KR100598491B1 - Double-layer cathode active materials and their preparing method for lithium secondary batteries - Google Patents

Abstract

The present invention discloses a positive electrode active material for a lithium secondary battery having a double layer structure, wherein the inside is composed of a nickel-based positive electrode active material and the outside is in contact with an electrolyte.

According to the configuration of the positive electrode active material for a lithium secondary battery having a double layer structure according to the present invention, the inside is composed of a nickel-based positive electrode having a high capacity characteristics, the outside in contact with the electrolyte is composed of a transition metal mixed-based positive electrode having excellent thermal safety, high capacity and high packing density The service life is improved and the thermal safety is excellent.

Double layer structure, coprecipitation method, positive electrode active material, high capacity, high safety

Description

A cathode active material for a lithium secondary battery having a double layer structure, a manufacturing method and a lithium secondary battery using the same {Double-layer cathode active materials and their preparing method for lithium secondary batteries}

1 is a perspective view of a reactor used in the production method of the present invention,

2a shows a composite oxide powder obtained by drying (Ni _0.8 Co _0.1 Mn _0.1 ) (OH) ₂ in a 110 ° C. warm air dryer for 12 hours, and FIG. 2b shows (Ni _0.8 Co _0.1 Mn _0.1 ) (OH) ₂ in (Ni _0.5 Mn _0.5 2C is a powder obtained by reacting (OH) ₂ for 1-2 hours, and FIG. 2C is a powder obtained by reacting (Ni _0.8 Co _0.1 Mn _0.1 ) (OH) ₂ with (Ni _0.5 Mn _0.5 ) (OH) ₂ for 2-3 hours. 2d is a powder obtained by reacting (Ni _0.8 Co _0.1 Mn _0.1 ) (OH) ₂ with (Ni _0.5 Mn _0.5 ) (OH) ₂ for 4 hours, FIG. 2e is a powder of (Ni _0.8 Co _0.2 ) (OH) ₂ , and FIG. 2f. Is a powder obtained by reacting (Ni _0.8 Co _0.2 ) (OH) ₂ with (Ni _0.45 Co _0.1 Mn _0.45 ) (OH) ₂ for 1 hour-2 hours, FIG. 2g shows (Ni _0.8 Co _0.2 ) (OH) ₂ in (Ni) Camera photograph of powder reacted with _0.45 Co _0.1 Mn _0.45 ) (OH) ₂ for 3 hours,

Figure 3a is (Ni _0.8 Co _0.1 Mn _0.1 ) (OH) ₂ And FE-SEM picture of precursor powder according to time-phase synthesis of {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _1/2 Mn _1/2 ) _1-x } (OH) ₂ (1) -powder before double layer formation, (2) -2 hours, (2) -3 hours, (3) -4 hours, Figure 3b shows {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _0.45 Co _0.1 Mn _0.45 ) _1-x } (OH) _{2 ,} Figure 3c FE-SEM photo of precursor powder according to Co amount of {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _0.4 Co _0.2 Mn _0.4 ) _1-x } (OH) ₂ , FIG. 3D shows (Ni _0.8 Co _0.2 ) (OH FE-SEM photo of precursor powders of) ₂ and (Ni _0.8 Co _0.2 ) x (Ni _0.45 Co _0.1 Mn _0.45 ) _1-x (OH) ₂ ,

4 is an EDX photograph of a powder obtained by reacting (Ni _0.8 Co _0.1 Mn _0.1 ) (OH) ₂ with (Ni _0.5 Mn _0.5 ) (OH) ₂ for 4 hours, (a) MnKα, (b) CoKα, and (c) NiKα,

5 is a TEM image photograph of a powder obtained by reacting (Ni _0.8 Co _0.1 Mn _0.1 ) (OH) ₂ with (Ni _0.5 Mn _0.5 ) (OH) ₂ .

6 is a FE-SEM photograph after grinding Li [(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _1/2 Mn _1/2 ) _1-x ] O ₂ cathode active material powder;

Figure 7a is a _{(Ni 0.8 Co 0.1 Mn 0.1)} (OH) {(Ni 0.8 Co 0.1 Mn 0.1) x (Ni 1/2 Mn 1/2) 1-x} (OH) ₂ in accordance with the double layer forming time of ₂ X-ray diffraction pattern of the precursor powder particles, FIG. 7B shows {(Ni _0.8 Co _0.2 ) _x (Ni _0.45 Co _0.1 Mn _0.45 ) _1-x } (OH) according to the bilayer formation time of (Ni _0.8 Co _0.2 ) (OH) ₂ . ₂ of X-ray diffraction pattern of the precursor powder particles,

8a is a bilayer powder synthesized over time of Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ and Li {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _1/2 Mn _1/2 ) _1-x } O ₂ . X-ray diffraction pattern for FIG. 8B shows Li [(Ni _0.8 Co _0.1 Mn _0.1 )] O ₂ , Li {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _1/2 Mn _1/2 ) _1-x } O ₂ And Li [(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _0.45 Co _0.1 Mn _0.45 ) _1-x ] O _2, Li [(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _0.4 Co _0.2 Mn _0.4 ) _1-x ] X-ray diffraction pattern of 3 hours double layered synthesized powder of O ₂ ,

9a shows powders synthesized over time of Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ and Li {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _1/2 Mn _1/2 ) _1-x } O ₂ . Charge and discharge curves discharged at 0.4 mA in the range of 3.0-4.3 V, Figure 9b shows Li [(Ni _0.8 Co _0.1 Mn _0.1 )] O ₂ , Li {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _1/2 Mn _{1 / 2} ) _1-x } O ₂ and Li [(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _0.45 Co _0.1 Mn _0.45 ) _1-x ] O _2, Li [(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _0.4 3 hours double layer formation of Co _0.2 Mn _0.4 ) _1-x ] O ₂ Charge / discharge curve discharged at 0.4 mA in 3.0-4.3V range,

Figure 10a is _{Li [Ni 0.8 Co 0.1 Mn 0.1} ] O ₂ in the composite powder according to 3.0 and the time-cycle data was discharged at 0.4mA at 4.3V range, Figure 10b _{Li [(Ni 0.8 Co 0.1 Mn} 0.1)] O ₂ , Li {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _1/2 Mn _1/2 ) _1-x } O ₂ and Li [(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _0.45 Co _0.1 Mn _0.45 ) 3-hour synthesized powder of _1-x ] O _2, Li [(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _0.4 Co _0.2 Mn _0.4 ) _1-x ] O ₂ was discharged at 0.4mA in the 3.0-4.3V range. Cycle Data,

11a shows a bilayer powder synthesized over time with Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ and Li {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _1/2 Mn _1/2 ) _1-x } O ₂ . Was thermally analyzed by Differential Scanning Calolimetry (DSC) by charging 4.3V, and FIG. 11B shows Li [(Ni _0.8 Co _0.1 Mn _0.1 )] O ₂ , Li {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _1/2 Mn _1/2 ) _1-x } O ₂ and Li [(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _0.45 Co _0.1 Mn _0.45 ) _1-x ] O _2, Li [(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _0.4 Co _0.2 Mn _0.4 ) _1-x ] O ₂ bilayer powder was 4.3V charged and thermally analyzed by Differential Scanning Calolimetry (DSC).

FIG. 12 shows differential scanning calolimetry (DSC) by charging Li [(Ni _0.8 Co _0.1 Mn _0.1 )] O ₂ , Li [(Ni _0.8 Co _0.1 Mn _0.1 )] O _1.95 F _0.05 , and powder 4.3V Thermally analyzed data,

FIG. 13 shows Li {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _1/2 Mn _1/2 ) _1-x } O ₂ , Li {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _1/2 ) for a bilayer. Mn _1/2 ) _1-x } O _1.95 F _0.05 , 4.3 V filled powder thermally analyzed by Differential Scanning Calolimetry (DSC),

14 is an X-ray diffraction pattern of a bilayer powder synthesized over time of Li [Ni _0.8 Co _0.2 ] O ₂ and Li {(Ni _0.8 Co _0.2 ) _x (Ni _0.45 Co _0.1 Mn _0.45 ) _1-x } O ₂ .

15 is a 3.0-4.3V range of a bilayer positive electrode active material synthesized according to time zones of Li [Ni _0.8 Co _0.2 ] O ₂ and Li [(Ni _0.8 Co _0.2 ) _x (Ni _0.45 Co _0.1 Mn _0.45 ) _1-x ] O ₂ . Charge / discharge curve discharged at 0.4mA

FIG. 16 is a _graph illustrating differential weight thermal analysis after charging 4.2 V of powders of Li [(Ni _0.8 Co _0.2 )] O ₂ and Li (Ni _0.8 Co _0.2 ) x (Ni _0.45 Co _0.1 Mn _0.45 ) _1-x ] O ₂ Data.

The present invention relates to a positive electrode active material for a lithium secondary battery having a double layer structure and a method of manufacturing the same, and more specifically, the inside is composed of a nickel-based cathode active material having a high capacity characteristics and the transition metal mixed-based cathode active material having a high safety characteristics The present invention relates to a cathode active material having a double layer structure having high capacity, high packing density, improved life characteristics, and excellent thermal safety, and a method of manufacturing the same.

Li-ion secondary batteries have been widely used as power sources for portable devices since they emerged in 1991 as small, light and large capacity batteries. Recently, with the rapid development of electronics, telecommunications, and computer industry, camcorders, mobile phones, notebook PCs, etc. have emerged and are developing remarkably, and the demand for lithium ion secondary battery as a power source to drive these portable electronic information communication devices is increasing day by day. It is increasing.

In particular, research on power sources for electric vehicles that hybridize an internal combustion engine and a lithium secondary battery has been actively conducted in the United States, Japan, and Europe. However, although the use of lithium ion batteries is considered as a large battery for electric vehicles in terms of energy density, nickel hydride batteries are still in the development stage and in particular in terms of safety, and the biggest challenge is high price and safety.

In particular, the positive electrode active materials such as LiCoO ₂ and LiNiO ₂ which are currently commercially used have a disadvantage in that the crystal structure is unstable due to de-lithography at the time of charging and thus the thermal characteristics are very poor.

That is, when a battery in an overcharged state is heated to 200 ° C. to 270, a sudden structural change occurs, and a reaction of releasing oxygen in the lattice proceeds due to such structural change (JRDahn et al., Solid State Ionics, 69,265). (1994).

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.

LiNiO ₂ having a layered structure such as LiCoO ₂ has a large discharge capacity but is difficult to synthesize a material having a pure layered structure, and Li _x Ni having a rocksalt type structure because of Ni ⁴⁺ ions which are highly reactive after charging. Excess oxygen is released as it transitions to _1-x O, which has not yet been commercialized due to lifetime and thermal instability.

To improve this, attempts have been made to replace a portion of nickel with a transition metal element to shift the exothermic start temperature to a slightly higher temperature side or to broaden the exothermic peak to prevent rapid exotherm (T.Ohzuku et al., J.). Electrochem. Soc., 142, 4033 (1995), Japanese Patent Application Laid-Open No. 237-361), yet no satisfactory results have been obtained.

In addition, LiNi _1-x Co _x O ₂ (x = 0.1-0.3) material, in which a part of nickel was substituted with cobalt, showed excellent charge and discharge characteristics and life characteristics, but thermal safety problems were not solved.

In addition, the composition of Li-Ni-Mn-based composite oxides partially substituted with Mn having excellent thermal stability at Ni sites or Li-Ni-Mn-Co-based composite oxides substituted with Mn and Co and many technologies related to the preparation thereof. Known.

For example, in Japanese Patent No. 8-171910, an alkaline solution is mixed with a mixed aqueous solution of Mn and Ni to coprecipitate Mn and Ni, and lithium hydroxide is mixed with the coprecipitation compound and then calcined to form LiNi _x Mn _1-x O ₂ ( 0.7≤x≤0.95) has been disclosed.

Recently, Japanese Patent No. 2000-227858 discloses a positive electrode active material having a new concept of making a solid solution by uniformly dispersing Mn and Ni compounds at the atomic level, instead of partially substituting a transition metal to LiNiO ₂ or LiMnO ₂ .

However, according to European Patent 0918041 or US Patent 6040090, LiNi _1-x Co _x Mn _y O ₂ (0 <y≤0.3) has improved thermal stability compared to conventional Ni and Co only materials, but due to the reactivity of Ni4 + There are problems to commercialize.

In addition, in European Patent 0872450 A1 and B1, Li _a Co _b Mn _c MdNi _{1- (b + c + d)} O ₂ (M = B, Al, Si.Fe ₎ in which Ni and other metals are substituted in place of Ni and Co. , Cr, Cu, Zn, W, Ti, Ga) type, but the thermal stability of the Ni-based still has not been solved.

Accordingly, the present invention has been made to solve the above problems of the prior art, the nickel-based anode having a high capacity characteristics inside the hydroxide using the coprecipitation method, the outside contacting the electrolyte is nickel, manganese, cobalt-based excellent thermal stability The present invention provides a cathode active material having a double layer structure composed of a positive electrode (hereinafter referred to as a transition metal mixed anode), which has high capacity, high packing density, improved lifetime characteristics, and excellent thermal safety.

In addition, another object of the present invention to provide a method for producing a positive electrode active material having the double layer structure.

In addition, another object of the present invention to provide a lithium secondary battery using a positive electrode active material having the double layer structure.

In order to achieve the above object, the present invention provides a cathode active material for a lithium secondary battery having a double-layer structure, characterized in that the inside is composed of a nickel-based positive electrode active material, the outer contacting the electrolyte is composed of a transition metal mixed-based positive electrode active material.

The inside is Li _{1 + δ} [Co _a Mn _b M _c Ni _{1- (a + b + c)} ] O ₂ (M is Mg, Zn, Ca, Sr, Cu, Zr, P, Fe, Al, Ga, At least one element selected from the group consisting of In, Cr, Ge, Sn, 0≤δ≤1 / 5, 0≤a≤0.5, 0≤b≤0.2, 0≤c≤0.1, 0≤a + b + c ≤ 0.5), the positive electrode active material for a lithium secondary battery having a double layer structure.

The outside is Li _{1 + δ} [Ni _x Mn _{xy / 2} Co _1-2x-z M _y N _z ] O _2-a P _a or Li _{1 + δ} [Ni _x Mn _{x + y} Co _{1-2 (x + y)} My] O _2-a P _a (M is at least one element selected from the group consisting of Mg, Zn, Ca, Sr, Cu, Zr, N is Fe, Al, Ga, In, Cr, Ge, Sn At least one element selected from the group consisting of: P = F or S, 0≤δ≤1 / 5, 0≤x≤1, 0≤y≤1 / 10, 0≤z≤1 / 10, 0≤a≤0.3 It is characterized by consisting of).

The Li _{1 + δ} [Co _a Mn _b M _c Ni _{1- (a + b + c)} ] O ₂ is the oxidation number of Co, Mn, and Ni is +3, M is +2, +3 is, + 4, +5, +6, or +2 consisting of one or more elements, +3, +4, +5, +6.

Li _{1 + δ} [Ni _x Mn _{xy / 2} Co _1-2x-z M _y N _z ] O _2-a P _a or Li _{1 + δ} [Ni _x Mn _{x + y} Co _{1-2 (x + y)} My] O _2-a P _a is characterized in that the oxidation of Ni is +2, the oxidation of Mn is +4, the oxidation of Co is +3, and the substituted metals M and N are +2 and +3, respectively. do.

Li _{1 + δ} [Ni _x Mn _{xy / 2} Co _1-2x-z M _y N _z ] O _2-a P _a or Li _{1 + δ} [Ni _x Mn _{x + y} Co _{1-2 (x + y)} The thickness of M _y ] O _2-a P _a is 4 to 50% of the total thickness of the double-layer positive electrode active material.

The average particle diameter of the nickel-based positive electrode active material is 0.1 to 2μm, characterized in that the total average particle diameter is 5 to 20μm.

In addition, the present invention is a step of obtaining a spherical precipitate by simultaneously mixing the nickel-based metal precursor, ammonia aqueous solution and basic solution in the reactor; Mixing the transition metal mixed metal precursor, the ammonia aqueous solution and the basic solution on the precipitate at the same time in a reactor to obtain a precipitate of the double layer composite metal hydroxide salt covered with the transition metal hydroxide; Drying or heat treating the precipitate to obtain a bilayer composite metal hydroxide / oxide; It provides a method for producing a cathode active material for a lithium secondary battery having a double layer structure comprising the four steps of obtaining a double layer lithium composite metal oxide by mixing a lithium precursor to the double layer composite metal hydroxide / oxide.

In the first step, an aqueous solution including two or more metal salts is mixed and used as a precursor. The molar ratio of ammonia and metal salts is 0.2 to 0.4, and the pH of the reaction solution is adjusted to 10.5 to 12 for 2 to 10 hours. It features.

The second step is characterized by adjusting the thickness of the outer layer by adjusting the reaction time to 1 to 10 hours.

The third step may be dried at 110 ° C. for 15 hours or heated at 400 to 550 ° C. for 5 to 10 hours.

The third step is characterized in that it comprises a step of preliminary baking by maintaining 400 ~ 650 ℃, 5 hours, 10 hours at 700 ~ 1100 ℃, 700 ℃ 10 hours annealing.

The fourth step is characterized in that the distilled water is removed after mixing the dried composite metal hydroxide or oxide and lithium precursor in an aqueous solution mixed with a chelating agent such as citric acid, tartaric acid, glycolic acid, maleic acid.

The present invention also provides a lithium secondary battery using the cathode active material for a lithium secondary battery having the double layer structure.

Hereinafter, a method of manufacturing a cathode active material for a lithium secondary battery having a double layer structure according to the present invention will be described in detail.

Method for producing a cathode active material for a lithium secondary battery having a double layer structure according to the present invention comprises the steps of obtaining a spherical precipitate by simultaneously mixing the nickel-based metal precursor, ammonia aqueous solution and basic solution in the reactor; Mixing the transition metal mixed metal precursor, the ammonia aqueous solution and the basic solution on the precipitate at the same time in a reactor to obtain a precipitate of the double layer composite metal hydroxide salt covered with the transition metal hydroxide; Drying or heat treating the precipitate to obtain a bilayer composite metal hydroxide / oxide; And a four step of obtaining a double layered lithium composite metal oxide by mixing a lithium precursor with the double layered composite metal hydroxide / oxide.

The cathode active material for a lithium secondary battery manufactured by the above method has Li _{1 + δ} [Co _a Mn _b M _c Ni _{1- (a + b + c)} ] O ₂ (M is Mg, Zn, Ca, Sr, Cu , Zr, P, Fe, Al, Ga, In, Cr, Ge, Sn at least one element selected from the group, 0≤δ≤1 / 5, 0≤a≤0.5, 0≤b≤0.2, 0≤ c≤0.1, 0≤a + b + c≤0.5), outside is Li _{1 + δ} [Ni _x Mn _{xy / 2} Co _1-2x-z M _y N _z ] O _2-a P _a or Li _{1+ δ} [Ni _x Mn _{x + y} Co _{1-2 (x + y)} M _y ] O _2-a P _a (M is at least one element selected from the group consisting of Mg, Zn, Ca, Sr, Cu, Zr, N is at least one element selected from the group consisting of Fe, Al, Ga, In, Cr, Ge, Sn, P = F or S, 0≤δ≤1 / 5, 0≤x≤1, 0≤y≤1 / 10, 0≤z≤1 / 10, 0≤a≤0.3) and a double layer structure. In the case of a layered cathode active material in which F is partially substituted with O, which is a general oxygen site, high rate characteristics and lifespan characteristics are greatly improved. (Patent application 10-2004-0021269)

The amount of "F" contained in the external transition metal mixed-based positive electrode active material is preferably 0.06 mol or less based on 1 mol of "O". This is because, 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.

As shown in FIG. 1, the reactor used for manufacturing the lithium secondary battery positive electrode active material of the present invention has a rotary wing designed in a reverse wing type, and has one or more baffles spaced apart from the inner wall by 2 to 3 cm. .

The reverse wing design is for up-down uniform mixing, 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 wave and increases the turbulent effect to increase the locality of the reaction solution. It is to solve the nonuniformity.

In the method of manufacturing the cathode active material of the present invention, unlike the ammonia complex method in which ammonia water is first mixed with a conventional metal solution and then precipitated, two or more types of metal salt solutions, aqueous ammonia solution, and NaOH solution are respectively added to the reactor. By introducing, it is possible to prevent the initial oxidation of manganese ions to obtain a precipitate in which the uniformity of particles and metal elements are uniformly distributed.

Hereinafter, the metal hydroxide method, which is a method of manufacturing a cathode active material for a lithium secondary battery having a layered rock salt structure and a double layer structure, will be described in detail.

First Co: Mn: M: Ni is a: b: c: 1- (a + b + c) (M is Mg, Zn, Ca, Sr, Cu, Zr, P, Fe, Al, Ga, In, Cr , Ge, Sn, 0≤δ≤1 / 5, 0≤a≤0.5, 0≤b≤0.2, 0≤c≤0.1, 0≤a + b + c≤0.5). At this time, it is preferable that the substituted metal salt is selected from two or more kinds. The nickel-based metal precursor, an aqueous ammonia solution and a basic solution are put into a reactor and mixed.

At this time, it is preferable that the metal aqueous solution is used in the concentration of 0.5 to 3M, the aqueous ammonia solution is used in the concentration of 0.2 to 0.4 of the aqueous metal solution, NaOH aqueous solution is used in the concentration of 4 to 5M.

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 NaOH aqueous solution is injected so that the pH of the mixed solution is maintained at 10.5 to 12, and the reaction time in the reactor is preferably adjusted to 2 to 20 hours.

To describe the first step in more detail, first, nickel, manganese, cobalt and substituted metal salts are dissolved in distilled water, and then introduced into the reactor with ammonia water solution and NaOH aqueous solution to cause precipitation. The coprecipitation method is a method of obtaining a composite hydroxide by simultaneously precipitating two or more elements by using a neutralization reaction in an aqueous solution.

Here, the average time the mixed solution stays in the reactor is adjusted to 6 hours, the pH is maintained at 10.5 to 11.5 and the reactor temperature is 50 ℃ to 60 ℃. The reason for raising the temperature of the reactor is that it is difficult to obtain a high-density complex hydroxide because the cobalt hydroxide produced is precipitated in complex salt form at a low temperature.

Next, after obtaining the precursor hydroxide to form the inner layer, the metal salt forming the outer layer is reacted for 1 to 10 hours under the same reaction conditions to obtain a composite hydroxide / oxide of a double layer structure. The thickness of the outer layer is controlled by the synthesis time of the outer layer precursor in the reactor.

As shown in FIG. 3, the average particle diameter of the primary particles formed by the nickel-based cathode active material manufactured by the co-precipitation method as described above is 0.1 to 15 μm, and is formed by the transition metal mixed-based cathode active material covering the surface of the primary particles. It is preferable that the average particle diameter of a secondary particle is 0.1-20 micrometers.

This is because the average particle size of the primary particles is set to 0.l-15 μm, thereby increasing the reactivity of charging and discharging and improving the high rate characteristics of the battery, while setting the average particle size of the secondary particles to 0.1-20 μm to provide a double layer structure. This is because the eggplant can increase the capacity of the electrode by increasing the chargeability of the cathode active material for a lithium secondary battery and improving the coating power.

In addition, Li _{1 + δ} [Ni _x Mn _{xy / 2} which is coated on the outside to take advantage of the high capacity characteristics of the internal Li _{1 + δ} [Co _a Mn _b M _c Ni _{1- (a + b + c)} ] O _{2 in} the bilayer structure Co _1-2x-z M _y N _z ] O _2-a P _a or Li _{1 + δ} [Ni _x Mn _{x + y} Co _{1-2 (x + y)} M _y ] O _2-a P _a It is preferable to make it 4 to 50% of the thickness of the whole double layer positive electrode active material. Furthermore, in order to make use of high capacity characteristic, it is preferable to set it as 4 to 30%, More preferably, it is 4 to 10%.

However, externally coated Li _{1 + δ} [Ni _x Mn _{xy / 2} Co _1-2x-z M _y N _z ] O _2-a P _a or Li _{1 + δ} [Ni _x Mn _{x + y} Co _{1-2 ( x + y) If} the thickness of M _y ] O _2-a P _a is less than 4%, the thermal stability is poor.

In addition, in the internal cathode active material Li _{1 + δ} [Co _a Mn _b M _c Ni _{1- (a + b + c)} ] O ₂ , the oxidation numbers of Ni, Co, and Mn are all +3, where M is +2. , +3, +4, +6)) Externally coated cathode active material Li _{1 + δ} [Ni _x Mn _{xy / 2} Co _1-2x-z M _y N _z ] O _2-a P _a and Li _{1+ δ} [Ni _x Mn _{x + y} Co _{1-2 (x + y)} M _y ] O _2-a P _a , the oxidation of Ni is +2, the oxidation of Mn is +4, and the oxidation of Co is +3 It is preferable that M which is a substituted metal is +2, and N is + trivalent.

Particularly, the oxidation number of Mn +4 can prevent the structure transition (Yan-Teller effect) caused by the oxidation / reduction reaction of +3 of Mn and +4 in existing tetragonal or layered LiMnO2. In order to stabilize the structure, lifespan characteristics can be improved.

Next, the obtained double layer composite metal hydroxide / oxide is washed with distilled water, filtered and dried at 110 ° C. for 15 hours or heat-treated at 450 ° C. for 5 hours to be used as a precursor.

Next, a dry method of sufficiently mixing the double layer composite metal hydroxide / oxide and the lithium precursor, or mixing the double layer composite metal hydroxide / oxide and the lithium precursor in an aqueous solution mixed with a chelating agent such as citric acid, tartaric acid, glycolic acid, maleic acid, and the like. Distilled water is removed using a wet method.

Finally, by baking for 10 to 25 hours in an oxidizing atmosphere of air or oxygen at 750 to 1000 ℃ to prepare a cathode active material for a lithium secondary battery having a double layer structure.

It is preferable that the specific target of the positive electrode active material for lithium secondary batteries which has a double layer structure manufactured by the said method is 0.1-3 m <^2> / g or less. This is because when the specific target exceeds 3 m ² / g, the reactivity with the electrolyte is increased and gas generation is increased.

In addition, in the case of using the reactor of the present invention, the tap density of the obtained hydroxide is improved by about 10% or more than in the case of using the conventional reactor. The tap density of the hydroxide is 1.95 g / cm 3, preferably 2.1 g / cm 3 or more, and more preferably 2.4 g / cm 3.

As an electrolyte that can be used in a lithium secondary battery using a cathode active material for a lithium secondary battery having a double layer structure made by the manufacturing method according to the present invention, an ester, for example, ethylene carbonate (ethylene carbornate) (EC), propylene carbonate ( cyclic carbonates such as propylene carbonate (PC), butylene carbonate (BC) and vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate non-cyclic carbonates such as carbonate (DEC), ethyl methyl carbonate (EMC) and zipurofilcarbonone (DPC), methyl formate (IMF), methyl acetate (MA), propionic acid Aliphatic carboxylic acid esters, such as methyl (MP) and ethyl propionate (MA), and cyclic carboxylic acid esters, such as butyl lactone (GBL), etc. are mentioned. As cyclic carbonate, EC, PC, VC, etc. are especially preferable. Moreover, it is also preferable to use aliphatic carboxylic acid ester in 20% or less of range as needed.

Lithium salts dissolved in the solvent include LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAlCl ₄ , LiSbF ₆ , LiSCN, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li (CF ₃ SO ₂ ) ₂ , LiAsF ₆ , LiN ( CF ₃ SO ₂ ) ₂ , LiB ₁₀ Cl ₁₀ , Lithium Bis (oxalato) borate (LiBOB), LiBoB, lower aliphatic lithium carbonate, lithium chloroborane, lithium tetraborate, and LiN (CF ₃ SO ₂ ) (C ₂ Imides such as F ₅ SO ₂ ), LiN (CF ₃ SO ₂ ) 2, LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) Can be used. The lithium salts may be used alone or in any combination within a range that does not impair the effects of the present invention. It is particularly preferable to use LiPF ₆ .

In addition, in order to render the electrolyte incombustible, carbon tetrachloride, ethylene trifluoride chloride, or phosphate containing phosphorus may be included in the electrolyte.

In addition, the following solid electrolytes can be used. Inorganic solid electrolytes include Li ₄ SiO ₄ , Li ₄ SiO ₄ -LiI-LiOH, xLi ₃ PO _4- (1-x) Li ₄ SiO ₄ , Li ₂ SiS ₃ , Li ₃ PO ₄ -Li ₂ S-SiS ₂ , Phosphorus sulfide compounds and the like are preferable.

As the organic solid electrolyte, it is preferable to use polyethylene oxide, polypropylene oxide, polyvinyl alcohol, polyvinylidene fluoride, fluoropropylene or the like, or polymer materials such as derivatives, mixtures and composites.

It is preferable to use a polyethylene-based or polypropylene-based polymer such as porous polyethylene.

 As the negative electrode material used in the invention, a compound capable of adsorbing and releasing lithium ions such as lithium, lithium alloy, alloy, intermetallic compound, carbon, organic compound, inorganic compound, metal complex and organic high molecular compound is used. It is preferable to use said compound individually or in combination arbitrarily in the range which does not impair the effect of this invention, respectively.

Examples of the lithium alloy include a Li-Al alloy, a Li-Al-Mn alloy, a Li-Al-Mg alloy, a Li-Al-Sn alloy, a Li-Al-In alloy, a Li-Al-Cd alloy, It is preferable to use a Li-Al-Te based alloy, a Li-Ga based alloy, a Li-Cd based alloy, a Li-In based alloy, a Li-Pb based alloy, a Li-Bi based alloy, a Li-Mg based alloy, or the like. .

As an alloy and an intermetallic compound, the compound of a transition metal and silicon, the compound of a transition metal, and tin, etc. can be used, Especially a compound of nickel and silicon is preferable.

Examples of carbonaceous materials include coke, pyrolytic carbon, natural graphite, artificial graphite, meso carbon micro beads, graphitized meso phase small spheres, vapor grown carbon, glassy carbon, and carbon fiber. (Poly acrylonitrile-based, pitch-based, cellulose-based, vapor-grown carbon-based), amorphous carbon, carbon from which organic materials are fired, and the like are preferably used. It is preferable to use these individually or in combination arbitrarily in the range which does not impair the effect of this invention, respectively.

In addition, it is preferable to use a packaging material composed of a metal can or aluminum and several layers of polymer layers.

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 16, but the present invention is not limited to these embodiments.

<Example 1>

After putting 4 liters of distilled water into the reactor (capacity 4L, the output of the rotary motor more than 80W), nitrogen gas was bubbled into the reactor at a rate of 1 liter / min to remove dissolved oxygen. Stirring at 1000 rpm while maintaining the temperature of the reactor at 50 ℃.

Nickel sulfate, manganese sulfate, and cobalt sulfate molar ratios of 1.92: 0.24: 0.24 were continuously added to a 2.4 M metal solution at 0.3 liters per hour, and 0.2 M ammonia solution at 0.03 liters per hour in the reactor. It was. In addition, a pH of 4.8 M sodium hydroxide solution was supplied to adjust the pH to maintain a pH of 11.

Impeller speed was adjusted to 1000 rpm. By adjusting the flow rate, the average residence time of the solution in the reactor was about 6 hours, and after the reaction reached a steady state, a steady state duration was given to the reactant to obtain a more dense composite metal hydroxide.

Nickel sulfate, manganese sulfate, and cobalt sulfate aqueous solutions supplied to the composite metal hydroxide at a steady state in a molar ratio of 1.92: 0.24: 0.24 were replaced with a molar ratio of nickel sulfate and manganese sulfate at 1 to 4 hours. The reaction was carried out under the same conditions as above and the samples reacted for 2 to 4 hours were collected for each time zone.

Next, a spherical nickel manganese cobalt composite hydroxide was continuously obtained through an overflow pipe. The composite metal hydroxide was filtered, washed with water, and dried in a 110 ° C. hot air dryer for 12 hours to obtain a precursor in the form of a metal composite oxide.

After mixing the precursor and lithium nitrate (LiNO ₃ ) in a 1: 1.15 molar ratio, the mixture was heated at a heating rate of 4 ° C./min and then maintained at 200 to 400 ° C. for 8 hours, followed by preliminary firing at 2 ° C./min. Heated at a rate of temperature increase and calcined at 750 ° C. to 800 ° C. for 10 to 20 hours to obtain Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ . Externally, Li {[Ni _0.8 Co _0.1 Mn _0.1 ] _x [Ni _1/2 Mn _1/2 ] _1-x } O ₂ positive electrode active material forming a double layer composed of Li [Ni _1/2 Mn _1/2 ] O ₂ A powder was obtained.

FIG. 2a is a composite oxide powder obtained by drying (Ni _0.8 Co _0.1 Mn _0.1 ) (OH) ₂ in a 110 ° C. warm air dryer for 12 hours, and FIG. 2b (Ni _0.8 Co _0.1 Mn _0.1 ) (OH) ₂ in (Ni _1/2) Mn _1/2 ) (OH) ₂ powder reacted for 1-2 hours, Figure 2c is (Ni _0.8 Co _0.1 Mn _0.1 ) (OH) ₂ to (Ni _1/2 Mn _1/2 ) (OH) ₂ 2 ₂ d is a photograph of a camera in which (Ni _0.8 Co _0.1 Mn _0.1 ) (OH) ₂ is reacted with (Ni _1/2 Mn _1/2 ) (OH) ₂ for 4 hours.

In the case of (Ni _0.8 Co _0.1 Mn _0.1 ) (OH) ₂ powder of FIG. 2A, the powder is brown, but (Ni _0.8 Co _0.1 Mn _0.1 ) (covered with (Ni _0.5 Mn _0.5 ) (OH) ₂ ) of FIGS. 2B to 2D ( In the case of OH) ₂ powder, the color turns black as the reaction time increases ((Ni _0.5 Mn _0.5 ) (OH) ₂ powder is black).

(1), (2), (3) and (4) of FIG. 3A are Ni _0.8 Co _0.1 Mn _0.1 ) (OH) ₂ and {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _1/2 Mn _1/2 ) Powder FE-SEM photograph of the time-phase reaction of _1-x } (OH) ₂ . A spherical particle shape was formed like the particle shape of (Ni _0.8 Co _0.1 Mn _0.1 ) (OH) ₂ . _{However, (Ni 0.8 Co 0.1 Mn 0.1} ) (OH) as compared to _{2 {(Ni 0.8 Co 0.1 Mn} 0.1) x (Ni 1/2 Mn 1/2) 1-x} (OH) 2 powders of reaction time slot It can be seen that the surface of is thickened in the shape of a thread.

4 is an EDX photograph of a powder obtained by reacting (Ni _0.8 Co _0.1 Mn _0.1 ) (OH) ₂ with (Ni _1/2 Mn _{1 / 2.5} ) (OH) ₂ for 4 hours, wherein Mn is (Ni _1/2 Mn ₁ It can be seen that the amount of Mn is more on the surface coated with ( ₂ ) (OH) ₂ , and Co and Ni are more present in the center of the powder particles. From this, it was confirmed that a double layer structure consisting of (Ni _0.8 Co _0.1 Mn _0.1 ) (OH) ₂ inside and (Ni _1/2 Mn _1/2 ) (OH) ₂ powder inside was well developed. The bilayer metal composite oxide powder is spherical with an average particle diameter of 5-10 μm, and the tap density of the powder is 1.7-2.0 g / cm 3.

FIG. 5 is a TEM-image photograph of a 3-hour reaction intermediate powder of {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _1/2 Mn _1/2 ) _1-x } (OH) ₂ . It can be seen that a double layer is formed in thickness.

92g of the double-layered composite metal hydroxide and 79.3g of lithium monohydrate were mixed and heated in an oxygen atmosphere at a rate of 4 ° C./min and then maintained at 200˜400 ° C. for 5 hours, followed by 2 ° C./min of 700 ° C. It baked at 900 degreeC for 20 hours. The tap density of the powder is 2.0-2.3 m ³ / g.

6 is a line after firing for 20 hours at 700 to 800 ° C. of a powder reacted with {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _1/2 Mn _1/2 ) _1-x } (OH) ₂ for 1 to 4 hours. The FE-SEM photograph shows that the double layer was well formed.

2A, 3A, 4, 5, and 6 from above, a double layer structure consisting of (Ni _0.8 Co _0.1 Mn _0.1 ) (OH) ₂ is formed inside and (Ni _0.5 Mn _0.5 ) (OH) ₂ powder is formed outside. It is confirmed that it is well developed. The bilayer metal composite oxide powder is spherical with an average particle diameter of 5-15 μm, and the tap density of the powder is 1.7-2.0 g / cm 3.

A slurry was prepared by mixing a positive electrode active material for a lithium secondary battery having a double layer structure prepared by the above method, acetylene black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder in a weight ratio of 80:10:10. The slurry was uniformly applied to an aluminum foil having a thickness of 20 μm, and vacuum dried at 120 ° C. to prepare a cathode for a lithium secondary battery.

The anode and the lithium foil were used as counter electrodes, and a porous polyethylene membrane (Celgard de LC, 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 manufactured coin battery was evaluated for the positive electrode active material in the 3.0 ~ 4.3 volt region using an electrochemical analyzer (Toyo System, Toscat 3100U).

<Example 2>

The calcining process was calcined at 770 ° C. for 20 hours to prepare a half cell.

<Example 3>

0.05 mol of ammonium fluoride (NH ₄ F) was mixed with 1 mol of (Ox) 1 mol of the double-layered composite metal hydroxide and calcined at 770 ° C. for 20 hours to prepare a half cell.

<Example 4>

Powders were synthesized in the same manner as in Example 1, except that nickel sulfate and manganese sulfate cobalt sulfate molar ratios were added in an amount of 1.08: 1.08: 0.24 and then reacted for 3 hours to prepare a coin-type half cell.

3b is a 3 hour reactant powder FE-SEM photograph of {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _0.45 Co _0.1 Mn _0.45 ) _1-x } (OH) ₂ . A spherical particle shape was formed as shown in (Ni _0.8 Co _0.1 Mn _0.1 ) (OH) ₂ particle shape in FIG. 3A (1). _{However, (Ni 0.8 Co 0.1 Mn 0.1} ) (OH) as compared to _{2 {(Ni 0.8 Co 0.1 Mn} 0.1) x (Ni 0.45 Co 0.1 Mn 0.45) 1-x} (OH) the surface of the _second powder pincushion shape You can see this is formed.

Example 5

Powders were synthesized in the same manner as in Example 4 and calcined at 770 ° C. for 20 hours to prepare a half cell.

<Example 6>

Powders were synthesized in the same manner as in Example 1 except that a metal aqueous solution containing nickel sulfate and manganese sulfate cobalt sulfate molar ratio of 0.96: 0.96: 0.48 was added for 3 hours to prepare a coin-type half cell. .

3c is a 3 hour reactant powder FE-SEM photograph of {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _0.45 Co _0.1 Mn _0.45 ) _1-x } (OH) ₂ . A spherical particle shape was formed as in the particle shape of (Ni _0.8 Co _0.1 Mn _0.1 ) (OH) ₂ in FIG. 3A (1). _{However, (Ni 0.8 Co 0.1 Mn 0.1} ) (OH) as compared to _{2 {(Ni 0.8 Co 0.1 Mn} 0.1) x (Ni 0.4 Co 0.2 Mn 0.4) 1-x} (OH) is pincushion-shaped surface of the powder of the _second You can see this is formed.

<Example 7>

The powder synthesized in the same manner as in Example 6 was fired at 770 ° C. for 20 hours to prepare a half cell.

<Example 8>

Inside, a metal aqueous solution mixed with nickel sulfate and cobalt sulfate molar ratio of 1.92: 0.48 was added to reach a steady state, followed by a metal aqueous solution mixed with nickel sulfate, manganese sulfate, and cobalt sulfate molar ratio of 1.08: 1.08: 0.24. A powder was synthesized in the same manner as in Example 1 except that the reaction was performed for only 1-3 hours.

FIG. 2E is a composite oxide powder obtained by drying (Ni _0.8 Co _0.2 ) (OH) ₂ in a 110 ° C. warm air dryer for 12 hours, and FIG. 2F is (Ni _0.8 Co _0.2 ) (OH) ₂ in (Ni _0.45 Co _0.1 Mn _0.45 ) ( OH) ₂ powder for 1 hour-2 hours, FIG. 2G is a camera photograph of a powder obtained by reacting (Ni _0.8 Co _0.2 ) (OH) ₂ with (Ni _0.45 Co _0.1 Mn _0.45 ) (OH) ₂ for 3 hours.

In the case of (Ni _0.8 Co _0.2 ) (OH) ₂ powder of FIG. 2E, it is light green, but (Ni _0.8 Co _0.2 ) (OH) covered with (Ni _0.45 Co _0.1 Mn _0.45 ) (OH) ₂ of FIGS. 2F to 2G. In the case of powder, the color turns black as the reaction time increases. (Ni _0.45 Co _0.1 Mn _0.45 ) (OH) ₂ powder is black).

3d is a FE-SEM photograph of precursor powders of (Ni _0.8 Co _0.2 ) (OH) ₂ and (Ni _0.8 Co _0.2 ) x (Ni _0.45 Co _0.1 Mn _0.45 ) _1-x (OH) ₂ . It became a particle form of spherical done well, as shown by (Ni _0.8 Co _0.2) compared to the surface of the _{(OH) 2 (Ni 0.8 Co} 0.2) x of the _{(Ni 0.45 Co 0.1 Mn 0.45)} 1-x (OH) 2 It can be seen that the surface is made of a thread shape.

It can be seen from the above FIG. 2E, FIG. 2F, FIG. 2G, and FIG. 3D that the formation of the double layer was well performed for the binary composite oxide.

Example 9

The powder synthesized in the same manner as in Example 8 was fired at 720 ° C. for 20 hours to prepare a half cell.

<Comparative Example 1a>

Synthesis was carried out in the same manner as in Example 1, except that [Ni _0.8 Co _0.1 Mn _0.1 ] (OH) ₂ was prepared.

FIG. 7A is an X-ray diffraction pattern of the precursor powder synthesized in Comparative Example 1 (a) and the powder synthesized according to time zones in Example 1. FIG. As can be seen, the longer the synthesis time, it can be seen that the characteristics of the powder forming the double layer appear in the diffraction pattern.

<Comparative Example 1b>

Synthesis was carried out in the same manner as in Example 1, except that [Ni _0.8 Co _0.2 ] (OH) ₂ was prepared.

FIG. 7B is an X-ray diffraction pattern of the precursor powder synthesized in Comparative Example 1 (b) and the powder synthesized according to the time zone in Example 8. FIG. It can also be seen that the longer the synthesis time, the properties of the powder forming the double layer appear in the diffraction pattern.

Comparative Example 2

Powders were prepared in the same manner as in Examples 2, 5 and 7, except that (Ni _0.8 Co _0.1 Mn _0.1 ) (OH) ₂ was prepared in Comparative Example 1 (a) and sintered at 750 ° C. for 20 hours. Prepare

Figure 8a is an X-ray diffraction pattern of the sintered powder particles prepared in Comparative Example 2 and the sintered powder particles prepared in Example 2, Figure 8b is a sintered powder particles prepared in Comparative Example 2, Example 2 formed a double layer for 3 hours X-ray diffraction patterns (XRD) of the sintered powder particles and the sintered powder particles of Examples 5 and 7. In the diffraction peaks of all the powders, the (006) and (102) peak separations, the (018) and (110) peak separations are well represented, and the lithium composite oxide has a space ratio of 1 or more. It can be seen that it has a hexagonal-NaFeO ₂ structure having a group R-3m and is a layered compound having excellent crystallinity even after being formed in a double layer structure.

Comparative Example 3

Except for the sintered powder particles prepared in Comparative Example 2, the powder was prepared by the method of Example 2, Example 5, Example 7.

FIG. 9a shows the results of charging and discharging at 0.4 kV in the 3.0-4.3 V range for the sintered powder particles prepared in Comparative Example 2 and the sintered powder particles according to time slots prepared in Example 2 as charge and discharge curves. Li {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _1/2 Mn _1/2 ) _1-x } O ₂ prepared by the method of Example 2 was synthesized according to the method of Comparative Example 1 by the method of Comparative Example 1 It shows a lower discharge capacity compared to Li [Ni _0.8 Co _0.1 Mn _0.1 ] O _{2 prepared} with ₂ . However, the discharge voltage is higher than that of Li [Ni _0.8 Co _0.1 Mn _0.1 ] O _{2, which} is a characteristic of Li [Ni _0.5 Mn _0.5 ] O _{2 in} the 3.5-3.8 V region. The discharge capacity of the second cycle is in the order of 2 hours, 3 hours, and 4 hours prepared in Comparative Examples 1 and 2, and the double layer positive electrode active material prepared in Example 2 is slightly lower in discharge capacity but higher in discharge capacity compared to Comparative Example 1. can see.

FIG. 9B shows a charge / discharge of 0.4 s in the 3.0-4.3 V range for the sintered powder particles prepared in Comparative Example 2 and the three-hour double-layer positive electrode active material powder prepared in Example 2, and the sintered powder particles prepared in Examples 5 and 7 One result is shown by the charge / discharge curve. Li {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _1/2 Mn _1/2 ) _1-x } O ₂ 3 hours prepared by the method of Example 2 synthesized by the method of Comparative Example 1 Comparative Example 2 It shows a slightly lower discharge capacity compared to Li [Ni _0.8 Co _0.1 Mn _0.1 ] O _{2 prepared} with. However, the discharge voltage is higher than that of Li [Ni _0.8 Co _0.1 Mn _0.1 ] O _{2, which} is a characteristic of Li [Ni _0.5 Mn _0.5 ] O _{2 in} the 3.5-3.8 V region.

The Li [(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _0.45 Co _0.1 Mn _0.45 ) _1-x ] O ₂ positive electrode active material synthesized for 3 hours by the method of Example 5 was synthesized by the method of Comparative Example 1 to Comparative Example 2 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ prepared using Li {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _1/2 Mn _1/2 ) _1-x } O ₂ synthesized for 3 hours by the method of Example ₂ In addition, the discharge capacity is lower, and the discharge voltage is not higher than that of Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ prepared in Comparative Example 2 in the 3.5-3.8V discharge region. The cathode active material of Li [(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _0.4 Co _0.2 Mn _0.4 ) _1-x ] O ₂ synthesized for 3 hours by the method of Example 7 was synthesized according to the method of Comparative Example 1 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O _{2 prepared} with Example 1 and Li {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _1/2 Mn _1/2 ) _1-x } O synthesized for 3 hours by the method of Example 1 _{It can} be seen that the discharge capacity is lower than ₂ and the discharge voltage is not higher than that of Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ prepared in Comparative Example 2 in the 3.5-3.8V discharge region.

The second discharge capacity is the positive electrode active material prepared in Comparative Example 1, prepared in Comparative Example 2, Examples 2, 5, and 7, and the double layer prepared by synthesis of Example 2 by the method of Example 2 compared with Comparative Example 1 It can be seen that it shows good characteristics.

<Comparative Example 4>

A powder was prepared in the same manner as in Examples 5 and 7, except that the sintered powder particles prepared in Comparative Example 2 and the 3 hour double layer positive electrode active material powder prepared in Example 2 were prepared.

FIG. 10a shows the discharge capacity according to the cycle tested at 0.4 kV in the 3.0-4.3 V range for the bilayer powder synthesized by time by the method of Example 2 and the sintered powder preparation prepared in Comparative Example 2. FIG.

The sintered powder particles prepared in Comparative Example 2 showed a decrease in capacity as a result of charge and discharge up to 70 cycles, whereas the bilayers according to time zones prepared in Example 2 showed better cycle characteristics than the sintered powder prepared in Comparative Example 2.

Figure 10b is the discharge capacity according to the cycle experimented with 0.4 s in the 3.0-4.3 V range for the sintered powder particles prepared in Comparative Example 2 and the three-layer double layer sintered powder prepared in Example 2, Example 5, Example 7 Indicated.

This also shows that the bilayered powders have better cycle characteristics than the sintered powders prepared in comparison 2.

Comparative Example 5

A powder was prepared in the same manner as in Example 2, Example 5, and Example 7, except for the sintered powder prepared in Comparative Example 2.

FIG. 11a shows the results of thermal analysis by differential thermal gravimetric analysis (DSC) by charging the sintered powder prepared in Comparative Example 2 and the bilayer sintered powder prepared in Example 2 at 4.3 V and 0.4 kPa. In the case of Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ , the exothermic peak starts to appear at 174.7 ° C. and the main exothermic peak appears around 218.7 ° C., but in Example 1, the exothermic peak starts to appear at about 200.8 ° C. 238.3 ℃ shows an increase of about 20 ℃ at the main exothermic peak. In Example 3, the exothermic peak appears at about 217.2 ° C. and the main exothermic peak is 250.2 ° C., which shows an increase of about 30 ° C. at the main exothermic peak. In addition, in Example 5, the exothermic peak appears at 220 ° C., and the main exothermic peak is 265.8 ° C., which shows an increase of about 50 ° C. Compared to Comparative Example 1, the powder having a double layer formed for a longer time shows better thermal stability. Giving.

FIG. 11 b shows the results of thermal analysis by differential thermal gravimetric analysis (DSC) by charging the sintered powder prepared in Comparative Example 2 and the sintered powder prepared in Examples 5 and 7 at 4.3 V and 0.4 kPa. . In Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ , the exothermic peak began to appear at 174.7 ° C., and the main exotherm peak appeared at around 218.7 ° C., but the heat generation was about 217.2 ° C. for the 3-hour bilayer powder prepared by the method of Example 2. The peak starts to appear and the main exothermic peak is 250.2 ° C, an increase of about 32 ° C from the main exothermic peak. In Example 5, the exothermic peak appears at about 216.7 ° C. and the main exothermic peak is 247.1 ° C., which shows an increase of about 30 ° C. at the main exothermic peak compared to the sintered powder prepared in Comparative Example 2. In addition, in Example 7, the exothermic peak appears at 206.5 ° C. and the main exothermic peak is 249.8 ° C., showing an increase of about 30 ° C. compared with the sintered powder prepared in Comparative Example 2.

As shown in Comparative Example 5, it can be seen that the sintered powder in which the double layer was formed has superior thermal stability even if another double layer was formed in the change in the amount of cobalt sulfate.

Comparative Example 6

Lithium fluoride 1.12 mol compared to the powder in (Ni _0.8 Co _0.1 Mn _0.1 ) OH ₂ powder synthesized in Comparative Example 1 (a), (O _x ) 1mol of the powder synthesized in Comparative Example 1 (a) 0.05 A double layer powder was prepared in the same manner as in Example 3 except that the mol was mixed and calcined at 770 ^° C. for 20 hours.

12 and 13 illustrate Li [Ni _0.8 Co _0.1 Mn _0.1 ] O _1.95 F _0.05 positive electrode active material synthesized in Comparative Example 6 and Li {(Ni _0.8 Co _0.1 Mn _0.1 ) _x (Ni _1/2 synthesized in Example 3; Mn _1/2 ) _1-x } O _1.95 F _0.05 After charging with 4.3V respectively, the thermal analysis by differential scanning calorimetry (DSC) is shown.

Compared with the positive electrode active material synthesized in Comparative Example 1 (a), the positive electrode active material calcined by anion-substituting lithium fluoride in Comparative Example 6 shows excellent results in thermal safety.

In addition, the double-layer positive electrode active material synthesized in Example 3 shows better results in thermal stability than the positive electrode active material synthesized in Example 1 and calcined in the same manner as in Example 2.

Comparative Example 7

[Ni _0.8 Co _0.2 ] (OH) ₂ synthesized in Comparative Example 1 (b) was synthesized in the same manner as in Example 8 except that the sintered at 720 ℃, 20 hours in the same manner as in Example 9 Sintered powder was prepared. In the diffraction peaks of all the powders, the (006) and (102) peak separations, the (018) and (110) peak separations are well represented, and the lithium composite oxide has a space ratio of 1 or more. It can be seen that it has a hexagonal-NaFeO ₂ structure having a group R-3m and is a layered compound having excellent crystallinity even after being formed in a double layer structure.

<Comparative Example 8>

The sintered powder prepared in Comparative Example 7 and the sintered powder synthesized in Example 9 were prepared.

FIG. 15 shows the discharge capacity of the intermediate sintered powder synthesized in Comparative Example 1 (b) and the cycle tested at 0.4 kV in the 3.0-4.3 V range for the time-phase powders prepared in Example 9. As shown in FIG. 14, the sintered powders prepared in Example 9 showed a lower discharge capacity than the sintered powders synthesized and sintered in Comparative Example 1 (b), but were synthesized in Comparative Example 1 (b) in a 3.5-3.8V region. The discharge voltage is higher than that of the sintered powder.

Comparative Example 9

The sintered powder prepared in Comparative Example 7 and the sintered powder synthesized in Example 9 were prepared.

FIG. 16 shows the results of thermal analysis by differential thermogravimetric analysis (DSC) after charging the sintered powder prepared in Comparative Example 7 and the sintered powder synthesized in Example 9 to 4.2V, respectively. In the case of Li [Ni0.8Co0.2] O2, the exothermic peak starts to appear at 200 ° C., and the main exothermic peak appears at around 220 ° C., but the 210 ° C. exothermic peak of the 3-hour double layer forming sintered powder prepared in Example 9 The main fever peak appeared around 255 ° C. It was also found that the calorific value was reduced by about 3/4 than that of Li [Ni0.8Co0.2] O2.

As described above, the present invention has been described for only one preferred embodiment, but it is apparent to those skilled in the art that various changes and modifications 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.

As described above, the positive electrode active material having a layered rock salt structure and a double layer structure prepared using the hydroxide co-precipitation method according to the present invention has a nickel-based anode having a high capacity characteristic inside, and a transition metal mixed system having excellent thermal safety at the outside in contact with the electrolyte. It is composed of anode, which has high capacity, high packing density, improved lifespan, and excellent thermal safety.

Claims (14)

In the positive electrode active material for a lithium secondary battery having a double layer structure, A cathode active material for a lithium secondary battery having a double layer structure, characterized in that the inside is composed of a nickel-based positive electrode active material, the outside in contact with the electrolyte is a transition metal mixed-based positive electrode active material. The method of claim 1, The inside is Li _{1 + δ} [Co _a Mn _b M _c Ni _{1- (a + b + c)} ] O ₂ (M is Mg, Zn, Ca, Sr, Cu, Zr, P, Fe, Al, Ga, At least one element selected from the group consisting of In, Cr, Ge, Sn, 0≤δ≤1 / 5, 0≤a≤0.5, 0≤b≤0.2, 0≤c≤0.1, 0≤a + b + c ≤ 0.5), the positive electrode active material for a lithium secondary battery having a double layer structure. The method of claim 1, The outside is Li _{1 + δ} [Ni _x Mn _{xy / 2} Co _1-2x-z M _y N _z ] O _2-a P _a or Li _{1 + δ} [Ni _x Mn _{x + y} Co _{1-2 (x + y)} My] O _2-a P _a (M is at least one element selected from the group consisting of Mg, Zn, Ca, Sr, Cu, Zr, N is Fe, Al, Ga, In, Cr, Ge, Sn At least one element selected from the group consisting of: P = F or S, 0≤δ≤1 / 5, 0≤x≤1, 0≤y≤1 / 10, 0≤z≤1 / 10, 0≤a≤0.3 A cathode active material for a lithium secondary battery having a double layer structure, characterized in that consisting of. The method of claim 2, The Li _{1 + δ} [Co _a Mn _b M _c Ni _{1- (a + b + c)} ] O ₂ is the oxidation number of Co, Mn, and Ni is +3, M is +2, +3 is, + A cathode active material for a lithium secondary battery having a double layer structure, wherein tetravalent, +5, +6, or +2, +3, +4, +5, and +6 are one or more elements. The method of claim 3, wherein Li _{1 + δ} [Ni _x Mn _{xy / 2} Co _1-2x-z M _y N _z ] O _2-a P _a or Li _{1 + δ} [Ni _x Mn _{x + y} Co _{1-2 (x + y)} My] O _2-a P _a is characterized in that the oxidation of Ni is +2, the oxidation of Mn is +4, the oxidation of Co is +3, and the substituted metals M and N are +2 and +3, respectively. A cathode active material for a lithium secondary battery having a double layer structure. The method of claim 3, wherein Li _{1 + δ} [Ni _x Mn _{xy / 2} Co _1-2x-z M _y N _z ] O _2-a P _a or Li _{1 + δ} [Ni _x Mn _{x + y} Co _{1-2 (x + y)} The thickness of M _y ] O _2-a P _a is _a positive electrode active material for a lithium secondary battery having a double layer structure, characterized in that 4 to 50% of the total thickness of the double layer positive electrode active material. The method of claim 1, The average particle diameter of the nickel-based positive electrode active material is 0.1 to 2μm, the total average particle diameter is 5 to 20μm, the positive electrode active material for a lithium secondary battery having a double layer structure. Mixing the nickel-based metal precursor, the ammonia aqueous solution and the basic solution into the reactor at the same time to obtain a spherical precipitate; Mixing the transition metal mixed metal precursor, the ammonia aqueous solution and the basic solution on the precipitate at the same time in a reactor to obtain a precipitate of the double layer composite metal hydroxide salt covered with the transition metal hydroxide; Drying or heat treating the precipitate to obtain a bilayer composite metal hydroxide / oxide; Method for producing a positive electrode active material for a lithium secondary battery having a double layer structure comprising the four steps of obtaining a double layer lithium composite metal oxide by mixing a lithium precursor to the double layer composite metal hydroxide / oxide. The method of claim 8, In the first step, an aqueous solution including two or more metal salts is mixed and used as a precursor. The molar ratio of ammonia and metal salts is 0.2 to 0.4, and the pH of the reaction solution is adjusted to 10.5 to 12 for 2 to 10 hours. A method of manufacturing a cathode active material for a lithium secondary battery having a double layer structure. The method of claim 8, The second step is a method for producing a cathode active material for a lithium secondary battery having a double layer structure, characterized in that by adjusting the reaction time to 1 to 10 hours to adjust the thickness of the outer layer. The method of claim 8, The third step is a method for manufacturing a cathode active material for a lithium secondary battery having a double layer structure characterized in that the drying for 15 hours at 110 ℃, or 5 to 10 hours at 400 to 550 ℃. The method of claim 8, The third step is a lithium secondary battery having a double-layer structure, characterized in that it comprises a step of preliminary baking by maintaining 400 ~ 650 ℃, 5 hours, 10 hours at 700 ~ 1100 ℃, annealing at 700 ℃ 10 hours Method for producing a positive electrode active material. The method of claim 8, The fourth step is a lithium secondary having a double layer structure characterized in that the distilled water is removed after mixing the dried composite metal hydroxide or oxide and lithium precursor in an aqueous solution mixed with a chelating agent such as citric acid, tartaric acid, glycolic acid, maleic acid, etc. Method for producing a positive electrode active material for a battery. A lithium secondary battery using a cathode active material for a lithium secondary battery having a double layer structure of claim 1 to claim 7.

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