / 30 mA). The results are shown in Figs. 3 to 10, wherein Fig. 3 shows the result of the analysis of Comparative Example 1. Fig.

As shown in Figs. 4 to 10, the negative electrode active materials of Examples 1 to 7 exhibited a single phase diffraction pattern of a tetragonal crystal structure. The lattice constant a of the negative active material of Example 1 was about 5.169 Å, c was about 6.268 Å, and the lattice constant ratio c / a was 1.26. The lattice constant a of the negative active material of Example 2 was about 5.164 Å, c was about 6.266 Å, and the lattice ratio c / a was 1.21.

Experimental Example 2: Evaluation of electrochemical characteristics of battery

The following experiment was conducted to evaluate the electrochemical characteristics (capacity and lifetime characteristics) of the negative electrode comprising the negative electrode active material of the present invention.

2-1. Manufacture of half cell

The electrochemical property evaluation (capacity and lifetime characteristics) of the negative electrode including the negative electrode active material prepared according to Examples 1 and 2 and Comparative Example 1 was performed as follows.

A negative electrode active material slurry was prepared by mixing 80 weight% of each of the negative electrode active materials of Examples 1 and 2, 10 weight% of graphite conductive material and 10 weight% of polytetrafluoroethylene binder in N-methylpyrrolidone solvent. The negative electrode active material slurry was applied to a copper foil current collector to prepare a negative electrode.

A separator made of a porous polypropylene film was inserted between the working electrode and the counter electrode with the metal anode being the working electrode and the metal lithium foil serving as the counter electrode, and propylene carbonate (PC), diethyl carbonate (DEC) (Coin type) of 2016 was prepared by dissolving LiPF ₆ in a concentration of 1 (mol / L) in a mixed solvent of ethylene carbonate (EC) (PC: DEC: EC = 1: 1: A half cell was prepared.

2-2. Electrochemical Characterization of Half Cells

The electrochemical characteristics of the half-cell produced in the above 2-1 were evaluated under the conditions of 0.1 C ↔ 0.1 C (one charge / discharge) between 0.01 and 2.0 V. The initial discharging capacity and initial efficiency of the negative active material of Examples 1 to 7 were measured after charging and discharging. The results are shown in Table 1 below. The charge-discharge efficiency of Example 1 is shown in Fig.

Initial discharge capacity (mAh / cc) Initial efficiency (%) Example 1 600 95 Example 2 620 92 Example 3 590 90 Example 4 590 90 Example 5 600 90 Example 6 590 90 Example 7 600 90 Comparative Example 1 570 85 Comparative Example 2 570 94

As shown in Table 1, the batteries including the negative electrode active materials of Examples 1 to 7 were significantly superior in the initial discharge capacity and charge / discharge efficiency to the batteries including the negative electrode active materials of Comparative Examples 1 and 2.

3: Lithium secondary battery
4: electrode assembly
5: anode
6: cathode
7: Separator
8: Case
11: cap plate
12: Gasket

Claims (12)

1. A negative active material for a lithium secondary battery comprising a compound represented by the following formula (1).
[Chemical Formula 1]
Li _{1 + x} Al _{1-x y} M _y O _{2 + z}
Wherein M is at least one element selected from the group consisting of B, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, and Zr in a range of 0.01? X? 0.5, 0? Y? 0.3, Mo, W, Ag, Sn, Ge, Si, and combinations thereof. The method according to claim 1,
Wherein M is selected from the group consisting of B, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Si and combinations thereof. The method according to claim 1,
Wherein the negative electrode active material has a tetragonal structure. The method according to claim 1,
Wherein the negative active material has a crystal lattice volume of 30% or less by insertion / desorption of lithium. The method according to claim 1,
In the negative electrode active material, an average oxidation number of metal Al is oxidized and reduced in the range of +3 to +5 due to lithium intercalation / deintercalation, which is an anode active material for a lithium secondary battery. The method according to claim 1,
Wherein the negative electrode active material has an oxidation-reduction potential of 0.01 to 1 V relative to lithium metal. A process for producing a negative electrode active material for a lithium secondary battery according to any one of claims 1 to 6, comprising the steps of mixing the lithium raw material, the Al raw material and the M raw material in a solid phase to prepare a mixture and heat-treating the mixture . 8. The method of claim 7,
Wherein the Al raw material is selected from the group consisting of Al, oxides and hydroxides thereof, and combinations thereof. 9. The method according to claim 7 or 8,
Wherein the heat treatment step is performed in a reducing atmosphere. 10. The method of claim 9,
Wherein the reducing atmosphere is selected from the group consisting of vacuum, nitrogen atmosphere, argon atmosphere, N ₂ / H ₂ mixed gas atmosphere, CO / CO ₂ mixed gas atmosphere, helium atmosphere, hydrogen gas atmosphere, A method for manufacturing a negative electrode active material for a battery. 9. The method according to claim 7 or 8,
Wherein the heat treatment is performed at a temperature of 300 to 1400 占 폚. An anode comprising the anode active material of any one of claims 1 to 6;
A cathode comprising a cathode active material; And
Non-aqueous electrolyte
&Lt; / RTI &gt;

Images