KR20040092245A - 5V spinel complex-oxide prepared by ultrasonic spray pyrolysis methode, method for preparing the same, and lithium secondary batteries using the same - Google Patents

Abstract

PURPOSE: Provided is a homogeneous composite oxide in the form of a solid solution, which has a particle diameter of 1-10 micrometers, provides excellent charge/discharge cycle and capacity maintenance characteristics, and thus is useful for a cathode active material for 5V-grade lithium secondary batteries. CONSTITUTION: The 5V-grade spinel composite oxide in the form of a solid solution is represented by the formula of Li1+x£Ni(1/2+a)Mn(3/2-2a)Moa|O4, wherein each of x and a ranges from 0 and 0.1. The composite oxide is prepared by the method comprising the steps of: forming a lithium-nickel-manganese composite solid solution oxide and a lithium-nickel-manganese-molybdenum composite solid solution oxide by an ultrasonic spray method; and calcining and annealing the lithium-nickel-manganese composite solid solution oxide and the lithium-nickel-manganese-molybdenum composite solid solution oxide.

Description

5Ｖ spinel complex-oxide prepared by ultrasonic spray pyrolysis methode, method for preparing the same, and lithium secondary batteries using the same}

The present invention relates to a cathode active material for a lithium secondary battery, and more particularly to the composition formula Li _{1 + x} [Ni ( _{1/2 + a} ) Mn ( _{3 / 2-2 a} ) Mo _a ] O ₄ (0≤x≤0.1, It relates to a 5V class spinel composite solid oxide of 0≤a≤0.1), a method for manufacturing the same, and a lithium secondary battery including the 5V class spinel composite solid oxide. Recently, charging and discharging have been repeatedly performed using portable electronic devices for information and communication such as mobile phones, PDAs, notebook PCs, portable electronic devices such as digital cameras, camcorders, MP3s, electric bicycles, and electric vehicles. The demand for secondary batteries used is growing exponentially. In particular, since the performance on the portability of these products depends on the secondary battery, which is a key component, the demand for a high performance battery is very large. The characteristics required for the battery have various aspects such as charge and discharge characteristics, lifespan, high rate characteristics and stability at high temperatures. Among lithium secondary batteries, 5V class spinel cathode active materials are the most popular cathode active materials because they have high energy density due to high voltage.

Commercially available lithium secondary batteries use LiCoO ₂ for the positive electrode and carbon for the negative electrode. However, cobalt, which is the starting material of cathode active material, has low reserves and is expensive, and there is a need to develop alternative anode materials due to toxicity and environmental pollution problems. LiNiO ₂ , LiCo _x Ni _1-x O ₂ and LiMn ₂ O ₄ are the anode materials currently being actively researched and developed. LiNiO ₂ which has the same layer structure as LiCoO ₂ is not commercialized due to difficulty in material synthesis of stoichiometric ratio and thermal stability problem, and LiMn ₂ O ₄ is commercialized in low cost products. However, the 4V spinel cathode active material LiMn ₂ O ₄ has the advantage of using manganese as a base material, but its life characteristics are not good because of the structural variation called Jahn-Teller distortion caused by manganese ³⁺ . Therefore, 5V-grade spinel cathode active materials have been studied as a material capable of overcoming the problems of low energy density while taking advantage of manganese oxide. The 5V spinel cathode active material is expected to be used as an electrode material capable of high output due to the improvement of energy density due to high voltage.

The most common method for producing a positive electrode active material is a solid phase reaction method, which is prepared by several processes of mixing and firing powders of carbonates or hydroxides of each element as raw materials. Disadvantages of the method include a lot of impurity inflow from the ball mill during mixing, a heterogeneous reaction is likely to occur, it is difficult to obtain a uniform phase, it is difficult to control the size of the powder particles uniformly, and the sinterability is poor, will be. On the other hand, in the wet method of controlling elemental elements in the atomic range, lithium salts (lithium nitrate, lithium hydroxide) and the like are initially used for the production of the positive electrode active material for lithium secondary batteries by ultrasonic spray pyrolysis. Spray pyrolysis has been proposed, which dissolves together, is sprayed by ultrasonic waves, and pyrolyzes through a reactor.

However, the spray pyrolysis method including lithium salts, due to the low vapor pressure of lithium, a large amount of lithium evaporates during spray pyrolysis, the amount of lithium of the final product obtained is out of the preferred range of the starting material. In addition, the production of manganese oxide of 3 ⁺ during the sintering reaction causes Yanteller distortion, and when the manganese oxide containing Mn ³⁺ is used as a positive electrode active material for lithium secondary batteries, the charge and discharge cycle is repeated, the determination of the active material The structure collapses and the battery life characteristics are also degraded.

Accordingly, an object of the present invention is to solve the above problems, and to provide a 5V class spinel cathode active material and a method of manufacturing the 5V class spinel cathode active material and molybdenum (Mo) partially used as a cathode active material of a lithium secondary battery. It is done.

In addition, an object of the present invention is to provide a lithium secondary battery comprising the 5V class spinel cathode active material.

1 is a SEM photograph of a composite solid oxide prepared by the method i) of Example 1. FIG.

2 is a SEM photograph of the composite solid oxide prepared by the method ii) of Example 1. FIG.

3 is an XRD pattern of a composite solid oxide prepared by the method ii) of Example 1. FIG.

4 is a charge / discharge curve of a half cell experimented at a voltage range of 3.5 to 5.0 mA and a constant current density of 0.2 mA / cm ² of the composite solid oxide prepared by the method ii) of Example 1. FIG.

FIG. 5 is a graph of discharge capacity of a half cell experimented at a voltage range of 3.5 to 5.0 mA and a constant current density of 0.2 mA / cm ² of the composite solid oxide prepared by the method ii) of Example 1. FIG.

6 is a SEM photograph of a composite solid oxide prepared by the method i) of Example 6. FIG.

7 is a SEM photograph of the composite solid oxide prepared by the method ii) of Example 6.

8 is an XRD pattern of the composite solid oxide prepared by the methods ii) to iv) of Example 6. FIG.

FIG. 9 is a charge / discharge curve of a half cell tested in a voltage range of 3.5 to 5.0 V and a constant current density of 0.2 mA / cm ² of the composite solid oxide prepared by the methods ii) to iv) of Example 6. FIG.

FIG. 10 is a graph of discharge capacity of a half cell tested in a voltage range of 3.5 to 5.0 V and a constant current density of 0.2 mA / cm ² of the composite solid oxide prepared by the methods ii) to iv) of Example 6. FIG.

FIG. 11 is a charge / discharge curve of a half cell tested in the voltage range of 3.5 to 5.0 V and the constant current density of 0.2 mA / cm ² of the composite solid solution oxides prepared by the methods ii) of Example 1 and ii) of Example 2. FIG.

To this end, the present invention is a 5V class of the composition formula Li _{1 + x} [Ni ( _{1/2 + a} ) Mn ( _{3 / 2-2a} ) Mo _a ] O ₄ ( _0≤x≤0.1 , _0≤a≤0.1 ) Provided is a spinel composite solid oxide.

In one embodiment, nickel, manganese, and molybdenum have a oxidation number of 2 ⁺ , 4 ⁺ , and 6 ⁺ , and provides a 5V class spinel composite solid oxide oxide having a total of 3 ⁺ oxidation numbers.

According to another embodiment of the present invention, there is provided a method of forming a lithium-nickel-manganese composite solid solution oxide, a lithium-nickel-manganese-molybdenum composite solid solution oxide through ultrasonic spray pyrolysis; And calcining and annealing the lithium-nickel-manganese composite solid oxide, and the lithium-nickel-manganese-molybdenum composite solid oxide, wherein the compositional formula Li _{1 + x} [Ni ( _{1/2 + a) Provided} is _a method for producing a 5V class spinel composite solid oxide of Mn ( _{3 / 2-2a} ) Mo _a ] O ₄ (0 _{≦ x ≦ 0.1} , 0 _{≦ a ≦ 0.1} ).

As an embodiment of the present invention, the step of forming a lithium-nickel-manganese composite solid solution oxide, lithium-nickel-manganese-molybdenum composite solid oxide through ultrasonic spray pyrolysis may include preparing a metal salt solution; Preparing a mixed solution of adding a chelating agent to the metal salt solution; Ultrasonically spraying the mixed solution to prepare a droplet; And thermally decomposing the droplet phase, wherein the composition formula Li _{1 + x} [Ni ( _{1/2 + a} ) Mn ( _{3 / 2-2a} ) Mo _a ] O ₄ (0 _{≦ x ≦ 0.1} , It provides a method for producing a 5V spinel composite solid oxide of 0≤a≤0.1).

In one embodiment, the chelating agent is selected from the group consisting of tartaric acid, urea, citric acid, formic acid, glycolic acid, polyacrylic acid, adipic acid, glycine Li _{1 + x} [Ni ( _{1 / Provided} is _a method for preparing a 5V class spinel composite solid oxide of _{2 + a} ) Mn ( _{3 / 2-2a} ) Mo _a ] O ₄ (0 _{≦ x ≦ 0.1} , 0 _{≦ a ≦ 0.1} ).

As another embodiment, the present invention provides a lithium secondary battery including the 5V class spinel composite solid oxide.

The 5V class spinel composite solid oxide of the present invention has a composition formula of Li _{1 + x} [Ni ( _{1/2 + a} ) Mn ( _{3 / 2-2a} ) Mo _a ] O ₄ . Where 0 ≦ x ≦ 0.1 and 0 ≦ a ≦ 0.1. When a is 0, the oxide is a lithium-nickel-manganese composite solid oxide of Formula 1 below.

Li _{1 + x} [Ni _1/2 Mn _3/2 ] O ₄ (0≤x≤0.1)

In order to form the lithium-nickel-manganese composite solid oxide, a metal salt is used as a precursor of a metal, and the metal salt is preferably selected from the group consisting of nitrate, acetate, chloride, and formate. First, a powdered lithium-nickel-manganese composite oxide is prepared by ultrasonic spray pyrolysis. The powdered composite oxide was calcined at 700 ° C. to 1100 ° C. and annealed at 700 ° C. for 12-48 hr to obtain a spinel structure lithium-nickel-manganese composite oxide having an average particle diameter of about 1-10 μm.

When a> 0, the compound is a lithium-nickel-manganese-molybdenum composite solid oxide of the formula (2).

Li _{1 + x} [Ni ( _{1/2 + a} ) Mn ( _{3 / 2-2a} ) Mo _a ] O ₄ (0 ≦ x ≦ 0.1, 0 <a ≦ 0.1)

Oxidation number of Ni in the above composition formula is ⁺ 2, Mn ⁺ 4, molybdenum is 6 ^+. Metal salts are used as precursors of metal lithium, nickel, and manganese to form the composite solid oxide oxide of lithium-nickel-manganese-molybdenum, and the metal salt is selected from the group consisting of nitrate, acetate, chloride, and formate. It is preferable. And molybdenum trioxide (MoO ₃ ) is used as a precursor of the metal molybdenum. First, a powdered lithium-nickel-manganese-molybdenum composite oxide is prepared by ultrasonic spray pyrolysis. The powdered composite oxide was calcined at 700 ° C. to 1,100 ° C. and annealed at 700 ° C. for 12-48 hr to obtain a spinel structure lithium-nickel-manganese-molybdenum composite oxide having an average particle diameter of about 1-10 μm.

Hereinafter, a method of preparing a composite solid oxide of Formula 1 and Formula 2 and a method of manufacturing a positive electrode and a coin battery using the composite solid oxide will be described in detail. However, the present invention is not limited to the following examples.

Example 1 ( Preparation of 5V class spinel cathode active material Li _{1 + x} [Ni _1/2 Mn _3/2 ] O ₄ )

1) Lithium nitrate (LiNO ₃ ) and nickel nitrate (Ni (NO ₃ ) ₂ · 6H ₂ O as starting materials to prepare 5V class spinel cathode active material Li _{1 + x} [Ni _1/2 Mn _3/2 ] O ₄ ) And manganese nitrate (Mn (NO ₃ ) ₂ .4H ₂ O) were used. The starting material was quantified in a stoichiometric ratio Li: Ni: Mn: = 1.02: 1/2: 3/2 and dissolved in distilled water. Urea was added as a chelating agent to the metal salt solution, followed by stirring to prepare a mixed solution. The stoichiometric ratio was made into urea: total metal ion = 0.2: 1. Next, the mixed solution was ultrasonically sprayed using a 1.7 MHz oscillator to generate droplets. The mixed solution of the droplet phase was passed through a vertical pyrolysis furnace at 500 ° C. to obtain a powdery solid solid oxide Li _1.02 [Ni _1/2 Mn _3/2 ] O ₄ . The powdered composite solid oxide was placed in an alumina container, calcined at 1000 ° C., and annealed at 700 ° C. to obtain a composite solid oxide Li _1.02 [Ni _1/2 Mn _3/2 ] O ₄ having a spinel structure as a final oxide.

ii) A spinel-structured composite solid oxide Li _1.02 [Ni _1/2 Mn _3/2 ] O ₄ was prepared in the same manner as in i) except that the vertical pyrolysis temperature was 1000 ° C.

Example 2 (Characteristic Evaluation of Composite Solid Oxide)

i) SEM

The SEM (trade name: JSM 6400, company name: JEOL, Japan) photographs of the composite solid oxide prepared in the method of Example 1 i) and ii) are shown in FIGS. 1 and 2. It can be seen that the size of the particles are uniform with a size of 1 ~ 5㎛.

ii) XRD

The X-ray diffraction pattern of the composite solid oxide prepared in the method ii) of Example 1 was measured using an X-ray diffraction analyzer (trade name: Rint-2000, company name: Rigaku, Japan) and this is shown in FIG. 3. .

Example 3 (Production of Anode)

In order to prepare a positive electrode with a 5V-grade spinel cathode active material prepared by the method of ii) of Example 1, 20 mg of a composite solid oxide, 8 mg of Teflonized acetylene black, and 4 mg of graphite were uniformly mixed. It was. The mixture was uniformly compressed at a pressure of 1 ton using stainless ex-met, and dried at 100 ° C. to prepare a cathode for a lithium secondary battery.

Example 4 (Manufacture of Coin Battery)

An anode prepared by the method of Example 3 and a lithium foil as a counter electrode, and a porous polyethylene membrane (Celgard ELC, Celgard 2300, thickness: 25㎛) as a separator, ethylene carbonate: dimethyl carbonate = 1 A coin cell of 2032 standard was prepared according to a conventional manufacturing process of a lithium battery using a 1 mol LiPF ₆ solution of a: 1 (volume ratio) mixed solvent as a liquid electrolyte.

Example 5 (Characteristic Evaluation of Battery)

In order to evaluate the characteristics of the battery manufactured by the method of Example 4 using an electrochemical analyzer (Toscat3000U, Japan, manufactured by Toyo), the potential region of 30 ℃, 3.5 ~ 5.0 V, and 0.2mA / cm ² Charge and discharge experiments were conducted under current density conditions. Charge and discharge curves and discharge capacities are shown in FIGS. 5 and 6. The initial discharge capacity was 128mAh / g, and the sustained discharge capacity was 130mAh / g until the 50th cycle.

Example 6 ( Preparation of 5V class spinel cathode active material Li _{1 + x} [Ni ( _{1/2 + a} ) Mn ( _{3 / 2-2a} ) Mo _a ] O ₄ )

i) Lithium nitrate (LiNO ₃ ) and nickel nitrate (LiNO ₃ ) as starting materials for preparing 5V class spinel cathode active material Li _{1 + x} [Ni ( _{1/2 + a} ) Mn ( _{3 / 2-2a} ) Mo _a ] O ₄ Ni (NO ₃ ) ₂ .6H ₂ O), manganese nitrate (Mn (NO ₃ ) ₂ .4H ₂ O), and molybdenum trioxide (MoO ₃ ) were used. The starting material was quantified in a ratio of Li: Ni: Mn: Mo = 1.02: 0.52: 1.46: 0.02 and dissolved in distilled water. In the case of molybdenum trioxide, however, since it does not dissolve in a general acid atmosphere, it was first dissolved in ammonia water (NH ₄ OH) and mixed. Urea was added as a chelating agent to the metal salt solution, followed by stirring to prepare a mixed solution. The stoichiometric ratio was made into urea: total metal ion = 0.2: 1. Next, the mixed solution was ultrasonically sprayed using a 1.7 MHz oscillator to generate droplets. The mixed solution of the liquid phase was passed through a vertical pyrolysis furnace at 500 ° C. to obtain a powdery solid solid oxide Li _1.05 (Ni _0.52 Mn _1.46 Mo _0.02 ) O ₄ . The powdered solid solid oxide was placed in an alumina container, calcined at 1000 ° C., and annealed at 700 ° C. to obtain a composite solid solid oxide Li _1.02 (Ni _0.52 Mn _1.46 Mo _0.02 ) O ₄ having a spinel structure as a final oxide.

Ii) A spinel-structured composite solid oxide Li _1.02 (Ni _0.52 Mn _1.46 Mo _0.02 ) O ₄ was prepared in the same manner as in i) except that the vertical pyrolysis temperature was 1000 ° C.

iii) A compound solid oxide Li _1.02 (Ni _0.51 Mn _1.48 Mo) having a spinel structure in the same manner as in ii), except that the starting material was quantitatively determined as Li: Ni: Mn: Mo = 1.02: 0.51: 1.48: 0.01 in stoichiometric ratio. _0.01 ) O ₄ was prepared.

iv) The composite solid oxide oxide Li _1.02 (Ni _0.55 Mn _1.40 Mo) having a spinel structure in the same manner as in ii) except that the starting material was quantitatively determined as Li: Ni: Mn: Mo = 1.02: 0.55: 1.40: 0.05 in a stoichiometric ratio. _0.05 ) O ₄ was prepared.

Example 7 Evaluation of Characteristics of Composite Solid Oxide

i) SEM

6 and 7 show SEM photographs of the composite solid solution oxide prepared by the method of Example 6) i) to ii). It can be seen that the size of the particles is uniform (?? ㎛).

ii) XRD

The X-ray diffraction pattern of the composite solid solution oxide prepared in the method ii) to iv) of Example 6 was measured using an X-ray diffraction analyzer, and the results are shown in FIG. 8. All samples prepared were very good in crystallinity.

Example 8 (Production of Anode)

A positive electrode was manufactured in the same manner as in Example 3, using the 5V spinel positive electrode active material prepared by the methods ii) to iv) of Example 6.

Example 9 (Manufacture of Coin Battery)

In the same manner as in Example 4, a coin battery including the positive electrode manufactured by the method of Example 8 was prepared.

Example 10 (evaluation of characteristics of battery)

In order to evaluate the characteristics of the coin battery manufactured by the method of Example 9, a potential region of 30 ° C., 3.5 to 5.0 V, and 0.2 mA / cm ² using an electrochemical analyzer (manufactured by Toyo, Toscat3000U, Japan) Charging and discharging experiments were conducted under current density conditions of. Charge and discharge curves and discharge capacities are shown in FIGS. 9 and 10. In all the cells manufactured, there was almost no capacity decrease with the cycle number.

Example 11 (Characteristic Evaluation of a Battery Comprising Lithium-Nickel-Manganese Composite Solid Oxide and Lithium-Nickel-Manganese-Molybdenum Composite Solid Oxide)

Charge and discharge experiments with a battery containing the composite solid oxide prepared by the method of Example 1 ii) and Example 6 ii) to compare the battery characteristics of the composite solid oxide partially substituted with molybdenum Was done. The pattern and the discharge capacity of the charge / discharge curve of FIG. 11 were found to substantially match.

The composite solid oxide of the present invention Li _{1 + x} [Ni ( _{1/2 + a} ) Mn ( _{3 / 2-2a} ) Mo _a ] O ₄ (0 _{≦ x ≦ 0.1} , 0 _{≦ a ≦ 0.1} ) has a particle diameter It is homogeneous with 1-10 micrometers, and is excellent in a battery characteristic, ie, a charge / discharge cycle characteristic, and a capacity storage characteristic, and can be used as a 5V class positive electrode active material for lithium secondary batteries.

Claims (6)

A 5V class spinel composite solid oxide of composition Li _{1 + x} [Ni ( _{1/2 + a} ) Mn ( _{3 / 2-2a} ) Mo _a ] O ₄ (0 _{≦ x ≦ 0.1} , 0 _{≦ a ≦ 0.1} ). The method of claim 1, wherein the nickel, manganese, and molybdenum 2 ^+, 4 ^+, and having an oxidation number of ⁺ 6, 5V-class spinel composite oxide solid solution, characterized in that having an oxidation number of a total of 3 ^+. Forming a lithium-nickel-manganese composite solid oxide, a lithium-nickel-manganese-molybdenum composite solid oxide through ultrasonic spray pyrolysis; And Calcining and annealing the lithium-nickel-manganese composite solid oxide and the lithium-nickel-manganese-molybdenum composite solid oxide, wherein the compositional formula Li _{1 + x} [Ni ( _{1/2 + a} ) A method for producing a 5V class spinel composite solid oxide of Mn ( _{3 / 2-2a} ) Mo _a ] O ₄ (0 _{≦ x ≦ 0.1} , 0 _{≦ a ≦ 0.1} ). The method of forming a lithium-nickel-manganese composite solid solution oxide and a lithium-nickel-manganese-molybdenum composite solid oxide by the ultrasonic spray pyrolysis of claim 3 Preparing a metal salt solution; Preparing a mixed solution of adding a chelating agent to the metal salt solution; Ultrasonically spraying the mixed solution to prepare a droplet; And A composition Li _{1 + x} [Ni ( _{1/2 + a} ) Mn ( _{3 / 2-2a} ) Mo _a ] O ₄ (0 _{≦ x ≦ 0.1} , 0 _≦ a≤0.1) of 5V spinel composite solid oxide production method. The chelating agent of claim 4, wherein the chelating agent is selected from the group consisting of tartaric acid, urea, citric acid, formic acid, glycolic acid, polyacrylic acid, adipic acid, glycine, Li _{1 + x} [Ni ( _{1/2 + a} ) Mn ( _{3 / 2-2a} ) Method for producing 5V class spinel composite solid oxide of Mo _a ] O ₄ (0 _{≦ x ≦ 0.1} , 0 _{≦ a ≦ 0.1} ). A lithium secondary battery comprising the 5V class spinel composite solid oxide of claim 1.