KR20060130964A - Core-shell spinel cathode active materials for lithium secondary batteries, lithium secondary batteries using the same and method for preparing thereof - Google Patents

Abstract

Provided are a positive electrode active material for lithium secondary batteries, which has high packing density and good thermal safety and is superior in life, capacity, and rate characteristics, and a manufacturing method thereof. The positive electrode active material for lithium secondary batteries has a core/shell multi-layered structure. The core portion is formed of Li_(1+a)Mn_(2-a)O_(4-y)A_(y), wherein A is at least one element selected from F or S, 0.04<=a<=0.15, and 0.02<=y<=0.15. The shell portion is formed of Li[Li_(a)(Mn_(1-x)M_(x))_(1-a)]_(2)O_(4-y)A_(y), wherein M is at least one element selected from the group consisting of Fe, Co, Ni, Cu, Cr, V, Ti, and Zn, 0.01<=a<=0.333, 0.01<=x<=0.6, and 0.02<=y<=0.15. The positive electrode active material particles have a particle size of 1-50mum.

Description

Core-shell spinel cathode active materials for lithium secondary batteries, lithium secondary batteries using the same and Method for preparing knowledge}

1 is a cross-sectional view of a reactor used in the production method of the present invention,

Figure 2 is a cross-sectional view of a double layer core shell structure of the positive electrode active material prepared in the present invention,

3 is a SEM photograph of (Ni _0.025 Mn _0.975 ) ₃ O ₄ precursor, which is a core part in the present invention,

Fig. 4 is a cross-sectional SEM photograph of _0.3 precursor ((Ni _0.025 Mn _0.975 ) ₃ O ₄ ) _0.7 (Ni _0.25 Mn _0.75 (OH) 2) which is a core-shell multilayer structure obtained by the present invention.

5 is a SEM photograph of the surface of ((Ni _0.025 Mn _0.975 ) ₃ O ₄ ) _0.7 (Ni _0.25 Mn _0.75 (OH) 2) _0.3 precursor having a core-shell multilayer structure obtained by the present invention.

6 is a SEM photograph of the precursor surface of the core-shell multilayer structure obtained in Example 3 of the present invention;

7 is an X-ray diffraction pattern of the precursor and manganese precursor of the core-shell multilayer structure obtained by the present invention,

8 is an X-ray diffraction pattern of a cathode active material and manganese oxide of the core-shell multilayer structure obtained by the present invention,

9 is a comparative X-ray diffraction pattern of a positive electrode active material with a fluorine-containing multi-layered core structure obtained by the present invention and a positive electrode active material after a 200 cycle battery test,

10 is a graph showing the life characteristics of the cathode active material synthesized in Examples 1 to 2 and Comparative Example 1 according to the charge and discharge cycle at high temperature (60 ℃),

11 is a graph showing the life characteristics according to the charge and discharge cycle at high temperature (60 ℃) of the positive electrode active material synthesized in Example 8, Comparative Example 5 of the present invention,

12 is a graph showing the life characteristics of the positive electrode active material synthesized in Example 3, Comparative Example 2 according to the charge and discharge cycle at high temperature (60 ℃),

13 is a graph showing the life characteristics of the positive electrode active material synthesized in Example 7, Comparative Example 4 according to the charge and discharge cycle at a high temperature (60 ℃),

14 is a graph showing the life characteristics of the positive electrode active material synthesized in Example 6 and Comparative Example 4 according to the charge and discharge cycle at a high temperature (60 ℃).

Lithium-ion secondary batteries have been widely used as mobile power sources for mobile devices since they were commercialized by Sony Corporation in Japan in 1991. Recently, with the rapid development of electronics, telecommunications, and computer industry, camcorders, mobile phones, notebook PCs, etc. have emerged, and they are developing remarkably, and the demand for lithium ion secondary battery is increasing day by day as a power source to drive these portable electronic information devices. Doing. Since 1997, Toyota Motor has put into practice a hybrid electric vehicle (HEV) using an internal combustion engine and nickel-hydrogen battery as its power source. Recently, research has been actively conducted to use a lithium secondary battery having a higher energy density and excellent low temperature operation characteristics than a nickel-hydrogen battery as a power source for a hybrid electric vehicle. In order to commercialize lithium secondary batteries for hybrid electric vehicles, low-cost materials should be used for cathode materials, which account for about 35% or more of battery material prices. The most suitable anode material for HEV is spinel-based LiMn ₂ O ₄ with low cost and high output characteristics operating at 4V potential. However, as the spinel LiMn ₂ O ₄ progresses in the charge / discharge cycle, manganese contained in the positive electrode material is dissolved in the electrolyte, thereby decreasing its capacity. In particular, this phenomenon is accelerated at a high temperature of more than 55 ℃ can not be used in actual batteries. To solve this problem, many studies have been conducted to substitute lithium and transition metals in manganese sites or fluorine in oxygen sites (J. of Power Sources, 101 (2001), 79). Among them, the most effective method is Li1 + xAlyMn2-x-yO4-zFz (0.04≤x≤0.06, 0.025≤y≤0.05, 0.01≤z≤0.05) in which lithium and Ni are slightly substituted with fluorine in oxygen. It is known to have the best lifespan (J. Electrochem. Soc. 148 (2001) A171). However, this material also slowly loses its capacity at high temperatures. Another method to solve this problem is to study the surface of the spinel anode material by coating ZnO to neutralize the hydrofluoric acid in the electrolyte and to protect the surface. However, this method also did not completely solve the problem of loss of manganese due to dissolved manganese.

Commercially available small lithium ion _secondary batteries use LiCoO ₂ for the positive electrode and carbon for the negative electrode. LiCoO ₂ is an excellent material having stable charging and discharging characteristics, excellent electronic conductivity, high stability, and flat discharge voltage characteristics. However, cobalt is low in reserve, expensive, and toxic to human body. LiN _0.8 Co _0.2 O ₂ or LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , Li [Ni _x Co _1-2x Mn _x ] O ₂ (LiNi _1/3 Co _{1) / 3} Mn _1/3 O ₂ , LiNi _1/2 Mn _1/2 O ₂ ). LiNi _0.8 Co _0.2 O ₂ or LiNi _0.8 Co _0.1 Mn _0.1 O ₂ having a layered structure such as LiCoO ₂ has not been commercialized due to the difficulty in material synthesis of stoichiometric ratios and problems in thermal stability. Recently, however, LiNi _0.8 Co _0.2 O ₂ or LiNi _0.8 Co _0.1 Mn _0.1 O ₂ with high capacity for core and layered transition metal LiNi _1/2 Mn _{1 /} with excellent life characteristics and thermal stability for shell ₂ O ₂ was the dramatic improvements in core-life characteristics and thermal stability by combining a positive electrode active material of the shell structure with (Korea Patent Application No. 10-2004-0118280). Recently, Li [Ni _1/3 Co _1/3 Mn _1/3 ] O ₂ , a type of Li [Ni _x Co _1-2x Mn _x ] O ₂ , has begun to replace LiCoO ₂ , and Japanese battery maker Sanyo and Sony Corp. The amount of use is increasing as a cathode material of a small battery mainly. Recently, some of the environmentally friendly and low-cost LiMn ₂ O ₄ is used in small batteries, but its use is expected to be mainly used in large batteries, especially hybrid electric vehicles (HEVs). However, the 4 V spinel LiMn ₂ O ₄ has a poor lifespan due to the structural variation called Jahn-Teller distortion due to Mn3 ⁺ and the resulting Mn dissolution. In particular, dissolution of manganese is accelerated by the reaction with hydrofluoric acid (HF) in the electrolyte at a high temperature of 55 ° C. or higher, and the lifespan characteristics rapidly decrease, making it difficult to commercialize.

Recently, a patent has been reported to manufacture a bilayer bipolar anode material consisting of a shell of 5V spinel LiNi _0.5 Mn _1.5 O ₄ which does not have manganese dissolution problems with spinel LiMn2O4 having 4V class potential as a core. Korean Patent Application No .: 10-2005-0027683). However, the anode material manufactured by the carbonate method has a large specific surface area and difficult composition control, which does not significantly improve the life characteristics. In addition, the manganese oxide produced by the coprecipitation method using the carbonate method is difficult to obtain a battery having a high energy density due to its low tap density. In addition, it is difficult to maintain the spherical particle shape when manufacturing the battery plate because it is composed of secondary particles having a weak binding force between the primary particles.

Therefore, the present invention synthesizes a monodisperse spherical 4 V class precursor material to solve various problems of capacity reduction due to manganese lysis at high temperature, which is a problem of the prior art. A core-shell precursor coated with a positive electrode active material precursor in a capsule form is synthesized. After mixing with a core-shell precursor and a lithium salt, a cathode active material for a lithium secondary battery having excellent lifetime characteristics and thermal safety is synthesized through high temperature firing.

In order to solve the above technical problem, the present inventors synthesize a spherical trimetal tetrametallic manganese tetraoxide ((Mn1-xMx) ₃ O ₄ )) precursor powder having a high tap density by co-precipitation using a hydroxide of core, which is a 4 V class precursor, The shell solved the problem of manganese dissolution by encapsulating a lithium excess spinel precursor having Mn ⁴⁺ ion which does not occur in contact with hydrofluoric acid in the electrolyte, on a 4 V class precursor in hydroxide form. The cathode material thus synthesized was high in packing density and had excellent life characteristics, capacity characteristics and rate characteristics.

In the present invention to achieve the above object in the positive electrode active material for a lithium secondary battery, the core portion is Li _{1 + a} Mn _2-a O _4-y A _y (A is at least one element of F or S, 0.04≤a ≤0.15, 0.02≤y≤0.15), and the shell portion is Li [Li _a (Mn _1-x M _x ) _1-a ] ₂ O _4-y A _y (M is Fe, Co, Ni, Cu, Cr, At least one element selected from the group consisting of V, Ti, and Zn, A is at least one element of F or S, 0.01≤a≤0.333, 0.01≤x≤0.6, 0.02≤y≤0.15) A cathode active material for lithium secondary batteries having a core-shell multilayer structure is provided.

In the present invention, in the cathode active material for a lithium secondary battery, the core portion is Li _{1 + a} [Mn _1-x M _x ] _2-a O _4-y A _y (M is Mg, Ca, Sr, Al, Ga, At least one element selected from the group consisting of Fe, Co, Ni, V, Ti, Cr, Cu, Zn, Zr, In, Sb, P, In, Ge, Sn, Mo, and W, A is F or S At least one of elements, 0.04 ≦ a ≦ 0.15, 0.02 ≦ x ≦ 0.25, 0.02 ≦ y ≦ 0.15), and the shell portion is Li [Li _a (Mn _1-x M _x ) _1-a ] ₂ O _{4- y} A _y (M is at least one element selected from the group consisting of Fe, Co, Ni, Cu, Cr, V, Ti and Zn, A is at least one element of F or S, 0.01≤a≤0.333, 0.01 ≤ x ≤ 0.6, 0.02 ≤ y ≤ 0.15) There is provided a cathode active material for a lithium secondary battery having a core-shell multilayer structure.

In addition, the thickness of the shell portion is characterized in that 1 to 50% of the total diameter of the positive electrode active material.

Particles of the positive electrode active material is characterized by having a particle diameter of 1 to 50㎛.

According to the present invention, there is provided an electrode for a lithium secondary battery, wherein the cathode active material is used.

According to the present invention, there is provided a lithium secondary battery, wherein the lithium secondary battery electrode is used.

A preferred method for producing a cathode active material for a lithium secondary battery having a core-shell multilayer structure of the present invention a) ammonia aqueous solution or ammonium sulfate salt ((NH ₄ ) ₂ SO ₄ ), manganese complex metal salt aqueous solution and basic aqueous solution air flow At the same time into a reactor controlled by the atmosphere at the same time followed by mixing to obtain a spherical composite metal oxide precipitate; b) Aqueous ammonia or ammonium sulphate ((NH ₄ ) ₂ SO ₄ ), the complex metal oxide precipitate, the transition metal mixed aqueous metal salt solution and the basic aqueous solution are simultaneously mixed in a reactor controlled by nitrogen flow to cover the transition metal hydroxide. Obtaining a precipitate of the bilayer composite metal hydroxide having a gin core shell structure; c) The composite metal oxide and composite metal hydroxide precipitates were filtered, washed with water and dried to obtain [(M _x Mn _1-x ) ₃ O ₄ ] _1-z [(M ' _y Mn _1-y ) (OH) ₂ ] obtaining a _z precursor and drying it or preheating it; d) a mixture of the precursor and lithium hydroxide (LiOH) / lithium fluoride (LiF), lithium hydroxide (LiOH) / lithium sulfide (Li2S) or lithium hydroxide (LiOH) / solid sulfur in a desired composition ratio and mixed 400 Core and shell multi-layer structure, comprising the step of maintaining at ~ 650 ℃ for more than 10 hours and grinding (grinding) and calcining at 700 ~ 1100 ℃ 6 hours to 25 hours and annealing at 500 ~ 700 ℃ 10 hours Provided is a method of manufacturing a cathode active material for a lithium secondary battery having a.

The metal salt of step a) and step b) is characterized in that any one of sulfate, nitrate, acetate, chloride and phosphate.

The basic aqueous solution in step a) and step b) is characterized in that sodium hydroxide (NaOH) or potassium hydroxide (KOH).

The metal salt solution in step a) is Mg, Ca, Sr, Al, Ga, Fe, Co, Ni, V, Ti, Cr, Cu, Zn, Zr, In, Sb, P, In, Ge, Sn, Mo And at least one metal salt selected from the group consisting of W and Mn salts are mixed and used at a concentration of 0.5 to 3 M. The aqueous ammonia solution is 0.2 to 0.4 concentrations of the manganese composite metal salt solution concentration and the basic aqueous solution is 4 to 5 M concentration. It was used.

The transition metal mixed-based metal salt aqueous solution in step b) is 0.5 to 3 M in an aqueous solution containing at least one metal salt and Mn salt selected from the group consisting of Fe, Co, Ni, Cu, Cr, V, Ti, and Zn. It is characterized by using a concentration of the aqueous solution of ammonia, the concentration of 0.2 to 0.4 of the aqueous solution of the transition metal-mixed metal salt, the basic aqueous solution of 4 to 5M concentration.

In the present invention, the reaction atmosphere of the mixed metal aqueous solution in the process a) is air flow, the pH is 9.5 to 10.5, the reaction temperature is 30 to 80 ℃, the reaction stirrer rpm is characterized in that 500 to 2000 do.

The reaction atmosphere of the mixed metal aqueous solution in the step b) is nitrogen flow, the pH is 10.5 to 12.5, the reaction temperature is within 30 to 80 ℃, the reaction stirrer rpm is characterized in that within 500 to 2000.

It is characterized by adjusting the thickness of the shell layer by adjusting the reaction time of step b) to 0.5 to 10 hours.

Step c) is dried for 15 hours at 110 ℃, or characterized in that for 5 to 10 hours heating at 400 to 550 ℃.

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

The cathode active material for a lithium secondary battery having a core-shell multilayer structure of the present invention has a core-shell multilayer structure, and in the cathode active material for a lithium secondary battery, the core portion is Li _{1 + a} Mn _2-a O _4-y A _y ( A is at least one element of F or S, 0.04 ≦ a ≦ 0.15, 0.02 ≦ y ≦ 0.15), and the shell portion is Li [Li _a (Mn _1-x M _x ) _1-a ] ₂ O _4-y A _y (M is at least one element selected from the group consisting of Fe, Co, Ni, Cu, Cr, V, Ti, and Zn, A is at least one element of F or S, 0.01≤a≤0.333, 0.01 ≤ x ≤ 0.6, 0.02 ≤ y ≤ 0.15).

In addition, the core part of the core part has a 4 V-class potential. The core part of the core part is Li _{1 + a} [Mn _1-x M _x ] _2-a O _4-y A _y (M is Mg, Ca, Sr, Al At least one element selected from the group consisting of Ga, Fe, Co, Ni, V, Ti, Cr, Cu, Zn, Zr, In, Sb, P, In, Ge, Sn, Mo, and W, A is At least one element of F or S, 0.04 ≦ a ≦ 0.15, 0.02 ≦ x ≦ 0.25, 0.02 ≦ y ≦ 0.15), and the outer shell portion is Li [Li _a (Mn _1-x M _x ) _{1- a} ] ₂ O _4-y A _y (M is at least one element selected from the group consisting of Fe, Co, Ni, Cu, Cr, V, Ti and Zn, A is at least one element of F or S, 0.01 ≦ a ≦ 0.333, 0.01 ≦ x ≦ 0.6, 0.02 ≦ y ≦ 0.15) are provided.

The amount of “F” contained in the transition metal mixed-based positive electrode active material of the shell portion is preferably 0.005 mol to 0.05 mol based on 1 mol of “O”. If the amount of "F" is too small, there is no effect of improving the lifetime and thermal safety, and if too large, the reversible capacity is reduced and the discharge characteristics are deteriorated.

In the present invention, fluorine and sulfur, which are anions contained in the core-shell composite cathode active material, are preferably 0.005 mol to 0.05 mol relative to 1 mol of oxygen. When the amount of the anion to be substituted is less than 0.005 mol relative to 1 mol of oxygen, there is no effect on improving the life and thermal safety, because if excessively more than 0.05 mol, the capacity of the active material is reduced and the life characteristics are also reduced.

In the present invention, ammonia aqueous solution or ammonium sulfate, mixed manganese metal salt mixed aqueous solution, and basic solution are mixed at the same time in a reactor by adjusting the pH to 9.5 to 10.5 under air flow to form spherical complex metal oxides after a certain time (12 to 24hr) reaction. 1 step to obtain; A core ammonia solution or ammonium sulfate, a transition metal mixed aqueous metal salt solution and a basic solution are mixed in the reactor at the same time by adjusting the pH to 10.5 to 11.5 under a nitrogen flow, and the composite metal hydroxide is coated on the composite metal oxide. Obtaining a precipitate of a composite metal oxide / hydroxide having a structure; Drying or heat treating the precipitate to obtain a composite metal hydroxide, oxide or composite metal oxide having a core-shell structure; Spinel-type lithium having a core-shell structure, comprising the step of mixing the core-shell composite metal precursor and a lithium salt and then calcining at 700 to 1100 ° C for 6 to 25 hours and annealing at 500 to 700 ° C. It provides a method for producing a cathode active material for a lithium secondary battery comprising the four steps of obtaining a composite metal oxide.

1 is a perspective view of a reactor used in the method of manufacturing a cathode active material of the present invention. The reactor has a rotor blade designed in the reverse wing type, four baffles are separated from the inner wall by 2-3cm, and these baffles are provided with a cylinder to uniformly mix the upper and lower parts of the reactor. It was. The reverse wing design is also designed for uniform mixing up and down, and the separation of the baffles installed on the inner surface of the reactor from the inner wall controls the intensity and concentration of the waves and increases the turbulent effect to increase the local nonuniformity of the reaction solution. It is to solve.

First Mn: M is 1-x: x (M is Mg, Ca, Sr, Al, Ga, Fe, Co, Ni, V, Ti, Cr, Cu, Zn, Zr, In, Sb, P, In, Ge At least one element selected from Sn, Mo, and W, in a ratio of 0.02 ≦ x ≦ 0.25). The composite metal precursor, ammonia aqueous solution and basic solution are put into a reactor and mixed.

The metal salt of step a) and step b) is preferably applied to any one of sulfate, nitrate, acetate, chloride and phosphate, the basic aqueous solution using sodium hydroxide (NaOH) or potassium hydroxide (KOH) It is preferable.

In this case, the aqueous manganese composite metal solution is used in the concentration of 0.5 to 3M, the aqueous ammonia solution is preferably used in the concentration of 0.2 to 0.4 of the manganese composite metal solution concentration, the aqueous solution of sodium hydroxide 4 to 5M concentration.

The concentration of the aqueous ammonia solution is 0.2 to 0.4 of the aqueous metal solution concentration because the ammonia reacts with the metal precursor one-to-one, but the intermediate product can be recovered and used as ammonia again, further increasing the crystallinity and stabilizing the positive electrode active material. This is because it is an optimal condition.

In addition, the pH of the mixed aqueous solution is injected to the aqueous solution of sodium hydroxide so as to maintain the 9.5 to 10.5 at the same time the reaction under air flow, the reaction time in the reactor is preferably adjusted to 12 to 20 hours.

In order to obtain spherical spinel-type composite metal oxide precursor powder having a high manganese content and a high tap density, it is necessary to react under air flow. Under an inert atmosphere of nitrogen or argon, a part of the formed Mn (OH) ₂ is oxidized to form an impurity phase of Mn ₂ O ₃ , while Mn (OH) ₂ has a needle-like shape, thus forming a spherical powder. Difficult to synthesize When the atmosphere of the reactor is tested under oxygen flow, spherical powder can be obtained, but the oxidation reaction rate of manganese is fast, so that the tap density of the powder is low and the particle size distribution of the powder is widened.

Next, after obtaining a precursor oxide to form a core (inner layer), the shell (outer layer) encapsulates a precursor hydroxide having a spinel composition of 4+ oxidation number of Mn on the composite metal oxide precursor. Particularly, the oxidation number of Mn is 4+, which prevents the structure transition (Yan-Teller effect) caused by oxidation / reduction reaction of 3+ and 4+ of Mn in existing tetragonal or layered LiMnO2. Stabilize the structure to solve the problem of melting manganese to improve the life characteristics.

The metal salt solution is changed as follows while leaving the composite metal oxide inside the reactor as it is. First, Mn: M 'is added to distilled water at a ratio of 1-y: y (M is at least one element selected from the group consisting of Fe, Co, Ni, Cu, Cr, V, Ti, and Zn, 0.01≤y≤0.6). Dissolve. The composite metal precursor, ammonia aqueous solution and basic solution are continuously supplied to the reactor using a metering pump, respectively. At this time, it is preferable that the mixed metal aqueous solution uses 0.5-3M concentration, the aqueous ammonia solution uses 0.2-0.4 concentration of the mixed metal aqueous solution concentration, and the sodium hydroxide aqueous solution uses 4-5 M concentration. Injecting the aqueous sodium hydroxide solution so that the pH of the mixed solution is maintained at 10.5 to 12.5 and reacted for 0.5 to 10 hours under a nitrogen flow to form a shell layer (Mn _1-y M ' _y ) (OH) ₂ layers. The nitrogen atmosphere and the pH range are conditions for forming an optimal hydroxide precursor.

The thickness of the shell layer can be controlled by the synthesis time of the shell layer precursor in the reactor, the thickness of the shell layer can be adjusted by adjusting the reaction time to 0.5 to 10 hours.

In addition, Li [LiaMn _1-x M _x ] ₂ O _4-y, which is externally coated to take advantage of the high power characteristics of internal Li _{1 + a} [Mn _1-x M _x ] ₂ O _4-y A _{y in} the core-shell structure The thickness of the A _y shell is preferably 1 to 50% of the total thickness of both active materials. In order to further utilize high output characteristics, it is preferable to set it as 30% or less, more preferably 20% or less. However, if the thickness of the shell layer Li [LiaMn _1-x M _x ] ₂ O _4-y A _y is less than 1%, the service life is poor.

The composite metal oxide / hydroxide having the core-shell structure thus obtained is washed with distilled water, filtered and dried at 110 ° C. for 15 hours or heated at 400 to 550 ° C. for 5 to 10 hours to use as a precursor.

Next, the precursor is mixed using a dry method or a wet method in which an aqueous solution containing a chelating agent such as citric acid, tartaric acid, glycolic acid, maleic acid, or the like is mixed with lithium hydroxide (LiOH) / lithium fluoride (LiF), lithium hydroxide (LiOH) / After mixing with any mixture of lithium sulfide (Li ₂ S) or lithium hydroxide (LiOH) / solid sulfur and preliminary firing at 400 to 650 ℃, mixed well and calcined for 6 to 25 hours in an oxidizing atmosphere at 700 to 1100 ℃ And annealing at 500 to 700 ° C. for 10 hours to prepare a cathode active material for a lithium secondary battery having a core-shell structure.

It is preferable that the specific target of the positive electrode active material for lithium secondary batteries which has the core-shell structure manufactured by the said method is 3 m <2> / g or less. This is because if the specific target is 3 m 2 / g or more, the reactivity with the electrolyte is increased and gas generation is increased.

In addition, when using the reactor of the present invention, the tap density of the obtained precursor is improved by about 40% or more than when using the conventional reactor. The tap density of the precursor is 1.5 g / cm 3, preferably at least 1.7 g / cm 3, more preferably 1.8 g / cm 3.

In addition, the present invention can provide a lithium secondary battery electrode, characterized in that using the positive electrode active material, it can provide a lithium secondary battery, characterized in that using the lithium secondary battery electrode.

Hereinafter, the following examples are given as non-limiting examples of the method for producing a cathode active material for a lithium secondary battery of the present invention, the present invention is not limited to these examples.

Example 1

In order to prepare 4 V spherical manganese composite oxide, first, 4 liters of distilled water was added to the coprecipitation reactor (capacity 4L, the output of the rotary motor more than 80 W) of FIG. By supplying air to the reactor at a rate of 1 L / min, the oxidizing atmosphere was maintained in the coprecipitation reactor. Stirring at 1100 rpm while maintaining the temperature of the reactor at 50 ℃. Manganese sulfate and nickel sulfate molar ratios of 0.975: 0.025 were mixed in a metal salt solution of 2M concentration 0.3L / hr, 4.28M concentration of ammonia water solution was added to the reactor at 0.03L / hr continuously. And 4M sodium hydroxide aqueous solution was supplied for pH adjustment so that it may be maintained at pH 10. The impeller speed was adjusted to 1100 rpm, and the average residence time of the reactants in the reactor was adjusted to about 6 hours to obtain _tri- nickel manganese tetraoxide (Mn _0.975 Ni _0.025 ) ₃ O ₄ .

The nickel nickel manganese tetraoxide (Mn _0.975 Ni _0.025 ) ₃ O ₄ obtained by the above method was discontinued from supplying the aqueous solution of nickel and manganese mixed metal sulfides, and then reacted to maintain the duration of the reaction of the already supplied composite metal solution completely. To obtain an oxide having a high density. To the synthesized trioxide nickel manganese oxide, an aqueous solution of a composite metal having a concentration of 2M mixed with a ratio of manganese sulfate: nickel sulfate at a ratio of 0.75: 0.25 was supplied. At this time, the aqueous ammonia solution was changed from 4.28M to 7.93M, and the gas supply was changed to nitrogen gas to make a reducing atmosphere. A sodium hydroxide solution at a concentration of 4M was supplied at 0.3 L / Hr to adjust the pH to 11 to have a core-shell structure in which a complex metal hydroxide (Mn _0.75 Ni _0.25 ) (OH) ₂ was encapsulated in a shell layer ((Mn _0.975 Ni _0.025 ) ₃ O ₄ ) _0.7 (Mn _0.75 Ni _0.25 (OH) ₂ ) _0.3 precursor was obtained. At this time, the manganese, nickel composite metal solution was supplied for 2 hours to make a shell layer, and reacted.

The ((Mn _0.975 Ni _0.025 ) ₃ O ₄ ) _0.7 (Mn _0.75 Ni _0.25 (OH) ₂ ) _0.3 precursor obtained by the reactor was washed with distilled water, filtered and dried in a 110 ° C. warm air dryer for 12 hours to remove residual moisture. Removed. The precursor was mixed with lithium hydroxide (LiOH) and lithium fluoride (LiF) in a 1: 1: 0.05 molar ratio, heated at a heating rate of 2 ° C / min, held at 500 ° C for 5 hours, and then calcined at 850 ° C for 12 hours. The core layer has a core / shell structure composed of Li _1.05 [Mn _1.9 Ni _0.05 ] O _3.95 F _0.05 and the shell layer of Li [Li _0.05 (Ni _0.5 Mn _1.5 ) _0.95 ] O _3.95 F _0.05 . [Li _1.05 [Mn _1.9 Ni _0.05 ] O _3.95 F _0.05 ] _0.7 · [Li [Li _0.05 (Ni _0.5 Mn _1.5 ) _0.95 ] O _3.95 F _0.05 ] A positive electrode active material powder having a spinel structure of _0.3 form was obtained.

Example 2

A positive electrode active material powder was synthesized in the same manner as in Example 1 except that the shell was synthesized in the core-shell reaction, except that the atmosphere was changed from a nitrogen atmosphere to an air atmosphere.

Example 3

A positive electrode active material powder was synthesized in the same manner as in Example 1 except that the precursor obtained by Example 1 and lithium hydroxide (LiOH) were mixed at a molar ratio of 1: 1.05.

Example 4

In order to prepare 4 V spherical manganese oxide, first, 4 liters of distilled water was put into a coprecipitation reactor (capacity 4L, the output of the rotary motor more than 80W), and then mixed with 0.07 ~ 0.1M ammonia solution in the coprecipitation reactor. By supplying air to the reactor at a rate of 1 L / min, the oxidizing atmosphere was maintained in the coprecipitation reactor. Stirring at 1100 rpm while maintaining the temperature of the reactor at 50 ℃. A manganese sulfate metal salt solution of 2 M concentration was 0.3 L / Hr, and an aqueous ammonia solution of 4.28 M concentration was 0.03 L / hr continuously. And 4M sodium hydroxide aqueous solution was supplied for pH adjustment so that pH may be maintained at 10. The impeller speed was adjusted to 1100 rpm, and the average residence time of the reactants in the reactor was adjusted to about 6 hours to obtain trimanganese tetraoxide Mn ₃ O ₄ precursor.

After stopping the supply of the manganese sulfate metal salt solution to the trimanganese tetraoxide Mn ₃ O ₄ obtained by the above method, the mixture was allowed to react to give a duration of time to complete the reaction of the composite metal solution so as to obtain an oxide having a high density. It was. To the synthesized trimanganese tetraoxide, a composite metal aqueous solution having a concentration of 2M containing a mixture of manganese sulfate: nickel sulfate at a ratio of 0.75: 0.25 was supplied. At this time, the aqueous ammonia solution was changed from 4.28M to 7.93M, and the gas supply was changed to nitrogen gas to make a reducing atmosphere. A sodium hydroxide solution at a concentration of 4M was supplied at 0.3 L / Hr to adjust the pH to 11 to have a core-shell structure in which the composite metal hydroxide, (Mn _0.75 Ni _0.25 ) (OH) _2, was encapsulated in the shell layer ((Mn ₃ O ₄ ) _0.7 (Mn _0.75 Ni _0.25 (OH) ₂ ) _0.3 ) precursors were obtained. At this time, the manganese, nickel composite metal solution was supplied for 2 hours to make a shell layer, and reacted.

The (Mn ₃ O ₄ ) _0.7 (Mn _0.75 Ni _0.25 (OH) ₂ ) _0.3 precursor obtained by the reactor was washed with distilled water, filtered and dried in a 110 ° C. warm air dryer for 12 hours to remove residual moisture. The precursor was mixed with lithium hydroxide (LiOH) and lithium fluoride (LiF) in a 1: 1: 0.05 molar ratio, heated at a heating rate of 2 ° C / min, held at 500 ° C for 5 hours, and then calcined at 850 ° C for 12 hours. The core layer was Li _1.05 Mn _1.95 O _3.95 F _0.05 and the shell layer [Li _1.05 Mn _1.95 having a core / shell structure composed of Li [Li _0.05 (Ni _0.5 Mn _1.5 ) _0.95 ] O _3.95 F _0.05 . O _3.95 F _0.05 ] _0.7 · [Li [Li _0.05 (Ni _0.5 Mn _1.5 ) _0.95 ] O _3.95 F _0.05 ] A cathode active material powder having a spinel structure of _0.3 form was obtained.

Example 5

In the shell synthesis in the core-shell reaction, a positive electrode active material powder was synthesized in the same manner as in Example 4 except for changing from a nitrogen atmosphere to an air atmosphere.

Example 6

A positive electrode active material powder was synthesized in the same manner as in Example 4 except that the precursor obtained by Example 4 and lithium hydroxide (LiOH) were mixed in a 1: 1.0 molar ratio.

Example 7

A positive electrode active material powder was synthesized in the same manner as in Example 5 except that the precursor obtained by Example 4 and lithium hydroxide (LiOH) were mixed at a molar ratio of 1: 1.05.

Example 8

The cathode active material powder was synthesized in the same manner as in Example 4 except for changing the temperature at calcination to 750 ° C. and using ammonium fluoride instead of lithium fluoride (LiF).

Example 9

(Mn _0.975 Ni _0.025 ) ₃ obtained by the above method for the preparation of a core-shell transition metal complex oxide and a hydroxide after the preparation as in the (Example 4) production of the spherical 4 V-class manganese composite oxide. After the supply of Ni and Mn to O ₄ was stopped, the metal salt solution already supplied was allowed to react to obtain a more dense oxide. Then, in order to coat (Ni _0.5 Mn _0.5 ) (OH) ₂ corresponding to the outer shell, the manganese sulfate and nickel sulfate metal salt solutions, which were mixed and supplied at a molar ratio of 0.975: 0.025, were supplied with nickel sulfate and manganese sulfate. The molar ratio was replaced with a 2 M concentration of 0.5: 0.5. Then, the ammonia solution was changed to 7.93M, and the gas supply was changed to nitrogen gas to make a reducing atmosphere. In order to adjust the pH to 11 by supplying a sodium hydroxide solution of 4M concentration was continuously added to the reactor at a rate of 1: 1 with a metal aqueous solution at 0.3L / Hr. Composite metal _{hydroxide, (Ni 0.5 Mn 0.5) (} OH 2) having a core-shell structure encapsulating _{(((Mn 0.975 Ni 0.025)} 3 O 4) 1-z (Ni 0.5 Mn 0.5) (OH) 2) z ) Precursors were obtained. At this time, the manganese, nickel composite metal solution was supplied for 2 hours to make a shell layer, and reacted.

The ((Mn _0.975 Ni _0.025 ) ₃ O ₄ ) _1-z (Ni _0.5 Mn _0.5 ) (OH) ₂ ) _z precursor obtained by the reactor was washed with distilled water, filtered and dried in a 110 ° C. warm air dryer for 12 hours. Residual water was removed. The precursor was mixed with lithium hydroxide (LiOH) and lithium fluoride (LiF) in a 1: 1: 0.05 molar ratio, heated at a heating rate of 2 ° C / min, held at 500 ° C for 5 hours, and then calcined at 900 ° C for 12 hours. The core layer is Li _1.05 Mn _1.9 Ni _0.05 O _3.95 F _0.05 and the shell layer has a core / shell structure composed of LiNi _0.5 Mn _0.5 O _1.95 F _0.05 [LiMn _1.95 Ni _0.05 O _3.95 F _0.05 ] _{1 -z} · [LiNi _0.5 Mn _0.5 O _3.95 F _0.05 ] A positive electrode active material powder having a _z- type spinel structure was obtained.

Comparative Example 1

Example 1 and Li except that Li _1.05 Mn _1.9 Ni _0.05 O _3.95 F _0.05 having no Li [Li _0.05 (Ni _0.5 Mn _1.5 ) _0.95 ] O _3.95 F _0.05 layer on the outside (shell layer) was prepared. Powders were synthesized in the same manner.

Comparative Example 2

The same method as in Example 3, except that Li _1.05 Mn _1.9 Ni _0.05 O ₄ having no Li [Li _0.05 (Ni _0.5 Mn _1.5 ) _0.95 ] O _3.95 F _0.05 layer on the outside (shell layer) was prepared in the preparation of the positive electrode active material. Powder was synthesized.

Comparative Example 3

The same method as in Example 1, except that Li _1.05 Mn _1.95 O _3.95 F _0.05 having no Li [Li _0.05 (Ni _0.5 Mn _1.5 ) _0.95 ] O _3.95 F _0.05 layer on the outside (shell layer) was prepared. Powder was synthesized.

[Comparative Example 4]

Example 6 to Example 7 and except that Li _1.05 Mn _1.95 O ₄ which does not have a Li [Li _0.05 (Ni _0.5 Mn _1.5 ) _0.95 ] O _3.95 F _0.05 layer on the outside (shell layer) in the preparation of the positive electrode active material Powders were synthesized in the same manner.

[Comparative Example 5]

The same method as in Example 8, except that Li _1.05 Mn _1.95 O _3.95 F _0.05 having no Li [Li _0.05 (Ni _0.5 Mn _1.5 ) _0.95 ] O _3.95 F _0.05 layer on the outside (shell layer) was prepared. Powder was synthesized.

XRD and SEM were used to evaluate the characteristics of the positive electrode active material of the double layer core-shell type prepared by the above Examples and Comparative Examples.

SEM photographs of the precursor of the core portion and the spinel precursor powder of the core-shell structure obtained in Example 1 are shown in Figs. 3, 4 and 5, respectively. In FIG. 3, the particles have a uniform size of about 5 to 8 μm, and in FIGS. 4 and 5, spherical powders of about 8 to 10 μm are uniform. It can be seen that all powders have a spherical morphology. And when comparing the SEM pictures of Figures 3 and 5, the difference in the surface can be clearly seen. And also in FIG. 6, since the composition of a shell part differs, the surface difference can be seen easily. In particular, the core-shell structure can be confirmed through the cross section of the powder in FIG. 4.

An X-ray diffraction pattern was obtained using an X-ray diffraction analyzer (Model No. Rint-2000, Rigaku Co., Japan). As a result of the precursor X-ray diffraction analysis shown in FIG. 7, a slight change can be seen based on the Mn ₃ O ₄ peak depending on the composition of the core shell. 8 is an X-ray diffraction analysis of the positive electrode active material obtained after calcination of the precursors shown in FIG. X-ray diffraction analysis showed no peaks related to any impurities, indicating a well-developed spinel cubic structure. 9 shows the results of X-ray diffraction analysis obtained after 200 cycle charge / discharge experiments after fabricating a battery using a cathode active material having a core-shell structure. This shows that it is well maintained without structural deformation after 200 cycles compared with the X-ray diffraction analysis of the cathode active material.

In order to evaluate the characteristics of the battery using the core-shell positive electrode active material prepared in Example 1 using a electrochemical analyzer (Model No .: Toscat 3000U, Toyo, Japan) 3.4 to 4.3 at high temperature (60 ℃) Charge and discharge experiments were conducted at a current density of 1.4 mA / cm 2 in the V potential region. In the electrode preparation, an electrode was prepared using the powder prepared in Example 1 as a cathode active material, and vacuum dried at 120 ° C. The prepared anode and lithium metal were used as counter electrodes, and a porous polyethylene membrane (manufactured by Celgard ELC, Celgard 2300, thickness: 25 μm) was used as a separator, and ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1. A coin battery was prepared according to a commonly known manufacturing process using a liquid electrolyte in which LiPF ₆ was dissolved at a concentration of 1 M in a solvent. The coin cell thus prepared was evaluated using the electrochemical analyzer (Toyo System, Toscat 3100U) to evaluate the cathode active material characteristics of the present invention.

FIG. 10 is a graph of lifespan versus discharge capacity at a high temperature (60 ° C.) of a battery using a spinel oxide of a core / shell structure prepared in Examples 1 and 2. FIG. The cycle characteristics in the 3.4–4.3V potential region were compared, but the cycle of manganese spinel at very high temperature (60 ° C.) was not very good. In order to solve the manganese dissolution problem, a lithium-excess Li [Li _0.05 (Ni _0.5 Mn _1.5 ) _0.95 ] O _3.95 F _0.05 spinel was synthesized as a shell part, and shows excellent capacity retention rate. In particular, the material synthesized in the nitrogen atmosphere shows the most excellent characteristics when the shell part is synthesized. In addition, fluorine (F) is substituted in the oxygen site to show better cycle characteristics. The cycle diagram shows that the active material with no shells showed 73.5% of the initial capacity after 70 cycles of charge and discharge, while the core and shell structures had excellent capacity of 97.9% and 98.2%, respectively, in the oxygen and nitrogen atmospheres during the shell reaction. Retention rate is shown.

In FIG. 11, an experiment was carried out using ammonium fluoride (NH ₄ F) instead of lithium fluoride when fluorine (F) was substituted. Although the cycle characteristics were slightly lower than those of lithium fluoride, the performance was slightly improved due to the influence of fluorine. To be seen.

In FIG. 12, although the initial capacity was lowered as a cycle characteristic compared to Example 3 and Comparative Example 2, a good characteristic showing a capacity retention rate of 97.5% at 70 cycles was shown. It showed good properties without substitution of materials such as fluorine or sulfur.

Finally, as shown in FIGS. 13 and 14, the cycle characteristics of the positive electrode active material obtained by experiments in the air atmosphere and the nitrogen atmosphere, respectively, are shown in the shell synthesis. Comparing the two figures, both produced significantly better results than shellless materials. However, experiments in nitrogen at the time of shell synthesis show better capacity retention although the initial capacity is slightly lower. In the case of a cathode-free cathode active material, the capacity of the core-shell structure is 97.6% and 95.7%, respectively. Indicated.

From this, the lithium secondary battery using the positive electrode active material having the double layer core / shell multilayer structure of the present invention shows excellent discharge capacity compared to the initial capacity even in the harsh experimental environment of high temperature of 60 ° C., showing excellent life characteristics. there was.

As described above, the present invention has been described for only one preferred embodiment, but it is apparent to the inventor that various modifications and changes can be made within the technical spirit of the present invention based on the above embodiments. It is natural that such variations and modifications fall within the scope of the appended claims.

In the cathode active material for a lithium secondary battery according to the present invention, the inner core nuclear material is a fluorine or sulfur-substituted spinel manganese mixture material having a 4 V class potential having low cost and high output characteristics, and the shell portion in contact with the electrolyte has thermal safety and lifespan. It is composed of spinel-based transition metal mixture system with excellent properties and low reactivity with electrolyte, and showed an excellent effect of dramatically improving life characteristics.

Claims (15)

In the cathode active material for a lithium secondary battery, The core portion is Li _{1 + a} Mn _2-a O _4-y A _y (A is at least one element of F or S, 0.04 ≦ a ≦ 0.15, 0.02 ≦ y ≦ 0.15), and the shell portion is Li [Li _a (Mn _1-x M _x ) _1-a ] ₂ O _4-y A _y (M is at least one element selected from the group consisting of Fe, Co, Ni, Cu, Cr, V, Ti, and Zn, A Is at least one element of F or S, and 0.01 ≦ a ≦ 0.333, 0.01 ≦ x ≦ 0.6, and 0.02 ≦ y ≦ 0.15). The cathode active material for a lithium secondary battery having a core-shell multilayer structure. In the cathode active material for a lithium secondary battery, The core portion is Li _{1 + a} [Mn _1-x M _x ] _2-a O _4-y A _y (M is Mg, Ca, Sr, Al, Ga, Fe, Co, Ni, V, Ti, Cr, Cu , Zn, Zr, In, Sb, P, In, Ge, Sn, Mo, and W at least one element selected from the group, A is at least one element of F or S, 0.04≤a≤0.15 , 0.02 ≦ _x ≦ 0.25, 0.02 ≦ y ≦ 0.15), and the shell portion is Li [Li _a (Mn _1-x M _x ) _1-a ] ₂ O _4-y A _y (M is Fe, Co, Ni, At least one element selected from the group consisting of Cu, Cr, V, Ti, and Zn, A is at least one element of F or S, 0.01≤a≤0.333, 0.01≤x≤0.6, 0.02≤y≤0.15) A cathode active material for a lithium secondary battery having a core-shell multilayer structure, characterized in that consisting of. The cathode active material according to claim 1 or 2, wherein the shell portion has a thickness of 1 to 50% of the diameter of the entire cathode active material. The cathode active material for lithium secondary battery according to claim 1 or 2, wherein the particles of the cathode active material have a particle diameter of 1 to 50 µm. The positive electrode active material of any one of Claims 1-4 is used, The lithium secondary battery electrode characterized by the above-mentioned. A lithium secondary battery, wherein the lithium secondary battery electrode of claim 5 is used. In the manufacturing method of the positive electrode active material for lithium secondary batteries which has a core-shell structure, a) an aqueous ammonia solution or ammonium sulfate ((NH ₄ ) ₂ SO ₄ ), an aqueous solution of manganese composite metal salt and a basic aqueous solution are simultaneously introduced into a reactor controlled by an atmosphere of air flow, followed by mixing to obtain a spherical composite metal oxide precipitate; b) Aqueous ammonia or ammonium sulphate ((NH ₄ ) ₂ SO ₄ ), the complex metal oxide precipitate, the transition metal mixed aqueous metal salt solution and the basic aqueous solution are simultaneously mixed in a reactor controlled by nitrogen flow to cover the transition metal hydroxide. Obtaining a precipitate of the bilayer composite metal hydroxide having a gin core shell structure; c) The composite metal oxide and composite metal hydroxide precipitates were filtered, washed with water and dried to obtain [(M _x Mn _1-x ) ₃ O ₄ ] _1-z [(M ' _y Mn _1-y ) (OH) ₂ ] obtaining a _z precursor and drying it or preheating it; d) Mixing the precursor and any one of lithium hydroxide (LiOH) / lithium fluoride (LiF), lithium hydroxide (LiOH) / lithium sulfide (Li ₂ S) or lithium hydroxide (LiOH) / solid sulfur in the desired composition ratio and mixed Core and shell characterized in that it comprises a step of maintaining at 400 ~ 650 ℃ for more than 10 hours and then grinding (grinding) and calcining at 700 ~ 1100 ℃ 6 hours to 25 hours and annealing at 500 ~ 700 ℃ 10 hours A method of manufacturing a cathode active material for a lithium secondary battery having a multilayer structure. The method according to claim 7, wherein the metal salt of step a) and step b) is any one of sulfate, nitrate, acetate, chloride and phosphate. . The method of claim 7, wherein the basic aqueous solution in steps a) and b) is sodium hydroxide (NaOH) or potassium hydroxide (KOH). . The metal salt solution of claim 7 is Mg, Ca, Sr, Al, Ga, Fe, Co, Ni, V, Ti, Cr, Cu, Zn, Zr, In, Sb, P, In At least one metal salt selected from the group consisting of Ge, Sn, Mo, and W and Mn salt are mixed and used at a concentration of 0.5 to 3 M. The aqueous ammonia solution is used at a concentration of 0.2 to 0.4 at a manganese composite metal salt solution concentration, and the basic aqueous solution is used. The manufacturing method of the positive electrode active material for lithium secondary batteries which has a core-shell multilayer structure characterized by using the thing of 4-5 M concentration. The method of claim 7, wherein the aqueous solution of the transition metal mixture-based metal salt in step b) is at least one metal salt and Mn salt selected from the group consisting of Fe, Co, Ni, Cu, Cr, V, Ti and Zn The aqueous solution is 0.5-3M concentration, the aqueous ammonia solution has a core shell multilayer structure, characterized in that the concentration of 0.2 to 0.4 of the transition metal mixed metal salt solution concentration, the basic aqueous solution of 4 to 5M concentration. Method for producing a cathode active material for a lithium secondary battery. The reaction atmosphere of the mixed metal aqueous solution in the step a) is air flow, pH is 9.5 to 10.5, the reaction temperature is 30 to 80 ℃, the reaction stirrer rpm is 500 to 2000 The manufacturing method of the positive electrode active material for lithium secondary batteries which has a core-shell multilayer structure made into. The reaction atmosphere of the mixed metal aqueous solution in step b) is nitrogen flow, pH is within 10.5 to 12.5, the reaction temperature is within 30 to 80 ℃, the reaction stirrer rpm is within 500 to 2000 The manufacturing method of the positive electrode active material for lithium secondary batteries which has a core-shell multilayer structure made into. The cathode for a lithium secondary battery according to any one of claims 7 to 13, wherein the thickness of the shell layer is adjusted by adjusting the reaction time of step b) to 0.5 to 10 hours. Method for producing an active material. The method of claim 7, wherein The step c) is dried for 15 hours at 110 ℃, or a method for manufacturing a cathode active material for a lithium secondary battery having a core shell multi-layer structure, characterized in that for 5 to 10 hours heating at 400 to 550 ℃.

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