KR101527532B1 - Electrode Active Material Having Improved Lithium Diffusivity and Lithium Secondary Battery Comprising The Same - Google Patents

Abstract

The present invention relates to an electrode active material characterized in that a carbon coating layer having a lithium transfer channel is formed on the surface of a lithium metal oxide having a spinel structure for inserting and desorbing lithium ions during charging and discharging and a lithium secondary Battery.

Description

TECHNICAL FIELD [0001] The present invention relates to an electrode active material having improved lithium diffusivity and a lithium secondary battery including the electrode active material.

The present invention relates to a secondary battery capable of repeated charge and discharge and an electrode active material constituting the secondary battery.

The increase in the price of energy sources due to the depletion of fossil fuels, the increase of interest in environmental pollution, and the demand for environmentally friendly alternative energy sources are becoming indispensable factors for future life. Various researches on power generation technologies such as nuclear power, solar power, wind power, and tidal power have been continuing, and electric power storage devices for more efficient use of such generated energy have also been attracting much attention.

Particularly, in the case of a lithium secondary battery, the demand for an energy source is rapidly increasing due to an increase in technology development and demand for a mobile device. Recently, the use of a lithium secondary battery as a power source for an electric vehicle (EV) and a hybrid electric vehicle , And the area of use is also expanding for applications such as power assisted power supply through gridization.

As the cathode active material, a lithium secondary battery may be a lithium-containing cobalt oxide such as LiCoO ₂ of a layered structure, a lithium-containing nickel oxide such as LiNiO ₂ of a layered crystal structure, or LiMn ₂ O ₄ of a spinel crystal structure And the same lithium-containing manganese oxide.

The lithium-containing manganese oxide of the spinel crystal structure has poor electrical conductivity, and the diffusion path of lithium ions becomes long due to the three-dimensional structure, so that the conductivity is not very good.

Carbon coatings are widely used to improve electrical conductivity.

The negative electrode of a conventional lithium secondary battery is a negative electrode active material mainly used for reversible intercalation and desorption of lithium ions while maintaining structural and electrical properties. In recent years, however, There have been many studies on an anode material and a lithium titanium oxide by a Li alloy reaction using silicon (Si) and tin (Sn).

Since lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) has a high operating voltage of 1.5 V, there is no generation of dendrite and lithium ions are structurally stable since there is little volume change during insertion / It is known as a material having excellent rate and lifetime characteristics.

Lithium titanium oxide has a drawback in that it is difficult to charge and discharge at a high speed with a low electric conductivity and the output density per volume is low.

In addition, although the theoretical capacity of lithium titanium oxide is 175 mAh / g and the capacity is improved to 160 to 170 mAh / g level at present, there is a problem that it has a limit of the capacity insufficient compared to the conventional carbonaceous anode material.

In the case of making a fast charge cell, the conduction path in the electrode must be very efficient in order to flow high current without side reaction.

Particularly, in order to make a cell having a desired capacity of lithium-titanium oxide having a small capacity, a thick coating is required, so efficient electrical connection is essential. Carbon coatings are widely used to improve electrical conductivity.

Carbon coatings can accelerate the transfer of electrons, but do not improve the conductivity of lithium ions.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and the technical problems required from the past.

An object of the present invention is to provide an electrode active material having a defect in a part of a layered crystal structure in a carbon coating layer and simultaneously improving electric conductivity and lithium ion conductivity, and a lithium secondary battery comprising the electrode active material.

In the electrode active material according to the present invention,

And a carbon coating layer having a lithium movement channel is formed on the surface of a lithium metal oxide having a spinel structure for inserting and desorbing lithium ions during charging and discharging.

The carbon coating layer may include a carbon compound, and the carbon compound may include a single carbon material consisting only of bonds of carbon (C) elements. The carbon compound may be graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Carbon fiber, and the like. However, the present invention is not limited to these.

In a specific embodiment of the present invention, the single carbon material may be graphite.

The coating amount of the conductive carbon coating layer may be 0.2 to 5 parts by weight per 100 parts by weight of the lithium metal oxide.

If the coating amount of the carbon coating layer is less than 0.2 parts by weight per 100 parts by weight of the lithium metal oxide, the desired electron conductivity can not be exhibited. If the coating amount exceeds 5 parts by weight, the coating layer becomes thick, It is not preferable.

The thickness of the carbon coating layer may be not less than 2 nm and not more than 50 nm.

If the thickness is less than 2 nm, the desired electron conductivity can not be exhibited. If the thickness is more than 50 nm, the carbon coating layer may act as a resistor, which is not preferable.

The carbon coating layer includes a group 13 element or a group 15 element in the periodic table. Specifically, the group 13 element or the group 15 element may replace part of carbon in the carbon coating layer.

As a result, in the carbon coating layer, a part of the hexagonal plane constituted by the carbon elements deviates from the planar arrangement, so that defects of the layered crystal structure are generated. As a result, the path connecting the defects can act as a path of lithium ion migration .

In a specific embodiment according to the present invention, the Group 13 element may be boron (B).

In a specific embodiment according to the present invention, the Group 15 element may be nitrogen (N).

The electrode active material of the present invention can be prepared by adding a carbon precursor, a Group 13 element source and a Group 15 element source to a solvent to prepare a coating solution, mixing the lithium metal oxide into a coating solution, and heat- have.

A carbon coating layer having a lithium transfer channel on the surface of the lithium metal oxide may be deposited by a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method. As the chemical vapor deposition method, a fluid phase chemical vapor deposition method, a rotational three-dimensional chemical vapor deposition method, a vibration chemical vapor deposition method, or the like can be used, and as the physical vapor deposition method, sputtering, vacuum annual method, plasma coating method and the like can be used.

In addition, the electrode active material of the present invention can be produced by dry mixing the carbon precursor, the Group 13 element source, and the Group 15 element source with the lithium metal oxide selectively using a mechanofusion apparatus, have.

Examples of the carbon precursor include hydrocarbons such as toluene, graphite such as natural graphite and artificial graphite; Carbon black, super-black black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, carbon nanotubes, carbon nanofibers, fluorenes and the like can be used.

The Group 13 element source may be a boron compound, an aluminum compound, a gallium compound, an indium compound, and the like, and specifically includes borax, boron oxide (B ₂ O ₃ ), boron-borane, ₅ H ₅ ) ₃ B), boron halide, and the like.

The Group 15 element source may be a nitrogen compound, a phosphorus compound, and the like, specifically, pyrrole, quinoline, pyridine, pyrimidine, and the like.

The present invention provides a lithium secondary battery having a structure in which an electrode assembly including an electrode active material and a porous polymer membrane and having a polymer membrane interposed between the anode and the cathode is housed in a battery case and sealed.

The lithium secondary battery may include a non-aqueous electrolyte containing a lithium salt.

The lithium secondary battery may be a lithium ion battery, a lithium ion polymer battery, or a lithium polymer battery.

The electrode may be a positive electrode or a negative electrode, and may be manufactured by a manufacturing method including the following processes.

In the electrode manufacturing method,

Dispersing or dissolving the binder in a solvent to prepare a binder solution;

Preparing an electrode mixture slurry by mixing the binder solution, the electrode active material, and the conductive material;

Coating the electrode mixture slurry on a current collector;

Drying the electrode; And

And compressing the electrode to a predetermined thickness.

In some cases, the rolled electrode may further be dried.

The binder solution preparation process is a process of dispersing or dissolving the binder in a solvent to prepare a binder solution.

The binder may be any binder known in the art and specifically includes polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE) A binder such as a fluorocarbon resin binder, a styrene-butadiene rubber, an acrylonitrile-butadiene rubber, a styrene-isoprene rubber, a carboxymethylcellulose (CMC), starch, hydroxypropylcellulose and regenerated cellulose One or more binders selected from the group consisting of a cellulose-based binder, a polyalcohol-based binder, a polyolefin-based binder including polyethylene, polypropylene, a polyimide-based binder, a polyester-based binder, a mussel adhesive, and a silane-based binder Mixtures or copolymers.

The solvent can be selectively used depending on the type of the binder. For example, organic solvents such as isopropyl alcohol, N-methylpyrrolidone (NMP), and acetone and water can be used.

As a specific example of the present invention, a binder solution for a positive electrode may be prepared by dispersing / dissolving PVdF in NMP (N-methyl pyrrolidone), or a styrene-butadiene rubber (SBR) / carboxy methyl cellulose (CMC) To prepare a negative electrode binder solution.

The electrode active material and the conductive material may be mixed / dispersed in the binder solution to prepare an electrode mixture slurry. The electrode slurry thus prepared can be transferred to a storage tank and stored until the coating process. In order to prevent the electrode mixture slurry from hardening in the storage tank, the electrode slurry can be continuously stirred.

The electrode active material may be a positive electrode active material or a negative electrode active material.

Specifically, the cathode active material may be a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Lithium manganese oxides such as Li _{1 + y} Mn _2-y O ₄ (where y is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ and LiMnO ₂ ; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; Formula _{LiNi 1-y M y O 2} ( where, the M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, y = 0.01 ~ 0.3 Im) Ni site type lithium nickel oxide which is represented by; Formula _{LiMn 2-y M y O 2} ( where, M = Co, Ni, Fe , Cr, and Zn, or Ta, y = 0.01 ~ 0.1 Im) or Li ₂ Mn ₃ MO ₈ (where, M = Fe, Co, Ni, Cu, or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with an alkaline earth metal ion; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ , and the like. However, the present invention is not limited to these.

In a non-limiting embodiment of the present invention, the electrode active material may include a lithium metal oxide having a spinel structure represented by the following chemical formula (1) as a cathode active material.

Li _x M _y Mn _{2 - y} O _{4 - z z} (1)

Wherein 0 < y < 2, 0 z < 0.2,

M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, ;

A is one or more of an anion of -1 or -2.

The maximum substitution amount of A may be less than 0.2 mol%. In a specific embodiment of the present invention, A may be at least one anion selected from the group consisting of halogens such as F, Cl, Br, I, S and N.

By substituting these anions, the binding force with the transition metal is improved and the structural transition of the compound is prevented, so that the lifetime of the battery can be improved. On the other hand, if the substitution amount of the anion A is too large (t? 0.2), the life characteristic is deteriorated due to the incomplete crystal structure, which is not preferable.

Specifically, the oxide of the formula (1) may be a lithium metal oxide represented by the following formula (2).

Li _x Ni _y Mn _2-y O ₄ (2)

In the above formula, 0.9? X? 1.2 and 0.4? Y? 0.5.

More specifically, the lithium metal oxide may be LiNi _0.5 Mn _1.5 O ₄ or LiNi _0.4 Mn _1.6 O ₄ .

The negative electrode active material may include, for example, carbon such as non-graphitized carbon or graphite carbon; _{Li x Fe 2 O 3 (0≤x≤1} ), Li x WO 2 (0≤x≤1), Sn x Me 1-x Me 'y O z (Me: Mn, Fe, Pb, Ge; Me' : Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, Halogen, 0 &lt; x &lt; Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{SnO, SnO 2, PbO, PbO} 2, Pb 2 O 3, Pb 3 O 4, Sb 2 O 3, Sb 2 O 4, Sb 2 O 5, GeO, GeO 2, Bi 2 O 3, Bi 2 O 4, Bi ₂ O ₅ and the like; Conductive polymers such as polyacetylene; Li-Co-Ni-based material, and the like.

In a non-limiting embodiment of the present invention, the electrode active material may include a lithium metal oxide as a negative electrode active material, and the lithium metal oxide may preferably be represented by the following chemical formula (3).

Li _a M ' _b O _{4-ca c} (3)

In the above formula, M 'is at least one element selected from the group consisting of Ti, Sn, Cu, Pb, Sb, Zn, Fe, In, Al and Zr;

a and b are 0.1? a? 4; Is determined according to the oxidation number of M 'in the range of 0.2? B? 4;

c is determined according to the oxidation number in the range of 0? c <0.2;

A is one or more of an anion of -1 or -2.

The oxide of the formula (3) may be represented by the following formula (4).

Li _a Ti _b O ₄ (4)

In the above formula, 0.5? A? 3, 1? B? 2.5.

The lithium metal oxide may be Li _0.8 Ti _2.2 O ₄ , Li _2.67 Ti _1.33 O ₄ , LiTi ₂ O ₄ , Li _1.33 Ti _1.67 O ₄ , Li _1.14 Ti _1.71 O _4, or the like. However, the present invention is not limited to these.

In a non-limiting embodiment of the present invention, the lithium metal oxide may be Li _1.33 Ti _1.67 O ₄ or LiTi ₂ O ₄ . Li _1.33 Ti _1.67 O ₄ has a spinel structure with less change in crystal structure during charging and discharging and excellent reversibility.

The lithium metal oxide can be produced by a production method known in the art and can be produced by, for example, a solid phase method, a hydrothermal method, a sol-gel method, or the like.

The lithium metal oxide may be in the form of secondary particles in which primary particles are aggregated.

The particle size of the secondary particles may be 200 nm to 30 탆.

When the particle diameter of the secondary particles is less than 200 nm, the adhesion force is lowered in the course of manufacturing the negative electrode. In order to compensate for this, the use of more binder is required, which is not preferable in terms of energy density. When the particle size of the secondary particles is more than 30 占 퐉, the diffusion rate of lithium ions is slow and it is difficult to realize a high output, which is not preferable.

The lithium metal oxide may be contained in an amount of 50 wt% or more to 100 wt% or less based on the weight of the entire negative electrode active material.

The conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

A filler or the like may be optionally added to the electrode mixture slurry as required. The filler is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery, and examples thereof include olefin-based polymerizers such as polyethylene and polypropylene; Fibrous materials such as glass fiber, carbon fiber and the like can be used.

The process of coating the electrode mixture slurry on the current collector is a process of passing the electrode mixture slurry through a coater head to coat the current collector with a predetermined pattern and a predetermined thickness.

The method of coating the electrode mixture slurry on the current collector may include a method of uniformly dispersing the electrode slurry on the current collector using a doctor blade or the like, a method of die casting, comma coating, screen printing, and the like. Alternatively, the electrode mixture slurry may be bonded to a collector by molding on a separate substrate and then pressing or laminating.

The current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery. For example, the current collector may be made of copper, stainless steel, aluminum, nickel, titanium, sintered carbon, a surface of copper or stainless steel A surface treated with carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy, or the like can be used.

The current collector may be formed in various shapes such as a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven fabric, or the like, by forming fine irregularities on the surface thereof to enhance the bonding force of the cathode active material.

Specifically, the cathode current collector may be a metal current collector including aluminum, and the anode current collector may be a metal current collector including copper. The electrode current collector may be a metal foil, and may be an aluminum foil or a copper foil.

The drying process is a process of removing the solvent and moisture in the slurry to dry the slurry coated on the metal current collector. In a specific example, the drying process is performed within one day in a vacuum oven at 50 to 200 ° C.

After the drying process, a cooling process may be further included, and the cooling process may be a slow cooling process to room temperature to form a recrystallized structure of the binder.

In order to increase the capacity density of the coated electrode and increase the adhesion between the current collector and the active materials, an electrode can be passed between two rolls heated at a high temperature and compressed to a desired thickness. This process is called the rolling process.

The electrode can be preheated before passing the electrode between two heated, heated rolls. The preheating process is a process of preheating the electrode before it is introduced into the roll to increase the compression effect of the electrode.

The electrode having completed the rolling process as described above can be dried within one day in a vacuum oven at 50 to 200 DEG C in a range satisfying a temperature equal to or higher than the melting point of the binder. The rolled electrode may be cut to a certain length and then dried.

After the drying process, a cooling process may be further included, and the cooling process may be a slow cooling process to room temperature to form a recrystallized structure of the binder.

The polymer membrane is a separator separating the anode and the cathode. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separator.

The separator is made of an insulating thin film having high ion permeability and mechanical strength. The pore diameter of the separator is generally 0.01 to 10 mu m and the thickness is generally 5 to 300 mu m.

Such separation membranes include, for example, olefinic polymers such as polypropylene, which are chemically resistant and hydrophobic; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like; Kraft paper and the like are used. Representative examples currently on the market include the Celgard ^R 2400, 2300 (from Hoechest Celanese Corp.), polypropylene separator (from Ube Industries Ltd. or Pall RAI), and polyethylene series (from Tonen or Entek).

In some cases, a gel polymer electrolyte may be coated on the separation membrane to increase the stability of the cell. Representative examples of such a gel polymer include polyethylene oxide, polyvinylidene fluoride, and polyacrylonitrile.

The electrode assembly may include both a jelly-roll type electrode assembly (or a wound electrode assembly), a stacked electrode assembly (or a stacked electrode assembly), or a stacked & folded electrode assembly having a structure known in the art.

In this specification, the stacked & folded type electrode assembly is a method of arranging unit cells having a structure in which a separator is interposed between an anode and a cathode on a separator sheet, folding and winding the separator sheet A stack &amp; folding type electrode assembly.

In addition, the electrode assembly may include an electrode assembly having a structure in which one of an anode and a cathode is laminated with a structure interposed therebetween, and is laminated by a method such as thermal fusion.

As the non-aqueous electrolyte, a non-aqueous electrolyte, an organic solid electrolyte, an inorganic solid electrolyte, or the like is used.

Examples of the nonaqueous electrolyte include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate , Gamma -butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, Diethyl ether, formamide, dimethyl formamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane A non-protonic organic solvent such as an ether, a methyl pyrophosphate, or an ethyl propionate is used as the solvent, a sulfone, a methyl sulfolane, a 1,3-dimethyl-2-imidazolidinone, a propylene carbonate derivative, a tetrahydrofuran derivative, .

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, Polymers containing ionic dissociation groups, and the like can be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides and sulfates of Li such as Li ₄ SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

The lithium salt is a material that is readily soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO 4, LiBF 4, LiB 10 Cl 10, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF _{6, LiSbF 6, LiAlCl 4,} CH 3 SO 3 Li, CF 3 SO 3 Li, LiSCN, LiC (CF 3 SO 2) 3, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, 4-phenylborate, imide, and the like can be used.

For the purpose of improving the charge / discharge characteristics and the flame retardancy, the electrolytic solution is preferably mixed with an organic solvent such as pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, Benzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, . In some cases, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further added to impart nonflammability. In order to improve the high-temperature storage characteristics, carbon dioxide gas may be further added. FEC (fluoro-ethylene carbonate, PRS (propene sultone), FPC (fluoro-propylene carbonate), and the like.

The lithium secondary battery according to the present invention can be used not only in a battery cell used as a power source of a small device but also as a unit cell in a middle- or large-sized battery module including a plurality of battery cells.

Also, the present invention provides a battery pack including the battery module as a power source of a middle- or large-sized device, wherein the middle- or large-sized device is an electric vehicle (EV), a hybrid electric vehicle (HEV) An electric vehicle including a plug-in hybrid electric vehicle (PHEV), a power storage device, and the like, but the present invention is not limited thereto.

The structure of the battery module and the battery pack and the method of manufacturing the battery module and the battery pack are well known in the art, so a detailed description thereof will be omitted herein.

As described above, the positive electrode active material according to the present invention has an effect of ensuring an efficient electron transfer path in the electrode for flowing a high current without side reaction and securing the movement path of lithium ions.

Therefore, the lithium secondary battery including the positive electrode active material can exhibit a high rate charge / discharge characteristic.

1 is a comparative experimental result comparing the high rate charge / discharge characteristics of the non-limiting embodiment and the comparative example according to the present invention.

Hereinafter, the present invention will be described in detail with reference to the following examples. However, the following examples are intended to illustrate the present invention, and the scope of the present invention is not limited thereto.

&Lt; Example 1 >

Pyridine was coated on the surface of LiNi _0.5 Mn _1.5 O ₄ by chemical vapor deposition (CVD) to prepare an electrode active material.

The electrode mixture was weighed in an amount of 90: 5: 5 as an electrode active material: Super-P: PVDF, and then mixed in a mixer to prepare an electrode mixture. An aluminum foil having a thickness of 20 [ After coating, the coating was rolled to a porosity of 40% and dried at 60 DEG C for 24 hours to prepare a working electrode.

A lithium metal as a counter electrode, and the polyethylene film as a separator: There is LiPF ₆ in (Celgard, thickness 20 ㎛) and an electrolyte dissolved 1 mol of EC: DMC: the amount of the EMC 1: 1: 1 by using the carbonate electrolyte A coin-type battery (N-doped C coating) was fabricated.

&Lt; Comparative Example 1 &

A cell (C coating) was prepared in the same manner as in Example 1, except that Toluene was coated on the surface of LiNi _0.5 Mn _1.5 O ₄ by chemical vapor deposition (CVD).

&Lt; Comparative Example 2 &

A battery (Bare) was fabricated in the same manner as in Comparative Example 1, except that a carbon coating layer was not formed on the surface of LiNi _0.5 Mn _1.5 O ₄ .

<Experimental Example 1>

The batteries of Example 1, Comparative Example 1 and Comparative Example 2 were charged at a charging current of 0.1 C at a temperature of 25 캜 and subjected to a charging / discharging test for 8 times while changing the discharging current to 0.1 C, 0.5 C and 1.0 C Respectively. Figure 1 shows the initial cycle discharge capacity as a function of the 0.1 C capacity of the first cycle.

Referring to FIG. 1, it can be seen that Example 1 exhibits a higher capacity retention rate than Comparative Examples 1 and 2 during high rate discharge.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims (18)

Characterized in that a carbon coating layer comprising a Group 13 element or a Group 15 element in the periodic table is formed on the surface of a lithium metal oxide having a spinel structure for inserting and desorbing lithium ions during charging and discharging, Electrode active material. 2. The electrode active material according to claim 1, wherein the lithium metal oxide is represented by the following formula (1): < EMI ID =
Li _x M _y Mn _{2 - y} O _{4 - z z} (1)
Wherein 0 < y < 2, 0 z &lt; 0.2,
M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, ;
A is one or more of an anion of -1 or -2. The electrode active material according to claim 2, wherein the oxide of the formula (1) is represented by the following formula (2)
Li _x Ni _y Mn _2-y O ₄ (2)
Wherein 0.9? X? 1.2, 0.4? Y? 0.5; The electrode active material according to claim 3, wherein the lithium metal oxide is LiNi _0.5 Mn _1.5 O ₄ or LiNi _0.4 Mn _1.6 O ₄ . 2. The electrode active material according to claim 1, wherein the lithium metal oxide is represented by the following formula (3): < EMI ID =
Li _a M ' _b O _{4-ca c} (3)
In the above formula, M 'is at least one element selected from the group consisting of Ti, Sn, Cu, Pb, Sb, Zn, Fe, In, Al and Zr;
a and b are 0.1? a? 4; Is determined according to the oxidation number of M 'in the range of 0.2? B? 4;
c is determined according to the oxidation number in the range of 0? c <0.2;
A is one or more of an anion of -1 or -2. The electrode active material according to claim 5, wherein the oxide of the formula (3) is represented by the following formula (4)
Li _a Ti _b O ₄ (4)
In the above formula, 0.5? A? 3, 1? B? 2.5. The electrode active material according to claim 6, wherein the lithium metal oxide is Li _1.33 Ti _1.67 O ₄ or LiTi ₂ O ₄ . The electrode active material according to claim 1, wherein the carbon coating layer comprises a carbon compound. The carbon compound according to claim 8, wherein the carbon compound is at least one selected from the group consisting of graphite, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, Electrode active material. delete The electrode active material according to claim 1, wherein the Group 13 element or the Group 15 element on the Periodic Table of Elements replaces a part of carbon of the carbon coating layer. 12. The electrode active material according to claim 11, wherein the Group 13 element is boron (B). 12. The electrode active material according to claim 11, wherein the Group 15 element is nitrogen (N). A lithium secondary battery comprising an electrode assembly including an electrode active material according to claim 1 and a polymer membrane, wherein the electrode assembly having a polymer membrane interposed between the anode and the cathode is embedded in the battery case. 15. The lithium rechargeable battery of claim 14, wherein the lithium secondary battery is a lithium ion battery. 15. The lithium secondary battery according to claim 14, wherein the lithium secondary battery is a lithium ion polymer battery. The lithium secondary battery according to claim 14, wherein the lithium secondary battery is a lithium polymer battery. The electrode active material according to claim 1, wherein the thickness of the carbon coating layer is in the range of 2 nm or more and 50 nm or less.

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