KR20150022225A - Cathode active material with reduced surface residues and a method of making the same - Google Patents

Abstract

The present invention relates to a lithium manganese-based positive electrode active material, which reduces the adsorption of by-products on surface by coating the surface of the lithium manganese-based positive electrode active material containing high amount of manganese with fluorine, and a manufacturing method thereof where the by-products on surface of the lithium manganese-based positive electrode active material are reduced, thereby preventing a positive electrode mixture slurry from turning into gelation. According to an embodiment of the present invention, the lithium manganese-based positive electrode active material has reduced by-products on the surface by using a fluorine coating layer. In the present invention, a secondary battery is manufactured with use of the positive electrode active material and accordingly has improved functions.

Description

[0001] The present invention relates to a cathode active material having reduced surface byproducts and a method of manufacturing the cathode active material,

The present invention relates to a cathode active material having reduced surface byproducts and a method for producing the same, and more particularly, to a lithium manganese cathode active material capable of reducing the adsorption of surface by-products by surface coating a lithium manganese cathode active material having a high manganese content with fluorine And a method for producing the same.

As technology development and demand for mobile devices have increased, there has been a rapid increase in demand for secondary batteries as energy sources. Among such secondary batteries, lithium secondary batteries, which exhibit high energy density and operating potential, long cycle life, Batteries have been commercialized and widely used.

In recent years, there has been a growing interest in environmental issues, and as a result, electric vehicles (EVs) and hybrid electric vehicles (HEVs), which can replace fossil-fueled vehicles such as gasoline vehicles and diesel vehicles, And the like.

Such electric vehicles (EV) and hybrid electric vehicles (HEV) use nickel metal hydride (Ni-MH) secondary batteries as a power source or lithium secondary batteries having high energy density, high discharge voltage and output stability. Is required to be used for an electric vehicle for 10 years or more under severe conditions in addition to high energy density and characteristics capable of exhibiting large output in a short period of time. Therefore, it is inevitable that safety and long- . In addition, a secondary battery used in an electric vehicle (EV), a hybrid electric vehicle (HEV) and the like requires excellent rate characteristics and power characteristics depending on the operating conditions of the vehicle.

At present, as a cathode active material of a lithium ion secondary battery, 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 structure, LiMn ₂ O ₄ of a spinel crystal structure And lithium-containing manganese oxides such as lithium manganese oxide and lithium manganese oxide.

LiCoO ₂ has excellent properties such as excellent cycle characteristics and is widely used at present. However, LiCoO ₂ is low in safety, is expensive due to the resource limit of cobalt as a raw material, and has a limitation in mass use as a power source for fields such as electric vehicles. Due to the nature of LiNiO _2, LiNiO ₂ is difficult to apply to actual mass production process at reasonable cost.

On the other hand, lithium manganese oxides such as LiMnO ₂ and LiMn ₂ O ₄ have the advantage of using manganese which is rich in resources and environment-friendly as a raw material, and thus attracts much attention as a cathode active material that can replace LiCoO ₂ . However, these lithium manganese oxides also have a disadvantage of poor cycle characteristics and the like. LiMnO ₂ has a disadvantage in that the initial capacity is small and dozens of charge-discharge cycles are required until a certain capacity is reached. In addition, LiMn ₂ O ₄ has a disadvantage in that the cycle capacity is seriously deteriorated as the cycle continues, and in particular, at a high temperature of 50 ° C or higher, the cycle characteristics are drastically lowered due to decomposition of the electrolytic solution and elution of manganese.

In particular, the Mn-rich cathode active material requires more Li than the other cathode materials in terms of the amount of Li that is required structurally, in addition to the layered LiMnO ₂ , in order to make the Li ₂ MnO ₃ structure. Therefore, the Mn-rich cathode active material basically has a high Li / Me ratio, for example, a Li / Me ratio in the range of 1.08 to 1.60, which leads to a relatively high amount of by-products present on the surface of the cathode material. Such by-products are not preferable because they cause gelation of the slurry during the anode coating.

Disclosure of Invention Technical Problem [8] The present invention provides a lithium manganese-based cathode active material having reduced surface byproducts.

Also, in the present invention, it is intended to prevent gelation of the positive electrode material mixture slurry by reducing surface byproducts of the lithium manganese-based positive electrode active material.

The present invention also provides a method for producing the above-mentioned cathode active material.

According to an aspect of the present invention, there is provided a lithium manganese-based cathode active material having a surface by-product reduced by a fluorine coating layer.

The fluorine coating layer may be formed with a Li-F-metal, Li-F-metal, or a combination of both.

The surface byproduct may be reduced by 30 to 70% by weight.

The surface byproduct may be one or a mixture of two or more selected from the group consisting of a hydroxyl group-containing compound, water, and a carbonate compound.

The fluorine coating layer may be 2 nm to 20 탆 thick.

The fluorine coating layer is of polyvinylidene fluoride (Polyvinylidene fluoride: PVdF), AlF 3, NH 4 F, CsF, KF, LiF, NaF, RbF, TiF, AgF, AgF₂, BaF 2, CaF 2, CuF 2, CdF 2 _{, FeF 2, HgF 2, Hg} 2 F 2, MnF 2, MgF 2, NiF 2, PbF 2, SnF 2, SrF 2, XeF 2, ZnF 2, AlF 2, BF 3, BiF 3, CeF 3, CrF 3 _{, DyF 3, EuF 3, GaF} 3, GdF 3, FeF 3, HoF 3, InF 3, LaF 3, LuF 3, MnF 3, NdF 3, VOF 3, PrF 3, SbF 3 ScF 3, SmF 3, TbF 3 _{, TiF 3, TmF 3, YF} 3, YbF 3, TIF 3, CeF 4, GeF 4, HfF 4, SiF 4, SnF 4, TiF 4, VF 4, ZrF 4, NbF 5, SbF 5, TaF 5, BiF ₅ , MoF ₆ , ReF ₆ , SF ₆ , WF ₆ , a fluorine-containing gas, and mixtures thereof.

The lithium manganese-based cathode active material may be represented by the following general formula (1)

[Chemical Formula 1]

Li _x Ni _y Mn _z Co _{1 - y - z} O ₂

In the above, z> y, z> 1-y-z, and x> 1.

In the above formula (1), the z / y value representing the Mn / Ni atom ratio may be 1 < z / y &lt;

The lithium manganese-based cathode active material may have a secondary particle size of 20 nm to 200 m longest diameter.

According to another aspect of the present invention, there is provided a process for producing a lithium manganese-based cathode active material for a lithium secondary battery, comprising the steps of:

(a) uniformly mixing a nickel compound, a manganese compound and a cobalt compound;

(b) adding a lithium compound and calcining to obtain a layered lithium manganese-based cathode active material; And

(c) fluorine coating the surface of the layered lithium manganese-based cathode active material.

The fluorine coating may be formed by a dry coating method.

According to another aspect of the present invention, there is provided a positive electrode for a lithium secondary battery produced from a slurry for a positive electrode material mixture containing the lithium manganese-based positive electrode active material for a lithium secondary battery.

According to still another aspect of the present invention, there is provided a lithium secondary battery including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is the positive electrode for the lithium secondary battery described above A lithium secondary battery is provided.

According to still another aspect of the present invention, there is provided a battery module including the above-described lithium secondary battery as a unit cell.

According to still another aspect of the present invention, there is provided a battery pack characterized in that the above-described battery module is included as a power source of a middle- or large-sized device.

The middle- or large-sized device may be an electric vehicle, a hybrid electric vehicle, a plug-in electric vehicle, or a power storage device.

According to the present invention, by-products can be prevented from being adsorbed on the surface of the cathode active material, and the phenomenon of gelation of the cathode mixture slurry is also prevented.

This improves the performance of the secondary battery manufactured using the cathode active material.

FIG. 1 is a graph showing that the surface of a lithium manganese-based cathode active material according to the present invention is fluorine-coated.
FIG. 2 is an analysis of the F-peak in FIG. 1, which is a graph showing that a Li-F-metal and / or an F-metal bond is formed on the surface of a cathode active material.

Hereinafter, the present invention will be described in detail. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

The lithium manganese-based cathode active material of the present invention is not particularly limited in terms of kind and structure as long as surface byproducts are reduced by fluorine coating. Non-limiting examples of the lithium manganese-based cathode active material include a structure in which a spinel structure is formed only on the surface A lithium manganese-based positive electrode active material.

According to one embodiment of the present invention, the layered lithium manganese-based cathode active material may be represented by the following formula 1 and its surface is coated with fluorine, but is not limited thereto:

[Chemical Formula 1]

Li _x Ni _y Mn _z Co _{1 - y - z} O ₂

In the above, z> y, z> 1-y-z, and x> 1.

In the above formula (1), the value of z / y representing the Mn / Ni atomic ratio is preferably 1 < z / y &lt; When the value of z / y is larger than the upper limit value, safety may be greatly deteriorated. When the value is smaller than the lower limit value, it is difficult to expect a higher capacity value.

The lithium manganese-based cathode active material may have a secondary particle size of the longest diameter of 20 nm to 200 m, but is not limited thereto.

The fluorine coating layer is applied to the surface of the layered lithium manganese-based cathode active material which is the coated matrix material to form a surface coating layer. The fluorine coating layer does not strictly function as a cathode active material but forms a coating layer on the surface of the lithium manganese cathode active material to reduce surface byproducts of the cathode active material and will be described below together with the cathode active material.

As the fluorine coating layer forms a coating layer on the surface of the lithium manganese-based cathode active material, fluorine (F) plays a role of holding Li and / or metal present on the surface of the lithium manganese-based cathode active material. At this time, fluorine forms a metal-F and / or Li-metal-F bond. Such bond formation can be confirmed by an experimental graph as shown in FIG. 1 and FIG. That is, the graph of the surface component analysis of FIG. 1 shows the existence of the F component, and FIG. 2, which is an analysis of the F peak in FIG. 1, shows that Li and F, Li- It can be seen that the peak appears at the position of the shape.

By coating the surface of the lithium manganese-based cathode active material with fluorine, it is possible to prevent the by-product from being adsorbed on the surface of the cathode active material. As a result, the lithium manganese-based cathode active material has a reduced surface by-product content, for example, by-products reduced to about 30 to 70% as compared with the non-fluorine-coated lithium manganese-based cathode active material. Typically, it exhibits a byproduct reduction of about 35% and may exhibit a by-product reduction of at least 50%.

As used herein, the term "surface by-product" or "by-product" means a substance that can be adsorbed due to the surface reactivity of the cathode active material, for example, a hydroxyl group-containing compound, water, a carbonate compound, and the like. A non-limiting example of the hydroxyl group-containing compound is LiOH. These by-products are not preferable because they cause gelation of the slurry during the anode coating.

Examples of the fluorine-containing compound used in the fluorine coating include polyvinylidene fluoride (PVdF), AlF ₃ and NH ₄ F, fluorine compounds such as CsF, KF, LiF, NaF, RbF, TiF, AgF, _{2, CaF 2, CuF 2,} CdF 2, FeF 2, HgF 2, Hg 2 F 2, MnF 2, MgF 2, NiF 2, PbF 2, SnF 2, SrF 2, XeF 2, ZnF 2, AlF 2, BF _{3, BiF 3, CeF 3,} CrF 3, DyF 3, EuF 3, GaF 3, GdF 3, FeF 3, HoF 3, InF 3, LaF 3, LuF 3, MnF 3, NdF 3, VOF 3, PrF 3, SbF ₃ ScF ₃ , SmF ₃ , TbF ₃ , TiF ₃ , TmF ₃ , YF ₃ , YbF ₃ , TIF ₃ , CeF ₄ , GeF ₄ , HfF ₄ , SiF ₄ , SnF ₄ , TiF ₄ , VF ₄ , ZrF ₄ , But are not limited to, NbF ₅ , SbF ₅ , TaF ₅ , BiF ₅ , MoF ₆ , ReF ₆ , SF ₆ , WF ₆ ,

Further, the fluorine coating layer may be 2 nm to 20 탆 thick, but is not limited thereto. If the coating layer is thinner than the lower limit value, the by-product adsorption may not be properly performed. If the coating layer is thicker than the upper limit value, migration of Li ions becomes difficult and the side reaction with the electrolyte increases.

The method for preparing the lithium manganese complex oxide for a lithium secondary battery of the present invention can be manufactured by the following steps, but is not limited thereto:

(a) uniformly mixing a nickel compound, a manganese compound and a cobalt compound;

(b) adding a lithium compound and calcining to obtain a layered lithium manganese-based cathode active material; And

(c) fluorine coating the surface of the layered lithium manganese-based cathode active material.

Non-limiting examples of the nickel _{compound, Ni (OH) 2, NiO} , NiOOH, NiCO 3 · 2Ni (OH) 2 · 4H 2 O, NiC 2 O 4 · 2H 2 O, Ni (NO 3) 2 · 6H 2 O, NiSO ₄ , NiSO ₄ .6H ₂ O, fatty acid nickel salts, and nickel halides. When Of these, the firing process from the viewpoint that not generate harmful substances such as NO _X and _{SO X, Ni (OH) 2} , NiO, NiOOH, NiCO 3 · 2Ni (OH) 2 · 4H 2 O , and NiC ₂ O ₄ · It is preferable that it does not contain a nitrogen atom or a sulfur atom in the baking treatment, such as 2H ₂ O. These nickel compounds may be used singly or in combination of two or more.

Non-limiting examples of manganese compounds include manganese oxides such as Mn ₂ O ₃ , MnO ₂ and Mn ₃ O ₄ , MnCO ₃ , Mn (NO ₃ ) ₂ , MnSO ₄ , manganese acetate, manganese dicarboxylate, And manganese salts such as fatty acid manganese salts, oxyhydroxides, and halides such as manganese chloride. Of these, MnO ₂ , Mn ₂ O ₃ and Mn ₃ O ₄ are preferable, because gases such as NO _x and SO _x and CO ₂ are not generated during the firing process, and they can be obtained at low cost as an industrial raw material to be. These manganese compounds may be used singly or in combination of two or more.

Non-limiting examples of cobalt compounds include _{Co (OH) 2, CoOOH,} CoO, Co 2 O 3, Co 3 O 4, Co (OCOCH 3) 2 · 4H 2 O, CoCl 2, Co (NO 3) 2 · 6H ₂ O and Co (SO 4) ₂ .7H ₂ O. Among them, in the calcination treatment, NO _x and SO _x It is in that it does not generate harmful substances such as _{Co (OH) 2, CoOOH,} CoO, Co 2 O 3 and Co ₃ O ₄ is preferred. Co (OH) ₂ and CoOOH are more industrially inexpensive and more preferable from the viewpoint of high reactivity. These cobalt compounds may be used singly or in combination of two or more.

The mixing method of the raw materials is not particularly limited, and the raw materials can be mixed by a wet or dry process. For example, a method using a device such as a ball mill, a vibration mill, or a bead mill may be used. Wet mixing is preferable because more uniform mixing is possible and the reactivity of the mixture in the firing process can be increased.

The mixing time may vary depending on the mixing method. However, as long as the raw materials are uniformly mixed at the particle level, any mixing time can be used. For example, mixing time for mixing by a ball mill (wet or dry mixing) is usually about 1 hour to 2 days, and the residence time for mixing by a bead mill (wet continuous method) is usually about 0.1 hour to 6 hours.

After wet grinding, the particles are dried in a conventional manner. The drying method is not particularly limited. However, spray drying is preferable from the viewpoint of uniformity of the produced particle material, powder fluidity and powder processing performance, and the ability to efficiently form spherical secondary particles.

A powder obtained by spray drying _{Li 2 CO 3, LiNO 3,} LiNO 2, LiOH, LiOH · H 2 O, LiH, LiF, LiCl, LiBr, LiI, CH 3 OOLi, Li 2 O, Li 2 SO 4, dicarboxylic A lithium compound such as a lithium carboxylate, a lithium carboxylate, a lithium carboxylate, a lithium salt, a lithium salt, a lithium salt, a fatty acid lithium salt or an alkyl lithium.

The powder mixture thus obtained is calcined. The firing conditions are determined depending on the composition and the lithium compound raw material to be used. The baking temperature is usually 800 ° C or higher, preferably 900 ° C or higher, more preferably 950 ° C or higher, and usually 1100 ° C or lower, preferably 1075 ° C or lower, more preferably 1050 ° C or lower.

Then, the surface of the lithium manganese-based cathode active material is coated with a fluorine-containing compound. The coating may be made of a dry coating, and it is preferable from the viewpoint that degradation of the properties of the cathode active material can be prevented by dry coating. Non-limiting examples of the coating method include a solid phase reaction in which a fluorine-containing compound and a cathode active material are mixed and heat-treated at an appropriate temperature, a spray drying method in which a fluorine-containing compound is dissolved and dispersed in a solvent, But is not limited thereto.

The thus prepared cathode active material of the present invention can constitute a cathode mixture together with a binder and a conductive material conventionally used in the art.

The binder may be added in an amount of 1 to 30 parts by weight based on 100 parts by weight of the positive electrode active material as a component for assisting the bonding of the positive electrode active material and the conductive material and the bonding to the current collector, But is not limited to. Specific examples of such a binder include, but are not limited to, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), fluorine rubber, styrene-butadiene rubber (SBR), cellulose- .

The conductive material may be added in an amount of 1 to 50 parts by weight based on 100 parts by weight of the cathode active material, but the content thereof is not particularly limited in the present invention. Specific examples of such a conductive material are not particularly limited as long as they have electrical conductivity without causing chemical change in the battery, and for example, a carbon black conductive material such as graphite or acetylene black can be used.

Examples of the dispersion medium include N-methyl-2-pyrrolidone, diacetone alcohol, dimethylformaldehyde, propylene glycol monomethyl ether, methyl cellosolve, ethyl cellosolve, butyl cellosolve, isopropyl cellosolve, But are not limited to, a dispersant selected from the group consisting of butyl ketone, n-butyl acetate, cellosolve acetate, toluene, xylene, and mixtures thereof.

The above-described positive electrode material mixture slurry is applied onto a positive electrode current collector and dried to form a positive electrode for a lithium secondary battery.

The positive electrode collector generally has a thickness of 10 to 500 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, sintered carbon, aluminum or stainless steel A surface treated with carbon, nickel, titanium, silver or the like may be used.

The thickness of the positive electrode mixture slurry on the positive electrode current collector is not particularly limited, but may be, for example, 10 to 300 μm, and the loading amount of the active material may be 5 to 50 mg / cm 2.

In another aspect of the present invention, there is provided a lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a lithium secondary battery including the electrolyte, wherein the positive electrode is used as the positive electrode .

In addition, a lithium secondary battery can be manufactured together with the anode by preparing and assembling a cathode, a separator, and an electrolyte according to a conventional method known in the art.

As a non-limiting example of the negative electrode active material, a conventional negative electrode active material that can be used for a negative electrode of a lithium secondary battery can be used. In particular, lithium metal or a lithium alloy, carbon, petroleum coke, activated carbon, Lithium-adsorbing materials such as graphite or other carbon-based materials and the like are preferable. Non-limiting examples of cathode current collectors include foils made by copper, gold, nickel or copper alloys or combinations thereof.

The separator may be a porous polyethylene, a polyolefin film of porous polypropylene, an organic / inorganic composite separator in which a porous coating layer is formed on a porous substrate, a nonwoven film, engineering plastic, no. As a process for applying a separator to a battery, lamination, stacking and folding of a separator and an electrode are possible in addition to a general winding process.

The electrolyte solution that can be used in one embodiment of the present invention is a salt having a structure such as A ⁺ B ^- , where A ⁺ includes ions consisting of alkali metal cations such as Li ⁺ , Na ⁺ , K ^{+ -} it is _{^{PF 6 -, BF 4 -,}} Cl -, Br -, I -, ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF 3 SO 2) 2 -, C (CF ₂ SO _{2) 3} ^- anion, or a salt containing an ion composed of a combination of propylene carbonate (PC) such as, ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl (DMP), dimethylsulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC), gamma-butyrolactone Or an organic solvent composed of a mixture thereof, but the present invention is not limited thereto.

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, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further added to impart nonflammability, or a carbon dioxide gas may be further added to improve the high-temperature storage characteristics. FEC (Fluoro-Ethylene carbonate ), PRS (Propene sultone), FPC (Fluoro-Propylene carbonate) and the like.

The electrolyte injection may be performed at an appropriate stage of the battery manufacturing process, depending on the manufacturing process and required properties of the final product. That is, it can be applied before assembling the cell or at the final stage of assembling the cell.

The 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 of 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.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the above-described embodiments. Embodiments of the invention are provided to more fully describe the present invention to those skilled in the art.

Example  1: Preparation of positive electrode

100 g of the layered lithium manganese compound (Mn <60% by weight) and 0.01 to 0.3 g of the fluorine-containing compound were mixed and heat-treated at 200 to 700 ° C for 1 to 10 hours to obtain a fluorine-coated lithium nickel-manganese- &Lt; / RTI &gt;

Next, the lithium manganese-based compound is mixed with 1 to 20% by weight of a carbon black conductive material and 1 to 20% by weight of a binder selected from the group consisting of PVDF, PTFE, fluorine rubber, styrene butadiene and a cellulose resin, -2-pyrrolidone to obtain a slurry.

Then, the slurry was applied to an aluminum current collector and dried at a temperature of 100 to 130 DEG C for 20 minutes to 2 hours to prepare a positive electrode.

Example  2: Preparation of anode

A positive electrode was prepared in the same manner as in Example 1, except that the morphology of the positive electrode active material was changed from a flake form to a plate form using an additive during synthesis of the positive electrode active material.

Example  3: Preparation of positive electrode

A positive electrode was prepared in the same manner as in Example 1, except that a layered lithium manganese compound (Mn? 60 wt%) in which the manganese content was increased was used.

Example  4 to 6: The lithium secondary battery  Produce

The positive electrodes obtained in Examples 1 to 3 were used as positive electrodes of lithium secondary batteries, respectively.

As the negative electrode, commercially available graphite was used as an anode active material, acetylene black / CMC / SBR were mixed at a weight ratio of 8: 1: 1, and the mixture was mixed in N-methylpyrrolidone as a solvent. The anode mixture slurry was coated on a copper foil having a thickness of 10 탆 by a doctor blade method, semi-dried, and cut to a predetermined size. At this time, the cell was dried at 120 DEG C for about one day in a vacuum state before assembly.

A polyethylene film was used as a separator, a separator was interposed between the positive electrode and the negative electrode, and the electrolyte membrane was housed in a battery can. Then, 1 mol of LiPF ₆ solution was added to the mixed solvent of EC / EMC = A battery was prepared according to the method.

Evaluation example : Cathode active material surface analysis

The cathode active material obtained in Example 1 was analyzed by X-ray photoelectron spectroscopy (XPS) and is shown in FIGS. 1 and 2 as 451-F. Likewise, the cathode active materials obtained in Examples 2 and 3 were analyzed by XPS and are shown in FIGS. 1 and 2 as 612-2-F and 719-1-F, respectively. As can be seen from the graphs of FIGS. 1 and 2, the lithium manganese-based cathode active material of the present invention forms a Li-F-metal and / or F-metal bond irrespective of the morphology and manganese composition ratio of the cathode active material, Thereby reducing the surface byproduct of the cathode active material.

Claims (16)

A lithium manganese cathode active material having reduced surface byproducts by a fluorine coating layer.
The method according to claim 1,
Wherein the fluorine coating layer is formed with a Li-F-metal, a Li-F-metal, or a combination of both.
The method according to claim 1,
Wherein the surface byproduct is reduced by 30 to 70% by weight.
The method according to claim 1,
Wherein the surface by-product is one or a mixture of two or more selected from the group consisting of a hydroxyl group-containing compound, water, and a carbonate compound.
The method according to claim 1,
Wherein the fluorine coating layer has a thickness of 2 nm to 20 占 퐉.
The method according to claim 1,
Fluoride fluorine coating layer is a polyvinylidene fluoride (Polyvinylidene fluoride: PVdF), AlF 3, NH 4 F, CsF, KF, LiF, NaF, RbF, TiF, AgF, AgF₂, BaF 2, CaF 2, CuF 2, CdF 2, _{FeF 2, HgF 2, Hg 2} F 2, MnF 2, MgF 2, NiF 2, PbF 2, SnF 2, SrF 2, XeF 2, ZnF 2, AlF 2, BF 3, BiF 3, CeF 3, CrF 3, _{DyF 3, EuF 3, GaF 3} , GdF 3, FeF 3, HoF 3, InF 3, LaF 3, LuF 3, MnF 3, NdF 3, VOF 3, PrF 3, SbF 3 ScF 3, SmF 3, TbF 3, _{TiF 3, TmF 3, YF 3} , YbF 3, TIF 3, CeF 4, GeF 4, HfF 4, SiF 4, SnF 4, TiF 4, VF 4, ZrF 4, NbF 5, SbF 5, TaF 5, BiF 5 , MoF ₆ , ReF ₆ , SF ₆ , WF ₆ , a fluorine-containing gas, and a mixture thereof.
The method according to claim 1,
Wherein the lithium manganese-based positive electrode active material is represented by the following formula (1).
[Chemical Formula 1]
Li _x Ni _y Mn _z Co _{1 - y - z} O ₂
In the above, z> y, z> 1-yz, and x> 1.
The method according to claim 1,
Wherein the z / y value of the Mn / Ni atomic ratio in the formula (1) is 1 < z / y? 20.
The method according to claim 1,
Wherein the lithium manganese-based cathode active material has a secondary particle size of the longest diameter of 20 nm to 200 m.
A method for producing a lithium manganese-based cathode active material, comprising the steps of:
(a) uniformly mixing a nickel compound, a manganese compound and a cobalt compound;
(b) adding a lithium compound and calcining to obtain a layered lithium manganese-based cathode active material; And
(c) fluorine coating the surface of the layered lithium manganese-based cathode active material.
11. The method of claim 10,
Wherein the fluorine coating is formed by a dry coating method.
A positive electrode for a lithium secondary battery, which is produced from a slurry for a positive electrode mixture comprising the lithium manganese-based positive electrode active material according to any one of claims 1 to 9.
1. A lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte,
The lithium secondary battery according to claim 12, wherein the anode is the anode for the lithium secondary battery.
A battery module comprising the lithium secondary battery according to claim 13 as a unit cell.
A battery pack comprising the battery module according to claim 14 as a power source of a middle- or large-sized device.
16. The method of claim 15,
Wherein the middle- or large-sized device is an electric vehicle, a hybrid electric vehicle, a plug-in electric vehicle, or a power storage device.

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