KR102464770B1 - Positive electrode active material for secondary battery, method for preparing the same and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention is a lithium cobalt-based oxide; and a coating portion formed on the particle surface of the lithium cobalt oxide, wherein the coating portion relates to a positive active material for a secondary battery including a transition metal-oxyanion compound.

Description

Cathode active material for secondary battery, manufacturing method thereof, and lithium secondary battery comprising same

The present invention relates to a cathode active material for a secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same.

Recently, with the rapid spread of electronic devices using batteries, such as mobile phones, notebook computers, and electric vehicles, the demand for small, lightweight and relatively high-capacity secondary batteries is rapidly increasing. In particular, a lithium secondary battery has been in the spotlight as a driving power source for a portable device because it is lightweight and has a high energy density. Accordingly, research and development efforts for improving the performance of lithium secondary batteries are being actively conducted.

A lithium secondary battery includes a positive electrode including a positive electrode active material capable of insertion/desorption of lithium ions, a negative electrode including a negative electrode active material capable of insertion/deintercalation of lithium ions, and an electrode having a microporous separator interposed between the positive electrode and the negative electrode It means a battery in which an electrolyte containing lithium ions is included in the assembly.

A lithium transition metal oxide is used as a cathode active material of a lithium secondary battery, and lithium metal, a lithium alloy, crystalline or amorphous carbon, or a carbon composite material is used as an anode active material. The active material is applied to the electrode current collector with an appropriate thickness and length, or the active material itself is applied in the form of a film and wound or laminated together with a separator, which is an insulator, to make an electrode group, and then put into a can or similar container, and then inject the electrolyte to manufacture a secondary battery.

As a positive active material of a lithium secondary battery, lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), lithium manganese oxide (LiMnO ₂ or LiMn ₂ O ₄ , etc.), lithium iron phosphate compound (LiFePO ₄ ), nickel cobalt manganese Lithium-based composite metal oxide (hereinafter simply referred to as 'NCM-based lithium oxide') or the like is used. In the case of lithium cobalt oxide (LiCoO ₂ ), there is a disadvantage in that the capacity is small at the same voltage compared to the three-component NCM-based lithium oxide, but it has advantages such as a high rolling density and is still a positive electrode active material with high usage. Recently, since the demand for high-capacity cell development is gradually increasing, there is a trend to increase the operating voltage to realize high-capacity when using lithium cobalt oxide (LiCoO ₂ ).

Due to the use of high voltage for increasing the capacity of lithium cobalt oxide (LiCoO ₂ ), the amount of Li usage (insertion/desorption lithium amount) of lithium cobalt oxide (LiCoO ₂ ) increases, increasing the possibility of structural instability and surface instability. As a result, there are problems such as metal elution and gas generation.

Accordingly, it is necessary to develop lithium cobalt oxide (LiCoO ₂ ) having structural stability even at a higher voltage of 4.5V or higher than the conventional 4.45V or lower and at the same time having improved surface stability.

Korean Patent Publication No. 2012-0034686

An object of the present invention is to provide a cathode active material of lithium cobalt oxide (LiCoO ₂ ) having excellent structural stability and surface stability even under a high voltage of 4.5V or more. Through this, it is possible to realize a high capacity and to provide a lithium secondary battery of lithium cobalt oxide (LiCoO ₂ ) with improved lifespan characteristics.

The present invention is a lithium cobalt-based oxide; and a coating part formed on the particle surface of the lithium cobalt-based oxide, wherein the coating part provides a cathode active material for a secondary battery including a transition metal-oxyanion compound.

In addition, the present invention comprises the steps of preparing a lithium cobalt-based oxide; mixing the lithium cobalt-based oxide and a transition metal-oxyanion compound; and heat-treating after the mixing step to form a coating portion including a transition metal-oxyanion compound on the particle surface of the lithium cobalt-based oxide; to provide.

In addition, the present invention provides a positive electrode and a lithium secondary battery including the positive electrode active material.

According to the present invention, it is possible to provide a cathode active material of lithium cobalt oxide (LiCoO ₂ ) having structural stability and surface stability even under a high voltage of 4.5V or more. When the positive electrode active material of the present invention is used, metal elution and gas generation can be suppressed even under high voltage. Further, according to the present invention, a lithium secondary battery of lithium cobalt oxide (LiCoO ₂ ) having a high capacity and improved lifespan characteristics can be provided.

1 is a scanning electron microscope (SEM, Scanning Electron Microscope) photograph of an enlarged observation of a cathode active material prepared according to Example 1. FIG.
2 is a scanning electron microscope (SEM, Scanning Electron Microscope) photograph of an enlarged observation of the positive electrode active material prepared according to Comparative Example 1. Referring to FIG.
3 is a graph evaluating the lifespan characteristics of a lithium secondary battery including a positive active material prepared according to Examples and Comparative Examples.
4 is a graph of measuring the amount of gas generated in a lithium secondary battery including a positive active material prepared according to Examples and Comparative Examples.

Hereinafter, the present invention will be described in more detail to help the understanding of the present invention. At this time, the terms or words used in the present specification and claims are not to be construed as being limited to conventional or dictionary meanings, and the inventor appropriately defines the concept of the term in order to explain his invention in the best way. It should be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle that it can be done.

The positive active material for a secondary battery of the present invention is a lithium cobalt-based oxide; and a coating portion formed on the particle surface of the lithium cobalt-based oxide, wherein the coating portion includes a transition metal-oxyanion compound.

The positive active material for a secondary battery of the present invention forms a coating portion containing a transition metal-oxyanion compound on the surface of a particle of lithium cobalt-based oxide, so that the coating portion serves as a surface protective layer, resulting in surface structural stability under high voltage can be secured, suppress side reactions with the electrolyte, and suppress metal elution and gas generation. Since oxyanions attract electrons to oxygen and have a high oxygen bonding strength, it is possible to effectively suppress metal elution and gas generation by preventing oxygen desorption and transition metal desorption. In addition, the transition metal-oxyanion (transition metal-oxyanion) compound can further improve lifespan characteristics by containing a transition metal cation, and further suppress gas generation.

The lithium cobalt-based oxide may be represented by the following formula (1).

[Formula 1]

Li _a Co _(1-x) A _x O ₂

In Formula 1, 0.95≤a≤1.1, 0≤x≤0.2, and A is at least one selected from the group consisting of Al, Ti, Zr, Mg, Nb, Ba, Ca, and Ta. For example, the lithium cobalt-based oxide may be LiCoO ₂ .

More preferably, the lithium cobalt-based oxide may have a molar ratio of lithium and metal elements (Co and A) excluding lithium (a molar ratio of lithium/metal elements (Co and A)) of 0.98 to 1.1.

The transition metal-oxyanion (transition metal-oxyanion) compound is M ^I ₃ AsO ₄ (arsenate), M ^I ₂ SeO ₄ (selenate), M ^I VO ₃ (vanadate), M ^I ₃ VO ₄ (vanadate), M It may be at least one selected from the group consisting of ^I ₂ WO _{4 (} tungstate), M ^I ₂ MoO ₄ (molybdate), M ^I ₂ CrO ₄ (chromate), and M ^I ₂ TeO ₄ (tellurate). In this case, M is a transition metal, and is expressed by the general formula of a salt containing each oxyanion.

More preferably, M ^I may be at least one transition metal selected from the group consisting of Ni, Co, Fe, Cu, Zn, Y, Zr, Nb and Cd.

More preferably, the transition metal-oxyanion (transition metal-oxyanion) compound is CoMoO ₄ , CoWO ₄ , CoAsO ₄ , CoSeO ₄ , CoVO ₄ , CoCrO ₄ , NiMoO ₄ , NiWO ₄ , NiAsO ₄ , NiSeO ₄ , NiVO ₄ , NiCrO ₄ , CuWO ₄ , CdWO ₄ , CdAsO ₄ , CdSeO ₄ , ZnSeO ₄ , ZnAsO ₄ , ZnMoO ₄ , ZrWO ₄ , ZrMoO ₄ , ZrSeO ₄ , ZrAsO ₄ , YAsO ₄ , YSeO ₄ and _{NbAsO 4 consisting} of It may be at least one selected from the group.

As in the present invention, by coating the lithium cobalt-based oxide with the transition metal-oxyanion compound, it can have structural stability and surface stability even under high voltage, for example, 4.5V or higher, and metal elution and It is possible to suppress gas generation, and improve high capacity and lifespan characteristics.

The transition metal-oxyanion (transition metal-oxyanion) compound may be included in an amount of 0.01 to 0.3 parts by weight based on 100 parts by weight of the lithium cobalt-based oxide, more preferably 0.03 to 0.2 parts by weight, more preferably 0.05 to 0.1 parts by weight. may be included. As the transition metal-oxyanion compound is coated within the above content range, it is possible to effectively secure surface structure stability under high voltage and suppress gas generation, and further, increase capacity reduction rate and resistance increase rate according to repeated charge/discharge It can be reduced, and it is possible to prevent a decrease in capacity due to an increase in the coating portion.

The cathode active material for a secondary battery of the present invention comprises the steps of preparing a lithium cobalt-based oxide; mixing the lithium cobalt-based oxide and a transition metal-oxyanion compound; and heat-treating after the mixing step to form a coating portion including a transition metal-oxyanion compound on the particle surface of the lithium cobalt-based oxide.

As the method of mixing the lithium cobalt-based oxide and the transition metal-oxyanion compound, a mixing method commonly used for forming a coating layer may be used without limitation, for example, dry mixing method, wet mixing method method or deposition method (atomic layer deposition). More preferably, the lithium cobalt-based oxide may be dry mixed with the transition metal-oxyanion compound.

In this case, the transition metal-oxyanion (transition metal-oxyanion) compound may be mixed in an amount of 0.01 to 0.3 parts by weight based on 100 parts by weight of the lithium cobalt-based oxide, more preferably 0.03 to 0.2 parts by weight, more preferably 0.05 to It can be mixed in 0.1 parts by weight.

The heat treatment after mixing the lithium cobalt-based oxide and the transition metal-oxyanion compound as described above may be performed at 500 to 900°C. More preferably, it may be heat-treated at 650 to 800°C, more preferably at 650 to 750°C. If the heat treatment temperature is less than 500°C, a problem may occur that unreacted transition metal-oxyanion compounds remain, and if it exceeds 900°C, the transition metal may be doped rather than coated on the cathode active material. can

In addition, the composition of the lithium cobalt-based oxide and the type of the transition metal-oxyanion compound are applied in the same manner as in the description of the positive active material for a secondary battery of the present invention.

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

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

In the positive electrode, the positive electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon on the surface of aluminum or stainless steel. , nickel, titanium, silver or the like surface-treated may be used. In addition, the positive electrode current collector may typically have a thickness of 3 to 500 μm, and may increase the adhesion of the positive electrode active material by forming fine irregularities on the surface of the positive electrode current collector. For example, it may be used in various forms, such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven body.

In addition, the positive active material layer may include a conductive material and a binder together with the above-described positive active material.

In this case, the conductive material is used to impart conductivity to the electrode, and in the configured battery, it can be used without any particular limitation as long as it does not cause chemical change and has electronic conductivity. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskeys such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or a conductive polymer such as a polyphenylene derivative, and the like, and any one of them or a mixture of two or more thereof may be used. The conductive material may be included in an amount of 1 to 30% by weight based on the total weight of the positive electrode active material layer.

In addition, the binder serves to improve adhesion between the positive electrode active material particles and the adhesive force between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC) ), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and any one of them or a mixture of two or more thereof may be used. The binder may be included in an amount of 1 to 30% by weight based on the total weight of the positive active material layer.

The positive electrode may be manufactured according to a conventional positive electrode manufacturing method except for using the above positive electrode active material. Specifically, the cathode active material and, optionally, a composition for forming a cathode active material layer including a binder and a conductive material may be coated on a cathode current collector, and then dried and rolled. In this case, the types and contents of the positive electrode active material, the binder, and the conductive material are as described above.

The solvent may be a solvent generally used in the art, dimethyl sulfoxide (DMSO), isopropyl alcohol (isopropyl alcohol), N-methylpyrrolidone (NMP), acetone (acetone) or water and the like, and any one of them or a mixture of two or more thereof may be used. The amount of the solvent used is enough to dissolve or disperse the positive electrode active material, the conductive material and the binder in consideration of the application thickness of the slurry and the production yield, and to have a viscosity capable of exhibiting excellent thickness uniformity when applied for the production of the positive electrode thereafter. do.

Alternatively, the positive electrode may be prepared by casting the composition for forming the positive electrode active material layer on a separate support, and then laminating a film obtained by peeling it from the support on the positive electrode current collector.

According to another embodiment of the present invention, an electrochemical device including the positive electrode is provided. The electrochemical device may specifically be a battery or a capacitor, and more specifically, a lithium secondary battery.

The lithium secondary battery specifically includes a positive electrode, a negative electrode positioned to face the positive electrode, a separator and an electrolyte interposed between the positive electrode and the negative electrode, and the positive electrode is as described above. In addition, the lithium secondary battery may optionally further include a battery container for accommodating the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member for sealing the battery container.

In the lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface. Carbon, nickel, titanium, silver, etc. surface-treated, aluminum-cadmium alloy, etc. may be used. In addition, the negative electrode current collector may have a thickness of typically 3 to 500 μm, and similarly to the positive electrode current collector, fine concavities and convexities may be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it may be used in various forms, such as a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven body.

The anode active material layer optionally includes a binder and a conductive material together with the anode active material. The anode active material layer may be formed by applying a composition for forming an anode including an anode active material, and optionally a binder and a conductive material on an anode current collector and drying, or casting the composition for forming a cathode on a separate support, and then , may be produced by laminating a film obtained by peeling from this support onto a negative electrode current collector.

As the anode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metal compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; metal oxides capable of doping and dedoping lithium, such as SiO _β (0 < β < 2), SnO ₂ , vanadium oxide, and lithium vanadium oxide; Alternatively, a composite including the metallic compound and a carbonaceous material such as a Si-C composite or a Sn-C composite may be used, and any one or a mixture of two or more thereof may be used. In addition, a metal lithium thin film may be used as the negative electrode active material. In addition, as the carbon material, both low crystalline carbon and high crystalline carbon may be used. As low crystalline carbon, soft carbon and hard carbon are representative, and as high crystalline carbon, natural or artificial graphite of amorphous, plate-like, scale-like, spherical or fibrous shape, and Kish graphite (Kish) graphite), pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, liquid crystal pitches (Mesophase pitches), and petroleum and coal tar pitch (petroleum or coal tar pitch) High-temperature calcined carbon such as derived cokes) is a representative example.

In addition, the binder and the conductive material may be the same as described above for the positive electrode.

On the other hand, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move, and it can be used without particular limitation as long as it is usually used as a separator in a lithium secondary battery, especially for the movement of ions in the electrolyte It is preferable to have a low resistance to and excellent electrolyte moisture content. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, and an ethylene/methacrylate copolymer, or these A laminated structure of two or more layers of may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, in order to secure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer material may be used, and may optionally be used in a single-layer or multi-layer structure.

In addition, examples of the electrolyte used in the present invention include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries, and are limited to these. it's not going to be

Specifically, the electrolyte may include an organic solvent and a lithium salt.

The organic solvent may be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, as the organic solvent, ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon-based solvents such as benzene and fluorobenzene; dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate, carbonate-based solvents such as PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (R is a C2-C20 linear, branched or cyclic hydrocarbon group, which may include a double bond aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; Or sulfolanes and the like may be used. Among these, a carbonate-based solvent is preferable, and a cyclic carbonate (for example, ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant capable of increasing the charge/discharge performance of the battery, and a low-viscosity linear carbonate-based compound ( For example, a mixture of ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate) is more preferable. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1:1 to about 1:9, the electrolyte may exhibit excellent performance.

The lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN(C ₂ F ₅ SO ₃ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ . LiCl, LiI, or LiB(C ₂ O ₄ ) ₂ and the like may be used. The concentration of the lithium salt is preferably used within the range of 0.1 to 2.0M. When the concentration of the lithium salt is included in the above range, since the electrolyte has appropriate conductivity and viscosity, excellent electrolyte performance may be exhibited, and lithium ions may move effectively.

In addition to the electrolyte components, the electrolyte includes, for example, haloalkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, tri Ethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imida One or more additives such as jolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol or aluminum trichloride may be further included. In this case, the additive may be included in an amount of 0.1 to 5% by weight based on the total weight of the electrolyte.

As described above, the lithium secondary battery including the positive electrode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics and capacity retention rate, so portable devices such as mobile phones, notebook computers, digital cameras, and hybrid electric vehicles ( It is useful in the field of electric vehicles such as hybrid electric vehicle, HEV).

Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

The battery module or battery pack is a power tool (Power Tool); electric vehicles, including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); Alternatively, it may be used as a power source for any one or more medium and large-sized devices in a system for power storage.

Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily carry out the present invention. However, the present invention may be embodied in several different forms and is not limited to the embodiments described herein.

Example One

Li ₁ synthesized with a Li/Co molar ratio of 1.06 _{. 06} After dry mixing CoO ₂ and CoMoO ₄ in a weight ratio of 100:0.1, heat treatment at 700° C. for 12 hours to obtain Li _{1 . 06} CoO ₂ A coating portion containing CoMoO ₄ was formed on the particle surface.

Example 2

Transition metal-oxyanion compound is CoMoO ₄ Instead, it was prepared in the same manner as in Example 1 except that CoWO ₄ was used.

comparative example One

Li ₁ synthesized with a Li/Co molar ratio of 1.06 without forming a coating part _{. 06} CoO ₂ was prepared.

comparative example 2

Li ₁ synthesized with a Li/Co molar ratio of 1.06 _{. 06} After dry mixing CoO ₂ and CoO in a weight ratio of 100:0.1, heat treatment was performed at 700° C. for 12 hours to prepare a cathode active material.

comparative example 3

CoMoO ₄ Instead, it was prepared in the same manner as in Example 1 except that Na ₂ MoO ₄ was used.

[ Experimental example 1: Observation of cathode active material]

1 (Example 1) and 2 (Comparative Example 1) are shown in Figures 1 (Example 1) and 2 (Comparative Example 1) of the positive active material prepared according to Example 1 and Comparative Example 1 was magnified and observed with a scanning electron microscope (SEM).

1 and 2 , it can be seen that the positive active material prepared according to Example 1 has some coating portions formed on the particle surfaces, and the positive electrode active material without the coating portion prepared according to Comparative Example 1 is the same as that of Example 1 In comparison, it shows a relatively smooth surface.

[ Experimental example 2: Life characteristics evaluation]

A composition for forming a positive electrode by using the positive electrode active material prepared in Examples 1 to 2 and Comparative Examples 1 to 3, and mixing carbon black and a PVDF binder in an N-methylpyrrolidone solvent in a weight ratio of 90:5:5 was prepared, coated on one side of an aluminum current collector, dried at 130° C. and then rolled to prepare a positive electrode, respectively. Meanwhile, lithium metal was used as the negative electrode.

An electrode assembly was prepared by interposing a separator of porous polyethylene between the positive electrode and the negative electrode prepared as described above, the electrode assembly was placed inside the case, and the electrolyte was injected into the case to prepare a lithium secondary battery. At this time, the electrolyte solution is prepared by dissolving lithium hexafluorophosphate (LiPF ₆ ) at a concentration of 1.0 M in an organic solvent consisting of ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate (mixed volume ratio of EC / DMC / EMC = 3 / 4 / 3) did.

For each lithium secondary battery cell (coin half cell) prepared as described above, after 0.2C charge in CCCV mode and 0.2C discharge in CC mode at 25°C, charge until 0.5C and 4.55V in CCCV mode, , The capacity retention rate (Capacity Retention [%]) was measured while charging and discharging 50 times by discharging to 3V at a current of 1.0C in CC mode. The results are shown in Table 1 and FIG. 3 .

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Capacity retention rate (%) after 50 cycles 92.3 86.6 64.3 44.9 20.5

Referring to Table 1 and Figure 3, compared to Comparative Examples 1 to 3, Examples 1 and 2, in which a coating portion was formed with a transition metal-oxyanion compound, had a higher capacity retention rate until charging and discharging 50 times. can be seen to appear. Specifically, when the cathode active material of Examples 1 and 2 coated with a compound containing an oxyanion having a higher oxygen bonding strength compared to Comparative Example 2 coated with CoO was used, the lifespan characteristics were The lifespan characteristics were improved when the positive active materials of Examples 1 and 2 coated with a compound containing a transition metal cation were used as compared to Comparative Example 3 coated with Na ₂ MoO ₄ .

[ Experimental example 3: Measurement of gas generation]

For each lithium secondary battery cell (coin half cell) prepared as described above, after 0.2C charge in CCCV mode at 25°C, 0.2C discharge in CC mode once, and then charge at 0.2C until 4.55V, then coin After removing the cell, immersing the charged positive electrode in 100 ml of electrolyte and storing it at 60° C. for 1 week, the amount of gas generation was measured. The results are shown in FIG. 4 .

Referring to Figure 4, compared to Comparative Examples 1 to 3, Examples 1 and 2, in which the coating part was formed with a transition metal-oxyanion compound, significantly reduced the amount of gas emitted when charging and discharging 50 times can be checked Specifically, when the cathode active material of Examples 1 and 2 coated with a compound containing an oxyanion having a higher oxygen bonding strength compared to Comparative Example 2 coated with CoO was used, the amount of gas generated was was decreased, and the amount of gas generated was reduced when the cathode active materials of Examples 1 and 2 coated with a compound containing transition metal cations were used as compared to Comparative Example 3 coated with Na ₂ MoO ₄ .

Claims (15)

lithium cobalt oxide; and
Including; a coating portion formed on the particle surface of the lithium cobalt-based oxide,
The coating part includes a transition metal-oxyanion compound,
The transition metal-oxyanion (transition metal-oxyanion) compound is CoMoO ₄ , CoWO ₄ , CoAsO ₄ , CoSeO ₄ , CoVO ₄ , CoCrO ₄ , NiMoO ₄ , NiWO ₄ , NiAsO ₄ , NiSeO ₄ , NiVO ₄ , NiCrO ₄ , At least from the group consisting of CuWO ₄ , CdWO ₄ , CdAsO ₄ , CdSeO ₄ , ZnSeO ₄ , ZnAsO ₄ , ZnMoO ₄ , ZrWO ₄ , ZrMoO ₄ , ZrSeO ₄ , ZrAsO ₄ , YAsO ₄ , YSeO ₄ , NbAsO ₄ and NbSeO ₄ . One or more, a cathode active material for a secondary battery.
delete delete delete According to claim 1,
The transition metal-oxyanion (transition metal-oxyanion) compound is a cathode active material for a secondary battery contained in an amount of 0.01 to 0.3 parts by weight based on 100 parts by weight of the lithium cobalt-based oxide.
According to claim 1,
The lithium cobalt-based oxide is a cathode active material for a secondary battery represented by the following formula (1).
[Formula 1]
Li _a Co _(1-x) A _x O ₂
In Formula 1, 0.95≤a≤1.1, 0≤x≤0.2, and A is at least one selected from the group consisting of Al, Ti, Zr, Mg, Nb, Ba, Ca, and Ta.
preparing a lithium cobalt-based oxide;
mixing the lithium cobalt-based oxide and a transition metal-oxyanion compound; and
Heat treatment after the mixing step to form a coating portion containing a transition metal-oxyanion (transition metal-oxyanion) compound on the surface of the particles of the lithium cobalt-based oxide;
including,
The transition metal-oxyanion (transition metal-oxyanion) compound is CoMoO ₄ , CoWO ₄ , CoAsO ₄ , CoSeO ₄ , CoVO ₄ , CoCrO ₄ , NiMoO ₄ , NiWO ₄ , NiAsO ₄ , NiSeO ₄ , NiVO ₄ , NiCrO ₄ , At least from the group consisting of CuWO ₄ , CdWO ₄ , CdAsO ₄ , CdSeO ₄ , ZnSeO ₄ , ZnAsO ₄ , ZnMoO ₄ , ZrWO ₄ , ZrMoO ₄ , ZrSeO ₄ , ZrAsO ₄ , YAsO ₄ , YSeO ₄ , NbAsO ₄ and NbSeO ₄ . One or more, a method of manufacturing a cathode active material for a secondary battery.
delete delete delete 8. The method of claim 7,
Mixing the lithium cobalt-based oxide and the transition metal-oxyanion (transition metal-oxyanion) compound,
A method for producing a cathode active material for a secondary battery, wherein the transition metal-oxyanion compound is mixed in an amount of 0.01 to 0.3 parts by weight based on 100 parts by weight of lithium cobalt oxide.
8. The method of claim 7,
The lithium cobalt-based oxide is a method for producing a cathode active material for a secondary battery represented by the following formula (1).
[Formula 1]
Li _a Co _(1-x) A _x O ₂
In Formula 1, 0.95≤a≤1.1, 0≤x≤0.2, and A is at least one selected from the group consisting of Al, Ti, Zr, Mg, Nb, Ba, Ca, and Ta.
8. The method of claim 7,
The heat treatment is a method of manufacturing a cathode active material for a secondary battery to perform heat treatment at 500 to 900 ℃.
A positive electrode for a secondary battery comprising the positive electrode active material according to any one of claims 1, 5 and 6.
A lithium secondary battery comprising the positive electrode according to claim 14 .

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