KR101991254B1 - Positive Active material with high Power density and longevity - Google Patents

Abstract

The present invention relates to a mixed cathode active material exhibiting a high output lifetime.
The mixed cathode active material according to the present invention exhibits a high energy density while exhibiting high stability by mixing a nickel cobalt aluminum composite oxide having a high energy density and a layered lithium nickel cobalt manganese composite oxide having a relatively high stability while controlling the particle diameter.

Description

[0001] The present invention relates to a positive active material with high power density and longevity,

The present invention relates to a mixed cathode active material exhibiting a high output lifetime.

As technology development and demand for mobile devices increase, the demand for secondary batteries as energy sources is rapidly increasing. Among these secondary batteries, a lithium secondary battery having a high energy density and voltage, a long cycle life, and a low self-discharge rate has been commercialized and widely used. In addition, as the interest in environmental issues grows, researches on electric vehicles and hybrid electric vehicles that can replace fossil fuel-based vehicles such as gasoline vehicles and diesel vehicles, which are one of the main causes of air pollution, . In recent years, studies on the use of lithium secondary batteries having high energy density and discharge voltage as power sources for electric vehicles and hybrid electric vehicles have been actively conducted, and some of them are in the commercialization stage.

LiCoO2, which is a typical anode material, has reached the practical limit of output power density and energy density. Especially, when it is used in high energy density application field, due to its structural instability, Thereby generating an exothermic reaction with the electrolyte in the cell, thereby causing the explosion of the battery. In order to improve the instability of LiCoO2, the use of lithium-containing manganese oxides such as LiMnO 2 of layered crystal structure and LiMn 2 O 4 of spinel crystal structure and lithium-containing nickel oxide (LiNiO 2) Research on the use of layered oxides has been steadily progressing.

The most representative Li [Ni1 / 3Co1 / 3Mn1 / 3] O2 among the three-component layered oxides changes from Ni2 + to Ni3 + or Ni4 + depending on the filling depth. However, unlike stable Ni2 +, Ni3 + or Ni4 + loses lattice oxygen due to instability and is reduced to Ni2 +. This lattice oxygen reacts with the electrolyte to change the surface properties of the electrode or increase the charge transfer impedance of the surface, The high-rate characteristics and the like are lowered, resulting in a problem that the energy density is low.

If a stable Group 13 metal such as B, Al, In, and Tl is additionally doped to LiNixCo1-xO2, the structural instability can be improved. Stable trivalent metal ions such as Al migrate or disperse between the NiO2 layers during charging and discharging to stabilize the hexagonal structure. Lix [Ni1-y-zCoyAlz] O2 (0.96 ≤ x ≤ 1.05, 0 ≤ y ≤ 0.2, 0 ≤ z ≤ 0.1) (NCA) with such a composition and structure has high thermal stability, high cycle life, And the stability of the layered structure by aluminum.

In addition to substituting cobalt, which is another transition metal, into the nickel sites at the precise position of LiNiO ₂ , which is a high-capacity cathode active material, as described above, NCA also has a structure in which Ni ⁺ Is a cathode active material doped with aluminum, which is a Group 13 metal having a stable +3 valence ion so as to prevent oxidation and provide structural stability. Accordingly, NCA is known to exhibit the highest capacity among the currently available cathode active materials for lithium secondary batteries. However, there is a problem that the safety is poor due to the high Ni content and the life characteristic is degraded.

In order to solve the above problems, it is an object of the present invention to provide a mixed cathode active material of a three-component layered oxide and an NCA compound.

Disclosure of the Invention In order to solve the above problems, the present invention provides a lithium composite oxide represented by the following Chemical Formula 1: And a lithium composite oxide having a layered structure represented by the following Chemical Formula 2; The present invention also provides a mixed cathode active material comprising the same.

???????? LiXNiyCo1-y-zAlzO2 (0.9? X? 1.3, 0.6? Y? 0.9, 0.02? Z?

Wherein M is at least one selected from the group consisting of Mg, Ti, Ca, B, and Al; LixNiyMnzCo1-y-zMsO2 wherein 0.9? X? 1.3; 0.3? Y? 0.8; 0.01? Z? 0.4; )

In the mixed cathode active material according to the present invention, 0 to 100 parts by weight of a lithium composite oxide having a layered structure represented by formula (2) per 100 parts by weight of the lithium composite oxide represented by the formula (1) .

In the mixed cathode active material according to the present invention, the lithium composite oxide represented by the formula (1) has a particle diameter of 10 to 15 탆.

In the mixed cathode active material according to the present invention, the lithium composite oxide represented by the formula (2) has a particle diameter of 1 to 6 탆.

The mixed cathode active material according to the present invention is characterized in that the particle size of the lithium composite oxide represented by the formula 1 is larger than the particle size of the lithium composite oxide represented by the formula 2 and the lithium composite oxide represented by the formula 1 The energy density is increased by filling the space between the anode and the cathode with the lithium composite oxide represented by the above formula (2).

In the mixed cathode active material according to the present invention, the lithium composite oxide represented by Formula 2 is LiNi1 / 3Mn1 / 3Co1 / 3O2.

The present invention also provides a positive electrode comprising the mixed cathode active material according to the present invention.

The present invention also provides a lithium secondary battery comprising a positive electrode according to the present invention.

The present invention also provides a middle- or large-sized device including the lithium secondary battery according to the present invention.

In the present invention, the middle- or large-sized device may be a power tool, an electric vehicle (EV), a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle , PHEV); Electric motorcycle including E-bike, E-scooter; Electric golf cart; Electric truck; An electric commercial vehicle or a system for electric power storage.

The mixed cathode active material according to the present invention exhibits a high energy density while exhibiting high stability by mixing a nickel cobalt aluminum composite oxide having a high energy density and a layered lithium nickel cobalt manganese composite oxide having a relatively high stability while controlling the particle diameter.

1 and 2 show the results of measuring the pellet density and the energy density of the active material prepared in Examples and Comparative Examples of the present invention.
FIGS. 3 and 4 are measurement results of life characteristics and energy characteristics of a battery including the active material prepared in Examples and Comparative Examples of the present invention.

Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited by the following examples.

< Example  1> Preparation of lithium composite oxide

< Example  1-1> Nickel cobalt aluminum  Synthesis of complex hydroxides

(NiSO _{4 ·} 6H ₂ O) and cobalt sulfate cahaldehydrate (CoSO _{4 ·} 7H ₂ O) metal solution were prepared so that the molar ratio of Ni: Co was 84.5: 15.5. 28% ammonia water as a complexing agent and 25% sodium hydroxide solution as a pH adjusting agent were used. A continuous reactor having an internal volume of 90 L filled with a 1 M aqueous ammonia solution was used and the pH of the initial solution was in the range of 11 to 12. The prepared 2.0 M nickel cobalt metal mixed solution, 28% ammonia water, and 25% sodium hydroxide solution were simultaneously and continuously introduced at a rate of 600 rpm using a metering pump while stirring. At this time, while the temperature in the reactor was maintained at 50 ° C., the metal mixture solution was fed at a rate of 7 L / hr and the ammonia water was fed at a rate of 0.5 L / hr. While sodium hydroxide was continuously supplied, Respectively. The residence time of the reactor was 8 hours. The slurry, which is the reaction product discharged through the reactor overflow in a continuous reaction, was collected.

Thereafter, the slurry thus obtained was collected at 90% in a batch type reactor having a volume of 90 L, the molar ratio of aluminum and the nickel cobalt metal mixed solution was adjusted to 5 mol% while maintaining the temperature at 50 ° C and the rotation speed at 600 rpm. (Al (NO3) 3) aqueous solution of 2.0M and a 25% sodium hydroxide solution as a co-agent were simultaneously added thereto. At this time, the feed rate of the aluminum nitrate solution was 2 L / hr, and the sodium hydroxide was reacted for 1 hour while adjusting the feed amount so that the pH in the reactor was maintained at 8 to 10. The slurry solution in the reactor was filtered, washed with distilled water of high purity, and then dried in a vacuum oven at 110 DEG C for 12 hours to obtain a nickel-cobalt aluminum complex hydroxide. The composition of nickel-cobalt-aluminum metal composite hydroxide was _{2 Ni 0 .8 Co 0 .15 Al} 0 .05 (OH).

The dried nickel cobalt aluminum complex hydroxide was heat-treated at 550 ° C for 6 hours in an air atmosphere to obtain a metal composite oxide. The resultant lithium hydroxide (LiOH? H2O) was dissolved in an aqueous solution of Li / (Ni + Co + Were mixed in a Cordilite crucible (Sega) and fired at 750 ° C for 20 hours in an oxygen atmosphere.

The composition is water the calcined lithium metal composite oxide was _{Li (Ni 0 .8 Co 0 .15} Al 0 .05) O 2.

< Example  1-2> Nickel cobalt aluminum  Synthesis of complex hydroxides

Li (Ni _0.9 Co _0.05 Al _0.05 ) O ₂ was produced in the same manner as in Example 1-1 except that the mixing ratio of the transition metal was different.

< Example  1-3> Nickel cobalt manganese  Synthesis of complex hydroxides

The concentration of the aqueous solution of the metal of 2.5 M in the molar ratio of nickel sulfate, cobalt sulfate and manganese sulfate in the ratio of 0.29: 0.13: 0.58 was adjusted to 0.8 liter / hour, and the concentration of the ammonia solution in the reactor / 0.8. &Lt; / RTI &gt; At this time, 0.5% polyvinyl alcohol (PVA) solution relative to ammonia metal salt was simultaneously added to the aqueous ammonia solution for particle size control and uniform distribution. The pH was adjusted to 11.5 by supplying a 25% aqueous solution of sodium hydroxide to adjust the pH. The average residence time of the solution was adjusted to about 10 hours, and the average temperature of the reaction tank was maintained at 45 to 55 ° C Respectively.

The resulting complex hydroxide was poured into caustic soda until pH of 12.5 was reached to remove unreacted metal salts, followed by filtration and washing with water, followed by drying in a 110 ° C hot air dryer for 12 hours to obtain a complex hydroxide type precursor. Hydroxide, then a solution of lithium so that the ratio is 1.11 in the concentration of the metal salt, then heated to 1 ℃ / min rate of temperature rise subjected to heat treatment in the manner described above was 10 hours and baked at _{950 ℃ LiNi 1/3 Mn 1} /3 Co _{1 / 3O} &lt; _{2 &} gt ;.

< Example  1-4> Nickel cobalt manganese  Synthesis of complex hydroxides

Example 1-3 In the same manner as in _{LiNi 0 .5 Mn 0 .2 Co 0} .3 O 2, LiNi 0 .6 Mn 0 .2 Co 0 .2 O to obtain a positive electrode active material powder represented by _2.

< Example  2> Preparation of mixed lithium composite oxide

The lithium composite oxides prepared in Examples 1-1 and 1-3 were mixed in the following proportions to prepare a mixed lithium composite oxide.

< Experimental Example > Depending on the mixing ratio pellet density  And energy density measurement

The pellet density and energy density of the mixed lithium composite oxide of Examples 2-1 to 2-4 and Comparative Examples 1 and 2 were measured and shown in FIG. 1 and Table 2 below.

1 and Table 2, it can be seen that as the mixing ratio of NCM increases, the pellet density and the energy density increase and then decrease.

< Experimental Example > Dependence of particle size of mixed lithium composite oxide pellet density  And energy density measurement

The pellet density and energy density of the mixed lithium composite oxide of Examples 2-1 to 2-4 and Comparative Examples 1 and 2 were measured and shown in FIG. 2 and Table 2.

< Manufacturing example >

The cathode active material for a lithium secondary battery produced according to each of the above Examples and Comparative Examples was mixed with acetylene black as a conductive agent and polyvinylidene fluoride (PVdF product name: solef6020) as a binder at a weight ratio of 90: 5: 5, . The slurry was uniformly coated on an aluminum foil having a thickness of 20 탆 and vacuum-dried at 130 캜 to prepare a positive electrode for a lithium secondary battery.

An electrolytic solution obtained by dissolving LiPF6 in a concentration of 1 M in a solvent mixed with ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3: 7 was used as a separator and the porous polyethylene film having a thickness of 25 탆 was used as the counter electrode and the lithium foil as the counter electrode To prepare a coin cell by a conventional method.

< Experimental Example > Evaluation of battery characteristics

The life characteristics and the energy density of the coin battery manufactured using the cathode active materials of the above examples and comparative examples were evaluated and shown in Table 2 and FIG. 3 and FIG.

Claims (9)

A lithium composite oxide containing Ni and Al and represented by the following Chemical Formula 1; And
And a lithium composite oxide having a layered structure represented by the following Chemical Formula 2,
A lithium composite oxide represented by the above formula (1); And the lithium composite oxide having a layered structure represented by the general formula (2) is in a range of 2.8 to 4.7 in terms of particle size ratio (large diameter / small particle diameter).
Li _x Ni _y Co ₁ -yz Al _z O ₂ (0.9? X? 1.3, 0.6? Y? 0.9, 0.02? Z? 0.1)
[Chemical Formula _{2] Li x Ni y Mn z} Co 1-yz M s O 2 (0.9≤x≤1.3, 0.3≤y≤0.8, 0.01≤z <0.4, 0≤s≤0.3, M is Mg, Ti, Ca , B, and Al)
The method according to claim 1,
Wherein the mixed cathode active material is mixed in a ratio of 0 to 100 parts by weight of a layered lithium composite oxide represented by Formula 2 per 100 parts by weight of the lithium composite oxide represented by Formula 1. [
The method according to claim 1,
Wherein the lithium composite oxide represented by Formula 1 has a particle diameter of 10 to 15 占 퐉.
The method according to claim 1,
Wherein the lithium composite oxide represented by the formula (2) has a particle diameter of 1 to 6 占 퐉.
The method according to claim 1,
Wherein [Formula 2] The lithium composite oxide is represented by _{LiNi 1/3 Mn 1/3} Co 1/3 O 2 in the mixed positive electrode active material according to claim.
An anode comprising the mixed cathode active material according to any one of claims 1 to 5.
A lithium secondary battery comprising the positive electrode according to claim 6.
A medium- or large-sized device characterized by comprising the lithium secondary battery according to claim 7.
9. The method of claim 8,
The middle- to large-sized devices include a power tool, an electric vehicle (EV), a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle (PHEV) Electric cars; Electric motorcycle including E-bike, E-scooter; Electric golf cart; Electric truck; An electric commercial vehicle or a system for power storage.

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