KR102537227B1 - Composite positive electrode active material, preparing method thereof, and lithium secondary battery comprising the same - Google Patents

Abstract

α-NaFeO ₂ lithium transition metal oxide with a layered crystal structure; And a lithium secondary battery containing a composite cathode active material containing a coating film containing a lithium metal oxide disposed on a (003) crystalline plane of the lithium transition metal oxide, a manufacturing method thereof, and a cathode containing the composite cathode active material. is presented

Description

Composite positive electrode active material, preparing method thereof, and lithium secondary battery comprising the same}

It relates to a composite cathode active material, a manufacturing method thereof, and a lithium secondary battery including the same.

Lithium secondary batteries are used for various purposes by having high voltage and high energy density. For example, in fields such as electric vehicles, lithium secondary batteries with excellent discharge capacity and lifespan characteristics are required because they can operate at high temperatures, charge or discharge a large amount of electricity, and must be used for a long time.

As a cathode active material for a lithium secondary battery, lithium cobalt oxide is widely used as a cathode active material because of its excellent energy density. However, such lithium cobalt oxide deteriorates battery characteristics due to a side reaction with an electrolyte in a high voltage region, and improvement thereof is required.

One aspect is to provide a composite cathode active material in which insertion/desorption of lithium is easy.

Another aspect is to provide a method for manufacturing the above-described composite cathode active material.

Another aspect is to provide a lithium secondary battery with improved output characteristics by employing a cathode including the above-described composite cathode active material.

According to one aspect, α-NaFeO ₂ lithium transition metal oxide having a layered crystal structure; and

A composite cathode active material containing a coating film containing a lithium metal oxide disposed on a (003) crystalline plane of the lithium transition metal oxide is provided.

According to another aspect, mixing a lithium precursor, a metal (M) precursor for forming a lithium metal oxide, and a metal precursor for forming a lithium transition metal oxide having an α-NaFeO ₂ layered crystal structure with a solvent to obtain a composite cathode active material precursor composition;

Forming a gel by adding and mixing a chelating agent to the composite cathode active material precursor composition;

subjecting the gel to a first heat treatment to obtain a first heat treated product;

A method for producing a composite cathode active material is provided, including the step of performing a second heat treatment on the product subjected to the first heat treatment and then cooling at a cooling rate of 5 ° C./min or less.

According to another aspect, mixing a lithium precursor and a metal (M) precursor for forming a lithium metal oxide with a solvent to obtain a lithium metal oxide precursor composition;

adding α-NaFeO ₂ layered lithium transition metal oxide to the lithium metal oxide precursor composition and then mixing it to form a gel;

subjecting the gel to a first heat treatment to obtain a first heat treated product; and

After performing the second heat treatment on the first heat-treated product, there is provided a method for producing a composite cathode active material for obtaining the above-described composite cathode active material comprising the step of cooling at a cooling rate of 5 ° C./min or less.

According to another aspect, a lithium secondary battery including a cathode including the above-described composite cathode active material is provided.

In the composite cathode active material according to an embodiment, the charge transfer resistance does not increase compared to the case where the coating film is formed only on the crystal plane in the c-axis direction, and the coating film is formed on the crystal plane in the a-axis and b-axis directions. A lithium secondary battery with improved characteristics can be manufactured.

1A schematically shows the structure of a composite cathode active material according to an embodiment.
1B is a schematic diagram of a lithium secondary battery according to an exemplary embodiment.
2a and 2b show the X-ray diffraction analysis (XRD) analysis results of the composite cathode active material of Examples 1-3, the lithium cobalt oxide of Comparative Example 1, and the composite cathode active material of Comparative Example 2 at 25 ° C.
3a and 3b show the composite cathode active material of Example 1, the lithium cobalt oxide of Comparative Example 1, and the composite cathode active material of Comparative Example 2 before heat treatment at 900 ° C., immediately after heat treatment, and cooling after heat treatment. The XRD analysis results are shown later.
4a to 4c show transmission electron microscope (TEM) analysis results for the composite cathode active material of Example 1.
5a to 5c show TEM results of the composite cathode active material of Comparative Example 2.
6 shows energy dispersive spectroscopy (EDS) analysis results for the composite cathode active material of Example 1.
7A shows a mapping image of the composite cathode active material of Example 1 using a scanning transmission electron microscope (STEM).
7B is a TEM image showing an enlarged atomic arrangement of the interface between LiCoO ₂ and Li ₂ SnO ₃ coating film in the result of analysis using STEM of the composite cathode active material prepared according to Example 1.
FIG. 7c shows a fast fourier transformation (FFT) pattern analysis result of the TEM image of FIG. 7b.
8 and 9, (a) and (c) show the crystal structure of LiCoO ₂ projected in the [010] and [310] directions, respectively, and (b) and (d) show Li ₂ SnO ₃ It shows the crystal structure of is projected in the [001] direction.
10 is a graph showing rate characteristics of coin cells manufactured according to Manufacturing Example 1 and Comparative Manufacturing Example 2.
11 is a result of measuring the charge transfer resistance of the composite cathode active material of Example 1 and the composite cathode active material of Comparative Example 2.

Hereinafter, a lithium secondary battery having a composite cathode active material, a manufacturing method thereof, and a cathode including the composite cathode active material according to exemplary embodiments will be described in more detail.

α-NaFeO ₂ lithium transition metal oxide with a layered crystal structure; and a coating film including a lithium metal oxide disposed on the (003) crystal plane of the lithium transition metal oxide.

In the composite cathode active material, the coating film containing lithium metal oxide is α-NaFeO ₂

In the lithium transition metal oxide having a layered crystal structure, it is disposed on a surface where lithium ions are not intercalated or deintercalated or a crystal surface in the c-axis direction.

The lithium metal oxide is C2/c of a monoclinic crystal system.

It has a space group crystal structure. When the lithium metal oxide has such a crystal structure, mismatch at the interface with the lithium transition metal oxide having a -NaFeO ₂ layered crystal structure can be minimized.

Lithium metal oxide is, for example, a compound represented by Formula 1 above.

[Formula 1]

Li ₂ MO ₃

In Formula 1, M is a metal having an oxidation number of +4.

The lithium metal oxide may be, for example, Li ₂ SnO ₃ , Li ₂ ZrO ₃ , Li ₂ TeO ₃ , Li ₂ RuO ₃ , Li ₂ TiO ₃ , Li ₂ MnO ₃ , Li ₂ PbO ₃ , Li ₂ HfO ₃ and combinations thereof. It is one or more selected from water.

The content of the lithium metal oxide is 5 mol% or less, for example 0.1 to 5 mol%, for example 2 to 5, based on the total content of the lithium transition metal oxide and lithium metal oxide of the α-NaFeO _two- layer crystal structure. is mol%. When the content of the lithium metal oxide is within the above range, the increase in charge transfer resistance due to the presence of the coating layer on the surface of the lithium transition metal oxide in the c-axis direction can be effectively suppressed.

A lithium transition metal oxide having an α-NaFeO ₂ layered crystal structure is, for example, lithium cobalt oxide (LiCoO ₂ ). Lithium cobalt oxide has a layered α-NaFeO ₂ structure in which CoO ₂ and Li layers continuously intersect, and R-3m It has a space group. Since such lithium cobalt oxide can be mass-produced and exhibits excellent battery characteristics, many studies are being conducted to commercialize it. However, in lithium cobalt oxide, cobalt is eluted from the electrolyte in a high voltage region of 4.4 V or higher, and battery characteristics are deteriorated due to side reactions with the electrolyte. Therefore, in order to use the reversible capacity in the high voltage region of 4.4 V or more, the surface coating of lithium cobalt oxide is essential.

It is common to coat the surface of the lithium cobalt oxide with a metal oxide-based or phosphate-based material. However, when carried out according to this method, all surfaces of the lithium cobalt oxide are coated with the above-described metal oxide-based or phosphate-based material. As a result, the charge transfer resistance is increased, and output characteristics of a lithium secondary battery having a positive electrode using the charge transfer resistance may be deteriorated.

Accordingly, the present inventors have developed lithium cobalt oxide in order to solve the above problems.

The surface coating of lithium cobalt oxide forms a coating film on the crystal plane in the c-axis direction, which is the remaining crystal plane except for the crystal plane where insertion/desorption of lithium ions proceeds. The present invention which effectively suppresses the increase in resistance has been completed.

1A schematically shows the structure of a composite cathode active material according to an embodiment.

α-NaFeO ₂ It has a structure in which a coating film (2) containing a lithium metal oxide is laminated on the surface of a lithium transition metal oxide (1) having a layered crystal structure. The coating film (2) is disposed on the (003) crystal plane of the lithium transition metal oxide (1) having an α-NaFeO ₂ layered crystal structure.

The thickness of the coating film is 1 to 100 nm, for example 1 to 80 nm, for example 10 to 60 nm. When the thickness of the coating film is within the above range, an increase in charge transfer resistance due to the coating of the lithium transition metal oxide can be effectively prevented.

The coating film may be a continuous or discontinuous film.

In the composite cathode active material according to one embodiment, the lithium metal oxide disposed on the (003) crystal plane of the lithium transition metal oxide and the lithium transition metal oxide of the α-NaFeO ₂ layered crystal structure are epitaxially grown in the same C-axis direction Layered structure have Thus, having a layered structure epitaxially grown in the C-axis direction can be confirmed through the TEM image and the FFT pattern of the TEM image.

In the composite cathode active material according to one embodiment, both LiCoO ₂ and Li ₂ SnO ₃ zone axes are (lm 0) in the TEM FFT pattern. The direction of the intersection of the planes belonging to the same crystal band, that is, the common edge, is called the crystal band axis of the crystal band. On the other hand, the composite cathode active material obtained by the conventional coating method does not have a zone axis of (lm 0).

Hereinafter, a method for manufacturing a composite cathode active material according to an embodiment will be described.

First, a first manufacturing method of a composite cathode active material according to an embodiment will be described.

A lithium precursor, a metal (M) precursor for forming a lithium metal oxide, and a metal precursor for forming a lithium transition metal oxide having _{a two-} layer crystal structure of α-NaFeO are mixed with a solvent to obtain a composite cathode active material precursor composition. Here, ethanol, methanol, isopropanol, etc. are used as the solvent.

The contents of the lithium precursor, the metal precursor for forming a lithium metal oxide, and the metal precursor for forming a lithium transition metal oxide having an α-NaFeO ₂ layered crystal structure are appropriately controlled to obtain a desired composition of a composite cathode active material.

According to one embodiment, when the content of the metal precursor for forming a lithium metal oxide is x mol (0≤x≤0.1), the content of the metal precursor for forming a lithium transition metal oxide having an α-NaFeO ₂ layered crystal structure is (1- x) mol, and the content of the lithium precursor is 1.03 (1+2x) mol.

A chelating agent is then added to the precursor composition and mixed to form a gel. The gel formation process is, for example, a process of removing the solvent by stirring and drying while heat-treating at 30 to 80 ° C.

The chelating agent traps metal ions present in the solution phase and prevents uneven distribution of metal ions during sol and gel formation, thereby facilitating mixing. As the chelating agent, for example, an organic acid is used. Examples of the organic acid include citric acid, citric acid, acrylic acid, tartaric acid, and glycoic acid.

A desired composite cathode active material may be obtained by performing a first heat treatment on the gel, then performing a second heat treatment on the first heat treated product, and then cooling at a cooling rate of 5 ° C./min or less.

The first heat treatment is carried out at 200 to 550 ° C, and the second heat treatment is 600 to 550 ° C.

It can be carried out at 950 °C. When the first heat treatment and the second heat treatment are performed in the above-described temperature range, a composite cathode active material having desired crystallinity can be obtained. In the first heat treatment and the second heat treatment, the temperature is raised under dry air or oxygen atmosphere and maintained for a predetermined time under each heat treatment condition. The temperature may be raised at a rate of, for example, 0.5 to 10 °C/min.

In the step of performing the cooling, the cooling rate is, for example, 0.1 to 5°C, for example, 1 to 5°C. The step of performing the cooling may be performed, for example, by controlling the cooling rate within the above range in the furnace after the second heat treatment.

The composite cathode active material obtained according to the above-described manufacturing method may be subjected to a pulverization process if necessary, and sieving may be performed to obtain a desired lithium cobalt oxide.

The second manufacturing method for manufacturing a composite cathode active material according to an embodiment is as follows.

A lithium metal oxide precursor composition is obtained by mixing a lithium precursor and a metal (M) precursor for forming lithium metal oxide with a solvent. Here, the metal precursor for forming lithium metal oxide is a coating film material.

A gel is formed by adding α-NaFeO ₂ layered crystal structure lithium transition metal oxide to the lithium metal oxide precursor composition and mixing. Subsequently, after the first heat treatment is performed on the gel, the product subjected to the first heat treatment is subjected to the second heat treatment, and then cooled at a cooling rate of 5 ° C./min or less to obtain a desired composite cathode active material.

In the second manufacturing method, the contents of the above-described lithium precursor, metal precursor for forming lithium metal oxide, and α-NaFeO ₂ layered crystal structure of lithium transition metal oxide are appropriately controlled to obtain a desired composition of the composite cathode active material.

α -NaFeO ₂ A lithium transition metal oxide having a layered crystal structure can be prepared according to a method widely known in the art. And, in the second manufacturing method, the type of solvent, the first and second heat treatment conditions, and the cooling conditions are the same as those of the first manufacturing method.

In the above-described first and second manufacturing methods, the metal (M) precursor for forming lithium metal oxide is, for example, tin chloride (SnCl ₂ ), zirconium chloride (ZrCl ₄ ), tellurium chloride (TeCl ₄ ), ruthenium chloride (RuCl ₄ ) , titanium chloride (TiCl ₄ ), manganese chloride (MnCl ₄ ), hafnium chloride (HfCl ₄ ), lead chloride (PbCl ₄ ), zirconium nitrate, zirconium acetate, zirconium oxalate, tellurium nitrate, tellurium acetate, tell Rurum oxalate, tellurium chloride, ruthenium nitrate, ruthenium acetate, ruthenium oxalate, titanium nitrate, titanium acetate, titanium oxalate, manganese nitrate, manganese acetate, manganese oxalate, hafnium nitrate, hafnium acetate, hafnium oxalate rate, and at least one selected from combinations thereof and combinations thereof.

The metal precursor for forming the α-NaFeO ₂ layered crystal structure of lithium transition metal oxide is, for example, at least one selected from the group consisting of cobalt nitrate, cobalt acetate, cobalt oxalate, and cobalt chloride.

As the lithium precursor, lithium hydroxide, lithium nitrate, lithium acetate, lithium sulfate, lithium fluoride or a mixture thereof is used.

An average particle diameter of the lithium cobalt oxide according to one embodiment is, for example, 0.05 to 20 μm. In addition, the C-axis orientation degree of lithium cobalt oxide (LiCoO ₂ ) is primarily very closely related to the (003) crystal plane.

According to the manufacturing method of the composite cathode active material according to an embodiment, lithium metal oxide is coated on the surface where intercalation and desorption of lithium does not occur, the (003) crystal surface, or the crystal surface in the c-axis direction of the lithium cobalt oxide. In this way, the reason why a lithium metal oxide such as Li ₂ SnO ₃ in the composite cathode active material is coated only on the (003) crystal plane of lithium cobalt oxide is that the lithium-oxygen distance of lithium cobalt oxide is coated on the (003) crystal plane of lithium cobalt oxide. The mismatch of the lithium-oxygen distance of Li ₂ SnO ₃ is smaller compared to the composite cathode active material in which Li ₂ SnO ₃ is coated on the crystal plane where lithium ion intercalation/deintercalation occurs in lithium cobalt oxide, so the final composite obtained This is because the structure of the cathode active material can be further stabilized. In the composite cathode active material in which Li ₂ SnO ₃ is coated on the (003) surface of lithium cobalt oxide, the mismatch between the lithium-oxygen distance of lithium cobalt oxide and the lithium-oxygen distance of Li ₂ SnO ₃ is, for example, 0.1 Very small, less than Å.

Using the composite cathode active material according to one embodiment, a cathode having excellent chemical stability even under high-temperature charging and discharging conditions and a lithium secondary battery with improved output characteristics can be manufactured by employing such a cathode.

Lithium cobalt oxide further contains at least one element selected from magnesium (Mg), calcium (Ca), strontium (Sr), titanium (Ti), zirconium (Zr), boron (B), aluminum (Al), and fluorine (F). can include If a positive electrode is prepared using lithium cobalt oxide further containing these elements, the electrochemical characteristics of the lithium secondary battery can be further improved. The content of the element is 0.001 to 0.1 mole based on 1 mole of cobalt.

Hereinafter, a process for manufacturing a lithium secondary battery using the above-described composite cathode active material as a cathode active material for a lithium secondary battery will be described, but a method for manufacturing a lithium secondary battery having a cathode, a negative electrode, a lithium salt-containing non-aqueous electrolyte, and a separator is described. I'm going to do it.

The positive electrode and the negative electrode are manufactured by applying and drying a composition for forming a positive active material layer and a composition for forming a negative active material layer, respectively, on a current collector.

The composition for forming the cathode active material is prepared by mixing a cathode active material, a conductive agent, a binder, and a solvent, and a composite cathode active material according to an embodiment is used as the cathode active material.

The binder is a component that assists in the binding of the active material and the conductive agent and the current collector, and is added in an amount of 1 to 50 parts by weight based on 100 parts by weight of the total weight of the positive electrode active material. Non-limiting examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, and polytetrafluorocarbons. roethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, various copolymers, and the like. The content is 1 to 5 parts by weight based on 100 parts by weight of the total weight of the positive electrode active material. When the content of the binder is within the above range, the binding force of the active material layer to the current collector is good.

The conductive agent is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fibers and metal fibers; fluorinated carbon; metal powders such as aluminum and nickel powder; conductive whiskeys such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

The content of the conductive agent is 1 to 5 parts by weight based on 100 parts by weight of the total weight of the positive electrode active material. When the content of the conductive agent is within the above range, the conductivity characteristics of the finally obtained electrode are excellent.

As a non-limiting example of the solvent, N-methylpyrrolidone and the like are used.

The amount of the solvent is 10 to 200 parts by weight based on 100 parts by weight of the positive electrode active material. When the content of the solvent is in the above range, the operation for forming the active material layer is easy.

The cathode current collector has a thickness of 3 to 500 μm, and is not particularly limited as long as it does not cause chemical change in the battery and has high conductivity. For example, stainless steel, aluminum, nickel, titanium, heat-treated carbon, Alternatively, aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, or the like may be used. The current collector may form fine irregularities on its surface to increase the adhesion of the positive electrode active material, and various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven fabrics are possible.

Separately, a composition for forming a negative active material layer is prepared by mixing a negative active material, a binder, a conductive agent, and a solvent.

As the negative active material, a material capable of intercalating and releasing lithium ions is used. As non-limiting examples of the negative active material, carbon-based materials such as graphite and carbon, lithium metal, alloys thereof, and silicon oxide-based materials may be used. According to one embodiment of the present invention, silicon oxide is used.

The binder is added in an amount of 1 to 50 parts by weight based on 100 parts by weight of the total weight of the negative electrode active material. Non-limiting examples of such a binder may use the same type as the positive electrode.

The conductive agent is used in an amount of 1 to 5 parts by weight based on 100 parts by weight of the total weight of the negative electrode active material. When the content of the conductive agent is within the above range, the conductivity characteristics of the finally obtained electrode are excellent.

The amount of the solvent is 10 to 200 parts by weight based on 100 parts by weight of the total weight of the negative electrode active material. When the content of the solvent is in the above range, the operation for forming the negative electrode active material layer is easy.

The conductive agent and the solvent may be the same type of material used in manufacturing the positive electrode.

As the negative electrode current collector, it is generally made to have a thickness of 3 to 500 μm. The negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery, and for example, the surface of copper, stainless steel, aluminum, nickel, titanium, heat-treated carbon, copper or stainless steel. For the surface treatment with carbon, nickel, titanium, silver, etc., an aluminum-cadmium alloy, etc. may be used. In addition, like the positive electrode current collector, fine irregularities may be formed on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

A separator is interposed between the positive electrode and the negative electrode manufactured according to the above process.

The separator has a pore diameter of 0.01 to 10 μm and a thickness of generally 5 to 300 μm. As specific examples, olefin-based polymers such as polypropylene and polyethylene; Alternatively, a sheet or non-woven fabric made of glass fibers is used. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may serve as a separator.

The lithium salt-containing non-aqueous electrolyte is composed of a non-aqueous electrolyte solution and lithium. Non-aqueous electrolytes, organic solid electrolytes, inorganic solid electrolytes, and the like are used as the non-aqueous electrolyte.

Examples of the non-aqueous electrolyte include, but are not limited to, N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1, 2-dimethoxyethane, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, N,N-formamide, N,N-dimethylformamide, acetonitrile, nitromethane, methyl formate, acetic acid methyl, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, An aprotic organic solvent such as ethyl propionate may be used.

Non-limiting examples of the organic solid electrolyte may include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, polyvinyl alcohol, polyvinylidene fluoride, and the like.

Examples of the inorganic solid electrolyte include, but are not limited to, Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Li ₄ SiO ₄ -LiI- LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ and the like can be used.

The lithium salt is a material that is soluble in the non-aqueous electrolyte, and includes, but is not limited to, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, (FSO ₂ ) ₂ NLi, (FSO ₂ ) ₂ NLi, lithium chloroborate, Lithium lower aliphatic carboxylic acid, lithium tetraphenylborate and the like can be used.

1B is a cross-sectional view schematically illustrating a representative structure of a lithium secondary battery according to an embodiment.

Referring to FIG. 1B , the lithium secondary battery 11 includes a positive electrode 13 including a composite positive electrode active material according to an embodiment, a negative electrode 12, and a separator disposed between the positive electrode 13 and the negative electrode 12. (14), an electrolyte (not shown) impregnated in the positive electrode 13, the negative electrode 12 and the separator 14, a battery case 15, and a cap assembly 16 encapsulating the battery case 15. It consists of the main part. The lithium secondary battery 11 may be configured by sequentially stacking a positive electrode 13 , a negative electrode 12 , and a separator 14 and then storing them in a battery case 15 in a rolled state. The battery case 15 is sealed together with the cap assembly 16 to complete the lithium secondary battery 10 .

The lithium secondary battery has excellent output characteristics and can be used not only for battery cells used as power sources for small devices, but also as unit cells for medium and large-sized battery packs or battery modules including a plurality of battery cells used as power sources for medium and large-sized devices. can also be used.

Examples of the medium-to-large-sized device include an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and the like, and electric bicycles. (E-bike), an electric two-wheeled vehicle including an electric scooter (E-scooter), a power storage device for power tools, and the like, but are not limited thereto.

It will be described in more detail through the following Examples and Comparative Examples. However, the examples are for illustrative purposes only and the scope of the invention is not limited thereto.

(Manufacture of composite cathode active material)

Example One

LiNO ₃ , Co(NO ₃ ) ₂ 6H ₂ O, and SnCl ₂ were mixed in a molar ratio of 1.05 0.95: 0.05, respectively, and dissolved in ethanol to prepare an ethanol solution containing a precursor for forming a composite cathode active material. Here, the content of ethanol was about 200 parts by weight based on 100 parts by weight of the total content of the precursor for forming the composite cathode active material.

Citric acid, a chelating agent, was dissolved in the solution in a molar ratio of 1:1 to the total amount of cations present in the solution. The solution was dried at 60° C. for 10 hours to remove the solvent in the solution to obtain a gel.

The gel was subjected to a first heat treatment at 300° C. for 5 hours, and then a powder was obtained. At this time, the temperature increase rate was controlled at 10°C/min. The obtained powder was again subjected to secondary heat treatment at 900 ° C. for 10 hours, and then cooled in a furnace to obtain a composite cathode active material. At this time, the heating rate during the first heat treatment and the second heat treatment was 10 ° C / min and the cooling rate was about 1 ° C / min. The composite cathode active material obtained according to Example 1 is LiCoO ₂ and It had a structure containing a Li ₂ SnO ₃ coating layer disposed on the (003) crystal plane (c-axis direction crystal plane) of LiCoO ₂ . The thickness of the Li ₂ SnO ₃ coating layer was about 50 nm, and the content of Li ₂ SnO ₃ in the Li ₂ SnO ₃ coating layer was 5 mol %.

Example 2-3

Except for changing the contents of LiNO ₃ , Co(NO ₃ ) ₂ 6H ₂ O, and SnCl ₂ so that the contents of Li ₂ SnO ₃ in the finally obtained composite cathode active material were 2 mol% and 1 mol%, respectively, A composite cathode active material was prepared in the same manner as in Example 1.

Example 4-5

A composite cathode active material was prepared in the same manner as in Example 1, except that in the step of cooling in the furnace, the cooling rates were changed to about 3° C./min and about 5° C./min, respectively.

Example 6

An ethanol solution containing a metal precursor was prepared by dissolving LiNO ₃ and Co(NO ₃ ) ₂ .6H ₂ O in ethanol at a molar ratio of Li:Co=1.03:1. Here, the content of ethanol was about 200 parts by weight based on 100 parts by weight of the total metal precursor.

Citric acid was dissolved in the metal precursor ethanol solution in a molar ratio of 1:1 to the total ratio of cations present in the solution. The resulting product was stirred at 60° C. for 10 hours until the solvent in the solution disappeared, and a gel was obtained.

The obtained gel is subjected to a first heat treatment at 300° C. for 5 hours, and then a powder is obtained. At this time, the heating temperature is set to 10°C/min. The obtained powder was further subjected to secondary heat treatment at 900° C. for 10 hours to obtain LiCoO ₂ . At this time, the heating rate is 10 ℃ / min, and the cooling rate is 10 ℃ / min or more.

Separately, LiNO ₃ and tin ethylhexanoisopropoxide (Tin(IV) ethylhexanoisopropoxide (Sn(OOC ₈ H ₁₅ ) ₂ (OC ₃ H ₇ ) ₂ )) were dissolved in isopropanol (IPA) at a ratio of 2:1. At this time, the total amount of Li ₂ SnO ₃ as a coating material is 5 mol% with respect to LiCoO ₂ .

After dispersing LiCoO ₂ obtained according to the above process in the solution, the mixture was stirred at room temperature (25° C.) for about 20 hours. After evaporating the solvent, the obtained product in gel form was calcined at 150° C. for 10 hours, and then a powder was obtained. The obtained powder was again calcined at 850° C. for 5 hours, and finally LiCoO ₂ coated with Li ₂ SnO ₃ was obtained through a wet coating method. At this time, the heating rate of the first heat treatment and the second heat treatment is set to 10°C/min, and the cooling rate is set to 1°C/min.

Example 7

The composite cathode active material (Li ₂ ZnO ₃ coating film was prepared in the same manner as in Example 1, except that zirconium (IV) acetylacetonate (Zr(C ₅ H ₈ O ₂ ) ₂ ) was used instead _of SnCl 2 ). 003) LiCoO ₂ ) disposed on the crystal plane. At this time, the heating rate during the first heat treatment and the second heat treatment was 10 ° C / min and the cooling rate was about 1 ° C / min. In the Li ₂ ZnO ₃ coating film, zirconium chloride was added so that the content of Li ₂ ZnO ₃ was 5 mol %.

comparative example One

An ethanol solution containing a metal precursor was prepared by dissolving LiNO ₃ and Co(NO ₃ ) ₂ .6H ₂ O in ethanol at a molar ratio of Li:Co=1.03:1. Here, the content of ethanol was about 200 parts by weight based on 100 parts by weight of the total metal precursor.

Citric acid was dissolved in the metal precursor ethanol solution in a molar ratio of 1:1 to the total ratio of cations present in the solution. The resulting product was stirred at 60° C. for 10 hours until the solvent in the solution disappeared, and a gel was obtained.

The obtained gel is subjected to a first heat treatment at 300° C. for 5 hours, and then a powder is obtained. At this time, the heating temperature is set to 10°C/min. The obtained powder was further subjected to secondary heat treatment at 900° C. for 10 hours to obtain LiCoO ₂ . At this time, the heating rate is set to 10°C/min and the cooling rate is set to 10°C/min.

comparative example 2

LiNO ₃ and tin ethylhexanoisopropoxide (Tin(IV) ethylhexanoisopropoxide (Sn(OOC ₈ H ₁₅ ) ₂ (OC ₃ H ₇ ) ₂ )) were dissolved in isopropanol (IPA) at a molar ratio of 2:1. At this time, the total amount of Li ₂ SnO ₃ as a coating material was controlled to be 5 mol% with respect to LiCoO ₂ .

After dispersing LiCoO ₂ obtained according to Comparative Example 1 in the solution, the mixture was stirred at room temperature (25° C.) for about 20 hours. The solvent was evaporated by heating at 60°C for 20 hours, and the resulting gel-like product was calcined at 150°C for 10 hours to obtain a powder. The obtained powder was again calcined at 850 ° C. for 5 hours, and finally a composite cathode active material was obtained through a wet coating method. At this time, the heating rate of the first heat treatment and the second heat treatment is 10 ° C / min, and the cooling rate is 10 ° C / min.

The composite cathode active material obtained according to Comparative Example 2 had a structure containing LiCoO ₂ and a coating film in which Li ₂ SnO ₃ was disposed on crystal planes of LiCoO ₂ in all directions.

(Example of production of lithium secondary battery)

production example One

A coin cell was manufactured as follows using the composite cathode active material prepared according to Example 1.

A uniformly dispersed cathode active material layer was formed by mixing a mixture of 96 g of lithium cobalt oxide (LiCoO ₂ ) obtained in Example 1, 2 g of polyvinylidene fluoride, 47 g of N-methylpyrrolidone as a solvent, and 2 g of carbon black as a conductive agent. A slurry was prepared for

The slurry prepared according to the above process was coated on an aluminum foil using a doctor blade to form a thin electrode plate, dried at 135 ° C. for more than 3 hours, and then subjected to rolling and vacuum drying processes to prepare a positive electrode.

A 2032 type coin cell was manufactured using the positive electrode and the lithium metal negative electrode. A separator (thickness: about 16 μm) made of a porous polyethylene (PE) film was interposed between the positive electrode and the lithium metal counter electrode, and an electrolyte was injected to prepare a coin cell.

At this time, as the electrolyte, a solution containing 1.3M LiPF ₆ dissolved in a solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 3:4:3 was used. .

production example 2-7

A lithium secondary battery was manufactured in the same manner as in Preparation Example 1, except that the composite cathode active material prepared in Examples 2 to 7 was used instead of the composite cathode active material prepared in Example 1.

Comparative production example 1-2

A lithium secondary battery was manufactured in the same manner as in Preparation Example 1, except that the composite cathode active material prepared in Comparative Examples 1 and 2 was used instead of the composite cathode active material prepared in Example 1.

evaluation example 1: room temperature (25 ° C) XRD analyze

XRD analysis was performed at 25° C. for the composite cathode active material prepared in Examples 1-3, the lithium cobalt oxide prepared in Comparative Example 1, and the composite cathode active material prepared in Comparative Example 2. XRD analysis was performed using a Bruker D2 phaser X-ray diffractometer with Cu Kα radiation (λ = 1.5406Å), and the XRD analysis results are shown in FIGS. 2a and 2b. 2a and 2b, bare is for the lithium cobalt oxide of Comparative Example 1, Sn 5%, Sn 2%, and Sn 1% are for the composite cathode active materials of Examples 1 to 3, respectively.

Referring to this, each phase of LiCoO ₂ and Li ₂ SnO ₃ was observed in the composite cathode active material prepared according to Examples 1-3. A peak appearing in a 2θ range of about 18.5 to 19.3° is for lithium cobalt oxide, and a peak appearing in a 2θ range of about 17.7° to 18.3° is for Li ₂ Sn0 ₃ .

When LiCoO ₂ was coated with Li ₂ SnO ₃ , even though the tin precursor was mixed and heat-treated, peak broadening and peak shift were not observed in the XRD pattern of LiCoO ₂ . In particular, in the composite cathode active material of Example 1 (when the content of Sn was 5 mol%), a (002) peak of Li ₂ SnO ₃ was observed around 18 ^o , which is a low solubility limit of Sn for LiCoO ₂ at room temperature ( This indicates that Sn is not doped into the structure of LiCoO ₂ at room temperature due to solubility limit).

evaluation example 2: high temperature XRD analyze

Before performing heat treatment at 900 ° C. on the composite cathode active material prepared according to Example 1, the lithium cobalt oxide manufactured according to Comparative Example 1, and the composite cathode active material prepared according to Comparative Example 2, after heat treatment at 900 ° C., After heat treatment at 900 ° C. and cooling, XRD analysis was performed. XRD analysis was performed using a Bruker D8 advance X-ray diffractometer with Cu Kα radiation (λ = 1.5406 Å), and the XRD analysis results are shown in FIGS. 3a and 3b. 3a and 3b, “before heating” indicates before heat treatment at 900 ° C, “900 ° C” indicates after heat treatment at 900 ° C, and after cooling “after cooling after heat treatment at 900 ° C. indicates

Referring to FIG. 3A, it was confirmed that the (002) peak of Li ₂ SnO ₃ near 18 ^o completely disappeared in the composite cathode active material of Example 1 at a high temperature (900 ° C), and the peak was observed again when it was cooled again. did In addition, bare LiCoO ₂ of Comparative Example 1 showed no significant change in peak shape at high temperature, as shown in FIG. 3b, whereas peak broadness was increased in the case of a material coated with 5 mol% of Li ₂ SnO ₃ . did This means that Li ₂ SnO ₃ reacts with LiCoO ₂ at high temperature and Sn is doped into LiCoO ₂ . In addition, due to the low solubility of Sn at low temperatures, phase separation into Li ₂ SnO ₃ and LiCoO ₂ occurs during the cooling process, and during this phase separation process, Li ₂ SnO ₃ is coated on the surface of LiCoO ₂ .

evaluation example 3: TEM and EDS analysis

TEM and EDS analysis were performed on the composite cathode active material prepared according to Example 1 and Comparative Example 2. TEM and EDS analysis was performed using JEOL's JEM-ARM200F microscope.

TEM and EDS analysis results for the composite cathode active material of Example 1 are shown in FIGS. 4a to 4c, and TEM and analysis results for the composite cathode active material of Comparative Example 2 are shown in FIGS. 5a to 5c.

TEM-EDS analysis using STEM was performed to confirm the shape of the Li ₂ SnO ₃ coating film, and the results are shown in FIGS. 4a to 4c. In order to confirm the coating shape, a sample was prepared by cutting the cross section of the particle using an ion-slicer, which was observed by STEM.

Referring to FIGS. 4A to 4C , it was confirmed that the coating film of the composite cathode active material of Example 1 was coated only on a specific surface of LiCoO ₂ . In comparison, the composite cathode active material of Comparative Example 2 was cooled at a faster cooling rate than that of Example 1, and Sn, which was present in a doped state at a high temperature, did not have sufficient time to diffuse to the surface of LiCoO ₂ . LiCoO ₂ existed in a phase-separated state only inside the particles (see FIGS. 5a to 5c).

Meanwhile, in order to confirm the thickness and shape of the coating film of Li ₂ SnO ₃ of the composite cathode active material prepared according to Example 1, TEM-EDS analysis was performed using STEM, and the results are shown in FIG. 6 . In FIG. 6, the distance represents the radius from the surface to the center of the composite cathode active material. In FIG. 6 , a distance of 0 nm represents the surface of the composite cathode active material, and an area of 150 nm distance represents the center of the composite cathode active material.

As shown in FIG. 6, as a result of checking the cross section of the Li ₂ SnO ₃ coated particle through EDS-line profile, it was confirmed that the Li ₂ SnO ₃ coating film was formed to a thickness of about 50 nm.

evaluation example 4: TEM and fast fourier transformation; FFT ) analyze

A scanning transmission electron microscope (STEM) and FFT analysis were performed on the composite cathode active material prepared in Example 1. For STEM and FFT analysis, a JEM-ARM200F microscope from JEOL was used as an analyzer.

STEM and FFT analysis results are shown in FIGS. 7a to 7c. Figure 7a shows an EDS mapping image using STEM and Figure 7b is an enlarged view of the square area of Figure 7a, a TEM image showing an enlarged atomic arrangement of the interface between LiCoO ₂ and Li ₂ SnO ₃ coating film. And FIG. 7C shows the FFT pattern of the TEM image of FIG. 7B.

Through this analysis, the growth direction of the coating film was observed. As a result of observing the atomic arrangement and FFT patterns of the LiCoO ₂ and Li ₂ SnO ₃ coatings through STEM images, it was confirmed that both the LiCoO ₂ and Li ₂ SnO ₃ coatings had a layered structure grown in the same c-axis direction. Through this, it can be seen that both materials are epitaxially grown in the c-axis direction, sharing the (002) plane of the Li ₂ SnO ₃ coating film, which is a layer structure, on the (003) crystal plane of the layer structure LiCoO ₂ . . This is because, as shown in FIG. 6a, when the two layered structures share the c-axis crystal plane, the mismatch at the phase boundary of the two materials LiCoO ₂ and Li ₂ SnO ₃ in terms of crystal structure becomes the smallest. . The mismatch that occurs when the two layered structures share the c-axis crystal plane is about 0.1 Å, as shown in FIG. However, when the other planes, that is, the a-axis and b-axis crystal planes are shared, the mismatch between the layers having the arrangement of [lithium-oxygen-transition metal-oxygen] is about 0.3 Å, as shown in FIG. occurs, which destabilizes the phase boundary with a much larger value than when sharing the c-axis crystal plane. That is, when Sn, which was doped at high temperature, undergoes phase separation with cooling in order to reduce the mismatch between these two materials, the coating layer of Li ₂ SnO ₃ phase separates only on the (003) surface of LiCoO ₂ , and eventually LiCoO ₂ Only the (003) surface of Li ₂ SnO ₃ is selectively coated.

evaluation example 5: Analysis of output characteristics

Output characteristics of the coin cells manufactured according to Manufacturing Example 1 and Comparative Manufacturing Example 1 were evaluated according to the following method.

Coin cells manufactured according to Manufacturing Example 1 and Comparative Manufacturing Example 1 were charged with a constant current up to 4.5V at a rate of 0.1C and discharged at a constant current up to 3.0V at a rate of 0.1C in the first cycle. The second cycle and the third cycle were repeatedly performed under the same conditions as the first cycle.

In the 4th cycle, the lithium secondary battery that had undergone the 3rd cycle was charged with a constant current up to 4.5V at a rate of 0.2C, and discharged with a constant current up to 3.0V at a rate of 0.2C. The 5th cycle and the 6th cycle were repeatedly performed under the same conditions as the 4th cycle.

In the 7th cycle, the lithium battery that had gone through the 6th cycle was charged with a constant current to 4.5V at a rate of 0.5C, and discharged with a constant current to 3.0V at a rate of 0.5C. The 8th cycle and the 9th cycle were repeatedly performed under the same conditions as the 7th cycle.

In the 10th cycle, the lithium battery that had passed through the 9th cycle was charged with a constant current to 4.5V at a rate of 1.0C, and discharged with a constant current to 3.0V at a rate of 1.0C. The 11th cycle and the 12th cycle were repeatedly performed under the same conditions as the 10th cycle.

In the 13th cycle, the lithium battery that had passed through the 12th cycle was charged with a constant current to 4.5V at a rate of 2.0C, and discharged with a constant current to 3.0V at a rate of 2.0C. The 14th cycle and the 15th cycle were repeatedly performed under the same conditions as the 13th cycle.

In the 16th cycle, the lithium battery that had passed through the 15th cycle was charged with a constant current to 4.5V at a rate of 5.0C and discharged with a constant current to 3.0V at a rate of 5.0C. The 17th cycle and the 18th cycle were repeatedly performed under the same conditions as the 16th cycle.

In the 19th cycle, the lithium battery that had passed through the 18th cycle was charged with a constant current to 4.5V at a rate of 7.0C, and discharged with a constant current to 3.0V at a rate of 7.0C. The 20th cycle and the 21st cycle were repeatedly performed under the same conditions as the 19th cycle.

In the 22nd cycle, the lithium battery that had passed through the 21st cycle was charged with a constant current up to 4.5V at a rate of 10C and discharged with a constant current up to 3.0V at a rate of 10.0C. The 23rd cycle and the 24th cycle were repeatedly performed under the same conditions as the 22nd cycle.

Output characteristics of the coin cells manufactured according to Manufacturing Example 1 and Comparative Manufacturing Example 2 are shown in FIG. 10 .

Referring to this, it can be seen that the coin cell of Manufacturing Example 1 has improved output characteristics compared to the coin cell of Comparative Manufacturing Example 2.

In addition, the output characteristics of the coin cell of Production Example 4-5 were evaluated by inspection in the same way as in the output evaluation method of the coin cell of Production Example 1 described above.

As a result of the evaluation, the coin cell of Manufacturing Example 4-5 exhibited an equivalent level of output characteristics compared to that of the coin cell of Manufacturing Example 1.

evaluation example 6: Impedance

In order to check the charge transfer resistance of the coin cell of Manufacturing Example 1 using the composite cathode active material of Example 1 and the coin cell of Comparative Manufacturing Example 2 using the composite cathode active material of Comparative Example 2, an AC impedance method was used in the OCV state to charge the charge Transfer resistance was measured. The measurement results are as shown in FIG. 11 .

Referring to this, this is a result consistent with the charge transfer resistance value analyzed by the AC impedance method. In other words, compared to the material coated on the entire surface of LiCoO ₂ by the conventional wet coating method, the material coated only on the (003) surface showed a smaller charge transfer resistance due to smooth insertion/desorption of lithium, and through this, the output characteristics were improved. Improved.

Although described with reference to the examples above, those skilled in the art will understand that various modifications and changes can be made without departing from the spirit and scope described in the claims below.

1: α-NaFeO lithium transition metal oxide with a _two- layered crystal structure
2: coating film containing lithium metal oxide
11: lithium secondary battery 12: negative electrode
13: anode 14: separator
15: battery case 16: cap assembly

Claims (21)

α-NaFeO ₂ lithium transition metal oxide with a layered crystal structure; and
A composite cathode active material containing a coating film containing a lithium metal oxide disposed only on a (003) crystalline plane of the lithium transition metal oxide. According to claim 1,
The lithium metal oxide is a composite cathode active material having a C2 / c space group structure of a monoclinic crystal system. According to claim 1,
A composite cathode active material in which the lithium metal oxide is a compound represented by Formula 1 below:
[Formula 1]
Li ₂ MO ₃
In Formula 1, M is a metal having an oxidation number of +4. According to claim 3,
The lithium metal oxide is one selected from Li ₂ SnO ₃ , Li ₂ ZrO ₃ , Li ₂ TeO3, Li ₂ RuO ₃ , Li ₂ TiO ₃ , Li ₂ MnO ₃ , Li ₂ PbO ₃ , Li ₂ HfO ₃ and combinations thereof. More than one composite cathode active material. According to claim 1,
The content of the lithium metal oxide is 5 mol% or less based on the total content of the α-NaFeO ₂ layered crystal structure of the lithium transition metal oxide and the lithium metal oxide. According to claim 1,
The α-NaFeO ₂ layered crystal structure of lithium transition metal oxide is
lithium cobalt oxide (LiCoO ₂ ); or
At least one element selected from magnesium (Mg), calcium (Ca), strontium (Sr), titanium (Ti), zirconium (Zr), boron (B), aluminum (Al), and fluorine (F) is further added to lithium cobalt oxide. A composite cathode active material, which is a compound containing According to claim 1,
The thickness of the coating film is a composite cathode active material of 1 to 100nm. According to claim 1,
The α-NaFeO lithium transition metal oxide having a _two- layered crystal structure and the lithium metal oxide disposed on the (003) crystal plane of the lithium transition metal oxide,
A composite cathode active material having a layered structure epitaxially grown in the same C-axis direction. Obtaining a composite cathode active material precursor composition by mixing a lithium precursor, a metal (M) precursor for forming a lithium metal oxide, and a metal precursor for forming a lithium transition metal oxide having a _two- layer crystal structure of α-NaFeO with a solvent;
Forming a gel by adding and mixing a chelating agent to the composite cathode active material precursor composition;
subjecting the gel to a first heat treatment to obtain a first heat treated product;
After performing a second heat treatment on the product subjected to the first heat treatment, cooling at a cooling rate of 5 ° C / min or less,
The method of manufacturing a composite cathode active material according to any one of claims 1 to 8, wherein the cooling rate is 1 to 5 ° C./min and the heating rate during the second heat treatment is greatly adjusted compared to the cooling rate. Obtaining a lithium metal oxide precursor composition by mixing a lithium precursor and a metal (M) precursor for forming a lithium metal oxide with a solvent;
adding α-NaFeO ₂ layered lithium transition metal oxide to the lithium metal oxide precursor composition and then mixing it to form a gel;
subjecting the gel to a first heat treatment to obtain a first heat treated product; and
After performing a second heat treatment on the product subjected to the first heat treatment, cooling at a cooling rate of 5 ° C./min or less,
The cooling rate is 1 to 5 ° C / min and the temperature increase rate during the second heat treatment is greatly adjusted compared to the cooling rate,
A method for producing a composite cathode active material for obtaining the composite cathode active material according to any one of claims 1 to 8. delete According to claim 9,
A method for producing a composite cathode active material in which the first heat treatment is performed at 200 to 550 ° C. According to claim 9,
A method for producing a composite cathode active material in which the second heat treatment is performed at 600 to 950 ° C. According to claim 9,
The metal (M) precursor for forming the lithium metal oxide is tin chloride (SnCl ₂ ), zirconium chloride (ZrCl ₄ ), tellurium chloride (TeCl ₄ ), ruthenium chloride (RuCl ₄ ), titanium chloride (TiCl ₄ ), manganese chloride (MnCl ₄ ), hafnium chloride (HfCl4), lead chloride (PbCl4), zirconium nitrate, zirconium acetate, zirconium(IV) acetylacetonate, zirconium oxalate, tellurium nitrate, tellurium acetate, tellurium oxalate, tellurium chloride, ruthenium nitrate, ruthenium acetate, ruthenium oxalate, titanium nitrate, titanium acetate, titanium oxalate, manganese nitrate, manganese acetate, manganese oxalate, hafnium nitrate, hafnium acetate, hafnium oxalate, and the like Method for producing a composite cathode active material of at least one selected from the combination. According to claim 9,
The α-NaFeO ₂ metal precursor for forming a lithium transition metal oxide having a layered crystal structure is at least one selected from cobalt nitrate, cobalt acetate, cobalt oxalate, and cobalt chloride Method for producing a composite cathode active material. According to claim 9,
The lithium precursor is a method for producing a composite cathode active material of lithium hydroxide, lithium nitrate, lithium acetate, lithium sulfate, lithium fluoride or a mixture thereof. A lithium secondary battery having a cathode comprising the composite cathode active material of any one of claims 1 to 8. According to claim 10,
The first heat treatment is carried out at 200 to 550 ° C,
A method for producing a composite cathode active material in which the second heat treatment is performed at 600 to 950 ° C. According to claim 10,
The lithium precursor is a method for producing a composite cathode active material of lithium hydroxide, lithium nitrate, lithium acetate, lithium sulfate, lithium fluoride or a mixture thereof. According to claim 10,
The metal (M) precursor for forming the lithium metal oxide is tin chloride (SnCl ₂ ), zirconium chloride (ZrCl ₄ ), tellurium chloride (TeCl ₄ ), ruthenium chloride (RuCl ₄ ), titanium chloride (TiCl ₄ ), manganese chloride (MnCl ₄ ), hafnium chloride (HfCl4), lead chloride (PbCl4), zirconium nitrate, zirconium acetate, zirconium(IV) acetylacetonate, zirconium oxalate, tellurium nitrate, tellurium acetate, tellurium oxalate, tellurium chloride, ruthenium nitrate, ruthenium acetate, ruthenium oxalate, titanium nitrate, titanium acetate, titanium oxalate, manganese nitrate, manganese acetate, manganese oxalate, hafnium nitrate, hafnium acetate, hafnium oxalate, and the like Method for producing a composite cathode active material of at least one selected from the combination. The method of claim 9, wherein the heating rate is 10 °C/min.

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