KR20200108536A - Manufacturing method of lithium-nickel-manganese oxide cathode active material for lithium secondary battery, manufacturing method of lithium secondary battery cathode and lithium secondary battery - Google Patents

Abstract

The present invention relates to a method for preparing a lithium-nickel-manganese oxide positive electrode active material for a lithium secondary battery, including the steps of: mixing a lithium source, a nickel source and a manganese source in a solvent to form a mixture; heating the mixture to carry out reaction; drying the resultant product; subjecting the dried product to the first heat treatment; and subjecting the resultant product to the second heat treatment under reductive atmosphere so that Ni metal may be eluted. The present invention also relates to a method for manufacturing a positive electrode of a lithium secondary battery, and a lithium secondary battery. According to the present invention, Ni metal in the particles is partially eluted and crystallized on the surface to provide improved electrical conductivity and excellent rate characteristics.

Description

Manufacturing method of lithium-nickel-manganese oxide cathode active material for lithium secondary battery, manufacturing method of lithium secondary battery (Manufacturing method of lithium-nickel-manganese oxide cathode active material for lithium secondary battery, manufacturing method of lithium secondary battery) cathode and lithium secondary battery}

The present invention relates to a method for manufacturing a positive electrode active material for a lithium secondary battery, a method for manufacturing a positive electrode for a lithium secondary battery, and a lithium secondary battery, and more particularly, a part of the Ni metal inside the particles is eluted and crystallized on the surface, thereby improving electrical conductivity. A method of manufacturing a lithium-nickel-manganese oxide positive electrode active material for a lithium secondary battery that can have excellent rate controlling characteristics, a method of manufacturing a positive electrode for a lithium secondary battery using the lithium-nickel-manganese oxide positive electrode active material for the lithium secondary battery, and a positive electrode of the lithium secondary battery It relates to a lithium secondary battery using.

Recently, the demand for rechargeable batteries that are used repeatedly charging and discharging with power sources such as portable electronic devices such as mobile phones, portable personal information terminals (PDAs), laptop computers, digital cameras, camcorders, MP3s, and electric vehicles and electric bicycles has rapidly increased. Are doing. In particular, since the performance of products such as portable electronic devices is influenced by secondary batteries, which are core parts, development of high-performance secondary batteries is required. The characteristics required for such a secondary battery have various aspects such as charge/discharge characteristics, life characteristics, high rate characteristics, and stability at high temperatures.

Among secondary batteries, lithium secondary batteries are attracting the most attention because of their high voltage and high energy density. Lithium secondary batteries using a spinel-structured composite oxide as a positive electrode active material are attracting the most attention because they have high energy density due to high voltage.

Most lithium _secondary batteries currently on the market use LiCoO ₂ for the positive electrode and carbon for the negative electrode. However, since cobalt (Co) used in the cathode active material has a small reserve and is expensive, is toxic to the human body, and causes environmental pollution, the development of a new alternative cathode active material is required.

As cathode active materials that are currently being actively studied, LiNiO ₂ , LiCo _x Ni _{1 - x} O ₂ , LiMn ₂ O _4, etc. are mentioned. LiNiO ₂ forming a layered structure has difficulty in synthesizing materials with a stoichiometric ratio, as well as a problem in thermal stability. LiMn ₂ O ₄ having a spinel structure has the advantage of using manganese (Mn) as a basic material, but a structural change called Jahn-Teller distortion caused by Mn ^{3 +} and a negative electrode as graphite The high-temperature life characteristics due to elution of Mn ^{2 +} are not good.

In addition, a general method for preparing a positive electrode active material is a solid-phase reaction method, in which a positive electrode active material is prepared by performing a process of mixing and firing several times using carbonates or hydroxides of each constituent element as a raw material. However, this method has a problem in that there are many impurities introduced from the ball mill during the mixing process, and it is difficult to obtain a uniform phase due to a non-uniform reaction, and the manufacturing time is long. In addition, the formation of manganese in oxidation number 3+ during firing causes Yan-Teller distortion, and when manganese oxide in which Mn ³⁺ is present is used as a cathode active material for lithium secondary batteries, the crystal structure of the cathode active material is repeated as the charge/discharge cycle is repeated. May collapse and the battery life characteristics may be deteriorated.

Korean Patent Publication No. 10-1772737

The problem to be solved by the present invention is a method for producing a lithium-nickel-manganese oxide positive electrode active material for a lithium secondary battery capable of improving electrical conductivity by being crystallized on the surface by eluting a part of the Ni metal inside the particle, and the above To provide a method of manufacturing a positive electrode for a lithium secondary battery using a lithium-nickel-manganese oxide positive electrode active material for a lithium secondary battery, and a lithium secondary battery using the positive electrode of the lithium secondary battery.

The present invention comprises the steps of forming a mixture by mixing a lithium source, a nickel source, and a manganese source with a solvent, heating the mixture to react, drying the reacted product, and first heat treatment of the dried product. It provides a method of manufacturing a lithium-nickel-manganese oxide positive electrode active material for a lithium secondary battery comprising the step of performing a second heat treatment in a reducing atmosphere and allowing the Ni metal to elute.

In the step of forming the mixture, the mixture may be formed by further mixing sugar (sucrose).

The lithium source may include at least one material selected from the group consisting of lithium nitrate (LiNO ₃ ), lithium sulfate (Li ₂ SO ₄ ), and lithium chloride (LiCl).

The nickel source may include at least one material selected from the group consisting of nickel nitrate (Ni(NO ₃ ) ₂ ), nickel sulfate (NiSO ₄ ), and nickel chloride (NiCl ₂ ).

The manganese source may include one or more substances from the group consisting of manganese nitrate (Mn(NO ₃ ) ₂ ), manganese sulfate (MnSO ₄ ), and manganese chloride (MnCl ₂ ).

It is preferable to mix the lithium source, the nickel source, and the manganese source so that the molar ratio of Li:Ni:Mn is 1:x:2-x (0<x≤0.5).

The first heat treatment is preferably performed in an oxidizing atmosphere.

The first heat treatment is preferably performed at a temperature of 700 to 900°C.

It may further include performing annealing at a temperature of 400 to 650°C after the first heat treatment.

The second heat treatment is preferably performed at a temperature of 650 to 900°C.

The second heat treatment is preferably performed in a mixed gas atmosphere of an inert gas and hydrogen (H ₂ ) gas.

It is preferable to use a water bath heating for the heating.

In addition, the present invention comprises the steps of preparing a composition for a positive electrode of a lithium secondary battery by mixing a lithium-nickel-manganese oxide positive electrode active material, a conductive material, a binder, and a solvent for a lithium secondary battery prepared by the above method, and for the positive electrode of the lithium secondary battery The composition is pressed to form an electrode, or the composition for a lithium secondary battery is coated on a metal foil to form an electrode, or the composition for a positive electrode for a lithium secondary battery is pushed with a roller to form a sheet and applied to a metal foil or a current collector. It provides a method for manufacturing a positive electrode for a lithium secondary battery, including the step of forming a positive electrode of the lithium secondary battery by attaching and forming the electrode in the form of an electrode and drying the resultant product formed in the electrode shape.

In addition, in the present invention, the positive electrode of the lithium secondary battery manufactured by the above method and the negative electrode including lithium metal are disposed to be spaced apart from each other, and between the positive electrode and the negative electrode, for preventing a short circuit between the positive electrode and the negative electrode. A separator is disposed, and the positive electrode and the negative electrode are provided with a lithium secondary battery, characterized in that impregnated with an electrolyte.

The lithium-nickel-manganese oxide positive electrode active material for a lithium secondary battery prepared according to the present invention has a spinel structure in which Ni metal is eluted (Ex-solution) in LiNi _x Mn _{2 - x} O ₄ (0<x≤0.5). It is in a crystallized state. The rate control characteristics are improved by the Ni metal (transition metal) eluted to the surface. Part of the Ni metal inside the particles is eluted and crystallized on the surface, so that electrical conductivity is improved, and excellent rate-limiting properties can be obtained.

1 is a schematic diagram showing a state in which Ni metal is eluted to the surface after a second heat treatment in a reducing atmosphere in a first heat treated state.
2 is a diagram illustrating a state of use of a lithium secondary battery according to an example.
3 is a positive electrode active material LiNi ₀ prepared according to the comparative example _{. 5} Mn _{1 . This} is a scanning electron microscope (SEM) picture showing ₅ O ₄ .
4 is a scanning electron microscope (SEM) photograph showing a cathode active material in which Ni metal prepared according to Example 1 is eluted.
5 is a diagram showing electrochemical analysis results of a lithium secondary battery manufactured according to a comparative example and a lithium secondary battery manufactured according to Example 1. FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the following embodiments are provided so that the present invention may be sufficiently understood by those of ordinary skill in the art, and may be modified in various other forms, and the scope of the present invention is limited to the embodiments described below. It does not become.

In the detailed description of the invention or in the claims, when any one component "includes" another component, it is not construed as being limited to consisting of only the component unless otherwise stated, and other components are further included. It should be understood that it may contain.

A method for preparing a lithium-nickel-manganese oxide positive electrode active material for a lithium secondary battery according to a preferred embodiment of the present invention comprises the steps of forming a mixture by mixing a lithium source, a nickel source, and a manganese source in a solvent, and heating the mixture to react And drying the reacted product, performing a first heat treatment on the dried product, and performing a second heat treatment on the first heat treated product in a reducing atmosphere to elute the Ni metal.

In the step of forming the mixture, the mixture may be formed by further mixing sugar (sucrose).

The lithium source may include at least one material selected from the group consisting of lithium nitrate (LiNO ₃ ), lithium sulfate (Li ₂ SO ₄ ), and lithium chloride (LiCl).

The nickel source may include at least one material selected from the group consisting of nickel nitrate (Ni(NO ₃ ) ₂ ), nickel sulfate (NiSO ₄ ), and nickel chloride (NiCl ₂ ).

The manganese source may include one or more substances from the group consisting of manganese nitrate (Mn(NO ₃ ) ₂ ), manganese sulfate (MnSO ₄ ), and manganese chloride (MnCl ₂ ).

It is preferable to mix the lithium source, the nickel source, and the manganese source so that the molar ratio of Li:Ni:Mn is 1:x:2-x (0<x≤0.5).

The first heat treatment is preferably performed in an oxidizing atmosphere.

The first heat treatment is preferably performed at a temperature of 700 to 900°C.

It may further include performing annealing at a temperature of 400 to 650°C after the first heat treatment.

The second heat treatment is preferably performed at a temperature of 650 to 900°C.

The second heat treatment is preferably performed in a mixed gas atmosphere of an inert gas and hydrogen (H ₂ ) gas.

It is preferable to use a water bath heating for the heating.

A method of manufacturing a positive electrode for a lithium secondary battery according to a preferred embodiment of the present invention comprises mixing a lithium-nickel-manganese oxide positive electrode active material for a lithium secondary battery prepared by the above method, a conductive material, a binder, and a solvent to prepare a composition for a positive electrode for a lithium secondary battery. In the manufacturing step, the composition for a positive electrode for a lithium secondary battery is pressed to form an electrode, or the composition for a lithium secondary battery is coated on a metal foil to form an electrode, or the composition for a positive electrode for a lithium secondary battery is used with a roller. And forming a positive electrode of a lithium secondary battery by pushing it into a sheet state and attaching it to a metal foil or a current collector to form an electrode, and drying the resultant product in the form of an electrode.

In a lithium secondary battery according to a preferred embodiment of the present invention, a positive electrode of a lithium secondary battery manufactured by the above method and a negative electrode including lithium metal are disposed to be spaced apart from each other, and the positive electrode and the negative electrode are disposed between the positive electrode and the negative electrode. A separator for preventing a short circuit of the negative electrode is disposed, and the positive electrode and the negative electrode are impregnated with an electrolyte.

Hereinafter, a method of manufacturing a lithium-nickel-manganese oxide positive electrode active material for a lithium secondary battery according to a preferred embodiment of the present invention will be described in more detail.

A lithium source, a nickel source, and a manganese source are mixed in a solvent to form a mixture. At this time, the mixture may be formed by further mixing sugar (sucrose). During the subsequent heat treatment, impurities such as impurities NiO _x and LiNiO _x are likely to be generated, and sugar is added to prevent this. Since the subsequent heat treatment process is performed by adding sugar, it is possible to suppress the formation of impurities by reacting with CO ₂ and blowing them as gas before impurities are formed. The solvent may be water (H ₂ O).

The lithium source may include at least one material selected from the group consisting of lithium nitrate (LiNO ₃ ), lithium sulfate (Li ₂ SO ₄ ), and lithium chloride (LiCl).

The nickel source may include at least one material selected from the group consisting of nickel nitrate (Ni(NO ₃ ) ₂ ), nickel sulfate (NiSO ₄ ), and nickel chloride (NiCl ₂ ).

The manganese source may include one or more substances from the group consisting of manganese nitrate (Mn(NO ₃ ) ₂ ), manganese sulfate (MnSO ₄ ), and manganese chloride (MnCl ₂ ).

It is preferable to mix the lithium source, the nickel source, and the manganese source so that the molar ratio of Li:Ni:Mn is 1:x:2-x (0<x≤0.5).

The mixture is heated to react. It is preferable to use a water bath heating for the heating. For example, the reaction is preferably carried out by heating a water bath at a temperature of about 80 to 200 ℃ using ethylene glycol. By heating the mixture, the lithium source, the nickel source, and the manganese source are completely dissolved in the solvent, and the reaction can be made more active.

Dry the reaction product. The drying is preferably performed at a temperature of about 100 to 150°C.

The dried result is subjected to a first heat treatment. The first heat treatment is preferably performed in an oxidizing atmosphere such as air or oxygen. The first heat treatment is preferably performed at a temperature of 700 to 900°C.

It may further include performing annealing at a temperature of 400 to 650°C after the first heat treatment. The annealing is preferably performed in an oxidizing atmosphere such as air or oxygen. The crystal structure can be stabilized by performing annealing.

The result of the first heat treatment is subjected to a second heat treatment in a reducing atmosphere so that the Ni metal is eluted. The second heat treatment is preferably performed at a temperature of 650 to 900°C. The second heat treatment is preferably performed in a mixed gas atmosphere of an inert gas and hydrogen (H ₂ ) gas. 1 is a schematic diagram showing a state in which Ni metal is eluted to the surface after a second heat treatment in a reducing atmosphere in a first heat treated state.

The lithium-nickel-manganese oxide positive electrode active material for lithium secondary batteries prepared in this way is crystallized from the surface after Ni metal is eluted (Ex-solution) in LiNi _x Mn _{2 - x} O ₄ (0<x≤0.5) having a spinel structure It is in a state. The rate control characteristics are improved by the Ni metal (transition metal) eluted to the surface. Part of the Ni metal (transition metal) inside the particles is eluted and crystallized on the surface, so that the electrical conductivity is improved, and excellent rate-limiting properties can be obtained.

The thus prepared lithium-nickel-manganese oxide positive electrode active material for a lithium secondary battery may be used to manufacture a positive electrode of a lithium secondary battery. Hereinafter, a method of manufacturing a positive electrode of a lithium secondary battery using the positive electrode active material will be described.

The lithium secondary battery positive electrode composition is prepared by mixing the lithium-nickel-manganese oxide positive electrode active material, a conductive material, a binder, and a solvent.

The composition for the positive electrode of the lithium secondary battery includes a positive electrode active material, 2 to 20 parts by weight of a conductive material based on 100 parts by weight of the positive electrode active material, 2 to 20 parts by weight of a binder based on 100 parts by weight of the positive electrode active material, and 100 parts by weight of the positive electrode active material. It may contain 100 to 300 parts by weight of a solvent. Since the lithium secondary battery positive electrode composition is in a paste form, it may be difficult to uniformly mix (completely disperse), but for a predetermined time (for example, 10 minutes to 12 hours) by using a mixer such as a planetary mixer. When stirred, a composition for a positive electrode for a lithium secondary battery suitable for manufacturing an electrode can be obtained. A mixer such as a planetary mixer enables the preparation of a uniformly mixed lithium secondary battery positive electrode composition.

The binder is polytetrafluoroethylene (PTFE), polyvinylidenefloride (PVDF), carboxymethylcellulose (CMC), polyvinyl alcohol (PVA), polyvinyl butyral (polyvinylidenefloride). vinyl butyral; PVB), poly-N-vinylpyrrolidone (PVP), styrene butadiene rubber (SBR), polyamide-imide, polyimide, etc. It can be used by mixing one or two or more selected.

The conductive material is not particularly limited as long as it is an electronic conductive material that does not cause chemical changes, and examples thereof include natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, Super-P, carbon fiber, copper, nickel, Metal powder or metal fibers such as aluminum and silver may be used.

The solvent may be an organic solvent such as ethanol (EtOH), acetone, isopropyl alcohol, N-methylpyrrolidone (NMP), propylene glycol (PG), or water.

A composition for a positive electrode of a lithium secondary battery in which a positive electrode active material, a binder, a conductive material, and a solvent are mixed is pressed to form an electrode, or the composition for a positive electrode of the lithium secondary battery is coated on a metal foil to form an electrode, or the lithium secondary battery The positive electrode composition is pushed with a roller to form a sheet, and is attached to a metal foil or a current collector to form an electrode.

When an example of forming an electrode is described in more detail, the composition for a positive electrode for a lithium secondary battery may be compressed and molded using a roll press molding machine. The roll press molding machine is aimed at improving electrode density and controlling the thickness of the electrode through rolling, a controller that can control the thickness and heating temperature of the rolls and rolls at the top and bottom, and a winding that can unwind and wind the electrode. Consists of wealth. As the rolled electrode passes through the roll press, the rolling process proceeds, and it is wound in a rolled state to complete the electrode. At this time, the pressurization pressure of the press is preferably 1 to 20 ton/cm 2 and the temperature of the roll is 0 to 150°C. The composition for a positive electrode for a lithium secondary battery that has undergone the press-compression process as described above undergoes a drying process. The drying process is carried out at a temperature of 100°C to 350°C, preferably 150°C to 300°C. In this case, when the drying temperature is less than 100°C, evaporation of the solvent is difficult, which is not preferable, and when drying at a high temperature exceeding 350°C, oxidation of the conductive material may occur, which is not preferable. Therefore, it is preferable that the drying temperature is at least 100°C or higher and does not exceed 350°C. And the drying process is preferably carried out for about 10 minutes to 6 hours at the same temperature as above. This drying process improves the strength of the electrode by drying the formed lithium secondary battery positive electrode composition (solvent evaporation) and binding the powder particles.

In addition, looking at another example of forming an electrode, the composition for a positive electrode of a lithium secondary battery is applied to a metal foil such as a titanium foil, an aluminum foil, and an aluminum etching foil. It may be coated, or the composition for a positive electrode of a lithium secondary battery is pushed with a roller to form a sheet (rubber type) and attached to a metal foil or a metal current collector to form an electrode shape. The aluminum etching foil means that the aluminum foil is etched in an uneven shape. The electrode shape that has undergone the above process is subjected to a drying process. It is carried out at a temperature of 100°C to 250°C, preferably 150°C to 200°C.

The lithium secondary battery positive electrode prepared as described above can be usefully applied to a lithium secondary battery of a desired type such as a coin cell.

2 is a diagram illustrating a state of use of a lithium secondary battery according to an example, and is a cross-sectional view of a coin-type lithium secondary battery to which a positive electrode of the lithium secondary battery is applied. In FIG. 1, reference numeral 190 denotes a metal cap as a conductor, reference numeral 160 denotes a separator made of a porous material for insulation and short-circuit prevention between the anode 120 and the cathode 110, and reference numeral 192 denotes a leakage of electrolyte. It is a gasket to prevent the insulation and to prevent short circuit. At this time, the positive electrode 120 and the negative electrode 110 are firmly fixed by a metal cap 190 and an adhesive.

The coin-type lithium secondary battery is disposed between the positive electrode 120 of the lithium secondary battery, the negative electrode 110 made of lithium metal, and the positive electrode 120 and the negative electrode 110, and is disposed between the positive electrode 120 and the negative electrode ( A separator 160 for preventing a short circuit of 120) is placed in the metal cap 190, and an electrolyte is injected between the anode 120 and the cathode 110, and then sealed with a gasket 192. can do.

The separator is a polyethylene nonwoven fabric, a polypropylene nonwoven fabric, a polyester nonwoven fabric, a polyacrylonitrile porous separator, a poly(vinylidene fluoride) hexafluoropropane copolymer porous separator, a cellulose porous separator, a kraft paper or rayon fiber, etc. It is not particularly limited as long as it is a separator generally used in the field.

The electrolyte may be an electrolyte in which an electrolyte such as LiPF ₆ , LiBF ₄ , LiClO ₄ , Li(CF ₃ SO ₂ ) ₂ , LiCF ₃ SO ₃ , LiSbF ₆ or LiAsF ₆ is dissolved in an organic solvent. The organic solvent is acetonitrile, propylene carbonate, ethylene carbonate, ethylmethyl carbonate, dimethyl carbonate, diethyl carbonate, butylene carbonate, vinylene carbonate, tetrahydrofuran, 1,2-dioxane, It may contain one or more substances selected from the group consisting of 2-methyltetrahydrofuran, butyrolactone, and dimethylformamide.

In the lithium secondary battery manufactured as described above, a positive electrode and a negative electrode are arranged to be spaced apart from each other, a separator for preventing a short circuit between the positive electrode and the negative electrode is disposed between the positive electrode and the negative electrode, and the positive electrode and the negative electrode Silver is impregnated in the electrolyte of a lithium secondary battery.

In the following, examples according to the present invention are specifically presented, and the present invention is not limited to the following examples.

<Example 1>

Lithium nitrate, nickel nitrate, and manganese nitrate were prepared as sources of lithium, nickel and manganese.

Lithium nitrate, nickel nitrate, manganese nitrate, and sugar were sequentially added to a beaker containing 200 ml of distilled water to form a mixture. At this time, the amounts of lithium nitrate, nickel nitrate, manganese nitrate, and sugar (sucrose) were respectively added to 0.021M, 0.01M, 0.03M, and 0.01M.

The mixture was stirred in a stirrer, and then heated in a water bath at 120° C. for 6 hours in ethylene glycol. The heating of the bath was performed until the mixture was squashed and then swollen over the beaker.

After drying the heated product in an oven at 120℃ for 24 hours, heat-treating in an air atmosphere for 3 hours at 800℃ in a vertical furnace, cooling to 600℃ and annealing at 600℃ for 12 hours After that, it was cooled down.

The annealed resultant was subjected to reduction heat treatment at 700° C. for 12 hours in a reducing atmosphere in which 5% by volume of H ₂ was mixed with Ar to obtain a positive electrode active material in which Ni metal was eluted.

Ni metal eluted cathode active material, conductive material Super-P (super-P) 0.1g, binder polyvinylidenefloride (PVDF) 0.1g and solvent N-methylpyrrolidone (NMP) 1.5g Uniformly mixed to prepare a lithium secondary battery positive electrode composition.

The composition for a positive electrode of a lithium secondary battery was uniformly pressed onto an Al foil at a pressure of 5 ton/cm2 using an Ex-met, and vacuum dried at 120° C. to prepare a positive electrode for a lithium secondary battery.

Using the positive electrode and lithium metal (cathode), a lithium secondary battery in the form of a coin cell having a diameter of 20 mm and a height of 3.2 mm was manufactured. Using a porous polyethylene membrane as a separator, and using a solution in which 1.15M LiPF ₆ is dissolved in a mixed solvent in which ethylene carbonate, ethylmethyl carbonate and dimethyl carbonate are mixed in a volume ratio of 3:3:4 is used as an electrolyte to prepare a lithium secondary battery According to the process, a 2032 standard coin cell was manufactured.

In order to evaluate the characteristics of the high-voltage lithium secondary battery manufactured in this way, a charge/discharge experiment was conducted by applying a voltage range of 3.5 to 5.0 V and various currents at room temperature using an electrochemical analysis device (Maccor, USA, S-4000). Proceeded.

A comparative example is presented so that the characteristics of Example 1 can be more easily grasped, and the comparative examples below are presented merely to aid understanding and are not prior art of the present invention.

<Comparative Example>

Lithium nitrate, nickel nitrate, and manganese nitrate were prepared as sources of lithium, nickel and manganese.

Lithium nitrate, nickel nitrate, manganese nitrate, and sugar were sequentially added to a beaker containing 200 ml of distilled water to form a mixture. At this time, the amounts of lithium nitrate, nickel nitrate, manganese nitrate, and sugar (sucrose) were respectively added to 0.021M, 0.01M, 0.03M, and 0.01M.

The mixture was stirred in a stirrer, and then heated in a water bath at 120° C. for 6 hours in ethylene glycol. The heating of the bath was performed until the mixture was squashed and then swollen over the beaker.

After drying the heated product in an oven at 120℃ for 24 hours, the dried product was heat-treated in an air atmosphere for 3 hours at 800℃ in a vertical furnace, cooled to 600℃, and then cooled to 600℃. After annealing for 12 hours, it was cooled by furnace to obtain a cathode active material LiNi _0.5 Mn _1.5 O ₄ .

Positive electrode active material LiNi _{0 . 5} Mn _{1 . 5} O ₄ 0.8g, conductive material Super-P 0.1g, binder polyvinylidenefloride (PVDF) 0.1g and solvent N-methylpyrrolidone (NMP) 1.5g uniformly By mixing, a composition for a positive electrode of a lithium secondary battery was prepared.

The composition for a positive electrode of a lithium secondary battery was uniformly pressed onto an Al foil at a pressure of 5 tons/cm 2 using an Ex-met, and vacuum dried at 120° C. to prepare a positive electrode for a lithium secondary battery. .

Using the positive electrode and lithium metal (cathode), a lithium secondary battery in the form of a coin cell having a diameter of 20 mm and a height of 3.2 mm was manufactured. Using a porous polyethylene membrane as a separator, and using a solution in which 1.15M LiPF ₆ is dissolved in a mixed solvent in which ethylene carbonate, ethylmethyl carbonate and dimethyl carbonate are mixed in a volume ratio of 3:3:4 is used as an electrolyte to prepare a lithium secondary battery According to the process, a 2032 standard coin cell was manufactured.

In order to evaluate the characteristics of the manufactured lithium secondary battery, a charge/discharge experiment was conducted by applying a voltage range of 3.5 to 5.0 V and various currents at room temperature using an electrochemical analysis device (Maccor, USA, S-4000). I did.

3 is a positive electrode active material LiNi ₀ prepared according to the comparative example _{. 5} Mn _{1 . 5} O ₄ is a scanning electron microscope (SEM) picture, and FIG. 4 is a scanning electron microscope (SEM) picture showing a cathode active material in which Ni metal manufactured according to Example 1 is eluted.

3 and 4, when comparing the positive electrode active material prepared according to the comparative example and the positive electrode active material prepared according to Example 1, small particles are distributed on the surface of the positive electrode active material in the positive electrode active material prepared according to Example 1. It can be seen that these small particles were formed by eluting Ni metal.

5 is a diagram showing electrochemical analysis results of a lithium secondary battery manufactured according to a comparative example and a lithium secondary battery manufactured according to Example 1. FIG.

5, it was found that the specific storage capacity of the lithium secondary battery manufactured according to Example 1 was superior to that of the lithium secondary battery manufactured according to the comparative example.

In the above, a preferred embodiment of the present invention has been described in detail, but the present invention is not limited to the above embodiment, and various modifications are possible by those of ordinary skill in the art.

110: cathode 120: anode
160: separator 190: metal cap
192: gasket

Claims (14)

Mixing a lithium source, a nickel source, and a manganese source in a solvent to form a mixture;
Heating the mixture to react;
Drying the reacted product;
Performing a first heat treatment on the dried product; And
A method of producing a lithium-nickel-manganese oxide positive electrode active material for a lithium secondary battery, comprising the step of allowing the Ni metal to elute by performing a second heat treatment on the first heat-treated result in a reducing atmosphere.
The method of claim 1, wherein in the forming of the mixture, the mixture is formed by further mixing sugar (sucrose).
The lithium secondary battery according to claim 1, wherein the lithium source contains at least one material selected from the group consisting of lithium nitrate (LiNO ₃ ), lithium sulfate (Li ₂ SO ₄ ), and lithium chloride (LiCl). Method for producing a lithium-nickel-manganese oxide positive electrode active material.
The method of claim 1, wherein the nickel source comprises at least one material selected from the group consisting of nickel nitrate (Ni(NO ₃ ) ₂ ), nickel sulfate (NiSO ₄ ), and nickel chloride (NiCl ₂ ). Method for producing a lithium-nickel-manganese oxide positive electrode active material for a lithium secondary battery.
The lithium of claim 1, wherein the manganese source contains at least one material from the group consisting of manganese nitrate (Mn(NO ₃ ) ₂ ), manganese sulfate (MnSO ₄ ) and manganese chloride (MnCl ₂ ). Method for producing a lithium-nickel-manganese oxide positive electrode active material for a secondary battery.
The lithium secondary according to claim 1, wherein the lithium source, the nickel source, and the manganese source are mixed so that the molar ratio of Li:Ni:Mn is 1:x:2-x (0<x≤0.5). Method for producing a lithium-nickel-manganese oxide positive electrode active material for batteries.
The method of claim 1, wherein the first heat treatment is performed in an oxidizing atmosphere. 7. A method of manufacturing a lithium-nickel-manganese oxide positive electrode active material for a lithium secondary battery.
The method of claim 1, wherein the first heat treatment is performed at a temperature of 700 to 900° C., wherein the lithium-nickel-manganese oxide positive electrode active material is performed for a lithium secondary battery.
The method of claim 8, further comprising performing annealing at a temperature of 400 to 650° C. after the first heat treatment. 12. The method of manufacturing a lithium-nickel-manganese oxide positive electrode active material for a lithium secondary battery.
The method of claim 1, wherein the second heat treatment is performed at a temperature of 650 to 900° C., wherein the lithium-nickel-manganese oxide positive electrode active material is performed for a lithium secondary battery.
The method of claim 1, wherein the second heat treatment is performed in a mixed gas atmosphere of an inert gas and hydrogen (H ₂ ) gas.
The method of claim 1, wherein the heating is performed by heating a bath water. The lithium-nickel-manganese oxide cathode active material for a lithium secondary battery is manufactured.
Mixing the lithium-nickel-manganese oxide positive electrode active material for a lithium secondary battery according to claim 1, a conductive material, a binder, and a solvent to prepare a composition for a positive electrode of a lithium secondary battery;
The composition for a positive electrode for a lithium secondary battery is pressed to form an electrode, or the composition for a positive electrode for a lithium secondary battery is coated on a metal foil to form an electrode, or the composition for a positive electrode for a lithium secondary battery is pushed with a roller to form a sheet. Attaching to a metal foil or a current collector to form an electrode shape; And
A method of manufacturing a positive electrode for a lithium secondary battery, comprising the step of forming a positive electrode of a lithium secondary battery by drying the resultant product formed in the form of an electrode.
The positive electrode of the lithium secondary battery manufactured by the method of claim 13 and the negative electrode including lithium metal are disposed to be spaced apart from each other,
A separator is disposed between the anode and the cathode to prevent a short circuit between the anode and the cathode,
The positive electrode and the negative electrode are lithium secondary battery, characterized in that impregnated in an electrolyte.

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