KR100999563B1 - Cathode active material for lithium secondary battery, method for preparing the same, and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention includes a high capacity first positive electrode active material, and a highly stable second positive electrode active material, wherein the first positive electrode active material and the second positive electrode active material are coated with an inorganic compound to provide a positive electrode active material for a lithium secondary battery. .

The positive electrode active material has a strong resistance to acids generated near the positive electrode active material, does not react with the electrolyte, and increases mobility of lithium ions present in the electrolyte. The lithium secondary battery using the positive electrode active material is excellent in charge and discharge characteristics, life characteristics, high voltage characteristics, rate characteristics, resistance characteristics, and discharge potential.

Mixed electrode, positive electrode active material, high temperature stability, high voltage stability, high capacity, rate characteristic, inorganic oxide, coating

Description

A cathode active material for a lithium secondary battery, a method of manufacturing the same, and a lithium secondary battery including the same TECHNICAL FIELD OF THE INVENTION

The present invention relates to a positive electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same. More particularly, the present invention relates to an acid generated near a positive electrode active material, and is resistant to an acid generated in the vicinity of the positive electrode active material and does not react with an electrolyte solution. The present invention relates to a cathode active material for a lithium secondary battery that increases mobility of lithium ions, a method of manufacturing the same, and a lithium secondary battery including the same.

Recently, the demand for lithium secondary batteries has rapidly increased as a power source for portable electronic devices such as PDAs, mobile phones, notebook computers, electric bicycles, and electric vehicles, replacing conventional batteries. In particular, since the product performance of such a portable device or a moving means depends on the performance of a secondary battery which is a key component, the demand for a high capacity, high output, high performance battery is very large.

Among them, the energy of the lithium secondary battery is mainly determined by the positive electrode active material. Commercially available small lithium secondary batteries use layered LiCoO ₂ for the positive electrode and carbon for the negative electrode. LiCoO ₂ is an excellent material having stable charge and discharge characteristics, excellent electronic conductivity, high thermal stability and flat discharge voltage characteristics. However, Co reserves are low, expensive, and toxic to humans, requiring the development of other anode materials.

LiNiO ₂ , LiCo _x Ni _{1 - x} O ₂ and LiMn ₂ O ₄ are the anode materials currently being actively researched and developed. However, LiNiO ₂ is not commercialized due to difficulty in material synthesis and thermal stability, and LiCo _x Ni _{1 - x} O ₂ does not have sufficient performance to replace LiCoO ₂ .

In addition, LiMn ₂ O ₄ with a spinel structure has a theoretical capacity of 148 mAh / g, which is smaller than that of other materials, and has a three-dimensional tunnel structure, so the diffusion resistance is large during intercalation and deintercalation of lithium ions. The coefficient is lower than that of LiCoO ₂ and LiNiO ₂ having a two-dimensional structure, and the cycle characteristics are poor due to the Jahn-Teller effect. In particular, the high temperature property at 55 ° C or higher is inferior to LiCoO ₂ and is not widely used in actual batteries.

Lithium secondary batteries using the positive electrode active materials have a problem in that their lifespan decreases rapidly as charging and discharging are repeated. This is due to a phenomenon caused by decomposition of the electrolyte or deterioration of the active material due to moisture or other effects inside the battery, and an increase in the internal resistance of the battery. Therefore, many efforts are being made to solve this problem.

Techniques for improving energy density and quantitative properties by adding TiO ₂ to LiCoO ₂ active materials have been studied (Electrochemical and Solid-State Letters, 4 (6), A65-A67 2001). There is also known a technique for improving the lifespan by surface treatment of natural graphite with aluminum (Electrochemical and Solid-State Letters, 4 (8), A109-A112, 2001). However, it is not yet completely solved the problem of deterioration of life or the generation of gas due to decomposition of the electrolyte during charging and discharging.

Korean Patent Publication No. 2003-32363 discloses a hydroxide containing a metal of Mg, Al, Co, K, Na, Ca, Si, Ti, Sn, V, Ge, Ga, B, As, and Zr on the surface of a positive electrode active material. Techniques for coating the side, oxyhydroxide, oxycarbonate, hydroxycarbonate salts are known. However, this technique also does not solve the problem of reducing the life of the cathode active material, especially LiCoO ₂ at high voltage.

In the case of the surface-modified positive electrode active material as described above, it is possible to obtain improved electrochemical properties due to the surface treatment layer, but it is not easy to simultaneously satisfy high voltage characteristics, rate characteristics, and cycle characteristics.

An object of the present invention is excellent resistance to acid generated near the positive electrode active material is less structural change of the positive electrode active material, not only the reaction between the positive electrode active material and the electrolyte is suppressed, but also increases the mobility of lithium ions present in the electrolyte It is to provide a positive electrode active material for a lithium secondary battery.

Another object of the present invention is to provide a method for producing the positive electrode active material for a lithium secondary battery.

Still another object of the present invention is to provide a lithium secondary battery including the cathode active material.

According to one embodiment of the present invention, a high capacity first positive electrode active material, and a second positive electrode active material of high stability, wherein the first positive electrode active material, and the second positive electrode active material is a lithium secondary coated with an inorganic compound Provided is a battery positive electrode active material.

According to another embodiment of the present invention, a mixture of a high capacity first positive electrode active material and a high stability second positive electrode active material is mixed with an inorganic compound, or the first positive electrode active material and the second positive electrode active material are coated with an inorganic oxide, respectively. It provides a method for producing a cathode active material for a lithium secondary battery comprising the step of mixing after.

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

The positive electrode active material for a lithium secondary battery of the present invention has excellent resistance to acids generated near the positive electrode active material, does not react with the electrolyte, and increases the mobility of lithium ions present in the electrolyte. The lithium secondary battery using the positive electrode active material is excellent in charge and discharge characteristics, life characteristics, high voltage characteristics, rate characteristics, resistance characteristics, and discharge potential.

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

According to one embodiment of the present invention, a high capacity first positive electrode active material, and a second positive electrode active material of high stability, wherein the first positive electrode active material, and the second positive electrode active material is a lithium secondary coated with an inorganic compound Provided is a battery positive electrode active material.

The said positive electrode active material is a mixed electrode which has the surface treatment layer of an inorganic compound. Here, a mixed electrode means the case where an electrode contains two or more types of active materials. The mixed electrode not only suppresses structural changes of the positive electrode active material and the reaction between the positive electrode active material and the electrolyte by increasing resistance to acid generated nearby, and increases the mobility of lithium ions present in the electrolyte, thereby providing charge and discharge characteristics. It is possible to fabricate a lithium secondary battery having improved life characteristics, high voltage characteristics, rate characteristics, resistance characteristics, and discharge potential.

The first positive electrode active material may be used as long as it is a high capacity positive electrode active material, and is particularly selected from the group consisting of a nickel-based lithium composite metal oxide having a layered structure, a lithium composite metal oxide having a 5V spinel structure, and a mixture thereof. Any one may be preferably used.

The first cathode active material is more preferably any one selected from the group consisting of a compound represented by the following formula (1), a compound represented by the formula (2), and combinations thereof.

[Formula 1]

Li _a Ni _x Co _y Mn _z M _{1 -xy- z} O ₂ Q _σ

(In Formula 1, M is selected from the group consisting of B, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, and combinations thereof Either element, Q is halogen or S, 1.0≤a≤1.2, 0.5 <x≤0.95, 0.0≤y≤0.7, 0.0≤z≤0.7, 0.0≤1-xyz≤0.3, and 0.0≤σ≤ 0.1)

[Formula 2]

Li _a Mn _{2 - x} M _x O ₄ Q _σ

(In Formula 2, M is B, Li, Mg, Al, Ca, Sr, Cr, V, Ti, Fe, Co, Ni, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, And any combination thereof, Q is halogen or S, and 1.0 ≦ a ≦ 1.3, 0.3 ≦ x ≦ 0.7, and 0.0 ≦ σ ≦ 0.1).

Any of the second positive electrode active materials can be used as long as they are highly stable positive electrode active materials. In particular, any one selected from the group consisting of a lithium composite metal oxide having a layered structure, a lithium composite metal oxide having a spinel structure, and a mixture thereof can be preferably used.

The second cathode active material is more preferably any one selected from the group consisting of compounds represented by the following Chemical Formulas 3 to 8, and combinations thereof.

(3)

Li _a Ni _x Co _y Mn _z M _{1 -xy- z} O ₂ Q _σ

(In Formula 3, M is selected from the group consisting of B, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, and combinations thereof Either element, Q is halogen or S, 1.0≤a≤1.2, 0.05≤x≤0.5, 0.0≤y≤0.7, 0.0≤z≤0.7, 0.0≤1-xyz≤0.3, and 0.0≤σ≤ 0.1)

[Formula 4]

Li _a Co _{1 - x} M _x O ₂ Q _σ

(In Formula 4, M is selected from the group consisting of Mg, B, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, and combinations thereof Any one element, Q is halogen or S, 1.0 ≦ a ≦ 1.2, 0.0 ≦ x ≦ 0.1, and 0.0 ≦ σ ≦ 0.1)

[Chemical Formula 5]

Li _a Mn _{1 - x} M _x O ₂ Q _σ

(In Formula 5, M is selected from the group consisting of B, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, and combinations thereof Any one element, Q is halogen or S, and 1.0 ≦ a ≦ 1.2, 0.0 ≦ x ≦ 0.5, and 0.0 ≦ σ ≦ 0.1)

[Formula 6]

Li _a Mn _{2 - x} M _x O ₄ Q _σ

(In Chemical Formula 6, M is B, Li, Mg, Al, Ca, Sr, Cr, V, Ti, Fe, Co, Ni, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, And a combination thereof, Q is halogen or S, and 1.0 ≦ a ≦ 1.3, 0.0 ≦ x ≦ 0.2, and 0.0 ≦ σ ≦ 0.1).

[Formula 7]

Li _{4 + a} Ti _{4 - x} M _x O ₁₂ Q _σ

(In Formula 7, M is Li, Mg, Al, Ca, Sr, Cr, V, Ti, Fe, Co, Ni, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, and these Any one element selected from the group consisting of Q, Q is halogen or S, and 0.0≤a≤0.1, 0.0≤x≤0.1, and 0.0≤σ≤0.1)

[Formula 8]

LiM _x PO ₄ Q _σ

(In Formula 8, M is in the group consisting of Co, Ni, Mn, Fe, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, and combinations thereof Any one element selected, Q is halogen or S, 0.0 ≦ a ≦ 0.1, 0.0 ≦ x ≦ 0.1, and 0.0 ≦ σ ≦ 0.02)

The cathode active material for a lithium secondary battery may include 1 wt% to 40 wt% of the first cathode active material, 60 wt% to 99 wt% of the second cathode active material, and 5 wt% to 40 wt% of the first cathode active material. It is more preferably included in%, 60 to 95% by weight of the second positive electrode active material.

When the content of the first positive electrode active material exceeds 40% by weight, it is difficult to improve stability through the characteristics of the second positive electrode active material, and when the content of the first positive electrode active material is less than 1% by weight, the capacity is greatly reduced, which is not preferable.

Any inorganic compound capable of coating the cathode active material may be used as long as it can have electrochemical characteristics. However, the inorganic compound may be preferably any one selected from the group consisting of metal oxides, metal halides, metal sulfides, metal nitrides, and mixtures thereof.

The metal halide is LiF, NaF, KF, MgF ₂ , CaF ₂ , CuF ₂ , CdF ₂ , FeF ₂ , MnF ₂ , MgF ₂ , NiF ₂ , PbF ₂ , SnF ₂ , SrF ₂ , XeF ₂ , ZnF ₂ , _{AlF 3, BF 3, BiF 3} , CeF 3, CrF 3, FeF 3, InF 3, LaF 3, MnF 3, NdF 3, VOF 3, YF 3, CeF 4, GeF 4, HfF 4, SiF 4, SnF 4 _{, TiF 4, VF 4, ZrF} 4, VF 5, NbF 5, SbF 5, TaF 5, BiF 5, MoF 6, ReF 6, SF 6, WF 6, and any one selected from the group consisting of a mixture of Metal fluorides can be preferably used.

The metal halide is a Group 3 transition metal, Group 4 transition metal, Group 5 transition metal, Group 6 transition metal, Group 7 transition metal, Group 8 transition metal, Group 9 transition metal, Group 13 element, Group 14 element, Group 15 Metal oxyfluoride containing any one element selected from the group consisting of an element, a lanthanide element, and a combination thereof can be preferably used. Specifically, the metal oxyfluoride is Sc, Y, Zr, V, Nb, Cr, Mo, W, Mn, Fe, Co, B, Al, Ga, In, Sn, As, La, Ce, Sm, Gd, And any one element selected from the group consisting of a combination thereof.

The metal oxide is composed of Mg, Ca, Sr, B, Al, Y, Zr, Mo, W, Cr, Fe, Co, Ni, Zn, Ga, Ge, In, Sn, Bi, P, and combinations thereof It is preferable that it is an oxide containing any element selected from the group.

The inorganic compound is preferably any one selected from the group consisting of MN _x , MCl _x , MBr _x , MS _x , and mixtures thereof, and is not limited to the type of the inorganic compound unless there is no problem in electrochemical properties. . M is Mg, Ca, Sr, B, Al, Y, Zr, Mo, W, Cr, Fe, Co, Ni, Zn, Ga, Ge, In, Sn, Bi, P, and combinations thereof Is any one element selected from, wherein x is 1 to 7.

The inorganic compound may further include any one substituent selected from the group consisting of an amine group, an acetate group, and a combination thereof. The amine group is a compound substituted with an ammonia group, and the acetate uses a common metal acetate. Generally the substituents are attached to the surface of the particles and are usually attached via complexing agents. As the complexing agent, a substance having a hydroxyl group such as ammonia and citric acid or glutamic acid may be used.

It is preferable that the said inorganic compound is nano size of 1-500 nm, and it is more preferable that it is 2-200 nm. When the size of the inorganic compound is less than 1 nm, the nanoparticles may be aggregated together to form particles of only the inorganic compound before adhering to the surface, and when the size of the inorganic compound exceeds 500 nm, the characteristics of the positive electrode active material may be reduced.

The average particle size of the first positive electrode active material and the second positive electrode active material is preferably 0.1 μm to 50 μm, more preferably 0.2 μm to 40 μm, and still more preferably 0.5 μm to 30 μm. When the size of the positive electrode active material is out of the range, the mixing may not occur uniformly due to the particle size difference between the first positive electrode active material and the second positive electrode active material, and thus it is difficult to expect the effect of the mixed electrode.

The lithium secondary battery positive electrode preferably contains 0.001 to 15 moles of the inorganic compound, more preferably 0.005 to 10 moles, more preferably 0.005 to 8 moles, based on 100 moles of the first positive electrode active material and the second positive electrode active material. It is even more desirable. If the content of the inorganic compound is less than the above range does not exhibit a sufficient coating effect, on the contrary, if it exceeds the above range, the electrochemical properties such as the discharge capacity and the rate characteristic of the battery is not preferable.

According to another embodiment of the present invention, a mixture of a high capacity first positive electrode active material and a high stability second positive electrode active material is mixed with an inorganic compound, or the first positive electrode active material and the second positive electrode active material are coated with an inorganic oxide, respectively. It provides a method for producing a cathode active material for a lithium secondary battery comprising the step of mixing after.

The method of coating the inorganic oxide on the positive electrode active material can be used as long as it is conventionally used, and is well known to an average person skilled in the art, and thus a detailed description thereof will be omitted.

Any method of mixing the first positive electrode active material and the second positive electrode active material may be used as long as it is a mixing method that is generally used. In particular, mixing using a mortar or mixing using a mill or a mixer may be used. desirable. It is also possible to carry out by adding a solvent in order to facilitate the mixing.

The solvent that can be added is preferably any one selected from the group consisting of water, alcohols, and mixtures thereof, which can prevent changes of the positive electrode active material and help smooth mixing. The alcohol may be preferably a lower alcohol having 1 to 4 carbon atoms, specifically, it is preferably any one selected from the group consisting of methanol, ethanol, isopropanol, and mixtures thereof.

When the mixing step of the positive electrode active material is finished, the mixed positive electrode active material may be dried or heat treated.

The drying can be carried out using a device commonly used in the art. At this time, the drying is preferably performed for 5 to 30 hours at 110 to 200 ℃ can reduce the deformation of the positive electrode active material. In addition, it may be dried in a vacuum state to reduce the deformation of the positive electrode active material.

The heat treatment is preferably performed for 2 to 10 hours at 300 to 1000 ℃. At this time, if the temperature of the heat treatment is less than 300 ℃ moisture and impurities are not removed properly, the purity is lowered, if the temperature exceeds 1000 ℃ particles grow or a reaction occurs between the first positive electrode active material and the second positive electrode active material Hard to get effect

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

The positive electrode active material is excellent in resistance to acids, the reactivity with the electrolyte is suppressed, thereby improving the capacity reduction of the lithium secondary battery comprising the same. In addition, the positive electrode active material improves the charge potential of the lithium secondary battery by improving the mobility of lithium ions to improve the discharge potential.

Therefore, the lithium secondary battery shows more excellent output characteristics at higher rates, not only excellent capacity and life characteristics, but also excellent thermal stability.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

The lithium secondary battery may be a lithium ion battery, a lithium ion polymer battery, or a lithium polymer battery according to the type of separator and electrolyte used, and may be cylindrical, square, coin type, or pouch type depending on the form.

1 is a schematic cross-sectional view of a rechargeable lithium battery according to one embodiment of the present invention. Referring to FIG. 1, the lithium secondary battery 4 includes an electrode assembly 44 including a positive electrode 42, a negative electrode 41, and a separator 43 existing between the positive electrode 42 and the negative electrode 41. To the case 45, the electrolyte (not shown) is injected into the upper portion of the case 45 and sealed with a cap plate 46 and a gasket 47, it can be manufactured by assembly.

The cathode 42 includes a cathode active material according to an embodiment of the present invention. The positive electrode 42 may be prepared by mixing the positive electrode active material, the conductive agent, and the binder to prepare a composition for forming a positive electrode active material layer, and then coating the composition on a positive electrode current collector such as aluminum foil and rolling the same. . Metal fluoride may optionally be further added when preparing the positive active material layer-forming composition.

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

In addition, any conductive material may be used as long as the conductive material is used in the battery. Examples thereof include natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, copper, nickel, aluminum, silver, and the like. Metal powders, metal fibers and the like can be used.

The negative electrode 41 includes a negative electrode active material. As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples of the negative electrode active materials include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fibers, and amorphous carbon, lithium, lithium alloys, alloys, intermetallic compounds, organic compounds, inorganic compounds, metal complexes, and lithium polymers such as organic polymer compounds. Use compounds that can intestine and release ions. Each of the above compounds can be used alone or in any combination within a range that does not impair the effects of the present invention.

More specifically, carbonaceous materials include coke, pyrolytic carbon, natural graphite, artificial graphite, meso carbon micro beads, graphitized meso face spheres, vapor grown carbon, glassy carbons, and polyacrylonitrile. Any one selected from the group consisting of carbon fiber based on nitrile (poly acrylonitrile), pitch-based, cellulose-based, vapor-grown carbon, amorphous carbon, carbon the organic material is fired and mixtures thereof, It can be used in arbitrary combination in the range which does not impair the effect of this invention.

As the lithium alloy, a Li-Al alloy, a Li-Al-Mn alloy, a Li-Al-Mg alloy, a Li-Al-Sn alloy, a Li-Al-In alloy, or a Li-Al-Cd alloy , Li-Al-Te based alloy, Li-Ga based alloy, Li-Cd based alloy, Li-In based alloy, Li-Pb based alloy, Li-Bi based alloy, Li-Mg based alloy and the like can be used. As an alloy and an intermetallic compound, the compound of a transition metal and silicon, the compound of a transition metal, and tin, etc. can be used, Especially a compound of nickel and silicon is preferable.

Like the positive electrode 42, the negative electrode 41 may also be prepared by mixing the negative electrode active material, a binder, and optionally a conductive material to prepare a composition for forming a negative electrode active material layer, and then coating the negative electrode current collector such as copper foil. Can be.

As the electrolyte (not shown), a non-aqueous electrolyte or a known solid electrolyte may be used, and a lithium salt is used.

The lithium salt is not particularly limited as a lithium salt commonly used, and for example, the lithium salt is LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAlCl ₄ , LiSbF ₆ , LiSCN, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li (CF ₃ SO ₂ ) ₂ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiB ₁₀ Cl ₁₀ , LiBOB (lithium Bis (oxalato) borate), lower aliphatic lithium carbonate, lithium chloroborane, tetraphenylboric acid Lithium, and LiN (CF ₃ SO ₂ ), LiN (C ₂ F ₅ SO ₂ ), LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂₎ are already available such as the dE (imide), such as acids.

The lithium salts may be used alone or in any combination within a range that does not impair the effects of the present invention, and it is particularly preferable to use LiPF ₆ .

Further, in order to render the electrolyte nonflammable, carbon tetrachloride, ethylene trifluorochloride, or phosphate containing phosphorus may be included in the electrolyte.

In addition to the electrolyte, any one solid electrolyte selected from the group consisting of an inorganic solid electrolyte, an organic solid electrolyte, and a mixture thereof may be used.

Examples of the inorganic solid electrolyte include Li ₄ SiO ₄ , Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₄ SiO ₄ , Li ₂ SiS ₃ , Li ₃ PO ₄ -Li ₂ S-SiS ₂ , and phosphorus sulfide compounds And any one selected from the group consisting of a mixture thereof can be used.

The organic solid electrolyte may be polyethylene oxide, polypropylene oxide, polyvinyl alcohol, polyvinylidene fluoride, fluoropropylene, or the like, derivatives, mixtures, or copolymers thereof.

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, any one selected from the group consisting of cyclic carbonates, chain carbonates, chain carboxylic acid esters, lactone compounds, and mixtures thereof can be preferably used.

The cyclic carbonate includes ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), and a mixture thereof. Any one selected from can be used.

The chain carbonate is selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) dipropyl carbonate (DPC), and mixtures thereof. You can use either one.

The chain carboxylic acid ester may be any one selected from the group consisting of methyl formate, methyl acetate, methyl propionate, ethyl propionate, and mixtures thereof. .

As the lactone compound, γ-butyrolactone (GBL) may be preferably used.

Meanwhile, the separator 43 may exist between the positive electrode 42 and the negative electrode 41 according to the type of the lithium secondary battery. As the separator 43, polyethylene, polypropylene, polyvinylidene fluoride or two or more multilayer films thereof may be used, and polyethylene / polypropylene two-layer separator, polyethylene / polypropylene / polyethylene three-layer separator, polypropylene / polyethylene Of course, a mixed multilayer film such as a polypropylene three-layer separator can be used.

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

Mixed electrode of LiCoO ₂ and Li [Ni _1/3 Co _1/3 Mn _1/3 ] O ₂

(Comparative Example 1-1)
LiCoO ₂ and Li [Ni _1/3 Co _1/3 Mn _1/3 ] O ₂ were mixed in a weight ratio of 90:10. The mixing was carried out for 10 minutes so that the positive electrode active material was put in a mortar and pests do not break. The mixed positive electrode active material was dried in a 110 ° C. vacuum oven, and heat treated at 400 ° C. for 5 hours to completely remove moisture to prepare a cathode active material for a lithium secondary battery.
Slurry was prepared by mixing the prepared 5b positive electrode active material, super-P as a conductive material, and polyvinylidene fluoride (PVdF) as a binder at a weight ratio of 85: 7.5: 7.5, respectively. The slurry was uniformly applied to an aluminum foil having a thickness of 20 μm, and vacuum dried at 120 ° C. to prepare a positive electrode.

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The prepared anode and lithium foil were used as counter electrodes, and a porous polyethylene membrane (manufactured by Celgard ELC, Celgard 2300, thickness: 25 μm) was used as a separator, and ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1. A coin cell was prepared according to a known manufacturing process using a liquid electrolyte in which LiPF ₆ was dissolved at a concentration of 1 M in a solvent.

( Comparative example  1-2)

A battery was manufactured in the same manner as in Comparative Example 1-1 except for using LiCoO ₂ and Li [Ni _1/3 Co _1/3 Mn _1/3 ] O ₂ at a weight ratio of 80:20.

( Comparative example  1-3)

A battery was manufactured in the same manner as in Comparative Example 1-1, except that LiCoO ₂ and Li [Ni _1/3 Co _1/3 Mn _1/3 ] O ₂ were used in a weight ratio of 70:30.

(Comparative Example 1-4)
A battery was manufactured in the same manner as in Comparative Example 1-1 except that only LiCoO _{2 was} used as the cathode active material.
(Comparative Example 1-5)

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A battery was manufactured in the same manner as in Comparative Example 1-1 except that only Li [N _1/3 Co _1/3 Mn _1/3 ] O _{2 was} used as the cathode active material.

Mixed electrode of Li [Ni _0.8 Co _0.15 Al _0.05 ] O ₂ and LiCoO ₂

( Example  2-1)

0.25 mol% of AlF ₃ coated Li [Ni _0.8 Co _0.15 Al _0.05 ] O ₂ and 0.25 mol% of AlF ₃ coated LiCoO ₂ were mixed at a weight ratio of 10:90 relative to the positive electrode active material. The mixing was carried out for 10 minutes so that the positive electrode active material was put in a mortar and pests do not break. The mixed positive electrode active material was dried in a 110 ° C. vacuum oven, and heat treated at 400 ° C. for 5 hours to completely remove moisture to prepare a cathode active material for a lithium secondary battery.
A slurry was prepared by mixing the prepared positive active material and the conductive material with super-P and polyvinylidene fluoride (PVdF) as a binder at a weight ratio of 85: 7.5: 7.5, respectively. The slurry was uniformly applied to an aluminum foil having a thickness of 20 μm, and vacuum dried at 120 ° C. to prepare a positive electrode.

The prepared anode and lithium foil were used as counter electrodes, and a porous polyethylene membrane (manufactured by Celgard ELC, Celgard 2300, thickness: 25 μm) was used as a separator, and ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1. A coin cell was prepared according to a known manufacturing process using a liquid electrolyte in which LiPF ₆ was dissolved at a concentration of 1 M in a solvent.

( Example  2-2)

The AlF ₃ coating is 0.25mol% compared to the positive electrode active material _{Li [Ni 0.8 Co 0.15 Al 0.05} ] O and is conducted except the ₂ and AlF ₃ to 20: 80 as a weight ratio of 0.25mol% coated LiCoO ₂ positive active material Example 2 The battery was manufactured by the same method as -1.

( Example  2-3)

The AlF ₃ coating is 0.25mol% compared to the positive electrode active material _{Li [Ni 0.8 Co 0.15 Al 0.05} ] O and is conducted except the ₂ and AlF ₃ to 30: 70 as a weight ratio of 0.25mol% coated LiCoO ₂ positive active material Example 2 The battery was manufactured by the same method as -1.

( Comparative example  2-1)

A battery was manufactured in the same manner as in Example 2-1, except that the cathode active material not coated with AlF ₃ was used.

( Comparative example  2-2)

A battery was manufactured in the same manner as in Example 2-2, except that the cathode active material not coated with AlF ₃ was used.

( Comparative example  2-3)

A battery was manufactured in the same manner as in Example 2-3, except that the cathode active material not coated with AlF ₃ was used.

( Comparative example  2-4)

A battery was manufactured in the same manner as in Example 2-1, except that only Li [Ni _0.8 Co _0.15 Al _0.05 ] O ₂ without AlF ₃ was used as the cathode active material.

( Experimental Example  One)

In order to find out the life characteristics of the batteries of Examples 2-1 to 2-3, Comparative Examples 1-1 to 1-5, and Comparative Examples 2-1 to 2-4, a charge / discharge device which is an electrochemical analyzer (Toyo, Japan) Company, Toscat 3000U), charging and discharging the coin cell prepared at 0.2 C-rate 50 times at 30 ℃ 3.0 to 4.5V using 30 to the percentage of life characteristics are shown in Table 1, and Table 2. 2 shows a graph comparing the charge and discharge characteristics of the battery of Example 2-1 and the battery of Comparative Example 2-1.

TABLE 1

Positive electrode active material Mixing ratio
(Weight ratio) Initial discharge capacity (mAh / g)
(0.2 C-rate) Life characteristic (%)
(( _50th capacity / _1st capacity) x 100) Comparative Example 1-1 LiCoO ₂ : Li [Ni _1/3 Co _1/3 Mn _1/3 ] O ₂ 90:10 183 67.8 Comparative Example 1-2 80:20 181.23 77.4 Comparative Example 1-3 70:30 178.27 84.7 Comparative Example 1-4 LiCoO ₂ - 188 60.6 Comparative Example 1-5 Li [Ni _1/3 Co _1/3 Mn _1/3 ] O ₂ - 179.5 86.1

Referring to Table 1, it can be seen that the discharge capacity of the battery using the mixed electrode of the positive electrode active material of Comparative Examples 1-1 to 1-3, which is not coated, is poor in terms of lifetime characteristics of 67.8% to 84.7%.

Also in the case of the discharge capacity of the battery it can be seen that Comparative Examples 1-1 to 1-3 is poor as 178.27 to 183.

TABLE 2

Positive electrode active material Mixing ratio
(Weight ratio) Initial discharge capacity
(mAh / g)
(0.2 C-rate) Life Characteristics (%)
(( _50th capacity / _1st capacity) x 100) Example 2-1 Li [Ni _0.8 Co _0.15 Al _0.05 ] O ₂ : LiCoO ₂ 10:90 191.23 94.5 Comparative Example 2-1 10:90 192.2 82.6 Example 2-2 20:80 189.57 95.3 Comparative Example 2-2 20:80 195 84.4 Example 2-3 30:70 194.13 97 Comparative Example 2-3 30:70 198.2 86.2 Comparative Example 2-4 Li [Ni _0.8 Co _0.15 Al _0.05 ] O ₂ - 187.66 87.5
Referring to Table 2 and FIG. 2, Comparative Example 2 in which the discharge capacity of the battery using the mixed electrode of the positive electrode active material coated with AlF ₃ of Examples 2-1 to 2-3 according to the present invention was not coated. It can be seen that the life characteristics are significantly improved from about 11% to about 12% compared to the batteries of -1 to 2-3. This is a result showing the improvement of life characteristics due to the influence of the coating layer of AlF ₃ . In addition, it was confirmed that there is a difference in the life characteristics according to the mixing ratio, it was confirmed that the energy density can be adjusted.

delete

( Experimental Example  2)

After charging to 0.2 C-rate up to 4.5 V and discharging up to 3.0 V with 0.2 C-rate in order to determine the rate characteristics of the battery of Examples 2-1 to 2-3, and Comparative Examples 2-1 to 2-3 , Charge up to 4.5 V with 0.2 C-rate Discharge up to 3.0 V with 0.5 C-rate, Charge up to 4.5 V with 0.2 C-rate Discharge up to 3.0 V with 1.0 C-rate, Charge up to 4.3 V with 0.2 C-rate, 2.0 C- Discharge rate up to 3.0 V is shown in Table 3 below to express the discharge capacity in each C-rate based on the discharge capacity at 0.2 C-rate discharge.

[Table 3]

0.2C-rate 0.5C-rate 1.0C-rate 2.0C-rate Example 2-1 Discharge capacity percentage 100% 97.6% 95.3% 93.2% Discharge capacity 191 mAh / g 186 mAh / g 182 mAh / g 178 mAh / g Comparative Example 2-1 Discharge capacity percentage 100% 97% 93.9% 87.5% Discharge capacity 195 mAh / g 189 mAh / g 183 mAh / g 171 mAh / g Example 2-2 Discharge capacity percentage 100% 98.2% 96.7% 94.8% Discharge capacity 193 mAh / g 189 mAh / g 186 mAh / g 182 mAh / g Comparative Example 2-2 Discharge capacity percentage 100% 97% 94% 88.5% Discharge capacity 197 mAh / g 190 mAh / g 184 mAh / g 173 mAh / g Example 2-3 Discharge capacity percentage 100% 98.6% 94% 95.2% Discharge capacity 194 mAh / g 192 mAh / g 189 mAh / g 185 mAh / g Comparative Example 2-3 Discharge capacity percentage 100% 97.2% 94% 88.8% Discharge capacity 199 mAh / g 193 mAh / g 187 mAh / g 176 mAh / g

Referring to Table 3, the battery of Examples 2-1 to 2-3 consisting of a mixed electrode of the positive electrode active material coated with AlF ₃ is Comparative Examples 2-1 to manufactured from a mixed electrode of the positive electrode active material not coated It can be seen that it has a higher rate characteristic than the battery of 2-3.

In particular, when looking at the discharge capacity at 2C-rate, the 2C-rate rate characteristic of Comparative Example 2-3 is 88.8%, while the 2C-rate rate characteristic of Example 2-3 is 95.2%, which leads to an increase of 6.4% I could confirm that.

All simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

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

Figure 2 is a graph comparing the charge and discharge characteristics of the battery of Example 2-1 and the battery of Comparative Example 2-1 of the present invention.

<Explanation of symbols for the main parts of the drawings>

4: lithium secondary battery 41: negative electrode

42: anode 43: separator

44 electrode assembly 45 case

46: cap plate 47: gasket

Claims (22)

A high capacity first positive electrode active material, and a high stability second positive electrode active material, The first positive electrode active material, and the second positive electrode active material is a positive electrode active material for a lithium secondary battery is coated with a metal halide, The first positive electrode active material is any one selected from the group consisting of a nickel-based lithium composite metal oxide having a layered structure, a lithium composite metal oxide having a 5V spinel structure, and a mixture thereof, The second positive electrode active material is any one selected from the group consisting of a lithium composite metal oxide having a layered structure, a lithium composite metal oxide having a spinel structure, and a mixture thereof. delete The method of claim 1, The first cathode active material is any one selected from the group consisting of a compound represented by Formula 1, a compound represented by Formula 2, and combinations thereof. [Formula 1] Li _a Ni _x Co _y Mn _z M _{1 -xy- z} O ₂ Q _σ (In Formula 1, M is selected from the group consisting of B, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, and combinations thereof Either element, Q is halogen or S, 1.0≤a≤1.2, 0.5 <x≤0.95, 0.0≤y≤0.7, 0.0≤z≤0.7, 0.0≤1-xyz≤0.3, and 0.0≤σ≤ 0.1) [Formula 2] Li _a Mn _{2 - x} M _x O ₄ Q _σ (In Formula 2, M is B, Li, Mg, Al, Ca, Sr, Cr, V, Ti, Fe, Co, Ni, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, And any combination thereof, Q is halogen or S, and 1.0 ≦ a ≦ 1.3, 0.3 ≦ x ≦ 0.7, and 0.0 ≦ σ ≦ 0.1). delete The method of claim 1, The second cathode active material is any one selected from the group consisting of a compound represented by the following Chemical Formulas 3 to 8, and a combination thereof. (3) Li _a Ni _x Co _y Mn _z M _{1 -xy- z} O ₂ Q _σ (In Formula 3, M is selected from the group consisting of B, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, and combinations thereof Either element, Q is halogen or S, 1.0≤a≤1.2, 0.05≤x≤0.5, 0.0≤y≤0.7, 0.0≤z≤0.7, 0.0≤1-xyz≤0.3, and 0.0≤σ≤ 0.1) [Formula 4] Li _a Co _{1 - x} M _x O ₂ Q _σ (In Formula 4, M is selected from the group consisting of Mg, B, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, and combinations thereof Any one element, Q is halogen or S, 1.0 ≦ a ≦ 1.2, 0.0 ≦ x ≦ 0.1, and 0.0 ≦ σ ≦ 0.1) [Chemical Formula 5] Li _a Mn _{1 - x} M _x O ₂ Q _σ (In Formula 5, M is selected from the group consisting of B, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, and combinations thereof Any one element, Q is halogen or S, 1.0 ≦ a ≦ 1.2, 0.0 ≦ x ≦ 0.5, and 0.0 ≦ σ ≦ 0.1) [Formula 6] Li _a Mn _{2 - x} M _x O ₄ Q _σ (In Chemical Formula 6, M is B, Li, Mg, Al, Ca, Sr, Cr, V, Ti, Fe, Co, Ni, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, And a combination thereof, Q is halogen or S, and 1.0 ≦ a ≦ 1.3, 0.0 ≦ x ≦ 0.2, and 0.0 ≦ σ ≦ 0.1). [Formula 7] Li _{4 + a} Ti _{4 - x} M _x O ₁₂ Q _σ (In Formula 7, M is Li, Mg, Al, Ca, Sr, Cr, V, Ti, Fe, Co, Ni, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, and these Any one element selected from the group consisting of Q, Q is halogen or S, and 0.0≤a≤0.1, 0.0≤x≤0.1, and 0.0≤σ≤0.1) [Formula 8] LiM _x PO ₄ Q _σ (In Formula 8, M is in the group consisting of Co, Ni, Mn, Fe, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, and combinations thereof Any one element selected, Q is halogen or S, 0.0 ≦ a ≦ 0.1, 0.0 ≦ x ≦ 0.1, and 0.0 ≦ σ ≦ 0.02) The method of claim 1, The cathode active material for a lithium secondary battery includes the first cathode active material in an amount of 1 to 40 wt% and the second cathode active material in an amount of 60 to 99 wt%. delete The method of claim 1, The metal halide includes a cathode active material for a rechargeable lithium battery including any one selected from the group consisting of an amine group, an acetate group, and a combination thereof. The method of claim 1, The metal halide is a cathode active material for a lithium secondary battery having a nano size of 1 to 500nm. The method of claim 1, The metal halide is LiF, NaF, KF, MgF ₂ , CaF ₂ , CuF ₂ , CdF ₂ , FeF ₂ , MnF ₂ , MgF ₂ , NiF ₂ , PbF ₂ , SnF ₂ , SrF ₂ , XeF ₂ , ZnF ₂ , _{AlF 3, BF 3, BiF 3} , CeF 3, CrF 3, FeF 3, InF 3, LaF 3, MnF 3, NdF 3, VOF 3, YF 3, CeF 4, GeF 4, HfF 4, SiF 4, SnF 4 _{, TiF 4, VF 4, ZrF} 4, VF 5, NbF 5, SbF 5, TaF 5, BiF 5, MoF 6, ReF 6, SF 6, WF 6, and any one selected from the group consisting of a mixture of A cathode active material for a lithium secondary battery, which is a metal fluoride. The method of claim 1, The metal halide is a Group 3 transition metal, Group 4 transition metal, Group 5 transition metal, Group 6 transition metal, Group 7 transition metal, Group 8 transition metal, Group 9 transition metal, Group 13 element, Group 14 element, Group 15 A cathode active material for a lithium secondary battery, which is a metal oxyfluoride containing any one element selected from the group consisting of an element, a lanthanide element, and a combination thereof. The method of claim 11, The metal oxyfluoride is Sc, Y, Zr, V, Nb, Cr, Mo, W, Mn, Fe, Co, B, Al, Ga, In, Sn, As, La, Ce, Sm, Gd, and these Comprising any one element selected from the group consisting of a lithium secondary battery positive electrode active material. delete The method of claim 1, The metal halide is any one selected from the group consisting of MCl _x , MBr _x and mixtures thereof. The positive electrode active material for a lithium secondary battery (M is Mg, Ca, Sr, B, Al, Y, Zr, Mo, W, Cr, Fe, Co, Ni, Zn, Ga, Ge, In, Sn, Bi, P, and any combination thereof, x is 1 to 7). The method of claim 1, An average particle size of the first positive electrode active material and the second positive electrode active material is 0.1 μm to 50 μm. The method of claim 1, The positive electrode for a lithium secondary battery comprises 0.001 to 15 moles of the metal halide with respect to 100 moles of the first positive electrode active material and the second positive electrode active material. Mixing a high capacity first positive electrode active material with a high stability second positive electrode active material and coating the metal halide or coating the first positive electrode active material and the second positive electrode active material with metal halide, respectively, and then mixing them. As a manufacturing method of the positive electrode active material for lithium secondary batteries, The first positive electrode active material is any one selected from the group consisting of a nickel-based lithium composite metal oxide having a layered structure, a lithium composite metal oxide having a 5V spinel structure, and a mixture thereof, The second cathode active material is any one selected from the group consisting of a lithium composite metal oxide having a layered structure, a lithium composite metal oxide having a spinel structure, and a mixture thereof. The method of claim 17, Said mixing is carried out using any one selected from the group consisting of induction, mill, mixer, and combinations thereof. The method of claim 17, The mixing is performed by adding any one selected from the group consisting of water, alcohol, and mixtures thereof. The method of claim 17, After the step of mixing the positive electrode active material further comprising the step of drying the mixed positive electrode active material at 110 to 200 ℃ for 5 to 30 hours. The method of claim 17, After the step of mixing the positive electrode active material further comprising the step of heat-treating the mixed positive electrode active material at 300 to 1000 ℃ for 2 to 10 hours. Claim 1, 3, 5, 6, 8 to 12, and the positive electrode comprising the positive electrode active material according to any one of claims 14 to 16; A negative electrode including a negative electrode active material; And Electrolyte existing between the positive electrode and the negative electrode Lithium secondary battery comprising a.

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