KR20200019571A - Nickel-based active material precursor for lithium secondary battery, preparing method thereof, nickel-based active material for lithium secondary battery formed thereof, and lithium secondary battery comprising positive electrode including the nickel-based active material - Google Patents

Abstract

Provided by the present invention is a nickel-based active material precursor for a lithium secondary battery, which includes a secondary particle having a plurality of particulate structures, wherein the particulate structure includes a porous core unit and a shell unit having a primary particle radially disposed on the porous core unit, and the long axis of the primary particle is the normal direction of the surface of the secondary particle in 50% or more of primary particles constituting the surface of the secondary particles. The use of the nickel-based active material precursor for a lithium secondary battery is able to obtain a nickel-based active material enabling easy insertion and separation of lithium and having a short diffusion distance of lithium ion. The lithium secondary battery manufactured using the positive electrode active material has an improved utilization rate of lithium and increases capacity and a life span by suppressing the breakage of an active material due to charging and discharging.

Description

Nickel-based active material precursor for a lithium secondary battery, a method of manufacturing the same, a nickel-based active material for a lithium secondary battery formed therefrom and a lithium secondary battery containing a positive electrode comprising the same based active material for lithium secondary battery formed specifically, and lithium secondary battery comprising positive electrode including the nickel-based active material}

The present invention relates to a nickel-based active material precursor for a lithium secondary battery, a manufacturing method thereof, a nickel-based active material for a lithium secondary battery formed therefrom, and a lithium secondary battery containing a positive electrode including the same.

With the development of portable electronic devices, communication devices, etc., there is a high necessity for the development of high energy density lithium secondary batteries. However, a high energy density lithium secondary battery may be deteriorated in safety and needs improvement. Lithium nickel manganese cobalt composite oxide, lithium cobalt oxide, etc. are used as a positive electrode active material of a lithium secondary battery. However, when using the positive electrode active material, the moving distance of lithium ions according to the secondary particle size during charge and discharge is determined, and the efficiency of charge and discharge is not high due to the physical distance. In addition, as the charge and discharge of the lithium secondary battery is repeated, cracks generated in the primary particles decrease the long-term life of the lithium secondary battery, increase resistance, and do not reach satisfactory levels of capacity characteristics.

One aspect is to provide a nickel-based active material precursor for a lithium secondary battery with improved lithium ion utilization.

Another aspect is to provide a method for producing the nickel-based active material precursor described above.

Another aspect is to provide a lithium secondary battery including the nickel-based active material obtained from the above-described nickel-based active material precursor and a positive electrode containing the same.

According to one side,

Including secondary particles having a plurality of particulate structures,

The particulated structure includes a shell portion having a porous core portion and primary particles disposed radially on the porous core portion,

At 50% or more of the primary particles constituting the surface of the secondary particles, a nickel-based active material precursor for a lithium secondary battery is provided in which the major axis of the primary particles is the normal direction of the surface of the secondary particles.

According to the other side

Supplying the feedstock at a first feed rate and stirring to form a precursor seed;

Supplying the feedstock to the precursor seed formed in the first step at a second feed rate and stirring to grow the precursor seed; And

And supplying the feedstock to the precursor seed grown in the second step at a third feed rate and stirring to control precursor seed growth,

The feedstock includes a complexing agent, a pH adjuster and a metal material for forming a nickel-based active material precursor,

A second supply rate of the metal raw material for forming the nickel-based active material precursor is greater than the first supply rate and the third supply rate is greater than the second supply rate, there is provided a method for producing a nickel-based active material precursor for a lithium secondary battery.

According to another aspect,

There is provided a nickel-based active material for a lithium secondary battery obtained from a nickel-based active material precursor.

According to another aspect,

Provided is a lithium secondary battery containing a positive electrode including a nickel-based active material for a lithium secondary battery.

When the nickel-based active material precursor for a lithium secondary battery according to one aspect is used, lithium can be easily diffused at the interface between the positive electrode active material and the electrolyte and a nickel-based active material can be easily diffused into the active material. In addition, it is possible to obtain a nickel-based active material that is easy to insert and detach lithium and has a short diffusion distance of lithium ions. In the lithium secondary battery manufactured using the cathode active material, the utilization rate of lithium is improved and the breakage of the active material due to charge and discharge is suppressed, thereby increasing capacity and lifespan.

1 is a schematic view of secondary particles included in a nickel-based active material precursor according to one embodiment.
FIG. 2A is a schematic partial perspective view of the particulated structure included in the secondary particles of FIG. 1. FIG.
FIG. 2B is a more detailed partial perspective view of the particulated structure included in the secondary particles of FIG. 1. FIG.
3 is a schematic cross-sectional view of the vicinity of the surface of the secondary particles contained in the nickel-based active material precursor according to one embodiment.
4A and 4B are high resolution TEM images of a cross section near the surface of the nickel-based active material prepared in Example 1;
5 is a schematic view of a lithium secondary battery according to an exemplary embodiment.

Hereinafter, a nickel-based active material precursor for a lithium secondary battery according to an embodiment of the present invention, a manufacturing method thereof, a nickel-based active material formed therefrom, and a lithium secondary battery having a positive electrode including the same will be described in detail. The following is presented by way of example, and the present invention is not limited thereto. The present invention is defined only by the scope of the claims to be described later.

As used herein, the term "particulate structure" means a structure in the form of particles formed by aggregation of a plurality of primary particles.

As used herein, the term "isotropical arrangement" refers to an arrangement in which the properties of the object are not changed even when the direction in which the object is observed is changed.

As used herein, the term "multicenter" means having a plurality of ideal centers within one particle. Multicore particles have a shorter length of movement of lithium ions from the particle surface to the particle center. Since the movement distance of the lithium ions is shortened, the internal resistance is reduced, and the particle structure is advantageous for the charge and discharge efficiency and the long life.

As used herein, the term "radial center" refers to the center of a particulate structure containing a porous core portion and a shell portion having primary particles arranged radially on the porous core portion as shown in FIGS. 2A and 2A.

As used herein, "radial" means a form in which the major axis of the primary particles included in the shell portion is arranged in a direction perpendicular to or perpendicular to the surface of the particulate structure as shown in FIGS. 2A and 2B. do.

As used herein, the "size" of a particle represents the average diameter when the particle is spherical and the average major axis length when the particle is non-spherical. Particle size can be measured using a particle size analyzer (PSA).

As used herein, the term “pore size” refers to the mean diameter of the pores or the opening width of the pores when the pores are spherical or circular. When the pores are non-spherical or non-circular, such as elliptical, the pore size means the average major axis length.

As used herein, the term “irregular porous pores” refers to pores whose pore size and shape are not regular and which are not uniform. The core portion including the irregular porous pores may include amorphous particles differently from the shell portion, and the amorphous particles are arranged without regularity, unlike the shell portion.

In the drawings, like reference numerals refer to like elements, and the size of each element in the drawings is exaggerated for clarity and convenience of description. In addition, the embodiments described below are merely exemplary, and various modifications are possible from these embodiments. In addition, in the layer structure described below, the expressions "upper" or "upper" include not only being directly in contact but also being indirectly on.

The nickel-based active material precursor for a lithium secondary battery according to one embodiment includes secondary particles including a plurality of particulate structures, wherein the particulate structure includes a porous core portion and a shell portion including primary particles radially disposed on the porous core portion. At least 50% of the primary particles constituting the surface of the secondary particles, wherein the major axis of the primary particles is in the normal direction of the surface of the secondary particles.

Referring to FIG. 1, the nickel-based active material precursor for a lithium secondary battery includes secondary particles 200 having a plurality of particulate structures 100. 2A and 2B, the particulate construct 100 includes a shell portion 20 having a porous core portion 10 and primary particles 30 radially disposed on the porous core 10 portion. . Referring to FIG. 3, at 50% or more of the primary particles 30a, 30b, 30c constituting the surface of the secondary particles 200 composed of the plurality of particulate constructs 100, the major axes 31, 31a, 31b of the primary particles are present. , 31c) is the normal direction of the surface of the secondary particles 200. For example, at 50% or more of the primary particles 30a, 30b, 30c constituting the surface of the secondary particles 200 composed of the plurality of particulate constructs 100, the major axes 31a, 31b, 31c of the primary particles are formed. It forms an angle (alpha) of 90 degrees with respect to the surface of the secondary particle 200. FIG.

2A, 2B, and 3, since the secondary particles 200 are assemblies of a plurality of particulate structures 100, the diffusion distance of lithium ions during charging and discharging at the time of charging and discharging as compared with conventional secondary particles composed of one particulate structure. Is shortened. Since the core part 10 of the particulate structure 100 is porous and the primary particles 30 are radially disposed on the core part 10 to constitute the shell part 20, the volume of the primary particles 30 during charging and discharging. Accept change effectively. Therefore, cracking of the secondary particles 200 due to the volume change of the secondary particles 200 during charging and discharging is suppressed. The (110) plane of the primary particles 30 is a crystal plane in which lithium ions are injected and released from a nickel-based active material obtained from a nickel-based active material precursor having a layered crystal structure. When the major axis 31, 31a, 31b, 31c of the primary particle which comprises the surface of the secondary particle 200 is a normal direction of the surface of the secondary particle 200, the interface of the nickel type active material obtained from a nickel type active material precursor, and electrolyte solution The diffusion of lithium is easy, and the diffusion of lithium ions into the nickel-based active material obtained from the nickel-based active material precursor is also easy. Therefore, the use of lithium ions in the nickel-based active material obtained from the nickel-based active material precursor made of such secondary particles 200 becomes easier.

Referring to FIGS. 2A and 2B, the “shell portion 20” is an area or particulate structure of 30 to 50 length%, for example, 40 length%, from the outermost part of the total distance from the center to the surface of the particulate structure 100. It means the area within 2 micrometers in the surface of (100). “Core part 10” is an area of 50 to 70 length%, for example 60 length%, or 2 at the surface of particulate structure 100 of the total distance from the center to the outermost part of particulate structure 100. It means the remaining area except the area within the micrometer. The center of the particulate construct 100 is, for example, the geometrical center of the particulate construct 100. In FIG. 2A and FIG. 2B, the particulate structure 100 has a perfect particle shape, but in the secondary particles 200 of FIG. 1 obtained by assembling a plurality of such particulate structures 100, a part of the particulate structure 100 is different from other particulate structures. By overlapping, the particulate construct 100 has a partial particle form.

2B and 3, in one exemplary secondary particle 200, the primary particles 30, 30a, 30b in which the major axes 31a, 31b, 31c of the primary particles are in the normal direction of the surface of the secondary particle 200. , 30c), 50% to 95%, 50% to 90%, 55% to 85%, 60% of the total primary particles (30, 30a, 30b, 30c) constituting the surface of the secondary particles 200 To 80%, 65% to 80%, or 70% to 80%. The use of lithium ions in the nickel-based active material precursor including the secondary particles 200 having the primary particle 30 content range is further facilitated. Also, referring to FIGS. 2A, 2B, and 3, in an exemplary secondary particle 200, the major particles 31a, 31b, and 31c of the primary particles are in the normal direction of the surface of the secondary particle 200. 30, 30a, 30b, 30c) is 50% to 95%, 50% to 90% of the total primary particles (30, 30a, 30b, 30c) constituting the shell portion 20 of the secondary particles 200, 55% to 85%, 60% to 80%, 65% to 80%, or 70% to 80%.

2B and 3, one exemplary primary particle 30, 30a, 30b, 30c is a non-spherical particle having a short axis and a long axis. The short axis is the axis connecting the points where the distances at any two ends of the primary particles 30, 30a, 30b, 30c are the smallest, and the long axis is the distance at any both ends of the primary particles 30, 30a, 30b, 30c. Is the axis connecting the largest point. The ratio of the short axis and the long axis of the primary particles 30, 30a, 30b, 30c is, for example, 1: 2 to 1:20, 1: 3 to 1:20, or 1: 5 to 1:15. The primary particles 30, 30a, 30b, and 30c have a ratio of the short axis and the long axis in this range, thereby making it easier to use lithium ions in the nickel-based active material obtained from the nickel-based active material precursor.

2B and 3, the primary particles 30, 30a, 30b, 30c are nonspherical particles, for example including plate particles. Plate particles are particles having two surfaces spaced apart from each other and having a large surface length compared to the thickness, which is the distance between the two surfaces. The length of the surface of the plate particles is the larger of the two lengths defining the surface. The two lengths defining the surface are different or equal to each other and are large relative to the thickness. The thickness of the plate particles is the length of the minor axis and the length of the surface is the length of the major axis. The shape of the surface of the plate particles is a polygon such as triangles, squares, pentagrams, hexagons, or the like, or is not limited to such as circular, elliptical, and the like, and may be used as long as it can be used as the surface form of plate particles in the art. Plate particles are, for example, nanodisks, square nanosheets, pentagonal nanosheets, hexagonal nanosheets. The specific shape of the plate particles depends on the specific conditions under which the secondary particles are made. The two opposing surfaces of the plate particles may not be parallel to each other, the angle between the surface and the side may be variously modified, the edges of the surface and the side may be round, and the surface and the side may be flat or curved, respectively. Can be. The ratio of the thickness and surface length of the plate particles is for example 1: 2 to 1:20, 1: 3 to 1:20, or 1: 5 to 1:15. The average thickness of one exemplary plate particle is 100 to 250 nm, or 100 nm to 200 nm, and the average surface length is 250 nm to 1100 nm, or 300 nm to 1000 nm. The average surface length of the plate particles is 2 to 10 times the average thickness. The plate particles have such ranges of thicknesses, average surface lengths, and ratios thereof, making it easier for the plate particles to be radially disposed on the porous core portion and consequently the use of lithium ions. And in the secondary particle 200, the long axis corresponding to the surface longitudinal direction of plate particle, ie, the long axis 31a, 31b, 31c of a primary particle, is arrange | positioned in the normal direction of the surface of a secondary particle 200. As the major axis of the plate particles is disposed in this direction, the lithium diffusion path is directed toward the surface of the secondary particles 200, and the crystal plane in which lithium ions are injected and released on the surface of the secondary particles 200, that is, the (110) plane of the plate particles is formed. As more exposed, lithium ions are more readily available in nickel-based active material precursors comprising plate particles as primary particles 30.

2B and 3, at 50% or more of the primary particles 30, 30a, 30b, and 30c constituting the surface of the secondary particle 200, the primary particles 30, 30a, 30b, and 30c may be formed. The long axis is disposed in the normal direction of the (110) plane of the primary particles 30, 30a, 30b, and 30c constituting the surface of the secondary particle 200. For example, at 60% to 80% of the primary particles 30, 30a, 30b, and 30c constituting the surface of the secondary particle 200, the major axis of the primary particles 30, 30a, 30b, and 30c is the secondary particle ( It is arrange | positioned in the normal direction of the (110) plane of the primary particle 30, 30a, 30b, 30c which comprises the surface of 200.

1 and 3, the secondary particles 200 have multiple cores and are formed of a plurality of particulate structures 100 arranged in an isotropic array. Since the secondary particles 200 include a plurality of particulate structures 100 and each of the particulate structures 100 includes a porous core portion 10 corresponding to the center, the secondary particles 200 have a plurality of centers. Therefore, in the nickel-based active material obtained from the nickel-based active material precursor, a path for moving lithium on from the plurality of centers inside the secondary particles 200 to the surface of the secondary particles 200 is shortened. As a result, the use of lithium ions in the nickel-based active material obtained from the nickel-based active material precursor is easier. In addition, in the nickel-based active material obtained from the nickel-based active material precursor, since the plurality of particulate structures 100 included in the secondary particles 200 have an isotropic arrangement arrangement without any directivity, a specific direction in which the secondary particles 200 are disposed Irrespective of the uniform lithium ion can be used. The secondary particles 200 are, for example, spherical or non-spherical, depending on the form in which the plurality of particulate structures 100 are assembled.

1 to 3, the size of the particulate structure 100 in the nickel-based active material precursor is, for example, 2um to 7um, 3um to 6um, 3um to 5um, or 3um to 4um. As the particulate structure 100 has such a size, it is easy to assemble the plurality of particulate structures 100 to have an isotropic arrangement, and to further utilize lithium ions in the nickel-based active material obtained from the nickel-based active material precursor. It becomes easy.

Referring to FIG. 1, in the nickel-based active material precursor, the size of the secondary particles 200 is, for example, 5 μm to 25 μm or 8 to 20 μm. As the secondary particles 200 have such a size, the use of lithium ions in the nickel-based active material obtained from the nickel-based active material precursor becomes easier.

2A and 2B, the pore size of the porous core 10 included in the particulate construct 100 is 150 nm to 1 μm, 150 nm to 550 nm, or 200 nm to 800 nm. In addition, the pore size of the shell portion 20 included in the particulate structure 100 is less than 150 nm, 100 nm or less, or 20 to 90 nm. The porosity of the porous core portion 10 included in the particulate construct 100 is 5 to 15%, or 5 to 10%. In addition, the porosity of the shell portion 20 included in the particulate construct 100 is 1 to 5%, or 1 to 3%. Since the particulate-form structure 100 has a pore size and porosity in this range, the capacity characteristics of the nickel-based active material obtained from the nickel-based active material precursor are excellent. In one exemplary particulate structure 100, the porosity of the shell portion 20 is controlled to be smaller than the porosity of the porous core portion 10. For example, the pore size and porosity in the porous core portion 10 are larger and irregularly controlled than the pore size and porosity in the shell portion 20. When the porosity in the porous core portion 10 and the shell portion 20 of the particulate structure 100 satisfies a range and a relationship, the density of the shell portion 20 increases as compared to the porous core portion 10, thereby the particulate structure The side reaction between 100 and the electrolyte is effectively suppressed.

In one exemplary particulate structure 100, there may be closed pores in the porous core portion 10 and closed pores and / or open pores in the shell portion 20. While the closed pores are difficult to contain an electrolyte or the like, the open pores may contain an electrolyte or the like in the pores of the particulate structure 100. In addition, irregular porous pores may exist in the porous core part 10 of the particulate structure 100. The core portion 10 including the irregular porous structure includes plate particles like the shell portion 20, and the plate particles of the core portion 10 are arranged without regularity, unlike the shell portion 20.

The nickel-based active material precursor may be a compound represented by Formula 1 below.

[Formula 1]

Ni _1-xyz Co _x Mn _y M _z (OH) ₂

In Formula 1, M is boron (B), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe) , An element selected from the group consisting of copper (Cu), zirconium (Zr) and aluminum (Al),

x≤ (1-x-y-z), y≤ (1-x-y-z), z≤ (1-x-y-z), 0 <x <1, 0≤y <1, and 0≤z <1. For example, it may be 0 <1-x-y-z <1.

As such, in the nickel-based active material precursor of Chemical Formula 1, the nickel content is larger than that of cobalt and the nickel content is larger than that of manganese. In Formula 1, 0 <x ≦ 1/3, 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.05, and 1/3 ≦ (1-x-y-z) ≦ 0.95.

According to one embodiment, in Chemical Formula 1, x may be 0.1 to 0.3, y may be 0.05 to 0.3, and z may be 0.

The nickel-based active material precursor is, for example, Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ , Ni _0.7 Co _0.15 Mn _0.15 (OH) ₂ , Ni _0.7 Co _0.1 Mn _0.2 (OH) ₂ , Ni _0.5 Co _0.2 Mn _0.3 (OH ) ₂ , Ni _1/3 Co _1/3 Mn _1/3 (OH) ₂ , Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ or Ni _0.85 Co _0.1 Al _0.05 (OH) ₂ .

Nickel-based active material precursor manufacturing method according to another embodiment, the first step of supplying a feedstock at a first feed rate and stirring to form a precursor seed (seed); A second step of supplying a feedstock to the precursor seed formed in the first step at a second feed rate and stirring to grow the precursor seed; And a third step of supplying a feedstock to the precursor seed grown in the second step at a third feed rate and stirring to control precursor seed growth, wherein the feedstock is a complexing agent, a pH adjuster, and a nickel-based active material precursor formation. And a metal feed material, wherein the second feed rate of the metal raw material for forming the nickel-based active material precursor is greater than the first feed rate and the third feed rate is greater than the second feed rate.

By sequentially increasing the feed rate of the metal raw materials in the first, second and third steps, the nickel-based active material precursor having the new structure described above is obtained. In the first, second and third stages, the reaction temperature is 40 to 60 ° C, the stirring power is 0.5 to 6.0 kW / m 3, the pH is in the range of 10 to 12, and the content of the complexing agent in the reaction mixture is 0.2 to 0,8M, for example in the range of 0.4-0.6M. Within this range, nickel-based active material precursors more compliant with the structures described above can be obtained.

In the first step, the pH is controlled and the precursor seed is formed and grown by introducing a metal raw material and a complexing agent at a constant rate into a reactor containing a complexing agent and a pH adjusting agent and containing a pH controlled aqueous solution. In the first step, the growth rate of the precursor particles may be 0.32 ㅁ 0.05 μm / hr. Stirring power of the reaction mixture in the first stage is 4 and less than 6 kW / m ^3, or 5.0kW / m ^3, pH may be more than 11 to 12 range. For example, in the first step, the feed rate of the metal raw material is 1.0 to 10.0 L / hr, for example 5.1 L / hr, and the feed rate of the complexing agent is 0.3 to 0.6 times the molar feeding rate of the metal raw material, for example 0.45 times. The temperature of the reaction mixture is 40 to 60 ° C., for example 50 ° C., and the pH of the reaction mixture is 11.20 to 11.70, for example 11.3 to 11.5.

The reaction conditions are changed in the second step to grow the precursor seeds produced in the first step. In the second step, the growth rate of the precursor seed is the same as the growth rate of the precursor seed in the first step or increases by 20% or more. The feed rate of the metal raw material in the second stage is 1.1 times or more, for example, 1.1 to 1.5 times compared to the feed rate of the metal raw material of the first stage, and the complexing agent concentration in the reaction mixture is the complexing agent in the first stage. It may be supplied so as to increase by 0.05 M or more, for example, 0.05 to 0.15 M based on the concentration. The stirring power of the reaction mixture in the second stage is at least 1 and less than 4 kW / m ³ , or 3.0 kW / m ³ , and the pH may range from 10.5 to 11. The average particle diameter (D50) of the precursor particles obtained in the second step may be 9 to 12㎛, for example about 10㎛.

In a third step, the growth rate of the particles is controlled in the precursor seed to obtain a nickel-based active material precursor for a lithium secondary battery. If the average particle diameter (D50) of the precursor particles in the second step reaches 9 to 12㎛, for example about 10㎛ proceeds to the third step. In the third step, the growth rate of the precursor particles may be increased two times or more, for example, three times or more than the second step. To this end, a portion of the reaction product inside the reactor that has undergone the second step may be removed to dilute the concentration of the reaction product inside the reactor. Products removed from inside the reactor can be used in other reactors. The feed rate of the metal raw material in the third stage is 1.1 times or more, for example, 1.1 times to 1.5 times compared to the feed rate of the metal raw material of the second stage, and the complexing agent concentration in the reaction mixture is the complexing agent in the second stage. It may be supplied so as to increase by 0.05 M or more, for example, 0.05 to 0.15 M based on the concentration. In the third step, the precipitate rapidly grows to obtain a nickel-based active material precursor. Stirring power of the reaction mixture in step 3 is greater than or equal to 1 and less than 0.5 kW / m ^3, or 0.8kW / m ^3, pH may be less than 10 to 10.5 range.

In the precursor manufacturing method, the feed rate of the metal raw material may increase sequentially as the first step, the second step, and the third step proceed. For example, the feed rate in the second stage of the metal raw material increases to 10 to 50% based on the feed rate in the first stage, and the feed rate in the third stage is based on the feed rate in the second stage. To 10 to 50%. By gradually increasing the feed rate of the metal raw material, a nickel-based active material precursor more suitable for the above-described structure can be obtained.

In the precursor preparation method, the stirring speed of the reaction mixture in the reactor may be sequentially reduced as the first, second and third steps proceed. As the stirring speed is gradually reduced in this manner, a nickel-based active material precursor that is more compatible with the above-described structure can be obtained.

In the precursor manufacturing method, the stirring power (eg, stirring speed) of the reaction mixture in the reactor may be sequentially reduced as the first, second, and third steps proceed. In the first step, the stirring power is 4 or more and 6 or less kW / m ³ , in the second step, the stirring power is 1 or more and less than 4 kW / m ³ , and in the third step, the stirring power is 0.5 or more and less than 1 kW / m ³ . Can be. As the stirring power (for example, the stirring speed) is gradually reduced in this manner, a nickel-based active material precursor more suitable for the above-described structure can be obtained.

In the precursor preparation method, the pH of the reaction mixture in the reactor may be sequentially reduced as it proceeds to the first, second and third steps. For example, the pH of the reaction mixture in the first to third steps may range from 10.10 to 11.50 when the reaction temperature is 50 ° C. For example, the pH of the reaction mixture in the third stage can be 1.1 to 1.4, or 1.2 to 1.4 lower than the pH of the reaction mixture in the first stage when the reaction temperature is 50 ° C. For example, at a reaction temperature of 50 ° C., the pH of the reaction mixture in the second stage is 0.55 to 0.85 lower than the pH of the reaction mixture in the first stage, and the pH of the reaction mixture in the third stage is It may be 0.35 to 0.55 lower than the pH of the reaction mixture. As the pH of the reaction mixture is gradually reduced in this manner, a nickel-based active material precursor more compliant with the above-described structure can be obtained.

In the precursor preparation method, the concentration of the complexing agent included in the reaction mixture in the second step may be increased compared to the concentration of the complexing agent included in the reaction mixture in the first step, and the reaction mixture in the third step is included. The concentration of the complexing agent may be increased compared to the concentration of the complexing agent included in the reaction mixture in the second step.

In order to control the growth rate of the nickel-based active material precursor particles, the input amount of the metal raw material for growing the particles is increased from 15 to 35%, for example, about 25% in the second step compared to the first step, and in the third step, compared to the second step. 20-35%, for example about 33%. In addition, in the second step, the ammonia water input amount may be increased by 10 to 35%, for example about 20%, based on the input amount of the ammonia water in the first step, thereby increasing the density of the particles.

The metal raw material may use a metal precursor corresponding to the composition of the nickel-based active material precursor. Metal raw materials are not limited to, for example, metal carbonates, metal sulfates, metal nitrates, metal chlorides, and the like, and can be used as long as they can be used as metal precursors in the art.

The pH regulator serves to lower the solubility of the metal ions in the reactor so that the metal ions precipitate into the hydroxide. pH adjusting agents are, for example, ammonium hydroxide, sodium hydroxide (NaOH), sodium carbonate (Na ₂ CO ₃ ), and the like. The pH adjusting agent is for example sodium hydroxide (NaOH).

The complexing agent plays a role in controlling the formation reaction rate of the precipitate in the coprecipitation reaction. Complexing agents are ammonium hydroxide (NH ₄ OH) (ammonia water), citric acid, citric acid, acrylic acid, tartaric acid, glycoic acid and the like. The content of the complexing agent is used at a conventional level. The complexing agent is, for example, ammonia water.

Nickel-based active material according to another embodiment is obtained from the above-described nickel-based active material precursor. The nickel-based active material is, for example, a compound represented by the following formula (2).

[Formula 2]

Li _a (Ni _1-xyz Co _x Mn _y M _z ) O ₂

In Formula 2, M is boron (B), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), tungsten (W), vanadium (V), chromium (Cr ), Iron (Fe), copper (Cu), zirconium (Zr), and aluminum (Al), and the element is selected from 1.0≤a≤1.3, x≤ (1-xyz), y≤ (1- xyz), z ≦ (1-xyz), 0 <x <1, 0 ≦ y <1, 0 ≦ z <1, 0 <1-xyz <1.

The compound represented by the formula (2) has a nickel content greater than that of cobalt and a nickel content greater than that of manganese. In Formula 2, 1.0 ≦ a ≦ 1.3, 0 <x ≦ 1/3, 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.05, 1/3 ≦ (1-x-y-z) ≦ 0.95.

In Formula 2, a may be 1 to 1.1, x may be 0.1 to 0.3, y may be 0.05 to 0.3, and z may be 0.

For example, the nickel content in the nickel-based active material may be 33 mol% to 95 mol%, for example, 50 to 90 mol%, for example, 60 to 85 mol%, based on the total transition metal content. The total transition metal content represents the total content of nickel, cobalt, manganese and M in the formula (2).

The nickel-based active material is, for example, LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , LiNi _0.7 Co _0.15 Mn _0.15 O ₂ , LiNi _0.7 Co _0.1 Mn _0.2 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , LiNi _1/3 Co _{1 / 3} Mn _1/3 O ₂ , LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , or LiNi _0.85 Co _0.1 Al _0.05 O ₂ .

The nickel-based active material may have substantially similar / identical particle structures and properties to the nickel-based active material precursor described above except that lithium is disposed in the crystal structure and hydroxide is changed to an oxide.

Since the secondary particles included in the nickel-based active material have multiple cores and consist of a plurality of particulate structures arranged in an isotropic array, the movement distance of lithium ions and electrons from the surface of the secondary particles to the center is reduced, so that lithium ions are inserted, Desorption becomes easy and electron transfer is easy. In addition, the particulate structure including the nickel-based active material has a porous core portion and primary particles disposed radially on the porous core portion to effectively accommodate the volume of the nickel-based active material during charge and discharge, thereby reducing the stress of the nickel-based active material. Can be. Therefore, the nickel-based active material obtained from the above-described nickel-based active material precursor has better capacity characteristics compared to the same composition even if the nickel content is not increased.

The nickel-based active material includes secondary particles including a plurality of particulate structures, and the particulate structure includes a porous core portion and a shell portion having primary particles disposed radially on the porous core portion, and constitutes a surface of the secondary particles. At 50% or more of the primary particles, the major axis of the primary particles is in the normal direction of the surface of the secondary particles. For example, at 60% to 80% of the primary particles constituting the surface of the secondary particles, the major axis of the primary particles is in the normal direction of the surface of the secondary particles. 4A and 4B, at 50% or more of the primary particles constituting the surface of the secondary particles, the major axis of the primary particles is the normal direction of the surface of the secondary particles. At 50% or more of the primary particles constituting the surface of the secondary particles, the major axis of each primary particle is in the [110] direction. 4A and 4B, in 60% to 80% of the primary particles constituting the surface of the secondary particles, the major axis of the primary particles is the normal direction of the surface of the secondary particles. At 60% to 80% of the primary particles constituting the surface of the secondary particles, the major axis of each primary particle is in the [110] direction. The (110) plane of the primary particles is a surface where lithium ions are injected and released from the nickel-based active material. When the major axis of the primary particles is in the normal direction of the surface of the secondary particles at the outermost part of the secondary particles, the nickel-based active material and the electrolyte solution The diffusion of lithium at the interface becomes easy, and the diffusion of lithium into the nickel-based active material is easy. Insertion and desorption of lithium in the nickel-based active material is easy, and the diffusion distance of lithium ions is shortened. The primary particles included in the nickel-based active material include plate particles, the major axis of the plate particles is in the normal direction of the surface of the secondary particles, and the plate particles may have a thickness and length ratio of 1: 2 to 1:20. have.

The method for producing the nickel-based active material from the nickel-based active material precursor is not particularly limited and may be, for example, dry.

The nickel-based active material may be prepared, for example, by mixing a lithium precursor and a nickel-based active material precursor at a predetermined molar ratio, and performing a first heat treatment (low temperature heat treatment) at 600 to 800 ° C.

The lithium precursor uses, for example, lithium hydroxide, lithium fluoride, lithium carbonate, or a mixture thereof. The mixing ratio of the lithium precursor and the nickel-based active material precursor is stoichiometrically controlled to prepare the nickel-based active material of Chemical Formula 2, for example.

Mixing may be dry mixing and may be performed using a mixer or the like. Dry mixing can be carried out using milling. Milling conditions are not particularly limited, but may be carried out such that there is little deformation such as micronization of the precursor used as starting material. The size of the lithium precursor mixed with the nickel-based active material precursor can be controlled in advance. The size (average particle diameter) of the lithium precursor is in the range of 5 to 15 mu m, for example about 10 mu m. The desired mixture can be obtained by milling a lithium precursor having such a size at 300 to 3,000 rpm with the precursor. When the temperature inside the mixer rises above 30 ° C. during the milling process, cooling may be performed to maintain the temperature inside the mixer at room temperature (25 ° C.).

Low temperature heat treatment is carried out in an oxidizing gas atmosphere. The oxidizing gas atmosphere uses an oxidizing gas such as oxygen or air, for example, the oxidizing gas is composed of 10 to 20% by volume of oxygen or air and 80 to 90% by volume of inert gas. The low temperature heat treatment may be performed in a range below the densification temperature while the reaction of the lithium precursor and the nickel-based active material precursor proceeds. The densification temperature is a temperature at which the crystallization is sufficiently made to implement the filling capacity that the active material can provide. Low temperature heat treatment is carried out, for example, at 600 to 800 ° C, specifically at 650 to 800 ° C. The low temperature heat treatment time varies depending on the heat treatment temperature and the like, but is for example 3 to 10 hours.

The method of manufacturing the nickel-based active material may further include a secondary heat treatment (high temperature heat treatment) step in which the exhaust gas is suppressed from inside the reactor after the low temperature heat treatment and is performed in an oxidizing gas atmosphere. High temperature heat treatment is carried out, for example, at 700 to 900 ° C. The high temperature heat treatment time varies depending on the high temperature heat treatment temperature and the like, but is for example 3 to 10 hours.

According to another exemplary embodiment, a lithium secondary battery includes a positive electrode, a negative electrode, and an electrolyte interposed therebetween including the above-described nickel-based active material for a lithium secondary battery.

The manufacturing method of the lithium secondary battery is not particularly limited and may be any method used in the art. The lithium secondary battery can be produced, for example, by the following method.

The positive electrode and the negative electrode are produced by coating and drying the positive electrode active material layer-forming composition and the negative electrode active material layer-forming composition on a current collector, respectively.

The composition for forming a positive electrode active material is prepared by mixing a positive electrode active material, a conductive agent, a binder, and a solvent, and a positive electrode active material according to one embodiment is used as the positive electrode active material.

The binder is added to 1 to 50 parts by weight based on 100 parts by weight of the total weight of the positive electrode active material as a component to assist in the bonding between the active material and the conductive agent and the bonding to the current collector. Non-limiting examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoro Ethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butyrene rubber, fluororubber, various copolymers, and the like.

The conductive agent is not particularly limited as long as it has conductivity without causing chemical change in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; Carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

As a non-limiting example of a solvent, N-methylpyrrolidone and the like are used.

The content of binders, conductive agents and solvents is at normal levels.

The positive electrode current collector has a thickness of 3 to 500 μm and is not particularly limited as long as it has high conductivity without causing chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, heat treated carbon, or Surface treated with carbon, nickel, titanium, silver, or the like on the surface of aluminum or stainless steel may be used. The current collector may form fine irregularities on its surface to increase the adhesion of the positive electrode active material, and may be in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

Separately, a negative electrode active material, a binder, a conductive agent, and a solvent are mixed to prepare a composition for forming a negative electrode active material layer. As the negative electrode active material, a material capable of occluding and releasing lithium ions is used. As a non-limiting example of the negative electrode active material, a carbon-based material such as graphite, lithium metal, an alloy thereof, a silicon oxide-based material, or the like may be used.

The binder is added in an amount of 1 to 50 parts by weight based on 100 parts by weight of the total weight of the negative electrode active material. Non-limiting examples of such a binder can use the same kind as the positive electrode.

The conductive agent is used in 1 to 5 parts by weight based on 100 parts by weight of the total weight of the negative electrode active material. When the content of the conductive agent is in the above range, the conductivity characteristics of the finally obtained electrode are excellent.

The solvent is used in an amount of 1 to 10 parts by weight based on 100 parts by weight of the total weight of the negative electrode active material. When the content of the solvent is within the above range, the operation for forming the negative electrode active material layer is easy.

As the conductive agent and the solvent, the same kind of material as that of the positive electrode may be used.

As the negative electrode current collector, it is generally made in a thickness of 3 to 500 mu m. Such a negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, the surface of copper, stainless steel, aluminum, nickel, titanium, heat treated carbon, copper or stainless steel Surface-treated with carbon, nickel, titanium, silver, and the like, and aluminum-cadmium alloys may be used. In addition, like the positive electrode current collector, fine concavities and convexities may be formed on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

A separator is interposed between the anode and the cathode manufactured according to this process.

The separator has a pore diameter of 0.01 to 10 µm and a thickness of 5 to 300 µm in general. Specific examples include olefin polymers such as polypropylene and polyethylene; Or sheets made of glass fibers or nonwoven fabrics are used. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separator.

A lithium salt containing non-aqueous electrolyte consists of a nonaqueous electrolyte solution and a lithium salt. As the nonaqueous electrolyte, a nonaqueous electrolyte, an organic solid electrolyte, an inorganic solid electrolyte, and the like are used.

Non-aqueous electrolytes include, but are not limited to, N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2 Dimethoxyethane, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, N, N-dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate , Phosphoric acid triester, trimethoxy methane, dioxolane derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, pyrion Aprotic organic solvents such as methyl acid and ethyl propionate can be used.

Examples of the organic solid electrolyte include, but are not limited to, polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, and the like. Examples of the solid electrolyte include, but are not limited to, Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ —Li ₂ S-SiS ₂ and the like may be used.

Lithium salt is a good material to dissolve in the non-aqueous electrolyte, non-limiting examples, such as LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO _{2 , LiAsF 6, LiSbF 6, LiAlCl} 4, CH 3 SO 3 Li, (CF 3 SO 2) 2 NLi, (FSO 2) 2 NLi, (FSO 2) 2 NLi, lithium chloro borate, lower aliphatic carboxylic acid lithium, Tetraphenyl lithium borate, lithium imide and the like can be used.

5 is a cross-sectional view schematically showing a representative structure of a lithium secondary battery according to one embodiment. Referring to FIG. 5, the lithium secondary battery 1 includes a positive electrode 3, a negative electrode 2, and a separator 4. The positive electrode 3, the negative electrode 2, and the separator 4 described above are wound or folded to be accommodated in the battery case 5. Subsequently, the organic electrolyte is injected into the battery case 5 and sealed with a cap assembly 6 to complete the lithium secondary battery 1. The battery case 5 may be cylindrical, rectangular, thin film, or the like. For example, the lithium secondary battery 1 may be a large thin film type battery. The lithium secondary battery may be a lithium ion battery.

A separator may be disposed between the positive electrode and the negative electrode to form a battery structure. The battery structure is stacked in a bi-cell structure, and then impregnated in an organic electrolyte, and the resultant is accommodated in a pouch and sealed to complete a lithium ion polymer battery. In addition, a plurality of battery structures may be stacked to form a battery pack, and the battery pack may be used in any device requiring a high capacity and a high output. For example, it can be used in notebooks, smartphones, electric vehicles and the like. In addition, the lithium secondary battery may be used in an electric vehicle (EV) because of its excellent storage stability, lifetime characteristics, and high rate characteristics at high temperatures. For example, it may be used in a hybrid vehicle such as a plug-in hybrid electric vehicle (PHEV).

It will be described in more detail through the following examples and comparative examples. However, the examples are provided for illustration only and are not limited thereto.

Preparation Example 1 Preparation of Nickel-Based Active Material Precursor (6: 2: 2): 3-Step Method

Nickel-based active material precursors (Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ ) were synthesized by coprecipitation. Nickel sulfate (NiSO ₄ .6H ₂ O), cobalt sulfate (CoSO ₄ .7H ₂ O) and manganese sulfate (MnSO ₄ .H ₂ O) as Ni as a metal raw material to form a nickel-based active material precursor in the following manufacturing process Ni: A mixed solution was prepared by dissolving in distilled water as a solvent such that Co: Mn = 6: 2: 2 molar ratio. In addition, ammonia water (NH ₄ OH) and sodium hydroxide (NaOH) as a precipitant were prepared to form a complex.

Stage 1: Feed rate 5.10 L / hr, Stirring power  5.0kW / ㎥, NH ₃ ㆍ H ₂ O 0.5M, pH 11.30 ~ 11.50

Ammonia water having a concentration of 0.5 mol / L (M) was added to the reactor to which the stirrer was attached. A metal raw material (mixed solution of nickel sulfate, cobalt sulfate, and manganese sulfate) of 2 mol / L (M) while maintaining a stirring power of 5.0 kW / m3 and a reaction temperature of 50 ° C 5.10 L / hr, 0.5 mol / L (M) Phosphorus ammonia water was added at 0.77 L / hr. Sodium hydroxide (NaOH) was then added to maintain pH. The pH of the reaction mixture in the reactor was maintained at 11.30 to 11.50. In this pH range, stirring was performed for 6 hours to carry out the first step reaction.

Stage 2: Feed rate 6.38 L / hr, Stirring power  3.0kW / ㎥, NH ₃ ㆍ H ₂ O 0.6M, pH 10.65 ~ 10.75

After the one-step reaction, the agitation power in the reactor was reduced to 3.0 kW / m3 and the reaction temperature was 50 ° C., while 6.38 L / hr and 0.6 mol / L (M) of ammonia water were used. 1.01 L / hr was added. Sodium hydroxide (NaOH) was then added to maintain pH. The pH of the reaction mixture in the reactor was maintained at 10.65-10.75. The reaction was stirred until the average particle diameter D50 of the particles in the reactor reached about 10 μm, and a two-step reaction was performed. A portion of the product obtained in the second step was then removed from the reactor to reduce the concentration of the product.

Stage 3: Feed rate 8.50 L / hr, Stirring power  0.8 kW / ㎥, NH ₃ ㆍ H ₂ O 0.7M, pH 10.10 ~ 10.20

After the two-step reaction, when the average particle diameter (D50) of the particles in the reactor reaches about 10 μm, the stirring power in the reactor is reduced to 0.8 kW / m 3 and the reaction temperature is maintained at about 50 ° C., while 2 mol / L (M ) 8.50 L / hr of metal raw material, 1.18 L / hr of ammonia water of 0.7 mol / L (M), and NaOH were added to maintain pH. The pH of the reaction mixture in the reactor was maintained at 10.10 to 10.20. In this pH range, the mixture was stirred for 6 hours to carry out a three-step reaction. Subsequently, the slurry solution in the reactor was filtered, washed with high purity distilled water, and then dried in a hot air oven for 24 hours to obtain a nickel-based active material precursor (Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ ).

Preparation Example 2 Preparation of Nickel-Based Active Material Precursor (7: 1.5: 1.5)

Nickel sulfate (NiSO ₄ .6H ₂ O), cobalt sulfate (CoSO ₄ .7H ₂ O) and manganese sulfate (MnSO ₄ -H ₂ O) were prepared as a metal raw material in Preparation Example 1 with Ni: Co: Mn = 6: 2: A nickel-based active material precursor (Ni _0.7 Co _0.15 Mn _0.15 (OH) ₂ ) was prepared in the same manner as in Preparation Example 1, except that the mixed solution was prepared such that the molar ratio of Ni: Co: Mn = 7: 1.5: 1.5. Synthesized.

Preparation Example 3 Preparation of Nickel-Based Active Material Precursor (7: 1: 2)

Nickel sulfate (NiSO ₄ -6H ₂ O), cobalt sulfate (CoSO ₄ -7H ₂ O) and manganese sulfate (MnSO ₄ -H ₂ O) were prepared as a metal raw material in Preparation Example 1 by Ni: Co: Mn = 6: 2: A nickel-based active material precursor (Ni _0.7 Co _0.1 Mn _0.2 (OH) ₂ ) was prepared in the same manner as in Preparation Example 1, except that the mixed solution was prepared so that the Ni: Co: Mn = 7: 1: 2 molar ratio was used. Synthesized.

Comparative Production Example 1 Preparation of Nickel-Based Active Material Precursor (6: 2: 2): One-Step Method

Nickel sulfate (NiSO ₄ ㆍ 6H ₂ O), cobalt sulfate (CoSO ₄ ㆍ 7H ₂ O), and manganese sulfate (MnSO ₄ · H ₂ O) may be used as a metal raw material to form a nickel-based active material precursor in the following comparative manufacturing process. A mixed solution was prepared by dissolving in distilled water, which was a solvent, in a: Co: Mn = 6: 2: 2 molar ratio, and ammonia water (NH ₄ OH) and sodium hydroxide (NaOH) as a precipitant were prepared to form a complex.

6.00 L / hr, 0.35 mol / L of metal raw material of 2 mol / L (M) while adding ammonia water having a concentration of 0.35 mol / L to a reactor equipped with a stirrer and maintaining a stirring speed of 250 rpm and a reaction temperature of 50 ° C M) ammonia water was added at the same time at a rate of 0.6 L / hr and NaOH was added to maintain pH. The reaction mixture in the reactor was maintained at pH 11.3 to 11.4. After stirring for 33 hours at this pH range, the reaction product was collected when the reaction became steady. After washing the collected reaction product, hot air drying was performed at 150 ° C. for 24 hours to obtain nickel. The active material precursor (Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ ) was prepared.

Comparative Production Example 2 Preparation of Nickel-Based Active Material Precursor (7: 1.5: 1.5)

In Comparative Production Example 1, nickel sulfate (NiSO ₄ -6H ₂ O), cobalt sulfate (CoSO ₄ -7H ₂ O), and manganese sulfate (MnSO ₄ -H ₂ O) were used as a metal raw material to form Ni: Co: Mn = 6: 2. A nickel-based active material precursor (Ni _0.7 Co _0.15 Mn _0.15 (OH) ₂ ) was prepared in the same manner as in Comparative Preparation Example 1, except that a mixed solution was prepared so that the Ni: Co: Mn = 7: 1.5: 1.5 molar ratio was used instead of the: 2 molar ratio. ) Was synthesized.

Comparative Production Example 3 Preparation of Nickel-Based Active Material Precursor (7: 1: 2)

In Comparative Production Example 1, nickel sulfate (NiSO ₄ · 6H ₂ O), cobalt sulfate (CoSO ₄ · 7H ₂ O), and manganese sulfate (MnSO _4? H ₂ O) were used as metal raw materials, and Ni: Co: Mn = 6: 2. A nickel-based active material precursor (Ni _0.7 Co _0.1 Mn _0.2 (OH) ₂ ) was prepared in the same manner as in Comparative Preparation Example 1, except that a mixed solution was prepared such that Ni: Co: Mn = 7: 1: 2 molar ratio instead of: 2 molar ratio. ) Was synthesized.

Example 1: Preparation of Nickel-Based Active Material

The composite metal hydroxide (Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ ) and lithium hydroxide (LiOH), which are nickel-based active material precursors prepared according to Preparation Example 1, were mixed dryly in a 1: 1 molar ratio, and were mixed in an oxygen atmosphere. Heat treatment was performed at 700 ° C. for 6 hours to obtain a nickel-based active material (LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ). The nickel-based active material thus obtained had a porous structure and the outside had a radial arrangement. The nickel-based active material was heat-treated at about 800 ° C. for 6 hours in an air atmosphere to disperse at least two radial centers of the primary particles so that the primary particle aggregates contained secondary particles arranged in a multicenter isotropic array. Nickel-based active material (LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ) was obtained.

Example 2: Preparation of Nickel-Based Active Material

A nickel-based active material was prepared in the same manner as in Example 1 except that the nickel-based active material precursor of Preparation Example 2 was used instead of the nickel-based active material precursor of Preparation Example 1.

Example 3: Preparation of Nickel-Based Active Material

A nickel-based active material was prepared in the same manner as in Example 1 except that the nickel-based active material precursor of Preparation Example 3 was used instead of the nickel-based active material precursor of Preparation Example 1.

Comparative Examples 1 to 3: Preparation of Nickel-Based Active Material

A nickel-based active material was prepared in the same manner as in Example 1 except that the nickel-based active material precursors prepared according to Comparative Preparation Examples 1 to 3 were used instead of the nickel-based active material precursors prepared according to Preparation Example 1, respectively. .

Production Example 1: Coin Cell Manufacturing

A coin cell was prepared using the nickel-based active material (LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ) obtained according to Example 1 as a cathode active material.

A mixture of 96 g of a nickel-based active material (LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ) obtained according to Example 1, ₂ g of polyvinylidene fluoride, 47 g of N-methylpyrrolidone as a solvent, and 2 g of carbon black as a conductive agent was mixed using a mixer. Bubbles were removed to prepare a slurry for forming the positive electrode active material layer uniformly dispersed.

The slurry prepared according to the above process was coated on aluminum foil using a doctor blade to form a thin electrode plate, which was dried at 135 ° C. for at least 3 hours, and then a cathode was manufactured by rolling and vacuum drying.

A 2032 type coin cell was manufactured using a lithium metal counter electrode as the positive electrode and the counter electrode. Between the positive electrode and the lithium metal counter electrode, a 2032 type coin cell was manufactured by injecting an electrolyte solution through a separator (thickness: about 16 μm) made of a porous polyethylene (PE) film. As the electrolyte solution, a solution containing 1.1 M LiPF ₆ dissolved in a solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 3: 5 was used.

Production Example 2: Coin Cell Manufacturing

A coin cell was manufactured by the same method as Preparation Example 1, except that the nickel-based active material of Example 2 was used instead of the nickel-based active material of Example 1.

Production Example 3: Coin Cell

A coin cell was prepared in the same manner as in Production Example 1, except that the nickel-based active material of Example 3 was used instead of the nickel-based active material of Example 1.

Comparative Production Examples 1 to 3: Coin Cell

A lithium secondary battery was manufactured according to the same method as in Preparation Example 1, except that the nickel-based active materials prepared according to Comparative Examples 1 to 3 were used instead of the nickel-based active materials prepared according to Example 1, respectively.

Evaluation Example 1 Long-axis orientation analysis of primary particles constituting the surface of secondary particles (nickel-based active material precursor)

For the nickel-based active material precursor particles prepared according to Production Examples 1 to 3 and Comparative Production Examples 1 to 3, the orientation of the primary particles existing in the outermost portion of the secondary particles was analyzed. In order to analyze the orientation of the primary particles, in the TEM image of the secondary particle cross-section, primary particles whose major axis is normal to the surface of the secondary particles among the primary particles disposed on the surface of the secondary particles were calculated. Long axis arranged in the normal direction on the surface of the secondary particles by calculating the number and area of the radially arranged particles of the primary particles disposed on the surface of the secondary particles in the TEM image of the cross section using a Leopard (Grain size analysis) program The proportion of primary particles having was calculated.

The results are shown in Table 1.

division % Of primary particles with long axis oriented normal to the secondary particle surface Preparation Example 1 62.54 Preparation Example 2 61.8 Preparation Example 3 65.41 Comparative Production Example 1 40.81 Comparative Production Example 2 45.45 Comparative Production Example 3 38.41

As shown in Table 1, in the nickel-based active material precursors of Preparation Examples 1 to 3, 50% or more of the primary particles present in the outermost portion of the secondary particles had a long axis in the normal direction of the secondary occupancy surface. In contrast, in the nickel-based active material precursors of Comparative Production Examples 1 to 3, only 46% or less of the primary particles had a long axis in the normal direction of the secondary occupancy surface.

Evaluation Example 2 Analysis of Long-axis Orientation of Primary Particles Comprising Secondary Particle Surfaces (Nickel-Based Active Material)

For the nickel-based active material particles prepared according to Examples 1 to 3 and Comparative Examples 1 to 3, the orientation of the primary particles existing in the outermost portion of the secondary particles was analyzed. In order to analyze the orientation of the primary particles, primary particles having a long axis of the primary particles in the normal direction of the surface of the secondary particles were calculated from the entire primary particles disposed on the surface of the secondary particles in the TEM image of the secondary particle cross section. Using the Leopard (Grain size analysis) program, the number and area of the radially arranged particles of the primary particles disposed on the surface of the secondary particles in the TEM image of the cross section are calculated to determine the major axis of the secondary particles surface in the normal direction. The branches were calculated for the proportion of primary particles.

As shown in FIGS. 4A and 4B, in the case of the nickel-based active material of Example 1, at 50% or more of the plurality of primary particles disposed on the surface of the secondary particles, the major axis of the primary particles was in the normal direction of the secondary occupancy surface. That is, the long axis of the primary particles was disposed in the normal direction of the (110) plane of the primary particles constituting the surface of the secondary particles, and the long axis of the primary particles was the normal direction of the surface of the secondary particles. That is, in the primary particles constituting the surface of the secondary particles, the major axis of each primary particle is in the [110] direction. On the contrary, although not shown in the drawings, in the nickel-based active materials of Comparative Examples 1 to 3, only 40% or less of the primary particles had the long axis of the primary particles in the normal direction of the surface of the secondary particles.

4A and 4B, the primary particles constituting the surface of the secondary particles are plate particles, and are radially disposed in the center direction on the surface of the particulate construct constituting the secondary particles. In addition, although not shown in the figure, it was confirmed that the particulated structure has a porous core portion.

Evaluation Example 3: Initial Charge Efficiency (I.C.E)

The coin cells prepared according to Production Examples 1 to 3 and Comparative Production Examples 1 to 3 were charged and discharged at 25 ° C. and once at 0.1C to form the cells. Subsequently, charging and discharging was performed once at 0.1 C to confirm initial charge and discharge characteristics. When charging, it started in CC (constant current) mode and then changed to CV (constant voltage) to cut off at 4.3V and 0.05C, and at discharge, to cutoff at 3.0V in CC (constant current) mode. Initial charge efficiency (I.C.E) was measured and shown in Table 2 according to Equation 1 below.

[Equation 1]

The initial charge-discharge efficiency [%] = [1 ^st cycle discharge capacity / 1 ^st cycle charge capacity] × 100

division Charge capacity (mAh / g) Discharge Capacity (mAh / g) I.C.E (%) (%) Production Example 1 197.8 190.0 96.0 Production Example 2 210.6 202.2 96.0 Production Example 3 206.1 196.8 95.5 Comparative Production Example 1 197.4 179.3 90.8 Comparative Production Example 2 209.4 190.5 91.0 Comparative Production Example 3 204.9 185.4 90.5

As shown in Table 2, the coin cells prepared according to Production Examples 1 to 3 have improved charge and discharge efficiency (initial characteristics) and initial discharge capacity as compared to the coin cells prepared in Comparative Production Examples 1 to 3.

1: lithium battery 2: negative electrode
3: anode 4: separator
5: battery case 6: cap assembly
10: core portion 20: shell portion
30, 30a, 30b, 30c: primary particles
31, 31a, 31b, 31c: long axis of primary particles
100: particulate structure
200: secondary particles

Claims (12)

Including secondary particles having a plurality of particulate structures,
The particulated structure includes a shell portion having a porous core portion and primary particles disposed radially on the porous core portion,
The nickel-based active material precursor for lithium secondary batteries, wherein at least 50% of the primary particles constituting the surface of the secondary particles have a long axis of the primary particles in a normal direction of the surface of the secondary particles. According to claim 1,
At 60% to 80% of the primary particles constituting the surface of the secondary particles, the long axis of the primary particles is the normal direction of the surface of the secondary particles, nickel-based active material precursor for a lithium secondary battery. According to claim 1,
The primary particles comprise plate particles,
The major axis of the plate particles is in the normal direction of the surface of the secondary particles,
The plate particles have a thickness and length ratio of 1: 2 to 1:20, the nickel-based active material precursor for a lithium secondary battery. According to claim 1,
At least 50% of the primary particles constituting the surface of the secondary particles, the long axis of the primary particles is disposed in the normal direction of the (110) plane, nickel-based active material precursor for a lithium secondary battery. According to claim 1,
The nickel-based active material precursor for lithium secondary batteries, wherein the secondary particles are made of a particulate structure arranged in a multi-core isotropic array. According to claim 1,
The pore size in the porous core portion is 150nm to 1㎛, porosity is 5 to 15%, the porosity of the shell portion is 1 to 5%, nickel-based active material precursor for a lithium secondary battery. According to claim 1,
The nickel-based active material precursor is a compound represented by the following formula 1, nickel-based active material precursor for a lithium secondary battery:
[Formula 1]
Ni _1-xyz Co _x Mn _y M _z (OH) ₂
In Formula 1, M is boron (B), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe) , An element selected from the group consisting of copper (Cu), zirconium (Zr) and aluminum (Al),
x≤ (1-xyz), y≤ (1-xyz), z≤ (1-xyz), 0 <x <1, 0≤y <1, and 0≤z <1. The method of claim 7, wherein
Nickel content of the nickel-based active material precursor is 33 mol% to 95 mol% based on the total content of the transition metal, the nickel-based active material precursor for a lithium secondary battery is higher than the content of manganese and cobalt. A first step of feeding and stirring the feedstock at a first feed rate to form precursor seeds;
A second step of supplying a feedstock to the precursor seed formed in the first step at a second feed rate and stirring to grow the precursor seed; And
And a third step of controlling precursor seed growth by supplying and stirring a feedstock to a precursor seed grown in the second step at a third feed rate,
The feedstock includes a complexing agent, a pH adjuster and a metal material for forming a nickel-based active material precursor,
The method of manufacturing the nickel-based active material precursor for lithium secondary batteries of claim 1, wherein the second feed rate of the metal raw material for forming the nickel-based active material precursor is greater than the first feed rate and the third feed rate is larger than the second feed rate. The method of claim 9,
Method for producing a nickel-based active material precursor for a lithium secondary battery, the stirring power of the reaction mixture is sequentially reduced toward the first step, the second step and the third step. The nickel-based active material for lithium secondary batteries obtained from the nickel-based active material precursor for lithium secondary batteries according to any one of claims 1 to 8. A lithium secondary battery comprising a positive electrode comprising a nickel-based active material for a lithium secondary battery of claim 11, a negative electrode and an electrolyte interposed therebetween.

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