KR102424399B1 - Positive active material for rechargeable lithium battery, method of preparing the same and rechargeable lithium battery incluidng the same - Google Patents

Abstract

a lithium nickel-based composite oxide including large particle diameter particles and small particle diameter particles having different average particle diameters, wherein the large particle diameter particles include secondary particles including a plurality of primary particles, and the small particle diameter particles include A cathode active material for a lithium secondary battery comprising lithium halide, wherein the large particle diameter particles have an average particle diameter (D50) of 10 to 20 μm, and the small particle diameter particles have an average particle diameter (D50) of 1 to 8 μm, a method for manufacturing the same And it relates to a lithium secondary battery including the same.

Description

Cathode active material for lithium secondary battery, manufacturing method thereof, and lithium secondary battery comprising same

A cathode active material for a lithium secondary battery, a manufacturing method thereof, and a lithium secondary battery including the same.

With the development of portable electronic devices and communication devices, there is a high need for the development of a lithium secondary battery having a high energy density.

This type of lithium secondary battery includes a positive electrode and a negative electrode in which an electrode active material layer including an electrode active material is formed on an electrode current collector. As a cathode active material, most materials capable of intercalation of lithium ions are lithium cobalt oxide (Li _x CoO ₂ ), lithium nickel oxide (Li _x NiO ₂ ), lithium nickel cobalt oxide (Li _x (NiCo)O ₂ ), Oxides such as lithium nickel cobalt manganese oxide (Li _x (NiCoMn)O ₂ ), spinel lithium manganese oxide (Li _x Mn ₂ O ₄ ), manganese dioxide (MnO ₂ ), or lithium iron phosphate (Li _x FePO ₄ ), lithium manganese Phosphates (Li _x MnPO ₄ ), such as olivine (olivine) type or NASICON type phosphates (phosphates), silicates (silicates), a polymer material and the like can be used.

As an anode active material, lithium metal or an alloy thereof or a compound capable of intercalation of lithium ions may be used. A polymer material or a carbon material may be used. Non-graphitizable carbon, or graphitizable carbon, carbon nanotube (CNT), carbon nanofiber (CNF), carbon nanowall (CNW), etc. The same carbon-based material may be used.

On the other hand, since the positive electrode active material having a porous structure has a large BET specific surface area, the residual lithium level on the surface of the positive electrode active material is very high. Accordingly, side reactions such as gas generation occur and ultimately the stability of the battery is impaired.

In the prior art, in order to reduce residual lithium, a cleaning process is performed after the production of the positive electrode active material, but the cost of the cleaning process is added, and there is a problem that the performance of the battery is reduced, such as damage to the surface of the positive electrode active material due to cleaning. is occurring In addition, a coating process of the positive electrode active material is additionally performed to reduce residual lithium, but there is a problem in that rate characteristics and capacity characteristics of the battery are deteriorated.

One embodiment provides a cathode active material for a lithium secondary battery in which residual lithium and gas generation on the surface of an active material are reduced, and a mixture density is improved.

Another embodiment provides a method of manufacturing the positive active material for a lithium secondary battery.

Another embodiment provides a lithium secondary battery including the positive active material for a lithium secondary battery.

One embodiment includes a lithium nickel-based composite oxide including large particle diameter particles and small particle diameter particles having different average particle diameters, wherein the large particle diameter particles include secondary particles including a plurality of primary particles, the The small particle diameter particles include lithium halide, the large particle diameter particles have an average particle diameter (D50) of 10 to 20 μm, and the small particle diameter particles have an average particle diameter (D50) of 1 to 8 μm, a positive electrode for a lithium secondary battery It provides an active material.

The small particle size particles may include secondary particles including a plurality of primary particles.

The small particle size particle may include a single crystal particle.

The large particle diameter secondary particles may include primary particles having an average thickness of 100 nm to 200 nm, and the average thickness of the primary particles included in the small particle diameter secondary particles may be 200 nm to 500 nm .

The large particle diameter particles may be included in an amount of 50 wt% to 90 wt% based on the total weight of the large particle diameter particles and the small particle diameter particles.

The lithium halide may be coated on the surface of the small particle size particle.

The lithium halide may be coated in the form of a film on the surface of the small particle size particles.

The lithium halide may include LiF.

The lithium halide may be included in an amount of 0.1 to 1.0 moles based on 100 moles of the small particle size particles.

The large particle diameter particles and the small particle diameter particles include secondary particles in which a plurality of plate-shaped primary particles are aggregated, and the (003) plane of the primary particles is oriented in the vertical direction with respect to the surface of the secondary particles. It may have a predetermined arrangement structure including tea particles.

The positive active material may have a half width of 0.15° to 0.17° of a (003) plane peak in X-ray diffraction spectrum analysis.

The large particle diameter particles and the small particle diameter particles may have a radial arrangement structure having one center or a multi-center radial arrangement structure having a plurality of centers.

The lithium nickel-based composite oxide may be a compound represented by Formula 1 below.

[Formula 1]

Li _a Ni _x Co _y M _1-xy O ₂

(In Formula 1, 0.9 ≤ a ≤ 1.05, 0.3 ≤ x ≤ 0.95, 0.05 ≤ y ≤ 0.3, M is Mn, Al, Cr, Fe, V, Mg, Ti, Zr, Nb, Mo, W, Cu, at least one metal element selected from Zn, Ga, In, Sn, La and Ce.)

The positive active material may include residual lithium of 1,400 ppm or less on the surface.

The positive active material may have a mixture density of 3.1 to 3.4 g/cm ³ . Another exemplary embodiment may include preparing a metal hydroxide precursor having a large particle diameter and a metal hydroxide precursor having a small particle diameter; preparing a mixture by mixing a large particle size metal hydroxide precursor and a lithium raw material, and heat-treating the mixture to prepare large particle size particles; preparing a mixture by mixing a small particle diameter metal hydroxide precursor, a lithium raw material, and a raw material of lithium halide (LiX), and heat-treating the mixture to prepare small particle diameter particles including lithium halide; It provides a method of manufacturing a positive electrode active material for a lithium secondary battery by mixing the large particle diameter particles and the small particle diameter particles to prepare a positive electrode active material.

Another embodiment may include a positive electrode including the positive active material; a negative electrode comprising an anode active material; And it provides a lithium secondary battery comprising an electrolyte.

It is possible to provide a positive electrode active material having an improved mixture density by including large particle diameter particles and small particle diameter particles having different average particle diameters.

It is possible to provide a lithium secondary battery with improved lifespan characteristics by including lithium halide in the positive electrode active material to reduce residual lithium on the surface of the positive electrode active material and suppress gas generation.

1 is a view schematically showing a positive electrode active material in which large particle diameter secondary particles and small particle diameter secondary particles are mixed.
2 is a view schematically showing a positive electrode active material in which large particle diameter secondary particles and small particle diameter single particles are mixed.
3 is a view schematically showing oriented primary particles constituting large particle diameter secondary particles.
4 is a schematic view showing the shape of the plate-shaped primary particles.
5 is a perspective view schematically illustrating a typical structure of a lithium secondary battery.
6 is a graph showing the amount of high-temperature gas generated by the coin cells prepared according to Examples 2-1 to 2-3, Example 3, and Comparative Example 2. Referring to FIG.

Hereinafter, embodiments of the present invention will be described in detail. However, this is provided as an example, and thus the present invention is not limited, and the present invention is only defined by the scope of the claims to be described later.

As used herein, "large particle diameter secondary particles" and "small particle diameter secondary particles" mean "large particle diameter lithium nickel-based composite oxide secondary particles" and "small particle diameter lithium nickel-based composite oxide secondary particles", respectively.

In addition, in this specification, "secondary particle" means "large particle diameter lithium nickel-based composite oxide secondary particle" or "small particle diameter lithium nickel-based composite oxide secondary particle", and "primary particle" means "large particle diameter lithium nickel It means "primary particle-based composite oxide particles" or "small-diameter lithium nickel-based composite oxide primary particles".

The secondary particles, for example, may be in the form of relatively large-sized particles composed of a plurality of primary particles physically and/or chemically aggregated, as well as a form in which the primary particles and secondary particles are mixed. , it may include a case made of only secondary particles. In addition, in the present specification, D50 refers to the particle diameter of particles corresponding to 50% of the total number of particles when the measured particles are arranged in order from smallest to largest.

In the present specification, the particle size and thickness may be measured using an electron microscope such as a scanning electron microscope or a field emission scanning electron microscope, or may be measured using a particle size distribution analyzer.

Hereinafter, a cathode active material according to an exemplary embodiment will be described with reference to FIGS. 1 to 4 .

1 is a diagram schematically showing a positive electrode active material in which large secondary particles and small secondary particles are mixed, and FIG. 2 is a diagram schematically showing a positive active material in which large secondary particles and small particle diameter single particles are mixed. , FIG. 3 is a view schematically showing oriented primary particles constituting secondary particles of large particle diameter. 4 is a schematic diagram showing the shape when the primary particles constituting the large particle size secondary particles and the primary particles constituting the small particle size secondary particles are plate-shaped.

Specifically, the positive active material for a lithium secondary battery according to an exemplary embodiment includes a lithium nickel-based composite oxide including large particle diameter particles and small particle diameter particles having different average particle diameters.

The large particle diameter particles may include secondary particles including a plurality of primary particles, and the small particle diameter particles include a single crystal particle (10a), a secondary particle including a plurality of primary particles ( 10), or a combination thereof.

Here, the single crystal particle refers to the structure of a monolith in which particles exist as independent phases in which the particles are not mutually aggregated in the morphology phase, and a grain boundary is formed within the particle. It does not have and exists alone and is composed of one particle, for example, may be a single crystal particle.

Referring to FIG. 1 , the positive electrode active material 1 according to an embodiment includes a lithium nickel-based composite oxide including large particle diameter secondary particles 20 and small particle diameter secondary particles 10 having different average particle diameters. can do. In addition, referring to FIG. 2 , the positive electrode active material 1a according to an embodiment includes a lithium nickel-based composite oxide including large particle diameter secondary particles 20 and small particle diameter single particles 10a having different average particle diameters. may include When the secondary particles having a large particle diameter having different average particle diameters and the secondary particles having a small particle diameter or a single particle having a small particle diameter are included, the density of the mixture of the positive electrode active material may be improved. The large particle diameter particles and the small particle diameter particles include secondary particles in which a plurality of plate-shaped primary particles are aggregated, and the (003) plane of the primary particles is oriented in the vertical direction with respect to the surface of the secondary particles. It may have a predetermined arrangement structure including tea particles.

The arrangement structure of the primary particles will be described with reference to FIG. 3 . Hereinafter, the large particle diameter secondary particles 20 will be described with reference to FIG. 3 , but it is obvious that the small particle diameter secondary particles 10 may be equally applied. Specifically, the (003) plane of the primary particle 21 may be oriented so as to be perpendicular to the surface of the secondary particle 20 . The surface means the outermost surface of the secondary particles (20). The (003) plane means a lattice plane corresponding to the Miller index (003). Also, the vertical direction means that the point where the major axis (a-axis) or minor axis (b-axis) of the (003) plane meets the surface of the secondary particles crosses each other while forming an angle of 70 to 110°, for example 80 to 100° do. When the (003) plane of the primary particle 21 is oriented so as to be perpendicular to the surface of the secondary particle 20, there are relatively many grain boundaries on the surface side of the secondary particle 20. A lithium diffusion path may be provided, and a large number of crystal surfaces capable of lithium transfer may be exposed, thereby improving lithium diffusion. Therefore, it is possible to secure high initial efficiency and capacity. In addition, by suppressing the stress caused by the volume change of the secondary particles 20 during charging and discharging, it is possible to suppress the occurrence of cracks, and it is possible to improve the lifespan characteristics of the battery.

In the positive active material according to the exemplary embodiment, the half width of the (003) plane peak in the X-ray diffraction spectrum analysis may be 0.15° to 0.17°. In the present invention, the Full Width at Half-Maximum (FWHM) is the peak width at the 1/2 position of the maximum peak intensity of the (003) plane obtained by X-ray diffraction spectrum analysis (XRD) of the positive active material. means to quantify (003) When the half width of the plane is within the above range, the size of the small particle diameter particles included in the positive active material increases, the high initial efficiency and capacity characteristics of the lithium secondary battery including the positive active material are improved, and the lithium secondary battery During the charging and discharging of the battery, it is possible to suppress the occurrence of cracks in the battery by suppressing the deformation caused by the volume change of the large particle diameter particles and the small particle diameter particles.

The large particle diameter secondary particles 20 and/or the small particle diameter secondary particles 10 may have a radial arrangement structure having one center or a multi-center radial arrangement structure having a plurality of centers. The primary particles 21 oriented as described above aggregate with each other to form secondary particles 20 . For example, the plurality of primary particles 21 may aggregate with each other to provide the secondary particles 20 having a large particle diameter having a radially arranged structure. The plurality of primary particles 21 are arranged toward one center to make surface contact along the c-axis (thickness) direction of the primary particles 21 to form secondary particles 20 having a radially arranged structure. can provide In another embodiment, the large particle diameter secondary particles 20 may have a multi-center radial arrangement structure having a plurality of centers. As described above, when the large-diameter secondary particles 20 have a single-center or multi-centre radial arrangement structure, removal/insertion of lithium to the center of the large-diameter secondary particles 20 is facilitated.

The lithium nickel-based composite oxide may be a compound represented by the following Chemical Formula 1:

[Formula 1]

Li _a Ni _x Co _y M _1-xy O ₂

In Formula 1, 0.9 ≤ a ≤ 1.05, 0.3 ≤ x ≤ 0.95, 0.05 ≤ y ≤ 0.3, M is Mn, Al, Cr, Fe, V, Mg, Ti, Zr, Nb, Mo, W, Cu, at least one metal element selected from Zn, Ga, In, Sn, La, and Ce.

In Formula 1, 0.98 ≤ a ≤ 1.02, 0.5 ≤ x ≤ 0.8, 0.1 ≤ y ≤ 0.3 or 0.98 ≤ a ≤ 1.02, 0.6 ≤ x ≤ 0.8, 0.1 ≤ y ≤ 0.3 may be, M is Mn or Al can

For example, the lithium nickel-based composite oxide may be at least one selected from LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , and LiNi _0.8 Co _0.1 Mn _0.1 O ₂ .

The small particle size particles 10 and 10a include lithium halide 13 . When the lithium halide 13 is included in the small particle size particles 10 and 10a, residual lithium generated on the surface of the positive electrode active material can be reduced and gas generation due to side reactions can be suppressed. Accordingly, it is possible to improve the lifespan characteristics of the battery by preventing side reactions between the positive electrode active material and the electrolyte during operation of the battery.

Specifically, the positive electrode active material (1, 1a) is a small particle diameter particles (that is, small particle diameter single particles (10a), small particle diameter secondary particles 10 and / or primary particles constituting the small particle diameter secondary particles ( 11)) may contain lithium halide 13 only, and in this case, when lithium halide is included in the large particle diameter secondary particles 20, or the large particle diameter secondary particles 20 and the small particle diameter particles Compared to the case where lithium halide is simultaneously included in the , the above-described effect may be more pronounced. The small particle diameter particles 10 and 10a have a larger Brunauer-Emmett-Teller (BET) specific surface area per unit weight and more residual lithium and gas generation than the large particle diameter secondary particles 20 . That is, when only the small particle diameter particles 10 and 10a include lithium halide, generation of residual lithium and generation of gas can be effectively suppressed with a relatively small amount of lithium halide.

On the other hand, the lithium halide 13 is the surface of the small particle diameter particles (that is, at least one of the small particle diameter single particle 10a, the small particle diameter secondary particle, and the primary particle 11 constituting the small particle diameter secondary particle 10). can be coated on For example, it may be coated on the surface of the small particle diameter single particle 10a, or both on the surface of the small particle diameter secondary particle 10 and on the surface of the primary particle 11 constituting the small particle diameter secondary particle 10 . It may be coated or coated only on the surface of the small particle diameter primary particles 11 . Accordingly, the lithium halide 13 may decrease the BET specific surface area of the small particle size particles by increasing the average particle diameter (D50) of the small particle size particles. Accordingly, generation of residual lithium and generation of gas on the surface of the positive electrode active material can be effectively suppressed.

The lithium halide 13 is coated on the surface of at least one of the small particle diameter single particles 10a, the small particle diameter secondary particles 10 and the primary particles 11 constituting the small particle diameter secondary particles 10 in the form of a film. can be According to the method for manufacturing the positive active material according to the embodiment, the lithium halide 13 may be uniformly coated on the surface of the particle in the form of a film. The lithium halide 13 may act as a flux during the high-temperature sintering process of the positive electrode active material to promote the growth of the primary particles 11, so that the BET specific surface area of the particle surface may be more effectively improved.

The lithium halide 13 may include at least one selected from LiF, LiCl, LiBr, and LiI, and in one embodiment, LiF may be preferably used.

The lithium halide 13 may be included in an amount of 0.1 to 1.0 moles, for example, 0.2 to 0.8 moles, or 0.25 to 0.75 moles, based on 100 moles of the small particle size particles. If the content of the lithium halide 13 exceeds the above range, since deterioration of the life of the lithium secondary battery including the positive active material may be accelerated, it is appropriately adjusted within the above range.

The large particle diameter particles may have an average particle diameter (D50) of 10 μm to 20 μm, for example, 10 μm or more, 11 μm or more, 12 μm or more, 13 μm or more, or 14 μm or more and 20 μm or less, 19 It may have an average particle diameter (D50) of less than or equal to 18 µm, less than or equal to 17 µm, less than or equal to 16 µm, or less than or equal to 15 µm. The small particle diameter particles may have an average particle diameter (D50) of 1 to 8 μm, for example, 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more and 8 μm or less, 7 μm or less, 6 μm or less. , may have an average particle diameter (D50) of 5 μm or less. When the average particle diameter of the large particle diameter particle and the small particle diameter particle respectively falls within the above range, the mixture density of the positive electrode active material may be increased. Accordingly, the capacity characteristics of the battery can be improved.

The average particle diameter difference (D50-D50) between the large particle diameter particles (D50) and the small particle diameter particles (D50) may be 9 to 12 μm, for example, 9 to 10 μm. Accordingly, the density of the mixture of the positive electrode active material may be increased, and the capacity characteristics of the battery may be improved.

The average particle diameter (D50) of the primary particles 21 constituting the large particle diameter secondary particles 20 may be, for example, about 200 nm to about 900 nm, for example, 200 nm to 800 nm, or 200 nm to 700 nm, or 300 nm to 600 nm, or 300 nm to 500 nm. In addition, the average particle diameter (D50) of the primary particles 11 constituting the small particle diameter secondary particles 10 may be from about 100 nm to about 900 nm, for example, from 100 nm to 800 nm, or from 100 nm to 700 nm. nm, or from 100 nm to 600 nm, or from 100 nm to 500 nm. In this case, it is possible to secure high initial efficiency and capacity of the battery, and it is possible to suppress the occurrence of cracks by suppressing the stress caused by the volume change of the secondary particles during charging and discharging.

The primary particles 21 constituting the large-diameter secondary particles 20 and the primary particles 11 constituting the small-diameter secondary particles may be plate-shaped. 4 is a schematic diagram showing the shape of a primary particle according to an embodiment. Referring to FIG. 4 , the primary particles according to one embodiment have a basic plate-like structure, such as (A) a polygonal nanoplate shape such as a hexagon, (B) a nanodisk shape, (C) a rectangular parallelepiped shape, and various detailed shapes can have In FIG. 4, a is the length of the major axis, b is the length of the minor axis, and t is the thickness. The thickness t of the primary particles may be formed smaller than the lengths a and b in the plane direction. The length a in the plane direction may be longer or the same as that of b.

Meanwhile, the thickness of the primary particles and the length of the major axis and the length of the minor axis may be measured using, for example, an electron microscope such as a scanning electron microscope or a field emission scanning electron microscope.

The primary particles 21 constituting the large particle diameter secondary particles 20 may have an average thickness of 100 nm to 200 nm, for example, 100 nm to 150 nm, or 100 nm or more, 110 nm or more, 120 nm or more, 130 nm or more, and 200 nm or less, 190 nm or less, 180 nm or less, 170 nm or less, 160 nm or less, 150 nm or less. When the average particle diameter of the large particle diameter primary particles 21 falls within the above range, high initial efficiency and capacity can be secured, and crack generation can be suppressed by suppressing the stress caused by the volume change of the secondary particles during charging and discharging. have. Accordingly, life characteristics can be improved.

The average long axis length of the primary particles 21 constituting the large particle diameter secondary particles 20 may be about 200 nm to about 900 nm, for example, 200 nm to 800 nm, or 200 nm to 700 nm, or 300 nm to 600 nm, or 300 nm to 500 nm. In this case, it is possible to secure high initial efficiency and capacity of the battery, and it is possible to suppress the occurrence of cracks by suppressing the stress caused by the volume change of the secondary particles during charging and discharging.

The primary particles 11 aggregated in the small particle diameter secondary particles 10 may have an average thickness of 200 nm to 500 nm, for example, 200 nm or more, 210 nm or more, 220 nm or more, 230 nm or more, and It may have an average thickness of 500 nm or less, 490 nm or less, 480 nm or less, 470 nm or less. When the average thickness of the primary particles 11 constituting the small particle diameter secondary particles 10 falls within the above range, the high initial efficiency and capacity characteristics of the lithium secondary battery including the positive active material are improved, and the lithium secondary During charging and discharging of the battery, it is possible to suppress the occurrence of cracks in the battery by suppressing the deformation caused by the volume change of the secondary particles.

In addition, the average long axis length of the primary particles 11 constituting the small particle diameter secondary particles 10 may be about 100 nm to about 900 nm, for example, 100 nm to 800 nm, or 100 nm to 700 nm , or from 100 nm to 600 nm, or from 100 nm to about 500 nm. In this case, it is possible to secure high initial efficiency and capacity of the battery, and it is possible to suppress the occurrence of cracks by suppressing the stress caused by the volume change of the secondary particles during charging and discharging.

The large particle size secondary particles 20 may have a BET specific surface area of 0.100 m ² /g to 0.600 m ² /g, for example, 0.100 m ² /g or more, 0.200 m ² /g or more, 0.300 m ² /g or more. or more, and may have a BET specific surface area of 0.600 m ² /g or less, 0.500 m ² /g or less, or 0.400 m ² /g or less. When the large particle diameter secondary particle 20 has a BET specific surface area within the above range, it is possible to secure high initial efficiency and capacity, and to suppress the occurrence of cracks resulting from stress caused by the volume change of secondary particles during battery charging and discharging. can Accordingly, it is possible to improve the life characteristics of the battery.

The small particle size secondary particles 10 may have a BET specific surface area of 0.300 m ² /g to 1.000 m ² /g, for example, 0.300 m ² /g or more, 0.400 m ² /g or more, 0.500 m ² /g or more. g or more and 1.000 m ² /g or less, 0.900 m ² /g or less, 0.800 m ² /g or less, 0.700 m ² /g or less BET specific surface area. When the BET specific surface area of the small particle diameter secondary particles 10 falls within the above range, the level of the lithium compound remaining on the surface can be lowered, and the side reaction area that occurs on the surface of the positive electrode active material when the battery is driven is reduced to prevent gas generation. can be reduced.

The large particle size particles may be included in an amount of 50 to 90% by weight based on the total weight of the large particle size particles and the small particle size particles, for example, 50% by weight or more, 55% by weight or more, 60% by weight or more, or 65% by weight or more. and 90 wt% or less, 85 wt% or less, 80 wt% or less, or 75 wt% or less.

The positive active materials 1 and 1a may contain residual lithium of 1,400 ppm or less on the surface, for example, 1,350 ppm or less, 1,300 ppm or less, 1,290 ppm or less, 1,280 ppm or less, 1,270 ppm or less, 1,260 ppm or less, 1,250 ppm or less Below, 1,230 ppm or less, 1,200 ppm or less, or 1,150 ppm or less of residual lithium may be included.

The positive active materials 1 and 1a may have a mixture density of 3.1 to 3.4 g/cm ³ or 3.2 g/cm ³ to 3.3 g/cm ³ . As the positive electrode active materials 1 and 1a include large particle diameter particles and small particle diameter particles having different average particle diameters, the mixing density of the positive electrode active material may be improved.

Hereinafter, a method of manufacturing a positive electrode active material according to an embodiment is provided.

The method for producing the positive electrode active material is to prepare a large particle diameter metal hydroxide precursor and a small particle diameter metal hydroxide precursor, mix a large particle diameter metal hydroxide precursor and a lithium raw material to prepare a mixture, and heat the mixture to prepare large particle diameter particles, ; preparing a mixture by mixing a small particle diameter metal hydroxide precursor, a lithium raw material, and a raw material of lithium halide (LiX), and heat-treating the mixture to prepare small particle diameter particles including lithium halide; and mixing the large particle diameter particles and the small particle diameter particles to prepare a positive electrode active material.

In one embodiment, the large particle size particle may be a secondary particle including a plurality of primary particles, and the small particle size particle may be a single crystal particle, or a second particle including a plurality of primary particles. tea particles, or a combination thereof.

The method for preparing the metal hydroxide precursor may be prepared in a first step, a second step, and a third step process according to the steps of forming the structure of the core, the intermediate layer, and the shell. In the first step, the second step, and the third step, process conditions such as the concentration and input amount of the metal raw material, the concentration and input amount of ammonia water as a complexing agent, and the input amount of the pH adjuster may be different.

Meanwhile, in the present specification, "core" refers to an area of 65 to 85 length % from the center of the total distance from the center to the surface of the secondary particles 10 and 20 . For example, in the lithium nickel-based composite oxide, the region may be the remaining region except for a region within 2 μm from the outermost layer. In addition, "shell (outside)" refers to a region of 5 to 15 length % from the outermost surface of the total distance from the center to the surface of the lithium nickel-based composite oxide or a region within 2 μm from the outermost of the lithium-nickel-based composite oxide. . "Intermediate layer" refers to the area remaining excluding the core and shell. In the present specification, the orientation of the primary particles 11 and 21 may be mainly made in the shell of the secondary particles 10 and 20 .

(First step) forming a core of the metal hydroxide precursor:

After adding a complexing agent and a pH adjusting agent to the reactor, a metal raw material is added to carry out the reaction. The stirring power of the reactor may be adjusted in the range of 0.1 to 6 kW/m ² , such as 1 to 3 kW/m ² , and the reaction may be carried out for 1 to 30 hours, or 5 to 30 hours, or 10 to 30 hours. have.

The complexing agent serves to control the reaction rate of the formation of a precipitate in the co-precipitation reaction, for example, ammonia water, citric acid, etc., and in one embodiment, ammonia water may be preferably used. The content of the complexing agent is used at a conventional level. For example, the concentration of the complexing agent may be 0.1M to 0.7M, for example about 0.2M to 0.5M.

The pH adjuster serves to control the pH of the reaction mixture to form a precipitate from the reaction mixture, for example, sodium hydroxide (NaOH), sodium carbonate (Na ₂ CO ₃ ), sodium oxalate (Na ₂ C ₂ O ₄ ), etc. , Preferably sodium hydroxide (NaOH) may be used. If the pH of the reaction mixture in the reactor changes as the reaction proceeds, a pH adjusting agent may be further added to control the reaction mixture, if necessary, and the pH of the reaction mixture is controlled in the range of 10 to 12.

A metal raw material is obtained by mixing a nickel compound, a manganese compound, a cobalt compound, etc. in pure water and stirring it. The concentration of the metal raw material may be 0.1M to 0.5M, for example, 0.3M, and the input amount of the metal raw material may be 50 ml/min to 100 ml/min.

Examples of the nickel compound include Ni(OH) ₂ , NiO, NiOOH, NiCO ₃ ·2Ni(OH) ₂ ·4H ₂ O, NiC ₂ O ₄ ·2H ₂ O, Ni(NO ₃ ) ₂ ·6H ₂ O, NiSO ₄ , NiSO ₄ .6H ₂ O, fatty acid nickel salt, nickel halide. Among them, from the viewpoint of not generating harmful substances such as NO _X and SO _X during the firing process, Ni(OH) ₂ , NiO, NiOOH, NiCO ₃ ·2Ni(OH) ₂ ·4H ₂ O, and NiC ₂ O ₄ - Like 2H ₂ O, it is preferable not to contain a nitrogen atom or a sulfur atom during the calcination treatment. These nickel compounds can be used individually by 1 type or in mixture of 2 or more types.

Examples of the manganese compound include manganese oxides such as Mn ₂ O ₃ , MnO ₂ , and Mn ₃ O ₄ , MnCO ₃ , Mn(NO ₃ ) ₂ , MnSO ₄ , manganese acetate, manganese dicarboxylic acid salt, manganese citrate, and fatty acid. There are manganese salts such as manganese salts, oxyhydroxides, and halides such as manganese chloride. Among them, MnO ₂ , Mn ₂ O ₃ and Mn ₃ O ₄ are preferable, because gases such as NO _x and SO _x and CO ₂ are not generated during calcination and can be obtained inexpensively as industrial raw materials. to be. These manganese compounds may be used alone or in combination of two or more.

Examples of cobalt compounds include Co(OH) ₂ , CoOOH, CoO, Co ₂ O ₃ , Co ₃ O ₄ , Co(OCOCH ₃ ) ₂ .4H ₂ O, CoCl ₂ , Co(NO ₃ ) ₂ .6H ₂ O, and Co(SO ₄ ) ₂ ·7H ₂ O. Among them, Co(OH) ₂ , CoOOH, CoO, Co ₂ O ₃ and Co ₃ O ₄ are preferable from the viewpoint of not generating harmful substances such as NO _x and SO _x during the calcination treatment. Co(OH) ₂ and CoOOH are industrially inexpensive and more preferable from the viewpoint of high reactivity. These cobalt compounds may be used alone or in combination of two or more.

(Second step) forming an intermediate layer of the metal hydroxide precursor:

A metal raw material and a complexing agent are added to the reaction product of the first step, the pH of the reaction mixture is controlled, and then the reaction is performed.

The stirring power of the second step may be reduced compared to the stirring power of the first step, and may be the same as the stirring power of the third step. The stirring power of the second step is in the range of 0.1 to 6 kW/m ² , and may be, for example, 1 to 3 kW/m ² . In the second step, the reaction may be carried out for 1 to 30 hours, or 5 to 30 hours, or 10 to 30 hours.

As specific conditions of the second step, the concentration of the complexing agent is, for example, 0.3 M to 1.0 M, the input amount of the complexing agent is 8 ml/min to 20 ml/min, or 8 ml/min to 12 ml/min, metal The input amount of the raw material may be 90 ml/min to 120 ml/min. In the second step, the input amount and concentration of the metal raw material and the complexing agent are increased in order to prevent a decrease in the growth rate according to the growth of the particles after the reaction of the product obtained in the first step for a predetermined time.

(Third step) finally preparing a metal hydroxide precursor, including forming a shell of the metal hydroxide precursor:

A metal raw material and a complexing agent are added to the result of the second step reaction, the pH of the reaction mixture is controlled, and then a reaction is performed to form a shell of a metal hydroxide precursor, and the obtained precursor is washed several times in deionized water (DI water). and reduced pressure filtering, and finally, through drying at a high temperature of 80 degrees or more, a metal hydroxide precursor is finally prepared.

The metal hydroxide precursor is manufactured to have excellent structural stability by properly maintaining pores formed between (001) crystal planes while minimizing exposure of (001) crystal planes.

The stirring power of the third step may be reduced compared to the stirring power of the first step, and may be the same as the stirring power of the second step. The stirring power of the third step is in the range of 0.1 to 6 kW/m ² , and may be, for example, 1 to 3 kW/m ² . In the third step, the reaction may be carried out for 1 hour to 30 hours, or 3 hours to 30 hours, or 10 to 30 hours.

After the reaction product obtained in the second step is reacted for a certain period of time, the input amount and concentration of the metal raw material and the complexing agent are increased in order to prevent a decrease in the growth rate according to the growth of the particles.

As the specific process conditions of the third step, the concentration of the complexing agent is 0.35 M to 1.0 M, the input amount of the complexing agent is 12 ml/min to 18 ml/min, or 12 ml/min to 25 ml/min, the input amount of the metal raw material may be 120 ml/min to 150 ml/min. These three-step reaction conditions greatly affect the surface depth of the porous layer in the metal hydroxide precursor.

Then, the large particle diameter metal hydroxide precursor and the lithium raw material are mixed and heat-treated to prepare the large particle diameter particles.

The large particle diameter metal hydroxide precursor powder obtained by spray drying was mixed with Li ₂ CO ₃ , LiNO ₃ , LiNO ₂ , LiOH, LiOH·H ₂ O, LiH, LiF, LiCl, LiBr, LiI, CH ₃ OOLi, Li ₂ O, Li ₂ SO ₄ , dicarboxylic acid lithium salt, lithium citrate, fatty acid lithium salt, lithium raw material such as alkyl lithium is mixed sufficiently. In this case, the molar ratio of Li: (Ni + Co + Mn) may exceed 1:1. Specifically, it may be 1.01:1 to 1.06:1, and more specifically 1.02:1 to 1.05:1.

In the step of obtaining the large-diameter particles, a doping material may be further included in the large-diameter metal hydroxide precursor together with the lithium raw material. As the doping material, a compound containing Ba, Mg, Al, Fe, Ti, W, B, Zr, or a combination thereof may be used, and specifically, a compound containing Al, Zr or a combination thereof may be used. .

The powder mixture thus obtained is subjected to a primary calcination treatment (heat treatment). This primary firing condition is determined according to the composition and the lithium raw material used. The firing temperature in the primary firing treatment is usually 800°C or higher, and is usually 1000°C or lower, preferably 950°C or lower, and more preferably 900°C or lower. After maintaining the temperature condition for a predetermined time during the primary firing treatment, the temperature may be decreased to 10° C. to 40° C. at a constant rate, thereby completing the first firing treatment process.

Then, the small particle size metal hydroxide precursor, the lithium raw material, and the raw material of lithium halide (LiX) are mixed and heat-treated to prepare small particle size particles including the lithium halide.

The small particle diameter metal hydroxide precursor powder obtained by spray drying is mixed with a lithium raw material, and the raw material of lithium halide is sufficiently mixed therein.

In the step of obtaining the small particle size particles, a doping material may be further included in the small particle size metal hydroxide precursor together with the lithium raw material and the lithium halide raw material. As the doping material, a compound containing Ba, Mg, Al, Fe, Ti, W, B, Zr, or a combination thereof may be used, and specifically, a compound containing Al, Zr or a combination thereof may be used. .

The types and mixing of lithium raw materials are the same as those described in the above-mentioned large particle size particle production.

Examples of raw materials for lithium halide include fluorine-based polymer compounds including polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-co-HFP), and a combination thereof; Or hydrogen fluoride, oxygen fluoride, hydrofluoric acid, hydrogen chloride, hydrochloric acid, chlorine oxide, chlorine fluoride oxide, bromine oxide, fluorosulfuric acid, bromine, hydrogen iodide, iodine oxide, periodic acid, etc. may be used, for example, NH ₄ F , NH ₄ Cl, NH ₄ Br, NH ₄ I, LiF, LiCl, LiBr, LiI, MnF ₂ , MnCl ₂ , MnBr ₂ , MnI ₂ or a combination thereof can be used, specifically, PVdF or LiF may be used.

The raw material of the lithium halide (LiX) may be mixed in an amount of 0.1 to 1 mol%, for example, 0.2 to 0.8 mol%, based on the small particle diameter metal hydroxide precursor.

On the other hand, since lithium fluoride (LiF) as an example of a raw material for lithium halide has a very high melting point of 835° C. or more, it is generally not soluble in a heat treatment temperature range (800 to 900° C.) for manufacturing a high nickel-based positive electrode active material. It is difficult to form a uniform coating on the surface of the positive electrode active material because it exists in a solid state without However, when the LiF is mixed with the lithium raw material, the melting point of LiF is greatly reduced compared to the case where LiF is present as a single phase, so that it may exist in a molten state in the temperature range at the time of manufacturing the high nickel-based positive electrode active material, It has the advantage of being able to uniformly coat the surface of the positive electrode active material in the form of a film.

In addition, when the small particle size particles are generated through the above process, the raw material of the lithium halide is also of the lithium nickel-based composite oxide secondary particles in the process of preparing the lithium nickel-based composite oxide by reacting the lithium raw material with the precursor. Penetrating into the interior, there is an advantage that can be uniformly coated in the form of a film not only on the surface of the secondary particles, but also on the surface of the primary particles constituting the same.

The powder mixture thus obtained is subjected to secondary firing treatment (heat treatment). The secondary firing conditions are the same as those described in the first firing conditions for the production of large particle diameter particles.

Then, the positive electrode active material according to the embodiment may be prepared by mixing the large particle diameter particles and the small particle diameter particles.

Another embodiment may include a positive electrode including the positive active material; a negative electrode comprising an anode active material; and an electrolyte; provides a lithium secondary battery comprising.

The positive electrode includes a current collector and a positive electrode active material layer formed on the current collector and including a positive electrode active material.

In the cathode active material layer, the content of the cathode active material may be 90 wt% to 98 wt% based on the total weight of the cathode active material layer. In addition, the positive active material layer may further include a binder and a conductive material. The content of the binder and the conductive material may be 1 wt% to 5 wt%, respectively, based on the total weight of the positive electrode active material layer.

The positive active material is the same as described above.

Examples of the binder include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, polyvinyl fluoride, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, and polyvinylidene fluoride. , polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc. may be used, but is not limited thereto.

Examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, and carbon fiber; metal-based substances such as metal powders such as copper, nickel, aluminum, and silver, or metal fibers; conductive polymers such as polyphenylene derivatives; Alternatively, a conductive material including a mixture thereof may be used.

As the current collector, an aluminum foil, a nickel foil, or a combination thereof may be used, but is not limited thereto.

The negative electrode includes a current collector and an anode active material layer including a negative active material formed on the current collector.

The negative active material includes a material capable of reversibly intercalating/deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

The material capable of reversibly intercalating/deintercalating the lithium ions is a carbon material, and any carbon-based negative active material generally used in lithium ion secondary batteries may be used, and a representative example thereof is crystalline carbon. , amorphous carbon or these may be used together. Examples of the crystalline carbon include graphite such as amorphous, plate-shaped, flake-shaped, spherical or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon ( hard carbon), mesophase pitch carbide, and calcined coke.

The lithium metal alloy includes lithium and Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn from the group consisting of Alloys of selected metals may be used.

Examples of the material capable of doping and dedoping lithium include Si, SiO _x (0 < x < 2), Si-Q alloy (wherein Q is an alkali metal, alkaline earth metal, group 13 element, group 14 element, group 15 element, 16 It is an element selected from the group consisting of group elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn, SnO ₂ , Sn-R alloy (wherein R is alkali metal, alkaline earth metal, group 13 element, 14 group element, group 15 element, group 16 element, transition metal, rare earth element, and an element selected from the group consisting of combinations thereof, not Sn), and the like, and also by mixing at least one of them with SiO ₂ can also be used. The elements Q and R include Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, One selected from the group consisting of S, Se, Te, Po, and combinations thereof may be used.

Examples of the transition metal oxide include vanadium oxide, lithium vanadium oxide or lithium titanium oxide.

The content of the anode active material in the anode active material layer may be 95 wt% to 99 wt% based on the total weight of the anode active material layer.

In one embodiment of the present invention, the negative active material layer includes a binder, and may optionally further include a conductive material. The content of the binder in the anode active material layer may be 1 wt% to 5 wt% based on the total weight of the anode active material layer. In addition, when the conductive material is further included, 90 wt% to 98 wt% of the negative active material, 1 wt% to 5 wt% of the binder, and 1 wt% to 5 wt% of the conductive material may be used.

The binder serves to well adhere the negative active material particles to each other and also to adhere the negative active material well to the current collector. As the binder, a water-insoluble binder, a water-soluble binder, or a combination thereof may be used.

Examples of the water-insoluble binder include styrene-butadiene rubber, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polyacrylonitrile, polystyrene, polyurethane, polytetrafluoroethylene, poly vinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or combinations thereof.

Examples of the water-soluble binder include acrylated styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber, ethylene oxide-containing polymer, polyvinylpyrrolidone, polyepicro Rohydrin, polyphosphazene, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, or a combination thereof.

When a water-soluble binder is used as the negative electrode binder, a cellulose-based compound capable of imparting viscosity may be further included as a thickener. As the cellulose-based compound, one or more of carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or alkali metal salts thereof may be mixed and used. As the alkali metal, Na, K or Li may be used. The amount of the thickener used may be 0.1 parts by weight to 3 parts by weight based on 100 parts by weight of the negative active material.

Examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, and carbon fiber; metal-based substances such as metal powders such as copper, nickel, aluminum, and silver, or metal fibers; conductive polymers such as polyphenylene derivatives; Alternatively, a conductive material including a mixture thereof may be used.

The current collector may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with conductive metal, and combinations thereof.

The electrolyte includes a non-aqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

Examples of the non-aqueous organic solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methylpropionate, ethylpropionate, decanolide, mevalo mevalonolactone, caprolactone, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, cyclohexanone, ethyl alcohol, isopropyl alcohol, R Nitriles such as -CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may contain a double bond aromatic ring or ether bond); amides such as dimethylformamide; Dioxolanes such as 1,3-dioxolane and sulfolanes may be used.

The organic solvent may be used alone or in a mixture of one or more, and when one or more of the organic solvents are mixed and used, the mixing ratio can be appropriately adjusted according to the desired battery performance, which can be widely understood by those in the art. have.

In addition, the organic solvent may further include an aromatic hydrocarbon-based organic solvent. Specific examples of the aromatic hydrocarbon-based organic solvent include benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-tri Fluorobenzene, 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1 ,2,4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, 1, 2,4-triiodobenzene, toluene, fluorotoluene, 2,3-difluorotoluene, 2,4-difluorotoluene, 2,5-difluorotoluene, 2,3,4-trifluoro Rottoluene, 2,3,5-trifluorotoluene, chlorotoluene, 2,3-dichlorotoluene, 2,4-dichlorotoluene, 2,5-dichlorotoluene, 2,3,4-trichlorotoluene, 2, 3,5-trichlorotoluene, iodotoluene, 2,3-diiodotoluene, 2,4-diiodotoluene, 2,5-diiodotoluene, 2,3,4-triiodotoluene, 2,3 ,5-triiodotoluene, xylene, and combinations thereof.

The electrolyte may further include vinylene carbonate or an ethylene carbonate-based compound as a lifespan improving additive.

Representative examples of the ethylene carbonate-based compound include difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate or fluoroethylene carbonate. can When such a life-enhancing additive is further used, its amount can be appropriately adjusted.

The lithium salt is dissolved in an organic solvent, serves as a source of lithium ions in the battery, enables the basic operation of a lithium secondary battery, and serves to promote movement of lithium ions between the positive electrode and the negative electrode. Representative examples of such lithium salts include LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiN(SO ₂ C ₂ F ₅ ) ₂ , Li(CF ₃ SO ₂ ) ₂ N, LiN(SO ₃ C ₂ F ₅ ) ₂ , LiC ₄ F ₉ SO ₃ , LiClO ₄ , LiAlO ₂ , LiAlCl ₄ , LiN(C _x F _2x+1 SO ₂ )(C _y F _2y+1 SO ₂ ), where x and y are natural numbers, for example It is an integer from 1 to 20), LiCl, LiI and LiB(C ₂ O ₄ ) ₂ (lithium bis(oxalato) borate: LiBOB) one or more selected from the group consisting of supporting (supporting) It is included as an electrolyte salt.It is recommended that the concentration of the lithium salt be used within the range of 0.1 M to 2.0 M. When the concentration of the lithium salt is included in the above range, the electrolyte has appropriate conductivity and viscosity, so that excellent electrolyte performance can be exhibited; Lithium ions can move effectively.

A separator may exist between the positive electrode and the negative electrode depending on the type of the lithium secondary battery. As such a separator, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used. A polyethylene/polypropylene two-layer separator, a polyethylene/polypropylene/polyethylene three-layer separator, and polypropylene/polyethylene/poly It goes without saying that a mixed multilayer film such as a propylene three-layer separator or the like can be used.

4 is a perspective view schematically illustrating a typical structure of a lithium secondary battery according to an embodiment.

Referring to FIG. 4 , the lithium secondary battery 100 includes a positive electrode 60 , a negative electrode 50 , and a separator 70 including a positive active material according to an exemplary embodiment. The above-described positive electrode 60 , negative electrode 50 , and separator 70 are wound or folded and accommodated in the battery case 80 . Then, an organic electrolyte is injected into the battery case 80 and sealed to complete the lithium secondary battery 100 . The battery case 80 may have a cylindrical shape, a square shape, a thin film shape, or the like.

The lithium secondary battery 100 may be a lithium ion battery.

A separator 70 may be disposed between the positive electrode 60 and the negative electrode 50 and wound or laminated to form an electrode assembly. When the electrode assembly is accommodated in the battery case 80, impregnated with an organic electrolyte, and the obtained resultant is sealed, the lithium secondary battery 100 is completed.

In addition, the lithium secondary battery is configured as a circuit to form a battery pack, and if necessary, a single or a plurality of packs may be used in any device requiring high capacity and high output. For example, it can be used in a laptop, a smart phone, an electric vehicle, and the like. In addition, since the lithium secondary battery has excellent storage stability, lifespan characteristics, and high rate characteristics at high temperatures, it can be used in electric vehicles (EVs). For example, it may be used in a hybrid vehicle such as a plug-in hybrid electric vehicle (PHEV).

Hereinafter, Examples and Comparative Examples of the present invention will be described. The following examples are only examples of the present invention, and the present invention is not limited to the following examples.

Example

Synthesis Example 1: Large particle diameter metal hydroxide precursor (Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ ) synthesis

Nickel sulfate, cobalt sulfate, and manganese sulfate were used as metal raw materials for forming the metal hydroxide precursor in the following manufacturing process. The reaction was carried out sequentially by dividing it into two steps.

[Step 1]

에서 교반동력 1.5kW/㎥, 금속원료 및 착화제(암모니아수)를 각각 9:1의 농도 비로 넣으면서 반응을 진행했다. 동시에 반응기 내 착화제의 농도가 0.30M이 되도록 유지하였다. 반응 중 NaOH를 투입하여 pH를 10 내지 11로 유지하였다. 반응 결과 얻어진 코어 입자의 평균 사이즈가 약 5.5㎛ 내지 6.5㎛ 범위인 것을 확인하고 제2 단계를 다음과 같이 실시하였다.First, ammonia water (NH ₃ ) having a concentration of 0.30M was put into the reactor. reaction temperature 50

The reaction was carried out while adding stirring power of 1.5kW/m3, metal raw materials and complexing agent (ammonia water) in a concentration ratio of 9:1, respectively. At the same time, the concentration of the complexing agent in the reactor was maintained to be 0.30M. During the reaction, NaOH was added to maintain the pH between 10 and 11. As a result of the reaction, it was confirmed that the average size of the obtained core particles was in the range of about 5.5 μm to 6.5 μm, and the second step was performed as follows.

[Step 2]

The reaction was carried out in the same manner as in the first step except that the stirring power was lowered to 1.0 kW/㎥, the metal raw material and the complexing agent were each changed to a concentration ratio of 7:1, and the concentration of the complexing agent in the reactor was changed to 0.35M. . It was confirmed that the average size of the product particles containing the core and the intermediate layer obtained by carrying out this reaction was 12 mu m to 13 mu m, and the reaction was terminated.

에서 24시간 동안 열풍 건조하여 대입경 금속 수산화물 전구체(Ni_0.6Co_0.2Mn_0.2(OH)₂)를 얻었다.After washing the resultant, the washed product is about 150

A large particle diameter metal hydroxide precursor (Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ ) was obtained by hot air drying for 24 hours.

Synthesis Example 2: Small particle size metal hydroxide precursor (Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ ) synthesis

Nickel sulfate, cobalt sulfate, and manganese sulfate were used as metal raw materials for forming the metal hydroxide precursor in the following manufacturing process.

Ammonia water (NH ₃ ) having a concentration of 0.30M was added to the reactor. At a reaction temperature of 40° C., the reaction was carried out while adding a stirring power of 2.0 kW/m 3 , a metal raw material and a complexing agent in a concentration ratio of 5:1. The concentration of the complexing agent in the reactor was maintained at 0.30M. During the reaction, NaOH was added to maintain the pH at 12-13. As a result of the reaction, it was confirmed that the average size of the obtained core particles was in the range of about 2.5 μm to 3.0 μm, and the reaction was terminated.

After washing the resultant, the washed resultant was dried with hot air at about 150° C. for 24 hours to obtain a metal hydroxide precursor having a small particle size (Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ ).

Example 1-1

(1) Preparation of positive electrode active material

(i) Preparation of secondary particles of large particle size

The large particle diameter metal hydroxide precursor Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ and LiOH prepared in Synthesis Example 1 were mixed in a molar ratio of 1:1, and then heat-treated to include LiNi _0.6 Co _0.2 Mn _0.2 O ₂ to obtain secondary particles having a large particle size. The heat treatment process was performed by raising the temperature from 25°C to 830°C at a rate of 2.0°C/min in an oxygen atmosphere, maintaining it at 830°C for 6 hours, and cooling it from 830°C to 25°C at a rate of 2.0°C/min. .

(ii) Preparation of small particle diameter secondary particles

The small particle diameter metal hydroxide precursor Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ , LiOH and LiF prepared in Synthesis Example 2 were mixed in a molar ratio of 1: 1: 0.0025, and then heat-treated to heat-treat a lithium nickel-based composite oxide LiNi _0.6 Co _0.2 Mn _0.2 Small particle diameter secondary particles containing O ₂ and LiF were obtained. The heat treatment process was performed by raising the temperature from 25°C to 830°C at a rate of 2.0°C/min in an oxygen atmosphere, maintaining it at 830°C for 6 hours, and cooling it from 830°C to 25°C at a rate of 2.0°C/min. .

(iii) Preparation of positive electrode active material

The prepared large particle diameter secondary particles (D50: 11.7 μm) and small particle diameter secondary particles (D50: 2.8 μm) were mixed in a 7:3 weight ratio to prepare a positive electrode active material. The average particle diameter (D50) of the secondary particles with large and small diameters was measured using a particle size distribution (PSD) measuring device .

(2) Preparation of coin cells

A mixture of the prepared cathode active material, carbon black carbon conductive agent (product name: Denka Black, manufactured by Denka Korea) and polyvinylidene fluoride (PVdF) in a weight ratio of 92:4:4 was mixed with N-methylpyrrolidone ( NMP) to prepare a slurry. The slurry was bar coated on an aluminum current collector having a thickness of 15 μm, dried at room temperature, dried once again under vacuum and 120° C., and rolled and punched to prepare a 45 μm thick positive plate.

Using the positive electrode prepared above, lithium metal as a counter electrode, PTFE separator and 1.3M LiPF ₆ mixed solvent of EC (ethylene carbonate), DEC (diethyl carbonate) and EMC (ethylmethyl carbonate) A coin cell was prepared using a solution dissolved in (3:4:3 volume ratio) as an electrolyte.

Example 1-2

The small particle diameter metal hydroxide precursor Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ , LiOH and LiF prepared in Synthesis Example 2 were mixed in a molar ratio of 1:1: 0.005 in the same manner as in Example 1-1. An active material was prepared, and a coin cell was prepared.

Examples 1-3

The small particle diameter metal hydroxide precursor Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ , LiOH and LiF prepared in Synthesis Example 2 were mixed in a molar ratio of 1:1: 0.0075 in the same manner as in Example 1-1. An active material was prepared, and a coin cell was prepared.

Example 2-1

Example 1-1, except that the heat treatment temperature of (i) the manufacturing process of large particle diameter secondary particles and (ii) the heat treatment temperature of the small particle diameter secondary particle manufacturing process of Example 1-1 was changed to 850 ° C. In the same manner, a positive active material and a coin cell were manufactured.

Example 2-2

The small particle diameter prepared in Synthesis Example 2 by changing the heat treatment temperature of the manufacturing process of (i) large particle diameter secondary particles and (ii) the small particle diameter secondary particle manufacturing process of Example 1-1 to 850 ° C. A cathode active material and a coin cell were prepared in the same manner as in Example 1-1, except that the metal hydroxide precursor Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ , LiOH and LiF were mixed in a molar ratio of 1:1:0.005.

Example 2-3

The small particle diameter prepared in Synthesis Example 2 by changing the heat treatment temperature of the manufacturing process of (i) large particle diameter secondary particles and (ii) the small particle diameter secondary particle manufacturing process of Example 1-1 to 850 ° C. A cathode active material and a coin cell were prepared in the same manner as in Example 1-1, except that the metal hydroxide precursor Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ , LiOH and LiF were mixed in a molar ratio of 1: 1: 0.0075.

Example 3

Small particle size single particle active material (manufacturer: Xiamen Tungsten Cathode) was mixed with LiF in a molar ratio of 1: 0.0025, and then heat treated to obtain small particle size single particles containing lithium nickel-based composite oxide LiNi _0.83 Co _0.11 Mn _0.06 O ₂ and LiF. got it The heat treatment process was performed by raising the temperature from 25°C to 850°C at a rate of 2.0°C/min in an oxygen atmosphere, maintaining it at 850°C for 6 hours, and cooling it from 850°C to 25°C at a rate of 2.0°C/min. .

A positive active material was prepared by mixing the secondary particles with a large particle diameter (D50 11.7 μm) prepared according to (i) of Example 1-1 and single particles with a small particle diameter (D50 2.8 μm) in a 7:3 weight ratio. The average particle diameter (D50) of secondary particles of large particle size and single particles of small particle size was measured using a particle size distribution (PSD) measuring device .

A coin cell was manufactured in the same manner as in Example 1-1 using the positive active material.

Comparative Example 1

The large particle diameter metal hydroxide precursor prepared in Synthesis Example 1 and the small particle diameter metal hydroxide precursor prepared in Synthesis Example 2 were mixed in a 7:3 weight ratio, and LiOH, Li:Metal (transition metal element moles) 1:1 molar ratio After mixing, heat treatment was performed to prepare a positive electrode active material. The heat treatment was performed by raising the temperature from 25°C to 830°C at a rate of 2.0°C/min in an oxygen atmosphere, maintaining it at 830°C for 6 hours, and cooling it from 830°C to 25°C at a rate of 2.0°C/min.

A coin cell was manufactured in the same manner as in Example 1-1 (2) except that the prepared positive active material was used.

Comparative Example 2

A positive electrode active material and a coin cell were prepared in the same manner as in Comparative Example 1 except that the heat treatment was performed at 850°C.

Comparative Example 3

PVDF was mixed with the positive active material prepared in Comparative Example 2 in a molar ratio of 1:0.0075 and heat-treated to prepare a final positive active material. The heat treatment was performed in an oxygen atmosphere at a rate of 2.0 °C/min from 25 °C to 400 °C, maintained at 400 °C for 6 hours, and cooled from 400 °C to 25 °C at a rate of 2 °C/min.

A coin cell was manufactured in the same manner as in Example 1-1 (2) except that the prepared positive active material was used.

Comparative Example 4

A mixed precursor obtained by mixing the large particle size metal hydroxide precursor prepared in Synthesis Example 1 and the small particle size metal hydroxide precursor prepared in Synthesis Example 2 in a 7:3 weight ratio, LiOH and LiF, was mixed in a molar ratio of 1:1:0.0075, followed by heat treatment Thus, a positive electrode active material including small particle diameter secondary particles, large particle diameter secondary particles and LiF was obtained. The heat treatment was performed in an oxygen atmosphere at a rate of 2.0°C/min from 25°C to 850°C, maintained at 850°C for 6 hours, and cooled from 850°C to 25°C at a rate of 2.0°C/min.

A coin cell was manufactured in the same manner as in Example 1-1 (2) except that the prepared positive active material was used.

Comparative Example 5

A mixed precursor prepared by mixing the large particle diameter metal hydroxide precursor prepared in Synthesis Example 1 and the small particle diameter metal hydroxide precursor prepared in Synthesis Example 2 in a 7:3 weight ratio, and LiOH and LiF in a 1: 1: 0.0025 molar ratio was mixed in Comparative Example It carried out similarly to 4, and obtained the positive electrode active material.

A coin cell was manufactured in the same manner as in Example 1-1 (2) except that the prepared positive active material was used.

Rating 1

Examples 1-1 to 1-3, Examples 2-1 to 2-3, Examples 3 and Comparative Examples 1 to 5, the sintering temperature and LiF content of the cathode active material prepared in X- using Cu Kα ray Line diffraction analysis (Scan rate: 0.96 degree/min, Scan step: 0.01 degree 2θ, Scan range: 10 to 90 degree) was performed. Table 1 shows the measurement results of the half-width of the (003) plane XRD peak and the c-axis lattice constant.

Firing temperature (℃) LiF content (mol)
(Compared to 100 moles of small particle diameter secondary particles) (003) plane XRD peak half width (degree) c-axis lattice constant (Å) Example 1-1 830 0.25 0.1658 14.245 Example 1-2 830 0.5 0.1650 14.247 Example 1-3 830 0.75 0.1642 14.246 Example 2-1 850 0.25 0.1537 14.238 Example 2-2 850 0.5 0.1535 14.235 Example 2-3 850 0.75 0.1543 14.238 Example 3 850 0.25 0.1301 14.230 Comparative Example 1 830 - 0.1856 14.245 Comparative Example 4 850 0.75 0.1454 14.241

Referring to Table 1, the full width at half maximum of the (003) plane XRD peak of the positive active materials according to Examples 1-1 to 1-3 was decreased compared to that of the positive active material according to Comparative Example 1, and from these results, It can be seen that the size of the primary particles included in the secondary particles of the small particle diameter of the positive electrode active material according to Examples 1-1 to 1-3 increased.

Specifically, through the half-width of the (003) plane XRD peak of the positive electrode active material according to Examples 1-1 to 1-3, as the content of LiF increases, the size of the primary particles included in the secondary particles with small particle diameter increases. It can be seen that the increase was found, and through the half-width of the (003) plane XRD peak of the positive electrode active material according to Examples 1-1 and 2-1, even when the sintering temperature was increased, 1 contained in the secondary particles of small particle diameter It can be seen that the size of the tea particles increased.

In addition, since there is almost no change in the c-axis lattice constant according to Examples 1-1 to 1-3, and Examples 2-1 to 2-3 and Example 3, the content of LiF is increased or It can be seen that the structural change due to the expansion in the c-axis direction is suppressed even when the firing temperature is increased, and the lifespan characteristics of the battery including the positive active material according to the embodiment are improved. In contrast, in the case of the positive active material according to Comparative Example 4, the half-maximum width of the (003) plane XRD peak was significantly reduced compared to the positive active material of Example, and from this, the secondary particles and small diameters of the positive active material according to Comparative Example 4 It can be predicted that the size of all secondary particles increases and F is included in excess, so that the lifespan characteristics of the battery decrease.

evaluation 2

Residual unreacted lithium present on the surface of the positive active material prepared in Examples 1-1 to 1-3, Examples 2-1 to 2-3, Example 3 and Comparative Examples 1 and 2 was measured by HCl titration, and the The results are shown in Table 2 below.

The method for measuring unreacted residual lithium is as follows. 10 g of the positive electrode active material was put into 100 ml of distilled water, stirred at a speed of 300 rpm for 30 minutes, and the solution portion was collected and pH change was measured while adding HCl. Since unreacted residual lithium exists in the form of Li ₂ CO ₃ , LiOH, when HCl is added, H ⁺ and CO ₃ ^2- and OH ^- ions react to make titration. The lithium content can be calculated.

Residual lithium content
(Li content in Li ₂ CO ₃ & LiOH/ppm) Example 1-1 1346 Example 1-2 1263 Examples 1-3 1225 Comparative Example 1 1451 Example 2-1 1245 Example 2-2 1187 Example 2-3 1142 Example 3 1262 Comparative Example 2 1409

Referring to Table 2, in Examples 1-1 to 1-3, Examples 2-1 to 2-3, and Example 3, the residual positive electrode active material compared to Comparative Examples 1 and 2 not containing lithium halide It can be confirmed that lithium is reduced.

evaluation 3

For the coin cells according to Examples 2-1 to 2-3, Example 3 and Comparative Example 2, at room temperature (25° C.), the voltage was 4.3V (vs. Li) at a current of 0.1C rate in the 1st cycle. It was charged with constant current until this, and then cut-off was performed at a current of 0.05C rate while maintaining 4.3V in constant voltage mode. After disassembling the charged battery, 5 positive electrode plates buffered at 4.3V were put in the pouch together with the electrolyte and stored in an oven at 80° C. The mass change due to the change in the volume of the pouch was converted by the Archimedes method. The results are shown in FIG. 5 .

Referring to FIG. 5 , in Examples 2-1 to 2-3 and Example 3, the amount of gas generated due to the side reaction was significantly reduced compared to Comparative Example 2 in which the lithium halide was not included in the small particle size.

Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the appended claims are also presented. It belongs to the scope of the right of the invention.

1: positive active material 1a: positive active material
10: small particle size secondary particle 10a: small particle size single particle
11: Small particle size primary particles
13: lithium halide 20: large particle size secondary particles
21: large particle size primary particles 100: lithium secondary battery
50: negative electrode 60: positive electrode
70: separator 80: battery case
90: cap assembly

Claims (20)

A lithium nickel-based composite oxide comprising large particle diameter particles and small particle diameter particles having different average particle diameters,
The large particle size particles include secondary particles including a plurality of primary particles,
Lithium halide is included only in the small particle size particles,
The large particle diameter particles have an average particle diameter (D50) of 10 to 20 μm, and the small particle diameter particles have an average particle diameter (D50) of 1 to 8 μm,
A cathode active material for a lithium secondary battery. According to claim 1,
The small particle size particle is a positive electrode active material for a lithium secondary battery comprising secondary particles including a plurality of primary particles. According to claim 1,
The small particle size particle comprises a single particle (single crystal particle), a positive electrode active material for a lithium secondary battery. According to claim 1,
The large particle diameter secondary particle is a cathode active material for a lithium secondary battery comprising primary particles having an average thickness of 100 nm to 200 nm. 3. The method of claim 2,
The small particle diameter secondary particles comprising primary particles having an average thickness of 200 to 500 nm, a cathode active material for a lithium secondary battery. According to claim 1,
The large particle size particles, 50 to 90% by weight based on the total weight of the large particle size particles and the small particle size particles, a positive active material for a lithium secondary battery. According to claim 1,
The lithium halide is coated on the surface of the small particle size particles, a positive electrode active material for a lithium secondary battery. 8. The method of claim 7,
The lithium halide is coated in the form of a film on the surface of the small particle size particles, a cathode active material for a lithium secondary battery. According to claim 1,
The lithium halide includes LiF, a positive active material for a lithium secondary battery. According to claim 1,
The lithium halide is contained in an amount of 0.1 mol to 1.0 mol based on 100 mol of the small particle size particles, a positive active material for a lithium secondary battery. According to claim 1,
The large particle diameter particles include secondary particles in which a plurality of plate-shaped primary particles are aggregated, and the (003) plane of the primary particles includes primary particles oriented in a vertical direction with respect to the surface of the secondary particles. A positive active material for a lithium secondary battery having a certain arrangement structure. 3. The method of claim 2,
The small particle size particles include secondary particles in which a plurality of plate-shaped primary particles are aggregated, and the (003) plane of the primary particles is oriented in a vertical direction with respect to the surface of the secondary particles. A positive active material for a lithium secondary battery having a certain arrangement structure. According to claim 1,
The positive active material is a positive active material for a lithium secondary battery having a half width of 0.15° to 0.17° of the (003) plane peak in the X-ray diffraction spectrum analysis. 12. The method of claim 11,
The large particle diameter particles have a radial array structure having one center or a multi-center radial arrangement structure having a plurality of centers, a cathode active material for a lithium secondary battery. 13. The method of claim 12,
The small particle size particles have a radially arranged structure having one center or a multi-center radially arranged structure having a plurality of centers, a cathode active material for a lithium secondary battery. According to claim 1,
The lithium nickel-based composite oxide is a compound represented by the following formula (1), a cathode active material for a lithium secondary battery:
[Formula 1]
Li _a Ni _x Co _y M _1-xy O ₂
(In Formula 1, 0.9 ≤ a ≤ 1.05, 0.3 ≤ x ≤ 0.95, 0.05 ≤ y ≤ 0.3, M is Mn, Al, Cr, Fe, V, Mg, Ti, Zr, Nb, Mo, W, Cu, at least one metal element selected from Zn, Ga, In, Sn, La and Ce.) According to claim 1,
The positive active material is a positive electrode active material for a lithium secondary battery comprising a residual lithium of 1,400 ppm or less on the surface. According to claim 1,
The positive active material has a mixture density of 3.1 to 3.4 g/cm ³ , a positive active material for a lithium secondary battery. To prepare a metal hydroxide precursor with a large particle diameter and a metal hydroxide precursor with a small particle diameter,
A mixture is prepared by mixing a large particle diameter metal hydroxide precursor and a lithium raw material, and the mixture is heat treated to prepare particles with a large particle diameter,
preparing a mixture by mixing a small particle size metal hydroxide precursor, a lithium raw material, and a raw material of lithium halide (LiX), and heat-treating the mixture to prepare small particle size particles containing lithium halide,
Mixing the large particle diameter particles and the small particle diameter particles to prepare a positive electrode active material,
A method of manufacturing a cathode active material for a lithium secondary battery. A positive electrode comprising the positive active material of claim 1;
a negative electrode comprising an anode active material; and
A lithium secondary battery comprising an electrolyte.

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