KR102650968B1 - Cathode active material precursor, cathode active material formed therefrom, preparation method thereof, cathode and lithium battery containing cathode active material - Google Patents

Abstract

At least one secondary particle comprising an aggregate of a plurality of primary particles, wherein the secondary particle includes a nickel-based lithium transition metal oxide having a layered crystal structure, and wherein the primary particle has a size of more than 400 nm. It includes primary particles (first primary particles), primary particles with a size of less than 150 nm (second primary particles), and primary particles with a size of 150 nm to 400 nm (third primary particles), and the area of the third primary particles is A cathode active material with a porosity of 80% or more based on the total area of the primary particles, and the secondary particles have a porosity of 10% or less with respect to the total area of the cathode active material, a method of manufacturing the same, a cathode and lithium battery containing the same, and a cathode active material precursor. is presented.

Description

Cathode active material precursor, cathode active material obtained therefrom, manufacturing method thereof, cathode active material precursor, cathode active material formed therefrom, preparation method thereof, cathode and lithium battery containing cathode active material}

It relates to a cathode active material precursor, a cathode active material obtained therefrom, a method of manufacturing the same, and a cathode and lithium battery including the same.

In order to meet the miniaturization and high performance of various devices, high energy density in addition to miniaturization and weight reduction of lithium batteries is becoming important. In order to implement lithium batteries that meet this importance, nickel-based positive electrode active materials with high capacity are being examined.

In addition, conventional nickel-based positive electrode active materials have reduced lifespan characteristics due to high surface residual lithium content and side reactions caused by cation mixing, and thermal stability does not reach a satisfactory level.

One aspect is to provide a positive electrode active material precursor having a large specific surface area and average particle diameter, a positive electrode active material formed therefrom and having a uniform size particle distribution, and a method for manufacturing the same.

Another aspect is to provide a positive electrode containing the positive electrode active material.

Another aspect is to provide a lithium battery with improved initial efficiency including the positive electrode.

Another aspect is providing the positive electrode active material precursor.

according to one side

At least one secondary particle comprising an aggregate of a plurality of primary particles, wherein the secondary particle includes a nickel-based lithium transition metal oxide having a layered crystal structure,

The primary particles include first primary particles having a size of more than 400 nm, second primary particles having a size of less than 150 nm, and third primary particles having a size of 150 nm to 400 nm,

A positive electrode active material is provided in which the area of the third primary particles is 80% or more based on the total area of the primary particles, and the secondary particles have a porosity of 10% or less with respect to the total area of the positive electrode active material.

According to another aspect, a positive electrode containing the above-described positive electrode active material is provided.

According to another aspect, a lithium battery including the above-described positive electrode is provided.

According to another aspect, a positive electrode active material precursor is provided, which is a vertical precursor of nickel-based lithium transition metal oxide, has a specific surface area of 8 to 25 m ² /g, and has an average particle diameter (D50) of 13.7 ㎛ or more, for example, 15 ㎛ or more. .

According to another aspect, mixing the above-described positive electrode active material precursor and lithium precursor and performing a primary heat treatment thereof;

Washing the first heat-treated product with water and drying it;

A method for producing a positive electrode active material is provided, including the step of secondary heat treatment of the dried product to obtain the above-described positive electrode active material, and the secondary heat treatment is performed at a lower temperature than the primary heat treatment.

By using the positive electrode active material according to one embodiment, a lithium battery with improved initial efficiency and improved capacity characteristics can be manufactured.

Figure 1a schematically shows the primary particle and secondary particle states of a positive electrode active material obtained from a positive electrode active material precursor according to an embodiment.
Figure 1b schematically shows the primary and secondary particle states of a positive electrode active material obtained from a common positive electrode active material precursor.
FIG. 2A is a diagram showing the state of primary particles of the positive electrode active material before and after the first cycle charge/discharge of the positive electrode active material according to one embodiment.
Figure 2b is a diagram showing the state of primary particles of a general positive electrode active material before and after the first cycle charge/discharge of the positive electrode active material.
3A to 3J are field emission differential scanning microscopy images of the surface state of the positive electrode active material precursor obtained according to Preparation Examples 1 to 5, respectively.
This is a scanning electron microscope (FE-SEM) photo.
Figures 4a to 4h are FE-SEM photographs of the surface state of the positive electrode active material precursor obtained according to Comparative Preparation Examples 1 to 4, respectively.
5A to 5E are field emission differential scanning microscopy images of the surface state of the positive electrode active material obtained according to Examples 1 to 5, respectively.
This is a scanning electron microscope (FE-SEM) photo.
5F to 5I are field emission differential scanning microscopy images of the surface state of the positive electrode active material obtained according to Comparative Examples 1 to 5, respectively.
This is a scanning electron microscope (FE-SEM) photo.
Figures 6a and 6b show changes in a-axis and c-axis constants according to the number of measurements as a result of will be.
Figures 6c and 6d show changes in a-axis and c-axis constants as a result of X-ray diffraction analysis of the positive electrode active material of Comparative Example 1 in the lithium battery manufactured according to Comparative Production Example 1.
Figure 7 schematically shows the structure of a lithium battery according to an embodiment.

Hereinafter, a positive electrode active material precursor according to example embodiments, a positive electrode active material obtained therefrom, a manufacturing method thereof, and a positive electrode and lithium battery including the same will be described in more detail.

At least one secondary particle comprising an aggregate of a plurality of primary particles, wherein the secondary particle includes a nickel-based lithium transition metal oxide having a layered crystal structure, and wherein the primary particle has a size of more than 400 nm. It includes primary particles (first primary particles), primary particles with a size of less than 150 nm (second primary particles), and primary particles with a size of 150 nm to 400 nm (third primary particles), and the area of the third primary particles is A positive electrode active material is provided in which the primary particles have a porosity of 80% or more based on the total area, and the secondary particles have a porosity of 10% or less based on the total area of the positive electrode active material.

The area of the first primary particles is 20% or less based on the total area of the primary particles, the area of the second primary particles is 9% or less based on the total area of the primary particles, and the secondary particles are based on the total area of the positive electrode active material. It has a porosity of 1 to 10%.

The area of the particles can be evaluated using SEM. And porosity can be measured using nitrogen isotherms according to the method of Barrett, Joyner, and Halenda (i.e., a BJH surface area). And the surface area can be determined using the method of Brunauer, Emmet, and Teller (i.e. a BET surface area).

The primary particles have a particle uniformity of 90% or more, the area of the first primary particles is 2.1 to 19.2%, for example, 2.1 to 15%, based on the total area of the primary particles, and the area of the second primary particles is 2.1 to 15% based on the total area of the primary particles. 0.1% to 8.6%, such as 0.1 to 5%, such as 0.1 to 3%, such as 0.1 to 1.5%, based on the total area of the particles.

The secondary particles have a porosity of 1.5 to 7% based on the total area of the positive electrode active material. Then, the particle size of each particle is measured using SEM, and then the particle size distribution is measured to correct particle uniformity.

The positive electrode active material according to one embodiment is formed from a positive active material precursor having a large specific surface area and average particle diameter and has uniform particle distribution, for example, uniform primary particle size distribution.

In order to practically implement a high-capacity nickel-based positive electrode, it is necessary to overcome the irreversibility caused by the inability of lithium that escapes during the first charging process to return, and at the same time, achieve high electrode density through mixing opposing positive electrode active materials and small-grain positive electrode active materials. There is a need. However, high-capacity nickel-based anodes generally have poor irreversibility, and when manufactured using a large-diameter active material with a large average particle diameter, the specific capacity can be further reduced. This specification provides a positive electrode active material that can improve these problems.

Nickel-rich positive electrode active materials with a nickel content of 80 mol% or more require improvement in initial efficiency to about 80 to 85%. In the first cycle, the discharge amount compared to the charge amount reaches 80-85%, and the lithium ions absorbed in the negative electrode during charging cannot be properly accommodated in the positive electrode during discharge, so the capacity of the lithium battery containing the positive electrode active material decreases. In order to solve this problem and improve the initial efficiency of the lithium battery, the size of the primary particles of the positive electrode active material is kept small and the uniformity of the primary particles is improved.

The positive electrode active material according to one embodiment improves initial efficiency by controlling the particle uniformity to 90% or more while maintaining the first primary particles with a size of more than 400 nm and the second primary particles with a size of less than 150 nm within the above-mentioned range. , lithium batteries with improved capacity can be manufactured by applying high electrode density.

FIG. 1A shows the states of primary particles (10) and secondary particles (11) in a positive electrode active material according to an embodiment, and FIG. 1B shows a positive electrode active material obtained using a plate-shaped positive electrode active material precursor, which is a common positive electrode active material precursor, for comparison with FIG. 1A. This shows the primary particle (10) and secondary particle (12) states. The particles of the secondary particles 12 in FIG. 1B have a larger average size and less uniformity than the particles of the secondary particles 11 of the positive electrode active material in FIG. 1A.

Referring to this, when a plate-shaped positive electrode active material precursor with a small specific surface area is mixed with a lithium precursor and heat-treated, a positive electrode active material containing large-sized and/or non-uniform primary particles is obtained, as shown in FIG. 1b. .

In comparison, a highly reactive positive electrode active material precursor with a specific surface area of 8 to 25 m ² /g and an average particle diameter of 13.7 ㎛ or more, for example, 15 ㎛ or more, is mixed with a lithium precursor and heat-treated to obtain the primary difference as shown in FIG. 1a. It is possible to obtain a positive electrode active material containing primary particles with small particle size and excellent particle uniformity without generating particles.

The specific surface area of the positive electrode active material precursor is, for example, 10 to 20 m ² /g, for example 11.76 to 19.92 m ² /g. And the average particle diameter of the positive electrode active material precursor is 13.7 μm or more, for example, 15 μm or more, for example, 17 μm or more, for example, 15 to 19.7 μm.

The positive electrode active material precursor according to one embodiment has a vertical plate network structure shape.

As used herein, the term “vertical planar structure” refers to plate particles growing toward the surface of a precursor, and can be observed in the form of a mesh on the surface due to the intersection between individual particles. More specifically, looking at the particle structure, it may mean that the thickness of the plate particle is smaller than the major axis length of the plate particle. It refers to a structure in which the length of one axis direction (i.e., thickness direction) is smaller than the length of the major axis in the other direction. Here, the major axis length may mean the maximum length based on the widest side of the plate particle.

The major axis length of the positive electrode active material precursor is 150 to 2,000 nm, for example, 150 to 1,500 nm. And the minor axis length of the positive electrode active material precursor is 10 to 100 nm, for example, 10 to 50 nm. The shape and major and minor axis length of the positive electrode active material precursor can be confirmed through SEM analysis. The aspect ratio of the positive electrode active material precursor is 5 to 500, for example 10 to 250, for example 20 to 100, and the aspect ratio represents the major axis length/minor axis length.

The secondary particles have a porosity of 10% or less, for example, 1 to 10%, for example, 1.5 to 7%, based on the total volume of the positive electrode active material. For example, it has a porosity of 2 to 6%, for example 1.8 to 2.5%. When this porosity is present, lithium ions can be sufficiently inserted during discharge, making it possible to manufacture a lithium battery with improved initial efficiency. When using the positive electrode active material of FIG. 1b, as shown in FIG. 2b, it contains secondary particles 12 containing large-sized and/or non-uniform primary particles, and during primary charging, as in the case of FIG. 1a, the charging capacity is It is similar, but initial efficiency is reduced because it does not accept enough lithium during the first discharge. For example, as shown in FIG. 2A, charged primary particles 10a are converted to discharged particles 10b after primary discharge. In contrast, as shown in FIG. 2B, only a portion of the charged primary particles 10a are converted to discharged particles 10b after the primary discharge.

The positive electrode active material of FIG. 1A does not contain conflicting and/or non-uniform primary particles compared to the positive electrode active material of FIG. 1B. Therefore, by using the positive electrode active material of FIG. 1A, a lithium battery with improved initial efficiency can be manufactured by allowing sufficient insertion of lithium ions during discharge, as shown in FIG. 2A.

The initial efficiency of the lithium battery according to one embodiment is 93% or more, for example, 95% or more, for example, 95 to 99%.

The positive electrode active material according to one embodiment reduces the content of residual lithium on the surface, thereby suppressing deterioration of the positive electrode active material and reducing gas generation, thereby improving the thermal stability of the lithium battery. In addition, by accommodating volume changes due to charging and discharging of primary particles and suppressing cracking or destruction of primary particles, a decrease in the mechanical strength of the positive electrode active material can be suppressed even after long-term charging and discharging. In addition, side reactions between the nickel-based lithium transition metal oxide having a layered crystal structure and the electrolyte can be efficiently suppressed, and the internal resistance of the lithium battery is reduced, thereby improving the cycle characteristics of the lithium battery.

The nickel-based lithium transition metal oxide having the layered crystal structure belongs to the rock salt layered structure (R-3m space group). By having the above-described crystal structure, the cycle characteristics and thermal stability of a lithium battery including a positive electrode active material can be further improved.

The term “grain boundary” refers to the interface of two adjacent primary particles. At this time, the interface between the primary particles exists inside the secondary particles.

The term “primary particles” refers to agglomerates together to form secondary particles, and the primary particles may have various shapes, including rod-shaped, square, or a combination thereof. And the term "secondary particles" refers to particles that are no longer agglomerated and have spherical properties.

In this specification, the term "size" may represent the average particle diameter when the particle is spherical, and may represent the major axis length when the particle is non-spherical. Particle size can be measured using SEM, for example.

In the positive electrode active material, the nickel content among the transition metals included in the nickel-based lithium transition metal oxide may be 80 mol% or more, for example, 90 mol% or more, for example, or 95 mol% or more. A high-capacity lithium battery can be manufactured by using a nickel-based lithium transition metal oxide with a nickel content within the above-mentioned range.

The nickel-based lithium transition metal oxide having a layered crystal structure may be one selected from compounds represented by the following formulas 1 to 4.

[Formula 1]

Li _x Ni _{1 -yz- α} Co _y Mn _z Me _α O ₂

In formula 1, 1≤x≤1.1, 0≤y≤0.2, 0≤z≤0.2, 0≤α≤0.05

Me is one or more metals selected from the group consisting of Zr, Al, Mg, Ti, Cu, W and B, and y+z+α≤0.3,

[Formula 2]

_{Li x} Co _{1 - y} M _y O _{2 - α}

[Formula 3]

Li _x Ni _{1 - y Me y} O _{2 - α}

[Formula 4]

Li _{x Ni 1 -y- z} Mn _y Ma _z O _{2 - α}

In Formulas 2 to 4, x, y, α, and Me may be selected independently of each other, 1≤x≤1.1, 0≤y≤0.9, 0<z≤0.2, 0≤α≤2, and M is One or more metals selected from the group consisting of Ni, Mn, Zr, Al, Mg, Ag, Mo, Ti, V, Cr, Fe, Cu, and B, and Me is Co, Zr, Al, Mg, Ag, Mo, Ti , V, Cr, Mn, Fe, Cu, and B, and Ma is a group consisting of Co, Zr, Al, Mg, Ag, Mo, Ti, V, Cr, Fe, Cu, and B. It is a metal selected from , and X is an element selected from the group consisting of F, S, and P.

In formulas 2 to 4 x is 1.00 to 1.09, for example 1.03 to 1.09, for example 1.03, 1.06 or 1.09.

The nickel-based lithium transition metal oxide having a layered crystal structure is one selected from compounds represented by the following formulas 5 to 7.

[Formula 5]

Li[Li _1-a Me _a ]O _{2 +d}

In Formula 5, 0.8≤a<1, 0≤d≤0.1,

wherein Me is one or more metals selected from the group consisting of Ni, Co, Mn, Al, V, Cr, Fe, Zr, Re, B, Ge, Ru, Sn, Ti, Nb, Mo and Pt,

[Formula 6]

Li[Li _1-xyz Ma _x Mb _y Mc _z ]O _2+d

In Formula 6, 0.8≤x+y+z<1, 0<x<1, 0<y<1, 0<z<1, 0≤d≤0.1,

Ma, Mb, and Mc are independently one or more metals selected from the group consisting of Mn, Co, Ni, and Al,

[Formula 7]

Li[Li _1-xyz Ni _x Co _y Mn _z ]O _2+d

In Formula 7, 0.8≤x+y+z<1; 0<x<1, 0<y<1, 0<z<1, 0≤d≤0.1.

For example, the nickel-based lithium transition metal oxide having the layered crystal structure may be a compound represented by the following formula (8).

[Formula 8]

aLi ₂ MnO ₃ -(1-a)LiMO ₂

In Formula 8, 0<a<1,

M is nickel (Ni), cobalt (Co), manganese (Mn), vanadium (V), chromium (Cr), iron (Fe), zirconium (Zr), rhenium (Re), aluminum (Al), and boron (B ), germanium (Ge), ruthenium (Ru), tin (Sn), titanium (Ti), niobium (Nb), molybdenum (Mo), and platinum (Pt).

The nickel-based lithium transition metal oxide having the layered crystal structure may be a compound represented by the following formula (9).

[Formula 9]

Li _x Ni _{1 -y- z} M _y Co _z O ₂

In Formula 9, 0.90≤x≤1.1, 0≤y≤0.2, 0<z≤0.2, 0.8≤1-y-z≤0.99.

M is selected from the group consisting of manganese (Mn), aluminum (Al), titanium (Ti), and calcium (Ca).

In Formula 9, 1-y-z is, for example, 0.8 to 0.91.

In formula 9 x is 1.0 to 1.09, for example 1.03 to 1.09, for example 1.03, 1.06 or 1.09.

Nickel-based lithium transition metal oxide is, for example, Li _{1 . 03} [Ni _0.91 Co _0.06 Mn _0.03 ]O _{2 ,} Li _1.03 [Ni _0.88 Co _0.08 Mn _0.04 ]O _{2 ,} Li _{1 . 03} [Ni _0.8 Co _0.15 Mn _0.05 ]O _{2 ,} Li _{1 . 03} [Ni _0.85 Co _0.10 Mn _0.05 ]O ₂ , Li _1.03 [Ni _0.91 Co _0.05 Mn _0.04 ]O _{2 ,} Li _{1 . 05} [Ni _0.91 Co _0.06 Mn _0.03 ]O _{2 ,} Li _{1 . 05} [Ni _0.88 Co _0.08 Mn _0.04 ]O _{2 ,} Li _1.05 [Ni _0.8 Co _0.15 Mn _0.05 ]O _{2 ,} Li _{1 . 05} [Ni _0.85 Co _0.10 Mn _0.05 ]O ₂ , Li _{1 . 05} [Ni _0.91 Co _0.05 Mn _0.04 ]O _{2, Li 1.06 [Ni 0.91 Co 0.06 Mn 0.03 ] O 2 , Li 1 . 06} [Ni _0.88 Co _0.08 Mn _0.04 ]O _{2 ,} Li _{1 . 06} [Ni _0.8 Co _0.15 Mn _0.05 ]O _{2 ,} Li _1.06 [Ni _0.85 Co _0.10 Mn _0.05 ]O ₂ , Li _{1 . 06} [Ni _0.91 Co _0.05 Mn _0.04 ]O _{2 ;} Li _{1 . 09} [Ni _0.91 Co _0.06 Mn _0.03 ]O _{2 ,} Li _1.09 [Ni _0.88 Co _0.08 Mn _0.04 ]O _{2 ,} Li _{1 . 09} [Ni _0.8 Co _0.15 Mn _0.05 ]O _{2 ,} Li _{1 . 09} [Ni _0.85 Co _0.10 Mn _0.05 ]O ₂ , or Li _1.09 [Ni _0.91 Co _0.05 Mn _0.04 ]O ₂ .

The average particle diameter of the primary particles in the positive electrode active material may be 0.01 to 1 ㎛, for example, 0.2 to 0.4 ㎛, but is not necessarily limited to this range and can be adjusted within a range that can provide improved charge and discharge characteristics.

The average particle diameter of the secondary particles in which the primary particles are aggregated in the positive electrode active material may be about 1㎛ to about 30㎛, for example, 10 to 20㎛, for example, about 13㎛ to about 15㎛, but is not necessarily limited to this range. It can be adjusted within a range that can provide improved charge/discharge characteristics.

According to one embodiment, the grain boundaries in the positive electrode active material have an average grain boundary length of about 50 nm to about 1000 nm, an average grain boundary thickness of about 1 nm to 200 nm, the direction of the length is parallel to the surface of the adjacent primary particle, and the thickness The direction may be perpendicular to the surface of the adjacent primary particle. Within this range of average grain boundary length and average grain boundary thickness, further improved charge and discharge characteristics can be provided.

According to another embodiment, a method for manufacturing a positive electrode active material is provided.

The manufacturing method includes preparing a mixture by mixing a positive electrode active material precursor and a lithium precursor, wherein the positive electrode active material precursor has a specific surface area of about 8 square meters per gram to about 25 square meters per gram and an average particle diameter of about. 13.7 ㎛ or more, and the positive electrode active material precursor is a vertical plate network-structured precursor of nickel-containing lithium transition metal oxide. heat-treating the mixture to produce a first product; washing the first product with water to produce a washed product; drying the washed product to produce a dried product; and manufacturing a positive electrode active material by heat treating the dried product, wherein the second heat treatment temperature is lower than the first heat treatment temperature.

According to another embodiment, the positive electrode active material includes the steps of mixing the above-described positive electrode active material precursor and a lithium precursor and performing a first heat treatment thereof; Washing the first heat-treated product with water and drying it; It can be manufactured including the step of secondary heat treatment of the dried product.

To remove residual lithium from the synthesized active material obtained according to the above process, additional cleaning/coating and heat treatment can be performed, and by using dehydrated LiOH as a raw material, the heat treatment time can be shortened and the production volume increased. . Heat treatment after cleaning can be performed in a wide range, for example in the range of 150 to 800°C, depending on the coating material.

The positive electrode active material precursor may be manufactured by controlling the pH of the mixture obtained by mixing a metal raw material for forming the positive active material precursor, a complexing agent, and a pH adjuster, and then performing a reaction.

The first heat treatment and the second heat treatment are performed in an oxidizing gas atmosphere, and the oxidizing gas atmosphere is implemented using oxygen or air.

The primary heat treatment and secondary heat treatment are carried out at, for example, 600 to 900°C, for example 730 to 760°C, for example 740 to 750°C. Secondary heat treatment can be performed at a lower temperature than primary heat treatment.

The primary heat treatment may be carried out at, for example, 650 to 800°C, for example 700 to 750°C, for example 730 to 750°C for 20 to 30 hours. The secondary heat treatment may be performed at, for example, 650 to 800°C, for example, 700 to 750°C for 10 to 30 hours.

According to one embodiment, the first heat treatment may be performed at 730 to 750°C for 20 to 30 hours, and the second heat treatment may be performed at 720°C for 24 hours.

The temperature increase rate during the first and second heat treatments is controlled in the range of 0.5 to 10°C/min, for example, 1 to 2°C/min.

In the step of washing and drying the first heat-treated product with water, drying may be performed at 50 to 150°C. Residual lithium present on the surface of the positive electrode active material can be efficiently removed through washing and drying with water.

The time for maintaining the heat treatment at the primary heat treatment temperature varies depending on the primary heat treatment temperature, but ranges from 2 to 20 hours, for example from 5 to 15 hours.

Since the secondary heat treatment temperature is lower than the primary heat treatment temperature, the rate of lowering from the primary heat treatment temperature to the secondary heat treatment temperature (temperature reduction rate) is, for example, 1 to 10°C/min. To reach this heat treatment temperature, the temperature lowering rate is controlled in the range of 0.5 to 10°C/min, for example, about 0.8 to 2.5°C/min.

The positive electrode active material obtained according to the above process has a density of 2.8 g/cc or more, for example, 2.9 to 3.1 g/cc after rolling.

After drying, a lithium cobalt oxide coating film can be formed on the surface of the positive electrode active material using a cobalt-containing salt, etc.

The above-mentioned positive electrode active material precursor may be hydroxide, carbonate, oxalate, etc. used in manufacturing the above-mentioned positive electrode active material.

This positive electrode active material precursor is obtained by mixing, for example, a cobalt precursor, a nickel precursor, and a manganese precursor and mixing a solvent thereto to obtain a metal precursor mixture. A coprecipitation reaction of this precursor mixture is performed to form a precipitate, which is then heat-treated to obtain the desired positive electrode active material precursor.

Water is used as the solvent. The metal precursor mixture may contain water as a solvent and may be an aqueous metal precursor solution.

During the coprecipitation reaction of the metal precursor mixture, a complexing agent such as aqueous ammonia is added and the pH of the reaction mixture is controlled using a pH adjuster such as aqueous sodium hydroxide solution.

The concentration of ammonia water is for example 20 to 35% by weight, for example 28% by weight. And the concentration of the sodium hydroxide solution is for example 15 to 40% by weight, for example 20 to 35% by weight.

Physical properties such as size, particle shape, specific surface area, and average particle diameter of the positive electrode active material precursor are influenced by the concentration of the metal precursor when manufacturing the precursor, the mixing ratio of transition metal and complexing agent such as ammonia water, reaction temperature, stirrer speed, reaction time, and pH range. receive

According to one embodiment, the temperature of the coprecipitation reaction is 30 to 50° C., for example, 40 to 45° C., and the mixing ratio of the complexing agent and the metal in the metal precursor mixture is, for example, 1:0.3 to 1:0.55, for example. For example, the molar ratio is 1:0.45 to 1:0.5. Here, metal refers to transition metals such as nickel, cobalt, and manganese contained in the positive electrode active material in addition to lithium when manufacturing the positive electrode active material.

The concentration of metal precursors such as cobalt precursor, nickel precursor, manganese precursor is for example 0.5 to 1.0M, for example 0.75 to 1M. And the pH range of the reaction mixture is, for example, 10 to 11 and the stirring speed of the reaction mixture is 300 to 500 rpm (revolutions per minute). The reaction time varies depending on the conditions described above, but ranges from 11 to 30 hours, for example from 16 to 26 hours.

As the cobalt precursor, nickel precursor, and manganese precursor, chloride, sulfate, and nitrate containing cobalt, nickel, and manganese can be used, respectively.

When manufacturing the above-described positive electrode active material precursor, heat treatment may be followed by a washing process using water and a drying process.

The rolling density of the positive electrode active material according to one embodiment is 2.7 g/cc or more, for example, 2.7 to 3.08 g/cc.

The positive electrode active material according to one embodiment may be used as a large particle diameter positive electrode active material when manufacturing a positive electrode. It can be mixed with a small particle size positive electrode active material and used as a bimodal positive electrode active material. The rolling density of the bimodal positive electrode active material, which is a mixture of a large particle size positive electrode active material and a small particle size positive electrode active material, is 3.3 g/cc or more, for example 3.5 to 4.0 g/cc, for example 3.6 to 4.00 g/cc, for example. It is 3.6 to 4.0 g/cc.

The average particle diameter of the small-diameter positive electrode active material is, for example, 2 to 5 μm. And the average particle diameter of the large particle diameter positive active material may be 15㎛ or more, for example, 16 to 25㎛. The mixing weight ratio of the large particle size positive electrode active material and the small particle size positive active material is 1:99 to 99:1, for example, 1:9 to 9:1, for example, 6:4 to 7:3.

In the lithium battery according to one embodiment, after discharging at 3.5V, the crystal lattice constant a obtained from The constant can be increased from 0.1 to 0.5%.

A positive electrode according to another embodiment may include the positive electrode active material described above.

For example, a positive electrode active material composition is prepared by mixing the above-described positive electrode active material, conductive agent, binder, and solvent. The positive electrode active material composition can be directly coated and dried on an aluminum current collector to manufacture a positive electrode with a positive electrode active material layer. Alternatively, the positive electrode active material composition may be cast on a separate support, and then the film obtained by peeling from the support may be laminated on the aluminum current collector to produce a positive electrode with a positive active material layer formed thereon.

Conductive agents include carbon black, graphite particles, natural graphite, artificial graphite, acetylene black, Ketjen black, and carbon fiber; carbon nanotubes; Metal powder or metal fiber or metal tube such as copper, nickel, aluminum, silver, etc.; Conductive polymers such as polyphenylene derivatives may be used, but are not limited to these, and any conductive agent that can be used in the relevant technical field can be used.

Binders include vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), mixtures of the above polymers, and styrene butadiene rubber. Polymers, etc. may be used, and solvents such as N-methylpyrrolidone (NMP), acetone, water, etc. may be used, but are not necessarily limited to these and any solvent that can be used in the art is possible.

The contents of the positive electrode active material, conductive agent, binder, and solvent are levels commonly used in lithium batteries. Depending on the use and configuration of the lithium battery, one or more of the conductive agent, binder, and solvent may be omitted.

Additionally, the positive electrode may additionally include other general positive electrode active materials in addition to the positive electrode active materials described above.

The general positive electrode active material is a lithium-containing metal oxide, and any material commonly used in the industry can be used without limitation. For example, one or more types of complex oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof can be used, and specific examples thereof include Li _a A _{1 - b} B _b D ₂ (above where 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li _a E _{1 - b} B _b O _{2 - c} D _c (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE _{2 - b} B _b O _{4 - c} D _c (in the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li _a Ni _{1 -b- c} Co _b B _c D _α (wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li _a Ni _{1 -b- c} Co _b B _c O _{2 - α} F _α (wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _{1 -b- c} Co _b B _c O _{2 - α} F ₂ (wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _{1 -b- c} Mn _b B _c D _α (wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li _a Ni _{1 -b- c} Mn _b B _c O _{2 - α} F _α (wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _{1 -b- c} Mn _b B _c O _{2 - α} F ₂ (wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _b E _c G _d O ₂ (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li _a Ni _b Co _c Mn _d GeO ₂ (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤0.5, 0.001 ≤ e ≤ 0.1); Li _a NiG _b O ₂ (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li _a CoG _b O ₂ (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li _a MnG _b O ₂ (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li _a Mn ₂ G _b O ₄ (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiIO ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2); Compounds represented by any of the chemical formulas of LiFePO ₄ can be used:

In the above formula, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

Of course, a cathode compound having a coating film on the surface can be used, or a mixture of the above compound and a compound having a coating film can be used. This coating film may include a coating element compound of an oxide, hydroxide, oxyhydroxide of the coating element, oxycarbonate of the coating element, or hydroxycarbonate of the coating element. The compounds that make up these coating films may be amorphous or crystalline. Coating elements included in the coating film may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. For the coating film formation process, any coating method may be used as long as the above compounds can be coated with these elements in a manner that does not adversely affect the physical properties of the positive electrode active material (e.g., spray coating, dipping method, etc.). Since this is well-understood by people working in the field, detailed explanation will be omitted.

According to another embodiment, the positive electrode can be manufactured by using the positive electrode active material according to the embodiment as a large particle size positive electrode active material and using it together with a small particle size positive electrode active material. In this way, the positive electrode may contain a bimodal positive electrode active material.

A lithium battery according to another embodiment employs a positive electrode containing the positive electrode active material, a negative electrode, and an electrolyte disposed between them. Lithium batteries can be manufactured in the following way.

First, an anode is manufactured according to the anode manufacturing method described above.

Next, the cathode can be manufactured as follows. The negative electrode can be manufactured in the same manner as the positive electrode except that a negative electrode active material is used instead of the positive electrode active material. Additionally, the conductive agent, binder, and solvent in the negative electrode active material composition may be the same as those for the positive electrode.

For example, a negative electrode active material composition is prepared by mixing a negative electrode active material, a conductive agent, a binder, and a solvent, and the negative electrode can be manufactured by coating the composition directly on a copper current collector. Alternatively, the negative electrode can be manufactured by casting the negative electrode active material composition on a separate support and laminating the negative electrode active material film peeled from the support to a copper current collector.

Additionally, the negative electrode active material may be any material that can be used as a negative electrode active material for a lithium battery in the art. For example, it may include one or more selected from the group consisting of lithium metal, metal alloyable with lithium, transition metal oxide, non-transition metal oxide, and carbon-based material.

For example, elements alloyable with lithium include Si, Sn, Al, Ge, Pb, Bi, Sb Si-Y alloy (where Y is an alkali metal, alkaline earth metal, group 13 to 16 element, transition metal, rare earth element) or a combination element thereof, but not Si), a Sn-Y alloy (wherein Y is an alkali metal, an alkaline earth metal, a Group 13 to Group 16 element, a transition metal, a rare earth element, or a combination element thereof, but not Sn), etc. You can. The element Y includes 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, S, It may be Se, Te, Po, or a combination thereof.

For example, the transition metal oxide may be lithium titanium oxide, vanadium oxide, lithium vanadium oxide, etc.

For example, the non-transition metal oxide may be SnO ₂ , SiO _x (0<x<2), etc.

The carbon-based material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be amorphous, plate-shaped, flake-shaped, spherical or fibrous, such as natural graphite or artificial graphite, and the amorphous carbon may be soft carbon (low-temperature sintered carbon) or hard carbon. carbon), mesophase pitch carbide, calcined coke, etc.

The contents of the negative electrode active material, conductive agent, binder, and solvent are levels commonly used in lithium batteries.

Next, a separator to be inserted between the anode and the cathode is prepared. Any separator commonly used in lithium batteries can be used. An electrolyte that has low resistance to ion movement and has excellent electrolyte moisturizing ability can be used. For example, it is selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and may be in the form of non-woven or woven fabric. For example, a rollable separator such as polyethylene or polypropylene may be used in a lithium ion battery, and a separator with excellent organic electrolyte impregnation ability may be used in a lithium ion polymer battery. For example, the separator can be manufactured according to the following method.

A separator composition is prepared by mixing polymer resin, filler, and solvent. The separator composition may be directly coated and dried on the top of the electrode to form a separator. Alternatively, after the separator composition is cast and dried on a support, a separator film peeled from the support is laminated on the electrode to form a separator.

The polymer resin used to manufacture the separator is not particularly limited, and any materials used in the binder of the electrode plate can be used. For example, vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, or mixtures thereof may be used.

Next, the electrolyte is prepared.

For example, the electrolyte may be an organic electrolyte. Additionally, the electrolyte may be solid. For example, it may be boron oxide, lithium oxynitride, etc., but it is not limited to these, and any solid electrolyte that can be used in the art can be used. The solid electrolyte may be formed on the cathode by a method such as sputtering.

Organic electrolytes can be prepared by dissolving lithium salt in an organic solvent.

The organic solvent may be any organic solvent that can be used in the art. For example, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate. , benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide , dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, or mixtures thereof.

The above lithium salt can also be used as long as it can be used as a lithium salt in the art. For example, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , 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), LiCl, LiI, or mixtures thereof.

As shown in FIG. 7, the lithium battery 1 includes a positive electrode 3, a negative electrode 2, and a separator 4. The above-described positive electrode (3), negative electrode (2), and separator (4) are wound or folded and accommodated in the battery case (5). Next, an organic electrolyte is injected into the battery case 5 and sealed with a cap assembly 6 to complete the lithium battery 1. The battery case may be cylindrical, prismatic, thin film, etc. For example, the lithium battery may be a large thin film type battery. The lithium battery may be a lithium ion battery.

A separator may be disposed between the anode and the cathode to form a battery structure. The battery structure is stacked in a bi-cell structure, then impregnated with an organic electrolyte solution, and the resulting product is placed in a pouch and sealed to complete the lithium ion polymer battery.

Additionally, a plurality of the battery structures are stacked to form a battery pack, and this battery pack can be used in all devices that require high capacity and high output. For example, it can be used in laptops, smartphones, electric vehicles, etc.

In addition, the lithium battery has excellent lifespan characteristics and high rate characteristics, so it can be used in electric vehicles (EV). For example, it can be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEV). Additionally, it can be used in fields that require large amounts of power storage. For example, it can be used in electric bicycles, power tools, etc.

It will be described in more detail through the following examples and comparative examples, but the scope of the invention is not limited to the following examples.

<Manufacture of positive electrode active material precursor>

Manufacturing example One

The positive electrode active material precursor was synthesized through the coprecipitation method described later. In the following preparation example, the concentration and NH ₄ OH/Me (Ni, Co and Mn) ratio of the metal precursor solution in which Ni sulfate, Co sulfate, and Mn sulfate are melted, reaction temperature, stirrer speed, reaction time, and The particle shape and size were controlled by adjusting the pH by adjusting the amount of sodium hydroxide (NaOH) added.

NiSO ₄ (H ₂ O) ₆ , CoSO ₄ and MnSO ₄ H ₂ O were added to water in a 10L batch reactor at a molar ratio of 85:10:5 to prepare a metal precursor aqueous solution of about 0.75M. Aqueous ammonia was added to the aqueous solution and the reaction was started while stirring the mixture at about 40°C. Then, aqueous sodium hydroxide solution was slowly added dropwise using a pH controller to control the pH of the reaction mixture to about 11. In this pH range, the reaction was performed for about 16 hours while stirring the reaction mixture in the reactor at a stirring speed of about 300 rpm to precipitate nickel cobalt manganese (Ni _0.85 Co _0.10 Mn _0.05 ) hydroxide from the aqueous precursor solution. The mixing molar ratio of about 0.75M aqueous precursor solution with aqueous ammonia and the total content of metal contained in the 0.75M aqueous metal precursor solution was about 1:0.45.

The precipitate obtained according to the above process was filtered, washed with water, and dried at about 150° C. to prepare nickel cobalt manganese hydroxide powder, which is a positive electrode active material precursor with a vertical structure. The conditions for producing the positive electrode active material precursor according to Preparation Example 1 are shown in Table 1 below.

Manufacturing example 2 to Manufacturing example 5, Comparative manufacturing example 1 to Manufacturing example 4

A positive electrode active material precursor was prepared in the same manner as Preparation Example 1, except that it was carried out according to the conditions shown in Table 1 below.

Furtherance
(Ni/Co/Mn) Metal precursor solution (M) Temperature (℃) pH NH ₄ OH/mixing molar ratio of total metal content in metal precursor aqueous solution stirring
speed (rpm) Response time (Hr) Comparative Manufacturing Example 1 85/10/5 1.5 50 11.5 0.25 500 12.0 Comparative Manufacturing Example 2 88/8/4 1.5 50 11.5 0.25 500 18.5 Comparative Manufacturing Example 3 6/3/91 1.5 50 11.5 0.25 500 21.5 Comparative Manufacturing Example 4 85/10/5 0.75 40 11.0 0.45 300 11.5 Manufacturing example 1 85/10/5 0.75 40 11.0 0.45 300 16.0 Manufacturing example 2 88/8/4 0.75 40 11.0 0.45 300 24.0 Manufacturing example 3 88/8/4 1.00 45 11.0 0.40 500 22.5 Manufacturing example 4 6/3/91 0.75 40 11.0 0.45 400 23.0 Production example 5 6/3/91 1.00 40 11.0 0.50 300 26.0

<Manufacture of positive electrode active material>

Raw materials were prepared by mixing LiOH-H ₂ O with the positive electrode active material precursor obtained according to the above process so that the Li/Me (transition metal) ratio was 1.03. The prepared raw materials were synthesized by heat treatment using a RHK electric furnace in an oxygen atmosphere. The synthesis conditions are as follows.

Example 1: Preparation of positive electrode active material

The positive electrode active material precursor powder and LiOH-H ₂ O obtained according to Preparation Example 1 were mixed so that the Li/Me (transition metal) ratio was 1.03, then placed in a furnace and heated at about 750°C (T1) while blowing dry air. The first heat treatment was performed for 30 hours.

The heat-treated product was then washed with water, dried at about 150°C, and then subjected to secondary heat treatment at 720°C (T2) in an oxidizing gas O ₂ atmosphere for 24 hours.

The manufacturing process conditions used when manufacturing the positive electrode active material according to Example 1 are shown in Table 2 below.

Example 2 to 5

A positive electrode active material was manufactured in the same manner as in Example 1, except that the first heat treatment was performed according to the conditions in Table 2 below. In Table 2, “temperature increase rate” represents the rate of raising the reaction temperature of the furnace for the first heat treatment, “holding section temperature” represents the first heat treatment temperature (T1), and “holding time” represents the first heat treatment temperature. Indicates the duration of the first heat treatment. And “temperature reduction rate” refers to the speed at which the temperature is reduced to adjust from the primary heat treatment temperature to the secondary heat treatment temperature.

Example 6

A positive electrode active material was manufactured in the same manner as in Example 1, except that the temperature increase rate and holding time in Table 2 below were changed to 0.8°C/min and 9 hours, respectively.

Comparative example 1 to Comparative example 4

A positive electrode active material was manufactured in the same manner as in Example 1, except that it was carried out according to the conditions in Table 2 below.

Furtherance
(Ni/Co/Mn) Temperature increase rate
(℃/min) Maintenance section
Temperature (℃) Holding time
(hr) Temperature drop rate (℃/mim) Comparative Example 1 85/10/5 1℃/min 750 11.5hrs 1.6℃/min Comparative example 2 88/8/4 740 Comparative example 3 6/3/91 740 Comparative example 4 85/10/5 750 Example 1 85/10/5 750 Example 2 88/8/4 740 Example 3 88/8/4 740 Example 4 6/3/91 740 Example 5 6/3/91 740

<Manufacture of lithium battery (half cell)>

Production example 1: Manufacturing of lithium battery (half cell)

A mixture of the positive electrode active material prepared in Example 1, a carbon conductive agent (Denka Black), and polyvinylidene fluoride (PVdF) at a weight ratio of 92:4:4 was mixed with N-methyl-pyrrolidone (NMP). A slurry was prepared by mixing together in an agate mortar. The slurry was bar coated on a 15㎛ thick aluminum current collector, dried at room temperature, dried again under vacuum and 120°C, and rolled and punched to produce a 55㎛ thick positive electrode.

Using the positive electrode prepared above, lithium metal was used as the counter electrode, and a PTFE separator and 1.15M LiPF ₆ were added to EC (ethylene carbonate), EMC (ethylmethyl carbonate), and DMC (dimethyl carbonate) (3:4). Each coin cell was manufactured using a solution dissolved in (:3 volume ratio) as an electrolyte.

Production example 2 to 6: Manufacturing of lithium battery

A lithium battery was manufactured in the same manner as Production Example 1, except that the positive electrode active material prepared in Examples 2 to 6 was used instead of the positive electrode active material prepared in Example 1.

Comparative production example 1 to 5: Preparation of lithium battery (half cell)

A lithium battery (half cell) was manufactured in the same manner as Manufacturing Example 1, except that the cathode active materials prepared according to Comparative Examples 1 to 5 were used instead of the cathode active materials prepared in Example 1.

Evaluation example One: Field emission type scanning electron microscope (Field Emission Scanning Electron Microscope :FE- SEM ) Image analysis

1) Preparation Examples 1-5 and Comparative Preparation Examples 1 to 4

To the positive electrode active material precursor obtained according to Preparation Examples 1-5 and Comparative Preparation Examples 1 to 4

FE-SEM analysis was performed. FE-SEM analysis was performed using Hitachi-S4300.

The FE-SEM analysis results of the positive electrode active material precursor prepared according to Preparation Example 1 are shown in Figures 3A and 3B, respectively. And the FE-SEM analysis results of the positive electrode active material precursor of Preparation Example 2 are shown in FIGS. 3C and 3D. And FIGS. 3E and 3F are for the positive electrode active material precursor of Preparation Example 3, and FIGS. 3G and 3H are for the positive electrode active material precursor of Preparation Example 4. And Figures 3i and 3j show the positive electrode active material precursor of Preparation Example 5.

The FE-SEM analysis results for the positive electrode active material precursors prepared according to Comparative Preparation Examples 1 to 4 are shown in FIGS. 4A to 4H, respectively.

With reference to this, the positive electrode active material precursors of Preparation Examples 1 to 5 had a vertical planar structure, whereas the positive electrode active material precursors of Comparative Preparation Examples 1 to 4 showed a less uniform structure. Here, the structure with reduced uniformity has a high density but low specific surface area because the precursor is covered with a stripe-like structure. In particular, the string-like structure has a significantly lower ratio of the long axis to the short axis compared to plate particles, and the porosity inside and on the surface of the precursor is small, showing low reactivity.

2) Examples 1-5 and Comparative Examples 1-4

Positive electrode active materials prepared according to Examples 1 to 5 and Comparative Examples 1 to 4

FE-SEM analysis results of the manufactured positive electrode active material were performed.

5A to 5E are field emission differential scanning microscopy images of the surface state of the positive electrode active material obtained according to Examples 1 to 5, respectively.

This is a scanning electron microscope (FE-SEM) photo. And FIGS. 5F to 5I are field emission scanning electron microscope (FE-SEM) photographs of the surface state of the positive electrode active material obtained according to Comparative Examples 1 to 4, respectively.

Looking at the cross section of the cathode active materials prepared according to Comparative Examples 1 to 4, the size distribution of primary particles is wide and the porosity is low, while the cathode active materials of Examples 1 to 5 made using vertical planar structure precursors are uniform in size. Secondary particles were created from the composition of one primary particle, and in particular, porosity existed between the primary particles.

Referring to this, Preparation Examples 1 to 5 have a large specific surface area and excellent reactivity.

By using a needle-type positive electrode active material precursor, the positive electrode active materials of FIGS. 5A to 5D with uniform and small primary particle sizes could be obtained. In comparison, the positive electrode active material precursors of Comparative Preparation Examples 1 to 4 are plate-shaped and have a smaller specific surface area than the positive electrode active material precursors of FIGS. 3A to 3J, and the primary particle size is large and non-uniform compared to the case where the positive electrode active material is synthesized under the same conditions as the positive electrode active material. I could tell it was going to happen.

Evaluation Example 2: Measurement of Brunauer-Emmett-Teller (BET) specific surface area , average particle diameter, major axis length, and minor axis length of positive electrode active material precursor

For the positive electrode active material precursor obtained according to Preparation Example 1-5 and Comparative Preparation Example 1-4

BET specific surface area, average particle diameter (D50), major axis length, minor axis length, and morphology were investigated and the results are shown in Table 3 below. BET specific surface area was measured using Mountech Macsorb. In addition, pretreatment to remove surface impurities before measuring BET must be performed at a low temperature to ensure accurate measurement without any change in the specific surface area of the precursor. Pretreatment of the precursor was performed at a low temperature of about 150°C to prevent changes in the precursor.

division precursor
shape BET specific surface area
( ^m2 /g) Average particle size (D50)
(㎛) Major axis length
(nm)
Shortened length
(nm) Manufacturing Example 1 Vertical Plate Network Structure
(vertical plane structure) 17.35 13.7 150-1500 10-45 Production example 2 19.92 16.8 150-1000 10-45 Production example 3 8.52 16.7 200-500 10-130 Production example 4 11.76 16.8 200-500 30-110 Production example 5 15.38 19.7 150-1000 10-45 Comparative Manufacturing Example 1 Normal 5.26 13.8 250-500 50-250 Comparative Manufacturing Example 2 7.29 16.5 250-600 50-250 Comparative Manufacturing Example 3 6.34 17.2 250-500 40-250 Comparative Manufacturing Example 4 vertical plane structure 18.42 9.73 150-1500 10-45

Referring to Table 3, the positive electrode active material precursors prepared according to Preparation Examples 1 to 5 had a BET specific surface area of 8.52 m ² /g or more and an average particle diameter of 13.7 ㎛ or more. In comparison, the positive electrode active material precursor prepared according to Comparative Preparation Examples 1 to 3 had a BET specific surface area of 7.29 m ² /g or less, which was smaller than that of the positive electrode active material of Preparation Examples 1 to 5. In addition, the positive electrode active material precursor prepared according to Comparative Preparation Example 4 had a large BET specific surface area, but the average particle diameter was 9.73㎛, which was very small compared to the positive electrode active materials of Preparation Examples 1 to 5.

In addition, the positive electrode active material precursors of Preparation Examples 1 to 5 showed a vertical plane structure compared to the positive electrode active material precursors of Comparative Preparation Examples 1 to 3, indicating that their morphologies were different.

Evaluation example 3: Of positive electrode active material Morphology and particle size distribution characteristics

Based on the FE-SEM analysis results for the positive electrode active material of Evaluation Example 1, the porosity of the positive electrode active materials of Examples 1 to 5 and the positive electrode active materials of Comparative Examples 1 to 4, and the area of the first primary particles having a size exceeding 400 nm. , the area of the second primary particles with a size of less than 150 nm, the average particle diameter of the third primary particles (area of the third primary particles) and the secondary particles with a size of 150 nm to 400 nm were investigated, and the results are shown in Table 4 below. .

division Morphology Porosity (%) Area of primary borrower (%) Area of second day borrower (%) Area of 3rd day borrowers (%) Average particle size of secondary particles
(D50)(㎛) Example 1 vertical plane
structure 2.3 7.4 0.2 92.4 15.0 Example 2 2.1 8.9 0.1 91.0 16.5 Example 3 1.8 2.1 8.6 89.3 16.5 Example 4 2.2 19.2 0.1 80.7 16.5 Example 5 2.5 18.9 0.1 81.0 17.0 Comparative Example 1 Normal 0.05 18.6 1.7 79.7 16.0 Comparative Example 2 0.05 14.5 6.4 79.1 17.0 Comparative Example 3 0.05 38.4 0.8 60.8 17.0 Comparative Example 4 vertical plane
structure 10.1 9.6 0.2 90.2 16.5

Referring to Table 4, it was found that the positive electrode active materials of Examples 1 to 3 had a reduced number of opposing primary particles with a size of 400 nm or more compared to the positive active material of Comparative Example 1. And the positive electrode active materials of Examples 1 to 5 have an area of 3rd primary particles of 80% or more, an area of 1st primary particles of 20% or less, and an area of 2nd primary particles of 9% or less compared to the total area of primary particles. It was found that the size of the primary particles was small and evenly distributed. Meanwhile, the positive electrode active material of Comparative Example 4 obtained from a positive electrode active material precursor with a BET specific surface area of 11 m ² /g or more was also compared to the positive electrode active materials of Comparative Examples 1 to 3. As a result, it was found that the number of primary particles with a size exceeding 400 nm was reduced. However, the positive electrode active material of Comparative Example 4 had unsatisfactory rolling density and volumetric capacity characteristics, as shown in Table 5 below, making it difficult to apply in practice.

Evaluation example 4: X-ray diffraction analysis

In-situ

In the lithium battery, changes in the crystal lattice constants a-axis and c-axis during the first charge and discharge were investigated and are shown in Figures 6A to 6D.

Figures 6A and 6B show changes in a-axis and c-axis constants as a result of X-ray diffraction analysis of the positive electrode active material of Example 1 in the lithium battery manufactured according to Production Example 1. And Figures 6C to 6D show changes in a-axis and c-axis constants as a result of X-ray diffraction analysis of the positive electrode active material of Comparative Example 1 in the lithium battery manufactured according to Comparative Production Example 1. At this time, the x-axis of Figures 6a-d corresponds to the number of XRD analysis (measurement) times. 1 to 21 were charging, 22 to 40 were discharging, and the change in lattice constant during the process was indicated. In particular, the increase in discharge capacity around 3.5V corresponds to measurement results 36 to 40.

Referring to this, the a-axis increase and c-axis decrease significantly occur around ~3.5V at the discharge end, and it can be seen that the lattice change of the specimen with high initial efficiency is greater. The results indicate that the lattice change during discharge can be greatly affected by the distribution of primary particle size, and support that in the case of active materials with large primary particles, stress distribution is difficult and discharge efficiency is reduced.

Evaluation example 5: charge/discharge characteristic

The lithium batteries manufactured according to Production Examples 1 to 5 and Comparative Production Examples 1 to 4 were charged at a constant current of 0.1C rate at 25°C until the voltage reached 4.35V (vs. Li). Subsequently, the discharge was performed at a constant current of 0.1C rate until the voltage reached 2.8V (vs. Li) (1 ^st cycle, formation cycle). The C rate refers to the discharge rate of the cell, and the total capacity of the cell is 1 hour of total discharge time, for example, the C rate of a battery with a discharge capacity of 1.6 ampere-hours is 1.6 amperes.

A lithium battery that has undergone 1 ^st cycle is charged at a constant current of 0.33C rate at 25°C until the voltage reaches 4.35V (vs. Li), and then cut off at a current of 0.05C rate while maintaining 4.35V in constant voltage mode. (cut-off). Subsequently, the discharge was performed at a constant current of 0.2C rate until the voltage reached 2.8V (vs. Li) (2 ^nd cycle).

A lithium battery that has undergone 2 ^nd cycles is charged at a constant current of 0.33C rate at 25°C until the voltage reaches 4.35V (vs. Li), and then cut-off at a current of 0.05C while maintaining 4.35V in constant voltage mode. (cut-off). Subsequently, the discharge was performed at a constant current of 1C rate until the voltage reached 2.8V (vs. Li) (3 ^rd cycle).

The lithium battery that had gone through the ^3rd cycle was repeated under the same conditions up to the ^51st cycle (repeated 50 times).

In all of the above charge/discharge cycles, a 10-minute pause was allowed after one charge/discharge cycle.

Some of the results of the charge and discharge experiment are shown in Table 5 below. And Table 5 below shows the rolling density and capacity per volume of the positive electrode active material.

1 ^st cycle charging capacity (mAh/g) initial efficiency
(%) rolling
density
(g/cc) capacity per volume
(mAh/c) Capacity maintenance rate
(%) Production example 1 236 94.9 2.70 599.4 98.2 Production example 2 242 94.2 2.97 671.2 90.4 Production example 3 244 93.9 3.02 685.5 93.5 Production example 4 247 94.7 3.04 699.2 89.2 Production example 5 246 94.7 3.08 708.4 88 Comparative production example 1 234 85.9 2.84 553.8 - Comparative Production Example 2 240 88.3 2.98 625.8 - Comparative Production Example 3 246 88.2 3.02 652.3 88 Comparative production example 4 235 95.7 2.65 591.0 -

As shown in Table 5, the initial efficiency of the lithium batteries of Production Examples 1 to 5 was improved compared to the lithium batteries of Comparative Production Examples 1 to 3.

The lithium battery of Production Example 1 had improved initial efficiency and capacity per volume compared to the lithium battery of Comparative Production Example 1. In addition, the lithium battery of Comparative Production Example 4 had an equivalent initial efficiency compared to the lithium battery of Production Example 1, but was further deteriorated compared to the rolling density and capacity characteristics per volume of the positive electrode active material used in the lithium battery of Production Example 1. The results were shown.

In addition, the initial efficiency and capacity per volume of the lithium battery of Production Example 6 were evaluated according to the same method as that of the lithium battery of Production Example 1.

As a result of the evaluation, it was found that the lithium battery of Production Example 6 showed equivalent initial efficiency and capacity per volume compared to the lithium battery of Production Example 1.

1: Lithium battery 2: Cathode
3: Anode 4: Separator
5: Battery case 6: Cap assembly

Claims (21)

At least one secondary particle comprising an aggregate of a plurality of primary particles, wherein the secondary particle includes a nickel-based lithium transition metal oxide having a layered crystal structure,
The primary particles include first primary particles having a size of more than 400 nm, second primary particles having a size of less than 150 nm, and third primary particles having a size of 150 nm to 400 nm,
A positive electrode active material in which the area of the tertiary primary particles is 80% or more based on the total area of the primary particles, and the secondary particles have a porosity of 10% or less based on the total area of the positive electrode active material. According to paragraph 1,
The area of the first primary particles is 20% or less based on the total area of the primary particles, the area of the second primary particles is 9% or less based on the total area of the primary particles, and the secondary particles are based on the total area of the positive electrode active material. A positive electrode active material having a porosity of 1 to 10%. According to paragraph 1,
The primary particles have particle uniformity of 90% or more,
The area of the first primary particles is 2.1 to 19.2% based on the total area of the primary particles, the area of the second primary particles is 0.1% to 8.6% based on the total area of the primary particles, and the secondary particles are the positive electrode active material. A positive electrode active material having a porosity of 1.5 to 7% relative to the total area. According to paragraph 1,
A positive electrode active material wherein at least one secondary particle containing the nickel-based lithium transition metal oxide having the layered crystal structure has an average particle diameter of 15 to 30 ㎛. According to paragraph 1,
A positive electrode active material in which the area of the third primary particles is 80 to 95%. According to paragraph 1,
The nickel-based lithium transition metal oxide having the layered crystal structure is a positive electrode active material belonging to the rock salt layered structure (R-3m space group). According to claim 1,
The nickel-based lithium transition metal oxide having a layered crystal structure is a positive electrode active material selected from the compounds represented by the following formulas 1 to 4:
[Formula 1]
Li _x Ni _1-yz-α Co _y Mn _z Me _α O ₂
In formula 1, 1≤x≤1.1, 0≤y≤0.2, 0≤z≤0.2, 0≤α≤0.05
Me is one or more metals selected from the group consisting of Zr, Al, Mg, Ti, Cu, W and B, and y+z+α≤0.3,
[Formula 2]
Li _x Co _1-y M _y O _{2- α}
[Formula 3]
Li _x Ni _1-y Me _y O _{2- α}
[Formula 4]
Li _x Ni _1-yz Mn _y Ma _z O _{2- α}
In Formulas 2 to 4, x, y, α, and Me may be selected independently of each other, 1≤x≤1.1, 0≤y≤0.9, 0<z≤0.2, 0≤α≤2, and M is One or more metals selected from the group consisting of Ni, Mn, Zr, Al, Mg, Ag, Mo, Ti, V, Cr, Fe, Cu, and B, and Me is Co, Zr, Al, Mg, Ag, Mo, Ti , V, Cr, Mn, Fe, Cu, and B, and Ma is a group consisting of Co, Zr, Al, Mg, Ag, Mo, Ti, V, Cr, Fe, Cu, and B. It is a metal selected from , and X is an element selected from the group consisting of F, S, and P. According to paragraph 1,
The nickel-based lithium transition metal oxide having a layered crystal structure is a positive electrode active material selected from the compounds represented by the following formulas 5 to 7:
[Formula 5]
Li[Li _1-a Me _a ]O _{2 +d}
In Formula 5, 0.8≤a<1, 0≤d≤0.1,
wherein Me is one or more metals selected from the group consisting of Ni, Co, Mn, Al, V, Cr, Fe, Zr, Re, B, Ge, Ru, Sn, Ti, Nb, Mo and Pt,
[Formula 6]
Li[Li _1-xyz Ma _x Mb _y Mc _z ]O _2+d
In Formula 6, 0.8≤x+y+z<1, 0<x<1, 0<y<1, 0<z<1, 0≤d≤0.1,
Ma, Mb, and Mc are independently one or more metals selected from the group consisting of Mn, Co, Ni, and Al,
[Formula 7]
Li[Li _1-xyz Ni _x Co _y Mn _z ]O _2+d
In Formula 7, 0.8≤x+y+z<1;0<x<1,0<y<1,0<z<1, 0≤d≤0.1. According to paragraph 1,
The nickel-based lithium transition metal oxide having a layered crystal structure is a positive electrode active material represented by the following formula (8):
[Formula 8]
aLi ₂ MnO ₃ -(1-a)LiMO ₂
In Formula 8, 0<a<1,
M is nickel (Ni), cobalt (Co), manganese (Mn), vanadium (V), chromium (Cr), iron (Fe), zirconium (Zr), rhenium (Re), aluminum (Al), and boron (B ), germanium (Ge), ruthenium (Ru), tin (Sn), titanium (Ti), niobium (Nb), molybdenum (Mo), and platinum (Pt). According to paragraph 1,
The nickel-based lithium transition metal oxide having a layered crystal structure is a positive electrode active material that is a compound represented by the following formula (9):
[Formula 9]
Li _x Ni _{1 -y- z} M _y Co _z O ₂
In Formula 9, 0.90≤x≤1.1, 0≤y≤0.2, 0<z≤0.2, 0.7≤1-yz≤0.99.
M is selected from the group consisting of manganese (Mn), aluminum (Al), titanium (Ti), and calcium (Ca). According to paragraph 1,
The nickel-based lithium transition metal oxide having a layered crystal structure is a positive electrode active material that is a compound represented by the following Chemical Formula 9a:
[Formula 9a]
Li _x Ni _{1 -y- z} Mn _x Co _y O ₂
In Formula 5a, 0.80≤x≤1.1, 0≤y≤0.2, 0<z≤0.2, 0.8≤1-yz≤0.99. According to clause 11,
The nickel-based lithium transition metal oxide having the layered crystal structure is Li _1.03 [Ni _0.91 Co _0.06 Mn _0.03 ]O _2, Li _{1 . 03} [Ni _0.88 Co _0.08 Mn _0.04 ]O _{2 ,} Li _{1 . 03} [Ni _0.8 Co _0.15 Mn _0.05 ]O _{2 ,} Li _1.03 [Ni _0.85 Co _0.10 Mn _0.05 ]O ₂ , Li _{1 . 03} [Ni _0.91 Co _0.05 Mn _0.04 ]O _{2 ,} Li _{1 . 05} [Ni _0.91 Co _0.06 Mn _0.03 ]O _{2 ,} Li _1.05 [Ni _0.88 Co _0.08 Mn _0.04 ]O _{2 ,} Li _{1 . 05} [Ni _0.8 Co _0.15 Mn _0.05 ]O _{2 ,} Li _{1 . 05} [Ni _0.85 Co _0.10 Mn _0.05 ]O ₂ , Li _1.05 [Ni _0.91 Co _0.05 Mn _0.04 ]O _{2 ,} Li _{1 . 06} [Ni _0.91 Co _0.06 Mn _0.03 ]O _{2 ,} Li _{1 . 06} [Ni _0.88 Co _0.08 Mn _0.04 ]O _{2 ,} Li _1.06 [Ni _0.8 Co _0.15 Mn _0.05 ]O _{2 ,} Li _{1 . 06} [Ni _0.85 Co _0.10 Mn _0.05 ]O ₂ , Li _{1 . 06} [Ni _0.91 Co _0.05 Mn _0.04 ]O _{2 ;} Li _1.09 [Ni _0.91 Co _0.06 Mn _0.03 ]O _2, Li _{1 . 09} [Ni _0.88 Co _0.08 Mn _0.04 ]O _{2 ,} Li _{1 . 09} [Ni _0.8 Co _0.15 Mn _0.05 ]O _{2 ,} Li _1.09 [Ni _0.85 Co _0.10 Mn _0.05 ]O ₂ , or Li _{1 . 09} [Ni _0.91 Co _0.05 Mn _0.04 ]O ₂ Phosphorus Cathode active material. According to paragraph 1,
The positive electrode active material is a large particle size positive electrode active material, the positive electrode active material further includes a small particle size positive electrode active material, and the positive electrode active material is a mixture of the large particle size positive electrode active material and the small particle size positive electrode active material, and the positive electrode active material has a rolling density of 3.3 g/cc or more. A positive electrode comprising the positive electrode active material of any one of claims 1 to 13. The anode of clause 14; cathode; and an electrolyte disposed between the anode and the cathode. According to clause 15,
A lithium battery having an initial efficiency of 93% or more and a density of the positive electrode after rolling of 2.8 g/cc or more. According to clause 15,
After discharging the lithium battery at 3.5V, the crystal lattice constant a obtained from Lithium batteries increasing by 0.5%. It is a positive electrode active material precursor used in manufacturing the positive electrode active material of claim 1,
The positive electrode active material precursor is a vertical precursor of nickel-based lithium transition metal oxide, has a specific surface area of 8 to 25 m ² /g, and an average particle diameter (D50) of 13.7 μm or more. According to clause 18,
The cathode active material precursor has a major axis length of 150 to 200 nm and a minor axis length of 10 to 100 nm. Mixing a positive electrode active material precursor and a lithium precursor and performing primary heat treatment on them;
Washing the first heat-treated product with water and drying it;
Obtaining the positive electrode active material of any one of claims 1 to 13, including the step of secondary heat treatment of the dried product, and the secondary heat treatment is performed at a lower temperature than the primary heat treatment,
The positive electrode active material precursor is a vertical precursor of nickel-based lithium transition metal oxide and has a specific surface area of 8 to 25 m ² /g and an average particle diameter (D50) of 13.7 μm or more. According to clause 20,
A method of producing a positive electrode active material in which the positive electrode active material precursor is manufactured by controlling the pH of a mixture obtained by mixing a metal raw material for forming a positive electrode active material precursor, a complexing agent, and a pH adjuster, and then performing a reaction.